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Ricker K, Cheng V, Hsieh CJ, Tsai FC, Osborne G, Li K, Yilmazer-Musa M, Sandy MS, Cogliano VJ, Schmitz R, Sun M. Application of the Key Characteristics of Carcinogens to Bisphenol A. Int J Toxicol 2024:10915818231225161. [PMID: 38204208 DOI: 10.1177/10915818231225161] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/12/2024]
Abstract
The ten key characteristics (KCs) of carcinogens are based on characteristics of known human carcinogens and encompass many types of endpoints. We propose that an objective review of the large amount of cancer mechanistic evidence for the chemical bisphenol A (BPA) can be achieved through use of these KCs. A search on metabolic and mechanistic data relevant to the carcinogenicity of BPA was conducted and web-based software tools were used to screen and organize the results. We applied the KCs to systematically identify, organize, and summarize mechanistic information for BPA, and to bring relevant carcinogenic mechanisms into focus. For some KCs with very large data sets, we utilized reviews focused on specific endpoints. Over 3000 studies for BPA from various data streams (exposed humans, animals, in vitro and cell-free systems) were identified. Mechanistic data relevant to each of the ten KCs were identified, with receptor-mediated effects, epigenetic alterations, oxidative stress, and cell proliferation being especially data rich. Reactive and bioactive metabolites are also associated with a number of KCs. This review demonstrates how the KCs can be applied to evaluate mechanistic data, especially for data-rich chemicals. While individual entities may have different approaches for the incorporation of mechanistic data in cancer hazard identification, the KCs provide a practical framework for conducting an objective examination of the available mechanistic data without a priori assumptions on mode of action. This analysis of the mechanistic data available for BPA suggests multiple and inter-connected mechanisms through which this chemical can act.
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Affiliation(s)
- Karin Ricker
- Office of Environmental Health Hazard Assessment, California Environmental Protection Agency, Oakland, CA, USA
| | - Vanessa Cheng
- Office of Environmental Health Hazard Assessment, California Environmental Protection Agency, Oakland, CA, USA
| | - Chingyi Jennifer Hsieh
- Office of Environmental Health Hazard Assessment, California Environmental Protection Agency, Sacramento, CA, USA
| | - Feng C Tsai
- Office of Environmental Health Hazard Assessment, California Environmental Protection Agency, Oakland, CA, USA
| | - Gwendolyn Osborne
- Office of Environmental Health Hazard Assessment, California Environmental Protection Agency, Oakland, CA, USA
| | - Kate Li
- Office of Environmental Health Hazard Assessment, California Environmental Protection Agency, Oakland, CA, USA
| | - Meltem Yilmazer-Musa
- Office of Environmental Health Hazard Assessment, California Environmental Protection Agency, Oakland, CA, USA
| | - Martha S Sandy
- Office of Environmental Health Hazard Assessment, California Environmental Protection Agency, Oakland, CA, USA
| | - Vincent J Cogliano
- Office of Environmental Health Hazard Assessment, California Environmental Protection Agency, Oakland, CA, USA
| | - Rose Schmitz
- Office of Environmental Health Hazard Assessment, California Environmental Protection Agency, Oakland, CA, USA
| | - Meng Sun
- Office of Environmental Health Hazard Assessment, California Environmental Protection Agency, Sacramento, CA, USA
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Campbell MA, Iyer P, Kaufman F, Kim A, Moran F, Niknam Y, Wu L, Sandy MS, Zeise L. Animal evidence considered in determination of cannabis smoke and Δ 9 -tetrahydrocannabinol as causing reproductive toxicity (developmental endpoint); Part I. somatic development. Birth Defects Res 2022; 114:1143-1154. [PMID: 36177831 DOI: 10.1002/bdr2.2099] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/31/2022] [Revised: 09/09/2022] [Accepted: 09/12/2022] [Indexed: 11/06/2022]
Abstract
OBJECTIVES On December 11, 2019, California's Developmental and Reproductive Toxicant Identification Committee (DARTIC) met to consider the addition of cannabis smoke and Δ9 -THC to the Proposition 65 list as causing reproductive toxicity (developmental endpoint). As the lead state agency for implementing Proposition 65, the Office of Environmental Health Hazard Assessment (OEHHA) reviewed and summarized the relevant scientific literature in the form of a hazard identification document (HID). Here we provide reviews based on the HID: shortened, revised, and reformatted for a larger audience. METHODS While the HID included both human and animal data, this set of three reviews will highlight the animal-derived data pertaining to somatic development (Part I), neurodevelopmental effects (Part II), and proposed neurodevelopmental mechanisms of action (Part III). RESULTS Endogenous cannabinoids (eCBs) and their receptors serve many critical functions in normal development. Δ9 -THC can interfere with these functions. Mechanistic studies employed techniques including: blocking Δ9 -THC binding to endocannabinoid (EC) receptors, inhibiting Δ9 -THC metabolism, and/or using animals expressing knockout mutations of EC receptors. Apical somatic effects of cannabis smoke or Δ9 -THC reported in whole animal studies included decreases in offspring viability and growth. Mechanistic studies discussed in Part I focused on Δ9 -THC effects on early embryos and implantation, immune development, and bone growth. CONCLUSIONS In reaching its decision to list cannabis and Δ9 -THC as a developmental toxicant under California's Proposition 65, the DARTIC considered biological plausibility and the consistency of mechanistic information with effects reported in human and whole animal studies.
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Affiliation(s)
- Marlissa A Campbell
- Office of Environmental Health Hazard Assessment, California Environmental Protection Agency, Sacramento, California, USA
| | - Poorni Iyer
- Office of Environmental Health Hazard Assessment, California Environmental Protection Agency, Sacramento, California, USA
| | - Farla Kaufman
- Office of Environmental Health Hazard Assessment, California Environmental Protection Agency, Sacramento, California, USA
| | - Allegra Kim
- Office of Environmental Health Hazard Assessment, California Environmental Protection Agency, Sacramento, California, USA
| | - Francisco Moran
- Office of Environmental Health Hazard Assessment, California Environmental Protection Agency, Sacramento, California, USA
| | - Yassaman Niknam
- Office of Environmental Health Hazard Assessment, California Environmental Protection Agency, Sacramento, California, USA
| | - Lily Wu
- Office of Environmental Health Hazard Assessment, California Environmental Protection Agency, Sacramento, California, USA
| | - Martha S Sandy
- Office of Environmental Health Hazard Assessment, California Environmental Protection Agency, Sacramento, California, USA
| | - Lauren Zeise
- Office of Environmental Health Hazard Assessment, California Environmental Protection Agency, Sacramento, California, USA
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Niknam Y, Iyer P, Campbell MA, Moran F, Sandy MS, Zeise L. Animal evidence considered in determination of cannabis smoke and Δ 9 -tetrahydrocannabinol as causing reproductive toxicity (developmental endpoint): Part III. Proposed neurodevelopmental mechanisms of action. Birth Defects Res 2022; 114:1169-1185. [PMID: 36125082 DOI: 10.1002/bdr2.2088] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/01/2022] [Revised: 08/16/2022] [Accepted: 08/28/2022] [Indexed: 11/09/2022]
Abstract
This review summarizes the most common potential pathways of neurodevelopmental toxicity due to perinatal exposure to Δ9 -tetrahydrocannabinol (Δ9 -THC) that lead to behavioral and other adverse outcomes (AOs). This is Part III in a set of reviews highlighting the animal-derived data considered by California's Developmental and Reproductive Toxicant Identification Committee (DARTIC) in 2019. The Hazard Identification Document (HID) provided to the DARTIC included a summary of human, whole animal, and mechanistic data on the neurodevelopmental toxicity of cannabis smoke and Δ9 -THC. The literature search for mechanistic data has been updated through 2020. We focus on mechanistic pathways relating to behavioral and other neurodevelopmental outcomes of perinatal exposure to Δ9 -THC. The endocannabinoid system (EC system) plays a crucial role in many processes involved in neurodevelopment and exposure to Δ9 -THC can alter these processes. Whole animal studies report changes in cognitive ability, behavior, and motor function after prenatal exposure to Δ9 -THC. Findings from mechanistic studies add to this evidence and further provide information regarding the pathways leading to these outcomes. Neuromechanistic studies can bridge the gaps between molecular initiating events and apical neurodevelopmental endpoints caused by a chemical. They offer insight into potential alterations in the same pathways by other chemicals that can also result in AOs. Studies of cannabinoid receptor agonist-induced molecular alterations and provide deep biological plausibility at the mechanistic level for the cognitive, behavioral, and motor impairments observed in animal studies after perinatal exposure to Δ9 -THC.
