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Goyak KO, Sarang SS, Franzen A, Borghoff SJ, Ryman-Rasmussen JP. Adverse outcome pathway (AOP): α2u-globulin nephropathy and kidney tumors in male rats. Crit Rev Toxicol 2022; 52:345-357. [PMID: 35862579 DOI: 10.1080/10408444.2022.2082269] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/31/2023]
Abstract
The National Research Council's vision of using adverse outcome pathways (AOPs) as a framework to assist with toxicity assessment for regulatory requirements of chemical assessment has continued to gain traction since its release in 2007. The need to expand the AOP knowledge base has gained urgency, with the U.S. Environmental Protection Agency's directive to eliminate reliance on animal toxicity testing by 2035. To meet these needs, our goal was to elucidate the AOP for male-rat-specific kidney cancer. Male-rat-specific kidney tumors occur through the ability of structurally diverse substances to induce α2u-globulin nephropathy (α2u-N), a well-studied mode of action (MoA) not relevant in humans that results in kidney tumor formation in male rats. An accepted AOP may help facilitate the differentiation from other kidney tumors MoAs. Following identification and review of relevant in vitro and in vivo literature, both the MIE and subsequent KEs were identified. Based on the weight of evidence from the various resources, the confidence in this AOP is high. Uses of this AOP include hazard identification, development of in vitro assays to determine if the MoA is through α2u-N and not relevant to humans resulting in decreased use of animals, and regulatory applications.
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Affiliation(s)
- Katy O Goyak
- ExxonMobil Biomedical Sciences, Inc., Annandale, VA, USA
| | | | - A Franzen
- ToxStrategies, Inc., Monroe, LA, USA
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2
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Api AM, Belsito D, Botelho D, Bruze M, Burton GA, Buschmann J, Cancellieri MA, Dagli ML, Date M, Dekant W, Deodhar C, Fryer AD, Jones L, Joshi K, Kumar M, Lapczynski A, Lavelle M, Lee I, Liebler DC, Moustakas H, Na M, Penning TM, Ritacco G, Romine J, Sadekar N, Schultz TW, Selechnik D, Siddiqi F, Sipes IG, Sullivan G, Thakkar Y, Tokura Y. RIFM fragrance ingredient safety assessment, dl-limonene (racemic), CAS Registry Number 138-86-3. Food Chem Toxicol 2021; 161 Suppl 1:112764. [PMID: 34896183 DOI: 10.1016/j.fct.2021.112764] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/29/2021] [Accepted: 12/06/2021] [Indexed: 11/17/2022]
Affiliation(s)
- A M Api
- Research Institute for Fragrance Materials, Inc., 50 Tice Boulevard, Woodcliff Lake, NJ, 07677, USA
| | - D Belsito
- Member Expert Panel, Columbia University Medical Center, Department of Dermatology, 161 Fort Washington Ave., New York, NY, 10032, USA
| | - D Botelho
- Research Institute for Fragrance Materials, Inc., 50 Tice Boulevard, Woodcliff Lake, NJ, 07677, USA
| | - M Bruze
- Member Expert Panel, Malmo University Hospital, Department of Occupational & Environmental Dermatology, Sodra Forstadsgatan 101, Entrance 47, Malmo, SE, 20502, Sweden
| | - G A Burton
- Member Expert Panel, School of Natural Resources & Environment, University of Michigan, Dana Building G110, 440 Church St., Ann Arbor, MI, 58109, USA
| | - J Buschmann
- Member Expert Panel, Fraunhofer Institute for Toxicology and Experimental Medicine, Nikolai-Fuchs-Strasse 1, 30625, Hannover, Germany
| | - M A Cancellieri
- Research Institute for Fragrance Materials, Inc., 50 Tice Boulevard, Woodcliff Lake, NJ, 07677, USA
| | - M L Dagli
- Member Expert Panel, University of Sao Paulo, School of Veterinary Medicine and Animal Science, Department of Pathology, Av. Prof. dr. Orlando Marques de Paiva, 87, Sao Paulo, CEP 05508-900, Brazil
| | - M Date
- Research Institute for Fragrance Materials, Inc., 50 Tice Boulevard, Woodcliff Lake, NJ, 07677, USA
| | - W Dekant
- Member Expert Panel, University of Wuerzburg, Department of Toxicology, Versbacher Str. 9, 97078, Würzburg, Germany
| | - C Deodhar
- Research Institute for Fragrance Materials, Inc., 50 Tice Boulevard, Woodcliff Lake, NJ, 07677, USA
| | - A D Fryer
- Member Expert Panel, Oregon Health & Science University, 3181 SW Sam Jackson Park Rd., Portland, OR, 97239, USA
| | - L Jones
- Research Institute for Fragrance Materials, Inc., 50 Tice Boulevard, Woodcliff Lake, NJ, 07677, USA
| | - K Joshi
- Research Institute for Fragrance Materials, Inc., 50 Tice Boulevard, Woodcliff Lake, NJ, 07677, USA
| | - M Kumar
- Research Institute for Fragrance Materials, Inc., 50 Tice Boulevard, Woodcliff Lake, NJ, 07677, USA
| | - A Lapczynski
- Research Institute for Fragrance Materials, Inc., 50 Tice Boulevard, Woodcliff Lake, NJ, 07677, USA
| | - M Lavelle
- Research Institute for Fragrance Materials, Inc., 50 Tice Boulevard, Woodcliff Lake, NJ, 07677, USA
| | - I Lee
- Research Institute for Fragrance Materials, Inc., 50 Tice Boulevard, Woodcliff Lake, NJ, 07677, USA
| | - D C Liebler
- Member Expert Panel, Vanderbilt University School of Medicine, Department of Biochemistry, Center in Molecular Toxicology, 638 Robinson Research Building, 2200 Pierce Avenue, Nashville, TN, 37232-0146, USA
| | - H Moustakas
- Research Institute for Fragrance Materials, Inc., 50 Tice Boulevard, Woodcliff Lake, NJ, 07677, USA
| | - M Na
- Research Institute for Fragrance Materials, Inc., 50 Tice Boulevard, Woodcliff Lake, NJ, 07677, USA
| | - T M Penning
- Member of Expert Panel, University of Pennsylvania, Perelman School of Medicine, Center of Excellence in Environmental Toxicology, 1316 Biomedical Research Building (BRB) II/III, 421 Curie Boulevard, Philadelphia, PA, 19104-3083, USA
| | - G Ritacco
- Research Institute for Fragrance Materials, Inc., 50 Tice Boulevard, Woodcliff Lake, NJ, 07677, USA
| | - J Romine
- Research Institute for Fragrance Materials, Inc., 50 Tice Boulevard, Woodcliff Lake, NJ, 07677, USA
| | - N Sadekar
- Research Institute for Fragrance Materials, Inc., 50 Tice Boulevard, Woodcliff Lake, NJ, 07677, USA
| | - T W Schultz
- Member Expert Panel, The University of Tennessee, College of Veterinary Medicine, Department of Comparative Medicine, 2407 River Dr., Knoxville, TN, 37996- 4500, USA
| | - D Selechnik
- Research Institute for Fragrance Materials, Inc., 50 Tice Boulevard, Woodcliff Lake, NJ, 07677, USA
| | - F Siddiqi
- Research Institute for Fragrance Materials, Inc., 50 Tice Boulevard, Woodcliff Lake, NJ, 07677, USA
| | - I G Sipes
- Member Expert Panel, Department of Pharmacology, University of Arizona, College of Medicine, 1501 North Campbell Avenue, P.O. Box 245050, Tucson, AZ, 85724-5050, USA
| | - G Sullivan
- Research Institute for Fragrance Materials, Inc., 50 Tice Boulevard, Woodcliff Lake, NJ, 07677, USA.
