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

Mechanical ventilation with high tidal volumes ( HVT) impairs lung liquid clearance (LLC) and downregulates alveolar epithelial Na-K-ATPase. We have previously reported that the Na-K-ATPase alpha(2)-subunit contributes to LLC in normal rat lungs. Here we tested whether overexpression of Na-K-ATPase alpha(2)-subunit in the alveolar epithelium would increase clearance in a HVT model of lung injury. We infected rat lungs with a replication-incompetent adenovirus that expresses Na-K-ATPase alpha(2)-subunit gene ( Ad alpha(2)) 7 days before HVT mechanical ventilation. HVT ventilation decreased LLC by similar to 50% in untreated, sham, and Adnull-infected rats. Overexpression of Na-K-ATPase alpha(2)-subunit prevented the decrease in clearance caused by HVT and was associated with significant increases in Na-K-ATPase alpha(2) protein abundance and activity in peripheral lung basolateral membrane fractions. Ouabain at 10(-5) M, a concentration that inhibits the alpha(2) but not the Na-K-ATPase alpha(1), decreased LLC in Ad alpha(2)- infected rats to the same level as sham and Adnull-infected lungs, suggesting that the increased clearance in Ad alpha(2) lungs was due to Na-K-ATPase alpha(2) expression and activity. In summary, we provide evidence that augmentation of the Na-K-ATPase alpha(2)-subunit, via gene transfer, may accelerate LLC in the injured lung.