In vitro modulation of primate coronary vascular muscle cell reactivity by ovarian steroid hormones

Repetitive catamenial myocardial infarction due to coronary artery spasm: a case report

Background

Coronary artery spasm is an established mechanism of myocardial infarction with non-obstructive coronary arteries (MINOCA). Various mechanisms have been proposed, ranging from vascular smooth muscle hyperreactivity to endothelial dysfunction, to autonomic nervous system dysregulation.

Case summary

We report a case of a 37-year-old woman who presented with recurrent non-ST elevation myocardial infarction (NSTEMI), coinciding with her menstrual periods. Intracoronary acetylcholine provocation testing resulted in coronary spasm in the left anterior descending artery (LAD) that was relieved with nitroglycerine. Initiating calcium channel blockade and suppressing cyclical variation in sex hormones resulted in improvement of her symptoms and cessation of monthly NSTEMI events due to coronary spasm.

Discussion

Initiating calcium channel blockade and suppressing cyclical variation in sex hormones resulted in improvement of her symptoms and cessation of monthly NSTEMI events due to coronary spasm. Catamenial coronary artery spasm is a rare, but clinically important, presentation of myocardial infarction with non-obstructive coronary arteries (MINOCA).

Adaptive increases in expression and vasodilator activity of estrogen receptor subtypes in a blood vessel-specific pattern during pregnancy

Normal pregnancy is associated with adaptive hemodynamic, hormonal, and vascular changes, and estrogen (E2) may promote vasodilation during pregnancy; however, the specific E2 receptor (ER) subtype, post-ER signaling mechanism, and vascular bed involved are unclear. We tested whether pregnancy-associated vascular adaptations involve changes in the expression/distribution/activity of distinct ER subtypes in a blood vessel-specific manner. Blood pressure (BP) and plasma E2 were measured in virgin and pregnant (day 19) rats, and the thoracic aorta, carotid artery, mesenteric artery, and renal artery were isolated for measurements of ERα, ERβ, and G protein-coupled receptor 30 [G protein-coupled ER (GPER)] expression and tissue distribution in parallel with relaxation responses to E2 (all ERs) and the specific ER agonist 4,4',4″-(4-propyl-[1H]-pyrazole-1,3,5-triyl)-tris-phenol (PPT; ERα), diarylpropionitrile (DPN; ERβ), and G1 (GPER). BP was slightly lower and plasma E2 was higher in pregnant versus virgin rats. Western blots revealed increased ERα and ERβ in the aorta and mesenteric artery and GPER in the aorta of pregnant versus virgin rats. Immunohistochemistry revealed that the increases in ERs were mainly in the intima and media. In phenylephrine-precontracted vessels, E2 and PPT caused relaxation that was greater in the aorta and mesenteric artery but similar in the carotid and renal artery of pregnant versus virgin rats. DPN- and G1-induced relaxation was greater in the mesenteric and renal artery than in the aorta and carotid artery, and aortic relaxation to G1 was greater in pregnant versus virgin rats. The nitric oxide synthase inhibitor N(ω)-nitro-l-arginine methyl ester with or without the cyclooxygenase inhibitor indomethacin with or without the EDHF blocker tetraethylammonium or endothelium removal reduced E2, PPT, and G1-induced relaxation in the aorta of pregnant rats, suggesting an endothelium-dependent mechanism, but did not affect E2-, PPT-, DPN-, or G1-induced relaxation in other vessels, suggesting endothelium-independent mechanisms. E2, PPT, DPN, and G1 caused relaxation of Ca(2+) entry-dependent KCl contraction, and the effect of PPT was greater in the mesenteric artery of pregnant versus virgin rats. Thus, during pregnancy, an increase in ERα expression in endothelial and vascular smooth muscle layers of the aorta and mesenteric artery is associated with increased ERα-mediated relaxation via endothelium-derived vasodilators and inhibition of Ca(2+) entry into vascular smooth muscle, supporting a role of aortic and mesenteric arterial ERα in pregnancy-associated vasodilation. GPER may contribute to aortic relaxation while enhanced ERβ expression could mediate other genomic vascular effects during pregnancy.

Disruption of coronary vasomotor function: the coronary spasm syndrome

Abnormal coronary vasoconstriction, or coronary spasm, can be the result of several factors, including local and neuroendocrine aberrations. It can manifest clinically as a coronary syndrome and plays an important role in the genesis of myocardial ischemia. Over the past half century, coronary angiography allowed the in vivo demonstration of spasm in patients who fit the initial clinical description of the condition as reported by Prinzmetal et al. Several clinical, basic, and more recently, genetic studies have provided insight into the pathogenesis, manifestations, and therapy of this condition. It is not uncommonly encountered in patients with coronary syndromes and absence of clearly pathologic lesions on angiography. Provocation tests utilizing pharmacologic and nonpharmacologic stimuli combined with imaging (echocardiography or coronary angiography) can help make the correct diagnosis. The use of calcium channel blockers and long-acting nitrates is currently considered standard of care and the overall prognosis appears to be good. The recent discovery of genetic abnormalities predisposing to abnormal spasm of the coronaries has stimulated interest in the development of targeted therapies for the management of this condition.

