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Yamada M, Suzuki T, Kohara A, Honma M. Carcinogenic risk of food additive AF-2 banned in Japan: a case study on reassessment of genotoxicity. Genes Environ 2023; 45:33. [PMID: 38053221 PMCID: PMC10696715 DOI: 10.1186/s41021-023-00292-3] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/26/2023] [Accepted: 11/27/2023] [Indexed: 12/07/2023] Open
Abstract
BACKGROUND Carcinogenic risk assessment studies have been repeatedly improved and are still being debated to find a goal. Evaluation might be changed if new approaches would be applied to some chemicals which means that new approaches may change the final assessment. In this paper, the risk assessment of a chemical, in particular the proper carcinogenicity, is examined using the long-banned food additive, 2-(2-furyl)-3-(5-nitro-2-furyl)-acrylamide, AF-2, as a case study. RESULTS First, Ames tests were carried out using strains TA1535, TA100, TA1538, and TA98 and their nitroreductase-deficient strains YG7127, YG7128, YG7129, and YG7130. The results showed that mutagenic activity was reduced by about 50% in the nitroreductase-deficient strains, indicating that part of the mutagenic activity shown in Ames test was due to bacterial metabolism. Second, in vivo genotoxicity tests were conducted, including the one that had not been developed in 1970's. Both a micronucleus test and a gene mutation assay using transgenic mice were negative. Third, assuming it is a genotoxic carcinogen, the virtual safety dose of 550 μg/day was calculated from the TD50 in rats with a probability of 10-5. CONCLUSION AF-2 has been shown to be carcinogenic to rodents and has previously been indicated to be genotoxic in vitro. However, the present in vivo genotoxicity study, it was negative in the forestomach, a target organ for cancer, particularly in the gene mutation assay in transgenic mice. Considering the daily intake of AF-2 in the 1970s and its virtually safety dose, the carcinogenic risk of AF-2 could be considered acceptable.
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Affiliation(s)
- Masami Yamada
- Department of Applied Chemistry, National Defense Academy, 1-10-20, Hashirimizu, Yokosuka, Kanagawa, 239-8686, Japan.
- Division of Genetics and Mutagenesis, National Institute of Health Sciences, 3-25-26, Tonomachi, Kawasaki-ku, Kawasaki city, Kanagawa, 210-9501, Japan.
| | - Takayoshi Suzuki
- Division of Genetics and Mutagenesis, National Institute of Health Sciences, 3-25-26, Tonomachi, Kawasaki-ku, Kawasaki city, Kanagawa, 210-9501, Japan
| | - Arihiro Kohara
- JCRB Cell Bank, National Institute of Biomedical Innovation, 7-6-8, Saito-asagi, Osaka, Ibaraki, 567-0085, Japan
| | - Masamitsu Honma
- Division of General Affairs, National Institute of Health Sciences, 3-25-26, Tonomachi, Kawasaki-ku, Kawasaki city, Kanagawa, 210-9501, Japan
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Ambroso JL, Dillberger J, Bruning-Barry R, Yang T. Assessment of the Carcinogenic Potential of Pretomanid in Transgenic Tg.rasH2 Mice. Int J Toxicol 2022; 41:367-379. [PMID: 35849539 PMCID: PMC9411704 DOI: 10.1177/10915818221113295] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
Pretomanid is a nitroimidazooxazine antimycobacterial drug that was approved as part of a three-drug oral regimen, consisting of bedaquiline, pretomanid, and linezolid, for 6-months treatment of adults with pulmonary extensively drug-resistant tuberculosis or with complicated forms of multidrug-resistant tuberculosis by the food and drug administration in the United States and regulatory bodies in over 10 other countries. Nitroaromatic compounds as a class carry a risk of genotoxicity and potential carcinogenicity based on reactive metabolite formation. A battery of good laboratory practice genotoxicity studies on pretomanid indicated that the compound was not genotoxic, however its hydroxy imidazole metabolite (M50) was genotoxic in the Ames assay. To assess the in vivo carcinogenic potential of pretomanid, hemizygous Tg.rasH2 mice were administered pretomanid once daily by oral gavage for 26 weeks. Male mice were given pretomanid in vehicle at doses of 0, 5, 15 and 40 mg/kg/day and female mice were given pretomanid in vehicle at doses of 0, 10, 30 and 80 mg/kg/day. Positive control mice of both sexes received intraperitoneal injections of urethane at 1000 mg/kg on Days 1, 3 and 5. There were no pretomanid-related early deaths, tumors, non-neoplastic microscopic findings, or gross necropsy findings at any dose level. The positive control gave the anticipated response of lung tumors. Oral administration of pretomanid to mice produced plasma exposure to the parent compound (high dose AUC of pretomanid 3 times the clinical AUC at the maximum recommended human dose) and exposure to the M50 metabolite (less than 10% of pretomanid) at all dose levels in both sexes. These data show that pretomanid was not carcinogenic in a transgenic mouse model at systemic exposures greater than human therapeutic exposures.
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Boddu RS, Perumal O, K D. Microbial nitroreductases: A versatile tool for biomedical and environmental applications. Biotechnol Appl Biochem 2020; 68:1518-1530. [PMID: 33156534 DOI: 10.1002/bab.2073] [Citation(s) in RCA: 9] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/05/2020] [Accepted: 11/02/2020] [Indexed: 12/24/2022]
Abstract
Nitroreductases, enzymes found mostly in bacteria and also in few eukaryotes, use nicotinamide adenine dinucleotide (NADH) or nicotinamide adenine dinucleotide phosphate (NADPH) as a cofactor for their activity and metabolize an enormous list of a diverse nitro group-containing compounds. Nitroreductases that are capable of metabolizing nitroaromatic and nitro heterocyclic compounds have drawn great attention in recent years owing to their biotechnological, biomedical, environmental, and human impact. These enzymes attracted medicinal chemists and pharmacologists because of their prodrug selectivity for activation/reduction of nitro compounds that wipe out pathogens/cancer cells, leaving the host/normal cells unharmed. It is applied in diverse fields of study like prodrug activation in treating cancer and leishmaniasis, designing fluorescent probes for hypoxia detection, cell imaging, ablation of specific cell types, biodegradation of nitro-pollutants, and interpretation of mutagenicity of nitro compounds. Keeping in view the immense prospects of these enzymes and a large number of research contributions in this area, the present review encompasses the enzymatic reaction mechanism, their role in antibiotic resistance, hypoxia sensing, cell imaging, cancer therapy, reduction of recalcitrant nitro chemicals, enzyme variants, and their specificity to substrates, reaction products, and their applications.
