title: Medroxyprogesterone abrogates the inhibitory effects of estradiol on vascular smooth muscle cells by preventing estradiol metabolism.
abstract: Sequential conversion of estradiol (E) to 2/4-hydroxyestradiols and 2-/4-methoxyestradiols (MEs) by CYP450s and catechol-O-methyltransferase, respectively, contributes to the inhibitory effects of E on smooth muscle cells (SMCs) via estrogen receptor-independent mechanisms. Because medroxyprogesterone (MPA) is a substrate for CYP450s, we hypothesized that MPA may abrogate the inhibitory effects of E by competing for CYP450s and inhibiting the formation of 2/4-hydroxyestradiols and MEs. To test this hypothesis, we investigated the effects of E on SMC number, DNA and collagen synthesis, and migration in the presence and absence of MPA. The inhibitory effects of E on cell number, DNA synthesis, collagen synthesis, and SMC migration were significantly abrogated by MPA. For example, E (0.1micromol/L) reduced cell number to 51+/-3.6% of control, and this inhibitory effect was attenuated to 87.5+/-2.9% by MPA (10 nmol/L). Treatment with MPA alone did not alter any SMC parameters, and the abrogatory effects of MPA were not blocked by RU486 (progesterone-receptor antagonist), nor did treatment of SMCs with MPA influence the expression of estrogen receptor-alpha or estrogen receptor-beta. In SMCs and microsomal preparations, MPA inhibited the sequential conversion of E to 2-2/4-hydroxyestradiol and 2-ME. Moreover, as compared with microsomes treated with E alone, 2-ME formation was inhibited when SMCs were incubated with microsomal extracts incubated with E plus MPA. Our findings suggest that the inhibitory actions of MPA on the metabolism of E to 2/4-hydroxyestradiols and MEs may negate the cardiovascular protective actions of estradiol in postmenopausal women receiving estradiol therapy combined with administration of MPA.
authors.affiliation: Department of Obstetrics and Gynecology, Clinic for Reproductive Endocrinology (NORD-1, D217), University Hospital Zurich, Zurich, 8091-CH, Switzerland. Raghvendra.dubey@usz.ch
authors.forename: Raghvendra K
authors.initials: RK
authors.lastname: Dubey
authors.forename: Edwin K
authors.initials: EK
authors.lastname: Jackson
authors.forename: Delbert G
authors.initials: DG
authors.lastname: Gillespie
authors.forename: Lefteris C
authors.initials: LC
authors.lastname: Zacharia
authors.forename: Dorothea
authors.initials: D
authors.lastname: Wunder
authors.forename: Bruno
authors.initials: B
authors.lastname: Imthurn
authors.forename: Marinella
authors.initials: M
authors.lastname: Rosselli
mesh_terms: D001011:Aorta / Q000166:cytology; D002465:Cell Movement / Q000187:drug effects; D002478:Cells, Cultured; D003280:Contraceptives, Oral, Synthetic / Q000494:pharmacology*; D003577:Cytochrome P-450 Enzyme System / Q000378:metabolism; D004347:Drug Interactions; D004958:Estradiol / Q000031:analogs & derivatives / Q000378:metabolism / Q000494:pharmacology*; D047628:Estrogen Receptor alpha / Q000378:metabolism; D047629:Estrogen Receptor beta / Q000378:metabolism; D004967:Estrogens / Q000493:pharmacokinetics*; D005260:Female; D006801:Humans; D008525:Medroxyprogesterone / Q000494:pharmacology*; D008861:Microsomes / Q000187:drug effects / Q000378:metabolism; D009131:Muscle, Smooth, Vascular / Q000166:cytology*; D032389:Myocytes, Smooth Muscle / Q000166:cytology / Q000187:drug effects* / Q000378:metabolism; D010982:Platelet-Derived Growth Factor / Q000494:pharmacology
chemical_list: D003280:Contraceptives, Oral, Synthetic; D047628:Estrogen Receptor alpha; D047629:Estrogen Receptor beta; D004967:Estrogens; D010982:Platelet-Derived Growth Factor; D004958:Estradiol; D003577:Cytochrome P-450 Enzyme System; C001390:2-hydroxyestradiol; D008525:Medroxyprogesterone