C70-06 Altered Regional Oxylipin Metabolism as a Potential Mechanism of Susceptibility to Muco-Obstructive Lung Disease

Abstract Rationale Regional differences in lung physiology contribute to the pathogenesis of muco-obstructive lung diseases (MOLDs). Distal airways are disproportionately affected in MOLDs and are distinguished from proximal airways by mucociliary clearance and cell composition. These differences reflect local variations in cellular signaling and airway surface liquid composition attributed to distal airway susceptibility in MOLDs. Elucidating regional lung lipid composition may identify molecular determinants of mucociliary clearance and additional therapies targeting features of MOLDs. We here compared regional differences in global lipid abundance and cellular expression of lipid-related genes derived from primary human proximal and distal airway epithelial cell cultures under different oxygen tensions to model characteristics of MOLDs. Methods Primary cell cultures of normal human proximal and distal airways were exposed to either normoxic conditions or 1% oxygen in a hypoxic chamber for a period of 5 days (N = 8/region, total N = 32). Apical washes and cell pellets were collected for both untargeted lipidomics and targeted oxylipins analysis by LC-MS/MS. The resulting data were analyzed separately and subsequently compared to scRNA-Seq or snRNA/ATAC multiome datasets derived from proximal and distal airway cultures and lung tissue from normal and cystic fibrosis patients to determine the relative contribution of cell type-specific gene expression to measured lipid abundance. Results Lipidomics assays yielded 760 unique lipids, over 100 of which were significantly different in secreted abundance between proximal and distal airway cultures. Regional differences were predominant in secreted oxylipins as evidenced by increased 15-lipoxygenase 1 (15-LOX) products secreted by proximal airways and increased cyclooxygenase (COX-2) products detected in distal airway apical washes. Interestingly, expression of arachidonate 15-lipoxygenase (ALOX15) was specific to ciliated cells, whereas prostaglandin-endoperoxide synthase 2 (PTGS2) was primarily expressed in distal airway secretory cells and alveolar type 2 cells in vivo. Importantly, differences between 15-LOX product abundance were diminished under hypoxic conditions, which was accompanied by 15-lipoxygenase type B (ALOX15B) expression in both proximal and distal airway cell cultures. Conclusions Our findings indicate that oxylipin production by 15-LOX and COX-2 is regionally distinct and is potentially determined in part by cell type-specific expression of ALOX15 and PTGS2. Additionally, the abatement of baseline differences in oxylipin abundance resulting from hypoxia implicates ALOX15B as an auxiliary mediator of regional oxylipin biosynthesis. Our study identifies potential therapeutic targets for the treatment of MOLDs and warrants additional experiments investigating the functional importance of regional oxylipin metabolism in relation to MOLD pathogenesis. This abstract is funded by: NIH NHLBI R01HL163602, CFF RDP BOUCHER19R0, BOUCHER19XX0, BOUCHERR22G0, and STEVEN24F0, NIH NIDDK DK065988, and a research grant from the Cystic Fibrosis Research Institute