title: Chronic exposure to nanosized, anatase titanium dioxide is not cyto- or genotoxic to Chinese hamster ovary cells.
abstract: Titanium dioxide nanoparticles (nano-TiO(2) ) are widely used in cosmetics, skin care products, paints, and water treatment processes. Disagreement remains regarding the safety of nano-TiO(2) , and little epidemiological data is available to provide needed resolution. Most studies have examined effects using acute exposure experiments with relatively few studies using a chronic exposure design. We examined cyto- and genotoxicity in CHO-K1 cells following 60 days of continuous exposure to defined levels of nano-TiO(2) (0, 10, 20, or 40 μg/ml). Oxidative stress increased in a concentration-dependent manner in short- (2 days) and long-term cultures, but long-term cultures had lower levels of oxidative stress. The primary reactive oxygen species appeared to be superoxide, and ROS indicators were lowered with the addition of superoxide dismutase (SOD). No cyto- or genotoxic effects were apparent using the XTT, trypan-blue exclusion, and colony-forming assays for viability and the Comet and Hprt gene mutation assays for genotoxicity. Nano-TiO(2) increased the percentage of cells in the G2/M phase of the cell cycle, but this effect did not appear to influence cell viability or cell division. Cellular Ti content was dose-dependent, but chronically exposed cells had lower amounts than acutely exposed cells. CHO cells appear to adapt to chronic exposure to nano-TiO(2) and detoxify excess ROS possibly through upregulation of SOD in addition to reducing particle uptake.
authors.affiliation: Department of Environmental Health Sciences, Tulane University, New Orleans, Louisiana 70112, USA.
authors.forename: Shuguang
authors.initials: S
authors.lastname: Wang
authors.forename: Lindsey A
authors.initials: LA
authors.lastname: Hunter
authors.forename: Zikri
authors.initials: Z
authors.lastname: Arslan
authors.forename: Michael G
authors.initials: MG
authors.lastname: Wilkerson
authors.forename: Jeffrey K
authors.initials: JK
authors.lastname: Wickliffe
mesh_terms: D000818:Animals; D016466:CHO Cells; D002453:Cell Cycle / Q000187:drug effects; D002470:Cell Survival / Q000187:drug effects; D020552:Comet Assay; D006224:Cricetinae; D003412:Cricetulus; D004249:DNA Damage; D004305:Dose-Response Relationship, Drug; D007041:Hypoxanthine Phosphoribosyltransferase / Q000235:genetics; D046529:Microscopy, Electron, Transmission; D009153:Mutagens / Q000633:toxicity*; D009154:Mutation; D053758:Nanoparticles; D018384:Oxidative Stress / Q000187:drug effects; D017382:Reactive Oxygen Species / Q000378:metabolism; D014025:Titanium / Q000633:toxicity*; D036401:Toxicity Tests, Chronic
chemical_list: D009153:Mutagens; D017382:Reactive Oxygen Species; C009495:titanium dioxide; D014025:Titanium; D007041:Hypoxanthine Phosphoribosyltransferase