β1-Na+,K+-ATPase gene therapy upregulates tight junctions to rescue lipopolysaccharide-induced acute lung injury

Acute lung injury (ALI) and acute respiratory distress syndrome (ARDS) are associated with diverse disorders and characterized by disruption of the alveolar-capillary barrier, leakage of edema fluid into the lung, and substantial inflammation leading to acute respiratory failure. Gene therapy is a potentially powerful approach to treat ALI/ARDS through repair of alveolar epithelial function. Herein, we show that delivery of a plasmid expressing beta 1-subunit of the Na+, K+-ATPase (beta 1-Na+, K+-ATPase) alone or in combination with epithelial sodium channel (ENaC) alpha 1-subunit using electroporation not only protected from subsequent lipopolysaccharide (LPS)-mediated lung injury, but also treated injured lungs. However, transfer of alpha 1-subunit of ENaC (alpha 1-ENaC) alone only provided protection benefit rather than treatment benefit although alveolar fluid clearance had been remarkably enhanced. Gene transfer of beta 1-Na+, K+-ATPase, but not alpha 1-ENaC, not only enhanced expression of tight junction protein zona occludins-1 (ZO-1) and occludin both in cultured cells and in mouse lungs, but also reduced pre-existing increase of lung permeability in vivo. These results demonstrate that gene transfer of beta 1-Na+, K+-ATPase upregulates tight junction formation and therefore treats lungs with existing injury, whereas delivery of alpha 1-ENaC only maintains pre-existing tight junction but not for generation. This indicates that the restoration of epithelial/endothelial barrier function may provide better treatment of ALI/ARDS.