C98-07 Sphingolipid Metabolism as a Driver of Sexual Dimorphism in COPD

Background Sex-related differences in the prevalence, clinical presentation, and progression of Chronic Obstructive Pulmonary Disease (COPD) remain incompletely understood. Emerging evidence suggests that sphingolipid metabolism, a key regulator of inflammation, apoptosis, and airway remodeling, may contribute to these differences. We investigated sex-specific alterations in sphingolipid pathways and their relationship to airway structure and function in COPD. Methods Formalin-fixed, paraffin-embedded (FFPE) lung sections from never-smoker (NSC) and ever-smoker (SC) controls and COPD patients were analyzed for ASAH1 (acid ceramidase, which hydrolyzes ceramide into sphingosine) and ORMDL3 (a negative regulator of de novo sphingolipid synthesis) expression by immunofluorescence. Paired plasma levels of key ceramides (C16, C24), sphingosine, and sphingosine-1-phosphate (S1P) were quantified using ELISA and targeted mass spectrometry. GeoMx® spatial transcriptomics was performed on airway regions to assess gene signatures and enriched pathways. Mechanistic validation was conducted in wild-type murine bronchi and primary human airway smooth muscle cells (ASMCs) exposed to cigarette smoke extract (CSE) ± ceramidase or sphingosine kinase inhibitors, and with estradiol stimulation where indicated. Results Immunofluorescence revealed elevated ASAH1 and ORMDL3 expression in COPD airways, most prominently in women, and correlated with airway smooth muscle remodeling. Plasma lipidomics showed sex-specific patterns: male COPD patients had higher circulating ceramides (C16/C24, P = 0.0229), while females displayed elevated S1P/sphingosine ratios (P = 0.0187), indicating enhanced conversion to S1P. Spatial transcriptomics confirmed ASAH1enrichment (P = 0.004) and revealed pathway activation in fatty acid metabolism (P = 6.7 × 10−4) and epithelial-mesenchymal transition (P = 1.3 × 10−4) in female emphysematous airways. Ex vivo, female murine bronchi exhibited greater CSE-induced reactivity, attenuated by sphingosine kinase inhibition, implicating S1P signaling in airway hyperresponsiveness. In human ASMCs, estradiol increased ASAH1, ORMDL3, S1P levels, and contractility, effects amplified by CSE and reversed by ceramidase inhibition, demonstrating estrogen-dependent enhancement of sphingolipid-driven airway remodeling. Conclusions COPD exhibits sex-specific sphingolipid dysregulation, with males showing ceramide accumulation and females displaying heightened S1P signaling and airway hyperreactivity. Targeting ASAH1 and ORMDL3 may represent sex-tailored therapeutic strategies: enhancing ceramidase activity to mitigate ceramide buildup in men, and modulating S1P signaling to limit airway remodeling in women. Future studies should validate these mechanisms in larger, hormonally stratified COPD cohorts. This abstract is funded by: HL149744; HL171622