文摘
We have investigated to determine the source of ceramide produced during the genotoxic apoptosis induced by the anti-cancer drug, camptothecin (CPT), in human prostate cancer LNCaP cells by measuring the activities of acid and neutral sphingomyelinases (SMase) and by using fumonisinB1 (FB1), the inhibitor of ceramide synthase involving de novo synthesis of ceramide. In contrast to time-dependent elevation of intracellular ceramide level after CPT-treatment, the activities of both SMases were not increased but rather decreased. Instead, pretreatment for 3h with FB1 (100μM), an inhibitor of ceramide synthase, almost completely abrogated ceramide accumulation observed in cells exposed to CPT for 18h. These results indicate that ceramide is produced via de novo pathway but not via sphingomyelin hydrolysis pathway. Furthermore, it is to be noted that the pretreatment with FB1 did not affect the CPT-induced apoptosis as assessed by DNA ladder formation, Hoechst 33342 staining, flow cytometry, and mitochondrial potential thereby leading us to propose that ceramide accumulation is independent of apoptosis in this system.
