Overexpression of the Na-K-ATPase α₂-subunit improves lung liquid clearance during ventilation-induced lung injury

Mechanical ventilation with high tidal volumes (HV_T) impairs lung liquid clearance (LLC) and downregulates alveolar epithelial Na-K-ATPase. We have previously reported that the Na-K-ATPase α₂-subunit contributes to LLC in normal rat lungs. Here we tested whether overexpression of Na-K-ATPase α₂-subunit in the alveolar epithelium would increase clearance in a HV_T model of lung injury. We infected rat lungs with a replication-incompetent adenovirus that expresses Na-K-ATPase α₂-subunit gene (Adα₂) 7 days before HVT mechanical ventilation. HVT ventilation decreased LLC by ∼50% in untreated, sham, and Adnull-infected rats. Overexpression of Na-K-ATPase α₂-subunit prevented the decrease in clearance caused by HVT and was associated with significant increases in Na-K-ATPase α₂ protein abundance and activity in peripheral lung basolateral membrane fractions. Ouabain at 10^-5 M, a concentration that inhibits the α₂ but not the Na-K-ATPase α₁, decreased LLC in Adα₂-infected rats to the same level as sham and Adnull-infected lungs, suggesting that the increased clearance in Adα₂ lungs was due to Na-K-ATPase α₂ expression and activity. In summary, we provide evidence that augmentation of the Na-K-ATPase α₂-subunit, via gene transfer, may accelerate LLC in the injured lung.