Objective   To explore the protective effects of quercetin (QE) on triptolide (TP) induced liver injury and the relevant mechanism.

  Methods   Forty C57BL/6 mice were equally divided into 4 groups, control group, TP model group, 20 mg/kg QE treatment group and 80 mg/kg QE treatment group randomly. The 20 mg/kg and 80 mg/kg QE groups were gastrointestinal administration with QE at the dose of 0.2 mL/10 g for 10 d, twice daily, while other groups were administrated with equivalent normal saline. Four hours post the last dose, animals were gastrointestinal administered with TP at a dose of 500 μg/kg per mouse, except for NS control. All the mice were sacrificed 22 h later, blood and liver tissue samples were collected. The pathologic change of liver tissue was detected by HE staining. The level of aminotransferase (AST) and aspartate alanine aminotransferase (ALT) in serum, and the level of glutathione (GSH), malondialdehyde (MDA) and superoxide dismutase (SOD) in liver tissue homogenates were detected using the commercial kits. The level of interleukin (IL)-17, IL-10 and IL-6 in liver tissue homogenates was measured by ELISA. Hepatic expression of Toll-like receptor 4 (TLR4) was detected by Western blot.

  Results   Compared with the control group, in the TP model group, hepatic lobule structure atrophied and even disappeared, hepatic cell necrosis and inflammatory cell infiltration are obvious. Additionally, in TP model group, serum ALT, AST and MDA levels were significantly increased, SOD and GSH levels were decreased, IL-6 and IL-17 levels were increased, IL-10 levels were decreased, and TLR4 protein levels were increased (P < 0.05). Compared with the TP model group, liver tissue injury and inflammatory cell infiltration were reduced in the QE group, and serum levels of ALT, AST, MDA, IL-6 and IL-17 were all decreased. TLR4 expression was down-regulated (P < 0.05) in both QE groups, and the decease levle was more significant in the high-dose QE group (P < 0.05, compared with the low-dose QE group).

  Conclusion   Quercetin can reduce TP-induced liver injury by reducing oxidative damage, promoting antioxidant and regulating cytokine secretion.