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

Loss of ADAM15 in female mice does not worsen pressure overload cardiomyopathy, independent of ovarian hormones

Cardiac hypertrophy is a common feature in several cardiomyopathies. We previously reported that loss of ADAM15 (disintegrin and metalloproteinase 15) worsened cardiac hypertrophy and dilated cardiomyopathy following cardiac pressure overload. Here, we investigated the impact of ADAM15 loss in female mice following cardiac pressure overload induced by transverse aortic constriction (TAC). Female Adam15-/- mice developed the same degree of cardiac hypertrophy, dilation, and dysfunction as the parallel female wild-type (WT) mice at 6 wk post-TAC. To determine if this is due to the protective effects of estrogen, which could mask the negative impact of Adam15 loss, WT and Adam15-/- mice underwent ovariectomy (OVx) 2 wk before TAC. Cardiac structure and function analyses were performed at 6 wk post-TAC. OVx similarly impacted females of both genotypes post-TAC. Calcineurin (Cn) activity was increased post-OVx-TAC, and more in Adam15-/- mice; however, this increase was not reflected in the total-to-phospho-NFAT levels. Integrin-α7 expression, which was upstream of Cn activation in male Adam15-/- -TAC mice, remained unchanged in female mice. However, activation of the mitogen-activated protein kinases (ERK, JNK, P38) was greater in Adam15-/--OVx-TAC than in WT-OVx-TAC mice. In addition, ADAM15 protein levels were significantly increased post-TAC in male but not in female WT mice. Myocardial fibrosis was comparable in non-OVx WT-TAC and Adam15-/- -TAC mice. OVx increased the perivascular fibrosis more in Adam15-/- compared with WT mice post-TAC. Our data demonstrate that loss of ovarian hormones did not fully replicate the male phenotype in the female Adam15-/- mice post-TAC. As ADAM15 levels were increased in males but not in females post-TAC, it is plausible that ADAM15 does not play a prominent role in post-TAC events in female mice. Our findings highlight the significance of factors other than sex hormones in mediating cardiomyopathies in females, which require a more thorough understanding.NEW & NOTEWORTHY Loss of ADAM15 in female mice, unlike the male mice, does not worsen the cardiomyopathy following cardiac pressure overload. Ovariectomy does not worsen the post-TAC cardiomyopathy in female Adam15-/- mice compared with female WT mice. Lack of deleterious impact of Adam15 deficiency in female mice is not because of the protective effects of ovarian hormones but could be due to a less prominent role of ADAM15 in cardiac response to post-TAC remodeling in female mice.

Mast Cells in Cardiac Remodeling: Focus on the Right Ventricle

In response to various stressors, cardiac chambers undergo structural remodeling. Long-term exposure of the right ventricle (RV) to pressure or volume overload leads to its maladaptive remodeling, associated with RV failure and increased mortality. While left ventricular adverse remodeling is well understood and therapeutic options are available or emerging, RV remodeling remains underexplored, and no specific therapies are currently available. Accumulating evidence implicates the role of mast cells in RV remodeling. Mast cells produce and release numerous inflammatory mediators, growth factors and proteases that can adversely affect cardiac cells, thus contributing to cardiac remodeling. Recent experimental findings suggest that mast cells might represent a potential therapeutic target. This review examines the role of mast cells in cardiac remodeling, with a specific focus on RV remodeling, and explores the potential efficacy of therapeutic interventions targeting mast cells to mitigate adverse RV remodeling.

Sex differences in the renin-angiotensin-aldosterone system and its roles in hypertension, cardiovascular, and kidney diseases

Cardiovascular disease is a pathology that exhibits well-researched biological sex differences, making it possible for physicians to tailor preventative and therapeutic approaches for various diseases. Hypertension, which is defined as blood pressure greater than 130/80 mmHg, is the primary risk factor for developing coronary artery disease, stroke, and renal failure. Approximately 48% of American men and 43% of American women suffer from hypertension. Epidemiological data suggests that during reproductive years, women have much lower rates of hypertension than men. However, this protective effect disappears after the onset of menopause. Treatment-resistant hypertension affects approximately 10.3 million US adults and is unable to be controlled even after implementing ≥3 antihypertensives with complementary mechanisms. This indicates that other mechanisms responsible for modulating blood pressure are still unclear. Understanding the differences in genetic and hormonal mechanisms that lead to hypertension would allow for sex-specific treatment and an opportunity to improve patient outcomes. Therefore, this invited review will review and discuss recent advances in studying the sex-specific physiological mechanisms that affect the renin-angiotensin system and contribute to blood pressure control. It will also discuss research on sex differences in hypertension management, treatment, and outcomes.

