Department of Medicine, University of Massachusetts Medical School, Worcester, MA.
Hepatology. 2019 Dec;70(6):2123-2141. doi: 10.1002/hep.30766. Epub 2019 Jun 24.
Cellular homeostais, that is normally maintained through autophagy, is disrupted in alcoholic liver disease (ALD). Because autophagy and exosome biogenesis share common elements, we hypothesized that increased exosome production in ALD may be linked to disruption of autophagic function. We found impaired autophagy both in ALD and alcoholic hepatitis (AH) mouse models and human livers with ALD as indicated by increased hepatic p62 and LC3-II levels. Alcohol reduced autophagy flux in vivo in chloroquine-treated mice as well as in vitro in hepatocytes and macrophages treated with bafilomycin A. Our results revealed that alcohol targets multiple steps in the autophagy pathway. Alcohol-related decrease in mechanistic target of rapamycin (mTOR) and Ras homolog enriched in brain (Rheb), that initiate autophagy, correlated with increased Beclin1 and autophagy-related protein 7 (Atg7), proteins involved in phagophore-autophagosome formation, in ALD. We found that alcohol disrupted autophagy function at the lysosomal level through decreased lysosomal-associated membrane protein 1 (LAMP1) and lysosomal-associated membrane protein 2 (LAMP2) in livers with ALD. We identified that micro-RNA 155 (miR-155), that is increased by alcohol, targets mTOR, Rheb, LAMP1, and LAMP2 in the authophagy pathway. Consistent with this, miR-155-deficient mice were protected from alcohol-induced disruption of autophagy and showed attenuated exosome production. Mechanistically, down-regulation of LAMP1 or LAMP2 increased exosome release in hepatocytes and macrophages in the presence and absence of alcohol. These results suggested that the alcohol-induced increase in exosome production was linked to disruption of autophagy and impaired autophagosome and lysosome function. Conclusion: Alcohol affects multiple genes in the autophagy pathway and impairs autophagic flux at the lysosome level in ALD. Inhibition of LAMP1 and LAMP2 promotes exosome release in ALD. We identified miR-155 as a mediator of alcohol-related regulation of autophagy and exosome production in hepatocytes and macrophages.
细胞内稳态通常通过自噬来维持，但在酒精性肝病 (ALD) 中会被打乱。由于自噬和外泌体生物发生共享共同的元素，我们假设在 ALD 中增加外泌体的产生可能与自噬功能的破坏有关。我们发现，在 ALD 和酒精性肝炎 (AH) 小鼠模型以及患有 ALD 的人类肝脏中，自噬都受到了损害，这表现为肝组织中 p62 和 LC3-II 水平的升高。在氯喹处理的小鼠体内以及在经巴弗洛霉素 A 处理的肝细胞和巨噬细胞中，酒精都降低了自噬流。我们的结果表明，酒精靶向自噬途径的多个步骤。酒精相关的雷帕霉素 (mTOR) 和 Ras 同源物富集在脑中 (Rheb) 减少，这会启动自噬，与 ALD 中 Beclin1 和自噬相关蛋白 7 (Atg7) 的增加相关，这些蛋白参与吞噬体-自噬体的形成。我们发现，酒精通过降低肝脏中酒精性肝病的溶酶体相关膜蛋白 1 (LAMP1) 和溶酶体相关膜蛋白 2 (LAMP2)，在溶酶体水平破坏了自噬功能。我们确定了 micro-RNA 155 (miR-155)，它被酒精上调，在自噬途径中靶向 mTOR、Rheb、LAMP1 和 LAMP2。与此一致，miR-155 缺陷型小鼠免受酒精引起的自噬破坏的保护作用，并显示出减弱的外泌体产生。从机制上讲，在存在和不存在酒精的情况下，下调 LAMP1 或 LAMP2 会增加肝细胞和巨噬细胞中外泌体的释放。这些结果表明，酒精诱导的外泌体产生增加与自噬的破坏以及自噬体和溶酶体功能的受损有关。结论：酒精会影响自噬途径中的多个基因，并在 ALD 中破坏溶酶体水平的自噬流。抑制 LAMP1 和 LAMP2 可促进 ALD 中外泌体的释放。我们确定 miR-155 是酒精调节肝细胞和巨噬细胞自噬和外泌体产生的介质。
