Estrogen receptor-mediated enhancement of venous relaxation in female rat: implications in sex-related differences in varicose veins.
ABSTRACT A greater incidence of varicose veins has been reported in premenopausal women than in men. We hypothesized that the sex differences in venous function reflect reduced constriction and enhanced venous dilation in women due to direct venous relaxation effects of estrogen on specific estrogen receptors (ER).
Circular segments of inferior vena cava (IVC) from male and female Sprague-Dawley rats were suspended between two wires, and isometric contraction (in mg/mg tissue) to phenylephrine, angiotensin II (AngII), and 96 mM KCl was measured. To investigate sex differences in venous smooth muscle, Ca(2+) release from the intracellular stores, and Ca(2+) entry from the extracellular space, the transient phenylephrine contraction in 0 Ca(2+) Krebs was measured. Extracellular CaCl(2) (0.1, 0.3, 0.6, 1, 2.5 mM) was added, and the [Ca(2+)](e)-dependent contraction was measured. To investigate sex differences in venous endothelial function, acetylcholine-induced relaxation was measured. To test the role of specific ERs, the amount of venous tissue ERs was measured using Western blots, and the venous relaxation in response to 17beta-estradiol (E2, activator of most ERs), 4,4,'4''-(4-propyl-[1H]-pyrazole-1,3,5-triyl)-tris-phenol (PPT; ERalpha agonist), 2,3-bis(4-hydroxyphenyl)-propionitrile (DPN; ERbeta agonist), and ICI 182,780 (ERalpha/ERbeta antagonist, and G protein-coupled receptor 30 [GPR30] agonist) was measured in IVC segments nontreated or treated with the nitric oxide synthase (NOS) inhibitor N(omega)-nitro-L-arginine methyl ester (L-NAME).
Phenylephrine caused concentration-dependent contraction that was less in female (max 104.2 +/- 16.2) than male IVC (172.4 +/- 20.4). AngII (10(-6))-induced contraction was also less in female (81.0 +/- 11.1) than male IVC (122.5 +/- 15.0). Phenylephrine contraction in 0 Ca(2+) Krebs was insignificantly less in female (4.8 +/- 1.8) than male IVC (7.2 +/- 1.7), suggesting little difference in the intracellular Ca(2+) release mechanism. In contrast, the [Ca(2+)](e)-dependent contraction was significantly reduced in female than male IVC. Also, contraction to membrane depolarization by 96 mM KCl, which stimulates Ca(2+) influx, was less in female (129.7 +/- 16.7) than male IVC (319.7 +/- 30.4), supporting sex differences in Ca(2+) entry. Acetylcholine relaxation was greater in female (max 80.6% +/- 4.1%) than male IVC (max 48.0% +/- 6.1%), suggesting sex differences in the endothelium-dependent relaxation pathway. Western blots revealed greater amounts of ERalpha, ERbeta, and GPR30 in female than male IVC. ER agonists caused concentration-dependent relaxation of phenylephrine contraction in female IVC. E2-induced relaxation (max 76.5% +/- 3.4%) was more than DPN (74.8% +/- 9.1%), PPT (71.4% +/- 12.5%), and ICI 182,780 (67.4% +/- 7.8%), and was similar in L-NAME-treated and nontreated IVC.
The reduced alpha-adrenergic, AngII, depolarization-induced, and [Ca(2+)](e)-dependent venous contraction in female rats is consistent with sex differences in the Ca(2+) entry mechanisms, possibly due to enhanced endothelium-dependent vasodilation and increased ER expression/activity in female rats. E2/ER-mediated venous relaxation in female rats is not prevented by NOS blockade, suggesting activation of an NO-independent relaxation pathway. The decreased venous contraction and enhanced E2/ER-mediated venous relaxation would lead to more distensible veins in female rats.
