Mouse islet cell lysis mediated by interleukin-1-induced Fas

This study was conducted to investigate the possible involvement of Fas in beta-cell death in insulitis of Type 1 (insulin-dependent) diabetes mellitus. Although primary cultured Balb/c mouse islet cells did not express Fas mRNA, 4-12 hours of treatment with 10(2)-10(5) U/l of mouse interleukin-l ct (IL-lcr) induced the expression of Fas mRNA, Surface Fas expression was detected by immunofluorescence flow cytometry using a non-cytolytic anti-Fas monoclonal antibody after 6 or 12 h of incubation with 10(3) U/l of IL-l alpha. Primary islet cells were resistant to an agonistic anti-Fas monoclonal antibody. However, 12 h pretreatment with IL-1 alpha sensitized islet cells to its cytolytic effect. Significant cell death was observed 24 h after the addition of anti-Fas, and progressively increased until 72 h, when specific Cr-51 release was 72 +/- 6 %. Agarose gel electrophoresis of DNA extracted from cells exposed to IL-1 alpha and agonistic anti-Fas showed inter-nucleosomal DNA fragmentation, a hallmark of apoptotic cell death. Since the Fas antibody showed no cross-reactive activity of tumour necrosis factor (TNF), the cytotoxic effect was not mediated by TNF receptors. A protein synthesis inhibitor cycloheximide augmented Fas-mediated islet cell death. The Fas-mediated killing of islet cells was not L-arginine-dependent, or blocked by N-G-monomethyl-L-arginine, beta-TC1 cells also expressed Fas mRNA when exposed to IL-1 alpha or IL-1 alpha plus interferon-gamma. These observations suggest that Fas-mediated apoptosis may be a mechanism of islet cell death in autoimmune insulitis.