S1PR3 agonist KRX-725 promotes bacterial clearance and affects the outcome of sepsis / 中华急诊医学杂志

ABSTRACT

Objective To study the role of KRX-725,a specific agonist of Sphingosin-1 phosphate receptor 3,S1PR3),in the function and mechanism of S1PR3 in respect of bacterial clearance.Methods Twenty healthy male C57BL/6 mice were randomly (random number) divided into two groupsKRX-725 group and control group.Septic mice model were established by intraperitoneal injection of E.coli (3 × 106),then KRX-725 (10 mg/kg) or the vehicle was administered intratracheally.Forty-eight-hour survival rate (n =12),bacterial colony numbers in peritoneal cavity and blood (n =5),and lung injury (n =3)were compared between two groups.In vitro,the peritoneal macrophages were stimulated by E.coli (cell∶E.coli=1∶10) with KRX-725 or the vehicle treatment.The reactive oxygen species (ROS) levels were detected by CM-H2DCFDA in macrophages.The bacteria clearance function of KRX-725 was observed by gentamicin protection test.Survival rates were analyzed with the Log-rank test.A 2-tailed student's t test was used to compare difference between two independent groups.Results Compared with the control group,the 48-hour survival rate of KRX-725 group was significantly higher (P ＜ 0.05).Bacterialload in the blood and the peritoneal lavage fluid (PLF) was greatly decreased in the KRX-725 group (bloodt =3.17,P ＜0.05;PLFt =4.07,P ＜0.01).The lung tissues injury was also obviously reduced in the KRX-725 group of 24 hours after the injection of E.coli (lung injury scoreKRX-725 group 1.4 ± 0.25;control group 2.4 ± 0.25) (t =2.89,P ＜ 0.05).In vitro,KRX-725 could up-regulate the ROS levels in macrophage at 20 min and 30 min after E.coli injected intra-peritoneally (20 min fluorescent intensityKRX-725 group 522.9 ± 38.76,control group 385.9 ± 15.90,P ＜ 0.05;30 min fluorescent intensityKRX-725 group 519.7 ±25.02,control group 384.5 ± 15.28,P ＜0.01).The bacterial load in the KRX-725 treated macrophage were significantly decreased at 3 h and 6 h after E.coli injected intra-peritoneally (3 hKRX-725 group 286.5 ±98.35,control group 710.8 ± 107.8,P ＜0.05;6 hKRX-725 group 72.5 ±6.45,control group 205.8 ±66.76,P ＜0.01).Conclusion In vivo,KRX-725 could improve the survival rate of septic mice,decrease the bacterial lioad in the blood and PLF,and reduce the lung injury.In vitro,KRX-725 could up-regulate the ROS level in macrophages and accelerate the bacterial clearance.