arsenite exposure is varied based on age and outcome measured Kathleen A Hershberger, Tess C Leut... more arsenite exposure is varied based on age and outcome measured Kathleen A Hershberger, Tess C Leuthner, Tanner A Waters and Joel N Meyer 1Nicholas School of the Environment, Duke University, Durham, NC 27708 2Institute of the Environment and Sustainability, University of California, Los Angeles (UCLA), Los Angeles, CA 90095 §Correspondence to: Joel N Meyer (joel.meyer@duke.edu (mailto:joel.meyer@duke.edu))
The consequences of damage to the mitochondrial genome (mtDNA) are poorly understood, although mt... more The consequences of damage to the mitochondrial genome (mtDNA) are poorly understood, although mtDNA is more susceptible to damage than nuclear DNA (nucDNA), and many environmental toxicants target the mitochondria. Reports from the toxicological literature suggest that exposure to early-life mitochondrial damage could lead to deleterious consequences later in life (the “Developmental Origins of Health and Disease” paradigm) but reports from other fields often report beneficial (“mitohormetic”) responses to such damage. Here, we test the effects of low (causing no change in lifespan) levels of ultraviolet C (UVC)-induced, irreparable mtDNA damage during early development inCaenorhabditis elegans. This exposure led to life-long reductions in mtDNA copy number and steady-state ATP levels, accompanied by increased oxygen consumption and altered metabolite profiles, suggesting inefficient mitochondrial function. Exposed nematodes were also developmentally delayed, reached smaller adult ...
The tobacco-specific carcinogen 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanol (NNAL), a metabolit... more The tobacco-specific carcinogen 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanol (NNAL), a metabolite of the tobacco-specific nitrosamine (TSNA) 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone (NNK), has been measured in urine samples from all participants aged 6 years and older from the National Health and Nutrition Examination Survey 2007-2008. Participants with a serum cotinine concentration of ≥ 10 ng/mL were identified as tobacco users, primarily cigarette smokers. Regression models were developed to calculate geometric mean NNAL concentrations adjusted for serum cotinine, urinary creatinine, cigarettes per day, and Federal Trade Commission tar values of the cigarettes smoked. Significant differences were found by gender (p=0.003) and race/ethnicity (p=0.022 for non-Hispanic white versus non-Hispanic black smokers), but not by menthol type of the cigarettes. Females and non-Hispanic white smokers had the highest adjusted means for urinary NNAL (353 and 336 pg/mL, respectively). The results from this study demonstrated significant relationships between NNAL concentrations and serum cotinine (p<0.001) and urine creatinine (p<0.001). The joint effect of linear and quadratic terms for number of cigarettes smoked per day was also statistically significant (p=0.001). In addition to addressing current NNK exposure levels, these results will form a baseline for future estimates of tobacco users' exposure to this carcinogen.
Page 294. 6 Reactive Oxygen Species and Oxidative Stress Richard T. Di Giulio and Joel N. Meyer C... more Page 294. 6 Reactive Oxygen Species and Oxidative Stress Richard T. Di Giulio and Joel N. Meyer CONTENTS Introduction..... 274 Reactive Oxygen ...
Mercury toxicity mechanisms have the potential to induce DNA damage and disrupt cellular processe... more Mercury toxicity mechanisms have the potential to induce DNA damage and disrupt cellular processes, like mitochondrial function. Proper mitochondrial function is important for cellular bioenergetics and immune signaling and function. Reported impacts of mercury on the nuclear genome (nDNA) are conflicting and inconclusive, and mitochondrial DNA (mtDNA) impacts are relatively unknown. In this study, we assessed genotoxic (mtDNA and nDNA), metabolic, and innate immune impacts of inorganic and organic mercury exposure in Caenorhabditis elegans. Genotoxic outcomes measured included DNA damage, DNA damage repair (nucleotide excision repair, NER; base excision repair, BER), and genomic copy number following MeHg and HgCl2 exposure alone and in combination with known DNA damage-inducing agents ultraviolet C radiation (UVC) and hydrogen peroxide (H2O2), which cause bulky DNA lesions and oxidative DNA damage, respectively. Following exposure to both MeHg and HgCl2, low-level DNA damage (∼0.2...
