ATTENUATION OF TGF-BETA-INDUCED APOPTOSIS IN PRIMARY CULTURES OF HEPATOCYTES BY CALPAIN INHIBITORS

Apoptosis induced in primary cultures of rat hepatocytes by transformi ng growth factor beta(1) (TGF-beta(1)) was greatly attenuated by inhib itors (5 mu M) of calpain I and calpain II, respectively. Both inhibit ors prevented the TGF-beta-elicited increase of nucleosomal DNA fragme nts and the occurrence of DNA-breaks in the TUNEL reaction. The detrim ental effect of TGF-beta on cell viability measured by the WST-1 test was strongly reduced by calpain inhibitors. Calpain II > I inhibitors suppressed spontaneous DNA cleavage in hepatocytes during culture and prevented the appearance of immunocytochemically visible TGF-beta (APA AP staining), which occurs in untreated parenchymal cell cultures. The data show that inactivation of calpains attenuates both the TGF-beta- elicited and the spontaneous apoptosis of cultured hepatocytes; the la tter effect is likely due to the suppression of endogenous TGF-beta ac tivation. It is suggested that calpains participate in these processes . (C) 1997 Academic Press.