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Head KZ, Bolatimi OE, Gripshover TC, Tan M, Li Y, Audam TN, Jones SP, Klinge CM, Cave MC, Wahlang B. Investigating the effects of long-term Aroclor 1260 exposure on fatty liver disease in a diet-induced obesity mouse model. FRONTIERS IN GASTROENTEROLOGY (LAUSANNE, SWITZERLAND) 2023; 2:1180712. [PMID: 37426695 PMCID: PMC10327714 DOI: 10.3389/fgstr.2023.1180712] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Indexed: 07/11/2023]
Abstract
Introduction Polychlorinated biphenyls (PCBs) are persistent environmental toxicants that have been implicated in numerous health disorders including liver diseases such as non-alcoholic fatty liver disease (NAFLD). Toxicant-associated NAFLD, also known as toxicant-associated fatty liver disease (TAFLD), consists of a spectrum of disorders ranging from steatosis and steatohepatitis to fibrosis and hepatocellular carcinoma. Previously, our group demonstrated that 12-week exposure to the PCB mixture, Aroclor 1260, exacerbated steatohepatitis in high-fat diet (HFD)-fed mice; however, the longer-term effects of PCBs on TAFLD remain to be elucidated. This study aims to examine the longer-term effects of Aroclor 1260 (>30 weeks) in a diet-induced obesity model to better understand how duration of exposure can impact TAFLD. Methods Male C57BL/6 mice were exposed to Aroclor 1260 (20 mg/kg) or vehicle control by oral gavage at the beginning of the study period and fed either a low-fat diet (LFD) or HFD throughout the study period. Results Aroclor 1260 exposure (>30 weeks) led to steatohepatitis only in LFD-fed mice. Several Aroclor 1260 exposed LFD-fed mice also developed hepatocellular carcinoma (25%), which was absent in HFD-fed mice. The LFD+Aroclor1260 group also exhibited decreased hepatic Cyp7a1 expression and increased pro-fibrotic Acta2 expression. In contrast, longer term Aroclor 1260 exposure in conjunction with HFD did not exacerbate steatosis or inflammatory responses beyond those observed with HFD alone. Further, hepatic xenobiotic receptor activation by Aroclor 1260 was absent at 31 weeks post exposure, suggesting PCB redistribution to the adipose and other extra-hepatic tissues with time. Discussion Overall, the results demonstrated that longer-term PCB exposure worsened TAFLD outcomes independent of HFD feeding and suggests altered energy metabolism as a potential mechanism fueling PCB mediated toxicity without dietary insult. Additional research exploring mechanisms for these longer-term PCB mediated toxicity in TAFLD is warranted.
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Affiliation(s)
- Kimberly Z. Head
- Division of Gastroenterology, Hepatology, and Nutrition, Department of Medicine, School of Medicine, University of Louisville, Louisville, KY, United States
- The Hepatobiology and Toxicology Center, University of Louisville, Louisville, KY, United States
| | - Oluwanifemi E. Bolatimi
- Department of Pharmacology and Toxicology, School of Medicine, University of Louisville, Louisville, KY, United States
| | - Tyler C. Gripshover
- Department of Pharmacology and Toxicology, School of Medicine, University of Louisville, Louisville, KY, United States
| | - Min Tan
- Department of Surgery, School of Medicine, University of Louisville, Louisville, KY, United States
| | - Yan Li
- Department of Surgery, School of Medicine, University of Louisville, Louisville, KY, United States
| | - Timothy N. Audam
- Center for Cardiometabolic Science, Department of Medicine, Division of Environmental Medicine, Christina Lee Brown Envirome Institute, University of Louisville, Louisville, KY, United States
| | - Steven P. Jones
- Center for Cardiometabolic Science, Department of Medicine, Division of Environmental Medicine, Christina Lee Brown Envirome Institute, University of Louisville, Louisville, KY, United States
| | - Carolyn M. Klinge
- Department of Biochemistry and Molecular Genetics, School of Medicine, University of Louisville, Louisville, KY, United States
- The Center for Integrative Environmental Health Sciences, University of Louisville, Louisville, KY, United States
| | - Matthew C. Cave
- Division of Gastroenterology, Hepatology, and Nutrition, Department of Medicine, School of Medicine, University of Louisville, Louisville, KY, United States
- The Hepatobiology and Toxicology Center, University of Louisville, Louisville, KY, United States
- Department of Pharmacology and Toxicology, School of Medicine, University of Louisville, Louisville, KY, United States
- Department of Biochemistry and Molecular Genetics, School of Medicine, University of Louisville, Louisville, KY, United States
- The Center for Integrative Environmental Health Sciences, University of Louisville, Louisville, KY, United States
- University of Louisville (UofL) Superfund Research Center, University of Louisville, Louisville, KY, United States
- Robley Rex Department of Veterans Affairs Medical Center, Louisville, KY, United States
| | - Banrida Wahlang
- Division of Gastroenterology, Hepatology, and Nutrition, Department of Medicine, School of Medicine, University of Louisville, Louisville, KY, United States
- The Hepatobiology and Toxicology Center, University of Louisville, Louisville, KY, United States
- The Center for Integrative Environmental Health Sciences, University of Louisville, Louisville, KY, United States
- University of Louisville (UofL) Superfund Research Center, University of Louisville, Louisville, KY, United States
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Derivatives of Plastics as Potential Carcinogenic Factors: The Current State of Knowledge. Cancers (Basel) 2022; 14:cancers14194637. [PMID: 36230560 PMCID: PMC9562888 DOI: 10.3390/cancers14194637] [Citation(s) in RCA: 6] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/27/2022] [Revised: 09/14/2022] [Accepted: 09/20/2022] [Indexed: 11/17/2022] Open
Abstract
Simple Summary Nowadays, micro- and nanoplastic particles can be found almost everywhere, being especially harmful for humans. Their absorption, primarily via inhalation and digestive routes, might lead to a particularly dangerous accumulation of those substances within the human body. Due to the alarming increase in contamination worldwide and excessive production of plastics and synthetic materials, there is an urgent need to investigate the effects of those substances on human health. So far, it has been observed that nano- and microplastics might be extremely harmful, leading to serious health conditions, such as cancers of various human body systems. Abstract Micro- and nanoplatics have been already reported to be potential carcinogenic/mutagenic substances that might cause DNA damage, leading to carcinogenesis. Thus, the effects of micro- and nanoplastics exposure on human health are currently being investigated extensively to establish clear relationships between those substances and health consequences. So far, it has been observed that there exists a definite correlation between exposure to micro- and nanoplastic particles and the onset of several cancers. Therefore, we have conducted research using PubMed, Web of Science, and Scopus databases, searching for all the research papers devoted to cancers that could be potentially related to the subject of exposure to nano- and microplastics. Ultimately, in this paper, we have discussed several cancers, including hepatocellular carcinoma, pancreatic cancer, pancreatic ductal adenocarcinoma, biliary tract cancer, and some endocrine-related cancers.
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Zhu DH, Nie FH, Zhang M, Wei W, Song QL, Hu Y, Kang DJ, Chen ZB, Lin HY, Chen JJ. Effects of Aroclor 1254 on Intestinal Immunity, Metabolism, and Microflora in Zebrafish. Front Nutr 2022; 9:929925. [PMID: 35911097 PMCID: PMC9328759 DOI: 10.3389/fnut.2022.929925] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/28/2022] [Accepted: 06/22/2022] [Indexed: 11/16/2022] Open
Abstract
Polychlorinated biphenyls (PCBs) are widely distributed environmental toxicants, whose biological toxicity is magnified step by step through the transmission of the food chain. However, there is little research about the effect of PCBs on intestinal epithelial barrier function. In this experiment, the effects of PCB exposure on the intestines of zebrafish were evaluated. Animals were exposed to Aroclor 1254 (5 μg/L, 10 μg/L, 15 μg/L). After 21 days, the changes in histology, enzyme biomarkers, intestinal microorganisms, and metabolomics were detected. The inflammation and oxidative stress in the intestines of zebrafish were observed. Additionally, there were significant changes in intestinal microbiota and tissue metabolism, most of which were associated with oxidative stress, inflammation, and lipid metabolism. The results showed that PCBs exposure resulted in intestinal inflammation and oxidative stress in zebrafish.Moreover, intestinal metabolites and intestinal microflora of zebrafish were also disturbed. This study verified that exposure can lead to intestinal damage and changes in intestinal metabolic capacity and microorganisms, enlightening the consequences of PCB exposure.