Pregnancy downregulates actin polymerization and pressure-dependent myogenic tone in ovine uterine arteries

Pregnancy is associated with significantly decreased uterine vascular tone and increased uterine blood flow. The present study tested the hypothesis that the downregulation of actin polymerization plays a key role in reduced vascular tone of uterine arteries in the pregnant state. Uterine arteries were isolated from nonpregnant and near-term pregnant sheep. Activation of protein kinase C significantly increased the filamentous:globular actin ratio and contractions in the uterine arteries, which were inhibited by an actin polymerization inhibitor cytochalasin B. The basal levels of filamentous:globular actin were significantly higher in nonpregnant uterine arteries than those in near-term pregnant sheep. Prolonged treatment (48 hours) of nonpregnant sheep with 17β-estradiol (0.3 nmol/L) and progesterone (100.0 nmol/L) caused a significant decrease in the filamentous:globular actin. In accordance, the treatment of near-term pregnant sheep for 48 hours with an estrogen antagonist ICI 182 780 (10.0 μmol/L) and progesterone antagonist RU 486 (1.0 μmol/L) significantly increased the levels of filamentous:globular actin. Increased intraluminal pressure from 20 to 100 mm Hg resulted in an initial increase in uterine arterial diameter and vascular wall Ca(2+) concentrations, followed by a decrease in the diameter at a constant steady-state level of Ca(2+). Cytochalasin B blocked pressure-induced myogenic constrictions without effect on vascular wall Ca(2+) levels and eliminated the differences in pressure-dependent myogenic tone between nonpregnant sheep and near-term pregnant sheep. The results indicate a key role of actin polymerization in protein kinase C-induced myogenic contractions and suggest a novel mechanism of sex steroid hormone-mediated downregulation of actin polymerization underlying the decreased myogenic tone of uterine arteries in pregnancy.

Chronic hypoxia inhibits sex steroid hormone-mediated attenuation of ovine uterine arterial myogenic tone in pregnancy

Previous studies in ovine uterine arteries have demonstrated that sex steroid hormones upregulate extracellular signal-regulated kinase 1/2 expression and downregulate the protein kinase C signaling pathway, resulting in the attenuated myogenic tone in pregnancy. The present study tested the hypothesis that chronic hypoxia during gestation inhibits the sex steroid-mediated adaptation of extracellular signal-regulated kinase 1/2 and protein kinase C signaling pathways and increases the myogenic tone of uterine arteries. Uterine arteries were isolated from nonpregnant and near-term pregnant sheep that had been maintained at sea level (≈300 m) or exposed to high-altitude (3801 m) hypoxia for 110 days. In contrast to the previous findings in normoxic animals, 17β-estradiol and progesterone failed to suppress protein kinase C-induced contractions and the pressure-induced myogenic tone in uterine arteries from hypoxic animals. Western analyses showed that the sex steroids lost their effects on extracellular signal-regulated kinase 1/2 expression and phospho- extracellular signal-regulated kinase 1/2 levels, as well as the activation of protein kinase C isozymes in uterine arteries of hypoxic ewes. In normoxic animals, pregnancy and the sex steroid treatments significantly increased uterine artery estrogen receptor-α and progesterone receptor B expression. Chronic hypoxia selectively downregulated estrogen receptor-α expression in uterine arteries of pregnant animals and eliminated the upregulation of estrogen receptor-α in pregnancy or by the steroid treatments observed in normoxic animals. The results demonstrate that, in the ovine uterine artery, chronic hypoxia in pregnancy inhibits the sex steroid hormone-mediated adaptation of decreased myogenic tone by downregulating estrogen receptor-α expression, providing a mechanism linking hypoxia and maladaptation of uteroplacental circulation and an increased risk of preeclampsia in pregnancy.

Direct chronic effect of steroid hormones in attenuating uterine arterial myogenic tone: role of protein kinase c/extracellular signal-regulated kinase 1/2

Pregnancy is associated with a significant decrease in uterine vascular tone and an increase in uterine blood flow. The present study tested the hypothesis that estrogen and progesterone differentially regulate the extracellular signal-regulated kinase (ERK)1/2 and protein kinase C (PKC) signaling pathways in vascular smooth muscle, resulting in a decrease in uterine vascular myogenic tone in pregnancy. Uterine arteries were isolated from nonpregnant and near-term pregnant sheep. Chronic treatment (48 hours) of nonpregnant uterine arteries with 17beta-estradiol and progesterone caused a significant decrease in PKC-mediated contractions and pressure-induced myogenic tone. In accordance, treatment of near-term pregnant uterine arteries for 48 hours with ICI 182780 and RU 486 significantly increased PKC-induced contractions and myogenic tone. In contrast, acute treatment for 30 minutes had no effect on uterine artery contractility. An ERK1/2 inhibitor, PD098059, restored the chronic effect of steroids on PKC-mediated contractions in nonpregnant sheep. ERK1/2 protein and mRNA levels were greater in near-term pregnant as compared with nonpregnant uterine arteries. 17beta-Estradiol and progesterone increased ERK1/2 protein in nonpregnant sheep. In agreement, ICI 182780 and RU 486 caused significant decreases in ERK1/2 protein in near-term pregnant sheep. Western blot showed 6 PKC isozymes, alpha, beta(I), beta(II), delta, epsilon, and zeta, in the uterine arteries. 17beta-Estradiol and progesterone decreased the particulate:cytosolic ratios of PKCalpha, epsilon, and zeta, respectively, in nonpregnant sheep. ICI 182780 and RU 486 increased the ratios in near-term pregnant sheep. The results indicate a direct chronic effect of the steroid hormones in the upregulation of ERK1/2 expression and downregulation of the PKC signaling pathway, resulting in attenuated myogenic tone of the uterine artery in pregnancy.

