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

Abstract

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 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 HVTmodel of lung injury. We infected rat lungs with a replication-incompetent adenovirus that expresses Na-K-ATPase α2-subunit gene (Adα2) 7 days before HVTmechanical ventilation. HVTventilation 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 HVTand was associated with significant increases in Na-K-ATPase α2protein abundance and activity in peripheral lung basolateral membrane fractions. Ouabain at 10−5M, a concentration that inhibits the α2but 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 Adα2lungs was due to Na-K-ATPase α2expression 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.