PI3K Signaling Pathway Regulates the Caspase-9 in Renal Tubular Epithelial Cells

Background: To evaluate how resveratrol regulates the IL-6 signaling in renal cell, pCMV6-IL-6 was overexpressed in the renal tubular epithelial cell line NRK-52E. Methods: IHC and TUNEL assay were used to identify the localization and apoptosis detection of the overexpression of IL-6 in NRK-52E cells. To identify the effect of overexpressed IL-6, the mitochondrial fraction was isolated and caspase activities and western blotting were performed. Results: Our results revealed that pCMV6-IL-6 was overexpressed in the nucleus and around the nuclear membrane of the cells. Moreover, the cell membrane showed no IL-6 overexpression, which may be suggest absence of the IL-6/IL-6R binding effect on the cell membrane. Furthermore, the results of the TUNEL assay demonstrated that pCMV6-IL-6-transfected cells showed features of apoptotic cells. The results of the caspase activity assay revealed that resveratrol significantly attenuated IL-6-induced caspase-3 activity but not attenuated IL-6-induced caspase-9 activity, indicating the antiapoptotic ability of resveratrol response on caspase-3 activity. The PI3K inhibitor could decrease the caspase-9 level, suggesting that the reduction of the caspase-9 level mediate by through the PI3K signaling pathway. Conclusions: Taken together, our results demonstrated that IL-6 expression not only in the cytosol but also in the nucleus of renal tubular epithelial cells. The PI3K signaling pathway regulates the caspase-9 in renal tubular epithelial cells.