Could transdermal estradiol + progesterone be a safer postmenopausal HRT? A review

Hormone replacement therapy (HRT) in young postmenopausal women is a safe and effective tool to counteract climacteric symptoms and to prevent long-term degenerative diseases, such as osteoporotic fractures, cardiovascular disease, diabetes mellitus and possibly cognitive impairment. The different types of HRT offer to many extent comparable efficacies on symptoms control; however, the expert selection of specific compounds, doses or routes of administration can provide significant clinical advantages. This paper reviews the role of the non-oral route of administration of sex steroids in the clinical management of postmenopausal women. Non-orally administered estrogens, minimizing the hepatic induction of clotting factors and others proteins associated with the first-pass effect, are associated with potential advantages on the cardiovascular system. In particular, the risk of developing deep vein thrombosis or pulmonary thromboembolism is negligible in comparison to that associated with oral estrogens. In addition, recent indications suggest potential advantages for blood pressure control with non-oral estrogens. To the same extent, a growing literature suggests that the progestins used in association with estrogens may not be equivalent. Recent evidence indeed shows that natural progesterone displays a favorable action on the vessels and on the brain, while this might not be true for some synthetic progestins. Compelling indications also exist that differences might also be present for the risk of developing breast cancer, with recent trials indicating that the association of natural progesterone with estrogens confers less or even no risk of breast cancer as opposed to the use of other synthetic progestins. In conclusion, while all types of hormone replacement therapies are safe and effective and confer significant benefits in the long-term when initiated in young postmenopausal women, in specific clinical settings the choice of the transdermal route of administration of estrogens and the use of natural progesterone might offer significant benefits and added safety.

Effects of female sex hormones on responses to CGRP, acetylcholine, and 5-HT in rat isolated arteries

BACKGROUND

Female sex hormones are implicated in the modulation of reactivity of a wide range of blood vessels under physiological as well as pathological conditions. Migraine, a neurovascular syndrome, is 3 times more prevalent in women during their reproductive period than in men.

OBJECTIVE

This study sets out to investigate the effects of the female sex steroids, 17beta-estradiol and progesterone (separately and in combination) on vasoactive responses to calcitonin gene-related peptide (CGRP), acetylcholine, and 5-hydroxytryptamine (5-HT) in rat isolated mesenteric, caudal, and basilar arteries.

METHODS

Female Sprague-Dawley rats were ovariectomized (Day 0) and 7 days later subcutaneously implanted with pellets releasing over a 21-day period 17beta-estradiol (0.25 mg), progesterone (50 mg), their combination, or placebo. On days 25-28, the animals were killed, arteries isolated and mounted in Mulvany myographs, and cumulative concentration response curves to CGRP, acetylcholine, and 5-HT were constructed.

RESULTS

The relaxant responses to CGRP were significantly potentiated in mesenteric and caudal arteries from rats treated with 17beta-estradiol as compared to the placebo-treated rats. Acetylcholine-induced relaxations were potentiated in the caudal artery from rats treated with the combination of 17beta-estradiol and progesterone, as compared to that from placebo-treated rats. The 5-HT-induced contractions in the 3 arteries were not significantly different in efficacy or potency.

CONCLUSION

Our results show that 17beta-estradiol potentiates CGRP-induced relaxations in the mesenteric and caudal arteries, while the combination treatment enhances acetylcholine-induced relaxations in the caudal artery. Although these in vitro experiments have been carried out in rats and a direct extrapolation to migraine in humans is not possible, our results may provide a new avenue to study the effects of sex steroids on vascular reactivity.

Differential vascular adaptive response to stress exposure in male and female rats: role of gonadal hormones and endothelial cells

Although there are reports concerning a vascular adaptive response to stress in males, this is not yet defined in females. The aim of this study was to delineate functional gender differences in the rat vascular adaptive response to stress and to determine the ability of sex hormones to modulate the stress-induced vascular adaptive response. Responses to noradrenaline were evaluated in aortas, with and without endothelium, from intact, gonadectomized and gonadectomized-hormone-replaced males and females submitted or not to stress (2-h immobilization). Reactivity of the aorta of stressed and non-stressed intact males and females (n = 6-14 per group) was also examined in the presence of L-NAME or indomethacin. Stress decreased and gonadectomy increased maximal responses to noradrenaline in aortas with intact endothelium from both genders. Stress also reduced noradrenaline potency in males. In females, but not males, stress decreased the gonadectomy-induced noradrenaline hyper-reactivity to near that of intact non-stressed rats. Hormone replacement restored the gonadectomy-induced impaired vascular adaptive response to stress. L-NAME, but not indomethacin, abolished the stress-induced decrease in aorta reactivity of males and females. None of the procedures altered reactivity of aortas denuded of endothelium.

CONCLUSION

Stress-induced vascular adaptive responses show gender differences. The magnitude of the adaptive response is dependent on testicular hormones and involves endothelial nitric oxide-system hyperactivity.

