Estrogen and enalapril attenuate the development of right ventricular hypertrophy induced by monocrotaline in ovariectomized rats

Pulmonary arterial hypertension: Sex matters

Pulmonary arterial hypertension (PAH) is a complex disease of multifactorial origin. While registries have demonstrated that women are more susceptible to the disease, females with PAH have superior right ventricle (RV) function and a better prognosis than their male counterparts, a phenomenon referred to as the 'estrogen paradox'. Numerous pre-clinical studies have investigated the involvement of sex hormones in PAH pathobiology, often with conflicting results. However, recent advances suggest that abnormal estrogen synthesis, metabolism and signalling underpin the sexual dimorphism of this disease. Other sex hormones, such as progesterone, testosterone and dehydroepiandrosterone may also play a role. Several non-hormonal factor including sex chromosomes and epigenetics have also been implicated. Though the underlying pathophysiological mechanisms are complex, several compounds that modulate sex hormones levels and signalling are under investigation in PAH patients. Further elucidation of the estrogen paradox will set the stage for the identification of additional therapeutic targets for this disease.

Pulmonary Arterial Hypertension: Emerging Principles of Precision Medicine across Basic Science to Clinical Practice

Pulmonary arterial hypertension (PAH) is an enigmatic and deadly vascular disease with no known cure. Recent years have seen rapid advances in our understanding of the molecular underpinnings of PAH, with an expanding knowledge of the molecular, cellular, and systems-level drivers of disease that are being translated into novel therapeutic modalities. Simultaneous advances in clinical technology have led to a growing list of tools with potential application to diagnosis and phenotyping. Guided by fundamental biology, these developments hold the potential to usher in a new era of personalized medicine in PAH with broad implications for patient management and great promise for improved outcomes.

Sex and gender in pulmonary arterial hypertension

Pulmonary arterial hypertension (PAH) is a rare disease characterised by pulmonary vascular remodelling and elevated pulmonary pressure, which eventually leads to right heart failure and death. Registries worldwide have noted a female predominance of the disease, spurring particular interest in hormonal involvement in the disease pathobiology. Several experimental models have shown both protective and deleterious effects of oestrogens, suggesting that complex mechanisms participate in PAH pathogenesis. In fact, oestrogen metabolites as well as receptors and enzymes implicated in oestrogen signalling pathways and associated conditions such as BMPR2 mutation contribute to PAH penetrance more specifically in women. Conversely, females have better right ventricular function, translating to a better prognosis. Along with right ventricular adaptation, women tend to respond to PAH treatment differently from men. As some young women suffer from PAH, contraception is of particular importance, considering that pregnancy in patients with PAH is strongly discouraged due to high risk of death. When contraception measures fail, pregnant women need a multidisciplinary team-based approach. This article aims to review epidemiology, mechanisms underlying the higher female predominance, but better prognosis and the intricacies in management of women affected by PAH.

Roles of Genetic Predisposition in the Sex Bias of Pulmonary Pathophysiology, as a Function of Estrogens : Sex Matters in the Prevalence of Lung Diseases

In addition to studies focused on estrogen mediation of sex-different regulation of systemic circulations, there is now increasing clinical relevance and research interests in the pulmonary circulation, in terms of sex differences in the morbidity and mortality of lung diseases such as inherent-, allergic- and inflammatory-based events. Thus, female predisposition to pulmonary artery hypertension (PAH) is an inevitable topic. To better understand the nature of sexual differentiation in the pulmonary circulation, and how heritable factors, in vivo- and/or in vitro-altered estrogen circumstances and changes in the live environment work in concert to discern the sex bias, this chapter reviews pulmonary events characterized by sex-different features, concomitant with exploration of how alterations of genetic expression and estrogen metabolisms trigger the female-predominant pathological signaling. We address the following: PAH (Sect.7.2) is characterized as an estrogenic promotion of its incidence (Sect. 7.2.2), as a function of specific germline mutations, and as an estrogen-elicited protection of its prognosis (Sect.7.2.1). More detail is provided to introduce a less recognized gene of Ephx2 that encodes soluble epoxide hydrolase (sEH) to degrade epoxyeicosatrienic acids (EETs). As a susceptible target of estrogen, Ephx2/sEH expression is downregulated by an estrogen-dependent epigenetic mechanism. Increases in pulmonary EETs then evoke a potentiation of PAH generation, but mitigation of its progression, a phenomenon similar to the estrogen-paradox regulation of PAH. Additionally, the female susceptibility to chronic obstructive pulmonary diseases (Sect. 7.3) and asthma (Sect.7.4), but less preference to COVID-19 (Sect. 7.5), and roles of estrogen in their pathogeneses are briefly discussed.

