title: Does cadmium affect the toxicokinetics of permethrin in Chironomus dilutus at sublethal level? Evidence of enzymatic activity and gene expression.
abstract: Pyrethroids and metals were simultaneously detected in aquatic environment and showed antagonistic lethality to the benthic invertebrate, Chironomus dilutus. Accelerated biotransformation of pyrethroids in organism by the presence of metals was proposed as the likely reason for the antagonism. Mechanistic explanation for the role of toxicokinetics of pyrethroids in the antagonistic interaction would help better understanding the reasons for the joint toxicity. The goal was achieved in the current study by evaluating the impact of cadmium on toxicokinetic parameters of permethrin in C. dilutus, and by explaining the interaction through quantifying the activity and gene expression of biotransformation-related enzymes. Toxicokinetic parameters were simulated using a first-order kinetic model. Bioconcentration factors and uptake and elimination rate constants for permethrin were not significantly changed with the addition of cadmium at sublethal level, neither did the activity of enzymes, including glutathione S-transferase (GST), carboxylesterase (CarE), catalase and lipid peroxidation. Yet, the activities of metabolism-related enzymes (GST and CarE) showed an elevating tendency with adding cadmium. Furthermore, the expression of metabolism-related genes, including cytochrome P450 and glutathione S-transferase genes were significantly up-regulated in C. dilutus exposed to a mixture of permethrin and cadmium compared with permethrin only. Although co-exposure to cadmium did not induce toxicokinetic changes of permethrin in C. dilutus, it did enhance the activity of metabolic enzymes which were encoded by the metabolism-related genes, suggesting an acceleration of biotransformation of permethrin to less toxic metabolites in the midges. This possibly explained the antagonistic interaction for permethrin and cadmium.
authors: State Key Laboratory of Organic Geochemistry, Guangzhou Institute of Geochemistry, Chinese Academy of Sciences, Guangzhou 510640, China; University of Chinese Academy of Sciences, Beijing 100049, China.
authors: Xin
authors: X
authors: Chen
authors: State Key Laboratory of Organic Geochemistry, Guangzhou Institute of Geochemistry, Chinese Academy of Sciences, Guangzhou 510640, China; School of Environment, Guangzhou Key Laboratory of Environmental Exposure and Health, and Guangdong Key Laboratory of Environmental Pollution and Health, Jinan University, Guangzhou 510632, China.
authors: Huizhen
authors: H
authors: Li
authors: School of Environment, Guangzhou Key Laboratory of Environmental Exposure and Health, and Guangdong Key Laboratory of Environmental Pollution and Health, Jinan University, Guangzhou 510632, China.
authors: Junjie
authors: J
authors: Zhang
authors: Division of Environmental Health, Illinois Department of Public Health, Springfield, IL 62761, USA.
authors: Yuping
authors: Y
authors: Ding
authors: School of Environment, Guangzhou Key Laboratory of Environmental Exposure and Health, and Guangdong Key Laboratory of Environmental Pollution and Health, Jinan University, Guangzhou 510632, China. Electronic address: youjing@jnu.edu.cn.
authors: Jing
authors: J
authors: You
mesh_terms: D000818:Animals; D001711:Biotransformation; D002104:Cadmium / Q000737:chemistry* / Q000378:metabolism*; D043182:Carboxylesterase / Q000378:metabolism; D002374:Catalase / Q000378:metabolism; D002683:Chironomidae / Q000378:metabolism*; D015870:Gene Expression / Q000187:drug effects; D005982:Glutathione Transferase / Q000378:metabolism; D007306:Insecticides / Q000494:pharmacology*; D015227:Lipid Peroxidation / Q000502:physiology; D026023:Permethrin / Q000737:chemistry* / Q000494:pharmacology*; D066007:Toxicokinetics; D014874:Water Pollutants, Chemical / Q000378:metabolism*
chemical_list: D007306:Insecticides; D014874:Water Pollutants, Chemical; D002104:Cadmium; D026023:Permethrin; D002374:Catalase; D005982:Glutathione Transferase; D043182:Carboxylesterase
keywords: Cadmium; Enzyme activity; Gene expression; Permethrin; Toxicokinetics