ABSTRACT
Objective:To design a modified S1PR3 specific agonist, GPS-725.017, and investigate its protective effect on acute lung injury by promoting macrophage clearance of bacteria.Methods:A short peptide derived from the intracellular region of S1PR3 receptor was named GPS725.017, which was modified with norleucine (Nle) and myristicacid (myr) at its N terminus. Mice were divided into the sham operation group, solvent group and GPS-725.017 treatment group. The acute lung injury model was induced by endotracheal injection of E. coli (5×10 6 CFU), and the experimental group was treated with GPS-725.017 (10 mg/kg). The 48-h survival rate of mice was recorded. After 5 h of modeling, the bacterial load and inflammatory cytokines in peripheral blood and lung were detected, and Vps34 protein content in alveolar macrophages was determined by Western blot. After 12-h of modeling, lung tissues were collected for H&E staining and pathological scores. Results:Compared with the solvent group, the survival rate of mice in the GPS-725.017 treatment group was significantly improved ( P<0.01), the bacterial CFU in blood and alveolar lavage fluid was significantly lower than that in the solvent group ( P<0.001), and the levels of TNF-α and IL-1β in blood and alveolar lavage fluid were significantly lower than those in the solvent group ( P<0.001). Western blot showed that the expression level of Vps34 protein in alveolar macrophages was significantly higher than that in the solvent group ( P<0.01). Histopathology result showed that the pathological damage of lung in the treatment group was significantly less than that in the solvent group ( P<0.001). Conclusions:The modified synthetic S1PR3 specific agonist GPS-725.017 could specifically activate the S1PR3 receptor on the membrane of alveolar macrophages and up-regulate the expression level of intracellular Vps34 protein, which can promote the removal of bacteria in alveolar macrophages, significantly reduce the degree of lung injury and improve the survival rate in ALI mice.
ABSTRACT
Objective To study the effects of the myristoyl-glycine modified peptide which derived from the second intracellular loop of sphingosine 1-phosphate receptor 3 (S1PR3) on activation of mitogenactivated protein kinases (MAPKs) pathway.Methods The phosphorylation levels of JNK and ERK in THP-1 cells were detected by western blot after GPS-725.017 stimulation.Statistical data analysis was conducted by multivariate analysis of variance.Results Western blot showed that 10 min after 30 μmol/L or 50 μmol/L GPS-725.017 stimulated,phosphorylation of ERK significantly increased in comparison with the solvent-treated group [30 μmol/L group:(3.10 ± 0.27) vs.(7.98 ± 0.45),P ＜ 0.01;50 μmol/L group:(4.78 ±0.44) vs.(25.98 ±2.32),P ＜0.01];after 50 μmol/L GPS-725.017 stimulated THP-1 cells for 5 min,10 min,20 min or 30 min,p-ERK or p-JNK level raised at different time points (P ＜0.01vs.solvent group).Conclusions GPS-725.017,a kind of myristoyl-glycine modified peptide derived from S1 PR3,could traverse cytomembrane and activate MAPKs pathway.This study provides an implication of targeting S1PR3 for clinical therapy on inflammatory diseases or sepsis.