Characterization of the cardiac renin angiotensin system in oophorectomized and estrogen-replete mRen2.Lewis rats

Poor sleep quality was associated with increased plasma aldosterone concentration in community dwellers, a cross-sectional study

Sleep is implicated in circulating aldosterone, whereas effects of overall sleep quality are not characterized. Therefore, we explored relationship of sleep quality with plasma aldosterone concentration (PAC) in general population. We evaluated sleep quality using Pittsburgh sleep quality index (PSQI) and measured PAC in adults cross-sectionally. We divided participants into very good, fairly good, fairly bad and very bad sleepers, compared PAC and log-PAC, and applied linear regression to examine association of PSQI score with log-PAC, in total, gender- and age-stratified (young, middle-aged and old) participants. Sensitivity analysis were performed by excluding hypertension, sleep disordered breathing (SDB), or both. Among 29,499 participants, PAC showed significant increase from very good to very bad sleepers in total (14.3 vs. 14.4 vs. 14.7 vs. 15.8ng/dL), and in male participants (13.1 vs. 13.6 vs. 14.1 vs. 14.9ng/dL), consistent in the young and the middle-aged (P for all < 0.001) and in log PAC of total, in male and in different age groups (P for trend < 0.001). PSQI score showed significant positive association with log-PAC in total (B, 95%CI: 0.007, 0.003-0.010, P < 0.001) in male participants (0.013, 0.008-0.018, P < 0.001), consistent in the young and the middle-aged and in adjusted models. In female, PSQI score showed significant positive association with log-PAC in the old-aged. Sensitivity analysis yielded consistent observation with main analysis. Poor sleep quality is associated with elevated PAC, in young and middle-aged male and in elder female, independent of SDB and hypertension, indicating potential involvement of sleep quality on regulation of circulating aldosterone.

The role of sex hormones in aldosterone biosynthesis and their potential impact on its mineralocorticoid receptor

Blood pressure (BP) regulation is a complex process involving various hormones, including aldosterone and its mineralocorticoid receptor. Mineralocorticoid receptor is expressed in several tissues, including the kidney, and plays a crucial role in regulating BP by controlling the sodium and water balance. During different stages of life, hormonal changes can affect mineralocorticoid receptor activity and aldosterone levels, leading to changes in BP. Increasing evidence suggests that sex steroids modulate aldosterone levels. Estrogens, particularly estradiol, mediate aldosterone biosynthesis by activating classical estrogen receptors and the G protein-coupled receptor. Progesterone acts as an anti-mineralocorticoid by inhibiting the binding of aldosterone to the mineralocorticoid receptor. Moreover, progesterone inhibits aldosterone synthase enzymes. The effect of testosterone on aldosterone synthesis is still a subject of debate. However, certain studies show that testosterone downregulates the mRNA levels of aldosterone synthase, leading to decreased plasma aldosterone levels.

Impact of RAAS Receptors and Membrane-Bound Transporter System in the Left Ventricle during the Long-Term Control of Hypertension

The Renin-Angiotensin-Aldosterone System (RAAS) has been implicated in systemic and neurogenic hypertension. The infusion of RAAS inhibitors blunted arterial pressure and efficacy of use-dependent synaptic transmission in sympathetic ganglia. The current investigation aims to elucidate the impact of RAAS-mediated receptors on left ventricular cardiomyocytes and the role of the sarcolemma-bound carrier system in the heart of the hypertensive transgene model. A significant increase in mRNA and the protein expression for angiotensin II (AngII) receptor subtype-1 (AT1R) was observed in (mREN2)27 transgenic compared to the normotensive rodents. Concurrently, there was an upregulation in AT1R and a downregulation in the MAS1 proto-oncogene protein receptor as well as the AngII subtype-2 receptor in hypertensive rodents. There were modifications in the expressions of sarcolemma Na+-K+-ATPase, Na+-Ca2+ exchanger, and Sarcoendoplasmic Reticulum Calcium ATPase in the transgenic hypertensive model. These observations suggest chronic RAAS activation led to a shift in receptor balance favoring augmented cardiac contractility and disruption in calcium handling through modifications of membrane-bound carrier proteins and blood pressure. The study provides insight into mechanisms underlying RAAS-mediated cardiac dysfunction and highlights the potential value of targeting the protective arm of AngII in hypertension.

Age and sex mediated effects of estrogen and Β3-adrenergic receptor on cardiovascular pathophysiology

Sex differences are consistently identified in determining the prevalence, manifestation, and response to therapies in several systemic disorders, including those affecting the cardiovascular (CV), skeletal muscle, and nervous system. Interestingly, such differences are often more noticeable as we age. For example, premenopausal women experience a lower risk of CV disease than men of the same age. While at an advanced age, with menopause, the risk of cardiovascular diseases and adverse outcomes increases exponentially in women, exceeding that of men. However, this effect appears to be reversed in diseases such as pulmonary hypertension, where women are up to seven times more likely than men to develop an idiopathic form of the disease with symptoms developing ten years earlier than their male counterparts. Explaining this is a complex question. However, several factors and mechanisms have been identified in recent decades, including a role for sex hormones, particularly estrogens and their related receptors. Furthermore, an emerging role in these sex differences has also been suggested for β-adrenergic receptors (βARs), which are essential regulators of mammalian physiology. It has in fact been shown that βARs interact with estrogen receptors (ER), providing further demonstration of their involvement in determining sexual differences. Based on these premises, this review article focused on the β3AR subtype, which shows important activities in adipose tissue but with new and interesting roles in regulating the function of cardiomyocytes and vascular cells. In detail, we examined how β3AR and ER signaling are intertwined and whether there would be sex- and age-dependent specific effects of these receptor systems.

Estrogen-mediated mechanisms in hypertension and other cardiovascular diseases

Cardiovascular disease (CVD) is the leading cause of death globally for men and women. Premenopausal women have a lower incidence of hypertension and other cardiovascular events than men of the same age, but diminished sex differences after menopause implicates 17-beta-estradiol (E2) as a protective agent. The cardioprotective effects of E2 are mediated by nuclear estrogen receptors (ERα and ERβ) and a G protein-coupled estrogen receptor (GPER). This review summarizes both established as well as emerging estrogen-mediated mechanisms that underlie sex differences in the vasculature during hypertension and CVD. In addition, remaining knowledge gaps inherent in the association of sex differences and E2 are identified, which may guide future clinical trials and experimental studies in this field.

Hypertension after the Menopause: What Can We Learn from Experimental Studies?

Hypertension is the most prevalent cardiovascular disease of the adult population and is closely associated with serious cardiovascular events. The burden of hypertension with respect to vascular and other organ damage is greater in women. These sex differences are not fully understood. The unique feature in women is their transition to menopause accompanied by profound hormonal changes that affect the vasculature that are also associated with changes of blood pressure. Results from studies of hormone replacement therapy and its effects on the cardiovascular system are controversial, and the timing of treatment after menopause seems to be important. Therefore, revealing potential sex- and sex hormone-dependent pathophysiological mechanisms of hypertension in experimental studies could provide valuable information for better treatment of hypertension and vascular impairment, especially in postmenopausal women. The experimental rat models subjected to ovariectomy mimicking menopause could be useful tools for studying the mechanisms of blood pressure regulation after menopause and during subsequent therapy.

