Pharmacological characterization of the mechanisms involved in the vasorelaxation induced by progesterone and 17β-estradiol on isolated canine basilar and internal carotid arteries

Calcium signaling in endothelial and vascular smooth muscle cells: sex differences and the influence of estrogens and androgens

Calcium signaling in vascular endothelial cells (ECs) and smooth muscle cells (VSMCs) is essential for the regulation of vascular tone. However, the changes to intracellular Ca2+ concentrations are often influenced by sex differences. Furthermore, a large body of evidence shows that sex hormone imbalance leads to dysregulation of Ca2+ signaling and this is a key factor in the pathogenesis of cardiovascular diseases. In this review, the effects of estrogens and androgens on vascular calcium-handling proteins are discussed, with emphasis on the associated genomic or nongenomic molecular mechanisms. The experimental models from which data were collected were also considered. The review highlights 1) in female ECs, transient receptor potential vanilloid 4 (TRPV4) and mitochondrial Ca2+ uniporter (MCU) enhance Ca2+-dependent nitric oxide (NO) generation. In males, only transient receptor potential canonical 3 (TRPC3) plays a fundamental role in this effect. 2) Female VSMCs have lower cytosolic Ca2+ levels than males due to differences in the activity and expression of stromal interaction molecule 1 (STIM1), calcium release-activated calcium modulator 1 (Orai1), calcium voltage-gated channel subunit-α1C (CaV1.2), Na+-K+-2Cl- symporter (NKCC1), and the Na+/K+-ATPase. 3) When compared with androgens, the influence of estrogens on Ca2+ homeostasis, vascular tone, and incidence of vascular disease is better documented. 4) Many studies use supraphysiological concentrations of sex hormones, which may limit the physiological relevance of outcomes. 5) Sex-dependent differences in Ca2+ signaling mean both sexes ought to be included in experimental design.

Non-genomic Effect of Estradiol on the Neurovascular Unit and Possible Involvement in the Cerebral Vascular Accident

Cerebrovascular diseases, such as ischemic cerebral vascular accident (CVA), are responsible for causing high rates of morbidity, mortality, and disability in the population. The neurovascular unit (NVU) during and after ischemic CVA plays crucial roles in cell regulation and preservation, the immune and inflammatory response, and cell and/or tissue survival and repair. Cellular responses to 17β-estradiol (E2) can be triggered by two mechanisms: one called classical or genomic, which is due to the activation of the "classical" nuclear estrogen receptors α (ERα) and β (ERβ), and the non-genomic or rapid mechanism, which is due to the activation of the G protein-coupled estrogen receptor 1 (GPER) that is located in the plasma membrane and some in intracellular membranes, such as in the Golgi apparatus and endoplasmic reticulum. Nuclear receptors can regulate gene expression and cellular functions. On the contrary, activating the GPER by E2 and/or its G-1 agonist triggers several rapid cell signaling pathways. Therefore, E2 or its G-1 agonist, by mediating GPER activation and/or expression, can influence several NVU cell types. Most studies argue that the activation of the GPER may be used as a potential therapeutic target in various pathologies, such as CVA. Thus, with this review, we aimed to summarize the existing literature on the role of GPER mediated by E2 and/or its agonist G-1 in the physiology and pathophysiology of NVU.

Effects of xenobiotics on CYP1 enzyme-mediated biotransformation and bioactivation of estradiol

Endogenous estradiol (E2) exerts diverse physiological and pharmacological activities, commonly used for hormone replacement therapy. However, prolonged and excessive exposure to E2 potentially increases estrogenic cancer risk. Reportedly, CYP1 enzyme-mediated biotransformation of E2 is largely concerned with its balance between detoxification and carcinogenic pathways. Among the three key CYP1 enzymes (CYP1A1, CYP1A2, and CYP1B1), CYP1A1 and CYP1A2 mainly catalyze the formation of nontoxic 2-hydroxyestradiol (2-OH-E2), while CYP1B1 specifically catalyzes the formation of genotoxic 4-hydroxyestradiol (4-OH-E2). 4-OH-E2 can be further metabolized to electrophilic quinone intermediates accompanied by the generation of reactive oxygen species (ROS), triggering DNA damage. Since abnormal alterations in CYP1 activities can greatly affect the bioactivation process of E2, regulatory effects of xenobiotics on CYP1s are essential for E2-associated cancer development. To date, thousands of natural and synthetic compounds have been found to show potential inhibition and/or induction actions on the three CYP1 members. Generally, these chemicals share similar planar polycyclic skeletons, the structural motifs and substituent groups of which are important for their inhibitory/inductive efficiency and selectivity toward CYP1 enzymes. This review comprehensively summarizes these known inhibitors and/or inductors of E2-metabolizing CYP1s based on chemical categories and discusses their structure-activity relationships, which would contribute to better understanding of the correlation between xenobiotic-regulated CYP1 activities and estrogenic cancer susceptibility.