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Affiliation(s)
- Ramya Sree Boddu
- Department of Biotechnology, National Institute of Technology, Warangal, India
| | - Onkara Perumal
- Department of Biotechnology, National Institute of Technology, Warangal, India
| | - Divakar K
- Department of Biotechnology, Sri Venkateswara College of Engineering, Sriperumbudur, India
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The IWGT in vitro Mammalian Cell Gene Mutation (MCGM) assays working group—Introductory remarks & consensus statements. MUTATION RESEARCH-GENETIC TOXICOLOGY AND ENVIRONMENTAL MUTAGENESIS 2019; 848:403061. [DOI: 10.1016/j.mrgentox.2019.05.017] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/26/2019] [Revised: 05/29/2019] [Accepted: 05/30/2019] [Indexed: 01/21/2023]
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Casino AD, Lukinović V, Bhatt R, Randle LE, Dascombe MJ, Fennell DBJ, Drew MGB, Bell A, Fielding AJ, Ismail FMD. Synthesis, Structural Determination, and Pharmacology of Putative Dinitroaniline Antimalarials. ChemistrySelect 2018. [DOI: 10.1002/slct.201801723] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Affiliation(s)
- Alessio del Casino
- School of Pharmacy and Biomolecular SciencesLiverpool John Moores University Byrom Street, Liverpool L3 3AF United Kingdom
| | - Valentina Lukinović
- School of Chemistry and the Photon Science InstituteThe University of Manchester, Manchester M13 9PL United Kingdom
| | - Rakesh Bhatt
- Henkel Loctite Adhesives LtdKelsey House, Wood Lane End Hemel Hempstead, Herts HP2 4RQ United Kingdom
| | - Laura E. Randle
- School of Pharmacy and Biomolecular SciencesLiverpool John Moores University Byrom Street, Liverpool L3 3AF United Kingdom
| | - Michael J. Dascombe
- Faculty of BiologyMedicine and HealthStopford Building The University of Manchester Oxford Road, Manchester M13 9PT United Kingdom
| | - Dr Brian J. Fennell
- School of Genetics and MicrobiologyMoyne InstituteTrinity College, Dublin 2 Ireland
| | - Michael G. B. Drew
- Department of ChemistryUniversity of Reading, Reading, Berks, RG6 6AD United Kingdom
| | - Angus Bell
- School of Genetics and MicrobiologyMoyne InstituteTrinity College, Dublin 2 Ireland
| | - Alistair J. Fielding
- School of Pharmacy and Biomolecular SciencesLiverpool John Moores University Byrom Street, Liverpool L3 3AF United Kingdom
| | - Fyaz M. D. Ismail
- School of Pharmacy and Biomolecular SciencesLiverpool John Moores University Byrom Street, Liverpool L3 3AF United Kingdom
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Liu Q, Zhang J, Luo X, Ihsan A, Liu X, Dai M, Cheng G, Hao H, Wang X, Yuan Z. Further investigations into the genotoxicity of quinoxaline-di-N-oxides and their primary metabolites. Food Chem Toxicol 2016; 93:145-57. [PMID: 27170491 DOI: 10.1016/j.fct.2016.04.029] [Citation(s) in RCA: 25] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/04/2016] [Revised: 04/26/2016] [Accepted: 04/28/2016] [Indexed: 12/15/2022]
Abstract
Quinoxaline-di-N-oxides (QdNOs) are potential antibacterial agents with a wide range of biological properties. Quinocetone (QCT), carbadox (CBX), olaquindox (OLA), mequindox (MEQ) and cyadox (CYA) are classical QdNOs. Though the genotoxicity of parent drugs has been evaluated, the genotoxicity of their primary N → O reduced metabolites remains unclear. In the present study, a battery of four different short-term tests, mouse lymphoma assay (MLA), Ames test, chromosomal aberration assay in vitro and bone marrow erythrocyte micronucleus assay in vivo was carried out to investigate the genotoxicity of the six primary N → O reduced metabolites. Additionally, the genotoxicity of five parent drugs was evaluated by the MLA. Strong genotoxicity of N1-MEQ, B-MEQ and B-CBX was found in three of the assays but not in the Ames assay, and the rank order was N1-MEQ>B-MEQ>B-CBX that is consistent with prototype QdNOs. Negative results for the five QdNOs were noted in the MLA. We present for the first time a comparison of the genotoxicity of primary N → O reduced metabolites, and evaluate the ability of five QdNOs to cause mutations in the MLA. The present study demonstrates that metabolites are involved in genetic toxicity mediated by QdNOs, and improve the prudent use of QdNOs for public health.
