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Elkin ER, Su AL, Dou JF, Colacino JA, Bridges D, Padmanabhan V, Harris SM, Boldenow E, Loch-Caruso R, Bakulski KM. Sexually concordant and dimorphic transcriptional responses to maternal trichloroethylene and/or N-acetyl cysteine exposure in Wistar rat placental tissue. Toxicology 2023; 483:153371. [PMID: 36396003 PMCID: PMC10078828 DOI: 10.1016/j.tox.2022.153371] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/19/2022] [Revised: 10/20/2022] [Accepted: 11/02/2022] [Indexed: 11/16/2022]
Abstract
Numerous Superfund sites are contaminated with the volatile organic chemical trichloroethylene (TCE). In women, exposure to TCE in pregnancy is associated with reduced birth weight. Our previous study reported that TCE exposure in pregnant rats decreased fetal weight and elevated oxidative stress biomarkers in placentae, suggesting placental injury as a potential mechanism of TCE-induced adverse birth outcomes. In this study, we investigated if co-exposure with the antioxidant N-acetylcysteine (NAC) attenuates TCE exposure effects on RNA expression. Timed-pregnant Wistar rats were exposed orally to 480 mg TCE/kg/day on gestation days 6-16. Exposure of 200 mg NAC/kg/day alone or as a pre/co-exposure with TCE occurred on gestation days 5-16 to stimulate antioxidant genes prior to TCE exposure. Tissue was collected on gestation day 16. In male and female placentae, we evaluated TCE- and/or NAC-induced changes to gene expression and pathway enrichment analyses using false discovery rate (FDR) and fold-change criteria. In female placentae, exposure to TCE caused significant differential expression 129 genes while the TCE+NAC altered 125 genes, compared with controls (FDR< 0.05 + fold-change >1). In contrast, in male placentae TCE exposure differentially expressed 9 genes and TCE+NAC differentially expressed 35 genes, compared with controls (FDR< 0.05 + fold-change >1). NAC alone did not significantly alter gene expression in either sex. Differentially expressed genes observed with TCE exposure were enriched in mitochondrial biogenesis and oxidative phosphorylation pathways in females whereas immune system pathways and endoplasmic reticulum stress pathways were differentially expressed in both sexes (FDR<0.05). TCE treatment was differentially enriched for genes regulated by the transcription factors ATF6 (both sexes) and ATF4 (males only), indicating a cellular condition triggered by misfolded proteins during endoplasmic reticulum stress. This study demonstrates novel genes and pathways involved in TCE-induced placental injury and showed antioxidant co-treatment largely did not attenuate TCE exposure effects.
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Affiliation(s)
- Elana R Elkin
- Department of Environmental Health Sciences, University of Michigan, Ann Arbor, MI, USA.
| | - Anthony L Su
- Department of Environmental Health Sciences, University of Michigan, Ann Arbor, MI, USA
| | - John F Dou
- Department of Epidemiology, University of Michigan, Ann Arbor, MI, USA
| | - Justin A Colacino
- Department of Environmental Health Sciences, University of Michigan, Ann Arbor, MI, USA; Department of Nutritional Sciences, University of Michigan, Ann Arbor, MI, USA
| | - Dave Bridges
- Department of Nutritional Sciences, University of Michigan, Ann Arbor, MI, USA
| | - Vasantha Padmanabhan
- Department of Environmental Health Sciences, University of Michigan, Ann Arbor, MI, USA; Department of Nutritional Sciences, University of Michigan, Ann Arbor, MI, USA; Department of Pediatrics, Michigan Medicine, Ann Arbor, MI, USA; Department of Obstetrics and Gynecology, Michigan Medicine, Ann Arbor, MI, USA
| | - Sean M Harris
- Department of Environmental Health Sciences, University of Michigan, Ann Arbor, MI, USA
| | - Erica Boldenow
- Department of Biology, Calvin University, Grand Rapids, MI, USA
| | - Rita Loch-Caruso
- Department of Environmental Health Sciences, University of Michigan, Ann Arbor, MI, USA
| | - Kelly M Bakulski
- Department of Epidemiology, University of Michigan, Ann Arbor, MI, USA
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2
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Elkin ER, Su AL, Kilburn BA, Bakulski KM, Armant DR, Loch-Caruso R. Toxicity assessments of selected trichloroethylene and perchloroethylene metabolites in three in vitro human placental models. Reprod Toxicol 2022; 109:109-120. [PMID: 35304307 PMCID: PMC9107309 DOI: 10.1016/j.reprotox.2022.03.003] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/02/2021] [Revised: 03/07/2022] [Accepted: 03/10/2022] [Indexed: 01/25/2023]
Abstract
Residential and occupational exposures to the industrial solvents perchloroethylene (PERC) and trichloroethylene (TCE) present public health concerns. In humans, maternal PERC and TCE exposures can be associated with adverse birth outcomes. Because PERC and TCE are biotransformed to toxic metabolites and placental dysfunction can contribute to adverse birth outcomes, the present study compared the toxicity of key PERC and TCE metabolites in three in vitro human placenta models. We measured cell viability and caspase 3 + 7 activity in the HTR-8/SVneo and BeWo cell lines, and caspase 3 + 7 activity in first trimester villous explant cultures. Cultures were exposed for 24 h to 5-100 µM S-(1,2-dichlorovinyl)-L-cysteine (DCVC) and S-(1,2,2-trichlorovinyl)-L-cysteine (TCVC), or 5-200 µM trichloroacetate (TCA) and dichloroacetate (DCA). DCVC significantly reduced cell viability and increased caspase 3 + 7 activity in HTR-8/SVneo cells at a lower concentration (20 µM) compared with concentrations toxic to BeWo cells and villous explants. Similarly, TCVC reduced cell viability and increased caspase 3 + 7 activity in HTR-8/SVneo cells but not in BeWo cells. TCA and DCA had only negligible effects on HTR-8/SVneo or BeWo cells. This study advances understanding of potential risks of PERC and TCE exposure during pregnancy by identifying metabolites toxic in placental cells and tissues.
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Affiliation(s)
- Elana R Elkin
- Department of Environmental Health Sciences, University of Michigan, Ann Arbor, Michigan, USA; Department of Nutritional Sciences, University of Michigan, Ann Arbor, Michigan, USA.
| | - Anthony L Su
- Department of Environmental Health Sciences, University of Michigan, Ann Arbor, Michigan, USA; Department of Nutritional Sciences, University of Michigan, Ann Arbor, Michigan, USA
| | - Brian A Kilburn
- Department of Nutritional Sciences, University of Michigan, Ann Arbor, Michigan, USA; Department of Obstetrics and Gynecology, Wayne State University School of Medicine, Detroit, Michigan, USA
| | - Kelly M Bakulski
- Department of Epidemiology, University of Michigan, Ann Arbor, Michigan, USA; Department of Nutritional Sciences, University of Michigan, Ann Arbor, Michigan, USA
| | - D Randall Armant
- Department of Nutritional Sciences, University of Michigan, Ann Arbor, Michigan, USA; Department of Obstetrics and Gynecology, Wayne State University School of Medicine, Detroit, Michigan, USA; Department of Anatomy and Cell Biology, Wayne State University School of Medicine, Detroit, Michigan, USA
| | - Rita Loch-Caruso
- Department of Environmental Health Sciences, University of Michigan, Ann Arbor, Michigan, USA
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3
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Liu Z, Wang M, Yu P, Li X, Lin Y, Duan Y, Tian Y, Zhu J, Deng Y, Li N. Maternal trichloroethylene exposure and metabolic gene polymorphisms may interact during fetal cardiovascular malformation. Reprod Toxicol 2021; 106:1-8. [PMID: 34555461 DOI: 10.1016/j.reprotox.2021.09.010] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/06/2021] [Revised: 09/09/2021] [Accepted: 09/16/2021] [Indexed: 10/20/2022]
Abstract
This study aimed to analyze the potential association between trichloroethylene (TCE) exposure and congenital heart disease (CHD) and to explore the effect of metabolic enzyme gene polymorphisms on heart development. A multicenter case-control study was conducted. The trichloroethylene concentrations were measured by UPLC-MSMS in urine. Fourteen SNPs in the GSTA1, GSTP1, MPO, NAT1, NAT2, CYP1A1, CYP1A2, CYP2E1 and EPHX1 genes were genotyped using an improved multiplex ligation detection reaction (iMLDR) technique. A total of 283 cases and 331 controls with maternal urine and/or venous blood were included in the present study. The median NAcDCVC was 7.65 ng/mL in the case group and 7.43 ng/mL in the control group. There was no significant difference in the NAcDCVC concentration between the CHD subtypes and controls (P > 0.05). The GA/AA of GSTA1 rs3957357 could increase the risk of CHDs under the dominant model (aOR = 2.26, 95 % CI: 1.31, 3.90), but other SNPs were not associated with CHDs (P > 0.05). GA or AA genotypes of GSTA1 rs3957357 with lower levels of TCE exposure were 3.53 times at risk relative to mothers carrying the wild type genotype. In conclusion, maternal exposure to trichloroethylene alone is not associated with the occurrence of fetal CHD and CHD subtypes. Maternal GSTA1 rs3957357 may increase the risk of CHD in offspring. TCE exposure and metabolic gene polymorphisms probably interact with each other to induce fetal cardiovascular malformation, but larger sample size studies are needed to confirm this hypothesis.