Nutraceuticals in the Treatment of Pulmonary Arterial Hypertension

Pulmonary arterial hypertension (PAH) is a severe disease characterized by the loss and obstructive remodeling of the pulmonary arterial wall, causing a rise in pulmonary arterial pressure and pulmonary vascular resistance, which is responsible for right heart failure, functional decline, and death. Although many drugs are available for the treatment of this condition, it continues to be life-threatening, and its long-term treatment is expensive. On the other hand, many natural compounds present in food have beneficial effects on several cardiovascular conditions. Several studies have explored many of the potential beneficial effects of natural plant products on PAH. However, the mechanisms by which natural products, such as nutraceuticals, exert protective and therapeutic effects on PAH are not fully understood. In this review, we analyze the current knowledge on nutraceuticals and their potential use in the protection and treatment of PAH, as well as whether nutraceuticals could enhance the effects of drugs used in PAH through similar mechanisms.

Right ventricular phenotype, function, and failure: a journey from evolution to clinics

The right ventricle has long been perceived as the "low pressure bystander" of the left ventricle. Although the structure consists of, at first glance, the same cardiomyocytes as the left ventricle, it is in fact derived from a different set of precursor cells and has a complex three-dimensional anatomy and a very distinct contraction pattern. Mechanisms of right ventricular failure, its detection and follow-up, and more specific different responses to pressure versus volume overload are still incompletely understood. In order to fully comprehend right ventricular form and function, evolutionary biological entities that have led to the specifics of right ventricular physiology and morphology need to be addressed. Processes responsible for cardiac formation are based on very ancient cardiac lineages and within the first few weeks of fetal life, the human heart seems to repeat cardiac evolution. Furthermore, it appears that most cardiogenic signal pathways (if not all) act in combination with tissue-specific transcriptional cofactors to exert inductive responses reflecting an important expansion of ancestral regulatory genes throughout evolution and eventually cardiac complexity. Such molecular entities result in specific biomechanics of the RV that differs from that of the left ventricle. It is clear that sole descriptions of right ventricular contraction patterns (and LV contraction patterns for that matter) are futile and need to be addressed into a bigger multilayer three-dimensional picture. Therefore, we aim to present a complete picture from evolution, formation, and clinical presentation of right ventricular (mal)adaptation and failure on a molecular, cellular, biomechanical, and (patho)anatomical basis.

Influence of gender in monocrotaline and chronic hypoxia induced pulmonary hypertension in obese rats and mice

BACKGROUND

Obesity and pulmonary hypertension (PH) share common characteristics, such as augmented inflammation and oxidative stress. However, the exact role of obesity in the pathology of PH is largely uninvestigated. Therefore, we have hypothesized that in the context of obesity the gender difference may have influence on development of PH in animal models of this disease.

METHODS

Animal experiments were conducted in monocrotaline (MCT) and chronic hypoxia (HOX) models of PH. Lean and obese Zucker rats or B6 mice of both genders were used for MCT or HOX models, respectively. Echocardiography, hemodynamic measurements, histology and immuno-histochemistry were performed to analyze various parameters, such as right ventricular function and hypertrophy, hemodynamics, pulmonary vascular remodeling and lung inflammation.

RESULTS

Both lean and obese male and female Zucker rats developed PH after a single MCT injection. However, negligible differences were seen between lean and obese male rats in terms of PH severity at the end stage of disease. Conversely, a more prominent and severe PH was observed in obese female rats compared to their lean counterparts. In contrast, HOX induced PH in lean and obese, male and female mice did not show any apparent differences.

CONCLUSION

Gender influences PH severity in obese MCT-injected rats. It is also an important factor associated with altered inflammation. However, further research is necessary to investigate and reveal the underlying mechanisms.