Potential role of female sex hormones in the pathophysiology of migraine

Clinical evidence indicates that female sex steroids may contribute to the high prevalence of migraine in women, as well as changes in the frequency or severity of migraine attacks that are in tandem with various reproductive milestones in women's life. While female sex steroids do not seem to be involved in the pathogenesis of migraine per se, they may modulate several mediators and/or receptor systems via both genomic and non-genomic mechanisms; these actions may be perpetuated at the central nervous system, as well as at the peripheral (neuro)vascular level. For example, female sex steroids have been shown to enhance: (i) neuronal excitability by elevating Ca(2+) and decreasing Mg(2+) concentrations, an action that may occur with other mechanisms triggering migraine; (ii) the synthesis and release of nitric oxide (NO) and neuropeptides, such as calcitonin gene-related peptide CGRP, a mechanism that reinforces vasodilatation and activates trigeminal sensory afferents with a subsequent stimulation of pain centres; and (iii) the function of receptors mediating vasodilatation, while the responses of receptors inducing vasoconstriction are attenuated. The serotonergic, adrenergic and gamma-aminobutyric acid (GABA)-ergic systems are also modulated by sex steroids, albeit to a varying degree and with potentially contrasting effects on migraine outcome. Taken together, female sex steroids seem to be involved in an array of components implicated in migraine pathogenesis. Future studies will further delineate the extent and the clinical relevance of each of these mechanisms, and will thus expand the knowledge on the femininity of migraine.

Mechanism of ST segment depression during exercise tests in patients with liver cirrhosis

PURPOSE

To our experience, ST segment depression is sometimes detected in an exercise electrocardiogram (ECG) test in patients with liver cirrhosis who have no significant coronary stenosis. In this study, the mechanism of ST segment depression in liver cirrhosis was examined using (99m)Tc-methoxy-isobutyl-isonitrile (MIBI) myocardial scintigraphy.

METHODS

Six patients with liver cirrhosis (LC group), and 15 normal subjects (N group) were examined. To evaluate the level of myocardial blood flow, a Bull's eye display of myocardial blood flow was performed after dividing the left ventricle into 9 segments. Exercise myocardial scintigraphy with MIBI was performed to obtain the increase in % uptake. Angiographies were performed with a CAG system by inserting a 5 French Judkins catheter via the right femoral artery.

RESULTS

No significant coronary stenosis was found in any of the LC patients. Neither a decrease in MIBI uptake nor defect was observed on Bull's eye images from the LC group. The mean % uptake increase was 61.0 +/- 5.6% in the N group. In the LC group, although neither a decrease in MIBI uptake nor a defect was visually observed on Bull's eye images obtained during exercise, the % uptake increases (mean: 52.5 +/- 5.8%) were lower than those of the N group (p<0.05).

CONCLUSION

These findings suggest that a disorder in coronary flow reserve occurs in liver cirrhosis patients, because the decreased MIBI uptake during exercise is due to the depression of flow-mediated vasodilatation controlled by the endothelium of the coronary artery and the estrogenic digitalis action of blood flow independency.

Metabolite ligands of estrogen receptor-beta reduce primate coronary hyperreactivity

Previous reports showed that 17beta-estradiol implants attenuate in vivo coronary hyperreactivity (CH), characterized by long-duration vasoconstrictions (in coronary angiographic experiments), in menopausal rhesus monkeys. Prolonged Ca2+ contraction signals that correspond with CH in coronary vascular muscle cells (VMC) to the same dual-constrictor stimulus, serotonin + the thromboxane analog U-46619, in estrogen-deprived VMC were suppressed by >72 h in 17beta-estradiol. The purpose of this study was to test whether an endogenous estrogen metabolite with estrogen receptor-beta (ER-beta) binding activity, estriol (E3), suppresses in vivo and in vitro CH. E3 treatment in vivo for 4 wk significantly attenuated the angiographically evaluated vasoconstrictor response to intracoronary serotonin + U-46619 challenge. In vitro treatment of rhesus coronary VMC for >72 h with nanomolar E3 attenuated late Ca2+ signals. This reduction of late Ca2+ signals also appeared after >72 h of treatment with subnanomolar 5alpha-androstane-3beta,17beta-diol (3beta-Adiol), an endogenous dihydrotestosterone metabolite with ER-beta binding activity. R,R-tetrahydrochrysene, a selective ER-beta antagonist, significantly blocked the E3- and 3beta-Adiol-mediated attenuation of late Ca2+ signal increases. ER-beta and thromboxane-prostanoid receptor (TPR) were coexpressed in coronary arteries and aorta. In vivo E3 treatment attenuated aortic TPR expression. Furthermore, in vitro treatment with E3 or 3beta-Adiol downregulated TPR expression in VMC, which was blocked for both agonists by pretreatment with R,R-tetrahydrochrysene. E3- and 3beta-Adiol-mediated reduction in persistent Ca2+ signals is associated with ER-beta-mediated attenuation of TPR expression and may partly explain estrogen benefits in coronary vascular muscle.

Medroxyprogesterone acetate and dihydrotestosterone induce coronary hyperreactivity in intact male rhesus monkeys

Coronary hyperreactivity (CH), characterized by persistent severe vasoconstrictions in response to vasoconstrictor challenge, is oppositely influenced by progesterone (P) and medroxyprogesterone acetate (MPA) treatment in surgically menopausal primates. In this study we tested whether multiweek MPA or dihydrotestosterone (DHT) exposure induced CH in intact male rhesus monkeys. Coronary angiographic experiments with intracoronary serotonin and the thromboxane A(2) analog U46619 stimulated brief vasoconstriction (for 1-3 min) in large epicardial coronaries in untreated male monkeys. In contrast, MPA- and DHT-treated monkeys displayed long-duration constrictions (>5 min), with significantly greater reductions in the minimal diameters of epicardial coronaries. Immunocytochemistry demonstrated androgen receptors (AR) and P receptors in aorta and coronary arteries, and immunocytochemistry and Western blotting showed AR and P receptors in rhesus coronary vascular muscle cells. In vivo, MPA or DHT increased thromboxane prostanoid (TP) receptor expression in the aorta. In vitro, MPA or DHT increased, whereas P did not change, TP receptor expression in primary coronary vascular muscle cell. This MPA- or DHT-mediated increase in TP receptor expression was attenuated by the AR antagonist flutamide. MPA or DHT induction of CH in intact adult male primates, hypothesized to occur via androgenic up-regulation of vascular muscle TP receptor expression, could predispose to CH-mediated myocardial ischemia.

