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Wu S, Daston G, Rose J, Blackburn K, Fisher J, Reis A, Selman B, Naciff J. Identifying chemicals based on receptor binding/bioactivation/mechanistic explanation associated with potential to elicit hepatotoxicity and to support structure activity relationship-based read-across. Curr Res Toxicol 2023; 5:100108. [PMID: 37363741 PMCID: PMC10285556 DOI: 10.1016/j.crtox.2023.100108] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/24/2023] [Revised: 06/02/2023] [Accepted: 06/06/2023] [Indexed: 06/28/2023] Open
Abstract
The liver is the most common target organ in toxicology studies. The development of chemical structural alerts for identifying hepatotoxicity will play an important role in in silico model prediction and help strengthen the identification of analogs used in structure activity relationship (SAR)- based read-across. The aim of the current study is development of an SAR-based expert-system decision tree for screening of hepatotoxicants across a wide range of chemistry space and proposed modes of action for clustering of chemicals using defined core chemical categories based on receptor-binding or bioactivation. The decision tree is based on ∼ 1180 different chemicals that were reviewed for hepatotoxicity information. Knowledge of chemical receptor binding, metabolism and mechanistic information were used to group these chemicals into 16 different categories and 102 subcategories: four categories describe binders to 9 different receptors, 11 categories are associated with possible reactive metabolites (RMs) and there is one miscellaneous category. Each chemical subcategory has been associated with possible modes of action (MOAs) or similar key structural features. This decision tree can help to screen potential liver toxicants associated with core structural alerts of receptor binding and/or RMs and be used as a component of weight of evidence decisions based on SAR read-across, and to fill data gaps.
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Edwards SW, Nelms M, Hench VK, Ponder J, Sullivan K. Mapping Mechanistic Pathways of Acute Oral Systemic Toxicity Using Chemical Structure and Bioactivity Measurements. FRONTIERS IN TOXICOLOGY 2022; 4:824094. [PMID: 35295211 PMCID: PMC8915918 DOI: 10.3389/ftox.2022.824094] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/28/2021] [Accepted: 01/31/2022] [Indexed: 12/16/2022] Open
Abstract
Regulatory agencies around the world have committed to reducing or eliminating animal testing for establishing chemical safety. Adverse outcome pathways can facilitate replacement by providing a mechanistic framework for identifying the appropriate non-animal methods and connecting them to apical adverse outcomes. This study separated 11,992 chemicals with curated rat oral acute toxicity information into clusters of structurally similar compounds. Each cluster was then assigned one or more ToxCast/Tox21 assays by looking for the minimum number of assays required to record at least one positive hit call below cytotoxicity for all acutely toxic chemicals in the cluster. When structural information is used to select assays for testing, none of the chemicals required more than four assays and 98% required two assays or less. Both the structure-based clusters and activity from the associated assays were significantly associated with the GHS toxicity classification of the chemicals, which suggests that a combination of bioactivity and structural information could be as reproducible as traditional in vivo studies. Predictivity is improved when the in vitro assay directly corresponds to the mechanism of toxicity, but many indirect assays showed promise as well. Given the lower cost of in vitro testing, a small assay battery including both general cytotoxicity assays and two or more orthogonal assays targeting the toxicological mechanism could be used to improve performance further. This approach illustrates the promise of combining existing in silico approaches, such as the Collaborative Acute Toxicity Modeling Suite (CATMoS), with structure-based bioactivity information as part of an efficient tiered testing strategy that can reduce or eliminate animal testing for acute oral toxicity.
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Affiliation(s)
- Stephen W. Edwards
- GenOmics, Bioinformatics, and Translational Research Center, RTI International, Research Triangle Park, Durham, NC, United States
| | - Mark Nelms
- GenOmics, Bioinformatics, and Translational Research Center, RTI International, Research Triangle Park, Durham, NC, United States
| | - Virginia K. Hench
- GenOmics, Bioinformatics, and Translational Research Center, RTI International, Research Triangle Park, Durham, NC, United States
| | - Jessica Ponder
- Physicians Committee for Responsible Medicine, Washington, DC, United States
| | - Kristie Sullivan
- Physicians Committee for Responsible Medicine, Washington, DC, United States
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Effects of p-Cresol on Oxidative Stress, Glutathione Depletion, and Necrosis in HepaRG Cells: Comparisons to Other Uremic Toxins and the Role of p-Cresol Glucuronide Formation. Pharmaceutics 2021; 13:pharmaceutics13060857. [PMID: 34207666 PMCID: PMC8228354 DOI: 10.3390/pharmaceutics13060857] [Citation(s) in RCA: 10] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/19/2021] [Revised: 06/03/2021] [Accepted: 06/06/2021] [Indexed: 12/14/2022] Open
Abstract
