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Oyagbemi AA, Adejumobi OA, Jarikre TA, Ajani OS, Asenuga ER, Gbadamosi IT, Adedapo ADA, Aro AO, Ogunpolu BS, Hassan FO, Falayi OO, Ogunmiluyi IO, Omobowale TO, Arojojoye OA, Ola-Davies OE, Saba AB, Adedapo AA, Emikpe BO, Oyeyemi MO, Nkadimeng SM, McGaw LJ, Kayoka-Kabongo PN, Oguntibeju OO, Yakubu MA. Clofibrate, a Peroxisome Proliferator-Activated Receptor-Alpha (PPARα) Agonist, and Its Molecular Mechanisms of Action against Sodium Fluoride-Induced Toxicity. Biol Trace Elem Res 2022; 200:1220-1236. [PMID: 33893992 DOI: 10.1007/s12011-021-02722-1] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 02/08/2021] [Accepted: 04/12/2021] [Indexed: 01/16/2023]
Abstract
Sodium fluoride (NaF) is one of the neglected environmental pollutants. It is ubiquitously found in the soil, water, and environment. Interestingly, fluoride has been extensively utilized for prevention of dental caries and tartar formation, and may be added to mouthwash, mouth rinse, and toothpastes. This study is aimed at mitigating fluoride-induced hypertension and nephrotoxicity with clofibrate, a peroxisome proliferator-activated receptor-alpha (PPARα) agonist. For this study, forty male Wistar rats were used and randomly grouped into ten rats per group, control, sodium fluoride (NaF; 300 ppm) only, NaF plus clofibrate (250 mg/kg) and NaF plus lisinopril (10 mg/kg), respectively, for 7 days. The administration of NaF was by drinking water ad libitum, while clofibrate and lisinopril were administered by oral gavage. Administration of NaF induced hypertension, and was accompanied with exaggerated oxidative stress; depletion of antioxidant defence system; reduced nitric oxide production; increased systolic, diastolic and mean arterial pressure; activation of angiotensin-converting enzyme activity and nuclear factor kappa-light-chain-enhancer of activated B cells (NF-κB); and testicular apoptosis. Treatment of rats with clofibrate reduced oxidative stress, improved antioxidant status, lowered high blood pressure through the inhibition of angiotensin-converting enzyme activity, mineralocorticoid receptor over-activation, and abrogated testicular apoptosis. Taken together, clofibrate could offer exceptional therapeutic benefit in mitigating toxicity associated with sodium fluoride.
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Affiliation(s)
- Ademola Adetokunbo Oyagbemi
- Department of Veterinary Physiology and Biochemistry, Faculty of Veterinary Medicine, University of Ibadan, Ibadan, Nigeria.
| | - Olumuyiwa Abiola Adejumobi
- Department of Veterinary Medicine, Faculty of Veterinary Medicine, University of Ibadan, Ibadan, Nigeria
| | - Theophilus Aghogho Jarikre
- Department of Veterinary Pathology, Faculty of Veterinary Medicine, University of Ibadan, Ibadan, Nigeria
| | - Olumide Samuel Ajani
- Department of Theriogenology, Faculty of Veterinary Medicine, University of Ibadan, Ibadan, Nigeria
| | - Ebunoluwa Racheal Asenuga
- Department of Veterinary Physiology and Biochemistry, Faculty of Veterinary Medicine, University of Benin, Benin, Nigeria
| | | | | | - Abimbola Obemisola Aro
- Department of Agriculture and Animal Health, College of Agriculture and Environmental Sciences, University of South Africa, Florida, South Africa
| | - Blessing Seun Ogunpolu
- Department of Veterinary Medicine, Faculty of Veterinary Medicine, University of Ibadan, Ibadan, Nigeria
| | - Fasilat Oluwakemi Hassan
- Department of Veterinary Physiology and Biochemistry, Faculty of Veterinary Medicine, University of Ibadan, Ibadan, Nigeria
| | - Olufunke Olubunmi Falayi
- Department of Veterinary Pharmacology and Toxicology, Faculty of Veterinary Medicine, University of Ibadan, Ibadan, Nigeria
| | - Iyanuoluwa Omolola Ogunmiluyi
- Department of Veterinary Pharmacology and Toxicology, Faculty of Veterinary Medicine, University of Ibadan, Ibadan, Nigeria
| | - Temidayo Olutayo Omobowale
- Department of Veterinary Medicine, Faculty of Veterinary Medicine, University of Ibadan, Ibadan, Nigeria
| | | | - Olufunke Eunice Ola-Davies
- Department of Veterinary Physiology and Biochemistry, Faculty of Veterinary Medicine, University of Ibadan, Ibadan, Nigeria
| | - Adebowale Benard Saba
- Department of Veterinary Pharmacology and Toxicology, Faculty of Veterinary Medicine, University of Ibadan, Ibadan, Nigeria
| | - Adeolu Alex Adedapo
- Department of Veterinary Pharmacology and Toxicology, Faculty of Veterinary Medicine, University of Ibadan, Ibadan, Nigeria
| | - Benjamin Obukowho Emikpe
- Department of Veterinary Pathology, Faculty of Veterinary Medicine, University of Ibadan, Ibadan, Nigeria
| | | | - Sanah Malomile Nkadimeng
- Phytomedicine Programme, Department of Paraclinical Science, Faculty of Veterinary Science, University of Pretoria, Old Soutpan Road, Onderstepoort, Pretoria, 0110, South Africa
| | - Lyndy Joy McGaw
- Phytomedicine Programme, Department of Paraclinical Science, Faculty of Veterinary Science, University of Pretoria, Old Soutpan Road, Onderstepoort, Pretoria, 0110, South Africa
| | - Prudence Ngalula Kayoka-Kabongo
- Department of Agriculture and Animal Health, College of Agriculture and Environmental Sciences, University of South Africa, Florida, South Africa
| | - Oluwafemi Omoniyi Oguntibeju
- Phytomedicine and Phytochemistry Group, Oxidative Stress Research Centre, Department of Biomedical Sciences, Faculty of Health and Wellness Sciences, Cape Peninsula University of Technology, Bellville, Cape Town, 7535, South Africa
| | - Momoh Audu Yakubu
- Department of Environmental & Interdisciplinary Sciences, College of Science, Engineering & Technology, Vascular Biology Unit, Center for Cardiovascular Diseases, Texas Southern University, Houston, TX, USA
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Sharapova T, Talaty N, Buck WR, Fossey S, Liguori MJ, Van Vleet TR. Reduced hepatic global hydroxymethylation in mice treated with non-genotoxic carcinogens is transiently reversible with a methyl supplemented diet. Toxicol Appl Pharmacol 2021; 415:115439. [PMID: 33549593 DOI: 10.1016/j.taap.2021.115439] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/08/2020] [Revised: 01/20/2021] [Accepted: 01/31/2021] [Indexed: 01/05/2023]
Abstract
Non-genotoxic carcinogens (NGCs) are known to cause perturbations in DNA methylation, which can be an early event leading to changes in gene expression and the onset of carcinogenicity. Phenobarbital (PB) has been shown to alter liver DNA methylation and hydroxymethylation patterns in mice in a time dependent manner. The goals of this study were to assess if clofibrate (CFB), a well-studied rodent NGC, would produce epigenetic changes in mice similar to PB, and if a methyl donor supplementation (MDS) would modulate epigenetic and gene expression changes induced by phenobarbital. CByB6F1 mice were treated with 0.5% clofibrate or 0.14% phenobarbital for 7 and 28 days. A subgroup of PB treated and control mice were also fed MDS diet. Liquid Chromatography-Ionization Mass Spectrometry (LC-MS) was used to quantify global liver 5-methylcytosine (5mC) and 5-hydroxymethylcytosine (5hmC) levels. Gene expression analysis was conducted using Affymetrix microarrays. A decrease in liver 5hmC but not 5mC levels was observed upon treatment with both CFB and PB with varying time of onset. We observed moderate increases in 5hmC levels in PB-treated mice when exposed to MDS diet and lower expression levels of several phenobarbital induced genes involved in cell proliferation, growth, and invasion, suggesting an early modulating effect of methyl donor supplementation. Overall, epigenetic profiling can aid in identifying early mechanism-based biomarkers of non-genotoxic carcinogenicity and increases the quality of cancer risk assessment for candidate drugs. Global DNA methylation assessment by LC-MS is an informative first step toward understanding the risk of carcinogenicity.
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Affiliation(s)
- T Sharapova
- Investigative Toxicology and Pathology, AbbVie Inc., North Chicago, IL, United States.
| | - N Talaty
- Discovery Platform Technologies, AbbVie Inc., North Chicago, IL, United States
| | - W R Buck
- Investigative Toxicology and Pathology, AbbVie Inc., North Chicago, IL, United States
| | - S Fossey
- Investigative Toxicology and Pathology, AbbVie Inc., North Chicago, IL, United States
| | - M J Liguori
- Investigative Toxicology and Pathology, AbbVie Inc., North Chicago, IL, United States
| | - T R Van Vleet
- Investigative Toxicology and Pathology, AbbVie Inc., North Chicago, IL, United States
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Ji Z, Settivari RS, LeBaron MJ. Pilot studies evaluating the nongenotoxic rodent carcinogens phenobarbital and clofibrate in the rat Pig-a assay. Environ Mol Mutagen 2019; 60:42-46. [PMID: 30338550 DOI: 10.1002/em.22232] [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] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/08/2018] [Revised: 07/16/2018] [Accepted: 07/17/2018] [Indexed: 06/08/2023]
Abstract
The Pig-a assay is an emerging and promising in vivo method to determine mutagenic potential of chemicals. Since its development in 2008, remarkable progress has been made in harmonizing and characterizing the test procedures, primarily using known mutagenic chemicals. The purpose of the present study was to evaluate specificity of the Pig-a assay using two nongenotoxic and well-characterized rodent liver carcinogens, phenobarbital and clofibrate, in male F344/DuCrl rats. Daily oral administration of phenobarbital or clofibrate at established hepatotoxic doses for 28 days resulted in substantial hepatic alterations, however, did not increase the frequency of Pig-a mutation markers (RETCD59- and RBCCD59- ) compared to vehicle control or pre-exposure (Day -5) mutant frequencies. These results are consistent with the existing literature on the nonmutagenic mode of action (MoA) of phenobarbital and clofibrate liver tumors. The present study contributes to the limited, but expanding evidence on the specificity of the Pig-a assay and further for the investigations of carcinogenic MoAs, i.e., mutagenic or nonmutagenic potential of chemicals. Environ. Mol. Mutagen. 60:42-46, 2019. © 2018 Wiley Periodicals, Inc.
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Affiliation(s)
- Zhiying Ji
- Toxicology and Environmental Research and Consulting, The Dow Chemical Company, Midland, Michigan
| | - Raja S Settivari
- Toxicology and Environmental Research and Consulting, The Dow Chemical Company, Midland, Michigan
| | - Matthew J LeBaron
- Toxicology and Environmental Research and Consulting, The Dow Chemical Company, Midland, Michigan
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Ji Z, LeBaron MJ. Applying the erythrocyte Pig-a assay concept to rat epididymal sperm for germ cell mutagenicity evaluation. Environ Mol Mutagen 2017; 58:485-493. [PMID: 28714084 DOI: 10.1002/em.22109] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/11/2017] [Revised: 05/18/2017] [Accepted: 05/18/2017] [Indexed: 06/07/2023]
Abstract
The Pig-a assay, a recently developed in vivo somatic gene mutation assay, is based on the identification of mutant erythrocytes that have an altered repertoire of glycosylphosphatidylinositol (GPI)-anchored cell surface markers. We hypothesized that the erythrocyte Pig-a assay concept could be applied to rat cauda epididymal spermatozoa (sperm) for germ cell mutagenicity evaluation. We used GPI-anchored CD59 as the Pig-a mutation marker and examined the frequency of CD59-negative sperm using flow cytometry. A reconstruction experiment that spiked un-labeled sperm (mutant-mimic) into labeled sperm at specific ratios yielded good agreement between the detected and expected frequencies of mutant-mimic sperm, demonstrating the analytical ability for CD59-negative sperm detection. Furthermore, this methodology was assessed in F344/DuCrl rats administered N-ethyl-N-nitrosourea (ENU), a prototypical mutagen, or clofibrate, a lipid-lowering drug. Rats treated with 1, 10, or 20 mg/kg body weight/day (mkd) ENU via daily oral garage for five consecutive days showed a dose-dependent increase in the frequency of CD59-negative sperm on study day 63 (i.e., 58 days after the last ENU dose). This ENU dosing regimen also increased the frequency of CD59-negative erythrocytes. In rats treated with 300 mkd clofibrate via daily oral garage for consecutive 28 days, no treatment-related changes were detected in the frequency of CD59-negative sperm on study day 85 (i.e., 57 days after the last dose) or in the frequency of CD59-negative erythrocytes on study day 29. In conclusion, these data suggest that the epidiymal sperm Pig-a assay in rats is a promising method for evaluating germ cell mutagenicity. Environ. Mol. Mutagen. 58:485-493, 2017. © 2017 Wiley Periodicals, Inc.
