TP induces hepatic intolerance to FasL-mediated hepatocyte apoptosis by inhibiting XIAP.

Triptolide (TP) is extracted from the traditional Chinese medicine Tripterygium wilfordii Hook. F. (TWHF). Its severe toxic side effects, especially hepatotoxicity, have limited the clinical application of TP-related drugs. In this study, we investigated the mechanism of the hepatotoxic effects of TP from the perspective that TP inhibited the expression of the pro-survival protein X-linked inhibitor of apoptosis protein (XIAP) and enhanced FasL-mediated apoptosis of hepatocytes. TP and CD95/Fas antibody (Jo-2) were administered by gavage to C57BL/6 mice for 7 consecutive days. After co-administration of TP and Jo-2, mouse livers showed large areas of necrosis and apoptosis and significantly increased Caspase-3 activity. KEGG pathway enrichment analysis indicated that TP may cause the development of liver injury through the apoptotic signaling pathway. Proteinprotein interaction networks showed that XIAP played an essential role in this process. TP reduced the protein expression of XIAP after combination treatment with Jo-2/FasL in vivo/in vitro. TP and FasL co-stimulation significantly increased microRNA-137 (miR-137) levels in AML12 cells, while inhibition of miR-137 expression induced a rebound in XIAP protein expression. In conclusion, TP presensitizes hepatocytes and enhances the sensitivity of hepatocytes to the Fas/FasL pathway by inhibiting the protein expression of XIAP, leading to hepatocyte apoptosis.