Abstract: AIM To investigate the effect and the potential mechanism of Sphingosine 1-phosphate (S1P) receptors in lipopolysaccharide (LPS)-induced macrophages migration and to observe the effect of S1P3 inhibitor on LPS-induced cardiac injury. METHODS Macrophages (murine Ana-1 cells) were cultured and exposed LPS and the expression of S1P receptors was detected by Western blotting. Cultured Ana-1 cells were then incubated with LPS or with or without pretreatment with S1P3 inhibitor (CAY-10444). Transwell assay was used to observe the migration of macrophages and Western blot assay was used to confirm that CAY-10444 could effectively inhibit S1P3 expression in Ana-1 cells and to detect Akt and p-Akt Ser473 protein. In vivo, LPS-induced heart injury mouse model was established to demonstrate the cardioprotective properties of S1P3 inhibitor. Mice in each experiment were randomly assigned to four groups: Control group (n=12), which was intraperitoneal with saline, LPS group (n=12), which was intraperitoneally injected with LPS (10 mg/kg), CAY-10444 group (n=12), which was intraperitoneally injected with CAY (1mg/kg) and LPS+CAY-10444 group (n=12), which was intraperitoneally injected with CAY 30min after LPS challenge. Tissue samples from the myocardium were collected and the pathological changes of myocardium were observed by hematoxylin-eosin (HE) staining. Immunohistochemistry was used to observe the expressions of mature macrophage-specific marker F4/80 and proinflammatory cytokines, including TNF-α, IL-1β and IL-6. Quantitative real-time PCR assay was used to detect mRNA level of B-type natriuretic peptide (BNP), F4/80 and proinflammatory cytokines. RESULTS Compared with those in the NC group, the expression of S1P3 in Ana-1 cells was up-regulated by LPS (P<0.01) and the amount of phosphorylated Akt (p-Akt Ser473/Akt) was significantly increased in LPS group (P<0.01). When pretreated with S1P3 inhibitor CAY-10444, the migration of macrophages increased when incubated with LPS (P<0.01), but CAY-10444 inhibited such effect (P<0.01). Compared with that in LPS group, S1P3 inhibitor also reduced the level of phosphorylation of Akt (Ser 473) (P<0.01). In vivo study, LPS treated mice exhibited severe heart injury characterized by the prominent cardiac inflammation in HE staining and higher mRNA level of BNP (P<0.01). The expressions of F4/80, TNF-α, IL-1β and IL-6 in myocardial tissue were markedly up-regulated after LPS challenge. However, treatment with CAY-10444 dramatically attenuated the cardiac histopathological changes in comparison with those in LPS group. The level of BNP was also decreased significantly in LPS+CAY group (P<0.01). Macrophage-specific marker and proinflammatory cytokines were down-regulated in LPS+CAY group (P<0.01). CONCLUSION Suppressed expression of S1P3 in macrophages could inhibit LPS-induced migration and the changes of phosphorylated Akt level might be involved in this process. The intervention of S1P3 inhibitor effectively ameliorates LPS-induced cardiac injury.