Article: Estrogen-induced activation of Erk-1 and Erk-2 requires the G protein-coupled receptor homolog, GPR30, and occurs via trans-activation of the epidermal growth factor receptor through release of HB-EGF.[show abstract] [hide abstract]
ABSTRACT: Estrogen rapidly activates the mitogen-activated protein kinases, Erk-1 and Erk-2, via an as yet unknown mechanism. Here, evidence is provided that estrogen-induced Erk-1/-2 activation occurs independently of known estrogen receptors, but requires the expression of the G protein-coupled receptor homolog, GPR30. We show that 17beta-estradiol activates Erk-1/-2 not only in MCF-7 cells, which express both estrogen receptor alpha (ER alpha) and ER beta, but also in SKBR3 breast cancer cells, which fail to express either receptor. Immunoblot analysis using GPR30 peptide antibodies showed that this estrogen response was associated with the presence of GPR30 protein in these cells. MDA-MB-231 breast cancer cells (ER alpha-, ER beta+) are GPR30 deficient and insensitive to Erk-1/-2 activation by 17beta-estradiol. Transfection of MDA-MB-231 cells with a GPR30 complementary DNA resulted in overexpression of GPR30 protein and conversion to an estrogen-responsive phenotype. In addition, GPR30-dependent Erk-1/-2 activation was triggered by ER antagonists, including ICI 182,780, yet not by 17alpha-estradiol or progesterone. Consistent with acting through a G protein-coupled receptor, estradiol signaling to Erk-1/-2 occurred via a Gbetagamma-dependent, pertussis toxin-sensitive pathway that required Src-related tyrosine kinase activity and tyrosine phosphorylation of tyrosine 317 of the Shc adapter protein. Reinforcing this idea, estradiol signaling to Erk-1/-2 was dependent upon trans-activation of the epidermal growth factor (EGF) receptor via release of heparan-bound EGF (HB-EGF). Estradiol signaling to Erk-1/-2 could be blocked by: 1) inhibiting EGF-receptor tyrosine kinase activity, 2) neutralizing HB-EGF with antibodies, or 3) down-modulating HB-EGF from the cell surface with the diphtheria toxin mutant, CRM-197. Our data imply that ER-negative breast tumors that continue to express GPR30 may use estrogen to drive growth factor-dependent cellular responses.Molecular Endocrinology 11/2000; 14(10):1649-60. · 4.54 Impact Factor
Article: Active immunization against endothelin-1 is associated with a decrease in plasma endothelin-1 and changes in vascular reactivity.[show abstract] [hide abstract]
ABSTRACT: Exogenous endothelin-1 (ET-1) or high concentrations of the peptide in pathological conditions have marked effects on vascular reactivity. In order to evaluate the role of endogenous ET-1 we investigated responsiveness of conduit (aorta) and of resistant-like (tail artery) vessels in ET-1-deficient rats. Elimination of circulating ET-1 was achieved by active immunization of Wistar rats with a peptide-haemocyanin conjugate (anti-ET-1 group), leading to a marked reduction in plasma level of the peptide in comparison with that of vehicle-treated animals (control group): 1.9 fmol/ml vs 4.9 fmol/ml, respectively. The immunization was associated with a slight elevation of mean arterial pressure, whereas heart rate remained unchanged. In the anti-ET-1 group rings of isolated aorta displayed reduced sensitivity to ET-1: EC50 = 6.57 nM vs 2.95 nM in the control group. Tail arteries of the ET-1-deficient rats showed diminished responses to ET-1, the maximal rise in perfusion pressure: +5.2 mmHg vs +13.6 mmHg in the control group. After immunization, rings of isolated aorta displayed no changes in endothelium-dependent relaxation to acetylcholine (Ach, EC50 = 0.20 microM vs 0.35 microM in the control group), whereas experiments on perfused tail artery showed a twofold reduction in Ach effects. Thus, depletion of circulating ET-1 induces slight changes in haemodynamics associated with altered vessel responsiveness to vasoactive substances.Journal of Cardiovascular Pharmacology 12/2000; 36(5 Suppl 1):S132-4. · 2.29 Impact Factor
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ABSTRACT: Blood vessels express estrogen receptors, but their role in cardiovascular physiology is not well understood. We show that vascular smooth muscle cells and blood vessels from estrogen receptor beta (ERbeta)-deficient mice exhibit multiple functional abnormalities. In wild-type mouse blood vessels, estrogen attenuates vasoconstriction by an ERbeta-mediated increase in inducible nitric oxide synthase expression. In contrast, estrogen augments vasoconstriction in blood vessels from ERbeta-deficient mice. Vascular smooth muscle cells isolated from ERbeta-deficient mice show multiple abnormalities of ion channel function. Furthermore, ERbeta-deficient mice develop sustained systolic and diastolic hypertension as they age. These data support an essential role for ERbeta in the regulation of vascular function and blood pressure.Science 02/2002; 295(5554):505-8. · 31.20 Impact Factor