Hyperoxia treatment of TREK-1/TREK-2/TRAAK-deficient mice is associated with a reduction in surfactant proteins.

We previously proposed a role for the 2-pore domain potassium (K2P) channel TREK-1 in hyperoxia (HO)-induced lung injury. To determine whether redundancy between the 3 TREK isoforms (TREK-1, TREK-2, TRAAK) could protect from HO-induced injury, we now examined the effect of deletion of all 3 TREK isoforms in a clinically relevant scenario of prolonged HO exposure and mechanical ventilation (MV). We exposed WT and TREK-1/TREK-2/TRAAK-deficient (triple ko) mice to either room air, 72 hours HO, MV (high and low tidal volume), or a combination of HO+MV, and measured quasi-static lung compliance, BAL protein concentration, histologic lung injury scores (LIS), cellular apoptosis, and cytokine levels. We determined surfactant gene and protein expression, and attempted to prevent HO-induced lung injury by prophylactically administering exogenous surfactant (Curosurf). HO treatment increased lung injury in triple ko but not WT mice, including an elevated LIS, BAL protein concentration, markers of apoptosis, decreased lung compliance, and a more proinflammatory cytokine phenotype. MV alone had no effect on lung injury markers. Exposure to HO+MV (low TV) further decreased lung compliance in triple ko but not WT mice, and HO+MV (high TV) was lethal for triple ko mice. In triple ko mice, the HO-induced lung injury was associated with decreased surfactant protein A (SPA) and SPC, but not SPB and SPD expression. However, these changes could not be explained by alterations in the transcription factors NF-1, NKX2.1/TTF or c-jun, or lamellar body levels. Prophylactic Curosurf administration did not improve lung injury scores or compliance in triple ko mice.

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