title: Responses of growth inhibition and antioxidant gene expression in earthworms (Eisenia fetida) exposed to tetrabromobisphenol A, hexabromocyclododecane and decabromodiphenyl ether.
abstract: Tetrabromobisphenol A (TBBPA), hexabromocyclododecane (HBCD) and decabromodiphenyl ether (BDE 209), suspected ubiquitous contaminants, account for the largest volume of brominated flame retardants (BFRs) since penta-BDE and octa-BDE have been phased out globally. In this paper, the growth inhibition and gene transcript levels of antioxidant enzymes (superoxide dismutase (SOD), catalase (CAT)) and the stress-response gene involved in the prevention of oxidative stress (Hsp70) of earthworms (Eisenia fetida) exposed to TBBPA, HBCD and BDE 209 were measured to identify the toxicity effects of selected BFRs on earthworms. The growth of earthworms treated by TBBPA at 200 and 400 mg/kg dw were inhibited at rate of 13.7% and 22.0% respectively, while there was no significant growth inhibition by HBCD and BDE 209. A significant (P<0.01) up-regulation of SOD expression level was observed in earthworms exposed to TBBPA at 50 mg/kg dw (1.77-fold) and to HBCD at 400 mg/kg dw (2.06-fold). The transcript level of Hsp70 gene was significantly up-regulated (P<0.01) when earthworms exposed to TBBPA at concentration of 50-200 mg/kg (2.16-2.19-fold) and HBCD at 400 mg/kg (2.61-fold). No significant variation of CAT gene expression in all the BFRs treatments was observed, neither does all the target gene expression level exposed to BDE 209. Assessed by growth inhibition and the changes at mRNA levels of encoding genes in earthworms, TBBPA showed the greatest toxicity, followed by HBCD and BDE 209, consistent with trends in molecular properties. The results help to understand the molecular mechanism of antioxidant defense.
authors.affiliation: State Key Laboratory of Urban and Regional Ecology, Research Center for Eco-Environmental Sciences, Chinese Academy of Sciences, Beijing 100085, China.
authors.forename: Ya-juan
authors.initials: YJ
authors.lastname: Shi
authors.affiliation: Beijing Municipal Environmental Monitoring Center, Beijing 100048, China.
authors.forename: Xiang-bo
authors.initials: XB
authors.lastname: Xu
authors.affiliation: National Center for Climate Change Strategy and International Cooperation, Beijing 100038, China.
authors.forename: Xiao-qi
authors.initials: XQ
authors.lastname: Zheng
authors.affiliation: State Key Laboratory of Urban and Regional Ecology, Research Center for Eco-Environmental Sciences, Chinese Academy of Sciences, Beijing 100085, China. Electronic address: yllu@rcees.ac.cn.
authors.forename: Yong-long
authors.initials: YL
authors.lastname: Lu
mesh_terms: D000818:Animals; D000975:Antioxidants / Q000378:metabolism*; D002374:Catalase / Q000235:genetics / Q000378:metabolism; D004781:Environmental Exposure / Q000009:adverse effects*; D005411:Flame Retardants / Q000009:adverse effects; D015870:Gene Expression / Q000187:drug effects* / Q000235:genetics; D018840:HSP70 Heat-Shock Proteins / Q000235:genetics / Q000378:metabolism; D055768:Halogenated Diphenyl Ethers / Q000009:adverse effects*; D006842:Hydrocarbons, Brominated / Q000009:adverse effects*; D009835:Oligochaeta / Q000187:drug effects* / Q000235:genetics / Q000378:metabolism; D018384:Oxidative Stress / Q000187:drug effects / Q000235:genetics; D011075:Polybrominated Biphenyls / Q000009:adverse effects*; D012333:RNA, Messenger / Q000235:genetics; D013482:Superoxide Dismutase / Q000235:genetics / Q000378:metabolism; D015854:Up-Regulation / Q000187:drug effects / Q000235:genetics
chemical_list: D000975:Antioxidants; D005411:Flame Retardants; D018840:HSP70 Heat-Shock Proteins; D055768:Halogenated Diphenyl Ethers; D006842:Hydrocarbons, Brominated; D011075:Polybrominated Biphenyls; D012333:RNA, Messenger; C089796:hexabromocyclododecane; D002374:Catalase; D013482:Superoxide Dismutase; C020806:tetrabromobisphenol A; C010902:decabromobiphenyl ether
keywords: Antioxidant enzymes; BDE 209; Brominated flame retardants; Gene expression; Growth inhibition; HBCD; Heat shock proteins; TBBPA