BACKGROUNDThe amiloride-sensitive epithelial sodium channel α-subunit (α-ENaC) is an important factor for alveolar fluid clearance during acute lung injury. The relationship between adenosine receptor A(2a) (A(2a)AR) expressed in alveolar epithelial cells and α-ENaC is poorly understood. We targeted the A(2a)AR in this study to investigate its role in the expression of α-ENaC and in acute lung injury.

METHODSA549 cells were incubated with different concentrations of A(2a)AR agonist CGS-21680 and with 100 µmol/L CGS-21680 for various times. Rats were treated with lipopolysaccharide (LPS) after CGS-21680 was injected. Animals were sacrificed and tissue was harvested for evaluation of lung injury by analysis of the lung wet-to-dry weight ratio, lung permeability and myeloperoxidase activity. RT-PCR and Western blotting were used to determine the mRNA and protein expression levels of α-ENaC in A549 cells and alveolar type II epithelial cells.

RESULTSBoth mRNA and protein levels of α-ENaC were markedly higher from 4 hours to 24 hours after exposure to 100 µmol/L CGS-21680. There were significant changes from 0.1 µmol/L to 100 µmol/L CGS-21680, with a positive correlation between increased concentrations of CGS-21680 and expression of α-ENaC. Treatment with CGS-21680 during LPS induced lung injury protected the lung and promoted α-ENaC expression in the alveolar epithelial cells.

CONCLUSIONActivation of A(2a)AR has a protective effect during the lung injury, which may be beneficial to the prognosis of acute lung injury.