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Chen C, Zhao T, Liu J, Zheng S, Zeng W, Zhang X, Cui Y, Zhong R. Effect of HHCB and Cd on phytotoxicity, accumulation, subcellular distribution and stereoselectivity of chiral HHCB in soil-plant systems. PLANT PHYSIOLOGY AND BIOCHEMISTRY : PPB 2023; 198:107699. [PMID: 37054615 DOI: 10.1016/j.plaphy.2023.107699] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/25/2023] [Revised: 03/21/2023] [Accepted: 04/07/2023] [Indexed: 05/07/2023]
Abstract
The toxicity of HHCB in the growth and development of plants is well known, but its uptake, subcellular distribution, and stereoselectivity, especially in a co-contamination environment, is not fully understood. Therefore, a pot experiment was performed to research the physiochemical response, and the fate of HHCB in pakchoi when the Cd co-existed in soil. The Chl contents were significantly lower, and the oxidative stress was aggravated under the co-exposure of HHCB and Cd. The accumulations of HHCB in roots were inhibited, and those in leaves were elevated. The transfer factors of HHCB in HHCB-Cd treatment increased. The subcellular distributions were analyzed in the cell walls, cell organelles, and cell soluble constituents of roots and leaves. In roots, the distribution proportion of HHCB followed cell organelle > cell wall > cell soluble constituent. In leaves, the distribution proportion of HHCB was different from that in roots. And the co-existing Cd made the distribution proportion of HHCB change. In the absence of Cd, the (4R,7S)-HHCB and (4R,7R)-HHCB were preferentially enriched in roots and leaves, and the stereoselectivity of chiral HHCB was more significant in roots than leaves. The co-existing Cd reduced the stereoselectivity of HHCB in plants. Our findings suggested that the fate of HHCB was affected by the co-existing Cd, so the risk of HHCB in the complicated environment should be paid more attention.
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Affiliation(s)
- Cuihong Chen
- Key Laboratory of Pollution Processes and Environmental Criteria (Ministry of Education)/Tianjin Engineering Center of Environmental Diagnosis and Contamination Remediation, College of Environmental Science and Engineering, Nankai University, Tianjin, 300350, China.
| | - Tong Zhao
- Xiong'an Urban Planning and Design Research Institute Co.Ltd, Baoding, Hebei, 071700, China
| | - Jinzheng Liu
- Key Laboratory of Pollution Processes and Environmental Criteria (Ministry of Education)/Tianjin Engineering Center of Environmental Diagnosis and Contamination Remediation, College of Environmental Science and Engineering, Nankai University, Tianjin, 300350, China
| | - Shimei Zheng
- College of Chemistry and Chemical and Environmental Engineering, Weifang University, Weifang, Shandong, 261061, China
| | - Wenlu Zeng
- Key Laboratory of Pollution Processes and Environmental Criteria (Ministry of Education)/Tianjin Engineering Center of Environmental Diagnosis and Contamination Remediation, College of Environmental Science and Engineering, Nankai University, Tianjin, 300350, China
| | - Xiaohui Zhang
- Engineering Research Center of Coal-based Ecological Carbon Sequestration Technology of the Ministry of Education, Shanxi Datong University, 037009, China
| | - Yuxiao Cui
- Key Laboratory of Pollution Processes and Environmental Criteria (Ministry of Education)/Tianjin Engineering Center of Environmental Diagnosis and Contamination Remediation, College of Environmental Science and Engineering, Nankai University, Tianjin, 300350, China
| | - Rong Zhong
- Key Laboratory of Pollution Processes and Environmental Criteria (Ministry of Education)/Tianjin Engineering Center of Environmental Diagnosis and Contamination Remediation, College of Environmental Science and Engineering, Nankai University, Tianjin, 300350, China
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Yang E, Wen B, Zhang Z, Huang H, Zhang S. Diastereomer- and enantiomer-selective accumulation and depuration of 1,2-dibromo-4-(1,2-dibromoethyl) cyclohexanes (DBE-DBCHs) and 1,2,5,6-tetrabromocyclooctanes (TBCOs) in earthworms (Eisenia fetida). THE SCIENCE OF THE TOTAL ENVIRONMENT 2022; 826:154145. [PMID: 35227722 DOI: 10.1016/j.scitotenv.2022.154145] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/02/2021] [Revised: 02/18/2022] [Accepted: 02/21/2022] [Indexed: 06/14/2023]
Abstract
Due to the regulation of hexabromocyclododecane (HBCD), much attention has been paid to its potential substitutes, 1,2-dibromo-4-(1,2-dibromoethyl) cyclohexane (DBE-DBCH) and 1,2,5,6-tetrabromocyclooctane (TBCO). DBE-DBCH and TBCO contain several diastereomers and enantiomers, which may exhibit different environmental behaviors and biological effects. In this study, the accumulation and depuration of individual DBE-DBCH and TBCO diastereomers by earthworms (Eisenia fetida) from diastereomer-contaminated soils were evaluated. The accumulation and depuration kinetics of DBE-DBCH and TBCO diastereomers followed one-compartment first-order kinetics. The biota soil accumulation factor (BSAF) of β-DBE-DBCH (2.74 goc glip-1) was 1.26 times that of α-DBE-DBCH (2.18 goc glip-1), while the BSAF of β-TBCO (2.15 goc glip-1) was 1.62 times that of α-TBCO (1.3 goc glip-1), showing the diastereomer-specific accumulation of DBE-DBCH and TBCO. DBE-DBCH and TBCO diastereomers appeared to be transformed in earthworm-soil systems; however, no evidence of bioisomerization of the four diastereomers in earthworms was found, and no potential metabolites of debromination and hydroxylation were detected. Furthermore, the selective enrichment of E1-α-DBE-DBCH and E1-β-DBE-DBCH (E1 represents the first enantiomer eluted) occurred in earthworms as the enantiomer fractions (EFs) for α-DBE-DBCH (0.562-0.763) and β-DBE-DBCH (0.516-0.647) were significantly greater than those in the technical products (0.501 for α-DBE-DBCH and 0.497 for β-DBE-DBCH, p < 0.05), especially in the depuration stage. The results demonstrated the diastereomer- and enantiomer-selective accumulation of DBE-DBCH and the diastereomer-selective accumulation of TBCO in the earthworm.
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Affiliation(s)
- Entai Yang
- State Key Laboratory of Environmental Chemistry and Ecotoxicology, Research Center for Eco-Environmental Sciences, Chinese Academy of Sciences, Beijing 100085, China; University of Chinese Academy of Sciences, Beijing 100049, China
| | - Bei Wen
- State Key Laboratory of Environmental Chemistry and Ecotoxicology, Research Center for Eco-Environmental Sciences, Chinese Academy of Sciences, Beijing 100085, China; University of Chinese Academy of Sciences, Beijing 100049, China.
| | - Zhenying Zhang
- State Key Laboratory of Environmental Chemistry and Ecotoxicology, Research Center for Eco-Environmental Sciences, Chinese Academy of Sciences, Beijing 100085, China; University of Chinese Academy of Sciences, Beijing 100049, China
| | - Honglin Huang
- State Key Laboratory of Environmental Chemistry and Ecotoxicology, Research Center for Eco-Environmental Sciences, Chinese Academy of Sciences, Beijing 100085, China
| | - Shuzhen Zhang
- State Key Laboratory of Environmental Chemistry and Ecotoxicology, Research Center for Eco-Environmental Sciences, Chinese Academy of Sciences, Beijing 100085, China; University of Chinese Academy of Sciences, Beijing 100049, China
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Zhu L, Huo X, Zhou J, Zhang Q, Wang W. Metabolic activation mechanism of 2,2',3,3',6,6'-hexachlorobiphenyl (PCB136) by cytochrome P450 2B6: A QM/MM approach. THE SCIENCE OF THE TOTAL ENVIRONMENT 2021; 776:145579. [PMID: 33652317 DOI: 10.1016/j.scitotenv.2021.145579] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/29/2020] [Revised: 01/28/2021] [Accepted: 01/28/2021] [Indexed: 06/12/2023]
Abstract
Cytochrome P450 enzymes (CYPs) play an essential role in the bio-transformation of polychlorinated biphenyls (PCBs). The present work implemented quantum mechanic/molecular mechanic methods (QM/MM) and density functional theory (DFT) to study the metabolic activation of 2,2',3,3',6,6'-hexachlorobiphenyl (PCB136) catalyzed by CYP2B6. Electrophilic additions at the Cα and Cβ positions generate different active intermediates. The electrophilic addition energy barrier of Cβ is 10.9 kcal/mol higher than that of Cα, and Cα is the preferred site for the electrophilic addition reaction. Based on the previous experimental studies, this work investigated the mechanism of converting active intermediates into OH-PCB136, which has high toxicity in a non-enzymatic environment. Structural analysis via the electrostatic and noncovalent interactions indicates that Phe108, Ile114, Phe115, Phe206, Phe297, Ala298, Leu363, Val367, TIP32475 and TIP32667 play crucial roles in substrate recognition and metabolism. The analysis suggests that the halogen-π interactions are important factors for the metabolism of CYP2B6 to halogenated environmental pollutants. This work improved the understanding of the metabolism and activation process of chiral PCBs, and can be used as a guide to improve the microbial degradation efficiency of PCB136.
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Affiliation(s)
- Ledong Zhu
- Environment Research Institute, Shandong University, Qingdao 266237, PR China
| | - Xinxi Huo
- Environment Research Institute, Shandong University, Qingdao 266237, PR China; Office of Supervisory and Audit, Shandong University, Qingdao 266237, PR China
| | - Jie Zhou
- Environment Research Institute, Shandong University, Qingdao 266237, PR China
| | - Qingzhu Zhang
- Environment Research Institute, Shandong University, Qingdao 266237, PR China.
| | - Wenxing Wang
- Environment Research Institute, Shandong University, Qingdao 266237, PR China
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Wang XS, Tan X, Zhang Y, Hu XX, Shen C, Huang YY, Fu HL, Yu RH, He CT. The enantiomer-selective metabolism of hexabromocyclododecanes (HBCDs) by human HepG2 cells. THE SCIENCE OF THE TOTAL ENVIRONMENT 2021; 768:144430. [PMID: 33736337 DOI: 10.1016/j.scitotenv.2020.144430] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/09/2020] [Revised: 12/06/2020] [Accepted: 12/07/2020] [Indexed: 06/12/2023]
Abstract
Although hepatic metabolism of hexabromocyclododecanes (HBCDs) played critical roles in the selective bioaccumulation of HBCDs in humans, the hepatic metabolism patterns of its enantiomers remained ambiguous. Aiming to elucidate the mechanism on hepatic metabolism of hexabromocyclododecanes (HBCDs) enantiomers, the enantiomers ((+)-α-HBCD, (-)-α-HBCD, (+)-γ-HBCD, and (-)-γ-HBCD), the diastereoisomers (α-, β-, and γ-HBCDs) and the mixed of α- and γ-HBCDs were incubated with human HepG2 cell under different exposure levels in the present study. The clearance percentages ranked as γ-HBCD enantiomers >β-HBCD enantiomers >α-HBCD enantiomers at the same exposure levels. The clearance percentages of (+)- and (-)-α-HBCDs increased when cells were exposed to racemic α-HBCD and the mixture of racemic α- and γ-HBCDs (p < 0.05). (-)-γ-HBCD was more resistant to human hepatic metabolism than (+)-γ-HBCD, leading to the enantiomer fractions (EFs) of γ-HBCD lower than 0.50. (-)-α-HBCD was slightly more metabolized when independently exposed to α-HBCD, while (+)-α-HBCD was more preferentially metabolized after exposure to α- and γ-HBCD mixtures. Hydroxylation and debromination HBCD metabolites were identified. In addition, the different EFs of HBCDs in cells and mediums suggested the selective transfer of chiral HBCDs and HBCD metabolites through the cell membrane. This study provided new insight into the enantiomer-selective metabolism of HBCDs.
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Affiliation(s)
- Xue-Song Wang
- School of Agriculture, Sun Yat-sen University, Guangzhou 510275, China; Guangdong Provincial Key Laboratory of Emergency Test for Dangerous Chemicals, China National Analytical Center Guangzhou (Guangdong Institute of Analysis), Guangdong Academy of Sciences, 100 Xianlie Middle Road, Guangzhou 510070, China
| | - Xiao Tan
- School of Agriculture, Sun Yat-sen University, Guangzhou 510275, China
| | - Yan Zhang
- School of Life Science, Sun Yat-sen University, Guangzhou 510275, China
| | - Xia-Xin Hu
- School of Agriculture, Sun Yat-sen University, Guangzhou 510275, China
| | - Chuang Shen
- School of Safety and Environmental Engineering, Hunan Institute of Technology, Hengyang 421002, China
| | - Ying-Ying Huang
- School of Safety and Environmental Engineering, Hunan Institute of Technology, Hengyang 421002, China
| | - Hui-Ling Fu
- School of Safety and Environmental Engineering, Hunan Institute of Technology, Hengyang 421002, China
| | - Ruo-Han Yu
- School of Life Science, Sun Yat-sen University, Guangzhou 510275, China
| | - Chun-Tao He
- School of Agriculture, Sun Yat-sen University, Guangzhou 510275, China.
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Li Y, Liang H, Qiu L. Enantioselective Bioaccumulation of the Chiral Insecticide Indoxacarb in Zebrafish (Danio rerio). ENVIRONMENTAL TOXICOLOGY AND CHEMISTRY 2021; 40:1007-1016. [PMID: 33238038 DOI: 10.1002/etc.4943] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/10/2020] [Revised: 06/08/2020] [Accepted: 11/21/2020] [Indexed: 06/11/2023]
Abstract
Indoxacarb is a typical chiral insecticide widely used in agricultural pest control. In the present study, zebrafish was used as a model animal to explore the enantioselective bioaccumulation behavior of indoxacarb to nontarget species in aquatic environments. Zebrafish were exposed to 0.025 and 0.1 mg/L rac-indoxacarb solution for 12 d under the semistatic method, and the bioconcentration factor (BCF) and enantiomeric fraction of zebrafish were investigated. The results showed that the (-)-R-indoxacarb preferentially accumulated in zebrafish. The BCF values at 0.025 mg/L exposure levels were 1079.8 and 83.4 L/kg for (-)-R-indoxacarb and (+)-S-indoxacarb after 12 d, respectively. The BCF values at 0.1 mg/L exposure levels were 1752.1 and 137.0 L/kg for (-)-R-indoxacarb and (+)-S-indoxacarb after 10 d, respectively. The half-life values of (-)-R-indoxacarb and (+)-S-indoxacarb were 3.47 and 2.05 d for 0.025 mg/L concentration exposure and 4.95 and 2.66 d for 0.1 mg/L concentration exposure, respectively. The enantiomeric fraction values were in the range of 0.48 to 0.55 and 0.89 to 1.00 for water and zebrafish samples, respectively. Studies on the enantioselective bioaccumulation behavior of indoxacarb will provide data for assessing the environmental fate and potential toxic effects of indoxacarb on aquatic organisms. Environ Toxicol Chem 2021;40:1007-1016. © 2020 SETAC.
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Affiliation(s)
- Yanhong Li
- Inner Mongolia Key Laboratory of Environmental Pollution Control and Waste Resource Reuse, School of Ecology and Environment, Inner Mongolia University, Hohhot, China
| | - Hongwu Liang
- Inner Mongolia Key Laboratory of Environmental Pollution Control and Waste Resource Reuse, School of Ecology and Environment, Inner Mongolia University, Hohhot, China
| | - Lihong Qiu
- Department of Applied Chemistry, College of Science, China Agricultural University, Beijing, China
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6
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Zhang CY, Flor S, Ludewig G, Lehmler HJ. Atropselective Partitioning of Polychlorinated Biphenyls in a HepG2 Cell Culture System: Experimental and Modeling Results. ENVIRONMENTAL SCIENCE & TECHNOLOGY 2020; 54:13817-13827. [PMID: 33059451 PMCID: PMC7642102 DOI: 10.1021/acs.est.0c02508] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/04/2023]
Abstract
Cell culture models are used to study the toxicity of polychlorinated biphenyls (PCBs); however, it is typically unknown how much PCB enters the cells and, for chiral PCBs, if the partitioning is atropselective. We investigated the partitioning of racemic PCB 91, PCB 95, PCB 132, and PCB 136 in HepG2 cells following a 72 h incubation. PCBs were present in the cell culture medium (60.7-88.8%), cells (8.0-14.6%), and dishes (2.3-7.8%) and displayed atropisomeric enrichment in the cells (enantiomeric fraction [EF] = 0.55-0.77) and dishes (EF = 0.53-0.68). Polyparameter linear free energy relationships coupled with a composition-based model provided a good estimate of the PCB levels in the cells and cell culture medium. The free concentration was subsequently used to extrapolate from the nominal cell culture concentration to PCB tissue levels and vice versa. This approach can be used for in vitro-in vivo extrapolations for all 209 PCB congeners. However, this model (and modified models based on descriptors incorporating atropselective interactions, i.e., relative retention times on chiral columns) did not predict the atropselective partitioning in the cell culture system. Improved chemical descriptors that account for the atropselective binding of PCBs to biological macromolecules are, therefore, needed to predict the atropselective partitioning of PCBs in biological systems.