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Affiliation(s)
- Di-Hua Zhu
- Department of Veterinary Medicine, College of Coastal Agriculture, Guangdong Ocean University, Zhanjiang, China
| | - Fang-Hong Nie
- College of Food Science and Technology, Guangdong Ocean University, Zhanjiang, China
| | - Min Zhang
- Department of Veterinary Medicine, College of Coastal Agriculture, Guangdong Ocean University, Zhanjiang, China
| | - Wan Wei
- Department of Veterinary Medicine, College of Coastal Agriculture, Guangdong Ocean University, Zhanjiang, China
| | - Qing-Lang Song
- Department of Veterinary Medicine, College of Coastal Agriculture, Guangdong Ocean University, Zhanjiang, China
| | - Yao Hu
- Department of Veterinary Medicine, College of Coastal Agriculture, Guangdong Ocean University, Zhanjiang, China
| | - Dan-Ju Kang
- Department of Veterinary Medicine, College of Coastal Agriculture, Guangdong Ocean University, Zhanjiang, China
| | - Zhi-Bao Chen
- Department of Veterinary Medicine, College of Coastal Agriculture, Guangdong Ocean University, Zhanjiang, China
| | - Hong-Ying Lin
- Department of Veterinary Medicine, College of Coastal Agriculture, Guangdong Ocean University, Zhanjiang, China
- *Correspondence: Jin-Jun Chen
| | - Jin-Jun Chen
- Department of Veterinary Medicine, College of Coastal Agriculture, Guangdong Ocean University, Zhanjiang, China
- Hong-Ying Lin
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Fair PA, Peden-Adams MM, Mollenhauer MAM, Bossart GD, Keil DE, White ND. Effects of an environmentally relevant PCB-mixture on immune function, clinical chemistry, and thyroid hormone levels in adult female B 6C 3F 1 mice. JOURNAL OF TOXICOLOGY AND ENVIRONMENTAL HEALTH. PART A 2021; 84:279-297. [PMID: 33357133 DOI: 10.1080/15287394.2020.1863887] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/12/2023]
Abstract
Polychlorinated biphenyls (PCBs) have been assessed for immunotoxicity; however, humans and wildlife are exposed to multiple PCBs environmentally. Therefore, the aim of this study was to examine the effects of a complex 37 PCB congener mixture identified in blubber specific to dolphins residing in the estuarine waters of Charleston, South Carolina. Immunotoxicity was determined in adult female B6C3F1 mice by assessing lymphocyte proliferation, splenic and thymic immunophenotypes, and IgM production. Mice were exposed via oral gavage to the PCB-mixture (0, 1.8, 3.6, 7.1, or 14.3 mg/kg/day) for 28 days to yield a targeted total administered dose (TAD) 0, 50, 100, 200, or 400 mg/kg. Significant increased liver weight occurred at the highest treatment. IgM production was suppressed compared to control for all treatments. Numbers of thymic CD4+/CD8+, CD4-/CD8-, and CD4+/CD8- cells were not altered, but numbers of thymic CD4-/CD8+ cells were significantly increased in the highest treatment. Lymphocyte proliferation was not markedly affected by any treatment. The numbers of splenic CD4/CD8 T-cells or MHCII+ cells were not significantly changed. Humoral immunity using the plaque-forming cell assay for determining the specific IgM antibody-forming cell response appeared to be the most sensitive endpoint affected. As the lowest concentration tested resulted in decreased IgM production and total and free thyroxine (T4) serum levels a NOAEL was not identified. The calculated ED50 for suppression of IgM production was 2.4 mg/kg/day.
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Affiliation(s)
- Patricia A Fair
- National Oceanic and Atmospheric Administration, National Ocean Service, Center for Coastal Environmental Health & Biomolecular Research, Charleston, SC, USA
| | - Margie M Peden-Adams
- Harry Reid Center for Environmental Studies, University of Nevada Las Vegas, Las Vegas, NV, USA
| | - Meagan A M Mollenhauer
- Molecular and Cellular Biology and Pathobiology, Medical University of South Carolina, Charleston, SC, USA
| | - Gregory D Bossart
- Animal Health, Research and Conservation, Georgia Aquarium, NW Atlanta, GA, USA
| | - Deborah E Keil
- Medical Laboratory Sciences, Department of Pathology, University of Utah School of Medicine, Salt Lake City, UT, USA
| | - Natasha D White
- National Oceanic and Atmospheric Administration, National Ocean Service, Center for Coastal Environmental Health & Biomolecular Research, Charleston, SC, USA
- Department of Education, National Oceanic and Atmospheric Administration, Silver Spring, MD, USA
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Engineering Burkholderia xenovorans LB400 BphA through Site-Directed Mutagenesis at Position 283. Appl Environ Microbiol 2020; 86:AEM.01040-20. [PMID: 32709719 DOI: 10.1128/aem.01040-20] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/05/2020] [Accepted: 07/15/2020] [Indexed: 11/20/2022] Open
Abstract
Biphenyl dioxygenase (BPDO), which is a Rieske-type oxygenase (RO), catalyzes the initial dioxygenation of biphenyl and some polychlorinated biphenyls (PCBs). In order to enhance the degradation ability of BPDO in terms of a broader substrate range, the BphAES283M, BphAEp4-S283M, and BphAERR41-S283M variants were created from the parent enzymes BphAELB400, BphAEp4, and BphAERR41, respectively, by a substitution at one residue, Ser283Met. The results of steady-state kinetic parameters show that for biphenyl, the k cat/Km values of BphAES283M, BphAEp4-S283M, and BphAERR41-S283M were significantly increased compared to those of their parent enzymes. Meanwhile, we determined the steady-state kinetics of BphAEs toward highly chlorinated biphenyls. The results suggested that the Ser283Met substitution enhanced the catalytic activity of BphAEs toward 2,3',4,4'-tetrachlorobiphenyl (2,3',4,4'-CB), 2,2',6,6'-tetrachlorobiphenyl (2,2',6,6'-CB), and 2,3',4,4',5-pentachlorobiphenyl (2,3',4,4',5-CB). We compared the catalytic reactions of BphAELB400 and its variants toward 2,2'-dichlorobiphenyl (2,2'-CB), 2,5-dichlorobiphenyl (2,5-CB), and 2,6-dichlorobiphenyl (2,6-CB). The biochemical data indicate that the Ser283Met substitution alters the orientation of the substrate inside the catalytic site and, thereby, its site of hydroxylation, and this was confirmed by docking experiments. We also assessed the substrate ranges of BphAELB400 and its variants with degradation activity. BphAES283M and BphAEp4-S283M were clearly improved in oxidizing some of the 3-6-chlorinated biphenyls, which are generally very poorly oxidized by most dioxygenases. Collectively, the present work showed a significant effect of mutation Ser283Met on substrate specificity/regiospecificity in BPDO. These will certainly be meaningful elements for understanding the effect of the residue corresponding to position 283 in other Rieske oxygenase enzymes.IMPORTANCE The segment from positions 280 to 283 in BphAEs is located at the entrance of the catalytic pocket, and it shows variation in conformation. In previous works, results have suggested but never proved that residue Ser283 of BphAELB400 might play a role in substrate specificity. In the present paper, we found that the Ser283Met substitution significantly increased the specificity of the reaction of BphAE toward biphenyl, 2,3',4,4'-CB, 2,2',6,6'-CB, and 2,3',4,4',5-CB. Meanwhile, the Ser283Met substitution altered the regiospecificity of BphAE toward 2,2'-dichlorobiphenyl and 2,6-dichlorobiphenyl. Additionally, this substitution extended the range of PCBs metabolized by the mutated BphAE. BphAES283M and BphAEp4-S283M were clearly improved in oxidizing some of the more highly chlorinated biphenyls (3 to 6 chlorines), which are generally very poorly oxidized by most dioxygenases. We used modeled and docked enzymes to identify some of the structural features that explain the new properties of the mutant enzymes. Altogether, the results of this study provide better insights into the mechanisms by which BPDO evolves to change and/or expand its substrate range and its regiospecificity.