The toxicological effects of p-cresol have primarily been attributed to its metabolism products; however, very little human data are available in the key organ (i.e., liver) responsible for the generation of these metabolites. Experiments were conducted in HepaRG cells utilizing the following markers of cellular toxicity: 2′-7′-dichlorofluorescein (DCF; oxidative stress) formation, total cellular glutathione (GSH) concentration, and lactate dehydrogenase (LDH; cellular necrosis) release. Concentrations of p-cresol, p-cresol sulfate, and p-cresol glucuronide were determined using validated assays. p-Cresol exposure resulted in concentration- and time-dependent changes in DCF (EC50 = 0.64 ± 0.37 mM at 24 h of exposure) formation, GSH (EC50 = 1.00 ± 0.07 mM) concentration, and LDH (EC50 = 0.85 ± 0.14 mM) release at toxicologically relevant conditions. p-Cresol was also relatively more toxic than 3-carboxy-4-methyl-5-propyl-2-furanpropanoic acid, indole-3-acetic acid, indoxyl sulfate, kynurenic acid, and hippuric acid on all markers. Although the exogenous administration of p-cresol sulfate and p-cresol glucuronide generated high intracellular concentrations of these metabolites, both metabolites were less toxic compared to p-cresol at equal-molar conditions. Moreover, p-cresol glucuronide was the predominant metabolite generated in situ from p-cresol exposure. Selective attenuation of glucuronidation (without affecting p-cresol sulfate formation, while increasing p-cresol accumulation) using independent chemical inhibitors (i.e., 0.75 mM l-borneol, 75 µM amentoflavone, or 100 µM diclofenac) consistently resulted in further increases in LDH release associated with p-cresol exposure (by 28.3 ± 5.3%, 30.0 ± 8.2% or 27.3 ± 6.8%, respectively, compared to p-cresol treatment). These novel data indicated that p-cresol was a relatively potent toxicant, and that glucuronidation was unlikely to be associated with the manifestation of its toxic effects in HepaRG cells.
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Hitschler J, Boles E. Improving 3-methylphenol (m-cresol) production in yeast via in vivo glycosylation or methylation. FEMS Yeast Res 2020; 20:6021368. [PMID: 33330906 DOI: 10.1093/femsyr/foaa063] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/17/2020] [Accepted: 12/02/2020] [Indexed: 11/15/2022] Open
Abstract
Heterologous expression of 6-methylsalicylic acid synthase (MSAS) together with 6-MSA decarboxylase enables de novo production of the platform chemical and antiseptic additive 3-methylphenol (3-MP) in the yeast Saccharomyces cerevisiae. However, toxicity of 3-MP prevents higher production levels. In this study, we evaluated in vivo detoxification strategies to overcome limitations of 3-MP production. An orcinol-O-methyltransferase from Chinese rose hybrids (OOMT2) was expressed in the 3-MP producing yeast strain to convert 3-MP to 3-methylanisole (3-MA). Together with in situ extraction by dodecane of the highly volatile 3-MA this resulted in up to 211 mg/L 3-MA (1.7 mM) accumulation. Expression of a UDP-glycosyltransferase (UGT72B27) from Vitis vinifera led to the synthesis of up to 533 mg/L 3-MP as glucoside (4.9 mM). Conversion of 3-MP to 3-MA and 3-MP glucoside was not complete. Finally, deletion of phosphoglucose isomerase PGI1 together with methylation or glycosylation and feeding a fructose/glucose mixture to redirect carbon fluxes resulted in strongly increased product titers, with up to 897 mg/L 3-MA/3-MP (9 mM) and 873 mg/L 3-MP/3-MP as glucoside (8.1 mM) compared to less than 313 mg/L (2.9 mM) product titers in the wild type controls. The results show that methylation or glycosylation are promising tools to overcome limitations in further enhancing the biotechnological production of 3-MP.
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Affiliation(s)
- Julia Hitschler
- Faculty of Biological Sciences, Institute of Molecular Biosciences, Goethe University Frankfurt, Max-von-Laue Straße 9, 60438 Frankfurt am Main, Germany
| | - Eckhard Boles
- Faculty of Biological Sciences, Institute of Molecular Biosciences, Goethe University Frankfurt, Max-von-Laue Straße 9, 60438 Frankfurt am Main, Germany
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Severe ARDS Complicating an Acute Intentional Cresol Poisoning. Case Rep Crit Care 2019; 2019:6756352. [PMID: 31531245 PMCID: PMC6721468 DOI: 10.1155/2019/6756352] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/04/2019] [Revised: 06/29/2019] [Accepted: 07/04/2019] [Indexed: 11/18/2022] Open
Abstract
Cresol is a phenol derivative used as a disinfectant that may cause gastrointestinal corrosive injury, central nervous system, cardiovascular disturbances, renal, and hepatic injury following intoxication. We present a case of a female patient who was admitted to the emergency department after ingesting an unknown amount of cresol; she was admitted with tachypnea, shortness of breath with low oxygen level in the blood. She did not develop hepatic or renal dysfunction. The gastrointestinal endoscopy was performed and showed esophagus and gastric erosins only. The patient was sedated and ventilated for 7 days. After receiving supportive intensive care, the patient recovered and was sent for psychiatric evaluation. Cresol intoxication can be fatal, and cause a respiratory failure with an acute respiratory distress syndrome (ARDS), hepatic, and renal injury. This shows the importance of intensive care in the management of cresol poisoning.
