1
|
Turnbull D, Rodricks JV. Assessment of Possible Carcinogenic Risk to Humans Resulting from Exposure to Di(2-ethylhexyl)phthalate (DEHP). ACTA ACUST UNITED AC 2016. [DOI: 10.3109/10915818509014509] [Citation(s) in RCA: 28] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022]
Abstract
The purpose of this work was to estimate the degree of risk that might be associated with human exposure to low levels of the plasticizer di(2-ethylhexyl)phthalate (DEHP). DEHP is a common component, sometimes at high concentrations, of polyvinyl chloride (PVC) plastics and was recently reported by the National Toxicology Program (NTP) to be carcinogenic in rats and mice, inducing hepatocellular tumors in both species. This work was also designed to illustrate an approach to risk assessment that attempts to incorporate all available biological data. Based on the dose-response data generated by the NTP bioassays, we have performed extrapolations of risk to low dose levels using several procedures, including some that incorporate inferences from the available data that shed light on the likely relationship between dose level and risk at low dose levels. In drawing these inferences, consideration was given to such factors as genotoxicity, metabolism and pharmacokinetics, and physiological and biochemical effects of DEHP that might reveal its mechanism of action. The relative merits of each of the various risk estimates are described, based on current understanding of DEHP's mode of biological action. It is concluded that DEHP's mechanism of carcinogenicity in rodents most likely involves its ability to induce peroxisome proliferation and related enzymatic changes, although other mechanisms cannot be excluded. If humans and rodents are assumed to be at the same risk at the same daily dose level of DEHP, application of the various low dose extrapolation models leads to the prediction that the daily dose resulting in a lifetime risk of no more than 1 in 1 million would be between 1.5 and 791 mg/kg per day, with the most likely figure being 116 mg/kg per day. If the carcinogenicity of DEHP is dependent upon its pattern of metabolism, however, it would be inappropriate to extrapolate from rodents to man without qualification because of the major quantitative differences in metabolism in rats, mice, and primates, including man. One of the major differences in metabolism of DEHP between rats and mice and primates is in production of a metabolite whose level may be an indicator of the level of peroxisomal activity and, hence, if the peroxisome proliferation theory of DEHP carcinogenicity is correct, of carcinogenic risk. However, the substantial doubt that exists regarding the applicability of rodent carcinogenicity data to humans must be expressed in qualitative terms.
Collapse
Affiliation(s)
- D. Turnbull
- Duncan Turnbull Environ Corporation 1000 Potomac Street, N.W. Washington, DC 20007
| | - J. V. Rodricks
- Duncan Turnbull Environ Corporation 1000 Potomac Street, N.W. Washington, DC 20007
| |
Collapse
|
2
|
|
3
|
Code JE, Perko KE, Yourtee DM, Holder AJ, Kostoryz E. A semi-empirical computational model for the inhibition of porcine cholesterol esterase. JOURNAL OF BIOMATERIALS SCIENCE-POLYMER EDITION 2007; 18:1457-74. [PMID: 17961327 DOI: 10.1163/156856207782246849] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
Cholesterol esterase significantly contributes to cell membrane structure. It also facilitates transfer of cholesterol and phospholipids across membranes. Inhibition of this enzyme by a number of xenobiotics has been reported. This research sought to confirm if a widely used methacrylate monomer, bisphenol A dimethacrylate, inhibits porcine cholesterol esterase since this and other methacrylates are known to leach from various biomaterial preparations. A quantum mechanically developed computational chemistry model is presented. Specific chemical information linking potential mechanisms of cholesterol esterase inhibition to chemical structure is shown. Model chemical descriptors identified the importance of maximum oxygen valency and molecular shape/size to cholesterol esterase inhibition. A porcine cholesterol esterase inhibition mechanism is inherent in bisphenol A dimethacrylate which mimics chemical properties of reported cholesterol esterase inhibitors. This predictive semiempirical quantum mechanical model can be used to design new cholesterol esterase non-inhibitors for biocompatible biomaterials used in an aqueous environment.