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Heiger-Bernays WJ, Tomsho KS, Basra K, Petropoulos ZE, Crawford K, Martinez A, Hornbuckle KC, Scammell MK. Human health risks due to airborne polychlorinated biphenyls are highest in New Bedford Harbor communities living closest to the harbor. THE SCIENCE OF THE TOTAL ENVIRONMENT 2020; 710:135576. [PMID: 31785914 PMCID: PMC7015809 DOI: 10.1016/j.scitotenv.2019.135576] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/18/2019] [Revised: 11/12/2019] [Accepted: 11/15/2019] [Indexed: 04/14/2023]
Abstract
In response to concerns raised by communities surrounding the New Bedford Harbor Superfund site, we completed a field and modeling study that concluded the harbor is the primary source of polychlorinated biphenyls (PCBs) in air around the harbor. The follow-up question from residents was whether the PCBs measured in air pose a risk to their health. The US Environmental Protection Agency focuses their site-specific, risk-based decisions for site clean-up on cancers. We focused our assessment on the non-cancer effects on the thyroid based on the congener specific patterns and concentrations of PCBs measured in air near and distant to the harbor. Human and animal studies of PCB-induced effects on the thyroid provide evidence to support our analysis. Drawing from the published toxicological data, we used a Margin of Exposure (MOE) approach to derive a human-equivalent concentration in air associated with human health effects on the thyroid. Based on the MOEs calculated herein, evaluation of the MOE indicates that changes in thyroid hormone levels are possible among people living adjacent to the Harbor. Changes in thyroid hormone levels are more likely among people who live near the harbor compared to residents living in areas distant from the harbor. This risk assessment documents potential health risks associated with proximity to a marine Superfund Site using site-specific ambient air PCB congener data.
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Affiliation(s)
- Wendy J Heiger-Bernays
- Boston University School of Public Health, Department of Environmental Health, 715 Albany St., Talbot Building, Boston, MA 02118, United States.
| | - Kathryn Scott Tomsho
- Boston University School of Public Health, Department of Environmental Health, 715 Albany St., Talbot Building, Boston, MA 02118, United States
| | - Komal Basra
- Boston University School of Public Health, Department of Environmental Health, 715 Albany St., Talbot Building, Boston, MA 02118, United States
| | - Zoe E Petropoulos
- Boston University School of Public Health, Department of Environmental Health, 715 Albany St., Talbot Building, Boston, MA 02118, United States
| | - Kathryn Crawford
- Boston University School of Public Health, Department of Environmental Health, 715 Albany St., Talbot Building, Boston, MA 02118, United States
| | - Andres Martinez
- Department of Civil & Environmental Engineering, IIHR-Hydroscience and Engineering, 4105 Seamans Center for the Engineering Arts and Sciences, The University of Iowa, Iowa City, IA 52242, United States
| | - Keri C Hornbuckle
- Department of Civil & Environmental Engineering, IIHR-Hydroscience and Engineering, 4105 Seamans Center for the Engineering Arts and Sciences, The University of Iowa, Iowa City, IA 52242, United States
| | - Madeleine K Scammell
- Boston University School of Public Health, Department of Environmental Health, 715 Albany St., Talbot Building, Boston, MA 02118, United States
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Garrido-Sanz D, Manzano J, Martín M, Redondo-Nieto M, Rivilla R. Metagenomic Analysis of a Biphenyl-Degrading Soil Bacterial Consortium Reveals the Metabolic Roles of Specific Populations. Front Microbiol 2018; 9:232. [PMID: 29497412 PMCID: PMC5818466 DOI: 10.3389/fmicb.2018.00232] [Citation(s) in RCA: 39] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/28/2017] [Accepted: 01/30/2018] [Indexed: 01/09/2023] Open
Abstract
Polychlorinated biphenyls (PCBs) are widespread persistent pollutants that cause several adverse health effects. Aerobic bioremediation of PCBs involves the activity of either one bacterial species or a microbial consortium. Using multiple species will enhance the range of PCB congeners co-metabolized since different PCB-degrading microorganisms exhibit different substrate specificity. We have isolated a bacterial consortium by successive enrichment culture using biphenyl (analog of PCBs) as the sole carbon and energy source. This consortium is able to grow on biphenyl, benzoate, and protocatechuate. Whole-community DNA extracted from the consortium was used to analyze biodiversity by Illumina sequencing of a 16S rRNA gene amplicon library and to determine the metagenome by whole-genome shotgun Illumina sequencing. Biodiversity analysis shows that the consortium consists of 24 operational taxonomic units (≥97% identity). The consortium is dominated by strains belonging to the genus Pseudomonas, but also contains betaproteobacteria and Rhodococcus strains. whole-genome shotgun (WGS) analysis resulted in contigs containing 78.3 Mbp of sequenced DNA, representing around 65% of the expected DNA in the consortium. Bioinformatic analysis of this metagenome has identified the genes encoding the enzymes implicated in three pathways for the conversion of biphenyl to benzoate and five pathways from benzoate to tricarboxylic acid (TCA) cycle intermediates, allowing us to model the whole biodegradation network. By genus assignment of coding sequences, we have also been able to determine that the three biphenyl to benzoate pathways are carried out by Rhodococcus strains. In turn, strains belonging to Pseudomonas and Bordetella are the main responsible of three of the benzoate to TCA pathways while the benzoate conversion into TCA cycle intermediates via benzoyl-CoA and the catechol meta-cleavage pathways are carried out by beta proteobacteria belonging to genera such as Achromobacter and Variovorax. We have isolated a Rhodococcus strain WAY2 from the consortium which contains the genes encoding the three biphenyl to benzoate pathways indicating that this strain is responsible for all the biphenyl to benzoate transformations. The presented results show that metagenomic analysis of consortia allows the identification of bacteria active in biodegradation processes and the assignment of specific reactions and pathways to specific bacterial groups.