Pathophysiology and risk factors of peripartum cardiomyopathy

Peripartum cardiomyopathy (PPCM) is a potentially fatal form of idiopathic heart failure with variable prevalence across different countries and ethnic groups. The cause of PPCM is unclear, but environmental and genetic factors and pregnancy-associated conditions such as pre-eclampsia can contribute to the development of PPCM. Furthermore, animal studies have shown that impaired vascular and metabolic function might be central to the development of PPCM. A better understanding of the pathogenic mechanisms involved in the development of PPCM is necessary to establish new therapies that can improve the outcomes of patients with PPCM. Pregnancy hormones tightly regulate a plethora of maternal adaptive responses, including haemodynamic, structural and metabolic changes in the cardiovascular system. In patients with PPCM, the peripartum period is associated with profound and rapid hormonal fluctuations that result in a brief period of disrupted cardiovascular (metabolic) homeostasis prone to secondary perturbations. In this Review, we discuss the latest studies on the potential pathophysiological mechanisms of and risk factors for PPCM, with a focus on maternal cardiovascular changes associated with pregnancy. We provide an updated framework to further our understanding of PPCM pathogenesis, which might lead to an improvement in disease definition.

The regional effect of serum hormone levels on cerebral blood flow in healthy nonpregnant women

Sex hormones estrogen (EST) and progesterone (PROG) have received increased attention for their important physiological action outside of reproduction. While studies have shown that EST and PROG have significant impacts on brain function, their impact on the cerebrovascular system in humans remains largely unknown. To address this, we used a multi-modal magnetic resonance imaging (MRI) approach to investigate the link between serum hormones in the follicular phase and luteal phase of the menstrual cycle (MC) with measures of cerebrovascular function (cerebral blood flow [CBF]) and structure (intracranial artery diameter). Fourteen naturally cycling women were recruited and assessed at two-time points of their MC. CBF was derived from pseudo-continuous arterial spin labeling while diameters of the internal carotid and basilar artery was assessed using time of flight magnetic resonance angiography, blood samples were performed after the MRI. Results show that PROG and EST had opposing and spatially distinct effects on CBF: PROG correlated negatively with CBF in anterior brain regions (r = -.86, p < .01), while EST correlations were positive, yet weak and most prominent in posterior areas (r = .78, p < .01). No significant correlations between either hormone or intracranial artery diameter were observed. These results show that EST and PROG have opposing and regionally distinct effects on CBF and that this relationship is likely not due to interactions with large intracranial arteries. Considering that CBF in healthy women appears tightly linked to their current hormonal state, future studies should consider assessing MC-related hormone fluctuations in the design of functional MRI studies in this population.

Role of pregnancy hormones and hormonal interaction on the maternal cardiovascular system: a literature review

Hormones have a vital duty in the conservation of physiological cardiovascular function during pregnancy. Alterations in oestrogen, progesterone and prolactin levels are associated with changes in the cardiovascular system to support the growing foetus and counteract pregnancy stresses. Pregnancy hormones are, however, also linked to numerous pathophysiological outcomes on the cardiovascular system. The expression and effects of the three main pregnancy hormones (oestrogen, prolactin and progesterone) vary depending on the gestation period. However, the reaction of a target cell also depends on the abundance of hormone receptors and impacts put forth by other hormones. Hormonal interaction may be synergistic, antagonistic or permissive. It is crucial to explore the cross talk of pregnancy hormones during gestation, as this may have a greater impact on the overall changes to the cardiovascular system.

