Center for Intestinal and Liver Inflammation Research, Ann and Robert H. Lurie Children's Hospital of Chicago Research Center, Feinberg School of Medicine, Northwestern University, Chicago, Illinois 60611, USA.
Mol Med. 2013 Jul 24;19(1):170-82. doi: 10.2119/molmed.2012.00260.
Efferocytosis is a unique phagocytic process for macrophages to remove apoptotic cells in inflammatory loci. This event is maintained by milk fat globule-EGF factor 8 (MFG-E8), but attenuated by high mobility group box 1 (HMGB1). Alcohol abuse causes injury and inflammation in multiple tissues. It alters efferocytosis, but precise molecular mechanisms for this effect remain largely unknown. Here, we showed that acute exposure of macrophages to alcohol (25 mmol/L) inhibited MFG-E8 gene expression and impaired efferocytosis. The effect was mimicked by hydrogen peroxide. Moreover, N-acetylcysteine (NAC), a potent antioxidant, blocked acute alcohol effect on inhibition of macrophage MFG-E8 gene expression and efferocytosis. In addition, recombinant MFG-E8 rescued the activity of alcohol-treated macrophages in efferocytosis. Together, the data suggest that acute alcohol exposure impairs macrophage efferocytosis via inhibition of MFG-E8 gene expression through a reactive oxygen species dependent mechanism. Alcohol has been found to suppress or exacerbate immune cell activities depending on the length of alcohol exposure. Thus, we further examined the role of chronic alcohol exposure on macrophage efferocytosis. Interestingly, treatment of macrophages with alcohol for seven days in vitro enhanced MFG-E8 gene expression and efferocytosis. However, chronic feeding of mice with alcohol caused increase in HMGB1 levels in serum. Furthermore, HMGB1 diminished efferocytosis by macrophages that were treated chronically with alcohol, suggesting that HMGB1 might attenuate the direct effect of chronic alcohol on macrophage efferocytosis in vivo. Therefore, we speculated that the balance between MFG-E8 and HMGB1 levels determines pathophysiological effects of chronic alcohol exposure on macrophage efferocytosis in vivo.
吞噬作用是巨噬细胞清除炎症部位凋亡细胞的一种独特的吞噬过程。这一过程由乳脂肪球 EGF 因子 8(MFG-E8)维持,但被高迁移率族蛋白 1(HMGB1)所减弱。酒精滥用会导致多个组织的损伤和炎症。它改变了吞噬作用,但这种效应的确切分子机制在很大程度上仍不清楚。在这里,我们表明巨噬细胞急性暴露于酒精(25mmol/L)会抑制 MFG-E8 基因表达并损害吞噬作用。过氧化氢可模拟这种效应。此外,N-乙酰半胱氨酸(NAC),一种有效的抗氧化剂,可阻断酒精对巨噬细胞 MFG-E8 基因表达和吞噬作用的急性抑制作用。此外,重组 MFG-E8 挽救了酒精处理的巨噬细胞在吞噬作用中的活性。总之,数据表明,急性酒精暴露通过依赖活性氧物质的机制抑制 MFG-E8 基因表达,从而损害巨噬细胞吞噬作用。已经发现酒精可以抑制或加剧免疫细胞的活性,这取决于酒精暴露的时间长短。因此,我们进一步研究了慢性酒精暴露对巨噬细胞吞噬作用的作用。有趣的是,体外用酒精处理巨噬细胞 7 天会增强 MFG-E8 基因表达和吞噬作用。然而,慢性给小鼠喂食酒精会导致血清中 HMGB1 水平升高。此外,HMGB1 降低了长期用酒精处理的巨噬细胞的吞噬作用,表明 HMGB1 可能减弱了慢性酒精对体内巨噬细胞吞噬作用的直接影响。因此,我们推测 MFG-E8 和 HMGB1 水平之间的平衡决定了慢性酒精暴露对体内巨噬细胞吞噬作用的病理生理影响。