50-Hz electromagnetic fields enhance cell proliferation and

BiochimicaetBiophysicaActa1743(2005)120–

129

/locate/bba

50-HzextremelylowfrequencyelectromagneticfieldsenhancecellproliferationandDNAdamage:Possibleinvolvement

ofaredoxmechanism

FedericaI.Wolfa,*,AngelaTorselloa,BeatriceTedescoa,SilviaFasanellaa,AlmaBoninsegnaa,

MarcelloD’Ascenzob,ClaudioGrassib,GianBattistaAzzenab,AchilleCittadinia

b

InstituteofGeneralPathologyandGiovanniXXIIICancerResearchCenter,L.goF.Vito,1-00168Rome,Italy

InstituteofHumanPhysiology,CatholicUniversityofSacredHeart,FacultyofMedicine,L.goF.Vito,1-00168Rome,Italy

Received11March2004;receivedinrevisedform2September2004;accepted8September2004

Availableonline19September2004

a

Abstract

HL-60leukemiacells,Rat-1fibroblastsandWI-38diploidfibroblastswereexposedfor24–72hto0.5–1.0-mT50-Hzextremelylowfrequencyelectromagneticfield(ELF-EMF).Thistreatmentinducedadose-dependentincreaseintheproliferationrateofallcelltypes,namelyabout30%increaseofcellproliferationafter72-hexposureto1.0mT.ThiswasaccompaniedbyincreasedpercentageofcellsintheS-phaseafter12-and48-hexposure.TheabilityofELF-EMFtoinduceDNAdamagewasalsoinvestigatedbymeasuringDNAstrandbreaks.Adose-dependentincreaseinDNAdamagewasobservedinallcelllines,withtwopeaksoccurringat24and72h.AsimilarpatternofDNAdamagewasobservedbymeasuringformationof8-OHdGadducts.TheeffectsofELF-EMFoncellproliferationandDNAdamagewerepreventedbypretreatmentofcellswithanantioxidantlikea-tocopherol,suggestingthatredoxreactionswereinvolved.Accordingly,Rat-1fibroblaststhathadbeenexposedtoELF-EMFfor3or24hexhibitedasignificantincreaseindichlorofluorescein-detectablereactiveoxygenspecies,whichwasbluntedbya-tocopherolpretreatment.CellsexposedtoELF-EMFandexaminedasearlyas6haftertreatmentinitiationalsoexhibitedmodificationsofNFnB-relatedproteins(p65-p50andInBa),whichweresuggestiveofincreasedformationofp65-p50orp65-p65activeforms,aprocessusuallyattributedtoredoxreactions.TheseresultssuggestthatELF-EMFinfluenceproliferationandDNAdamageinbothnormalandtumorcellsthroughtheactionoffreeradicalspecies.ThisinformationmaybeofvalueforappraisingthepathophysiologicconsequencesofanexposuretoELF-EMF.D2004ElsevierB.V.Allrightsreserved.

Keywords:8-OHdG;Singlestrandbreak;Cellcycle;DCF;NFnB;InB;a-Tocopherol

1.Introduction

Environmentalexposuretoextremelylowfrequency(ELF)electromagneticfields(EMF)isstronglyincreasedindevelopedcountriesasaconsequenceofthedistributionanduseofelectricity.

SinceWertheimerandLeeper[1]arguedthatthefrequencyofchildhoodcancercorrelatedtotheelectrical

*Correspondingauthor.FedericaI.WolfInstituteofGeneralPathology,CatholicUniversityofSacredHeart,FacultyofMedicine,L.goF.Vito,1-00168Rome,Italy.Tel.:+39063016619;fax:+39063012753.