Sex, Gender, and Sex Hormones in Pulmonary Hypertension and Right Ventricular Failure

Pulmonary hypertension (PH) encompasses a syndrome of diseases that are characterized by elevated pulmonary artery pressure and pulmonary vascular remodeling and that frequently lead to right ventricular (RV) failure and death. Several types of PH exhibit sexually dimorphic features in disease penetrance, presentation, and progression. Most sexually dimorphic features in PH have been described in pulmonary arterial hypertension (PAH), a devastating and progressive pulmonary vasculopathy with a 3-year survival rate <60%. While patient registries show that women are more susceptible to development of PAH, female PAH patients display better RV function and increased survival compared to their male counterparts, a phenomenon referred to as the "estrogen paradox" or "estrogen puzzle" of PAH. Recent advances in the field have demonstrated that multiple sex hormones, receptors, and metabolites play a role in the estrogen puzzle and that the effects of hormone signaling may be time and compartment specific. While the underlying physiological mechanisms are complex, unraveling the estrogen puzzle may reveal novel therapeutic strategies to treat and reverse the effects of PAH/PH. In this article, we (i) review PH classification and pathophysiology; (ii) discuss sex/gender differences observed in patients and animal models; (iii) review sex hormone synthesis and metabolism; (iv) review in detail the scientific literature of sex hormone signaling in PAH/PH, particularly estrogen-, testosterone-, progesterone-, and dehydroepiandrosterone (DHEA)-mediated effects in the pulmonary vasculature and RV; (v) discuss hormone-independent variables contributing to sexually dimorphic disease presentation; and (vi) identify knowledge gaps and pathways forward. © 2020 American Physiological Society. Compr Physiol 10:125-170, 2020.

Role of Gender in Regulation of Redox Homeostasis in Pulmonary Arterial Hypertension

Pulmonary arterial hypertension (PAH) is one of the diseases with a well-established gender dimorphism. The prevalence of PAH is increased in females with a ratio of 4:1, while poor survival prognosis is associated with the male gender. Nevertheless, the specific contribution of gender in disease development and progression is unclear due to the complex nature of the PAH. Oxidative and nitrosative stresses are important contributors in PAH pathogenesis; however, the role of gender in redox homeostasis has been understudied. This review is aimed to overview the possible sex-specific mechanisms responsible for the regulation of the balance between oxidants and antioxidants in relation to PAH pathobiology.

The Role of G Protein-Coupled Receptors in the Right Ventricle in Pulmonary Hypertension

Pressure overload of the right ventricle (RV) in pulmonary arterial hypertension (PAH) leads to RV remodeling and failure, an important determinant of outcome in patients with PAH. Several G protein-coupled receptors (GPCRs) are differentially regulated in the RV myocardium, contributing to the pathogenesis of RV adverse remodeling and dysfunction. Many pharmacological agents that target GPCRs have been demonstrated to result in beneficial effects on left ventricular (LV) failure, such as beta-adrenergic receptor and angiotensin receptor antagonists. However, the role of such drugs on RV remodeling and performance is not known at this time. Moreover, many of these same receptors are also expressed in the pulmonary vasculature, which could result in complex effects in PAH. This manuscript reviews the role of GPCRs in the RV remodeling and dysfunction and discusses activating and blocking GPCR signaling to potentially attenuate remodeling while promoting improvements of RV function in PAH.

The phenomena of mechanical interaction of segments of hypertrophied myocardium

The main aims of adaptation mechanisms of heart contractility are to regulate the stroke volume and optimize the global heart function. These mechanisms manifest themselves in hearts of healthy animals and in hearts with severe hypertrophy in different ways. Severe right ventricle hypertrophy was induced by single treatment with monocrotaline. Young rats of both sexes were used to prevent influences of sex hormones on the development of right ventricular hypertrophy. Serial duplex method is used as a model of interaction of two ventricular wall segments. In serial duplex the muscles are in connection 'end-to-end' and subjected to mutual deformations during contractions. It is important to establish the fine-tuning phenomena and evaluate their expressiveness in healthy hearts and hearts with severe hypertrophy. Mild force transient processes occur on muscle connection to serial duplex and on muscle separation from duplex in all experimental groups. These transients manifest themselves as slow changes in the amplitude of muscle contraction from cycle to cycle. During the muscle interaction in the serial duplex, evident transient processes in the mutual amplitude of deformations in all experimental groups are observed. The greatest changes in the length occur in the relaxation phase of the contraction cycle. The loss of interaction between ventricular muscles of rats with severe heart hypertrophy is the most likely cause of an additional deterioration in the heart pumping function. New targets may occur for the recovery of contractility of hearts with severe hypertrophy.