Successful treatment of refractory vasospastic angina with corticosteroids: coronary arterial hyperactivity caused by local inflammation?

BACKGROUND

Although vasospastic angina usually responds well to treatment with calcium antagonists and/or nitrates, there have been anecdotal case reports of refractory vasospastic angina resistant to intensive treatment with high doses of calcium antagonists and nitrates.

METHODS AND RESULTS

Four patients with vasospastic angina, which was refractory to intensive treatment with high doses of calcium antagonists and nitrates, were completely controlled after administration of corticosteroids. Although none of the 4 patients showed eosinophilia, all had bronchial asthma or chronic thyroiditis, and in 2 cases, the activity of vasospastic angina corresponded with that of bronchial asthma.

CONCLUSIONS

These findings suggest that in these patients, coronary spasm may have been induced by arterial hyperreactivity because of local inflammation in the coronary arterial wall and that the corticosteroids suppressed the arterial hyperreactivity by alleviating the inflammation. Corticosteroids may be considered as a treatment choice for patients with refractory vasospastic angina, particularly when the patient has an allergic tendency, such as bronchial asthma.

Prevention of coronary hyperreactivity in preatherogenic menopausal rhesus monkeys by transdermal progesterone

OBJECTIVE

To test if transdermal progesterone (P) confers coronary vascular protection in surgically menopausal preatherosclerotic rhesus monkeys.

METHODS AND RESULTS

Ovariectomized rhesus monkeys fed an atherogenic diet (AD) for 19 months were treated with an investigational transdermal P cream (n=7) or identical placebo cream (n=5) for 4 weeks. Aorta and carotids showed fatty streaks and Oil Red O staining demonstrated lipid deposition. Serum P levels in P-treated rhesus monkeys (0.6 ng/mL) were significantly greater than placebo (0.2 ng/mL). Significant elevation of cholesterol, LDL cholesterol, and HDL cholesterol, was noted in all animals. Lp(a) was significantly attenuated in the AD-fed P-treated monkeys. Coronary angiographic experiments stimulating vasoconstriction by intracoronary injections of serotonin plus U46619 showed exaggerated prolonged actions amplified by AD, but significant protection against severe prolonged vasoconstriction in P-treated monkeys. Immunocytochemistry confirmed co-expression of P and thromboxane prostanoid (TP) receptors in coronaries and aorta. Western blotting demonstrated TP receptor attenuation in vascular muscle after P treatment.

CONCLUSIONS

Coronary hyperreactivity, a putative component of coronary artery disease mediated via increased vascular muscle thromboxane prostanoid receptors, can be prevented by subphysiological levels of P, not only in nonatherosclerotic (previously shown) but also in preatherosclerotic primates.

Coronary vasospasm and the regulation of coronary blood flow

Under physiologic conditions, epicardial arteries contribute minimally to coronary vascular resistance. However, in the presence of endothelial dysfunction, stimuli that normally produce vasodilation may instead cause constriction. Examples include neural release of acetylcholine or norepinephrine, platelet activation and production of serotonin and thrombin, and release of local factors such as bradykinin. This shift from a primary endothelial-mediated vasodilator influence to one of endothelial dysfunction and unchecked vasoconstriction is precisely the milieu in which coronary vasospasm is observed. This condition, which typically occurs during periods of relatively sedentary activity, is associated with focal and transient obstruction of an epicardial arterial segment resulting in characteristic echocardiographic changes and symptoms of myocardial ischemia. This review highlights the current understanding of mechanisms regulating the coronary circulation during health and examines the pathophysiologic changes that occur with coronary spasm. Genetic and other predisposing conditions are addressed, as well as novel therapies based on recent mechanistic insights of the coronary contractile dysfunction associated with coronary spasm.

Progesterone administration after trauma and hemorrhagic shock improves cardiovascular responses

OBJECTIVE

Studies have shown that female rats during the proestrus stage have significantly improved cell and organ functions after trauma-hemorrhage compared with male and ovariectomized females. This study investigated the hypothesis that progesterone can improve the depressed cardiovascular function in sex steroid-deficient female rats (i.e., ovariectomized females) after trauma-hemorrhage and resuscitation.

DESIGN

Prospective study.

SETTING

University laboratory.

SUBJECTS

Ovariectomized female Sprague-Dawley rats (weight, 250-300 g).

INTERVENTIONS

Rats underwent a 5-cm midline laparotomy (i.e., soft-tissue trauma), were bled to a mean arterial pressure of 35 mm Hg for approximately 90 mins, and were then resuscitated using Ringer's lactate. A single dose of progesterone (25 mg/kg of body weight) or vehicle was administered subcutaneously during resuscitation.