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Affiliation(s)
- Zhen Liu
- National Center for Birth Defect Monitoring, Department of Obstetrics, West China Second University Hospital, Sichuan University, Chengdu, Sichuan, China; Key Laboratory of Birth Defects and Related Diseases of Women and Children (Sichuan University), Ministry of Education, Chengdu, Sichuan, China
| | - Meixian Wang
- National Center for Birth Defect Monitoring, Department of Obstetrics, West China Second University Hospital, Sichuan University, Chengdu, Sichuan, China; Key Laboratory of Birth Defects and Related Diseases of Women and Children (Sichuan University), Ministry of Education, Chengdu, Sichuan, China
| | - Ping Yu
- Key Laboratory of Birth Defects and Related Diseases of Women and Children (Sichuan University), Ministry of Education, Chengdu, Sichuan, China; Development and Related Diseases of Women and Children Key Laboratory of Sichuan Province, Chengdu, Sichuan, China
| | - Xiaohong Li
- National Center for Birth Defect Monitoring, Department of Obstetrics, West China Second University Hospital, Sichuan University, Chengdu, Sichuan, China
| | - Yuan Lin
- Department of Obstetrics & Gynecology, Fujian Provincial Maternal and Child Health Care Hospital, Fuzhou, Fujian, China
| | - Yinghong Duan
- Department of Obstetrics & Gynecology, Huize Maternal and Child Health Care Hospital, Qujing, Yunnan, China
| | - Yan Tian
- Department of Obstetrics & Gynecology, Maternal and Child Health Hospital of Liupanshui, Liupanshui, Guizhou, China
| | - Jun Zhu
- National Center for Birth Defect Monitoring, Department of Obstetrics, West China Second University Hospital, Sichuan University, Chengdu, Sichuan, China; Key Laboratory of Birth Defects and Related Diseases of Women and Children (Sichuan University), Ministry of Education, Chengdu, Sichuan, China; Development and Related Diseases of Women and Children Key Laboratory of Sichuan Province, Chengdu, Sichuan, China
| | - Ying Deng
- National Center for Birth Defect Monitoring, Department of Obstetrics, West China Second University Hospital, Sichuan University, Chengdu, Sichuan, China; Key Laboratory of Birth Defects and Related Diseases of Women and Children (Sichuan University), Ministry of Education, Chengdu, Sichuan, China.
| | - Nana Li
- Key Laboratory of Birth Defects and Related Diseases of Women and Children (Sichuan University), Ministry of Education, Chengdu, Sichuan, China; Development and Related Diseases of Women and Children Key Laboratory of Sichuan Province, Chengdu, Sichuan, China.
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Urban JD, Wikoff DS, Chappell GA, Harris C, Haws LC. Systematic evaluation of mechanistic data in assessing in utero exposures to trichloroethylene and development of congenital heart defects. Toxicology 2020; 436:152427. [PMID: 32145346 DOI: 10.1016/j.tox.2020.152427] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/06/2019] [Revised: 02/18/2020] [Accepted: 03/02/2020] [Indexed: 01/23/2023]
Abstract
The hypothesis that in utero exposures to low levels of trichloroethylene (TCE) may increase the risk of congenital heart defects (CHDs) in offspring remains a subject of substantial controversy within the scientific community due primarily to the reliance on an inconsistent and unreproducible experimental study in rats. To build on previous assessments that have primarily focused on epidemiological and experimental animal studies in developing conclusions, the objective of the current study is to conduct a systematic evaluation of mechanistic data related to in utero exposures to TCE and the development of CHDs. The evidence base was heterogeneous; 79 mechanistic datasets were identified, characterizing endpoints which ranged from molecular to organismal responses in seven species, involving both in vivo and in vitro study designs in mammalian and non-mammalian models. Of these, 24 datasets were considered reliable following critical appraisal using a study quality tool that employs metrics specific to the study type. Subsequent synthesis and integration demonstrated that the available mechanistic data: 1) did not support the potential for CHD hazard in humans, 2) did not support the biological plausibility of a response in humans based on organization via a putative adverse outcome pathway for valvulo-septal cardiac defects, and 3) were not suitable for serving as candidate studies in risk assessment. Findings supportive of an association were generally limited to in ovo chicken studies, in which TCE was administered in high concentration solutions via direct injection. Results of these in ovo studies were difficult to interpret for human health risk assessment given the lack of generalizability of the study models (including dose relevance, species-specific biological differences, variations in the construct of the study design, etc.). When the mechanistic data are integrated with findings from previous evaluations of human and animal evidence streams, the totality of evidence does not support CHDs as a critical effect in TCE human health risk assessment.
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Affiliation(s)
- Jonathan D Urban
- ToxStrategies, Inc., 9390 Research Blvd, Ste. 100, Austin, TX, 78759, USA.
| | - Daniele S Wikoff
- ToxStrategies, Inc., 31 College Place, Ste. B118, Asheville, NC, 28801, USA
| | - Grace A Chappell
- ToxStrategies, Inc., 31 College Place, Ste. B118, Asheville, NC, 28801, USA
| | - Craig Harris
- Department of Environmental Health Sciences, School of Public Health, University of Michigan, 1415 Washington Heights, Ann Arbor, MI, 48109, USA
| | - Laurie C Haws
- ToxStrategies, Inc., 9390 Research Blvd, Ste. 100, Austin, TX, 78759, USA
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Elkin ER, Harris SM, Su AL, Lash LH, Loch-Caruso R. Placenta as a target of trichloroethylene toxicity. ENVIRONMENTAL SCIENCE. PROCESSES & IMPACTS 2020; 22:472-486. [PMID: 32022077 PMCID: PMC7103546 DOI: 10.1039/c9em00537d] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/10/2023]
Abstract
Trichloroethylene (TCE) is an industrial solvent and a common environmental contaminant detected in thousands of hazardous waste sites. Risk of exposure is a concern for workers in occupations that use TCE as well as for residents who live near industries that use TCE or who live near TCE-contaminated sites. Although renal, hepatic and carcinogenic effects of TCE have been documented, less is known about TCE impacts on reproductive functions despite epidemiology reports associating maternal TCE exposure with adverse pregnancy outcomes. Toxicological evidence suggests that the placenta mediates at least some of the adverse pregnancy outcomes associated with TCE exposure. Toxicology studies show that the TCE metabolite, S-(1,2-dichlorovinyl)-l-cysteine (DCVC) generates toxic effects such as mitochondrial dysfunction, apoptosis, oxidative stress, and release of prostaglandins and pro-inflammatory cytokines in placental cell lines. Each of these mechanisms of toxicity have significant implications for placental functions and, thus, ultimately the health of mother and developing child. Despite these findings there remain significant gaps in our knowledge about effects of TCE on the placenta, including effects on specific placental cell types and functions as well as sex differences in response to TCE exposure. Due to the critical role that the placenta plays in pregnancy, future research addressing some of these knowledge gaps could lead to significant gains in public health.