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Affiliation(s)
| | | | | | | | - Rafael Rivilla
- Departamento de Biología, Facultad de Ciencias, Universidad Autónoma de Madrid, Madrid, Spain
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8
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Wahlang B, Prough RA, Falkner KC, Hardesty JE, Song M, Clair HB, Clark BJ, States JC, Arteel GE, Cave MC. Polychlorinated Biphenyl-Xenobiotic Nuclear Receptor Interactions Regulate Energy Metabolism, Behavior, and Inflammation in Non-alcoholic-Steatohepatitis. Toxicol Sci 2015; 149:396-410. [PMID: 26612838 DOI: 10.1093/toxsci/kfv250] [Citation(s) in RCA: 42] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/25/2022] Open
Abstract
Polychlorinated biphenyls (PCBs) are environmental pollutants associated with non-alcoholic-steatohepatitis (NASH), diabetes, and obesity. We previously demonstrated that the PCB mixture, Aroclor 1260, induced steatohepatitis and activated nuclear receptors in a diet-induced obesity mouse model. This study aims to evaluate PCB interactions with the pregnane-xenobiotic receptor (Pxr: Nr1i2) and constitutive androstane receptor (Car: Nr1i3) in NASH. Wild type C57Bl/6 (WT), Pxr(-/-) and Car(-/-) mice were fed the high fat diet (42% milk fat) and exposed to a single dose of Aroclor 1260 (20 mg/kg) in this 12-week study. Metabolic phenotyping and analysis of serum, liver, and adipose was performed. Steatohepatitis was pathologically similar in all Aroclor-exposed groups, while Pxr(-/-) mice displayed higher basal pro-inflammatory cytokine levels. Pxr repressed Car expression as evident by increased basal Car/Cyp2b10 expression in Pxr(-/-) mice. Both Pxr(-/-) and Car(-/-) mice showed decreased basal respiratory exchange rate (RER) consistent with preferential lipid metabolism. Aroclor increased RER and carbohydrate metabolism, associated with increased light cycle activity in both knockouts, and decreased food consumption in the Car(-/-) mice. Aroclor exposure improved insulin sensitivity in WT mice but not glucose tolerance. The Aroclor-exposed, Pxr(-/-) mice displayed increased gluconeogenic gene expression. Lipid-oxidative gene expression was higher in WT and Pxr(-/-) mice although RER was not changed, suggesting PCB-mediated mitochondrial dysfunction. Therefore, Pxr and Car regulated inflammation, behavior, and energy metabolism in PCB-mediated NASH. Future studies should address the 'off-target' effects of PCBs in steatohepatitis.
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Affiliation(s)
| | | | - K Cameron Falkner
- Department of Medicine Division of Gastroenterology, Hepatology and Nutrition, University of Louisville School of Medicine, Louisville, KY 40202
| | | | - Ming Song
- Department of Medicine Division of Gastroenterology, Hepatology and Nutrition, University of Louisville School of Medicine, Louisville, KY 40202
| | | | | | | | | | - Matthew C Cave
- *Department of Pharmacology and Toxicology; Department of Biochemistry and Molecular Genetics; Department of Medicine Division of Gastroenterology, Hepatology and Nutrition, University of Louisville School of Medicine, Louisville, KY 40202; The Robley Rex Veterans Affairs Medical Center, Louisville, KY 40206; and The KentuckyOne Health Jewish Hospital Liver Transplant Program, Louisville, KY 40202
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9
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Hu J, Qian M, Zhang Q, Cui J, Yu C, Su X, Shen C, Hashmi MZ, Shi J. Sphingobium fuliginis HC3: a novel and robust isolated biphenyl- and polychlorinated biphenyls-degrading bacterium without dead-end intermediates accumulation. PLoS One 2015; 10:e0122740. [PMID: 25875180 PMCID: PMC4395236 DOI: 10.1371/journal.pone.0122740] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/11/2014] [Accepted: 02/12/2015] [Indexed: 11/19/2022] Open
Abstract
Biphenyl and polychlorinated biphenyls (PCBs) are typical environmental pollutants. However, these pollutants are hard to be totally mineralized by environmental microorganisms. One reason for this is the accumulation of dead-end intermediates during biphenyl and PCBs biodegradation, especially benzoate and chlorobenzoates (CBAs). Until now, only a few microorganisms have been reported to have the ability to completely mineralize biphenyl and PCBs. In this research, a novel bacterium HC3, which could degrade biphenyl and PCBs without dead-end intermediates accumulation, was isolated from PCBs-contaminated soil and identified as Sphingobium fuliginis. Benzoate and 3-chlorobenzoate (3-CBA) transformed from biphenyl and 3-chlorobiphenyl (3-CB) could be rapidly degraded by HC3. This strain has strong degradation ability of biphenyl, lower chlorinated (mono-, di- and tri-) PCBs as well as mono-CBAs, and the biphenyl/PCBs catabolic genes of HC3 are cloned on its plasmid. It could degrade 80.7% of 100 mg L -1 biphenyl within 24 h and its biphenyl degradation ability could be enhanced by adding readily available carbon sources such as tryptone and yeast extract. As far as we know, HC3 is the first reported that can degrade biphenyl and 3-CB without accumulation of benzoate and 3-CBA in the genus Sphingobium, which indicates the bacterium has the potential to totally mineralize biphenyl/PCBs and might be a good candidate for restoring biphenyl/PCBs-polluted environments.
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Affiliation(s)
- Jinxing Hu
- Department of Environmental Engineering, College of Environmental and Resource Sciences, Zhejiang University, Hangzhou, China
| | - Mingrong Qian
- Institute of Quality and Standard on Agricultural Products, Zhejiang Academy of Agricultural Sciences, Hangzhou, China
| | - Qian Zhang
- Department of Environmental Engineering, College of Environmental and Resource Sciences, Zhejiang University, Hangzhou, China
| | - Jinglan Cui
- Department of Environmental Engineering, College of Environmental and Resource Sciences, Zhejiang University, Hangzhou, China
| | - Chunna Yu
- College of Life and Environmental Sciences, Hangzhou Normal University, Hangzhou, China
| | - Xiaomei Su
- Department of Environmental Engineering, College of Environmental and Resource Sciences, Zhejiang University, Hangzhou, China
| | - Chaofeng Shen
- Department of Environmental Engineering, College of Environmental and Resource Sciences, Zhejiang University, Hangzhou, China
| | - Muhammad Z. Hashmi
- Department of Environmental Engineering, College of Environmental and Resource Sciences, Zhejiang University, Hangzhou, China
| | - Jiyan Shi
- Department of Environmental Engineering, College of Environmental and Resource Sciences, Zhejiang University, Hangzhou, China
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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: 282] [Impact Index Per Article: 31.3] [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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11
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Wahlang B, Falkner KC, Clair HB, Al-Eryani L, Prough RA, States JC, Coslo DM, Omiecinski CJ, Cave MC. Human receptor activation by aroclor 1260, a polychlorinated biphenyl mixture. Toxicol Sci 2014; 140:283-97. [PMID: 24812009 DOI: 10.1093/toxsci/kfu083] [Citation(s) in RCA: 67] [Impact Index Per Article: 6.7] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022] Open
Abstract
Polychlorinated biphenyls (PCBs) are persistent environmental toxicants, present in 100% of U.S. adults and dose-dependently associated with obesity and non-alcoholic fatty liver disease (NAFLD). PCBs are predicted to interact with receptors previously implicated in xenobiotic/energy metabolism and NAFLD. These receptors include the aryl hydrocarbon receptor (AhR), pregnane xenobiotic receptor (PXR), constitutive androstane receptor (CAR), peroxisome proliferator-activated receptors (PPARs), liver-X-receptor (LXRα), and farnesoid-X-receptor (FXR). This study evaluates Aroclor 1260, a PCB mixture with congener composition mimicking that of human adipose tissue, and selected congeners, as potential ligands for these receptors utilizing human hepatoma-derived (HepG2) and primate-derived (COS-1) cell lines, and primary human hepatocytes. Aroclor 1260 (20 μg/ml) activated AhR, and PCB 126, a minor component, was a potent inducer. Aroclor 1260 activated PXR in a simple concentration-dependent manner at concentrations ≥10 μg/ml. Among the congeners tested, PCBs 138, 149, 151, 174, 183, 187, and 196 activated PXR. Aroclor 1260 activated CAR2 and CAR3 variants at lower concentrations and antagonize CAR2 activation by the CAR agonist, CITCO, at higher concentrations (≥20 μg/ml). Additionally, Aroclor 1260 induced CYP2B6 in primary hepatocytes. At subtoxic doses, Aroclor 1260 did not activate LXR or FXR and had no effect on LXR- or FXR-dependent induction by the agonists T0901317 or GW4064, respectively. Aroclor 1260 (20 μg/ml) suppressed PPARα activation by the agonist nafenopin, although none of the congeners tested demonstrated significant inhibition. The results suggest that Aroclor 1260 is a human AhR, PXR and CAR3 agonist, a mixed agonist/antagonist for CAR2, and an antagonist for human PPARα.