Heart Failure in Menopause: Treatment and New Approaches

Aging is an important risk factor for the development of heart failure (HF) and half of patients with HF have preserved ejection fraction (HFpEF) which is more common in elderly women. In general, sex differences that lead to discrepancies in risk factors and to the development of cardiovascular disease (CVD) have been attributed to the reduced level of circulating estrogen during menopause. Estrogen receptors adaptively modulate fibrotic, apoptotic, inflammatory processes and calcium homeostasis, factors that are directly involved in the HFpEF. Therefore, during menopause, estrogen depletion reduces the cardioprotection. Preclinical menopause models demonstrated that several signaling pathways and organ systems are closely involved in the development of HFpEF, including dysregulation of the renin-angiotensin system (RAS), chronic inflammatory process and alteration in the sympathetic nervous system. Thus, this review explores thealterations observed in the condition of HFpEF induced by menopause and the therapeutic targets with potential to interfere with the disease progress.

Lipids and diastolic dysfunction: Recent evidence and findings

AIM

Diastolic dysfunction is the decreased flexibility of the left ventricle due to the impaired ability of the myocardium to relax and plays an important role in the pathogenesis of heart failure. Lipid metabolism is a well-known contributor to cardiac conditions, including ventricular function. In this article, we aimed to review the literature addressing the connections between lipids, their storage, and metabolism with left ventricular diastolic dysfunction.

DATA SYNTHESIS

We searched Google scholar, Pubmed, Embase and Researchgate for our keywords: "Diastolic function", "Fat" and "Lipid profile". Initially, 250 articles were selected by title and 84 of them were chosen as most relevant and directly reviewed.

CONCLUSIONS

Alterations of lipid metabolism in cardiac muscle and cardiac lipid content can occur in many conditions, including consumption of a high-fat diet, obesity, metabolic syndrome, and non-alcoholic fatty liver disease (NAFLD). These conditions induce alterations in myocardial lipid metabolism, increase myocardial fat content and epicardial fat thickness and increase inflammation and oxidative stress which ultimately lead to cardiac lipotoxicity and diastolic dysfunction. The effects of lipids on diastolic function can differ based on gender. Lipid profile and metabolism are as important in the pathogenesis of diastolic dysfunction as they are in other cardiovascular disorders. A more careful look at cardiac lipid metabolism in molecular, histological and gross levels results in more precise understanding of its role in myocardial function and leads to development of potential treatments for diastolic dysfunction.

Amplifying effect of chronic lisinopril therapy on diastolic function and the angiotensin-(1-7) Axis by the G1 agonist in ovariectomized spontaneously hypertensive rats

G protein-coupled estrogen receptor (GPER) activation by G1 attenuates diastolic dysfunction from estrogen loss, which may be partly due to suppression of angiotensin II pathological actions. We aimed to determine the independent effects of 8 weeks of G1 (100 µg/kg/d, subcutaneous pellet), ACE-inhibition (ACEi; lisinopril 10 mg/kg, drinking water), or combination therapy versus vehicle in the ovariectomized (OVX) spontaneously hypertensive rat (SHR) on cardiac function and morphometrics (echocardiography), serum equilibrium of angiotensins (mass spectroscopy) and cardiac components of the RAS (Western blotting). G1 alone and when combined with ACEi enhanced myocardial relaxation (é: 30 and 17%) and diastolic wall strain (DWS: 76 and 68%) while reducing relative wall thickness (RWT: 20 and 33%) and filling pressures (E/é: 30 and 37%). Cardiac expression levels of Mas receptor (Mas-R) and ACE2 also increased in the presence of G1. Strong antihypertensive effects of lisinopril monotherapy were associated with reductions in RWT, collagen deposition and E/é without overtly altering é or DWS. Chronic ACEi also increased cardiac levels of Mas-R and AT₁-R and tilted the circulating RAS toward the formation of Ang-(1-7), which was amplified in the presence of G1. In vitro studies further revealed that an inhibitor to prolyl endopeptidase (PEP), but not to neprilysin, significantly reduced serum Ang-(1-7) levels in G1-treated rats, suggesting that G1 might be increasing Ang-(1-7) formation via PEP. We conclude that activating GPER with G1 augments components of the cardiac RAS and improves diastolic function without lowering blood pressure, and that lisinopril-induced blood pressure control and cardiac alterations in OVX SHR are permissive in facilitating G1 to augment Ang-(1-7) in serum, thereby strengthening its cardioprotective benefits.

The effect of estrogen in coronavirus disease 2019

The outcomes of coronavirus disease 2019 (COVID-19) vary between men and women. Some statistical reports have shown that men have a higher risk of developing COVID-19 and suffer from worse outcomes than females. Although there are many factors that can explain the high prevalence of COVID-19 in men, such as lifestyle habits and the different profile of comorbidities among sexes, the distinctions between male and female immune systems cannot be ignored. It has been sufficiently shown that sex differences have a critical influence on the shaping of immune response, which then leads to different pathogenesis in infectious diseases. Compared with males, females typically have a more effective innate and adaptive immune response to viral infections in COVID-19. What's more, there is a growing body of evidence showing that estrogen exerts an effect on the regulation of immune response. This article examines the effect and mechanism of estrogen on COVID-19.

G protein-coupled estrogen receptor 1: a novel target to treat cardiovascular disease in a sex-specific manner?

As an agonist of the classical nuclear receptors, estrogen receptor-α and -β (NR3A1/2), estrogen has been assumed to inhibit the development of cardiovascular disease in premenopausal women. Indeed, reduced levels of estrogen after menopause are believed to contribute to accelerated morbidity and mortality rates in women. However, estrogen replacement therapy has variable effects on cardiovascular risk in postmenopausal women, including increased serious adverse events. Interestingly, preclinical studies have shown that selective activation of the novel membrane-associated G protein-coupled estrogen receptor, GPER, can promote cardiovascular protection. These benefits are more evident in ovariectomised than intact females or in males. It is therefore possible that selective targeting of the GPER in postmenopausal women could provide cardiovascular protection with fewer adverse effects that are caused by conventional 'receptor non-specific' estrogen replacement therapy. This review describes new data regarding the merits of targeting GPER to treat cardiovascular disease with a focus on sex differences.

Mineralocorticoid receptor blockade with finerenone improves heart function and exercise capacity in ovariectomized mice

AIMS

In post-menopausal women, incidence of heart failure with preserved ejection fraction is higher than in men. Hormonal replacement therapies did not demonstrate benefits. We tested whether the non-steroidal mineralocorticoid receptor antagonist finerenone limits the progression of heart failure in ovariectomized (OVX) mice with metabolic disorders.

METHODS AND RESULTS

Ovariectomy was performed in 4-month-old mice, treated or not at 7 months old for 1 month with finerenone (Fine) 1 mg/kg/day. Left ventricular (LV) cardiac and coronary endothelial functions were assessed by echocardiography, catheterization, and myography. Blood pressure was measured by plethysmography. Insulin and glucose tolerance tests were performed. Exercise capacity and spontaneous activity were measured on treadmill and in combined indirect calorimetric cages equipped with voluntary running wheel. OVX mice presented LV diastolic dysfunction without modification of ejection fraction compared with controls (CTL), whereas finerenone improved LV filling pressure (LV end-diastolic pressure, mmHg: CTL 3.48 ± 0.41, OVX 6.17 ± 0.30**, OVX + Fine 3.65 ± 0.55† , **P < 0.01 vs. CTL, † P < 0.05 vs. OVX) and compliance (LV end-diastolic pressure-volume relation, mmHg/RVU: CTL 1.65 ± 0.42, OVX 4.77 ± 0.37***, OVX + Fine 2.87 ± 0.26†† , ***P < 0.001 vs. CTL, †† P < 0.01 vs. OVX). Acetylcholine-induced endothelial-dependent relaxation of coronary arteries was impaired in ovariectomized mice and improved by finerenone (relaxation, %: CTL 86 ± 8, OVX 38 ± 3**, OVX + Fine 83 ± 7†† , **P < 0.01 vs. CTL, †† P < 0.01 vs. OVX). Finerenone improved decreased ATP production by subsarcolemmal mitochondria after ovariectomy. Weight gain, increased blood pressure, and decreased insulin and glucose tolerance in OVX mice were improved by finerenone. The exercise capacity at race was diminished in untreated OVX mice only. Spontaneous activity measurements in ovariectomized mice showed decreased horizontal movements, reduced time spent in a running wheel, and reduced VO2 and VCO2 , all parameters improved by finerenone.