Targeting active sites of inflammation using inherent properties of tissue-resident mast cells

Mast cells play a pivotal role in initiating and directing host's immune response. They reside in tissues that primarily interface with the external environment. Activated mast cells respond to environmental cues throughout acute and chronic inflammation through releasing immune mediators via rapid degranulation, or long-term de novo expression. Mast cell activation results in the rapid release of a variety of unique enzymes and reactive oxygen species. Furthermore, the increased density of mast cell unique receptors like mas related G protein-coupled receptor X2 also characterizes the inflamed tissues. The presence of these molecules (either released mediators or surface receptors) are particular to the sites of active inflammation, and are a result of mast cell activation. Herein, the molecular design principles for capitalizing on these novel mast cell properties is discussed with the goal of manipulating localized inflammation. STATEMENT OF SIGNIFICANCE: Mast cells are immune regulating cells that play a crucial role in both innate and adaptive immune responses. The activation of mast cells causes the release of multiple unique profiles of biomolecules, which are specific to both tissue and disease. These unique characteristics are tightly regulated and afford a localized stimulus for targeting inflammatory diseases. Herein, these important mast cell attributes are discussed in the frame of highlighting strategies for the design of bioresponsive functional materials to target regions of inflammations.

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.

Involvement of Polyamines From Cardiac Mast Cells in Myocardial Remodeling Induced by Pressure Overload Through Mitochondrial Permeability Transition Pore Opening

Objective

Polyamines mainly contain spermine (SPM), spermidine (SPD), and putrescine (PUT). Many research results suggest that polyamines participate in cell proliferation, differentiation, and the regulation of gene expression, and have a close relationship with the occurrence and development of many diseases. However, the role and possible mechanisms of action of polyamines from cardiac mast cells in myocardial remodeling induced by pressure overload remain to be elucidated.

Methods

Pressure overload was induced by abdominal aortic constriction (AAC). Toluidine blue staining was used to visualize mast cells in cardiac tissue. The polyamine content of cardiac tissue was analyzed using high-performance liquid chromatography. Opening of the mitochondrial permeability transition pore (MPTP) was determined by the Ca²⁺-induced swelling of isolated cardiac mitochondria, measured as a reduction in A₅₂₀.

Results

Compared with sham rats, the cardiac mast cell density, the polyamine content (PUT, SPB, and SPM), and myocardial MPTP opening in rats with AAC were significantly increased (P < 0.05), and were accompanied by increased myocardial fibrosis and heart weight/body weight ratio. Intraperitoneal injection of polyamines mimicked these results, and these effects were reversed by cromolyn sodium, a mast cell stabilizer (P < 0.05). Myocardial MPTP opening increased in rats with AAC (P < 0.05), and the three polyamines also increased myocardial MPTP opening (P < 0.05).

Conclusion

Mast cell-derived polyamines are involved in pressure overload-induced myocardial remodeling by increasing opening of the MPTP.

Mast Cells Trigger Disturbed Bone Healing in Osteoporotic Mice

Mast cells are important tissue-resident sensor and effector immune cells but also play a major role in osteoporosis development. Mast cells are increased in numbers in the bone marrow of postmenopausal osteoporotic patients, and mast cell-deficient mice are protected from ovariectomy (OVX)-induced bone loss. In this study, we showed that mast cell-deficient Mcpt5-Cre R-DTA mice were protected from OVX-induced disturbed fracture healing, indicating a critical role for mast cells in the pathomechanisms of impaired bone repair under estrogen-deficient conditions. We revealed that mast cells trigger the fracture-induced inflammatory response by releasing inflammatory mediators, including interleukin-6, midkine (Mdk), and C-X-C motif chemokine ligand 10 (CXCL10), and promote neutrophil infiltration into the fracture site in OVX mice. Furthermore, mast cells were responsible for reduced osteoblast and increased osteoclast activities in OVX mice callus, as well as increased receptor activator of NF-κB ligand serum levels in OVX mice. Additional in vitro studies with human cells showed that mast cells stimulate osteoclastogenesis by releasing the osteoclastogenic mediators Mdk and CXCL10 in an estrogen-dependent manner, which was mediated via the estrogen receptor alpha on mast cells. In conclusion, mast cells negatively affect the healing of bone fractures under estrogen-deficient conditions. Hence, targeting mast cells might provide a therapeutic strategy to improve disturbed bone repair in postmenopausal osteoporosis. © 2021 The Authors. Journal of Bone and Mineral Research published by Wiley Periodicals LLC on behalf of American Society for Bone and Mineral Research (ASBMR).

Innate Immune Cells in Pressure Overload-Induced Cardiac Hypertrophy and Remodeling

Pressure overload and heart failure are among the leading causes of cardiovascular morbidity and mortality. Accumulating evidence suggests that inflammatory cell activation and release of inflammatory mediators are of vital importance during the pathogenesis of these cardiac diseases. Yet, the roles of innate immune cells and subsequent inflammatory events in these processes remain poorly understood. Here, we outline the possible underlying mechanisms of innate immune cell participation, including mast cells, macrophages, monocytes, neutrophils, dendritic cells, eosinophils, and natural killer T cells in these pathological processes. Although these cells accumulate in the atrium or ventricles at different time points after pressure overload, their cardioprotective or cardiodestructive activities differ from each other. Among them, mast cells, neutrophils, and dendritic cells exert detrimental function in experimental models, whereas eosinophils and natural killer T cells display cardioprotective activities. Depending on their subsets, macrophages and monocytes may exacerbate cardiodysfunction or negatively regulate cardiac hypertrophy and remodeling. Pressure overload stimulates the secretion of cytokines, chemokines, and growth factors from innate immune cells and even resident cardiomyocytes that together assist innate immune cell infiltration into injured heart. These infiltrates are involved in pro-hypertrophic events and cardiac fibroblast activation. Immune regulation of cardiac innate immune cells becomes a promising therapeutic approach in experimental cardiac disease treatment, highlighting the significance of their clinical evaluation in humans.