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Affiliation(s)
- Zhiying Ji
- Toxicology and Environmental Research and Consulting, The Dow Chemical Company, Midland, Michigan, 48674
| | - Matthew J LeBaron
- Toxicology and Environmental Research and Consulting, The Dow Chemical Company, Midland, Michigan, 48674
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Nesfield SR, Williams TC, Hoivik DJ, Miller RT, Allen JS, Selinger K, Rickert D, Santostefano MJ. Evaluation of the Carcinogenic Potential of Clofibrate in the Neonatal Mouse. Int J Toxicol 2016; 24:341-8. [PMID: 16257853 DOI: 10.1080/10915810500210401] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.0] [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: 10/25/2022]
Abstract
This study was conducted in support of the International Life Sciences Institute (ILSI) alternative carcinogenicity models initiative to evaluate the carcinogenic potential of clofibrate, a nongenotoxic peroxisome proliferator-activated receptor (PPAR) α agonist, following oral administration to neonatal mice. Male and female neonatal CD-1 mice were dosed with clofibrate at doses of 100, 250, and 500 mg/kg or with the positive control, diethyl-nitrosamine (DEN), at 2 mg/kg by oral gavage on days 9 and 16 post birth and observed for approximately 1 year for the development of tumors. Plasma levels of clofibric acid after the second administration increased with dose, but were not dose proportional. Clofibrate administered by gavage on litter days 9 and 16 to neonatal mice at doses of 100, 250, or 500 mg/kg did not produce a carcinogenic effect. The positive control DEN did produce tumors in the liver and lung (single and multiple adenomas and carcinomas) and harderian gland (adenoma) of both sexes. Non-neoplastic lesions related to DEN treatment were confined to myocardial degeneration/fibrosis and testicular interstitial hyperplasia in males, and to glomerulonephrosis and gastritis in both sexes.
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Torrey CE, Campbell JA, Hoivik DJ, Miller RT, Allen JS, Mann PC, Selinger K, Rickert D, Savina PM, Santostefano MJ. Evaluation of the Carcinogenic Potential of Clofibrate in the p53+/− Mouse. Int J Toxicol 2016; 24:289-99. [PMID: 16257849 DOI: 10.1080/10915810500210237] [Citation(s) in RCA: 6] [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: 10/25/2022]
Abstract
This study was conducted as part of International Life Sciences Institute (ILSI) program to evaluate the carcinogenic potential of clofibrate, a nongenotoxic, peroxisome proliferator-activated receptor (PPAR) α agonist, following oral administration to p53+ /− heterozygous mice for a minimum of 26 weeks. p-Cresidine, a urinary bladder carcinogen, was given orally at 400 mg/kg/day as a positive control. Initial clofibrate doses were 50, 250, and 400 mg/kg/day for males and 50, 200, and 500 mg/kg/day for females. Due to unexpected mortality during the first week of dosing, clofibrate doses were lowered to 25, 75, and 100 mg/kg/day for males and 25, 75, and 125 mg/kg/day for females. Clinical signs and mortality were greater in p53+ /− than wild-type (WT) mice. With the exception of liver weights, no marked differences in any other parameters either between the sexes or between WT and p53+ /− mice were noted. Moderate increases in liver weights noted in WT males given 100 mg/kg/day clofibrate were not associated with any microscopic changes. No neoplastic response was observed in p53+ /−mice after 6 months of exposure to clofibrate at doses up to 100 mg/kg/day for males and 125 mg/kg/day for females. Transitional-cell hyperplasia and carcinoma of the urinary bladder were noted in both sexes given p-cresidine, demonstrating that the p53+ /− mouse responded to a known mouse carcinogen as expected. Clofibrate produced non-neoplastic findings in the adrenals, pancreas, and prostate, whereas p-cresidine affected the kidney, liver, pancreas, and spleen.
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Affiliation(s)
- Carla E Torrey
- GlaxoSmithKline, Safety Assessment, Research Triangle Park, North Carolina 27709, USA
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Abstract
Morphological changes induced by clofibrate in type-1 predominant soleus, type-2 predominant tensor fasciae latae, and type-1 and -2 mixed biceps femoris muscles and diaphragm in rats were investigated. Administration of the agent at 500 or 750 mg/kg/day by oral gavage for 14 or 28 days caused lesions in the soleus muscle and diaphragm, bur no changes in the tensor fasciae latae and biceps femoris muscles. In soleus muscle, vacuolation of muscle fibers was observed in all animals treated with clofibrate, and degeneration of muscle fibers and infiltration of leukocytes were noted at 750 mg/kg/day. In diaphragm, vacuolation of muscle fibers was also observed in all animals treated with clofibrate, and these lesions were located in type-1 skeletal muscles densely stained with NADH-TR. The vacuoles seen in soleus muscle and diaphragm were positive for oil red O staining. In addition, increase of lipid droplets and mitochondrial hypertrophy was seen in soleus muscle, ultrastructurally. These data suggest that sensitivity to clofibrate-induced muscle toxicity differs among muscles, with type-1 fibers being susceptible.
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Affiliation(s)
- Miyoko Okada
- Toxicology Laboratory, Mitsubishi Pharma Corporation, Kisarazu, Chiba, Japan.
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Fernandes D, Schnell S, Porte C. Can pharmaceuticals interfere with the synthesis of active androgens in male fish? An in vitro study. Mar Pollut Bull 2011; 62:2250-2253. [PMID: 21820682 DOI: 10.1016/j.marpolbul.2011.07.011] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/12/2011] [Revised: 07/07/2011] [Accepted: 07/10/2011] [Indexed: 05/31/2023]
Abstract
The in vitro interference of fibrate (gemfibrozil, clofibrate, clofibric acid), anti-inflammatory (ibuprofen, diclofenac), and anti-depressive (fluoxetine, fluvoxamine) drugs with key enzymatic activities-C17,20-lyase and CYP11β-involved in the synthesis of active androgens in gonads of male carp have been investigated. Among the tested compounds, fluvoxamine and fluoxetine were the strongest inhibitors of C17,20-lyase and CYP11β enzymes, with IC50s in the range of 321-335 μM and 244-550 μM, respectively. To our knowledge this is the first report on the interaction of pharmaceutical compounds with enzymatic systems involved in the synthesis of oxy-androgens. As oxy-androgens are known to influence spermatogenesis and stimulate reproductive behavior and secondary sexual characteristics in male fish, this work highlights the need for further investigating these endpoints when designing specific in vivo studies to assess the endocrine disruptive effect of pharmaceuticals in fish.
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Affiliation(s)
- Denise Fernandes
- Environmental Chemistry Department, IDAEA-CSIC, Jordi Girona 18, 08034 Barcelona, Spain.
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Wang J, Liu X, Wang H, Wu T, Hu X, Qin F, Wang Z. Expression of two cytochrome P450 aromatase genes is regulated by endocrine disrupting chemicals in rare minnow Gobiocypris rarus juveniles. Comp Biochem Physiol C Toxicol Pharmacol 2010; 152:313-20. [PMID: 20594974 DOI: 10.1016/j.cbpc.2010.05.007] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/22/2010] [Revised: 05/23/2010] [Accepted: 05/25/2010] [Indexed: 01/08/2023]
Abstract
To elucidate the effects of endocrine disrupting chemicals (EDCs) on aromatase, the rare minnow ovarian and brain P450 aromatase (cyp19a1a and cyp19a1b) cDNA and their 5'-flanking regions were isolated and characterized. RT-PCR analysis revealed that the rare minnow cyp19a1a mRNA was predominantly expressed in ovary while cyp19a1b was predominantly expressed in brain. Sequences for binding sites of steroidogenic factor-1, peroxisome proliferators-activated receptor, aryl hydrocarbon receptor, CCAAT/enhancer binding protein, estrogen responsive element, glucocorticoid responsive element, and retinoic acid receptor were identified on promoter regions of cyp19a1 genes. The influence of several EDCs on the transcript abundance of cyp19a1a and cyp19a1b was investigated in rare minnow juveniles. Clofibrate did not influence the expression of either cyp19a1 genes. Exposure to 1nM ethinylestradiol (EE2) for 3days significantly downregulated the expression of cyp19a1a gene, however 0.1 and 1 nM EE2 significantly increased the gene expression of cyp19a1b. Exposure to 100 and 1000 nM 4-nonylphenol (NP) significantly suppressed the cyp19a1a expression, but it had no effect on the expression of cyp19a1b gene. Bisphenol A (BPA) strongly suppressed the cyp19a1b gene expression from 0.1 to 10 nM and significantly suppressed the gene expression of cyp19a1a only at 10 nM. These results indicate that EDCs may influence the expression of cyp19a1 genes through differential transcriptional modulation in rare minnow juveniles.
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Affiliation(s)
- Jingjing Wang
- College of Animal Science and Technology, Northwest A&F University, Shaanxi Key Laboratory of Molecular Biology for Agriculture, Yangling, Shaanxi 712100, China
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Tilton SC, Orner GA, Benninghoff AD, Carpenter HM, Hendricks JD, Pereira CB, Williams DE. Genomic profiling reveals an alternate mechanism for hepatic tumor promotion by perfluorooctanoic acid in rainbow trout. Environ Health Perspect 2008; 116:1047-55. [PMID: 18709148 PMCID: PMC2516568 DOI: 10.1289/ehp.11190] [Citation(s) in RCA: 57] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/17/2007] [Accepted: 05/07/2008] [Indexed: 05/20/2023]
Abstract
BACKGROUND Perfluorooctanoic acid (PFOA) is a potent hepatocarcinogen and peroxisome proliferator (PP) in rodents. Humans are not susceptible to peroxisome proliferation and are considered refractory to carcinogenesis by PPs. Previous studies with rainbow trout indicate they are also insensitive to peroxisome proliferation by the PP dehydroepiandrosterone (DHEA), but are still susceptible to enhanced hepatocarcinogenesis after chronic exposure. OBJECTIVES In this study, we used trout as a unique in vivo tumor model to study the potential for PFOA carcinogenesis in the absence of peroxisome proliferation compared with the structurally diverse PPs clofibrate (CLOF) and DHEA. Mechanisms of carcinogenesis were identified from hepatic gene expression profiles phenotypically anchored to tumor outcome. METHODS We fed aflatoxin B(1) or sham-initiated animals 200-1,800 ppm PFOA in the diet for 30 weeks for tumor analysis. We subsequently examined gene expression by cDNA array in animals fed PFOA, DHEA, CLOF, or 5 ppm 17beta-estradiol (E(2), a known tumor promoter) in the diet for 14 days. RESULTS PFOA (1,800 ppm or 50 mg/kg/day) and DHEA treatments resulted in enhanced liver tumor incidence and multiplicity (p < 0.0001), whereas CLOF showed no effect. Carcinogenesis was independent of peroxisome proliferation, measured by lack of peroxisomal beta-oxidation and catalase activity. Alternately, both tumor promoters, PFOA and DHEA, resulted in estrogenic gene signatures with strong correlation to E(2) by Pearson correlation (R = 0.81 and 0.78, respectively), whereas CLOF regulated no genes in common with E(2). CONCLUSIONS These data suggest that the tumor-promoting activities of PFOA in trout are due to novel mechanisms involving estrogenic signaling and are independent of peroxisome proliferation.
