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

Abstract

This study was conducted to investigate the possible involvement of Fas in (β-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 102-105 U/l of mouse interleukin-1α (IL-1α) 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 103 U/l of IL-1α. Primary islet cells were resistant to an agonistic anti-Fas monoclonal antibody. However, 12 h pretreatment with IL-1α 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 51Cr release was 72 ± 6%. Agarose gel electrophoresis of DNA extracted from cells exposed to IL-1α and agonistic anti Fas showed internucleosomal 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. (β-TC1 cells also expressed Fas mRNA when exposed to IL-1α or IL-1α plus interferon-γ. These observations suggest that Fas-mediated apoptosis may be a mechanism of islet cell death in autoimmune insulitis.