MEASUREMENTS

At 20 hrs after trauma-hemorrhage or sham operation, cardiac output and heart performance and the circulating blood volume were assessed using the indocyanine green dilution technique and a left ventricular catheter. Furthermore, the binding activity of progesterone receptors in nuclear extracts of left ventricular tissue was determined.

RESULTS

Cardiac output, heart performance, and circulating blood volume were significantly decreased in vehicle-treated animals after trauma-hemorrhage. Administration of progesterone significantly improved cardiac output and heart performance and increased the circulating blood volume. This was associated with an increased progesterone receptor activity in the left ventricular nuclear extracts.

CONCLUSION

Because administration of progesterone after trauma-hemorrhage in sex steroid-deficient females improved cardiovascular responses, this hormone seems to be a useful adjunct for the treatment of cardiovascular depression in postmenopausal and ovariectomized female trauma patients.

Rapid inhibition of the contraction of rat tail artery by progesterone is mediated by inhibition of calcium currents

Progesterone induced rapid relaxation of KCl-contracted tail artery helical strips from rats. The effect was dose dependent, with an IC50 (inhibitory concentration which produces 50% of the maximal response) of 8.9 microM progesterone. The actions of progesterone were not blocked by bicuculline, indicating that in this tissue the non-genomic actions of progesterone were not mediated via a gamma-aminobutyric acid (GABA)-A receptor. Fura-2 was used to measure intracellular calcium levels ([Ca(2+)](i)) in isolated vascular smooth muscle cells (VSMC). Incubation of cultured VSMC for 15 min with progesterone (10 microM) resulted in an inhibition of the KCl-induced [Ca(2+)](i )increase. The whole-cell patch-clamp technique was used to examine Ca(2+)-channel currents in the membrane of isolated VSMC. Progesterone suppressed the L-type Ca(2+)-channel currents in cells held at a potential of -40 mV. The effects of progesterone were quickly reversed by washout in all three experimental protocols suggesting that these effects on vascular tissues are non-genomic. The correlation of the effects on all these preparations, their time course and reversibility suggested that the rapid relaxation of the rat tail artery induced by progesterone is mediated at least in part by inhibition of L-type calcium channels, leading to inhibition of calcium responses in the VSMC of this tissue.

Estrogen increases iNOS expression in the ovine coronary artery

Estrogen is believed to protect postmenopausal women from coronary vascular disease, in part by increasing production of nitric oxide (NO). In this study, we investigated the possibility that transcriptional activation of inducible NO synthase (iNOS) is responsible for a component of the estrogen-induced increase in coronary blood flow. Twenty-two ewes were instrumented with Doppler flow probes on their left circumflex coronary and pulmonary arteries. Nine ewes received 17beta-estradiol (1 microg/kg), and the coronary vascular response was followed for 16 h. Estradiol significantly increased coronary blood flow by 22 +/- 4% over baseline and the peak response occurred at 2 h (P < 0.01). To examine the effect of estrogen on NOS expression in the ovine coronary artery, 17 noninstrumented animals were killed 2 h after administration of estradiol or vehicle. Coronary arteries were analyzed for ovine iNOS and endothelial NOS (eNOS) expression by semiquantitative RT-PCR. PCR primers were based on partial cDNA clones for ovine eNOS and iNOS isolated as part of this study. The expression of iNOS was significantly increased (27-fold) by the administration of estradiol, whereas the expression of eNOS was much weaker (2-fold). To confirm these effects in vivo, additional instrumented animals received either the estrogen receptor (ER) antagonist ICI-182,780 (n = 5), the iNOS antagonist dexamethasone (n = 5), or pyrrolidine dithiocarbamic acid, an inhibitor of nuclear factor-kappaB (n = 5). All three antagonists inhibited estrogen-induced increases in coronary blood flow and increases in cardiac output by over 85%. These results strongly support the hypothesis that 17beta-estradiol increases coronary blood flow in the unanesthetized nonpregnant ewe via an ER-dependent mechanism that results in an increase in both eNOS and iNOS expression.

Nongenomic vasodilator action of progesterone on primate coronary arteries

In the present investigation, we test the hypothesis that progesterone can rapidly relax, via a nongenomic mechanism, persistent flow occluding, agonist-activated coronary artery (CA) vasospasm, and hyperreactive vascular muscle cell (VMC) Ca(2+) responses in ovariectomized rhesus monkeys. CA vasospasm, induced by injection of 100 microM serotonin and 1 microM U-46619 (5-HT+U; 1 ml/30 s), resulted in a decrease in CA diameter (phi) from 1.8 +/- 0.2 to 0.3 +/- 0.1 mm at the site of focal constriction. Injection of 100 ng progesterone into the CA significantly relieved the severe vasoconstriction (1.3 +/- 0.2 mm) and reestablished distal flow in 3 min; the preconstriction phi was completely restored in 8.2 +/- 2.6 min (n = 6). Similarly, cell impermeant albumin-conjugated progesterone, but not albumin-conjugated 17 beta-estradiol, decreased 5-HT+U stimulated VMC Ca(2+) responses (250 +/- 34% of basal 30 min after stimulation) back to the prestimulation level (113 +/- 17% of basal) in 25 min (half time = 7 min). The presence of a rapid vasodilator action of progesterone in the primate CA and isolated VMC suggests its benefits in hormone replacement therapy may also include nongenomic vascular relaxant actions.

