PROMOTION OF HEAT-INDUCED APOPTOSIS IN FM3A CELLS BY PROTEASE INHIBITORS

Although it has been shown that proteases may play a positive role in causing apoptosis of some cells, we report here that, on the contrary, protease inhibitors can promote heat-induced apoptosis in FM3A cells. Cysteine protease inhibitor, s-Epoxy-succinyl-L-leucylamido-(4-guanid ino)butane (E-64, 100 mu g/ml) and aspartate protease inhibitor, pepst atin-A (100 mu g/ml) were used to test hyperthermic effect on FM3A cel ls and showed remarkable cytotoxicity when they were present in cell s uspension during heating at 44 degrees C, The cytotoxicity was due to promotion of heat-induced apoptosis as judged by DNA agarose electroph oresis. Furthermore, using flow cytometric analysis, we observed a dec rease in the G(0)/G(1), phase cell and an increase in the S phase cell as well as increased apoptosis after heat shock. E-64 and pepstatin-A exhibited a promotive effect on the changes of cell cycle induced by heat. The data presented suggest that the enhancement of hyperthermic cell killing by protease inhibitors may be related to promotion of hea t-induced apoptosis and changes of cell cycle. (C) 1996 Academic Press , Inc.