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Affiliation(s)
- Elana R Elkin
- Department of Environmental Health Sciences, University of Michigan, Ann Arbor, MI 48109-2029, USA.
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6
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DeSesso JM, Coder PS, York RG, Budinsky RA, Pottenger LH, Sen S, Lucarell JM, Bevan C, Bus JS. Trichloroethylene in drinking water throughout gestation did not produce congenital heart defects in Sprague Dawley rats. Birth Defects Res 2019; 111:1217-1233. [PMID: 31197966 PMCID: PMC7432160 DOI: 10.1002/bdr2.1531] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/17/2019] [Revised: 04/23/2019] [Accepted: 05/09/2019] [Indexed: 02/05/2023]
Abstract
BACKGROUND Trichloroethylene (TCE) was negative for developmental toxicity after inhalation and oral gavage exposure of pregnant rats but fetal cardiac defects were reported following drinking water exposure throughout gestation. Because of the deficiencies in this latter study, we performed another drinking water study to evaluate whether TCE causes heart defects. METHODS Groups of 25 mated Sprague Dawley rats consumed water containing 0, 0.25, 1.5, 500, or 1,000 ppm TCE from gestational day 1-21. TCE concentrations were measured at daily formulation, when placed into water bottles each day and when water bottles were removed from cages. Four additional mated rats per group were used for plasma measurements. At termination, fetal hearts were carefully dissected fresh and examined. RESULTS All TCE concentrations were >90% of target when initially placed in water bottles and when bottles were placed on cages. All dams survived with no clinical signs. Rats in the two higher dose groups consumed less water/day than other groups but showed no changes in maternal or fetal weights. The only fetal cardiac observation was small (<1 mm) membranous ventricular septal defect occurring in all treated and water control groups; incidences were within the range of published findings for naive animals. TCE was not detected in maternal blood, but systemic exposure was confirmed by detecting its primary oxidative metabolite, trichloroacetic acid, although only at levels above the quantitation limit in the two higher dose groups. CONCLUSIONS Ingesting TCE in drinking water ≤1,000 ppm throughout gestation does not cause cardiac defects in rat offspring.
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Affiliation(s)
- John M. DeSesso
- ExponentAlexandriaVirginia
- Georgetown University School of MedicineWashingtonDistrict of Columbia
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7
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DeSesso JM, Coder PS, York RG, Budinsky RA, Pottenger LH, Sen S, Lucarell JM, Bevan C, Bus JS. Response to the comments of Runyan et al. on "Trichloroethylene in drinking water throughout gestation did not produce congenital heart defects in Sprague Dawley rats". Birth Defects Res 2019; 111:1237-1239. [PMID: 31419071 DOI: 10.1002/bdr2.1577] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/24/2019] [Accepted: 07/27/2019] [Indexed: 11/10/2022]
Affiliation(s)
- John M DeSesso
- Exponent, Alexandria, Virginia.,Georgetown University School of Medicine, Washington, DC
| | | | | | | | - Lynn H Pottenger
- Olin Corporation, Midland, Michigan.,LHP Tox Consult, LLC, Midland, Michigan
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8
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Arts J, Kellert M, Pottenger L, Theuns-van Vliet J. Evaluation of developmental toxicity of Methyl Chloride (Chloromethane) in rats, mice, and rabbits. Regul Toxicol Pharmacol 2019; 103:274-281. [DOI: 10.1016/j.yrtph.2019.02.001] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/12/2018] [Accepted: 02/04/2019] [Indexed: 11/26/2022]
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9
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Loch-Caruso R, Hassan I, Harris SM, Kumar A, Bjork F, Lash LH. Trichloroethylene exposure in mid-pregnancy decreased fetal weight and increased placental markers of oxidative stress in rats. Reprod Toxicol 2018; 83:38-45. [PMID: 30468822 DOI: 10.1016/j.reprotox.2018.11.002] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/15/2018] [Revised: 11/09/2018] [Accepted: 11/19/2018] [Indexed: 12/29/2022]
Abstract
Although epidemiology studies have associated maternal trichloroethylene (TCE) exposure with decreased birth weight and preterm birth, mechanistic explanations for these associations are currently lacking. We hypothesized that TCE targets the placenta with adverse consequences for pregnancy outcomes. Pregnant Wistar rats were exposed orally to vehicle or 480 mg TCE/kg body weight from gestational days (gd) 6-16, and tissues were collected on gd 16. Exposure to TCE significantly decreased average fetal weight without reducing maternal weight. In placenta, TCE significantly increased 8-hydroxy-deoxyguanosine, global 5-hydroxymethylcytosine, and mRNA expression of Tet3, which codes for an enzyme involved in 5-hydroxymethylcytosine formation. Furthermore, glutathione S-transferase activity and immunohistochemical staining were increased in placentas of TCE-exposed rats. The present study provides the first evidence that TCE increases markers of oxidative stress in placenta in a fetal growth restriction rat model, providing new insight into the placenta as a potentially relevant target for TCE-induced adverse pregnancy outcomes.
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Affiliation(s)
- Rita Loch-Caruso
- Department of Environmental Health Sciences, University of Michigan School of Public Health, Ann Arbor, MI, 48109-2029, USA.
| | - Iman Hassan
- Department of Environmental Health Sciences, University of Michigan School of Public Health, Ann Arbor, MI, 48109-2029, USA.
| | - Sean M Harris
- Department of Environmental Health Sciences, University of Michigan School of Public Health, Ann Arbor, MI, 48109-2029, USA.
| | - Anjana Kumar
- Department of Environmental Health Sciences, University of Michigan School of Public Health, Ann Arbor, MI, 48109-2029, USA.
| | - Faith Bjork
- Department of Environmental Health Sciences, University of Michigan School of Public Health, Ann Arbor, MI, 48109-2029, USA.
| | - Lawrence H Lash
- Department of Pharmacology, Wayne State University School of Medicine, 540 East Canfield Avenue, Detroit, MI, 48201, USA.
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10
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Issa O, Hassoun EA, Williams FE. Developmental effects of trichloroacetate in Zebrafish embryos: Association with the production of superoxide anion. J Biochem Mol Toxicol 2018; 33:e22259. [DOI: 10.1002/jbt.22259] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/06/2018] [Accepted: 10/12/2018] [Indexed: 11/08/2022]
Affiliation(s)
- Omar Issa
- Department of Pharmacology and Experimental Therapeutics; College of Pharmacy and Pharmaceutical Sciences, The University of Toledo Health Science Campus; Toledo Ohio
| | - Ezdihar A. Hassoun
- Department of Pharmacology and Experimental Therapeutics; College of Pharmacy and Pharmaceutical Sciences, The University of Toledo Health Science Campus; Toledo Ohio
| | - Frederick E. Williams
- Department of Pharmacology and Experimental Therapeutics; College of Pharmacy and Pharmaceutical Sciences, The University of Toledo Health Science Campus; Toledo Ohio
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11
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Wikoff D, Urban JD, Harvey S, Haws LC. Role of Risk of Bias in Systematic Review for Chemical Risk Assessment: A Case Study in Understanding the Relationship Between Congenital Heart Defects and Exposures to Trichloroethylene. Int J Toxicol 2018; 37:125-143. [PMID: 29357719 PMCID: PMC5888777 DOI: 10.1177/1091581818754330] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/09/2022]
Abstract
The National Academy of Science has recommended that a risk of bias (RoB; credibility of the link between exposure and outcome) assessment be conducted on studies that are used as primary data sources for hazard identification and dose-response assessment. Few applications of such have been conducted. Using trichloroethylene and congenital heart defects (CHDs) as a case study, we explore the role of RoB in chemical risk assessment using the National Toxicology Program's Office of Health Assessment and Translation RoB tool. Selected questions were tailored to evaluation of CHD and then applied to 12 experimental animal studies and 9 epidemiological studies. Results demonstrated that the inconsistent findings of a single animal study were likely explained by the limitations in study design assessed via RoB (eg, lack of concurrent controls, unvalidated method for assessing outcome, unreliable statistical methods, etc). Such limitations considered in the context of the body of evidence render the study not sufficiently reliable for the development of toxicity reference values. The case study highlights the utility of RoB as part of a robust risk assessment process and specifically demonstrates the role RoB can play in objectively selecting candidate data sets to develop toxicity values.
