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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]

Abstract: Cisplatin is a chemotherapeutic agent used for treating solid tumors. However, nephrotoxicity is the dose-limiting factor in its clinical use. The present study was aimed to determine whether altered regulation of the local nitric oxide (NO) and natriuretic peptide (NP) systems is involved in the pathogenesis of cisplatin-induced nephropathy. Cisplatin (6mg/kg) was injected intraperitoneally into male Sprague–Dawley rats. The control group was not treated with cisplatin. Expression levels of nitric oxide synthase (NOS), nitrotyrosine, soluble guanylyl cyclase and neutral endopeptidase (NEP) in the kidneys were determined 4days after treatment by semiquantitative immunoblotting. mRNA expression of NPs and natriuretic peptide receptors (NPRs) was determined by real-time polymerase chain reaction. The activities of soluble and particulate guanylyl cyclase were determined by measuring the amount of cyclic 3′,5′-guanosine monophosphate (cGMP) generated in responses to sodium nitroprusside and atrial natriuretic peptide (ANP), respectively. In the test rats, creatinine clearance was decreased, while sodium and water excretion were increased. The expression of inducible NOS (iNOS) and nitrotyrosine was increased in the cortex/outer stripe of outer medullar and inner medullar, while that of endothelial and neuronal NOS was decreased in the inner medullar. Excretion of NO metabolites was increased in these rats. The catalytic activity of soluble guanyly cyclase was blunted in the papilla after cisplatin was administered. The mRNA expression of ANP, brain natriuretic peptide, and C-type natriuretic peptide was increased, while that of NPR-A and NPR-C were decreased in the test rats. The catalytic activity of soluble and particulate guanylyl cyclase in the papilla was blunted after cisplatin was administered. In conclusion, increased production of NO by iNOS may contribute to cytotoxic injury, resulting in cisplatin-induced nephropathy, while the up-regulation of renal natriuretic peptide synthesis together with the down-regulation of NEP and NPR-C may contribute to the natriuresis and diuresis seen in cisplatin-induced nephropathy. [Copyright &y& Elsevier]