蛋白酶体活性中心低分子量多肽7亚基在酒精性肝病中的表达及其意义

An experimental study on the relationship between proteasome LMP7 subunit and alcoholic liver disease

目的研究蛋白酶体活性中心低分子量多肽7（LMP7）亚基与酒精性肝病发生和发展的关系。方法采用酒精灌胃的方法建立大鼠酒精性脂肪肝模型，HE染色观察肝脏病理变化，实时荧光定量RT-PCR测定肝组织中LMP7亚基mRNA的表达情况，Western blot测定LMP7亚基蛋白含量。结果肝脏病理学结果显示：脂肪肝组主要为小泡性脂肪变，小叶内点状坏死，肝小叶结构完整；肝炎组肝小叶结构破坏，可见明显淤血、Mallory小体、炎性细胞浸润，肝细胞明显肿胀；肝炎对照组病变减轻，肝小叶结构明显恢复，肝内瘀血显著减轻，可见散在点状坏死。与正常对照组相比，脂肪肝组LMP7亚基mRNA水平为对照组的36％，肝炎对照组为51％，肝炎组为26％。Western blot结果：正常对照组LMP7亚基蛋白含量为0．50±0．01，脂肪肝组为0．39±0．02，肝炎对照组为0．38±0．02，肝炎组为0．30±0．04。结论蛋白酶体活性中心LMP7亚基mRNA及蛋白的表达在酒精性肝病组下调，这可能是酒精性肝病蛋白酶体活性下降的原因之一，它在酒精性肝病中可能起重要作用。

Objective To investigate the relationships between proteasome active center LMP7 subunit and the occurrence and development of alcoholic liver disease. Methods Eighty 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^-1·d^-1 to the model group rats in the first 4 weeks. In the next 4 weeks, 40% ethanol in a dose of 5 g·kg^-1·d^-1 was used, and then in the last 4 weeks, 50% ethanol in a dose of 6 g·kg^-1·d^-1 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 subuint mRNA was examined by reverse transcription and real-time PCR. The content of LMP7 subunit protein was determined by Western blot. Results The 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 hepatits control group. The differences of the LMP7 protein content and mRNA expression correlated with the severity of the pathological alterations of the livers. Condusions The 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.