Heart Angiotensin-Converting Enzyme and Angiotensin-Converting Enzyme 2 Gene Expression Associated With Male Sex and Salt-Sensitive Hypertension in the Dahl Rat

Angiotensin-converting enzyme 2 (ACE 2) in the heart including its sex dependency in the hypertensive heart, has not been much studied compared to ACE. In the present study, we used the Dahl salt-sensitive rat exposed to fructose and salt to model a hypertensive phenotype in males, females, and ovariectomized females. Blood pressure was measured by the tale-cuff technique in the conscious state. Expression of RAS-related genes ACE, ACE2, angiotensin II receptor type 1, Mas1, and CMA1 in the heart were quantified. The results revealed small but significant differences between male and female groups. The main results indicate the presence of a male preponderance for an increase in ACE and ACE2 gene expression. The results are in accordance with the role of androgens or male chromosomal complement in controlling the expression of the two ACE genes.

Effects of hormone replacement therapy on left ventricular diastolic function in postmenopausal women: a systematic review and meta-analysis

BACKGROUND

Postmenopausal women tend to experience significant changes in left ventricular diastolic function (LVDF). However, there are conflicting reports about LVDF between postmenopausal women on hormone replacement therapy (HRT) and those not on HRT. This meta-analysis is to evaluate the effects of HRT on LVDF in postmenopausal women.

METHODS

We conducted a systemic review of randomized controlled trials published up to December 31 2019 using Embase, Pubmed, and the Cochrane library database.

RESULTS

Eight studies involving 668 postmenopausal women were identified. Our analysis indicated that the ratio of the peak velocity during early filing to late filling from atrial contraction improvement in HRT group was better than that in placebo group (MD 0.20, 95%CI 0.12 to 0.28). There was a significant reduction in deceleration time and left ventricular mass index in HRT group compared with placebo group (MD -21.01, 95%CI -40.11 to -1.91 vs MD -8.26, 95%CI -14.10 to -2.42). No significant difference was observed in left ventricular end systole diameter (MD 0.80, 95%CI -0.72 to 2.31), left ventricular end diastole diameter (MD -0.07, 95%CI -1.25 to 1.10), left atrial size (MD -0.33, 95%CI -1.34 to 0.68)and the isovolumic relaxation time (MD -12.08, 95%CI -27.65 to 3.5).

CONCLUSIONS

Our meta-analysis illustrated that postmenopausal women seem to obtain more beneficial effects from HRT on LVDF, though future studies are required to elucidate the specific mechanisms for this phenomenon.

The Roles of Noncardiomyocytes in Cardiac Remodeling

Cardiac remodeling is a common characteristic of almost all forms of heart disease, including cardiac infarction, valvular diseases, hypertension, arrhythmia, dilated cardiomyopathy and other conditions. It is not merely a simple outcome induced by an increase in the workload of cardiomyocytes (CMs). The remodeling process is accompanied by abnormalities of cardiac structure as well as disturbance of cardiac function, and emerging evidence suggests that a wide range of cells in the heart participate in the initiation and development of cardiac remodeling. Other than CMs, there are numerous noncardiomyocytes (non-CMs) that regulate the process of cardiac remodeling, such as cardiac fibroblasts and immune cells (including macrophages, lymphocytes, neutrophils, and mast cells). In this review, we summarize recent knowledge regarding the definition and significant effects of various non-CMs in the pathogenesis of cardiac remodeling, with a particular emphasis on the involved signaling mechanisms. In addition, we discuss the properties of non-CMs, which serve as targets of many cardiovascular drugs that reduce adverse cardiac remodeling.

Is Cardiac Diastolic Dysfunction a Part of Post-Menopausal Syndrome?

Post-menopausal women exhibit an exponential increase in the incidence of heart failure with preserved ejection fraction compared with men of the same age, which indicates a potential role of hormonal changes in subclinical and clinical diastolic dysfunction. This paper reviews the preclinical evidence that demonstrates the involvement of estrogen in many regulatory molecular pathways of cardiac diastolic function and the clinical data that investigates the effect of estrogen on diastolic function in post-menopausal women. Published reports show that estrogen deficiency influences both early diastolic relaxation via calcium homeostasis and the late diastolic compliance associated with cardiac hypertrophy and fibrosis. Because of the high risk of diastolic dysfunction and heart failure with preserved ejection fraction in post-menopausal women and the positive effects of estrogen on preserving cardiac function, further clinical studies are needed to clarify the role of endogenous estrogen or hormone replacement in mitigating the onset and progression of heart failure with preserved ejection fraction in women.

