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  • 1.
    Bergström, Mats
    et al.
    Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Faculty of Pharmacy, Department of Pharmaceutical Biosciences.
    Yates, Roger
    Wall, Anders
    Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Faculty of Medicine, Department of Oncology, Radiology and Clinical Immunology.
    Kågedal, Matts
    Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Faculty of Pharmacy, Department of Pharmaceutical Biosciences, Division of Pharmacokinetics and Drug Therapy.
    Syvänen, Stina
    Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Faculty of Pharmacy, Department of Pharmaceutical Biosciences, Division of Pharmacokinetics and Drug Therapy.
    Långström, Bengt
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Biochemistry and Organic Chemistry.
    Blood-brain barrier penetration of zolmitriptan--modelling of positron emission tomography data2006In: Journal of Pharmacokinetics and Pharmacodynamics, ISSN 1567-567X, E-ISSN 1573-8744, Vol. 33, no 1, p. 75-91Article in journal (Refereed)
    Abstract [en]

    Positron emission tomography (PET) with the drug radiolabelled allows a direct measurement of brain or other organ kinetics, information which can be essential in drug development. Usually, however, a PET-tracer is administered intravenously (i.v.), whereas the therapeutic drug is mostly given orally or by a different route to the PET-tracer. In such cases, a recalculation is needed to make the PET data representative for the alternative administration route. To investigate the blood-brain barrier penetration of a drug (zolmitriptan) using dynamic PET and by PK modelling quantify the brain concentration of the drug after the nasal administration of a therapeutic dose. [11C]Zolmitriptan at tracer dose was administered as a short i.v. infusion and the brain tissue and venous blood kinetics of [11C]zolmitriptan was measured by PET in 7 healthy volunteers. One PET study was performed before and one 30 min after the administration of 5 mg zolmitriptan as nasal spray. At each of the instances, the brain radioactivity concentration after subtraction of the vascular component was determined up to 90 min after administration and compared to venous plasma radioactivity concentration after correction for radiolabelled metabolites. Convolution methods were used to describe the relationship between arterial and venous tracer concentrations, respectively between brain and arterial tracer concentration. Finally, the impulse response functions derived from the PET studies were applied on plasma PK data to estimate the brain zolmitriptan concentration after a nasal administration of a therapeutic dose. The studies shows that the PET data on brain kinetics could well be described as the convolution of venous tracer kinetics with an impulse response including terms for arterial-to-venous plasma and arterial-to-brain impulse responses. Application of the PET derived impulse responses on the plasma PK from nasal administration demonstrated that brain PK of zolmitriptan increased with time, achieving about 0.5 mg/ml at 30 min and close to a maximum of 1.5 mg/ml after 2 hr. A significant brain concentration was observed already after 5 min. The data support the notation of a rapid brain availability of zolmitriptan after nasal administration.

  • 2. Bogdanović, Renée Marie
    et al.
    Syvänen, Stina
    Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Faculty of Medicine, Department of Public Health and Caring Sciences, Geriatrics.
    Michler, Christina
    Russmann, Vera
    Eriksson, Jonas
    Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Faculty of Pharmacy, Department of Medicinal Chemistry, Preclinical PET Platform.
    Windhorst, Albert D
    Lammertsma, Adriaan A
    de Lange, Elisabeth C
    Voskuyl, Rob A
    Potschka, Heidrun
    (R)-[(11)C]PK11195 brain uptake as a biomarker of inflammation and antiepileptic drug resistance: Evaluation in a rat epilepsy model2014In: Neuropharmacology, ISSN 0028-3908, E-ISSN 1873-7064, Vol. 85, p. 104-112Article in journal (Refereed)
    Abstract [en]

    Neuroinflammation has been suggested as a key determinant of the intrinsic severity of epilepsy. Glial cell activation and associated inflammatory signaling can influence seizure thresholds as well as the pharmacodynamics and pharmacokinetics of antiepileptic drugs. Based on these data, we hypothesized that molecular imaging of microglia activation might serve as a tool to predict drug refractoriness of epilepsy. Brain uptake of (R)-[(11)C]PK11195, a ligand of the translocator protein 18 kDa and molecular marker of microglia activation, was studied in a chronic model of temporal lobe epilepsy in rats with selection of phenobarbital responders and non-responders. In rats with drug-sensitive epilepsy, (R)-[(11)C]PK11195 brain uptake values were comparable to those in non-epileptic controls. Analysis in non-responders revealed enhanced brain uptake of up to 39% in different brain regions. The difference might be related to the fact that non-responders exhibited higher baseline seizure frequencies than responders indicating a more pronounced intrinsic disease severity. In hippocampal sections, ED1 immunostaining argued against a general difference in microglia activation between both groups. Our data suggest that TSPO PET imaging might serve as a biomarker for drug resistance in temporal lobe epilepsy. However, it needs to be considered that our findings indicate that the TSPO PET data might merely reflect seizure frequency. Future experimental and clinical studies should further evaluate the validity of TSPO PET data to predict the response to phenobarbital and other antiepileptic drugs in longitudinal studies with scanning before drug exposure and with a focus on the early phase following an epileptogenic brain insult.

  • 3.
    Eriksson, Olof
    et al.
    Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Faculty of Medicine, Department of Oncology, Radiology and Clinical Immunology, Radiology.
    Wallberg, Andreas
    Syvänen, Stina
    Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Faculty of Pharmacy, Department of Pharmaceutical Biosciences.
    Josephsson, Raymond
    Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Faculty of Medicine, Department of Medical Sciences, Clinical Virology.
    Långström, Bengt
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Biochemistry and Organic Chemistry.
    Bergström, Mats
    Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Faculty of Pharmacy, Department of Pharmaceutical Biosciences.
    A computerized Infusion Pump for control of tissue tracer concentration during Positron Emission Tomography in vivo Pharmacokinetic/Pharmacodynamic measurements2008In: BMC Medical Physics, ISSN 1756-6649, E-ISSN 1756-6649, Vol. 8, no 2Article in journal (Refereed)
    Abstract [en]

    BACKGROUND:

    A computer controlled infusion pump (UIPump) for regulation of target tissue concentration of radioactive compounds was developed for use in biological research and tracer development for PET.

    METHODS:

    Based on observed tissue or plasma kinetics after a bolus injection of the tracer an algorithm calculates the infusion needed to obtain a specified target kinetic curve. A computer feeds this infusion scheme into an infusion pump connected to an animal via a venous catheter. The concept was validated using [11C]Flumazenil administrated to Sprague-Dawley rats where the whole brain distribution and kinetic of the tracer was measured over time using a microPET-scanner. The accuracy and precision of the system was assessed by producing steady-state levels of the tracer and by mimicking kinetics after oral administration.

    RESULTS:

    Various kinetic profiles could be generated, including rapid achievement of constant levels, or step-wise increased levels. The resulting tissue curves had low deviation from the target curves according to the specified criteria: AUC (%): 4.2 +/- 2.8, Maximal deviation (%): 13.6 +/- 5.0 and R2: 0.95 +/- 0.02.

    CONCLUSION:

    The UIPump-system is suitable for use in PET-research for assessment of PK/PD properties by simulation of different tracer tissue kinetics in vivo.

  • 4.
    Fang, Xiaotian
    et al.
    Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Faculty of Medicine, Department of Public Health and Caring Sciences.
    Hultqvist, Greta
    Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Faculty of Medicine, Department of Public Health and Caring Sciences, Geriatrics.
    Meier, Silvio
    Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Faculty of Medicine, Department of Public Health and Caring Sciences.
    Sehlin, Dag
    Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Faculty of Medicine, Department of Public Health and Caring Sciences.
    Syvänen, Stina
    Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Faculty of Medicine, Department of Public Health and Caring Sciences.
    A small bispecific antibody-based construct based on bapineuzumab as a PET tracer for amyloid beta pathology in brain2017In: Meeting abstractArticle in journal (Other academic)
  • 5.
    Fang, Xiaotian T.
    et al.
    Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Faculty of Medicine, Department of Public Health and Caring Sciences, Geriatrics.
    Eriksson, Jonas
    Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Faculty of Pharmacy, Department of Medicinal Chemistry, Preclinical PET-MRI Platform. PET Centre, Uppsala University Hospital, 751 85 Uppsala, Sweden.
    Antoni, Gunnar
    Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Faculty of Pharmacy, Department of Medicinal Chemistry, Preclinical PET-MRI Platform. Uppsala University Hospital, 751 85 Uppsala, SwedenUppsala University Hospital, 751 85 Uppsala, Sweden.
    Yngve, Ulrika
    Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Faculty of Pharmacy, Department of Medicinal Chemistry, Preclinical PET-MRI Platform. Uppsala University Hospital, 751 85 Uppsala, SwedenUppsala University Hospital, 751 85 Uppsala, Sweden.
    Cato, Linda
    Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Faculty of Medicine, Department of Public Health and Caring Sciences, Geriatrics.
    Lannfelt, Lars
    Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Faculty of Medicine, Department of Public Health and Caring Sciences, Geriatrics.
    Sehlin, Dag
    Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Faculty of Medicine, Department of Public Health and Caring Sciences, Geriatrics.
    Syvänen, Stina
    Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Faculty of Medicine, Department of Public Health and Caring Sciences, Geriatrics.
    Brain mGluR5 in mice with amyloid beta pathology studied with in vivo [(11)C]ABP688 PET imaging and ex vivo immunoblotting2017In: Neuropharmacology, ISSN 0028-3908, E-ISSN 1873-7064, Vol. 113, no Pt A, p. 293-300, article id S0028-3908(16)30459-2Article in journal (Refereed)
    Abstract [en]

    Alzheimer's disease (AD) is characterized by aggregation of amyloid beta (Aβ) into insoluble plaques. Intermediates, Aβ oligomers (Aβo), appear to be the mechanistic cause of disease. The de facto PET AD ligand, [(11)C]PIB, binds and visualizes Aβ plaque load, which does not correlate well with disease severity. Therefore, finding a dynamic target that changes with pathology progression in AD is of great interest. Aβo alter synaptic plasticity, inhibit long-term potentiation, and facilitate long-term depression; key mechanisms involved in memory and learning. In order to convey these neurotoxic effects, Aβo requires interaction with the metabotropic glutamate 5 receptor (mGluR5). The aim was to investigate in vivo mGluR5 changes in an Aβ pathology model using PET. Wild type C57/BL6 (wt) and AβPP transgenic mice (tg-ArcSwe), 4, 8, and 16 months old, were PET scanned with [(11)C]ABP688, which is highly specific to mGluR5, to investigate changes in mGluR5. Mouse brains were extracted postscan and mGluR5 and Aβ protofibril levels were assessed with immunoblotting and ELISA respectively. Receptor-dense brain regions (hippocampus, thalamus, and striatum) displayed higher [(11)C]ABP688 concentrations corresponding to mGluR5 expression pattern. Mice had similar uptake levels of [(11)C]ABP688 regardless of genotype or age. Immunoblotting revealed general decline in mGluR5 expression and elevated levels of mGluR5 in 16 months old tg-ArcSwe compared with wt mice. [(11)C]ABP688 could visualize mGluR5 in the mouse brain. In conclusion, mGluR5 levels were found to decrease with age and tended to be higher in tg-ArcSwe compared with wt mice, however these changes could not be quantified with PET.

  • 6.
    Fang, Xiaotian T.
    et al.
    Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Faculty of Medicine, Department of Public Health and Caring Sciences, Geriatrics.
    Sehlin, Dag
    Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Faculty of Medicine, Department of Public Health and Caring Sciences, Geriatrics.
    Lannfelt, Lars
    Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Faculty of Medicine, Department of Public Health and Caring Sciences, Geriatrics.
    Syvänen, Stina
    Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Faculty of Medicine, Department of Public Health and Caring Sciences, Geriatrics.
    Hultqvist, Greta
    Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Faculty of Medicine, Department of Public Health and Caring Sciences, Geriatrics. Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Faculty of Pharmacy, Department of Pharmaceutical Biosciences.
    Efficient and inexpensive transient expression of multispecific multivalent antibodies in Expi293 cells2017In: Biological Procedures Online, ISSN 1480-9222, E-ISSN 1480-9222, Vol. 19, article id 11Article in journal (Refereed)
    Abstract [en]

    Background: Immunotherapy is a very fast expanding field within drug discovery and, hence, rapid and inexpensive expression of antibodies would be extremely valuable. Antibodies are, however, difficult to express. Multifunctional antibodies with additional binding domains further complicate the expression. Only few protocols describe the production of tetravalent bispecific antibodies and all with limited expression levels.