| | - Y Thakkar
- Research Institute for Fragrance Materials, Inc., 50 Tice Boulevard, Woodcliff Lake, NJ, 07677, USA
| | - Y Tokura
- Member Expert Panel, The Journal of Dermatological Science (JDS), Editor-in-Chief, Professor and Chairman, Department of Dermatology, Hamamatsu University School of Medicine, 1-20-1 Handayama, Higashi-ku, Hamamatsu, 431-3192, Japan
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3
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Bastaki M, Api AM, Aubanel M, Bauter M, Cachet T, Demyttenaere JCR, Diop MM, Harman CL, Hayashi SM, Krammer G, Lu V, Marone PA, Mendes O, Renskers KJ, Schnabel J, Tsang SY, Taylor SV. Dietary administration of β-caryophyllene and its epoxide to Sprague-Dawley rats for 90 days. Food Chem Toxicol 2019; 135:110876. [PMID: 31610257 DOI: 10.1016/j.fct.2019.110876] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/13/2019] [Revised: 10/04/2019] [Accepted: 10/06/2019] [Indexed: 02/01/2023]
Abstract
Two independent 90-day GLP-compliant studies were conducted in Sprague-Dawley rats with β-caryophyllene or β-caryophyllene epoxide, two common flavoring and fragrance materials. Dietary concentrations of β-caryophyllene were 3500; 7000; and 21,000 ppm for males and 3500; 14,000; and 56,000 ppm for females. Dietary concentrations of β-caryophyllene epoxide were 1750; 10,500; and 21,000 ppm. There were no deaths or clinical toxicity attributable to either substance administration. Statistically significant, dose-dependent reductions in body weight, body weight gain, food consumption, and food efficiency at the highest dietary concentrations of β-caryophyllene, but not of β-caryophyllene epoxide, were attributed to palatability issues. Neither β-caryophyllene nor β-caryophyllene epoxide influenced estrus cyclicity or sperm parameters. Macroscopic and microscopic findings were primarily related to changes in the kidneys of male rats, consistent with α2u-globulin nephropathy, and in the liver of male and female rats, including hepatocyte hypertrophy at the middle and high intake levels. These changes correlated with increased absolute and relative organ weights. Since the kidney findings were a species- and sex-specific effect, the NOAEL in each study was based on hepatocyte hypertrophy at the two highest dietary concentrations and were determined to be 222 mg/kg bw/day for β-caryophyllene and 109 mg/kg bw/day for β-caryophyllene epoxide.
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Affiliation(s)
- Maria Bastaki
- International Organization of the Flavor Industry, 1101 17th Street N.W., Suite 700, Washington, DC, 20036, USA
| | - Anne Marie Api
- Research Institute for Fragrance Materials, Inc., 50 Tice Boulevard, Woodcliff Lake, NJ, 07677, USA
| | - Michel Aubanel
- Kerry Flavours France, Zl du Plan BP 82067, 63 Avenue Jean Maubert, 06131, Grasse Cedex, France
| | - Mark Bauter
- Product Safety Labs, 2394 US Highway 130, Dayton, NJ, 08810, USA
| | - Thierry Cachet
- International Organization of the Flavor Industry, Avenue des Arts 6, B-1210, Brussels, Belgium
| | | | | | - Christie L Harman
- Flavor and Extract Manufacturers Association, 1101 17th Street N.W., Suite 700, Washington, DC, 20036, USA
| | - Shim-Mo Hayashi
- Japan Flavor and Fragrance Materials Association, Sankeinihonbashi Bldg. 6F, 4-7-1 Nihonbashi-Honcho, Chuo-ku, Tokyo, 103-0023, Japan
| | - Gerhard Krammer
- Symrise AG, Muehlenfeldstrasse 1, 37603, Holzminden, Germany
| | - Vivian Lu
- International Organization of the Flavor Industry, 1101 17th Street N.W., Suite 700, Washington, DC, 20036, USA
| | - Palma Ann Marone
- Product Safety Labs, 2394 US Highway 130, Dayton, NJ, 08810, USA
| | - Odete Mendes
- Product Safety Labs, 2394 US Highway 130, Dayton, NJ, 08810, USA
| | - Kevin J Renskers
- Takasago International Corporation, 4 Volvo Drive, Rockleigh, NJ, 07647, USA
| | - Jürgen Schnabel
- Givaudan International SA, Kemptpark 50, 8310 Kemptthal, Switzerland
| | - Sai Yee Tsang
- Research Institute for Fragrance Materials, Inc., 50 Tice Boulevard, Woodcliff Lake, NJ, 07677, USA
| | - Sean V Taylor
- International Organization of the Flavor Industry, 1101 17th Street N.W., Suite 700, Washington, DC, 20036, USA.
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4
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Johnson W, Bergfeld WF, Belsito DV, Hill RA, Klaassen CD, Liebler D, Marks JG, Shank RC, Slaga TJ, Snyder PW, Andersen FA. Safety assessment of isoparaffins as used in cosmetics. Int J Toxicol 2013; 31:269S-95S. [PMID: 23283704 DOI: 10.1177/1091581812463087] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
Abstract
The safety of isoparaffins as used in cosmetic products is reviewed in this safety assessment. These ingredients function mostly as solvents and also function as emollients in the 0001% to 90% concentration range. The Cosmetic Ingredient Review (CIR) Expert Panel has reviewed relevant animal and clinical data and concluded that these ingredients are safe in the present practices of use and concentration described in this safety assessment.
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5
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The FEMA GRAS assessment of aliphatic and aromatic terpene hydrocarbons used as flavor ingredients. Food Chem Toxicol 2011; 49:2471-94. [DOI: 10.1016/j.fct.2011.06.011] [Citation(s) in RCA: 53] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/17/2010] [Revised: 05/20/2011] [Accepted: 06/01/2011] [Indexed: 01/15/2023]
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Abstract
Tert-Butanol is an important intermediate in industrial chemical synthesis, particularly of fuel oxygenates. Human exposure to tert-butanol may occur following fuel oxygenate metabolism or biodegradation. It is poorly absorbed through skin, but is rapidly absorbed upon inhalation or ingestion and distributed to tissues throughout the body. Elimination from blood is slower and the half-life increases with dose. It is largely metabolised by oxidation via 2-methyl-1,2-propanediol to 2-hydroxyisobutyrate, the dominant urinary metabolites. Conjugations also occur and acetone may be found in urine at high doses. The single-dose systemic toxicity of tert-butanol is low, but it is irritant to skin and eyes; high oral doses produce ataxia and hypoactivity and repeated exposure can induce dependence. Tert-Butanol is not definable as a genotoxin and has no effects specific for reproduction or development; developmental delay occurred only with marked maternal toxicity. Target organs for toxicity clearly identified are kidney in male rats and urinary bladder, particularly in males, of both rats and mice. Increased tumour incidences observed were renal tubule cell adenomas in male rats and thyroid follicular cell adenomas in female mice and, non-significantly, at an intermediate dose in male mice. The renal adenomas were associated with alpha(2u)-globulin nephropathy and, to a lesser extent, exacerbation of chronic progressive nephropathy. Neither of these modes of action can function in humans. The thyroid tumour response could be strain-specific. No thyroid toxicity was observed and a study of hepatic gene expression and enzyme induction and thyroid hormone status has suggested a possible mode of action.
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Affiliation(s)
- Douglas McGregor
- Toxicity Evaluation Consultants, Aberdour, Scotland, United Kingdom.
