Inverse Relationship between Urinary Retinol-Binding Protein, Beta-2- Microglobulin, and Blood Manganese Levels in School-Age Children from an E-Waste Recycling Town - Environmental Contamination: Health Risks and Ecological Restoration - page 189

An. unexpected. inding. in. this. study. in. children. was. an. overall. inverse.
relationship. between. β 2 -MG. and. RBP. and. observed. Mn. levels,. similar. to.
effects.described.in.some.experimental.animal.models..To.our.knowledge,.
there. are. no. reports. showing. evidence. of. tubular. effects. at. such. levels. of.
Mn.. Manganese. porphyrin. can. reduce. renal. injury. and. mitochondrial.
damage. during. ischemia/reperfusion. in. rats. (Saba. et. al.. 2007).. Such. an.
association. between. MnB. and. urinary. β 2 -MG. and. RBP. may. be. biologi-
cally. plausible.. Environmental. exposure. is. a. complex. mixture. of. hazard-
ous.compounds.with.different.mechanisms.of.toxicity..Oxidative.stress.has.
been.suggested.to.be.an.important.molecular.mechanism.of.toxic.effects.of.
environmental.pollutants.such.as.lead.and.cadmium.in.the.kidney.(Jurczuk.
et.al..2006,.Conterato.et.al..2007)..Mn.is.a.constituent.of.mitochondrial.man-
ganese.superoxide.dismutase.(Mn-SOD),.which.plays.an.important.role.in.
protection. against. oxidative. stress. (Luk. et. al.. 2005).. It. was. reported. that.
Mn-SOD. attenuates. Cisplatin-induced. renal. injury. (Davis. et. al.. 2001).. The.
in vitro .antioxidant.action.of.Mn.in.differently.mediated.lipid.peroxidation.
conditions. and. its. ability. to. scavenge. superoxide. anions. and. oxygen-free.
radicals. have. been. described. (Coassin. 1992,. Hussain. and. Ali. 1999,. Anand.
and.Kanwar.2001)..Low.dose.of.Mn.may.have.an.antioxidant.effect.in.kid-
neys.of.gentamicin-administrated.rats,.but.its.high.doses.had.no.beneicial.
effect. (Atessahin. et. al.. 2003).. It. seems. that. currently. observed. Mn. levels.
in. themselves. have. no. signiicantly. harmful. effect. on. renal. tubular. func-
tion.in.children..Whether.the.higher.levels.of.Mn.in.children.may.result.in.
adverse.effects.on.other.parameters.of.renal.tubule.function.needs.further.
investigation.
There.are.several.limitations.to.this.study..This.was.a.cross-sectional.study,.
which.limits.interpretation.of.the.results.for.a.causal.relationship.and.the.time.
course.of.exposures.and.effects..However,.this.is.the.irst.study.concerning.
renal.tubular.effects.and.MnB.in.school-age.children.in.an.e-waste-polluted.
area..The.present.study.demonstrates.that.MnB.are.inversely.associated.with.
β 2 -MG. and. RBP. (sensitive. markers. of. renal. tubular. damage). of. school-age.
children. in. an. e-waste. recycling. town.. RBP. in. children. from. Guiyu. were.
higher.than.those.of.control,.similar.to.MnB..It.seems.that.elevated.levels.of.
Mn.may.result.in.adverse.effects.on.renal.tubular.function.
Acknowledgment
This. work. was. supported. by. the. Scientiic. Research. Foundation. for. the.
Returned. Overseas. Chinese. Scholars,. State. Education. Ministry;. and. 211.
project.of.Guang.Dong.Province..The.authors.would.like.to.thank.Dr..Harold.
W..Cook.for.English.language.editing.