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12
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Harris AP, Ismail KA, Nunez M, Martopullo I, Lencinas A, Selmin OI, Runyan RB. Trichloroethylene perturbs HNF4a expression and activity in the developing chick heart. Toxicol Lett 2018; 285:113-120. [PMID: 29306027 DOI: 10.1016/j.toxlet.2017.12.027] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/30/2017] [Revised: 12/23/2017] [Accepted: 12/29/2017] [Indexed: 12/11/2022]
Abstract
Exposure to trichloroethylene (TCE) is linked to formation of congenital heart defects in humans and animals. Prior interactome analysis identified the transcription factor, Hepatocyte Nuclear Factor 4 alpha (HNF4a), as a potential target of TCE exposure. As a role for HNF4a is unknown in the heart, we examined developing avian hearts for HNF4a expression and for sensitivity to TCE and the HNF4a agonist, Benfluorex. In vitro analysis using a HNF4a reporter construct showed both TCE and HFN4a to be antagonists of HNF4a-mediated transcription at the concentrations tested. HNF4a mRNA is expressed transiently in the embryonic heart during valve formation and cardiac development. Embryos were examined for altered gene expression in the presence of TCE or Benfluorex. TCE altered expression of selected mRNAs including HNF4a, TRAF6 and CYP2C45. There was a transition between inhibition and induction of marker gene expression in embryos as TCE concentration increased. Benfluorex was largely inhibitory to selected markers. Echocardiography of exposed embryos showed reduced cardiac function with both TCE and Benfluorex. Cardiac contraction was reduced by 29% and 23%, respectively at 10 ppb. The effects of TCE and Benfluorex on autocrine regulation of HNF4a, selected markers and cardiac function argue for a functional interaction of TCE and HNF4a. Further, the dose-sensitive shift between inhibition and induction of marker expression may explain the nonmonotonic-like dose response observed with TCE exposure in the heart.
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Affiliation(s)
- Alondra P Harris
- Department of Cellular & Molecular Medicine, University of Arizona, Tucson, AZ 85724-5044, United States
| | - Kareem A Ismail
- Department of Cellular & Molecular Medicine, University of Arizona, Tucson, AZ 85724-5044, United States
| | - Martha Nunez
- Department of Cellular & Molecular Medicine, University of Arizona, Tucson, AZ 85724-5044, United States
| | - Ira Martopullo
- Department of Cellular & Molecular Medicine, University of Arizona, Tucson, AZ 85724-5044, United States
| | - Alejandro Lencinas
- Department of Cellular & Molecular Medicine, University of Arizona, Tucson, AZ 85724-5044, United States
| | - Ornella I Selmin
- Department of Nutritional Sciences, University of Arizona, Tucson, AZ 85724-5044, United States
| | - Raymond B Runyan
- Department of Cellular & Molecular Medicine, University of Arizona, Tucson, AZ 85724-5044, United States.
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13
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Elkin ER, Harris SM, Loch-Caruso R. Trichloroethylene metabolite S-(1,2-dichlorovinyl)-l-cysteine induces lipid peroxidation-associated apoptosis via the intrinsic and extrinsic apoptosis pathways in a first-trimester placental cell line. Toxicol Appl Pharmacol 2018; 338:30-42. [PMID: 29129777 PMCID: PMC5741094 DOI: 10.1016/j.taap.2017.11.006] [Citation(s) in RCA: 44] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/24/2017] [Revised: 11/07/2017] [Accepted: 11/08/2017] [Indexed: 12/31/2022]
Abstract
Trichloroethylene (TCE), a prevalent environmental contaminant, is a potent renal and hepatic toxicant through metabolites such as S-(1, 2-dichlorovinyl)-l-cysteine (DCVC). However, effects of TCE on other target organs such as the placenta have been minimally explored. Because elevated apoptosis and lipid peroxidation in placenta have been observed in pregnancy morbidities involving poor placentation, we evaluated the effects of DCVC exposure on apoptosis and lipid peroxidation in a human extravillous trophoblast cell line, HTR-8/SVneo. We exposed the cells in vitro to 10-100μM DCVC for various time points up to 24h. Following exposure, we measured apoptosis using flow cytometry, caspase activity using luminescence assays, gene expression using qRT-PCR, and lipid peroxidation using a malondialdehyde quantification assay. DCVC significantly increased apoptosis in time- and concentration-dependent manners (p<0.05). DCVC also significantly stimulated caspase 3, 7, 8 and 9 activities after 12h (p<0.05), suggesting that DCVC stimulates the activation of both the intrinsic and extrinsic apoptotic signaling pathways simultaneously. Pre-treatment with the tBID inhibitor Bl-6C9 partially reduced DCVC-stimulated caspase 3 and 7 activity, signifying crosstalk between the two pathways. Additionally, DCVC treatment increased lipid peroxidation in a concentration-dependent manner. Co-treatment with the antioxidant peroxyl radical scavenger (±)-α-tocopherol attenuated caspase 3 and 7 activity, suggesting that lipid peroxidation mediates DCVC-induced apoptosis in extravillous trophoblasts. Our findings suggest that DCVC-induced apoptosis and lipid peroxidation in extravillous trophoblasts could contribute to poor placentation if similar effects occur in vivo in response to TCE exposure, indicating that further studies into this mechanism are warranted.
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Affiliation(s)
- Elana R Elkin
- Department of Environmental Health Sciences, University of Michigan, 1415 Washington Heights, Ann Arbor, MI 48109-2029, USA.
| | - Sean M Harris
- Department of Environmental Health Sciences, University of Michigan, 1415 Washington Heights, Ann Arbor, MI 48109-2029, USA.
| | - Rita Loch-Caruso
- Department of Environmental Health Sciences, University of Michigan, 1415 Washington Heights, Ann Arbor, MI 48109-2029, USA.
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DeSesso JM, Risotto SP. Review of TCE cardiac defects data by Makris et al. is not systematic. Reprod Toxicol 2017; 71:134. [PMID: 28577896 DOI: 10.1016/j.reprotox.2017.05.012] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/23/2017] [Accepted: 05/25/2017] [Indexed: 11/26/2022]
Affiliation(s)
- John M DeSesso
- Center for Health Sciences, Exponent, 1800 Diagonal Road, Suite 500, Alexandria, Virginia 22314, United States; Department of Biochemistry and Molecular & Cellular Biology Georgetown University School of Medicine Washington DC 20057, United States.
| | - Stephen P Risotto
- Chemical Products & Technology Division, American Chemistry Council, Washington DC, 20002, United States
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15
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Makris SL. The systematic review of TCE cardiac defects (Makris et al., 2016). Reprod Toxicol 2017; 71:124-125. [PMID: 28571977 DOI: 10.1016/j.reprotox.2017.05.013] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/26/2017] [Accepted: 05/25/2017] [Indexed: 11/17/2022]
Affiliation(s)
- Susan L Makris
- U.S. Environmental Protection Agency, Office of Research and Development, National Center for Environmental Assessment, 1200 Pennsylvania Avenue, NW (MC 8623P), Washington, DC 20460, United States.
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16
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Makris SL, Scott CS, Fox J, Knudsen TB, Hotchkiss AK, Arzuaga X, Euling SY, Powers CM, Jinot J, Hogan KA, Abbott BD, Hunter ES, Narotsky MG. A systematic evaluation of the potential effects of trichloroethylene exposure on cardiac development. Reprod Toxicol 2016; 65:321-358. [PMID: 27575429 PMCID: PMC9113522 DOI: 10.1016/j.reprotox.2016.08.014] [Citation(s) in RCA: 30] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/10/2016] [Revised: 07/27/2016] [Accepted: 08/25/2016] [Indexed: 11/26/2022]
Abstract
The 2011 EPA trichloroethylene (TCE) IRIS assessment, used developmental cardiac defects from a controversial drinking water study in rats (Johnson et al. [51]), along with several other studies/endpoints to derive reference values. An updated literature search of TCE-related developmental cardiac defects was conducted. Study quality, strengths, and limitations were assessed. A putative adverse outcome pathway (AOP) construct was developed to explore key events for the most commonly observed cardiac dysmorphologies, particularly those involved with epithelial-mesenchymal transition (EMT) of endothelial origin (EndMT); several candidate pathways were identified. A hypothesis-driven weight-of-evidence analysis of epidemiological, toxicological, in vitro, in ovo, and mechanistic/AOP data concluded that TCE has the potential to cause cardiac defects in humans when exposure occurs at sufficient doses during a sensitive window of fetal development. The study by Johnson et al. [51] was reaffirmed as suitable for hazard characterization and reference value derivation, though acknowledging study limitations and uncertainties.