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Affiliation(s)
- Chun-Yun Zhang
- Department of Occupational and Environmental Health, The University of Iowa, Iowa City, Iowa 52242, United States
| | - Susanne Flor
- Department of Occupational and Environmental Health, The University of Iowa, Iowa City, Iowa 52242, United States
| | - Gabriele Ludewig
- Department of Occupational and Environmental Health, The University of Iowa, Iowa City, Iowa 52242, United States
| | - Hans-Joachim Lehmler
- Department of Occupational and Environmental Health, The University of Iowa, Iowa City, Iowa 52242, United States
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7
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Li X, Zhang C, Wang K, Lehmler HJ. Fatty liver and impaired hepatic metabolism alter the congener-specific distribution of polychlorinated biphenyls (PCBs) in mice with a liver-specific deletion of cytochrome P450 reductase. ENVIRONMENTAL POLLUTION (BARKING, ESSEX : 1987) 2020; 266:115233. [PMID: 32712482 PMCID: PMC7492420 DOI: 10.1016/j.envpol.2020.115233] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/02/2020] [Revised: 06/22/2020] [Accepted: 07/10/2020] [Indexed: 05/09/2023]
Abstract
Polychlorinated biphenyls (PCBs) are persistent organic pollutants that are linked to adverse health outcomes. PCB tissue levels are determinants of PCB toxicity; however, it is unclear how factors, such as an altered metabolism and/or a fatty liver, affect PCB distribution in vivo. We determined the congener-specific disposition of PCBs in mice with a liver-specific deletion of cytochrome P450 reductase (KO), a model of fatty liver with impaired hepatic metabolism, and wild-type (WT) mice. Eight-week-old male WT (MWT, n = 3), male KO (MKO, n = 5), female WT (FWT, n = 4), and female KO mice (FKO, n = 4) were exposed orally to Aroclor 1254. PCBs were quantified in adipose, blood, brain, and liver tissues by gas chromatography-mass spectrometry. The ΣPCB levels followed the rank order adipose > liver ∼ brain > blood in WT and adipose ∼ liver > brain > blood in KO mice. PCB levels were much higher in the liver of KO than WT mice, irrespective of the sex. A comparison across exposure groups revealed minor genotype and sex-dependent differences in the PCB congener profiles (cos Θ > 0.92). Within each exposure group, tissue profiles showed small differences between tissues (cos Θ = 0.85 to 0.98). These differences were due to a decrease in metabolically more labile PCB congeners and an increase in congeners resistant to metabolism. The tissue-to-blood ratio of PCBs decreased for adipose, increased for the brain, and remained constant for the liver with an increase in chlorination. While these ratios did not follow the trends predicted using a composition-based model, the agreement between experimental and calculated partition coefficients was reasonable. Although the distribution of PCBs differs between KO and WT mice, the magnitude of the partitioning of PCBs from the blood into tissues can be approximated using composition-based models.
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Affiliation(s)
- Xueshu Li
- Department of Occupational and Environmental Health, College of Public Health, University of Iowa, Iowa City, IA, 52242, USA
| | - Chunyun Zhang
- Department of Occupational and Environmental Health, College of Public Health, University of Iowa, Iowa City, IA, 52242, USA
| | - Kai Wang
- Department of Biostatistics, College of Public Health, University of Iowa, Iowa City, IA, 52242, USA
| | - Hans-Joachim Lehmler
- Department of Occupational and Environmental Health, College of Public Health, University of Iowa, Iowa City, IA, 52242, USA.
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8
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Li X, Zhang C, Wang K, Lehmler HJ. Fatty liver and impaired hepatic metabolism alter the congener-specific distribution of polychlorinated biphenyls (PCBs) in mice with a liver-specific deletion of cytochrome P450 reductase. ENVIRONMENTAL POLLUTION (BARKING, ESSEX : 1987) 2020. [PMID: 32712482 DOI: 10.25820/data.006117] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Subscribe] [Scholar Register] [Indexed: 05/15/2023]
Abstract
Polychlorinated biphenyls (PCBs) are persistent organic pollutants that are linked to adverse health outcomes. PCB tissue levels are determinants of PCB toxicity; however, it is unclear how factors, such as an altered metabolism and/or a fatty liver, affect PCB distribution in vivo. We determined the congener-specific disposition of PCBs in mice with a liver-specific deletion of cytochrome P450 reductase (KO), a model of fatty liver with impaired hepatic metabolism, and wild-type (WT) mice. Eight-week-old male WT (MWT, n = 3), male KO (MKO, n = 5), female WT (FWT, n = 4), and female KO mice (FKO, n = 4) were exposed orally to Aroclor 1254. PCBs were quantified in adipose, blood, brain, and liver tissues by gas chromatography-mass spectrometry. The ΣPCB levels followed the rank order adipose > liver ∼ brain > blood in WT and adipose ∼ liver > brain > blood in KO mice. PCB levels were much higher in the liver of KO than WT mice, irrespective of the sex. A comparison across exposure groups revealed minor genotype and sex-dependent differences in the PCB congener profiles (cos Θ > 0.92). Within each exposure group, tissue profiles showed small differences between tissues (cos Θ = 0.85 to 0.98). These differences were due to a decrease in metabolically more labile PCB congeners and an increase in congeners resistant to metabolism. The tissue-to-blood ratio of PCBs decreased for adipose, increased for the brain, and remained constant for the liver with an increase in chlorination. While these ratios did not follow the trends predicted using a composition-based model, the agreement between experimental and calculated partition coefficients was reasonable. Although the distribution of PCBs differs between KO and WT mice, the magnitude of the partitioning of PCBs from the blood into tissues can be approximated using composition-based models.
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Affiliation(s)
- Xueshu Li
- Department of Occupational and Environmental Health, College of Public Health, University of Iowa, Iowa City, IA, 52242, USA
| | - Chunyun Zhang
- Department of Occupational and Environmental Health, College of Public Health, University of Iowa, Iowa City, IA, 52242, USA
| | - Kai Wang
- Department of Biostatistics, College of Public Health, University of Iowa, Iowa City, IA, 52242, USA
| | - Hans-Joachim Lehmler
- Department of Occupational and Environmental Health, College of Public Health, University of Iowa, Iowa City, IA, 52242, USA.
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9
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Luo C, Hu B, Wang S, Wang Y, Zhao Z, Wang Y, Li J, Zhang G. Distribution and Chiral Signatures of Polychlorinated Biphenyls (PCBs) in Soils and Vegetables around an e-Waste Recycling Site. JOURNAL OF AGRICULTURAL AND FOOD CHEMISTRY 2020; 68:10542-10549. [PMID: 32916050 DOI: 10.1021/acs.jafc.0c00479] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/11/2023]
Abstract
The distribution and composition of polychlorinated biphenyls (PCBs) within soil-plant systems around a notorious e-waste recycling site were investigated. The average total PCB concentrations in rhizospheric soils (RSs) and nonrhizospheric soils (NRSs) were 2160 and 1270 pg g-1 dry weight (DW), respectively. PCBs were more enriched in RS than NRS for most vegetable species. PCB accumulation in plant tissues varied greatly among plant cultivars, ranging from 4020 to 14 500 pg g-1 DW in shoots and from 471 to 24 400 pg g-1 DW in roots. The compositions of PCBs in soil and plants showed that hexa- and hepta-chlorinated PCBs were preferentially accumulated in soils, while tri- and tetra-PCBs were abundant in plant tissues. These results indicated that low-chlorinated PCBs might be prone to accumulation and transfer within plants, which was confirmed by the relationship between the root concentration factor and octanol-water coefficient. The first eluting enantiomers of PCB 84 and PCB 95 were preferentially transferred between the soil and plants, while the stereoselectivity of PCB 136 varied among plant species. A significant difference in enantiomeric fractionation of PCB 84 between the soil and roots indicated that enantiomeric enhancement of PCB 84 occurred during its translocation from soil to root, whereas no such difference was observed in these chiral PCBs during their translocation from the root to the shoot.
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Affiliation(s)
- Chunling Luo
- Guangzhou Institute of Geochemistry, Chinese Academy of Sciences, Guangzhou 510640, China
- Joint Institute for Environmental Research and Education, South China Agricultural University, Guangzhou 510642, China
| | - Beibei Hu
- Guangzhou Institute of Geochemistry, Chinese Academy of Sciences, Guangzhou 510640, China
- University of Chinese Academy of Sciences, Beijing 100049, China
| | - Shaorui Wang
- Guangzhou Institute of Geochemistry, Chinese Academy of Sciences, Guangzhou 510640, China
| | - Yan Wang
- Key Laboratory of Industrial Ecology and Environmental Engineering (MOE), School of Environmental Science and Technology, Dalian University of Technology, Dalian 116024, China
| | - Zhen Zhao
- College of Marine Ecology and Environment, Shanghai Ocean University, Shanghai 201306, China
| | - Yujie Wang
- School of Environmental Science and Engineering, Guangdong University of Technology, Guangzhou 510640, China
| | - Jun Li
- Guangzhou Institute of Geochemistry, Chinese Academy of Sciences, Guangzhou 510640, China
| | - Gan Zhang
- Guangzhou Institute of Geochemistry, Chinese Academy of Sciences, Guangzhou 510640, China
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10
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Grimm FA, Klaren WD, Li X, Lehmler HJ, Karmakar M, Robertson LW, Chiu WA, Rusyn I. Cardiovascular Effects of Polychlorinated Biphenyls and Their Major Metabolites. ENVIRONMENTAL HEALTH PERSPECTIVES 2020; 128:77008. [PMID: 32701041 PMCID: PMC7377239 DOI: 10.1289/ehp7030] [Citation(s) in RCA: 18] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/03/2023]
Abstract
BACKGROUND Xenobiotic metabolism is complex, and accounting for bioactivation and detoxification processes of chemicals remains among the most challenging aspects for decision making with in vitro new approach methods data. OBJECTIVES Considering the physiological relevance of human organotypic culture models and their utility for high-throughput screening, we hypothesized that multidimensional chemical-biological profiling of chemicals and their major metabolites is a sensible alternative for the toxicological characterization of parent molecules vs. metabolites in vitro. METHODS In this study, we tested 25 polychlorinated biphenyls (PCBs) [PCB 3, 11, 52, 126, 136, and 153 and their relevant metabolites (hydroxylated, methoxylated, sulfated, and quinone)] in concentration-response (10 nM-100μM) for effects in human induced pluripotent stem cell (iPSC)-derived cardiomyocytes (CMs) and endothelial cells (ECs) (iPSC-derived and HUVECs). Functional phenotypic end points included effects on beating parameters and intracellular Ca2+ flux in CMs and inhibition of tubulogenesis in ECs. High-content imaging was used to evaluate cytotoxicity, mitochondrial integrity, and oxidative stress. RESULTS Data integration of a total of 19 physicochemical descriptors and 36 in vitro phenotypes revealed that chlorination status and metabolite class are strong predictors of the in vitro cardiovascular effects of PCBs. Oxidation of PCBs, especially to di-hydroxylated and quinone metabolites, was associated with the most pronounced effects, whereas sulfation and methoxylation of PCBs resulted in diminished bioactivity. DISCUSSION Risk characterization analysis showed that although in vitro derived effective concentrations exceeded the levels measured in the general population, risks cannot be ruled out due to the potential for population variability in susceptibility and the need to fill data gaps using read-across approaches. This study demonstrated a strategy for how in vitro data can be used to characterize human health risks from PCBs and their metabolites. https://doi.org/10.1289/EHP7030.
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Affiliation(s)
- Fabian A. Grimm
- Department of Veterinary Integrative Biosciences, College of Veterinary Medicine and Biomedical Sciences, Texas A&M University, College Station, Texas, USA
| | - William D. Klaren
- Department of Veterinary Integrative Biosciences, College of Veterinary Medicine and Biomedical Sciences, Texas A&M University, College Station, Texas, USA
| | - Xueshu Li
- Department of Occupational and Environmental Health, College of Public Health, The University of Iowa, Iowa City, Iowa, USA
| | - Hans-Joachim Lehmler
- Department of Occupational and Environmental Health, College of Public Health, The University of Iowa, Iowa City, Iowa, USA
| | - Moumita Karmakar
- Department of Statistics, College of Science, Texas A&M University, College Station, Texas, USA
| | - Larry W. Robertson
- Department of Occupational and Environmental Health, College of Public Health, The University of Iowa, Iowa City, Iowa, USA
| | - Weihsueh A. Chiu
- Department of Veterinary Integrative Biosciences, College of Veterinary Medicine and Biomedical Sciences, Texas A&M University, College Station, Texas, USA
| | - Ivan Rusyn
- Department of Veterinary Integrative Biosciences, College of Veterinary Medicine and Biomedical Sciences, Texas A&M University, College Station, Texas, USA
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11
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Wu X, Zhai G, Schnoor JL, Lehmler HJ. Atropselective Disposition of 2,2',3,4',6-Pentachlorobiphenyl (PCB 91) and Identification of Its Metabolites in Mice with Liver-Specific Deletion of Cytochrome P450 Reductase. Chem Res Toxicol 2019; 33:1328-1338. [PMID: 31403789 DOI: 10.1021/acs.chemrestox.9b00255] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023]
Abstract
Hepatic cytochrome P450 enzymes metabolize chiral polychlorinated biphenyls (PCBs) to hydroxylated metabolites (OH-PCBs). Animal models with impaired metabolism of PCBs are one approach to study how the atropselective oxidation of PCBs to OH-PCBs contributes to toxic outcomes, such as neurodevelopmental disorders, following PCB exposure. We investigated the disposition of PCB 91, a para-substituted PCB congener, in mice with a liver-specific deletion of the cytochrome P450 reductase (cpr) gene (KO mice). KO mice and wild-type (WT) mice were exposed orally to racemic PCB 91 (30 mg/kg b.w.). Levels and enantiomeric fractions of PCB 91 and its hydroxylated metabolites were determined in tissues 3 days after PCB exposure and in excreta on days 1-3 after PCB exposure. PCB 91, but not OH-PCB levels were higher in KO compared to WT mice. The elevated fat and protein content in the liver of KO mice resulted in the hepatic accumulation of PCB 91. OH-PCBs were detected in blood, liver, and excreta samples of KO and WT mice. 2,2',3,4',6-Pentachlorobiphenyl-5-ol (5-91) was the major metabolite. A considerable percent of the total PCB 91 dose (%TD) was excreted with the feces as 5-91 (23%TD and 31%TD in KO and WT mice, respectively). We tentatively identified glucuronide and sulfate metabolites present in urine samples. The PCB 91 atropisomer eluting first on the chiral column (E1-PCB 91) displayed genotype-dependent atropisomeric enrichment, with a more pronounced atropisomeric enrichment observed in WT compared to KO mice. E1-atropisomers of 5-91 and 2,2',3,4',6-pentachlorobiphenyl-4-ol (4-91) were enriched in blood and liver, irrespective of the genotype; however, the extent of the enrichment of E1-5-91 was genotype dependent. These differences in atropselective disposition are consistent with slower metabolism of PCB 91 in KO compared to WT mice and the accumulation of the parent PCB in the fatty liver of KO mice.