E-mailaddress:fwolf@rm.unicatt.it(F.I.Wolf).0167-4889/$-seefrontmatterD2004ElsevierB.V.Allrightsreserved.doi:10.1016/j.bbamcr.2004.09.005

wiringconfigurationrunningnearbytheirhouses,thecorrelationbetweenELF-EMFexposureandcancerriskhasbecomeamatterofpublicconcern.Asaconsequence,thepossibleeffectsofELF-EMFonbiologicalsystemswereextensivelyinvestigated.Someepidemiologicalstud-iesofferedpositiveevidenceforacorrelationbetweenexposuretoELF-EMFandincreasedincidenceofbrain,breastandhematologicalmalignancies,buttheseresultshavenotbeenconfirmedinotherstudies[2–5].Studieswithlaboratoryanimalssimilarlyproducedinconclusiveorcontradictoryresults;thesmallnumberofanimalsexam-inedandthelackofproperlystandardisedexposureparametersmayhavecontributedtosuchnegativeor

F.I.Wolfetal./BiochimicaetBiophysicaActa1743(2005)120–129121

inconsistentresults[6,7].InvitrostudieshaveexploredthepotentialeffectsofELF-EMFoncellproliferation[8],apoptosis[9,10],differentiation[11],genotoxicity[12]andproto-oncogenemodulation[13–15];again,theresultsremainedinconclusiveoropentodebate.ItisunclearhowELF-EMFwouldinfluencecellularbehavior,butaplausiblehypothesisisthatELF-EMFaffectmembranestructureandpermeabilitytosmallmolecules.Inarecentstudy,wehaveshownthatinneuroendocrinecellsELF-EMFexposureincreasedCa2+currentsduetooverexpres-sionofvoltage-gatedCa2+channels,anoccurrencethatmaywellbecorrelatedwithproliferativeevents[16].AnotherinterestinghypothesisisthatELF-EMFinterferewithchemicalreactionsinvolvingfreeradicalproduction(seeRef.[17]forreview).

Itiswellestablishedthatfreeradicalshavepleiotropiceffectswhichmayvaryfromcytotoxictomitogenicresponsesdependingonthedoseintensity,thedurationofexposure,andthetypeofcellortissue[18].Freeradicals,e.g.,hydroxylradicals,caninteractwithDNAandformprimarily8-OHdGadducts,resultinginsinglestrandbreaks[19].Adductsorstrandbreaksarerecognisedandusuallyremovedquiteefficientlybyspecificrepairmechanisms.Nevertheless,DNAdamagecouldbecomeasiteofmutationandakeysteptocarcinogenesisifthedamagewereextensiveenoughtoovercometherepaircapacityofthecell[20,21].Ontheotherhand,ithasbeendemonstratedthatlowlevelsofreactiveoxygenspeciestriggerintracellularsignalsthatinvolvethetran-scriptionofgenesandleadtoresponsesincludingproliferation[22,23].Oneofthebestcharacterizedredox-modulatablesignalsinvolvesNFnB,whichcantriggerproliferationorapoptosis[24,25].NFnB/Relproteins,primarilycomposedofheterodimersofp50/p65,arepresentinthecytoplasmintheirinactiveformassociatedwithIkBs.Activationoccursafterphosphor-ylationofInBaandtranslocationofp50/p65intothenucleuswhere,afterfurtherphosphorylationofthep65subunit,itbindstoDNAandfunctionsasatranscriptionfactor.Inseveralstudies,overexpressionandnucleartranslocationofp65wereshowntocorrelatewiththetranscriptionactivityofNFkB[26].ActivationofNFnBthroughphosphorylationofInBhasalsobeeninvestigatedindetailandshowntobeassociatedwithreceptor-mediatedsignalslikeCTLA4[27].Otheractivationmechanisms,mediatedbyredoxreactions,havealsobeendescribed.

Inthisstudyweevaluatedtheeffectsof50-HzELF-EMFoncellproliferation,cellcycledistributionandDNAdamageinnormalcells(embryonichumanlungfibroblasts,WI-38),neoplasticcells(humanpromyelocyticleukemiacells,HL-60) …… 此处隐藏：6112字，全部文档内容请下载后查看。喜欢就下载吧 ……