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RIFM fragrance ingredient safety assessment, anisyl alcohol, CAS registry number 105-13-5. Food Chem Toxicol 2019; 134 Suppl 1:110702. [PMID: 31356918 DOI: 10.1016/j.fct.2019.110702] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/10/2019] [Revised: 07/24/2019] [Accepted: 07/25/2019] [Indexed: 11/23/2022]
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Lester C, Reis A, Laufersweiler M, Wu S, Blackburn K. Structure activity relationship (SAR) toxicological assessments: The role of expert judgment. Regul Toxicol Pharmacol 2018; 92:390-406. [DOI: 10.1016/j.yrtph.2017.12.026] [Citation(s) in RCA: 15] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/20/2017] [Revised: 12/19/2017] [Accepted: 12/31/2017] [Indexed: 12/17/2022]
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Andersen A. Final Report on the Safety Assessment of Sodium p -Chloro- m -Cresol, p -Chloro- m -Cresol, Chlorothymol, Mixed Cresols, m -Cresol, o -Cresol, p -Cresol, Isopropyl Cresols, Thymol, o -Cymen-5-ol, and Carvacrol1. Int J Toxicol 2016; 25 Suppl 1:29-127. [PMID: 16835130 DOI: 10.1080/10915810600716653] [Citation(s) in RCA: 58] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022]
Abstract
Sodium p -Chloro- m -Cresol, p -Chloro- m -Cresol (PCMC), Mixed Cresols, m -Cresol, o -Cresol, p -Cresol, Isopropyl Cresols, Thymol, Chlorothymol, o -Cymen-5-ol, and Carvacrol are substituted phenols used as cosmetic biocides/preservatives and/or fragrance ingredients. Only PCMC, Thymol, and o -Cymen-5-ol are reported to be in current use, with the highest concentration of use at 0.5% for o -Cymen-5-ol in perfumes. The use of PCMC in cosmetics is restricted in Europe and Japan. Cresols can be absorbed through skin, the respiratory tract, and the digestive tract; metabolized by the liver; and excreted by the kidney as glucuronide and sulfate metabolites. Several of these cresols increase the dermal penetration of other agents, including azidothymidine. In acute oral toxicity studies, LD50 values were in the 200 to 5000 mg/kg day-1 range across several species. In short-term studies in rats and mice, an o -Cresol, m -Cresol, p -Cresol or m -Cresol/ p -Cresol mixture at 30,000 ppm in the diet produced increases in liver and kidney weights, deficits in liver function, bone marrow hypocellularity, irritation to the gastrointestinal tract and nasal epithelia, and atrophy of female reproductive organs. The no observed effect levels (NOEL) of o -Cresol was 240 mg/kg in mink and 778 mg/kg in ferrets in short-term feeding studies, with no significant dose-related toxicity (excluding body weight parameters). In mice, 0.5% p -Cresol, but neither m -Cresol nor o -Cresol, caused loss of pigmentation. Short-term and subchronic oral toxicity tests performed with various cresols using mice, rats, hamsters, and rabbits resulted in no observed adverse effect levels (NOAELs) for mice of 625 ppm and rats of 50 mg/kg day -1, although the NOEL was 2000 ppm ina chronic study using rats. In rabbits, 160 mg/kg PCMC was found to produce irritation and erythema, but no systemic effects. Hamsters dosed with 1.5% p -Cresol in diet for 20 weeks had a greater incidence of mild and moderate forestomach hyperplasia as compared to the control. Acute inhalation toxicity studies using rats yielded LC50 values ranging from > 20 mg/m3 for o -Cresol to > 583 mg/m3 for PCMC. No deaths were recorded in mice given o -Cresol at 50 mg/m3. Cats exposed (short-term) to 9 to 50 mg/m3 of o -Cresol developed inflammation and irritation of the upper respiratory tract, pulmonary edema, and hemorrhage and perivascular sclerosis in the lungs. Rats exposed (subchronic) to o -Cresol at 9 mg/m3 had changes in leukocytes, spinal cord smears, nervous activity, liver function, blood effects, clinical signs, and neurological effects. In guinea pigs, exposure to 9 mg/m3 produced changes in hemoglobin concentrations and electrocardiograms (EKGs). Rats exposed (subchronic) to 0.05 mg/m3 Mixed Cresols by inhalation exhibited central nervous system (CNS) excitation, denaturation of lung protein, and decreased weight gain. All cresols appear to be ocular irritants. Numerous sensitization studies have been reported and most positive reactions were seen with higher concentrations of Cresol ingredients. Developmental toxicity is seen in studies of m -Cresol, o -Cresol, and p -Cresol, but only at maternally toxic levels. In a reproductive toxicity study of a mixture of m -Cresol and p -Cresol using mice under a continuous breeding protocol, 1.0% caused minimal adult reproductive and significant postnatal toxicity in the presence of systemic maternal toxicity. The o -Cresol NOAEL was 0.2% for both reproductive and general toxicity in both generations. Cresol ingredients were generally nongenotoxic in bacterial, fruit fly, and mammalian cell assays. Thymol did not induce primary lung tumors in mice. No skin tumors were found in mice exposed dermally to m -Cresol, o -Cresol, or p -Cresol for 12 weeks. In the tryphan blue exclusion assay, antitumor effects were observed for Thymol and Carvacrol. Clinical patch testing with 2% PCMC may produce irritant reactions, particularly in people with multiple patch test reactions, that are misinterpreted as allergic responses. o -Cresol, p -Cresol, Thymol, Carvacrol, and o -Cymen-5-ol caused no dermal irritation at or above use concentrations. In two predictive patch tests, PCMC did not produce a sensitization reaction. Overall, these ingredients are not significant sensitizing or photosensitizing agents. The Cosmetic Ingredient Review (CIR) Expert Panel noted some of these ingredients may increase the penetration of other cosmetic ingredients and advised cosmetic formulators to take this into consideration. The CIR Expert Panel concluded that the toxic effects of these ingredients are observed at doses higher than would be available from cosmetics. A concentration limitation of 0.5% was chosen to ensure the absence of a chemical leukoderma effect. For p -Cresol and Mixed Cresols (which contain p -Cresol), the Panel considered that the available data are insufficient to support the safety of these two ingredients in cosmetics. Studies that would demonstrate no chemical leukoderma at concentrations of use of p -Cresol and Mixed Cresols, or would demonstrate a dose response from which a safe concentration could be derived, are needed.