Collapse
Affiliation(s)
- J E Code
- School of Pharmacy, University of Missouri-Kansas City, Kansas City, MO, USA.
| | | | | | | | | |
Collapse
|
4
|
Smith RE, Burmaster S, Glaros AG, Eick JD, Walde P, Kostoryz EL, Yourtee DM. Aromatic dental monomers affect the activity of cholesterol esterase. BIOCHIMICA ET BIOPHYSICA ACTA 2001; 1550:100-6. [PMID: 11738092 DOI: 10.1016/s0167-4838(01)00275-8] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
Abstract
The dental restorative monomer, BISGMA (2,2-bis[4-(2-hydroxy-3-methacryloxypropoxy)phenyl]propane), and bisphenol A diglycidyl ether (BADGE) increase the velocity of the reaction catalyzed by pancreatic cholesterol esterase (CEase, bovine). The metabolite of these monomers, bisphenol A bis(2,3-dihydroxypropyl) ether, and a common plasticizer, di-2-ethylhexyl phthalate (DEHP), also increase the velocity of CEase-catalyzed ester hydrolysis. BISGMA at concentrations of 1.5-8.0 microM increases the velocity to 126-169% of its value in the absence of BISGMA. Increasing BISGMA above 8 microM caused no further increase in velocity. BADGE at 7-25 microM increases the velocity to 112-205% of its value without BADGE. The metabolite of BISGMA and BADGE at concentrations of 2.0-7.1 microM increases the velocity to 103-113% of its value without metabolite. DEHP at concentrations of 0.52-4.3 microM increases the velocity to 108-187% of its value without DEHP. On the other hand, bisphenol A dimethacrylate is a competitive inhibitor of CEase, with a K(i) of 3.1 microM.
Collapse
Affiliation(s)
- R E Smith
- School of Pharmacy, University of Missouri-Kansas City, Kansas City, MO 64108, USA
| | | | | | | | | | | | | |
Collapse
|
5
|
Willhite CC. Weight-of-evidence versus strength-of-evidence in toxicologic hazard identification: Di(2-ethylhexyl)phthalate (DEHP). Toxicology 2001; 160:219-26. [PMID: 11246142 DOI: 10.1016/s0300-483x(00)00451-0] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
Abstract
Toxicokinetic and mode of action data for DEHP reduce the concern for its potential carcinogenic hazard to human health. Chronic, high dose ingestion of DEHP and related peroxisome proliferators (PP) by mice and rats precipitate the following: activation of peroxisome proliferator activated receptor (PPARalpha) and its binding to peroxisome proliferator response elements (PPREs) within promoters of PP-responsive genes, peroxisome proliferation, increased microsomal fatty acid oxidation, increased hepatic hydrogen peroxide, hepatomegaly, hyperplasia and subsequent neoplasia. Neither peroxisome proliferation nor increased liver cancer occur in patients treated with pharmacologic doses of PP. Species differences in endogenous PPARalpha expression and differential activity of the peroxisome proliferator response element (PPRE) contribute to the failure of humans to respond in a manner qualitatively similar to that of rats or mice. Where it can be demonstrated that a mechanism for rodent tumor formation has no relevance for humans, then a substance which elicits a carcinogenic response in the test species via that mechanism should not be classified as anything other than an animal carcinogen. Systemic noncarcinogenic endpoints are available for definition of a DEHP reference dose. Considerable difficulty is encountered in the revision of promulgated regulations and in public risk communication when a material is no longer considered a carcinogenic hazard to humans.
Collapse
Affiliation(s)
- C C Willhite
- Department of Toxic Substances Control, State of California, 700 Heinz Street, Suite 200, Berkeley, CA 94710, USA
| |
Collapse
|
6
|
Malcolm AR, Mills LJ. Inhibition of gap-junctional intercellular communication between Chinese hamster lung fibroblasts by di(2-ethylhexyl) phthalate (DEHP) and trisodium nitrilotriacetate monohydrate (NTA). Cell Biol Toxicol 1989; 5:145-53. [PMID: 2766028 DOI: 10.1007/bf00122649] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/02/2023]
Abstract
Di(2-ethylhexyl)phthalate and trisodium nitrilotriacetate monohydrate, two apparently nongenotoxic carcinogens, were tested for effects on gap-junctional communication between Chinese hamster V79 lung fibroblasts. Both compounds inhibited gap-junctional communication in a concentration-dependent manner. The inhibiting effects of these chemicals on gap-junctional communication in vitro correlate with their tumor-promoting activity. Such results further support the hypothesis that inhibition of gap-junctional communication is an in vitro biomarker for some tumor-promoting chemicals.
