Occupational endotoxin exposure, DNA methylation changes, and immune-cell remodeling: an epigenome-wide association study in two cohorts

Background: Millions of textile and agricultural workers inhale organic dust containing endotoxin, an exposure associated with impaired respiratory function. However, the underlying biological pathways remain unclear. We conducted a two-cohort epigenome-wide association study (EWAS) to identify airborne endotoxin-associated DNA methylation (DNAm) alterations and pathways. Methods: In the discovery phase, we compared blood DNAm in 281 endotoxin-exposed cotton workers and 253 unexposed silk-workers from the Shanghai Textile Worker Study (STWS) measured using Illumina MethylationEPICv2 arrays. STWS endotoxin assessment combined detailed work histories and onsite measurements. For targeted parallel validation, we tested STWS signals in 686 incident lung cancer cases and 683 matched controls from the Shanghai Women's Health Study (SWHS), using occupation-derived low, medium, or high exposure-intensity ranks based on published evidence. To gain biological insight, we analyzed pathway enrichment, immune-cell composition, DNAm inflammation risk scores (IRSs), and respiratory phenotype associations in STWS. Results: In STWS, we identified 36 epigenome-wide significant DNAm sites (P<5e-8), of which, 35 were hypomethylated. Among 30 sites testable in SWHS, 18 had concordant effect directions, and four were nominally significant: cg11869499 (POLG; P=0.041), cg16290931 (TSKS; P=0.044), cg05019530 (EPIC1; P=0.042), and cg26033526 (PSMB9/TAP1; P=0.013). Enrichment implicated immune and signal-transduction pathways, including IgSF cell-adhesion-molecule signaling (FDR=8.2e-6;). Neutrophil were higher in cotton workers than in silk workers (63.5% vs 58.9%, p=7.52e-10). Cumulative endotoxin was associated with higher CRP-based IRSs, which showed the most consistent associations with lower lung function and airflow obstruction. Conclusions: Our EWAS findings suggest that occupational endotoxin may operate partly through immune-cell composition and inflammatory pathways.