CONCLUSIONS

Finerenone improved cardiovascular dysfunction and exercise capacity after ovariectomy-induced LV diastolic dysfunction with preserved ejection fraction.

Sex and COVID-19: A Protective Role for Reproductive Steroids

Evidence shows coronavirus disease 2019 (COVID-19)-induced symptom severity and mortality is more frequent in men than in women, suggesting sex steroids may play a protective role. Female reproductive steroids, estrogen and progesterone, and its metabolite allopregnanolone, are anti-inflammatory, reshape competence of immune cells, stimulate antibody production, and promote proliferation and repair of respiratory epithelial cells, suggesting they may protect against COVID-19 symptoms.

Overexpression of angiotensin converting enzyme 2 reduces anxiety-like behavior in female mice

Accumulating evidence has revealed an intricate role for the renin-angiotensin system (RAS) in the progression or alleviation of stress-related disorders. Along these lines, the 'pro-stress' actions of angiotensin-II (Ang-II) are largely thought to be mediated by the angiotensin type-1a receptor (AT1aR). On the other hand, a counter regulatory limb of the RAS that depends on the conversion of Ang-II to angiotensin-(1-7) by angiotensin-converting enzyme 2 (ACE2) has been postulated to exert stress-dampening actions. We have previously found that augmenting ACE2 activity is potently anxiolytic and blunts stress-induced activation of the hypothalamic-pituitary-adrenal (HPA) axis in male mice. Whether increasing ACE2 activity also relieves stress and anxiety in females has not yet been determined. Consequently, this series of experiments tests the hypothesis that augmenting ACE2 expression is anxiolytic and dampens the activity of the HPA axis in female mice. Using the Cre-LoxP system, we generated female mice that were homo-, heterozygous or wild-type for a mutated allele resulting in ubiquitous overexpression of ACE2. Next, we used qPCR to determine that levels of ACE2 mRNA isolated from central and peripheral tissues was dependent on genotype. That is, mice homo- and heterozygous for the ACE2 overexpression had significantly greater levels of ACE2 mRNA relative to littermate matched wild-type controls. Interestingly, anxiety-like behavior as determined by the elevated plus maze, light-dark box and novelty-induced hypophagia tests was also affected by genotype. Specifically, ACE2 overexpression significantly decreased anxiety-like behavior in paradigms dependent on approach-avoidance conflict and novelty; however, locomotor activity was similar amongst the genotypes. Final experiments measured plasma corticosterone to evaluate whether increasing ACE2 alters basal and/or stress-induced HPA axis activity. In contrast to what was previously found in males, increasing ACE2 expression had no effect on plasma corticosterone under basal conditions or subsequent to an acute restraint challenge. Collectively, these results suggest that increasing ACE2 expression potently elicits anxiolysis in female mice without altering HPA axis activity.

Differential Expression of the Angiotensin-(1-12)/Chymase Axis in Human Atrial Tissue

BACKGROUND

Heart chymase rather than angiotensin (Ang)-converting enzyme has higher specificity for Ang I conversion into Ang II in humans. A new pathway for direct cardiac Ang II generation has been revealed through the demonstration that Ang-(1-12) is cleaved by chymase to generate Ang II directly. Herein, we address whether Ang-(1-12), chymase messenger RNA (mRNA), and activity levels can be differentiated in human atrial tissue from normal and diseased hearts and if these measures associate with various pathologic heart conditions.

MATERIALS AND METHODS

Atrial appendages were collected from 11 nonfailing donor hearts and 111 patients undergoing heart surgery for the correction of valvular heart disease, resistant atrial fibrillation, or ischemic heart disease. Chymase mRNA was analyzed by real-time polymerase chain reaction and enzymatic activity by high-performance liquid chromatography using Ang-(1-12) as the substrate. Ang-(1-12) levels were determined by immunohistochemical staining.

RESULTS

Chymase gene transcripts, chymase activity, and immunoreactive Ang-(1-12) expression levels were higher in left atrial tissue compared with right atrial tissue, irrespective of cardiac disease. In addition, left atrial chymase mRNA expression was significantly higher in stroke versus nonstroke patients and in cardiac surgery patients who had a history of postoperative atrial fibrillation versus nonatrial fibrillation. Correlation analysis showed that left atrial chymase mRNA was positively related to left atrial enlargement, as determined by echocardiography.

CONCLUSIONS

As Ang-(1-12) expression and chymase gene transcripts and enzymatic activity levels were positively linked to left atrial size in patients with left ventricular heart disease, an important alternate Ang II forming pathway, via Ang-(1-12) and chymase, in maladaptive atrial and ventricular remodeling in humans is uncovered.

Is Sex a Determinant of COVID-19 Infection? Truth or Myth?

Purpose of Review

Angiotensin-converting enzyme 2 (ACE2), a specific high-affinity angiotensin II-hydrolytic enzyme, is the vector that facilitates cellular entry of SARS-CoV-1 and the novel SARS-CoV-2 coronavirus. SARS-CoV-2, which crossed species barriers to infect humans, is highly contagious and associated with high lethality due to multi-organ failure, mostly in older patients with other co-morbidities.

Recent Findings

Accumulating clinical evidence demonstrates that the intensity of the infection and its complications are more prominent in men. It has been postulated that potential functional modulation of ACE2 by estrogen may explain the sex difference in morbidity and mortality.

Summary

We review here the evidence regarding the role of estrogenic hormones in ACE2 expression and regulation, with the intent of bringing to the forefront potential mechanisms that may explain sex differences in SARS-CoV-2 infection and COVID-19 outcomes, assist in management of COVID-19, and uncover new therapeutic strategies.

Multifunctional Role of Chymase in Acute and Chronic Tissue Injury and Remodeling

Chymase is the most efficient Ang II (angiotensin II)-forming enzyme in the human body and has been implicated in a wide variety of human diseases that also implicate its many other protease actions. Largely thought to be the product of mast cells, the identification of other cellular sources including cardiac fibroblasts and vascular endothelial cells demonstrates a more widely dispersed production and distribution system in various tissues. Furthermore, newly emerging evidence for its intracellular presence in cardiomyocytes and smooth muscle cells opens an entirely new compartment of chymase-mediated actions that were previously thought to be limited to the extracellular space. This review illustrates how these multiple chymase-mediated mechanisms of action can explain the residual risk in clinical trials of cardiovascular disease using conventional renin-angiotensin system blockade.

