PCTR1 improves pulmonary edema fluid clearance through activating the sodium channel and lymphatic drainage in lipopolysaccharide‐induced ARDS

Abstract Acute respiratory distress syndrome (ARDS) is a lethal clinical syndrome characterized by damage of the epithelial barriers and accumulation of pulmonary edema fluid. Protectin conjugates in tissue regeneration 1 (PCTR1), an endogenously produced lipid mediator, are believed to exert anti‐inflammatory and pro‐resolution effects. PCTR1 (1 µg/kg) was injected at 8 hr after lipopolysaccharide (LPS; 14 mg/kg) administration, and the rate of pulmonary fluid clearance was measured in live rats at 1 hr after PCTR1 treatment. The primary type II alveolar epithelial cells were cultured with PCTR1 (10 nmol/ml) and LPS (1 μg/ml) for 8 hr. PCTR1 effectively improved pulmonary fluid clearance and ameliorated morphological damage and reduced inflammation of lung tissue, as well as improved the survival rate in the LPS‐induced acute lung injury (ALI) model. Moreover, PCTR1 markedly increased sodium channel expression as well as Na, K‐ATPase expression and activity in vivo and in vitro. In addition, PCTR1i also upregulated the expression of LYVE‐1 in vivo. Besides that, BOC‐2, HK7, and LY294002 blocked the promoted effect of PCTR1 on pulmonary fluid clearance. Taken together, PCTR1 upregulates sodium channels' expression via activating the ALX/cAMP/P‐Akt/Nedd4‐2 pathway and increases Na, K‐ATPase expression and activity to promote alveolar fluid clearance. Moreover, PCTR1 also promotes the expression of LYVE‐1 to recover the lymphatic drainage resulting in the increase of lung interstitial fluid clearance. In summary, these results highlight a novel systematic mechanism for PCTR1 in pulmonary edema fluid clearance after ALI/ARDS, suggesting its potential role in a therapeutic approach for ALI/ARDS.