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Affiliation(s)
| | - K Cameron Falkner
- Department of Medicine, Division of Gastroenterology, Hepatology and Nutrition
| | - Heather B Clair
- Department of Biochemistry and Molecular Biology, University of Louisville School of Medicine, Louisville, Kentucky 40202
| | | | - Russell A Prough
- Department of Biochemistry and Molecular Biology, University of Louisville School of Medicine, Louisville, Kentucky 40202
| | | | - Denise M Coslo
- Center for Molecular Toxicology, Penn State University, University Park, Pennsylvania 16802
| | - Curtis J Omiecinski
- Center for Molecular Toxicology, Penn State University, University Park, Pennsylvania 16802
| | - Matthew C Cave
- Department of Pharmacology and Toxicology Department of Medicine, Division of Gastroenterology, Hepatology and Nutrition The Robley Rex Veterans Affairs Medical Center, Louisville, Kentucky 40206
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12
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Sustained expression of CYPs and DNA adduct accumulation with continuous exposure to PCB126 and PCB153 through a new delivery method: Polymeric implants. Toxicol Rep 2014; 1:820-833. [PMID: 25530946 PMCID: PMC4266188 DOI: 10.1016/j.toxrep.2014.09.010] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022] Open
Abstract
Polymeric implants successfully achieved continuous exposure to PCBs in rats. PCB126 resulted in significant oxidative DNA damage (8-oxodG) in rat liver and lung. PCB126 or in combination with PCB153 induced PON1 and its activity in the liver. The induction was even greater for PON3 and AhR gene transcription. Co-treatment reduced mammary PCB153 and increased liver PCB126 and PCB153 levels.
A new delivery method via polymeric implants was used for continuous exposure to PCBs. Female Sprague-Dawley rats received subcutaneous polymeric implants containing PCB126 (0.15% load), PCB153 (5% load), or both, for up to 45 d and release kinetics and tissue distribution were measured. PCB153 tissue levels on day 15 were readily detected in lung, liver, mammary and serum, with highest levels in the mammary tissue. PCB126 was detected only in liver and mammary tissues. However, a completely different pharmacokinetics was observed on co-exposure of PCB153 and PCB126, with a 1.8-fold higher levels of PCB153 in the liver whereas a 1.7-fold lower levels in the mammary tissue. PCB126 and PCB153 caused an increase in expression of key PCB-inducible enzymes, CYP 1A1/2 and 2B1/2, respectively. Serum and liver activities of the antioxidant enzymes, PON1 and PON3, and AhR transcription were also significantly increased by PCB126. 32P-postlabeling for polar and lipophilic DNA-adducts showed significant quantitative differences: PCB126 increased 8-oxodG, an oxidative DNA lesion, in liver and lung tissues. Adduct levels in the liver remained upregulated up to 45 d, while some lung DNA adducts declined. This is the first demonstration that continuous low-dose exposure to PCBs via implants can produce sustained tissue levels leading to the accumulation of DNA-adducts in target tissue and induction of indicator enzymes. Collectively, these data demonstrate that this exposure model is a promising tool for long-term exposure studies.
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13
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Ludewig G, Robertson LW. Polychlorinated biphenyls (PCBs) as initiating agents in hepatocellular carcinoma. Cancer Lett 2013; 334:46-55. [PMID: 23211541 PMCID: PMC3648605 DOI: 10.1016/j.canlet.2012.11.041] [Citation(s) in RCA: 62] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/29/2012] [Revised: 11/20/2012] [Accepted: 11/25/2012] [Indexed: 12/11/2022]
Abstract
PCBs are carcinogens, but for many decades it was assumed that PCBs may not possess initiating activity. Initiation is a process that involves changes in the DNA sequence, often, but not exclusively produced through DNA adduction by a reactive compound or reactive oxygen species (ROS). DNA adducts can be detected by (32)P-postlabeling, a method that Dr. Ramesh Gupta co-developed and refined. Today these types of assays together with other mechanistic studies provide convincing evidence that specific PCB congeners can be biotransformed to genotoxic and therefore potentially initiating metabolites. This review will provide an overview of our current knowledge of PCBs' genotoxic potential and mechanism of action, emphasizing the contributions of Dr. Ramesh Gupta during his tenures at the Universities of Kentucky and Louisville.
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Affiliation(s)
- Gabriele Ludewig
- The University of Iowa, 100 Oakdale Campus, IREH, Iowa City, IA 52242-5000, United States.
| | - Larry W Robertson
- The University of Iowa, 100 Oakdale Campus, IREH, Iowa City, IA 52242-5000, United States
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14
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Lai IK, Chai Y, Simmons D, Watson WH, Tan R, Haschek WM, Wang K, Wang B, Ludewig G, Robertson LW. Dietary selenium as a modulator of PCB 126-induced hepatotoxicity in male Sprague-Dawley rats. Toxicol Sci 2011; 124:202-14. [PMID: 21865291 DOI: 10.1093/toxsci/kfr215] [Citation(s) in RCA: 27] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/30/2023] Open
Abstract
Homeostasis of selenium (Se), a critical antioxidant incorporated into amino acids and enzymes, is disrupted by exposure to aryl hydrocarbon receptor (AhR) agonists. Here we examined the importance of dietary Se in preventing the toxicity of the most toxic polychlorinated biphenyl congener, 3,3',4,4',5-pentachlorobiphenyl (PCB 126), a potent AhR agonist. Male Sprague-Dawley rats were fed a modified AIN-93 diet with differing dietary Se levels (0.02, 0.2, and 2 ppm). Following 3 weeks of acclimatization, rats from each dietary group were given a single ip injection of corn oil (vehicle), 0.2, 1, or 5 μmol/kg body weight PCB 126, followed 2 weeks later by euthanasia. PCB exposure caused dose-dependent increases in liver weight and at the highest PCB 126 dose decreases in whole body weight gains. Hepatic cytochrome P-450 (CYP1A1) activity was significantly increased even at the lowest dose of PCB 126, indicating potent AhR activation. PCB exposure diminished hepatic Se levels in a dose-dependent manner, and this was accompanied by diminished Se-dependent glutathione peroxidase activity. Both these effects were partially mitigated by Se supplementation. Conversely, thioredoxin (Trx) reductase activity and Trx oxidation state, although significantly diminished in the lowest dietary Se groups, were not affected by PCB exposure. In addition, PCB 126-induced changes in hepatic copper, iron, manganese, and zinc were observed. These results demonstrate that supplemental dietary Se was not able to completely prevent the toxicity caused by PCB 126 but was able to increase moderately the levels of several key antioxidants, thereby maintaining them roughly at normal levels.