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Wirbisky SE, Damayanti NP, Mahapatra CT, Sepúlveda MS, Irudayaraj J, Freeman JL. Mitochondrial Dysfunction, Disruption of F-Actin Polymerization, and Transcriptomic Alterations in Zebrafish Larvae Exposed to Trichloroethylene. Chem Res Toxicol 2016; 29:169-79. [PMID: 26745549 DOI: 10.1021/acs.chemrestox.5b00402] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/07/2023]
Abstract
Trichloroethylene (TCE) is primarily used as an industrial degreasing agent and has been in use since the 1940s. TCE is released into the soil, surface, and groundwater. From an environmental and regulatory standpoint, more than half of Superfund hazardous waste sites on the National Priority List are contaminated with TCE. Occupational exposure to TCE occurs primarily via inhalation, while environmental TCE exposure also occurs through ingestion of contaminated drinking water. Current literature links TCE exposure to various adverse health effects including cardiovascular toxicity. Current studies aiming to address developmental cardiovascular toxicity utilized rodent and avian models, with the majority of studies using relatively higher parts per million (mg/L) doses. In this study, to further investigate developmental cardiotoxicity of TCE, zebrafish embryos were treated with 0, 10, 100, or 500 parts per billion (ppb; μg/L) TCE during embryogenesis and/or through early larval stages. After the appropriate exposure period, angiogenesis, F-actin, and mitochondrial function were assessed. A significant dose-response decrease in angiogenesis, F-actin, and mitochondrial function was observed. To further complement this data, a transcriptomic profile of zebrafish larvae was completed to identify gene alterations associated with the 10 ppb TCE exposure. Results from the transcriptomic data revealed that embryonic TCE exposure caused significant changes in genes associated with cardiovascular disease, cancer, and organismal injury and abnormalities with a number of targets in the FAK signaling pathway. Overall, results from our study support TCE as a developmental cardiovascular toxicant, provide molecular targets and pathways for investigation in future studies, and indicate a need for continued priority for environmental regulation.
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Affiliation(s)
- Sara E Wirbisky
- School of Health Sciences, ‡Agricultural and Biological Engineering, §Department of Forestry and Natural Resources, ∥Purdue Center for Cancer Research, Purdue University , West Lafayette, Indiana 47907, United States
| | - Nur P Damayanti
- School of Health Sciences, ‡Agricultural and Biological Engineering, §Department of Forestry and Natural Resources, ∥Purdue Center for Cancer Research, Purdue University , West Lafayette, Indiana 47907, United States
| | - Cecon T Mahapatra
- School of Health Sciences, ‡Agricultural and Biological Engineering, §Department of Forestry and Natural Resources, ∥Purdue Center for Cancer Research, Purdue University , West Lafayette, Indiana 47907, United States
| | - Maria S Sepúlveda
- School of Health Sciences, ‡Agricultural and Biological Engineering, §Department of Forestry and Natural Resources, ∥Purdue Center for Cancer Research, Purdue University , West Lafayette, Indiana 47907, United States
| | - Joseph Irudayaraj
- School of Health Sciences, ‡Agricultural and Biological Engineering, §Department of Forestry and Natural Resources, ∥Purdue Center for Cancer Research, Purdue University , West Lafayette, Indiana 47907, United States
| | - Jennifer L Freeman
- School of Health Sciences, ‡Agricultural and Biological Engineering, §Department of Forestry and Natural Resources, ∥Purdue Center for Cancer Research, Purdue University , West Lafayette, Indiana 47907, United States
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18
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Chiu WA, Jinot J, Scott CS, Makris SL, Cooper GS, Dzubow RC, Bale AS, Evans MV, Guyton KZ, Keshava N, Lipscomb JC, Barone S, Fox JF, Gwinn MR, Schaum J, Caldwell JC. Human health effects of trichloroethylene: key findings and scientific issues. ENVIRONMENTAL HEALTH PERSPECTIVES 2013; 121:303-11. [PMID: 23249866 PMCID: PMC3621199 DOI: 10.1289/ehp.1205879] [Citation(s) in RCA: 142] [Impact Index Per Article: 12.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/10/2012] [Accepted: 12/17/2012] [Indexed: 05/19/2023]
Abstract
BACKGROUND In support of the Integrated Risk Information System (IRIS), the U.S. Environmental Protection Agency (EPA) completed a toxicological review of trichloroethylene (TCE) in September 2011, which was the result of an effort spanning > 20 years. OBJECTIVES We summarized the key findings and scientific issues regarding the human health effects of TCE in the U.S. EPA's toxicological review. METHODS In this assessment we synthesized and characterized thousands of epidemiologic, experimental animal, and mechanistic studies, and addressed several key scientific issues through modeling of TCE toxicokinetics, meta-analyses of epidemiologic studies, and analyses of mechanistic data. DISCUSSION Toxicokinetic modeling aided in characterizing the toxicological role of the complex metabolism and multiple metabolites of TCE. Meta-analyses of the epidemiologic data strongly supported the conclusions that TCE causes kidney cancer in humans and that TCE may also cause liver cancer and non-Hodgkin lymphoma. Mechanistic analyses support a key role for mutagenicity in TCE-induced kidney carcinogenicity. Recent evidence from studies in both humans and experimental animals point to the involvement of TCE exposure in autoimmune disease and hypersensitivity. Recent avian and in vitro mechanistic studies provided biological plausibility that TCE plays a role in developmental cardiac toxicity, the subject of substantial debate due to mixed results from epidemiologic and rodent studies. CONCLUSIONS TCE is carcinogenic to humans by all routes of exposure and poses a potential human health hazard for noncancer toxicity to the central nervous system, kidney, liver, immune system, male reproductive system, and the developing embryo/fetus.
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Affiliation(s)
- Weihsueh A Chiu
- National Center for Environmental Assessment, U.S. Environmental Protection Agency (EPA), Washington, DC, USA.
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19
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Colman J, Rice GE, Wright JM, Hunter ES, Teuschler LK, Lipscomb JC, Hertzberg RC, Simmons JE, Fransen M, Osier M, Narotsky MG. Identification of developmentally toxic drinking water disinfection byproducts and evaluation of data relevant to mode of action. Toxicol Appl Pharmacol 2011; 254:100-26. [DOI: 10.1016/j.taap.2011.02.002] [Citation(s) in RCA: 33] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/30/2008] [Revised: 04/22/2010] [Accepted: 04/22/2010] [Indexed: 12/26/2022]
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Makwana O, King NMP, Ahles L, Selmin O, Granzier HL, Runyan RB. Exposure to low-dose trichloroethylene alters shear stress gene expression and function in the developing chick heart. Cardiovasc Toxicol 2010; 10:100-7. [PMID: 20186580 PMCID: PMC3069695 DOI: 10.1007/s12012-010-9066-y] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Trichloroethylene is an organic solvent used as an industrial degreasing agent. Due to its widespread use and volatile nature, TCE is a common environmental contaminant. Trichloroethylene exposure has been implicated in the etiology of heart defects in human populations and animal models. Recent data suggest misregulation of Ca2+ homeostasis in H9c2 cardiomyocyte cell line after TCE exposure. We hypothesized that misregulation of Ca2+ homeostasis alters myocyte function and leads to changes in embryonic blood flow. In turn, changes in cardiac flow are known to cause cardiac malformations. To investigate this hypothesis, we dosed developing chick embryos in ovo with environmentally relevant doses of TCE (8 and 800 ppb). RNA was isolated from control and treated embryos at specific times in development for real-time PCR analysis of blood flow markers. Effects were observed on Endothelin-1 (ET-1), Nitric Oxide Synthase-3 (NOS-3) and Krüppel-like Factor 2 (KLF2) expression relative to TCE exposure and consistent with reduced flow. Further, we measured function in the developing heart after TCE exposure by isolating cardiomyocytes and measuring half-width of contraction and sarcomere lengths. These functional data showed a significant increase in half-width of contraction after TCE exposure. These data suggest that perturbation of cardiac function contributes to the etiology of congenital heart defects in TCE-exposed embryos.
