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Activated T-cells and macrophages infiltrate pancreatic islets early in the pathogenesis of type 1 diabetes. Their secretion of different pro-inflammatory cytokines such as interleukin (IL)-1beta, interferon (IFN)-gamma, and tumor necrosis factor (TNF)-alpha affects beta-cell function. Here we report that a combination of these cytokines inhibits insulin release, stimulates inducible nitric oxide synthase (iNOS), and upregulates the surface expression of Fas in NIT-1 beta-cells and intact mouse islets. Using iNOS-deficient and Fas-deficient islets, respectively, we investigated the relative contribution of NO and Fas upregulation in cytokine-induced beta-cell damage. Interestingly, inhibition of insulin release did not occur in the absence of NO production. However, de novo expression of Fas-specific mRNA and Fas cell surface expression were detected and thus appear to be NO-independent. The lack of NO production partially protected islets from cytokine-induced apoptosis but had no effect on cell death induced by cell surface cross-linking of Fas with soluble Fas ligand (FasL). The absence of FasL on alpha-cells and the degree of apoptosis observed in Fas-deficient islets exclude the possibility of cytokine-induced fratricide. In conclusion, pro-inflammatory cytokines exert a cytotoxic effect on beta-cells via an NO-dependent pathway and, in parallel, render beta-cells susceptible to Fas:FasL-mediated, NO-independent cell death triggered by activated T-cells.

Original publication

DOI

10.2337/diabetes.49.1.39

Type

Journal article

Journal

Diabetes

Publication Date

01/2000

Volume

49

Pages

39 - 47

Keywords

Animals, Apoptosis, Cell Membrane, Cytokines, Fas Ligand Protein, Insulin, Insulin Secretion, Islets of Langerhans, Membrane Glycoproteins, Mice, Mice, Inbred Strains, Nitric Oxide, Nitric Oxide Synthase, Nitric Oxide Synthase Type II, fas Receptor