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Affiliation(s)
- Yassaman Niknam
- Office of Environmental Health Hazard Assessment (OEHHA)/Reproductive and Cancer Hazard Assessment Branch (RCHAB), California Environmental Protection Agency, Sacramento, California, USA
| | - Poorni Iyer
- Office of Environmental Health Hazard Assessment (OEHHA)/Reproductive and Cancer Hazard Assessment Branch (RCHAB), California Environmental Protection Agency, Sacramento, California, USA
| | - Marlissa A Campbell
- Office of Environmental Health Hazard Assessment (OEHHA)/Reproductive and Cancer Hazard Assessment Branch (RCHAB), California Environmental Protection Agency, Sacramento, California, USA
| | - Francisco Moran
- Office of Environmental Health Hazard Assessment (OEHHA)/Reproductive and Cancer Hazard Assessment Branch (RCHAB), California Environmental Protection Agency, Sacramento, California, USA
| | - Martha S Sandy
- Office of Environmental Health Hazard Assessment (OEHHA)/Reproductive and Cancer Hazard Assessment Branch (RCHAB), California Environmental Protection Agency, Sacramento, California, USA
| | - Lauren Zeise
- Office of Environmental Health Hazard Assessment (OEHHA)/Reproductive and Cancer Hazard Assessment Branch (RCHAB), California Environmental Protection Agency, Sacramento, California, USA
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Li K, Ricker K, Tsai FC, Hsieh CJ, Osborne G, Sun M, Marder ME, Elmore S, Schmitz R, Sandy MS. Estimated Cancer Risks Associated with Nitrosamine Contamination in Commonly Used Medications. Int J Environ Res Public Health 2021; 18:9465. [PMID: 34574388 PMCID: PMC8467924 DOI: 10.3390/ijerph18189465] [Citation(s) in RCA: 25] [Impact Index Per Article: 8.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 07/31/2021] [Revised: 09/02/2021] [Accepted: 09/04/2021] [Indexed: 12/31/2022]
Abstract
Many nitrosamines are potent carcinogens, with more than 30 listed under California's Proposition 65. Recently, nitrosamine contamination of commonly used drugs for treatment of hypertension, heartburn, and type 2 diabetes has prompted numerous Food and Drug Administration (FDA) recalls in the US. These contaminants include the carcinogens NDMA (N-nitrosodimethylamine) and NDEA (N-nitrosodiethylamine) and the animal tumorigen NMBA (N-nitroso-N-methyl-4-aminobutyric acid). NMBA and NDEA are metabolically and/or structurally related to NDMA, an N-nitrosomethyl-n-alkylamine (NMA), and 12 other carcinogenic NMAs. These nitrosamines exhibit common genotoxic and tumorigenic activities, with shared target tumor sites amongst chemicals and within a given laboratory animal species. We use the drug valsartan as a case study to estimate the additional cancer risks associated with NDMA and NDEA contamination, based on nitrosamine levels reported by the US FDA, cancer potencies developed by California's Proposition 65 program and the US Environmental Protection Agency (EPA), and specific exposure scenarios. These estimates suggest that nitrosamine contamination in drugs that are used long-term can increase cancer risks and pose a serious concern to public health.
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Affiliation(s)
- Kate Li
- Office of Environmental Health Hazard Assessment (OEHHA), California Environmental Protection Agency, Oakland, CA 94612, USA; (K.L.); (K.R.); (F.C.T.); (G.O.); (S.E.)
| | - Karin Ricker
- Office of Environmental Health Hazard Assessment (OEHHA), California Environmental Protection Agency, Oakland, CA 94612, USA; (K.L.); (K.R.); (F.C.T.); (G.O.); (S.E.)
| | - Feng C. Tsai
- Office of Environmental Health Hazard Assessment (OEHHA), California Environmental Protection Agency, Oakland, CA 94612, USA; (K.L.); (K.R.); (F.C.T.); (G.O.); (S.E.)
| | - ChingYi J. Hsieh
- Office of Environmental Health Hazard Assessment (OEHHA), California Environmental Protection Agency, Sacramento, CA 95812, USA; (C.J.H.); (M.S.); (M.E.M.); (R.S.)
| | - Gwendolyn Osborne
- Office of Environmental Health Hazard Assessment (OEHHA), California Environmental Protection Agency, Oakland, CA 94612, USA; (K.L.); (K.R.); (F.C.T.); (G.O.); (S.E.)
| | - Meng Sun
- Office of Environmental Health Hazard Assessment (OEHHA), California Environmental Protection Agency, Sacramento, CA 95812, USA; (C.J.H.); (M.S.); (M.E.M.); (R.S.)
| | - M. Elizabeth Marder
- Office of Environmental Health Hazard Assessment (OEHHA), California Environmental Protection Agency, Sacramento, CA 95812, USA; (C.J.H.); (M.S.); (M.E.M.); (R.S.)
| | - Sarah Elmore
- Office of Environmental Health Hazard Assessment (OEHHA), California Environmental Protection Agency, Oakland, CA 94612, USA; (K.L.); (K.R.); (F.C.T.); (G.O.); (S.E.)
| | - Rose Schmitz
- Office of Environmental Health Hazard Assessment (OEHHA), California Environmental Protection Agency, Sacramento, CA 95812, USA; (C.J.H.); (M.S.); (M.E.M.); (R.S.)
| | - Martha S. Sandy
- Office of Environmental Health Hazard Assessment (OEHHA), California Environmental Protection Agency, Oakland, CA 94612, USA; (K.L.); (K.R.); (F.C.T.); (G.O.); (S.E.)
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Schildroth S, Osborne G, Smith AR, Yip C, Collins C, Smith MT, Sandy MS, Zhang L. Occupational exposure to antimony trioxide: a risk assessment. Occup Environ Med 2020; 78:oemed-2020-106980. [PMID: 33243757 PMCID: PMC8149478 DOI: 10.1136/oemed-2020-106980] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/11/2020] [Revised: 10/20/2020] [Accepted: 11/02/2020] [Indexed: 01/21/2023]
Abstract
OBJECTIVES The US National Toxicology Program (NTP) recently recommended in its Report on Carcinogens Monograph for Antimony Trioxide that antimony trioxide be listed as 'reasonably anticipated to be a human carcinogen' based on sufficient evidence of carcinogenicity in experimental animals and supporting evidence from mechanistic studies. Our goal was to estimate the possible human cancer risk from occupational exposure to antimony trioxide. METHODS We selected data from 2-year inhalation studies in male and female mice conducted by the NTP and performed cancer dose-response analyses using cancer models and benchmark dose methods developed by the US Environmental Protection Agency. In these analyses, we generated benchmark doses and cancer slope factors for antimony trioxide, and then estimated human cancer risk under various exposure scenarios. Typical and worst-case inhalation scenarios in multiple occupational settings were used in risk estimation. RESULTS In typical case scenarios, the occupational cancer risk from antimony trioxide was estimated to be 0.025 (25 in 1000) for persons working with flame retardants in plastics and textiles for 40 years. Under worst-case scenarios, the occupational cancer risk was estimated to be 0.11 (110 in 1000) for persons working with flame retardants in plastics and textiles. At the current Occupational Safety and Health Administration Permissible Exposure Limit, the cancer risk for occupational inhalation exposure of antimony trioxide was estimated to be 0.096 (96 in 1000). CONCLUSION The risk estimates calculated in this study suggest that exposure to antimony trioxide at levels present in certain occupational settings results in a large increase in the risk of developing cancer.
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Affiliation(s)
- Samantha Schildroth
- Division of Environmental Health Sciences, University of California Berkeley School of Public Health, Berkeley, California, USA
- Department of Environmental Health, Boston University School of Public Health, Boston, Massachusetts, USA
| | - Gwendolyn Osborne
- Office of Environmental Health Hazard Assessment, Oakland, California, USA
| | - Anna R Smith
- Division of Environmental Health Sciences, University of California Berkeley School of Public Health, Berkeley, California, USA
| | - Caryn Yip
- Division of Environmental Health Sciences, University of California Berkeley School of Public Health, Berkeley, California, USA
- Department of Occupational and Environmental Health, University of Iowa College of Public Health, Iowa City, Iowa, USA
| | - Caroline Collins
- Division of Environmental Health Sciences, University of California Berkeley School of Public Health, Berkeley, California, USA
- California Department of Public Health, Richmond, California, USA
| | - Martyn T Smith
- Division of Environmental Health Sciences, University of California Berkeley School of Public Health, Berkeley, California, USA
| | - Martha S Sandy
- Office of Environmental Health Hazard Assessment, Oakland, California, USA
| | - Luoping Zhang
- Division of Environmental Health Sciences, University of California Berkeley School of Public Health, Berkeley, California, USA
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Smith MT, Guyton KZ, Kleinstreuer N, Borrel A, Cardenas A, Chiu WA, Felsher DW, Gibbons CF, Goodson WH, Houck KA, Kane AB, La Merrill MA, Lebrec H, Lowe L, McHale CM, Minocherhomji S, Rieswijk L, Sandy MS, Sone H, Wang A, Zhang L, Zeise L, Fielden M. The Key Characteristics of Carcinogens: Relationship to the Hallmarks of Cancer, Relevant Biomarkers, and Assays to Measure Them. Cancer Epidemiol Biomarkers Prev 2020; 29:1887-1903. [PMID: 32152214 PMCID: PMC7483401 DOI: 10.1158/1055-9965.epi-19-1346] [Citation(s) in RCA: 45] [Impact Index Per Article: 11.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/01/2019] [Revised: 01/15/2020] [Accepted: 03/04/2020] [Indexed: 12/21/2022] Open
Abstract
The key characteristics (KC) of human carcinogens provide a uniform approach to evaluating mechanistic evidence in cancer hazard identification. Refinements to the approach were requested by organizations and individuals applying the KCs. We assembled an expert committee with knowledge of carcinogenesis and experience in applying the KCs in cancer hazard identification. We leveraged this expertise and examined the literature to more clearly describe each KC, identify current and emerging assays and in vivo biomarkers that can be used to measure them, and make recommendations for future assay development. We found that the KCs are clearly distinct from the Hallmarks of Cancer, that interrelationships among the KCs can be leveraged to strengthen the KC approach (and an understanding of environmental carcinogenesis), and that the KC approach is applicable to the systematic evaluation of a broad range of potential cancer hazards in vivo and in vitro We identified gaps in coverage of the KCs by current assays. Future efforts should expand the breadth, specificity, and sensitivity of validated assays and biomarkers that can measure the 10 KCs. Refinement of the KC approach will enhance and accelerate carcinogen identification, a first step in cancer prevention.See all articles in this CEBP Focus section, "Environmental Carcinogenesis: Pathways to Prevention."