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Affiliation(s)
- Om Makwana
- Department of Cell Biology and Anatomy, University of Arizona, 1501 N Campbell Avenue, PO Box 245044, Tucson, AZ 85724-5044, USA
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21
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Caldwell PT, Manziello A, Howard J, Palbykin B, Runyan RB, Selmin O. Gene expression profiling in the fetal cardiac tissue after folate and low-dose trichloroethylene exposure. ACTA ACUST UNITED AC 2010; 88:111-27. [PMID: 19813261 DOI: 10.1002/bdra.20631] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
Abstract
BACKGROUND Previous studies show gene expression alterations in rat embryo hearts and cell lines that correspond to the cardio-teratogenic effects of trichloroethylene (TCE) in animal models. One potential mechanism of TCE teratogenicity may be through altered regulation of calcium homeostatic genes with a corresponding inhibition of cardiac function. It has been suggested that TCE may interfere with the folic acid/methylation pathway in liver and kidney and alter gene regulation by epigenetic mechanisms. According to this hypothesis, folate supplementation in the maternal diet should counteract TCE effects on gene expression in the embryonic heart. APPROACH To identify transcriptional targets altered in the embryonic heart after exposure to TCE, and possible protective effects of folate, we used DNA microarray technology to profile gene expression in embryonic mouse hearts with maternal TCE exposure and dietary changes in maternal folate. RESULTS Exposure to low doses of TCE (10 ppb) caused extensive alterations in transcripts encoding proteins involved in transport, ion channel, transcription, differentiation, cytoskeleton, cell cycle, and apoptosis. Exogenous folate did not offset the effects of TCE exposure on normal gene expression, and both high and low levels of folate produced additional significant changes in gene expression. CONCLUSIONS A mechanism by which TCE induces a folate deficiency does not explain altered gene expression patterns in the embryonic mouse heart. The data further suggest that use of folate supplementation, in the presence of this toxin, may be detrimental and not protective of the developing embryo.
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Affiliation(s)
- Patricia T Caldwell
- Department of Veterinary Science and Microbiology, University of Arizona, Tucson, Arizona 85721-0038, USA
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22
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Rufer ES, Hacker TA, Flentke GR, Drake VJ, Brody MJ, Lough J, Smith SM. Altered cardiac function and ventricular septal defect in avian embryos exposed to low-dose trichloroethylene. Toxicol Sci 2009; 113:444-52. [PMID: 19910388 DOI: 10.1093/toxsci/kfp269] [Citation(s) in RCA: 39] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
Trichloroethylene (TCE) is the most frequently reported organic groundwater contaminant in the United States. It is controversial whether gestational TCE exposure causes congenital heart defects. The basis for TCE's proposed cardiac teratogenicity is not well understood. We previously showed that chick embryos exposed to 8 ppb TCE during cardiac morphogenesis have reduced cardiac output and increased mortality. To further investigate TCE's cardioteratogenic potential, we exposed in ovo chick embryos to TCE and evaluated the heart thereafter. Significant mortality was observed following TCE exposures of 8-400 ppb during a narrow developmental period (Hamburger-Hamilton [HH] stages 15-20, embryo day ED2.3-3.5) that is characterized by myocardial expansion, secondary heart looping, and endocardial cushion formation. Of the embryos that died, most did so between ED5.5 and ED6.5. Echocardiography of embryos at ED5.5 found that TCE-exposed hearts displayed significant functional and morphological heterogeneity affecting heart rate, left ventricular mass, and wall thickness. Individual embryos were identified with cardiac hypertrophy as well as with hypoplasia. Chick embryos exposed to 8 ppb TCE at HH17 that survived to hatch exhibited a high incidence (38%, p < 0.01, n = 16) of muscular ventricular septal defects (VSDs) as detected by echocardiography and confirmed by gross dissection; no VSDs were found in controls (n = 14). The TCE-induced VSDs may be secondary to functional impairments that alter cardiac hemodynamics and subsequent ventricular foramen closure, an interpretation consistent with recent demonstrations that TCE impairs calcium handling in cardiomyocytes. These data demonstrate that TCE is a cardiac teratogen for chick.
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Affiliation(s)
- Echoleah S Rufer
- Molecular and Environmental Toxicology Center, University of Wisconsin-Madison, Madison, Wisconsin 53706, USA
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23
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Tabrez S, Ahmad M. Toxicity, biomarkers, genotoxicity, and carcinogenicity of trichloroethylene and its metabolites: a review. JOURNAL OF ENVIRONMENTAL SCIENCE AND HEALTH. PART C, ENVIRONMENTAL CARCINOGENESIS & ECOTOXICOLOGY REVIEWS 2009; 27:178-196. [PMID: 19657920 DOI: 10.1080/10590500903091340] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/28/2023]
Abstract
Trichloroethylene (TCE) is a prevalent occupational and environmental contaminant that has been reported to cause a variety of toxic effects. This article reviews toxicity, mutagenicity, and carcinogenicity caused by the exposure of TCE and its metabolites in the living system as well as on their (TCE and its metabolites) toxicity biomarkers.
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24
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Trichloroethylene and Trichloroacetic Acid Regulate Calcium Signaling Pathways in Murine Embryonal Carcinoma Cells P19. Cardiovasc Toxicol 2008; 8:47-56. [DOI: 10.1007/s12012-008-9014-2] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/08/2008] [Accepted: 03/28/2008] [Indexed: 10/22/2022]
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25
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Williams AL, DeSesso JM. Trichloroethylene and ocular malformations: analysis of extant literature. Int J Toxicol 2008; 27:81-95. [PMID: 18293215 DOI: 10.1080/10915810701876760] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/22/2022]
Abstract
An evaluation of the scientific literature for trichloroethylene (TCE) identified two reports of ocular defects, specifically microphthalmia/anophthalmia, following prenatal TCE exposure in rats. Herein, these reports are analyzed in detail and interpreted within the context of other developmental TCE exposure studies. The ocular findings following prenatal TCE exposure are reported in studies that were not designed specifically for developmental safety assessment, and thus did not use standard experimental practices. Furthermore, these findings most commonly occurred at TCE doses associated with considerable maternal toxicity. Among the 18 published studies using developmental TCE exposures, only 3 used doses sufficiently high enough to result in maternal toxicity, and of these, only the 2 discussed in detail in this paper demonstrated ocular defects in the offspring. Furthermore, statistically significant effects were only observed at doses that were above the currently accepted guideline limit dose of 1000 mg/kg body weight. All other TCE developmental exposure studies failed to demonstrate ocular defects as a result of prenatal exposure. These results suggest that the micro-/anophthalmia findings were likely a consequence of delivery of an extremely high bolus TCE dose that is irrelevant to human environmental exposure scenarios.