Background: Parkinson’s disease (PD) is one of the most common neurodegenerative disorders involv... more Background: Parkinson’s disease (PD) is one of the most common neurodegenerative disorders involving devastating loss of dopaminergic neurons in the substantia nigra. Early steps in PD pathogenesis include mitochondrial dysfunction, and mutations in mitochondrial genes have been linked to familial forms of the disease. However, low penetrance of mutations indicates a likely important role for environmental factors in PD risk through gene by environment interactions. Herein, we study how genetic deficiencies in mitochondrial dynamics processes including fission, fusion, and mitophagy interact with environmental exposures to impact neurodegeneration. Methods: We utilized the powerful model organism Caenorhabditis elegans to study ultraviolet C radiation (UVC)- and 6-hydroxydopamine-induced degeneration of fluorescently-tagged dopaminergic neurons in the background of fusion deficiency (MFN1/2 homolog, fzo-1), fission deficiency (DMN1L homolog, drp-1), and mitochondria-specific autopha...
The roundworm Caenorhabitis elegans has been an established model organism for the study of genet... more The roundworm Caenorhabitis elegans has been an established model organism for the study of genetics and developmental biology, including studies of transcriptional regulation, since the 1970s. This model organism has continued to be used as a classical model system as the field of transcriptional regulation has expanded to include scientific advances in epigenetics and chromatin biology. In the last several decades, C. elegans has emerged as a powerful model for environmental toxicology, particularly for the study of chemical genotoxicity. Here, we outline the utility and applicability of C. elegans as a powerful model organism for mechanistic studies of environmental influences on the epigenome. Our goal in this article is to inform the field of environmental epigenetics of the strengths and limitations of the well-established C. elegans model organism as an emerging model for medium-throughput, in vivo exploration of the role of exogenous chemical stimuli in transcriptional regul...
Environmental and molecular mutagenesis, Jan 5, 2018
Mitochondrial DNA (mtDNA) copy number (CN) and damage in circulating white blood cells have been ... more Mitochondrial DNA (mtDNA) copy number (CN) and damage in circulating white blood cells have been proposed as effect biomarkers for pollutant exposures. Studies have shown that mercury accumulates in mitochondria and affects mitochondrial function and integrity; however, these data are derived largely from experiments in model systems, rather than human population studies that evaluate the potential utility of mitochondrial exposure biomarkers. We measured mtDNA CN and damage in white blood cells (WBCs) from 83 residents of nine communities in the Madre de Dios region of the Peruvian Amazon that vary in proximity to artisanal and small-scale gold mining. Prior research from this region reported high levels of mercury in fish and a significant association between food consumption and human total hair mercury level of residents. We observed that mtDNA CN and damage were both associated with consumption of fruit and vegetables, higher diversity of fruit consumed, residential location, a...
Exercise and caloric restriction improve health, including reducing risk of cardiovascular diseas... more Exercise and caloric restriction improve health, including reducing risk of cardiovascular disease, neurological disease, and cancer. However, molecular mechanisms underlying these protections are poorly understood, partly due to the cost and time investment of mammalian long-term diet and exercise intervention studies. We subjected Caenorhabditis elegans nematodes to a 6-day, twice daily swimming exercise regimen, during which time the animals also experienced brief, transient food deprivation. Accordingly, we included a non-exercise group with the same transient food deprivation, a non-exercise control with ad libitum access to food, and a group that exercised in food-containing medium. Following these regimens, we assessed mitochondrial health and sensitivity to mitochondrial toxicants. Exercise protected against age-related decline in mitochondrial morphology in body-wall muscle. Food deprivation increased organismal basal respiration; however, exercise was the sole intervention...
Zebrafish are an attractive model organism for toxicology; however, an important consideration in... more Zebrafish are an attractive model organism for toxicology; however, an important consideration in translating between species is xenobiotic metabolism/bioactivation. CYP2E1 metabolizes small hydrophobic molecules, e.g. ethanol, cigarette smoke, and diesel exhaust components. CYP2E1 is thought to only be conserved in mammals, but recent reports identified homologous zebrafish cytochrome P450s. Herein, ex vivo biochemical measurements show that unlike mammals, zebrafish possess a low-affinity 4-nitrophenol hydroxylase (Km ∼0.6 mM) in hepatic microsomes and mitochondria that is inducible only 1.5- to 2-fold by ethanol and is insensitive to 4-methylpyrazole inhibition. In closing, we suggest creating improved models to study CYP2E1 in zebrafish.