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Affiliation(s)
- Qianying Liu
- National Reference Laboratory of Veterinary Drug Residues (HZAU) and MAO Key Laboratory for Detection of Veterinary Drug Residues, Huazhong Agricultural University, Wuhan, Hubei 430070, China
| | - Jianwu Zhang
- MOA Laboratory for Risk Assessment of Quality and Safety of Livestock and Poultry Products, Huazhong Agricultural University, Wuhan, Hubei 430070, China
| | - Xun Luo
- MOA Laboratory for Risk Assessment of Quality and Safety of Livestock and Poultry Products, Huazhong Agricultural University, Wuhan, Hubei 430070, China
| | - Awais Ihsan
- Department of Biosciences, COMSATS Institute of Information Technology, Sahiwal, Pakistan
| | - Xianglian Liu
- MOA Laboratory for Risk Assessment of Quality and Safety of Livestock and Poultry Products, Huazhong Agricultural University, Wuhan, Hubei 430070, China
| | - Menghong Dai
- Hubei Collaborative Innovation Center for Animal Nutrition and Feed Safety, Wuhan, Hubei, China
| | - Guyue Cheng
- Hubei Collaborative Innovation Center for Animal Nutrition and Feed Safety, Wuhan, Hubei, China
| | - Haihong Hao
- Hubei Collaborative Innovation Center for Animal Nutrition and Feed Safety, Wuhan, Hubei, China
| | - Xu Wang
- Hubei Collaborative Innovation Center for Animal Nutrition and Feed Safety, Wuhan, Hubei, China.
| | - Zonghui Yuan
- National Reference Laboratory of Veterinary Drug Residues (HZAU) and MAO Key Laboratory for Detection of Veterinary Drug Residues, Huazhong Agricultural University, Wuhan, Hubei 430070, China; MOA Laboratory for Risk Assessment of Quality and Safety of Livestock and Poultry Products, Huazhong Agricultural University, Wuhan, Hubei 430070, China; Hubei Collaborative Innovation Center for Animal Nutrition and Feed Safety, Wuhan, Hubei, China.
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Hung WL, Lu CH, Liao CD, Hwang LS. Safety evaluation of nano/sub-microsized lignan glycosides from sesame meal. Food Control 2013. [DOI: 10.1016/j.foodcont.2012.07.028] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
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The Evolution, Scientific Reasoning and Use of ICH S2 Guidelines for Genotoxicity Testing of Pharmaceuticals. GLOBAL APPROACH IN SAFETY TESTING 2013. [DOI: 10.1007/978-1-4614-5950-7_6] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/14/2023]
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Sharma AK, Soussaline F, Sallette J, Dybdahl M. The influence of the number of cells scored on the sensitivity in the comet assay. Mutat Res 2012; 749:70-5. [PMID: 22981767 DOI: 10.1016/j.mrgentox.2012.07.003] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/11/2012] [Revised: 06/08/2012] [Accepted: 07/25/2012] [Indexed: 10/27/2022]
Abstract
The impact on the sensitivity of the in vitro comet assay by increasing the number of cells scored has only been addressed in a few studies. The present study investigated whether the sensitivity of the assay could be improved by scoring more than 100 cells. Two cell lines and three different chemicals were used: Caco-2 cells were exposed to ethylmethane sulfonate and hydrogen peroxide in three concentrations, and HepG2 cells were exposed to ethylmethane sulfonate, hydrogen peroxide and benzo[a]pyrene in up to four concentrations, in four to five independent experiments. The scoring was carried out by means of a fully automated scoring system and the results were analyzed by evaluating the % tail DNA of 100-700 randomly selected cells for each slide consisting of two gels. By increasing the number of cells scored, the coefficients of variance decreased, leading to an improved sensitivity of the assay. A two-way ANOVA analysis of variance showed that the contribution from the two variables "the number of cells scored" and "concentration" on the total variation in the coefficients of variance dataset was statistically significant (p<0.05). The increase in sensitivity was demonstrated by the possibility to detect an increase in % tail DNA with statistical significance at lower concentrations. The results indicated that for low levels of DNA damage, below 9% tail DNA, scoring of 600 cells increased the sensitivity compared with scoring of 100 cells. For relatively low levels of DNA damage, about 9-16% tail DNA, scoring of 300 cells increased the sensitivity. Thus, the recommendation for the optimum number of cells scored would be 600 and 300 for low and relatively low levels of DNA damage, respectively. The findings from this study could be particularly important for bio-monitoring studies where small differences in DNA-damage levels could be relevant.
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Affiliation(s)
- Anoop Kumar Sharma
- Technical University of Denmark, National Food Institute, Søborg, Denmark.
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Tweats D, Bourdin Trunz B, Torreele E. Genotoxicity profile of fexinidazole--a drug candidate in clinical development for human African trypanomiasis (sleeping sickness). Mutagenesis 2012; 27:523-32. [PMID: 22539226 DOI: 10.1093/mutage/ges015] [Citation(s) in RCA: 36] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
The parasitic disease human African trypanomiasis (HAT), also known as sleeping sickness, is a highly neglected fatal condition endemic in sub-Saharan Africa, which is poorly treated with medicines that are toxic, no longer effective or very difficult to administer. New, safe, effective and easy-to-use treatments are urgently needed. Many nitroimidazoles possess antibacterial and antiprotozoal activity and examples such as tinidazole are used to treat trichomoniasis and guardiasis, but concerns about toxicity including genotoxicity limit their usefulness. Fexinidazole, a 2-substituted 5-nitroimidazole rediscovered by the Drugs for Neglected Diseases initiative (DNDi) after extensive compound mining of public and pharmaceutical company databases, has the potential to become a short-course, safe and effective oral treatment, curing both acute and chronic HAT. This paper describes the genotoxicity profile of fexinidazole and its two active metabolites, the sulfoxide and sulfone derivatives. All the three compounds are mutagenic in the Salmonella/Ames test; however, mutagenicity is either attenuated or lost in Ames Salmonella strains that lack one or more nitroreductase(s). It is known that these enzymes can nitroreduce compounds with low redox potentials, whereas their mammalian cell counterparts cannot, under normal conditions. Fexinidazole and its metabolites have low redox potentials and all mammalian cell assays to detect genetic toxicity, conducted for this study either in vitro (micronucleus test in human lymphocytes) or in vivo (ex vivo unscheduled DNA synthesis in rats; bone marrow micronucleus test in mice), were negative. Thus, fexinidazole does not pose a genotoxic hazard to patients and represents a promising drug candidate for HAT. Fexinidazole is expected to enter Phase II clinical trials in 2012.