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Affiliation(s)
- Alan Andersen
- Cosmetic Ingredient Review, Washington, DC 20036, USA
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Persico AM, Napolioni V. Urinary p-cresol in autism spectrum disorder. Neurotoxicol Teratol 2013; 36:82-90. [DOI: 10.1016/j.ntt.2012.09.002] [Citation(s) in RCA: 109] [Impact Index Per Article: 9.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/13/2012] [Revised: 09/04/2012] [Accepted: 09/04/2012] [Indexed: 01/02/2023]
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Altraif I, Dafalla M. Murrah and Sunn herbs induced liver failure. Ann Saudi Med 2010; 30:165-7. [PMID: 20220271 PMCID: PMC2855072 DOI: 10.4103/0256-4947.60527] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/27/2022] Open
Affiliation(s)
- Ibrahim Altraif
- From the Department of Hepatobiliary Sciences and Liver Transplantation, Hepatology Section, King Abdulaziz Medical City, Riyadh, Saudi Arabia
| | - Mutasim Dafalla
- From the Department of Hepatobiliary Sciences and Liver Transplantation, Hepatology Section, King Abdulaziz Medical City, Riyadh, Saudi Arabia
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Walgren JL, Mitchell MD, Thompson DC. Role of Metabolism in Drug-Induced Idiosyncratic Hepatotoxicity. Crit Rev Toxicol 2008; 35:325-61. [PMID: 15989140 DOI: 10.1080/10408440590935620] [Citation(s) in RCA: 200] [Impact Index Per Article: 12.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/23/2022]
Abstract
Rare adverse reactions to drugs that are of unknown etiology, or idiosyncratic reactions, can produce severe medical complications or even death in patients. Current hypotheses suggest that metabolic activation of a drug to a reactive intermediate is a necessary, yet insufficient, step in the generation of an idiosyncratic reaction. We review evidence for this hypothesis with drugs that are associated with hepatotoxicity, one of the most common types of idiosyncratic reactions in humans. We identified 21 drugs that have either been withdrawn from the U.S. market due to hepatotoxicity or have a black box warning for hepatotoxicity. Evidence for the formation of reactive metabolites was found for 5 out of 6 drugs that were withdrawn, and 8 out of 15 drugs that have black box warnings. For the other drugs, either evidence was not available or suitable studies have not been carried out. We also review evidence for reactive intermediate formation from a number of additional drugs that have been associated with idiosyncratic hepatotoxicity but do not have black box warnings. Finally, we consider the potential role that high dosages may play in these adverse reactions.