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Meek MEB, Bucher JR, Cohen SM, Dellarco V, Hill RN, Lehman-McKeeman LD, Longfellow DG, Pastoor T, Seed J, Patton DE. A Framework for Human Relevance Analysis of Information on Carcinogenic Modes of Action. Crit Rev Toxicol 2008; 33:591-653. [PMID: 14727733 DOI: 10.1080/713608373] [Citation(s) in RCA: 281] [Impact Index Per Article: 17.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/23/2022]
Abstract
The human relevance framework (HRF) outlines a four-part process, beginning with data on the mode of action (MOA) in laboratory animals, for evaluating the human relevance of animal tumors. Drawing on U.S. EPA and IPCS proposals for animal MOA analysis, the HRF expands those analyses to include a systematic evaluation of comparability, or lack of comparability, between the postulated animal MOA and related information from human data sources. The HRF evolved through a series of case studies representing several different MOAs. HRF analyses produced divergent outcomes, some leading to complete risk assessment and others discontinuing the process, according to the data available from animal and human sources. Two case examples call for complete risk assessments. One is the default: When data are insufficient to confidently postulate a MOA for test animals, the animal tumor data are presumed to be relevant for risk assessment and a complete risk assessment is necessary. The other is the product of a data-based finding that the animal MOA is relevant to humans. For the specific MOA and endpoint combinations studied for this article, full risk assessments are necessary for potentially relevant MOAs involving cytotoxicity and cell proliferation in animals and humans (Case Study 6, chloroform) and formation of urinary-tract calculi (Case Study 7, melamine). In other circumstances, when data-based findings for the chemical and endpoint combination studied indicate that the tumor-related animal MOA is unlikely to have a human counterpart, there is little reason to continue the risk assessment for that combination. Similarly, when qualitative considerations identify MOAs specific to the test species or quantitative considerations indicate that the animal MOA is unlikely to occur in humans, such hazard findings are generally conclusive and further risk assessment is not necessary for the endpoint-MOA combination under study. Case examples include a tumor-related protein specific to test animals (Case Study 3, d-limonene), the tumor consequences of hormone suppression typical of laboratory animals but not humans (Case Study 4, atrazine), and chemical-related enhanced hormone clearance rates in animals relative to humans (Case Study 5, phenobarbital). The human relevance analysis is highly specific for the chemical-MOA-tissue-endpoint combination under analysis in any particular case: different tissues, different endpoints, or alternative MOAs for a given chemical may result in different human relevance findings. By providing a systematic approach to using MOA data, the HRF offers a new tool for the scientific community's overall effort to enhance the predictive power, reliability and transparency of cancer risk assessment.
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8
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Dietrich DR, Heussner AH, O'Brien E, Gramatté T, Runkel M, Rumpf S, Day BW. Propiverine-induced accumulation of nuclear and cytosolic protein in F344 rat kidneys: isolation and identification of the accumulating protein. Toxicol Appl Pharmacol 2008; 233:411-9. [PMID: 18929589 DOI: 10.1016/j.taap.2008.09.014] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/25/2008] [Revised: 09/10/2008] [Accepted: 09/11/2008] [Indexed: 11/30/2022]
Abstract
Male and female F344 rats but not B6C3F1 mice exposed for 104 weeks to propiverine hydrochloride (1-methylpiperid-4-yl 2,2-diphenyl-2-(1-propoxy)acetate hydrochloride), used for treatment of patients with neurogenic detrusor overactivity (NDO) and overactive bladder (OAB), presented with an accumulation of proteins in the cytosol and nuclei of renal proximal tubule epithelial cells, yet despite this, no increased renal tumor incidence was observed. In order to provide an improved interpretation of these findings and a better basis for human health risk assessment, male and female F344 rats were exposed for 16 weeks to 1000 ppm propiverine in the diet, the accumulating protein was isolated from the kidneys via cytosolic and nuclear preparations or laser-capture microdissection and analyzed using molecular weight determination and mass spectrometry. The accumulating protein was found to be d-amino acid oxidase (DAAO), an enzyme involved in amino and fatty acid metabolism. Subsequent reanalysis of kidney homogenate and nuclear samples as well as tissue sections using western blot and DAAO-immunohistochemistry, confirmed the presence and localization of DAAO in propiverine-treated male and female F344 rats. The accumulation of DAAO only in rats, and the limited similarity of rat DAAO with other species, including humans, suggests a rat-specific mechanism underlying the drug-induced renal DAAO accumulation with little relevance for patients chronically treated with propiverine.
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Affiliation(s)
- D R Dietrich
- Environmental Toxicology, University of Konstanz, 78457 Konstanz, Germany.
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9
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Aronson DB, Bosch S, Gray DA, Howard PH, Guiney PD. A comparative human health risk assessment of p-dichlorobenzene-based toilet rimblock products versus fragrance/surfactant-based alternatives. JOURNAL OF TOXICOLOGY AND ENVIRONMENTAL HEALTH. PART B, CRITICAL REVIEWS 2007; 10:467-526. [PMID: 17934948 DOI: 10.1080/15287390600975103] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/25/2023]
Abstract
A comparison of the human health risk to consumers using one of two types of toilet rimblock products, either a p-dichlorobenzene-based rimblock or two newer fragrance/surfactant-based alternatives, was conducted. Rimblock products are designed for global use by consumers worldwide and function by releasing volatile compounds into indoor air with subsequent exposure presumed to be mainly by inhalation of indoor air. Using the THERdbASE exposure model and experimentally determined emission data, indoor air concentrations and daily intake values were determined for both types of rimblock products. Modeled exposure concentrations from a representative p-dichlorobenzene rimblock product are an order of magnitude higher than those from the alternative rimblock products due to its nearly pure composition and high sublimation rate. Lifetime exposure to p-dichlorobenzene or the subset of fragrance components with available RfD values is not expected to lead to non-cancer-based adverse health effects based on the exposure concentrations estimated using the THERdbASE model. A similar comparison of cancer-based effects was not possible as insufficient data were available for the fragrance components.
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Affiliation(s)
- Dallas B Aronson
- Syracuse Research Corporation, North Syracuse, New York 13212, USA
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Lock EA, Hard GC. Chemically induced renal tubule tumors in the laboratory rat and mouse: review of the NCI/NTP database and categorization of renal carcinogens based on mechanistic information. Crit Rev Toxicol 2004; 34:211-99. [PMID: 15239388 DOI: 10.1080/10408440490265210] [Citation(s) in RCA: 91] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/26/2022]
Abstract
The incidence of renal tubule carcinogenesis in male and female rats or mice with 69 chemicals from the 513 bioassays conducted to date by the NCI/NTP has been collated, the chemicals categorized, and the relationship between carcinogenesis and renal tubule hyperplasia and exacerbation of the spontaneous, age-related rodent disease chronic progressive nephropathy (CPN) examined. Where information on mechanism or mode of action exists, the chemicals have been categorized based on their ability to directly or indirectly interact with renal DNA, or on their activity via epigenetic pathways involving either direct or indirect cytotoxicity with regenerative hyperplasia, or exacerbation of CPN. Nine chemicals were identified as directly interacting with DNA, with six of these producing renal tubule tumors at high incidence in rats of both sexes, and in some cases also in mice. Ochratoxin A was the most potent compound in this group, producing a high tumor incidence at very low doses, often with metastasis. Three chemicals were discussed in the context of indirect DNA damage mediated by an oxidative free radical mechanism, one of these being from the NTP database. A third category included four chemicals that had the potential to cause DNA damage following conjugation with glutathione and subsequent enzymatic activation to a reactive species, usually a thiol-containing entity. Two chemicals were allocated into the category involving a direct cytotoxic action on the renal tubule followed by sustained compensatory cell proliferation, while nine were included in a group where the cell loss and sustained increase in renal tubule cell turnover were dependent on lysosomal accumulation of the male rat-specific protein, alpha2mu-globulin. In a sixth category, morphologic evidence on two chemicals indicated that the renal tumors were a consequence of exacerbated CPN. For the remaining chemicals, there were no pertinent data enabling assignment to a mechanistic category. Accordingly, these chemicals, acting through an as yet unknown mechanism, were grouped as either being associated with an enhancement of CPN (category 7, 16 chemicals), or not associated with enhanced CPN (category 8, 4 chemicals). A ninth category dealt with 11 chemicals that were regarded as producing increases in renal tubule tumors that did not reach statistical significance. A 10th category discussed 6 chemicals that induced renal tumors in mice but not in rats, plus 8 chemicals that produced a low incidence of renal tubule tumors in mice that did not reach statistical significance. As more mechanistic data are generated, some chemicals will inevitably be placed in different groups, particularly those from categories 7 and 8. A large number of chemicals in the series exacerbated CPN, but those in category 7 especially may be candidates for inclusion in category 6 when further information is gleaned from the relevant NTP studies. Also, new data on specific chemicals will probably expand category 5 as cytotoxicity and cell regeneration are identified as obligatory steps in renal carcinogenesis in more cases. Additional confirmatory outcomes arising from this review are that metastases from renal tubule tumors, while encountered with chemicals causing DNA damage, are rare with those acting through an epigenetic pathway, with the exception being fumonisin B1; that male rats and mice are generally more susceptible than female rats and mice to chemical induction of renal tubule tumors; and that a background of atypical tubule hyperplasia is a useful indicator reflecting a chemically associated renal tubule tumor response. With respect to renal tubule tumors and human risk assessment, chemicals in categories 1 and 2, and possibly 3, would currently be judged by linear default methods; chemicals in category 4 (and probably some in category 3) as exhibiting a threshold of activity warranting the benchmark approach; and those in categories 5 and 6 as representing mechanisms that have no relevance for extrapolation to humans.