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Affiliation(s)
- David Tweats
- Drugs for Neglected Diseases initiative, 15 Chemin Louis-Dunant, Geneva CH-1202, Switzerland.
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Koller M, Lingenhoehl K, Schmutz M, Vranesic IT, Kallen J, Auberson YP, Carcache DA, Mattes H, Ofner S, Orain D, Urwyler S. Quinazolinedione sulfonamides: a novel class of competitive AMPA receptor antagonists with oral activity. Bioorg Med Chem Lett 2011; 21:3358-61. [PMID: 21531559 DOI: 10.1016/j.bmcl.2011.04.017] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/09/2011] [Revised: 03/28/2011] [Accepted: 04/03/2011] [Indexed: 10/18/2022]
Abstract
Quinazoline-2,4-diones with a sulfonamide group attached to the N(3) ring atom constitute a novel class of competitive AMPA receptor antagonists. One of the synthesized compounds, 28, shows nanomolar receptor affinity, whereas other examples of the series display oral anticonvulsant activity in animal models.
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Affiliation(s)
- Manuel Koller
- Novartis Institutes for BioMedical Research, Global Discovery Chemistry, 4002 Basel, Switzerland.
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Dearfield KL, Thybaud V, Cimino MC, Custer L, Czich A, Harvey JS, Hester S, Kim JH, Kirkland D, Levy DD, Lorge E, Moore MM, Ouédraogo-Arras G, Schuler M, Suter W, Sweder K, Tarlo K, van Benthem J, van Goethem F, Witt KL. Follow-up actions from positive results of in vitro genetic toxicity testing. ENVIRONMENTAL AND MOLECULAR MUTAGENESIS 2011; 52:177-204. [PMID: 20963811 DOI: 10.1002/em.20617] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/19/2010] [Revised: 06/16/2010] [Accepted: 06/18/2010] [Indexed: 05/30/2023]
Abstract
Appropriate follow-up actions and decisions are needed when evaluating and interpreting clear positive results obtained in the in vitro assays used in the initial genotoxicity screening battery (i.e., the battery of tests generally required by regulatory authorities) to assist in overall risk-based decision making concerning the potential effects of human exposure to the agent under test. Over the past few years, the International Life Sciences Institute (ILSI) Health and Environmental Sciences Institute (HESI) Project Committee on the Relevance and Follow-up of Positive Results in In Vitro Genetic Toxicity (IVGT) Testing developed a decision process flow chart to be applied in case of clear positive results in vitro. It provides for a variety of different possibilities and allows flexibility in choosing follow-up action(s), depending on the results obtained in the initial battery of assays and available information. The intent of the Review Subgroup was not to provide a prescriptive testing strategy, but rather to reinforce the concept of weighing the totality of the evidence. The Review Subgroup of the IVGT committee highlighted the importance of properly analyzing the existing data, and considering potential confounding factors (e.g., possible interactions with the test systems, presence of impurities, irrelevant metabolism), and chemical modes of action when analyzing and interpreting positive results in the in vitro genotoxicity assays and determining appropriate follow-up testing. The Review Subgroup also examined the characteristics, strengths, and limitations of each of the existing in vitro and in vivo genotoxicity assays to determine their usefulness in any follow-up testing.
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Affiliation(s)
- Kerry L Dearfield
- U.S. Department of Agriculture, Food Safety and Inspection Service, Washington, District of Columbia, USA
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Torreele E, Bourdin Trunz B, Tweats D, Kaiser M, Brun R, Mazué G, Bray MA, Pécoul B. Fexinidazole--a new oral nitroimidazole drug candidate entering clinical development for the treatment of sleeping sickness. PLoS Negl Trop Dis 2010; 4:e923. [PMID: 21200426 PMCID: PMC3006138 DOI: 10.1371/journal.pntd.0000923] [Citation(s) in RCA: 203] [Impact Index Per Article: 14.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/29/2010] [Accepted: 11/22/2010] [Indexed: 01/22/2023] Open
Abstract
Background Human African trypanosomiasis (HAT), also known as sleeping sickness, is a fatal parasitic disease caused by trypanosomes. Current treatment options for HAT are scarce, toxic, no longer effective, or very difficult to administer, in particular for the advanced, fatal stage of the disease (stage 2, chronic HAT). New safe, effective and easy-to-use treatments are urgently needed. Here it is shown that fexinidazole, a 2-substituted 5-nitroimidazole rediscovered by the Drugs for Neglected Diseases initiative (DNDi) after extensive compound mining efforts of more than 700 new and existing nitroheterocycles, could be a short-course, safe and effective oral treatment curing both acute and chronic HAT and that could be implemented at the primary health care level. To complete the preclinical development and meet the regulatory requirements before initiating human trials, the anti-parasitic properties and the pharmacokinetic, metabolic and toxicological profile of fexinidazole have been assessed. Methods and Findings Standard in vitro and in vivo anti-parasitic activity assays were conducted to assess drug efficacy in experimental models for HAT. In parallel, a full range of preclinical pharmacology and safety studies, as required by international regulatory guidelines before initiating human studies, have been conducted. Fexinidazole is moderately active in vitro against African trypanosomes (IC50 against laboratory strains and recent clinical isolates ranged between 0.16 and 0.93 µg/mL) and oral administration of fexinidazole at doses of 100 mg/kg/day for 4 days or 200 mg/kg/day for 5 days cured mice with acute and chronic infection respectively, the latter being a model for the advanced and fatal stage of the disease when parasites have disseminated into the brain. In laboratory animals, fexinidazole is well absorbed after oral administration and readily distributes throughout the body, including the brain. The absolute bioavailability of oral fexinidazole was 41% in mice, 30% in rats, and 10% in