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Affiliation(s)
- Martyn T Smith
- Division of Environmental Health Sciences, School of Public Health, University of California Berkeley, Berkeley, California.
| | - Kathryn Z Guyton
- Monographs Programme, International Agency for Research on Cancer, Lyon, France
| | - Nicole Kleinstreuer
- Division of Intramural Research, Biostatistics and Computational Biology Branch, National Institute of Environmental Health Sciences (NIEHS), Research Triangle Park, North Carolina
- National Toxicology Program Interagency Center for the Evaluation of Alternative Toxicological Methods, National Institute of Environmental Health Sciences, Research Triangle Park, North Carolina
| | - Alexandre Borrel
- Division of Intramural Research, Biostatistics and Computational Biology Branch, National Institute of Environmental Health Sciences (NIEHS), Research Triangle Park, North Carolina
| | - Andres Cardenas
- Division of Environmental Health Sciences, School of Public Health, University of California Berkeley, Berkeley, California
| | - Weihsueh A Chiu
- Veterinary Integrative Biosciences, Texas A&M University, College Station, Texas
| | - Dean W Felsher
- Division of Oncology, Departments of Medicine and Pathology, Stanford University School of Medicine, Stanford, California
| | - Catherine F Gibbons
- Office of Research and Development, US Environmental Protection Agency, Washington, D.C
| | - William H Goodson
- California Pacific Medical Center Research Institute, San Francisco, California
| | - Keith A Houck
- Office of Research and Development, US Environmental Protection Agency, Research Triangle Park, North Carolina
| | - Agnes B Kane
- Department of Pathology and Laboratory Medicine, Alpert Medical School, Brown University, Providence, Rhode Island
| | - Michele A La Merrill
- Department of Environmental Toxicology, University of California, Davis, California
| | - Herve Lebrec
- Comparative Biology & Safety Sciences, Amgen Research, Amgen Inc., Thousand Oaks, California
| | - Leroy Lowe
- Getting to Know Cancer, Truro, Nova Scotia, Canada
| | - Cliona M McHale
- Division of Environmental Health Sciences, School of Public Health, University of California Berkeley, Berkeley, California
| | - Sheroy Minocherhomji
- Comparative Biology & Safety Sciences, Amgen Research, Amgen Inc., Thousand Oaks, California
| | - Linda Rieswijk
- Division of Environmental Health Sciences, School of Public Health, University of California Berkeley, Berkeley, California
- Institute of Data Science, Maastricht University, Maastricht, the Netherlands
| | - Martha S Sandy
- Office of Environmental Health Hazard Assessment, California Environmental Protection Agency, Oakland, California
| | - Hideko Sone
- Yokohama University of Pharmacy and National Institute for Environmental Studies, Tsukuba Ibaraki, Japan
| | - Amy Wang
- Office of the Report on Carcinogens, Division of National Toxicology Program, The National Institute of Environmental Health Sciences, Research Triangle Park, North Carolina
| | - Luoping Zhang
- Division of Environmental Health Sciences, School of Public Health, University of California Berkeley, Berkeley, California
| | - Lauren Zeise
- Office of Environmental Health Hazard Assessment, California Environmental Protection Agency, Oakland, California
| | - Mark Fielden
- Expansion Therapeutics Inc, San Diego, California
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Smith A, Kaufman F, Sandy MS, Cardenas A. Cannabis Exposure During Critical Windows of Development: Epigenetic and Molecular Pathways Implicated in Neuropsychiatric Disease. Curr Environ Health Rep 2020; 7:325-342. [PMID: 32441004 PMCID: PMC7458902 DOI: 10.1007/s40572-020-00275-4] [Citation(s) in RCA: 34] [Impact Index Per Article: 8.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/27/2022]
Abstract
PURPOSE OF REVIEW Cannabis exposure during critical windows of development may have intergenerational physiological consequences disrupting epigenetic programming and marks. This review examines the literature relating to pre-gestational and prenatal cannabinoid exposure and its effect on genes and molecular pathways related to the development of psychiatric disease. RECENT FINDINGS Developmental cannabis exposure alters epigenetic processes with functional gene consequences. These include potentially heritable alterations in genes and molecular pathways critical for brain development and associated with autism spectrum disorder (ASD), attention deficit hyperactivity disorder (ADHD), schizophrenia, addiction, and other psychiatric diseases. Cannabis consumption and mental health illness in adolescents and young adults are increasing in the United States (U.S.), and recent studies suggest that cannabis consumption during critical periods of brain development could contribute to mental health illness through epigenetic mechanisms. These findings warrant future studies and consideration by regulators and health communicators.
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Affiliation(s)
- Anna Smith
- Division of Environmental Health Sciences, School of Public Health, University of California, Berkeley, CA, USA
- Center for Computational Biology, University of California, Berkeley, CA, USA
| | - Farla Kaufman
- Office of Environmental Health Hazard Assessment, California Environmental Protection Agency, Sacramento, CA, USA
| | - Martha S Sandy
- Office of Environmental Health Hazard Assessment, California Environmental Protection Agency, Sacramento, CA, USA
| | - Andres Cardenas
- Division of Environmental Health Sciences, School of Public Health, University of California, Berkeley, CA, USA.
- Center for Computational Biology, University of California, Berkeley, CA, USA.
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Hsieh CJ, Sun M, Osborne G, Ricker K, Tsai FC, Li K, Tomar R, Phuong J, Schmitz R, Sandy MS. Response to “Comment on Coumarin Hazard Identification”. Int J Toxicol 2020; 39:493-494. [DOI: 10.1177/1091581820945412] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022]
Affiliation(s)
- ChingYi Jennifer Hsieh
- Office of Environmental Health Hazard Assessment, CalEPA, Sacramento and Oakland, CA, USA
| | - Meng Sun
- Office of Environmental Health Hazard Assessment, CalEPA, Sacramento and Oakland, CA, USA
| | - Gwendolyn Osborne
- Office of Environmental Health Hazard Assessment, CalEPA, Sacramento and Oakland, CA, USA
| | - Karin Ricker
- Office of Environmental Health Hazard Assessment, CalEPA, Sacramento and Oakland, CA, USA
| | - Feng C. Tsai
- Office of Environmental Health Hazard Assessment, CalEPA, Sacramento and Oakland, CA, USA
| | - Kate Li
- Office of Environmental Health Hazard Assessment, CalEPA, Sacramento and Oakland, CA, USA
| | - Rajpal Tomar
- Office of Environmental Health Hazard Assessment, CalEPA, Sacramento and Oakland, CA, USA
- Retired
| | - Jimmy Phuong
- Department of Biomedical and Health Informatics, University of Washington, Seattle, WA, USA
| | - Rose Schmitz
- Office of Environmental Health Hazard Assessment, CalEPA, Sacramento and Oakland, CA, USA
| | - Martha S. Sandy
- Office of Environmental Health Hazard Assessment, CalEPA, Sacramento and Oakland, CA, USA
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Hsieh CJ, Sun M, Osborne G, Ricker K, Tsai FC, Li K, Tomar R, Phuong J, Schmitz R, Sandy MS. Cancer Hazard Identification Integrating Human Variability: The Case of Coumarin. Int J Toxicol 2019; 38:501-552. [PMID: 31845612 DOI: 10.1177/1091581819884544] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/28/2022]
Abstract
Coumarin is a naturally occurring sweet-smelling benzopyrone that may be extracted from plants or synthesized for commercial uses. Its uses include as a flavoring agent, fragrance enhancer, and odor-masking additive. We reviewed and evaluated the scientific evidence on the carcinogenicity of coumarin, integrating information from carcinogenicity studies in animals with mechanistic and other relevant data, including data from toxicogenomic, genotoxicity, and metabolism studies, and studies of human variability of a key enzyme, CYP2A6. Increases in tumors were observed in multiple studies in rats and mice in multiple tissues. Our functional pathway analysis identified several common cancer-related biological processes/pathways affected by coumarin in rat liver following in vivo exposure and in human primary hepatocytes exposed in vitro. When coumarin 7-hydroxylation by CYP2A6 is compromised, this can lead to a shift in metabolism to the 3,4-epoxidation pathway and increased generation of electrophilic metabolites. Mechanistic data align with 3 key characteristics of carcinogens, namely formation of electrophilic metabolites, genotoxicity, and induction of oxidative stress. Considerations of metabolism, human variability in CYP2A6 activity, and coumarin hepatotoxicity in susceptible individuals provide additional support for carcinogenicity concern. Our analysis illustrates the importance of integrating information on human variability in the cancer hazard identification process.