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Affiliation(s)
- Jennie L Walgren
- Pfizer Global Research and Development, Worldwide Safety Sciences, Chesterfield, Missouri 63017, USA
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Klee N, Gustavsson L, Kosmehl T, Engwall M, Erdinger L, Braunbeck T, Hollert H. Changes in toxicity and genotoxicity of industrial sewage sludge samples containing nitro- and amino-aromatic compounds following treatment in bioreactors with different oxygen regimes. ENVIRONMENTAL SCIENCE AND POLLUTION RESEARCH INTERNATIONAL 2004; 11:313-20. [PMID: 15506634 DOI: 10.1007/bf02979645] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/24/2023]
Abstract
GOALS, SCOPE AND BACKGROUND From 2005, deposition of organic waste will be banned in Sweden. Likewise, in Germany and Austria, similar bans are being planned, and further countries will probably follow. Thus, there is a need to develop new methods and to refine established techniques for sludge management in the whole of the European Union. For this end, there is also an urgent need for appropriate ecotoxicological approaches to elucidate and assess the hazard potential of sewage sludge. Therefore, the present study was designed to assess the capacity of various established sludge treatment methods using different oxygen regimes to degrade recalcitrant nitro-substituted organic compounds and reduce their toxicity. Sewage sludge samples from a wastewater treatment plant in Sweden (Cambrex Karlskoga AB, industrial area Björkborn) receiving wastewater from industries manufacturing pharmaceutical substances, chemical intermediates and explosives were processed with different sludge treatment methods. Among other treatment methods, bioreactors (for anaerobic and aerobic sludge treatment) were used. In the present investigation, a battery of in vitro bioassays was employed to compare the cytotoxic and genotoxic potentials of different fractions of sludge samples in order to elucidate whether the treatments were suitable to reduce the toxicity of the sludge. METHODS In order to investigate the cytotoxicity of the extracts of treated and untreated sludge samples, the acute cytotoxicity test with the permanent cell line RTL-W1 was used. Genotoxicity was tested by means of the comet assay (single cell gel electrophoresis) with RTL-W1 cells, and mutagenicity was assessed with the Ames test using the Salmonella typhimurium strains TA98, TA98NR and TA100. Sludge toxicity was tested in different fractions of organic extracts produced by acetone and hexane extractions. The subsequent clean-up procedure (silica gel chromatography and elution with hexane and dichloromethane) resulted in two fractions, a lipophilic hexane-fraction and a semi-lipophilic dichloromethane-fraction. For the genotoxicity and mutagenicity tests, these fractions were reunited at equal ratios. RESULTS AND DISCUSSION The acute cytotoxicity test with RTL-W1 cells revealed a high cytotoxic potential for the semi-lipophilic DM-fractions of all sludge samples with NR50 values (= effective concentration for 50% cell death in the neutral red test) from 8.9 up to 20 mg sludge d.w./ml medium. A low cytotoxic potential for the hexane fractions of the untreated sludge samples (NR50 400 to > 400 mg sludge d.w./ml medium) was observed, whereas the hexane fractions of the treated sludge samples showed elevated cytotoxicity increasing further with treatment in the bioreactors. The comet assay indicated that three out of eight of the reunited fractions had a significant genotoxic potential. Whereas the genotoxic potential of one sample treated anaerobically was very high with an induction factor of 11.6, a similar sample (taken from the same anaerobic reactor four months later) and one untreated sample showed lower potentials. The samples treated in another anaerobic bioreactor as well as the samples treated aerobically showed no genotoxic potential. Results indicate that aerobic treatment was basically adequate for reducing the genotoxicity of the sludge, whereas anaerobic treatment was only partly useful for reduction of genotoxicity. The Ames test revealed a very high mutagenic potential for the reunited fractions of the untreated sludge samples with strain TA98 (maximum induction factors (IFmax) up to 45) and a relatively high potential for one of the samples treated aerobically (S2, IFmax = 18 (TA98, S9-)), thus documenting the suitability of both anaerobic and aerobic treatments to reduce the mutagenicity of the samples, however, with the aerobic treatment being less effective. CONCLUSIONS Overall, none of the microbiological treatments for wastewater sludge in bioreactors was found to be ideal for general toxicity reduction of the sludge samples. Whereas cytotoxicity of the sludge increased or levelled off in most cases following either treatment, genotoxicity both increased or decreased after anaerobic treatment, depending on the specific sample. However, mutagenicity could generally be reduced by anaerobic treatment and, to a lesser degree, by aerobic treatment. RECOMMENDATIONS AND PERSPECTIVES The complex modification of the diverse damage potentials of sludge sample extracts by use of an in vitro biotest battery following treatment for toxicity reduction in bioreactors showed that considerations of different toxicological endpoints is essential for an adequate hazard assessment. Whereas in the case of cytotoxicity reduction, the reactors proved ineffective, mutagenicity could be reduced significantly at least in some cases in this case study.
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Affiliation(s)
- Nina Klee
- Department of Zoology, Aquatic Ecology and Toxicology Group, Morphology and Ecology Section, University of Heidelberg, Im Neuenheimer Feld 230, D-69120 Heidelberg, Germany
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Abstract
Protein-bound uremic retention solutes are molecules with low molecular weight (MW) but should be considered middle or high MW substances. This article describes the best known substances of this group, which include p-cresol, indoxyl sulfate, hippuric acid, 3-carboxy-4-methyl-5-propyl-2-furan-propionic acid (CMPF), and homocysteine. At concentrations encountered during uremia, p-cresol inhibits phagocyte function and decreases leukocyte adhesion to cytokine-stimulated endothelial cells. CMPF has been implicated in anemia and neurologic abnormalities of uremia. CMPF could alter the metabolism of drugs of inhibiting their binding to albumin and their tubular excretion. Indoxyl sulfate administrated to uremic rats increases the rate of progression of renal failure. Hippuric acid inhibits glucose utilization in the muscle, and its serum concentration is correlated with neurologic symptoms of uremia. Homocysteine predisposes uremic patients to cardiovascular disease through impairment of endothelial and smooth muscle cell functions. The removal of protein-bound compounds by conventional hemodialysis is low. Other strategies to decrease their concentrations include increase in dialyze pore size, daily hemodialysis, peritoneal dialysis, reduction of production or acceleration of degradation, and preservation of residual renal function.
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Affiliation(s)
- Philippe Brunet
- EMI 0019, Faculté de Pharmacie, Université de la Méditerraneé, Marseille, France.