    Methods: Here, we describe a protocol that can produce functional tetravalent, bispecific antibodies at around 22 mg protein/l to a low cost. The expression system is based on the Expi293 cells, which have been adapted to grow in denser cultures than HEK293 cells and gives higher expression yields. The new protocol transfects the Expi293 cells with PEI (which has a negligible cost).

    Results: The protocol has been used to generate multiple variants of tetra-and hexavalent bispecific antibodies with yields of around 22 mg protein/l within 10 days. All materials are commercially available and the implementation of the protocol is inexpensive and straightforward. The bispecific antibodies generated in our lab were capable of binding to all antigens with similar affinity as the original antibody. Two of the bispecific antibodies have also been used in transgenic mice as positron emission tomography (PET) ligands to successfully detect amyloid-beta (A beta) aggregates in vivo.

    Conclusions: This protocol is the first describing transfection of the human Expi293 cells with PEI. It can be used to generate functional multi-specific antibodies in high amounts. The use of biological drugs, and in particular multispecific antibodies, is rapidly increasing, hence improved protocols such as the one presented here are highly valuable.

  • 7. Froklage, Femke E
    et al.
    Syvänen, Stina
    Leiden University.
    Hendrikse, N Harry
    Huisman, Marc C
    Molthoff, Carla Fm
    Tagawa, Yoshihiko
    Reijneveld, Jaap C
    Heimans, Jan J
    Lammertsma, Adriaan A
    Eriksson, Jonas
    VU University Medical Center Amsterdam.
    de Lange, Elizabeth Cm
    Voskuyl, Rob A
    [11C]Flumazenil brain uptake is influenced by the blood-brain barrier efflux transporter P-glycoprotein.2012In: EJNMMI research, ISSN 2191-219X, Vol. 2, p. 12-Article in journal (Refereed)
    Abstract [en]

    BACKGROUND: [11C]Flumazenil and positron emission tomography (PET) are used clinically to assess gamma-aminobutyric acid (GABA)-ergic function and to localize epileptic foci prior to resective surgery. Enhanced P-glycoprotein (P-gp) activity has been reported in epilepsy and this may confound interpretation of clinical scans if [11C]flumazenil is a P-gp substrate. The purpose of this study was to investigate whether [11C]flumazenil is a P-gp substrate.

    METHODS: [11C]Flumazenil PET scans were performed in wild type (WT) (n = 9) and Mdr1a/1b, (the genes that encode for P-gp) double knockout (dKO) (n = 10) mice, and in naive rats (n = 10). In parallel to PET scanning, [11C]flumazenil plasma concentrations were measured in rats. For 6 of the WT and 6 of the dKO mice a second, [11C]flumazenil scan was acquired after administration of the P-gp inhibitor tariquidar. Cerebral [11C]flumazenil concentrations in WT and Mdr1a/1b dKO mice were compared (genetic disruption model). Furthermore, pre and post P-gp-blocking cerebral [11C]flumazenil concentrations were compared in all animals (pharmacological inhibition model).

    RESULTS: Mdr1a/1b dKO mice had approximately 70% higher [11C]flumazenil uptake in the brain than WT mice. After administration of tariquidar, cerebral [11C]flumazenil uptake in WT mice increased by about 80% in WT mice, while it remained the same in Mdr1a/1b dKO mice. In rats, cerebral [11C]flumazenil uptake increased by about 60% after tariquidar administration. Tariquidar had only a small effect on plasma clearance of flumazenil.

    CONCLUSIONS: The present study showed that [11C]flumazenil is a P-gp substrate in rodents. Consequently, altered cerebral [11C]flumazenil uptake, as observed in epilepsy, may not reflect solely GABAA receptor density changes but also changes in P-gp activity.

  • 8. Gaitonde, P.
    et al.
    Trame, M. N.
    Syvanen, Stina
    Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Faculty of Medicine, Department of Public Health and Caring Sciences, Geriatrics.
    Lesko, L. J.
    Schmidt, S.
    Mechanism-Based Evaluation of Codeine Toxicity in Children2014In: Clinical Pharmacology and Therapeutics, ISSN 0009-9236, E-ISSN 1532-6535, Vol. 95, p. S42-S43Article in journal (Other academic)
  • 9.
    Gustafsson, Sofia
    et al.
    Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Faculty of Pharmacy, Department of Pharmaceutical Biosciences.
    Eriksson, Jonas
    Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Faculty of Pharmacy, Department of Medicinal Chemistry, Organic Pharmaceutical Chemistry.
    Syvänen, Stina
    Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Faculty of Medicine, Department of Public Health and Caring Sciences, Geriatrics.
    Eriksson, Olof
    Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Faculty of Pharmacy, Department of Medicinal Chemistry, Division of Molecular Imaging.
    Hammarlund-Udenaes, Margareta
    Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Faculty of Pharmacy, Department of Pharmaceutical Biosciences.
    Antoni, Gunnar
    Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Faculty of Pharmacy, Department of Medicinal Chemistry, Division of Molecular Imaging.
    Combined PET and microdialysis for in vivo estimation of drug blood-brain barrier transport and brain unbound concentrations2017In: NeuroImage, ISSN 1053-8119, E-ISSN 1095-9572, Vol. 155, p. 177-186Article in journal (Refereed)
    Abstract [en]

    Methods to investigate blood-brain barrier transport and pharmacologically active drug concentrations in the human brain are limited and data translation between species is challenging. Hence, there is a need to further develop the read-out of techniques like positron emission tomography ( PET) for studying neuropharmacokinetics. PET has a high translational applicability from rodents to man and measures total drug concentrations in vivo. The aim of the present study was to investigate the possibility of translating total drug concentrations, acquired through PET, to unbound concentrations, resembling those measured in the interstitial fluid by microdialysis sampling. Simultaneous PET scanning and brain microdialysis sampling were performed in rats throughout a 60 min infusion of [N-methyl-C-11] oxycodone in combination with a therapeutic dose of oxycodone and during a 60 min follow up period after the end of infusion. The oxycodone concentrations acquired with PET were converted into unbound concentrations by compensating for brain tissue binding and brain intracellular distribution, using the unbound volume of distribution in brain (Vu, brain), and were compared to microdialysis measurements of unbound concentrations. A good congruence between the methods was observed throughout the infusion. However, an accumulating divergence in the acquired PET and microdialysis data was apparent and became more pronounced during the elimination phase, most likely due to the passage of radioactive metabolites into the brain. In conclusion, the study showed that PET can be used to translate non-invasively measured total drug concentrations into unbound concentrations as long as the contribution of radiolabelled metabolites is minor or can be compensated for.

  • 10.
    Gustafsson, Sofia
    et al.
    Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Faculty of Pharmacy, Department of Pharmaceutical Biosciences.
    Lindström, Veronica
    Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Faculty of Medicine, Department of Public Health and Caring Sciences, Geriatrics.
    Ingelsson, Martin
    Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Faculty of Medicine, Department of Public Health and Caring Sciences, Geriatrics.
    Hammarlund-Udenaes, Margareta
    Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Faculty of Pharmacy, Department of Pharmaceutical Biosciences.
    Syvänen, Stina
    Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Faculty of Medicine, Department of Public Health and Caring Sciences, Geriatrics.
    Intact blood-brain barrier transport of small molecular drugs in animal models of amyloid beta and alpha-synuclein pathology2018In: Neuropharmacology, ISSN 0028-3908, E-ISSN 1873-7064, Vol. 128, p. 482-491Article in journal (Refereed)
    Abstract [en]

    Pathophysiological impairment of the neurovascular unit, including the integrity and dynamics of the blood-brain barrier (BBB), has been denoted both a cause and consequence of neurodegenerative diseases. Pathological impact on BBB drug delivery has also been debated. The aim of the present study was to investigate BBB drug transport, by determining the unbound brain-to-plasma concentration ratio (K-p,K-uu,K-brain), in aged A beta PP-transgenic mice, alpha-synuclein transgenic mice, and wild type mice. Mice were dosed with a cassette of five compounds, including digoxin, levofloxacin (1 mg/kg, s.c.), paliperidone, oxycodone, and diazepam (0.25 mg/kg, s.c.). Brain and blood were collected at 0.5,1, or 3 h after dosage. Drug concentrations were measured using LC-MS/MS. The total brain-to-plasma concentration ratio was calculated and equilibrium dialysis was used to determine the fraction of unbound drug in brain and plasma for all compounds. Together, these three measures were used to determine the Kp,uu,brain value. Despite A beta or alpha-synuclein pathology in the current animal models, no difference was observed in the extent of drug transport across the BBB compared to wild type animals for any of the compounds investigated. Hence, the present study shows that the concept of a leaking barrier within neurodegenerative conditions has to be interpreted with caution when estimating drug transport into the brain. The capability of the highly dynamic BBB to regulate brain drug exposure still seems to be intact despite the presence of pathology. (C) 2017 The Authors. Published by Elsevier Ltd.

  • 11.
    Hammarlund-Udenaes, Margareta
    et al.
    Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Faculty of Pharmacy, Department of Pharmaceutical Biosciences.
    Fridén, Markus
    Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Faculty of Pharmacy, Department of Pharmaceutical Biosciences.
    Syvänen, Stina
    Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Faculty of Pharmacy, Department of Pharmaceutical Biosciences.
    Gupta, Anubha
    Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Faculty of Pharmacy, Department of Pharmaceutical Biosciences.
    On the rate and extent of drug delivery to the brain2008In: Pharmaceutical research, ISSN 0724-8741, E-ISSN 1573-904X, Vol. 25, no 8, p. 1737-1750Article, review/survey (Refereed)
    Abstract [en]

    To define and differentiate relevant aspects of blood-brain barrier transport and distribution in order to aid research methodology in brain drug delivery. Pharmacokinetic parameters relative to the rate and extent of brain drug delivery are described and illustrated with relevant data, with special emphasis on the unbound, pharmacologically active drug molecule. Drug delivery to the brain can be comprehensively described using three parameters: Kp,uu (concentration ratio of unbound drug in brain to blood), CLin (permeability clearance into the brain), and Vu,brain (intra-brain distribution). The permeability of the blood-brain barrier is less relevant to drug action within the CNS than the extent of drug delivery, as most drugs are administered on a continuous (repeated) basis. Kp,uu can differ between CNS-active drugs by a factor of up to 150-fold. This range is much smaller than that for log BB ratios (Kp), which can differ by up to at least 2,000-fold, or for BBB permeabilities, which span an even larger range (up to at least 20,000-fold difference). Methods that measure the three parameters Kp,uu, CLin, and Vu,brain can give clinically valuable estimates of brain drug delivery in early drug discovery programmes.

  • 12.
    Hultqvist, Greta
    et al.
    Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Faculty of Medicine, Department of Public Health and Caring Sciences, Geriatrics.
    Syvänen, Stina
    Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Faculty of Medicine, Department of Public Health and Caring Sciences, Geriatrics.
    Fang, Xiaotian T.
    Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Faculty of Medicine, Department of Public Health and Caring Sciences, Geriatrics.
    Lannfelt, Lars
    Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Faculty of Medicine, Department of Public Health and Caring Sciences, Geriatrics.
    Sehlin, Dag
    Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Faculty of Medicine, Department of Public Health and Caring Sciences, Geriatrics.
    Bivalent Brain Shuttle Increases Antibody Uptake by Monovalent Binding to the Transferrin Receptor2017In: Theranostics, ISSN 1838-7640, E-ISSN 1838-7640, Vol. 7, no 2, p. 308-318Article in journal (Refereed)
    Abstract [en]

    The blood-brain barrier (BBB) is an obstacle for antibody passage into the brain, impeding the development of immunotherapy and antibody-based diagnostics for brain disorders. In the present study, we have developed a brain shuttle for active transport of antibodies across the BBB by receptor-mediated transcytosis. We have thus recombinantly fused two single-chain variable fragments (scFv) of the transferrin receptor (TfR) antibody 8D3 to the light chains of mAb158, an antibody selectively binding to A beta protofibrils, which are involved in the pathogenesis of Alzheimer's disease (AD). Despite the two TfR binders, a monovalent interaction with TfR was achieved due to the short linkers that sterically hinder bivalent binding to the TfR dimer. The design enabled efficient receptor-mediated brain uptake of the fusion protein. Two hours after administration, brain concentrations were 2-3% of the injected dose per gram brain, comparable to small molecular drugs and 80-fold higher than unmodified mAb158. After three days, fusion protein concentrations in AD transgenic mouse brains were 9-fold higher than in wild type mice, demonstrating high in vivo specificity. Thus, our innovative recombinant design markedly increases mAb158 brain uptake, which makes it a strong candidate for improved Aa immunotherapy and as a PET radioligand for early diagnosis and evaluation of treatment effect in AD. Moreover, this approach could be applied to any target within the brain.

