ABSTRACT
Previously, we proposed a new perspective of triptolide (TP)-associated hepatotoxicity: liver hypersensitivity upon lipopolysaccharide (LPS) stimulation. However, the mechanisms for TP/LPS-induced hepatotoxicity remained elusive. The present study aimed to clarify the role of LPS in TP/LPS-induced hepatotoxicity and the mechanism by which TP induces liver hypersensitivity upon LPS stimulation. TNF- inhibitor, etanercept, was injected intraperitoneally into mice to investigate whether induction of TNF- by LPS participated in the liver injury induced by TP/LPS co-treatment. Mice and hepatocytes pretreated with TP were stimulated with recombinant TNF- to assess the function of TNF- in TP/LPS co-treatment. Additionally, time-dependent NF-B activation and NF-B-mediated pro-survival signals were measured and . Finally, overexpression of cellular FLICE-inhibitory protein (FLIP), the most potent NF-B-mediated pro-survival protein, was measured and to assess its function in TP/LPS-induced hepatotoxicity. Etanercept counteracted the toxic reactions induced by TP/LPS. TP-treatment sensitized mice and hepatocytes to TNF-, revealing the role of TNF- in TP/LPS-induced hepatotoxicity. Mechanistic studies revealed that TP inhibited NF-B dependent pro-survival signals, especially FLIP, induced by LPS/TNF-. Moreover, overexpression of FLIP alleviated TP/LPS-induced hepatotoxicity and TP/TNF--induced apoptosis . Mice and hepatocytes treated with TP were sensitive to TNF-, which was released from LPS-stimulated immune cells. These and other results show that the TP-induced inhibition of NF-B-dependent transcriptional activity and FLIP production are responsible for liver hypersensitivity.