OBJECTIVE  To evaluate the protective effect of different doses of epigallocatechingallate(EGCG) on cisplatin-induced liver injury in rats and to explore its possible mechanism.

METHODS  Sixty-six Wistar rats were randomly divided into seven groups: control group, cisplatin group(CIS), low dose group(20 mg·kg⁻¹ EGCG+CIS), middle dose group(40 mg·kg⁻¹ EGCG+CIS), high dose group(80 mg·kg⁻¹ EGCG+CIS), EGCG control group(40 mg·kg⁻¹ EGCG), inhibitor group(40 mg·kg⁻¹ EGCG+CIS+ML385). Rats in each group were orally administered with corresponding doses of drugs continuously for 28 d. On the 26th day, except for the Control group and EGCG control group, the rats were intraperitoneally injected with CIS(7 mg·kg⁻¹) to establish the liver injury model. In the inhibitor group, ML385(30 mg·kg⁻¹) was injected intraperitoneally on the 26th day, and serum and liver tissues were collected on the 29th day. Firstly, the serum ALT and AST levels were measured by biochemical analyzer, and then the liver tissue lesions were observed by HE staining to preliminarily evaluate the protective effect of EGCG on liver injury induced by CIS in rats, and the optimal dose was screened. Secondly, the ultrastructure of liver tissue was observed by electron microscope. TUNEL was used to detect the apoptosis of liver cells. The contents of SOD, GSH and MDA in liver tissue were determined by kits. Western blotting was used to detect the expression of apoptosis-related proteins(Cleaved Caspase-3, Bcl-2, Bax) and Keap1/Nrf2 signaling pathway-related proteins.

RESULTS  Compared with the Control group, the body weight of rats in the CIS group decreased significantly(P<0.05), and serum ALT and AST levels were significantly increased(P<0.01); Histopathological examination showed irregular arrangement of hepatic cords, infiltration of a large number of inflammatory cells, and severe liver injury. Compared with the CIS group, the body weight of the rats in the medium dose group increased significantly(P<0.05), and liver function indexes decreased significantly(P<0.01), the structure of hepatic cords was clear and inflammatory cell infiltration was relieved. The protective effect of low and high doses was not obvious. Therefore, the medium dose group(40 mg·kg⁻¹ EGCG) was selected for the subsequent experiment. Transmission electron microscopy results showed that EGCG pretreatment could improve mitochondrial swelling. TUNEL results showed that EGCG pretreatment reduced the apoptosis rate of liver tissue cells. The results of the kit showed that compared with the CIS group, the MDA content of liver tissue in the medium dose EGCG group was significantly decreased(P<0.05), and the activities of SOD and GSH were significantly increased(P<0.05); Western blotting results showed that EGCG could up-regulate the protein expressions of Nrf2, Bcl-2, NQO1 and HO-1, and down-regulate the protein expressions of Bax, Keap1 and Cleaved Caspase-3 in rat liver tissues. The protective effect of EGCG was abolished by the administration of ML385, an inhibitor of Nrf2 signaling pathway.

CONCLUSION  EGCG pretreatment(40 mg·kg⁻¹) may alleviate CIS-induced liver injury in rats by improving oxidative stress and apoptosis in liver tissue through Keap1/Nrf2 signaling pathway.