This study will examine the interaction of environmental pollutants, primarily pro-estrogenic/estrogenic pesticides and structurally related compounds (e.g., methoxychlor and chlorotrianisene) with several mammalian enzyme systems and determine the molecular mechanisms of how such interactions could produce subtle or overt toxicities. Methoxychlor (M), a pesticide with pro-estrogenic activity, contains approx. 50 contaminants, among these chlorotrianisene (TACE), a triphenylethylene derivative that exhibits estrogenic/anti-estrogenic characteristics. Tamoxifen, a TACE analog, with anti-breast cancer therapeutic activity, will serve as a model for triphenylethylene compounds. In rodent and human, M and TACE are demethylated by hepatic cytochrome P450s (CYP) into estrogenic products and M & TACE are metabolically activated, forming reactive intermediates (RI) that bind covalently to hepatic proteins. The potency of the estrogenic metabolites of M and TACE will be determined with respect to binding and activation of the two isoforms of estrogen receptor (ER-alpha and -beta). This may explain the dilemma that certain compounds are estrogenic in one tissue and anti-estrogenic or inactive in another tissue. The structures of the RI of M &TACE will be deduced from their glutathione or N-acetylcysteine adducts. The major M-binding protein in liver, protein disulfide isomerase (PDI) is a chaperone enzyme that catalyzes the proper folding of proteins. The covalent binding of M to PDI and treatment of rats with M appears to diminish hepatic PDI activity. Such decrease in PDI activity is of utmost importance, since malfolded proteins may elicit significant toxicity. The mechanisms of the effects of metabolic activation of methoxychlor, TACE and Tamoxifen on PDI activity in vitro and the effect of treatment with these compounds on PDI in vivo, will be explored. The mechanism by which M and TACE diminish hepatic steroidal 5-alpha-reductase, an enzyme converting testosterone into DHT (an active male hormone and important for reproduction in females), will be determined. Whether M-metabolites are anti-androgenic in vitro and in vivo will be explored. If affirmative, it would suggest that the mechanism of M-mediated lowering of 5-alpha-reductase is due to the anti-androgenic metabolites. The mechanism of hydroxylation of phenolic M-metabolites in particular and of phenols in general (forming catechols) by CYP3A4, the major human P450, will be investigated. CYP3A4 catalyzes the metabolism of the majority of drugs and is involved in drug-drug interaction. Understanding the mechanism of 3A4 activity would be useful in predicting drug interactions and drug:drug-metabolite interactions.

Agency
National Institute of Health (NIH)
Institute
National Institute of Environmental Health Sciences (NIEHS)
Type
Research Project (R01)
Project #
5R01ES000834-28
Application #
6518019
Study Section
Alcohol and Toxicology Subcommittee 4 (ALTX)
Program Officer
Heindel, Jerrold
Project Start
1978-07-01
Project End
2004-06-30
Budget Start
2002-07-01
Budget End
2003-06-30
Support Year
28
Fiscal Year
2002
Total Cost
$353,457
Indirect Cost
Name
University of Massachusetts Medical School Worcester
Department
Pharmacology
Type
Schools of Medicine
DUNS #
660735098
City
Worcester
State
MA
Country
United States
Zip Code
01655
Gennings, Chris; Carrico, Caroline; Factor-Litvak, Pam et al. (2013) A cohort study evaluation of maternal PCB exposure related to time to pregnancy in daughters. Environ Health 12:66
Parte, Priyanka; Kupfer, David (2005) Oxidation of tamoxifen by human flavin-containing monooxygenase (FMO) 1 and FMO3 to tamoxifen-N-oxide and its novel reduction back to tamoxifen by human cytochromes P450 and hemoglobin. Drug Metab Dispos 33:1446-52
Hu, Y; Krausz, K; Gelboin, H V et al. (2004) CYP2C subfamily, primarily CYP2C9, catalyses the enantioselective demethylation of the endocrine disruptor pesticide methoxychlor in human liver microsomes: use of inhibitory monoclonal antibodies in P450 identification. Xenobiotica 34:117-32
Hazai, Eszter; Gagne, Peter V; Kupfer, David (2004) Glucuronidation of the oxidative cytochrome P450-mediated phenolic metabolites of the endocrine disruptor pesticide: methoxychlor by human hepatic UDP-glucuronosyl transferases. Drug Metab Dispos 32:742-51
Hu, Y; Dehal, S S; Hynd, G et al. (2003) CYP2D6-mediated catalysis of tamoxifen aromatic hydroxylation with an NIH shift: similar hydroxylation mechanism in chicken, rat and human liver microsomes. Xenobiotica 33:141-51
Hu, Yiding; Kupfer, David (2002) Metabolism of the endocrine disruptor pesticide-methoxychlor by human P450s: pathways involving a novel catechol metabolite. Drug Metab Dispos 30:1035-42
Hu, Yiding; Kupfer, David (2002) Enantioselective metabolism of the endocrine disruptor pesticide methoxychlor by human cytochromes P450 (P450s): major differences in selective enantiomer formation by various P450 isoforms. Drug Metab Dispos 30:1329-36
Blizard, D; Sueyoshi, T; Negishi, M et al. (2001) Mechanism of induction of cytochrome p450 enzymes by the proestrogenic endocrine disruptor pesticide-methoxychlor: interactions of methoxychlor metabolites with the constitutive androstane receptor system. Drug Metab Dispos 29:781-5
Williams, D E; Katchamar, S; Larsen-Su, S A et al. (2001) Concurrent flavin-containing monooxygenase down regulation and cytochrome P450 induction by dietary indoles in the rat: implication for drug-drug interactions. Adv Exp Med Biol 500:635-8
Katchamart, S; Stresser, D M; Dehal, S S et al. (2000) Concurrent flavin-containing monooxygenase down-regulation and cytochrome P-450 induction by dietary indoles in rat: implications for drug-drug interaction. Drug Metab Dispos 28:930-6

Showing the most recent 10 out of 52 publications