Inhibition of PARP activation by enalapril is crucial for its renoprotective effect in cisplatin-induced nephrotoxicity in rats

Oxidative stress-induced PARP activation has been recognized to be a main factor in the pathogenesis of cisplatin-induced nephrotoxicity. Accumulating literature has revealed that ACE inhibitors may exert beneficial effect in several disease models via preventing PARP activation. Based on this hypothesis, we have evaluated the renoprotective effect of enalapril, an ACE inhibitor, and its underlying mechanism(s) in cisplatin-induced renal injury in rats. Male Albino Wistar rats were orally administered normal saline or enalapril (10, 20 and 40?mg/kg) for 10 days. Nephrotoxicity was induced by a single dose of cisplatin (8?mg/kg; i.p.) on the 7th day. The animals were thereafter sacrificed on the 11th day and both the kidneys were excised and processed for biochemical, histopathological, molecular, and immunohistochemical studies. Enalapril (40?mg/kg) significantly prevented cisplatin-induced renal dysfunction. In comparison to cisplatin-treated group, the elevation of BUN and creatinine levels was significantly less in this group. This improvement in kidney injury markers was well substantiated with reduced PARP expression along with phosphorylation of MAPKs including JNK/ERK/p38. Enalapril, in a dose-dependent fashion, attenuated cisplatin-induced oxidative stress as evidenced by augmented GSH, SOD and catalase activities, reduced TBARS and oxidative DNA damage (8-OHDG), and Nox-4 protein expression. Moreover, enalapril dose dependently inhibited cisplatin-induced inflammation (NF-κB/IKK-β/IL-6/Cox-2/TNF-α expressions), apoptosis (increased Bcl-2 and reduced p53, cytochrome c, Bax and caspase-3 expressions, and TUNEL/DAPI positivity) and preserved the structural integrity of the kidney. Thus, enalapril attenuated cisplatin-induced renal injury via inhibiting PARP activation and subsequent MAPKs/TNF-α/NF-κB mediated inflammatory and apoptotic response.     

Characterization of monoclonal antibodies specific for rabbit renal brush-border hydrolases: application to immunohistological localization

By use of immunodepletion studies, we characterized four monoclonal antibodies reactive with rabbit brush-border (BB) as specific for aminopeptidase N (AP), dipeptidylpeptidase IV (DPPIV), neutral endopeptidase (EP), and angiotensin-converting enzyme (ACE), and we used these antibodies for immunohistochemical detection of these four hydrolases. Expression within the kidney was studied by light and electron microscopy. All four hydrolases are expressed on the various segments of the proximal tubule. In addition, EP and DPPIV are detectable on visceral epithelial cells of the glomerulus and AP on the cells of Bowman's capsule. Outside the kidney, the four hydrolases are expressed within the digestive and genital tracts, where AP, EP, and DPPIV predominate on epithelial structures, whereas ACE is essentially located in vascular structures. The latter localization is also characteristic of ACE in the other organs studied, where clear-cut systematic distribution of the other hydrolases was often difficult to demonstrate. In addition, AP, DPPIV, and EP were detected on lymphoid cells. As compared to reports of data obtained essentially by enzymatic or immunoradiometric assays, these observations suggest considerable interspecies variations of extrarenal expression of the major BB hydrolases. This should be taken into account in attempting to define a general physiological role for a given enzyme.