title: Prolonged STAT1 activation is associated with interferon-gamma priming for interleukin-1-induced inducible nitric-oxide synthase expression by islets of Langerhans.
abstract: In this study, the ability of interferon-gamma (IFN-gamma) to prime rat and nonobese diabetic (NOD) mouse islets for interleukin-1 (IL-1)-stimulated expression of inducible nitric-oxide synthase (iNOS) has been examined. IL-1-induced iNOS expression by rat islets is concentration-dependent with maximal expression occurring in response to 1.0 unit/ml. Individually, neither 0.1 unit/ml IL-1 nor 150 units/ml IFN-gamma stimulates iNOS expression or nitrite production by rat islets. However, a 30-60-min pulse of rat islets with IFN-gamma, followed by washing to remove the cytokine and continued culture with 0.1 unit/ml IL-1 for 40 h, results in iNOS expression and nitrite production to levels similar in magnitude to the individual effects of 1.0 unit/ml IL-1. A 1-h pulse with IFN-gamma primes for IL-1-induced islet degeneration that is mediated by the expression of iNOS and increased production of nitric oxide. IFN-gamma also primes for IL-1-induced iNOS expression and nitrite formation by NOD mouse islets. The priming actions of IFN-gamma appear to be selective for beta-cells, as IFN-gamma primes for IL-1-induced nitrite formation by primary beta-cells and RINm5F insulinoma cells, but not primary alpha-cells. The priming actions of IFN-gamma for IL-1-induced iNOS expression do not require de novo protein synthesis as preincubation of RINm5F cells with cycloheximide does not inhibit iNOS mRNA accumulation under priming conditions. The priming actions of IFN-gamma on IL-1-induced iNOS expression persists for extended periods of up to 7 days and are associated with persistent signal transducers and activators of transcription (STAT)-1 activation. A 30-min pulse of rat islets with IFN-gamma stimulates STAT1 phosphorylation, and STAT1 remains phosphorylated for up to 7 days following IFN-gamma removal. In addition, STAT1 remains nuclear for up to 7 days after IFN-gamma removal. These results indicate that IFN-gamma primes for IL-1-induced islet degeneration via a nitric oxide-dependent mechanism. These findings also provide evidence that the priming actions of IFN-gamma for IL-1-induced iNOS expression by islets are associated with the prolonged phosphorylation and activation of STAT1.
authors.affiliation: Edward A. Doisy Department of Biochemistry, St. Louis University School of Medicine, St. Louis, Missouri 63104, USA.
authors.forename: M R
authors.initials: MR
authors.lastname: Heitmeier
authors.forename: A L
authors.initials: AL
authors.lastname: Scarim
authors.forename: J A
authors.initials: JA
authors.lastname: Corbett
mesh_terms: D000818:Animals; D003513:Cycloheximide / Q000494:pharmacology; D004268:DNA-Binding Proteins / Q000378:metabolism*; D005455:Fluorescent Antibody Technique; D005786:Gene Expression Regulation / Q000187:drug effects; D007340:Insulinoma / Q000378:metabolism; D007371:Interferon-gamma / Q000494:pharmacology*; D007375:Interleukin-1 / Q000494:pharmacology*; D007515:Islets of Langerhans / Q000187:drug effects*; D008297:Male; D051379:Mice; D016688:Mice, Inbred NOD; D009569:Nitric Oxide / Q000378:metabolism; D019001:Nitric Oxide Synthase / Q000378:metabolism*; D052247:Nitric Oxide Synthase Type II; D010766:Phosphorylation; D012333:RNA, Messenger / Q000378:metabolism; D051381:Rats; D017207:Rats, Sprague-Dawley; D050794:STAT1 Transcription Factor; D015398:Signal Transduction; D015534:Trans-Activators / Q000378:metabolism*; D015533:Transcriptional Activation / Q000187:drug effects; D014407:Tumor Cells, Cultured
chemical_list: D004268:DNA-Binding Proteins; D007375:Interleukin-1; D012333:RNA, Messenger; D050794:STAT1 Transcription Factor; C494080:Stat1 protein, mouse; C494081:Stat1 protein, rat; D015534:Trans-Activators; D009569:Nitric Oxide; D007371:Interferon-gamma; D003513:Cycloheximide; D019001:Nitric Oxide Synthase; D052247:Nitric Oxide Synthase Type II; C496317:Nos2 protein, mouse; C496318:Nos2 protein, rat