Protectin DX promotes the inflammatory resolution via activating COX-2/L-PGDS-PGD2 and DP1 receptor in acute respiratory distress syndrome

•Cyclooxygenase-2 (COX-2) and Lipocalin-type prostaglandin D synthase (L-PGDS) have a biphasic activation character in ARDS model induced by lipopolysaccharide.•Secondary peak of COX-2/L-PGDS-PGD2 displayed a pro-resolving action in the inflammatory resolution of ARDS model distinguishing from traditional concepts.•Secondary peak of L-PGDS-PGD2 serves its pro-resolving role via activating DP1 receptor.•Protectin DX (PDX) significantly ameliorated the inflammatory injury of ARDS model via enhancing the expression of secondary peak COX-2/L-PGDS-derived-PGD2.•The pro-resolving effect of PDX was through the activation of DP1 receptor.