Changes in the number of mast cells, expression of fibroblast growth factor-2 and extent of interstitial fibrosis in established and advanced hypertensive heart disease

INTRODUCTION

An increasing number of studies have shed light on the role of cardiac mast cells in the pathogenesis of hypertension-induced myocardial remodeling. Mast cells promote fibroblast activation, myofibroblast differentiation and subsequent collagen accumulation through the action of tryptase, chymase, histamine and fibroblast growth factor-2. The aim of the present study was to report on the changes in the number of mast cells as evaluated through toluidine blue, tryptase and c-kit staining, to assess the extent of interstitial fibrosis and correlate it with the changes in the number of mast cells and to analyze the immunohistochemical expression of fibroblast growth factor-2 in two groups of spontaneously hypertensive rats indicative of established and advanced hypertensive heart disease. A novel aspect of our work was the analysis of all parameters in the right ventricle.

MATERIAL AND METHODS

For the present study, we used 6- and 12-month-old spontaneously hypertensive rats. A light microscopic study was conducted on sections stained with hematoxylin and eosin and toluidine blue. For the immunohistochemical study we used monoclonal antibodies against mast cell tryptase and fibroblast growth factor-2 and a polyclonal antibody against c-kit. The expression of fibroblast growth factor-2 was assessed semi-quantitatively through ImageJ. The number of mast cells was evaluated on toluidine blue-, tryptase- and c-kit-stained sections and a comparative statistical analysis with the Mann-Whitney test was conducted between the two age groups. A separate statistical analysis between results obtained through immunostaining for tryptase and for c-kit was conducted in each age group with the Wilcoxon signed-rank test. The extent of fibrosis was assessed quantitatively on slides stained with Mallory's trichrome stain as a percentage of the whole tissue and compared between the two age groups. Spearman's correlation was used to test whether a correlation exists between the number of mast cells and the percentage of interstitial fibrosis.

RESULTS

Mast cells with typical cytoplasmic granules were visualized in the interstitial tissue and in the perivascular zone in both age groups. In both ventricles, their number increased significantly in 12-month-old animals as evaluated through all three staining methods. Moreover, immunostaining for tryptase and for c-kit yielded comparable results. The immunoreactivity of fibroblast growth factor-2 increased in both ventricles in older animals. Expression of this protein was particularly intensive in the cytoplasm of connective tissue cells with the characteristic features of mast cells mainly found in the areas of fibrotic alterations in 12-month-old spontaneously hypertensive rats. In both ventricles, interstitial fibrosis was more extensive throughout the myocardium of older animals and was positively correlated with the changes in the number of mast cells in both age groups.

CONCLUSION

The present study reported for the first time that the increase in the number of mast cells, observed as hypertension-induced myocardial changes progress, is statistically significant and confirmed that this process takes place in both ventricles. This increase is accompanied by a higher expression of fibroblast growth factor-2 and is more strongly correlated with the more pronounced interstitial fibrosis in older animals, further supporting the role of mast cells in the structural changes taking place in the myocardium in response to systemic hypertension.

Comparison of exercise training and estrogen supplementation on mast cell-mediated doxorubicin-induced cardiotoxicity

Cardiac inflammation has been proposed as one of the primary mechanisms of anthracycline-induced acute cardiotoxicity. A reduction in cardiac inflammation might also reduce cardiotoxicity. This study aimed to evaluate the potential of estrogen therapy and regular exercise on attenuating cardiac inflammation in the context of doxorubicin-induced cardiomyopathy. Ovariectomized rats were randomly allocated into estrogen supplementation, exercise training, and mast cell stabilizer treatment groups. Eight weeks after ovariectomy, rats received six cumulative doses of doxorubicin for two weeks. Echocardiography demonstrated a progressive decrease in ejection fraction in doxorubicin-treated rats without hypertrophic effect. This systolic defect was completely prevented by either estrogen supplementation or mast cell stabilizer treatment but not by regular exercise. As a heart disease indicator, increased β-myosin heavy chain expression induced by doxorubicin could only be prevented by estrogen supplementation. Decrease in shortening and intracellular Ca²⁺ transients of cardiomyocytes were due to absence of female sex hormones without further effects of doxorubicin. Again, estrogen supplementation and mast cell stabilizer treatment prevented these changes but exercise training did not. Histological analysis indicated that the hyperactivation of cardiac mast cells in ovariectomized rats was augmented by doxorubicin. Estrogen supplementation and mast cell stabilizer treatment completely prevented both increases in mast cell density and degranulation, whereas exercise training partially attenuated the hyperactivation. Our results, therefore, suggest that estrogen supplementation acts similarly to mast cell stabilizers in attenuating the effects of doxorubicin. Ineffectiveness of regular exercise in preventing the acute cardiotoxicity of doxorubicin might be due to a lesser effect on preventing cardiac inflammation.