  • 13.
    Imgenberg-Kreuz, Juliana
    et al.
    Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Faculty of Medicine, Department of Medical Sciences, Molecular Medicine. Uppsala University, Science for Life Laboratory, SciLifeLab.
    Sandling, Johanna K.
    Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Faculty of Medicine, Department of Medical Sciences, Rheumatology. Uppsala University, Science for Life Laboratory, SciLifeLab.
    Carlsson Almlöf, Jonas
    Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Faculty of Medicine, Department of Medical Sciences, Molecular Medicine. Uppsala University, Science for Life Laboratory, SciLifeLab.
    Omdal, Roald
    Norheim, Katrine Braekke
    Eloranta, Maija-Leena
    Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Faculty of Medicine, Department of Medical Sciences, Rheumatology. Uppsala University, Science for Life Laboratory, SciLifeLab.
    Rönnblom, Lars
    Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Faculty of Medicine, Department of Medical Sciences, Rheumatology. Uppsala University, Science for Life Laboratory, SciLifeLab.
    Syvänen, Ann-Christine
    Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Faculty of Medicine, Department of Public Health and Caring Sciences, Geriatrics. Uppsala University, Science for Life Laboratory, SciLifeLab.
    Nordmark, Gunnel
    Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Faculty of Medicine, Department of Medical Sciences, Rheumatology. Uppsala University, Science for Life Laboratory, SciLifeLab.
    Genome-Wide Analysis of DNA Methylation Profiles in Multiple Tissues in Primary Sjogren's Syndrome2015In: Scandinavian Journal of Immunology, ISSN 0300-9475, E-ISSN 1365-3083, Vol. 81, no 5, p. 412-412Article in journal (Other academic)
  • 14.
    Kaya, Ibrahim
    et al.
    Univ Gothenburg, Sahlgrenska Acad, Dept Psychiat & Neurochem, S-43180 Molndal, Sweden..
    Brinet, Dimitri
    Univ Gothenburg, Sahlgrenska Acad, Dept Psychiat & Neurochem, S-43180 Molndal, Sweden.;Univ Gothenburg, Dept Chem & Mol Biol, S-41296 Gothenburg, Sweden..
    Michno, Wojciech
    Univ Gothenburg, Sahlgrenska Acad, Dept Psychiat & Neurochem, S-43180 Molndal, Sweden..
    Syvänen, Stina
    Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Faculty of Medicine, Department of Public Health and Caring Sciences, Geriatrics.
    Sehlin, Dag
    Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Faculty of Medicine, Department of Public Health and Caring Sciences, Geriatrics.
    Zetterberg, Henrik
    Univ Gothenburg, Sahlgrenska Acad, Dept Psychiat & Neurochem, S-43180 Molndal, Sweden.;Sahlgrens Univ Hosp, Clin Neurochem Lab, S-43180 Molndal, Sweden.;UCL, Inst Neurol, Dept Mol Neurosci, London WC1N 3BG, England..
    Blennow, Kaj
    Univ Gothenburg, Sahlgrenska Acad, Dept Psychiat & Neurochem, S-43180 Molndal, Sweden.;Sahlgrens Univ Hosp, Clin Neurochem Lab, S-43180 Molndal, Sweden..
    Hanrieder, Jorg
    Univ Gothenburg, Sahlgrenska Acad, Dept Psychiat & Neurochem, S-43180 Molndal, Sweden.;UCL, Inst Neurol, Dept Mol Neurosci, London WC1N 3BG, England.;Chalmers, Dept Chem & Chem Engn, S-41296 Gothenburg, Sweden..
    Delineating Amyloid Plaque Associated Neuronal Sphingolipids in Transgenic Alzheimer's Disease Mice (tgArcSwe) Using MALDI Imaging Mass Spectrometry2017In: ACS Chemical Neuroscience, ISSN 1948-7193, E-ISSN 1948-7193, Vol. 8, no 2, p. 347-355Article in journal (Refereed)
    Abstract [en]

    The major pathological hallmarks of Alzheimer's disease (AD) are the progressive aggregation and accumulation of beta-amyloid (A beta) and hyperphosphorylated tau protein into neurotoxic deposits. A beta aggregation has been suggested as the critical early inducer, driving the disease progression. However, the factors that promote neurotoxic A beta aggregation remain elusive. Imaging mass spectrometry (IMS) is a powerful technique to comprehensively elucidate the spatial distribution patterns of lipids, peptides, and proteins in biological tissue sections. In the present study, matrix-assisted laser desorption/ionization (MALDI) mass spectrometry (MS)-based imaging was used on transgenic Alzheimer's disease mouse (tgArcSwe) brain tissue to investigate the sphingolipid microenvironment of individual A beta plaques and elucidate plaque-associated sphingolipid alterations. Multivariate data analysis was used to interrogate the IMS data for identifying pathologically relevant, anatomical features based on their lipid chemical profile. This approach revealed sphingolipid species that distinctly located to cortical and hippocampal deposits, whose A beta identity was further verified using fluorescent amyloid staining and immunohistochemistry. Subsequent multivariate statistical analysis of the spectral data revealed significant localization of gangliosides and ceramides species to A beta positive plaques, which was accompanied by distinct local reduction of sulfatides. These plaque-associated changes in sphingolipid levels implicate a functional role of sphingolipid metabolism in A beta plaque pathology and AD pathogenesis. Taken together, the presented data highlight the potential of imaging mass spectrometry as a powerful approach for probing A beta plaque-associated lipid changes underlying AD pathology.

  • 15.
    Lundquist, Pinelopi
    et al.
    Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Faculty of Pharmacy, Department of Pharmaceutical Biosciences.
    Roman, Magnus
    Uppsala Imanet.
    Syvänen, Stina
    Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Faculty of Pharmacy, Department of Pharmaceutical Biosciences.
    Hartvig, Per
    Hospital Pharmacy, University Hospital.
    Blomquist, Gunnar
    Uppsala Imanet.
    Hammarlund-Udenaes, Margareta
    Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Faculty of Pharmacy, Department of Pharmaceutical Biosciences.
    Långström, Bengt
    Uppsala Imanet.
    Effect on [11C]DASB binding after tranylcypromine-induced increase in serotonin concentration: positron emission tomography studies in monkeys and rats2007In: Synapse, ISSN 0887-4476, E-ISSN 1098-2396, Vol. 61, no 6, p. 440-449Article in journal (Refereed)
    Abstract [en]

    Several research groups have demonstrated that under specific conditions, in vivo neuroreceptor binding techniques can be used to measure acute changes in the concentrations of endogenous transmitters in the vicinity of neuroreceptors. The aim of this study was to investigate whether [11C]-3-amino-4-(2-dimethylaminomethyl-phenylsulfanyl)-benzonitrile ([11C]DASB) binding to the plasma membrane serotonin transporter (SERT) in the rhesus monkey and rat brain decreased after a pharmacologically-induced increase in the interstitial serotonin (5HT) concentration. Three rhesus monkeys were given repeated single boluses of [11C]DASB in sequential positron emission tomography (PET) experiments. Rats were given the tracer as a bolus dose plus a constant infusion. In vivo binding in both models was studied before and after presumably having increased interstitial 5HT concentrations using tranylcypromine (TCP), which inhibits the enzyme (monoamine oxidase, MAO), that degrades 5HT. The rat brain tissue was analyzed using high-performance liquid chromatography (HPLC) to determine the proportion of the PET signal comprising unchanged [11C]DASB. The binding of [11C]DASB in the thalamus decreased in both rhesus monkeys and rats after TCP administration. The possibility of using [11C]DASB as a tool for monitoring changes in endogenous serotonin concentrations merits further investigation.

  • 16.
    Magnusson, Kristina
    et al.
    Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Faculty of Medicine, Department of Public Health and Caring Sciences, Geriatrics.
    Sehlin, Dag
    Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Faculty of Medicine, Department of Public Health and Caring Sciences, Geriatrics.
    Syvänen, Stina
    Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Faculty of Medicine, Department of Public Health and Caring Sciences, Geriatrics.
    Svedberg, Marie M.
    Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Faculty of Medicine, Department of Public Health and Caring Sciences, Geriatrics. Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Faculty of Pharmacy, Department of Medicinal Chemistry, Preclinical PET Platform.
    Philipson, Ola
    Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Faculty of Medicine, Department of Public Health and Caring Sciences, Geriatrics.
    Soderberg, Linda
    Tegerstedt, Karin
    Holmquist, Mats
    Gellerfors, Pär
    Tolmachev, Vladimir
    Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Faculty of Medicine, Department of Radiology, Oncology and Radiation Science, Biomedical Radiation Sciences.
    Antoni, Gunnar
    Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Faculty of Pharmacy, Department of Medicinal Chemistry, Preclinical PET Platform.
    Lannfelt, Lars
    Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Faculty of Medicine, Department of Public Health and Caring Sciences, Geriatrics.
    Hall, Håkan
    Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Faculty of Pharmacy, Department of Medicinal Chemistry, Preclinical PET Platform.
    Nilsson, Lars N. G.
    Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Faculty of Medicine, Department of Public Health and Caring Sciences, Geriatrics.
    Specific Uptake of an Amyloid-beta Protofibril-Binding Antibody-Tracer in A beta PP Transgenic Mouse Brain2013In: Journal of Alzheimer's Disease, ISSN 1387-2877, E-ISSN 1875-8908, Vol. 37, no 1, p. 29-40Article in journal (Refereed)
    Abstract [en]

    Evidence suggests that amyloid-beta (A beta) protofibrils/oligomers are pathogenic agents in Alzheimer's disease (AD). Unfortunately, techniques enabling quantitative estimates of these species in patients or patient samples are still rather limited. Here we describe the in vitro and ex vivo characteristics of a new antibody-based radioactive ligand, [I-125]mAb158, which binds to A beta protofibrils with high affinity. [I-125]mAb158 was specifically taken up in brain of transgenic mice expressing amyloid-beta protein precursor (A beta PP) as shown ex vivo. This was in contrast to [I-125]mAb-Ly128 which does not bind to A beta. The uptake of intraperitoneally-administered [I-125]mAb158 into the brain was age- and time-dependent, and saturable in A beta PP transgenic mice with modest A beta deposition. Brain uptake was also found in young A beta PP transgenic mice that were devoid of A beta deposits, suggesting that [I-125]mAb158 targets soluble A beta protofibrils. The radioligand was diffusely located in the parenchyma, sometimes around senile plaques and only occasionally colocalized with cerebral amyloid angiopathy. A refined iodine-124-labeled version of mAb158 with much improved blood-brain barrier passage and a shorter plasma half-life might be useful for PET imaging of A beta protofibrils.

  • 17. Müllauer, Julia
    et al.
    Kuntner, Claudia
    Bauer, Martin
    Bankstahl, Jens P
    Müller, Markus
    Voskuyl, Rob A
    Langer, Oliver
    Syvänen, Stina
    Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Faculty of Medicine, Department of Public Health and Caring Sciences, Geriatrics.
    Pharmacokinetic modeling of P-glycoprotein function at the rat and human blood--brain barriers studied with (R)-[11C]verapamil positron emission tomography.2012In: EJNMMI Research, ISSN 2191-219X, E-ISSN 2191-219X, Vol. 2, article id 58Article in journal (Refereed)
    Abstract [en]

    ABSTRACT: BACKGROUND: This study investigated the influence of P-glycoprotein (P-gp) inhibitor tariquidar on the pharmacokinetics of P-gp substrate radiotracer (R)-[11C]verapamil in plasma and brain of rats and humans by means of positron emission tomography (PET). METHODS: Data obtained from a preclinical and clinical study, in which paired (R)-[11C]verapamil PET scans were performed before, during, and after tariquidar administration, were analyzed using nonlinear mixed effects (NLME) modeling. Administration of tariquidar was included as a covariate on the influx and efflux parameters (Qin and Qout) in order to investigate if tariquidar increased influx or decreased outflux of radiotracer across the blood--brain barrier (BBB). Additionally, the influence of pilocarpine-induced status epilepticus (SE) was tested on all model parameters, and the brain-to-plasma partition coefficient (VT-NLME) was calculated. RESULTS: Our model indicated that tariquidar enhances brain uptake of (R)-[11C]verapamil by decreasing Qout. The reduction in Qout in rats during and immediately after tariquidar administration (sevenfold) was more pronounced than in the second PET scan acquired 2 h after tariquidar administration (fivefold). The effect of tariquidar on Qout in humans was apparent during and immediately after tariquidar administration (twofold reduction in Qout) but was negligible in the second PET scan. SE was found to influence the pharmacological volume of distribution of the central brain compartment Vbr1. Tariquidar treatment lead to an increase in VT-NLME, and pilocarpine-induced SE lead to increased (R)-[11C]verapamil distribution to the peripheral brain compartment. CONCLUSIONS: Using NLME modeling, we were able to provide mechanistic insight into the effects of tariquidar and SE on (R)-[11C]verapamil transport across the BBB in control and 48 h post SE rats as well as in humans.

