Endothelium-independent effect of estrogen on Ca2+-activated K+ channels in human coronary artery smooth muscle cells (original) (raw)
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American journal of physiology. Heart and circulatory physiology, 2012
Androgens are reported to have both beneficial and detrimental effects on human cardiovascular health. The aim of this study was to characterize nongenomic signaling mechanisms in coronary artery smooth muscle (CASM) and define the ionic basis of testosterone (TES) action. TES-induced relaxation of endothelium-denuded porcine coronary arteries was nearly abolished by 20 nM iberiotoxin, a highly specific inhibitor of large-conductance, calcium-activated potassium (BK(Ca)) channels. Molecular patch-clamp studies confirmed that nanomolar concentrations of TES stimulated BK(Ca) channel activity by ∼100-fold and that inhibition of nitric oxide synthase (NOS) activity by N(G)-monomethyl-L-arginine nearly abolished this effect. Inhibition of nitric oxide (NO) synthesis or guanylyl cyclase activity also attenuated TES-induced coronary artery relaxation but did not alter relaxation due to 8-bromo-cGMP. Furthermore, we detected TES-stimulated NO production in porcine coronary arteries and in ...
AJP: Endocrinology and Metabolism, 2011
Estrogens can either relax or contract arteries via rapid, nongenomic mechanisms involving classic estrogen receptors (ER). In addition to ERα and ERβ, estrogen may also stimulate G protein-coupled estrogen receptor 1 (GPER) in nonvascular tissue; however, a potential role for GPER in coronary arteries is unclear. The purpose of this study was to determine how GPER activity influenced coronary artery reactivity. In vitro isometric force recordings were performed on endothelium-denuded porcine arteries. These studies were augmented by RT-PCR and single-cell patch-clamp experiments. RT-PCR and immunoblot studies confirmed expression of GPER mRNA and protein, respectively, in smooth muscle from either porcine or human coronary arteries. G-1, a selective GPER agonist, produced a concentration-dependent relaxation of endothelium-denuded porcine coronary arteries in vitro. This response was attenuated by G15, a GPER-selective antagonist, or by inhibiting large-conductance calcium-activated potassium (BK(Ca)) channels with iberiotoxin, but not by inhibiting NO signaling. Last, single-channel patch-clamp studies demonstrated that G-1 stimulates BK(Ca) channel activity in intact smooth muscle cells from either porcine or human coronary arteries but had no effect on channels isolated in excised membrane patches. In summary, GPER activation relaxes coronary artery smooth muscle by increasing potassium efflux via BK(Ca) channels and requires an intact cellular signaling mechanism. This novel action of estrogen-like compounds may help clarify some of the controversy surrounding the vascular effects of estrogens.
AJP: Heart and Circulatory Physiology, 2007
Sex steroids exert profound and controversial effects on cardiovascular function. For example, estrogens have been reported to either ameliorate or exacerbate coronary heart disease. Although estrogen dilates coronary arteries from a variety of species, the molecular basis for this acute, nongenomic effect is unclear. Moreover, we know very little of how estrogen affects human coronary artery smooth muscle cells (HCASMC). The purpose of this study was to elucidate nongenomic estrogen signal transduction in HCASMC. We have used tissue (arterial tension studies), cellular (single-channel patch clamp, fluorescence), and molecular (protein expression) techniques to now identify novel targets of estrogen action in HCASMC: type I (neuronal) nitric oxide synthase (nNOS) and phosphatidylinositol 3-kinase (PI3-kinase)Akt. 17β-Estradiol (E2) increased NO-stimulated fluorescence in HCASMC, and cell-attached patch-clamp experiments revealed that stimulation of nNOS leads to increased activity o...
Oestrogen directly inhibits the cardiovascular L-type Ca2+ channel Cav1.2
Biochemical and Biophysical Research Communications, 2007
Oestrogen can modify the contractile function of vascular smooth muscle and cardiomyocytes. The negative inotropic actions of oestrogen on the heart and coronary vasculature appear to be mediated by L-type Ca 2+ channel (Ca v 1.2) inhibition, but the underlying mechanisms remain elusive. We tested the hypothesis that oestrogen directly inhibits the cardiovascular L-type Ca 2+ current, I CaL . The effect of oestrogen on I CaL was measured in Ca v 1.2-transfected HEK-293 cells using the whole-cell patch-clamp technique. The current revealed typical activation and inactivation profiles of nifedipine-and cadmium-sensitive I CaL . Oestrogen (50 lM) rapidly reduced I CaL by 50% and shifted voltage-dependent activation and availability to more negative potentials. Furthermore, oestrogen blocked the Ca 2+ channel in a rate-dependent way, exhibiting higher efficiency of block at higher stimulation frequencies. Our data suggest that oestrogen inhibits I CaL through direct interaction of the steroid with the channel protein.