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12
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Gao B, Zhao S, Zhang Z, Li L, Hu K, Kaziem AE, He Z, Hua X, Shi H, Wang M. A potential biomarker of isofenphos-methyl in humans: A chiral view. ENVIRONMENT INTERNATIONAL 2019; 127:694-703. [PMID: 30991225 DOI: 10.1016/j.envint.2019.04.018] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/13/2019] [Revised: 03/28/2019] [Accepted: 04/06/2019] [Indexed: 06/09/2023]
Abstract
Isofenphos-methyl (IFP) is a very active and persistent chiral insecticide. However, IFP has lower activity against acetylcholinesterases (AChEs). Previously, it was confirmed that phosphorothioate organophosphorus pesticides with N-alkyl (POPN) require activation by oxidative desulfuration and N-dealkylation. In this work, we demonstrated that IFP could be metabolized in human liver microsomes to isofenphos-methyl oxon (IFPO, 52.7%), isocarbophos (ICP, 14.2%) and isocarbophos oxon (ICPO, 11.2%). It was found that (R)-IFP was preferentially degraded compared to the (S)-enantiomer, and the enantiomeric fraction (EF) value reached 0.61 at 60 min. However, (S)-enantiomers of the three metabolites, were degraded preferentially, and the EF values ranged from 0.34 to 0.45. Cytochrome P450 (CYP) isoforms CYP3A4, CYP2E1, and CYP1A2 and carboxylesterase enzyme have an essential role in the enantioselective metabolism of IFP; but, the enzymes that participate in the degradation of IFP metabolites are different. The AChE inhibition bioassay indicated that ICPO is the only effective inhibitor of AChE. The covalent molecular docking has proposed that the metabolites of IFP and its analogs after N-dealkylation and oxidative desulfuration will possess the highest inhibitory activity against AChE. This study is the first to demonstrate that ICPO can be regarded as a potential biomarker for the biomonitoring of IFP and ICP exposure in humans.
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Affiliation(s)
- Beibei Gao
- Department of Pesticide Science, College of Plant Protection, Nanjing Agricultural University, State and Local Joint Engineering Research Center of Green Pesticide Invention and Application, Nanjing, Jiangsu 210095, China
| | - Shuangshuang Zhao
- Department of Pesticide Science, College of Plant Protection, Nanjing Agricultural University, State and Local Joint Engineering Research Center of Green Pesticide Invention and Application, Nanjing, Jiangsu 210095, China
| | - Zhaoxian Zhang
- Department of Pesticide Science, College of Plant Protection, Nanjing Agricultural University, State and Local Joint Engineering Research Center of Green Pesticide Invention and Application, Nanjing, Jiangsu 210095, China
| | - Lianshan Li
- Department of Pesticide Science, College of Plant Protection, Nanjing Agricultural University, State and Local Joint Engineering Research Center of Green Pesticide Invention and Application, Nanjing, Jiangsu 210095, China
| | - Kunming Hu
- Department of Pesticide Science, College of Plant Protection, Nanjing Agricultural University, State and Local Joint Engineering Research Center of Green Pesticide Invention and Application, Nanjing, Jiangsu 210095, China
| | - Amir E Kaziem
- Department of Pesticide Science, College of Plant Protection, Nanjing Agricultural University, State and Local Joint Engineering Research Center of Green Pesticide Invention and Application, Nanjing, Jiangsu 210095, China; Department of Environmental Agricultural Science, Institute of Environmental Studies and Research, Ain Shams University. Cairo11566, Egypt
| | - Zongzhe He
- Department of Pesticide Science, College of Plant Protection, Nanjing Agricultural University, State and Local Joint Engineering Research Center of Green Pesticide Invention and Application, Nanjing, Jiangsu 210095, China
| | - Xiude Hua
- Department of Pesticide Science, College of Plant Protection, Nanjing Agricultural University, State and Local Joint Engineering Research Center of Green Pesticide Invention and Application, Nanjing, Jiangsu 210095, China
| | - Haiyan Shi
- Department of Pesticide Science, College of Plant Protection, Nanjing Agricultural University, State and Local Joint Engineering Research Center of Green Pesticide Invention and Application, Nanjing, Jiangsu 210095, China
| | - Minghua Wang
- Department of Pesticide Science, College of Plant Protection, Nanjing Agricultural University, State and Local Joint Engineering Research Center of Green Pesticide Invention and Application, Nanjing, Jiangsu 210095, China.
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13
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Lu Q, Qiu L, Yu L, Zhang S, de Toledo RA, Shim H, Wang S. Microbial transformation of chiral organohalides: Distribution, microorganisms and mechanisms. JOURNAL OF HAZARDOUS MATERIALS 2019; 368:849-861. [PMID: 30772625 DOI: 10.1016/j.jhazmat.2019.01.103] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/13/2018] [Revised: 01/29/2019] [Accepted: 01/30/2019] [Indexed: 05/27/2023]
Abstract
Chiral organohalides including dichlorodiphenyltrichloroethane (DDT), Hexabromocyclododecane (HBCD) and polychlorinated biphenyls (PCBs) raise a significant concern in the environmental occurrence, fate and ecotoxicology due to their enantioselective biological effects. This review provides a state-of-the-art overview on enantioselective microbial transformation of the chiral organohalides. We firstly summarized worldwide field assessments of chiral organohalides in a variety of environmental matrices, which suggested the pivotal role of microorganisms in enantioselective transformation of chiral organohalides. Then, laboratory studies provided experimental evidences to further link enantioselective attenuation of chiral organohalides to specific functional microorganisms and enzymes, revealing mechanistic insights into the enantioselective microbial transformation processes. Particularly, a few amino acid residues in the functional enzymes could play a key role in mediating the enantioselectivity at the molecular level. Finally, major challenges and further developments toward an in-depth understanding of the enantioselective microbial transformation of chiral organohalides are identified and discussed.
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Affiliation(s)
- Qihong Lu
- School of Environmental Science and Engineering, Sun Yat-Sen University, 510275 Guangzhou, China; Environmental Microbiome Research Center, Sun Yat-Sen University, 510275 Guangzhou, China
| | - Lan Qiu
- School of Environmental Science and Engineering, Sun Yat-Sen University, 510275 Guangzhou, China
| | - Ling Yu
- School of Environmental Science and Engineering, Sun Yat-Sen University, 510275 Guangzhou, China; Environmental Microbiome Research Center, Sun Yat-Sen University, 510275 Guangzhou, China
| | - Shangwei Zhang
- UFZ Department of Ecological Chemistry, Helmholtz Centre for Environmental Research, Permoserstraße 15, 04318 Leipzig, Germany
| | - Renata Alves de Toledo
- Department of Civil and Environmental Engineering, Faculty of Science and Technology, University of Macau, 999078 Macau SAR, China
| | - Hojae Shim
- Department of Civil and Environmental Engineering, Faculty of Science and Technology, University of Macau, 999078 Macau SAR, China
| | - Shanquan Wang
- School of Environmental Science and Engineering, Sun Yat-Sen University, 510275 Guangzhou, China; Environmental Microbiome Research Center, Sun Yat-Sen University, 510275 Guangzhou, China; Guangdong Provincial Key Laboratory of Environmental Pollution Control and Remediation Technology, 510275 Guangzhou, China.
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14
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Uwimana E, Ruiz P, Li X, Lehmler HJ. Human CYP2A6, CYP2B6, AND CYP2E1 Atropselectively Metabolize Polychlorinated Biphenyls to Hydroxylated Metabolites. ENVIRONMENTAL SCIENCE & TECHNOLOGY 2019; 53:2114-2123. [PMID: 30576102 PMCID: PMC6380921 DOI: 10.1021/acs.est.8b05250] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/03/2023]
Abstract
Exposure to chiral polychlorinated biphenyls (PCBs) has been associated with neurodevelopmental disorders. Their hydroxylated metabolites (OH-PCBs) are also potentially toxic to the developing human brain; however, the formation of OH-PCBs by human cytochrome P450 (P450) isoforms is poorly investigated. To address this knowledge gap, we investigated the atropselective biotransformation of 2,2',3,4',6-pentachlorobiphenyl (PCB 91), 2,2',3,5',6-pentachlorobiphenyl (PCB 95), 2,2',3,3',4,6'-hexachlorobiphenyl (PCB 132), and 2,2',3,3',6,6'-hexachlorobiphenyl (PCB 136) by different human P450 isoforms. In silico predictions with ADMET Predictor and MetaDrug software suggested a role of CYP1A2, CYP2A6, CYP2B6, CYP2E1, and CYP3A4 in the metabolism of chiral PCBs. Metabolism studies with recombinant human enzymes demonstrated that CYP2A6 and CYP2B6 oxidized PCB 91 and PCB 132 in the meta position and that CYP2A6 oxidized PCB 95 and PCB 136 in the para position. CYP2B6 played only a minor role in the metabolism of PCB 95 and PCB 136 and formed meta-hydroxylated metabolites. Traces of para-hydroxylated PCB metabolites were detected in incubations with CYP2E1. No hydroxylated metabolites were present in incubations with CYP1A2 or CYP3A4. Atropselective analysis revealed P450 isoform-dependent and congener-specific atropselective enrichment of OH-PCB metabolites. These findings suggest that CYP2A6 and CYP2B6 play an important role in the oxidation of neurotoxic PCBs to chiral OH-PCBs in humans.
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Affiliation(s)
- Eric Uwimana
- Interdisciplinary Graduate Program in Human Toxicology and Department of Occupational and Environmental Health, University of Iowa, Iowa City, IA 52242, United States
| | - Patricia Ruiz
- Division of Toxicology and Human Health Sciences, Computational Toxicology and Methods Development Lab, Agency for Toxic Substances and Disease Registry, Atlanta, GA 30333, United States
| | - Xueshu Li
- Interdisciplinary Graduate Program in Human Toxicology and Department of Occupational and Environmental Health, University of Iowa, Iowa City, IA 52242, United States
| | - Hans-Joachim Lehmler
- Interdisciplinary Graduate Program in Human Toxicology and Department of Occupational and Environmental Health, University of Iowa, Iowa City, IA 52242, United States
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15
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Zhan J, Liang Y, Liu D, Ma X, Li P, Liu C, Liu X, Wang P, Zhou Z. Antibiotics may increase triazine herbicide exposure risk via disturbing gut microbiota. MICROBIOME 2018; 6:224. [PMID: 30545405 PMCID: PMC6291969 DOI: 10.1186/s40168-018-0602-5] [Citation(s) in RCA: 37] [Impact Index Per Article: 6.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/28/2018] [Accepted: 11/25/2018] [Indexed: 05/30/2023]
Abstract
BACKGROUND Antibiotics are commonly used worldwide, and pesticide is a kind of xenobiotic to which humans are frequently exposed. The interactive impact of antibiotics on pesticides has rarely been studied. We aim to investigate the effects of antibiotics on the pesticide exposure risk and whether gut microbiota altered by antibiotics has an influence on pesticide bioavailability. Furthermore, we explored the mechanisms of gut microbiota affecting the fate of pesticides in the host. RESULTS The oral bioavailability of triazine herbicides significantly increased in the rats treated with ampicillin or antibiotic cocktails. The antibiotic-altered gut microbiota directly influenced the increased pesticide bioavailability through downregulating hepatic metabolic enzyme gene expression and upregulating intestinal absorption-related proteins. CONCLUSIONS Antibiotics could increase the pesticide bioavailability and thereby may increase the pesticide exposure risk. The antibiotic-altered gut microbiota that could alter the hepatic metabolic enzyme gene expression and intestinal absorption-related proteome was a critical cause of the increased bioavailability. This study revealed an undiscovered potential health impact of antibiotics and reminded people to consider the co-exposed xenobiotics when taking antibiotics.
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Affiliation(s)
- Jing Zhan
- Beijing Advanced Innovation Center for Food Nutrition and Human Health, College of Science, China Agricultural University, No. 2, West Yuanmingyuan Road, Beijing, 100193, People's Republic of China
| | - Yiran Liang
- Beijing Advanced Innovation Center for Food Nutrition and Human Health, College of Science, China Agricultural University, No. 2, West Yuanmingyuan Road, Beijing, 100193, People's Republic of China
| | - Donghui Liu
- Beijing Advanced Innovation Center for Food Nutrition and Human Health, College of Science, China Agricultural University, No. 2, West Yuanmingyuan Road, Beijing, 100193, People's Republic of China
| | - Xiaoran Ma
- Beijing Advanced Innovation Center for Food Nutrition and Human Health, College of Science, China Agricultural University, No. 2, West Yuanmingyuan Road, Beijing, 100193, People's Republic of China
| | - Peize Li
- Beijing Advanced Innovation Center for Food Nutrition and Human Health, College of Science, China Agricultural University, No. 2, West Yuanmingyuan Road, Beijing, 100193, People's Republic of China
| | - Chang Liu
- Beijing Advanced Innovation Center for Food Nutrition and Human Health, College of Science, China Agricultural University, No. 2, West Yuanmingyuan Road, Beijing, 100193, People's Republic of China
| | - Xueke Liu
- Beijing Advanced Innovation Center for Food Nutrition and Human Health, College of Science, China Agricultural University, No. 2, West Yuanmingyuan Road, Beijing, 100193, People's Republic of China
| | - Peng Wang
- Beijing Advanced Innovation Center for Food Nutrition and Human Health, College of Science, China Agricultural University, No. 2, West Yuanmingyuan Road, Beijing, 100193, People's Republic of China.
| | - Zhiqiang Zhou
- Beijing Advanced Innovation Center for Food Nutrition and Human Health, College of Science, China Agricultural University, No. 2, West Yuanmingyuan Road, Beijing, 100193, People's Republic of China.
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16
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Chen Y, Zhu N, Luo Y, Hu K, Liu Y. Featured structure-activity relationships for some tri- and tetrachlorobiphenyls in human CYP2E1-activated mutagenicity - Impact of the extent of ortho-chlorination. CHEMOSPHERE 2018; 210:467-475. [PMID: 30025364 DOI: 10.1016/j.chemosphere.2018.06.169] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/30/2018] [Revised: 06/05/2018] [Accepted: 06/27/2018] [Indexed: 06/08/2023]
Abstract
Polychlorinated biphenyls (PCBs) as a group of persistent organic pollutants are confirmed human carcinogens; however, their mutagenicity remains mostly unknown. We have reported the mutagenicity of some PCBs with one to four chlorines in mammalian cells expressing human CYP2E1. To further explore the structural requirements for the mutagenicity of PCBs, eight tri- and tetrachlorobiphenyls untested before were investigated for the induction of gene mutations and micronuclei in a V79-derived cell line expressing both human CYP2E1 and sulfotransferase (SULT) 1A1 (V79-hCYP2E1-hSULT1A1), with SULT1A1 activity inhibited by pentachlorophenol, a potent SULT1 inhibitor. 2,2',6-Tri-, 2,3',6-tri, 2,4',6-tri-, and 2,2',5-trichlorobiphenyls (PCBs 19, 27, 32, and 18, respectively) induced micronuclei and gene mutations in V79-hCYP2E1-hSULT1A1 cells, at potencies slightly higher than 2,6-dichlorobiphenyl, but one order of magnitude below that by 2,3,3'- and 2,3,4'-trichlorobiphenyls as reported recently; in the parental V79-Mz cells, they were nonmutagenic and weak in micronuclei induction. Among the four tetrachlorobiphenyls with varying number of ortho chlorines, 2,3,3',4'-tetrachlorobiphenyl (PCB 56) induced both micronuclei and gene mutations in V79-hCYP2E1-hSULT1A1 cells with a potency greater than the above compounds; however, 2,2',3,3'-tetrachlorobiphenyl was equivocal and 2,2',3,6'-tetra- and 2,2',6,6'-tetrachlorobiphenyls inactive in V79-hCYP2E1-hSULT1A1 cells. Immunofluorescent staining of micronuclei formed by PCBs 32 and 56 in V79-hCYP2E1-hSULT1A1 cells with centromere protein B antibodies indicated that they were predominantly whole chromosomes, implying aneugenic potentials. This study suggests that tri- and tetrachlorobiphenyls with a single ortho chlorine can be most mutagenic under activation by human CYP2E1, and greater numbers of ortho chlorines may cause a drastic decline in the activity, especially for tetrachlorobiphenyls.
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Affiliation(s)
- Yuting Chen
- Department of Toxicology, School of Public Health, Southern Medical University, 1023 S. Shatai Road, Guangzhou 510515, China
| | - Na Zhu
- Department of Toxicology, School of Public Health, Southern Medical University, 1023 S. Shatai Road, Guangzhou 510515, China
| | - Yuyi Luo
- Department of Toxicology, School of Public Health, Southern Medical University, 1023 S. Shatai Road, Guangzhou 510515, China
| | - Keqi Hu
- Department of Toxicology, School of Public Health, Southern Medical University, 1023 S. Shatai Road, Guangzhou 510515, China
| | - Yungang Liu
- Department of Toxicology, School of Public Health, Southern Medical University, 1023 S. Shatai Road, Guangzhou 510515, China.