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26
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Carney EW, Thorsrud BA, Dugard PH, Zablotny CL. Developmental toxicity studies in Crl:CD (SD) rats following inhalation exposure to trichloroethylene and perchloroethylene. ACTA ACUST UNITED AC 2007; 77:405-12. [PMID: 17066414 DOI: 10.1002/bdrb.20091] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
Abstract
The potential for trichloroethylene (TCE) and perchloroethylene (PERC) to induce developmental toxicity was investigated in Crl:CD (SD) rats whole-body exposed to target concentrations of 0, 50, 150 or 600 ppm TCE or 0, 75, 250 or 600 ppm PERC for six hours/day, seven days/week on gestation day (GD) 6-20 and 6-19, respectively. Actual chamber concentrations were essentially identical to target with the exception of the low PERC exposure level, which was 65 ppm. The highest exposure levels exceeded the limit concentration (2 mg/L) specified in the applicable test guidelines. Maternal necropsies were performed the day following the last exposure. Dams exposed to 600 ppm TCE exhibited maternal toxicity, as evidenced by decreased body weight gain (22% less than control) during GD 6-9. There were no maternal effects at 50 or 150 ppm TCE and no indications of developmental toxicity (including heart defects or other terata) at any exposure level tested. Therefore, the TCE NOEC for maternal toxicity was 150 ppm, whereas the embryo/fetal NOEC was 600 ppm. Maternal responses to PERC were limited to slight, but statistically significant reductions in body weight gain and feed consumption during the first 3 days of exposure to 600 ppm, resulting in a maternal NOEC of 250 ppm. Developmental effects at 600 ppm consisted of reduced gravid uterus, placental and fetal body weights, and decreased ossification of thoracic vertebral centra. Developmental effects at 250 ppm were of minimal toxicological significance, being limited to minor decreases in fetal and placental weight. There were no developmental effects at 65 ppm.
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Affiliation(s)
- E W Carney
- Toxicology and Environmental Research and Consulting, The Dow Chemical Company, Midland, Michigan 48674, USA.
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27
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Warren DA, Graeter LJ, Channel SR, Eggers JS, Goodyear CD, Macmahon KL, Sudberry GL, Latendresse JR, Fisher JW, Baker WH. Trichloroethylene, trichloroacetic acid, and dichloroacetic acid: do they affect eye development in the Sprague-Dawley rat? Int J Toxicol 2006; 25:279-84. [PMID: 16815816 DOI: 10.1080/10915810600745975] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/24/2022]
Abstract
Maternal exposure to high doses of trichloroethylene (TCE) and its oxidative metabolites, trichloroacetic acid (TCA) and dichloroacetic acid (DCA), has been implicated in eye malformations in fetal rats, primarily micro-/anophthalmia. Subsequent to a cardiac teratology study of these compounds (Fisher et al. 2001, Int. J. Toxicol. 20:257-267), their potential to induce ocular malformations was examined in a subset of the same experimental animals. Pregnant, Sprague-Dawley Crl:CDR BR rats were orally treated on gestation days (GDs) 6 to 15 with bolus doses of either TCE (500 mg/kg/day), TCA (300 mg/kg/day), DCA (300 mg/kg/day), or all-trans retinoic acid (RA; 15 mg/kg/day). The heads of GD 21 fetuses were not only examined grossly for external malformations, but were sectioned using a modified Wilson's technique and subjected to computerized morphometry that allowed for the quantification of lens area, globe area, medial canthus distance, and interocular distance. Gross ocular malformations were essentially absent in all treatment groups except for the RA group in which 26% of fetuses exhibited micro-/anophthalmia. Using the litter as the experimental unit of analysis, lens area, globe area, and interocular distance were statistically significantly reduced in the DCA treatment group. Statistically significant reductions in lens and globe areas also occurred in the RA treatment group, all four ocular measures were reduced in the TCA treatment group but none significantly so, and TCE was without effect. Because DCA, TCA, and RA treatments were associated with significant reductions in fetal body weight (bw), data were also statistically analyzed after bw adjustment. Doing so dramatically altered the results of treatment group comparisons, but the severity of bw reduction and the degree of change in ocular measures did not always correlate. This suggests that bw reduction may not be an adequate explanation for all the changes observed in ocular measures. Thus, it is unclear whether DCA specifically disrupted ocular development even under these provocative exposure conditions. Clearly, however, if TCE is capable of disrupting ocular development in the Sprague-Dawley rat, a higher dose than that employed in the present study is required.
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Affiliation(s)
- D A Warren
- Air Force Research Laboratory, Human Effectiveness Directorate, Wright-Patterson AFB, Ohio, USA.
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28
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Drake VJ, Koprowski SL, Lough J, Hu N, Smith SM. Trichloroethylene exposure during cardiac valvuloseptal morphogenesis alters cushion formation and cardiac hemodynamics in the avian embryo. ENVIRONMENTAL HEALTH PERSPECTIVES 2006; 114:842-7. [PMID: 16759982 PMCID: PMC1480523 DOI: 10.1289/ehp.8781] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Indexed: 05/10/2023]
Abstract
It is controversial whether trichloroethylene (TCE) is a cardiac teratogen. We exposed chick embryos to 0, 0.4, 8, or 400 ppb TCE/egg during the period of cardiac valvuloseptal morphogenesis (2-3.3 days' incubation) . Embryo survival, valvuloseptal cellularity, and cardiac hemodynamics were evaluated at times thereafter. TCE at 8 and 400 ppb/egg reduced embryo survival to day 6.25 incubation by 40-50%. At day 4.25, increased proliferation and hypercellularity were observed within the atrioventricular and outflow tract primordia after 8 and 400 ppb TCE. Doppler ultrasound revealed that the dorsal aortic and atrioventricular blood flows were reduced by 23% and 30%, respectively, after exposure to 8 ppb TCE. Equimolar trichloroacetic acid (TCA) was more potent than TCE with respect to increasing mortality and causing valvuloseptal hypercellularity. These results independently confirm that TCE disrupts cardiac development of the chick embryo and identifies valvuloseptal development as a period of sensitivity. The hypercellular valvuloseptal profile is consistent with valvuloseptal heart defects associated with TCE exposure. This is the first report that TCA is a cardioteratogen for the chick and the first report that TCE exposure depresses cardiac function. Valvuloseptal hypercellularity may narrow the cardiac orifices, which reduces blood flow through the heart, thereby compromising cardiac output and contributing to increased mortality. The altered valvuloseptal formation and reduced hemodynamics seen here are consistent with such an outcome. Notably, these effects were observed at a TCE exposure (8 ppb) that is only slightly higher than the U.S. Environmental Protection Agency maximum containment level for drinking water (5 ppb) .
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Affiliation(s)
- Victoria J Drake
- Department of Nutritional Sciences, University of Wisconsin-Madison, Madison, Wisconsin 53706, USA
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29
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Hardin BD, Kelman BJ, Brent RL. Trichloroethylene and dichloroethylene: a critical review of teratogenicity. ACTA ACUST UNITED AC 2006; 73:931-55. [PMID: 16342278 DOI: 10.1002/bdra.20192] [Citation(s) in RCA: 35] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
Abstract
Trichloroethylene (TCE) and dichloroethylene (DCE) are high-volume industrial chemicals frequently found as contaminants in public drinking water supplies. The developmental toxicity of both chemicals has been evaluated in laboratory and epidemiologic studies. It has been suggested that TCE and DCE are specific cardiac teratogens and that drinking water contaminated with them increases the risk of congenital heart defects in exposed human populations. In contrast, other laboratory and epidemiologic studies do not find an increase in developmental effects, either in general or specifically affecting the heart. This laboratory and epidemiologic base was reviewed to evaluate the strengths and weaknesses of the conflicting published reports. We conclude that the weight of experimental and epidemiologic evidence does not support the hypothesis that TCE or DCE is a selective developmental toxicant in general or a cardiac teratogen specifically.
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Mishima N, Hoffman S, Hill EG, Krug EL. Chick embryos exposed to trichloroethylene in an ex ovo culture model show selective defects in early endocardial cushion tissue formation. ACTA ACUST UNITED AC 2006; 76:517-27. [PMID: 16933305 DOI: 10.1002/bdra.20283] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
Abstract
BACKGROUND Formation of the primitive heart is a critical step for establishing a competent circulatory system necessary for continued morphogenesis, and as such has significant potential as a target for environmental insult. The goal of this study was to identify the initial cellular events that precede more superficially observable abnormalities resulting from exposing early chick embryos to trichloroethylene (TCE). METHODS A whole embryo culture method was used to assess the susceptibility of endocardial epithelial-mesenchymal transformation in the early chick heart to TCE. This method has the benefits of maintaining the anatomical relationships of developing tissues and organs, instantaneously exposing precisely staged embryos to quantifiable levels of TCE in a protein-free medium, and the ability to directly monitor developmental morphology. RESULTS A minority of embryos (Hamburger and Hamilton [HH] stage 13-14) exposed to TCE (10-80 ppm) were not viable after 24 hr in culture and exhibited a variety of gross malformations in a dose-dependent fashion. However, the majority of treated embryos remained viable and developed into HH stage 17 embryos that were superficially indistinguishable from vehicle-treated controls. Further analysis of the hearts of these superficially normal embryos by whole-mount confocal microscopy revealed selective reduction in the number of atrioventricular canal mesenchymal cells. Additionally, those mesenchymal cells that did develop migrated abnormally as long thin cords of adherent cells. CONCLUSIONS The regional selectivity of these effects in the chick heart suggests a critical window of susceptibility to TCE in the epithelial-mesenchymal transformation of atrioventricular canal endocardium.
