A new perspective of triptolide-associated hepatotoxicity: the relevance of NF-κB and NF-κB-mediated cellular FLICE-inhibitory protein

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-alpha inhibitor, etanercept, was injected intraperitoneally into mice to investigate whether induction of TNF-alpha by LPS participated in the liver injury induced by TP/LPS co-treatment. Mice and hepatocytes pretreated with TP were stimulated with recombinant TNF-alpha to assess the function of TNF-alpha in TP/LPS co-treatment. Additionally, time-dependent NF-kappa B activation and NF-kappa B-mediated pro-survival signals were measured in vivo and in vitro. Finally, overexpression of cellular FLICE-inhibitory protein (FLIP), the most potent NF-kappa B-mediated pro-survival protein, was measured in vivo and in vitro 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-alpha, revealing the role of TNF-alpha in TP/LPS-induced hepatotoxicity. Mechanistic studies revealed that TP inhibited NF-kappa B dependent pro-survival signals, especially FLIP, induced by LPS/TNF-alpha. Moreover, overexpression of FLIP alleviated TP/LPS-induced hepatotoxicity in vivo and TP/TNF-alpha-induced apoptosis in vitro. Mice and hepatocytes treated with TP were sensitive to TNF-alpha, which was released from LPS-stimulated immune cells. These and other results show that the TP-induced inhibition of NF-kappa B-dependent transcriptional activity and FLIP production are responsible for liver hypersensitivity. (C) 2020 Chinese Pharmaceutical Association and Institute of Materia Medica, Chinese Academy of Medical Sciences. Production and hosting by Elsevier B.V.