Chemoreflex function and brain blood flow during upright posture in men and women

Orthostatic intolerance is more common in women than men, and some studies have found that women in the early follicular (EF) phase of the menstrual cycle experience the greatest feelings of lightheadedness. Chemoreflex function while supine or upright was investigated to determine the potential contribution of ventilatory control to these phenomena. Men (n = 13) and women (n = 14) were tested while supine and 70° upright (head-up tilt [HUT]) and given: (1) normoxia or (2) hypercapnia (5% CO₂ ). Women were tested during the EF phase (days 2-5) and the midluteal phase (ML; days 18-24). During HUT, all groups reduced cerebrovascular resistance index (men: 1.45 ± 0.08 to 1.42 ± 0.07 mmHg/(cm·sec), EF: 1.38 ± 0.11 to 1.26 ± 0.10 mmHg/(cm·sec), ML: 1.25 ± 0.07 to 1.09 ± 0.07 mmHg/(cm·sec); P ≤ 0.019); however, only men increased ventilation (men: 11.99 ± 0.65 to 13.24 ± 0.83 L/min; P < 0.01). In response to hypercapnia in the supine position, men had a smaller increase of diastolic middle cerebral artery velocity compared to women in the ML phase (men: +9.1 ± 2.0 cm/sec, ML: +15.7 ± 3.1 cm/sec, P = 0.039). During hypercapnia in HUT (compared to hypercapnia while supine), all groups had an augmented increase of ventilation (men: +7.46 ± 1.34 vs. +5.84 ± 1.09 L/min, EF: +6.71 ± 0.83 vs. +5.48 ± 0.66 L/min, ML: +7.99 ± 1.13 vs. +5.65 ± 0.81 L/min; P ≤ 0.028), suggesting that all groups experienced augmentation of the CO₂ chemoreflex; however, only men had an augmented increase of mean arterial pressure (+0.10 ± 0.58 to +4.71 ± 0.87 mmHg; P ≤ 0.017). Our results indicate that men have different ventilatory responses to upright tilt compared to women, and that the CO₂ chemoreflex response is enhanced in upright posture in both sexes. Furthermore, sexually dimorphic blood pressure responses to this chemoreflex enhancement are evident.

Sex differences in the vascular function and related mechanisms: role of 17β-estradiol

The incidence of cardiovascular disease (CVD) is lower in premenopausal women but increases with age and menopause compared with similarly aged men. Based on the prevalence of CVD in postmenopausal women, sex hormone-dependent mechanisms have been postulated to be the primary factors responsible for the protection from CVD in premenopausal women. Recent Women’s Health Initiative studies, Cochrane Review studies, the Early Versus Late Intervention Trial with Estradiol Study, and the Kronos Early Estrogen Prevention Study have suggested that beneficial effects of hormone replacement therapy (HRT) are seen in women of <60 yr of age and if initiated within <10 yr of menopause. In contrast, the beneficial effects of HRT are not seen in women of >60 yr of age and if commenced after 10 yr of menopause. The higher incidence of CVD and the failure of HRT in postmenopausal aged women could be partly associated with fundamental differences in the vascular structure and function between men and women and in between pre- and postmenopausal women, respectively. In this regard, previous studies from human and animal studies have identified several sex differences in vascular function and associated mechanisms. The female sex hormone 17β-estradiol regulates the majority of these mechanisms. In this review, we summarize the sex differences in vascular structure, myogenic properties, endothelium-dependent and -independent mechanisms, and the role of 17β-estradiol in the regulation of vascular function.

Neuroprotection by progesterone after transient cerebral ischemia in stroke-prone spontaneously hypertensive rats