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Affiliation(s)
- ChingYi Jennifer Hsieh
- Office of Environmental Health Hazard Assessment, CalEPA, Sacramento and Oakland, CA, USA
| | - Meng Sun
- Office of Environmental Health Hazard Assessment, CalEPA, Sacramento and Oakland, CA, USA
| | - Gwendolyn Osborne
- Office of Environmental Health Hazard Assessment, CalEPA, Sacramento and Oakland, CA, USA
| | - Karin Ricker
- Office of Environmental Health Hazard Assessment, CalEPA, Sacramento and Oakland, CA, USA
| | - Feng C Tsai
- Office of Environmental Health Hazard Assessment, CalEPA, Sacramento and Oakland, CA, USA
| | - Kate Li
- Office of Environmental Health Hazard Assessment, CalEPA, Sacramento and Oakland, CA, USA
| | - Rajpal Tomar
- Office of Environmental Health Hazard Assessment, CalEPA, Sacramento and Oakland, CA, USA.,Retired
| | - Jimmy Phuong
- Department of Biomedical and Health Informatics, University of Washington, Seattle, WA, USA
| | - Rose Schmitz
- Office of Environmental Health Hazard Assessment, CalEPA, Sacramento and Oakland, CA, USA
| | - Martha S Sandy
- Office of Environmental Health Hazard Assessment, CalEPA, Sacramento and Oakland, CA, USA
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McHale CM, Osborne G, Morello-Frosch R, Salmon AG, Sandy MS, Solomon G, Zhang L, Smith MT, Zeise L. Assessing health risks from multiple environmental stressors: Moving from G×E to I×E. Mutat Res Rev Mutat Res 2017; 775:11-20. [PMID: 29555026 DOI: 10.1016/j.mrrev.2017.11.003] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/24/2017] [Revised: 11/21/2017] [Accepted: 11/22/2017] [Indexed: 02/06/2023]
Abstract
Research on disease causation often attempts to isolate the effects of individual factors, including individual genes or environmental factors. This reductionist approach has generated many discoveries, but misses important interactive and cumulative effects that may help explain the broad range of variability in disease occurrence observed across studies and individuals. A disease rarely results from a single factor, and instead results from a broader combination of factors, characterized here as intrinsic (I) and extrinsic (E) factors. Intrinsic vulnerability or resilience emanates from a variety of both fixed and shifting biological factors including genetic traits, while extrinsic factors comprise all biologically-relevant external stressors encountered across the lifespan. The I×E concept incorporates the multi-factorial and dynamic nature of health and disease and provides a unified, conceptual basis for integrating results from multiple areas of research, including genomics, G×E, developmental origins of health and disease, and the exposome. We describe the utility of the I×E concept to better understand and characterize the cumulative impact of multiple extrinsic and intrinsic factors on individual and population health. New research methods increasingly facilitate the measurement of multifactorial and interactive effects in epidemiological and toxicological studies. Tiered or indicator-based approaches can guide the selection of potentially relevant I and E factors for study and quantification, and exposomics methods may eventually produce results that can be used to generate a response function over the life course. Quantitative data on I×E interactive effects should generate a better understanding of the variability in human response to environmental factors. The proposed I×E concept highlights the role for broader study design in order to identify extrinsic and intrinsic factors amenable to interventions at the individual and population levels in order to enhance resilience, reduce vulnerability and improve health.
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Affiliation(s)
- Cliona M McHale
- Superfund Research Center, School of Public Health, University of California, Berkeley, CA 94720, USA.
| | - Gwendolyn Osborne
- Office of Environmental Health Hazard Assessment, California Environmental Protection Agency, Oakland, CA 94612, USA
| | - Rachel Morello-Frosch
- Superfund Research Center, School of Public Health, University of California, Berkeley, CA 94720, USA; Department of Environmental Science, Policy and Management, University of California, Berkeley, CA 94720, USA
| | - Andrew G Salmon
- Office of Environmental Health Hazard Assessment, California Environmental Protection Agency, Oakland, CA 94612, USA
| | - Martha S Sandy
- Office of Environmental Health Hazard Assessment, California Environmental Protection Agency, Oakland, CA 94612, USA
| | - Gina Solomon
- California Environmental Protection Agency, Sacramento, CA 95814, USA
| | - Luoping Zhang
- Superfund Research Center, School of Public Health, University of California, Berkeley, CA 94720, USA
| | - Martyn T Smith
- Superfund Research Center, School of Public Health, University of California, Berkeley, CA 94720, USA
| | - Lauren Zeise
- Office of Environmental Health Hazard Assessment, California Environmental Protection Agency, Oakland, CA 94612, USA
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11
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Guyton KZ, Kyle AD, Aubrecht J, Cogliano VJ, Eastmond DA, Jackson M, Keshava N, Sandy MS, Sonawane B, Zhang L, Waters MD, Smith MT. Improving prediction of chemical carcinogenicity by considering multiple mechanisms and applying toxicogenomic approaches. Mutat Res 2008; 681:230-240. [PMID: 19010444 DOI: 10.1016/j.mrrev.2008.10.001] [Citation(s) in RCA: 59] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/17/2008] [Revised: 10/10/2008] [Accepted: 10/14/2008] [Indexed: 11/24/2022]
Abstract
While scientific knowledge of the potential health significance of chemical exposures has grown, experimental methods for predicting the carcinogenicity of environmental agents have not been substantially updated in the last two decades. Current methodologies focus first on identifying genotoxicants under the premise that agents capable of directly damaging DNA are most likely to be carcinogenic to humans. Emphasis on the distinction between genotoxic and non-genotoxic carcinogens is also motivated by assumed implications for the dose-response curve; it is purported that genotoxicants would lack a threshold in the low dose region, in contrast to non-genotoxic agents. However, for the vast majority of carcinogens, little if any empirical data exist to clarify the nature of the cancer dose-response relationship at low doses in the exposed human population. Recent advances in scientific understanding of cancer biology-and increased appreciation of the multiple impacts of carcinogens on this disease process-support the view that environmental chemicals can act through multiple toxicity pathways, modes and/or mechanisms of action to induce cancer and other adverse health outcomes. Moreover, the relationship between dose and a particular outcome in an individual could take multiple forms depending on genetic background, target tissue, internal dose and other factors besides mechanisms or modes of action; inter-individual variability and susceptibility in response are, in turn, key determinants of the population dose-response curve. New bioanalytical approaches (e.g., transcriptomics, proteomics, and metabolomics) applied in human, animal and in vitro studies could better characterize a wider array of hazard traits and improve the ability to predict the potential carcinogenicity of chemicals.
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Affiliation(s)
- Kathryn Z Guyton
- National Center for Environmental Assessment, Office of Research and Development, US Environmental Protection Agency, 1200 Pennsylvania Avenue, NW Washington, DC 20460, USA.
| | - Amy D Kyle
- School of Public Health, University of California, Berkeley, CA 94720, USA
| | - Jiri Aubrecht
- Drug Safety Research and Development, Pfizer Global Research and Development, Groton, CT 06340, USA
| | | | - David A Eastmond
- Environmental Toxicology Graduate Program and Department of Cell Biology & Neuroscience, University of California, Riverside, CA 92521, USA
| | - Marc Jackson
- Integrated Laboratory Systems (ILS), Inc., P.O. Box 13501, Research Triangle Park, NC 27709, USA
| | - Nagalakshmi Keshava
- National Center for Environmental Assessment, Office of Research and Development, US Environmental Protection Agency, 1200 Pennsylvania Avenue, NW Washington, DC 20460, USA
| | - Martha S Sandy
- California Environmental Protection Agency, Office of Environmental Health Hazard Assessment, Oakland, CA 94612, USA
| | - Babasaheb Sonawane
- National Center for Environmental Assessment, Office of Research and Development, US Environmental Protection Agency, 1200 Pennsylvania Avenue, NW Washington, DC 20460, USA
| | - Luoping Zhang
- School of Public Health, University of California, Berkeley, CA 94720, USA
| | - Michael D Waters
- Integrated Laboratory Systems (ILS), Inc., P.O. Box 13501, Research Triangle Park, NC 27709, USA
| | - Martyn T Smith
- School of Public Health, University of California, Berkeley, CA 94720, USA
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13
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Abstract
In this study we assessed the two forms of monoamine oxidase (MAO) in the caudate, putamen, and substantia nigra of young (4-year-old), intermediate-aged (11-year-old), and aged (20-year-old) squirrel monkeys and in the striata of young (2-month-old) and older (10-month-old) C57Bl/6 mice. MAO A and B activities were determined by measuring the rate of oxidation of the specific substrates phenethylamine and serotonin. In squirrel monkey, the vast majority of MAO activity was MAO B with activity of this isoform 10 times greater than of MAO A, while in mice the activity of the two forms was approximately equivalent. Although mice demonstrated nearly twofold selective increases in striatal MAO B between 2 and 10 months of age, neither MAO B nor A showed statistically significant changes with age in squirrel monkeys. These results document the marked differences between nonhuman primates and rodents with respect to the relative activities and the effects of age on MAO A and B, and indicate that increased MAO is not an inevitable feature of aging.
