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Background: Nicotine is, to a large extent, responsible for smoking-mediated renal dysfunction. This study investigated nicotine’s effects on renal tubular epithelial cell apoptosis in vitro and it explored the mechanisms underlying its effects. Methods: Human proximal tubular epithelial (HK-2) cells were treated with nicotine. Cell viability was examined by using the WST-1 assay. Intracellular levels of reactive oxygen species (ROS) and the expression of mitogen-activated protein kinase (MAPK) and nuclear factor-κB (NF-κB) proteins were determined. The messenger ribonucleic acid and the protein expression associated with the nicotine acetylcholine receptors (nAChRs) in HK-2 cells was examined, and apoptosis was detected using flow cytometry, cell cycle analysis, and immunoblot analysis. Results: The HK-2 cells were endowed with nAChRs. Nicotine treatment reduced cell viability dose dependently, increased ROS levels, and increased extracellular signal-regulated kinase (ERK), c-Jun N-terminal kinase (JNK), and p38 MAPK expression. Nicotine increased NF-κB activation, which was attenuated by N-acetyl-L-cysteine, and ERK and JNK inhibitors, but was not affected by a p38 MAPK inhibitor. Nicotine increased the Bax/Bcl-2 ratio, which was attenuated by N-acetyl-L-cysteine, the NF-κB inhibitor, Bay 11–7082, and hexamethonium, a non-specific nAChR blocker. Flow cytometry revealed nicotine-induced G2/M phase arrest. While nicotine treatment increased the expression of phosphorylated cdc2 and histone H3, a marker of G2/M phase arrest, hexamethonium and Bay 11–7082 pretreatment reduced their expression. Conclusions: Nicotine caused apoptosis in HK-2 cells by inducing ROS generation that activated the NF-κB signaling pathway via the MAPK pathway and it arrested the cell cycle at the G2/M phase. Nicotine-induced apoptosis in HK-2 cells involves the nAChRs. [ABSTRACT FROM AUTHOR]

Abstract: Macrophage-stimulating protein (MSP) and its receptor, recepteur d’origine nantais (RON), play an important role in cell proliferation and migration. We have investigated the role of MSP in hydrogen peroxide (H2O2)-induced renal tubular apoptosis. Human renal proximal tubular (HK-2) cells were incubated with H2O2 for 24h in the presence of different concentrations of MSP, and cell viability was measured by MTT assay. The protein expression of Bax, Bcl-2, caspase-3, mitogen-activated protein kinases (MAPKs), phosphatidylinositol-3-kinase (PI3K)/Akt, and nuclear factor-kappa B (NF-κB) was determined by semiquantitative immunoblotting. Apoptosis was assessed by flow cytometry analysis after HK-2 cells were stained with fluorescein isothiocyanate-conjugated annexin V protein and propidium iodide. H2O2 treatment decreased cell viability in HK-2 cells; this was counteracted by MSP pretreatment. H2O2 treatment induced an increased ratio of Bax/Bcl-2, cleaved caspase-3, and the number of condensed nuclei, which was also counteracted by MSP. Flow cytometry analysis showed H2O2-induced apoptosis, and its prevention by MSP treatment. Increased protein expression of phospho-p38 MAPK was attenuated by MSP, while phospho-extracellular signal-regulated kinase and c-Jun-N-terminal kinase were not affected. H2O2 induced NF-κB activation and IκB-α degradation, but the increased nuclear NF-κB activation was counteracted by MSP or by a p38 MAPK inhibitor. H2O2 treatment decreased expression of phospho-PI3K and phospho-Akt, which was reversed by MSP pretreatment. These findings suggest that MSP attenuates H2O2-induced apoptosis in HK-2 cells by modulating the p38 and NF-κB, as well as PI3K/Akt, signaling pathways. [Copyright &y& Elsevier]

Highlights: [•] MSP/RON system is activated in rat kidney damaged by gentamicin. [•] MSP inhibits GM-induced cellular apoptosis and inflammation in HK-2 cells. [•] MSP attenuates GM-induced activation of MAPKs and NF-κB pathways in HK-2 cells. [ABSTRACT FROM AUTHOR]