  • 18. Potschka, H.
    et al.
    Bogdanovic, R. M.
    Syvänen, Stina
    Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Faculty of Medicine, Department of Public Health and Caring Sciences, Geriatrics.
    Michler, C.
    Russmann, V
    Eriksson, Jonas
    Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Faculty of Pharmacy, Department of Medicinal Chemistry, Preclinical PET Platform.
    Windhorst, A. D.
    Lammertsma, A. A.
    de Lange, E. C.
    Voskuyl, R. A.
    Molecular Imaging of Inflammation Reveals Differences Between Drug-Resistant and Drug-Sensitive Animals in a Chronic Model of Temporal Lobe Epilepsy2014In: Epilepsia, ISSN 0013-9580, E-ISSN 1528-1167, Vol. 55, no Suppl. 2, p. 32-32Article in journal (Other academic)
  • 19.
    Sehlin, Dag
    et al.
    Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Faculty of Medicine, Department of Public Health and Caring Sciences, Geriatrics.
    Fang, Xiaotian T.
    Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Faculty of Medicine, Department of Public Health and Caring Sciences, Geriatrics.
    Cato, Linda
    Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Faculty of Medicine, Department of Public Health and Caring Sciences, Geriatrics.
    Antoni, Gunnar
    Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Faculty of Pharmacy, Department of Medicinal Chemistry, Division of Molecular Imaging.
    Lannfelt, Lars
    Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Faculty of Medicine, Department of Public Health and Caring Sciences, Geriatrics.
    Syvänen, Stina
    Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Faculty of Medicine, Department of Public Health and Caring Sciences, Geriatrics.
    Antibody-based PET imaging of amyloid beta in mouse models of Alzheimer's disease2016In: Nature Communications, ISSN 2041-1723, E-ISSN 2041-1723, Vol. 7, article id 10759Article in journal (Refereed)
    Abstract [en]

    Owing to their specificity and high-affinity binding, monoclonal antibodies have potential as positron emission tomography (PET) radioligands and are currently used to image various targets in peripheral organs. However, in the central nervous system, antibody uptake is limited by the blood-brain barrier (BBB). Here we present a PET ligand to be used for diagnosis and evaluation of treatment effects in Alzheimer's disease. The amyloid beta (A beta) antibody mAb158 is radiolabelled and conjugated to a transferrin receptor antibody to enable receptor-mediated transcytosis across the BBB. PET imaging of two different mouse models with Ab pathology clearly visualize A beta in the brain. The PET signal increases with age and correlates closely with brain A beta levels. Thus, we demonstrate that antibody-based PET ligands can be successfully used for brain imaging.

  • 20.
    Sehlin, Dag
    et al.
    Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Faculty of Medicine, Department of Public Health and Caring Sciences, Geriatrics.
    Fang, Xiaotian T.
    Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Faculty of Medicine, Department of Public Health and Caring Sciences, Geriatrics.
    Meier, Silvio R.
    Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Faculty of Medicine, Department of Public Health and Caring Sciences, Geriatrics.
    Jansson, Malin
    Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Faculty of Medicine, Department of Public Health and Caring Sciences, Geriatrics.
    Syvänen, Stina
    Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Faculty of Medicine, Department of Public Health and Caring Sciences, Geriatrics.
    Pharmacokinetics, biodistribution and brain retention of a bispecific antibody-based PET radioligand for imaging of amyloid-beta2017In: Scientific Reports, ISSN 2045-2322, E-ISSN 2045-2322, Vol. 7, article id 17254Article in journal (Refereed)
    Abstract [en]

    Monoclonal antibodies (mAbs) have not been used as positron emission tomography (PET) ligands for in vivo imaging of the brain because of their limited passage across the blood-brain barrier (BBB). However, due to their high affinity and specificity, mAbs may be an attractive option for brain PET if their brain distribution can be facilitated. In the present study, a F(ab')(2) fragment of the amyloidbeta (A beta) protofibril selective mAb158 was chemically conjugated to the transferrin receptor (TfR) antibody 8D3 to enable TfR mediated transcytosis across the BBB. The generated bispecific protein, 8D3-F(ab')(2)-h158, was subsequently radiolabeled and used for microPET imaging of A beta pathology in two mouse models of AD. [124I]8D3-F(ab')(2)-h158 was distributed across the BBB several fold more than unmodified mAbs in general and its accumulation in the brain reflected disease progression, while its concentration in blood and other organs remained stable across all age groups studied. Cerebellum was largely devoid of 8D3-F(ab')(2)-h158 in young and middle aged mice, while mice older than 18 months also showed some accumulation in cerebellum. In a longer perspective, the use of bispecific antibodies as PET ligands may enable in vivo 'immunohistochemistry' also of other proteins in the brain for which PET radioligands are lacking.

  • 21.
    Syvänen, Stina
    Uppsala University, Medicinska vetenskapsområdet, Faculty of Pharmacy, Department of Pharmaceutical Biosciences.
    Active transporters in the blood-brain barrier: A simulation study and a Positrion Emmission Tomography study.2005Licentiate thesis, monograph (Other scientific)
  • 22.
    Syvänen, Stina
    Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Faculty of Pharmacy, Department of Pharmaceutical Biosciences.
    Blood-Brain Barrier Transport: Investigation of Active Efflux using Positron Emission Tomography and Modelling Studies2008Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    This thesis examines the transport of exogenous molecules across the blood-brain barrier (BBB), focusing on active efflux, using positron emission tomography (PET), computer simulation and modelling. P-glycoprotein (P-gp) inhibition was studied using [11C]verapamil and [11C]hydroxyurea was investigated as a new marker for active efflux transport. Simulations were carried out to explore the importance of the efflux transporter location in the BBB. Brain concentrations of [11C]verapamil, [11C]GR205171 and [18F]altanserin were compared in various laboratory animal species and in humans.

    A central aspect of the studies has been the novel combination of dynamic PET imaging of the brain pharmacokinetics of a labelled drug, administered through an exponential infusion scheme allowing time-resolved consequence analysis of P-gp inhibition, and mathematical modelling of the obtained data. The methods are applicable to drugs under development and can be used not only in rodents but also in higher species, potentially even in humans, to investigate the effects of P-gp or other transporters on drug uptake in the brain.

    The inhibition of P-gp by cyclosporin A (CsA) and the subsequent change in brain concentrations of [11C]verapamil occurred rapidly in the sense that [11C]verapamil uptake increased rapidly after CsA administration but also in the sense that the increased uptake was rapidly reversible. The P-gp inhibition was best described by an inhibitory indirect effect model in which CsA decreased the transport of [11C]verapamil out of the brain. The model indicated that approximately 90% of the transport of [11C]verapamil was P-gp-mediated. The low brain concentrations of [11C]hydroxyurea appeared to be a result of slow transport across the BBB rather than active efflux. This exemplifies why the extent and the rate of brain uptake should be approached as two separate phenomena. The brain-to-plasma concentration ratios for the three studied radiotracers differed about 10-fold be-tween species, with lower concentrations in rodents than in humans, monkeys and pigs. The increase in brain concentrations after P-gp inhibition was somewhat greater in rats than in the other species.

    The findings demonstrate a need to include the dynamics of efflux inhibition in the experimental design and stress the importance of the choice of species in preclinical studies of new drug candidates.

    List of papers
    1. Pharmacokinetic consequences of active drug efflux at the blood-brain barrier
    Open this publication in new window or tab >>Pharmacokinetic consequences of active drug efflux at the blood-brain barrier
    2006 (English)In: Pharmaceutical research, ISSN 0724-8741, E-ISSN 1573-904X, Vol. 23, no 4, p. 705-717Article in journal (Refereed) Published
    Abstract [en]

    PURPOSE: The objective of this simulation study was to investigate how the nature, location, and capacity of the efflux processes in relation to the permeability properties influence brain concentrations. METHODS: Reduced brain concentrations can be due to either influx hindrance, a gatekeeper function in the luminal membrane, which has been suggested for ABCB1 (P-glycoprotein), or efflux enhancement by transporters that pick up molecules on one side of the luminal or abluminal membrane and release them on the other side. Pharmacokinetic models including passive transport, influx hindrance, and efflux enhancement were built using the computer program MATLAB. The simulations were based on experimentally obtained parameters for morphine, morphine-3-glucuronide, morphine-6-glucuronide, and gabapentin. RESULTS: The influx hindrance process is the more effective for keeping brain concentrations low. Efflux enhancement decreases the half-life of the drug in the brain, whereas with influx hindrance the half-life is similar to that seen with passive transport. The relationship between the influx and efflux of the drug across the blood-brain barrier determines the steady-state ratio of brain to plasma concentrations of unbound drug, K(p,uu). CONCLUSIONS: Both poorly and highly permeable drugs can reach the same steady-state ratio, although the time to reach steady state will differ. The volume of distribution of unbound drug in the brain does not influence K(p,uu), but does influence the total brain-to-blood ratio K(p) and the time to reach steady state in the brain.

    National Category
    Pharmaceutical Sciences
    Identifiers
    urn:nbn:se:uu:diva-96869 (URN)10.1007/s11095-006-9780-0 (DOI)16575498 (PubMedID)
    Available from: 2008-03-26 Created: 2008-03-26 Last updated: 2018-01-13Bibliographically approved
    2. Duration and degree of cyclosporin induced P-glycoprotein inhibition in the rat blood-brain barrier can be studied with PET
    Open this publication in new window or tab >>Duration and degree of cyclosporin induced P-glycoprotein inhibition in the rat blood-brain barrier can be studied with PET
    Show others...
    2006 (English)In: NeuroImage, ISSN 1053-8119, E-ISSN 1095-9572, Vol. 32, no 3, p. 1134-1141Article in journal (Refereed) Published
    Abstract [en]

    Active efflux transporters in the blood-brain barrier lower the brain concentrations of many drug molecules and endogenous substances and thus affect their central action. The objective of this investigation was to study the dynamics of the entire inhibition process of the efflux transporter P-glycoprotein (P-gp), using positron emission tomography (PET). The P-gp marker [C-11]verapamil was administered to anesthetized rats as an i.v. bolus dose followed by graded infusions via a computerized pump system to obtain a steady-state concentration of [C-11]verapamil in brain. The P-gp modulator cyclosporin A (CsA) (3, 10 and 25 mg/kg) was administered as a short bolus injection 30 min after the start of the [C-11]verapamil infusion. The CsA pharmacokinetics was studied in whole blood in a parallel group of rats. The CsA blood concentrations were used as input to model P-gp inhibition. The inhibition of P-gp was observed as a rapid increase in brain concentrations of [C-11]verapamil, with a maximum after 5, 7.5 and 17.5 min for the respective doses. The respective increases in maximal [C-11]verapamil concentrations were 1.5, 2.5 and 4 times the baseline concentration. A model in which CsA inhibited P-gp by decreasing the transport of [C-11]verapamil out from the brain resulted in the best fit. Our data suggest that it is not the CsA concentration in blood, but rather the CsA concentration in an effect compartment, probably the endothelial cells of the blood-brain barrier that is responsible for the inhibition of P-gp.

