Objective: To test whether nonalcoholic hepatic steatosis sensitizes carbon tetrachloride (CCl4)-induced liver injury, and to assess the therapeutic effect of Chinese medicine extracts of Dangfei Liganning capsules (当飞利肝宁胶囊) and their potential underlying mechanisms. Methods: Male Wistar rats were fed a high-fat diet to induce nonalcoholic fatty liver disease (NAFLD) or a normal diet (N). Eight weeks later, a nonlethal dose of CCl4 was applied intraperitoneally. From the start, HF-CCl4 rats were administered daily Dangyao extracts (D), Dangfei Liganning capsules (DF), or Diammonium Glycyrrhizinate (G) intragastrically. Rats were sacrificed 48 h after CCl4 administration. In addition to serum biochemistry, liver histopathology was observed using hematoxylin-eosin (HE) and oil red O staining, and hepatic levels of triglyceride (TG), malondialdehyde (MDA), glutathione (GSH), superoxide dismutase (SOD), caspase-3 activation and cytochrome P450 (CYP2E1) expression were assessed. Results: There was almost no response to the nonlethal dose of CCl4 in the N control group. However, the HF group demonstrated massive steatosis, and elevated levels of serum ALT and AST, liver MDA, CYP2E1, and caspase-3 activation, whereas the levels of GSH and SOD were significantly decreased. All indexes assessed were dramatically worse in the HF-CCl4 group compared to the HF group, in addition to the more severe steatosis, hepatocyte ballooning, and inflammatory infiltration apparent in the centrilobular area. The medicines we tested affected the pathological changes in HF-CCl4 rats to differing degrees: DF and G led to improvements in all of the above examined indexes, including an obvious improvement in histopathology, and DF improved serum ALT and MDA levels more markedly than G, whereas D extracts produced only mild liver injury attenuation. Conclusion: Liver with NAFLD is more sensitive to hepatotoxicity; furthermore, the disrupted balance of oxidative stress and anti-oxidant defense contributes to the underlying mechani
