The Effect Of Rapamycin On The Interaction Between Salmonella Typhi Plasmid And Macrophage

Objective: To study the effect of autophagy agonist rapamycin (RAPA) on the interaction between Salmonella typhi plasmid pRST98 and macrophage J774A.1.Methods: Salmonella typhi carrying pRST98, ST8 and Salmonella typhi without pRST98, ST10 were used as experimental strains, and Salmonella typhimurium strain SR-11 carrying a 100 Kb virulence plasmid was used as a positive control. The optimal working concentration of RAPA was determined by Giemsa staining and serial dilution method; J774A.1 was cultivated with RPMI 1640 containing RAPA or not overnight, and then three strains were added. At 0-h time point, 2, 4, 8, 12 and 24 h the expression of autophagic protein Beclin-1 was determined by western blot; apoptosis assay was detected by flow cytometry staining with PI; ultrastructure changes of J774A.1 were observed by transmission electron microscope.Results: The optimal concentration of RAPA was 25μg/ml; the expression of Beclin-1 at 2 h was SR-11 group < ST8 group < ST10 group, and the tendency appeared at 0-h time point after RAPA treatment; the apoptosis rate displayed a tendency of SR-11 group > ST8 group > ST10 group, and after interference with RAPA the apoptosis rate of ST8 and SR-11 group decreased, meanwhile ST10 group increased (P < 0.05); the observation by transmission electron microscope showed that bacteria were surrounded by bilayer membrane at 2 ~ 4 h, and apoptosis was observed from 12 h, and the infection of ST8 group lessened, the infection of ST10 group aggratated with RAPA.Conclusions: pRST98 could inhibit autophagy at an early stage; RAPA could reduce the apoptosis of Salmonella typhi group carrying pRST98, but enhance the apoptosis of Salmonella typhi group without pRST98.