Advancing knowledge of right ventricular pathophysiology in chronic pressure overload: Insights from experimental studies

The right ventricle (RV) has to face major changes in loading conditions due to cardiovascular diseases and pulmonary vascular disorders. Clinical experience supports evidence that the RV better compensates for volume than for pressure overload, and for chronic than for acute changes. For a long time, right ventricular (RV) pathophysiology has been restricted to patterns extrapolated from left heart studies. However, the two ventricles are anatomically, haemodynamically and functionally distinct. RV metabolic properties may also result in a different behaviour in response to pathological conditions compared with the left ventricle. In this review, current knowledge of RV pathophysiology is reported in the setting of chronic pressure overload, including recent experimental findings and emerging concepts. After a time-varying compensated period with preserved cardiac output despite overload conditions, RV failure finally occurs, leading to death. The underlying mechanisms involved in the transition from compensatory hypertrophy to maladaptive remodelling are not completely understood.

Sex differences in stretch-dependent effects on tension and Ca(2+) transient of rat trabeculae in monocrotaline pulmonary hypertension

We aim to compare the effects of stretch on isometric tension/Ca(2+) transient in the right ventricular trabeculae of control (CONT) and hypertensive (MCT, monocrotaline application) adult male and female rats. The treatment with MCT resulted in RV hypertrophy in males only. Blunted active force-length relation and substantially prolonged twitch were found in MCT-males but not MCT-females (vs same-sex CONT). Ca(2+) transient was prolonged in both MCT-treated groups but extremely so in the MCT-males. The gradual stretch resulted in a distinct "bump" on Ca(2+) transient decline in CONT and MCT-treated groups. The integral magnitude of the "bump" was unaffected by the treatment with MCT in males or females but was larger in males vs females. The rate of "bump" development was significantly slower in MCT-males. In conclusion, the sex-specific differences in the stretch-dependent regulation of [Ca(2+)] i may underlie preservation of the Frank-Starling mechanism in female rat myocardium in monocrotaline-induced pulmonary hypertension.

Pulmonary arterial hypertension: basis of sex differences in incidence and treatment response

Pulmonary arterial hypertension (PAH) is a complex disease characterized by elevated pulmonary arterial pressure, pulmonary vascular remodelling and occlusive pulmonary vascular lesions, leading to right heart failure. Evidence from recent epidemiological studies suggests the influence of gender on the development of PAH with an approximate female to male ratio of 4:1, depending on the underlying disease pathology. Overall, the therapeutic strategy for PAH remains suboptimal with poor survival rates observed in both genders. Endogenous sex hormones, in particular 17β oestradiol and its metabolites, have been implicated in the development of the disease; however, the influence of sex hormones on the underlying pathobiology remains controversial. Further understanding of the influence of sex hormones on the normal and diseased pulmonary circulation will be critical to our understanding the pathology of PAH and future therapeutic strategies. In this review, we will discuss the influence of sex hormones on the development of PAH and address recent controversies.

The effects of gender difference on monocrotaline-induced pulmonary hypertension in rats

The present study aimed to compare the effect of gender difference on hemodynamic consequences in the development of monocrotaline (MCT)-induced pulmonary hypertension in rat. The effect of antioxidant enzyme systems on the development of pulmonary hypertension mediated by the phytotoxin MCT and the effect of gender on these antioxidant systems were also investigated. For this purpose, the right ventricular pressures (RVPs) and right ventricular/heart weight (HW) ratios were compared between groups and the glutathione (GSH) level and superoxide dismutase (SOD), catalase (CAT) and glutathione-S-transferase (GST) activities were determined in lung and liver tissue samples of rats. RVP and right ventricular/HW ratios significantly increased in the MCT group compared to the control group. In the MCT group, RVP was significantly higher in males than females. MCT-induced pulmonary hypertension resulted in decreased GSH level, decreased GST and SOD activities and increased CAT activity in lung and liver tissues of both male and female rats. In addition, the lung and liver GSH level and GST and SOD levels were higher in female control rats compared to male control rats. The results of the present study, that antioxidant enzyme activities were different between the groups, highlight the possible role of oxidative stress in the pathogenesis of MCT-induced pulmonary hypertension in rats. Moreover, the lower antioxidant defense capacity of male rats than female rats may be considered as a cause of more aggressive course of MCT-induced pulmonary hypertension in males compared to females.