Estrogen modulates the differential expression of cardiac myocyte chymase isoforms and diastolic function

Chymases, a family of serine proteases with chymotryptic activity, play a significant role in cardiac angiotensin II (Ang II) formation from its substrate Ang-(1-12) in both human and rodent models. No studies, to date, have assessed the differences in enzymatic activity among these isoforms in Ang II formation, particularly in the cardiomyocyte (CM). Using PCR and DNA sequencing, we demonstrated that MCP-1, MCP-2, MCP-4, and MCP-5 mRNAs are expressed in the CM of both spontaneously hypertensive rats (SHR) and normotensive Wistar-Kyoto rats (WKY). While rMCP-1 and rMCP-5 gene transcripts were higher than that of other isoforms in both rat strains, WKY CM exhibits higher levels of rMCP-1 and rMCP-5 mRNAs compared to the SHR CM. Ovariectomy (OVX) increased the expression of rMCP-1 and rMCP-5 mRNAs in WKY. In SHR, OVX was associated with a blunted increase in rMCP-1 mRNA compared to OVX normotensive WKY. Chymase activity, measured as Ang II formation from Ang-(1-12), significantly correlated with rMCP-1 and rMCP-5 mRNA expression in both rat strains. Both rMCP-1 and rMCP-5 mRNA expressions were positively correlated with progressive diastolic dysfunction (increasing the ratio of early mitral inflow velocity-to-early mitral annular velocity, E/e') and expanding chamber dimensions or increasing left ventricular internal diameter end diastole. These data show rMCP-1 and rMCP-5 as the Ang II forming chymase isoforms participating in the loss of normal cardiac function due to OVX in rodents.

Female Heart Health: Is GPER the Missing Link?

The G Protein-Coupled Estrogen Receptor (GPER) is a novel membrane-bound receptor that mediates non-genomic actions of the primary female sex hormone 17β-estradiol. Studies over the past two decades have elucidated the beneficial actions of this receptor in a number of cardiometabolic diseases. This review will focus specifically on the cardiac actions of GPER, since this receptor is expressed in cardiomyocytes as well as other cells within the heart and most likely contributes to estrogen-induced cardioprotection. Studies outlining the impact of GPER on diastolic function, mitochondrial function, left ventricular stiffness, calcium dynamics, cardiac inflammation, and aortic distensibility are discussed. In addition, recent data using genetic mouse models with global or cardiomyocyte-specific GPER gene deletion are highlighted. Since estrogen loss due to menopause in combination with chronological aging contributes to unique aspects of cardiac dysfunction in women, this receptor may provide novel therapeutic effects. While clinical studies are still required to fully understand the potential for pharmacological targeting of this receptor in postmenopausal women, this review will summarize the evidence gathered thus far on its likely beneficial effects.

Sex differences in endothelial function important to vascular health and overall cardiovascular disease risk across the lifespan

Diseases of the cardiovascular system are the leading cause of morbidity and mortality in men and women in developed countries, and cardiovascular disease (CVD) is becoming more prevalent in developing countries. The prevalence of atherosclerotic CVD in men is greater than in women until menopause, when the prevalence of CVD increases in women until it exceeds that of men. Endothelial function is a barometer of vascular health and a predictor of atherosclerosis that may provide insights into sex differences in CVD as well as how and why the CVD risk drastically changes with menopause. Studies of sex differences in endothelial function are conflicting, with some studies showing earlier decrements in endothelial function in men compared with women, whereas others show similar age-related declines between the sexes. Because the increase in CVD risk coincides with menopause, it is generally thought that female hormones, estrogens in particular, are cardioprotective. Moreover, it is often proposed that androgens are detrimental. In truth, the relationships are more complex. This review first addresses female and male sex hormones and their receptors and how these interact with the cardiovascular system, particularly the endothelium, in healthy young women and men. Second, we address sex differences in sex steroid receptor-independent mechanisms controlling endothelial function, focusing on vascular endothelin and the renin-angiotensin systems, in healthy young women and men. Finally, we discuss sex differences in age-associated endothelial dysfunction, focusing on the role of attenuated circulating sex hormones in these effects.

Estradiol Treatment Initiated Early After Ovariectomy Regulates Myocardial Gene Expression and Inhibits Diastolic Dysfunction in Female Cynomolgus Monkeys: Potential Roles for Calcium Homeostasis and Extracellular Matrix Remodeling

Background Left ventricular ( LV ) diastolic dysfunction often precedes heart failure with preserved ejection fraction, the dominant form of heart failure in postmenopausal women. The objective of this study was to determine the effect of oral estradiol treatment initiated early after ovariectomy on LV function and myocardial gene expression in female cynomolgus macaques. Methods and Results Monkeys were ovariectomized and randomized to receive placebo (control) or oral estradiol at a human-equivalent dose of 1 mg/day for 8 months. Monkeys then underwent conventional and tissue Doppler imaging to assess cardiac function, followed by transcriptomic and histomorphometric analyses of LV myocardium. Age, body weight, blood pressure, and heart rate were similar between groups. Echocardiographic mitral early and late inflow velocities, mitral annular velocities, and mitral E deceleration slope were higher in estradiol monkeys (all P<0.05), despite similar estimated LV filling pressure. MCP1 (monocyte chemoattractant protein 1) and LV collagen staining were lower in estradiol animals ( P<0.05). Microarray analysis revealed differential myocardial expression of 40 genes (>1.2-fold change; false discovery rate, P<0.05) in estradiol animals relative to controls, which implicated pathways associated with better calcium ion homeostasis and muscle contraction and lower extracellular matrix deposition ( P<0.05). Conclusions Estradiol treatment initiated soon after ovariectomy resulted in enhanced LV diastolic function, and altered myocardial gene expression towards decreased extracellular matrix deposition, improved myocardial contraction, and calcium homeostasis, suggesting that estradiol directly or indirectly modulates the myocardial transcriptome to preserve cardiovascular function.

G protein-coupled estrogen receptor (GPER) deficiency induces cardiac remodeling through oxidative stress

Oxidative stress has been implicated in the unfavorable changes in cardiac function and remodeling that occur after ovarian estrogen loss. Using ovariectomized rat models, we previously reported that the cardioprotective actions of estrogen are mediated by the G protein-coupled estrogen receptor (GPER). Here, in 9-month-old, female cardiomyocyte-specific GPER knockout (KO) mice vs sex- and age-matched wild-type (WT) mice, we found increased cardiac oxidative stress and oxidant damage, measured as a decreased ratio of reduced glutathione to oxidized glutathione, increased 4-hydroxynonenal and 8-hydroxy-2'-deoxyguanosine (8-oxo-DG) staining, and increased expression of oxidative stress-related genes. GPER KO mice also displayed increased heart weight, cardiac collagen deposition, and Doppler-derived filling pressure, and decreased percent fractional shortening and early mitral annular velocity compared with WT controls. Treatment of GPER KO mice for 8 weeks with phosphonium [10-(4,5-dimethoxy-2-methyl 3,6-dioxo-1,4-cyclohexadien-1-yl)decyl] triphenyl-,mesylate (MitoQ), a mitochondria-targeted antioxidant, significantly attenuated these measures of cardiac dysfunction, and MitoQ decreased 8-oxo-DG intensity compared with treatment with an inactive comparator compound, (1-decyl)triphenylphosphonium bromide (P <0.05). A real-time polymerase chain reaction array analysis of 84 oxidative stress and antioxidant defense genes revealed that MitoQ attenuates the increase in NADPH oxidase 4 and prostaglandin-endoperoxide synthase 2 and the decrease in uncoupling protein 3 and glutathione S-transferase kappa 1 seen in GPER KO mice. Our findings suggest that the cardioprotective effects of GPER include an antioxidant role and that targeted strategies to limit oxidative stress after early noncancerous surgical extirpation of ovaries or menopause may help limit alterations in cardiac structure and function related to estrogen loss.