dogs. Furthermore, fexinidazole is rapidly metabolised in vivo to at least two biologically active metabolites (a sulfoxide and a sulfone derivative) that likely account for a significant portion of the therapeutic effect. Key pharmacokinetic parameter after oral absorption in mice for fexinidazole and its sulfoxide and sulfone metabolites are a Cmax of 500, 14171 and 13651 ng/mL respectively, and an AUC0–24 of 424, 45031 and 96286 h.ng/mL respectively. Essentially similar PK profiles were observed in rats and dogs. Toxicology studies (including safety pharmacology and 4-weeks repeated-dose toxicokinetics in rat and dog) have shown that fexinidazole is well tolerated. The No Observed Adverse Event Levels in the 4-weeks repeated dose toxicity studies in rats and dogs was 200 mg/kg/day in both species, with no issues of concern identified for doses up to 800 mg/kg/day. While fexinidazole, like many nitroheterocycles, is mutagenic in the Ames test due to bacterial specific metabolism, it is not genotoxic to mammalian cells in vitro or in vivo as assessed in an in vitro micronucleus test on human lymphocytes, an in vivo mouse bone marrow micronucleus test, and an ex vivo unscheduled DNA synthesis test in rats. Conclusions The results of the preclinical pharmacological and safety studies indicate that fexinidazole is a safe and effective oral drug candidate with no untoward effects that would preclude evaluation in man. The drug has entered first-in-human phase I studies in September 2009. Fexinidazole is the first new clinical drug candidate with the potential for treating advanced-stage sleeping sickness in thirty years. This article describes the preclinical profile of fexinidazole, a new drug candidate with the potential to become a novel, oral, safe and effective short-course treatment for curing both stage 1 and 2 human African trypanosomiasis and replace the old and highly problematic treatment modalities available today. Fexinidazole is orally available and rapidly metabolized in two metabolites having equivalent biological activity to the parent and contributing significantly to the in vivo efficacy in animal models of both stage 1 and 2 HAT. Animal toxicology studies indicate that fexinidazole has an excellent safety profile, with no particular issues identified. Fexinidazole is a 5-nitroimidazole and, whilst it is Ames-positive, it is devoid of any genetic toxicity in mammalian cells and therefore does not pose a genotoxic risk for use in man. Fexinidazole, which was rediscovered through a process of compound mining, is the first new drug candidate for stage 2 HAT having entered clinical trials in thirty years, and has the potential to revolutionize therapy of this fatal disease at a cost that is acceptable in the endemic regions.
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Affiliation(s)
- Els Torreele
- Drugs for Neglected Diseases initiative (DNDi), Geneva, Switzerland.
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Mattes H, Carcache D, Kalkman HO, Koller M. alpha-Amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid (AMPA) antagonists: from bench to bedside. J Med Chem 2010; 53:5367-82. [PMID: 20356304 DOI: 10.1021/jm901688m] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- Henri Mattes
- Novartis Pharma AG, Werk Klybeck, WKL-122-241 Postfach, CH-4002 Basel, Switzerland.
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15
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Ben L, Jones ED, Zhou E, Li C, Baylis DC, Yu S, Wang M, He X, Coates JAV, Rhodes DI, Pei G, Deadman JJ, Xie X, Ma D. Studies on the structure–activity relationship of 1,3,3,4-tetra-substituted pyrrolidine embodied CCR5 receptor antagonists. Part 1: Tuning the N-substituents. Bioorg Med Chem Lett 2010; 20:4012-4. [DOI: 10.1016/j.bmcl.2010.05.102] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/12/2010] [Revised: 05/11/2010] [Accepted: 05/27/2010] [Indexed: 11/30/2022]
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Feuerbach D, Loetscher E, Neurdin S, Koller M. Comparative pharmacology of the human NMDA-receptor subtypes R1-2A, R1-2B, R1-2C and R1-2D using an inducible expression system. Eur J Pharmacol 2010; 637:46-54. [PMID: 20394742 DOI: 10.1016/j.ejphar.2010.04.002] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/04/2009] [Revised: 03/09/2010] [Accepted: 04/01/2010] [Indexed: 11/27/2022]
Abstract
Pharmacological characterization of N-methyl-D-aspartate (NMDA) receptors has been hampered by the difficulty to outwit cytotoxicity after functional expression in recombinant systems. In this study a muristerone-inducible expression system for the NNMDA-R1 subunit was used. This was combined with constitutive expression of NMDA-R2A, 2B, 2C and 2D in different cell clones. After establishment of the cell lines, quantitative RT-PCR demonstrated the inducibility of the NNMDA-R1 subunit, and verified the expression of the NMDA-R2 subunits in the different cell clones. Functional responses were characterized using calcium influx through the ion channel as a robust assay system. Stimulation of the NMDA-receptor subtypes in the different cell lines led to calcium transients which were rising gradually, peaked after 30-160 s and declined thereafter very slowly. The expression of the four different NMDA-receptor subtypes in the same cellular background allowed a direct pharmacological comparison of the different receptors. Glutamate showed the highest potency at the NMDA-R1-2D. NMDA displayed at all subtypes a lower potency compared to glutamate and was a partial agonist except at the NMDA-R1-2D. 20 antagonists were tested in this study and the pharmacological characterization of the inhibition of glutamate-evoked elevation of intracellular free Ca(2+) revealed a distinct rank order of antagonist potency for each receptor subtype. These data illustrate that assessment of calcium transients upon receptor stimulation in the same cellular background is a powerful tool to compare the functional effects of compounds acting at the different NMDA-R2 receptors.
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Affiliation(s)
- Dominik Feuerbach
- Neuroscience Research, Novartis Institutes for BioMedical Research, Basel, Switzerland.
