Enhanced lupus progression in alcohol-administered Fc gamma receptor-IIb–deficiency lupus mice, partly through leaky gut-induced inflammation

Alcohol can induce a leaky gut, with translocation of microbial molecules from the gut into the blood circulation. Although the contribution of inflammation to organ-mediated damage in lupus has been previously demonstrated, the mechanistic roles of alcohol consumption in lupus activation are not known. Herein, we tested the effects of 10-week lasting alcohol administration on organ damages and immune responses in 8-week-old lupus-prone Fc gamma receptor IIb–deficient (FcγRIIb^−/−) mice. Our study endpoints were evaluation of systemic inflammation and assessment of fecal dysbiosis along with endotoxemia. In comparison with alcohol-administered wild-type mice, FcγRIIb^−/− mice demonstrated more prominent liver damage (enzyme, histological score, apoptosis, malondialdehyde oxidant) and serum interleukin(IL)-6 levels, despite a similarity in leaky gut (fluorescein isothiocyanate–dextran assay, endotoxemia and gut occludin-1 immunofluorescence), fecal dysbiosis (microbiome analysis) and endotoxemia. All alcohol-administered FcγRIIb^−/− mice developed lupus-like characteristics (serum anti-dsDNA, proteinuria, serum creatinine and kidney injury score) with spleen apoptosis, whereas control FcγRIIb^−/− mice showed only a subtle anti-dsDNA. Both alcohol and lipopolysaccharide (LPS) similarly impaired enterocyte integrity (transepithelial electrical resistance), and only LPS, but not alcohol, upregulated the IL-8 gene in Caco-2 cells. In macrophages, alcohol mildly activated supernatant cytokines (tumor necrosis factor-α and IL-6), but not M1 polarization–associated genes (IL-1β and iNOS), whereas LPS prominently induced both parameters (more prominent in FcγRIIb^−/− macrophages than wild type). There was no synergy in LPS plus alcohol compared with LPS alone in both enterocytes and macrophages. In conclusion, alcohol might exacerbate lupus-like activity partly through a profound inflammation from the leaky gut in FcγRIIb^−/− mice.