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Koizumi M, Noda A, Ito Y, Furukawa M, Fujii S, Kamata E, Ema M, Hasegawa R. Higher susceptibility of newborn than young rats to 3-methylphenol. J Toxicol Sci 2003; 28:59-70. [PMID: 12820538 DOI: 10.2131/jts.28.59] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/02/2022]
Abstract
To determine susceptibility of infants to 3-methylphenol, a repeated dose toxicity study was conducted with oral administration to newborn and young rats. In an 18-day newborn study from postnatal days 4 to 21 at doses of 30, 100 and 300 mg/kg/day, various clinical signs including deep respiration, hypersensitivity on handling and tremors under contact stimulus, and depressed body weight gain were observed at 300 mg/kg. At 100 mg/kg, hypersensitivity and tremors were also noted in a small number of males only on single days during the dosing period. No adverse effects were observed in the 30 mg/kg group. There were no abnormalities of physical development, sexual maturation and reflex ontogeny. The no observed adverse effect level (NOAEL) for newborn rats was considered to be 30 mg/kg/day and the unequivocally toxic level 300 mg/kg/day. In a 28-day study starting at 5 weeks of age, clinical signs and depression of body weight gain, as observed in the newborn rats, appeared in both sexes at 1000 mg/kg but not 300 mg/kg. The NOAEL and the unequivocally toxic level were 300 mg/kg/day and 1,000 mg/kg/day, respectively. From these results, newborn rats were concluded to be 3 to 10 times more susceptible to 3-methylphenol than young rats. However, the realistic no adverse effect dose for the newborn must be slightly lower than 100 mg/kg/day, at which the toxicity incidence was very low, rather than 30 mg/kg/day. Based on this speculation and the equal toxicity at unequivocally toxic levels, the differences in the susceptibility to 3-methylphenol could be concluded to be 3 to 4 times. This is consistent with the results of our previous comparative studies on 4-nitrophenol, 2,4-dinitrophenol and 3-aminophenol, which showed 2 to 4 times differences in the susceptibility between newborn and young rats.
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Affiliation(s)
- Mutsuko Koizumi
- National Institute of Health Sciences, 1-18-1 Kamiyoga, Setagaya-ku, Tokyo 158-8501, Japan
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Kamijo Y, Soma K, Kokuto M, Ohbu M, Fuke C, Ohwada T. Hepatocellular injury with hyperaminotransferasemia after cresol ingestion. Arch Pathol Lab Med 2003; 127:364-6. [PMID: 12653586 DOI: 10.5858/2003-127-0364-hiwhac] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
Abstract
A 42-year-old man attempted suicide by ingesting about 150 mL of a saponated cresol solution containing about 50% cresol. His serum aminotransferase concentrations were elevated, and a coagulopathy was present at the time of admission, 15 hours after ingestion. The hyperaminotransferasemia and coagulopathy worsened on the second day, but resolved thereafter with supportive therapy. Histologic examination of a biopsy specimen obtained on the 14th day demonstrated focal dropout of hepatocytes (which were replaced by reticulin and collagen fibers), ballooning or hydropic degeneration of hepatocytes, and rapid regeneration with small hepatocytes in the periportal zones as well as in the centrilobular zones. A rapid onset of illness with periportal hepatocellular injury is inconsistent with damage due to a hepatotoxic metabolite of p-cresol produced by cytochrome P450, which has been suggested by studies in vitro. A direct transient noxious effect mediated via the portal or arterial circulation may be involved in hepatic injury after cresol ingestion.
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Affiliation(s)
- Yoshito Kamijo
- Department of Emergency and Critical Care Medicine, Kitasato University, School of Medicine, Sagamihara Kanagawa, Japan. yk119kitasato-u.ac.jp
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Yao D, Zhang F, Yu L, Yang Y, van Breemen RB, Bolton JL. Synthesis and reactivity of potential toxic metabolites of tamoxifen analogues: droloxifene and toremifene o-quinones. Chem Res Toxicol 2001; 14:1643-53. [PMID: 11743747 DOI: 10.1021/tx010137i] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Tamoxifen remains the endocrine therapy of choice in the treatment of all stages of hormone-dependent breast cancer. However, tamoxifen has been shown to increase the risk of endometrial cancer which has stimulated research for new effective antiestrogens, such as droloxifene and toremifene. In this study, the potential for these compounds to cause cytotoxic effects was investigated. One potential cytotoxic mechanism could involve metabolism of droloxifene and toremifene to catechols, followed by oxidation to reactive o-quinones. Another cytotoxic pathway could involve the oxidation of 4-hydroxytoremifene to an electrophilic quinone methide. Comparison of the amounts of GSH conjugates formed from 4-hydroxytamoxifen, droloxifene, and 4-hydroxytoremifene suggested that 4-hydroxytoremifene is more effective at formation of a quinone methide. However, all three substrates formed similar amounts of o-quinones. Both the tamoxifen-o-quinone and toremifene-o-quinone reacted with deoxynucleosides to give corresponding adducts. However, the toremifene-o-quinone was shown to be considerably more reactive than the tamoxifen-o-quinone in terms of both kinetic data as well as the yield and type of deoxynucleoside adducts formed. Since thymidine formed the most abundant adducts with the toremifene-o-quinone, sufficient material was obtained for characterization by (1)H NMR, COSY-NMR, DEPT-NMR, and tandem mass spectrometry. Cytotoxicity studies with tamoxifen, droloxifene, 4-hydroxytamoxifen, 4-hydroxytoremifene, and their catechol metabolites were carried out in the human breast cancer cell lines S30 and MDA-MB-231. All of the metabolites tested showed cytotoxic effects that were similar to the parent antiestrogens which suggests that o-quinone formation from tamoxifen, droloxifene, and 4-hydroxytoremifene is unlikely to contribute to their cytotoxicity. However, the fact that the o-quinones formed adducts with deoxynucleosides in vitro implies that the o-quinone pathway might contribute to the genotoxicity of the antiestrogens in vivo.