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Affiliation(s)
- I Irwin
- Parkinson's Institute, Sunnyvale, CA 94089, USA
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14
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Abstract
Parkinson's disease (PD) is thought to develop as a result of interactions between genetic susceptibility factors and environmental exposures. One candidate gene is CYP2D6, which codes for the debrisoquine 4-hydroxylase cytochrome P450. Impairment of debrisoquine 4-hydroxylase activity has been associated with an increased risk of PD in patients with younger age at disease onset. Genotyping studies in patients with an older age at onset have reported modest increases in risk associated with the CYP2D6 B and A alleles; however, the risk for young-onset PD has not been adequately evaluated. We designed a case-control study to investigate the role of nonfunctional CYP2D6 allelic risk factors for young-onset PD in a sizable patient population and compared the distributions of CYP2D6 genotypes between young-onset ( < or = 51 years) PD patients (n = 108) and controls (n = 236). In contrast with the results from genotyping studies conducted among patients with an older age at onset, there were no significant differences in CYP2D6 allelic frequencies between young-onset PD cases and controls. The frequency of the B allele was slightly lower in the young-onset PD cases than in the controls (0.14 versus 0.20) (X2 = 2.66, p = 0.10). The presence of one or more B alleles was not associated with an increased risk of young-onset PD (odds ratio 0.58; 95% CI 0.33 to 1.00), nor was the presence of one or more nonfunctional alleles (i.e., A, B, D, and D2) (odds ratio 0.68; 95% CI 0.41 to 1.13). This study suggests that the young-onset PD population may differ from the older-onset population with respect to risk factors.
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Affiliation(s)
- M S Sandy
- Parkinson's Institute, Sunnyvale, CA, USA
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15
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Irwin I, DeLanney LE, McNeill T, Chan P, Forno LS, Murphy GM, Di Monte DA, Sandy MS, Langston JW. Aging and the nigrostriatal dopamine system: a non-human primate study. Neurodegeneration 1994; 3:251-65. [PMID: 7531106] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Subscribe] [Scholar Register] [Indexed: 01/25/2023]
Abstract
The present study examined neurochemical, morphological and functional markers of the nigrostriatal dopamine system in young, intermediate-aged and old squirrel monkeys. Striking reductions in motoric activity were observed with advancing age. significant age-related loss of dopamine occurred in the substantia nigra (70%) and the putamen (30%) but not in the caudate. There was a strong correlation between the reductions in motoric activity and the loss of putamen dopamine. However, nigrostriatal dopamine loss did not appear to be the consequence of age-related loss of dopaminergic nigral neurons since the number of tyrosine immunoreactive cells was not significantly different among the three age groups. These results suggest that the aging squirrel monkey demonstrates the age-related loss of nigrostriatal dopamine thought to occur in humans and identify this non-human primate as a useful model to further investigate the underlying mechanism(s) and functional consequences of age-related decline of the nigrostriatal dopamine system. In addition, the selective loss of dopamine in the putamen but not the caudate parallels the regional vulnerability observed in Parkinson's disease, an age-related neurodegenerative disorder, raising the possibility of a relationship between normal aging and the development of this disease. Finally, because the number of tyrosine hydroxylase (TH) positive cells remains constant with age, these results raise the possibility that therapeutic strategies aimed at increasing dopamine concentrations may benefit elderly individuals.
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Affiliation(s)
- I Irwin
- Parkinson's Institute, Sunnyvale, California 94089
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16
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Abstract
Six patients with progressive supranuclear palsy (PSP) and 12 age-matched disease-free subjects participated in this study designed to compare rates of ATP production by intact mitochondria from biopsied skeletal muscle. When pyruvate and malate were used as metabolic substrates, rates of ATP production were 0.184 +/- 0.025 mumol/min/U of citrate synthase (CS) activity (a mitochondrial marker) in control subjects and 0.131 +/- 0.051 mumol/min/U of CS in PSP patients. In the presence of succinate, rates of ATP formation were 0.137 +/- 0.02 mumol/min/U of CS in controls and 0.109 +/- 0.04 mumol/min/U of CS in patients. With N,N,N',N'-tetramethyl-p-phenylenediamine (TMPD) and ascorbate, rates were 0.034 +/- 0.008 mumol/min/U of CS in controls and 0.022 +/- 0.01 mumol/min/U of CS in PSP subjects. Differences between the control and PSP populations reached statistical significance with pyruvate/malate and TMPD/ascorbate. No differences in either muscle histopathology or histochemistry were found between patient and control subjects. Results of this study suggest that oxidative phosphorylation defects occur in muscle mitochondria from patients with PSP.
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17
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Abstract
An alteration within the mitochondrial DNA (mtDNA) has been hypothesized to underlie the deficiencies in mitochondrial complex I activity observed in the platelets, striatal muscle, and brain tissue of individuals with Parkinson's disease. Here we utilized the polymerase chain reaction (PCR) to analyze mtDNA obtained from the platelets of nonmedicated patients with early Parkinson's disease (n = 8) and aged-matched controls (n = 6) for the presence of deletion(s) or addition(s) equal to or greater than 50-100 base pairs. Initial attention was focused upon detecting a 4.977 kb deletion previously found in the brains of parkinsonian patients and some aged controls. Indeed, a large deletion of approximately 5.0 kb was observed in the platelet mtDNA from all parkinsonian individuals. However, this defect was also found in all age-matched controls as well as in a group of young healthy subjects (n = 5). In addition, we searched for the presence of smaller changes in platelet mtDNA from parkinsonian patients by PCR analysis of four mtDNA segments that code for seven of the complex I polypeptides. No large deletions or additions were detected within these four regions of mtDNA in any of the disease or age-matched control samples. We conclude that (a) a 4.977 kb deletion is apparently present in a subpopulation of platelet mtDNA from all individuals, and (b) no macrosequence alteration in mtDNA is likely to underlie the deficiency in complex I activity reported in platelet mitochondria from parkinsonian patients.
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Affiliation(s)
- M S Sandy
- California Parkinson's Foundation, San Jose 95128
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18
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Chiocca SM, Sandy MS, Cerutti PA. Genotypic analysis of N-ethyl-N-nitrosourea-induced mutations by Taq I restriction fragment length polymorphism/polymerase chain reaction in the c-H-ras1 gene. Proc Natl Acad Sci U S A 1992; 89:5331-5. [PMID: 1351680 PMCID: PMC49285 DOI: 10.1073/pnas.89.12.5331] [Citation(s) in RCA: 24] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
In genotypic mutation analysis DNA sequence changes are determined without the in vivo or in vitro selection of phenotypically altered cells. We have studied the induction of base-pair changes by N-ethyl-N-nitrosourea in Taq I endonuclease recognition site 2508-2511 (TCGA) of the c-H-ras1 gene in human fibroblasts by the restriction fragment length polymorphism/polymerase chain reaction (RFLP/PCR) method. This site contains the four bases, and all 12 possible single base-pair changes can be monitored. The transition of guanine to adenine at position 2510 was the major mutation detected by lambda plaque oligonucleotide hybridization and quantitative sequence analysis of the RFLP/PCR products. It involves the G residue of the CpG sequence of the coding strand. Data calibration with an internal mutant standard indicates that absolute frequencies for this transition lie in the range of 4-12 x 10(-7). The present study documents the capacity of the RFLP/PCR approach to measure mutagen-induced base-pair changes in a specific gene sequence without the selection of a phenotypically altered cell.
