Activation of Nrf2 by cadmium and its role in protection against cadmium-induced apoptosis in rat kidney cells.
Kidney is the primary target organ in chronic cadmium (Cd) toxicity, and oxidative stress plays an important role in this process. The nuclear transcription factor Nrf2 binds to antioxidant response elements (AREs) and regulates genes involved in protecting cells from oxidative damage. Whether kidney cells respond to Cd by activating Nrf2 is unknown. This study was designed to examine the Cd-induced activation of Nrf2 transcriptional activity in a stable rat kidney cell line, NRK-52E, and to investigate the protection this might offer against apoptosis. The cells were treated with 5-20 microM CdCl(2) for 5 h, followed by a recovery period of up to 24 h. A concentration-dependent increase (up to 2.9-fold) in the level of reactive oxygen species was noted upon termination of 5-h Cd treatment. The Nrf2-ARE binding activity also increased and peaked (6.1-fold) at 10 microM Cd concentration. Time-course study revealed that the binding activity increased at 1 h of Cd treatment and peaked 2 h post Cd treatment. Apoptosis was detected 6 h post treatment with Cd and a concentration- and time-dependent increase in the apoptotic cell population occurred during the next 18 h. Over-expression of Nrf2 by transient transfection conferred resistance against Cd-induced apoptosis. Conversely, suppression of Nrf2 expression by specific siRNA resulted in greater sensitivity of the cells to Cd by decreasing the levels of two antioxidant enzymes, hemeoxygenase-1 and glutamate-cysteine ligase. Taken together, these results suggest that in kidney cells the activation of Nrf2 is an adaptive intracellular response to Cd-induced oxidative stress, and that Nrf2 is protective against Cd-induced apoptosis.
Chen
Jun
J
Department of Biomedical and Pharmaceutical Science, and Center for Molecular Toxicology, College of Pharmacy, University of Rhode Island, Kingston, RI 02881, USA.
Shaikh
Zahir A
ZA
D000818:Animals; D017209:Apoptosis / Q000187:drug effects*; D019256:Cadmium Chloride / Q000008:administration & dosage / Q000633:toxicity*; D002460:Cell Line; D004305:Dose-Response Relationship, Drug; D005786:Gene Expression Regulation; D005721:Glutamate-Cysteine Ligase / Q000378:metabolism; D051547:Heme Oxygenase-1 / Q000378:metabolism; D007687:Kidney Tubules, Proximal / Q000166:cytology / Q000187:drug effects* / Q000378:metabolism; D051267:NF-E2-Related Factor 2 / Q000187:drug effects* / Q000235:genetics / Q000378:metabolism; D018384:Oxidative Stress / Q000187:drug effects*; D034741:RNA, Small Interfering / Q000008:administration & dosage; D051381:Rats; D017382:Reactive Oxygen Species / Q000378:metabolism; D013997:Time Factors; D014162:Transfection
D051267:NF-E2-Related Factor 2; D034741:RNA, Small Interfering; D017382:Reactive Oxygen Species; D051547:Heme Oxygenase-1; D005721:Glutamate-Cysteine Ligase; D019256:Cadmium Chloride