We investigated the neuroprotective effects of progesterone (P4) treatment in stroke-prone spontaneously hypertensive rats (SHRSPs) given 60-min transient middle cerebral artery occlusion (tMCAO). The treatment groups were: (1) Wistar-Kyoto (normotensive sham), (2) SHRSP (hypertensive sham), (3) tMCAO SHRSPs (SHRSP+tMCAO), and (4) SHRSP+tMCAO+P4. P4 (8mg/kg) was administered 1h after occlusion and then daily for 14days. We measured cerebral infarction volume, blood pressure and body weight. Behavioral outcomes were analyzed at post-stroke days 3, 9, and 14. To assess morphological protection we measured activation of microglia and astrocytes, oxidative stress, apoptosis, expression of vascular endothelial growth factor (VEGF), an angiogenic marker, and IL-1β, a marker of inflammation, on day 14 post-stroke. There was no effect of P4 on body weight or systolic blood pressure compared to the SHRSP+tMCAO group. However, grip strength and sensory neglect measures in the P4 group were improved compared to SHRSP+tMCAO. In addition, significantly larger infarct volumes were seen in the SHRSP+tMCAO group compared to SHRSP+tMCAO+P4. Increased markers of the injury cascade such as macrophages, activated astrocytes, superoxide anion and apoptotic cells observed in the SHRSP+tMCAO group were significantly decreased by P4. We conclude that, despite hypertensive comorbidity, P4 improves functional outcomes and attenuates stroke infarct in hypertensive rats by reducing superoxide anion expression and by decreasing inflammation and neuronal apoptosis.

Estrogen receptor subtypes mediate distinct microvascular dilation and reduction in [Ca2+]I in mesenteric microvessels of female rat

Estrogen interacts with estrogen receptors (ERs) to induce vasodilation, but the ER subtype and post-ER relaxation pathways are unclear. We tested if ER subtypes mediate distinct vasodilator and intracellular free Ca(2+) concentration ([Ca(2+)]i) responses via specific relaxation pathways in the endothelium and vascular smooth muscle (VSM). Pressurized mesenteric microvessels from female Sprague-Dawley rats were loaded with fura-2, and the changes in diameter and [Ca(2+)]i in response to 17β-estradiol (E2) (all ERs), PPT (4,4',4''-[4-propyl-(1H)-pyrazole-1,3,5-triyl]-tris-phenol) (ERα), diarylpropionitrile (DPN) (ERβ), and G1 [(±)-1-[(3aR*,4S*,9bS*)-4-(6-bromo-1,3-benzodioxol-5-yl)-3a,4,5,9b-tetrahydro:3H-cyclopenta(c)quinolin-8-yl]-ethanon] (GPR30) were measured. In microvessels preconstricted with phenylephrine, ER agonists caused relaxation and decrease in [Ca(2+)]i that were with E2 = PPT > DPN > G1, suggesting that E2-induced vasodilation involves ERα > ERβ > GPR30. Acetylcholine caused vasodilation and decreased [Ca(2+)]i, which were abolished by endothelium removal or treatment with the nitric oxide synthase blocker Nω-nitro-l-arginine methyl ester (L-NAME) and the K(+) channel blockers tetraethylammonium (nonspecific) or apamin (small conductance Ca(2+)-activated K(+) channel) plus TRAM-34 (1-[(2-chlorophenyl)diphenylmethyl]-1H-pyrazole) (intermediate conductance Ca(2+)-activated K(+) channel), suggesting endothelium-derived hyperpolarizing factor-dependent activation of KCa channels. E2-, PPT-, DPN-, and G1-induced vasodilation and decreased [Ca(2+)]i were not blocked by L-NAME, TEA, apamin plus TRAM-34, iberiotoxin (large conductance Ca(2+)- and voltage-activated K(+) channel), 4-aminopyridine (voltage-dependent K(+) channel), glibenclamide (ATP-sensitive K(+) channel), or endothelium removal, suggesting an endothelium- and K(+) channel-independent mechanism. In endothelium-denuded vessels preconstricted with phenylephrine, high KCl, or the Ca(2+) channel activator Bay K 8644 (1,4-dihydro-2,6-dimethyl-5-nitro-4-[2-(trifluoromethyl)phenyl]-3-pyridinecarboxylic acid methyl ester), ER agonist-induced relaxation and decreased [Ca(2+)]i were with E2 = PPT > DPN > G1 and not inhibited by the guanylate cyclase inhibitor ODQ [1H-(1,2,4)oxadiazolo(4,3-a)quinoxalin-1-one], and showed a similar relationship between decreased [Ca(2+)]i and vasorelaxation, supporting direct effects on Ca(2+) entry in VSM. Immunohistochemistry revealed ERα, ERβ, and GPR30 mainly in the vessel media and VSM. Thus, in mesenteric microvessels, ER subtypes mediate distinct vasodilation and decreased [Ca(2+)]i (ERα > ERβ > GPR30) through endothelium- and K(+) channel-independent inhibition of Ca(2+) entry mechanisms of VSM contraction.