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Affiliation(s)
- S M Chiocca
- Department of Carcinogenesis, Swiss Institute for Experimental Cancer Research, Epalinges, Lausanne
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19
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Abstract
Antimycin A, KCN, and 1-methyl-4-phenylpyridinium ion (MPP+) all produced a marked depletion of cellular GSH levels in freshly isolated hepatocytes. This effect was consistently observed before the onset of cytotoxicity and seemed to be correlated with the loss of cellular ATP induced by these mitochondrial poisons. Concentrations of GSSG remained unchanged both intracellularly and extracellularly, indicating that oxidation was not involved in the events leading to GSH depletion. Approximately 40% of the decrease of intracellular GSH was accounted for by efflux of this tripeptide, assessed by increased formation of cysteinyl-glutathione when hepatocytes were incubated in the presence of 0.2 mM cystine. Therefore, an overall loss of glutathione was observed during incubations with all three inhibitors of mitochondrial function. Addition of 10 mM fructose to the incubation media substantially protected against GSH depletion caused by antimycin A, KCN, and MPP+. These results indicate that energy-dependent mechanisms are involved in the maintenance of intracellular GSH levels, and suggest that GSH depletion may be a general phenomenon associated with impairment of mitochondrial function.
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Affiliation(s)
- K Mithöfer
- Department of Biomedical and Environmental Health Sciences, School of Public Health, University of California, Berkeley 94720
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20
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Sandy MS, Chiocca SM, Cerutti PA. Genotypic analysis of mutations in Taq I restriction recognition sites by restriction fragment length polymorphism/polymerase chain reaction. Proc Natl Acad Sci U S A 1992; 89:890-4. [PMID: 1736304 PMCID: PMC48350 DOI: 10.1073/pnas.89.3.890] [Citation(s) in RCA: 29] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/28/2022] Open
Abstract
Point mutations in somatic cells play a role in the etiology of several classes of human pathologies. Experimental procedures are required that allow the detection and quantitation of such mutations in disease-related genes in tissue biopsy samples without the need for the selection of mutated cells. We describe the genotypic analysis of single base pair mutations in the Taq I endonuclease recognition sequence TCGA, residues 2508-2511 of exon 2 of the human c-H-ras1 gene, by the restriction fragment length polymorphism/polymerase chain reaction (RFLP/PCR) approach. The high thermostability of Taq I endonuclease allows the continuous removal of eventual residual wild-type sequences during the thermocycling of the PCR and reduces polymerase errors in the final RFLP/PCR product to a minimum. As few as five copies of a mutant standard containing two base pair changes in the chosen Taq I site could be rescued from 10(8) copies of wild-type DNA. Taq I RFLP/PCR holds promise for the monitoring of mutations in biochemical epidemiology.
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Affiliation(s)
- M S Sandy
- Department of Carcinogenesis, Swiss Institute for Experimental Cancer Research, Epalinges/Lausanne
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21
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Abstract
Several links exist between the two mechanisms of neuronal degeneration (i.e., oxygen radical production and mitochondrial damage) proposed to have a role in Parkinson's disease. Indeed, mitochondria are critical targets for the toxic injury induced by oxygen radicals, and experimental evidence suggests that mitochondrial damage may cause an increased generation of oxygen radicals. A potentially important link between these two mechanisms of neurodegeneration is glutathione. Because of the scavenging activity of glutathione against accumulation of oxygen radicals, its decrease in the brains of parkinsonian patients has been interpreted as a sign of oxidative stress; however, this change may also result from or lead to mitochondrial damage. It is conceivable therefore that regardless of whether oxidative stress or mitochondrial damage represents the initial insult, these toxic mechanisms may both contribute to neuronal degeneration via changes in glutathione levels.
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Affiliation(s)
- D A Di Monte
- California Parkinson's Foundation, San Jose 95128
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22
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Cotgreave IA, Weis M, Berggren M, Sandy MS, Moldéus PW. Determination of the intracellular protein thiol distribution of hepatocytes using monobromobimane derivatisation of intact cells and isolated subcellular fractions. J Biochem Biophys Methods 1988; 16:247-54. [PMID: 3221035 DOI: 10.1016/0165-022x(88)90058-9] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/04/2023]
Abstract
The derivatisation of intact rat hepatocytes with monobromobimane resulted in rapid labelling of accessible protein thiols in several subcellular fractions. The derivatisation procedure did not cause acute cytotoxicity, nor did it alter the buoyant densities of the fractions or their gross protein compositions. Quantitation of the fluorescence irreversibly associated with the fractions demonstrated considerable intracellular heterogeneity in this pool of thiols. Values were highest in cytosol (ca. 90 nmol/mg protein), intermediate in microsomes (ca. 65 nmol/mg protein) and mitochondria (ca. 45 nmol/mg protein) and lowest in a crude fraction containing both nuclei and plasma membrane (ca. 35 nmol/mg protein). Similar values were obtained from microsomes and cytosol derivatised after fractionation but there were significant increases of ca. 100% in corresponding values from isolated mitochondria and the nuclear/plasma membrane fraction. These results are discussed in terms of the dynamic fluxes in monobromobimane protein thiols during fractionation and the applicability of this noninvasive method to studies of the mechanism(s) of toxicity of reactive xenobiotics and the role(s) of protein thiols in normal cellular function.
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Affiliation(s)
- I A Cotgreave
- Department of Toxicology, Karolinska Institutet, Stockholm, Sweden
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23
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Di Monte D, Sandy MS, Blank L, Smith MT. Fructose prevents 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP)-induced ATP depletion and toxicity in isolated hepatocytes. Biochem Biophys Res Commun 1988; 153:734-40. [PMID: 3260098 DOI: 10.1016/s0006-291x(88)81156-2] [Citation(s) in RCA: 44] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/04/2023]
Abstract
The loss of viability of isolated rat hepatocytes exposed to either 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) or its toxic metabolite 1-methyl-4-phenylpyridinium ion (MPP+) was prevented by addition of fructose to the incubation medium. This protection was dependent on fructose concentration, being complete at 10 mM. Addition of fructose dramatically delayed MPTP- and MPP+-induced depletion of ATP and was accompanied by a significant accumulation of lactate, indicating the occurrence of enhanced glycolytic production of ATP. Glucose was much less effective against MPTP and MPP+ toxicity, probably because it is a relatively poor substrate for glycolysis in liver cells. We conclude that depletion of ATP is a critical event in MPTP cytotoxicity in our in vitro model system, and that the use of alternative sources of ATP production may represent an important protective device against the effects of this toxic agent.
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Affiliation(s)
- D Di Monte
- Department of Biomedical and Environmental Health Sciences, School of Public Health, University of California, Berkeley 94720
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24
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Abstract
The cellular content of vitamin E was measured in isolated rat hepatocytes exposed to various types of chemical injury. Vitamin E was determined as alpha-tocopherol by HPLC with in-line uv and electrochemical detection. The cytotoxicity of diquat, a redox cycling compound, was accompanied by a decrease in cellular alpha-tocopherol and a stimulation of lipid peroxidation. Both the loss of alpha-tocopherol and the accumulation of lipid peroxidation products could be prevented by addition of either the antioxidant N,N'-diphenyl-p-phenylenediamine (DPPD) or the reducing agent dithiothreitol (DTT). DTT also prevented the oxidation of soluble and protein thiols and completely protected against cytotoxicity, while DPPD addition only delayed the onset of hepatocyte death. Cytotoxic doses of the naphthoquinone, menadione, and the pyridine compounds 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine and 1-methyl-4-phenyl-pyridinium ion did not deplete alpha-tocopherol levels, nor did they result in significant lipid peroxidation. On the other hand, a peroxidizing, but noncytotoxic dose of ADP-Fe3+ rapidly decreased cellular alpha-tocopherol levels. These data demonstrate that cellular alpha-tocopherol loss is neither a prerequisite for, nor a necessary consequence of toxicity. Moreover, a substantial depletion (ca. 50%) of alpha-tocopherol does not necessarily result in cell death. Although alpha-tocopherol protects against the oxidation of cellular lipids, the maintenance of hepatocyte alpha-tocopherol content does not prevent the oxidation of soluble and protein thiols. These other targets of oxidative damage seem to play a more critical role in hepatocyte toxicity.
