uu.seUppsala University Publications
Change search
CiteExportLink to record
Permanent link

Direct link
Cite
Citation style
  • apa
  • ieee
  • modern-language-association
  • vancouver
  • Other style
More styles
Language
  • de-DE
  • en-GB
  • en-US
  • fi-FI
  • nn-NO
  • nn-NB
  • sv-SE
  • Other locale
More languages
Output format
  • html
  • text
  • asciidoc
  • rtf
Phenobarbital suppresses vitamin D3 25-hydroxylase expression: A potential new mechanism for drug-induced osteomalacia
Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Faculty of Pharmacy, Department of Pharmaceutical Biosciences.
Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Faculty of Pharmacy, Department of Pharmaceutical Biosciences, Pharmaceutical Biochemistry.
Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Faculty of Pharmacy, Department of Pharmaceutical Biosciences.
Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Faculty of Pharmacy, Department of Pharmaceutical Biosciences.
2007 (English)In: Biochemical and Biophysical Research Communications - BBRC, ISSN 0006-291X, E-ISSN 1090-2104, Vol. 357, no 3, 603-607 p.Article in journal (Refereed) Published
Abstract [en]

Prolonged therapy with phenobarbital may cause vitamin D deficiency or osteomalacia. In the current study, we propose a novel mechanism for drug-induced osteomalacia involving impaired bioactivation of vitamin D3 due to decreased 25-hydroxylation of vitamin D3 in liver. The present data, using the pig as model, demonstrate direct effects by phenobarbital on the expression of CYP27A1 and CYP2D25, two important 25-hydroxylases. Treatment by phenobarbital markedly reduced the rate of 25-hydroxylation by primary hepatocytes and suppressed the cellular CYP27A1 mRNA levels. The rate of 25-hydroxylation by two different purified 25-hydroxylases, microsomal CYP2D25, and mitochondrial CYP27A1, respectively, was dose-dependently inhibited by phenobarbital. Reporter assay experiments in liver-derived HepG2 cells revealed a marked PXR-mediated transcriptional downregulation of the CYP2D25 promoter. In addition, the data indicate that phenobarbital might affect the mRNA stability of CYP2D25. Taken together, the data suggest that vitamin D3 25-hydroxylation may be suppressed by phenobarbital. A downregulation of 25-hydroxylation by phenobarbital may explain, at least in part, the increased risk of osteomalacia, bone loss, and fractures in long-term phenobarbital therapy.

Place, publisher, year, edition, pages
2007. Vol. 357, no 3, 603-607 p.
Keyword [en]
Bioactivation of vitamin D3, 25-Hydroxylation, Hepatocytes, Expression, Transcriptional regulation, Osteomalacia
National Category
Pharmaceutical Sciences
Identifiers
URN: urn:nbn:se:uu:diva-97880DOI: 10.1016/j.bbrc.2007.03.177ISI: 000246382700006PubMedID: 17445763OAI: oai:DiVA.org:uu-97880DiVA: diva2:172975
Available from: 2008-11-28 Created: 2008-11-28 Last updated: 2011-02-02Bibliographically approved
In thesis
1. Regulation of Vitamin D 25-hydroxylases: Effects of Vitamin D Metabolites and Pharmaceutical Compounds on the Bioactivation of Vitamin D
Open this publication in new window or tab >>Regulation of Vitamin D 25-hydroxylases: Effects of Vitamin D Metabolites and Pharmaceutical Compounds on the Bioactivation of Vitamin D
2008 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

A 700bp portion of the promoter of CYP2D25, the porcine microsomal vitamin D 25-hydroxylase was isolated and sequenced. The computer analysis of the sequence revealed the existence of a putative VDRE at 220 bp upstream of the transcription start site. A CYP2D25 promoter-luciferase reporter plasmid was constructed in order to study the transcriptional regulation of the gene. Treatment with the vitamin D metabolites calcidiol and calcitriol suppressed the promoter, provided that the nuclear receptors VDR and RXR were overexpressed. Phenobarbital was also capable of suppressing the promoter if the nuclear receptors PXR or CAR were overexpressed.

The 25-hydroxylases are not expressed solely in liver but in a wide array of other organs as well. It is therefore possible at least in theory to study the vitamin D 25-hydroxylation in human subjects using cells from extrahepatic organs, from which biopsy retrieval is easier than from the liver. Dermal fibroblasts are frequently used to study different pathological conditions in human subjects and they are easy to come by. Dermal fibroblasts were shown to express two vitamin D 25-hydroxylases: CYP27A1 and CYP2R1. The expression pattern of CYP2R1 displayed considerable interindividual variation. The fibroblasts were also capable of measurable vitamin D 25-hydroxylation, which makes dermal fibroblasts a possible tool in studying vitamin D 25-hydroxylation in human subjects.

Little is known about the regulation of expression and activity of the human vitamin D 25-hydroxylases. Therefore dermal fibroblasts – expressing CYP2R1 and CYP27A1 – and human prostate cancer LNCaP cells, that express CYP2R1 and CYP2J2, were treated with calcitriol and phenobarbital and efavirenz, two drugs that give rise to vitamin D deficiency. Treatment decreased the mRNA levels of CYP2R1 and CYP2J2 provided that the treated cells also expressed the necessary nuclear receptors. CYP27A1 did not respond to any of the treatments. The treatments also managed to decrease the 25-hydroxylating activity of the cells.

The results show that vitamin D 25-hydroxylases can be regulated by both endogenous and xenobiotic compounds.

Place, publisher, year, edition, pages
Uppsala: Acta Universitatis Upsaliensis, 2008. 47 p.
Series
Digital Comprehensive Summaries of Uppsala Dissertations from the Faculty of Pharmacy, ISSN 1651-6192 ; 87
Keyword
CYP2D25, vitamin D 25-hydroxylase, transcriptional regulation, vitamin D, CYP2R1, CYP2J2, CYP27A1, phenobarbital, efavirenz, fibroblast, LNCaP
National Category
Pharmaceutical Sciences
Identifiers
urn:nbn:se:uu:diva-9412 (URN)978-91-554-7362-4 (ISBN)
Public defence
2008-12-19, C8:321, BMC, Husargatan 3, Uppsala, 09:15
Opponent
Supervisors
Available from: 2008-11-28 Created: 2008-11-28Bibliographically approved

Open Access in DiVA

No full text

Other links

Publisher's full textPubMed

Authority records BETA

Ellfolk, MariaNorlin, MariaWikvall, Kjell

Search in DiVA

By author/editor
Ellfolk, MariaNorlin, MariaWikvall, Kjell
By organisation
Department of Pharmaceutical BiosciencesPharmaceutical Biochemistry
In the same journal
Biochemical and Biophysical Research Communications - BBRC
Pharmaceutical Sciences

Search outside of DiVA

GoogleGoogle Scholar

doi
pubmed
urn-nbn

Altmetric score

doi
pubmed
urn-nbn
Total: 802 hits
CiteExportLink to record
Permanent link

Direct link
Cite
Citation style
  • apa
  • ieee
  • modern-language-association
  • vancouver
  • Other style
More styles
Language
  • de-DE
  • en-GB
  • en-US
  • fi-FI
  • nn-NO
  • nn-NB
  • sv-SE
  • Other locale
More languages
Output format
  • html
  • text
  • asciidoc
  • rtf