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Genotoxicity revaluation of three commercial nitroheterocyclic drugs: nifurtimox, benznidazole, and metronidazole. J Parasitol Res 2009; 2009:463575. [PMID: 20981287 PMCID: PMC2963127 DOI: 10.1155/2009/463575] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/24/2009] [Revised: 07/09/2009] [Accepted: 08/03/2009] [Indexed: 12/28/2022] Open
Abstract
Nitroheterocyclic compounds are widely used as therapeutic agents against a variety of protozoan and bacterial infections. However, the literature on these compounds, suspected of being carcinogens, is widely controversial. In this study, cytotoxic and genotoxic potential of three drugs, Nifurtimox (NFX), Benznidazole (BNZ), and Metronidazole (MTZ) was re-evaluated by different assays. Only NFX reduces survival rate in actively proliferating cells. The compounds are more active for base-pair substitution than frameshift induction in Salmonella; NFX and BNZ are more mutagenic than MTZ; they are widely dependent from nitroreduction whereas microsomal fraction S9 weakly affects the mutagenic potential. Comet assay detects BNZ- and NFX-induced DNA damage at doses in the range of therapeutically treated patient plasma concentration; BNZ seems to mainly act through ROS generation whereas a dose-dependent mechanism of DNA damaging is suggested for NFX. The lack of effects on mammalian cells for MTZ is confirmed also in MN assay whereas MN induction is observed for NFX and BNZ. The effects of MTZ, that shows comparatively low reduction potential, seem to be strictly dependent on anaerobic/hypoxic conditions. Both NFX and BNZ may not only lead to cellular damage of the infective agent but also interact with the DNA of mammalian cells.
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Lin MC, Cheng HW, Tsai YC, Liao PL, Kang JJ, Cheng YW. Podophyllin, but not the constituents quercetin or kaempferol, induced genotoxicityin vitroandin vivothrough ROS production. Drug Chem Toxicol 2009; 32:68-76. [DOI: 10.1080/01480540802433757] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/20/2022]
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Zhang Z, Che W, Liang Y, Wu M, Li N, Shu Y, Liu F, Wu D. Comparison of cytotoxicity and genotoxicity induced by the extracts of methanol and gasoline engine exhausts. Toxicol In Vitro 2007; 21:1058-65. [PMID: 17512694 DOI: 10.1016/j.tiv.2007.04.001] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/06/2006] [Revised: 02/25/2007] [Accepted: 04/02/2007] [Indexed: 11/22/2022]
Abstract
Gasoline engine exhaust has been considered a major source of air pollution in China, and methanol is considered as a potential substitute for gasoline fuel. In this study, the genotoxicity and cytotoxicity of organic extracts of condensate, particulate matters (PM) and semivolatile organic compounds (SVOC) of gasoline and absolute methanol engine exhaust were examined by using MTT assay, micronucleus assay, comet assay and Ames test. The results have showed that gasoline engine exhaust exhibited stronger cytotoxicity to human lung carcinoma cell lines (A549 cell) than methanol engine exhaust. Furthermore, gasoline engine exhaust increased micronucleus formation, induced DNA damage in A549 cells and increased TA98 revertants in the presence of metabolic activating enzymes in a concentration-dependent manner. In contrast, methanol engine exhaust failed to exhibit these adverse effects. The results suggest methanol may be used as a cleaner fuel for automobile.
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Affiliation(s)
- Zunzhen Zhang
- Department of Environmental Health, West China College of Public Health, Sichuan University, No. 16, Section 3, Ren Min Nan Road, Chengdu 610041, People's Republic of China.
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21
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Kirkland DJ, Aardema M, Banduhn N, Carmichael P, Fautz R, Meunier JR, Pfuhler S. In vitro approaches to develop weight of evidence (WoE) and mode of action (MoA) discussions with positive in vitro genotoxicity results. Mutagenesis 2007; 22:161-75. [PMID: 17369606 DOI: 10.1093/mutage/gem006] [Citation(s) in RCA: 83] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022] Open
Abstract
A recent analysis by Kirkland et al. [Kirkland, D., Aardema, M., Henderson, L. and Müller, L. (2005) Evaluation of the ability of a battery of 3 in vitro genotoxicity tests to discriminate rodent carcinogens and non-carcinogens. I. Sensitivity, specificity and relative predictivity. Mutat. Res. 584, 1-256] demonstrated an extremely high false positive rate for in vitro genotoxicity tests when compared with carcinogenicity in rodents. In many industries, decisions have to be made on the safety of new substances, and health risk to humans, without rodent carcinogenicity data being available. In such cases, the usual way to determine whether a positive in vitro genotoxicity result is relevant (i.e. indicates a hazard) for humans is to develop weight of evidence (WoE) or mode of action (MoA) arguments. These are based partly on further in vitro investigations, but usually rely heavily on tests for genotoxicity in one or more in vivo assays. However, for certain product types in the European Union, the use of animals for genotoxicity testing (as well as for other endpoints) will be prohibited within the next few years. Many different examples have been described that indicate DNA damage and genotoxic responses in vitro can arise through non-relevant in vitro events that are a result of the test systems and conditions used. The majority of these non-relevant in vitro events can be grouped under a category of 'overload of normal physiology' that would not be expected to occur in exposed humans. However, obtaining evidence in support of such MoAs is not easy, particularly for those industries prohibited from carrying out in vivo testing. It will become necessary to focus on in vitro studies to provide evidence of non-DNA, threshold or in vitro-specific processes and to discuss the potential for such genotoxic effects to occur in exposed humans. Toward this end, we surveyed the published literature for in vitro approaches that may be followed to determine whether a genotoxic effect observed in vitro will occur in humans. Unfortunately, many of the approaches we found are based on only a few published examples and validated approaches with consensus recommendations often do not exist. This analysis highlights the urgent need for developing consensus approaches that do not rely on animal studies for dealing with in vitro genotoxins.
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Affiliation(s)
- D J Kirkland
- Covance Laboratories Limited, Otley Road, Harrogate HG3 1PY, UK.
