title: MFG-E8 and HMGB1 are involved in the mechanism underlying alcohol-induced impairment of macrophage efferocytosis.
abstract: 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.
authors.affiliation: 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.
authors.forename: Xiao
authors.initials: X
authors.lastname: Wang
authors.forename: Heng-Fu
authors.initials: HF
authors.lastname: Bu
authors.forename: Wei
authors.initials: W
authors.lastname: Zhong
authors.forename: Akihiro
authors.initials: A
authors.lastname: Asai
authors.forename: Zhanxiang
authors.initials: Z
authors.lastname: Zhou
authors.forename: Xiao-di
authors.initials: XD
authors.lastname: Tan
mesh_terms: D000818:Animals; D000954:Antigens, Surface / Q000502:physiology*; D002460:Cell Line; D000431:Ethanol / Q000008:administration & dosage*; D024243:HMGB1 Protein / Q000502:physiology*; D017737:Macrophages, Peritoneal / Q000187:drug effects* / Q000502:physiology; D008297:Male; D051379:Mice; D008810:Mice, Inbred C57BL; D008894:Milk Proteins; D010587:Phagocytosis / Q000187:drug effects / Q000502:physiology*; D051381:Rats
chemical_list: D000954:Antigens, Surface; D024243:HMGB1 Protein; C582808:HMGB1 protein, mouse; C490919:Mfge8 protein, mouse; D008894:Milk Proteins; D000431:Ethanol
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