International journal of hygiene and environmental health, Jan 10, 2017
Household air pollution is a major contributor to death and disability worldwide. Over 95% of rur... more Household air pollution is a major contributor to death and disability worldwide. Over 95% of rural Guatemalan households use woodstoves for cooking or heating. Woodsmoke contains carcinogenic or fetotoxic polycyclic aromatic hydrocarbons (PAHs) and volatile organic compounds (VOCs). Increased PAHs and VOCs have been shown to increase levels of oxidative stress. We examined PAH and VOC exposures among recently pregnant rural Guatemalan women exposed to woodsmoke and compared exposures to levels seen occupationally or among smokers. Urine was collected from 23 women who were 3 months post-partum three times over 72h: morning (fasting), after lunch, and following dinner or use of wood-fired traditional sauna baths (samples=68). Creatinine-adjusted urinary concentrations of metabolites of four PAHs and eight VOCs were analyzed by liquid chromatography-mass spectrometry. Creatinine-adjusted urinary biomarkers of oxidative stress, 8-isoprostane and 8-OHdG, were analyzed using enzyme-link...
The C. elegans biological responses to metal-based nanoparticles are reviewed. A cross-disciplina... more The C. elegans biological responses to metal-based nanoparticles are reviewed. A cross-disciplinary workflow for nanoparticles screening in vivo is proposed.
Current protocols in toxicology / editorial board, Mahin D. Maines (editor-in-chief) ... [et al.], 2016
Mitochondria are a target of many drugs and environmental toxicants; however, how toxicant-induce... more Mitochondria are a target of many drugs and environmental toxicants; however, how toxicant-induced mitochondrial dysfunction contributes to the progression of human disease remains poorly understood. To address this issue, in vivo assays capable of rapidly assessing mitochondrial function need to be developed. Here, using the model organism Caenorhabditis elegans, we describe how to rapidly assess the in vivo role of the electron transport chain, glycolysis, or fatty acid oxidation in energy metabolism following toxicant exposure, using a luciferase-expressing ATP reporter strain. Alterations in mitochondrial function subsequent to toxicant exposure are detected by depleting steady-state ATP levels with inhibitors of the mitochondrial electron transport chain, glycolysis, or fatty acid oxidation. Differential changes in ATP following short-term inhibitor exposure indicate toxicant-induced alterations at the site of inhibition. Because a microplate reader is the only major piece of e...
arsenite exposure is varied based on age and outcome measured Kathleen A Hershberger, Tess C Leut... more arsenite exposure is varied based on age and outcome measured Kathleen A Hershberger, Tess C Leuthner, Tanner A Waters and Joel N Meyer 1Nicholas School of the Environment, Duke University, Durham, NC 27708 2Institute of the Environment and Sustainability, University of California, Los Angeles (UCLA), Los Angeles, CA 90095 §Correspondence to: Joel N Meyer (joel.meyer@duke.edu (mailto:joel.meyer@duke.edu))
The consequences of damage to the mitochondrial genome (mtDNA) are poorly understood, although mt... more The consequences of damage to the mitochondrial genome (mtDNA) are poorly understood, although mtDNA is more susceptible to damage than nuclear DNA (nucDNA), and many environmental toxicants target the mitochondria. Reports from the toxicological literature suggest that exposure to early-life mitochondrial damage could lead to deleterious consequences later in life (the “Developmental Origins of Health and Disease” paradigm) but reports from other fields often report beneficial (“mitohormetic”) responses to such damage. Here, we test the effects of low (causing no change in lifespan) levels of ultraviolet C (UVC)-induced, irreparable mtDNA damage during early development inCaenorhabditis elegans. This exposure led to life-long reductions in mtDNA copy number and steady-state ATP levels, accompanied by increased oxygen consumption and altered metabolite profiles, suggesting inefficient mitochondrial function. Exposed nematodes were also developmentally delayed, reached smaller adult ...
The tobacco-specific carcinogen 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanol (NNAL), a metabolit... more The tobacco-specific carcinogen 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanol (NNAL), a metabolite of the tobacco-specific nitrosamine (TSNA) 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone (NNK), has been measured in urine samples from all participants aged 6 years and older from the National Health and Nutrition Examination Survey 2007-2008. Participants with a serum cotinine concentration of ≥ 10 ng/mL were identified as tobacco users, primarily cigarette smokers. Regression models were developed to calculate geometric mean NNAL concentrations adjusted for serum cotinine, urinary creatinine, cigarettes per day, and Federal Trade Commission tar values of the cigarettes smoked. Significant differences were found by gender (p=0.003) and race/ethnicity (p=0.022 for non-Hispanic white versus non-Hispanic black smokers), but not by menthol type of the cigarettes. Females and non-Hispanic white smokers had the highest adjusted means for urinary NNAL (353 and 336 pg/mL, respectively). The results from this study demonstrated significant relationships between NNAL concentrations and serum cotinine (p<0.001) and urine creatinine (p<0.001). The joint effect of linear and quadratic terms for number of cigarettes smoked per day was also statistically significant (p=0.001). In addition to addressing current NNK exposure levels, these results will form a baseline for future estimates of tobacco users' exposure to this carcinogen.