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Affiliation(s)
- Noboru Mishima
- Department of Cell Biology and Anatomy, Medical University of South Carolina, Charleston, South Carolina 29425, USA
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Watson RE, Jacobson CF, Williams AL, Howard WB, DeSesso JM. Trichloroethylene-contaminated drinking water and congenital heart defects: a critical analysis of the literature. Reprod Toxicol 2005; 21:117-47. [PMID: 16181768 DOI: 10.1016/j.reprotox.2005.07.013] [Citation(s) in RCA: 42] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/19/2005] [Revised: 07/12/2005] [Accepted: 07/19/2005] [Indexed: 11/20/2022]
Abstract
The organic solvent trichloroethylene (TCE) is a metal degreasing agent and an intermediate in the production of fluorochemicals and polyvinyl chloride. TCE is also a common, persistent drinking water contaminant. Several epidemiological studies have alleged links between TCE exposure during pregnancy and offspring health problems including congenital heart defects (CHDs); however, the results of these studies are inconsistent, difficult to interpret, and involve several confounding factors. Similarly, the results of animal studies examining the potential of TCE to elicit cardiac anomalies have been inconsistent, and they have often been performed at doses far exceeding the highest levels ever reported in the drinking water. To determine what is known about the relationship between TCE and the incidence of CHDs, a comprehensive analysis of all available epidemiological data and animal studies was performed. Additionally, in vivo and in vitro studies examining possible mechanisms of action for TCE were evaluated. The specific types of heart defects alleged to have been caused by TCE in animal and human epidemiology studies were categorized by the morphogenetic process responsible for the defect in order to determine whether TCE might disrupt any specific developmental process. This analysis revealed that no single process was clearly affected by TCE, providing support that gestational TCE exposure does not increase the prevalence of CHDs. As a final evaluation, application of Hill's causality guidelines to the collective body of data revealed no indication of a causal link between gestational TCE exposure at environmentally relevant concentrations and CHDs.
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Affiliation(s)
- Rebecca E Watson
- Mitretek Systems, 3150 Fairview Park Drive, Falls Church, VA 22033, USA
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Silbergeld EK, Patrick TE. Environmental exposures, toxicologic mechanisms, and adverse pregnancy outcomes. Am J Obstet Gynecol 2005; 192:S11-21. [PMID: 15891707 DOI: 10.1016/j.ajog.2004.06.117] [Citation(s) in RCA: 53] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Environmental risk factors (defined as those agents and stresses that are generally the responsibility of environmental agencies) are often tangible indicators of economic and social disparity in the United States. Many site-specific analyses have reported that communities of color and poverty are exposed more often and more intensively to such environmental hazards as lead, air pollution, agrochemicals, incinerator emissions, and releases from hazardous waste sites. Thus, exposures to these toxicants may explain part of the socioeconomic disparity that is observed in terms of risks of adverse pregnancy outcomes. The purpose of this study was to describe the associations between certain environmental exposures and reproductive outcomes through a discussion of both epidemiologic and animal model studies. In addition, we list potential sources of exposure data and describe physiologic changes in pregnancy that may increase the likelihood of both external exposures and increased internal dose. Several models for further study of environmental risk factors are suggested to increase our understanding of gene-environment interactions toward the goal of indentifying preventable risk factors to improve reproductive outcomes of particular concern to disadvantaged populations.
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Affiliation(s)
- Ellen K Silbergeld
- Johns Hopkins University, Bloomberg School of Public Health, Baltimore, MD 21205, USA.
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Yauck JS, Malloy ME, Blair K, Simpson PM, McCarver DG. Proximity of residence to trichloroethylene-emitting sites and increased risk of offspring congenital heart defects among older women. ACTA ACUST UNITED AC 2005; 70:808-14. [PMID: 15390315 DOI: 10.1002/bdra.20060] [Citation(s) in RCA: 65] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
Abstract
BACKGROUND Previous studies suggest that trichloroethylene (TCE) is a selective cardiac teratogen. We tested the hypothesis that the odds of maternal residence close to TCE-emitting sites would be greater among infants with congenital heart defects (CHDs) than among infants without CHDs. METHODS We conducted a case-control study of 4025 infants, identified from hospital and birth records, born from 1997 to 1999 to Milwaukee, Wisconsin mothers. A geographic information system was used to calculate distances between maternal residences and TCE sites. We used classification tree analysis to determine appropriate values by which to dichotomously categorize mothers by TCE exposure (exposed: residence within 1.32 miles of at least one TCE site) and age (older: >/=38 years), and logistic regression to test for CHD risk factors. RESULTS The proportion of mothers who were both older and had presumed TCE exposure was more than six-fold greater among case infants than among control infants (3.3% [8/245] versus 0.5% [19/3780]). When adjusted for other variables, CHD risk was over three-fold greater among infants of older, exposed mothers compared to infants of older, nonexposed mothers (adjusted OR, 3.2; 95% CI, 1.2-8.7). Older maternal age, alcohol use, chronic hypertension, and preexisting diabetes were each associated with CHDs (adjusted ORs, 1.9, 2.1, 2.8, 4.1; 95% CIs, 1.1-3.5, 1.1-4.2, 1.2-6.7, 1.5-11.2, respectively), but residence close to TCE sites alone was not. CONCLUSIONS Our findings suggest that maternal age and TCE exposure interact to increase CHD risk, although the mechanism by which this occurs is unknown. A prospective study is underway to confirm this finding.
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Affiliation(s)
- Jennifer S Yauck
- Department of Pediatrics, Medical College of Wisconsin, Milwaukee, Wisconsin 53226, USA.
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Selmin O, Thorne PA, Caldwell PT, Johnson PD, Runyan RB. Effects of trichloroethylene and its metabolite trichloroacetic acid on the expression of vimentin in the rat H9c2 cell line. Cell Biol Toxicol 2005; 21:83-95. [PMID: 16142583 DOI: 10.1007/s10565-005-0124-3] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/02/2004] [Accepted: 05/03/2005] [Indexed: 12/21/2022]
Abstract
Trichloroethylene (TCE) and its metabolite trichloroacetic acid (TCAA) are environmental contaminants with specific toxicity for the embryonic heart. In an effort to identify the cellular pathways disrupted by TCE and TCAA during heart development, we investigated their effects on expression of vimentin, a marker of cardiac differentiation. Previous studies had shown that the level of vimentin transcript was inhibited in rat embryonic heart after maternal exposure to TCE via drinking water. In the same study, maternal exposure to TCAA produced the opposite effect, inducing an increased level of vimentin mRNA. In this study, we selected an in vitro system, the rat cardiac myoblast cell line H9c2, to further characterize the molecular mechanisms used by TCE and TCAA to disrupt normal heart development. In particular, we investigated the effects of both toxicants on vimentin, at both the RNA and protein levels, using dose-response and time course curves. Our experimental findings indicate that vimentin expression is affected by TCE and TCAA in H9c2 cells similarly as in vivo. The work is significant because it provides a suitable in vitro model for studies looking at toxicant effects on myocardiac cells, and it suggests that vimentin is a good marker of TCE exposure in the embryonic heart.
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Affiliation(s)
- O Selmin
- Department of Veterinary Sciences and Microbiology, University of Arizona, Tucson, Arizona 85721-0090, USA.
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