Collapse
Affiliation(s)
- A R Malcolm
- Environmental Research Laboratory, U.S. EPA, Narragansett, Rhode Island
| | | |
Collapse
|
7
|
Parmar D, Srivastava SP, Seth PK. Studies on gamma-glutamyl transpeptidase (GGT) after di(2-ethylhexyl) phthalate (DEHP) exposure. J Appl Toxicol 1987; 7:249-51. [PMID: 2887608 DOI: 10.1002/jat.2550070405] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/03/2023]
Abstract
Administration of Di(2-ethylhexyl)phthalate (DEHP) at doses of 250, 500, 1000 and 2000 mg/kg to adult rats was found to significantly increase the activity of gamma-glutamyl transpeptidase (GGT) in liver and serum in a dose-dependent manner. The data indicate that DEHP can be hepatotoxic since an increase in serum GGT levels are indicative of hepatobiliary dysfunction and liver malignancy. An assay of GGT in serum of the individuals exposed to DEHP could be helpful in early detection of liver disorders due to this widely used plasticizer.
Collapse
|
8
|
Shukla RR, Albro PW. In-vitro modulation of protein kinase C activity by environmental chemical pollutants. Biochem Biophys Res Commun 1987; 142:567-72. [PMID: 3028416 DOI: 10.1016/0006-291x(87)90311-1] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/03/2023]
Abstract
A number of environmental chemical pollutants have been reported to cause tumors or help in the propagation of tumors in experimental animals. The in-vitro effects of a few chemical contaminants were studied on the histone phosphorylation and 3H Phorbol dibutyrate (PdBu) binding of partially purified Ca2+/phospholipid dependent protein kinase c (PKC) from the brains of Fischer F344 and B6C3F1 mice. The enzyme was prepared by a modified method which gave approximately 75-fold purification. A differential effect of various compounds was observed on the phosphorylation activity and PdBu binding of PKC from rats and mice. The reported tumor promoting ability and effect on protein kinase C activity appeared to be related in the case of the rat enzyme, although causality cannot be inferred.
Collapse
|
9
|
Hawkins JM, Jones WE, Bonner FW, Gibson GG. The effect of peroxisome proliferators on microsomal, peroxisomal, and mitochondrial enzyme activities in the liver and kidney. Drug Metab Rev 1987; 18:441-515. [PMID: 3286171 DOI: 10.3109/03602538708994130] [Citation(s) in RCA: 185] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/05/2023]
Affiliation(s)
- J M Hawkins
- Biochemistry Department, University of Surrey, England, U.K
| | | | | | | |
Collapse
|
10
|
Komitowski D, Schmezer P, Schmitt B, Muto S. Image analysis of hepatocyte nuclei in assessing di(2-ethylhexyl)phthalate effects eluding detection by conventional microscopy. Toxicology 1986; 41:11-9. [PMID: 3750335 DOI: 10.1016/0300-483x(86)90100-9] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/07/2023]
Abstract
The effect of di(2-ethylhexyl)phthalate (DEHP) administered in single intraperitoneal doses of 30, 300 and 3000 mg/kg in Syrian golden hamsters was studied by means of routine pathologic investigations, electron microscopy and image analysis. The morphological evaluations did not show apparent differences between the control and treated animals. Such differences, however, were recognized by using image analysis. They concerned morphology of the hepatocyte nuclei and were defined by quantitative parameters reflecting geometrical, optical and structural properties. Of importance for differentiating dose/effect relationships were features of chromatin structure. In order to describe those features we developed special algorithms capable of identifying and characterizing regions of condensed chromatin as subimages. These were distinguished by their size, shape and optical density and showed typical distributions within the nucleus. As our results demonstrate, image analysis methods permit detection of DEHP related pathology in animals which, as far as is evident from routine morphologic evaluations, belong to the no-effect experimental group.