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Affiliation(s)
- Susan C Tilton
- Department of Environmental and Molecular Toxicology, Oregon State University, Corvallis, Oregon, USA.
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Abstract
Within the scope of the Rat Liver Foci Bioassay the model carcinogens N-nitrosomorpholine (NNM), 2-acetylaminoflouren (2-AAF), phenobarbital (PB), and clofibrate (CF) were analyzed concerning their potency and dose-response relationship to induce foci of altered hepatocytes (FAHs), which are known to be precursor lesions of liver adenoma and carcinoma. The medium-term experiment follows an initiation-promotion protocol using diethylnitrosamine (DEN) as initiator. The present report deals with the application of two biologically based models for hepatocarcinogenesis, the two-stage clonal expansion model (TSCEM), and a color-shift model with beta distributed growth rates (CSMbeta). Both models yield similar conclusions concerning the mode of action of the carcinogens. However, the fit of CSMbeta appears closer to the observations than the fit of TSCEM. The analysis shows that application of a single dose of DEN has a persistent effect on the rate of FAH induction, especially in female rats. Overall, striking differences in the effect of the carcinogens were observed between male and female animals. 2-AAF shows a strong promoting effect in males, whereas in females the initiating effect dominates. NNM has both initiating and promoting effect, but in females, the rate of FAH formation seems to reach saturation at high dose. In the doses applied in the present experiment, PB has the weakest carcinogenic effect. Although PB alone does not induce FAH during the observation period, it increases the rate of FAH formation when applied following initiation with DEN. CF reduces the number and area fraction of GSTP-stained FAH, probably because it suppresses the placental form of glutathione S-transferase-positive phenotype.
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Affiliation(s)
- Jutta Groos
- Central Unit Biostatistics, German Cancer Research Center, Heidelberg, Germany
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Abstract
The efficacy of high-resolution (1)H nuclear magnetic resonance ((1)H-NMR) spectroscopy-based metabonomics was studied in a model of rat liver toxicity. Hepatotoxicities were induced in male rats using methylene dianiline, clofibrate and galactosamine. Twenty-four-hr urine from days 1 to 5 after treatment were subjected to (1)H-NMR evaluation of the biochemical effects. Blood were also taken at Days 2, 3 and 5 to examine biochemical changes associated with hepatotoxicities, and histopathological changes were evaluated at termination. Increases in liver enzymes were observed in animals treated with methylene dianiline or galactosamine, and histopathological analysis revealed changes associated with hepatobiliary damage and hepatocellular necrosis in methylene dianiline- and galactosamine-treated animals, respectively. Principal component analysis and statistical Spotfire analyses were used to visualize similarities and differences in urine biochemical profiles produced by (1)H-NMR spectra. The biochemical effects of methylene dianiline and galactosamine were characterized by elevated levels of glucose, fructose, beta-hydroxybutyrate, alanine, acetoacetate, lactate and creatine and decreased levels of hippurate, 2-oxoglutarate, citrate, succinate, trimethylamine-N-oxide, taurine and N-acetylglutamate in rat urine. Clofibrate treatment elevated the levels of N-methylnicotinamide and 3,4-dihydroxymandelate and decreased the levels of 2-oxoglutarate and N-acetylaspartate. This work shows that combinations of (1)H-NMR and pattern recognition are powerful tools in the evaluation of the biochemical effects of xenobiotics in liver.
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Affiliation(s)
- Kenji Ishihara
- Tsukuba Research, Drug Safety Research Laboratories, Eisai Co., Ltd., Ibaraki-ken, Japan.
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Clare MG, Lorenzon G, Akhurst LC, Marzin D, van Delft J, Montero R, Botta A, Bertens A, Cinelli S, Thybaud V, Lorge E. SFTG international collaborative study on in vitro micronucleus test. Mutation Research/Genetic Toxicology and Environmental Mutagenesis 2006; 607:37-60. [PMID: 16765631 DOI: 10.1016/j.mrgentox.2006.04.001] [Citation(s) in RCA: 48] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
Abstract
This study on the in vitro micronucleus assay, comprising 11 laboratories using human lymphocytes, was coordinated by an organizing committee supported by the SFTG (the French branch of the European Environmental Mutagen Society). Nine coded substances were assessed for their ability to induce micronuclei in human lymphocytes in vitro, mitomycin C being used as a positive control. Cultures were exposed to the test substances for a short (early or late) time or for a long time, followed by a short or long recovery period, in the presence of cytochalasin B. Each chemical was evaluated, generally in two laboratories, using three treatment schedules at least twice. The data were assessed for acceptability, and then classified as negative, positive or equivocal. Two of seven genotoxic compounds, namely colchicine and bleomycin, clearly induced micronuclei. Reproducible results were difficult to obtain for some substances, which tended to be those acting at specific stages of the cell cycle. Cytosine arabinoside, diethylstilboestrol and 5-fluorouracil were classified as equivocal. Urethane and thiabendazole were classified as negative. The two presumed non-genotoxic compounds, mannitol and clofibrate, did not induce micronuclei. Repeat testing, exposing cells at both an early and late time after mitogenic stimulation, was needed to detect substances classified as equivocal. These results show the importance of achieving sufficient inhibition of nuclear division to avoid the possibility of missing an effect. The evaluation of micronuclei in mononucleated as well as binucleated cells was particularly useful to detect aneugens. There were no false positive results using lymphocytes, indicating a high specificity. It is concluded that the clastogenic or aneugenic potential in vitro of the substances tested was correctly identified in this study, but that refining the protocol to take into account factors such as the stages of the cell cycle exposed to the compound, or the duration of recovery would be likely to improve the sensitivity of detection using lymphocytes.
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Affiliation(s)
- M Gillian Clare
- Department of Genetic Toxicology, Safety Assessment, Astra Charnwood, Loughborough, Leics, UK.
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Kudo T, Asano J, Shimizu T, Nanashima N, Fan Y, Akita M, Ookawa K, Hayakari M, Yokoyama Y, Suto K, Tsuchida S. Different susceptibility to peroxisome proliferator-induced hepatocarcinogenesis in rats with polymorphic glutathione transferase genes. Cancer Sci 2006; 97:703-9. [PMID: 16800819 DOI: 10.1111/j.1349-7006.2006.00247.x] [Citation(s) in RCA: 9] [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] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022] Open
Abstract
Although peroxisomal bifunctional enzyme (enoyl-CoA hydratase/L-3-hydroxyacyl-CoA dehydrogenase; BE) is a positive marker for peroxisome proliferation, it is completely absent or expressed very weakly in rat hepatic preneoplastic and neoplastic lesions induced by peroxisome proliferators (PP). After administration of PP for 8-15 weeks, some rats exhibit BE-negative preneoplastic foci but other rats do not. In the present study, to investigate the involvement of glutathione S-transferase (GST) M1 gene polymorphism in interindividual differences in susceptibility to PP, we developed a method to determine the genotypes of rats. We then examined whether rats with one type encoding 198Asn-199Cys (NC-type) or another encoding 198Lys-199Ser (KS-type) exhibit differences in clofibrate (CF) susceptibility. After administration of 0.3% CF for 6 weeks or more, BE-negative foci were found immunohistochemically in KS/KS-type rats, but not in NC/NC-type rats. The number of BE-negative foci in KS/KS rats was 15.3 +/- 9.0 foci/cm2 of liver section after 6 weeks of CF administration, and the values did not alter thereafter. The mean areas of BE-negative foci in KS/KS rat livers increased during the period from 6 to 60 weeks. At weeks 30 and 60, almost all BE-negative foci exhibited a clear cell phenotype, a type of preneoplastic hepatic lesion. BE-negative foci were devoid of peroxisome proliferator-activated receptor alpha, whereas surrounding tissues were positive for the receptor. These results indicate that rats that are polymorphic for the GST M1 gene exhibit different susceptibilities to CF in vivo.
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Affiliation(s)
- Toshihiro Kudo
- Second Department of Biochemistry, Hirosaki University School of Medicine, 5 Zaifu- cho, Hirosaki 036-8562, Japan
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Wakata A, Matsuoka A, Yamakage K, Yoshida J, Kubo K, Kobayashi K, Senjyu N, Itoh S, Miyajima H, Hamada S, Nishida S, Araki H, Yamamura E, Matsui A, Thybaud V, Lorenzon G, Marzin D, Lorge E. SFTG international collaborative study on in vitro micronucleus test. Mutation Research/Genetic Toxicology and Environmental Mutagenesis 2006; 607:88-124. [PMID: 16782396 DOI: 10.1016/j.mrgentox.2006.04.003] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 10/24/2022]
Abstract
In this report, are presented the results of an international collaborative study on the in vitro micronucleus assay, using CHL cells. Fourteen laboratories participated in this study which was coordinated by an organizing committee supported by the SFTG (the French branch of the European Environmental Mutagen Society). Nine coded substances, having different modes of action and at different levels were assessed in the in vitro micronucleus test, using a common protocol. Mitomycin C was used as a positive control. In order to help to define a standard protocol on CHL cells, short and long treatment periods followed by various recovery times, with or without cytochalasin B, were compared. After an evaluation of the acceptability of the assays, the tested chemicals were classified as negative, positive or equivocal. Mannitol and clofibrate were judged as negative in all treatment schedules. Bleomycin was positive in all the treatment schedules, with an increase in the number of micronucleated cells in both mononucleate and binucleate cells when using cytochalasin B. This was also shown for the aneugens colchicine, diethylstilboestrol and griseofulvin, as expected. Urethane was judged as equivocal only after long treatment with cytochalasin B, and negative in all other treatment schedules. In any case, no genotoxic compound would have been missed with schedules including a short and a long treatment time, whether the treatment was followed by a recovery period or not and whether cytochalasin B was used or not. Thus, these results show that CHL cells were suitable for accurately detecting clastogenic and aneugenic compounds of various types in the in vitro micronucleus test.
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Affiliation(s)
- Akihiro Wakata
- Astellas Pharma Inc., Drug Safety Research Laboratories, Osaka, Japan
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Lorge E, Thybaud V, Aardema MJ, Oliver J, Wakata A, Lorenzon G, Marzin D. SFTG international collaborative study on in vitro micronucleus test I. General conditions and overall conclusions of the study. Mutat Res 2006; 607:13-36. [PMID: 16815079 DOI: 10.1016/j.mrgentox.2006.04.006] [Citation(s) in RCA: 77] [Impact Index Per Article: 4.3] [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: 10/24/2022]
Abstract
This study, coordinated by the SFTG (French branch of European Environmental Mutagen Society), included 38 participants from Europe, Japan and America. Clastogens (bleomycin, urethane), including base and nucleoside analogs (5-fluorouracil and cytosine arabinoside), aneugens and/or polyploidy inducers (colchicine, diethylstilboestrol, griseofulvin and thiabendazole), as well as non-genotoxic compounds (mannitol and clofibrate), were tested. Four cell types were used, i.e. human lymphocytes in the presence of cytochalasin B and CHO, CHL and L5178Y cell lines, in the presence or absence of cytochalasin B, with various treatment-recovery schedules. Mitomycin C was used as a positive control for all cell types. Mannitol and clofibrate were consistently negative in all cell types and with all treatment-recovery conditions. Urethane, known to induce questionable clastogenicity, was not found as positive. Bleomycin and mitomycin C were found positive in all treatment-recovery conditions. The base and nucleoside analogs were less easy to detect, especially 5-fluorouracil due to the interference with cytotoxicity, while cytosine arabinoside was detected in all cell types depending on the treatment-recovery schedule. Aneugens (colchicine, diethylstilboestrol and griseofulvin) were all detected in all cell types. In this study, the optimal detection was ensured when a short treatment followed by a long recovery was associated with a long continuous treatment without recovery. There was no impact of the presence or absence of cytochalasin B on the detection of micronucleated cells on cell lines. Scoring micronucleated cells in both mononucleated and binucleated cells when using cytochalasin B was confirmed to be useful for the detection and the identification of aneugens. In conclusion, these results, together with previously published validation studies, provide a useful contribution to the optimisation of a study protocol for the detection of both clastogens and aneugens in the in vitro micronucleus test.
