Abstract: BACKGROUND: Studies have shown NOX protein expression up-regulated in myocardium, skeletal muscle, kidney, and brain under stess conditions, while its role in alcoholic liver damage pathology was unclear.
OBJECTIVE: To investigate the role of NOX mediated oxidative stress under liver normal physiology and alcoholic liver damage pathology.
METHODS: 6 Male C57BL/6J mice were randomly divided into normal control group and normal drug group, with 3 mice in each group. Mice in normal drug group were intraperitoneally injected by 10 mg/Kg Apocynin for 4 consecutive days, while normal control group was injected with the same dose of solvent. Lipid metabolism related indexes in serum and liver tissues of mice were detected, and the protein expressions of NOX2 and NOX4 in liver tissues were determined. 18 Male C57BL/6J mice were randomly divided into common group, alcoholic liver damage (ALD) group and ALD combined with drug group, with 6 mice in each group. ALD model was constructed by Lieber-DeCarli liquid diet with TP4030C in common group as well as TP4030B in ALD group and ALD combined with drug group. Mice in ALD combined with drug group was intraperitoneally injected with 10 mg/Kg Apocynin 6 days a week for 6 weeks, while mice in other two groups were injected with the same dose of solvent. The mice body weight, epididymal fat relative content, liver index and skeletal muscle relative content, was either recorded or calculated. Glucose tolerance test was used to detect mice insulin sensitivity, and the serum liver function damage (alanine aminotransferase, ALT and Aspartate aminotransferase, AST) and lipid metabolism indexes were measured by commercial chemical kits. The liver tissue malondialdehyde (MDA), superoxide dismutase (SOD), triglycerides (TG), high-density lipoprotein cholesterol (HDL-C), and low-density lipoprotein cholesterol (LDL-C) was determined by colorimetry. The change of hepatocyte damage was observed by using HE staining. Western blot was applied to detect NOX2, and NOX4 protein expression in liver tissue. Ethic approval was obtained from the Experimental Animal Ethics Committee of Hunan University in China (approval No. HNUBI0202101007).
RESULTS AND CONCLUSION: Compared with normal control group, the content of TG in liver tissue and the levels of serum ALT and AST increased significantly in normal drug group; the level of HDL-C and the expressions of NOX2 and NOX4 decreased evidently in liver tissue. Compared to common group, the relative content of epididymal fat, as well as the content of HDL-C in both serum and liver tissue were strikingly decreased in ALD group and the level of serum ALT increased; the levels of TG, LDL-C and the protein expression of NOX4 were particularly increased in liver tissue. Compared to ALD group, the levels of HDL-C in both serum and liver tissue increased notably in ALD combined with drug group ; the serum ALT level, the content of LDL-C in liver and the protein expression of NOX4 decreased remarkably. In conclusion, inhibiting NOX alleviates hepatocyte damage and lipid metabolism disorder; Apocynin has different effects on liver physiology and pathological state of ALD.

Key words: alcoholic liver damage, oxidative stress, NADPH oxidase, NOX4, lipid metabolism, apocynin