Page 294. 6 Reactive Oxygen Species and Oxidative Stress Richard T. Di Giulio and Joel N. Meyer C... more Page 294. 6 Reactive Oxygen Species and Oxidative Stress Richard T. Di Giulio and Joel N. Meyer CONTENTS Introduction..... 274 Reactive Oxygen ...
Mercury toxicity mechanisms have the potential to induce DNA damage and disrupt cellular processe... more Mercury toxicity mechanisms have the potential to induce DNA damage and disrupt cellular processes, like mitochondrial function. Proper mitochondrial function is important for cellular bioenergetics and immune signaling and function. Reported impacts of mercury on the nuclear genome (nDNA) are conflicting and inconclusive, and mitochondrial DNA (mtDNA) impacts are relatively unknown. In this study, we assessed genotoxic (mtDNA and nDNA), metabolic, and innate immune impacts of inorganic and organic mercury exposure in Caenorhabditis elegans. Genotoxic outcomes measured included DNA damage, DNA damage repair (nucleotide excision repair, NER; base excision repair, BER), and genomic copy number following MeHg and HgCl2 exposure alone and in combination with known DNA damage-inducing agents ultraviolet C radiation (UVC) and hydrogen peroxide (H2O2), which cause bulky DNA lesions and oxidative DNA damage, respectively. Following exposure to both MeHg and HgCl2, low-level DNA damage (∼0.2...
Background: Parkinson’s disease (PD) is one of the most common neurodegenerative disorders involv... more Background: Parkinson’s disease (PD) is one of the most common neurodegenerative disorders involving devastating loss of dopaminergic neurons in the substantia nigra. Early steps in PD pathogenesis include mitochondrial dysfunction, and mutations in mitochondrial genes have been linked to familial forms of the disease. However, low penetrance of mutations indicates a likely important role for environmental factors in PD risk through gene by environment interactions. Herein, we study how genetic deficiencies in mitochondrial dynamics processes including fission, fusion, and mitophagy interact with environmental exposures to impact neurodegeneration. Methods: We utilized the powerful model organism Caenorhabditis elegans to study ultraviolet C radiation (UVC)- and 6-hydroxydopamine-induced degeneration of fluorescently-tagged dopaminergic neurons in the background of fusion deficiency (MFN1/2 homolog, fzo-1), fission deficiency (DMN1L homolog, drp-1), and mitochondria-specific autopha...
The roundworm Caenorhabitis elegans has been an established model organism for the study of genet... more The roundworm Caenorhabitis elegans has been an established model organism for the study of genetics and developmental biology, including studies of transcriptional regulation, since the 1970s. This model organism has continued to be used as a classical model system as the field of transcriptional regulation has expanded to include scientific advances in epigenetics and chromatin biology. In the last several decades, C. elegans has emerged as a powerful model for environmental toxicology, particularly for the study of chemical genotoxicity. Here, we outline the utility and applicability of C. elegans as a powerful model organism for mechanistic studies of environmental influences on the epigenome. Our goal in this article is to inform the field of environmental epigenetics of the strengths and limitations of the well-established C. elegans model organism as an emerging model for medium-throughput, in vivo exploration of the role of exogenous chemical stimuli in transcriptional regul...
Environmental and molecular mutagenesis, Jan 5, 2018
Mitochondrial DNA (mtDNA) copy number (CN) and damage in circulating white blood cells have been ... more Mitochondrial DNA (mtDNA) copy number (CN) and damage in circulating white blood cells have been proposed as effect biomarkers for pollutant exposures. Studies have shown that mercury accumulates in mitochondria and affects mitochondrial function and integrity; however, these data are derived largely from experiments in model systems, rather than human population studies that evaluate the potential utility of mitochondrial exposure biomarkers. We measured mtDNA CN and damage in white blood cells (WBCs) from 83 residents of nine communities in the Madre de Dios region of the Peruvian Amazon that vary in proximity to artisanal and small-scale gold mining. Prior research from this region reported high levels of mercury in fish and a significant association between food consumption and human total hair mercury level of residents. We observed that mtDNA CN and damage were both associated with consumption of fruit and vegetables, higher diversity of fruit consumed, residential location, a...