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Affiliation(s)
- Edward A Lock
- Syngenta Central Toxicology Laboratory, Macclesfield, Cheshire, United Kingdom.
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11
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Vijayaraghavan M, Wanibuchi H, Karim R, Yamamoto S, Masuda C, Nakae D, Konishi Y, Fukushima S. Dimethylarsinic acid induces 8-hydroxy-2'-deoxyguanosine formation in the kidney of NCI-Black-Reiter rats. Cancer Lett 2001; 165:11-7. [PMID: 11248413 DOI: 10.1016/s0304-3835(00)00711-4] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Dirnethylarsenic peroxyl radical [(CH(3))(2)AsOO] has been postulated to be responsible for DNA damage induced by dimethylarsinic acid (DMA). In an effort to elucidate the possible mechanism of tumor-inducing potential of DMA, an experiment was designed to investigate the formation of 8-hydroxy-2'-deoxyguanosine (8-OHdG), a specific marker of oxidative base damage in the kidney tissues of NCI-Black Reiter (NBR) rats. Animals were divided into four groups and administered the vehicle - saline, 5, 10 and 20 mg/kg body weight respectively of DMA by gavage, once a day, 5 days a week, for a period of 4 weeks. DMA induced increase of 8-OHdG levels in the kidney of the rats treated, with the highest level at the dose of 10 mg/kg body weight. Analysis of the kidney for cell proliferation employing PCNA-positive index showed greater proliferation in the tissues of treated rats. However, DMA did not have any influence on apoptosis in this regimen. Histopathological examination of the kidney selections revealed the presence of vacuolated degeneration and dilation of the proximal tubule cells in two groups (10 and 20 mg/kg body weight). This study provides evidence to substantiate the role of DMA in inducing oxidative DNA damage in the kidney.
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Affiliation(s)
- M Vijayaraghavan
- Department of Pathology, Osaka City University Medical School, 1-4-3, Asahi-mach, Abeno-ku, 545-8585, Osaka, Japan
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12
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Takaba K, Saeki K, Suzuki K, Wanibuchi H, Fukushima S. Significant overexpression of metallothionein and cyclin D1 and apoptosis in the early process of rat urinary bladder carcinogenesis induced by treatment with N-butyl-N-(4-hydroxybutyl)nitrosamine or sodium L-ascorbate. Carcinogenesis 2000; 21:691-700. [PMID: 10753205 DOI: 10.1093/carcin/21.4.691] [Citation(s) in RCA: 22] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022] Open
Abstract
Effects of a genotoxic bladder carcinogen, N-butyl-N-(4-hydroxybutyl)nitrosamine (BBN) and a non-genotoxic bladder promoter, sodium L-ascorbate (Na-AsA), on protein expression, cell proliferation and apoptosis of the bladder epithelium with or without the influence of testicular castration were investigated. Male F344 rats were divided into six groups (groups 1-6). BBN was given with 0.05% drinking water to groups 1 and 4 for 8 weeks, groups 2 and 5 received diet with 5% Na-AsA. Then the animals were treated without any chemicals. Groups 3 and 6 were non-treated controls. Testicular castration was carried out 2 weeks before commencement of chemical treatment on groups 4-6. The total observation period was 18 weeks. Overexpression of cyclin D1 was induced by BBN but not Na-AsA and the degree of overexpression was higher in the order simple hyperplasia, papillary or nodular hyperplasia, papilloma and carcinoma. Metallothionein (MT) was also overexpressed in bladder epithelium treated with BBN but not Na-AsA, but was decreased in papillomas and never found in a carcinoma. Cyclin D1-positive cells were essentially MT-negative. Therefore, it is speculated that MT protects genes from insult by genotoxic carcinogens and its lack is associated with tumor development. Apoptotic cell death occurred during treatment with BBN and Na-AsA and after their withdrawal. Chromatin condensation of many G0/G(1) cells was particularly marked on flow cytometry analysis 1 week after cessation of treatment, this being considered as an early apoptotic change. Although testicular castration had no influence on the above events, it resulted in decreased tumor formation as compared with the case of similarly treated intact animals. Our data demonstrate that overexpression of MT and cyclin D1 is specific for treatment with a genotoxic carcinogen, and suggest that MT overexpression may play an important suppressive role in the early stages of rat urinary bladder carcinogenesis.
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Affiliation(s)
- K Takaba
- Toxicological Research Laboratories, Kyowa Hakko Kogyo Co. Ltd, 2548 Fujimagari, Ube, Yamaguchi 755-8501, Japan.
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13
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Vijayaraghavan M, Wanibuchi H, Yamamoto S, Hakoi K, Nakae D, Konishi Y, Fukushima S. Lack of Promoting Potential of Dimethylarsinic Acid in the Kidney of Male NCI-Black Reiter Rats. J Toxicol Pathol 2000. [DOI: 10.1293/tox.13.87] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/19/2022] Open
Affiliation(s)
| | - Hideki Wanibuchi
- Department of Pathology, Osaka City University Medical School, Abeno-ku, Osaka 545-8585, Japan
| | - Shinji Yamamoto
- Department of Pathology, Osaka City University Medical School, Abeno-ku, Osaka 545-8585, Japan
| | - Katsuo Hakoi
- Department of Pathology, Osaka City University Medical School, Abeno-ku, Osaka 545-8585, Japan
| | - Dai Nakae
- Department of Oncological Pathology, Cancer Center, Nara Medical University, Kashihara, Nara 634-8521, Japan
| | - Yoichi Konishi
- Department of Oncological Pathology, Cancer Center, Nara Medical University, Kashihara, Nara 634-8521, Japan
| | - Shoji Fukushima
- Department of Pathology, Osaka City University Medical School, Abeno-ku, Osaka 545-8585, Japan
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14
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Barter JA, Sherman JH. An evaluation of the carcinogenic hazard of 1,4-dichlorobenzene based on internationally recognized criteria. Regul Toxicol Pharmacol 1999; 29:64-79. [PMID: 10051419 DOI: 10.1006/rtph.1998.1269] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
1,4-Dichlorobenzene (1,4-DCB) was shown to induce the formation of male rat renal tubule tumors and male and female mouse liver tumors when administered in a chronic bioassay. Since the original carcinogenicity findings, an extensive body of mechanistic information has been developed to elucidate the mode of action by which 1,4-DCB induces these effects and to evaluate the human relevance of the observed animal tumors. In addition, some regulatory and authoritative bodies (U.S. EPA and IARC) have developed rigorous scientific criteria for the amount and types of evidence needed to establish that a material causes kidney toxicity and tumors in male rats through a specific mechanism, alpha-2u-globulin nephropathy. This paper summarizes the mechanistic data developed for 1,4-DCB, which affords an understanding of the lack of human relevance of the male rat renal tubule tumors and mouse liver tumors; assesses that mechanistic data set utilizing the defined set of evaluation criteria formulated by U.S. EPA and IARC for alpha-2u-globulin nephropathy; and discusses the predictive power of mechanistic data developed to elucidate the mode of action of 1,4-DCB in inducing mouse liver tumors. Finally, there is a discussion of how some, but not all, regulatory and authoritative bodies have incorporated this substantial mechanistic data set for 1, 4-DCB into their cancer hazard evaluations and concluded that 1, 4-DCB presents little, if any, cancer hazard to humans.
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Affiliation(s)
- J A Barter
- PPG Industries, Inc., Pittsburgh, Pennsylvania 15272, USA.
