Mechanism of Fas-mediated apoptosis of pancreatic β-cells.

点击翻译按钮获取中文摘要

We transfected human Fas cDNA into a mouse β-cell line (βTC1) and established a β-cell clone expressing human Fas. This clone, designated hFas/βTC1, underwent apoptosis when exposed to anti-Fas showing hallmarks of apoptosis, i.e. , chromatin condensation, nucleolar disintegration, internucleosomal DNA fragmentation, and Annexin V staining. The crosslinking of Fas by anti-Fas resulted in the elevation of caspase-3-like, but not caspase-1-like, protease activity. A caspase-3 inhibitor attenuated the Fas-mediated β-cell apoptosis. Furthermore, an antisense caspase-3 construct blocked caspase-3 activation and substantially suppressed Fas-triggered apoptosis of hFas/βTC1 cells. These observations suggest the essential role of caspase-3 in Fas-mediated apoptosis of the β-cell line. Fas-mediated apoptosis of hFas/βTC1 cells was augmented by the addition of oleate, suggesting that fatty acids may be involved in β cell apoptosis associated with ketoacidosis. To assess the effects of caspase inhibitors on insulitis of NOD mice, we started injections of z-VAD-fmk of 0.2 mg/day following a cyclophosphamide injection. Diabetes developed in 8 of 15 control mice and in 5 of 15 treated mice. All treated mice survived during the 21-day experiment while 3 mice died in the control group. Insulitis remained mild in 3 of 15 control mice and in 9 of 15 treated mice. Thus autoimmune insulitis may be partially attenuated by inhibition of caspases.