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Affiliation(s)
- Elisabeth Lorge
- Servier Group, Drug Safety Assessment, Orleans-Gidy, France.
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Torrey CE, Wall HG, Campbell JA, Kwanyuen P, Hoivik DJ, Miller RT, Allen JS, Jayo MJ, Selinger K, Santostefano MJ. Evaluation of the carcinogenic potential of clofibrate in the FVB/Tg.AC mouse after dermal application--part II. Int J Toxicol 2005; 24:327-39. [PMID: 16257852 DOI: 10.1080/10915810500208199] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.4] [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: 10/25/2022]
Abstract
This study was conducted as part of the International Life Sciences Institute (ILSI) Alternatives to Carcinogenicity Testing program and evaluated the carcinogenic potential of clofibrate, a nongenotoxic, peroxisome proliferator-activated receptor (PPAR) alpha agonist following dermal application to transgenic Tg.AC and nontransgenic FVB mice for a minimum of 26 weeks. Clofibrate doses of 12, 28, or 36 mg/200 microl/day were used. Positive controls for papilloma formation were benzene (174.8 mg/200 microl), and 12-o-tetradecanoylphorbol-13-acetate (TPA [0.00250 mg/200 microl]). Clofibrate was tolerated at doses up to 36 mg/200 microl. In Tg.AC mice, clofibrate produced a dose-related increase in the incidence of mice with cutaneous papillomas; and dose-related decreases in mean time to first tumor, mean multiplicity of tumors per mouse, and mean weeks to maximal yield, as well as numerous nonneoplastic microscopic lesions in the liver, kidney, spleen, and skin. Benzene and TPA induced both neoplastic and/or non-neoplastic proliferative lesions in Tg.AC mice. Clofibrate did not increase the incidence or multiplicity of papillomas, or any other tumors in FVB mice. These data show that the Tg.AC dermal model has increased sensitivity in detecting skin papillomas caused by the nongenotoxic rodent carcinogen, clofibrate, compared to wild type FVB mice, at systemic exposures that are 3x higher than the systemic exposure observed in humans taking clofibrate (AUC = 1100 microg.h/ml) at the recommended maximum therapeutic dose of 500 mg. In addition, this study supports the proposed concept that Tg.AC model may detect compounds with nongenotoxic carcinogenic potential in a shorter timeframe than conventional mouse carcinogenicity bioassays.
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Affiliation(s)
- Carla E Torrey
- GlaxoSmithKline, Safety Assessment, Research Triangle Park, North Carolina 27709, USA
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Torrey CE, Wall HG, Campbell JA, Kwanyuen P, Hoivik DJ, Miller RT, Allen JS, Jayo MJ, Selinger K, Savina PM, Santostefano MJ. Evaluation of the carcinogenic potential of clofibrate in the FVB/Tg.AC mouse after oral administration--part I. Int J Toxicol 2005; 24:313-25. [PMID: 16257851 DOI: 10.1080/10915810500208264] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.4] [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: 10/25/2022]
Abstract
This study was conducted as part of the International Life Sciences Institute (ILSI) program to evaluate the carcinogenic potential of clofibrate, a nongenotoxic, peroxisome proliferator-activated receptor (PPAR) alpha agonist following oral administration to Tg.AC (transgenic) and wild-type FVB (nontransgenic) mice for a minimum for 6 months. Clofibrate was well tolerated at doses up to 500 (males) and 650 (females) mg/kg/day. Oral administration of clofibrate to Tg.AC or FVB (wild-type) male and female mice for 6 months did not result in the increased formation of neoplastic lesions. Epithelial hyperplasia in the urinary bladder (Tg.AC and FVB) and prostate gland (Tg.AC only), and interstitial-cell hyperplasia in the testes (Tg.AC) were noted at 500 mg/kg/day. Non-neoplastic nonproliferative findings included hepatic hypertrophy and hematopoietic changes (myeloid hyperplasia, myelodysplasia, lymphoid depletion, and erythropoiesis) in Tg.AC and FVB mice of both sexes; reproductive (cystic degeneration and dilatation, hypospermia, spermatocele, dilated inspissated protein) and urogenital (tubular-cell hypertrophy, degenerative/regenerative nephropathy, necrosis/fibrosis) changes in Tg.AC and FVB male mice; congestion in the lung in male Tg.AC mice; gall bladder dilatation in female Tg.AC mice; and adrenal (intracellular lipofuscinosis and atrophy) and heart (eosinophillic myofibers) findings in Tg.AC mice of both sexes and in female FVB mice. The results of this study indicate that the clofibrate is not carcinogenic when administered to Tg.AC mice by oral gavage for 6 months at doses up to 500 (males) and 650 (females) mg/kg/day, which did produce liver hypertrophy.
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Affiliation(s)
- Carla E Torrey
- GlaxoSmithKline, Safety Assessment, Research Triangle Park, North Carolina 27709, USA
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Nesfield SR, Clarke CJ, Hoivik DJ, Miller RT, Allen JS, Selinger K, Santostefano MJ. Evaluation of the carcinogenic potential of clofibrate in the rasH2 mouse. Int J Toxicol 2005; 24:301-11. [PMID: 16257850 DOI: 10.1080/10915810500210278] [Citation(s) in RCA: 18] [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: 10/25/2022]
Abstract
The purpose of the study was to support of the International Life Sciences Institute (ILSI) alternative carcinogenicity models initiative to evaluate the carcinogenic potential of the nongenotoxic carcinogen, clofibrate, a peroxisome proliferator-activated receptor (PPAR) alpha agonist, following oral administration to rasH2 mice. Peroxisome proliferators are one of the most widely studied of the nongenotoxic carcinogens and have diverse industrial and therapeutic uses (Gonzalez et al. J. Nat. Cancer Inst. 90: 1702-1709, 1998); however, the nongenotoxic mechanism of carcinogenicity is currently unknown. Male mice were administered doses of clofibrate at 50, 100, or 200 mg/kg/day and female mice were administered doses of 50, 150, or 250 mg/kg/day by oral gavage at 10 ml/kg for 27 weeks. In addition, rasH2 male and female mice were treated with N-nitroso-N-methylurea (NMU). Nontransgenic male and female mice were treated with 200 and 250 mg/kg/day, respectively, of clofibrate. The NMU-treated mice were given a single intraperitoneal dose of 75 mg/kg, which was followed by a 90-day observation period; all others were sacrificed after 6 months of daily dosing. Hepatocellular neoplasms were observed in clofibrate-treated rasH2 male mice after 6 months of treatment but not in nontransgenic males or females. Clofibrate treatment (250 mg/kg/day) of female rasH2 mice was associated with a slight increase in the incidence of various neoplasms (harderian gland, lungs, skin, spleen, tail, thymus, and uterus) compared with untreated transgenic mice and with similarly treated nontransgenic mice. Non-neoplastic changes were found in the liver of transgenic and nontransgenic mice of both sexes and in the kidneys of male mice. NMU produced findings are consistent with previous studies. The data suggest that the rasH2 mice are a good model for testing epigenetic carcinogens in a shorter timeframe than conventional mouse carcinogenicity bioassays.
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Santostefano MJ, Hoivik DJ, Miller RT. Investigations of clofibrate in alternative carcinogenicity models. Int J Toxicol 2005; 24:285-8. [PMID: 16257848 DOI: 10.1080/10915810500210369] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/25/2022]
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Nunes B, Carvalho F, Guilhermino L. Acute toxicity of widely used pharmaceuticals in aquatic species: Gambusia holbrooki, Artemia parthenogenetica and Tetraselmis chuii. Ecotoxicol Environ Saf 2005; 61:413-9. [PMID: 15922808 DOI: 10.1016/j.ecoenv.2004.08.010] [Citation(s) in RCA: 16] [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] [Subscribe] [Scholar Register] [Received: 11/03/2003] [Revised: 08/18/2004] [Accepted: 08/25/2004] [Indexed: 05/02/2023]
Abstract
Pharmaceuticals are continuously dispersed into the environment as a result of human and veterinary use, posing relevant environmental concerns. This study evaluated the acute toxicity of three therapeutic agents (diazepam, clofibrate, and clofibric acid) and a detergent (sodium dodecyl sulfate; SDS) in three aquatic species, namely the euryhaline fish Gambusia holbrooki, the hypersaline crustacean Artemia parthenogenetica, and the marine algae Tetraselmis chuii. The ranking of 50% lethal concentrations (LC50) for the two animal species and 50% inhibitory concentration (IC50) for the algal species was, in decreasing order, clofibric acid > SDS > diazepam > clofibrate for G. holbrooki, clofibric acid > clofibrate > SDS > diazepam for A. parthenogenetica, and clofibric acid > clofibrate > SDS > diazepam for T. chuii. These differences show that the intrinsic nature of test organisms must be considered when evaluating the toxicity of these agents to aquatic ecosystems.
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Affiliation(s)
- B Nunes
- ICBAS, Instituto de Ciências Biomédicas Abel Salazar, Departamento de Estudos de Populações, Laboratório de Ecotoxicologia, Universidade do Porto, Largo Prof. Abel Salazar, 2, 4099-003 Porto, Portugal.
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Jolly RA, Goldstein KM, Wei T, Gao H, Chen P, Huang S, Colet JM, Ryan TP, Thomas CE, Estrem ST. Pooling samples within microarray studies: a comparative analysis of rat liver transcription response to prototypical toxicants. Physiol Genomics 2005; 22:346-55. [PMID: 15914576 DOI: 10.1152/physiolgenomics.00260.2004] [Citation(s) in RCA: 47] [Impact Index Per Article: 2.5] [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: 11/22/2022] Open
Abstract
Combining or pooling individual samples when carrying out transcript profiling using microarrays is a fairly common means to reduce both the cost and complexity of data analysis. However, pooling does not allow for statistical comparison of changes between samples and can result in a loss of information. Because a rigorous comparison of the identified expression changes from the two approaches has not been reported, we compared the results for hepatic transcript profiles from pooled vs. individual samples. Hepatic transcript profiles from a single-dose time-course rat study in response to the prototypical toxicants clofibrate, diethylhexylphthalate, and valproic acid were evaluated. Approximately 50% more transcript expression changes were observed in the individual (statistical) analysis compared with the pooled analysis. While the majority of these changes were less than twofold in magnitude ( approximately 80%), a substantial number were greater than twofold (approximately 20%). Transcript changes unique to the individual analysis were confirmed by quantitative RT-PCR, while all the changes unique to the pooled analysis did not confirm. The individual analysis identified more hits per biological pathway than the pooled approach. Many of the transcripts identified by the individual analysis were novel findings and may contribute to a better understanding of molecular mechanisms of these compounds. Furthermore, having individual animal data provided the opportunity to correlate changes in transcript expression to phenotypes (i.e., histology) observed in toxicology studies. The two approaches were similar when clustering methods were used despite the large difference in the absolute number of transcripts changed. In summary, pooling reduced resource requirements substantially, but the individual approach enabled statistical analysis that identified more gene expression changes to evaluate mechanisms of toxicity. An individual animal approach becomes more valuable when the overall expression response is subtle and/or when associating expression data to variable phenotypic responses.
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Affiliation(s)
- Robert A Jolly
- Lilly Research Laboratories, Greenfield, Indiana 46140, USA
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Nunes B, Carvalho F, Guilhermino L. Acute and chronic effects of clofibrate and clofibric acid on the enzymes acetylcholinesterase, lactate dehydrogenase and catalase of the mosquitofish, Gambusia holbrooki. Chemosphere 2004; 57:1581-1589. [PMID: 15519403 DOI: 10.1016/j.chemosphere.2004.09.018] [Citation(s) in RCA: 18] [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] [Subscribe] [Scholar Register] [Received: 11/04/2003] [Revised: 09/08/2004] [Accepted: 09/10/2004] [Indexed: 05/24/2023]
Abstract
The objective of this study was to investigate both acute and chronic effects of clofibrate and clofibric acid on the enzymes acetylcholinesterase (AChE), lactate dehydrogenase (LDH) and catalase (CAT) of the mosquitofish (Gambusia holbrooki). AChE, commonly used as a biomarker of neurotoxicity, was determined in the total head. LDH, an important enzyme of anaerobic metabolism, was quantified in dorsal muscle, and CAT, enzyme which has been used as indicative parameter of peroxisome proliferation, was determined in the liver. Furthermore, alterations of body and liver weight were also determined, through the calculation of the ratios final body weight/initial body weight, liver weight/final body weight, liver weight/gills weight and liver weight/head weight. Acute exposure of G. holbrooki to both clofibrate and clofibric acid induced a decrease in liver CAT activity, an increase in muscle LDH activity, while no effects were observed on AChE activity. However, chronic exposure did not alter significantly the enzymatic activities, suggesting reduced or null effects over these pathways, relative to effects reported in other species. No effects were observed for the calculated ratios, except a significant weight reduction for males chronically exposed to clofibrate.