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Affiliation(s)
- D Yao
- Department of Medicinal Chemistry and Pharmacognosy (M/C 781), College of Pharmacy, University of Illinois at Chicago, 833 South Wood Street, Chicago, Illinois 60612-7231, USA
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18
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Reed M, Fujiwara H, Thompson DC. Comparative metabolism, covalent binding and toxicity of BHT congeners in rat liver slices. Chem Biol Interact 2001; 138:155-70. [PMID: 11672698 DOI: 10.1016/s0009-2797(01)00270-8] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/18/2022]
Abstract
The metabolism, covalent binding and hepatotoxicity of butylated hydroxytoluene (BHT, 4-methyl-2,6-di-t-butylphenol) and two congeners (E-BHT, 4-ethyl-2,6-di-t-butylphenol; I-BHT, 4-isopropyl-2,6-di-t-butylphenol) were compared using precision-cut liver slices prepared from phenobarbital (PB)-treated male Sprague-Dawley rats. At equimolar concentrations (1 mM) BHT was the most toxic of the three compounds, causing an 80% decrease in cell viability over a 6 h incubation period. E-BHT was intermediate in toxicity while the isopropyl derivative was relatively nontoxic. Intracellular glutathione levels decreased prior to the onset of cytotoxicity. The cytochrome P450 inhibitor metyrapone completely inhibited the toxicity of all three compounds. The rates of metabolism of the three compounds to glutathione conjugates were compared in both PB-treated microsomes and PB-induced liver slices. In both models, the rate of formation was greatest for BHT, followed by E-BHT and I-BHT. Synthetic quinone methides (QMs) were prepared from each parent phenol and the rates of reactivity with three nucleophiles (water, methanol and glutathione) were compared. With each nucleophile, BHTQM was the most reactive, while I-BHTQM was the least reactive. Finally, covalent binding to protein was assessed in two ways. First, alkylation of an isolated model protein (bovine insulin) was measured in a microsomal enzyme activation system by mass spectrometry. Incubations with BHT produced the greatest extent of protein alkylation, followed by E-BHT, while no alkylation was observed with I-BHT. In the second system, covalent binding to cellular protein was assessed in rat liver PB microsomes and tissue slices by Western blotting using an antibody specific for the tert-butylphenol portion of the compounds. Binding was greatest for BHT, intermediate for E-BHT and could not be detected for I-BHT. The alkylation pattern for E-BHT was strikingly similar to that of BHT, suggesting that both compounds bound similar proteins. In summary, our results suggest that for hindered phenols such as BHT, increasing the length of the 4-alkyl substituent retards the rate of formation of reactive intermediates, significantly reduces the electrophilicity of the reactive intermediate, and greatly reduces the amount but not the selectivity of covalent binding to cellular protein, thereby reducing the toxicity of the parent compound.
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Affiliation(s)
- M Reed
- Lovelace Respiratory Research Institute, 2425 Ridgecrest Dr SE, Albuquerque, NM 87108, USA
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Kitagawa A. Effects of cresols (o-, m-, and p-isomers) on the bioenergetic system in isolated rat liver mitochondria. Drug Chem Toxicol 2001; 24:39-47. [PMID: 11307633 DOI: 10.1081/dct-100103084] [Citation(s) in RCA: 18] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/03/2022]
Abstract
It is known that o-, m- and p-cresols exert a toxic effect on rat liver cells. However, there is little information on the mechanism for the hepatotoxicity of cresols. We, therefore, investigated the effects of o-, m-, and p-cresols on the bioenergetic system using isolated rat liver mitochondria. When o-, m- or p-cresol was added to liver mitochondria with glutamate or succinate at concentrations of 0.3 to 6.0 mumol/mg protein, each cresol isomer reduced the rate of state 3 respiration dose-dependently. Three cresol isomers at 6.0 mumol/mg protein each inhibited state 3 respiration in liver mitochondria with glutamate or succinate by about 60 or 20%, respectively. The three isomers affected NAD- and succinate-linked respirations in liver mitochondria, by which the respiratory control ratio was dose-dependently attenuated. The inhibitory effects of o-, m- and p-cresols on the NAD-linked respiration were stronger than those on the succinate-linked respiration. However, three cresol isomers had little effect on the P/O ratio in liver mitochondria with glutamate or succinate. Three cresol isomers at 15 mumol/mg protein each induced the swelling in the absence of Ca2+ in medium and accelerated the swelling of liver mitochondria in the presence of Ca2+ in medium. These results indicate that o-, m- and p-cresols inhibit liver mitochondrial respiration and induce or accelerate the swelling of liver mitochondria, and suggest that liver mitochondria may be one of the targets for the hepatotoxic actions of cresols.