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17
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Kania-Korwel I, Lukasiewicz T, Barnhart CD, Stamou M, Chung H, Kelly KM, Bandiera S, Lein PJ, Lehmler HJ. Editor's Highlight: Congener-Specific Disposition of Chiral Polychlorinated Biphenyls in Lactating Mice and Their Offspring: Implications for PCB Developmental Neurotoxicity. Toxicol Sci 2018; 158:101-115. [PMID: 28431184 DOI: 10.1093/toxsci/kfx071] [Citation(s) in RCA: 22] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
Abstract
Chiral polychlorinated biphenyl (PCB) congeners have been implicated by laboratory and epidemiological studies in PCB developmental neurotoxicity. These congeners are metabolized by cytochrome P450 (P450) enzymes to potentially neurotoxic hydroxylated metabolites (OH-PCBs). The present study explores the enantioselective disposition and toxicity of 2 environmentally relevant, neurotoxic PCB congeners and their OH-PCB metabolites in lactating mice and their offspring following dietary exposure of the dam. Female C57BL/6N mice (8-weeks old) were fed daily, beginning 2 weeks prior to conception and continuing throughout gestation and lactation, with 3.1 µmol/kg bw/d of racemic 2,2',3,5',6-pentachlorobiphenyl (PCB 95) or 2,2',3,3',6,6'-hexachlorobiphenyl (PCB 136) in peanut butter; controls received vehicle (peanut oil) in peanut butter. PCB 95 levels were higher than PCB 136 levels in both dams and pups, consistent with the more rapid metabolism of PCB 136 compared with PCB 95. In pups and dams, both congeners were enriched for the enantiomer eluting second on enantioselective gas chromatography columns. OH-PCB profiles in lactating mice and their offspring were complex and varied according to congener, tissue and age. Developmental exposure to PCB 95 versus PCB 136 differentially affected the expression of P450 enzymes as well as neural plasticity (arc and ppp1r9b) and thyroid hormone-responsive genes (nrgn and mbp). The results suggest that the enantioselective metabolism of PCBs to OH-PCBs may influence neurotoxic outcomes following developmental exposures, a hypothesis that warrants further investigation.
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Affiliation(s)
- Izabela Kania-Korwel
- Department of Occupational and Environmental Health, College of Public Health, The University of Iowa, Iowa City, Iowa
| | - Tracy Lukasiewicz
- Department of Occupational and Environmental Health, College of Public Health, The University of Iowa, Iowa City, Iowa
| | - Christopher D Barnhart
- Department of Molecular Biosciences, School of Veterinary Medicine, University of California, Davis, California
| | - Marianna Stamou
- Department of Molecular Biosciences, School of Veterinary Medicine, University of California, Davis, California
| | - Haeun Chung
- Faculty of Pharmaceutical Sciences, The University of British Columbia, Vancouver, British Columbia V6T 1Z3, Canada
| | - Kevin M Kelly
- Department of Occupational and Environmental Health, College of Public Health, The University of Iowa, Iowa City, Iowa
| | - Stelvio Bandiera
- Faculty of Pharmaceutical Sciences, The University of British Columbia, Vancouver, British Columbia V6T 1Z3, Canada
| | - Pamela J Lein
- Department of Molecular Biosciences, School of Veterinary Medicine, University of California, Davis, California
| | - Hans-Joachim Lehmler
- Department of Occupational and Environmental Health, College of Public Health, The University of Iowa, Iowa City, Iowa
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18
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Li X, Holland EB, Feng W, Zheng J, Dong Y, Pessah IN, Duffel MW, Robertson LW, Lehmler HJ. Authentication of synthetic environmental contaminants and their (bio)transformation products in toxicology: polychlorinated biphenyls as an example. ENVIRONMENTAL SCIENCE AND POLLUTION RESEARCH INTERNATIONAL 2018; 25:16508-16521. [PMID: 29322390 PMCID: PMC6015536 DOI: 10.1007/s11356-017-1162-0] [Citation(s) in RCA: 23] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/11/2017] [Accepted: 12/26/2017] [Indexed: 04/15/2023]
Abstract
Toxicological studies use "specialty chemicals" and, thus, should assess and report both identity and degree of purity (homogeneity) of the chemicals (or toxicants) under investigation to ensure that other scientists can replicate experimental results. Although detailed reporting criteria for the synthesis and characterization of organic compounds have been established by organic chemistry journals, such criteria are inconsistently applied to the chemicals used in toxicological studies. Biologically active trace impurities may lead to incorrect conclusions about the chemical entity responsible for a biological response, which in turn may confound risk assessment. Based on our experience with the synthesis of PCBs and their metabolites, we herein propose guidelines for the "authentication" of synthetic PCBs and, by extension, other organic toxicants, and provide a checklist for documenting the authentication of toxicants reported in the peer-reviewed literature. The objective is to expand guidelines proposed for different types of biomedical and preclinical studies to include a thorough authentication of specialty chemicals, such as PCBs and their derivatives, with the goal of ensuring transparent and open reporting of scientific results in toxicology and the environmental health sciences.
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Affiliation(s)
- Xueshu Li
- Department of Occupational and Environmental Health, College of Public Health, The University of Iowa, Iowa City, IA, USA
| | - Erika B Holland
- Department of Biological Sciences, California State University of Long Beach, Long Beach, CA, USA
| | - Wei Feng
- Department of Molecular Biosciences, School of Veterinary Medicine, University of California, Davis, CA, USA
| | - Jing Zheng
- Department of Molecular Biosciences, School of Veterinary Medicine, University of California, Davis, CA, USA
| | - Yao Dong
- Department of Molecular Biosciences, School of Veterinary Medicine, University of California, Davis, CA, USA
| | - Isaac N Pessah
- Department of Molecular Biosciences, School of Veterinary Medicine, University of California, Davis, CA, USA
| | - Michael W Duffel
- Department of Pharmaceutical Sciences and Experimental Therapeutics, College of Pharmacy, The University of Iowa, Iowa City, IA, USA
| | - Larry W Robertson
- Department of Occupational and Environmental Health, College of Public Health, The University of Iowa, Iowa City, IA, USA
| | - Hans-Joachim Lehmler
- Department of Occupational and Environmental Health, College of Public Health, The University of Iowa, Iowa City, IA, USA.
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19
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Pěnčíková K, Brenerová P, Svržková L, Hrubá E, Pálková L, Vondráček J, Lehmler HJ, Machala M. Atropisomers of 2,2',3,3',6,6'-hexachlorobiphenyl (PCB 136) exhibit stereoselective effects on activation of nuclear receptors in vitro. ENVIRONMENTAL SCIENCE AND POLLUTION RESEARCH INTERNATIONAL 2018; 25:16411-16419. [PMID: 29124635 PMCID: PMC5943194 DOI: 10.1007/s11356-017-0683-x] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/01/2017] [Accepted: 11/02/2017] [Indexed: 04/16/2023]
Abstract
PCB 136 is an environmentally relevant chiral PCB congener, which has been found in vivo to be present in form of rotational isomers (atropisomers). Its atropselective biotransformation or neurotoxic effects linked with sensitization of ryanodine receptor suggest that it might interact also with other intracellular receptors in a stereospecific manner. However, possible atropselective effects of PCB 136 on nuclear receptor transactivation remain unknown. Therefore, in this study, atropselective effects of PCB 136 on nuclear receptors controlling endocrine signaling and/or expression of xenobiotic and steroid hormone catabolism were investigated. PCB136 atropisomers were found to exert differential effects on estrogen receptor (ER) activation; (+)-PCB 136 was estrogenic, while (-)-PCB 136 was antiestrogenic. In contrast, inhibition of androgen receptor (AR) activity was not stereospecific. Both PCB136 stereoisomers induced the constitutive androgen receptor (CAR)-dependent gene expression; however, no significant stereospecificity of PCB 136 atropisomers was observed. PCB136 was a partial inducer of the pregnane X receptor (PXR)-dependent gene expression. Here, (-)-PCB 136 was a significantly more potent inducer of PXR activity than (+)-PCB 136. Taken together, the present results indicate that at least two nuclear receptors participating in endocrine regulation or metabolism, ER and PXR, could be regulated in an atropselective manner by chiral PCB 136. The enantioselective enrichment of PCB atropisomers in animal and human tissues may thus have significant consequences for endocrine-disrupting effects of chiral ortho-substituted PCB congeners.
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Affiliation(s)
- Kateřina Pěnčíková
- Department of Chemistry and Toxicology, Veterinary Research Institute, 62100, Brno, Czech Republic
| | - Petra Brenerová
- Department of Chemistry and Toxicology, Veterinary Research Institute, 62100, Brno, Czech Republic
| | - Lucie Svržková
- Department of Chemistry and Toxicology, Veterinary Research Institute, 62100, Brno, Czech Republic
| | - Eva Hrubá
- Department of Chemistry and Toxicology, Veterinary Research Institute, 62100, Brno, Czech Republic
| | - Lenka Pálková
- Department of Chemistry and Toxicology, Veterinary Research Institute, 62100, Brno, Czech Republic
| | - Jan Vondráček
- Department of Cytokinetics, Institute of Biophysics of the Czech Academy of Sciences, 62165, Brno, Czech Republic
| | - Hans-Joachim Lehmler
- Department of Occupational and Environmental Health, College of Public Health, University of Iowa, Iowa City, IA, 52242, USA
| | - Miroslav Machala
- Department of Chemistry and Toxicology, Veterinary Research Institute, 62100, Brno, Czech Republic.
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Dhakal K, Gadupudi GS, Lehmler HJ, Ludewig G, Duffel MW, Robertson LW. Sources and toxicities of phenolic polychlorinated biphenyls (OH-PCBs). ENVIRONMENTAL SCIENCE AND POLLUTION RESEARCH INTERNATIONAL 2018; 25:16277-16290. [PMID: 28744683 PMCID: PMC5785587 DOI: 10.1007/s11356-017-9694-x] [Citation(s) in RCA: 47] [Impact Index Per Article: 7.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/14/2017] [Accepted: 06/30/2017] [Indexed: 04/16/2023]
Abstract
Polychlorinated biphenyls (PCBs), a group of 209 congeners that differ in the number and position of chlorines on the biphenyl ring, are anthropogenic chemicals that belong to the persistent organic pollutants (POPs). For many years, PCBs have been a topic of interest because of their biomagnification in the food chain and their environmental persistence. PCBs with fewer chlorine atoms, however, are less persistent and more susceptible to metabolic attack, giving rise to chemicals characterized by the addition of one or more hydroxyl groups to the chlorinated biphenyl skeleton, collectively known as hydroxylated PCBs (OH-PCBs). In animals and plants, this biotransformation of PCBs to OH-PCBs is primarily carried out by cytochrome P-450-dependent monooxygenases. One of the reasons for infrequent detection of lower chlorinated PCBs in serum and other biological matrices is their shorter half-lives, and their metabolic transformation, resulting in OH-PCBs or their conjugates, such as sulfates and glucuronides, or macromolecule adducts. Recent biomonitoring studies have reported the presence of OH-PCBs in human serum. The occurrence of OH-PCBs, the size of this group (there are 837 mono-hydroxyl PCBs alone), and their wide spectra of physical characteristics (pKa's and log P's ranging over 5 to 6 orders of magnitude) give rise to a multiplicity of biological effects. Among those are bioactivation to electrophilic metabolites that can form covalent adducts with DNA and other macromolecules, interference with hormonal signaling, inhibition of enzymes that regulate cellular concentrations of active hormones, and interference with the transport of hormones. This new information creates an urgent need for a new perspective on these often overlooked metabolites.
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Affiliation(s)
- Kiran Dhakal
- Interdisciplinary Graduate Program in Human Toxicology, Graduate College, The University of Iowa, Iowa City, IA, USA
- Department of Occupational and Environmental Health, College of Public Health, The University of Iowa, 100 Oakdale Campus #219 IREH, Iowa City, IA, 52242-5000, USA
| | - Gopi S Gadupudi
- Interdisciplinary Graduate Program in Human Toxicology, Graduate College, The University of Iowa, Iowa City, IA, USA
- Department of Occupational and Environmental Health, College of Public Health, The University of Iowa, 100 Oakdale Campus #219 IREH, Iowa City, IA, 52242-5000, USA
| | - Hans-Joachim Lehmler
- Interdisciplinary Graduate Program in Human Toxicology, Graduate College, The University of Iowa, Iowa City, IA, USA
- Department of Occupational and Environmental Health, College of Public Health, The University of Iowa, 100 Oakdale Campus #219 IREH, Iowa City, IA, 52242-5000, USA
| | - Gabriele Ludewig
- Interdisciplinary Graduate Program in Human Toxicology, Graduate College, The University of Iowa, Iowa City, IA, USA
- Department of Occupational and Environmental Health, College of Public Health, The University of Iowa, 100 Oakdale Campus #219 IREH, Iowa City, IA, 52242-5000, USA
| | - Michael W Duffel
- Interdisciplinary Graduate Program in Human Toxicology, Graduate College, The University of Iowa, Iowa City, IA, USA
- Department of Pharmaceutical Sciences and Experimental Therapeutics, College of Pharmacy, The University of Iowa, Iowa City, IA, USA
| | - Larry W Robertson
- Interdisciplinary Graduate Program in Human Toxicology, Graduate College, The University of Iowa, Iowa City, IA, USA.
- Department of Occupational and Environmental Health, College of Public Health, The University of Iowa, 100 Oakdale Campus #219 IREH, Iowa City, IA, 52242-5000, USA.
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21
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Xie W, Yang F. CYP450 enzyme-specific enantioselective species-specific response for metalaxyl in in vitro hepatic cells. ECOTOXICOLOGY AND ENVIRONMENTAL SAFETY 2018; 149:10-18. [PMID: 29145161 DOI: 10.1016/j.ecoenv.2017.10.065] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/28/2017] [Revised: 10/27/2017] [Accepted: 10/31/2017] [Indexed: 06/07/2023]
Abstract
Although enantioselective accumulation of chiral pesticide has been reported in organisms, the mechanisms remain unclear. In this study, the effects of chiral pesticide metalaxyl on CYP1A1, CYP1A2, CYP2B1, CYP2B2, CYP2E1 and CYP3A were investigated in human hepatoma HepG2, rat hepatic H4IIE, chicken hepatic LMH and grass carp hepatic L8824 cells. Moreover, the residual concentrations and enantiomeric ratios (ERs) of metalaxyl were also detected in the medium. The results showed the responses of these CYP450s to metalaxyl were enzyme-dependent and species-dependent in the four cells. CYP1A1, CYP1A2, and CYP2B1 were induced in HepG2 cells, CYP2A1 and CYP2B1 were induced in H4IIE cells, CYP1A1 and CYP2B1 were induced in LMH cells, and CYP2B1 was induced in L8824 cells. The enantioselective residual of metalaxyl was detected in the medium and found to be species-specific. HepG2, H4IIE and LMH cells were inclined to attenuate S-metalaxyl and lead to decrease of ER of metalaxyl, while L8824 cells were inclined to remove R-metalaxyl and resulted in an inverse shift of ER. These findings suggest an enantioselective metabolism of metalaxyl in various species which is not only related with CYP450s and CYP450 enzyme-specific, but also species-specific.
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Affiliation(s)
- Wei Xie
- Key Laboratory of Environmental Remediation and Ecological Health MOE, College of Environmental and Resource Sciences, Zhejiang University, No. 388, Yuhangtang Road, Hangzhou 310058, China; China Nuclear Power Engineering Co., Ltd, Beijing 100840, China
| | - Fangxing Yang
- Key Laboratory of Environmental Remediation and Ecological Health MOE, College of Environmental and Resource Sciences, Zhejiang University, No. 388, Yuhangtang Road, Hangzhou 310058, China.