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Affiliation(s)
- B Nunes
- ICBAS, Instituto de Ciências Biomédicas de Abel Salazar, Departamento de Estudos de Populações, Laboratório de Ecotoxicologia, Universidade do Porto, Largo Prof. Abel Salazar, 2, 4099-003 Porto, Portugal.
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Kazeto Y, Place AR, Trant JM. Effects of endocrine disrupting chemicals on the expression of CYP19 genes in zebrafish (Danio rerio) juveniles. Aquat Toxicol 2004; 69:25-34. [PMID: 15210295 DOI: 10.1016/j.aquatox.2004.04.008] [Citation(s) in RCA: 109] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/25/2003] [Revised: 03/15/2004] [Accepted: 04/14/2004] [Indexed: 05/24/2023]
Abstract
Cytochrome P450 aromatase (CYP19) is the key steroidogenic enzyme responsible for conversion of androgens to estrogens which play a critical role in developmental sex differentiation and adult reproductive cycles in vertebrates. To evaluate the potential roles of endocrine disrupting chemicals (EDC) on reproductive physiology of fish, the influence of multiple classes of EDC on the transcript abundance of two CYP19 isoforms, CYP19A1 and A2, were investigated in zebrafish juveniles. The pharmaceutical, clofibrate, and the pesticide, atrazine, did not influence the expression of either CYP19 gene. Estrogenic compounds, nonylphenol (NP) and a pharmaceutical estrogen, ethinylestradiol (EE), strongly enhanced the expression of CYP19A2 gene in dose-dependent manner. Exposure to benzo[a]pyrene (BaP) significantly increased CYP19A2 transcript abundance. Furthermore, BaP when co-treated with EE partially suppressed EE-induced upregulation of CYP19A2. In contrast, the expression of CYP19A1 was basically resistant to EDC treatment although EE at high concentration (1-100 nM) downregulated its expression. These findings suggest that multiple classes of EDC may potentially perturb developmental and reproductive physiology in fish through differential transcriptional modulation of the CYP19 genes with the most evident disruption in neural tissue.
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Affiliation(s)
- Yukinori Kazeto
- Center of Marine Biotechnology, University of Maryland Biotechnology Institute, Baltimore, MD 21202, USA
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Ulrich RG, Rockett JC, Gibson GG, Pettit SD. Overview of an interlaboratory collaboration on evaluating the effects of model hepatotoxicants on hepatic gene expression. Environ Health Perspect 2004; 112:423-7. [PMID: 15033591 PMCID: PMC1241895 DOI: 10.1289/ehp.6675] [Citation(s) in RCA: 45] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/10/2023]
Abstract
DNA microarrays and related tools offer promise for identification of pathways involved in toxic responses to xenobiotics. To be useful for risk assessment, experimental data must be challenged for reliability and interlaboratory reproducibility. Toward this goal, the Hepatotoxicity Working Group of the International Life Sciences Institute (ILSI) Health and Environmental Sciences Institute (HESI) Technical Committee on Application of Genomics to Mechanism-Based Risk Assessment evaluated and compared biological and gene expression responses in rats exposed to two model hepatotoxins--clofibrate and methapyrilene. This collaborative effort provided an unprecedented opportunity for the working group to evaluate and compare multiple biological, genomic, and toxicological parameters across different laboratories and microarray platforms. Many of the results from this collaboration are presented in accompanying articles in this mini-monograph, whereas others have been published previously. (Italic)In vivo(/Italic) studies for both compounds were conducted in two laboratories using a standard experimental protocol, and RNA samples were distributed to 16 laboratories for analysis on six microarray platforms. Histopathology, clinical chemistry, and organ weight changes were consistent with reported effects. Gene expression results demonstrated reasonable agreement between laboratories and across platforms. Discrepancies in expression profiles of some individual genes were largely due to platform differences and approaches to data analysis rather than to biological or interlaboratory variability. Despite these discrepancies there was overall agreement in the biological pathways affected by these compounds, demonstrating that transcriptional profiling is reproducible between laboratories and can reliably identify affected pathways necessary to provide mechanistic insight. This effort represents an important first step toward the use of transcriptional profiling in risk assessment.
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Affiliation(s)
- Roger G Ulrich
- Rosetta Inpharmatics, Merck Research Laboratories, Kirkland, Washington, USA
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Baker VA, Harries HM, Waring JF, Duggan CM, Ni HA, Jolly RA, Yoon LW, De Souza AT, Schmid JE, Brown RH, Ulrich RG, Rockett JC. Clofibrate-induced gene expression changes in rat liver: a cross-laboratory analysis using membrane cDNA arrays. Environ Health Perspect 2004; 112:428-38. [PMID: 15033592 PMCID: PMC1241896 DOI: 10.1289/ehp.6677] [Citation(s) in RCA: 45] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/10/2023]
Abstract
Microarrays have the potential to significantly impact our ability to identify toxic hazards by the identification of mechanistically relevant markers of toxicity. To be useful for risk assessment, however, microarray data must be challenged to determine reliability and interlaboratory reproducibility. As part of a series of studies conducted by the International Life Sciences Institute Health and Environmental Science Institute Technical Committee on the Application of Genomics to Mechanism-Based Risk Assessment, the biological response in rats to the hepatotoxin clofibrate was investigated. Animals were treated with high (250 mg/kg/day) or low (25 mg/kg/day) doses for 1, 3, or 7 days in two laboratories. Clinical chemistry parameters were measured, livers removed for histopathological assessment, and gene expression analysis was conducted using cDNA arrays. Expression changes in genes involved in fatty acid metabolism (e.g., acyl-CoA oxidase), cell proliferation (e.g., topoisomerase II-Alpha), and fatty acid oxidation (e.g., cytochrome P450 4A1), consistent with the mechanism of clofibrate hepatotoxicity, were detected. Observed differences in gene expression levels correlated with the level of biological response induced in the two in vivo studies. Generally, there was a high level of concordance between the gene expression profiles generated from pooled and individual RNA samples. Quantitative real-time polymerase chain reaction was used to confirm modulations for a number of peroxisome proliferator marker genes. Though the results indicate some variability in the quantitative nature of the microarray data, this appears due largely to differences in experimental and data analysis procedures used within each laboratory. In summary, this study demonstrates the potential for gene expression profiling to identify toxic hazards by the identification of mechanistically relevant markers of toxicity.
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Affiliation(s)
- Valerie A Baker
- Safety and Environmental Assurance Centre, Unilever Research Colworth, Sharnbrook, Bedfordshire, United Kingdom.
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Ammerschlaeger M, Beigel J, Klein KU, Mueller SO. Characterization of the species-specificity of peroxisome proliferators in rat and human hepatocytes. Toxicol Sci 2004; 78:229-40. [PMID: 14976357 DOI: 10.1093/toxsci/kfh071] [Citation(s) in RCA: 55] [Impact Index Per Article: 2.8] [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: 11/14/2022] Open
Abstract
Peroxisome proliferation is a well-defined pleiotropic effect that is mediated by the ligand inducible transcription factor peroxisome proliferator-activated receptor (PPAR) alpha. Because marked peroxisome proliferation occurs in rodents but not in humans, we aimed to elucidate the molecular and cellular determinants of this species-specificity in hepatocytes. Analysis of peroxisomal marker enzyme activities confirmed that peroxisome proliferators induced acyl-CoA oxidase (ACOX) and to a lesser extent catalase in rat hepatocytes, but not in human hepatoma HepG2 cells. Transient transfection assays revealed that ciprofibrate and Wy 14,643 induced rat but not human PPARalpha-mediated reporter gene activity in rat FAO and primary hepatocytes on rat but not on human PPARalpha response elements (PPREs). In contrast, in human HepG2 and primary human hepatocytes, peroxisome proliferators did not induce either human or rat PPARalpha activity regardless of rat or human PPRE sequences. In addition, no induction of ACOX gene expression was observed in human hepatocytes independent of the expression level of human PPARalpha. Remarkably, no distinct peroxisome proliferation related responses were observed in human hepatocytes when rat PPARalpha was transfected, although human hepatocytes were responsive to PPARalpha-mediated induction of carnitine palmitoyl transferase-1A and 3-hydroxy-3-methylglutaryl-CoA synthase. These results confirmed that PPARalpha and PPREs are important determinants for the species-specificity of peroxisome proliferation. Nevertheless, our results showed that human hepatocytes limit the extent of peroxisome proliferation regardless of PPARalpha expression.
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Kiyosawa N, Watanabe T, Sakuma K, Kanbori M, Niino N, Ito K, Yamoto T, Manabe S. Phylogenetic tree facilitates the understanding of gene expression data on drug metabolizing enzymes obtained by microarray analysis. Toxicol Lett 2004; 145:281-9. [PMID: 14580899 DOI: 10.1016/j.toxlet.2003.08.004] [Citation(s) in RCA: 10] [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] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
Abstract
The gene expression data of drug metabolizing enzymes (DMEs) in male F344 rat livers were examined after treatments with phenobarbital (PB), clofibrate (CPIB), 3-methylcholanthrene (3-MC) or butylated hydroxyanisole (BHA) using an Affymetrix GeneChip system. Nucleotide sequence-based phylogenetic trees combined with a heat map, that presents both quantitative and qualitative data, were created. Most DME gene probes were successfully classified into the corresponding gene families, although a few were not due to the presence of non-coding or promoter region sequences in the target gene. There were also some data discrepancies among probes of the same gene family, indicating the inappropriate design of these probes. With this method, microarray probes with confusing nomenclature and quality differences can be identified. In addition, a good correlation between the gene expression data and protein data was confirmed, indicating the usefulness of this method for the comprehensive monitoring of DME activity in rat livers treated with xenobiotics.
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Affiliation(s)
- Naoki Kiyosawa
- Medicinal Safety Research Labs, Sankyo Co Ltd, 717 Horikoshi, Fukuroi, Shizuoka 437-0065, Japan.
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Jung JW, Park JS, Hwang JW, Kang KS, Lee YS, Song BS, Lee GJ, Yeo CD, Kang JS, Lee WS, Jeon KS, Um CH, Kim YS, Oh MJ, Youn JP, Li P, Park JE, Hwang SY. Gene Expression Analysis of Peroxisome Proliferators- and Phenytoin-Induced Hepatotoxicity Using cDNA Microarray. J Vet Med Sci 2004; 66:1329-33. [PMID: 15585944 DOI: 10.1292/jvms.66.1329] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.1] [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: 11/22/2022] Open
Abstract
The recent DNA microarray technology enables us to understand a large number of gene expression profiling. The technology has potential possibility to comprehend mechanism of multiple genes were related to compounds which have toxicity in biological system. So, the toxicogenomics through this technology may be very powerful for understanding the effect of unknown toxic mechanisms in biological system. We have studied that the effect of compounds related to hepatotoxin in vivo system using DNA microarray and classified chemicals which have been well characterized. We have studied three compounds; 2 peroxisome proliferators: Clofibrate (ethyl-p-chlorophenoxyisobutyrate), gemfibrozil (5-2[2,5-dimethyl-phenoxy]2-2-dimethyl-pentanonic), and an antiepileptic drug: phenytoin (5,5-diphenylhydantoin). Male Sprague-Dawely VAF(+) albino rats of 5-6 weeks old were treated with each compound for 24 hr and 2 weeks. 4.8 K cDNA microarray in house has been used for gene expression profiling. We found that the clustering of gene expression had similarity like as the toxic phenotype of compounds.
