OBJECTIVESTo investigate the relationships between proteasome active center LMP7 subunit and the occurrence and development of alcoholic liver disease.

METHODSEighty male Wistar rats, 170 to 190 g, were randomly divided into two groups: a model group (60 rats) and a control group (20 rats). The model group was given alcoholic intragastric administration plus an olive oil diet. Gavage, twice a day, was used to administer ethanol (30%) in a dose of 4 g/kg/d to the model group rats in the first 4 weeks. In the next 4 weeks, 40% ethanol in a dose of 5 g/kg/d was used, and then in the last 4 weeks, 50% ethanol in a dose of 6 g/kg/d was used. After infusion for 12 weeks, 15 rats (fatty liver group) were sacrificed. Others were divided into two groups; one was the hepatitis group with continued alcohol intragastric administration, the other was the hepatitis control group, receiving equal amounts of normal saline. Both groups were sacrificed after 4 weeks. By HE staining, histological pathology of the rat livers was analyzed. The expression of proteasome LMP7 subunit mRNA was examined by reverse transcription and real-time PCR. The content of LMP7 subunit protein was determined by Western blot.

RESULTSThe LMP7 mRNA level of the fatty liver group was 36% of the control group. The level of the hepatitis control group was 51% of the control group. The level of the hepatitis group was the lowest, which was only 26% of the control group. Western blot results showed that the level of the LMP7 protein content of the control group was 0.50+/-0.01; the level was 0.39+/-0.02 of the fatty liver group; 0.30+/-0.04 of the hepatitis group, and 0.38+/-0.02 of the hepatitis control group. The differences of the LMP7 protein content and mRNA expression correlated with the severity of the pathological alterations of the livers.

CONCLUSIONSThe proteasome LMP7 mRNA expression and protein content decreased in the alcoholic liver group. It may be one of the factors responsible for the decreased activity of proteasome and may play an important role in the pathogenesis of alcoholic liver disease.