Background: At all stages of chronic obstructive pulmonary disease (COPD) severity, men have more severe emphysema than women, whereas women have higher serum levels of pro-inflammatory molecules than men. A dysregulation of sphingolipid, in particular ceramide, metabolism, has been implicated in sex-related differences in COPD presentation.

Aims: to determine if the dysregulation of sphingolipid pathway may drive sex differences in COPD.

Methods: Digital spatial transcriptomics analyses and immunofluorescence staining were performed on lungs from never- (NSC) and ever-smoker (SC) controls and COPD (GOLD1-4) patients. Bronchi harvested from male and female C57BL/6 mice were incubated with cigarette smoke extract (CSE) to perform functional studies + a sphingosine kinase inhibitor (SKI-II). Primary male human bronchial smooth muscle cells (HBSM) were exposed to CSE and +/- estradiol, to perform contractility assays and molecular studies.

Results: Spatial RNA analysis and immunofluorescence staining confirmed a higher expression of ASAH1 and ORMDL3 (key regulators of sphingolipid metabolism) in bronchi from female NSC and SC vs COPD. Similarly, only bronchi from female mice had increased reactivity to CSE, but the treatment with SKI-II inhibited such CSE-induced hyperreactivity. HBSM cells treated with estradiol showed a higher level of ASAH1 expression and higher contractility to carbachol than vehicle cells. CSE treatment reduced cellular contraction, then restored by OEA (ceramidase inhibitor) pre-treatment, only in estradiol-treated cells.

Conclusions: the sex differences observed in COPD symptoms might be associated to an estrogen-dependent dysregulation of sphingolipid metabolism