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Affiliation(s)
- Jin-Wook Jung
- Department of Biochemistry and Molecular Biology, Hanyang University & Genocheck Co., Ltd., South Korea
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Kramer JA, Blomme EAG, Bunch RT, Davila JC, Jackson CJ, Jones PF, Kolaja KL, Curtiss SW. Transcription profiling distinguishes dose-dependent effects in the livers of rats treated with clofibrate. Toxicol Pathol 2003; 31:417-31. [PMID: 12851107 DOI: 10.1080/01926230390202353] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.0] [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: 10/25/2022]
Abstract
Peroxisome proliferators such as the fibrates act via the peroxisome proliferator activated receptor (PPAR)-alpha as hypolipidemic agents. Many peroxisome proliferators are also nongenotoxic hepatic carcinogens and hepatotoxicants in rodents. We performed transcription profiling using cDNA microarrays on livers of rats treated for 5 days with 3 doses of the peroxisome proliferator clofibrate. All 3 doses had hepatic effects as assessed by liver to body weight ratio, alanine aminotransferase (ALT) increases and histopathology examination. Analysis of the transcription profiling data identified changes in the expression of many genes within several mechanistic pathways that support existing hypotheses regarding peroxisome proliferator mediated carcinogenicity. Additionally, the transcription profiling, histopathology, and clinical chemistry results suggested a biphasic response to clofibrate. These findings provide insight into the pathogenesis of toxic and carcinogenic effects of clofibrate in rodents and demonstrate the ability of cDNA microarrays to provide information regarding mechanisms of toxicity identified during the drug development process.
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Affiliation(s)
- Jeffrey A Kramer
- Pharmacia Corporation, Global Toxicology, 800 N. Lindbergh Blvd., St Louis, Missouri 63167, USA.
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Ittrich C, Deml E, Oesterle D, Küttler K, Mellert W, Brendler-Schwaab S, Enzmann H, Schladt L, Bannasch P, Haertel T, Mönnikes O, Schwarz M, Kopp-Schneider A. Prevalidation of a rat liver foci bioassay (RLFB) based on results from 1600 rats: a study report. Toxicol Pathol 2003; 31:60-79. [PMID: 12597450 DOI: 10.1080/01926230390173888] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.1] [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
A rat liver foci bioassay (RLFB) based on an initiation-promotion protocol employing preneoplastic foci of altered hepatocytes (FAH) as an endpoint, was prevalidated in 5 different laboratories. FAH were identified by immunohistochemical demonstration of glutathione-S-transferase (placental form, GSTP) and by staining with hematoxilin/eosin (H&E), and their area fraction was quantified morphometrically. The four model hepatocarcinogens N-nitrosomorpholine, 2-acetylaminofluoren, phenobarbital, and clofibrate were selected according to characteristic differences in their presumed mode of action, and tested in a total of 1,600 male and female rats at 2 different dose levels. The chemicals were found to differ characteristically in their potency and dose-response relationship to induce FAH when given alone or when administered following initiation with diethylnitrosamine. The interlaboratory variation was small for results obtained with the GSTP-stain and somewhat larger with respect to H&E. The assessment of the carcinogenic potential of the four chemicals by the different laboratories was in the same range and the nature of their dose-response relationships did not differ essentially between laboratories. Our results suggest that this RLFB is a sensitive bioassay, providing potentially valuable information for risk assessment including the classification of carcinogenic chemicals according to their mode of action.
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Affiliation(s)
- Carina Ittrich
- Central Unit Biostatistics, German Cancer Research Center (DKFZ), P.O. Box 101949, D-69009 Heidelberg, Germany
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Hamadeh HK, Bushel PR, Jayadev S, Martin K, DiSorbo O, Sieber S, Bennett L, Tennant R, Stoll R, Barrett JC, Blanchard K, Paules RS, Afshari CA. Gene expression analysis reveals chemical-specific profiles. Toxicol Sci 2002; 67:219-31. [PMID: 12011481 DOI: 10.1093/toxsci/67.2.219] [Citation(s) in RCA: 333] [Impact Index Per Article: 15.1] [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: 11/14/2022] Open
Abstract
The application of gene expression profiling technology to examine multiple genes and signaling pathways simultaneously promises a significant advance in understanding toxic mechanisms to ultimately aid in protection of public health. Public and private efforts in the new field of toxicogenomics are focused on populating databases with gene expression profiles of compounds where toxicological and pathological endpoints are well characterized. The validity and utility of a toxicogenomics is dependent on whether gene expression profiles that correspond to different chemicals can be distinguished. The principal hypothesis underlying a toxicogenomic or pharmacogenomic strategy is that chemical-specific patterns of altered gene expression will be revealed using high-density microarray analysis of tissues from exposed organisms. Analyses of these patterns should allow classification of toxicants and provide important mechanistic insights. This report provides a verification of this hypothesis. Patterns of gene expression corresponding to liver tissue derived from chemically exposed rats revealed similarity in gene expression profiles between animals treated with different agents from a common class of compounds, peroxisome proliferators [clofibrate (ethyl-p-chlorophenoxyisobutyrate), Wyeth 14,643 ([4-chloro-6(2,3-xylidino)-2-pyrimidinylthio]acetic acid), and gemfibrozil (5-2[2,5-dimethylphenoxy]2-2-dimethylpentanoic acid)], but a very distinct gene expression profile was produced using a compound from another class, enzyme inducers (phenobarbital).
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Affiliation(s)
- Hisham K Hamadeh
- National Institute of Environmental Health Sciences, P.O. Box 12233, MD2-04, Research Triangle Park, NC 27709, USA
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Hamano T, Kobayashi K, Sakairi T, Hayashi M, Mutai M. Peroxisome proliferator-activated receptor alpha (PPAR alpha) agonist, WY-14,643, increased transcription of myosin light chain-2 in cardiomyocytes. J Toxicol Sci 2001; 26:275-84. [PMID: 11871124 DOI: 10.2131/jts.26.275] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.7] [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: 11/02/2022]
Abstract
Peroxisome proliferator-activated receptors (PPARs) are nuclear hormone receptors that can be activated by xenobiotics and natural fatty acids. To assess the potential physiological activity of PPAR ligands on cardiac muscular cells, the effects of PPAR alpha agonist, WY-14,643, on both rat hearts and a rat cardiomyocyte cell line (H9c2 cells) were investigated. Male F344 rats were fed a diet containing WY-14,643 at a concentration of 100 ppm for 26 weeks. Cardiac muscular hypertrophy was revealed by morphometric analysis in which the diameter of the muscular fibers in WY-14,643-treated rats was larger than those of control rats. Using H9c2 cells in vitro, the protein content per cell was increased in a dose-dependent manner with the treatment of WY-14,643. The transcription of myosin light chain-2 (MLC-2), a parameter of myocardial hypertrophy, was increased in H9c2 cells transfected with the rat MLC-2/luciferase fusion gene by WY-14,643 as well as other peroxisome proliferators, clofibrate and di(2-ethylhexyl) phthalate. In addition, accumulation of myosin light chain protein was confirmed in H9c2 cells treated with WY-14,643 at 10 micrograms/ml for 7 days or more by immunohistochemistry. These results suggest that PPAR alpha ligands have a potential to regulate MLC-2, which is a contractile protein in cardiomyocytes and may play a part of role in the pathogenesis of cardiac hypertrophy.
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Affiliation(s)
- T Hamano
- Toxicology Laboratory, Mitsubishi Pharma Co., 100-5 Yana, Kisarazu-shi, Chiba 292-0812, Japan
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Abstract
Peroxisome proliferators have been found to induce hepatocarcinogenesis in rodents, and may cause mitochondrial damage. Consistent with this, clofibrate increased hepatic mitochondrial oxidative DNA and protein damage in mice. The present investigation aimed to study the mechanism by which this might occur by examining the effect of clofibrate on freshly isolated mouse liver mitochondria and a cultured hepatocyte cell line, AML-12. Mitochondrial membrane potential (Delta Psi(m)) was determined by using the fluorescent dye 5,5',6,6'-tetrachloro-1,1', 3,3'-tetraethyl-benzimidazolylcarbocyanine iodide (JC-1) and tetramethylrhodamine methyl ester (TMRM). Application of clofibrate at concentrations greater than 0.3 mM rapidly collapsed the Delta Psi(m) both in liver cells and in isolated mitochondria. The loss of Delta Psi(m) occurred prior to cell death and appeared to involve the mitochondrial permeability transition (MPT), as revealed by calcein fluorescence studies and the protective effect of cyclosporin A (CsA) on the decrease in Delta Psi(m). Levels of reactive oxygen species (ROS) were measured with the fluorescent probes 5-(and-6)-carboxy-2',7'-dichlorofluorescein diacetate (DCFDA) and dihydrorhodamine 123 (DHR123). Treatment of the hepatocytes with clofibrate caused a significant increase in intracellular and mitochondrial ROS. Antioxidants such as vitamin C, deferoxamine, and catalase were able to protect the cells against the clofibrate-induced loss of viability, as was CsA, but to a lesser extent. These results suggest that one action of clofibrate might be to impair mitochondrial function, so stimulating formation of ROS, which eventually contribute to cell death.
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Affiliation(s)
- B Qu
- Department of Biochemistry, Faculty of Medicine, National University of Singapore, Singapore, Singapore
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Pugh G, Isenberg JS, Kamendulis LM, Ackley DC, Clare LJ, Brown R, Lington AW, Smith JH, Klaunig JE. Effects of di-isononyl phthalate, di-2-ethylhexyl phthalate, and clofibrate in cynomolgus monkeys. Toxicol Sci 2000; 56:181-8. [PMID: 10869467 DOI: 10.1093/toxsci/56.1.181] [Citation(s) in RCA: 76] [Impact Index Per Article: 3.2] [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: 11/15/2022] Open
Abstract
The effects of the peroxisome proliferators di-isononyl phthalate (DINP) and di-2-ethylhexyl phthalate (DEHP) were evaluated in young adult male cynomolgus monkeys after 14 days of treatment, with emphasis on detecting hepatic and other effects seen in rats and mice after treatment with high doses of phthalates. Groups of 4 monkeys received DINP (500 mg/kg/day), DEHP (500 mg/kg/day), or vehicle (0.5% methyl cellulose, 10 ml/kg) by intragastric intubation for 14 consecutive days. Clofibrate (250 mg/kg/day), a hypolipidemic drug used for cholesterol reduction in human patients was used as a reference substance. None of the test substances had any effect on body weight or liver weights. Histopathological examination of tissues from these animals revealed no distinctive treatment-related effects in the liver, kidney, or testes. There were also no changes in any of the hepatic markers for peroxisomal proliferation, including peroxisomal beta-oxidation (PBOX) or replicative DNA synthesis. Additionally, in situ dye transfer studies using fresh liver slices revealed that DINP, DEHP, and clofibrate had no effect on gap junctional intercellular communication (GJIC). None of the test substances produced any toxicologically important changes in urinalysis, hematology, or clinical chemistry; however, clofibrate produced some emesis, small increases in serum triglyceride, decreased calcium, and decreased weights of testes/epididymides and thyroid/parathyroid. The toxicological significance of these small changes is questionable. The absence of observable hepatic effects in monkeys at doses that produce hepatic effects in rodents suggests that DINP, DEHP, and clofibrate would also not elicit in primates other effects such as liver cancer. These data, along with results from in vitro hepatocyte studies, indicate that rodents are not good animal models for predicting the hepatic effects of phthalates in primates, including humans.
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Affiliation(s)
- G Pugh
- Exxon Biomedical Sciences, Inc., East Millstone, New Jersey 08875, USA
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Abstract
Hepatic drug metabolizing enzyme activities were determined, after treatment with clofibrate, in transgenic mice carrying human c-Ha-ras (rasH2 mice). Changes in the drug metabolizing enzyme activities in these mice by gene integration were also evaluated. Male and female rasH2 mice (Tg) and the litter mates not carrying the gene (non-Tg) received orally 500 mg/kg of clofibrate or the vehicle for 12 consecutive days. Liver homogenate and microsomes were prepared and the contents and activities of cytochrome P450 (CYP), cytochrome b5 content and enzyme activities related to peroxisome proliferation were determined. Relative liver weights, CYP4A and activities of catalase and carnitine palmitoyl transferase increased to the same extent in Tg and non-Tg mice treated with clofibrate. In Tg and non-Tg groups that received vehicle, contents and activities of CYP and cytchrome b5 contents were comparable. It was concluded that gene integration did not alter drug metabolizing enzymes and responses to clofibrate.