Progesterone regulation of vascular thromboxane A(2) receptors in rhesus monkeys

We hypothesized that progesterone regulates thromboxane A(2) receptor (TxA(2)R) density in primate vascular muscle and that TxA(2)R density correlates with coronary reactivity in vivo and in vitro. Reactivity to serotonin + U-46619 was determined by angiography in surgically postmenopausal [ovariectomized (Ovx)] rhesus monkeys without progesterone replacement and after 2-wk progesterone treatment (1-2 ng/ml). In untreated Ovx animals, 100 micromol/l serotonin + 1 micromol/l U-46619 (syringe concentrations) provoked vasospasm-like constrictions in six of six monkeys; zero of six progesterone-treated monkeys developed vasospasms. Sustained Ca(2+) responses in vascular muscle cells isolated from Ovx coronaries (208 +/- 63% of basal 20 min after stimulation) treated with serotonin + U-46619 contrasted with transient Ca(2+) responses (143 +/- 18% of basal and decreasing 5 min after stimulation) in progesterone-treated monkeys. The maximum density of [1S-(1I,2J(5Z),3I(1E,3R*),4I)]-7-[3-(3-hydroxy-4-(4'-[(125)I]iodophenoxy)- 1-butenyl)-7-oxabicyclo[2.2.1]heptan-2-yl]-5-heptenoic acid ([(125)I]-BOP) binding was greater (P < 0.01) in carotid arteries and aortic membranes from Ovx (109 +/- 11 fmol/mg) compared with progesterone-treated (43 +/- 15 fmol/mg) monkeys. TxA(2)R immunolabeling revealed greater coronary TxA(2)R labeling in Ovx compared with progesterone-treated monkeys. The results suggest that progesterone can decrease arterial TxA(2)R in Ovx monkeys.

Effect of estrogen replacement therapy on distribution of myocardial blood flow in female anesthetized rabbits

Estrogen replacement therapy reduces risk of cardiovascular events by altering coronary vasoregulation and distribution of blood flow. Vessel reactivity and blood flow distribution were assessed in anesthetized female rabbits in the following groups: 1) sham, 2) ovariectomy, 3) ovariectomy + 17beta-estradiol, and 4) ovariectomy + dehydroepiandrosterone. After a 2-wk treatment, cardiac hemodynamics, vascular reserve, and blood flow were evaluated during the following infusions: 1) NaCl, or vehicle (0.5 ml/min), 2) acetylcholine (2 mg/kg), 3) isoproterenol (2 mg. kg(-1). min(-1)), and 4) chromonar (8 mg/kg). In hearts from ovariectomized rabbits, autoregulatory blood flow was preserved despite lower diastolic perfusion pressures (55 +/- 8 vs. 64 +/- 8 mmHg in sham) and rate-pressure product (14.4 +/- 0.8 vs. 19.3 +/- 0.8 beats/min. mmHg x 10(-3)). Estrogen replacement therapy restored coronary pressure and reserve, and all drugs increased vascular conductance. In conclusion, in hearts from ovariectomized rabbits, vascular reserve declined because coronary pressure was lower; however, blood flow was preserved at a higher level than expected for oxygen demand. Estrogen replacement therapy restores myocardial oxygen supply-demand indices and returns coronary pressure-flow data to levels observed in animals with intact ovaries.

Effect of progesterone on the contractile response of isolated pulmonary artery in rabbits

The purpose of this study was to assess the direct effect of progesterone on rabbit pulmonary arteries and to examine the mechanism of its action. Rings of pulmonary artery from male rabbits were suspended in organ baths containing Krebs solution, and isometric tension was measured. The response to progesterone was investigated in arterial rings contracted with noradrenaline (NA), KCl, and CaCl2. The effects of endothelium, nitric oxide(NO), prostaglandins, cyclic GMP(cGMP), and the adrenergic β-receptor on progesterone-induced relaxation were also assessed. Progesterone inhibited the vasocontractivity to NA, KCl, and CaCl2, and relaxed rabbit pulmonary artery. The relaxing response of progesterone in pulmonary artery was significantly reduced by removal of endothelium, inhibitors of nitric oxide synthase and guanylate cyclase, but not by prostaglandin synthase inhibitor and blockage of the adrenergic β-receptor. In Ca2+-free (0.1 mM EGTA) Krebs solution, progesterone inhibited NA-induced contraction that was intracellular Ca2+-dependent, but didn't affect the contraction of extracellular Ca2+-dependent component. Our results suggest that progesterone induces relaxation of isolated rabbit pulmonary arteries partially via NO and cGMP. Progesterone may also inhibit Ca2+ influx through potential-dependent calcium channels (PDCs) and Ca2+ release from intracellular stores.Key words: progesterone, pulmonary artery, Ca2+ channel, endothelium.

Estrogens, progestins, selective estrogen receptor modulators, and the arterial tree

We reviewed studies of the effects of different estrogens, progestins, and selective estrogen receptor modulators at the coronary and carotid arterial sites to help determine their likely effects on cardiovascular morbidity and mortality. All English-language studies published between 1997 and 2000 on MEDLINE, Current Contents, and Best Evidence were reviewed, including in vitro, other animal, human physiologic, and clinical trial studies. We synthesize, assess limitations, and integrate across systems with the in vivo experience in humans to evaluate the clinical context. Estrogens have favorable direct effects in most circumstances, progestins oppose these effects, and early studies suggest that selective estrogen receptor modulators are protective. In some systems the dosage, route of delivery, and type of progestin may be important and risk factors may modulate hormone effects. The evaluation of endothelial dysfunction gives a unique in vivo opportunity to assess the vascular properties of hormones, although the relationship between the in vivo physiologic effects of hormones and clinical outcomes remains to be determined.