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Affiliation(s)
- Ian K Lai
- Interdisciplinary Graduate Program in Human Toxicology, College of Public Health, University of Iowa, Iowa City, Iowa 52242, USA
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15
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Senthilkumar PK, Klingelhutz AJ, Jacobus JA, Lehmler H, Robertson LW, Ludewig G. Airborne polychlorinated biphenyls (PCBs) reduce telomerase activity and shorten telomere length in immortal human skin keratinocytes (HaCat). Toxicol Lett 2011; 204:64-70. [PMID: 21530622 DOI: 10.1016/j.toxlet.2011.04.012] [Citation(s) in RCA: 37] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/15/2010] [Revised: 04/12/2011] [Accepted: 04/14/2011] [Indexed: 12/17/2022]
Abstract
PCBs, a group of 209 individual congeners, are ubiquitous environmental pollutants and classified as probable human carcinogens. One major route of exposure is by inhalation of these industrial compounds, possibly daily from inner city air and/or indoor air in contaminated buildings. Hallmarks of aging and carcinogenesis are changes in telomere length and telomerase activity. We hypothesize that semi-volatile PCBs, like those found in inner city air, are capable of disrupting telomerase activity and altering telomere length. To explore this possibility, we exposed human skin keratinocytes to a synthetic Chicago Airborne Mixture (CAM) of PCBs, or the prominent airborne PCB congeners, PCB28 or PCB52 for up to 48 days and determined telomerase activity, telomere length, cell proliferation, and cell cycle distribution. PCBs 28, 52 and CAM significantly reduced telomerase activity from days 18-48. Telomere length was shortened by PCB 52 from day 18 and PCB 28 and CAM from days 30 on. All PCBs decreased cell proliferation from day 18; only PCB 52 produced a small increase of cells in G0/G1 of the cell cycle. This significant inhibition of telomerase activity and reduction of telomere length by PCB congeners suggest a potential mechanism by which these compounds could lead to accelerated aging and cancer.
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Affiliation(s)
- P K Senthilkumar
- Interdisciplinary Graduate Program in Human Toxicology, The University of Iowa, Iowa City, IA, United States
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16
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Kopec AK, Burgoon LD, Ibrahim-Aibo D, Burg AR, Lee AW, Tashiro C, Potter D, Sharratt B, Harkema JR, Rowlands JC, Budinsky RA, Zacharewski TR. Automated dose-response analysis and comparative toxicogenomic evaluation of the hepatic effects elicited by TCDD, TCDF, and PCB126 in C57BL/6 mice. Toxicol Sci 2010; 118:286-97. [PMID: 20702594 DOI: 10.1093/toxsci/kfq236] [Citation(s) in RCA: 49] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
Abstract
The toxic equivalency factor (TEF) approach recommended by the World Health Organization is used to quantify dioxin-like exposure concentrations for mixtures of polychlorinated dibenzo-dioxins, -furans, and polychlorinated biphenyls (PCBs), including 2,3,7,8-tetrachlorodibenzofuran (TCDF) and 3,3',4,4',5-pentachlorobiphenyl (PCB126) relative to 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD). Whole-genome microarrays were used to evaluate the hepatic gene expression potency of TCDF and PCB126 relative to TCDD with complementary histopathology, tissue level analysis, and ethoxyresorufin-O-deethylase (EROD) assay results. Immature ovariectomized C57BL/6 mice were gavaged with 0.001, 0.01, 0.03, 0.1, 0.3, 1, 3, 10, 30, 100, and 300 μg/kg TCDD and TEF-adjusted doses (TEF for TCDF and PCB126 is 0.1) of TCDF or PCB126 (1, 3, 10, 30, 100, 300, 1000, and 3000 μg/kg of TCDF or PCB126) or sesame oil vehicle and sacrificed 24 h post dose. In general, TCDD, TCDF, and PCB126 tissue levels, as well as histopathological effects, were comparable when comparing TEF-adjusted doses. Automated dose-response modeling (ToxResponse Modeler) of the microarray data identified 210 TCDF and 40 PCB126 genes that exhibited sigmoidal dose-response curves with comparable slopes when compared with TCDD. These similar responses were used to calculate a median TCDF gene expression relative potency (REP) of 0.06 and a median PCB126 gene expression REP of 0.02. REPs of 0.02 were also calculated for EROD induction for both compounds. Collectively, these data suggest that differences in the ability of the liganded aryl hydrocarbon receptor:AhR nuclear translocator complex to elicit differential hepatic gene expression, in addition to pharmacokinetic differences between ligands, influence their potency in immature ovariectomized C57BL/6 mice.
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Affiliation(s)
- Anna K Kopec
- Department of Biochemistry & Molecular Biology, Michigan State University, East Lansing, Michigan 48824, USA
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17
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Martin L, Klaassen CD. Differential effects of polychlorinated biphenyl congeners on serum thyroid hormone levels in rats. Toxicol Sci 2010; 117:36-44. [PMID: 20573785 DOI: 10.1093/toxsci/kfq187] [Citation(s) in RCA: 51] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
Abstract
Polychlorinated biphenyls (PCBs) are known to reduce serum thyroxine (T(4)) in rats, but the relative effects of individual PCB congeners on thyroid hormones are not known. Thus, male Sprague-Dawley rats were administered Aroclor 1254, Aroclor 1242 (4, 8, 16, or 32 mg/kg/day), PCB 95 (2,2',3,5',6-pentachlorobiphenyl), PCB 99 (2,2',4,4',5-pentachlorobiphenyl), PCB 118 (2,3',4,4',5-pentachlorobiphenyl) (2, 4, 8, or 16 mg/kg/day), PCB 126 (3,3'4,4',5-pentachlorobiphenyl) (2.5, 5, 10, 20, or 40 microg/kg/day), TCDD (2,3,7,8-tetrachlorodibenzo-p-dioxin) (0.14, 0.43, 1.3, or 3.9 microg/kg/day), or corn oil via oral gavage for 7 days. Rats were necropsied 24 h after the last dose. Serum thyroid hormone levels were evaluated by radioimmunoassay, and induction of hepatic Cyp1a (a TCDD-inducible protein) and Cyp2b (a phenobarbital [PB]-inducible protein) activity was determined by ethoxyresorufin-O-deethylase and pentoxyresorufin-O-deethylase assays, respectively. Significant increases in Cyp1a activity occurred in response to PCBs, except PCB 95 and PCB 99. Aroclor 1254, PCB 99, and PCB 118 significantly induced Cyp2b activity. Serum total T(4) and free T(4) were dramatically reduced in response to each of the seven treatments in a dose-dependent manner. The marked T(4) reductions occurred in response to Aroclor 1254, PCB 99 (a PB-type congener), and PCB 118 (a mixed-type congener). In contrast, reductions in serum triiodothyronine (total and free) were variable and mild, and serum thyroid-stimulating hormone was not significantly affected by any of the compounds. These data indicate that the PB and mixed-type PCB congeners are more effective than the TCDD-type PCB congeners at reducing serum T(4).
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Affiliation(s)
- Lori Martin
- Department of Pharmacology, Toxicology and Therapeutics, University of Kansas Medical Center, Kansas City, Kansas 66160, USA
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18
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Chan K, Lehmler HJ, Sivagnanam M, Feng CY, Robertson L, O'Brien PJ. Cytotoxic effects of polychlorinated biphenyl hydroquinone metabolites in rat hepatocytes. J Appl Toxicol 2010; 30:163-71. [PMID: 19830680 DOI: 10.1002/jat.1483] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/05/2022]
Abstract
Polychlorinated biphenyls (PCBs) are persistent organic pollutants that exhibit various toxic effects in animals and exposed human populations. The molecular mechanisms of PCB toxicity have been attributed to the toxicological properties of its metabolites, such as hydroquinones, formed by cytochrome-P-450 oxidation. The effects of PCB hydroquinone metabolites towards freshly isolated rat hepatocytes were investigated. Hydroquinones can be oxidized to semiquinones and/or quinone metabolites. These metabolites can conjugate glutathione or can oxidize glutathione as a result of redox cycling. This depletes hepatocyte glutathione, which can inhibit cellular defence mechanisms, causing cell death and an increased susceptibility to oxidative stress. However in the following, glutathione-depleted hepatocytes became more resistant to the hydroquinone metabolites of PCBs. This suggested that their glutathione conjugates were toxic and that there was a third type of quinone toxicity mechanism which involved a hydrogen peroxide-accelerated autoxidation of the hydroquinones to form toxic electrophilic quinone and semiquinone-glutathione conjugates.