Blunting of cardioprotective actions of estrogen in female rodent heart linked to altered expression of cardiac tissue chymase and ACE2

Background:

Diastolic dysfunction develops in response to hypertension and estrogen (E2) loss and is a forerunner to heart failure (HF) in women. The cardiac renin–angiotensin system (RAS) contributes to diastolic dysfunction, but its role with respect to E2 and blood pressure remain unclear.

Methods:

We compared the effects of ovariectomy (OVX) or sham surgery on the cardiac RAS, left ventricular (LV) structure/function, and systemic/intracardiac pressures of spontaneously hypertensive rats (SHRs: n = 6 intact and 6 OVX) and age-matched Wistar-Kyoto (WKY: n = 5 intact and 4 OVX) controls.

Results:

WKY rats were more sensitive to OVX than SHRs with respect to worsening of diastolic function, as reflected by increases in Doppler-derived filling pressures (E/e′) and reductions in myocardial relaxation (e′). This pathobiologic response in WKY rats was directly linked to increases in cardiac gene expression and enzymatic activity of chymase and modest reductions in ACE2 activity. No overt changes in cardiac RAS genes or activities were observed in SHRs, but diastolic function was inversely related to ACE2 activity.

Conclusion:

Endogenous estrogens exert a more significant regulatory role upon biochemical components of the cardiac RAS of WKY versus SHRs, modulating the lusitropic and structural components of its normotensive phenotype.

Biological Sex Modulates the Adrenal and Blood Pressure Responses to Angiotensin II

The relationship between biological sex and aldosterone on blood pressure (BP) is unclear. We hypothesized that sex would modify the interaction between aldosterone and vascular responses to salt intake and angiotensin II (AngII). To test this hypothesis, in 1592 subjects from the well-controlled Hypertensive Pathotype cohort, we compared responses of women and men to chronic (BP and aldosterone levels in response to dietary salt) and acute (BP, renal plasma flow, and aldosterone responses to AngII infusion) manipulations. Women had a 30% higher salt sensitivity of BP than men (P<0.0005) regardless of age or hypertension status, a greater BP response to AngII, and a 15% greater aldosterone response to AngII on both restricted and liberal salt diets (P<0.005). Furthermore, there was an interaction (P=0.003) between sex and aldosterone on BP response to AngII. Women also had a greater (P<0.01) increment in renal plasma flow in response to AngII than men. To assess potential mechanisms for this sex effect, we compared aldosterone responses to AngII or potassium from rat zona glomerulosa cells and observed greater aldosterone production in female than male zona glomerulosa cells basally and in response to both agonists (P<0.0001). In a rodent model of aldosterone-mediated cardiovascular disease induced by increased AngII and low NO, circulating aldosterone levels (P<0.01), myocardial damage (P<0.001), and proteinuria (P<0.05) were greater in female than male rats despite having similar BP responses. Thus, increased aldosterone production likely contributes to sex differences in cardiovascular disease, suggesting that women may be more responsive to mineralocorticoid receptor blockade than men.

Critical role of the chymase/angiotensin-(1-12) axis in modulating cardiomyocyte contractility

BACKGROUND

Angiotensin-(1-12) [Ang-(1-12)] is a chymase-dependent source for angiotensin II (Ang II) cardiac activity. The direct contractile effects of Ang-(1-12) in normal and heart failure (HF) remain to be demonstrated. We assessed the hypothesis that Ang-(1-12) may modulate [Ca²⁺]_i regulation and alter cardiomyocyte contractility in normal and HF rats.

METHODS AND RESULTS

We compared left ventricle (LV) myocyte contractile and calcium transient ([Ca²⁺]_iT) responses to angiotensin peptides in 16 SD rats with isoproterenol-induced HF and 16 age-matched controls. In normal myocytes, versus baseline, Ang II (10^-6 M) superfusion significantly increased myocyte contractility (dL/dt_max: 40%) and [Ca²⁺]_iT (29%). Ang-(1-12) (4 × 10^-6 M) caused similar increases in dL/dt_max (34%) and [Ca²⁺]_iT (25%). Compared with normal myocytes, superfusion of Ang II and Ang-(1-12) in myocytes obtained from rats with isoproterenol-induced HF caused similar but significantly attenuated positive inotropic actions with about 42% to 50% less increases in dL/dt_max and [Ca²⁺]_iT. Chymostatin abolished Ang-(1-12)-mediated effects in normal and HF myocytes. The presence of an inhibitory cAMP analog, Rp-cAMPS prevented Ang-(1-12)-induced inotropic effects in both normal and HF myocytes. Incubation of HF myocytes with pertussis toxin (PTX) further augmented Ang II-mediated contractility.

CONCLUSIONS

Ang-(1-12) stimulates cardiomyocyte contractile function and [Ca²⁺]_iT in both normal and HF rats through a chymase mediated action. Altered inotropic responses to Ang-(1-12) and Ang II in HF myocytes are mediated through a cAMP-dependent mechanism that is coupled to both stimulatory G and inhibitory PTX-sensitive G proteins.

Renin angiotensin aldosterone inhibition in the treatment of cardiovascular disease

A collective century of discoveries establishes the importance of the renin angiotensin aldosterone system in maintaining blood pressure, fluid volume and electrolyte homeostasis via autocrine, paracrine and endocrine signaling. While research continues to yield new functions of angiotensin II and angiotensin-(1-7), the gap between basic research and clinical application of these new findings is widening. As data accumulates on the efficacy of angiotensin converting enzyme inhibitors and angiotensin II receptor blockers as drugs of fundamental importance in the treatment of cardiovascular and renal disorders, it is becoming apparent that the achieved clinical benefits is suboptimal and surprisingly no different than what can be achieved with other therapeutic interventions. We discuss this issue and summarize new pathways and mechanisms effecting the synthesis and actions of angiotensin II. The presence of renin-independent non-canonical pathways for angiotensin II production are largely unaffected by agents inhibiting renin angiotensin system activity. Hence, new efforts should be directed to develop drugs that can effectively block the synthesis and/or action of intracellular angiotensin II. Improved drug penetration into cardiac or renal sites of disease, inhibiting chymase the primary angiotensin II forming enzyme in the human heart, and/or inhibiting angiotensinogen synthesis would all be more effective strategies to inhibit the system. Additionally, given the role of angiotensin II in the maintenance of renal homeostatic mechanisms, any new inhibitor should possess greater selectivity of targeting pathogenic angiotensin II signaling processes and thereby limit inappropriate inhibition.

