Maresin Conjugates in Tissue Regeneration 1 improves alveolar fluid clearance by up-regulating alveolar ENaC, Na, K-ATPase in lipopolysaccharide-induced acute lung injury.

Maresin Conjugates in Tissue Regeneration 1 (MCTR1) is a newly identified macrophage-derived sulfido-conjugated mediator that stimulates the resolution of inflammation. This study assessed the role of MCTR1 in alveolar fluid clearance (AFC) in a rat model of acute lung injury (ALI) induced by lipopolysaccharide (LPS). Rats were intravenously injected with MCTR1 at a dose of 200 ng/rat, 8 hours after administration of 14 mg/kg LPS. The level of AFC was then determined in live rats. Primary rat ATII (Alveolar Type II) epithelial cells were also treated with MCTR1 (100 nmol/L) in a culture medium containing LPS for 8 hours. MCTR1 treatment improved AFC (18.85 +/- 2.07 vs 10.11 +/- 1.08, P < .0001) and ameliorated ALI in rats. MCTR1 also significantly promoted AFC by up-regulating epithelial sodium channel (ENaC) and Na+-K+-adenosine triphosphatase (Na, K-ATPase) expressions in vivo. MCTR1 also activated Na, K-ATPase and elevated phosphorylated-Akt (P-Akt) by up-regulating the expression of phosphorylated Nedd4-2 (P-Nedd4-2) in vivo and in vitro. However, BOC-2 (ALX inhibitor), KH7 (cAMP inhibitor) and LY294002 (PI3K inhibitor) abrogated the improved AFC induced by MCTR1. Based on the findings of this study, MCTR1 may be a novel therapeutic approach to improve reabsorption of pulmonary oedema during ALI/acute respiratory distress syndrome (ARDS).