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15
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Rásonyi T, Schlatter J, Dietrich DR. The role of alpha2u-globulin in ochratoxin A induced renal toxicity and tumors in F344 rats. Toxicol Lett 1999; 104:83-92. [PMID: 10048753 DOI: 10.1016/s0378-4274(98)00347-6] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/16/2022]
Abstract
The mycotoxin ochratoxin A (OTA) was shown to be a potent kidney carcinogen in rats demonstrating a marked sex difference in the response. Compared to female rats, male rats had a 10-fold higher incidence of kidney carcinomas. The objective of this study was to investigate whether this sex difference in tumor response is due to an exacerbation of effect resulting from the interaction of the male rat specific urinary protein alpha2u-globulin (alpha2u) with OTA. Male and female rats were treated by oral gavage with OTA (1 mg/kg per day), D-limonene (dL; 1650 mg/kg per day) as a positive control or corn oil for 7 consecutive days. OTA induced severe renal lesions predominantly in the P3 region of the proximal tubules. The lesions consisted of necrotic cells and cell exfoliations. No hyaline droplets were found in the P2 segment following OTA treatment, whereas dL induced the expected accumulation of droplets. The results suggest that OTA induced kidney lesions are in all characteristic points different from the known alpha2u-nephropathy induced by dL. Based on these experiments the male rat specific protein alpha2u does not seem to be involved in the mechanism(s) leading to the high tumor incidence observed in OTA exposed male rats.
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Affiliation(s)
- T Rásonyi
- Institute of Toxicology, Swiss Federal Institute of Technology (ETH) and University of Zurich, Schwerzenbach
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16
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Bird MG, Burleigh-Flayer HD, Chun JS, Douglas JF, Kneiss JJ, Andrews LS. Oncogenicity Studies of Inhaled Methyl Tertiary-butyl Ether (MTBE) in CD-1 Mice and F-344 Rats. J Appl Toxicol 1998. [DOI: 10.1002/(sici)1099-1263(199705)17:1+3.0.co;2-k] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
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17
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Lehman-McKeeman LD, Caudill D, Rodriguez PA, Eddy C. 2-sec-butyl-4,5-dihydrothiazole is a ligand for mouse urinary protein and rat alpha 2u-globulin: physiological and toxicological relevance. Toxicol Appl Pharmacol 1998; 149:32-40. [PMID: 9512724 DOI: 10.1006/taap.1997.8343] [Citation(s) in RCA: 20] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Mouse urinary protein (MUP) and alpha 2u-globulin are structurally homologous proteins that belong to a superfamily of ligand-binding proteins and represent the major urinary proteins excreted by adult male mice and rats, respectively. Although a variety of xenobiotics bind to alpha 2u-globulin and produce a male rat-specific hyaline droplet nephropathy, no endogenous ligand for this protein has been identified. Despite extensive sequence homology. MUP does not bind to hyaline droplet-inducing agents. While performing experiments with purified MUP, we observed that it presented with a strong, distinctive odor reminiscent of mouse urine. To determine whether this odor was the result of contamination or degradation or was attributed to an endogenous ligand bound to the protein, the protein was subjected to thermal desorption and any released volatile compounds were detected with a gas chromatograph equipped with an external sniff port and mass spectrometer. With this approach, two odorous compounds were detected at the sniff port by a human observer, but only one was present in sufficient mass to allow identification. This compound, which presented with the characteristic odor, was subsequently identified as 2-sec butyl-4,5-dihydrothiazole (DHT) by GC/MS/matrix isolation IR and NMR analyses. The identification of DHT was confirmed by comparing the chromatographic and spectral properties to those of the synthesized authentic compound. In direct contrast, purified urinary alpha 2u-globulin did not present with an obvious odor, and no volatile ligands were detected on this protein. Although DHT is a major endogenous ligand for MUP, it was also found to competitively inhibit the binding of [14C]d-limonene-1,2-epoxide to alpha 2u-globulin with relatively high affinity (Ki = 2.3 microM). When dosed orally to F344 rats, DHT (1 mmol/kg for 3 days) caused the characteristic exacerbation of hyaline droplets in male rat kidneys and increased renal levels of immunoreactive alpha 2u-globulin about threefold over control levels. These results indicate that despite structural homology, MUP and alpha 2u-globulin are distinguished by the presence of a volatile endogenous ligand only on the former, a distinction that may reflect differences in the physiological functions of the two proteins. Furthermore, although DHT can bind to both MUP and alpha 2u-globulin, renal toxicity was only observed in rats, thereby emphasizing the unique toxicological properties of alpha 2u-globulin in the development of hyaline droplet nephropathy.
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Affiliation(s)
- L D Lehman-McKeeman
- Human Safety Department, Procter and Gamble Co., Miami Valley Laboratories, Cincinnati, Ohio 45253-8707, USA
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18
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Abstract
Laboratory studies with classical renal carcinogens in the rat and mouse, as well as research investigation with some of the chemicals proving positive for the kidney in National Toxicology Program carcinogenicity bioassays, have demonstrated the existence of a range of diverse mechanisms underlying rodent kidney carcinogenesis. The classical carcinogens used as experimental models for studying renal tumor pathogenesis, such as the nitrosamines, are genotoxic and interact directly with DNA, forming DNA adducts with mutagenic potential. In contrast, potassium bromate and ferric nitrilotriacetate (Fe-NTA), also effective renal carcinogens, appear to cause indirect damage to DNA mediated by oxidative stress. A number of nongenotoxic chemicals are associated with epigenetic renal tumor induction in rodents, and the activity of these tends to involve prolonged stimulation of cell proliferation throughout the duration of exposure. This mode of action reflects a sustained regenerative response, either due to direct chemical toxicity to the tubule cells, as with chloroform, or to indirect cytotoxicity associated with lysosomal overload, as in alpha2u-globulin accumulation in male rats resulting from the administration of such chemicals as d-limonene and tetrachloroethylene. The histopathologic nature of hydroquinone renal carcinogenesis suggests that an additional epigenetic pathway to renal tubule tumor formation in rats may be through chemical-mediated exacerbation of, and interaction with, the age-related spontaneous renal disease, chronic progressive nephropathy. These various mechanistic pathways have implications for the nature of the induced cancer process with respect to tumor incidence, latency, malignancy, and sex predisposition.
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Affiliation(s)
- G C Hard
- American Health Foundation, Valhalla, New York 10595, USA
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19
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Kim S, Qualls CW, Reddy G, Stair EL. 1,3,5-Trinitrobenzene-induced alpha-2u-globulin nephropathy. Toxicol Pathol 1997; 25:195-201. [PMID: 9125778 DOI: 10.1177/019262339702500209] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/04/2023]
Abstract
Male and female Fischer-344 (F-344) and male NCI-Black-Reiter (NBR) rats were dosed with 0, 35.5, or 71 mg 1,3,5-trinitrobenzene (TNB)/kg/day for 10 days. Male F-344 rats were dosed with TNB (0 and 35.5 mg/kg) for 20 and 30 days. Hematoxylin and eosin and Mallory-Heidenhain stains and alpha-2u-globulin and proliferating cell nuclear antigen immunohistochemical stains were performed on kidney sections. All treated male F-344 rats exhibited dose-related accumulation of hyaline droplets containing alpha-2u-globulin in proximal tubules. The kidney weights were significantly increased in male and female rats treated with TNB. Significant increases in cell proliferation in proximal tubules were observed in male F-344 rats. Renal changes observed in TNB-treated rats appeared identical to those from other chemicals that induce alpha-2u-globulin nephropathy in male rats. No hyaline droplet accumulation was found in female F-344 and male NBR rats at any doses. We can conclude that TNB induces dose-related exacerbation of hyaline droplets containing alpha-2u-globulin in male rat kidney and subsequent cell proliferation.