Sex differences and sex steroids in lung health and disease

Sex differences in the biology of different organ systems and the influence of sex hormones in modulating health and disease are increasingly relevant in clinical and research areas. Although work has focused on sex differences and sex hormones in cardiovascular, musculoskeletal, and neuronal systems, there is now increasing clinical evidence for sex differences in incidence, morbidity, and mortality of lung diseases including allergic diseases (such as asthma), chronic obstructive pulmonary disease, pulmonary fibrosis, lung cancer, as well as pulmonary hypertension. Whether such differences are inherent and/or whether sex steroids play a role in modulating these differences is currently under investigation. The purpose of this review is to define sex differences in lung structure/function under normal and specific disease states, with exploration of whether and how sex hormone signaling mechanisms may explain these clinical observations. Focusing on adult age groups, the review addresses the following: 1) inherent sex differences in lung anatomy and physiology; 2) the importance of certain time points in life such as puberty, pregnancy, menopause, and aging; 3) expression and signaling of sex steroid receptors under normal vs. disease states; 4) potential interplay between different sex steroids; 5) the question of whether sex steroids are beneficial or detrimental to the lung; and 6) the potential use of sex steroid signaling as biomarkers and therapeutic avenues in lung diseases. The importance of focusing on sex differences and sex steroids in the lung lies in the increasing incidence of lung diseases in women and the need to address lung diseases across the life span.

Development of pulmonary arterial hypertension in mice over-expressing S100A4/Mts1 is specific to females

BACKGROUND

Idiopathic and familial forms of pulmonary arterial hypertension (PAH) occur more frequently in women than men. However, the reason for this remains unknown. Both the calcium binding protein S100A4/Mts1 (Mts1) and its endogenous receptor (receptor for advanced glycosylation end products; RAGE) have been implicated in the development of PAH. We wished to investigate if the Mts1/RAGE pathway may play a role in the gender bias associated with PAH.

METHODS

We investigated the effects of gender on development of PAH in mice over-expressing Mts1 (Mts1+ mice) via measurement of pulmonary arterial remodeling, systolic right ventricular pressure (sRVP) and right ventricular hypertrophy (RVH). Gender differences in pulmonary arterial Mts1 and RAGE expression were assessed by qRT-PCR and immunohistochemistry. Western blotting and cell counts were used to investigate interactions between 17β-estradiol, Mts1 and RAGE on proliferation of human pulmonary artery smooth muscle cells (hPASMCs). Statistical analysis was by one-way analysis of variance with Dunnetts post test or two-way analysis of variance with Bonferronis post test, as appropriate.

RESULTS

Female Mts1+ mice developed increased sRVP and pulmonary vascular remodeling, whereas male Mts1+ mice remained unaffected. The development of plexiform-like lesions in Mts1+ mice was specific to females. These lesions stained positive for both Mts1 and RAGE in the endothelial and adventitial layers. Expression of pulmonary arterial Mts1 was greater in female than male Mts1+ mice, and was localised to the medial and adventitial layers in non plexiform-like pulmonary arteries. RAGE gene expression and immunoreactivity were similar between male and female Mts1+ mice and RAGE staining was localised to the endothelial layer in non plexiform-like pulmonary arteries adjacent to airways. In non-plexiform like pulmonary arteries not associated with airways RAGE staining was present in the medial and adventitial layers. Physiological concentrations of 17β-estradiol increased Mts1 expression in hPASMCs. 17β-estradiol-induced hPASMC proliferation was inhibited by soluble RAGE, which antagonises the membrane bound form of RAGE.

CONCLUSIONS

Mts1 over-expression combined with female gender is permissive to the development of experimental PAH in mice. Up-regulation of Mts1 and subsequent activation of RAGE may contribute to 17β-estradiol-induced proliferation of hPASMCs.

Myocardial AKT: the omnipresent nexus

One of the greatest examples of integrated signal transduction is revealed by examination of effects mediated by AKT kinase in myocardial biology. Positioned at the intersection of multiple afferent and efferent signals, AKT exemplifies a molecular sensing node that coordinates dynamic responses of the cell in literally every aspect of biological responses. The balanced and nuanced nature of homeostatic signaling is particularly essential within the myocardial context, where regulation of survival, energy production, contractility, and response to pathological stress all flow through the nexus of AKT activation or repression. Equally important, the loss of regulated AKT activity is primarily the cause or consequence of pathological conditions leading to remodeling of the heart and eventual decompensation. This review presents an overview compendium of the complex world of myocardial AKT biology gleaned from more than a decade of research. Summarization of the widespread influence that AKT exerts upon myocardial responses leaves no doubt that the participation of AKT in molecular signaling will need to be reckoned with as a seemingly omnipresent regulator of myocardial molecular biological responses.

