Alcohol and Cannabinoids Differentially Regulate Macrophage Polarization, with Co-Exposure Producing an Antagonistic Immunomodulatory Effect

Concurrent alcohol and cannabis use (“crossfading”) is increasingly prevalent, especially among adolescents, yet its toxicological impact on pulmonary innate immunity remains largely unexplored. Alveolar macrophages (AMs) orchestrate inflammatory responses in the lung, and dysregulated macrophage polarization is a hallmark of alcohol-associated lung disease. Although alcohol and cannabinoids individually modulate immune function, the mechanisms by which their co-exposure alters macrophage activation and inflammatory signaling in the lung are largely unknown. AMs are highly sensitive to xenobiotic exposure and play a central role in regulating inflammatory and cytotoxic responses. In this study, we investigated how acute ethanol exposure, synthetic cannabinoid exposure, and their combined exposure affect macrophage viability, polarization, and the release of inflammatory mediators via cannabinoid receptor (CB1R/CB2R)-dependent pathways. Human THP-1-derived macrophages and KG-1 macrophage-like cells were exposed to ethanol, the CB1/CB2 agonist WIN 55,212-2, or both, with selective pharmacological antagonism of CB1R and CB2R. Ethanol exposure activated and polarized macrophages toward a pro-inflammatory M1 phenotype, accompanied by increased secretion of pro-inflammatory cytokines MCP-1, TGF-α, IFN-β, IL-6, and TNF-α. In contrast, WIN 55,212-2 promoted anti-inflammatory M2 polarization and increased IL-10 and IL-4 production. Notably, co-exposure to ethanol and WIN produced an antagonistic immunomodulatory response, characterized by the suppression of ethanol-induced M1 polarization and attenuation of pro-inflammatory cytokine release. Mechanistically, pharmacological CB1R blockade reduced ethanol-induced M1 polarization and cytokine secretion, whereas CB2R blockade exacerbated these effects, underscoring divergent roles for cannabinoid receptors in regulating pulmonary macrophage responses. This study provides novel findings demonstrating the mechanism by which alcohol–cannabinoid co-use reshapes macrophage immune phenotypes and identifies the endocannabinoid system as a potential therapeutic target for alcohol-related inflammatory lung disease.