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Affiliation(s)
- N Katsutani
- Department of Developmental Safety Assessment Research, Eisai Company, Gifu, Japan.
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Nagai MK, Farber E. The slow induction of resistant hepatocytes during initiation of hepatocarcinogenesis by the nongenotoxic carcinogen clofibrate. Exp Mol Pathol 1999; 67:144-9. [PMID: 10600397 DOI: 10.1006/exmp.1999.2258] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.2] [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: 11/22/2022]
Abstract
This study was designed to explore whether a well-known nongenotoxic liver carcinogen, clofibrate, would induce rare resistant hepatocytes similar to those seen during initiation of hepatocarcinogenesis with many genotoxic carcinogens. Male young adult F344 rats were exposed to a control diet containing 0.5% (w/w) clofibrate for 3, 6, or 10 months. After 1 month on a diet free of clofibrate, the animals were assayed for resistant hepatocytes by a standardized selection procedure using 2-acetylaminofluorene as the inhibitor and partial hepatectomy as a strong stimulus for cell proliferation. No resistant hepatocytes were found in the animals exposed to clofibrate for 3 months or in any of a series of control animals. However, animals on the clofibrate for 6 and 10 months contained resistant hepatocytes that were clonally expanded to produce hepatocyte nodules. These nodules were indistinguishable on gross and microscopic examination from hepatocyte nodules seen in animals in which nodules are induced with one of many different genotoxic carcinogens. Also, like those nodules, the nodules seen in the animals exposed to clofibrate stained positively for glutathione S-transferase 1-1 and gamma-glutamyl transpeptidase and negatively for ATPase. The evidence from this study indicates that the nongenotoxic carcinogen, clofibrate, induces early cellular changes in the liver that are very similar to those induced by many different genotoxic carcinogens. These changes are manifest as a resistance phenotype in a few scattered hepatocytes that now can be clonally expanded selectively to form hepatocyte nodules. However, the resistant hepatocytes are induced by clofibrate much more slowly. Whether this basic similarity pertains to the later steps in the hepatocarcinogenic process remains to be studied.
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Affiliation(s)
- M K Nagai
- Department of Pathology and Department of Biochemistry, University of Toronto School of Medicine, Medical Science Building, Toronto, Ontario, M5S 1A8, Canada
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Abstract
Clofibrate is a peroxisome proliferator that can cause hepatic cancer in rodents. It has been suggested that oxidative damage is involved in this hepatocarcinogenesis, although the data are conflicting. We confirmed that clofibrate causes oxidative damage in nuclei from the livers of mice treated with this substance, measured both as protein carbonyls and levels of 8-hydroxy-2'-deoxyguanosine (8-OHdG) in DNA. In addition, clofibrate also affects mitochondria, causing elevated levels of carbonyls and 8-OHdG, increased state 4 respiration and decreased adenosine triphosphatase (ATPase) activity. No evidence for clofibrate-induced lipid peroxidation in mitochondria was obtained. We propose that mitochondria may be a major target of injury and a source of oxidative stress in clofibrate-treated animals.
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Affiliation(s)
- B Qu
- Department of Biochemistry, National University of Singapore, Singapore
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Abstract
Conjugated linoleic acid (CLA) is reported as having several beneficial effects including anticarcinogenic, cholesterol-lowering and anti-atherogenic properties; however, CLA has also been reported as a putative peroxisome proliferator in mice. In this study the ability of CLA to cause peroxisome proliferation in the rat, as measured by accepted enzyme markers was investigated. Male Wistar rats were fed a semi-purified diet containing 0.0, 1.5 or 5.0 energy % CLA for 4 weeks. A positive control group were given 250 mg clofibrate/kg by gavage for 4 days. Hepatic cyanide-insensitive palmitoyl coenzyme A (PCoA) oxidase and carnitine acetyl transferase (CAT) activities and total cytochrome P450 (CYP) levels were measured. CLA had no effect on body weight or liver/body weight ratios, but clofibrate significantly increased mean liver/body weight ratio by 41.6%. Clofibrate-treated rats showed typical changes with increases in hepatic PCoA oxidase and CAT activity (5.8-fold and 22.8-fold) and in total CYP (1.66-fold) compared with control. There were no differences between the control group and the groups fed CLA for either the peroxisomal enzymes or total CYP. These results suggest that CLA does not act in the rat as a classical peroxisome proliferator and that there may be a species difference in the effects on rat and mice.
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Affiliation(s)
- P A Jones
- SEAC Toxicology Unit, Unilever Research Colworth, Sharnbrook, Bedfordshire, UK
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Shoda T, Mitsumori K, Onodera H, Toyoda K, Uneyama C, Imazawa T, Hirose M. The relationship between decrease in Cx32 and induction of P450 isozymes in the early phase of clofibrate hepatocarcinogenesis in the rat. Arch Toxicol 1999; 73:373-80. [PMID: 10550479 DOI: 10.1007/s002040050676] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.0] [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: 11/28/2022]
Abstract
To examine the relationship between the decrease in connexin 32 (Cx32) and induction of P450 isozymes in the early phase of clofibrate hepatocarcinogenesis, a total of 20 male F344 rats were initiated with a single intraperitoneal injection of 150 mg/kg of diethylnitrosamine (DEN) or given the saline vehicle alone and starting 2 weeks later given diet containing 0.18, 0.09, and 0% clofibrate for 6 weeks. All animals were subjected to two-thirds partial hepatectomy at week 3 and killed at week 8. Absolute and relative (ratios to body weight) liver weights were significantly increased in the DEN + clofibrate groups compared with the DEN-alone group. Diffuse hepatocellular hypertrophy with granular cytoplasmic eosinophilia characterized by a marked increase in peroxisomes and smooth endoplasmic reticulum, was observed in the clofibrate treated rats. Induction of cytochrome P450 (CYP) 4A1 and 2B1/2 was noted in the DEN + clofibrate groups, this being most marked in the CYP 2B1 case. Immunohistochemically, positive immunostaining for anti-CYP 4A1 and CYP 2B1 were observed diffusely and centrilobularly, respectively. The numbers and areas of Cx32-positive spots per hepatocyte in the centrilobular areas in the treated rats were significantly decreased in an essentially dose-dependent manner, but no changes were observed in periportal areas. The numbers and areas of foci positive for glutathione S-transferase placental form (GST-P) were decreased in a dose dependent manner in the clofibrate treated groups. These results suggest that the CYP 2B1/2 induction and Cx32 decrease in centrilobular hepatocytes, similarly to those thought to be involved in the hepatic promotion mechanism of phenobarbital, may also play important roles in clofibrate actions in the liver, in addition to its causation of oxidative DNA injury.
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Affiliation(s)
- T Shoda
- Division of Pathology, National Institute of Health Sciences 1-18-1 Kamiyoga, Setagaya-ku, Tokyo 158-8501, Japan
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Sano M, Hagiwara A, Tamano S, Hasegawa R, Imaida K, Ito N, Shirai T. Dose-dependent induction of carcinomas and glutathione S-transferase placental form negative eosinophilic foci in the rat liver by di(2-ethylhexyl)phthalate after diethylnitrosamine initiation. J Toxicol Sci 1999; 24:177-86. [PMID: 10478332 DOI: 10.2131/jts.24.3_177] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.4] [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: 11/02/2022]
Abstract
The dose-dependence of di(2-ethylhexyl)phthalate (DEHP) hepatocarcinogenicity was investigated in male F344 rats which were initially injected with diethylnitrosamine (200 mg/kg, i.p.) and subjected to partial hepatectomy at week 3. The animals were administered DEHP in the diet at concentrations of 30, 300, 3,000, or 12,000 ppm starting 2 weeks after the DEN injection for up to 46 weeks and killed at weeks 8, 24, 48 and 52. Additional groups were given clofibrate (3,000 ppm in diet) or basal diet instead of the DEHP diet. Incidences of hepatocellular carcinomas were 75% (9/12, P < 0.01) for 12,000 ppm, 10% (1/10) for 3,000 ppm, 7% (1/14) for 300 ppm, 0% (0/13) for 30 ppm, 15% (2/13) for clofibrate, and 8% (1/13) for the basal diet group at week 52, 4 weeks after cessation of chemical feeding. Development of glutathione S-transferase placental form (GST-P) positive foci was only slightly increased by clofibrate-administration at week 52 and consistently lower than the control level in the DEHP-treated groups after 24 weeks. In contrast, GST-P negative eosinophilic foci were dose-dependently increased in the more than 300 ppm DEHP and clofibrate treated groups. At the 30 ppm dose level, however, no morphological changes were apparent in the liver. Thus, the non-observed effect level regarding the promotional activity of hepatocarcinogenesis was demonstrated at 30 ppm, the effects being predictable on the basis of development of GST-P negative eosinophilic foci.
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MESH Headings
- Adenoma, Liver Cell/chemically induced
- Adenoma, Liver Cell/enzymology
- Adenoma, Liver Cell/pathology
- Animals
- Body Weight/drug effects
- Carcinoma, Hepatocellular/chemically induced
- Carcinoma, Hepatocellular/enzymology
- Carcinoma, Hepatocellular/pathology
- Clofibrate/toxicity
- Cocarcinogenesis
- Diethylhexyl Phthalate/toxicity
- Dimethylnitrosamine/toxicity
- Dose-Response Relationship, Drug
- Glutathione S-Transferase pi
- Glutathione Transferase/analysis
- Glutathione Transferase/biosynthesis
- Isoenzymes/analysis
- Isoenzymes/biosynthesis
- Liver/drug effects
- Liver/enzymology
- Liver/pathology
- Liver Neoplasms, Experimental/chemically induced
- Liver Neoplasms, Experimental/enzymology
- Liver Neoplasms, Experimental/pathology
- Male
- No-Observed-Adverse-Effect Level
- Organ Size/drug effects
- Precancerous Conditions/chemically induced
- Precancerous Conditions/enzymology
- Precancerous Conditions/pathology
- Rats
- Rats, Inbred F344
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Affiliation(s)
- M Sano
- First Department of Pathology, Nagoya City University Medical School, Japan
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42
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Hall M, Matthews A, Webley L, Harling R. Effects of di-isononyl phthalate (DINP) on peroxisomal markers in the marmoset-DINP is not a peroxisome proliferator. J Toxicol Sci 1999; 24:237-44. [PMID: 10478338 DOI: 10.2131/jts.24.3_237] [Citation(s) in RCA: 18] [Impact Index Per Article: 0.7] [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: 11/02/2022]
Abstract
In the present study the systemic toxic potential of di-isononyl phthalate (DINP) was assessed in a 13-week study in marmosets. Particular attention was given to its potential for hepatic peroxisome proliferation. Three groups of four male and four female marmosets received DINP, by oral gavage administration, at dosages of 100, 500 or 2500 mg/kg/day for 13 weeks. A fourth group served as a concurrent Control group and received the vehicle (1% methylcellulose and 0.5% Tween) only. A fifth group received clofibrate at a dosage of 500 mg/kg/day to provide a positive Control for liver peroxisome activity. At the end of the treatment period, the animals were killed and their livers were removed. 3000 x g supernatant and microsomal subcellular fractions were prepared from homogenised liver by differential centrifugation. The peroxisomal marker enzyme activity, cyanide-insensitive palmitoyl CoA oxidase, was assayed in the former, while cytochrome P450 concentration and lauric acid 11- and 12-hydroxylase activities (selective for CYP2E1 and 4A, respectively) were assayed in the microsomes. No statistically significant changes were seen in any of these parameters measured following DINP treatment, compared with the Control. Clofibrate treatment resulted in an approximately 100% increase (p < 0.01) in both male and female marmoset cyanide-insensitive palmitoyl CoA oxidase activity and a similar increase (p < 0.05) in male (only) lauric acid 11-hydroxylase activity. No other changes were statistically significant at the 5% level. These data provide no evidence that DINP was acting as a peroxisome proliferator when administered to marmosets under the conditions of the study.