Cardiomyocyte Senescence and Cellular Communications Within Myocardial Microenvironments

Cardiovascular diseases have become the leading cause of human death. Aging is an independent risk factor for cardiovascular diseases. Cardiac aging is associated with maladaptation of cellular metabolism, dysfunction (or senescence) of cardiomyocytes, a decrease in angiogenesis, and an increase in tissue scarring (fibrosis). These events eventually lead to cardiac remodeling and failure. Senescent cardiomyocytes show the hallmarks of DNA damage, endoplasmic reticulum stress, mitochondria dysfunction, contractile dysfunction, hypertrophic growth, and senescence-associated secreting phenotype (SASP). Metabolism within cardiomyocytes is essential not only to fuel the pump function of the heart but also to maintain the functional homeostasis and participate in the senescence of cardiomyocytes. The senescence of cardiomyocyte is also regulated by the non-myocytes (endothelial cells, fibroblasts, and immune cells) in the local microenvironment. On the other hand, the senescent cardiomyocytes alter their phenotypes and subsequently affect the non-myocytes in the local microenvironment and contribute to cardiac aging and pathological remodeling. In this review, we first summarized the hallmarks of the senescence of cardiomyocytes. Then, we discussed the metabolic switch within senescent cardiomyocytes and provided a discussion of the cellular communications between dysfunctional cardiomyocytes and non-myocytes in the local microenvironment. We also addressed the functions of metabolic regulators within non-myocytes in modulating myocardial microenvironment. Finally, we pointed out some interesting and important questions that are needed to be addressed by further studies.

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.

Role of cardiac mast cells in exercise training-mediated cardiac remodeling in angiotensin II-infused ovariectomized rats

AIMS

Regular exercise is recommended in postmenopausal women to prevent the development of heart disease, but mechanism underlying the protection is not completely understood. Many studies have suggested that exercise training notably mediated whole body immune and inflammatory functions. Whether exercise training prevents cardiac dysfunction after deprivation of female sex hormones by inhibiting cardiac immune activation is therefore interesting.

MAIN METHODS

Nine-week treadmill running program was introduced in sham-operated and ovariectomized rats. In addition, chronic angiotensin II infusion was further challenged to activate pathological cardiac remodeling. Cardiac remodeling in associated with the density and degranulation of cardiac mast cells was then evaluated.

KEY FINDINGS

With exogenous angiotensin II-induced hypertension, cardiac hypertrophy with myocardial fibrosis was shown similarly in both sham-operated controls and ovariectomized rats. Although exercise training did not prevent cardiac hypertrophy, myocardial fibrosis was abolished by exercise. While ovariectomy increased both cardiac mast cell density and degranulation percentage, angiotensin II infusion only enhanced mast cell density. Exercise training could not decrease the density of mast cells, but it did normalize the percentage of degranulation in all groups. Correlation analysis suggested that cardiac mast cell activation is inversely associated with cardiomyocyte hypertrophy due to exercise training but is directly correlated to cardiac hypertrophy by angiotensin II infusion.

SIGNIFICANCE

Exercise training could attenuate cardiac mast cell hyperactivation induced by either deprivation of female sex hormones or excessive angiotensin II. Additionally, cardiac mast cells could be a solution in the distinction between physiological and pathological hypertrophic development.

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.

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.

Cardiomyocyte-targeted and 17β-estradiol-loaded acoustic nanoprobes as a theranostic platform for cardiac hypertrophy

Background

Theranostic perfluorocarbon nanoprobes have recently attracted attention due to their fascinating versatility in integrating diagnostics and therapeutics into a single system. Furthermore, although 17β-estradiol (E2) is a potential anti-hypertrophic drug, it has severe non-specific adverse effects in various organs. Therefore, we have developed cardiomyocyte-targeted theranostic nanoprobes to achieve concurrent targeted imaging and treatment of cardiac hypertrophy.

Results

We had successfully synthesized E2-loaded, primary cardiomyocyte (PCM) specific peptide-conjugated nanoprobes with perfluorocarbon (PFP) as a core (PCM-E2/PFPs) and demonstrated their stability and homogeneity. In vitro and in vivo studies confirmed that when exposed to low-intensity focused ultrasound (LIFU), these versatile PCM-E2/PFPs can be used as an amplifiable imaging contrast agent. Furthermore, the significantly accelerated release of E2 enhanced the therapeutic efficacy of the drug and prevented systemic side effects. PCM-E2/PFPs + LIFU treatment also significantly increased cardiac targeting and circulation time. Further therapeutic evaluations showed that PCM-E2/PFPs + LIFU suppressed cardiac hypertrophy to a greater extent compared to other treatments, revealing high efficiency in cardiac-targeted delivery and effective cardioprotection.

Conclusion

Our novel theranostic nanoplatform could serve as a potential theranostic vector for cardiac diseases.

