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

Abstract

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.

Cytokines activate genes of the endocytotic pathway in insulin-producing RINm5F cells

“…1 and Table 2). This more pronounced change of the gene expression pattern in response to a combination of cytokines is a well-known characteristic of insulin-producing cells [6,26,27]. These results were confirmed and extended by a quantification of the gene expression using quantitative real time RT-PCR measurements.…”

Effects of Inflammatory Factors on Mesenchymal Stem Cells and Their Role in the Promotion of Tumor Angiogenesis in Colon Cancer

“…TNF-␣ or perhaps other cytokines are required to cause MSCs to produce and secrete cytokines. It has been reported previously that IFN-␥ and TNF-␣ synergize in the induction of gene expression in various cells (31)(32)(33), including MSCs (34), but little is known about the expression of VEGF and other pro-angiogenic factors. The mechanism of this synergy between these two cytokines is not fully understood.…”

Successful Therapy of Lethal Murine Visceral Leishmaniasis with Cystatin Involves Up-Regulation of Nitric Oxide and a Favorable T Cell Response

“…Further, the in vivo administration of anti-IFN-␥ or anti-TNF-␣ mAbs could block the induction of cystatin-mediated protection against L. donovani infection. The immunologic stimulus for the production of cytotoxic levels of NO in vitro by murine macrophages is the synergistic effect of IFN-␥ and exogenous TNF or microbes and microbial products to stimulate endogenous release of TNF-␣ by macrophages (31)(32)(33)(34). Exogenous agent-stimulated TNF acts in an autocrine fashion to amplify the actual synthesis and release of NO by IFN-␥-primed cells (33,35).…”