Oestrogen directly inhibits the cardiovascular L-type Ca{sup 2+} channel Ca{sub v}1.2
Biochem Biophys Res Commun, 2007
Oestrogen can modify the contractile function of vascular smooth muscle and cardiomyocytes. The negative inotropic actions of oestrogen on the heart and coronary vasculature appear to be mediated by L-type Ca 2+ channel (Ca v 1.2) inhibition, but the underlying mechanisms remain elusive. We tested the hypothesis that oestrogen directly inhibits the cardiovascular L-type Ca 2+ current, I CaL . The effect of oestrogen on I CaL was measured in Ca v 1.2-transfected HEK-293 cells using the whole-cell patch-clamp technique. The current revealed typical activation and inactivation profiles of nifedipine-and cadmium-sensitive I CaL . Oestrogen (50 lM) rapidly reduced I CaL by 50% and shifted voltage-dependent activation and availability to more negative potentials. Furthermore, oestrogen blocked the Ca 2+ channel in a rate-dependent way, exhibiting higher efficiency of block at higher stimulation frequencies. Our data suggest that oestrogen inhibits I CaL through direct interaction of the steroid with the channel protein.
Hypertension, 2007
This study investigated the contribution of estrogen receptors (ERs) ␣ and  for epicardial coronary artery function, vascular NO bioactivity, and superoxide (O 2 Ϫ ) formation. Porcine coronary rings were suspended in organ chambers and precontracted with prostaglandin F 2␣ to determine direct effects of the selective ER agonists 4,4Ј,4Љ-(4-propyl-[ 1 H]pyrazole-1,3,5-triyl)tris-phenol (PPT) or 2,3-bis(4-hydroxyphenyl)-propionitrile (DPN) or the nonselective ER agonist 17-estradiol. Indirect effects on contractility to U46619 and relaxation to bradykinin were assessed and effects on NO, nitrite, and O 2 Ϫ formation were measured in cultured cells. Within 5 minutes, selective ER␣ activation by PPT, but not 17-estradiol or the ER agonist DPN, caused rapid, NO-dependent, and endotheliumdependent relaxation (49Ϯ5%; PϽ0.001 versus ethanol). PPT also caused sustained endothelium-and NO-independent vasodilation similar to 17-estradiol after 60 minutes (72Ϯ3%; PϽ0.001 versus ethanol). DPN induced endotheliumdependent NO-independent relaxation via endothelium-dependent hyperpolarization (40Ϯ4%; PϽ0.01 versus ethanol). 17-Estradiol and PPT, but not DPN, attenuated the responses to U46619 and bradykinin. All of the ER agonists increased NO and nitrite formation in vascular endothelial but not smooth muscle cells and attenuated vascular smooth muscle cell O 2
Modulation of the BK channel by estrogens: examination at single channel level
Molecular Membrane Biology, 2006
BK channels regulate vascular tone by hyperpolarizing smooth muscle in response to fluctuating calcium concentrations. Oestrogen has been reported to lower blood pressure by increasing BK channel open probability through direct binding to the regulatory b1-subunit(s) associated with the channel. The present investigation demonstrates that 17b-oestradiol activates the BK channel complex by increasing the burst duration of channel openings. A subconductance state was observed in 25% of recordings following the addition of 17b-oestradiol and could reflect uncoupling between the pore forming a1-subunit and the regulatory b1-subunit. We also present evidence that more than one b1-subunit is required to facilitate binding of 17b-oestradiol to the channel complex.
Increased Expression of the Cardiac L-type Calcium Channel in Estrogen Receptor-deficient Mice
The Journal of General Physiology, 1997
Steroid hormones control the expression of many cellular regulators, and a role for estrogen in cardiovascular function and disease has been well documented. To address whether the activity of the L-type Ca 2 ϩ channel, a critical element in cardiac excitability and contractility, is altered by estrogen and its nuclear receptor, we examined cardiac myocytes from male mice in which the estrogen receptor gene had been disrupted (ERKO mice). Binding of dihydropyridine Ca 2 ϩ channel antagonist isradipine (PN200-110) was increased 45.6% in cardiac membranes from the ERKO mice compared to controls, suggesting that a lack of estrogen receptors in the heart increased the number of Ca 2 ϩ channels. Whole-cell patch clamp of acutely dissociated adult cardiac ventricular myocytes indicated that Ca 2 ϩ channel current was increased by 49% and action potential duration was increased by 75%. Examination of electrocardiogram parameters in ERKO mice showed a 70% increase in the QT interval without significant changes in PQ or QRS intervals. These results show that the membrane density of the cardiac L-type Ca 2 ϩ channel is regulated by the estrogen receptor and suggest that decreased estrogen may lead to an increase in the number of cardiac L-type Ca 2 ϩ channels, abnormalities in cardiac excitability, and increased risk of arrhythmia and cardiovascular disease.
Journal of Vascular Research, 2013
The G protein-coupled estrogen receptor GPER1/GPR30 is implicated in blood pressure regulation but the mechanisms are not identified. Here, we hypothesize that GPER1 controls blood pressure by regulating vascular smooth muscle cell Ca2+ handling. Treatment with the GPER1 agonist G-1 (in the µM concentration range) acutely reduced spontaneous and synchronous Ca2+ spike activity in A7r5 vascular smooth muscle cells expressing mRNA for GPER1. Furthermore, G-1 (1 µM) attenuated the thromboxane A2 analogue U46619-stimulated Ca2+ spike activity but had no effect on the U46619-induced increase in the basal level of Ca2+. The voltage-sensitive L-type Ca2+ channel blocker nifedipine (100 nM) reduced Ca2+ spike activity similar to G-1. Pharmacological, but not physiological, concentrations of the estrogen 17β-estradiol reduced Ca2+ spike activity. The GPER1 antagonist G-15 blocked G-1-induced downregulation of Ca2+ spike activity, supporting a GPER1-dependent mechanism. G-1 (1 µM) and nifedip...