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Zhan J, Liang Y, Liu D, Liu C, Liu H, Wang P, Zhou Z. Organochlorine pesticide acetofenate and its hydrolytic metabolite in rabbits: Enantioselective metabolism and cytotoxicity. PESTICIDE BIOCHEMISTRY AND PHYSIOLOGY 2018; 145:76-83. [PMID: 29482734 DOI: 10.1016/j.pestbp.2018.01.007] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/15/2017] [Revised: 01/11/2018] [Accepted: 01/17/2018] [Indexed: 06/08/2023]
Abstract
Acetofenate (AF) is a chiral organochlorine pesticide used for controlling hygiene pests. In this study, the metabolism of AF in rabbits in vivo and in vitro was investigated and the primary chiral metabolite acetofenate-alcohol (AF-A) was analyzed. The cytotoxicity of AF and AF-A was also determined. AF in rabbits in vivo was eliminated so rapidly that AF could not be detected within 10min after intravenous administration at 20mg/kg (body weight), and AF-A was quickly formed. In vitro metabolism assay, using plasma and liver microsomes, showed that AF was also quickly metabolized to AF-A and the metabolic process was significantly enantioselective with preferential degradation of (-)-AF and formation of (-)-AF-A. The cytotoxicity of AF and AF-A were investigated by assessing cell proliferation, apoptosis and generation of reactive oxygen species. The results showed that AF and AF-A induce enantioselective cytotoxicity. This study will be helpful for improving knowledge about the metabolism and toxicity of AF on an enantiomeric level and providing evidence to understand the potential environmental risk.
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Affiliation(s)
- Jing Zhan
- Beijing Advanced Innovation Center for Food Nutrition and Human Health, College of Science, Agricultural University, Beijing 100193, China
| | - Yiran Liang
- Beijing Advanced Innovation Center for Food Nutrition and Human Health, College of Science, Agricultural University, Beijing 100193, China
| | - Donghui Liu
- Beijing Advanced Innovation Center for Food Nutrition and Human Health, College of Science, Agricultural University, Beijing 100193, China
| | - Chang Liu
- Beijing Advanced Innovation Center for Food Nutrition and Human Health, College of Science, Agricultural University, Beijing 100193, China
| | - Hui Liu
- Beijing Advanced Innovation Center for Food Nutrition and Human Health, College of Science, Agricultural University, Beijing 100193, China
| | - Peng Wang
- Beijing Advanced Innovation Center for Food Nutrition and Human Health, College of Science, Agricultural University, Beijing 100193, China
| | - Zhiqiang Zhou
- Beijing Advanced Innovation Center for Food Nutrition and Human Health, College of Science, Agricultural University, Beijing 100193, China.
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23
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Wang S, Luo C, Zhang D, Wang Y, Song M, Yu Z, Wang Y, Zhang G. Reflection of Stereoselectivity during the Uptake and Acropetal Translocation of Chiral PCBs in Plants in the Presence of Copper. ENVIRONMENTAL SCIENCE & TECHNOLOGY 2017; 51:13834-13841. [PMID: 29096434 DOI: 10.1021/acs.est.7b03350] [Citation(s) in RCA: 21] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/07/2023]
Abstract
Plant uptake and acropetal translocation of polychlorinated biphenyls (PCBs) is a major concern, with many uncertainties, especially when plants are exposed to coexisting PCBs and metals. Studying atropisomer selectivity behavior is a well-proven method for identifying the biotransformation process of chiral PCBs in plants. This study investigated the uptake, translocation, and stereoselectivity of PCB95 and PCB136 (3 μg/L in hydroponics and 200 μg/kg in pot experiment) by monocot corn and dicot sunflower after copper (Cu) exposure (50 μmol/L in hydroponics and 400 mg/kg in pot experiment). Cu exposure led to significantly increased PCBs accumulation in roots and enhanced their acropetal translocation from roots to shoots, attributed to Cu-induced root damage. In the absence of Cu, the first-eluting enantiomer of PCB95 and second-eluting enantiomer of PCB136 were preferentially enriched in the shoots and roots of both the monocot and the dicot, and the enantioselectivity of chiral PCBs was more pronounced in shoots than in roots. Cu exposure significantly reduced the stereoselectivity of PCB95 and PCB136 in the defective root system, implying that PCB95 and PCB136 uptake into roots after Cu exposure changed from active biotransformation to passive diffusion. Our findings suggest that the ecological risk of PCB95 and PCB136 uptake and accumulation in plants is underestimated at sites cocontaminated with metals and PCBs and, for the first time, reveal the mechanism associated with the uptake and biotransformation of chiral PCBs in plants after exposure to both heavy metals and chiral PCBs.
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Affiliation(s)
- Shaorui Wang
- Guangzhou Institute of Geochemistry, Chinese Academy of Sciences , Guangzhou 510640, China
| | - Chunling Luo
- Guangzhou Institute of Geochemistry, Chinese Academy of Sciences , Guangzhou 510640, China
- College of Natural Resources and Environment, South China Agricultural University , Guangzhou, 510642, China
| | - Dayi Zhang
- School of Environment, Tsinghua University , Beijing, 100084, China
| | - Yan Wang
- Key Laboratory of Industrial Ecology and Environmental Engineering (MOE), School of Environmental Science and Technology, Dalian University of Technology , Dalian 116024, China
| | - Mengke Song
- College of Natural Resources and Environment, South China Agricultural University , Guangzhou, 510642, China
| | - Zhiqiang Yu
- Guangzhou Institute of Geochemistry, Chinese Academy of Sciences , Guangzhou 510640, China
| | - Yujie Wang
- School of Environmental Science and Engineering, Guangdong University of Technology , Guangzhou, 510006, China
| | - Gan Zhang
- Guangzhou Institute of Geochemistry, Chinese Academy of Sciences , Guangzhou 510640, China
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Uwimana E, Maiers A, Li X, Lehmler HJ. Microsomal Metabolism of Prochiral Polychlorinated Biphenyls Results in the Enantioselective Formation of Chiral Metabolites. ENVIRONMENTAL SCIENCE & TECHNOLOGY 2017; 51:1820-1829. [PMID: 28038482 PMCID: PMC5300040 DOI: 10.1021/acs.est.6b05387] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/24/2016] [Revised: 12/23/2016] [Accepted: 12/30/2016] [Indexed: 05/20/2023]
Abstract
Polychlorinated biphenyl (PCB) congeners with multiple ortho chlorine substituents and their metabolites exist as stable rotational isomers, or atropisomers, that are nonsuperimposable mirror images of each other. Additionally, the oxidation of certain axially prochiral PCBs, such as 2,2',4,6'-tetrachlorobiphenyl (PCB 51) and 2,2',4,5,6'-pentachlorobiphenyl (PCB 102), in the meta position of the symmetrically substituted phenyl ring is expected to form axially chiral hydroxylated metabolites (OH-PCBs); however, the formation of chiral OH-PCBs from prochiral PCBs has not been demonstrated experimentally. Here, we investigate if the oxidation of PCB 51 and PCB 102 by different microsomal preparations results in the formation of chiral OH-PCBs. Gas chromatographic analysis revealed that PCB 51 and PCB 102 were metabolized to 2,2',4,6'-tetrachlorobiphenyl-3'-ol (OH-PCB 51) and 2,2',4,5,6'-pentachlorobiphenyl-3'-ol (OH-PCB 102), respectively, by liver microsomes from male rats pretreated with different inducers; untreated male monkeys, guinea pigs, rabbits, and hamsters; and female dogs. The formation of both metabolites was inducer- and species-dependent. Both OH-PCB 51 and OH-PCB 102 were chiral and formed enantioselectively by all microsomal preparations investigated. These findings demonstrate that axially chiral PCB metabolites are formed from axially prochiral PCB congeners, a fact that should be considered when studying the environmental fate, transport, and toxicity of OH-PCBs.
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Huang H, Zhang S, Lv J, Wen B, Wang S, Wu T. Experimental and Theoretical Evidence for Diastereomer- and Enantiomer-Specific Accumulation and Biotransformation of HBCD in Maize Roots. ENVIRONMENTAL SCIENCE & TECHNOLOGY 2016; 50:12205-12213. [PMID: 27741390 DOI: 10.1021/acs.est.6b03223] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/06/2023]
Abstract
Diastereomer- and enantiomer-specific accumulation and biotransformation of hexabromocyclododecane (HBCD) in maize (Zea mays L.) were investigated. Molecular interactions of HBCD with plant enzymes were further characterized by homology modeling combined with molecular docking. The (-)α-, (-)β-, and (+)γ-HBCD enantiomers accumulated to levels in maize significantly higher than those of their corresponding enantiomers. Bioisomerization from (+)/(-)-β- and γ-HBCDs to (-)α-HBCD was frequently observed, and (-)γ-HBCD was most easily converted, with bioisomerization efficiency of 90.5 ± 8.2%. Mono- and dihydroxyl HBCDs, debrominated metabolites including pentabromocyclododecene (PBCDe) and tetrabromocyclododecene (TBCDe), and HBCD-GSH adducts were detected in maize roots. Patterns of hydroxylated and debrominated metabolites were significantly different among HBCD diastereomers and enantiomers. Three pairs of HBCD enantiomers were selectively bound into the active sites and interacted with specific residues of maize enzymes CYP71C3v2 and GST31. (+)α-, (-)β-, and (-)γ-HBCDs preferentially bound to CYP71C3v2, whereas (-)α-, (-)β-, and (+)γ-HBCDs had strong affinities to GST31, consistent with experimental observations that (+)α-, (-)β-, and (-)γ-HBCDs were more easily hydroxylated, and (-)α-, (-)β-, and (+)γ-HBCDs were more easily isomerized and debrominated in maize compared to their corresponding enantiomers. This study for the first time provided both experimental and theoretical evidence for stereospecific behaviors of HBCD in plants.
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Affiliation(s)
- Honglin Huang
- State Key Laboratory of Environmental Chemistry and Ecotoxicology, Research Center for Eco-Environmental Sciences, Chinese Academy of Sciences , P.O. Box 2871, Beijing 100085, China
| | - Shuzhen Zhang
- State Key Laboratory of Environmental Chemistry and Ecotoxicology, Research Center for Eco-Environmental Sciences, Chinese Academy of Sciences , P.O. Box 2871, Beijing 100085, China
- University of Chinese Academy of Sciences , Beijing 100049, China
| | - Jitao Lv
- State Key Laboratory of Environmental Chemistry and Ecotoxicology, Research Center for Eco-Environmental Sciences, Chinese Academy of Sciences , P.O. Box 2871, Beijing 100085, China
| | - Bei Wen
- State Key Laboratory of Environmental Chemistry and Ecotoxicology, Research Center for Eco-Environmental Sciences, Chinese Academy of Sciences , P.O. Box 2871, Beijing 100085, China
| | - Sen Wang
- State Key Laboratory of Environmental Chemistry and Ecotoxicology, Research Center for Eco-Environmental Sciences, Chinese Academy of Sciences , P.O. Box 2871, Beijing 100085, China
- Department of Environmental Sciences, College of Urban and Environmental Sciences, Northwest University , Xi'an 710027, China
| | - Tong Wu
- State Key Laboratory of Environmental Chemistry and Ecotoxicology, Research Center for Eco-Environmental Sciences, Chinese Academy of Sciences , P.O. Box 2871, Beijing 100085, China
- School of Environmental Science and Engineering, Hebei University of Science and Technology , Hebei 050018, China
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26
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Liu J, Shah MB, Zhang Q, Stout CD, Halpert JR, Wilderman PR. Coumarin Derivatives as Substrate Probes of Mammalian Cytochromes P450 2B4 and 2B6: Assessing the Importance of 7-Alkoxy Chain Length, Halogen Substitution, and Non-Active Site Mutations. Biochemistry 2016; 55:1997-2007. [PMID: 26982502 DOI: 10.1021/acs.biochem.5b01330] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/11/2023]
Abstract
Using a combined structural and biochemical approach, the functional importance of a recently described peripheral pocket bounded by the E-, F-, G-, and I-helices in CYP2B4 and 2B6 was probed. Three series of 4-substituted-7-alkoxycoumarin derivatives with -H, -CH3, or -CF3 at the 4 position of the coumarin core were used initially to monitor functional differences between CYP2B4 and 2B6. 7-Ethoxy-4-(trifluoromethyl)coumarin (7-EFC) displayed the highest catalytic efficiency among these substrates. Mutants were made to alter side-chain polarity (V/E194Q) or bulk (F/Y244W) to alter access to the peripheral pocket. Modest increases in catalytic efficiency of 7-EFC O-deethylation by the mutants were magnified considerably by chlorination or bromination of the substrate ethoxy chain. A structure of CYP2B6 Y244W in complex with (+)-α-pinene was solved at 2.2 Å and showed no CYMAL-5 in the peripheral pocket. A ligand free structure of CYP2B4 F244W was solved at 3.0 Å with CYMAL-5 in the peripheral pocket. In both instances, comparison of the respective wild-type and mutant CYP2B enzymes revealed that CYMAL-5 occupancy of the peripheral pocket had little effect on the topology of active site residue side-chains, despite the fact that the peripheral pocket and active site are located on opposite sides of the I-helix. Analysis of available CYP2B structures suggest that the effect of the amino acid substitutions within the peripheral pocket derive from altered interactions between the F and G helices.
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Affiliation(s)
- Jingbao Liu
- School of Pharmacy, University of Connecticut , Storrs, Connecticut 06269, United States
| | - Manish B Shah
- School of Pharmacy, University of Connecticut , Storrs, Connecticut 06269, United States
| | - Qinghai Zhang
- Department of Molecular Biology, The Scripps Research Institute , La Jolla, California 92037, United States
| | - C David Stout
- Department of Molecular Biology, The Scripps Research Institute , La Jolla, California 92037, United States
| | - James R Halpert
- School of Pharmacy, University of Connecticut , Storrs, Connecticut 06269, United States
| | - P Ross Wilderman
- School of Pharmacy, University of Connecticut , Storrs, Connecticut 06269, United States
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Kania-Korwel I, Lehmler HJ. Chiral polychlorinated biphenyls: absorption, metabolism and excretion--a review. ENVIRONMENTAL SCIENCE AND POLLUTION RESEARCH INTERNATIONAL 2016; 23:2042-57. [PMID: 25651810 PMCID: PMC4527964 DOI: 10.1007/s11356-015-4150-2] [Citation(s) in RCA: 57] [Impact Index Per Article: 7.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/15/2014] [Accepted: 01/19/2015] [Indexed: 05/20/2023]
Abstract
Seventy eight out of the 209 possible polychlorinated biphenyl (PCB) congeners are chiral, 19 of which exist under ambient conditions as stable rotational isomers that are non-superimposable mirror images of each other. These congeners (C-PCBs) represent up to 6 % by weight of technical PCB mixtures and undergo considerable atropisomeric enrichment in wildlife, laboratory animals, and humans. The objective of this review is to summarize our current knowledge of the processes involved in the absorption, metabolism, and excretion of C-PCBs and their metabolites in laboratory animals and humans. C-PCBs are absorbed and excreted by passive diffusion, a process that, like other physicochemical processes, is inherently not atropselective. In mammals, metabolism by cytochrome P450 (P450) enzymes represents a major route of elimination for many C-PCBs. In vitro studies demonstrate that C-PCBs with a 2,3,6-trichlorosubstitution pattern in one phenyl ring are readily oxidized to hydroxylated PCB metabolites (HO-PCBs) by P450 enzymes, such as rat CYP2B1, human CYP2B6, and dog CYP2B11. The oxidation of C-PCBs is atropselective, thus resulting in a species- and congener-dependent atropisomeric enrichment of C-PCBs and their metabolites. This atropisomeric enrichment of C-PCBs and their metabolites likely plays a poorly understood role in the atropselective toxicity of C-PCBs and, therefore, warrants further investigation.
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Affiliation(s)
- Izabela Kania-Korwel
- Department of Occupational and Environmental Health, College of Public Health, The University of Iowa, UI Research Park, Iowa City, IA, 52242, USA
| | - Hans-Joachim Lehmler
- Department of Occupational and Environmental Health, College of Public Health, The University of Iowa, UI Research Park, Iowa City, IA, 52242, USA.
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28
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Grimm FA, Hu D, Kania-Korwel I, Lehmler HJ, Ludewig G, Hornbuckle KC, Duffel MW, Bergman A, Robertson LW. Metabolism and metabolites of polychlorinated biphenyls. Crit Rev Toxicol 2015; 45:245-72. [PMID: 25629923 PMCID: PMC4383295 DOI: 10.3109/10408444.2014.999365] [Citation(s) in RCA: 280] [Impact Index Per Article: 31.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/06/2014] [Accepted: 12/11/2014] [Indexed: 11/13/2022]
Abstract
Abstract The metabolism of polychlorinated biphenyls (PCBs) is complex and has an impact on toxicity, and thereby on the assessment of PCB risks. A large number of reactive and stable metabolites are formed in the processes of biotransformation in biota in general, and in humans in particular. The aim of this document is to provide an overview of PCB metabolism, and to identify the metabolites of concern and their occurrence. Emphasis is given to mammalian metabolism of PCBs and their hydroxyl, methylsulfonyl, and sulfated metabolites, especially those that persist in human blood. Potential intracellular targets and health risks are also discussed.
