Cadmium-induced apoptosis in rat kidney epithelial cells involves decrease in nuclear factor-kappa B activity.
Renal epithelial cells undergo apoptosis upon exposure to cadmium (Cd). Transcription factors, such as nuclear factor-kappa B (NF-kappaB), mediate the expression of a number of genes involved in apoptosis. The present study was designed to examine the involvement of this transcription factor in Cd-induced apoptosis. Rat kidney proximal tubular epithelial cells, NRK-52E, were incubated with up to 20 microM CdCl2 in serum-free medium for 5 h followed by incubation in serum-containing medium (without Cd) for an additional 12 h. The cells accumulated 582 +/- 19 ng Cd/mg protein after 5-h exposure to 20 microM Cd. As a result of Cd exposure, the DNA-binding activity of the p65 subunit of NF-kappaB was decreased in a concentration- and time-dependent manner. The activity of tumor necrosis factor-alpha-induced inhibitor of kappa B (IkappaB) kinase alpha was also inhibited by Cd. In addition, the phosphorylation of IkappaB-alpha and NF-kappaB p65, as well as the levels of NF-kappaB target gene products, cIAP-1 and cIAP-2, were reduced. Pretreatment of the cells with the antioxidant U83836E or butylated hydroxytoluene preserved the DNA-binding activity and blocked the Cd-induced decease in IkappaB-alpha phosphorylation. Cd exposure caused the activation of caspase-3, -7, and -9 and DNA fragmentation. By flow cytometry, 14.6 and 30.5% apoptosis was detected at 6 and 12 h after stopping the Cd exposure. Overexpression of NF-kappaB p65 by transient transfection protected the cells from the Cd-induced apoptosis. Conversely, attenuation of NF-kappaB activity by pretreatment with SN50, an NF-kappaB nuclear translocation inhibitor, potentiated apoptosis. These results suggest that Cd-induced apoptosis involves suppression of NF-kappaB activity which may be mediated by oxidative stress.
Xie
Jianxun
J
Department of Biomedical and Pharmaceutical Sciences and Center for Molecular Toxicology, College of Pharmacy, University of Rhode Island, Kingston, Rhode Island 02881, USA.
Shaikh
Zahir A
ZA
D000818:Animals; D017209:Apoptosis / Q000187:drug effects*; D001483:Base Sequence; D002104:Cadmium / Q000633:toxicity*; D002460:Cell Line; D024202:Electrophoretic Mobility Shift Assay; D004847:Epithelial Cells / Q000187:drug effects / Q000378:metabolism; D005434:Flow Cytometry; D007668:Kidney / Q000166:cytology / Q000187:drug effects* / Q000378:metabolism; D016328:NF-kappa B / Q000378:metabolism*; D009841:Oligonucleotides; D010766:Phosphorylation; D051381:Rats
D016328:NF-kappa B; D009841:Oligonucleotides; D002104:Cadmium