An in vivo and in vitro model on the protective effect of cilnidipine on contrast-induced nephropathy via regulation of apoptosis and CaMKII/mPTP pathway

Contrast-induced nephropathy (CIN) is an acute kidney injury (AKI) observed after the administration of contrast media. Calcium channel blockers (CCBs) have been reported to exert a renal protective effect. This study aims to investigate the role of cilnidipine, a novel CCBs, on CIN by regulating the calcium/calmodulin-dependent protein kinase II(CaMKII)/mitochondrial permeability transition pore (mPTP) pathway. Here, iohexol, a representative contrast media, was used to establish CIN model. KN-93 (CaMKII inhibitor) and atractyloside (mPTP opener) were administered in rats, and CaMKII overexpression was used in Human proximal tubular epithelial cells. Markers of renal injury (serum creatinine, blood urea nitrogen, and urinary NAGL), hematoxylin-eosin stain, oxidative stress (ROS, superoxide dismutase [SOD], and malondialdehyde [MDA] levels), cell death (MTT and terminal deoxynucleotidyl transferase-mediated deoxyuridine triphosphate nick end labeling [TUNEL]), mitochondrial function (mPTP, mitochondrial membrane potential [MMP], and ATP) were assessed. Western blots were used to measure the expression levels of Bax/Bcl-2, caspase-3, CaMKII/mPTP signaling pathways. Results showed that cilnidipine markedly improved kidney function, and alleviated tubular cell apoptosis, oxidative stress and mitochondrial damage induced by iohexol in vitro and in vivo. The underlying mechanism may be that cilnidipine relieved CaMKII activation and mPTP opening induced by iohexol. All of these protective effects of cilnidipine were attenuated by CaMKII overexpression and atractyloside (mPTP opener) pretreatment. Moreover, KN-93 (CaMKII inhibitor) treatment showed a similar renal protective effect with cilnidipine, while the protective effect of cilnidipine on kidney in CIN rats was not further suppressed by KN-93 cotreatment. These in vitro and in vivo results point toward the fact that cilnidipine might be a novel therapeutic drug against contrast-induced nephrotoxicity in a CaMKII-dependent manner.