Role of the two-pore domain potassium channel TREK-1 in hyperoxia- and mechanical stretch-induced alveolar epithelial injury.

Hyperoxia (HO) and mechanical ventilation (MV) are the mainstay of treatment for patients with acute respiratory failure, but both interventions can also accelerate further lung injury, highlighting the need for better therapeutic approaches. We previously found that HO decreases epithelial TREK-1 expression and promotes epithelial inflammation, but the consequences of TREK-1 deficiency in a clinically relevant system of combined HO + ST (stretch) exposure remain unknown. We found that in both mouse lung tissue and primary human alveolar epithelial cells, HO + ST downregulates TREK-1 protein levels. The injurious consequences of TREK-1 downregulation are evidenced in alveolar epithelial cells following pharmacological and genetic TREK-1 inhibition and in lungs of TREK-1 KO mice by potentiation of HO + ST-induced cytosolic ROS production, caspase-8 and caspase-1 activation, IL-1β production, and MIP-1α, and CXCL-10/IP-10 secretion. In addition, HO + MV-exposed TREK-1 KO mice show increased histological lung injury scores, total cell, macrophage, and neutrophil counts in the bronchoalveolar lavage fluid (BALF). Mechanistically, HO + ST depolarized the epithelial electrical membrane potential (Em) and raised iCa(2+) levels, which was potentiated after pharmacological and genetic TREK-1 inhibition. Both Ca(2+) influx through voltage-gated Ca(2+) channels and Ca(2+) release from intracellular stores increased iCa(2+) levels following TREK-1 inhibition. Intratracheal administration of two structurally different pharmacological TREK-1 activators (ML335, BL1249) improved HO + ST-induced BALF total and differential cell counts, total protein levels, ROS production, caspase-8 and capase-1 production, and cytokine concentrations. Therefore, these findings highlight TREK-1 as new potential target for intervention against HO + ST/MV-induced lung and epithelial injury and lay the groundwork for future rational drug development.NEW & NOTEWORTHY No targeted interventions exist that improve the outcomes of patients with acute lung injury/ARDS. A few studies investigated Na(+) and Ca(2+) channels/transporters for potential therapeutic intervention but with limited translational success. This study highlights the regulatory role of TREK-1 K(+) channels during HO+stretch/mechanical ventilation-induced lung injury in ROS production, caspase activation, cytokine secretion, and explores the underlying TREK-1-mediated signaling mechanisms. These preclinical findings lay the groundwork for future rational drug design targeting TREK-1 channels.