Electronic supplementary material

The online version of this article (10.1186/s12951-018-0360-3) contains supplementary material, which is available to authorized users.

Chymase released from hypoxia-activated cardiac mast cells cleaves human apoA-I at Tyr192 and compromises its cardioprotective activity

ApoA-I, the main structural and functional protein of HDL particles, is cardioprotective, but also highly sensitive to proteolytic cleavage. Here, we investigated the effect of cardiac mast cell activation and ensuing chymase secretion on apoA-I degradation using isolated rat hearts in the Langendorff perfusion system. Cardiac mast cells were activated by injection of compound 48/80 into the coronary circulation or by low-flow myocardial ischemia, after which lipid-free apoA-I was injected and collected in the coronary effluent for cleavage analysis. Mast cell activation by 48/80 resulted in apoA-I cleavage at sites Tyr¹⁹² and Phe²²⁹, but hypoxic activation at Tyr¹⁹² only. In vitro, the proteolytic end-product of apoA-I with either rat or human chymase was the Tyr¹⁹²-truncated fragment. This fragment, when compared with intact apoA-I, showed reduced ability to promote migration of cultured human coronary artery endothelial cells in a wound-healing assay. We propose that C-terminal truncation of apoA-I by chymase released from cardiac mast cells during ischemia impairs the ability of apoA-I to heal damaged endothelium in the ischemic myocardium.

Mast Cells: Key Contributors to Cardiac Fibrosis

Historically, increased numbers of mast cells have been associated with fibrosis in numerous cardiac pathologies, implicating mast cells in the development of cardiac fibrosis. Subsequently, several approaches have been utilised to demonstrate a causal role for mast cells in animal models of cardiac fibrosis including mast cell stabilising compounds, rodents deficient in mast cells, and inhibition of the actions of mast cell-specific proteases such as chymase and tryptase. Whilst most evidence supports a pro-fibrotic role for mast cells, there is evidence that in some settings these cells can oppose fibrosis. A major gap in our current understanding of cardiac mast cell function is identification of the stimuli that activate these cells causing them to promote a pro-fibrotic environment. This review will present the evidence linking mast cells to cardiac fibrosis, as well as discuss the major questions that remain in understanding how mast cells contribute to cardiac fibrosis.

Synergistic effect of estradiol and testosterone protects against IL-6-inducedcardiomyocyte apoptosismediated by TGF-β1

OBJECTIVE

Basic studies have verified that estradiol or androgen is influential on cardioprotection, howeversynergistic effects of estradiol and testosterone on heart failure (HF) are still unknown. This study aimed to evaluate the association among sex hormones and heart failure risk factors.

METHODS

142 controls and 196 patients with HF were selected for this study. Serum levels of estradiol, testosterone, Brain natriuretic peptide precursor, transforming growth factor-β1, β2 and β3, lipid-lipoprotein profile, glucose, high-sensitivity C-reactive protein, serum creatinine, microglobulin, uric acid, alanine aminotransferase, aspartate aminotransferase were determined. H9c2 cardiac myocytes were used to investigate the effect of estradiol and testosterone on cardiomyocytes apoptotic involved in TGF-β1. Signaling pathway of caspase 3, Bax, Bcl-2, caspase 8 and TGF-β was determined during the IL-6 induced apoptotic.

RESULTS

First, our results showed that compared with the control, the E2/T ratio decreased from 6.32±9.89 to 3.43±3.16 (P <0.001) in female, from 4.00±8.14 to 7.80±11.35 (P<0.001) in male with heart failure, and the level of TGF-β1 increased. What's more, these changes were favorably associated with the cardiac function classification. Univariate and multivariate logistic regression analysis showed that serum E2/T ratio, TGF-β1 and NT-proBNP were independent risk factor in heart failure patients. Second, we found that TGF-β1 was upregulated in rat H9c2 cardiomyocyte induced by IL-6, and TGF-β1 regulates the apoptosis of rat H9c2 cardiomyocyte. Furthermore, we verified the beneficial effects of the defined appropriate E2/T ratio on cardiomyocyte apoptotic mediated by TGF-β1.

CONCLUSION

The balance of the serum E2/T ratio was broken in patients with heart failure, and an imbalanced E2/T ratio showed a strong association with heart failure risk factors, and E2 combined with T play a synergistic effect on anti-apoptosis involved in TGF-β1.

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.

Gender-specific association of decreased estimated glomerular filtration rate and left vertical geometry in the general population from rural Northeast China

Background

Left ventricular hypertrophy (LVH) is common and associated with cardiovascular outcomes among patients with known chronic kidney disease (CKD). However, the link between decreased estimated glomerular filtration rate (eGFR) and left ventricular (LV) geometry remains poorly explored in general population. In this study, we examined the gender-specific association between eGFR and LVH in the general population from rural Northeast China.

