title: NADPH oxidase activation is required in reactive oxygen species generation and cell transformation induced by hexavalent chromium.
abstract: Hexavalent chromium [Cr(VI)] is a well-known human carcinogen associated with the incidence of lung cancer. Although overproduction of reactive oxygen species (ROS) has been suggested to play a major role in its carcinogenicity, the mechanisms of Cr(VI)-induced ROS production remain unclear. In this study, we investigated the role of NADPH oxidase (NOX), one of the major sources of cellular ROS, in Cr(VI)-induced oxidative stress and carcinogenesis. We found that short-term exposure to Cr(VI) (2μM) resulted in a rapid increase in ROS generation in Beas-2B cells, and concomitantly increased NOX activity and expression of NOX members (NOX1-3 and NOX5) and subunits (p22(phox), p47(phox), p40(phox), and p67(phox)). Cr(VI) also induced phosphorylation of p47(phox) and membrane translocation of p47(phox) and p67(phox), further confirming NOX activation. Knockdown of p47(phox) with a short hairpin RNA attenuated the ROS production induced by Cr(VI). Chronic exposure (up to 3 months) to low doses of Cr(VI) (0.125, 0.25, and 0.5μM) also promoted ROS generation and the expression of NOX subunits, such as p47(phox) and p67(phox), but inhibited the expression of main antioxidant enzymes, such as superoxidase dismutase (SOD) and glutathione peroxidase (GPx). Chronic Cr(VI) exposure resulted in transformation of Beas-2B cells, increasing cell proliferation, anchorage independent growth in soft agar, and forming aggressive tumors in nude mice. Stable knockdown of p47(phox) or overexpression of SOD1, SOD2, or catalase (CAT) eliminated Cr(VI)-induced malignant transformation. Our results suggest that NOX plays an important role in Cr(VI)-induced ROS generation and carcinogenesis.
authors: Graduate Center for Toxicology, 1095 V.A. Drive, 306 Health Sciences Research Building, Lexington, KY 40536, USA.
authors: Xin
authors: X
authors: Wang
authors: Young-Ok
authors: YO
authors: Son
authors: Qingshan
authors: Q
authors: Chang
authors: Lijuan
authors: L
authors: Sun
authors: J Andrew
authors: JA
authors: Hitron
authors: Amit
authors: A
authors: Budhraja
authors: Zhuo
authors: Z
authors: Zhang
authors: Zunji
authors: Z
authors: Ke
authors: Fei
authors: F
authors: Chen
authors: Jia
authors: J
authors: Luo
authors: Xianglin
authors: X
authors: Shi
mesh_terms: D000818:Animals; D001980:Bronchi / Q000187:drug effects / Q000378:metabolism / Q000473:pathology; D002273:Carcinogens / Q000633:toxicity*; D002460:Cell Line; D002462:Cell Membrane / Q000187:drug effects / Q000378:metabolism; D002470:Cell Survival / Q000187:drug effects; D002471:Cell Transformation, Neoplastic / Q000139:chemically induced; D002840:Chromates / Q000633:toxicity*; D002857:Chromium / Q000633:toxicity*; D004789:Enzyme Activation; D004847:Epithelial Cells / Q000187:drug effects / Q000378:metabolism / Q000473:pathology; D020868:Gene Silencing; D006801:Humans; D051379:Mice; D008819:Mice, Nude; D019255:NADPH Oxidases / Q000096:biosynthesis*; D009368:Neoplasm Transplantation; D009369:Neoplasms / Q000188:drug therapy / Q000473:pathology; D018384:Oxidative Stress / Q000187:drug effects; D010088:Oxidoreductases / Q000378:metabolism; D010766:Phosphorylation / Q000187:drug effects; D034741:RNA, Small Interfering / Q000235:genetics; D017382:Reactive Oxygen Species / Q000378:metabolism*; D014162:Transfection; D023041:Xenograft Model Antitumor Assays
chemical_list: D002273:Carcinogens; D002840:Chromates; D034741:RNA, Small Interfering; D017382:Reactive Oxygen Species; D002857:Chromium; C074702:chromium hexavalent ion; C016104:sodium bichromate; D010088:Oxidoreductases; D019255:NADPH Oxidases