Synergistic activation of NF-κb and inducible isoform of nitric oxide synthase induction by interferon-γ and tumor necrosis factor-α in INS-1 cells

✍ Scribed by Nobuo Sekine; Toshio Ishikawa; Tomoki Okazaki; Michio Hayashi; Claes B. Wollheim; Toshiro Fujita

• Publisher: John Wiley and Sons
• Year: 2000
• Tongue: English
• Weight: 332 KB
• Volume: 184
• Category: Article
• ISSN: 0021-9541
• DOI: 10.1002/(sici)1097-4652(200007)184:1<46::aid-jcp5>3.0.co;2-l

✦ Synopsis

Interferon-gamma (IFN-gamma) is known to exert deleterious effects on pancreatic beta-cells and is implicated in the development of type 1 (autoimmune) diabetes mellitus. In this study, we investigated signaling mechanisms mediating the effects of IFN-gamma in pancreatic beta-cells using a differentiated rat insulin-secreting cell line, INS-1, with special reference to the activation of transcription factors STAT (signal transducers and activators of transcription)1 and NF-kappaB. Exposure of INS-1 cells to 100 IU/ml IFN-gamma for 24 h resulted in significant inhibition of nutrient-induced insulin secretion associated with impaired metabolism. In combination with tumor necrosis factor-alpha (TNF-alpha) (50 ng/ml), IFN-gamma elicited severe cytotoxicity and induced the expression of the inducible isoform of nitric oxide synthase (iNOS) mRNA. IFN-gamma promoted tyrosine phosphorylation and DNA-binding of STAT1 through Janus kinase (JAK)1 activation without apparent phosphorylation of JAK2. TNF-alpha did not affect STAT1 activation, but stimulated DNA-binding and transcriptional activity of NF-kappaB, both of which were further increased by IFN-gamma. These effects of IFN-gamma and TNF-alpha seem physiologically relevant, because either inhibition of STAT1 by the tyrosine kinase inhibitor herbimycin A or that of NF-kappaB by sulfasalazine resulted in the reduction of iNOS mRNA expression. In conclusion, IFN-gamma activates STAT1 and potentiates TNF-alpha-induced NF-kappaB activation in INS-1 cells, thereby inducing iNOS and cell destruction.