Methods

This survey was conducted from July 2012 to August 2013. A total of 10907 participants (5,013 men and 5,894 women) from the rural Northeast China were randomly selected and examined. LV mass index (LVMI) was used to define LVH (LVMI > 46.7 g/m^2.7 in women; > 49.2 g/m^2.7 in men). LV geometry was defined as normal, or with concentric remodeling, eccentric or concentric hypertrophy, according to relative wall thickness (RWT) and LVMI. Mildly decreased eGFR was defined as eGFR ≥ 60 and < 90 ml/min/1.73 m², and moderate-severely decreased eGFR was defined as eGFR < 60 ml/min/1.73 m².

Results

As eGFR decreased, LVH showed a gradual increase in the entire study population. Multivariate analysis revealed a gender-specific relationship between eGFR and LV geometry. Only in men, mildly decreased eGFR was associated with concentric remodeling [odds ratio (OR): =1.58; 95% CI: 1.14–2.20; P < 0.01] and concentric LVH OR = 1.63; 95% CI: 1.15–2.31; P < 0.01). And only in men, moderate-severely decreased eGFR was a risk factor for concentric LVH (OR = 4.56; 95% CI: 2.14–9.73; P < 0.001) after adjusting for confounding factors.

Conclusions

These findings suggested that decreased eGFR was a risk factor for LV geometry in men, and a gender-specific difference should be taken into account in clinical practice.

Estrogen receptor antagonism exacerbates cardiac structural and functional remodeling in female rats

We have previously demonstrated the cardioprotective effects of ovarian hormones against adverse ventricular remodeling imposed by chronic volume overload. Here, we assess the estrogen receptor dependence of this cardioprotection. Four groups of female rats were studied: sham-operated (Sham), volume overloaded [aortocaval fistula (ACF)], Sham treated with estrogen receptor antagonist ICI 182,780 (Sham + ICI), and ACF treated with ICI. Cardiac function was assessed temporally using echocardiogram, and tissue samples were collected at 5 days and 6 wk postsurgery. All rats with volume overload had significantly increased cardiac output (96 ± 32 ml/min for ACF and 108 ± 11 ml/min for ACF + ICI vs. 31 ± 2 for Sham, P < 0.05). At 6 wk, volume overload induced significant left ventricular (LV) hypertrophy in both untreated and treated ACF groups. Both ACF groups developed significantly increased LV end-diastolic diameter (LVEDD), indicating LV dilatation, with the ACF + ICI group having the greatest increase (340%, relative to Sham). Ejection fraction was significantly reduced in the ACF + ICI group (23% reduction) at 6 wk postsurgery compared with untreated ACF (P < 0.05). Interstitial collagen staining was significantly reduced by volume overload, with estrogen receptor antagonism causing greater collagen loss at both 5 days and 6 wk postsurgery. Furthermore, volume overload induced a significant increase in LV wall stress only in rats treated with estrogen antagonist. These data indicate that estrogen receptor signaling is essential for sex hormone-dependent cardioprotection against adverse remodeling. The maintenance of myocardial extracellular matrix collagen appears to play a key role in this cardioprotection.

NEW & NOTEWORTHY

We assessed the estrogen receptor (ER) dependence of female-specific cardioprotection using a rat model of chronic volume-overload stress. ER antagonism worsened ventricular wall stress, ventricular dilation, and cardiac dysfunction induced by volume overload. Further, blocking ERs resulted in cardiac remodeling and functional changes similar to that previously found in ovariectomized rats.

Effect of Age, Estrogen Status, and Late-Life GPER Activation on Cardiac Structure and Function in the Fischer344×Brown Norway Female Rat

Age-associated changes in cardiac structure and function, together with estrogen loss, contribute to the progression of heart failure with preserved ejection fraction in older women. To investigate the effects of aging and estrogen loss on the development of its precursor, asymptomatic left ventricular diastolic dysfunction, echocardiograms were performed in 10 middle-aged (20 months) and 30 old-aged (30 months) female Fischer344×Brown-Norway rats, 4 and 8 weeks after ovariectomy (OVX) and sham procedures (gonads left intact). The cardioprotective potential of administering chronic G1, the selective agonist to the new G-protein-coupled estrogen receptor (GPER), was further evaluated in old rats (Old-OVX+G1) versus age-matched, vehicle-treated OVX and gonadal intact rats. Advanced age and estrogen loss led to decreases in myocardial relaxation and elevations in filling pressure, in part, due to reductions in phosphorylated phospholamban and increases in cardiac collagen deposition. Eight weeks of G-protein-coupled estrogen receptor activation in Old-OVX+G1 rats reversed the adverse effects of age and estrogen loss on myocardial relaxation through increases in sarcoplasmic reticulum Ca²⁺ ATPase expression and reductions in interstitial fibrosis. These findings may explain the preponderance of heart failure with preserved ejection fraction in older postmenopausal women and provide a promising, late-life therapeutic target to reverse or halt the progression of left ventricular diastolic dysfunction.

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.

