Epoxyeicosatrienoic acids protect airway epithelial mitochondria by activating the cAMP/PKA-DRP1 Ser637 axis in cigarette smoke-induced lung injury.

BACKGROUND

Cigarette smoke–induced airway epithelial injury is a central pathological feature of chronic obstructive pulmonary disease (COPD) and is closely associated with mitochondrial dysfunction. Excessive dynamin-related protein 1 (DRP1)–mediated mitochondrial fission contributes to epithelial oxidative stress and apoptosis; however, the endogenous regulatory mechanisms limiting aberrant DRP1 activation in the airway epithelium remain poorly understood. Epoxyeicosatrienoic acids (EETs), lipid mediators metabolized by soluble epoxide hydrolase (EPHX2), have been implicated in lung protection, but their role in regulating mitochondrial dynamics in cigarette smoke–exposed airway epithelium has not been established.

METHODS

Wild-type and EPHX2-/- mice were exposed to chronic cigarette smoke to evaluate mitochondrial morphology, oxidative stress, epithelial apoptosis, and lung mechanics. In vitro, BEAS-2B airway epithelial cells were exposed to cigarette smoke extract (CSE) with pharmacological or genetic modulation of EET signaling. Mitochondrial structure and function, including reactive oxygen species production, mitochondrial membrane potential, and DRP1 phosphorylation status, were assessed using confocal microscopy, transmission electron microscopy, and immunoblotting.

RESULTS

Chronic cigarette smoke exposure induced marked mitochondrial fragmentation, increased oxidative stress, and epithelial apoptosis, accompanied by enhanced DRP1 activation. Genetic deletion of EPHX2 or exogenous EET supplementation preserved mitochondrial network integrity and significantly attenuated DRP1-mediated mitochondrial fission in both in vivo and in vitro models. In vivo, restoration of inhibitory DRP1 Ser637 phosphorylation was associated with reduced mitochondrial fragmentation, whereas in vitro EETs promoted inhibitory DRP1 Ser637 phosphorylation via activation of the cAMP/PKA signaling pathway, thereby limiting pathological mitochondrial fission and mitigating epithelial cell injury.

CONCLUSIONS

EETs act as endogenous modulators of mitochondrial dynamics in airway epithelial cells. By restraining DRP1-mediated mitochondrial fission, EET signaling protects against cigarette smoke–induced mitochondrial dysfunction and epithelial injury, supporting the EPHX2–EET axis as a mechanistically and clinically relevant pathway for further translational investigation in COPD.