The role of neutrophils in triptolide-induced liver injury.

Triptolide (TP) induces severe liver injury, but its hepatotoxicity mechanisms are still unclear. Inflammatory responses may be involved in the pathophysiology. Neutrophils are the first-line immune effectors for sterile and non-sterile inflammatory responses. Thus, the aim of the present study was to investigate the neutrophilic inflammatory response in TP-induced liver injury in C57BL/6 mice. Our results showed that neutrophils were recruited and accumulated in the liver, which was parallel to or slightly after the development of liver injury. Neutrophils induced release of myeloperoxidase and up-regulation of CD11b, which caused cytotoxicity and hepatocyte death. Hepatic expressions of CXL1, TNF-α, IL-6, and MCP1 were increased significantly to regulate neutrophils recruitment and activation. Up-regulation of toll like receptors 4 and 9 also facilitated neutrophils infiltration. Moreover, neutrophils depletion using an anti-Gr1 antibody showed mild protection against TP overdose. These results indicated that neutrophils accumulation might be the secondary response, not the cause of TP-induced liver injury. In conclusion, the inflammatory response including neutrophil infiltration may play a role in TP-induced hepatotoxicity, but may not be severe enough to cause additional liver injury.

Activation of natural killer T cells contributes to triptolide-induced liver injury in mice.

Triptolide (TP) is the main active ingredient of Tripterygium wilfordii Hook.f, which has attracted great interest due to its promising efficacy for autoimmune diseases and tumors. However, severe adverse reactions, especially hepatotoxicity, have restricted its approval in the market. In the present study we explored the role of hepatic natural killer T (NKT) cells in the pathogenesis of TP-induced liver injury in mice. TP (600 µg/kg/day, i.g.) was administered to female mice for 1, 3, or 5 days. We found that administration of TP dose-dependently induced hepatotoxicity, evidenced by the body weight reduction, elevated serum ALT and AST levels, as well as significant histopathological changes in the livers. However, the mice were resistant to the development of TP-induced liver injury when their NKT cells were depleted by injection of anti-NK1.1 mAb (200 µg, i.p.) on days -2 and -1 before TP administration. We further revealed that TP administration activated NKT cells, dominantly releasing Th1 cytokine IFN-γ, recruiting neutrophils and macrophages, and leading to liver damage. After anti-NK1.1 injection, however, the mice mainly secreted Th2 cytokine IL-4 in the livers and exhibited a significantly lower percentage of hepatic infiltrating neutrophils and macrophages upon TP challenge. The activation of NKT cells was associated with the upregulation of Toll-like receptor (TLR) signaling pathway. Collectively, these results demonstrate a novel role of NKT cells contributing to the mechanisms of TP-induced liver injury. More importantly, the regulation of NKT cells may promote effective measures that control drug-induced liver injury.