ANTIAPOPTOTIC EFFECT OF BENZYLOXYCARBONYL-ASPARTYL-(BETA-TERTIER-BUTYL ESTER)-BROMOMETHYLKETONE (Z-D(OTBU)-BMK), AN INTERMEDIATE OF INTERLEUKIN-1-BETA CONVERTING-ENZYME INHIBITORS

The effect of several interleukin-1 beta converting enzyme (ICE) inhib itors on apoptosis was examined. The ICE inhibitors tested were peptid e aldehydes such as ethyloxycarbonyl-Ala-Tyr-Val-Ala-Asp-aldehyde (Eto co-AYVAD-CHO), acetyl-Tyr-Val-Ala-Asp-aldehyde (Ac-WAD-CHO), benzyloxy carbonyl-Val-His-Asp-aldehyde (Z-VHD-CHO), a tetrapeptide chloromethyl ketone, acetyl-Tyr-Val-Ala-Asp-chloromethylketone (Ac-YVAD-Cmk) and th eir common intermediate benzyloxycarbonyl-Asp-(beta-tertier-butyl este r)-bromomethylketone (Z-D(OtBu)-Bmk). Apoptosis was induced with sever al chemical agents conventionally used for this purpose in THP-I, L929 , NB-41A3 cell lines and mouse thymocytes. DNA fragmentation during ap optosis was measured by conventional gel electrophoresis and ELISA. Th e cell morphology was examined by hematoxylin/eosin staining method. C ell viability was also monitored by MTT assay. Contrary to expectation s, the peptide aldehydes listed above and Ac-YVAD-Cmk, known as highly specific ICE inhibitors, did not inhibit the apoptosis of these cell types. However, Z-D(OtBu)-Bmk, which had no relevant inhibitory activi ty on ICE, potently blocked the DNA fragmentation in THP-I cells and t hymocytes whichever of the inducing agents was used. In the other two cell lines Z-D(OtBu)-Bmk was inactive. The apoptotic cell morphology w as also inhibited by Z-D(OtBu)-Bmk. Nevertheless, Z-D(OtBu)-Bmk failed to prevent the loss of mitochondrial activity and the cell destructio n in the late phase of apoptosis. These data suggest that ICE is not i nvolved in the apoptotic cell death induced by chemical agents. Thus, Z-D(OtBu)-Bmk, a common intermediate of some ICE inhibitors, may be a useful antiapoptotic agent for studying the early events of apoptosis in some cell types. (C) 1997 International Society for Immunopharmacol ogy.