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Affiliation(s)
- Katie Chan
- Department of Pharmaceutical Sciences, Faculty of Pharmacy, University of Toronto, 144 College St., Toronto, ON, Canada M5S 3M2
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19
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Zhu C, Zheng T, Kilfoy BA, Han X, Ma S, Ba Y, Bai Y, Wang R, Zhu Y, Zhang Y. A birth cohort analysis of the incidence of papillary thyroid cancer in the United States, 1973-2004. Thyroid 2009; 19:1061-6. [PMID: 19732011 PMCID: PMC2833179 DOI: 10.1089/thy.2008.0342] [Citation(s) in RCA: 112] [Impact Index Per Article: 7.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
Abstract
BACKGROUND The incidence of papillary thyroid cancer has been reported to be increasing during the past three decades, with a 65-126% increase between 1975 and 2004. The reason for the increase is currently unknown. This study examined the incidence pattern of papillary thyroid cancer in the United States, and evaluated the components of birth cohort (defined based on year of birth), time period, and age as determinants of the observed time trend of the disease. METHODS Using the data from the National Cancer Institute's Surveillance, Epidemiology, and End Results program for 1973-2004, we conducted both univariate analysis and age-period-cohort modeling to evaluate birth cohort patterns and evaluate age, period, and cohort effects on incidence trends over time. RESULTS The increasing incidence showed a clear birth cohort pattern for both men and women. The results from age-period-cohort modeling showed that, while period effect appeared to have had an impact on the observed incidence trends, birth cohort effect may also explain part of the increasing trend in papillary thyroid carcinoma during the study period, especially among women. CONCLUSION While a period effect that is likely due to advancements in diagnostic techniques and increased medical detection of small thyroid nodules may explain some of the observed increase in the incidence, we speculate that birth cohort-related changes in environmental exposures (such as increased exposure to diagnostic X-rays and polybrominated diphenyl ethers) have also contributed to the observed increase in papillary thyroid cancer during the past decades.
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Affiliation(s)
- Cairong Zhu
- Yale University School of Public Health, New Haven, Connecticut
- West China School of Public Health, Sichuan University, Chengdu, China
| | - Tongzhang Zheng
- Yale University School of Public Health, New Haven, Connecticut
| | | | - Xuesong Han
- Yale University School of Public Health, New Haven, Connecticut
| | - Shuangge Ma
- Yale University School of Public Health, New Haven, Connecticut
| | - Yue Ba
- Yale University School of Public Health, New Haven, Connecticut
- School of Public Health, Zhengzhou University, Zhengzhou, China
| | - Yana Bai
- Yale University School of Public Health, New Haven, Connecticut
- School of Public Health, Lanzhou University, Lanzhou, China
| | - Rong Wang
- Yale University School of Public Health, New Haven, Connecticut
| | - Yong Zhu
- Yale University School of Public Health, New Haven, Connecticut
| | - Yawei Zhang
- Yale University School of Public Health, New Haven, Connecticut
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Inhibition of the promotion of hepatocarcinogenesis by 2,2',4,4',5,5'-hexachlorobiphenyl (PCB-153) by the deletion of the p50 subunit of NF-kappa B in mice. Toxicol Appl Pharmacol 2008; 232:302-8. [PMID: 18644402 DOI: 10.1016/j.taap.2008.06.013] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/26/2008] [Revised: 06/12/2008] [Accepted: 06/24/2008] [Indexed: 02/07/2023]
Abstract
Polychlorinated biphenyls (PCBs) are persistent and ubiquitous environmental chemicals that bioaccumulate and have hepatic tumor promoting activity in rodents. The present study examined the effect of deleting the p50 subunit of NF-kappaB on the hepatic tumor promoting activity of 2,2',4,4',5,5'-hexachlorobiphenyl (PCB-153) in mice. Both wild-type and p50-/- male mice were injected i.p. with diethylnitrosamine (DEN, 90 mg/kg) and then subsequently injected biweekly with 20 i.p. injections of PCB-153 (300 micromol/kg/injection). p50 deletion decreased the tumor incidence in both PCB- and vehicle-treated mice, whereas PCB-153 slightly (P=0.09) increased the tumor incidence in wild-type and p50-/- mice. PCB-153 increased the total tumor volume in both wild-type and p50-/- mice, but the total tumor volume was not affected by p50 deletion in either PCB- or vehicle-treated mice. The volume of tumors that were positive for glutamine synthetase (GS), which is indicative of mutations in the beta-catenin gene, was increased in both wild-type and p50-/- mice administered PCB-153 compared to vehicle controls, and inhibited in p50-/- mice compared to wild-type mice (in both PCB- and vehicle-treated mice). The volume of tumors that were negative for GS was increased in p50-/- mice compared to wild-type mice but was not affected by PCB-153. PCB-153 increased cell proliferation in normal hepatocytes in wild-type but not p50-/- mice; this increase was inhibited in p50-/- mice. In hepatic tumors, the rate of cell proliferation was much higher than in normal hepatocytes, but was not affected by PCB treatment or p50 deletion. The rate of apoptosis, as measured by the TUNEL assay, was not affected by PCB-153 or p50 deletion in normal hepatocytes. In hepatic tumors, the rate of apoptosis was lower than in normal hepatocytes; PCB-153 slightly (P=0.10) increased apoptosis in p50-/- but not wild-type mice; p50 deletion had no effect. Taken together, these data indicate that the absence of the NF-kappaB p50 subunit inhibits the promoting activity of PCB-153 and alters the proliferative and apoptotic changes in mouse liver in the response to PCBs.
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Zhang Y, Guo GL, Han X, Zhu C, Kilfoy BA, Zhu Y, Boyle P, Zheng T. Do Polybrominated Diphenyl Ethers (PBDEs) Increase the Risk of Thyroid Cancer? ACTA ACUST UNITED AC 2008; 1:195-199. [PMID: 19122824 DOI: 10.1016/j.bihy.2008.06.003] [Citation(s) in RCA: 56] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022]
Abstract
An increased incidence of thyroid cancer has been reported in many parts of the world including the United States during the past several decades. Recently emerging evidence has demonstrated that polyhalogenated aromatic hydrocarbons (PHAHs), particularly polybrominated diphenyl ethers (PBDEs), alter thyroid hormone homeostasis and cause thyroid dysfunction. However, few studies have been conducted to test whether exposure to PBDEs and other PHAHs increases the risk of thyroid cancer. Here, we hypothesize that elevated exposure to PHAHs, particularly PBDEs, increases the risk of thyroid cancer and may explain part of the increase in incidence of thyroid cancer during the past several decades. In addition, genetic and epigenetic variations in metabolic pathway genes may alter the expression and function of metabolic enzymes which are involved in the metabolism of endogenous thyroid hormones and the detoxification of PBDEs and other PHAHs. Such variation may result in different individual susceptibilities to PBDEs and other PHAHs and the subsequent development of thyroid cancer. The investigation of this hypothesis will lead to an improved understanding of the role of PBDEs and other PHAHs in thyroid tumorigenesis and may provide a real means to prevent this deadly disease.
