Background: Given the same amount of exposure to tobacco smoke, women are more likely to develop more severe airflow limitation at an earlier age than men. Also, at all stages of chronic obstructive pulmonary disease (COPD) severity, men have more severe emphysema than women. Sphingolipids are metabolically active entities involved in the control of inflammation, and their expression patterns are estrogen-dependent.

Aims: In COPD, there is an alteration of sphingosine pathways and metabolites. We aimed to determine whether estrogen levels affect the sphingosine pathway in COPD.

Methods: Bronchi harvested from male and female C57BL/6 mice were incubated with cigarette smoke extract (CSE) and estradiol to perform functional studies + a sphingosine inhibitor (SKI-II) ex-vivo. Primary human lung epithelial cells were exposed to increasing concentrations of CSE, to perform molecular studies in vitro. Digital spatial transcriptomics analyses were performed on ever and never-smoker control and COPD (GOLD1-4, n=6-17/group) lungs.

Results: Ex-vivo, bronchi from female mice only had increased reactivity to CSE, but the treatment with SKI-II inhibited such CSE-induced hyperreactivity. In vitro, CSE incubation induced an increase in ORMDL3, a key sphingolipid biosynthesis regulator, protein expression in the supernatant. Spatial RNA analysis showed an increased expression of Asah1, a ceramidase involved in sphingolipid metabolism, and Ormdl3 mRNA in alveoli and bronchi from COPD vs. controls.

Conclusions: in COPD, there is an estrogen-dependent dysregulation of the sphingolipid metabolism which might underlie the sex-differences observed in COPD presentation.