Ethanol Inhibits High-Affinity Immunoglobulin E Receptor (Fc[epsilon]RI) Signaling in Mast Cells by Suppressing the Function of Fc[epsilon]RI-Cholesterol Signalosome

Ethanol has multiple effects on biochemical events in a variety of cell types, including the high-affinity immunoglobulin E receptor (Fc[epsilon]RI) signaling in antigen-activated mast cells. However, the underlying molecular mechanism remains unknown. To get better understanding of the effect of ethanol on Fc[epsilon]RI-mediated signaling we examined the effect of short-term treatment with non-toxic concentrations of ethanol on Fc[epsilon]RI signaling events in mouse bone marrow-derived mast cells. We found that 15 min exposure to ethanol inhibited antigen-induced degranulation, calcium mobilization, expression of proinflammatory cytokine genes (tumor necrosis factor-[alpha], interleukin-6, and interleukin-13), and formation of reactive oxygen species in a dose-dependent manner. Removal of cellular cholesterol with methyl-[beta]-cyclodextrin had a similar effect and potentiated some of the inhibitory effects of ethanol. In contrast, exposure of the cells to cholesterol-saturated methyl-[beta]-cyclodextrin abolished in part the inhibitory effect of ethanol on calcium response and production of reactive oxygen species, supporting lipid-centric theories of ethanol action on the earliest stages of mast cell signaling. Further studies showed that exposure to ethanol and/or removal of cholesterol inhibited early Fc[epsilon]RI activation events, including tyrosine phosphorylation of the Fc[epsilon]RI [beta] and [gamma] subunits, SYK kinases, LAT adaptor protein, phospholipase C[gamma], STAT5, and AKT and internalization of aggregated Fc[epsilon]RI. Interestingly, ethanol alone, and particularly in combination with methyl-[beta]-cyclodextrin, enhanced phosphorylation of negative regulatory tyrosine 507 of LYN kinase. Finally, we found that ethanol reduced passive cutaneous anaphylactic reaction in mice, suggesting that ethanol also inhibits Fc[epsilon]RI signaling under in vivo conditions. The combined data indicate that ethanol interferes with early antigen-induced signaling events in mast cells by suppressing the function of Fc[epsilon]RI-cholesterol signalosomes at the plasma membrane.