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Affiliation(s)
- M S Sandy
- Department of Biomedical & Environmental Health Sciences, School of Public Health, University of California, Berkeley 94720
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25
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Di Monte D, Shinka T, Sandy MS, Castagnoli N, Smith MT. Quantitative analysis of 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine metabolism in isolated rat hepatocytes. Drug Metab Dispos 1988; 16:250-5. [PMID: 2898342] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/03/2023] Open
Abstract
The biotransformation of the tertiary amine 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) was studied in isolated rat hepatocytes, in order to assess the relative contributions of the metabolic reactions previously described in studies with subcellular preparations. The oxidative pathway which produces the toxic metabolite 1-methyl-4-phenylpyridinium ion (MPP+) via the generation of the 2,3-dihydropyridinium derivative, MPDP+, accounted for approximately 90% of MPTP metabolism by hepatocytes. Mitochondrial monoamine oxidase type B (MAO B) was specifically responsible for the initial step of this conversion. In the endoplasmic reticulum, cytochrome P-450 catalyzed the demethylation of MPTP to form PTP, while the flavin-containing monooxygenase (FMO) was responsible for the generation of MPTP N-oxide. No other metabolite was detected in our hepatocyte incubations under any of the experimental conditions used. After pretreatment with the specific MAO B inhibitor, deprenyl, the rates of production of the two microsomal metabolites were enhanced, but the overall rate of MPTP conversion decreased by more than 60%. On the other hand, no significant difference in the rate of MPTP metabolism was found after the inhibition of cytochrome P-450 by SKF 525-A or with the use of methimazole, a competitive substrate for FMO. The SKF 525-A and methimazole treatments selectively inhibited the formation of PTP and MPTP N-oxide, respectively, but had no significant effect on the rate and extent of MPTP toxicity. MPP+ was the only metabolite which accumulated within the cell compartment under all the experimental conditions.(ABSTRACT TRUNCATED AT 250 WORDS)
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Affiliation(s)
- D Di Monte
- Department of Biomedical and Environmental Health Sciences, School of Public Health, University of California, Berkeley 94720
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26
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Sandy MS, Di Monte D, Cohen P, Smith MT. Role of active oxygen in paraquat and 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) cytotoxicity. Basic Life Sci 1988; 49:795-801. [PMID: 3266922 DOI: 10.1007/978-1-4684-5568-7_127] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/05/2023]
Affiliation(s)
- M S Sandy
- Department of Biomedical and Environmental Health Sciences, School of Public Health, University of California, Berkeley 94720
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27
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Sandy MS, Moldeus P, Ross D, Smith MT. Cytotoxicity of the redox cycling compound diquat in isolated hepatocytes: involvement of hydrogen peroxide and transition metals. Arch Biochem Biophys 1987; 259:29-37. [PMID: 2825600 DOI: 10.1016/0003-9861(87)90466-8] [Citation(s) in RCA: 35] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/02/2023]
Abstract
Diquat is a hepatotoxin whose toxicity in vivo and in vitro is mediated by redox cycling and greatly enhanced by pretreatment with 1,3-bis(2-chloroethyl)-1-nitrosourea (BCNU), an inhibitor of glutathione reductase. The mechanism by which redox cycling mediates diquat cytotoxicity is unclear, however. Here, we have attempted to examine the roles of three potential products of redox cycling, namely superoxide anion radical (O2-.), hydrogen peroxide (H2O2), and hydroxyl radical (.OH), in the toxicity of diquat to BCNU-treated isolated hepatocytes. Addition of high concentrations of catalase, but not superoxide dismutase, to the incubations provided some protection against the toxic effect of diquat, but much better protection was observed when catalase was added in combination with the iron chelator desferrioxamine. Addition of desferrioxamine alone also provided considerable protection, whereas the addition of copper ions enhanced diquat cytotoxicity. Taken together, these results indicate that both H2O2 and the transition metals iron and copper could play major roles in the cytotoxicity of diquat. The role of O2-. remains less clear, however, but studies with diethylenetriaminepentaacetic acid indicate that O2-. is unlikely to significantly contribute to the reduction of Fe3+ to Fe2+. The hydroxyl radical or a related species seems the most likely ultimate toxic product of the H2O2/Fe2+ interaction, but hydroxyl radical scavengers afforded only minimal protection.
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Affiliation(s)
- M S Sandy
- Department of Biomedical and Environmental Health Sciences, School of Public Health, University of California, Berkeley 94720
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28
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Di Monte D, Sandy MS, Smith MT. Increased efflux rather than oxidation is the mechanism of glutathione depletion by 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP). Biochem Biophys Res Commun 1987; 148:153-60. [PMID: 3499902 DOI: 10.1016/0006-291x(87)91089-8] [Citation(s) in RCA: 30] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/06/2023]
Abstract
Incubation of isolated hepatocytes in the presence of either the parkinsonian-inducing compound 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) or its putative toxic metabolite 1-methyl-4-phenylpyridinium ion (MPP+) led to a depletion of intracellular reduced glutathione (GSH), which was mostly recovered as glutathione disulfide (GSSG). However, both MPTP- and MPP+-induced glutathione perturbances were relatively unaffected by the prior inhibition of glutathione reductase with 1,3-bis(2-chloroethyl)-1-nitrosourea (BCNU), suggesting that intracellular oxidation was not the major mechanism involved in the GSH loss. Inclusion of cystine in the incubation mixtures revealed a time-dependent formation of cysteinyl glutathione (CySSG), indicating that an increased efflux was mostly responsible for the MPTP- and MPP+-induced GSH depletion. Therefore, the measurement of GSSG, which is apparently formed extracellularly, was not associated with oxidative stress.
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Affiliation(s)
- D Di Monte
- Department of Biomedical and Environmental Health Sciences, School of Public Health, University of California, Berkeley 94720
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Cotgreave IA, Sandy MS, Berggren M, Moldéus PW, Smith MT. N-acetylcysteine and glutathione-dependent protective effect of PZ51 (Ebselen) against diquat-induced cytotoxicity in isolated hepatocytes. Biochem Pharmacol 1987; 36:2899-904. [PMID: 3632716 DOI: 10.1016/0006-2952(87)90200-0] [Citation(s) in RCA: 67] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/06/2023]
Abstract
The glutathione peroxidase (GSH-Px)-like reduction of H2O2 by the selenoorganic compound 2-phenyl-1,2-benzoisoselenazol-3(H)-one (PZ51: Ebselen) was studied using glutathione (GSH) and the therapeutic agent N-acetylcysteine (NAC) to provide reducing equivalents. In a purely chemical system containing H2O2 and in an enzymatic system of glucose/glucose oxidase-generated H2O2 Ebselen alone did not reduce H2O2. Ebselen in combination with either GSH (1 mM) or NAC (1 mM) was capable of reducing H2O2 in both systems. In these non-cellular systems GSH was a more effective source of reducing equivalents than NAC. The GSH-Px-like activity of Ebselen was further investigated in a cellular system. The redox-cycling bipyridylium compound diquat generates active oxygen species, depletes intracellular glutathione, and is cytotoxic in isolated hepatocytes pretreated with the glutathione reductase inhibitor 1,3-bis(Z-chloro-ethyl)-1-nitrosourea (BCNU). Ebselen alone did not ameliorate diquat cytotoxicity, but in combination with either GSH (1 mM) or NAC (1 mM) it produced a significant delay in diquat-induced cytotoxicity. Further additions of either GSH (0.5 mM) or NAC (0.5 mM) at 30 min intervals provided significantly more protection against diquat-induced cytotoxicity and intracellular GSH depletion than the single 1 mM addition. Thus, the combination of Ebselen and NAC may provide an effective antidote in cases of overexposure to bipyridylium herbicides, such as diquat and paraquat.
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Ekström G, Di Monte D, Sandy MS, Smith MT. Comparative toxicity and antioxidant activity of 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine and its monoamine oxidase B-generated metabolites in isolated hepatocytes and liver microsomes. Arch Biochem Biophys 1987; 255:14-8. [PMID: 3496045 DOI: 10.1016/0003-9861(87)90289-x] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/06/2023]
Abstract
MPTP (1-Methyl-4-phenyl-1,2,3,6-tetrahydropyridine) is converted by monoamine oxidase B to its putative toxic metabolite MPP+ (1-methyl-4-phenylpyridinium ion) via MPDP+ (1-methyl-4-phenyl-2,3-dihydropyridinium ion). Both the parent compound and these two major metabolites were toxic to isolated rat hepatocytes with MPDP+ being the most toxic and MPP+ the least effective. MPP+ produced a slight increase in lipid peroxidation above control levels in hepatocytes, while both MPTP and MPDP+ showed antioxidant effects. The latter two compounds also protected against chemically and nonchemically induced lipid peroxidation in rat liver microsomes. MPDP+ was effective at much lower concentrations than MPTP. MPDP+ was also markedly more efficient when NADPH was used to induce microsomal lipid peroxidation. Lipid peroxidation as a consequence of oxygen radical generation is therefore unlikely to be involved in MPTP toxicity in vitro and the rationale of using chain-breaking antioxidants as protective agents in vivo needs a more careful evaluation.