Mast Cell Inhibition Attenuates Cardiac Remodeling and Diastolic Dysfunction in Middle-aged, Ovariectomized Fischer 344 × Brown Norway Rats

The incidence of left ventricular diastolic dysfunction (LVDD) increases in women after menopause, yet the mechanisms are unclear. Because mast cells participate in the pathological processes of various cardiac diseases, we hypothesized that mast cell inhibition would protect against estrogen loss-induced LVDD. The mast cell stabilizer, cromolyn sodium (30 mg·kg·d), or vehicle was administered subcutaneously by osmotic minipump to ovariectomized (OVX) female Fischer 344 × Brown Norway (F344BN) rats starting at 4 weeks after surgery. Eight weeks after OVX, systolic blood pressure increased by 20% in OVX versus sham rats, and this effect was attenuated after 4 weeks of cromolyn treatment. Also, cromolyn mitigated the adverse reductions in myocardial relaxation (e') and increases in left ventricle (LV) filling pressures (E/e'), LV mass, wall thicknesses, and interstitial fibrosis from OVX. Although cardiac mast cell number was increased after OVX, cardiac chymase activity was not overtly altered by estrogen status and tended to decrease by cromolyn. Contrariwise, Ang II content was greater in hearts of OVX versus sham rats, and cromolyn attenuated this effect. Taken together, mast cell inhibition with cromolyn attenuates LV remodeling and LVDD in OVX-Fischer 344 × Brown Norway rats possibly through actions on the heart level and/or through vasodilatory effects at the vascular level.

Blunting of estrogen modulation of cardiac cellular chymase/RAS activity and function in SHR

The relatively low efficacy of ACE-inhibitors in the treatment of heart failure in women after estrogen loss may be due to their inability to reach the intracellular sites at which angiotensin (Ang) II is generated and/or the existence of cell-specific mechanisms in which ACE is not the essential processing pathway for Ang II formation. We compared the metabolic pathway for Ang II formation in freshly isolated myocytes (CMs) and non-myocytes (NCMs) in cardiac membranes extracted from hearts of gonadal-intact and ovariectomized (OVX) adult WKY and SHR rats. Plasma Ang II levels were higher in WKY vs. SHR (strain effect: WKY: 62 ± 6 pg/ml vs. SHR: 42 ± 9 pg/ml; p < 0.01), independent of OVX. The enzymatic activities of chymase, ACE, and ACE2 were higher in NCMs versus CMs, irrespective of whether assays were performed in cardiac membranes from WKY or SHR or in the presence or absence of OVX. E2 depletion increased chymase activity, but not ACE activity, in both CMs and NCMs. Moreover, cardiac myocyte chymase activity associated with diastolic function in WKYs and cardiac structure in SHRs while no relevant functional and structural relationships between the classic enzymatic pathway of Ang II formation by ACE or the counter-regulatory Ang-(1-7) forming path from Ang II via ACE2 were apparent. The significance of these novel findings is that targeted cell-specific chymase rather than ACE inhibition may have a greater benefit in the management of HF in women after menopause.

Novel Cardiac Intracrine Mechanisms Based on Ang-(1-12)/Chymase Axis Require a Revision of Therapeutic Approaches in Human Heart Disease

PURPOSE OF THE REVIEW

Drugs targeting the renin-angiotensin system (RAS), namely angiotensin-converting enzyme (ACE) inhibitors and angiotensin receptor blockers, are the most commonly prescribed drugs for patients with or at risk for cardiovascular events. However, new treatment strategies aimed at mitigating the rise of the heart failure pandemic are warranted because clinical trials show that RAS blockers have limited benefits in halting disease progression. The main goal of this review is to put forward the concept of an intracrine RAS signaling through the novel angiotensin-(1-12)/chymase axis as the main source of deleterious angiotensin II (Ang II) in cardiac maladaptive remodeling leading to heart failure (HF).

RECENT FINDINGS

Expanding traditional knowledge, Ang II can be produced in tissues independently from the circulatory renin-angiotensin system. In the heart, angiotensin-(1-12) [Ang-(1-12)], a recently discovered derivative of angiotensinogen, is a precursor of Ang II, and chymase rather than ACE is the main enzyme contributing to the direct production of Ang II from Ang-(1-12). The Ang-(1-12)/chymase axis is an independent intracrine pathway accounting for the trophic, contractile, and pro-arrhythmic Ang II actions in the human heart. Ang-(1-12) expression and chymase activity have been found elevated in the left atrial appendage of heart disease subjects, suggesting a pivotal role of this axis in the progression of HF. Recent meta-analysis of large clinical trials on the use of ACE inhibitors and angiotensin receptor blockers in cardiovascular disease has demonstrated an imbalance between patients that significantly benefit from these therapeutic agents and those that remain at risk for heart disease progression. Looking to find an explanation, detailed investigation on the RAS has unveiled a previously unrecognized complexity of substrates and enzymes in tissues ultimately associated with the production of Ang II that may explain the shortcomings of ACE inhibition and angiotensin receptor blockade. Discovery of the Ang-(1-12)/chymase axis in human hearts, capable of producing Ang II independently from the circulatory RAS, has led to the notion that a tissue-delimited RAS signaling in an intracrine fashion may account for the deleterious effects of Ang II in the heart, contributing to the transition from maladaptive cardiac remodeling to heart failure. Targeting intracellular RAS signaling may improve current therapies aimed at reducing the burden of heart failure.

Dysregulation of microRNAs and renin-angiotensin system in high salt diet-induced cardiac dysfunction in uninephrectomized rats

Uninephrectomy is not associated with major adverse events in cardiovascular and renal functions of live kidney donors. The effect of high salt diet on the quality of life of live kidney donors is largely unknown. Hence in this study, we aimed to determine the effect of high salt diet on the alterations of renin-angiotensin system and microRNAs leading to CV and renal dysfunction in uninephrectomized rats. In order to mimic clinical scenario, uninephrectomized male Sprague Dawley rats were fed initially with normal pellet diet for 12 weeks and then for 20 weeks with high salt (10% w/w NaCl) diet. At the end of the study, biochemical, functional, histological and molecular parameters were measured. High salt diet feeding resulted in renal dysfunction & fibrosis, decreased baroreflex sensitivity, increased in vivo cardiovascular reactivity to angiotensin II owing to upregulation of angiotensin II type 1 receptors and L-type calcium channels leading to cardiovascular dysfunction in uninephrectomized rats (UNX+HSD) worse than that of normal (binephric) rats fed with high salt diet (HSD). Protein expression of functional and hypertrophic protein markers revealed decreased SERCA, p-AMPK and increased p-AKT. Interestingly, levels of miR-25, miR-451 and miR-155 increased and miR-99 decreased in heart of uninephrectomized rats fed with high salt. However, circulating miR-25 and miR-451 levels decreased and miR-99b increased in these animals. Our study points out that since tissue and circulating levels of miRNAs are not similar, caution must be exercised during the usage of miRs as diagnostic or prognostic biomarkers. To our knowledge, we are the first to show that epigenetic alterations result in cardiac dysfunction in uninephrectomized rats fed with high salt diet.

Sex differences in vascular physiology and pathophysiology: estrogen and androgen signaling in health and disease

Sex differences between women and men are often overlooked and underappreciated when studying the cardiovascular system. It has been long assumed that men and women are physiologically similar, and this notion has resulted in women being clinically evaluated and treated for cardiovascular pathophysiological complications as men. Currently, there is increased recognition of fundamental sex differences in cardiovascular function, anatomy, cell signaling, and pathophysiology. The National Institutes of Health have enacted guidelines expressly to gain knowledge about ways the sexes differ in both normal function and diseases at the various research levels (molecular, cellular, tissue, and organ system). Greater understanding of these sex differences will be used to steer future directions in the biomedical sciences and translational and clinical research. This review describes sex-based differences in the physiology and pathophysiology of the vasculature, with a special emphasis on sex steroid receptor (estrogen and androgen receptor) signaling and their potential impact on vascular function in health and diseases (e.g., atherosclerosis, hypertension, peripheral artery disease, abdominal aortic aneurysms, cerebral aneurysms, and stroke).

