The Effects Of MTOR Signaling Pathway On Human Renal Tubular Epithelium Cell Apoptosis Induced By Iopromide

ObjectiveTo explore the effects of mTOR signaling pathway on contrast induced acute kidney injury. To probe whether rapamycin or lysophosphatidic acid could improve the apoptosis caused by contrast media.Methods1. Human renal tubular epithelial cells(HK-2) were divided into normal group,iopromide group, high concentration rapamycin group, low concentration rapamycin group, high concentration lysophosphatidic acid group and low concentration lysophosphatidic acid group. The western blotting assay was used to detect the expression of mTOR signaling pathway downstream proteins and phosphorylated proteins in different drug concentrations and time points.2. HK-2 cells were divided into normal group, iopromide group, rapamycin group and lysophosphatidic acid group. Flow cytometry was used to measure the effect of iopromide on HK-2 cell apoptosis in different time points, and to explore whether rapamycin or lysophosphatidic acid could improve the apoptosis caused by iopromide at different concentrations and time points.Results1. The results of western blotting assay showed that the expression of Total-mTOR in each group had no significant change at 24h(P>0.05). The expression of p-mTOR,Total-P70S6 K, p-P70S6 K, Total-4EBP1 and p-4EBP1 in iopromide group were lower than that in normal control group(P<0.05). The expression of p-mTOR,Total-P70S6 K, p-P70S6 K, Total-4EBP1 and p-4EBP1 in rapamycin group were lower than that in iopromide group(P<0.05), but there was no significant difference on the expression of all proteins between high and low dose rapamycin groups(P>0.05). The expression of p-mTOR, Total-P70S6 K, p-P70S6 K, Total-4EBP1 and p-4EBP1 in lysophosphatidic acid group were higher than that in iopromide group(P<0.05), but there was no significant difference on the expression of all proteins between high andlow dose lysophosphatidic acid group(P>0.05). The trend of protein expression measured at 48 h was almost the same with that measured at 24 h. The expression of p-mTOR, Total-P70S6 K, p-P70S6 K, Total-4EBP1 and p-4EBP1 in iopromide and rapamycin groups decreased in time-dependent manner(P<0.05), while the expression of p-mTOR, Total-P70S6 K, p-P70S6 K, Total-4EBP1 and p-4EBP1 in lysophosphatidic acid group rose in time-dependent manner(P<0.05).2. The results of flow cytometry showed that the rate of apoptosis in iopromide group was significantly higher than that in normal cells group(P<0.05). In iopromide group, the rate of apoptosis at 48 h was higher than that at 24h(P<0.05). The rate of apoptosis in lysophosphatidic acid group was lower than that in iopromide group(P<0.05). However, in lysophosphatidic acid group, there is no difference on the rate of apoptosis btween 24 h and 48h(P>0.05). The rate of apoptosis in rapamycin group was lower than that in iopromide group(P<0.05). In rapamycin group, the rate of apoptosis at 48 h was lower than that at 24h(P<0.05).At 24 h, the rate of apoptosis in rapamycin group was higher than that in lysophosphatidic acid group(P<0.05). At48 h, the rate of apoptosis in rapamycin group was lower than that in lysophosphatidic acid group(P<0.05).Conclusion1. mTOR signaling pathway is one molecular mechanism of contrast induced acute kidney injury.2.Iopromide induced cell apoptosis by inhibition of mTOR signaling pathway.3. Lysophosphatidic acid reduces iopromide induced cell apoptosis by activation of mTOR signaling pathway.4. Rapamycin can inhibit mTOR, however, maybe its pleiotropic effects ultimately reduce cell apoptosis caused by iopromide.