Collapse
|
11
|
Teirlynck OA, Belpaire F. Disposition of orally administered di-(2-ethylhexyl) phthalate and mono-(2-ethylhexyl) phthalate in the rat. Arch Toxicol 1985; 57:226-30. [PMID: 4091646 DOI: 10.1007/bf00324782] [Citation(s) in RCA: 28] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023]
Abstract
The disposition of di-(2-ethylhexyl) phthalate (DEHP) and mono-(2-ethylhexyl) phthalate (MEHP) was studied in the rat. Three hours after a single oral dose of DEHP (2.8 g/kg), plasma concentrations of 8.8 +/- 1.7 micrograms/ml DEHP and 63.2 +/- 8.7 micrograms/ml MEHP were reached. MEHP levels declined with a half-life of 5.2 +/- 0.5 h. The ratio of the area under the plasma concentration-time curve of MEHP to that of DEHP was 16.1 +/- 6.1. When 14C-DEHP was administered, 19.3 +/- 3.3% of the radioactivity was excreted in the urine within 72 h, the rest being excreted in the faeces. The urinary excretion rate of total radioactivity declined with a half-life of 7.9 +/- 0.5 h. Single administration of MEHP (0.4 g/kg) resulted in plasma concentrations of 84.1 +/- 14.9 micrograms/ml 3 h after dosing; the half-life of MEHP was 5.5 +/- 1.1 h. Multiple dosing with DEHP (2.8 g/kg/day) for 7 consecutive days produced no accumulation of DEHP or MEHP in plasma.
Collapse
|
12
|
Teirlynck OA, Rosseel MT. Determination of di- and mono(2-ethylhexyl) phthalate in plasma by gas chromatography. JOURNAL OF CHROMATOGRAPHY 1985; 342:399-405. [PMID: 4055963 DOI: 10.1016/s0378-4347(00)84534-x] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/08/2023]
|
13
|
Lake BG, Rijcken WR, Gray TJ, Foster JR, Gangolli SD. Comparative studies of the hepatic effects of di- and mono-n-octyl phthalates, di-(2-ethylhexyl) phthalate and clofibrate in the rat. ACTA PHARMACOLOGICA ET TOXICOLOGICA 1984; 54:167-76. [PMID: 6720315 DOI: 10.1111/j.1600-0773.1984.tb01913.x] [Citation(s) in RCA: 50] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/21/2023]
Abstract
The oral administration of di-n-octyl phthalate (DNOP), mono-n-octyl phthalate (MNOP), di-(2-ethylhexyl) phthalate (DEHP) and clofibrate to young male Sprague-Dawley rats for 14 days resulted in liver enlargement. Morphological examination of liver sections from DEHP and clofibrate treated rats, but not from either DNOP or MNOP treated animals, revealed increased numbers of peroxisomes (microbodies). Both DEHP and clofibrate treatment markedly stimulated the activities of certain peroxisomal marker enzymes whereas DNOP and MNOP produced only marginal effects. Similarly both DEHP and clofibrate, but not DNOP or MNOP, increased microsomal cytochrome P-450 content and markedly stimulated microsomal lauric acid hydroxylation activity. The results thus demonstrate that whilst the branched chain phthalate ester DEHP induced peroxisomal proliferation, the straight chain analogue DNOP and its metabolite MNOP were essentially inactive. In addition, DEHP treatment appeared to induce similar form(s) of cytochrome P-450 in rat liver to those previously described after clofibrate administration.
