Cadmium (Cd2+) exposure differentially elicits both cell proliferation and cell death related responses in SK-RC-45

Abstract

Cadmium (Cd2+) is a major nephrotoxic environmental pollutant, affecting mostly proximal convoluted tubule (PCT) cells of the mammalian kidney, while conditionally Cd2+ could also elicit protective responses with great variety and variability in different systems. The present study was designed to evaluate the molecular mechanism of Cd2+ toxicity on human PCT derived Renal Cell Carcinoma (RCC), SK-RC-45 and compare its responses with normal human PCT derived cell line, NKE. Exposure of SK-RC-45 cells with different concentrations of CdCl2 (e.g. 0, 10 and 20μM) in serum free medium for 24h generate considerable amount of ROS, accompanied with decreased cell viability and alternations in the cellular and nuclear morphologies, heat shock responses and GCLC mediated protective responses. Also phosphatidylserine externalization, augmentation in the level of caspase-3, PARP, BAD, Apaf1 and cleaved caspase-9 along with decreased expression of Bcl2 and release of cytochrome c confirmed that, Cd2+ dose dependently induces solely intrinsic pathway of apoptosis in SK-RC-45, independent of JNK. Furthermore, the non-toxic concentration (10μM) of Cd2+ induced nuclear translocation of Nrf2 and increased expression in the level of HO-1 enzyme suggesting that at the milder concentration, Cd2+ induces protective signaling pathways. On the other hand, exposure of NKE to different concentrations of CdCl2 (e.g. 0, 10, 20, 30 and 50μM) under the same conditions elevate stronger heat shock and SOD2 mediated protective responses. In contrary to the RCC PCT, the normal PCT derived cell follows JNK dependent and extrinsic pathways of apoptosis. Cumulatively, these results suggest that Cd2+ exposure dose dependently elicit both cell proliferative and cell death related responses in SK-RC-45 cells and is differentially regulated with respect to normal kidney epithelia derived NKE cells.