Regression of cardiovascular remodeling in hypertension: Novel relevant mechanisms

Asymptomatic organ damage due to progressive kidney damage, cardiac hypertrophy and remodeling put hypertensive patients at high risk for developing heart and renal failure, myocardial infarction and stroke. Current antihypertensive treatment normalizes high blood pressure, partially reverses organ damage, and reduces the incidence of heart and renal failure. Activation of the renin-angiotensin system (RAS) is a primary mechanism of progressive organ damage and, specifically, a major cause of both renal and cardiovascular fibrosis. Currently, inhibition of the RAS system [mainly with angiotensin I converting enzyme inhibitors or angiotensin II (Ang II) receptor antagonists] is the most effective antihypertensive strategy for normalizing blood pressure and preventing target organ damage. However, residual organ damage and consequently high risk for cardiovascular events and renal failure still persist. Accordingly, in hypertension, it is relevant to develop new therapeutic perspectives, beyond reducing blood pressure to further prevent/reduce target organ damage by acting on pathways that trigger and maintain cardiovascular and renal remodeling. We review here relevant novel mechanisms of target organ damage in hypertension, their role and evidence in prevention/regression of cardiovascular remodeling and their possible clinical impact as well. Specifically, we focus on the signaling pathway RhoA/Rho kinase, on the impact of the vasodilatory peptides from the RAS and some insights on the role of estrogens and myocardial chymase in cardiovascular hypertensive remodeling.

THE AUTOCRINE ROLE OF TRYPTASE IN PRESSURE OVERLOAD-INDUCED MAST CELL ACTIVATION, CHYMASE RELEASE AND CARDIAC FIBROSIS

BACKGROUND

Cardiac mast cell (MC) proteases, chymase and tryptase, increase proliferation and collagen synthesis in cultured cardiac fibroblasts. However, the question as to why preventing individually the actions of either protease prevents fibrosis when both are released upon MC activation remains unanswered. Since tryptase has the ability to activate MCs in noncardiac tissues via the protease-activated receptor-2 (PAR-2), there is the possibility that its, in vivo, fibrotic role is due to its ability to induce MC degranulation thereby amplifying the release of chymase.

METHODS

This study sought to delineate the interactions between tryptase and chymase in myocardial remodeling secondary to transverse aortic constriction (TAC) for 5 wks in male Sprague Dawley rats untreated or treated with either the tryptase inhibitor, nafamostat mesilate or MC membrane stabilizing drug, nedocromil (n=6/group). In addition, ventricular slices from 6 rat hearts were incubated with tryptase, tryptase plus nafamostat mesilate or chymostatin for 24 h.

RESULTS AND CONCLUSION

The results indicate the presence of PAR-2 on MCs and that tryptase inhibition and nedocromil prevented TAC-induced fibrosis and increases in MC density, activation, and chymase release. Tryptase also significantly increased chymase concentration in ventricular tissue culture media, which was prevented by the tryptase inhibitor. Hydroxyproline concentration in culture media was significantly increased with tryptase incubation as compared to the control group and the tryptase group incubated with nafamostat mesilate or chymostatin. We conclude that tryptase contributes to TAC-induced cardiac fibrosis primarily via activation of MCs and the amplified release of chymase.

Role of chymase in the local renin-angiotensin system in keloids: inhibition of chymase may be an effective therapeutic approach to treat keloids

Background

Histologically, keloids contain excess fibroblasts and an overabundance of dermal collagen. Recently, it was reported that chymase induced a profibrotic response via transforming growth factor-β1 (TGF-β1)/Smad activation in keloid fibroblasts (KFs). However, the role of chymase in the local renin-angiotensin system (RAS) in keloids has not been elucidated. This study aims to determine whether chymase plays an important role in the local RAS in keloids.

Methods

We compared the expression and activity of chymase in keloids and normal skin tissues using Western blotting and radioimmunoassay, and studied the expression of TGF-β1, interleukin-1β, collagen I, hydroxyproline, and angiotensin II in KFs after chymase and inhibitors’ treatment.

Results

The results revealed an increased activity of chymase in keloid tissues, and that chymase enhanced the expression of angiotensin II, collagen I, TGF-β1, and interleukin-1β in KFs. Blockade of the chymase pathway involved in the local RAS lowered the expression of these signaling factors.

Conclusion

This research suggests that inhibition of chymase might be an effective therapeutic approach to improve the clinical treatment of keloids.

Cardiac nonmyocytes in the hub of cardiac hypertrophy

Cardiac hypertrophy is characterized by complex multicellular alterations, such as cardiomyocyte growth, angiogenesis, fibrosis, and inflammation. The heart consists of myocytes and nonmyocytes, such as fibroblasts, vascular cells, and blood cells, and these cells communicate with each other directly or indirectly via a variety of autocrine or paracrine mediators. Accumulating evidence has suggested that nonmyocytes actively participate in the development of cardiac hypertrophy. In this review, recent progress in our understanding of the importance of nonmyocytes as a hub for induction of cardiac hypertrophy is summarized with an emphasis of the contribution of noncontact communication mediated by diffusible factors between cardiomyocytes and nonmyocytes in the heart.

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.