Collapse
|
14
|
Kornbrust DJ, Barfknecht TR, Ingram P, Shelburne JD. Effect of di(2-ethylhexyl) phthalate on DNA repair and lipid peroxidation in rat hepatocytes and on metabolic cooperation in Chinese hamster V-79 cells. JOURNAL OF TOXICOLOGY AND ENVIRONMENTAL HEALTH 1984; 13:99-116. [PMID: 6716514 DOI: 10.1080/15287398409530484] [Citation(s) in RCA: 33] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/21/2023]
Abstract
Experiments were conducted to test the hypothesis that the hepatocarcinogenicity of di(2-ethylhexyl) phthalate (DEHP) is due to its ability to produce DNA damage, either directly or as a result of the proliferation of peroxisomes and accompanying increased production of H2O2 and other DNA--damaging oxygen radicals induced by sustained exposure to the plasticizer. DNA repair, as assessed by the autoradiographic measurement of unscheduled DNA synthesis (UDS), was not observed in primary rat hepatocytes exposed in vitro to 10(-5)-10(-2) M DEHP or in vivo by a single gavage dose of 5 g DEHP/kg body weight administered 2, 15, or 24 h prior to the isolation of hepatocytes. Thus, DEHP does not appear to directly produce repairable DNA damage in rat hepatocytes. Sustained feeding of DEHP at a dietary concentration of 2% led to a marked proliferation of peroxisomes in the liver after 4 wk. Additional administration of a single gavage dose of 5 g DEHP/kg body weight to animals fed the 2% diet for 4 or 8 wk, as well as to 4-wk-fed animals that were also pretreated with 3-amino-1,2,4-triazole to inhibit endogenous catalase activity, did not induce any detectable DNA repair in hepatocytes isolated 15 h following the single gavage dose of DEHP. Lipid peroxidation measured in the 9000 X g supernatant of livers from animals treated with a single dose of 5 g DEHP/kg body weight or the 2% DEHP diet for 6 wk plus a single dose of 5 g/kg body weight did not differ from controls. These findings suggest that DEHP does not elicit DNA damage or lipid peroxidation in liver consequent to the proliferation of peroxisomes resulting from prolonged administration. In addition, at noncytotoxic concentrations DEHP failed to produce a positive response in the Chinese hamster V-79 metabolic cooperation assay for tumor promoters.
Collapse
|
15
|
Thomas JA, Thomas MJ. Biological effects of di-(2-ethylhexyl) phthalate and other phthalic acid esters. Crit Rev Toxicol 1984; 13:283-317. [PMID: 6386344 DOI: 10.3109/10408448409023761] [Citation(s) in RCA: 153] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/19/2023]
Abstract
Esters of o-phthalic acid are widely distributed in the ecosystem. The phthalate acid esters (PAE's) are used as plasticizers in the manufacture of polyvinylchlorides. They are also used as solvents in certain industrial processes and as vehicles for pesticides. The PAE's are used in enormous quantities for a variety of industrial uses in the formulation of plastics. While there are a number of important PAE's, di-ethylhexyl phthalate has perhaps been used the most extensively in the formulation of plastics used in medical devices and blood bag assemblies. The metabolism, biodistribution and excretion varies to some extent among the various PAE's. There are species differences with respect to the metabolism of the PAE's. The route of administration, and the level and length of exposure, are known to affect the toxicological profile of the various PAE's. There is little evidence of bioaccumulation of the various PAE's, and only at very large doses have there been reports of overt toxicity. Evidence for the carcinogenicity of certain PAE's apparently is related to prolonged exposure to high levels.
Collapse
|
16
|
Kluwe WM, Haseman JK, Huff JE. The carcinogenicity of di(2-ethylhexyl) phthalate (DEHP) in perspective. JOURNAL OF TOXICOLOGY AND ENVIRONMENTAL HEALTH 1983; 12:159-69. [PMID: 6355494 DOI: 10.1080/15287398309530414] [Citation(s) in RCA: 29] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/19/2023]
Abstract
The commonly used plasticizer di(2-ethylhexyl) phthalate (DEHP) was recently tested for chronic toxic potential by incorporation into the diet of rats and mice for approximately 2 yr. Upon reviewing the test results, the sponsoring organization concluded that DEHP was carcinogenic to the rats and mice, as indicated by increased occurrences of liver tumors in the DEHP-exposed animals in comparison to controls. Another group has disagreed with this conclusion, however, citing perceived methodological deficiencies and improper interpretations in the study, and has also suggested that rodents may not be adequate models of human response to DEHP. This communication compares the conduct of the DEHP bioassay favorably with state-of-the-art procedures in animal carcinogenicity testing and documents approval of the study interpretations by several independent peer review groups. The carcinogenic potential of DEHP is placed in perspective by evaluating the evidence for DEHP-induced tumors in rodent species in light of dose response relationships, other biochemical and toxicological effects of DEHP, and its comparative metabolism and disposition in rodent and primate species. A composite analysis of the currently available information indicates that DEHP has been shown to be carcinogenic to rodents in a valid chronic test, indicating that it should be considered as a potential carcinogen in humans, as well. Further experimental inquiry will be required, however, to accurately assess the potential health risks posed to humans by exposure to small amounts of this plasticizer.
Collapse
|