Ethanol suppresses phagosomal adhesion maturation, Rac activation, and subsequent actin polymerization during FcγR-mediated phagocytosis

Clinical and laboratory investigations have provided evidence that ethanol suppresses normal lung immunity. Our initial studies revealed that acute ethanol exposure results in transient suppression of phagocytosis of Pseudomonas aeruginosa by macrophages as early as 3 h after initial exposure. Focusing on mechanisms by which ethanol decreases macrophage Fcγ-receptor (FcγR) phagocytosis we targeted the study on the focal adhesion and cytoskeletal elements that are necessary for phagosome progression. Ethanol inhibited macrophage phagocytosis of IgG-coated bead recruitment of actin to the site of the phagosome, dampened the phosphorylation of vinculin, but had no effect on paxillin phosphorylation suggesting a loss in “phagosomal adhesion” maturation. Moreover, our observations revealed that FcγR-phagocytosis induced Rac activation, which was increased by only 50% in ethanol exposed cells, compared to 175% in the absence of ethanol. This work is the first to show evidence of the cellular mechanisms involved in the ethanol-induced suppression of FcγR-mediated phagocytosis.

► In vivo ethanol attenuates Pseudomonas aeruginosa phagocytosis by alveolar macrophages.
► Acute ethanol suppresses vinculin phosphorylation during FcγR phagosytosis.
► Actin polymerization at phagosome is inhibited with prior ethanol exposure.
► Lower Rac, but not Rho, activity can explain the decreased phagosome maturation.
► Paxillin phosphorylation or VavGEF were not altered following ethanol exposure.