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Smith MT, Ekström G, Sandy MS, Di Monte D. Studies on the mechanism of 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine cytotoxicity in isolated hepatocytes. Life Sci 1987; 40:741-8. [PMID: 3492653 DOI: 10.1016/0024-3205(87)90301-8] [Citation(s) in RCA: 30] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/06/2023]
Abstract
Oxidative stress and covalent binding have been proposed as possible mechanisms involved in the cytotoxic effects of the parkinsonism-causing compound 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP). However, the toxicity induced by MPTP in isolated rat hepatocytes seems to be relatively independent of oxygen radical-induced oxidative stress. Here we demonstrate that MPTP cytotoxicity is not potentiated by pretreatment with 1,3-bis(2-chloroethyl)-1-nitrosourea (BCNU), an inhibitor of glutathione reductase, nor prevented by the antioxidant N,N'-diphenyl-p-phenylenediamine (DPPD) or the iron-chelating agent desferrioxamine. Moreover, preincubation of hepatocytes with diethylmaleate to lower the level of intracellular reduced glutathione (to 20% of the initial value) did not affect either the rate or extent of MPTP cytotoxicity. Thus, nucleophilic soluble thiols do not seem to play a protective role against MPTP-induced cell damage, in contrast to what one would have expected if covalent protein binding and oxidative stress were involved as toxic mechanisms. On the other hand, MPTP cytotoxicity was potentiated by pretreatment of hepatocytes with cytochrome P-450 inhibitors (e.g., SKF 525A and metyrapone) and a more rapid depletion of ATP was observed in these experimental conditions. We conclude that mitochondrial damage and subsequent ATP depletion are likely to play a critical role in the toxicity of MPTP to isolated hepatocytes and that the metabolism of MPTP via the cytochrome P-450 monooxygenase system can be considered to be a detoxifying pathway.
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Sandy MS, Moldeus P, Ross D, Smith MT. Role of redox cycling and lipid peroxidation in bipyridyl herbicide cytotoxicity. Studies with a compromised isolated hepatocyte model system. Biochem Pharmacol 1986; 35:3095-101. [PMID: 3019355 DOI: 10.1016/0006-2952(86)90392-8] [Citation(s) in RCA: 120] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/03/2023]
Abstract
The role of active oxygen species and lipid peroxidation in the toxic effects of diquat, paraquat and other bipyridyl herbicides remains controversial. In vitro studies have shown that these compounds are potent generators of active oxygen species by redox cycling and that they stimulate lipid peroxidation. In vivo studies have failed, however, to show clear evidence of lipid peroxidation resulting from toxic exposures to these compounds. We have directly compared the abilities of three bipyridyl herbicides, diquat (DQ), paraquat (PQ) and benzyl viologen (BV), to generate superoxide anion radical (O2-.) in rat liver microsomes and H2O2 in hepatocytes and correlated this with their relative toxicities to a compromised isolated hepatocyte system. DQ was the most potent generator of O2-. and H2O2, being slightly more potent than BV and much better than PQ. This ability of the bipyridyls to generate active oxygen was positively correlated with the ability to induce toxicity in hepatocytes pretreated with 1,3-bis-(2-chloroethyl)-1-nitrosourea (BCNU) to inhibit their glutathione reductase activity, i.e. DQ greater than BV greater than PQ. DQ caused a rapid depletion of cellular GSH and a concomitant increase in GSSG in this system. Toxicity, measured as loss of plasma membrane integrity, was pronounced after only 30-60 min of incubation and was accompanied by a significant increase in lipid peroxidation. The onset of lipid peroxidation could not be separated temporally from the expression of toxicity. However, the total inhibition of lipid peroxidation by the antioxidants Trolox C, promethazine and N,N'-diphenyl-p-phenylenediamine only delayed toxicity, indicating that, even though lipid peroxidation may play some role in enhancing bipyridyl herbicide toxicity, it is not essential for the toxicity to manifest itself.
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Ross D, Thor H, Threadgill MD, Sandy MS, Smith MT, Moldéus P, Orrenius S. The role of oxidative processes in the cytotoxicity of substituted 1,4-naphthoquinones in isolated hepatocytes. Arch Biochem Biophys 1986; 248:460-6. [PMID: 3017211 DOI: 10.1016/0003-9861(86)90499-6] [Citation(s) in RCA: 63] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/03/2023]
Abstract
In order to clarify the role of oxidative processes in cytotoxicity we have studied the metabolism and toxicity of 2-methyl-1,4-naphthoquinone (menadione) and its 2,3 dimethyl (DMNQ) and 2,3 diethyl (DENQ) analogs in isolated rat hepatocytes. The two analogs, unlike menadione, cannot alkylate nucleophiles directly and were considerably less toxic than menadione. This decreased toxicity was consistent with the inability of DMNQ and DENQ to alkylate but we also found them to undergo lower rates of redox cycling in hepatocytes and a higher ratio of two electron as opposed to one electron reduction relative to menadione. Thus, facile analysis of the respective roles of alkylation and oxidation in cytotoxicity was not possible using these compounds. In hepatocytes pretreated with bischloroethyl-nitrosourea (BCNU) to inhibit glutathione reductase, all three naphthoquinones caused a potentiation of reduced glutathione (GSH) removal/oxidized glutathione (GSSG) generation and cytotoxicity relative to that observed in control cells. These data show that inhibition of hepatocyte glutathione reductase by BCNU results in enhanced naphthoquinone-induced oxidative challenge and subsequent cellular toxicity. That DMNQ and DENQ are cytotoxic, albeit at high concentrations, and that this cytotoxicity is potentiated by BCNU pretreatment suggest that oxidative processes alone can be a determinant of cytotoxicity.
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Di Monte D, Sandy MS, Ekström G, Smith MT. Comparative studies on the mechanisms of paraquat and 1-methyl-4-phenylpyridine (MPP+) cytotoxicity. Biochem Biophys Res Commun 1986; 137:303-9. [PMID: 3487318 DOI: 10.1016/0006-291x(86)91210-6] [Citation(s) in RCA: 122] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/06/2023]
Abstract
1-methyl-4-phenylpyridine (MPP+) is the putative toxic metabolite of 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) and is structurally similar to the herbicide paraquat (PQ++). We have therefore compared the effects of MPP+ and PQ++ on a well characterized experimental model, namely isolated rat hepatocytes. PQ++ generates reactive oxygen species within cells by redox cycling and its toxicity to hepatocytes was potentiated by pretreatment with 1,3-bis(2-chloroethyl)-1-nitrosourea (BCNU), an inhibitor of glutathione reductase. In BCNU-treated cells, PQ++ caused GSH depletion, lipid peroxidation and cell death. These cytotoxic effects were prevented by the antioxidant N,N'-diphenyl-p-phenylenediamine (DPPD) and the iron-chelating agent desferrioxamine. MPP+ also caused GSH depletion in BCNU-treated hepatocytes but its cytotoxicity was not markedly affected by BCNU, nor was it accompanied by significant lipid peroxidation. DPPD and desferrioxamine also failed to prevent MPP+-induced cell death. We conclude that the production of active oxygen species is likely to play a major role in PQ++ cytotoxicity, while MPP+-induced cell damage may involve additional, more important toxic mechanisms.
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Di Monte D, Jewell SA, Ekström G, Sandy MS, Smith MT. 1-Methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) and 1-methyl-4-phenylpyridine (MPP+) cause rapid ATP depletion in isolated hepatocytes. Biochem Biophys Res Commun 1986; 137:310-5. [PMID: 3487319 DOI: 10.1016/0006-291x(86)91211-8] [Citation(s) in RCA: 144] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/06/2023]
Abstract
1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) and its oxidized metabolite 1-methyl-4-phenylpyridine (MPP+) produce a rapid depletion of intracellular ATP in isolated rat hepatocytes. This effect was dose-dependent and was consistently observed before the onset of toxicity. The monoamine oxidase inhibitor pargyline provided significant protection against MPTP-induced cell death and ATP loss, but had no effect with MPP+. Thus, ATP depletion may play a critical role in MPTP toxicity, possibly via the metabolic production of MPP+.
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Smith MT, Sandy MS. Role of extracellular Ca2+ in toxic liver injury: comparative studies with the perfused rat liver and isolated hepatocytes. Toxicol Appl Pharmacol 1985; 81:213-9. [PMID: 4060150 DOI: 10.1016/0041-008x(85)90157-7] [Citation(s) in RCA: 27] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023]
Abstract
The role of extracellular Ca2+ in toxic liver injury was examined in two in vitro models of the rat liver, the isolated perfused liver and isolated hepatocytes. The toxins t-butylhydroperoxide and carbon tetrachloride, as well as the Ca2+ ionophore, heptafluorodimethyloctanedione (FOD), were employed to induce cellular injury and death. Lipid peroxidation was also measured as the formation of thiobarbituric acid-reactive products. Cell death was measured by the release of lactate dehydrogenase in the perfused liver model and by the uptake of trypan blue in isolated hepatocytes. Toxin-induced cellular injury and death occurred in both in vitro models in the presence and absence of extracellular Ca2+, indicating that an influx of Ca2+ was not essential for toxic liver injury. The degree of toxicity seen in the perfused liver model was independent of increases or decreases in the total calcium concentration present in the liver tissue, providing further evidence that cell death is not dictated solely by changes in cellular calcium content. Isolated hepatocytes differed from the perfused liver, however, undergoing more lipid peroxidation and toxin-induced cell death when incubated in the absence of extracellular Ca2+ than in its presence. While suggesting that extracellular Ca2+ concentrations may have some influence on the expression of toxicity, these results demonstrate the nonessential role extracellular Ca2+ plays in the events leading to toxic liver injury.
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