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Affiliation(s)
- FA Grimm
- Interdisciplinary Graduate Program in Human Toxicology, Department of Pharmaceutical Sciences & Experimental Therapeutics, University of Iowa
| | - D Hu
- Department of Civil and Environmental Engineering, University of Iowa
| | - I Kania-Korwel
- Department of Occupational & Environmental Health, University of Iowa
| | - HJ Lehmler
- Interdisciplinary Graduate Program in Human Toxicology, Department of Occupational & Environmental Health, University of Iowa
| | - G Ludewig
- Interdisciplinary Graduate Program in Human Toxicology, Department of Occupational & Environmental Health, University of Iowa
| | - KC Hornbuckle
- Interdisciplinary Graduate Program in Human Toxicology, Department of Civil and Environmental Engineering, University of Iowa
| | - MW Duffel
- Interdisciplinary Graduate Program in Human Toxicology, Department of Pharmaceutical Sciences & Experimental Therapeutics, University of Iowa
| | - A Bergman
- Swedish Toxicology Sciences Research Center (SWETOX), Forskargatan 20, SE-151 36 Södertälje, SWEDEN
| | - LW Robertson
- Interdisciplinary Graduate Program in Human Toxicology, Department of Occupational & Environmental Health, University of Iowa
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29
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Monooxygenase, peroxidase and peroxygenase properties and reaction mechanisms of cytochrome P450 enzymes. ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 2015; 851:1-61. [PMID: 26002730 DOI: 10.1007/978-3-319-16009-2_1] [Citation(s) in RCA: 67] [Impact Index Per Article: 7.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/16/2022]
Abstract
This review examines the monooxygenase, peroxidase and peroxygenase properties and reaction mechanisms of cytochrome P450 (CYP) enzymes in bacterial, archaeal and mammalian systems. CYP enzymes catalyze monooxygenation reactions by inserting one oxygen atom from O2 into an enormous number and variety of substrates. The catalytic versatility of CYP stems from its ability to functionalize unactivated carbon-hydrogen (C-H) bonds of substrates through monooxygenation. The oxidative prowess of CYP in catalyzing monooxygenation reactions is attributed primarily to a porphyrin π radical ferryl intermediate known as Compound I (CpdI) (Por•+FeIV=O), or its ferryl radical resonance form (FeIV-O•). CYP-mediated hydroxylations occur via a consensus H atom abstraction/oxygen rebound mechanism involving an initial abstraction by CpdI of a H atom from the substrate, generating a highly-reactive protonated Compound II (CpdII) intermediate (FeIV-OH) and a carbon-centered alkyl radical that rebounds onto the ferryl hydroxyl moiety to yield the hydroxylated substrate. CYP enzymes utilize hydroperoxides, peracids, perborate, percarbonate, periodate, chlorite, iodosobenzene and N-oxides as surrogate oxygen atom donors to oxygenate substrates via the shunt pathway in the absence of NAD(P)H/O2 and reduction-oxidation (redox) auxiliary proteins. It has been difficult to isolate the historically elusive CpdI intermediate in the native NAD(P)H/O2-supported monooxygenase pathway and to determine its precise electronic structure and kinetic and physicochemical properties because of its high reactivity, unstable nature (t½~2 ms) and short life cycle, prompting suggestions for participation in monooxygenation reactions of alternative CYP iron-oxygen intermediates such as the ferric-peroxo anion species (FeIII-OO-), ferric-hydroperoxo species (FeIII-OOH) and FeIII-(H2O2) complex.
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Dai S, Wong CS, Qiu J, Wang M, Chai T, Fan L, Yang S. Enantioselective accumulation of chiral polychlorinated biphenyls in lotus plant (Nelumbonucifera spp.). JOURNAL OF HAZARDOUS MATERIALS 2014; 280:612-618. [PMID: 25218260 DOI: 10.1016/j.jhazmat.2014.08.034] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/02/2014] [Revised: 08/11/2014] [Accepted: 08/12/2014] [Indexed: 06/03/2023]
Abstract
Enantioselective accumulation of chiral polychlorinated biphenyls (PCBs) 91, 95, 136, 149, 176 and 183 was investigated in lotus plants (Nelumbonucifera spp.) exposed to these chemicals via spiked sediment, to determine uptake and possible biotransformation for aquatic phytoremediation purposes. The concentrations of most PCBs were greatest in roots at 60 d (19.6 ± 1.51-70.6 ± 6.14 μg kg(-1)), but were greatest in stems and leaves at 120 d (25.3 ± 6.14-95.5 ± 19.4 μg kg(-1) and 17.4 ± 4.41-70.4 ± 10.4 μg kg(-1), respectively). Total amounts were greatest at 120 d and significantly higher in roots than those in stems and in leaves (1,457 ± 220-5,852 ± 735 ng, 237 ± 47.1-902 ± 184 ng and 202 ± 60.3-802 ± 90.2 ng, respectively), but represented less than 0.51% of the total mass of PCBs added to sediments, indicating that lotus plants were unlikely to remove appreciable amounts of PCBs from contaminated sediments. Racemic PCB residues in sediment indicate no enantioselective biodegradation by sedimentary microbial consortia over the entire experiment. Preferential accumulation of the (-)-enantiomers of PCBs 91, 95 and 136 were observed in roots, stems and leaves, but non-enantioselective accumulation was observed for PCBs 149, 176 and 183. These results indicate that aquatic plants can accumulate PCBs enantioselectively via root uptake, possibly by biotransformation within plant tissues as observed for terrestrial plants. This is also the first report to identify optical rotation of the atropisomers of PCBs 91 and 95.
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Affiliation(s)
- Shouhui Dai
- Institute of Quality Standard & Testing Technology for Agro-Products, Key Laboratory of Agro-product Quality and Safety, Chinese Academy of Agricultural Sciences; Key Laboratory of Agri-food Quality and Safety, Ministry of Agriculture, Beijing 100081, China; State Key Laboratory of Organic Geochemistry, Guangzhou Institute of Geochemistry, Chinese Academy of Sciences, Guangzhou 510640, China
| | - Charles S Wong
- Richardson College for the Environment, University of Winnipeg, Winnipeg MB R3B 2E9, Canada
| | - Jing Qiu
- Institute of Quality Standard & Testing Technology for Agro-Products, Key Laboratory of Agro-product Quality and Safety, Chinese Academy of Agricultural Sciences; Key Laboratory of Agri-food Quality and Safety, Ministry of Agriculture, Beijing 100081, China.
| | - Min Wang
- Institute of Quality Standard & Testing Technology for Agro-Products, Key Laboratory of Agro-product Quality and Safety, Chinese Academy of Agricultural Sciences; Key Laboratory of Agri-food Quality and Safety, Ministry of Agriculture, Beijing 100081, China
| | - Tingting Chai
- Institute of Quality Standard & Testing Technology for Agro-Products, Key Laboratory of Agro-product Quality and Safety, Chinese Academy of Agricultural Sciences; Key Laboratory of Agri-food Quality and Safety, Ministry of Agriculture, Beijing 100081, China
| | - Li Fan
- Institute of Quality Standard & Testing Technology for Agro-Products, Key Laboratory of Agro-product Quality and Safety, Chinese Academy of Agricultural Sciences; Key Laboratory of Agri-food Quality and Safety, Ministry of Agriculture, Beijing 100081, China
| | - Shuming Yang
- Institute of Quality Standard & Testing Technology for Agro-Products, Key Laboratory of Agro-product Quality and Safety, Chinese Academy of Agricultural Sciences; Key Laboratory of Agri-food Quality and Safety, Ministry of Agriculture, Beijing 100081, China
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31
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James MO, Kleinow KM. Seasonal influences on PCB retention and biotransformation in fish. ENVIRONMENTAL SCIENCE AND POLLUTION RESEARCH INTERNATIONAL 2014; 21:6324-33. [PMID: 23494683 PMCID: PMC3706481 DOI: 10.1007/s11356-013-1611-3] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/03/2013] [Accepted: 02/28/2013] [Indexed: 05/22/2023]
Abstract
There is extensive evidence that fish from waters with polychlorinated biphenyls (PCB)-contaminated sediments accumulate PCBs and related chemicals and that people who eat fish from contaminated waters have higher body burdens of PCBs and PCB metabolites than those who do not. PCBs and their metabolites are potentially toxic; thus, it is important to human health to understand the uptake, biotransformation, and elimination of PCBs in fish since these processes determine the extent of accumulation. The intestinal uptake of PCBs present in the diet of fish into fish tissues is a process that is influenced by the lipid composition of the diet. Biotransformation of PCBs in fish, as in mammals, facilitates elimination, although many PCB congeners are recalcitrant to biotransformation in fish and mammals. Sequential biotransformation of PCBs by cytochrome P450 and conjugation pathways is even less efficient in fish than in mammalian species, thus contributing to the retention of PCBs in fish tissues. A very important factor influencing overall PCB disposition in fish is water temperature. Seasonal changes in water temperature produce adaptive physiological and biochemical changes in fish. While uptake of PCBs from the diet is similar in fish acclimated to winter or summer temperatures, there is evidence that elimination of PCBs occurs much more slowly when the fish is acclimated at low temperatures than at warmer temperatures. Research to date suggests that the processes of elimination of PCBs are modulated by several factors in fish including seasonal changes in water temperature. Thus, the body burden of PCBs in fish from a contaminated location is likely to vary with season.
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Affiliation(s)
- Margaret O James
- Department of Medicinal Chemistry, University of Florida, Gainesville, FL, 32605, USA,
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32
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Manzetti S, van der Spoel ER, van der Spoel D. Chemical Properties, Environmental Fate, and Degradation of Seven Classes of Pollutants. Chem Res Toxicol 2014; 27:713-37. [DOI: 10.1021/tx500014w] [Citation(s) in RCA: 79] [Impact Index Per Article: 7.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022]
Affiliation(s)
- Sergio Manzetti
- Uppsala
Center for Computational Chemistry, Science for Life Laboratory, Department
of Cell and Molecular Biology, University of Uppsala, Box 596, SE-75124 Uppsala, Sweden
- Fjordforsk A.S., Midtun, 6894 Vangsnes, Norway
| | - E. Roos van der Spoel
- Uppsala
Center for Computational Chemistry, Science for Life Laboratory, Department
of Cell and Molecular Biology, University of Uppsala, Box 596, SE-75124 Uppsala, Sweden
| | - David van der Spoel
- Uppsala
Center for Computational Chemistry, Science for Life Laboratory, Department
of Cell and Molecular Biology, University of Uppsala, Box 596, SE-75124 Uppsala, Sweden
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33
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Wu X, Kammerer A, Lehmler HJ. Microsomal oxidation of 2,2',3,3',6,6'-hexachlorobiphenyl (PCB 136) results in species-dependent chiral signatures of the hydroxylated metabolites. ENVIRONMENTAL SCIENCE & TECHNOLOGY 2014; 48:2436-44. [PMID: 24467194 PMCID: PMC3983324 DOI: 10.1021/es405433t] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/05/2013] [Revised: 01/16/2014] [Accepted: 01/27/2014] [Indexed: 05/18/2023]
Abstract
Chiral polychlorinated biphenyls (PCBs) display variable atropisomeric enrichment in wildlife and animal models, especially at higher trophic levels. These differences in PCBs' chiral signatures are, at least in part, due to species-dependent oxidation of PCBs to hydroxylated PCB metabolites (OH-PCBs). Here, we investigate the hypothesis that the cytochrome P450 (P450) enzyme-mediated oxidation of chiral PCBs results in species-dependent differences in the chiral signatures of OH-PCBs (i.e., the direction and extent of OH-PCBs' atropisomeric enrichment). To investigate this hypothesis, we incubated PCB 136, a representative chiral PCB, with pooled human liver microsomes (HLMs) or liver microsomes from male guinea pig, hamster, monkey, mouse, and rabbit or female dog and determined average profiles and chiral signatures of the OH-PCBs. 2,2',3,3',6,6'-Hexachlorobiphenyl-4-ol (4-136) was the major metabolite in incubations with HLMs and monkey and rabbit microsomes. 2,2',3,3',6,6'-Hexachlorobiphenyl-5-ol (5-136) was the major metabolite formed by microsomes from all other species. Both 4-136 and 5-136 were formed atropselectively in all microsomal incubations; however, the direction and extent of the atropisomeric enrichment of both OH-PCB metabolites showed considerable differences across microsomal preparations obtained from different species. These differences in OH-PCBs' atropisomeric enrichment may not only be toxicologically relevant but may also be useful to study sources and transport of OH-PCBs in the environment.
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34
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Hrycay E, Forrest D, Liu L, Wang R, Tai J, Deo A, Ling V, Bandiera S. Hepatic bile acid metabolism and expression of cytochrome P450 and related enzymes are altered in Bsep (-/-) mice. Mol Cell Biochem 2014; 389:119-32. [PMID: 24399466 DOI: 10.1007/s11010-013-1933-y] [Citation(s) in RCA: 30] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/10/2013] [Accepted: 12/18/2013] [Indexed: 02/06/2023]
Abstract
The bile salt export pump (BSEP/Bsep; gene symbol ABCB11/Abcb11) translocates bile salts across the hepatocyte canalicular membrane into bile in humans and mice. In humans, mutations in the ABCB11 gene cause a severe childhood liver disease known as progressive familial intrahepatic cholestasis type 2. Targeted inactivation of mouse Bsep produces milder persistent cholestasis due to detoxification of bile acids through hydroxylation and alternative transport pathways. The purpose of the present study was to determine whether functional expression of hepatic cytochrome P450 (CYP) and microsomal epoxide hydrolase (mEH) is altered by Bsep inactivation in mice and whether bile acids regulate CYP and mEH expression in Bsep (-/-) mice. CYP expression was determined by measuring protein levels of Cyp2b, Cyp2c and Cyp3a enzymes and CYP-mediated activities including lithocholic acid hydroxylation, testosterone hydroxylation and alkoxyresorufin O-dealkylation in hepatic microsomes prepared from female and male Bsep (-/-) mice fed a normal or cholic acid (CA)-enriched diet. The results indicated that hepatic lithocholic acid hydroxylation was catalyzed by Cyp3a/Cyp3a11 enzymes in Bsep (-/-) mice and that 3-ketocholanoic acid and murideoxycholic acid were major metabolites. CA feeding of Bsep (-/-) mice increased hepatic Cyp3a11 protein levels and Cyp3a11-mediated testosterone 2β-, 6β-, and 15β-hydroxylation activities, increased Cyp2b10 protein levels and Cyp2b10-mediated benzyloxyresorufin O-debenzylation activity, and elevated Cyp2c29 and mEH protein levels. We propose that bile acids upregulate expression of hepatic Cyp3a11, Cyp2b10, Cyp2c29 and mEH in Bsep (-/-) mice and that Cyp3a11 and multidrug resistance-1 P-glycoproteins (Mdr1a/1b) are vital components of two distinct pathways utilized by mouse hepatocytes to expel bile acids.
