Interferon-gamma-induced interferon regulatory factor-1 (IRF-1) expression in rodent and human islet cells precedes nitric oxide production.
The radical nitric oxide (NO) may be a mediator of beta-cell damage in IDDM. The cytokines IFN-gamma and IL-1beta are required for expression of the enzyme nitric oxide synthase (iNOS), and NO production by human pancreatic islets. In this study, possible mechanisms by which IFN-gamma participates in iNOS messenger RNA (mRNA) expression were evaluated in both rodent and human islets cells. Addition of IFN-gamma, before or after arrest of IL-1beta-induced iNOS gene transcription by actinomycin D, did not prolong iNOS mRNA half life in the rat insulin-producing cell line RINm5F (RIN cells). IFN-gamma also failed to modify IL-1beta-induced activation of the transcription factor kappaB (NF-kappaB) in RIN cells, as determined by electrophoretic mobility shift assay. However, IFN-gamma induced an early (30 min(-1) h) increase in interferon regulatory factor-1 (IRF-1) mRNA expression and a later (2 h) 19-fold increase in RIN cell nuclear IRF-1 protein content, an effect further potentiated by IL-1beta. The total cellular content of IRF-1 protein increased by 30- to 50-fold in human islets exposed for 2-8h to IFN-gamma or IFN-gamma + IL-1beta. IL-1beta alone induced a marginal and transient increase in IRF-1. It has been previously reported that nicotinamide prevents IL-1beta-induced IRF-1 expression in rat pancreatic islets. However, nicotinamide (20 mM) presently failed to prevent IL-1beta + IFN-gamma-induced IRF-1 protein expression in human pancreatic islets. In conclusion, the effects of IFN-gamma on iNOS expression can neither be explained by iNOS mRNA stabilization nor increased NF-kappaB activation. However, IFN-gamma induces an early increase in cellular IRF-1 content, and this may contribute to increased iNOS mRNA expression.
Flodström
M
M
Department of Medical Cell Biology, Uppsala University, Sweden. malin.flodstrom@medcellbiol.uu.se
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D000293:Adolescent; D000328:Adult; D000818:Animals; D002460:Cell Line; D002648:Child; D004268:DNA-Binding Proteins / Q000096:biosynthesis*; D003720:Densitometry; D004790:Enzyme Induction; D006801:Humans; D050856:Interferon Regulatory Factor-1; D007371:Interferon-gamma / Q000494:pharmacology*; D007375:Interleukin-1 / Q000494:pharmacology; D007515:Islets of Langerhans / Q000187:drug effects / Q000378:metabolism*; D008875:Middle Aged; D016328:NF-kappa B / Q000378:metabolism; D009536:Niacinamide / Q000494:pharmacology; D009569:Nitric Oxide / Q000096:biosynthesis*; D019001:Nitric Oxide Synthase / Q000096:biosynthesis / Q000235:genetics; D010750:Phosphoproteins / Q000096:biosynthesis*; D011499:Protein Processing, Post-Translational; D012333:RNA, Messenger / Q000378:metabolism; D051381:Rats; D014157:Transcription Factors
D004268:DNA-Binding Proteins; C494257:IRF1 protein, human; D050856:Interferon Regulatory Factor-1; D007375:Interleukin-1; C494259:Irf1 protein, rat; D016328:NF-kappa B; D010750:Phosphoproteins; D012333:RNA, Messenger; D014157:Transcription Factors; D009536:Niacinamide; D009569:Nitric Oxide; D007371:Interferon-gamma; D019001:Nitric Oxide Synthase