    Keywords
    PET, ["C]verapamil, p-glycoprotein, cyclosporin, pharmacokinetics, modeling, blood-brain barrier, active efflux
    National Category
    Pharmaceutical Sciences
    Identifiers
    urn:nbn:se:uu:diva-96870 (URN)10.1016/j.neuroimage.2006.05.047 (DOI)000240470300019 ()16857389 (PubMedID)
    Available from: 2008-03-26 Created: 2008-03-26 Last updated: 2018-01-13Bibliographically approved
    3. Pharmacokinetics of P-glycoprotein inhibition in the rat blood-brain barrier
    Open this publication in new window or tab >>Pharmacokinetics of P-glycoprotein inhibition in the rat blood-brain barrier
    Show others...
    2008 (English)In: Journal of Pharmaceutical Sciences, ISSN 0022-3549, E-ISSN 1520-6017, Vol. 97, no 12, p. 5386-5400Article in journal (Refereed) Published
    Abstract [en]

    This article describes the experimental set-up and pharmacokinetic modeling of P-glycoprotein function in the rat blood-brain barrier using [(11)C]verapamil as the substrate and cyclosporin A as an inhibitor of P-gp. [(11)C]verapamil was administered to rats as an i.v. bolus dose followed by graded infusions to obtain steady-state concentrations in the brain during 70 min. CsA was administered as a bolus followed by a constant infusion 20 min after the start of the [(11)C]verapamil infusion. The brain uptake of [(11)C]verapamil over 2 h was portrayed in a sequence of PET scans in parallel with measurement of [(11)C]verapamil concentrations in blood and plasma and CsA concentrations in blood. Mixed effects modeling in NONMEM was used to build a pharmacokinetic model of CsA-induced P-gp inhibition. The brain pharmacokinetics of [(11)C]verapamil was well described by a two-compartment model. The effect of CsA on the uptake of [(11)C]verapamil in the brain was best described by an inhibitory indirect effect model with an effect on the transport of [(11)C]verapamil out of the brain. The CsA concentration required to obtain 50% of the maximal inhibition was 4.9 microg/mL (4.1 microM). The model parameters indicated that 93% of the outward transport of [(11)C]verapamil was P-gp mediated.

    Keywords
    PET, pharmacokinetics, pharmacokinetic/pharmacodynamic models, P-glycoprotein, blood-brain barrier, active transport, drug interactions, efflux pumps, metabolism, population pharmacokinetics/pharmacodynamics
    National Category
    Medical and Health Sciences
    Identifiers
    urn:nbn:se:uu:diva-96871 (URN)10.1002/jps.21359 (DOI)000261313200030 ()18384156 (PubMedID)
    Available from: 2008-03-26 Created: 2008-03-26 Last updated: 2017-12-14Bibliographically approved
    4. PET-evaluated transport of [11C]hydroxyurea across the rat blood-brain barrier -: lack of influence of cyc-losporin and probenecid
    Open this publication in new window or tab >>PET-evaluated transport of [11C]hydroxyurea across the rat blood-brain barrier -: lack of influence of cyc-losporin and probenecid
    Show others...
    2007 (English)In: Drug Metabolism Letters, ISSN 1872-3128, Vol. 1, no 3, p. 189-194Article in journal (Refereed) Published
    Abstract [en]

    The transport of hydroxyurea, a ribonucleoside reductase inhibitor, over biological membranes is slow and it has therefore been suggested that the substance could interact with an active efflux transporter. The transport of [11C]hydroxyurea into the rat brain was therefore studied after administration of the multidrug resistance protein inhibitor probenecid (50 and 150 mg/kg), the P-glycoprotein inhibitor cyclosporin A (25 mg/kg), hydroxyurea (50, 150 and 450 mg/kg) and mannitol (25%). None of the intervention drugs affected the brain uptake of [11C]hydroxyurea. The brain-toplasma concentration ratios (Kp), with or without intervention drug, were in the range 0.12-0.25 after 60 min of [11C]hydroxyurea infusion. [11C]Verapamil, a P-glycoprotein substrate with low brain penetration, was used to study the ability of hydroxyurea to inhibit P-glycoprotein. Administration of hydroxyurea (150 and 450 mg/kg) did not increase brain concentrations of [11C]verapamil. It is therefore unlikely that hydroxyurea is a substrate for or an inhibitor of Pglycoprotein or a substrate for a probenecid sensitive transport system. The low brain concentrations may instead be the result of slow uptake due to the hydrophilic nature of hydroxyurea.

     

    Keywords
    PET, [11C]hydroxyurea, [11C]verapamil, pharmacokinetics, blood-brain barrier, active efflux
    National Category
    Pharmaceutical Sciences
    Identifiers
    urn:nbn:se:uu:diva-96872 (URN)10.2174/187231207781369799 (DOI)19356042 (PubMedID)
    Available from: 2008-03-26 Created: 2008-03-26 Last updated: 2018-01-13Bibliographically approved
    5. Species differences in blood-brain barrier transport of three PET radiotracers with emphasis on P-glycoprotein and plasma protein binding
    Open this publication in new window or tab >>Species differences in blood-brain barrier transport of three PET radiotracers with emphasis on P-glycoprotein and plasma protein binding
    Show others...
    Manuscript (Other academic)
    Identifiers
    urn:nbn:se:uu:diva-96873 (URN)
    Available from: 2008-03-26 Created: 2008-03-26 Last updated: 2011-04-12
  • 23.
    Syvänen, Stina
    et al.
    Uppsala Imanet, GE Healthcare.
    Barletta, Julien
    Blomquist, Gunnar
    Långström, Bengt
    Bergström, Mats
    PET-evaluated transport of [11C]hydroxyurea across the rat blood-brain barrier -: lack of influence of cyc-losporin and probenecid2007In: Drug Metabolism Letters, ISSN 1872-3128, Vol. 1, no 3, p. 189-194Article in journal (Refereed)
    Abstract [en]

    The transport of hydroxyurea, a ribonucleoside reductase inhibitor, over biological membranes is slow and it has therefore been suggested that the substance could interact with an active efflux transporter. The transport of [11C]hydroxyurea into the rat brain was therefore studied after administration of the multidrug resistance protein inhibitor probenecid (50 and 150 mg/kg), the P-glycoprotein inhibitor cyclosporin A (25 mg/kg), hydroxyurea (50, 150 and 450 mg/kg) and mannitol (25%). None of the intervention drugs affected the brain uptake of [11C]hydroxyurea. The brain-toplasma concentration ratios (Kp), with or without intervention drug, were in the range 0.12-0.25 after 60 min of [11C]hydroxyurea infusion. [11C]Verapamil, a P-glycoprotein substrate with low brain penetration, was used to study the ability of hydroxyurea to inhibit P-glycoprotein. Administration of hydroxyurea (150 and 450 mg/kg) did not increase brain concentrations of [11C]verapamil. It is therefore unlikely that hydroxyurea is a substrate for or an inhibitor of Pglycoprotein or a substrate for a probenecid sensitive transport system. The low brain concentrations may instead be the result of slow uptake due to the hydrophilic nature of hydroxyurea.

     

  • 24.
    Syvänen, Stina
    et al.
    Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Faculty of Pharmacy, Department of Pharmaceutical Biosciences.
    Blomquist, Gunnar
    Appel, Lieuwe
    Hammarlund-Udenaes, Margareta
    Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Faculty of Pharmacy, Department of Pharmaceutical Biosciences, Division of Pharmacokinetics and Drug Therapy.
    Långström, Bengt
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Biochemistry and Organic Chemistry, Organic Chemistry.
    Bergström, Mats
    Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Faculty of Pharmacy, Department of Pharmaceutical Biosciences.
    Predicting brain concentrations of drug using positron emission tomography and venous input: modeling of arterial-venous concentration differences2006In: European Journal of Clinical Pharmacology, ISSN 0031-6970, E-ISSN 1432-1041, Vol. 62, no 10, p. 839-848Article in journal (Refereed)
    Abstract [en]

    OBJECTIVE

    In a positron emission tomography (PET) study, the concentrations of the labeled drug (radiotracer) are often different in arterial and venous plasma, especially immediately following administration. In a PET study, the transfer of the drug from plasma to brain is usually described using arterial plasma concentrations, whereas venous sampling is standard in clinical pharmacokinetic studies of new drug candidates. The purpose of the study was to demonstrate the modeling of brain drug kinetics based on PET data in combination with venous blood sampling and an arterio-venous transform (T(av)).

    METHODS

    Brain kinetics (C(br)) was described as the convolution of arterial plasma kinetics (C(ar)) with an arterial-to-brain impulse response function (T(br)). The arterial plasma kinetics was obtained as venous plasma kinetics (C(ve)) convolved with the inverse of the arterio-venous transform (T(av) (-1)). The brain kinetics was then given by C(br)=C(ve)*T(av) (-1)*T(br). This concept was applied on data from a clinical PET study in which both arterial and venous plasma sampling was done in parallel to PET measurement of brain drug kinetics. The predictions of the brain kinetics based on an arterial input were compared with predictions using a venous input with and without an arterio-venous transform.

    RESULTS

    The venous based models for brain distribution, including a biexponential arterio-venous transform, performed comparably to models based on arterial data and better than venous based models without the transform. It was also shown that three different brain regions with different shaped concentration curves could be modeled with a common arterio-venous transform together with an individual brain distribution model.

    CONCLUSION

    We demonstrated the feasibility of modeling brain drug kinetics based on PET data in combination with venous blood sampling and an arterio-venous transform. Such a model can in turn be used for the calculation of brain kinetics resulting from an arbitrary administration mode by applying this model on venous plasma pharmacokinetics. This would be an important advantage in the development of drugs acting in the brain, and in other circumstances when the effect is likely to be closer related to the brain than the plasma concentration.

  • 25.
    Syvänen, Stina
    et al.
    Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Faculty of Pharmacy, Department of Pharmaceutical Biosciences.
    Blomquist, Gunnar
    Sprycha, Margareta
    Höglund, A. Urban
    Roman, Magnus
    Eriksson, Olof
    Hammarlund-Udenaes, Margareta
    Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Faculty of Pharmacy, Department of Pharmaceutical Biosciences.
    Långström, Bengt
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Biochemistry and Organic Chemistry.
    Bergström, Mats
    Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Faculty of Pharmacy, Department of Pharmaceutical Biosciences.
    Duration and degree of cyclosporin induced P-glycoprotein inhibition in the rat blood-brain barrier can be studied with PET2006In: NeuroImage, ISSN 1053-8119, E-ISSN 1095-9572, Vol. 32, no 3, p. 1134-1141Article in journal (Refereed)
    Abstract [en]

    Active efflux transporters in the blood-brain barrier lower the brain concentrations of many drug molecules and endogenous substances and thus affect their central action. The objective of this investigation was to study the dynamics of the entire inhibition process of the efflux transporter P-glycoprotein (P-gp), using positron emission tomography (PET). The P-gp marker [C-11]verapamil was administered to anesthetized rats as an i.v. bolus dose followed by graded infusions via a computerized pump system to obtain a steady-state concentration of [C-11]verapamil in brain. The P-gp modulator cyclosporin A (CsA) (3, 10 and 25 mg/kg) was administered as a short bolus injection 30 min after the start of the [C-11]verapamil infusion. The CsA pharmacokinetics was studied in whole blood in a parallel group of rats. The CsA blood concentrations were used as input to model P-gp inhibition. The inhibition of P-gp was observed as a rapid increase in brain concentrations of [C-11]verapamil, with a maximum after 5, 7.5 and 17.5 min for the respective doses. The respective increases in maximal [C-11]verapamil concentrations were 1.5, 2.5 and 4 times the baseline concentration. A model in which CsA inhibited P-gp by decreasing the transport of [C-11]verapamil out from the brain resulted in the best fit. Our data suggest that it is not the CsA concentration in blood, but rather the CsA concentration in an effect compartment, probably the endothelial cells of the blood-brain barrier that is responsible for the inhibition of P-gp.