Estrogens and development of pulmonary hypertension: interaction of estradiol metabolism and pulmonary vascular disease

Severe pulmonary arterial hypertension (PAH) is characterized by clustered proliferation of endothelial cells (ECs) in the lumina of small size pulmonary arteries resulting in concentric obliteration of the lumina and formation of complex vascular structures known as plexiform lesions. This debilitating disease occurs more frequently in women, yet both animal studies in classical models of PAH and limited clinical data suggest protective effects of estrogens: the estrogen paradox in pulmonary hypertension. Little is known about the role of estrogens in PAH, but one line of evidence strongly suggests that the vascular protective effects of 17β-estradiol (estradiol; E2) are mediated largely by its downstream metabolites. Estradiol is metabolized to 2-hydroxyestradiol (2HE) by CYP1A1/CYP1B1, and 2HE is converted to 2-methoxyestradiol (2ME) by catechol-O-methyl transferase. 2ME is extensively metabolized to 2-methoxyestrone, a metabolite that lacks biologic activity, but which may be converted back to 2ME. 2ME has no estrogenic activity, and its effects are mediated by estrogen receptors–independent mechanism(s). Notably, in systemic and pulmonary vascular ECs, smooth muscle cells, and fibroblasts, 2ME exerts stronger antimitotic effects than E2 itself. E2 and 2ME, despite having similar effects on other cardiovascular cells, have opposing effects on ECs; that is, in ECs, E2 is promitogenic, proangiogenic, and antiapoptotic, whereas 2ME is antimitogenic, antiangiogenic, and proapoptotic. This may have significant ramifications in severe PAH that involves uncontrolled proliferation of monoclonal apoptosis-resistant ECs. Based on its cellular effects, 2ME should be expected to attenuate the progression of disease and provide protection in severe PAH. In contrast, E2, due to its mitogenic, angiogenic, and antiapoptotic effects (otherwise desirable in normal quiescent ECs), may even adversely affect endothelial remodeling in PAH, and this may be even more significant if the E2's effects on injured endothelium are not opposed by 2ME (eg, in the event of reduced E2 conversion to 2ME due to hypoxia, inflammation, drugs, environmental factors, or genetic polymorphism of metabolizing enzymes). This review focuses on the effects of estrogens and their metabolites on pulmonary vascular pathobiology and the development of experimental PAH and offers potential explanation for the estrogen paradox in PAH. Furthermore, we propose that unbalanced estradiol metabolism may lead to the development of PAH. Recent animal data and studies in patients with PAH support this concept.

Preventive effects of raloxifene, a selective estrogen receptor modulator, on monocrotaline-induced pulmonary hypertension in intact and ovariectomized female rats

We investigated whether the chronic treatment with raloxifene, a selective estrogen receptor modulator, prevents the development of monocrotaline-induced pulmonary hypertension in ovary-intact and ovariectomized female rats. Four weeks after a single subcutaneous injection of monocrotaline (60 mg/kg), right ventricular systolic pressure, right ventricle-to-left ventricle plus septal weight ratio, pulmonary arterial medial thickening and endothelin-1 levels in right ventricular tissue increased significantly in both female rats, compared with saline-treated control rats. These monocrotaline-induced alterations were much greater in ovariectomized rats than the changes in intact females. Daily oral administration of raloxifene (10 mg/kg/day for 4 weeks) significantly attenuated the increase in right ventricular systolic pressure to the same levels in both groups of animals, but raloxifene suppressed the increases in right ventricle-to-left ventricle plus septal weight ratio and pulmonary arterial medial thickness more efficiently in ovariectomized females than the case with intact females. In addition, raloxifene completely suppressed the increase in right ventricular endothelin-1 levels in ovariectomized rats, but not in intact females. These data suggest that chronic treatment with raloxifene effectively prevents the development of monocrotaline-induced pulmonary hypertension in ovariectomized female rats than in intact females, at least in part, by suppressing right ventricular endothelin-1 overproduction.