Exercise and caloric restriction improve health, including reducing risk of cardiovascular diseas... more Exercise and caloric restriction improve health, including reducing risk of cardiovascular disease, neurological disease, and cancer. However, molecular mechanisms underlying these protections are poorly understood, partly due to the cost and time investment of mammalian long-term diet and exercise intervention studies. We subjected Caenorhabditis elegans nematodes to a 6-day, twice daily swimming exercise regimen, during which time the animals also experienced brief, transient food deprivation. Accordingly, we included a non-exercise group with the same transient food deprivation, a non-exercise control with ad libitum access to food, and a group that exercised in food-containing medium. Following these regimens, we assessed mitochondrial health and sensitivity to mitochondrial toxicants. Exercise protected against age-related decline in mitochondrial morphology in body-wall muscle. Food deprivation increased organismal basal respiration; however, exercise was the sole intervention...
Zebrafish are an attractive model organism for toxicology; however, an important consideration in... more Zebrafish are an attractive model organism for toxicology; however, an important consideration in translating between species is xenobiotic metabolism/bioactivation. CYP2E1 metabolizes small hydrophobic molecules, e.g. ethanol, cigarette smoke, and diesel exhaust components. CYP2E1 is thought to only be conserved in mammals, but recent reports identified homologous zebrafish cytochrome P450s. Herein, ex vivo biochemical measurements show that unlike mammals, zebrafish possess a low-affinity 4-nitrophenol hydroxylase (Km ∼0.6 mM) in hepatic microsomes and mitochondria that is inducible only 1.5- to 2-fold by ethanol and is insensitive to 4-methylpyrazole inhibition. In closing, we suggest creating improved models to study CYP2E1 in zebrafish.
International journal of hygiene and environmental health, Jan 10, 2017
Household air pollution is a major contributor to death and disability worldwide. Over 95% of rur... more Household air pollution is a major contributor to death and disability worldwide. Over 95% of rural Guatemalan households use woodstoves for cooking or heating. Woodsmoke contains carcinogenic or fetotoxic polycyclic aromatic hydrocarbons (PAHs) and volatile organic compounds (VOCs). Increased PAHs and VOCs have been shown to increase levels of oxidative stress. We examined PAH and VOC exposures among recently pregnant rural Guatemalan women exposed to woodsmoke and compared exposures to levels seen occupationally or among smokers. Urine was collected from 23 women who were 3 months post-partum three times over 72h: morning (fasting), after lunch, and following dinner or use of wood-fired traditional sauna baths (samples=68). Creatinine-adjusted urinary concentrations of metabolites of four PAHs and eight VOCs were analyzed by liquid chromatography-mass spectrometry. Creatinine-adjusted urinary biomarkers of oxidative stress, 8-isoprostane and 8-OHdG, were analyzed using enzyme-link...
The C. elegans biological responses to metal-based nanoparticles are reviewed. A cross-disciplina... more The C. elegans biological responses to metal-based nanoparticles are reviewed. A cross-disciplinary workflow for nanoparticles screening in vivo is proposed.
Current protocols in toxicology / editorial board, Mahin D. Maines (editor-in-chief) ... [et al.], 2016
Mitochondria are a target of many drugs and environmental toxicants; however, how toxicant-induce... more Mitochondria are a target of many drugs and environmental toxicants; however, how toxicant-induced mitochondrial dysfunction contributes to the progression of human disease remains poorly understood. To address this issue, in vivo assays capable of rapidly assessing mitochondrial function need to be developed. Here, using the model organism Caenorhabditis elegans, we describe how to rapidly assess the in vivo role of the electron transport chain, glycolysis, or fatty acid oxidation in energy metabolism following toxicant exposure, using a luciferase-expressing ATP reporter strain. Alterations in mitochondrial function subsequent to toxicant exposure are detected by depleting steady-state ATP levels with inhibitors of the mitochondrial electron transport chain, glycolysis, or fatty acid oxidation. Differential changes in ATP following short-term inhibitor exposure indicate toxicant-induced alterations at the site of inhibition. Because a microplate reader is the only major piece of e...
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