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Ku WW, Bigger A, Brambilla G, Glatt H, Gocke E, Guzzie PJ, Hakura A, Honma M, Martus HJ, Obach RS, Roberts S. Strategy for genotoxicity testing—Metabolic considerations. MUTATION RESEARCH-GENETIC TOXICOLOGY AND ENVIRONMENTAL MUTAGENESIS 2007; 627:59-77. [PMID: 17141553 DOI: 10.1016/j.mrgentox.2006.10.004] [Citation(s) in RCA: 74] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/28/2006] [Revised: 07/31/2006] [Accepted: 08/14/2006] [Indexed: 02/04/2023]
Abstract
The report from the 2002 International Workshop on Genotoxicity Tests (IWGT) Strategy Expert Group emphasized metabolic considerations as an important area to address in developing a common strategy for genotoxicity testing. A working group convened at the 2005 4th IWGT to discuss this area further and propose practical strategy recommendations. To propose a strategy, the working group reviewed: (1) the current status and deficiencies, including examples of carcinogens "missed" in genotoxicity testing, established shortcomings of the standard in vitro induced S9 activation system and drug metabolite case examples; (2) the current status of possible remedies, including alternative S9 sources, other external metabolism systems or genetically engineered test systems; (3) any existing positions or guidance. The working group established consensus principles to guide strategy development. Thus, a human metabolite of interest should be represented in genotoxicity and carcinogenicity testing, including evaluation of alternative genotoxicity in vitro metabolic activation or test systems, and the selection of a carcinogenicity test species showing appropriate biotransformation. Appropriate action triggers need to be defined based on the extent of human exposure, considering any structural knowledge of the metabolite, and when genotoxicity is observed upon in vitro testing in the presence of metabolic activation. These triggers also need to be considered in defining the timing of human pharmaceutical ADME assessments. The working group proposed two strategies to consider; a more proactive approach, which emphasizes early metabolism predictions to drive appropriate hazard assessment; and a retroactive approach to manage safety risks of a unique or "major" metabolite once identified and quantitated from human clinical ADME studies. In both strategies, the assessment of the genotoxic potential of a metabolite could include the use of an alternative or optimized in vitro metabolic activation system, or direct testing of an isolated or synthesized metabolite. The working group also identified specific areas where more data or experiences need to be gained to reach consensus. These included defining a discrete exposure action trigger for safety assessment and when direct testing of a metabolite of interest is warranted versus the use of an alternative in vitro activation system, a universal recommendation for the timing of human ADME studies for drug candidates and the positioning of metabolite structural knowledge (through in silico systems, literature, expert analysis) in supporting metabolite safety qualification. Lastly, the working group outlined future considerations for refining the initially proposed strategies. These included the need for further evaluation of the current in vitro genotoxicity testing protocols that can potentially perturb or reduce the level of metabolic activity (potential alterations in metabolism associated with both the use of some solvents to solubilize test chemicals and testing to the guidance limit dose), and proposing broader evaluations of alternative metabolic activation sources or engineered test systems to further challenge the suitability of (or replace) the current induced liver S9 activation source.
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Affiliation(s)
- Warren W Ku
- Pfizer Global Research and Development, Drug Safety Research and Development, Groton, CT 06340, USA.
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Lambert IB, Singer TM, Boucher SE, Douglas GR. Detailed review of transgenic rodent mutation assays. Mutat Res 2005; 590:1-280. [PMID: 16081315 DOI: 10.1016/j.mrrev.2005.04.002] [Citation(s) in RCA: 252] [Impact Index Per Article: 13.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/17/2005] [Revised: 04/04/2005] [Accepted: 04/12/2005] [Indexed: 11/17/2022]
Abstract
Induced chromosomal and gene mutations play a role in carcinogenesis and may be involved in the production of birth defects and other disease conditions. While it is widely accepted that in vivo mutation assays are more relevant to the human condition than are in vitro assays, our ability to evaluate mutagenesis in vivo in a broad range of tissues has historically been quite limited. The development of transgenic rodent (TGR) mutation models has given us the ability to detect, quantify, and sequence mutations in a range of somatic and germ cells. This document provides a comprehensive review of the TGR mutation assay literature and assesses the potential use of these assays in a regulatory context. The information is arranged as follows. (1) TGR mutagenicity models and their use for the analysis of gene and chromosomal mutation are fully described. (2) The principles underlying current OECD tests for the assessment of genotoxicity in vitro and in vivo, and also nontransgenic assays available for assessment of gene mutation, are described. (3) All available information pertaining to the conduct of TGR assays and important parameters of assay performance have been tabulated and analyzed. (4) The performance of TGR assays, both in isolation and as part of a battery of in vitro and in vivo short-term genotoxicity tests, in predicting carcinogenicity is described. (5) Recommendations are made regarding the experimental parameters for TGR assays, and the use of TGR assays in a regulatory context.
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Affiliation(s)
- Iain B Lambert
- Mutagenesis Section, Environmental Health Sciences Bureau, Healthy Environments and Consumer Safety Branch, 0803A, Health Canada, Ottawa, Ont., Canada K1A 0L2.
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Brendler-Schwaab S, Hartmann A, Pfuhler S, Speit G. The in vivo comet assay: use and status in genotoxicity testing. Mutagenesis 2005; 20:245-54. [PMID: 15899933 DOI: 10.1093/mutage/gei033] [Citation(s) in RCA: 161] [Impact Index Per Article: 8.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
Abstract
The in vivo comet assay (single cell gel electrophoresis assay) in its alkaline version (pH >13) is being increasingly used in genotoxicity testing of substances such as industrial chemicals, biocides, agrochemicals, food additives and pharmaceuticals. Recommendations for an appropriate performance of the test using OECD guidelines for other in vivo genotoxicity tests have been published. In this review, we critically discuss the biological significance of comet assay effects in general and the status of the test in current strategies for genotoxicity testing. Examples for practical applications of the in vivo comet assay and potential consequences of positive and negative test results are given. The significance of comet assay results for hazard identification and risk assessment is discussed. In accordance with international guidelines for genotoxicity testing the in vivo comet assay is recommended for follow-up testing of positive in vitro findings. It is particularly useful as a tool for the evaluation of local genotoxicity, especially for organs/cell types which cannot easily be evaluated with other standard tests. A positive result in an appropriately performed in vivo comet assay indicates genotoxicity of the test compound in the tissue tested and gains particular significance when a mutagenic potential of the test compound has already been demonstrated in vitro. Such findings will have practical consequences in the risk assessment processes and further development of substances.
