Acute lung injury (ALI) is a devastating disease characterized by
pulmonary edema. Removal of
edema from the air spaces of lung is a critical function of the
epithelial sodium channel (ENaC) in ALI. The molecular mechanisms behind resolution of
pulmonary edema are incompletely understood.
MicroRNA's (
miRNA) are crucial gene regulators and are dysregulated in various diseases including ALI. Recent studies suggest that microRNA-16 (miR-16) targets
serotonin transporter (SERT) involved in the
serotonin (5-HT) transmitter system. Alterations in
serotonin levels have been reported in various
pulmonary diseases. However, the role of miR-16 on its target SERT, and ENaC, a key
ion channel involved in the resolution of
pulmonary edema, have not been studied. In the present study, the expression patterns of miR-16, SERT, ENaC and
serotonin were investigated in mice exposed to room air and
hyperoxia. The effects of miR-16 overexpression on ENaC, SERT, TGF-β and Nedd4 in human alveolar epithelial cells were analyzed. miR-16 and ENaC were downregulated in mice exposed to
hyperoxia. miR-16 downregulation in mouse lung was correlated with an increase in SERT expression and
pulmonary edema. Overexpression of miR-16 in human alveolar epithelial cells (A549) suppressed SERT and increased ENaCβ levels when compared to control-vector transfected cells. In addition, miR-16 over expression suppressed TGFβ release, a critical inhibitor of ENaC. Interestingly Nedd4, a negative regulator of ENaC remained unaltered in miR-16 over expressed A549 cells when compared to controls. Taken together, our data suggests that miR-16 upregulates ENaC, a major
sodium channel involved in resolution of
pulmonary edema in ALI.