APOPTOSIS AS A MECHANISM OF 2-CHLOROETHYLETHYL SULFIDE-INDUCED CYTOTOXICITY

Apoptosis is a mode of active cell death. We have examined whether 2-c hloroethylethyl sulfide (CEES), a sulfur vesicating agent, triggers ap optosis as a cytotoxic mechanism, Incubation of thymocytes with CEES, resulted in an induction of apoptotic features of cell death. Treatmen t of cells with 100 mu M CEES for 5 h increased DNA fragmentation to s imilar to 40% of control. The fragmentation of DNA was visualized by a garose gel electrophoresis. It showed ladder pattern of DNA fragmentat ion, which indicates internucleosomal cleavage of DNA. Further evidenc e of apoptosis was observed in morphological changes of nuclei by usin g the terminal deoxynucleotidyl transferase-mediated dUTP-biotin nick end labeling (TUNEL) method. The percentage of TUNEL positive cells wa s dependent upon CEES concentrations. CEES induced the classical morph ological features of apoptosis in nucleus, These features were accompa nied by condensation of chromatin, which arranged in sharply declined clumps and fragmentation of nucleus, To study requirement for synthesi s of new protein in CEES-induced apoptosis, we studied the effect of c ycloheximide for apoptotic activity. This protein synthesis inhibitor did not suppress the CEES-induced apoptotic activity. Taken together, these results suggest that CEES-induced apoptosis as a cytotoxic mecha nism and this process occurs independent of synthesis of new protein. (C) 1998 Published by Elsevier Science Ireland Ltd. All rights reserve d.