Clastogenicity, photo-clastogenicity or pseudo-photo-clastog

Mutation Research607(2006)215–224

Clastogenicity,photo-clastogenicity or pseudo-photo-clastogenicity: Genotoxic effects of zinc oxide in the dark,in pre-irradiated or simultaneously irradiated Chinese hamster ovary cells

Eric K.Dufour a,?,Tirukalikundram Kumaravel b,Gerhard J.Nohynek a,

David Kirkland b,Herv′e Toutain a

a L’Or′e al Research and Development,Worldwide Safety Department,92600Asni`e res,France

b COVANCE Laboratories Ltd,Oatley Road,Harrogate,North Yorkshire HG31PY,UK

Received26January2006;received in revised form5April2006;accepted12April2006

Available online21June2006

Abstract

Zinc oxide(ZnO),a widely used ingredient in dermatological preparations and sunscreens,is clastogenic in vitro,but not in vivo. Given that ZnO has an approximately four-fold greater clastogenic potency in the presence of UV light when compared with that in the dark,it has been suggested to be photo-clastogenic.In order to clarify whether this increased potency is a genuine photo-genotoxic effect,we investigated the clastogenicity of ZnO(mean particle size,100nm)in Chinese hamster ovary(CHO)cells in the dark (D),in pre-irradiated(PI,i.e.UV irradiation of cells followed by treatment with ZnO)and in simultaneously irradiated(SI,i.e.ZnO treatment concurrent with UV irradiation)CHO cells at UV doses of350and700mJ/cm2.The cytotoxicity of ZnO to CHO cells under the different irradiation conditions was as follows:SI>PI>D.In the dark,ZnO produced a concentration-related increase in chromosome aberrations(CA).In PI or SI CHO cells,ZnO was clastogenic at signi?cantly lower concentrations(approximately two-to four-fold)when compared with effective concentrations in the dark,indicating an increased susceptibility of CHO cells to ZnO-mediated clastogenic effects due to UV irradiation per se.The incidence of CA in SI or PI cells was generally higher than that in the dark.At similar ZnO concentrations,SI conditions generally produced higher CA incidence than PI conditions. However,when ZnO concentrations producing similar cytotoxicity were compared,CA incidences under PI or SI conditions were nearly identical.The modest increase in the clastogenic potency of ZnO following UV irradiation contrasts with the results observed with genuine photo-clastogenic agents,such as8-MOP,which may produce an increase in clastogenic potency of>15,000-fold under SI conditions.Our results provide evidence that,under conditions of in vitro photo-clastogenicity tests,UV irradiation of the cellular test system per se may produce a slight increase in the genotoxic potency of compounds that are clastogenic in the dark. In conclusion,our data suggest that minor increases in clastogenic potency under conditions of photo-genotoxicity testing do not necessarily represent a photo-genotoxic effect,but may occur due to an increased sensitivity of the test system subsequent to UV irradiation.

?2006Elsevier B.V.All rights reserved.

Keywords:Zinc oxide nanoparticles;CAS1314-13-2;Chinese hamster ovary cells;Clastogenicity;Photo-clastogenicity;Photo-genotoxicity Abbreviations:ZnO,zinc oxide nanoparticles;CA,chromosome aberration;CHO cells,Chinese hamster ovary cells;V-79cells,Chinese hamster V-79cells;GLP,good laboratory practice;PI,pre-irradiation or pre-irradiated;SI,simultaneous irradiation or simultaneously irradiated; 3T3NRU PT,neutral red uptake phototoxicity test on3T3mouse?broblasts

?Corresponding author.Tel.:+33147567905;fax:+33147564492.

E-mail address:edufour@1d26b30f76c66137ee0619d0(E.K.Dufour).

1383-5718/$–see front matter?2006Elsevier B.V.All rights reserved.

doi:10.1016/j.mrgentox.2006.04.015

216 E.K.Dufour et al./Mutation Research607(2006)215–224

1.Introduction

Zinc(Zn)is one of the most important trace ele-ments in the mammalian organism and is involved in homeostasis,immune response,oxidative stress,apop-tosis and ageing[1].Zn is also an essential component of mammalian androgen receptors,DNA repair enzymes and DNA or RNA synthesis,stability,proliferation and transcription[2,3].In animal models,Zn de?ciency has been associated with adverse reproductive effects includ-ing reduced fertility,foetal malformations and growth retardation in late pregnancy,whereas labour abnormal-ities,congenital malformations,and preterm labour have been reported in otherwise healthy women with low serum Zn concentrations[4].Zn and its salts were non-carcinogenic in rodents after inhalation,oral uptake or intra-peritoneal administrations,whereas Zn-de?ciency was shown to enhance the susceptibility of rodents to known carcinogens,such as4-nitroquinoline-N-oxide or cadmium.Finally,moderate dietary Zn-supplementation offered protection against carcinogenic substances[5].

Genotoxicity studies on Zn,its salts or its oxide(ZnO) had equivocal results.Although most in vitro and all in vivo tests were negative[5,6],Zn salts were reported to be slightly positive in in vitro genotoxicity tests,such as the Ames test or chromosome aberration(CA)test in cultured human lymphocytes[5].Similarly,results with Zn acetate in the Mouse Lymphoma Assay or in Chinese hamster ovary(CHO)cells were reported to be positive,albeit at high concentrations[7].Recently,the EU Scienti?c Committee on Toxicity,Ecotoxicity and the Environment concluded that Zn and its salts are not expected to be mutagens or carcinogens under the expected human exposure conditions[8].

Zinc oxide(ZnO)is widely used in dermatological preparations and sunscreens[9].In the European Union, sunscreens are regulated under the EU Cosmetics Direc-tive and require an extensive safety dossier as described in the Notes of Guidance of the EU Scienti?c Committee on Cosmetics and Non-Food Products(SCCNFP).These Guidelines stipulate that UV?lters should be examined for genotoxicity,photo-toxicity,photo-sensitisation,as well as photo-genotoxicity in appropriate tests such as …… 此处隐藏：38943字，全部文档内容请下载后查看。喜欢就下载吧 ……