Abstract Rationale Alcohol use disorder (AUD) increases risk for respiratory infections by 2-4-fold compared to non-AUD individuals. Alveolar macrophages (AMs) are key to immune defense in the lower respiratory tract, but chronic ethanol (EtOH) exposure impairs AM pathogen phagocytosis and clearance via excessive oxidative stress and suppression of mitochondrial bioenergetics. Hyaluronic acid (HA) is an extracellular matrix polysaccharide, and HA signaling mediates inflammation in numerous lung diseases. In general, low molecular weight HA (LMW HA) is pro-inflammatory, whereas high molecular weight HA (HMW HA), produced by HA synthase 2 (HAS2), is anti-inflammatory. Since EtOH-induced AMs exhibit an anti-inflammatory phenotype, we hypothesized that EtOH promotes HMW HA synthesis in the lung small airways via increased AM HAS2, leading to suppressed AM mitochondrial bioenergetics and impaired phagocytic capacity. Methods Bronchoalveolar lavage fluid (BALF) was collected from mice fed either regular drinking water or drinking water containing 20% w/v EtOH for 12wks, and de-identified BALF samples were collected from subjects with AUD (median AUDIT score=21) and individuals without AUD. A murine AM cell line, MH-S cells, were treated ± 0.08% EtOH for 3d (similar effects seen in AUD) ± 1μM of 4-methylumbelliferone (4-MU, a HAS2 inhibitor) for the last 24h. HA content in BALF and released from MH-S were measured using an ELISA-like assay. HAS1, HAS2, and HAS3 protein levels were measured by immunoblotting. Mitochondrial bioenergetics were assessed by Cell Mito Stress Test using an extracellular flux bioanalyzer. Phagocytic index was determined by measuring internalization and clearance of pH-sensitive fluorescence-labeled Staphylococcus aureus. Results EtOH or AUD increased HA content in BALF and MH-S culture media. EtOH increased HAS2 protein; suppressed mitochondrial basal respiration, ATP-linked respiration, maximal respiration, and spare respiratory capacity; and impaired S. aureus phagocytosis and clearance. Inhibition of HAS2 via treatment with 4-MU reversed these EtOH-induced effects. Conclusions AUD may increase susceptibility to respiratory infections via enhanced HA content in the lungs, which can suppress AM mitochondrial bioenergetics and impair phagocytic capacity. Our data support therapeutic strategies to inhibit HAS2 activity to improve lung immunometabolism in AUD. This abstract is funded by: R01AA026086 (SMY), 1IK2CX000643 (AJM), F31AA029938 (KMC)
Yeligar et al. (2026) studied this question.