Role of the Two-Pore-Domain Potassium channel TREK-1 (K2P2.1) 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-1beta production, and MIP-1alpha 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 BALF. Mechanistically, HO+ST depolarized the epithelial electrical membrane potential (Em) and raised iCa2+ levels, which was potentiated after pharmacological and genetic TREK-1 inhibition. Both Ca2+ influx through voltage-gated Ca2+ channels and Ca2+ release from intracellular stores increased iCa2+ 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.