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Affiliation(s)
- S Kim
- Department of Veterinary Pathology, College of Veterinary Medicine, Oklahoma State University, Stillwater 74078, USA
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20
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Adams TB, Hallagan JB, Putnam JM, Gierke TL, Doull J, Munro IC, Newberne P, Portoghese PS, Smith RL, Wagner BM, Weil CS, Woods LA, Ford RA. The FEMA GRAS assessment of alicyclic substances used as flavour ingredients. Food Chem Toxicol 1996; 34:763-828. [PMID: 8972877 DOI: 10.1016/s0278-6915(96)00051-8] [Citation(s) in RCA: 37] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/03/2023]
Abstract
For over 35 years, an independent panel of expert scientists has served as the primary body for evaluating the safety of flavour ingredients. This group, the Expert Panel of the Flavor and Extract Manufacturers' Association (FEMA), has achieved international recognition from the flavour industry, government regulatory bodies including the Food and Drug Administration, and the toxicology community for its unique contributions. To date, the Expert Panel has evaluated the safety of more than 1700 flavour ingredients and determined the vast majority to be "generally recognized as safe" (GRAS). Elements that are fundamental to the safety evaluation of flavour ingredients include exposure, structural analogy, metabolism, pharmacokinetics and toxicology. Flavour ingredients are evaluated individually taking into account the available scientific information on the group of structurally related substances. The elements of the GRAS assessment program as they have been applied by the Expert Panel to the group of 119 alicyclic substances used as flavour ingredients, and the relevant scientific data which provide the basis for the GRAS status of these substances, are described herein.
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Affiliation(s)
- T B Adams
- Flavor and Extract Manufacturers' Association, Washington, DC, USA
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21
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Kimura J, Takahashi S, Ogiso T, Yoshida Y, Akagi K, Hasegawa R, Kurata M, Hirose M, Shirai T. Lack of chemoprevention effects of the monoterpene d-limonene in a rat multi-organ carcinogenesis model. Jpn J Cancer Res 1996; 87:589-94. [PMID: 8766522 PMCID: PMC5921134 DOI: 10.1111/j.1349-7006.1996.tb00264.x] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/02/2023] Open
Abstract
Modifying effects of dietary administration of the monoterpene d-limonene were examined using a multi-organ carcinogenesis model. Groups of twenty F344 male rats were treated sequentially with N-diethylnitrosamine (DEN, i.p.), N-methyl-N-nitrosourea (MNU, i.p.), 1,2-dimethylhydrazine (DMH, s.c.), N-butyl-N-(4-hydroxybutyl)nitrosamine (BBN, in drinking water) and dihydroxy-di-N-propylnitrosamine (DHPN, in drinking water) during the first 4 weeks (DMBDD treatment), and then d-limonene was administered in the diet, at the dose of 2.0, 1.0 or 0.5%. The maximal tolerable dose was 2.0% under the present conditions. Further groups were treated with DMBDD or 2.0% d-limonene alone as controls. All surviving animals were killed at week 28, and major organs were examined histopathologically for development of preneoplastic and neoplastic lesions. The incidences and/or multiplicities of renal atypical tubules and adenomas were increased in animals fed 2.0% d-limonene. The immunohistochemical reactivity for alpha2u-globulin in the proximal tubules was greater in rats fed d-limonene than in the carcinogen alone group. No enhancing or inhibitory effect was noted for tumor development in other organs. The present results indicate a lack of any chemopreventive effect of d-limonene in any organ of male rats under the present experimental conditions.
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Affiliation(s)
- J Kimura
- First Department of Pathology, Nagoya City University Medical School, Nagoya, Japan
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22
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Williams GM, Karbe E, Fenner-Crisp P, Iatropoulos MJ, Weisburger JH. Risk assessment of carcinogens in food with special consideration of non-genotoxic carcinogens. Scientific arguments for use of risk assessment and for changing the Delaney Clause specifically. EXPERIMENTAL AND TOXICOLOGIC PATHOLOGY : OFFICIAL JOURNAL OF THE GESELLSCHAFT FUR TOXIKOLOGISCHE PATHOLOGIE 1996; 48:209-15. [PMID: 8672879 DOI: 10.1016/s0940-2993(96)80046-7] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/01/2023]
Abstract
The document "Risk Assessment of Carcinogens in Food with Special Consideration of Non-Genotoxic Carcinogens" was produced by the International Federation of Societies of Toxicologic Pathologists on the occasion of its triannual meeting in Tours, France, April 23-26, 1995. Subsequently, it was endorsed by the North American Society of Toxicologic Pathologists at its annual meeting in San Diego, CA, USA, June 11-15, 1995. This document was written to address up-to-date risk assessment of carcinogens and anachronisms in the Delaney Clause of the US Federal Food, Drug and Cosmetic Act which have become evident since its enactment in 1958. In the intervening years, major progress has been made in understanding mechanisms of cancer induction and in recognizing causes of human cancer. The Clause in conjunction with its present legal interpretation and implementation does not provide for rational, scientific evaluation of carcinogens. It ignores the fact that the diverse mechanisms now known to underlie cancer increases in rodents exposed to high doses of chemicals are often inapplicable to man. In this regard, current evaluation of chemicals based on the tenets of the Delaney Clause is irrational in many cases. The document presents several examples of chemicals to which humans may be exposed through food and which illustrate the need for science-based risk assessment. Appropriate risk assessment methods are available to provide assurance of negligible risk, and accordingly, it is recommended that the Delaney Clause be rescinded as it has outlived its usefulness. This will enable US governmental agencies to regulate the use of chemicals in foods by using appropriate current scientific methods on a case by case basis within the context of other relevant legislation.
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Affiliation(s)
- G M Williams
- Division of Pathology and Toxicology, American Health Foundation, Valhalla, NY 10595, USA
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23
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Williams GM, Whysner J. Epigenetic carcinogens: evaluation and risk assessment. EXPERIMENTAL AND TOXICOLOGIC PATHOLOGY : OFFICIAL JOURNAL OF THE GESELLSCHAFT FUR TOXIKOLOGISCHE PATHOLOGIE 1996; 48:189-95. [PMID: 8672874 DOI: 10.1016/s0940-2993(96)80041-8] [Citation(s) in RCA: 52] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/01/2023]
Abstract
Regulatory policies in the U.S. have been developed based upon a single model of cancer causation, which assumes chemical-induced genetic alterations. Such a model predicts some degree of cancer risk even at extremely low exposure levels. Many chemicals that produce tumors in experimental animals have been shown to act by epigenetic mechanisms that do not involve an attack by the chemical on DNA leading to subsequent genetic alteration. Such indirect mechanisms require prolonged exposures to high levels of chemicals for the production of tumors. For chemicals that are carcinogenic in this manner, the cancer mechanism would not be operative at exposures below a threshold at which the relevant cellular effect does not occur. Also, in contrast to DNA-reactive mechanisms, epigenetic effects may be unique to the rodent species used for testing. Certain chemical tumorigens have been well studied and provide examples for the use of mechanistic information in risk assessment. Butylated hydroxyanisole and saccharin are nongenotoxic food additives for which no risk to humans is predicted based upon low exposure levels and the likelihood that humans are either insensitive or much less sensitive to the tumorigenic effects found in rodent test species. For another non-genotoxic food additive d-limonene, the mechanism that underlies kidney tumor development in male rats is not expected to be operative in humans at all. The pharmaceutical phenobarbital represents a large group of non-genotoxic liver microsome enzyme inducers, which produce liver cancer in mice at levels that are near to therapeutic doses in humans. Epidemiology studies have not shown phenobarbital-related tumors in humans, indicating that humans may be less sensitive to the effects of phenobarbital. The mechanistic considerations involved in the risk assessment of these agents demonstrate that humans are not at risk from current exposure levels of many epigenetic carcinogens.