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González Borroto JI, Pérez Machado G, Creus A, Marcos R. Comparative genotoxic evaluation of 2-furylethylenes and 5-nitrofurans by using the comet assay in TK6 cells. Mutagenesis 2005; 20:193-7. [PMID: 15817571 DOI: 10.1093/mutage/gei026] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
Abstract
The genotoxicity of three 2-furylethylene derivatives and four 5-nitrofurans was evaluated by using the comet assay in human lymphoblastoid cultured TK6 cells. The 2-furylethylene derivatives were 2-furyl-1-nitroethene, 1-(5-bromofur-2-yl)-2-nitroethene and 1-(5-bromofur-2-yl)-2-bromo-2-nitroethene, while the 5-nitrofurans were nitrofurantoin, nitrofurazone, furazolidone and 5-nitro-2-furanacrolein. The treatments lasted for 3 h in the absence of metabolic activation. No genotoxic effects were observed for two of the 2-furylethylene compounds, while the derivative 1-(5-bromofur-2-yl)-2-nitroethene showed a statistically significant response mainly at the highest concentration tested; this effect was considered biologically relevant and the compound was classified as slightly genotoxic. On the other hand, for the classical 5-nitrofurans tested there is a tendency towards a dose-related increase of the DNA damage in the comet assay and the observed increases for the parameters analysed (Olive tail moment, tail % DNA and tail length) were significant for all compounds. Then, the four 5-nitrofurans tested were considered genotoxic. These results show that the position of the nitro group influences the genotoxicity of the assayed compounds. Thus, in this comet assay, the 2-furylethylene derivatives having the nitro group attached outside the furan ring appear to be much less genotoxic than the 5-nitrofurans.
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Affiliation(s)
- Jorge I González Borroto
- Grup de Mutagènesi, Departament de Genètica i de Microbiologia, Facultat de Ciències, Universitat Autònoma de Barcelona, 08193 Bellaterra, Spain
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Egito LCM, de Medeiros SRB, Medeiros MG, Price JC, Egito EST. Evaluation of the relationship of the molecular aggregation state of amphotericin B in medium to its genotoxic potential. J Pharm Sci 2005; 93:1557-65. [PMID: 15124213 DOI: 10.1002/jps.20038] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
Abstract
This work analyzes the genotoxicity potential, in the G2 phase of the cellular cycle, of an amphotericin B (AmB) commercially available form (Fungizone), and correlates it with the physicochemical properties of this product in aqueous media. The genotoxic studies were performed using peripheral blood lymphocytes from human donors. The chromosome aberrations and mitotic index were determined. Absorption spectra of Fungizone were obtained by dispersion of the stock solution in water for injection at various AmB concentrations, and using different cuvette path lengths for spectrophotometric determination. The absorption spectra of Fungizone in water are concentration dependent. High concentrations of Fungizone present a spectrum with an intense band at 340 nm, characteristic of AmB self-association. Conversely, at low concentrations, the spectra are similar to those obtained with AmB in methanol, with a positive band at 409 nm, assigned to AmB monomeric form. Similarly, the cytogenetic analysis shows an important decrease on the mitotic index, which is also concentration dependent when compared with control. Furthermore, the chromosome aberrations present a small, not statistically significant, increase only at the highest concentration. The results suggest that the Fungizone presents a cytotoxicity similar to membrane pore formation in mammalian cells that depends on the existence of self-associated AmB. In the presence of only monomeric forms, this phenomenon disappears. However, no genotoxicity was observed in this study.
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Affiliation(s)
- Lucila C M Egito
- Departamento de Biologia Celular e Genética, Universidade Federal do Rio Grande do Norte, P.O. Box 1575, 59072-970, Natal/RN, Brazil
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González Borroto JI, Pérez G, Creus A, Marcos R. Genotoxicity testing of the furylethylene derivative 1-(5-bromofur-2-yl)-2-bromo-2-nitroethene in cultured human lymphocytes. Food Chem Toxicol 2004; 42:187-93. [PMID: 14667464 DOI: 10.1016/j.fct.2003.08.012] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
Abstract
The genotoxic potential of the compound 1-(5-bromofur-2-yl)-2-bromo-2-nitroethene (G-1) was evaluated in peripheral blood lymphocytes cultured in vitro, at concentrations ranging from 1 to 20 microg/ml. Micronuclei (MN) and sister-chromatid exchanges (SCE) were scored as biomarkers of genotoxic effects. To detect the role of metabolic enzymes on the genotoxicity of this furylethylenic derivative, cultures for MN and SCE demonstrations were treated for 3 h with and without the S9 microsomal fraction as well as for 48 h without S9. Under the conditions of the study, the test agent did not induce significant increases in the frequency of micronucleated cells, irrespective of the presence/absence of the metabolic fraction. Nevertheless, a slight/moderate increase in the SCE frequency was observed in those cultures treated without the S9 mix. In addition, cytotoxic/cytostatic effects of the G-1 compound were observed mainly in cultures without S9 fraction, as indicated by the reduction of cell proliferation measured by the cytokinesis block proliferation index (CBPI) and the proliferative rate index (PRI).
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Affiliation(s)
- Jorge I González Borroto
- Grup de Mutagènesi, Departament de Genètica i de Microbiologia, Facultat de Ciències, Universitat Autònoma de Barcelona, 08193 Bellaterra, Spain
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