The heart as a target for oestrogens

Observational studies have consistently shown a markedly decreased risk of cardiovascular disease in postmenopausal women when treated with oestrogens. This review discusses plausible mechanisms for the physiological effects of oestrogens in healthy and diseased hearts. Oestrogens have well-documented effects on blood lipids and the regulators of the cardiovascular system, which should reduce risk. In addition, the heart is a primary target for oestrogens with functional oestrogen receptors in the coronary vasculature and on cardiac myocytes and fibroblasts. Rapid oestrogen effects include vasodilatation and anti-arrhythmic effects by actions on ion channels, and some of these effects may be pharmacological rather than physiological. Longer term responses to physiological levels of oestrogen include an increased expression of nitric oxide synthase in myocytes and endothelial cells as well as proinflammatory and pro-arrhythmic effects. Oestrogens induce growth of non-proliferating fibroblasts but inhibit the replication of proliferating fibroblasts. In contrast to the observational studies, two randomised, controlled studies of oestrogen and progestins in postmenopausal women with coronary heart disease have now shown increased coronary events, especially in the first year of study, and no change in the progression of coronary atherosclerosis. Further studies of the complex effects of oestrogens on healthy and diseased animal models are essential. Large clinical trials of the newer selective oestrogen receptor modulators to lower cardiovascular risk in both males and females should be considered as a priority.

Chronic 17beta-estradiol replacement increases nitric oxide-mediated vasodilation of guinea pig coronary microcirculation

BACKGROUND

Estrogen is cardioprotective of the coronary circulation by mechanisms incompletely understood. This study determined the effect of chronic 17beta-estradiol replacement on dilator responses to acetylcholine and sodium nitroprusside of the isolated coronary microcirculation.

METHODS AND RESULTS

Adult female guinea pigs were ovariectomized, and a 21-day-release pellet containing 0.0, 0.1, 0.25, 0.5, or 1.0 mg 17beta-estradiol was implanted subcutaneously. Serum estradiol concentrations ranged from 3.9 to 74.9 pg/mL, increasing with the dose of estradiol. After 19 to 20 days, the animals were euthanized, and their hearts were removed and perfused with buffer at constant flow on an isolated heart apparatus. Both perfusion pressure and contractile force were measured in prostaglandin F(2alpha)-constricted hearts. Vasodilation to the cumulative addition of the endothelium-dependent agonist acetylcholine (10(-9) to 10(-5) mol/L) and the nitric oxide (NO) donor sodium nitroprusside (10(-9) to 10(-5) mol/L) was measured before and after NO synthesis inhibition by nitro-L-arginine (LNA, 10(-4) mol/L). Baseline coronary resistance was unaltered by estradiol, although LNA increased resistance in estradiol-treated hearts more than in ovariectomized controls. Chronic 17beta-estradiol increased sensitivity (measured by -log EC(50) values) but not maximal response to acetylcholine compared with ovariectomized controls. Differences were abolished by LNA at all doses of estradiol. Sodium nitroprusside-induced dilation was unaffected by estradiol replacement.

CONCLUSIONS

Chronic 17beta-estradiol replacement, at doses producing hormone levels within the physiological range, enhances dilator sensitivity of the coronary microcirculation through enhanced NO production by the endothelium, independent of changes in NO sensitivity of the vascular smooth muscle. Thus, estradiol enhances NO production as a protective mechanism of the coronary microcirculation.

Differential effects of 17beta-estradiol and testosterone on the contractile responses of porcine coronary arteries

1. We investigated the effects of short-term exposure to physiological levels of 17beta-estradiol and testosterone on vasocontractile responses in porcine coronary artery rings. 2. Concentration-response curves to endothelin-1, 5-hydroxytryptamine, the thromboxane analogue U46619 and KCl were constructed in endothelium-intact and endothelium-disrupted artery rings. 3. Thirty minutes exposure to 17beta-estradiol (1 and 30 nM) significantly attenuated vasoconstriction to endothelin-1, 5-hydroxytryptamine and U46619. Conversely, the same concentrations of testosterone significantly potentiated responses elicited by these contractile agents. These inhibitory effects of 17beta-estradiol and enhancing actions of testosterone on contractions were endothelium-independent. KCl-mediated contractions were unaffected by the presence of either sex hormones. 4. The oestrogen receptor antagonists, tamoxifen (10 microM) and ICI 182,780 (10 microM), were unable to reverse the inhibitory influence 1 nM 17beta-estradiol had on the agonist-mediated contractile responses. Similarly, the androgen receptor antagonists, flutamide (10 microM) and cyproterone acetate (10 microM), failed to affect the potentiating activities of 1 nM testosterone. The alteration in vasoconstrictive responses observed following acute exposure to either 1 nM 17beta-estradiol and 1 nM testosterone were apparent even in the presence of the protein synthesis inhibitor cycloheximide (10 microM) and the transcription inhibitor actinomycin D (10 microM). 6. In conclusion, we report a unique type of sex hormone action on the coronary vasculature. These events occur at low nanomolar concentrations of 17beta-estradiol and testosterone, are insensitive to conventional sex hormone receptor antagonists, are not blocked by de novo protein synthesis inhibitors and have rapid time-courses that are uncharacteristic of classical genomic activities.