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Affiliation(s)
- M Hall
- Department of In Vitro Metabolism, Huntingdon Life Sciences Limited, England
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43
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Muhlenkamp CR, Gill SS. A glucose-regulated protein, GRP58, is down-regulated in C57B6 mouse liver after diethylhexyl phthalate exposure. Toxicol Appl Pharmacol 1998; 148:101-8. [PMID: 9465269 DOI: 10.1006/taap.1997.8323] [Citation(s) in RCA: 12] [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] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023]
Abstract
Diethylhexyl phthalate (DEHP) is a widely used plasticizer that induces peroxisome proliferation in rodents. Prolonged exposure to DEHP results in a variety of toxic effects, the most significant of which appears to be an increased incidence of liver cancer and male reproductive toxicity in rodents. Accompanying these toxic effects is the induction of a number of genes within the liver, particularly those genes involved in peroxisomal fatty acid beta-oxidation and members of the cytochrome P450 family, CYP4A. In order to explore which additional genes may be altered by DEHP exposure, mRNA differential display was performed using total liver RNA from male C57B6 mice that were treated with either O or 2% DEHP in their diet for 7 days. In doing so, a number of partial cDNAs representing messages that are potentially differentially expressed have been isolated. One of these cDNAs was found to be similar to the previously cloned gene, GRP58. Analysis by RNase protection assay and North hybridization have shown that the transcript for GRP58 is down-regulated in the liver after DEHP exposure. Analysis of dose-response exposures to DEHP by reverse transcription (RT)-PCR confirm these results and also shows that GRP58 is not altered in kidney or testis. Immunoblot analysis using GRP58-specific antibodies also shows a decrease in GRP58 protein levels in DEHP-treated mice. Moreover, exposure of mice to another peroxisome proliferator, clofibrate, results in a slight down-regulation of GRP58 at the highest dose, 0.5%. Thus, it appears as if DEHP and clofibrate can use different pathways to affect gene expression.
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Affiliation(s)
- C R Muhlenkamp
- Department of Entomology, University of California, Riverside 92521, USA
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Ashby J, Lefevre PA, Odum J, Tinwell H, Kennedy SJ, Beresford N, Sumpter JP. Failure to confirm estrogenic activity for benzoic acid and clofibrate: implications for lists of endocrine-disrupting agents. Regul Toxicol Pharmacol 1997; 26:96-101. [PMID: 9339486 DOI: 10.1006/rtph.1997.1158] [Citation(s) in RCA: 30] [Impact Index Per Article: 1.1] [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: 02/05/2023]
Abstract
Earlier reports that benzoic acid is uterotrophic to the rat and mouse and that clofibrate is uterotrophic to the rat have not been confirmed. The studies reported here involved the use of a range of test protocols and dose levels, including the protocols/dose levels used by the original investigators. In addition, both chemicals were inactive in a human estrogen receptor (hER alpha) yeast estrogenicity assay. It is concluded that benzoic acid and clofibrate are not estrogenic in the assays used here. This conclusion has implications for the compilation of lists of endocrine-disrupting chemicals.
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Affiliation(s)
- J Ashby
- Zeneca Central Toxicology Laboratory, Macclesfield, Cheshire, United Kingdom
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Mehrotra K, Morgenstern R, Lundqvist G, Becedas L, Bengtsson Ahlberg M, Georgellis A. Effects of peroxisome proliferators and/or hypothyroidism on xenobiotic-metabolizing enzymes in rat testis. Chem Biol Interact 1997; 104:131-45. [PMID: 9212780 DOI: 10.1016/s0009-2797(97)00020-3] [Citation(s) in RCA: 19] [Impact Index Per Article: 0.7] [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: 02/04/2023]
Abstract
The objectives of the present work were to study the effects of certain peroxisome proliferators on xenobiotic-metabolizing enzyme activities in the testes of normal and hypothyroid rats, i.e. phenol sulfotransferases (pST), phenol UDP-glucuronosyl transferases (pUDPGT), glutathione transferases (GST), catalase, epoxide hydrolase (EH), glutathione peroxidase (GPX) and NAD(P)H quinone oxidoreductase (QR). Adult male rats (normal and hypothyroid) were treated for 10 days with clofibrate (0.5%), perfluorooctanoic acid (0.5%, PFOA), acetylsalisylic acid (1%, ASA) and di(2-ethylhexyl)phthalate (2%, DEHP) in their diet. The results show that treatment of normal rats with peroxisome proliferators dramatically affects the activities of xenobiotic-metabolizing enzymes (40-60% reduction). The highest effects are seen in catalase activity (50-60% with PFOA and ASA), pUDPGT (55% with PFOA), pST (55% with PFOA) and QR (50% with DEHP). These effects are not seen or are weaker after induction of hypothyroidism. Taken together, it is concluded that different classes of peroxisome proliferators have different effects on rat testicular xenobiotic-metabolizing enzymes.
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Affiliation(s)
- K Mehrotra
- Department of Biochemistry, Wallenberg Laboratory, Stockholm University, Sweden
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Ito S, Tateno C, Tuda M, Yoshitake A. Immunohistochemical demonstration of the gap junctional protein connexin 32 and proliferating cell nuclear antigen in glutathione S-transferase placental form-negative lesions of rat liver induced by diethylnitrosamine and clofibrate. Toxicol Pathol 1996; 24:690-5. [PMID: 8994295 DOI: 10.1177/019262339602400603] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.1] [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: 02/03/2023]
Abstract
The distributions of a gap junctional protein, connexin 32 (cx 32), and proliferating cell nuclear antigen (PCNA) were examined immunohistochemically in glutathione S-transferase placental form (GST-P)-negative foci, induced in rat liver by initiation with diethylnitrosamine (DEN, 200 mg/kg) followed by promotion with clofibrate (1% in diet) in an in vivo medium-term assay system for hepatocarcinogenesis. The results were compared to those in GST-P-positive foci induced by DEN alone. The treatment with clofibrate caused the appearance of GST-P-negative foci, increased in size as compared to GST-P-positive foci in the same liver or induced by the DEN alone. The proportion of PCNA-positive hepatocytes in GST-P-negative foci was significantly higher than in the surrounding parenchyma, indicating increased cell proliferation. The numbers of cx 32-positive spots per hepatocyte in GST-P-negative foci were clearly decreased, reaching 65.4% at week 20 and 51.8% at week 30 of values for surrounding normal hepatocytes. In GST-P-positive foci induced by DEN, only a slight decrease (80%) was observed at week 8. These findings show that a positive association between the sustained inhibition of gap junctional intercellular communication and increased cell proliferation of GST-P-negative foci in Fischer-344 male rats induced with DEN and promoted with clofibrate.
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Affiliation(s)
- S Ito
- Environmental Health Science Laboratory, Sumitomo Chemical Co., Ltd., Osaka, Japan
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47
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Tsuda H, Asamoto M, Iwahori Y, Hori T, Ota T, Baba-Toriyama H, Uehara N, Kim DJ, Krutovskikh VA, Takasuka N, Tsuchiya T, Mutai M, Tatematsu M, Yamasaki H. Decreased connexin32 and a characteristic enzyme phenotype in clofibrate-induced preneoplastic lesions not shared with spontaneously occurring lesions in the rat liver. Carcinogenesis 1996; 17:2441-8. [PMID: 8968061 DOI: 10.1093/carcin/17.11.2441] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.3] [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: 02/03/2023] Open
Abstract
Two different types of focal preneoplastic lesions, tentatively named Type I and II lesions, were recognized in the liver of rats chronically treated with clofibrate for 104 weeks. Type I lesions were characterized by mostly negative glucose-6-phosphate dehydrogenase (G6PD) activity (6 out of 10, 60%) and positive expression of succinate dehydrogenase (10 out of 10, 100%), in addition to the previously documented complete lack of expression of glutathione S-transferase, placental form (GST-P) and gamma-glutamyl transpeptidase (GGT). Furthermore, most importantly, Type I lesions exhibited a clear decrease in immunohistochemically demonstrated connexin32 (Cx32) spot counts on their hepatocyte membranes, similarly to nitrosamine-induced lesions. In contrast, Type II lesions, mostly small in size and positively expressing GST-P and/or GGT and G6PD, similarly to their previously reported nitrosamine-induced counterparts, did not exhibit a significant decrease in Cx32 count. In addition, spontaneously occurring lesions, again sharing the same enzyme phenotype, did not show a decrease in Cx32. The results indicate that: (i) a clear distinction between the two lesions, with Type I being involved in clofibrate-induced tumors and Type II being more likely to be spontaneous in nature; (ii) a decrease in Cx32 is closely linked to lesion development and possibly stage of progression, irrespective of the enzyme phenotype and the applied carcinogen; (iii) the unaltered condition of Cx32 may suggest a slow growing or non-progressive nature.
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Affiliation(s)
- H Tsuda
- Chemotherapy Division, National Cancer Center Research Institute, Chuo-ku, Tokyo, Japan
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48
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Yamoto T, Ohashi Y, Furukawa T, Teranishi M, Manabe S, Makita T. Change of the sex-dependent response to clofibrate in F344 rat liver during postnatal development. Toxicol Lett 1996; 85:77-83. [PMID: 8650696 DOI: 10.1016/0378-4274(96)03643-0] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.2] [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: 02/01/2023]
Abstract
Although it has been reported that male rats are more responsive than females to peroxisome proliferation induced by clofibrate, these sex differences have been confirmed in young adult rats. Using 4-, 8-, and 12-week-old F344 rats, postnatal change of the sex-dependent response to clofibrate was investigated. These animals were administered 200 mg/kg body wt./day clofibrate by gavage for 7 days. In 4-week-old rats clofibrate-dependent changes (hepatomegaly, induction of hepatic microsomal and peroxisomal enzymes, proliferation of smooth endoplasmic reticulum and peroxisomes of hepatocytes) were slight in both sexes. In 8- and 12-week-old rats clofibrate-induced changes of males were moderate, whereas those of females were slight. These results suggest that the responsiveness of immature rat to clofibrate is weak and in males the susceptibility is gradually strong during postnatal development.
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Affiliation(s)
- T Yamoto
- Laboratory Animal Science and Toxicology Laboratories, Sankyo Co. Ltd., Shizuoka, Japan
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49
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Abstract
Exposure to perfluorocarboxylic acids, pthalate esters, and some hypolipidemic agents results in the proliferation of peroxisomes in the rodent liver. The structural diversity of these compounds suggests mechanistic diversity in their toxicity as well. To establish reliable biomarkers of peroxisome proliferation (PP) in compounds with distinct chemical toxicities, this study investigated the effect of in vivo exposure to perfluoro-n-octanoic acid, perfluoro-n-decanoic acid, di(2-ethylhexyl)phthalate (DEHP) and clofibrate on two-dimensional electrophoretic protein patterns of rat hepatic sulfotransferases, ST1A1, ST1C1 and ST2A1. After exposure to peroxisome proliferative doses, both ST1A1 and ST1C1 abundance in whole liver homogenates was significantly reduced, but only as a result of perfluorocarboxylic and exposure. The well-established PPs, DEHP and clofibrate had no effect on sulfotransferase expression whatsoever. The observed down-regulation of these STs is significant with respect to their normal detoxication activities and its potential correlation to carcinogenesis warrants further study. The present investigation supports previous studies that demonstrate the unique features of perfluorocarboxylic acid toxicity, relative to classic peroxisome proliferators and endorses the continued use of 2D protein-mapping of Sts and other proteins as biomarkers of chemical toxicity.
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Affiliation(s)
- F Witzmann
- Department of Biology, Indiana University Purdue University, Columbus 47203, USA
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50
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Clofibrate. IARC Monogr Eval Carcinog Risks Hum 1996; 66. [PMID: 9097129] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [MESH Headings] [Grants] [Subscribe] [Scholar Register] [Indexed: 02/04/2023]
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