Total ginsenosides inhibit the right ventricular hypertrophy induced by monocrotaline in rats

Ginsenosides have been reported to release nitric oxide (NO) and decrease intracellular free Ca(2+) in cardiovascular system, which play important roles in antihypertrophic effect. This study investigated the potential inhibitory effect of total ginsenosides (TG) on right ventricular hypertrophy induced by monocrotaline (MCT, 60 mg/kg/d) and examined the possible antihypertrophic mechanism in male Sprague Dawley rats. MCT-intoxicated animals were treated with TG (20, 40, 60 mg/kg/d) for 18 d. TG treatment ameliorated MCT-induced elevations in right ventricular peak systolic pressure, right ventricular hypertrophy and the expression of atrial natriuretic peptide; N(G)-nitro-L-arginine-methyl ester (L-NAME), an NO synthase (NOS) inhibitor, had no influence on these inhibitory effects of TG 40 mg/kg/d, and TG at this dose had no any effect on the eNOS mRNA expression, suggesting the limited rule of NO in TG's effects. To further examine the mechanisms of the protection, the expression of calcineurin and its catalytic subunit CnA, as well as extracellular signal-regulated kinase-1 (ERK-1) and mitogen-activated protein kinase (MAPK) Phosphatase-1 (MKP-1) was examined. TG treatment significantly suppressed MCT-induced elevations of these signaling pathways in a dose-dependent manner. In summary, TG is effective in protecting against MCT-induced right ventricle hypertrophy, possibly through lowering pulmonary hypertension. Multiple molecular mechanisms appeared to be involved in this protection, such as the suppression of MCT-activated calcineurin and ERK signaling pathways.

Pathophysiological basis of right ventricular remodeling

The pathophysiology of right ventricular (RV) remodeling is a complex process and may include unique elements not observed in left ventricular (LV) remodeling. The RV also has a relatively irregular geometry not accounted for in LV analyses. RV remodeling includes basic changes in geometry, wall thickness, and ventricular pressure-volume relationships. Also, myocyte dimensions and number increase, and myocardial extracellular matrix and biochemical milieu are modified. Remodeling has been associated with such diseases as pulmonary hypertension, lung transplant, LV pathology, Chagas' disease, and arrhythmogenic right ventricular cardiomyopathy. Disease progression may lead to further RV changes, including hypertrophy, dilatation, and subsequently to variable alterations in RV hemodynamic status. The multiple methods to assess RV hypertrophy include cine magnetic resonance imaging and 3-D echocardiography. Each technique offers different precision in evaluating RV dimensions and functional performance characteristics. Strategies to prevent RV remodeling include pharmacological agents, such as vasodilators and angiotensin-converting enzyme inhibitors, as well as more invasive interventions, such as ventricular assist devices.

Inhibitory effect of ginsenoside Rb1 on cardiac hypertrophy induced by monocrotaline in rat

Ginseng, the root of Panax ginseng, has been used as folk medicine in the treatment of various diseases for thousands of years in China. Ginsenoside Rb1 (Rb1), one of the effective components of ginseng, has been reported to release nitric oxide and decrease intracellular free Ca2+ in cardiac myocytes, both of which play important roles in antihypertrophic effect. This study was to investigate the potential effect of Rb1 on right ventricular hypertrophy (RVH) induced by monocrotaline (MCT) and its possible influence on calcineurin (CaN) signal trasnsduction pathway. MCT-treated animals were administered with Rb1 (10 and 40 mg /kg) from day 1 to day 14 (preventive administration) or from day 15 to day 28 (therapeutic administration), or with vehicle as corresponding controls. After 2 weeks, significantly hypertrophic reactions, including RVH index and the expressions of atrial natriuretic peptide mRNA, appeared in right ventricle of all MCT-treated animals (p < 0.05), which were significantly decreased with some improvements of myocardial pathomorphology in both Rb1 prevention- and therapy-groups (p < 0.05). Similarly, MCT-treatment caused the high expressions of mRNA and/or proteins of CaN, NFAT3 and GATA4 from cardiocytes (p < 0.05) and Rb1 could alleviate the expressions of these factors above (p < 0.05). These results suggest that Rb1 treatment can inhibit the RVH induced by MCT, which may be involved in its inhibitory effects on CaN signal transduction pathway.