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Affiliation(s)
- Yawei Zhang
- School of Epidemiology and Public Health, Yale University, New Haven, CT 06520, USA
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22
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Walker NJ, Yoshizawa K, Miller RA, Brix AE, Sells DM, Jokinen MP, Wyde ME, Easterling M, Nyska A. Pulmonary lesions in female Harlan Sprague-Dawley rats following two-year oral treatment with dioxin-like compounds. Toxicol Pathol 2007; 35:880-9. [PMID: 18098034 PMCID: PMC2633090 DOI: 10.1080/01926230701748396] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/20/2023]
Abstract
Dioxin and dioxin-related compounds have been associated with high incidences of pulmonary dysfunctions and/or cancers in humans. To evaluate the relative potencies of effects of these compounds, the National Toxicology Program completed a series of two-year bioassays which were conducted using female Harlan Sprague-Dawley rats. The rats were treated orally for up to 2 years with 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD), 3,3',4,4',5-pentachlorobiphenyl (PCB126), 2,3,4,7,8-pentachlorodibenzofuran (PeCDF), and a ternary mixture of TCDD, PCB126 and PeCDF. In addition to treatment-related effects reported in other organs, a variety of pulmonary lesions were observed that were related to exposure. Pulmonary CYP1A1-associated 7-ethoxyresorufin-O-deethylase (EROD) activity was increased in all dosed groups. The most common non-neoplastic lesions, which occurred in all studies, were bronchiolar metaplasia and squamous metaplasia of the alveolar epithelium. Cystic keratinizing epithelioma was the most commonly observed neoplasm which occurred in all studies. A low incidence of squamous cell carcinoma was associated only with PCB126 treatment. Potential mechanisms leading to altered differentiation and/or proliferation of bronchiolar and alveolar epithelia may be through CYP1A1 induction or disruption of retinoid metabolism.
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Affiliation(s)
- Nigel J Walker
- National Toxicology Program, National Institute of Environmental Health Sciences, Research Triangle Park, North Carolina 27709, USA.
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Robertson LW, Berberian I, Borges T, Chen LC, Chow CK, Glauert HP, Filser JG, Thomas H. Suppression of peroxisomal enzyme activities and cytochrome P450 4A isozyme expression by congeneric polybrominated and polychlorinated biphenyls. PPAR Res 2007; 2007:15481. [PMID: 18274624 PMCID: PMC2220027 DOI: 10.1155/2007/15481] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/30/2007] [Accepted: 08/10/2007] [Indexed: 12/03/2022] Open
Abstract
The purpose of this study was to determine the effects of PCBs and PBBs on peroxisome proliferator-activated receptor-alpha-(PPARalpha-) associated enzyme activities or protein levels. Male Sprague-Dawley rats were administered a single IP injection (150 mu mol/kg) of either 3,3',4,4'-tetrabromobiphenyl, 3,3',4,4'-tetrachlorobiphenyl, 3,3',5,5'-tetrabromobiphenyl, 2',3,3',4,5-pentachlorobiphenyl, 3,3',4,4',5-pentachlorobiphenyl, 2,2',3,3',5,5'-hexachlorobiphenyl, or 3,3',4,4',5,5'-hexabromobiphenyl in corn oil (10 ml/kg). One week later, the activities of catalase, peroxisomal fatty acyl-CoA oxidase, and peroxisomal beta-oxidation as well as cytochrome P450 4A (CYP4A) protein content were determined in subcellular liver fractions. None of the peroxisomal enzyme activities were significantly increased by any of the halogenated biphenyl congeners tested. Except for minor (approx. 25%) increases in the total CYP4A content following treatment with 2,2',3,3',5,5'-hexachlorobiphenyl and 3,3',5,5'-tetrabromobiphenyl, CYP4A protein contents were not increased by any treatment. The two Ah receptor agonists, 3,3',4,4'-tetrabromobiphenyl and 3,3',4,4',5-pentachlorobiphenyl, significantly diminished the liver content of CYP4A proteins and activities of the peroxisomal enzymes studied. Since a range of congeners with different biologic and toxicologic activities were selected for this study, it may be concluded that the polyhalogenated biphenyls do not induce peroxisome proliferation in the male rat, but rather certain members of this class of compounds down regulate peroxisome-associated enzymes. Since PCBs and PBBs do not increase enzyme activities and expression of proteins associated with PPARalpha, these agents are therefore exerting their carcinogenic and promoting activities by some other mechanism.
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Affiliation(s)
- Larry W Robertson
- Graduate Center for Toxicology, University of Kentucky, Funkhouser Building, Lexington, KY, USA.
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Shields PG. Understanding population and individual risk assessment: the case of polychlorinated biphenyls. Cancer Epidemiol Biomarkers Prev 2006; 15:830-9. [PMID: 16702358 DOI: 10.1158/1055-9965.epi-06-0222] [Citation(s) in RCA: 38] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022] Open
Abstract
Decisions about how to improve or protect the public health can be, and sometimes necessarily are, made on imprecise science. The regulation of potential human carcinogens in the environment entails a population-risk assessment process intended to reduce risks to less than one additional cancer in 100,000 or 1,000,000 persons. These risk assessment processes, however, may be miscommunicated or misinterpreted in the context of individual cancer risks by scientists, regulators, the lay media, and the public. This commentary will review methods for establishing a causal relationship between carcinogen exposures and cancer risk. It will use the case of polychlorinated biphenyls (PCB) as an example of how to place scientific data into the context of human exposure and cancer risk. PCBs are widespread environmental contaminants and most people have detectable levels of PCBs in their bodies. The primary source for exposure in the general population is through the diet. PCBs are carcinogens in experimental animal models, but how this information can be extrapolated to human risk remains uncertain. PCB experimental studies provide data that are used to regulate and control human exposure, although the epidemiologic evidence fails to establish PCBs as human carcinogens. Thus, what is used for population-risk assessment may not be appropriate for individual-risk assessment or concluding that a causal relationship exists between PCB exposure and cancer risk. The hazards from a carcinogen designated by regulatory and review agencies as a "probable" human carcinogen is often misunderstood out of context about the magnitude of the risk and in what settings. How scientists communicate their results in scientific articles can strongly influence how others interpret their data. Misunderstandings from both the use of regulatory and review-agency opinions and the conclusions espoused by scientists occur in the media, among private physicians counseling their patients about cancer risk, and in the legal settings where plaintiffs seek compensation for exposure and alleged harm (or future harm). This can lead to false conclusions about what caused a cancer in a specific patient, undue anxiety about future cancer risk, inappropriate cancer screening, and attendant increased morbidity due to increased uses of the medical system and complication rates from medical procedures. The communication of research findings by scientists must be presented with caution, resisting the temptation to extrapolate, inappropriately, research data to the general population.
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Kiliç N, Sandal S, Colakoğlu N, Kutlu S, Seyran A, Yilmaz B. Endocrine Disruptive Effects of Polychlorinated Biphenyls on the Thyroid Gland in Female Rats. TOHOKU J EXP MED 2005; 206:327-32. [PMID: 15997204 DOI: 10.1620/tjem.206.327] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022]
Abstract
Polychlorinated biphenyls (PCBs) are persistent environmental pollutants. Aroclor 1221 (A1221) and Aroclor 1254 (A1254) are commercial PCB mixtures with low and high number of chlorination, respectively. We have comparatively investigated effects of A1221 and A1254 on serum levels of thyroid hormones and thyroid gland histology in adult female Wistar rats. Animals were subcutaneously injected with A1221 (10 mg/kg) or A1254 (10 mg/kg) for six weeks. One group of animals served as control. At the end, all animals were decapitated and trunk blood collected. Serum levels of triiodothyronine (T3) and thyroxine (T4) were measured by the electrochemiluminescence immunoassay method. Thyroid glands were removed for histopathological examination under light microscopy. Serum total T4 levels were significantly increased in A1221- and A1254-treated rats (p < 0.05). Serum free T4 levels were significantly increased in the A1254-treated rats (p < 0.01), but not in the A1221-treated rats. In contrast, the treatment with A1221 caused a significant increase in serum free T3 concentrations (p < 0.05) but not with A1254. Notably, either A1221 or A1254 caused distinct histopathological changes, such as formation of many microfollicles in the thyroid gland, which mimic the changes seen in thyrotoxicosis. In conclusion, both PCB mixtures induce toxic effects in the thyroid gland regardless of their degree of chlorination. We suggest that these environmental contaminants may disrupt thyroid hormone homeostasis in exposed individuals and thus pose a threat to human health.
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Affiliation(s)
- Nermin Kiliç
- Department of Biochemistry, Firat University, Medical School, Elazig, Turkey
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