  • 26.
    Syvänen, Stina
    et al.
    Leiden University.
    de Lange, Elizabeth C
    Tagawa, Yoshihiko
    Schenke, Maarten
    Molthoff, Carla F M
    Windhorst, Albert D
    Lammertsma, Adriaan A
    Voskuyl, Rob A
    Simultaneous in vivo measurements of receptor density and affinity using [11C]flumazenil and positron emission tomography: comparison of full saturation and steady state methods.2011In: NeuroImage, ISSN 1053-8119, E-ISSN 1095-9572, Vol. 57, no 3, p. 928-37Article in journal (Refereed)
    Abstract [en]

    The binding of PET radiotracer [(11)C]flumazenil to the GABA(A) receptors is described by the receptor density (B(max)) and binding affinity (K(D)). The estimation of B(max) and K(D) is usually based on Scatchard analysis including at least two PET scans at steady state of various specific activities. Recently, a novel full saturation method to estimate both B(max) and K(D) was proposed, in which a saturating dose of flumazenil is given to cover a wide range of different receptor occupancies within a single scan. The aim of the present study was a direct comparison of steady state and full saturation methods for determining B(max) and K(D) of [(11)C]flumazenil in the same group of male Sprague-Dawley rats. Fourteen rats underwent 3 consecutive [(11)C]flumazenil scans of 30 min duration each. A tracer dose was injected at the start of the first scan. Prior to the second scan the tracer was mixed with 5, 20, 100 or 500 μg unlabelled (cold) flumazenil to cover a wide range of receptor occupancies during the scan. The third scan was performed during a constant intravenous infusion of unlabelled flumazenil, resulting in ~50% GABA(A) receptor occupancy. The first and third scans were part of the steady state method, whilst the second scan was performed according to the full saturation method. For both methods, B(max) and K(D) were then derived by compartmental modelling. Both methods yielded similar B(max) and K(D) estimates. The full saturation method yielded B(max) values of 37 ± 5.8 ng · mL(-1) and K(D) values of 7.6 ± 2.0 ng · mL(-1), whilst the steady state method yielded B(max) values of 33 ± 5.4 ng · mL(-1) and K(D) values of 7.1 ± 0.8 ng · mL(-1). The main advantage of the full saturation method is that B(max) and K(D) can be obtained from a single PET scan.

  • 27.
    Syvänen, Stina
    et al.
    Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Faculty of Medicine, Department of Public Health and Caring Sciences, Geriatrics.
    Edén, Desireé
    Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Faculty of Medicine, Department of Medical Sciences, Clinical Chemistry.
    Sehlin, Dag
    Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Faculty of Medicine, Department of Public Health and Caring Sciences, Geriatrics.
    Cationization increases brain distribution of an amyloid-beta protofibril selective F(ab')2 fragment2017In: Biochemical and Biophysical Research Communications - BBRC, ISSN 0006-291X, E-ISSN 1090-2104, Vol. 493, no 1, p. 120-125Article in journal (Refereed)
    Abstract [en]

    Antibodies and fragments thereof are, because of high selectivity for their targets, considered as potential therapeutics and biomarkers for several neurological disorders. However, due to their large molecular size, antibodies/fragments do not easily penetrate into the brain. The aim of the present study was to improve the brain distribution via adsorptive-mediated transcytosis of an amyloid-beta (A beta) protofibril selective F(ab')2 fragment (F(ab')2-h158). F(ab')2-h158 was cationized to different extents and the specific and unspecific binding was studied in vitro. Next, cationized F(ab')2-h158 was labelled with iodine-125 and its brain distribution and pharmacokinetics was studied in mice. Cationization did not alter the in vitro affinity to A beta protofibrils, but increased the unspecific binding somewhat. Ex vivo experiments revealed a doubling of brain concentrations compared with unmodified F(ab')2-h158 and in vivo imaging with single photon emission computed tomography (SPECT) showed that the cationized F(ab')2-h158, but not the unmodified F(ab')2-h158 could be visualized in the brain. To conclude, cationization is a means to increase brain concentrations of therapeutic antibodies or fragments and may facilitate the use of antibodies/fragments as imaging biomarkers in the brain.

  • 28.
    Syvänen, Stina
    et al.
    Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Faculty of Medicine, Department of Public Health and Caring Sciences, Geriatrics.
    Eriksson, Jonas
    Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Faculty of Pharmacy, Department of Medicinal Chemistry, Preclinical PET Platform.
    Advances in PET Imaging of P-Glycoprotein Function at the Blood-Brain Barrier.2013In: ACS Chemical Neuroscience, ISSN 1948-7193, E-ISSN 1948-7193, Vol. 4, no 2, p. 225-237Article, review/survey (Refereed)
    Abstract [en]

    Efflux transporter P-glycoprotein (P-gp) at the blood-brain barrier (BBB) restricts substrate compounds from entering the brain and may thus contribute to pharmacoresistance observed in patient groups with refractory epilepsy and HIV. Altered P-gp function has also been implicated in neurodegenerative diseases such as Alzheimer's and Parkinson's disease. Positron emission tomography (PET), a molecular imaging modality, has become a promising method to study the role of P-gp at the BBB. The first PET study of P-gp function was conducted in 1998, and during the past 15 years two main categories of P-gp PET tracers have been investigated: tracers that are substrates of P-gp efflux and tracers that are inhibitors of P-gp function. PET, as a noninvasive imaging technique, allows translational research. Examples of this are preclinical investigations of P-gp function before and after administering P-gp modulating drugs, investigations in various animal and disease models, and clinical investigations regarding disease and aging. The objective of the present review is to give an overview of available PET radiotracers for studies of P-gp and to discuss how such studies can be designed. Further, the review summarizes results from PET studies of P-gp function in different central nervous system disorders.

  • 29.
    Syvänen, Stina
    et al.
    Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Faculty of Pharmacy, Department of Pharmaceutical Biosciences.
    Eriksson, Jonas
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Biochemistry and Organic Chemistry.
    Genchel, Tove
    Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Faculty of Pharmacy, Department of Pharmaceutical Biosciences, Pharmaceutical Biochemistry.
    Lindhe, Örjan
    Antoni, Gunnar
    Långström, Bengt
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Biochemistry and Organic Chemistry.
    Synthesis of two potential NK1-receptor ligands using [1-11C]ethyl iodide and [1-11C]propyl iodide and initial PET-imaging2007In: BMC Medical Imaging, ISSN 1471-2342, E-ISSN 1471-2342, Vol. 7, p. 6-Article in journal (Refereed)
    Abstract [en]

    BACKGROUND:

    The previously validated NK1-receptor ligand [O-methyl-11C]GR205171 binds with a high affinity to the NK1-receptor and displays a slow dissociation from the receptor. Hence, it cannot be used in vivo for detecting concentration changes in substance P, the endogenous ligand for the NK1-receptor. A radioligand used for monitoring these changes has to enable displacement by the endogenous ligand and thus bind reversibly to the receptor. Small changes in the structure of a receptor ligand can lead to changes in binding characteristics and also in the ability to penetrate the blood-brain barrier. The aim of this study was to use carbon-11 labelled ethyl and propyl iodide with high specific radioactivity in the synthesis of two new and potentially reversible NK1-receptor ligands with chemical structures based on [O-methyl-11C]GR205171.

    METHODS:

    [1-11C]Ethyl and [1-11C]propyl iodide with specific radioactivities of 90 GBq/μmol and 270 GBq/μmol, respectively, were used in the synthesis of [O-methyl-11C]GR205171 analogues by alkylation of O-desmethyl GR205171. The brain uptake of the obtained (2S,3S)-N-(1-(2- [1-11C]ethoxy-5-(3-(trifluoromethyl)-4H-1,2,4-triazol-4-yl)phenyl)ethyl)-2-phenylpiperidin-3-amine (I) and (2S,3S)-2-phenyl-N-(1-(2- [1-11C]propoxy-5-(3-(trifluoromethyl)-4H-1,2,4-triazol-4-yl)phenyl)ethyl)piperidin-3-amine (II) was studied with PET in guinea pigs and rhesus monkeys and compared to the uptake of [O-methyl-11C]GR205171.

    RESULTS:

    All ligands had similar uptake distribution in the guinea pig brain. The PET-studies in rhesus monkeys showed that (II) had no specific binding in striatum. Ligand (I) had moderate specific binding compared to the [O-methyl-11C]GR205171. The ethyl analogue (I) displayed reversible binding characteristics contrary to the slow dissociation rate shown by [O-methyl-11C]GR205171.

    CONCLUSION:

    The propyl-analogue (II) cannot be used for detecting changes in NK1-ligand levels, while further studies should be performed with the ethyl-analogue (I).

  • 30.
    Syvänen, Stina
    et al.
    Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Faculty of Medicine, Department of Public Health and Caring Sciences, Geriatrics.
    Fang, Xiaotian T.
    Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Faculty of Medicine, Department of Public Health and Caring Sciences, Geriatrics.
    Hultqvist, Greta
    Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Faculty of Medicine, Department of Public Health and Caring Sciences, Geriatrics.
    Falting, J.
    BioArctic AB..
    Antoni, Gunnar
    Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Faculty of Pharmacy, Department of Medicinal Chemistry, Division of Molecular Imaging. Uppsala Univ Hosp, PET Ctr..
    Lannfelt, Lars
    Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Faculty of Medicine, Department of Public Health and Caring Sciences, Geriatrics.
    Sehlin, Dag
    Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Faculty of Medicine, Department of Public Health and Caring Sciences, Geriatrics. Uppsala Univ, Uppsala, Sweden..
    Antibody-based PET radioligands for imaging of amyloid-beta protofibrils2017In: Journal of Cerebral Blood Flow and Metabolism, ISSN 0271-678X, E-ISSN 1559-7016, Vol. 37, p. 84-84Article in journal (Other academic)
  • 31.
    Syvänen, Stina
    et al.
    Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Faculty of Medicine, Department of Public Health and Caring Sciences, Geriatrics.
    Fang, Xiaotian T.
    Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Faculty of Medicine, Department of Public Health and Caring Sciences, Geriatrics.
    Hultqvist, Greta
    Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Faculty of Medicine, Department of Public Health and Caring Sciences, Geriatrics.
    Meier, Silvio R.
    Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Faculty of Medicine, Department of Public Health and Caring Sciences, Geriatrics.
    Lannfelt, Lars
    Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Faculty of Medicine, Department of Public Health and Caring Sciences, Geriatrics.
    Sehlin, Dag
    Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Faculty of Medicine, Department of Public Health and Caring Sciences, Geriatrics.
    A bispecific Tribody PET radioligand for visualization of amyloid-beta protofibrils - a new concept for neuroimaging2017In: NeuroImage, ISSN 1053-8119, E-ISSN 1095-9572, Vol. 148, p. 55-63Article in journal (Refereed)
    Abstract [en]

    Antibodies are highly specific for their target molecules, but their poor brain penetrance has restricted their use as PET ligands for imaging of targets within the CNS. The aim of this study was to develop an antibody-based radioligand, using the Tribody(TM) format, for PET imaging of soluble amyloid-beta (All) protofibrils, which are suggested to cause neurodegeneration in Alzheimer's disease. Antibodies, even when expressed in smaller engineered formats, are large molecules that do not enter the brain in sufficient amounts for imaging purposes. Hence, their transport across the blood-brain barrier (BBB) needs to be facilitated, for example through interaction with the transferrin receptor (TfR). Thus, a Fab fragment of the TfR antibody 8D3 was fused with two single chain variable fragments (scFv) of the A beta protofibril selective antibody mAb158. Five Tribody proteins (A1-A5) were generated with different linkers between the Fab-8D3 and scFv-158. All proteins bound to TfR and All protofibrils in vitro. Three of the proteins (A1-A3) were radiolabeled with iodine-125 and studied ex vivo in wild-type (wt) and transgenic mice overexpressing human All. The systemic pharmacokinetics were similar with half-lives in blood of around 9 h for all three ligands. Brain concentrations at 2 h were around 1% of the injected dose per gram brain tissue, which is similar to what is observed for small molecular radioligands and at least 10-fold higher than antibodies in general. At 72 h, transgenic mice showed higher concentrations of radioactivity in the brain than wt mice (12, 15- and 16-fold for Al, A2 and A3 respectively), except in the cerebellum, an area largely devoid of A beta pathology. A3 was then labelled with iodine-124 for in vivo positron emission tomography (PET) imaging. Brain concentrations were quantified in six different regions showing a clear distinction both quantitatively and visually between wt and transgenic mice and a good correlation with A beta pathology. We have thus produced a recombinant, bispecific protein, actively transported into the brain, for PET imaging within the CNS. In a longer perspective, this technique may enable imaging of other proteins involved in neurodegenerative diseases for which imaging agents are completely lacking today.

