Interferon-gamma-induced interferon regulatory factor-1 (IRF-1) expression in rodent and human islet cells precedes nitric oxide production

Endocrinology. 1997 Jul;138(7):2747-53. doi: 10.1210/endo.138.7.5286.

Abstract

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.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Adolescent
  • Adult
  • Animals
  • Cell Line
  • Child
  • DNA-Binding Proteins / biosynthesis*
  • Densitometry
  • Enzyme Induction
  • Humans
  • Interferon Regulatory Factor-1
  • Interferon-gamma / pharmacology*
  • Interleukin-1 / pharmacology
  • Islets of Langerhans / drug effects
  • Islets of Langerhans / metabolism*
  • Middle Aged
  • NF-kappa B / metabolism
  • Niacinamide / pharmacology
  • Nitric Oxide / biosynthesis*
  • Nitric Oxide Synthase / biosynthesis
  • Nitric Oxide Synthase / genetics
  • Phosphoproteins / biosynthesis*
  • Protein Processing, Post-Translational
  • RNA, Messenger / metabolism
  • Rats
  • Transcription Factors*

Substances

  • DNA-Binding Proteins
  • IRF1 protein, human
  • Interferon Regulatory Factor-1
  • Interleukin-1
  • Irf1 protein, rat
  • NF-kappa B
  • Phosphoproteins
  • RNA, Messenger
  • Transcription Factors
  • Niacinamide
  • Nitric Oxide
  • Interferon-gamma
  • Nitric Oxide Synthase