Sphingosine‐1‐Phosphate Induces an Anti‐Inflammatory Phenotype in Macrophages During Inflammation

Activated macrophages acquire a pro‐inflammatory (classical) or anti‐inflammatory (alternative) phenotype that influences atherosclerosis. We examined the anti‐inflammatory effects of S1P on LPS‐stimulated cytokine secretion in primary C57BL/6J (B6) mouse peritoneal macrophages. LPS upregulated mRNA expression of the pro‐inflammatory cytokines TNF‐alpha and MCP‐1 by several‐fold. S1P treatment reduced TNF‐alpha mRNA by 3‐fold (p = 0.0061) and MCP‐1 by 2‐fold (p<0.001). S1P decreased both TNF‐alpha and MCP‐1 secretion by LPS‐stimulated macrophages by approximately 40%. Alternative macrophage activation is characterized by induction of the anti‐inflammatory Th2 cytokine IL‐10 and arginase‐1. S1P triggered a 10‐fold increase in IL‐10 mRNA expression (p<0.001) and a 2‐fold increase in arginase‐1 mRNA level (p<0.001). Arginase‐1 enzyme activity was increased by 35%. Activation of the S1P1R using the S1P1R agonist SEW2871 had no effect on macrophage activation. Also, similarly, the uncoupling of S1P1 G i signaling with pertussis toxin did not alter the protective effect of S1P. However, the S1P2R antagonist JTE‐013 completely blocked the protective effect of S1P, suggesting that S1P2 is responsible, at least in part, for the alternative activation of macrophages during inflammation. We therefore conclude that S1P promotes the alternative anti‐inflammatory macrophage phenotype though action on S1P2.