Estrogen receptor profiling and activity in cardiac myocytes

Estrogen signaling appears critical in the heart. However a mechanistic understanding of the role of estrogen in the cardiac myocyte is lacking. Moreover, there are multiple cell types in the heart and multiple estrogen receptor (ER) isoforms. Therefore, we studied expression, localization, transcriptional and signaling activity of ERs in isolated cardiac myocytes. We found only ERα RNA (but no ERβ RNA) in cardiac myocytes using two independent methods. The vast majority of full-length ERα protein (ERα66) localizes to cardiac myocyte nuclei where it is competent to activate transcription. Alternate isoforms of ERα encoded by the same genomic locus (ERα46 and ERα36) have differential transcriptional activity in cardiac myocytes but also primarily localize to nuclei. In contrast to other reports, no ERα isoform is competent to activate MAPK or PI3K signaling in cardiac myocytes. Together these data support a role for ERα at the level of transcription in cardiac myocytes.

Intracrine angiotensin II functions originate from noncanonical pathways in the human heart

Although it is well-known that excess renin angiotensin system (RAS) activity contributes to the pathophysiology of cardiac and vascular disease, tissue-based expression of RAS genes has given rise to the possibility that intracellularly produced angiotensin II (Ang II) may be a critical contributor to disease processes. An extended form of angiotensin I (Ang I), the dodecapeptide angiotensin-(1-12) [Ang-(1-12)], that generates Ang II directly from chymase, particularly in the human heart, reinforces the possibility that an alternative noncanonical renin independent pathway for Ang II formation may be important in explaining the mechanisms by which the hormone contributes to adverse cardiac and vascular remodeling. This review summarizes the work that has been done in evaluating the functional significance of Ang-(1-12) and how this substrate generated from angiotensinogen by a yet to be identified enzyme enhances knowledge about Ang II pathological actions.

Regular exercise modulates cardiac mast cell activation in ovariectomized rats

It is well accepted that regular exercise is a significant factor in the prevention of cardiac dysfunction; however, the cardioprotective mechanism is as yet not well defined. We have examined whether regular exercise can modulate the activity of cardiac mast cells (CMC) after deprivation of female sex hormones, as well as the density and percentage degranulation of mast cells, in ventricular tissue of ovariectomized (OVX) rats after an 11-week running program. A significant increase in CMC density with a greater percentage degranulation was induced after ovarian sex hormone deprivation. Increased CMC density was prevented by estrogen supplements, but not by regular training. To the contrary, increased CMC degranulation in the OVX rat heart was attenuated by exercise training, but not by estrogen supplement. These findings indicate a significant correlation between the degree of CMC degranulation and myocyte cross-section area. However, no change in the expression of inflammatory mediators, including chymase, interleukin-6, and interleukin-10, was detected. Taken together, these results clearly indicate one of the cardioprotective mechanisms of regular aerobic exercise is the modulation of CMC activation.

Cardiac angiotensin-(1-12) expression and systemic hypertension in rats expressing the human angiotensinogen gene

Angiotensin-(1-12) [ANG-(1-12)] is processed into ANG II by chymase in rodent and human heart tissue. Differences in the amino acid sequence of rat and human ANG-(1-12) render the human angiotensinogen (hAGT) protein refractory to cleavage by renin. We used transgenic rats harboring the hAGT gene [TGR(hAGT)L1623] to assess the non-renin-dependent effects of increased hAGT expression on heart function and arterial pressure. Compared with Sprague-Dawley (SD) control rats (n= 11), male homozygous TGR(hAGT)L1623 (n= 9) demonstrated sustained daytime and nighttime hypertension associated with no changes in heart rate but increased heart rate lability. Increased heart weight/tibial length ratio and echocardiographic indexes of cardiac hypertrophy were associated with modest reduction of systolic function in hAGT rats. Robust human ANG-(1-12) immunofluorescence within myocytes of TGR(hAGT)L1623 rats was associated with a fourfold increase in cardiac ANG II content. Chymase enzymatic activity, using the rat or human ANG-(1-12) as a substrate, was not different in the cardiac tissue of SD and hAGT rats. Since both cardiac angiotensin-converting enzyme (ACE) and ACE2 activities were not different among the two strains, the changes in cardiac structure and function, blood pressure, and left ventricular ANG II content might be a product of an increased cardiac expression of ANG II generated through a non-renin-dependent mechanism. The data also underscore the existence in the rat of alternate enzymes capable of acting on hAGT protein. Homozygous transgenic rats expressing the hAGT gene represent a novel tool to investigate the contribution of human relevant renin-independent cardiac ANG II formation and function.

Role of Mas receptor in renal blood flow response to angiotensin-(1-7) in ovariectomized estradiol treated rats

The angiotensin 1-7 (Ang 1-7), is abundantly produced in kidneys and antagonizes the function of angiotensin II through Mas receptor (MasR) or other unknown mechanisms. In the current study, the role of MasR and steroid hormone estrogen on renal blood flow response to Ang 1-7 administration was investigated in ovariectomized (OV) female rats. OV female Wistar-rats received estradiol (500 μg/kg/week) or vehicle for two weeks. In the day of the experiment, the animals were anesthetized, cannulated, and the responses including mean arterial pressure, renal blood flow (RBF), and renal vascular resistance at the constant level of renal perfusion pressure to graded infusion of Ang 1-7 at 0, 100 and 300 ng/kg/min were determined in OV and OV estradiol-treated (OVE) rats, treated with vehicle or MasR antagonist; A779. RBF response to Ang 1-7 infusion increased dose-dependently in vehicle (Pdose <0.001) and A779-treated (Pdose <0.01) animals. However, when MasR was blocked, the RBF response to Ang 1-7 significantly increased in OV animals compared with OVE rats (P<0.05). When estradiol was limited by ovariectomy, A779 increased RBF response to Ang 1-7 administration, while this response was attenuated in OVE animals.

Role of Mas Receptor Antagonist A799 in Renal Blood Flow Response to Ang 1-7 after Bradykinin Administration in Ovariectomized Estradiol-Treated Rats

Background. The accompanied role of Mas receptor (MasR), bradykinin (BK), and female sex hormone on renal blood flow (RBF) response to angiotensin 1-7 is not well defined. We investigated the role of MasR antagonist (A779) and BK on RBF response to Ang 1-7 infusion in ovariectomized estradiol-treated rats. Methods. Ovariectomized Wistar rats received estradiol (OVE) or vehicle (OV) for two weeks. Catheterized animals were subjected to BK and A799 infusion and mean arterial pressure (MAP), RBF, and renal vascular resistance (RVR) responses to Ang 1-7 (0, 100, and 300 ng kg⁻¹ min⁻¹) were determined. Results. Percentage change of RBF (%RBF) in response to Ang1-7 infusion increased in a dose-dependent manner. In the presence of BK, when MasR was not blocked, %RBF response to Ang 1-7 in OVE group was greater than OV group significantly (P < 0.05). Infusion of 300 ng kg⁻¹ min⁻¹ Ang 1-7 increased RBF by 6.9 ± 1.9% in OVE group versus 0.9 ± 1.8% in OV group. However when MasR was blocked, %RBF response to Ang 1-7 in OV group was greater than OVE group insignificantly. Conclusion. Coadministration of BK and A779 compared to BK alone increased RBF response to Ang 1-7 in vehicle treated rats. Such observation was not seen in estradiol treated rats.