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Affiliation(s)
- G M Williams
- American Health Foundation, Valhalla, NY 10595-1599, USA
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24
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Saner C, Weibel B, Wurgler FE, Sengstag C. Metabolism of promutagens catalyzed by Drosophila melanogaster CYP6A2 enzyme in Saccharomyces cerevisiae. ENVIRONMENTAL AND MOLECULAR MUTAGENESIS 1996; 27:46-58. [PMID: 8625948 DOI: 10.1002/(sici)1098-2280(1996)27:1<46::aid-em7>3.0.co;2-c] [Citation(s) in RCA: 55] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/22/2023]
Abstract
The somatic mutation and recombination test (SMART) in Drosophila melanogaster allows screening of chemicals for genotoxicity in a multicellular organism. In order to correlate data obtained in the SMART with those from genotoxicity tests in rodents, it is important to learn more on the variety of drug-metabolizing enzymes present in this insect and to identify their substrate specificities. In this study we have concentrated on the phase I enzyme cytochrome P450 6A2, which is the first cytochrome P450 cloned from Drosophila. A genomic CYP6A2 DNA fragment and its corresponding cDNA were cloned and sequenced, revealing a previously unidentified intron with an inframe stop codon. This intron is invariantly present in an insecticide resistant [OR(R)] and a sensitive (flr3) strain. Developmental Northern analysis of CYP6A2 mRNA demonstrated a peak of expression in the third larval and pupal stage. CYP6A2 mRNA was found to be present in the insecticide-resistant strain at higher levels than in the insecticide-sensitive strain. Therefore, insecticide resistance might be correlated with enhanced CYP6A2 expression. The substrate specificity of CYP6A2 enzyme was investigated by coexpressing CYP6A2 cDNA with the cDNA for human NADPH-cytochrome P450 reductase in the yeast Saccharomyces cerevisiae. The transformed strain activated the mycotoxin aflatoxin B1 to a product that induced gene conversion, scored at the trp5 locus. Two other compounds, 7,12-dimethylbenz[a]anthracene (DMBA) and 3-amino-1-methyl-5H-pyrido[4,3-b]indole (Trp-P-2), were metabolized in the transformed strain to cytotoxic products.
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Affiliation(s)
- C Saner
- Institute of Toxicology, Swiss Federal Institute of Technology, Schwerzenbach, Switzerland
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25
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Affiliation(s)
- G C Hard
- American Health Foundation, Valhalla, New York 10595, USA
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26
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Lock EA. Mechanisms underlying species-specificity in target organ toxicity. ARCHIVES OF TOXICOLOGY. SUPPLEMENT. = ARCHIV FUR TOXIKOLOGIE. SUPPLEMENT 1995; 17:367-74. [PMID: 7786173 DOI: 10.1007/978-3-642-79451-3_32] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/27/2023]
Affiliation(s)
- E A Lock
- Research Toxicology Section, Zeneca Central Toxicology Laboratory, Alderley Park, Cheshire
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27
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Dietrich DR, Rasonyi T. Preneoplastic lesions in kidney and carcinogenesis by non-genotoxic compounds. ARCHIVES OF TOXICOLOGY. SUPPLEMENT. = ARCHIV FUR TOXIKOLOGIE. SUPPLEMENT 1995; 17:536-46. [PMID: 7786190 DOI: 10.1007/978-3-642-79451-3_47] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/27/2023]
Affiliation(s)
- D R Dietrich
- Institute of Toxicology, Swiss Federal Institute of Technology, Schwerzenbach
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28
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Garland EM, St John M, Asamoto M, Eklund SH, Mattson BJ, Johnson LS, Cano M, Cohen SM. A comparison of the effects of sodium saccharin in NBR rats and in intact and castrated male F344 rats. Cancer Lett 1994; 78:99-107. [PMID: 7514092 DOI: 10.1016/0304-3835(94)90037-x] [Citation(s) in RCA: 20] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/25/2023]
Abstract
High doses of sodium saccharin (NaSac) increase proliferation in the bladder of the rat, with a male preponderance. The possibility that alpha 2u-globulin is involved in its mechanism of action was evaluated by feeding it at 7.5% of the diet to NCI-Black-Reiter (NBR) male rats, which do not synthesize liver-derived alpha 2u-globulin. NaSac affected urinary parameters similarly in F344 and NBR male rats, but NBR rats consumed more water leading to greater urinary volume. NaSac produced less proliferation in NBR than in intact F344 rats, with intermediate changes in castrated F344 males, which had intermediate urinary alpha 2u-globulin levels.
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Affiliation(s)
- E M Garland
- Department of Pathology and Microbiology, University of Nebraska Medical Center, Omaha 68198-3135
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29
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MacDonald JS, Lankas GR, Morrissey RE. Toxicokinetic and mechanistic considerations in the interpretation of the rodent bioassay. Toxicol Pathol 1994; 22:124-40. [PMID: 7973360 DOI: 10.1177/019262339402200206] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/28/2023]
Abstract
When chemicals that are nongenotoxic in conventional assays produce increases in tumor incidence in rodents in chronic bioassays, the determination of the significance of these data for human safety is a challenging task. An important first step in this process is consideration of available data on the mechanism of action and biological properties of the chemical as well as pharmacokinetic and metabolism data in the species showing the response. In recent years, there has been an increase in the understanding of so-called "secondary mechanisms" of carcinogenesis (e.g., thyroid tumors in rats following exposure to enzyme inducers). Application of these data may assist in determination of human risk. There are 2 important questions that will be explored and developed: Are there biological effects produced in the test species that could explain the increase in tumor incidence, and will these effects be reproduced in humans? What is the exposure to the chemical that is associated with the increase in tumors, and how does this relate to exposure in humans?
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Affiliation(s)
- J S MacDonald
- Merck Research Laboratories, West Point, Pennsylvania 19486
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30
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Hard GC, Whysner J. Risk assessment of d-limonene: an example of male rat-specific renal tumorigens. Crit Rev Toxicol 1994; 24:231-54. [PMID: 7945892 DOI: 10.3109/10408449409021607] [Citation(s) in RCA: 55] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/28/2023]
Abstract
The naturally occurring food constituent d-limonene has been found to cause tumors at high doses only in the kidney of the male rat in association with the development of hyaline droplet nephropathy. In contrast, neither kidney tumors nor the associated nephropathy have been found in female rats or mice at much higher doses. Adult male rats produce large quantities of a specific low-molecular-weight protein in the liver, which is known as alpha 2U-globulin (alpha 2U-g). With administration of sufficient doses of d-limonene to male rats, this protein has been found to accumulate excessively in the P2 segment cells of renal proximal tubules, resulting in hyaline droplet formation as a manifestation of protein overload. Hyaline droplet accumulation is the first stage in a unique sequence of nephropathic lesions (also known as alpha 2U-g nephropathy), including granular casts in the outer medulla and linear mineralization in the papilla. The mechanism underlying protein accumulation appears to be the reversible binding of chemical to alpha 2U-g with subsequent prolongation of its half-life in the tubule cell. In the case of d-limonene, the minor metabolite d-limonene-1,2-oxide has been shown to be the primary chemical species that binds reversibly to alpha 2U-g, impeding the normal process of lysosomal proteinase degradation of alpha 2U-g. The ensuing nephropathy is associated with a sustained increase in compensatory renal tubule cell proliferation, which provides the putative mechanistic link with renal tumor formation possibly through tumor promotion of spontaneously initiated cells or enhanced spontaneous mutagenesis. This proposed mechanism has been supported by additional information, including negative genotoxicity tests for d-limonene and its oxide metabolites, experimentally verified tumor promotion, and enhanced cell proliferation primarily in P2 segment tubule cells in male F344 rats, but no such effects in the alpha 2U-g-deficient NBR rat. The mechanism of d-limonene tumor development does not appear to be possible in humans since neither the quantity nor the type of protein that binds d-limonene or d-limonene-1,2-oxide is present. The deduction that the renal tumors induced in male rats are not relevant to human carcinogenicity in the hazard evaluation step of risk assessment completes the evaluation of human risk for d-limonene. Consequently, it can be concluded that d-limonene does not pose any carcinogenic or nephrotoxic risk to humans.(ABSTRACT TRUNCATED AT 400 WORDS)
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Affiliation(s)
- G C Hard
- Division of Pathology and Toxicology, American Health Foundation, Valhalla, NY 10595
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31
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Rodgers IS, Baetcke KP. Interpretation of male rat renal tubule tumors. ENVIRONMENTAL HEALTH PERSPECTIVES 1993; 101 Suppl 6:45-52. [PMID: 7517352 PMCID: PMC1520005 DOI: 10.1289/ehp.93101s645] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/11/2023]
Abstract
Based on an analysis of recent scientific studies, a Technical Panel of the U.S. Environmental Protection Agency's (EPA) Risk Assessment Forum recently advised EPA risk assessors against using information on certain male rat renal tubule tumors to assess human risk under conditions specified in a new Forum report. Risk assessment approaches generally assume that chemicals producing tumors in laboratory animals are a potential cancer hazard to humans. For most chemicals, including classical rodent kidney carcinogens such as N-ethyl-N-hydroxyethylnitrosamine, this extrapolation remains appropriate. Some chemicals, however, induce accumulation of alpha 2u-globulin (alpha 2u-g), a low molecular weight protein, in the male rat kidney. The alpha 2u-g accumulation initiates a sequence of events that appears to lead to renal tubule tumor formation. Female rats and other laboratory mammals administered the same chemicals do not accumulate low molecular weight protein in the kidney, and they do not develop renal tubule tumors. Because humans appear to be more like other laboratory animals than like the male rat, in this special situation, the male rat is not a good model for assessing human risk. The Forum report stresses the need for full scrutiny of a substantial set of data to determine when it is reasonable to presume that renal tumors in male rats are linked to a process involving alpha 2u-g accumulation and to select appropriate procedures for estimating human risks under such circumstances.