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Affiliation(s)
- Eugene Hrycay
- Faculty of Pharmaceutical Sciences, The University of British Columbia, Vancouver, BC, V6T1Z3, Canada
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35
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Yang D, Kania-Korwel I, Ghogha A, Chen H, Stamou M, Bose DD, Pessah IN, Lehmler HJ, Lein PJ. PCB 136 atropselectively alters morphometric and functional parameters of neuronal connectivity in cultured rat hippocampal neurons via ryanodine receptor-dependent mechanisms. Toxicol Sci 2014; 138:379-92. [PMID: 24385416 DOI: 10.1093/toxsci/kft334] [Citation(s) in RCA: 59] [Impact Index Per Article: 5.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/12/2023] Open
Abstract
We recently demonstrated that polychlorinated biphenyl (PCB) congeners with multiple ortho chlorine substitutions sensitize ryanodine receptors (RyRs), and this activity promotes Ca²⁺-dependent dendritic growth in cultured neurons. Many ortho-substituted congeners display axial chirality, and we previously reported that the chiral congener PCB 136 (2,2',3,3',6,6'-hexachlorobiphenyl) atropselectively sensitizes RyRs. Here, we test the hypothesis that PCB 136 atropisomers differentially alter dendritic growth and other parameters of neuronal connectivity influenced by RyR activity. (-)-PCB 136, which potently sensitizes RyRs, enhances dendritic growth in primary cultures of rat hippocampal neurons, whereas (+)-PCB 136, which lacks RyR activity, has no effect on dendritic growth. The dendrite-promoting activity of (-)-PCB 136 is observed at concentrations ranging from 0.1 to 100 nM and is blocked by pharmacologic RyR antagonism. Neither atropisomer alters axonal growth or cell viability. Quantification of PCB 136 atropisomers in hippocampal cultures indicates that atropselective effects on dendritic growth are not due to differential partitioning of atropisomers into cultured cells. Imaging of hippocampal neurons loaded with Ca²⁺-sensitive dye demonstrates that (-)-PCB 136 but not (+)-PCB 136 increases the frequency of spontaneous Ca²⁺ oscillations. Similarly, (-)-PCB 136 but not (+)-PCB 136 increases the activity of hippocampal neurons plated on microelectrode arrays. These data support the hypothesis that atropselective effects on RyR activity translate into atropselective effects of PCB 136 atropisomers on neuronal connectivity, and suggest that the variable atropisomeric enrichment of chiral PCBs observed in the human population may be a significant determinant of individual susceptibility for adverse neurodevelopmental outcomes following PCB exposure.
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Affiliation(s)
- Dongren Yang
- Department of Molecular Biosciences, School of Veterinary Medicine, University of California, Davis, California 95616
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36
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Stamou M, Wu X, Kania-Korwel I, Lehmler HJ, Lein PJ. Cytochrome p450 mRNA expression in the rodent brain: species-, sex-, and region-dependent differences. Drug Metab Dispos 2013; 42:239-44. [PMID: 24255117 DOI: 10.1124/dmd.113.054239] [Citation(s) in RCA: 27] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/22/2023] Open
Abstract
Cytochrome P450 (P450) enzymes play a critical role in the activation and detoxication of many neurotoxic chemicals. Although research has largely focused on P450-mediated metabolism in the liver, emerging evidence suggests that brain P450s influence neurotoxicity by modulating local metabolite levels. As a first step toward better understanding the relative role of brain P450s in determining neurotoxic outcome, we characterized mRNA expression of specific P450 isoforms in the rodent brain. Adult mice (male and female) and rats (male) were treated with vehicle, phenobarbital, or dexamethasone. Transcripts for CYP2B, CYP3A, CYP1A2, and the orphan CYP4X1 and CYP2S1 were quantified in the liver, hippocampus, cortex, and cerebellum by quantitative (real-time) polymerase chain reaction. These P450s were all detected in the liver with the exception of CYP4X1, which was detected in rat but not mouse liver. P450 expression profiles in the brain varied regionally. With the exception of the hippocampus, there were no sex differences in regional brain P450 expression profiles in mice; however, there were marked species differences. In the liver, phenobarbital induced CYP2B expression in both species. Dexamethasone induced hepatic CYP2B and CYP3A in mice but not rats. In contrast, brain P450s did not respond to these classic hepatic P450 inducers. Our findings demonstrate that P450 mRNA expression in the brain varies by region, regional brain P450 profiles vary between species, and their induction varies from that of hepatic P450s. These novel data will be useful for designing mechanistic studies to examine the relative role of P450-mediated brain metabolism in neurotoxicity.
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Affiliation(s)
- Marianna Stamou
- Department of Molecular Biosciences, School of Veterinary Medicine, University of California, Davis, California (M.S., P.J.L.) and Department of Occupational and Environmental Health, College of Public Health, The University of Iowa, Iowa City, Iowa (X.W., I.K.-K., H.-J.L.)
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37
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Kania-Korwel I, Lehmler HJ. Chlordane and heptachlor are metabolized enantioselectively by rat liver microsomes. ENVIRONMENTAL SCIENCE & TECHNOLOGY 2013; 47:8913-22. [PMID: 23799267 PMCID: PMC3748599 DOI: 10.1021/es401916a] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/08/2023]
Abstract
Chlordane, heptachlor, and their metabolites are chiral persistent organic pollutants that undergo enantiomeric enrichment in the environment. This study investigated the enantioselective metabolism of both chlordane isomers and heptachlor, major components of technical chlordane, by liver microsomes prepared from male rats treated with corn oil (CO) or inducers of CYP2B (PB; phenobarbital) and CYP3A enzymes (DX; dexamethasone), isoforms induced by chlordane treatment. The extent of the metabolism of all three parent compounds was dependent on the microsomal preparation used and followed the rank order PB > DX > CO. The mass balances ranged from 49 to 130% of the parent compound added to the microsomal incubations. Both cis- and trans-chlordane were enantioselectively metabolized to oxychlordane (EF = 0.45-0.89) and 1,2-dichlorochlordene (EF = 0.42-0.90). Heptachlor was metabolized enantioselectively, with heptachlor epoxide B (EF = 0.44-0.54) being the only metabolite. Interestingly, the direction on the enrichment for oxychlordane, 1,2-dichlorochlordene, and heptachlor epoxide differed depending on the microsomal preparation. These findings demonstrate that the direction and extent of the enantioselective metabolism of both chlordane isomers and heptachlor is P450 isoform-dependent and can be modulated by the induction of P450 enzymes.
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Affiliation(s)
- Izabela Kania-Korwel
- Department of Occupational and Environmental Health, College of Public Health, The University of Iowa, Iowa City, Iowa, USA.
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38
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Wu X, Kania-Korwel I, Chen H, Stamou M, Dammanahalli KJ, Duffel M, Lein PJ, Lehmler HJ. Metabolism of 2,2',3,3',6,6'-hexachlorobiphenyl (PCB 136) atropisomers in tissue slices from phenobarbital or dexamethasone-induced rats is sex-dependent. Xenobiotica 2013; 43:933-47. [PMID: 23581876 DOI: 10.3109/00498254.2013.785626] [Citation(s) in RCA: 35] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/04/2023]
Abstract
1. Chiral polychlorinated biphenyls (PCBs) such as PCB 136 enantioselectively sensitize the ryanodine receptor (RyR). In light of recent evidence that PCBs cause developmental neurotoxicity via RyR-dependent mechanisms, this suggests that enantioselective PCB metabolism may influence the developmental neurotoxicity of chiral PCBs. However, enantioselective disposition of PCBs has not been fully characterized. 2. The effect of sex and cytochrome P450 (P450) enzyme induction on the enantioselective metabolism of PCB 136 was studied using liver tissue slices prepared from naïve control (CTL), phenobarbital (PB; CYP2B inducer) or dexamethasone (DEX; CYP3A inducer) pretreated adult Sprague-Dawley rats. PCB 136 metabolism was also examined in hippocampal slices derived from untreated rat pups. 3. In liver tissue slices, hydroxylated PCB (OH-PCB) profiles depended on sex and inducer pretreatment, and OH-PCB levels followed the rank orders male > female and PB > DEX > CTL. In contrast, the enantiomeric enrichment of PCB 136 and its metabolites was independent of sex and inducer pretreatment. Only small amounts of PCB 136 partitioned into hippocampal tissue slices and no OH-PCB metabolites were detected. 4. Our results suggest that enantioselective metabolism, sex and induction status of P450 enzymes in the liver may modulate the neurotoxic outcomes of developmental exposure to chiral PCBs.
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Affiliation(s)
- Xianai Wu
- Department of Occupational and Environmental Health, College of Public Health, The University of Iowa , Iowa City, IA , USA
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39
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Zheng J, Yan X, Chen SJ, Peng XW, Hu GC, Chen KH, Luo XJ, Mai BX, Yang ZY. Polychlorinated biphenyls in human hair at an e-waste site in China: composition profiles and chiral signatures in comparison to dust. ENVIRONMENT INTERNATIONAL 2013; 54:128-133. [PMID: 23454108 DOI: 10.1016/j.envint.2013.01.018] [Citation(s) in RCA: 39] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/06/2012] [Revised: 01/06/2013] [Accepted: 01/29/2013] [Indexed: 06/01/2023]
Abstract
We analyzed the polychlorinated biphenyls (PCBs) in human hair collected from an electronic waste (e-waste) recycling area in southern China and compared their composition profiles and chiral signatures to those of workplace and domestic dust. The PCB concentrations showed significant age dependence in dismantling workers' hair but not in residents' hair. Among residents, PCB concentrations decreased in the following order: elderly people>students>pre-school children>adults. The PCB homologue and congener profiles of the workers' hair were similar to those of the workplace dust. However, the PCB homologue profile of the residents' hair was clearly different from that of the domestic dust. The chiral congener CB95 generally exhibited a racemic or near-racemic composition in both hair and dust, with enantiomer fractions (EFs) ranging from 0.485 to 0.525 in hair and from 0.479 to 0.504 in dust. The EFs of CB132 in dust (0.477-0.513) were closer to a racemic chiral signature than those in hair (0.378-0.521), but this difference was not significant. Our results suggest that the chiral signature of PCBs may be a better tool than the PCB composition profile for identifying the external and internal sources of organic contaminants in human hair. Further measurements of chiral PCB signatures in hair and blood from the same individuals are needed to identify the external and internal sources of PCBs in human hair.
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Affiliation(s)
- Jing Zheng
- Center for Environmental Health Research, South China Institute of Environmental Sciences, Ministry of Environmental Protection, Guangzhou 510655, China
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40
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Lu Z, Kania-Korwel I, Lehmler HJ, Wong CS. Stereoselective formation of mono- and dihydroxylated polychlorinated biphenyls by rat cytochrome P450 2B1. ENVIRONMENTAL SCIENCE & TECHNOLOGY 2013; 47:12184-92. [PMID: 24060104 PMCID: PMC3870094 DOI: 10.1021/es402838f] [Citation(s) in RCA: 39] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/18/2023]
Abstract
Changes in atropisomer composition of chiral polychlorinated biphenyls (PCBs) and their mono- and dihydroxylated metabolites (OH- and diOH-PCBs) via rat cytochrome P450 2B1 (CYP2B1) mediated biotransformation were investigated in vitro. Rat CYP2B1 could stereoselectively biotransform chiral PCBs to generate meta-OH-PCBs as the major metabolites after 60 min incubations. Nonracemic enantiomer fractions (EFs: concentration ratios of the (+)-atropisomer or the first-eluting atropisomer over the total concentrations of two atropisomers) of 5-OH-PCBs, were 0.17, 0.20, 0.85, 0.77, and 0.41 for incubations with PCBs 91, 95, 132, 136, and 149, respectively. CYP-mediated stereoselective formation of diOH-PCBs from OH-PCBs was observed for the first time. After 60 min stereoselective biotransformation, the EFs of both 4-OH-PCB 95 and 5-OH-PCB 95 changed from racemic (i.e., 0.50) to 0.62 and 0.46, respectively. These transformations generated statistically nonracemic 4,5-diOH-PCB 95, with EFs of 0.53 and 0.58 for 4-OH-PCB 95 and 5-OH-PCB 95 incubations, respectively. Biotransformation of PCBs 91 and 136 also generated 4,5-diOH-PCB 91 and 4,5-diOH-PCB 136, respectively. These in vitro results were consistent with that observed for stereoselective PCB biotransformation by rat liver microsomes and in vivo. Biotransformation interference between two atropisomers of PCB 136 was investigated for the first time in this study. The biotransformation process of (-)-PCB 136 was significantly disrupted by the presence of (+)-PCB 136 but not the other way around. Thus, stereoselective metabolism of chiral PCBs and OH-PCBs by CYPs is a major mechanism for atropisomer composition change of PCBs and their metabolites in the environment, with the degree of composition change dependent, at least in part, on stereoselective interference of atropisomers with each other at the enzyme level.
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Affiliation(s)
- Zhe Lu
- Department of Chemistry, University of Manitoba, Winnipeg, MB, R3T 2N2, Canada
| | - Izabela Kania-Korwel
- Department of Occupational and Environmental Health, College of Public Health, University of Iowa, Iowa City, Iowa 52242,United States
| | - Hans-Joachim Lehmler
- Department of Occupational and Environmental Health, College of Public Health, University of Iowa, Iowa City, Iowa 52242,United States
- Corresponding authors: Lehmler--Phone: +1-319-335-4310; Fax: +1-319-335-4290; Wong--Phone: +1-204-786-9335; Fax: +1-204-775-2114;
| | - Charles S. Wong
- Department of Chemistry, University of Manitoba, Winnipeg, MB, R3T 2N2, Canada
- Department of Environmental Studies and Sciences and Department of Chemistry, Richardson College for the Environment, University of Winnipeg, Winnipeg, MB, R3B 2E9, Canada
- Corresponding authors: Lehmler--Phone: +1-319-335-4310; Fax: +1-319-335-4290; Wong--Phone: +1-204-786-9335; Fax: +1-204-775-2114;
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41
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Kania-Korwel I, Lehmler HJ. Assigning atropisomer elution orders using atropisomerically enriched polychlorinated biphenyl fractions generated by microsomal metabolism. J Chromatogr A 2012; 1278:133-44. [PMID: 23347976 DOI: 10.1016/j.chroma.2012.12.041] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/18/2012] [Revised: 12/18/2012] [Accepted: 12/19/2012] [Indexed: 11/17/2022]
Abstract
Changes in the enantiomeric fraction of chiral polychlorinated biphenyls (PCBs) are a powerful tool to investigate the movement of PCBs in the environment, for example as part of source apportionment and ecological studies. Environmental studies typically employ a series of cyclodextrin-based gas chromatography columns to separate all environmentally relevant PCB congeners. The elution order of most PCB atropisomers has not been established on different enantioselective columns due to the unavailability of analytical standards. To overcome this limitation, the current study generated atropisomerically enriched fractions of chiral PCBs with rat liver microsomes. Subsequently, the enrichment profile of the enriched PCB fractions was used to determine the elution order of PCB atropisomers on selected enantioselective gas chromatography columns. While the elution order of PCB 95, 131, 132, 136, 149 and 176 atropisomers was identical on all enantioselective columns investigated, an inversion of the elution order was observed for PCB 45, 84, 91 and 174 atropisomers on a few columns. These results demonstrate that atropisomerically enriched fractions obtained from microsomal metabolism can be used to unambiguously establish the relative elution order of the atropisomers of PCBs and potentially other environmental pollutant, especially if pure enantiomers are not available.
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Affiliation(s)
- Izabela Kania-Korwel
- Department of Occupational and Environmental Health, College of Public Health, University of Iowa, Iowa City, IA 52242, USA
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42
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Hrycay EG, Bandiera SM. The monooxygenase, peroxidase, and peroxygenase properties of cytochrome P450. Arch Biochem Biophys 2012; 522:71-89. [DOI: 10.1016/j.abb.2012.01.003] [Citation(s) in RCA: 83] [Impact Index Per Article: 6.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/24/2011] [Revised: 12/22/2011] [Accepted: 01/04/2012] [Indexed: 12/30/2022]
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43
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Wu X, Pramanik A, Duffel MW, Hrycay EG, Bandiera SM, Lehmler HJ, Kania-Korwel I. 2,2',3,3',6,6'-Hexachlorobiphenyl (PCB 136) is enantioselectively oxidized to hydroxylated metabolites by rat liver microsomes. Chem Res Toxicol 2011; 24:2249-57. [PMID: 22026639 DOI: 10.1021/tx200360m] [Citation(s) in RCA: 49] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Developmental exposure to multiple ortho-substituted polychlorinated biphenyls (PCBs) causes adverse neurodevelopmental outcomes in laboratory animals and humans by mechanisms involving the sensitization of Ryanodine receptors (RyRs). In the case of PCB 136, the sensitization of RyR is enantiospecific, with only (-)-PCB 136 being active. However, the role of enantioselective metabolism in the developmental neurotoxicity of PCB 136 is poorly understood. The present study employed hepatic microsomes from phenobarbital (PB)-, dexamethasone (DEX)- and corn oil (VEH)-treated male Sprague-Dawley rats to investigate the hypothesis that PCB 136 atropisomers are enantioselectively metabolized by P450 enzymes to potentially neurotoxic, hydroxylated PCB 136 metabolites. The results demonstrated the time- and isoform-dependent formation of three metabolites, with 5-OH-PCB 136 (2,2',3,3',6,6'-hexachlorobiphenyl-5-ol) being the major metabolite. The formation of 5-OH-PCB 136 increased with the activity of P450 2B enzymes in the microsomal preparation, which is consistent with PCB 136 metabolism by rat P450 2B1. The minor metabolite 4-OH-PCB 136 (2,2',3,3',6,6'-hexachlorobiphenyl-4-ol) was produced by a currently unidentified P450 enzyme. An enantiomeric enrichment of (-)-PCB 136 was observed in microsomal incubations due to the preferential metabolism of (+)-PCB 136 to the corresponding 5-OH-PCB 136 atropisomer. 4-OH-PCB 136 displayed an enrichment of the atropisomer formed from (-)-PCB 136; however, the enrichment of this metabolite atropisomer did not affect the enantiomeric enrichment of the parent PCB because 4-OH-PCB 136 is only a minor metabolite. Although the formation of 5- and 4-OH-PCB 136 atropisomers increased with time, the enantioselective formation of the OH-PCB metabolites resulted in constant enantiomeric enrichment, especially at later incubation times. These observations not only demonstrate that the chiral signatures of PCBs and their metabolites in wildlife and humans are due to metabolism by P450 enzymes but also suggest that the enantioselective formation of neurotoxic PCB 136 metabolites, such as 4-OH-PCB 136, may play a role in the developmental neurotoxicity of PCBs.
