Triptolide leads to hepatic intolerance to exogenous lipopolysaccharide and natural-killer-cell mediated hepatocellular damage by inhibiting MHC class I molecules

•NK cells mediate hepatocellular damage in TP induced hepatic LPS intolerance.•TP exhibits potent inhibitory effect on hepatocyte MHC-I of B6 mice.•MHC-I inhibition leads to NK cell mediated cytotoxicity against self-hepatocytes.•Overexpression of hepatocyte H-2Kb protects against TP- and LPS-induced LPS injury. Tripterygium wilfordii Hook. F (TWHF) is used as a traditional Chinese medicine, called thunder god vine, based on its efficacy for treating inflammatory diseases. However, its hepatotoxicity has limited its clinical application. Triptolide (TP) is the major active and toxic component of TWHF. Previous studies reported that a toxic pretreatment dose of TP leads to hepatic intolerance to exogenous lipopolysaccharide (LPS) stimulation, and to acute liver failure, in mice, but the immune mechanisms of TP-sensitised hepatocytes and the TP-induced excessive immune response to LPS stimulation are unknown. To identify both the key immune cell population and mechanism involved in TP-induced hepatic intolerance of exogenous LPS. In vitro and in vivo experiments were conducted to investigate the inhibitory signal of natural killer (NK) cells maintained in hepatocytes, and the ability of TP to impair that signal. Flow cytometry was performed to determine NK cell activity and hepatocyte histocompatibility complex (MHC) class I molecules expression; the severity of liver injury was determined based on blood chemistry values, and drug- or cell-mediated hepatocellular damage, by measuring lactate dehydrogenase (LDH) release. In vivo H-2Kb transduction was carried out using an adeno-associated viral vector. Interferon (IFN)-γ-mediated necroptosis occurred in C57BL/6N mice treated with 500 μg TP/kg and 0.1 mg LPS/kg to induce fulminant hepatitis. Primary hepatocytes pretreated with TP were more prone to necroptosis when exposed to recombinant murine IFN-γ. In mice administered TP and LPS, the intracellular IFN-γ levels of NK cells increased significantly. Subsequent study confirmed that NK cells were activated and resulted in potent hepatocellular toxicity. In vivo and in vitro TP administration significantly inhibited MHC class I molecules in murine hepatocytes. An in vitro analysis demonstrated the susceptibility of TP-pretreated hepatocytes to NK-cell-mediated cytotoxicity, an effect that was significantly attenuated by the induction of hepatocyte MHC-I molecules by IFN-α. In vivo induction or overexpression of hepatocyte MHC-I also protected mouse liver against