Diabetic nephropathy is a common causative factor of chronic kidney disease (CKD). DPP-4 inhibitor has the ability to improve kidney function and renal microvasculature. In the present study, we investigate the deleterious effects of IS on proximal tubular cells and the protective role of DPP-4 inhibitor. Human kidney 2 (HK-2) cells were exposed to IS in the presence or absence of DPP-4 inhibitor. Effects of DPP-4 inhibitor on viability of HK-2 cells were determined by MTT assay. Reactive oxygen species (ROS) production was examined using fluorescent microscopy. Levels of cleaved caspase-3, transforming growth factor-beta (TGF-β), α-smooth muscle actin (α-SMA) and NF-kappaB p65 and phosphorylation of AKT and extracellular signal-regulated kinase (ERK) were detected by immunoblotting. Production of ROS and level of cleaved caspase-3 were increased by IS in a dose-dependent manner. The phosphorylation of AKT and ERK p65 were decreased alongside activation of NF-κB. Expression of TGF-β and α-SMA, were upregulated in IS-treated HK-2 cells. Treatment with DPP-4 inhibitor resulted in a significant increase in cell viability and a decrease of ROS production in IS-treated HK-2 cells. DPP-4 inhibitor restored IS-induced deactivations of AKT and ERK and inhibited activation of NF-κB in IS-treated HK-2 cells. Moreover, DPP-4 inhibitor could also attenuate IS-induced up-regulation of TGF-β and α-SMA expression. These findings suggest that DPP-4 inhibitor possesses anti-apoptotic activity to ameliorate the IS-induced renal damage, which may be partly attributed to regulating ROS/p38MAPK/ERK and PI3K-AKT pathways as well as downstream NF-κB signaling pathway.

-Background: Indoxyl sulfate is considered to play a pathological role in the progression of chronic kidney disease. The aim of this study was to investigate the deleterious effects of indoxyl sulfate on kidney mesangial cells. Materials and Methods: Rat renal mesangial cells were exposed to indoxyl sulfate at a serial concentrations. Cytotoxicity of indoxyl sulfate on renal mesangial cells was determined using MTT assay. Protein levels of cleaved caspase-3, angiotensin, angiotensin converting enzyme (ACE) and renin were detected by immunoblotting. Reverse transcriptional PCR was performed to determine the mRNA expression. Results: Level of cleaved caspase-3 was augmented while the cell viability was inhibited by indoxyl sulfate in a dose-dependent manner. The mRNA expressions of pro-renin and ACE were upregulated in mesangial cells exposed to indoxyl sulfate. Level of renin and ACE was increased in response to indoxyl sulfate exposure in time-dependent fashion. Conclusion: Indoxyl sulfate increased viability and induced cell death of renal mesangial cells, which is time-dependent. The loss of cell viability is attributed to caspase-3 activity through apoptosis pathway. RAS in renal mesangial cells is activated in response to indoxyl sulfate treatment.