Benzylpenicyllin and acetylcysteine protection from α-amanitin-induced apoptosis in human hepatocyte cultures

Abstract

High mortality rate in Amanita phalloides (death cap) intoxications is a result of the acute liver failure following hepatocyte damage due to hepatocellular uptake of amatoxins. α-Amanitin (α-AMA), the major amatoxin, blocks a RNA polymerase II, which results in inhibition of transcription of DNA and protein synthesis processes and leads to hepatocyte death. α-AMA is also a strong apoptosis inductor and may play a significant role in pathogenesis of hepatic damage in course of amanitin intoxication. The aim of this study was to examine mechanisms of α-AMA-induced apoptosis in human hepatocytes, as well as in determining if commonly clinically used antidotes benzylpenicillin (BPCN) and N-acetylcysteine (ACC) are able to protect human hepatocytes against α-AMA-induced apoptosis. The experiment was performed on cultured human hepatocytes. Viability of cultured hepatocytes was assessed using the MTT assay, whereas apoptosis processes were evaluated by the electron microscopy, detection of DNA laddering, determination of caspase-3 activity, and measuring annexin V, p53 and Bcl-2 protein concentration. Cytotoxicity and apoptosis evaluation were performed after 24 h of exposure to α-AMA and/or tested antidotes.Both ACC and BPCN were well tolerated by human hepatocyte cultures, and exposure to those substances did not reduce cell viability nor induce apoptosis. Exposure of hepatocytes to α-AMA at concentration 2μM resulted in derangement of cell cultures, apoptosis and significant reduction in cell viability. α-AMA-induced apoptosis in human heptocyte cultures is p53- and caspase-3-dependent. Human hepatocyte cultures are exposed simultaneously to α-AMA and tested antidotes (BPCN or ACC) showed significantly higher cell viability and significantly lower values of apoptosis markers compared to the cultures exposed to α-AMA only.