  • 32.
    Syvänen, Stina
    et al.
    Division of Pharmacology,LACDR, Leiden University, Box 9502, 2300 RA Leiden, The Netherlands.
    Hammarlund-Udenaes, Margareta
    Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Faculty of Pharmacy, Department of Pharmaceutical Biosciences.
    Using PET Studies of P-gp Function to Elucidate Mechanisms Underlying the Disposition of Drugs2010In: Current Topics in Medicinal Chemistry, ISSN 1568-0266, E-ISSN 1873-4294, Vol. 10, no 17, p. 1799-1809Article, review/survey (Refereed)
    Abstract [en]

    This paper discusses the basic principles of drug/P-glycoprotein (P-gp) interaction, focusing on the methodology and design of positron emission tomography (PET) studies investigating P-gp function. The requirements of a good PET P-gp radiotracer are also evaluated. (R)-[C-11]verapamil is used as an example, as this drug is the most common tracer for P-gp studies, but [C-11]loperamide, [C-11]desmethyl-loperamide and other compounds are also mentioned. The article also discusses the various study designs that can be used for PET drug disposition studies, such as administration of the inhibitor before or after the radiolabeled drug (tracer) and the use of bolus injections or infusions. Concepts such as the unbound partition coefficient (K-p,K-uu) and the volume of distribution of unbound drug in brain (V-u,V-brain), which are not easily measured directly with PET, can be used to describe the impact of protein binding and non-specific binding on drug distribution in brain tissue. It is concluded that new imaging probes will be required if the role of PET in studies of the interactions of drugs with efflux transporters is to expand.

  • 33.
    Syvänen, Stina
    et al.
    Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Faculty of Pharmacy, Department of Pharmaceutical Biosciences.
    Hooker, Andrew
    Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Faculty of Pharmacy, Department of Pharmaceutical Biosciences.
    Rahman, Obaidur
    Wilking, Helena
    Blomquist, Gunnar
    Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Faculty of Medicine, Department of Oncology, Radiology and Clinical Immunology.
    Långström, Bengt
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Biochemistry and Organic Chemistry.
    Bergström, Mats
    Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Faculty of Pharmacy, Department of Pharmaceutical Biosciences.
    Hammarlund-Udenaes, Margareta
    Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Faculty of Pharmacy, Department of Pharmaceutical Biosciences.
    Pharmacokinetics of P-glycoprotein inhibition in the rat blood-brain barrier2008In: Journal of Pharmaceutical Sciences, ISSN 0022-3549, E-ISSN 1520-6017, Vol. 97, no 12, p. 5386-5400Article in journal (Refereed)
    Abstract [en]

    This article describes the experimental set-up and pharmacokinetic modeling of P-glycoprotein function in the rat blood-brain barrier using [(11)C]verapamil as the substrate and cyclosporin A as an inhibitor of P-gp. [(11)C]verapamil was administered to rats as an i.v. bolus dose followed by graded infusions to obtain steady-state concentrations in the brain during 70 min. CsA was administered as a bolus followed by a constant infusion 20 min after the start of the [(11)C]verapamil infusion. The brain uptake of [(11)C]verapamil over 2 h was portrayed in a sequence of PET scans in parallel with measurement of [(11)C]verapamil concentrations in blood and plasma and CsA concentrations in blood. Mixed effects modeling in NONMEM was used to build a pharmacokinetic model of CsA-induced P-gp inhibition. The brain pharmacokinetics of [(11)C]verapamil was well described by a two-compartment model. The effect of CsA on the uptake of [(11)C]verapamil in the brain was best described by an inhibitory indirect effect model with an effect on the transport of [(11)C]verapamil out of the brain. The CsA concentration required to obtain 50% of the maximal inhibition was 4.9 microg/mL (4.1 microM). The model parameters indicated that 93% of the outward transport of [(11)C]verapamil was P-gp mediated.

  • 34.
    Syvänen, Stina
    et al.
    Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Faculty of Medicine, Department of Public Health and Caring Sciences, Geriatrics.
    Hultqvist, Greta
    Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Faculty of Pharmacy, Department of Pharmaceutical Biosciences.
    Gustavsson, Tobias
    Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Faculty of Medicine, Department of Public Health and Caring Sciences, Geriatrics.
    Gumucio, Astrid
    Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Faculty of Medicine, Department of Public Health and Caring Sciences, Geriatrics.
    Laudon, Hanna
    BioArctic AB, Stockholm, Sweden.
    Söderberg, Linda
    BioArctic AB, Stockholm, Sweden.
    Ingelsson, Martin
    Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Faculty of Medicine, Department of Public Health and Caring Sciences, Geriatrics.
    Lannfelt, Lars
    Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Faculty of Medicine, Department of Public Health and Caring Sciences, Geriatrics. BioArctic AB, Stockholm, Sweden.
    Sehlin, Dag
    Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Faculty of Medicine, Department of Public Health and Caring Sciences, Geriatrics.
    Efficient clearence of A beta protofibrils in A beta PP-transgenic mice treated with a brain-penetrating bifunctional antibody2018In: Alzheimer's Research & Therapy, ISSN 0065-6755, E-ISSN 1758-9193, Vol. 10, article id 49Article in journal (Refereed)
    Abstract [en]

    Background: Amyloid-beta (A beta) immunotherapy is one of the most promising disease-modifying strategies for Alzheimer's disease (AD) Despite recent progress targeting aggregated forms of A beta, low antibody brain penetrance remains a challenge In the piesent study, we used transferrin receptor (TfR)-mediated transcytosis to facilitate brain uptake of our previously developed A beta protofibril-selective mAb158, with the aim of increasing the efficacy of immunotherapy directed toward soluble A beta protofibills. Methods: A beta protein precursor (A beta PP)-transgenic mice (tg-ArcSwe) were given a single dose of mAb158, modified for TfR-mediated transcytosis (RmAb158-scFvSDB), in companson with an equimolar dose or a tenfold higher dose of unmodified recombinant mAb158 (RmAb158) Soluble A beta protofibrills and total A beta in the brain were measured by enzyme-linked immunosorbent assay (ELISA) Brain distribution of radiolabeled antibodies was visualized by positron emission tomography (PET) and ex vivo autoiadiography. Results: ELISA analysis of Tris-buffered saline brain extracts demonstrated a 40% reduction of soluble A beta protofibrils in both RmAb158-scFv8D3- and high-dose RmAb158-treated mice, whereas there was no A beta protofibril reduction in mice treated with a low dose of RmAb158. Further, ex vivo autoradiography and PET imaging revealed diffeient brain distribution patterns of RmAb158-scFv8D3 and RmAb158, suggesting that these antibodies may affect A beta levels by different mechanisms. Conclusions: With a combination of biochemical and imaging analyses, this study demonstrates that antibodies engineered to be transported across the blood brain barrier can be used to increase the efficacy of A beta immunotherapy. This strategy may allow for decreased antibody doses and thereby reduced side effects and treatment costs.

  • 35.
    Syvänen, Stina
    et al.
    Leiden University.
    Labots, Maaike
    Tagawa, Yoshihiko
    Eriksson, Jonas
    VU University Medical Center Amsterdam.
    Windhorst, Albert D
    Lammertsma, Adriaan A
    de Lange, Elizabeth C
    Voskuyl, Rob A
    Altered GABAA Receptor Density and Unaltered Blood-Brain Barrier Transport in a Kainate Model of Epilepsy: An In Vivo Study Using 11C-Flumazenil and PET.2012In: Journal of Nuclear Medicine, ISSN 0161-5505, E-ISSN 1535-5667, Vol. 53, no 12, p. 1974-1983Article in journal (Refereed)
    Abstract [en]

    The aim of the present study was to investigate if flumazenil blood-brain barrier transport and binding to the benzodiazepine site on the γ-aminobutyric acid A (GABA(A)) receptor complex is altered in an experimental model of epilepsy and subsequently to study if changes in P-glycoprotein (P-gp)-mediated efflux of flumazenil at the blood-brain barrier may confound interpretation of (11)C-flumazenil PET in epilepsy. METHODS: The transport of flumazenil across the blood-brain barrier and the binding to the benzodiazepine site on the GABA(A) receptors in 5 different brain regions was studied and compared between controls and kainate-treated rats, a model of temporal lobe epilepsy, with and without tariquidar pretreatment. In total, 29 rats underwent 2 consecutive (11)C-flumazenil PET scans, each one lasting 30 min. The tracer was mixed with different amounts of isotopically unmodified flumazenil (4, 20, 100, or 400 μg) to cover a wide range of receptor occupancies during the scan. Before the second scan, the rats were pretreated with a 3 or 15 mg/kg dose of the P-gp inhibitor tariquidar. The second scan was then obtained according to the same protocol as the first scan. RESULTS: GABA(A) receptor density, B(max), was estimated as 44 ± 2 ng⋅mL(-1) in the hippocampus and as 33 ± 2 ng⋅mL(-1) in the cerebellum, with intermediate values in the occipital cortex, parietal cortex, and caudate putamen. B(max) was decreased by 12% in kainate-treated rats, compared with controls. The radiotracer equilibrium dissociation constant, K(D), was similar in both rat groups and all brain regions and was estimated as 5.9 ± 0.9 ng⋅mL(-1). There was no difference in flumazenil transport across the blood-brain barrier between control and kainate-treated rats, and the effect of tariquidar treatment was similar in both rat groups. Tariquidar treatment also decreased flumazenil transport out of the brain by 73%, increased the volume of distribution in the brain by 24%, and did not influence B(max) or K(D), compared with baseline(.) CONCLUSION: B(max) was decreased in kainate-treated rats, compared with controls, but no alteration in the blood-brain barrier transport of flumazenil was observed. P-gp inhibition by tariquidar treatment increased brain concentrations of flumazenil in both groups, but B(max) estimates were not influenced, suggesting that (11)C-flumazenil scanning is not confounded by alterations in P-gp function.

  • 36.
    Syvänen, Stina
    et al.
    Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Faculty of Pharmacy, Department of Pharmaceutical Biosciences.
    Lindhe, Örjan
    Palner, Mikael
    Kornum, Birgitte R
    Rahman, Obaidur
    Långström, Bengt
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Biochemistry and Organic Chemistry.
    Knudsen, Gitte M
    Hammarlund-Udenaes, Margareta
    Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Faculty of Pharmacy, Department of Pharmaceutical Biosciences.
    Species differences in blood-brain barrier transport of three positron emission tomography radioligands with emphasis on P-glycoprotein transport2009In: Drug Metabolism And Disposition, ISSN 0090-9556, E-ISSN 1521-009X, Vol. 37, no 3, p. 635-643Article in journal (Refereed)
    Abstract [en]

    Species differences occur in the brain concentrations of drugs, but the reasons for these differences are not yet apparent. This study was designed to compare brain uptake of three radiolabeled P-glycoprotein (P-gp) substrates across species using positron emission tomography. Brain concentrations and brain-to-plasma ratios were compared; [11C]verapamil in rats, guinea pigs, and monkeys; [11C](S)-(2-methoxy-5-(5-trifluoromethyltetrazol-1-yl)-phenylmethylamino)-2(S)-phenylpiperidine (GR205171) in rats, guinea pigs, monkeys, and humans; and [18F]altanserin in rats, minipigs, and humans. The fraction of the unbound radioligand in plasma was studied along with its metabolism. The effect of P-gp inhibition was investigated by administering cyclosporin A (CsA). Pronounced species differences were found in the brain and brain-to-plasma concentrations of [11C]verapamil, [11C]GR205171, and [18F]altanserin with higher brain distribution in humans, monkeys, and minipigs than in rats and guinea pigs. For example, the brain-to-plasma ratio of [11C]GR205171 was almost 9-fold higher in humans compared with rats. The species differences were still present after P-gp inhibition, although the increase in brain concentrations after P-gp inhibition was somewhat greater in rats than in the other species. Differences in plasma protein binding and metabolism did not explain the species-related differences. The findings are important for interpretation of brain drug delivery when extrapolating preclinical data to humans. Compounds found to be P-gp substrates in rodents are likely to also be substrates in higher species, but sufficient blood-brain barrier permeability may be retained in humans to allow the compound to act at intracerebral targets.

  • 37.
    Syvänen, Stina
    et al.
    Leiden University.
    Luurtsema, Gert
    Molthoff, Carla F M
    Windhorst, Albert D
    Huisman, Marc C
    Lammertsma, Adriaan A
    Voskuyl, Rob A
    de Lange, Elizabeth C
    (R)-[11C]verapamil PET studies to assess changes in P-glycoprotein expression and functionality in rat blood-brain barrier after exposure to kainate-induced status epilepticus.2011In: BMC medical imaging, ISSN 1471-2342, Vol. 11, p. 1-Article in journal (Refereed)
    Abstract [en]

    BACKGROUND: Increased functionality of efflux transporters at the blood-brain barrier may contribute to decreased drug concentrations at the target site in CNS diseases like epilepsy. In the rat, pharmacoresistant epilepsy can be mimicked by inducing status epilepticus by intraperitoneal injection of kainate, which leads to development of spontaneous seizures after 3 weeks to 3 months. The aim of this study was to investigate potential changes in P-glycoprotein (P-gp) expression and functionality at an early stage after induction of status epilepticus by kainate.