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Affiliation(s)
- I S Rodgers
- U.S. Environmental Protection Agency, Washington, DC 20460
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Takahashi K, Lindamood C, Maronpot RR. Retrospective study of possible alpha-2 mu-globulin nephropathy and associated cell proliferation in male Fischer 344 rats dosed with t-butyl alcohol. ENVIRONMENTAL HEALTH PERSPECTIVES 1993; 101 Suppl 5:281-5. [PMID: 7516874 PMCID: PMC1519457 DOI: 10.1289/ehp.93101s5281] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/11/2023]
Abstract
Tert-butyl alcohol, an important commodity chemical, additive to unleaded gasoline, and contaminant of drinking water, was evaluated for toxicity and was found to enhance nephropathy in male Fischer 344 rats. Because male rats treated with t-butyl alcohol for 2 years had a low incidence of renal cortical tumors, additional renal sections for the 90-day toxicity study were examined for the presence of hyaline droplet accumulation, nephropathy, and evidence of replicative DNA synthesis (S-phase nuclei) to indirectly and retrospectively investigate a possible role of alpha-2 mu-globulin in the pathogenesis of the nephropathy. Dose levels for t-butyl alcohol were 0, 0.25, 0.5, 1, 2, and 4% (w/v) administered in drinking water. Significant body weight gain depressions were observed in all treated males, and there was an absolute weight loss in the 4% male group, none of which survived to the end of the study. Except for the 4% dose group, there was a treatment-related increase in hyaline droplet accumulation in the renal proximal tubules with crystalline, rectangular, and rhomboid forms of the protein evident. The severity of nephropathy was enhanced in treated rats, except for the 4% dose group. Replicative DNA synthesis, as measured by immunohistochemical staining for proliferating cell nuclear antigen, was increased in proximal tubules of rats dosed with 2% t-butyl alcohol. It is concluded that t-butyl alcohol exacerbated nephropathy in male Fischer 344 rats and increased renal accumulation of hyaline protein material consistent with alpha-2 mu-globulin deposition.
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Affiliation(s)
- K Takahashi
- Institute of Environmental Toxicology, Tokyo, Japan
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Melnick RL. An alternative hypothesis on the role of chemically induced protein droplet (alpha 2u-globulin) nephropathy in renal carcinogenesis. Regul Toxicol Pharmacol 1992; 16:111-25. [PMID: 1279759 DOI: 10.1016/0273-2300(92)90052-b] [Citation(s) in RCA: 42] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/26/2022]
Abstract
Based on associations between the accumulation of protein droplets containing alpha 2u-globulin in proximal tubular epithelial cells and increased incidences of renal tubular neoplasms in male rats, it has been suggested that the carcinogenicity of chemicals that cause alpha 2u-globulin nephropathy is unique to animals that synthesize this protein. Chemicals that caused alpha 2u-globulin nephropathy and renal carcinogenicity in male rats have not been shown to produce renal tumors in animals that lack the capability for hepatic alpha 2u-globulin synthesis, including female rats, male NBR rats, or mice of either sex. Because humans do not synthesize alpha 2u-globulin it has been suggested that chemicals which cause renal toxicity associated with alpha 2u-globulin accumulation do not pose an increased cancer risk to humans. In this review on the association between alpha 2u-globulin nephropathy and renal carcinogenesis, it is apparent that (a) there are data inconsistent with the hypothesis linking these occurrences, (b) alternative mechanisms of renal toxicity and carcinogenicity are plausible, (c) data on quantitative dose-response correspondences between the various stages of alpha 2u-globulin nephropathy and renal carcinogenicity are limited, and (d) a greater understanding of the molecular changes occurring during renal carcinogenesis is needed before assuming that the current hypothesis is correct. Future research aimed at resolving issues raised in this paper should help determine whether or not the association between alpha 2u-globulin nephropathy and renal carcinogenesis represents a cause-and-effect relationship.
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Affiliation(s)
- R L Melnick
- Division of Biometry and Risk Assessment, National Institute of Environmental Health Sciences, Research Triangle Park, North Carolina 27709
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Lehman-McKeeman LD, Caudill D. Biochemical basis for mouse resistance to hyaline droplet nephropathy: Lack of relevance of the α2u-globulin protein superfamily in this male rat-specific syndrome. Toxicol Appl Pharmacol 1992; 112:214-21. [PMID: 1371614 DOI: 10.1016/0041-008x(92)90190-4] [Citation(s) in RCA: 36] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
Abstract
It is well-established that binding of a chemical to alpha 2u-globulin is the rate-limiting step in the development of male rat-specific hyaline droplet nephropathy. Mice synthesize mouse urinary protein (MUP), a protein which is very similar to alpha 2u-globulin, but this protein does not render the mouse sensitive to a similar renal toxicity. Therefore, the purpose of the present study was to determine the biochemical basis for mouse resistance to hyaline droplet nephropathy. Male Fischer 344 rats and B6C3F1 mice excreted 12.24 +/- 0.60 and 14.88 +/- 0.99 mg of alpha 2u-globulin and MUP daily, indicating that quantitative differences in protein excretion were not involved in the species specificity of the nephropathy. With d-limonene as a model hyaline droplet inducing agent, both rat and mouse liver microsomes oxidized the terpene to its 1,2-epoxide (the metabolite that binds reversibly to alpha 2u-globulin in vivo), demonstrating that metabolic differences do not determine the mouse resistance to this lesion. In spite of the formation of the epoxide intermediate, no binding of [14C]d-limonene equivalents to mouse kidney proteins was observed. In contrast, about 40% of the d-limonene equivalents in male rat kidney was reversibly bound to renal proteins. The renal reabsorption of alpha 2u-globulin and MUP was markedly different, as rats reabsorbed about 60% of the total filtered load of alpha 2u-globulin, but MUP was not reabsorbed by the mouse kidney. Given the absence of MUP in mouse kidney, in vitro equilibrium saturation binding studies were also conducted to determine whether MUP could bind the epoxide metabolite. alpha 2u-Globulin bound [14C]d-limonene-1,2-oxide with an apparent Kd of 4 x 10(-7) M. However, under identical experimental conditions, MUP failed to bind the epoxide. These data indicate that two major biochemical differences between alpha 2u-globulin and MUP contribute to mouse resistance to hyaline droplet nephropathy. Under both in vivo and in vitro conditions, MUP does not bind d-limonene-1,2-oxide, the rate-limiting step in the development of the nephropathy. However, even if MUP did bind the epoxide, the fact that it is not reabsorbed into the mouse kidney precludes its involvement in a syndrome involving renal protein overload. Finally, the absence of an interaction between d-limonene, a model hyaline droplet inducer, and the protein most similar to alpha 2u-globulin suggests that no other protein in the alpha 2u-globulin superfamily is likely to cause hyaline droplet nephropathy in other species.
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Affiliation(s)
- L D Lehman-McKeeman
- Human & Environmental Safety Division, Miami Valley Laboratories, Procter & Gamble Company, Cincinnati, Ohio 45239
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