GPR30 decreases cardiac chymase/angiotensin II by inhibiting local mast cell number

Chronic activation of the novel estrogen receptor GPR30 by its agonist G1 mitigates the adverse effects of estrogen (E2) loss on cardiac structure and function. Using the ovariectomized (OVX) mRen2.Lewis rat, an E2-sensitive model of diastolic dysfunction, we found that E2 status is inversely correlated with local cardiac angiotensin II (Ang II) levels, likely via Ang I/chymase-mediated production. Since chymase is released from cardiac mast cells during stress (e.g., volume/pressure overload, inflammation), we hypothesized that GPR30-related cardioprotection after E2 loss might occur through its opposing actions on cardiac mast cell proliferation and chymase production. Using real-time quantitative PCR, immunohistochemistry, and immunoblot analysis, we found mast cell number, chymase expression, and cardiac Ang II levels were significantly increased in the hearts of OVX-compared to ovary-intact mRen2.Lewis rats and the GPR30 agonist G1 (50 mg/kg/day, s.c.) administered for 2 weeks limited the adverse effects of estrogen loss. In vitro studies revealed that GPR30 receptors are expressed in the RBL-2H3 mast cell line and G1 inhibits serum-induced cell proliferation in a dose-dependent manner, as determined by cell counting, BrdU incorporation assay, and Ki-67 staining. Using specific antagonists to estrogen receptors, blockage of GPR30, but not ERα or ERβ, attenuated the inhibitory effects of estrogen on BrdU incorporation in RBL-2H3 cells. Further study of the mechanism underlying the effect on cell proliferation showed that G1 inhibits cyclin-dependent kinase 1 (CDK1) mRNA and protein expression in RBL-2H3 cells in a dose-dependent manner.

Angiotensin-(1-12): a chymase-mediated cellular angiotensin II substrate

The classical view of biochemical pathways for the formation of biologically active angiotensins continues to undergo significant revision as new data uncovers the existence of important species differences between humans and rodents. The discovery of two novel substrates that, cleaved from angiotensinogen, can lead to direct tissue angiotensin II formation has the potential of radically altering our understanding of how tissues source angiotensin II production and explain the relative lack of efficacy that characterizes the use of angiotensin converting enzyme inhibitors in cardiovascular disease. This review addresses the discovery of angiotensin-(1-12) as an endogenous substrate for the production of biologically active angiotensin peptides by a non-renin dependent mechanism and the revealing role of cardiac chymase as the angiotensin II convertase in the human heart. This new information provides a renewed argument for exploring the role of chymase inhibitors in the correction of cardiac arrhythmias and left ventricular systolic and diastolic dysfunction.

Estrogen inhibits mast cell chymase release to prevent pressure overload-induced adverse cardiac remodeling

Estrogen regulation of myocardial chymase and chymase effects on cardiac remodeling are unknown. To test the hypothesis that estrogen prevents pressure overload-induced adverse cardiac remodeling by inhibiting mast cell (MC) chymase release, transverse aortic constriction or sham surgery was performed in 7-week-old intact and ovariectomized (OVX) rats. Three days before creating the constriction, additional groups of OVX rats began receiving 17β-estradiol, a chymase inhibitor, or a MC stabilizer. Left ventricular function, cardiomyocyte size, collagen volume fraction, MC density and degranulation, and myocardial and plasma chymase levels were assessed 18 days postsurgery. Aortic constriction resulted in ventricular hypertrophy in intact and OVX groups, whereas collagen volume fraction was increased only in OVX rats. Chymase protein content was increased by aortic constriction in the intact and OVX groups, with the magnitude of the increase being greater in OVX rats. MC density and degranulation, plasma chymase levels, and myocardial active transforming growth factor-β1 levels were increased by aortic constriction only in OVX rats. Estrogen replacement markedly attenuated the constriction-increased myocardial chymase, MC density and degranulation, plasma chymase, and myocardial active transforming growth factor-β1, as well as prevented ventricular hypertrophy and increased collagen volume fraction. Chymostatin attenuated the aortic constriction-induced ventricular hypertrophy and collagen volume fraction in the OVX rats similar to that achieved by estrogen replacement. Nedocromil yielded similar effects, except for the reduction of chymase content. We conclude that the estrogen-inhibited release of MC chymase is responsible for the cardioprotection against transverse aortic constriction-induced adverse cardiac remodeling.

Prenatal exposure to lipopolysaccharide results in local RAS activation in the adipose tissue of rat offspring

BACKGROUND

Adult metabolic syndrome may originate in part during fetal or early life. This study was designed to investigate the effects of prenatal exposure to lipopolysaccharide (LPS) on adipose development and local renin-angiotensin system (RAS) activation in rat offspring.

METHODS

Pregnant rats were randomly divided into three groups (n = 8 in each), including an NS group (pregnant rats were only treated with 0.5 ml normal saline from the 8th to the 14th day of gestation); an LPS group (pregnant rats were injected intraperitoneally with 0.79 mg/kg LPS on the 8th, 10th and 12th days of pregnancy); and an LPS+pyrrolidine dithiocarbamate (PDTC) group (identical to the LPS group except that 100 mg/kg PDTC was administered from the 8th to the 14th day of gestation).

RESULTS

Prenatal exposure to LPS resulted in increased blood pressure, adipose coefficient and body weight in rat offspring. Specifically, during the infancy of the offspring rats, the LPS stimulus promoted the differentiation of adipose cells, diminishing their diameters and proportions while simultaneously increasing cell number. In contrast, once the rats were grown, adipose cell differentiation was inhibited, and the diameters and proportions of the cells were increased. Moreover, each component of the RAS was changed and was shown to be activated. PDTC, an inhibitor of NF-κB, could reverse the influence of the stimulus during pregnancy.

CONCLUSION

Prenatal exposure to LPS in rats results in increased blood pressure, adipose coefficient, body weight and activation of adipose RAS in offspring.

Role of estrogen in diastolic dysfunction

The prevalence of left ventricular diastolic dysfunction (LVDD) sharply increases in women after menopause and may lead to heart failure. While evidence suggests that estrogens protect the premenopausal heart from hypertension and ventricular remodeling, the specific mechanisms involved remain elusive. Moreover, whether there is a protective role of estrogens against cardiovascular disease, and specifically LVDD, continues to be controversial. Clinical and basic science have implicated activation of the renin-angiotensin-aldosterone system (RAAS), linked to the loss of ovarian estrogens, in the pathogenesis of postmenopausal diastolic dysfunction. As a consequence of increased tissue ANG II and low estrogen, a maladaptive nitric oxide synthase (NOS) system produces ROS that contribute to female sex-specific hypertensive heart disease. Recent insights from rodent models that mimic the cardiac phenotype of an estrogen-insufficient or -deficient woman (e.g., premature ovarian failure or postmenopausal), including the ovariectomized congenic mRen2.Lewis female rat, provide evidence showing that estrogen modulates the tissue RAAS and NOS system and related intracellular signaling pathways, in part via the membrane G protein-coupled receptor 30 (GPR30; also called G protein-coupled estrogen receptor 1). Complementing the cardiovascular research in this field, the echocardiographic correlates of LVDD as well as inherent limitations to its use in preclinical rodent studies will be briefly presented. Understanding the roles of estrogen and GPR30, their interactions with the local RAAS and NOS system, and the relationship of each of these to LVDD is necessary to identify new therapeutic targets and alternative treatments for diastolic heart failure that achieve the cardiovascular benefits of estrogen replacement without its side effects and contraindications.