    METHODS: (R)-[11C]verapamil, which is currently the most frequently used positron emission tomography (PET) ligand for determining P-gp functionality at the blood-brain barrier, was used in kainate and saline (control) treated rats, at 7 days after treatment. To investigate the effect of P-gp on (R)-[11C]verapamil brain distribution, both groups were studied without or with co-administration of the P-gp inhibitor tariquidar. P-gp expression was determined using immunohistochemistry in post mortem brains. (R)-[11C]verapamil kinetics were analyzed with approaches common in PET research (Logan analysis, and compartmental modelling of individual profiles) as well as by population mixed effects modelling (NONMEM).

    RESULTS: All data analysis approaches indicated only modest differences in brain distribution of (R)-[11C]verapamil between saline and kainate treated rats, while tariquidar treatment in both groups resulted in a more than 10-fold increase. NONMEM provided most precise parameter estimates. P-gp expression was found to be similar for kainate and saline treated rats.

    CONCLUSIONS: P-gp expression and functionality does not seem to change at early stage after induction of anticipated pharmacoresistant epilepsy by kainate.

  • 38.
    Syvänen, Stina
    et al.
    Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Faculty of Medicine, Department of Public Health and Caring Sciences, Geriatrics.
    Russmann, Vera
    Verbeek, Joost
    Eriksson, Jonas
    Department of Nuclear Medicine & PET Research, VU University Medical Center, Amsterdam, The Netherlands.
    Labots, Maaike
    Zellinger, Christina
    Seeger, Natalie
    Schuit, Robert
    Rongen, Marissa
    van Kooij, Rolph
    Windhorst, Albert D.
    Lammertsma, Adriaan A.
    de Lange, Elizabeth C.
    Voskuyl, Rob A.
    Koepp, Matthias
    Potschka, Heidrun
    [C-11]quinidine and [C-11]laniquidar PET imaging in a chronic rodent epilepsy model: Impact of epilepsy and drug-responsiveness2013In: Nuclear Medicine and Biology, ISSN 0969-8051, E-ISSN 1872-9614, Vol. 40, no 6, p. 764-775Article in journal (Refereed)
    Abstract [en]

    Introduction: To analyse the impact of both epilepsy and pharmacological modulation of P-glycoprotein on brain uptake and kinetics of positron emission tomography (PET) radiotracers [C-11]quinidine and [C-11]laniquidar.

    Methods: Metabolism and brain kinetics of both [C-11]quinidine and [C-11]laniquidar were assessed in naive rats, electrode-implanted control rats, and rats with spontaneous recurrent seizures. The latter group was further classified according to their response to the antiepileptic drug phenobarbital into "responders" and "non-responders". Additional experiments were performed following pre-treatment with the P-glycoprotein modulator tariquidar.

    Results: [C-11]quinidine was metabolized rapidly, whereas [C-11]laniquidar was more stable. Brain concentrations of both radiotracers remained at relatively low levels at baseline conditions. Tariquidar pre-treatment resulted in significant increases of [C-11]quinidine and [C-11]laniquidar brain concentrations. In the epileptic subgroup "non-responders", brain uptake of [C-11]quinidine in selected brain regions reached higher levels than in electrode-implanted control rats. However, the relative response to tariquidar did not differ between groups with full blockade of P-glycoprotein by 15 mg/kg of tariquidar. For [C-11]laniquidar differences between epileptic and control animals were only evident at baseline conditions but not after tariquidar pretreatment.

    Conclusions: We confirmed that both [C-11]quinidine and [C-11]laniquidar are P-glycoprotein substrates. At full P-gp blockade, tariquidar pre-treatment only demonstrated slight differences for [C-11]quinidine between drug-resistant and drug-sensitive animals.

  • 39.
    Syvänen, Stina
    et al.
    Leiden University.
    Schenke, Maarten
    van den Berg, Dirk-Jan
    Voskuyl, Rob A
    de Lange, Elizabeth C
    Alteration in P-glycoprotein functionality affects intrabrain distribution of quinidine more than brain entry-a study in rats subjected to status epilepticus by kainate.2012In: The AAPS journal, ISSN 1550-7416, Vol. 14, no 1, p. 87-96Article in journal (Refereed)
    Abstract [en]

    This study aimed to investigate the use of quinidine microdialysis to study potential changes in brain P-glycoprotein functionality after induction of status epilepticus (SE) by kainate. Rats were infused with 10 or 20 mg/kg quinidine over 30 min or 4 h. Plasma, brain extracellular fluid (brain ECF), and end-of-experiment total brain concentrations of quinidine were determined during 7 h after the start of the infusion. Effect of pretreatment with tariquidar (15 mg/kg, administered 30 min before the start of the quinidine infusion) on the brain distribution of quinidine was assessed. This approach was repeated in kainate-treated rats. Quinidine kinetics were analyzed with population modeling (NONMEM). The quinidine microdialysis assay clearly revealed differences in brain distribution upon changes in P-glycoprotein functionality by pre-administration of tariquidar, which resulted in a 7.2-fold increase in brain ECF and a 40-fold increase in total brain quinidine concentration. After kainate treatment alone, however, no difference in quinidine transport across the blood-brain barrier was found, but kainate-treated rats tended to have a lower total brain concentration but a higher brain ECF concentration of quinidine than saline-treated rats. This study did not provide evidence for the hypothesis that P-glycoprotein function at the blood-brain barrier is altered at 1 week after SE induction, but rather suggests that P-glycoprotein function might be altered at the brain parenchymal level.

  • 40.
    Syvänen, Stina
    et al.
    Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Faculty of Pharmacy, Department of Pharmaceutical Biosciences.
    Xie, Ruija
    Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Faculty of Pharmacy, Department of Pharmaceutical Biosciences.
    Sahin, Selma
    Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Faculty of Pharmacy, Department of Pharmaceutical Biosciences.
    Hammarlund-Udenaes, Margareta
    Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Faculty of Pharmacy, Department of Pharmaceutical Biosciences.
    Pharmacokinetic consequences of active drug efflux at the blood-brain barrier2006In: Pharmaceutical research, ISSN 0724-8741, E-ISSN 1573-904X, Vol. 23, no 4, p. 705-717Article in journal (Refereed)
    Abstract [en]

    PURPOSE: The objective of this simulation study was to investigate how the nature, location, and capacity of the efflux processes in relation to the permeability properties influence brain concentrations. METHODS: Reduced brain concentrations can be due to either influx hindrance, a gatekeeper function in the luminal membrane, which has been suggested for ABCB1 (P-glycoprotein), or efflux enhancement by transporters that pick up molecules on one side of the luminal or abluminal membrane and release them on the other side. Pharmacokinetic models including passive transport, influx hindrance, and efflux enhancement were built using the computer program MATLAB. The simulations were based on experimentally obtained parameters for morphine, morphine-3-glucuronide, morphine-6-glucuronide, and gabapentin. RESULTS: The influx hindrance process is the more effective for keeping brain concentrations low. Efflux enhancement decreases the half-life of the drug in the brain, whereas with influx hindrance the half-life is similar to that seen with passive transport. The relationship between the influx and efflux of the drug across the blood-brain barrier determines the steady-state ratio of brain to plasma concentrations of unbound drug, K(p,uu). CONCLUSIONS: Both poorly and highly permeable drugs can reach the same steady-state ratio, although the time to reach steady state will differ. The volume of distribution of unbound drug in the brain does not influence K(p,uu), but does influence the total brain-to-blood ratio K(p) and the time to reach steady state in the brain.

  • 41. Verbeek, Joost
    et al.
    Eriksson, Jonas
    VU University Medical Center Amsterdam.
    Syvänen, Stina
    Leiden University.
    Labots, Maaike
    de Lange, Elizabeth C M
    Voskuyl, Rob A
    Mooijer, Martinus P J
    Rongen, Marissa
    Lammertsma, Adriaan A
    Windhorst, Albert D
    [11C]phenytoin revisited: synthesis by [11C]CO carbonylation and first evaluation as a P-gp tracer in rats.2012In: EJNMMI Research, ISSN 2191-219X, E-ISSN 2191-219X, Vol. 2, no 1, p. 36-Article in journal (Refereed)
    Abstract [en]

    ABSTRACT: BACKGROUND: At present, several positron emission tomography (PET) tracers are in use for imaging Pglycoprotein (P-gp) function in man. At baseline, substrate tracers such as R-[11C]verapamil display low brain concentrations with a distribution volume of around 1. [11C]phenytoin is supposed to be a weaker P-gp substrate, which may lead to higher brain concentrations at baseline. This could facilitate assessment of P-gp function when P-gp is upregulated. The purpose of this study was to synthesize [11C]phenytoin and to characterize its properties as a P-gp tracer. METHODS: [11C]CO was used to synthesize [11C]phenytoin by rhodium-mediated carbonylation. Metabolism and, using PET, brain pharmacokinetics of [11C]phenytoin were studied in rats. Effects of P-gp function on [11C]phenytoin uptake were assessed using predosing with tariquidar. RESULTS: [11C]phenytoin was synthesized via [11C]CO in an overall decay-corrected yield of 22 +/- 4%. At 45 min after administration, 19% and 83% of radioactivity represented intact [11C]phenytoin in the plasma and brain, respectively. Compared with baseline, tariquidar predosing resulted in a 45% increase in the cerebral distribution volume of [11C]phenytoin. CONCLUSIONS: Using [11C]CO, the radiosynthesis of [11C]phenytoin could be improved. [11C]phenytoin appeared to be a rather weak P-gp substrate.

  • 42.
    Verbeek, Joost
    et al.
    VU University Medical Center Amsterdam.
    Syvänen, Stina
    Leiden University.
    Schuit, Robert C
    Eriksson, Jonas
    VU University Medical Center Amsterdam.
    de Lange, Elizabeth C
    Windhorst, Albert D
    Luurtsema, Gert
    Lammertsma, Adriaan A
    Synthesis and preclinical evaluation of [11C]D617, a metabolite of (R)-[11C]verapamil.2012In: Nuclear Medicine and Biology, ISSN 0969-8051, E-ISSN 1872-9614, Vol. 39, no 4, p. 530-9Article in journal (Refereed)
    Abstract [en]

    OBJECTIVES: (R)-[(11)C]verapamil is widely used as a positron emission tomography (PET) tracer to evaluate P-glycoprotein (P-gp) functionality at the blood-brain barrier in man. A disadvantage of (R)-[(11)C]verapamil is the fact that its main metabolite, [(11)C]D617, also enters the brain. For quantitative analysis of (R)-[(11)C]verapamil data, it has been assumed that the cerebral kinetics of (R)-[(11)C]verapamil and [(11)C]D617 are the same. The aim of the present study was to investigate whether the cerebral kinetics of (R)-[(11)C]verapamil and [(11)C]D617 are indeed similar and, if so, whether [(11)C]D617 itself could serve as an alternative PET tracer for P-gp.

    METHODS: [(11)C]D617 was synthesized and its ex vivo biodistribution was investigated in male rats at four time points following intravenous administration of [(11)C]D617 (50 MBq) without (n=4) or with (n=4) pretreatment with the P-gp inhibitor tariquidar (15 mg·kg(-1), intraperitoneally). Brain distribution was further assessed using consecutive PET scans (n=8) before and after pretreatment with tariquidar (15 mg·kg(-1), intravenously), as well as metabolite analysis (n=4).

    RESULTS: The precursor for the radiosynthesis of [(11)C]D617, 5-amino-2-(3,4-dimethoxy-phenyl)-2-isopropyl-pentanitrile (desmethyl D617), was synthesized in 41% overall yield. [(11)C]D617 was synthesized in 58%-77% decay-corrected yield with a radiochemical purity of ≥99%. The homogeneously distributed cerebral volume of distribution (V(T)) of [(11)C]D617 was 1.1, and this increased 2.4-fold after tariquidar pretreatment.

    CONCLUSION: V(T) of [(11)C]D617 was comparable to that of (R)-[(11)C]verapamil, but its increase after tariquidar pretreatment was substantially lower. Hence, (R)-[(11)C]verapamil and [(11)C]D617 do not show similar brain kinetics after inhibition of P-gp with tariquidar.

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