Complement C3a Receptor 1 and Complement C5a Receptor 1 Are Dual Contributors of Chronic-Plus-Binge-Induced Hepatic...

Alcohol-associated liver disease (ALD) is the leading cause of liver-related mortality worldwide. ALD progresses through chronic, nonresolving inflammation and immune dysfunction, yet the mechanisms driving this dysfunction remain unclear. Here, we characterized the intracellular complement system, the complosome, using explanted liver tissue from patients with ALD, chronic-plus-binge feeding to anaphylatoxin receptor-deficient mice, and in vitro models of macrophage activation. Anaphylatoxin receptor expression was increased in CD68⁺ macrophages from ALD explants compared with healthy donor liver. In ethanol-fed mice, chronic-plus-binge exposure increased surface expression of complement C3a receptor 1 (C3aR1) and complement C5a receptor 1 (C5aR1), as well as the intracellular C5aR1 pool on CD11b^intF4/80^hi Kupffer cells. C5aR1^-/-, but not C3aR1^-/- mice, were protected from binge ethanol-induced liver injury, whereas deficiency of either receptor protected from ethanol-induced expression of proinflammatory cytokines and hepatic immune cell recruitment. In bone marrow-derived macrophages, ethanol and lipopolysaccharide treatment increased expression of intracellular complement components C3, C5, C3aR1, and C5aR1; anaphylatoxin receptors were co-expressed with lysosomal and mitochondrial membrane markers, supporting a functional intracellular signaling compartment. Lipopolysaccharide-induced NOD-like receptor protein 3 (NLRP3) expression and IL-1β production were attenuated in C3aR1- and C5aR1-deficient bone marrow-derived macrophages. Notably, C3aR1/C5aR1^-/- double-knockout mice were protected from ethanol-induced liver injury and inflammation. In conclusion, ethanol enhances intracellular complosome components in macrophages and anaphylatoxin receptors promote nonresolving inflammation in ALD.