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Regulation of cytokine-induced nitric oxide production in insulin-producing cells
Uppsala University, Medicinska vetenskapsområdet, Faculty of Medicine, Department of Medical Cell Biology.
1998 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Cytokine-induced expression of the inducible form of nitric oxide synthase (iNOS) and production of nitric oxide (NO) may contribute to pancreatic β-cell damage during the development of type 1 diabetes. iNOS catalyses the conversion of arginine into citrulline and NO, a reaction regulated by the amount of expressed iNOS enzyme and by the cellular availability of arginine. Activation of the transcriptional regulator nuclear factor κB (NF-κB) is required for the expression of iNOS in diverse rodent cells. Activation of NF-κB was presently observed to be necessary but not sufficient for the induction of iNOS by cytokines (IL-1β + IFN-γ + TNF-α) in human islets. This suggests that other transcription factors may play a role in this process. IFN-γ alone or in combination with IL-1β induced the expression of the transcription factor interferon regulatory factor-l (IRF-1) both in rodent and human islets. IRF-1 is necessary for iNOS expression by murine macrophages and may therefore also contribute to the expression of iNOS in insulin-producing cells. Synthesis of NO by cytokine-exposed purified rat β-cells, rodent and human islets was found to depend on the presence of extracellular arginine or citrulline, with arginine levels similar to that observed in plasma (80-200 µM) limiting NO-production. Cytokine-stimulated purified rat β-cells and human and rat islets used citrulline as efficiently as arginine for NO-synthesis, suggesting an intracellular generation of arginine by a citrulline-NO cycle. In line with this hypothesis, IL-1β or IFN-γ + TNF-α enhanced mRNA expression and enzyme activity of argininosuccinate synthetase (AS), the rate-limiting enzyme in the citrulline-NO cycle, in insulin-producing cells. This was paralleled by the induction of iNOS mRNA. Moreover, IL-1β increased arginine accumulation by purified rat β-cells.

It is concluded that NF-κB, and possibly IRF-1, contribute to the expression of iNOS in cytokine-exposed insulin-producing rat β-cells and intact human and rat islets. Cytokines also increase the β-cell capacity to accumulate arginine and activate the citrulline-NO cycle. This adaptive response in cytokine-exposed insulin-producing cells may be of relevance to assure an adequate arginine supply for durable NO synthesis.

Place, publisher, year, edition, pages
Uppsala: Acta Universitatis Upsaliensis , 1998. , [4], 75 p.
Series
Comprehensive Summaries of Uppsala Dissertations from the Faculty of Medicine, ISSN 0282-7476 ; 735
Keyword [en]
Cell biology, Diabetes, pancreatic islets, insulin-producing cells, cytokines, nitric oxide, inducible nitric oxide synthase, nuclear factor-kappaB, interferon regulatory factor-1, arginine, citrulline, argininosuccinate synthetase, insulin release
Keyword [sv]
Cellbiologi
National Category
Cell and Molecular Biology
Research subject
Medical Cell Biology
Identifiers
URN: urn:nbn:se:uu:diva-132ISBN: 91-554-4120-3 (print)OAI: oai:DiVA.org:uu-132DiVA: diva2:160855
Public defence
1998-02-06, lecture hall B21, Uppsala Biomedical Centre, Uppsala University, Uppsala, 09:15
Available from: 1998-01-16 Created: 1998-01-16Bibliographically approved

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