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Affiliation(s)
- A Kitagawa
- Department of Nutrition, Faculty of Wellness, Chukyo Women's University, Ohbu, Japan
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Thompson DC, Perera K, London R. Spontaneous hydrolysis of 4-trifluoromethylphenol to a quinone methide and subsequent protein alkylation. Chem Biol Interact 2000; 126:1-14. [PMID: 10826650 DOI: 10.1016/s0009-2797(99)00162-3] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
4-Trifluoromethylphenol (4-TFMP) was cytotoxic to precision-cut rat liver slices as indicated by loss of intracellular potassium. Intracellular glutathione levels decreased and fluoride ion levels increased in a time and concentration-dependent manner. The cytotoxicity of 4-TFMP did not appear to be due to the release of fluoride, however, since equimolar concentrations of sodium fluoride or potassium fluoride were not toxic. The ortho isomer (2-TFMP), which had a threefold slower rate of fluoride release, was much less toxic to liver slices. In incubations without slices, 4-TFMP spontaneously hydrolyzed in aqueous buffer at physiological pH to form 4-hydroxybenzoic acid via a quinone methide intermediate. The quinone methide was trapped by the addition of glutathione. Analysis of the glutathione adduct indicated that all of the fluorine atoms were lost during the hydrolysis, yielding a cresol derivative with the glutathione moiety attached to a benzylic carbonyl group. The glutathione conjugate was the primary product formed at low alkylphenol/glutathione ratios; however, at higher 4-TFMP concentrations additional unidentified products were observed. 4-TFMP also inhibited the in vitro enzyme activity of purlfied glyceraldehyde-3-phosphate dehydrogenase, a sulfhydryl-dependent enzyme, in a time and concentration-dependentmanner. Loss of thiol residues closely paralleled the loss in enzyme activity. The coaddition of glutathione prevented 4-TFMP-induced loss of enzyme activity. The cytotoxicity of 4-TFMP therefore appears to be due to spontaneous quinone methide formation and subsequent alkylation of cellular macromolecules.
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Affiliation(s)
- D C Thompson
- Department of Medical Pharmacology and Toxicology, Texas A&M University Health Science Center, College Station 77843-1114, USA.
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De Kimpe J, Cornelis R, Vanholder R. In vitro methylation of arsenite by rabbit liver cytosol: effect of metal ions, metal chelating agents, methyltransferase inhibitors and uremic toxins. Drug Chem Toxicol 1999; 22:613-28. [PMID: 10536752 DOI: 10.3109/01480549908993171] [Citation(s) in RCA: 23] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022]
Abstract
The methylation of carrier-free 74As-arsenite by liver cytosol of Flemish Giant rabbits is highly susceptible to additions of trace elements. In vitro supplementation of essential trace elements like zinc (Zn2+), vanadium (V5+), iron (Fe2+), copper (Cu2+) and selenate was shown to increase the methylation efficiency. Trivalent metal ions (e.g. Al3+, Cr3+ and Fe3+), Hg2+, Tl+ and SeO3(2-) had a deleterious effect. The inhibitory effect of EDTA, oxime and many divalent cations (Ca2+, Mg2+, Sr2+, ...) suggest a co-factor role for a specific divalent metal ion, possibly Zn2+. Chelating agents used in clinical treatment of acute and chronic inorganic arsenic poisoning lower the methylation capacity of cytosol by rendering the trivalent arsenic unavailable for the methyltransferase enzymes. S-adenosylhomocysteine and periodate-oxidized adenosine, inhibitors of s-adenosylmethionine dependent methylation pathways, inhibit the methylation of arsenite. Pyrogallol, a catechol-O-methyltransferase inhibitor, blocks the action of arsenite- and monomethylarsonic methyltransferase enzymes, suggesting a close structural relationship between the active sites of the different enzymes. Some uraemic toxins, namely oxalate, p-cresol, hypoxanthine, homocysteine and myo-inositol, inhibit arsenic methylation.
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Affiliation(s)
- J De Kimpe
- Laboratory for Analytical Chemistry, University of Ghent, Belgium
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Hashimoto T, Iida H, Dohi S. Marked increases of aminotransferase levels after cresol ingestion. Am J Emerg Med 1998; 16:667-8. [PMID: 9827743 DOI: 10.1016/s0735-6757(98)90171-1] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022] Open
Abstract
A 26-year-old woman developed marked increases in levels of aminotransferases about 24 hours after ingestion of 70 mL of 50% cresol. Responding to supportive measures, the patient recovered without any significant complications. Cresol and/or its metabolite may have caused transient hepato-cellular injury in this patient. In cresol poisoning, hepato-cellular injury can manifest even after a 24-hour asymptomatic period.
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Affiliation(s)
- T Hashimoto
- Department of Anesthesiology and Critical Care Medicine, Gifu University School of Medicine, Gifu City, Japan
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