Abstract: The present study was performed to examine whether paricalcitol may prevent the cisplatin-induced kidney injury. Furthermore, potential molecular mechanisms underlying the protective effect of paricalcitol were explored. Male Sprague–Dawley rats were treated with vehicle (n=12), cisplatin (n=12, 6mg/kg/day, i.p.), or cisplatin+paricalcitol (n=12, 0.2μg/kg/day, s.c.) for 4days. In another series of experiment, HK-2 cells were treated with cisplatin (50μM), with or without paricalcitol (0.2ng/ml). Paricalcitol counteracted the cisplatin-induced decline in renal function. Paricalcitol also suppressed the expression of TGF-β1, Smad signaling, and the subsequent epithelial-to-mesenchymal process in cisplatin-treated rats. The expression of P-p53 and p21 was increased in cisplatin-induced nephropathy. These changes were completely prevented or significantly attenuated with paricalcitol co-treatment. The expression of p27kip1 was increased in cisplatin-treated rats, which was, however, further augmented by the paricalcitol co-treatment. In HK-2 cells, cisplatin increased the expression of p-ERK1/2 and P-p38. Cisplatin also increased the expression of fibronectin and CTGF. Cisplatin increased the expression of pro-apoptotic markers. The expression of CDK2 and Cyclin E as well as that of PCNA was increased. These changes were completely prevented or significantly attenuated by the paricalcitol pretreatment. In contrast, cisplatin increased the expression of p27kip1, which was further augmented by the paricalcitol-pretreatment. These results suggest that paricalcitol may ameliorate cisplatin-induced renal injury by suppressing the fibrotic, apoptotic and proliferative factors. Its underlying mechanisms may include inhibition of TGF-β1, mitogen-activated protein kinase signaling, p53-induced apoptosis, and augmentation of p27kip1. [Copyright &y& Elsevier]

Background. The aldehyde products of lipid peroxidation such as 4-hydroxy-2-hexenal (HHE) might be responsible for the pathogenesis of kidney injury. The present study was aimed to investigate the effects of HHE on renal tubular epithelial cells and its signaling mechanisms.Methods. Human proximal tubular epithelial (HK-2) cells were treated with 10 μM of HHE. Cell viability was examined using 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay. The fluorescent probe 2′,7′-dichlorofluorescein diacetate was used to measure intracellular levels of reactive oxygen species (ROS). The protein expression of NF-κB, mitogen-activated protein kinase (MAPK), pro-apoptoic Bax and anti-apoptotic protein Bcl-2 was determined by semiquantitative immunoblotting. Apoptosis was assessed by flow cytometry analysis after the cells were stained by fluorescein isothiocyanate-conjugated annexin V protein and propidium iodine.Results. Treatment with various doses of HHE resulted in dose-dependent decreases of cell viability and increases of ROS. HHE increased the expression of p38 MAPK, extracellular signal-regulated kinase (ERK) and c-Jun N-terminal kinase (JNK). HHE induced NF-κB activation and IκB-α degradation. Increased nuclear NF-κB activation was blocked by inhibitors of ERK (PD98059) or JNK (SP600125), but not affected by p38 MAPK inhibitor (SB203580). Flow cytometry analysis revealed HHE-induced apoptosis. HHE decreased the expression of Bcl-2, while it increased that of Bax, which was attenuated by the treatment of NF-κB inhibitor (Bay 11-7082) or N-acetyl-L-cysteine (NAC). An inhibition of NF-κB prevented HHE-induced apoptosis.Conclusions. HHE-induced tubular cell apoptosis is mediated by modulation of Bax and Bcl-2 via ROS generation. HHE-mediated accumulation of ROS may induce redox-sensitive transcription factor, NF-κB, through activation of ERK and JNK, resulting in cellular apoptosis in HK-2 cells. [ABSTRACT FROM PUBLISHER]

G-protein-coupled receptor 40 (GPR40) has an anti-apoptotic effect in pancreatic β-cells. However, its role in renal tubular cell apoptosis remains unclear. To explore the role of GPR40 in renal tubular apoptosis, a two-week unilateral ureteral obstruction (UUO) mouse model was used. The protein expression of GPR40 was decreased, while the Bax/Bcl-2 protein expression ratio, the expression of tumor necrosis factor (TNF)-α mRNA, and angiotensin II type 1 receptor (AT1R) protein were increased in mice with UUO. In vitro, pretreatment of rat proximal tubular (NRK52E) cells with GW9508, a GPR40 agonist, attenuated the decreased cell viability, increased the Bax/Bcl-2 protein expression ratio, increased protein expression of cleaved caspase-3 and activated the nuclear translocation of nuclear factor-κB (NF-κB) p65 subunit induced by TNF-α treatment. TNF-α treatment significantly increased the expression of AT1R protein and the generation of reactive oxygen species (ROS), whereas GW9508 treatment markedly reversed these effects. Pretreatment with GW1100, a GPR40 antagonist, or silencing of GPR40 in NRK52E cells promoted the increased expression of the cleaved caspase-3 protein by TNF-α treatment. Our results demonstrate that decreased expression of GPR40 is associated with apoptosis via TNF-α and AT1R in the ureteral obstructed kidney. The activation of GPR40 attenuates TNF-α-induced apoptosis by inhibiting AT1R expression and ROS generation through regulation of the NF-κB signaling pathway. [ABSTRACT FROM AUTHOR]