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Affiliation(s)
- Xianai Wu
- Department of Occupational and Environmental Health, College of Public Health, University of Iowa, Iowa City, Iowa 52242, USA
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44
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Lu Z, Wong CS. Factors affecting phase I stereoselective biotransformation of chiral polychlorinated biphenyls by rat cytochrome P-450 2B1 isozyme. ENVIRONMENTAL SCIENCE & TECHNOLOGY 2011; 45:8298-8305. [PMID: 21863805 DOI: 10.1021/es200673q] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/31/2023]
Abstract
In vitro incubations of rat cytochrome P-450 (CYP) 2B1 isozyme with three chiral polychlorinated biphenyl (PCB) congeners (PCBs 45, 95, and 132) were performed to investigate factors affecting phase I stereoselective biotransformation. Rat CYP2B1 preferentially biotransformed the second-eluting atropisomers of PCBs 45 and 95 at low substrate concentration ranges (≤15 μM). Biotransformation competition by different congeners was also observed, with increasing competition at higher chlorination. Competition decreased the biotransformation rates of each congener stereoselectively, affecting atropisomeric composition. No atropisomeric enrichment was observed for PCB 132 upon incubation of the racemate. However, under the same conditions, significant differences in biotransformation kinetics were observed in individual atropisomer incubations, indicating that (+)-PCB 132 and (-)-PCB 132 were competitively biotransformed. Homology modeling and docking studies suggested that each atropisomer had different interactions with rat CYP2B1 and could dock with the isozyme at different locations. This is one possible explanation for stereoselective biotransformation and competition of chiral PCBs at the molecular level. Our results suggest that the lack of predictive capability for stereoselectivity of PCBs and other chiral pollutants in biota may be due to competitive and/or inhibitory activities of different substrates, including individual enantiomers of the same compound.
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Affiliation(s)
- Zhe Lu
- Department of Chemistry, University of Manitoba , Winnipeg, Manitoba R3T 2N2, Canada
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Zhang X, Wang S, Wang Y, Xia T, Chen J, Cai X. Differential enantioselectivity of quizalofop ethyl and its acidic metabolite: direct enantiomeric separation and assessment of multiple toxicological endpoints. JOURNAL OF HAZARDOUS MATERIALS 2011; 186:876-882. [PMID: 21159424 DOI: 10.1016/j.jhazmat.2010.11.081] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/28/2010] [Revised: 10/24/2010] [Accepted: 11/21/2010] [Indexed: 05/30/2023]
Abstract
Transformation products usually differ in environmental and toxicological properties compared to the parent contaminants, thus causing potential and unknown environmental risks. To elucidate differential chiral recognition of the aryloxypropanoate herbicide quizalofop ethyl (QE) and its primary product (quizalofop acid, QA), their enantiomeric separation and toxicological impacts to two freshwater algae were investigated. Addition of trace water (0.02-0.08%, v/v) to the mobile phase selectively affected retention of analyte and induced simultaneous enantio-separation for the two compounds with intrinsical water-specific resolution mechanisms, although they both possessed a chiral center in the 2-position of propionates. In algal suspensions, QE was rapidly degraded to produce the acid metabolite (QA), and the product further declined, whereas a reduction of QA as starting compound did not occur. Uptake and/or transformation of QE and QA were found a lack of enantioselectivity and isomer inversion, while cellular membrane permeability, membrane potential and algal growth showed enantioselectivity to different extents. These results suggested the presence of receptor chirality that was involved in the toxicological processes but invalid for uptake and transformation. Therefore, quizalofop acid, identified as environmentally relevant contaminant associated with application of the herbicide, participated in the toxicological processes of the parent compound, and exhibited distinct toxicological and chromatographic retention properties.
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Affiliation(s)
- Xiaoxiang Zhang
- Key Laboratory of Industrial Ecology and Environmental Engineering (Ministry of Education), School of Environmental Science and Technology, Dalian University of Technology, Dalian, China
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Milanowski B, Lulek J, Lehmler HJ, Kania-Korwel I. Assessment of the disposition of chiral polychlorinated biphenyls in female mdr 1a/b knockout versus wild-type mice using multivariate analyses. ENVIRONMENT INTERNATIONAL 2010; 36:884-92. [PMID: 19923000 PMCID: PMC2891895 DOI: 10.1016/j.envint.2009.10.007] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/02/2008] [Revised: 10/06/2009] [Accepted: 10/12/2009] [Indexed: 05/17/2023]
Abstract
Polychlorinated biphenyls (PCBs) are present in the environment as complex mixtures, which make it challenging to identify PCB congeners that may be subject to active transport processes. Here we employ a transgenic mouse model in combination with multivariate analyses to investigate if chiral PCBs 91, 95, 132, 136, 149, 174, 176 and 183 are subject to active (enantioselective) transport by multidrug resistance (MDR) transporters. A synthetic PCB mixture containing these congeners was administered orally to female FVB or mdr1a/1b knockout mice. Due to the short half-life of chiral PCB congeners, mice were euthanized after 24h and PCB concentrations and enantiomeric fractions were determined in selected tissues and excreta. Principal component analysis did not reveal differences between wild-type and mdr1a/1b knockout mice. However, Hotelling T(2)-test revealed significantly lower PCB concentrations and a more pronounced enantiomeric enrichment in the adipose tissue of mdr1a/1b knockout mice. These differences are due to higher body weights and higher fecal fat contents of mdr1a/1b knockout mice. Analysis of the enantiomeric fractions of PCBs 91, 95, 136, 149 and 174 showed a significant enantiomeric enrichment for all five congeners in wild-type and mdr1a/1b knockout mice. Overall, by studying a PCB mixture in a transgenic mouse model in combination with a multivariate data reduction approach, PCBs 91, 95, 136, 149 and 174 could be excluded as substrates of multidrug resistance transporters 1a/b.
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Affiliation(s)
- Bartłomiej Milanowski
- Department of Pharmaceutical Technology, Poznań University of Medical Sciences, 6 Grunwaldzka Street, 60-780 Poznań, Poland
- Department of Occupational and Environmental Health, University of Iowa, School of Public Health, University of Iowa, 100 Oakdale Campus, #124 IREH, Iowa City, IA 52242-5000, United States
| | - Janina Lulek
- Department of Pharmaceutical Technology, Poznań University of Medical Sciences, 6 Grunwaldzka Street, 60-780 Poznań, Poland
| | - Hans-Joachim Lehmler
- Department of Occupational and Environmental Health, University of Iowa, School of Public Health, University of Iowa, 100 Oakdale Campus, #124 IREH, Iowa City, IA 52242-5000, United States
| | - Izabela Kania-Korwel
- Department of Occupational and Environmental Health, University of Iowa, School of Public Health, University of Iowa, 100 Oakdale Campus, #124 IREH, Iowa City, IA 52242-5000, United States
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Kania-Korwel I, El-Komy MH, Veng-Pedersen P, Lehmler HJ. Clearance of polychlorinated biphenyl atropisomers is enantioselective in female C57Bl/6 mice. ENVIRONMENTAL SCIENCE & TECHNOLOGY 2010; 44:2828-35. [PMID: 20384376 PMCID: PMC2855138 DOI: 10.1021/es901781p] [Citation(s) in RCA: 36] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/21/2023]
Abstract
Changes in the enantiomeric composition of polychlorinated biphenyls (PCBs) can not only be used to investigate environmental and biological transport processes, but also have human health implications because of enantiospecific adverse health effects. To further understand differences in the disposition of PCB atropisomers in vivo, the present study investigates the toxicokinetics of PCB atropisomers in female C57Bl/6 mice after oral administration of a mixture of several PCBs, including racemic PCBs 91, 95, 132, 136, 149, 174, and 176. On the Chirasil-Dex column, an enrichment of the second eluting atropisomers was generally observed, whereas only the first eluting atropisomers E1-PCB 95, (-)-PCB 132, and (-)-PCB 149 had half-lives that were distinctively longer compared to the second eluting atropisomers. The bioavailability normalized clearance of first eluting atropisomers in blood was faster compared to that of second eluting atropisomers. The opposite trend was observed for the accumulation factors in adipose tissue, which is consistent with the slower clearance of the first eluting atropisomer. The only exception was PCB 174, which showed no differences in the toxicokinetic parameters of both atropisomers. Together, the differences in the toxicokinetics of PCB atropisomers point toward enantioselective biotransformation processes as the origin of PCB's enantiomeric enrichment in mammals and, possibly, humans.
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Affiliation(s)
- Izabela Kania-Korwel
- Department of Occupational and Environmental Health, College of Public Health, The University of Iowa, Iowa City, Iowa 52242
| | - Mohammed H.M.E. El-Komy
- Division of Pharmaceutics, College of Pharmacy, The University of Iowa, Iowa City, Iowa 52242
| | - Peter Veng-Pedersen
- Division of Pharmaceutics, College of Pharmacy, The University of Iowa, Iowa City, Iowa 52242
| | - Hans-Joachim Lehmler
- Department of Occupational and Environmental Health, College of Public Health, The University of Iowa, Iowa City, Iowa 52242
- To whom correspondence should be addressed: Hans-Joachim Lehmler, University of Iowa, Department of Occupational and Environmental Health, 100 Oakdale Campus #221 IREH, Iowa City, Iowa 52242, Phone: (319) 335-4211, Fax: (319) 335-4290,
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Lehmler HJ, Harrad SJ, Hühnerfuss H, Kania-Korwel I, Lee CM, Lu Z, Wong CS. Chiral polychlorinated biphenyl transport, metabolism, and distribution: a review. ENVIRONMENTAL SCIENCE & TECHNOLOGY 2010; 44:2757-66. [PMID: 20384371 PMCID: PMC2855137 DOI: 10.1021/es902208u] [Citation(s) in RCA: 106] [Impact Index Per Article: 7.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/17/2023]
Abstract
Chirality can be exploited to gain insight into enantioselective fate processes that may otherwise remain undetected because only biological, but not physical and chemical transport and transformation processes in an achiral environment will change enantiomer compositions. This review provides an in-depth overview of the application of chirality to the study of chiral polychlorinated biphenyls (PCBs), an important group of legacy pollutants. Like other chiral compounds, individual PCB enantiomers may interact enantioselectively (or enantiospecifically) with chiral macromolecules, such as cytochrome P-450 enzymes or ryanodine receptors, leading to differences in their toxicological effects and the enantioselective formation of chiral biotransformation products. Species and congener-specific enantiomer enrichment has been demonstrated in environmental compartments, wildlife, and mammals, including humans, typically due to a complex combination of biotransformation processes and uptake via the diet by passive diffusion. Changes in the enantiomer composition of chiral PCBs in the environment have been used to understand complex aerobic and anaerobic microbial transformation pathways, to delineate and quantify PCB sources and transport in the environment, to gain insight into the biotransformation of PCBs in aquatic food webs, and to investigate the enantioselective disposition of PCBs and their methylsulfonyl PCBs metabolites in rodents. Overall, changes in chiral signatures are powerful, but currently underutilized tools for studies of environmental and biological processes of PCBs.
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Affiliation(s)
- Hans-Joachim Lehmler
- Department of Occupational and Environmental Health, College of Public Health, University of Iowa, Iowa City, Iowa 52242, USA.
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Audet-Walsh E, Auclair-Vincent S, Anderson A. Glucocorticoids and phenobarbital induce murine CYP2B genes by independent mechanisms. Expert Opin Drug Metab Toxicol 2010; 5:1501-11. [PMID: 19732027 DOI: 10.1517/17425250903234709] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/05/2022]
Abstract
BACKGROUND Genes for CYP of the 2B subfamily (CYP2B genes) have long been known to be inducible in murine liver by phenobarbital and phenobarbital-like inducers. More recently, it has become clear that glucocorticoids can also induce these genes by a mechanism independent of that of phenobarbital-like inducers. OBJECTIVE To summarize the evidence for the existence of two distinct molecular mechanisms for induction of murine CYP2B genes and to analyze the wider implications of this situation for inducible xenobiotic metabolism. METHODS The mechanism of action of phenobarbital-like inducers of murine CYP2B genes is first briefly summarized. The role of glucocorticoids in the induction of various proteins, particularly rat phosphoenolpyruvate carboxykinase, where transcriptional activation is achieved via a glucocorticoid response unit, is also discussed. Finally, recent results are presented on glucocorticoid induction of murine CYP2B genes, including evidence for the presence of a functional glucocorticoid response unit in the rat CYP2B2 gene and for the role of constitutive androstane receptor as an accessory factor in this response. RESULTS/CONCLUSION Murine CYP2B genes are seen to respond to two distinct regulatory mechanisms, but much remains to be learned concerning the interactions between these two regulatory loops, as well as the details of glucocorticoid induction.
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Affiliation(s)
- Etienne Audet-Walsh
- Centre de recherche en cancérologie de l'Université Laval, L'Hôtel-Dieu de Québec, CHUQ, 11, côte du Palais, Québec, Canada
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Pessah IN, Lehmler HJ, Robertson LW, Perez CF, Cabrales E, Bose DD, Feng W. Enantiomeric specificity of (-)-2,2',3,3',6,6'-hexachlorobiphenyl toward ryanodine receptor types 1 and 2. Chem Res Toxicol 2009; 22:201-7. [PMID: 18954145 DOI: 10.1021/tx800328u] [Citation(s) in RCA: 66] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Polychlorinated biphenyls (PCBs) with unsymmetrical chlorine substitutions and multiple orthosubstitutions that restrict rotation around the biphenyl bond may exist in two stable enantiomeric forms.Stereospecific binding and functional modification of specific biological signaling targets have not been previously described for PCB atropisomers. We report that (-)-2,2',3,3',6,6'-hexachlorobiphenyl [(-)-PCB 136] enhances the binding of [3H]ryanodine to high-affinity sites on ryanodine receptors type 1(RyR1) and type 2 (RyR2) (EC50 values ~0.95 microM), whereas (+)-PCB 136 is inactive at < or =10 microM.(-)-PCB 136 induces a rapid release of Ca2+ from microsomal vesicles by selective sensitization of RyRs, an effect not antagonized by (+)-PCB 136. (-)-PCB 136 (500nM) enhances the activity of reconstituted RyR1 channels 3-fold by stabilizing the open and destabilizing the closed conformational states. The enantiomeric specificity is also demonstrated in intact HEK 293 cells expressing RyR1 where exposure to (-)-PCB 136 (100 nM; 12 h) sensitizes responses to caffeine, whereas (+)-PCB 136 does not. These data show enantiomeric specificity of (-)-PCB 136 toward a broadly expressed family of microsomal Ca2+ channels that may extend to other chiral noncoplanar PCBs and related structures.Evidence for enantioselective enrichment of PCBs in biological tissues that express RyR1 and RyR2channels may provide new mechanistic leads about their toxicological impacts on human health
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Affiliation(s)
- Isaac N Pessah
- Department of VM, Molecular Biosciences and UC Davis Center for Children's Environmental Health, University of California, One Shields Avenue, Davis, California 95616, USA.
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