Moderate Pulmonary Arterial Hypertension in Male Mice Lacking the Vasoactive Intestinal Peptide Gene

Background— Vasoactive intestinal peptide (VIP), a pulmonary vasodilator and inhibitor of vascular smooth muscle proliferation, has been reported absent in pulmonary arteries from patients with idiopathic pulmonary arterial hypertension (PAH). We have tested the hypothesis that targeted deletion of the VIP gene may lead to PAH with pulmonary vascular remodeling.

Methods and Results— We examined VIP knockout (VIP −/− ) mice for evidence of PAH, right ventricular (RV) hypertrophy, and pulmonary vascular remodeling. Relative to wild-type control mice, VIP −/− mice showed moderate RV hypertension, RV hypertrophy confirmed by increased ratio of RV to left ventricle plus septum weight, and enlarged, thickened pulmonary artery and smaller branches with increased muscularization and narrowed lumen. Lung sections also showed perivascular inflammatory cell infiltrates. No systemic hypertension and no arterial hypoxemia existed to explain the PAH. The condition was associated with increased mortality. Both the vascular remodeling and RV remodeling were attenuated after a 4-week treatment with VIP.

Conclusions— Deletion of the VIP gene leads to spontaneous expression of moderately severe PAH in mice during air breathing. Although not an exact model of idiopathic PAH, the VIP −/− mouse should be useful for studying molecular mechanisms of PAH and evaluating potential therapeutic agents. VIP replacement therapy holds promise for the treatment of PAH, and mutations of the VIP gene may be a factor in the pathogenesis of idiopathic PAH.

Adjuvant strategies for prevention of glomerulosclerosis

The glomerulosclerosis which frequently complicates diabetes and severe hypertension is mediated primarily by increased mesangial production and activation of transforming growth factor-beta (TGF-beta), which acts on mesangial cells to boost their production of matrix proteins while suppressing extracellular proteolytic activity. Hyperglycemia and glomerular hypertension work in various complementary ways to stimulate superoxide production via NADPH oxidase in mesangial cells; the resulting oxidant stress results in the induction and activation of TFG-beta. Nitric oxide, generated by glomerular capillaries and by mesangial cells themselves, functions physiologically to oppose mesangial TGF-beta overproduction; however, NO bioactivity is compromised by oxidant stress. In addition to low-protein diets and drugs that suppress angiotensin II activity, a variety of other agents and measures may have potential for impeding the process of glomerulosclerosis. These include vitamin E, which blunts the rise in mesangial diacylglycerol levels induced by hyperglycemia; statins and (possibly) policosanol, which down-regulate NADPH oxidase activity by diminishing isoprenylation of Rac1; lipoic acid, whose potent antioxidant activity antagonizes the impact of oxidant stress on TGF-beta expression; pyridoxamine, which inhibits production of advanced glycation endproducts; arginine, high-dose folate, vitamin C, and salt restriction, which may support glomerular production of nitric oxide; and estrogen and soy isoflavones, which may induce nitric oxide synthase in glomerular capillaries while also interfering with TGF-beta signaling. Further research along these lines may enable the development of complex nutraceuticals which have important clinical utility for controlling and preventing glomerulosclerosis and renal failure. Most of these measures may likewise reduce risk for left ventricular hypertrophy in hypertensives, inasmuch as the signaling mechanisms which mediate this disorder appear similar to those involved in glomerulosclerosis.

Effects of estrogens on cardiovascular structure in uninephrectomized SHRsp rats

BACKGROUND

The risk of cardiovascular disease in uremic patients is greater in male than in female patients. Estrogens seem to play a cardioprotective role until menopause. Experimental data on the effect of estrogens on cardiovascular damage are controversial and potential underlying mechanisms especially in renal failure have not been fully clarified.

METHODS

Three-month-old female uninephrectomized stroke-prone spontaneously hypertensive (SHRsp) rats were sham-operated or ovariectomized. Subsequently, they received either vehicle (sesame oil) or 17-beta-3 benzoate estradiol (E2) (25 microg/day) or estriol (E3) (0.02 mg/day), respectively. After 3 months the animals were sacrified and the organs were harvested using pressure-controlled perfusion fixation. Stereologic parameters such as capillary length density (L(V)), mean intercapillary distance (MID), and volume density of the interstitial tissue (Vv) were quantitated. Additionally, expression of transforming growth factor-beta (TGF-beta), vascular endothelial growth factor (VEGF), flt-1, endothelial nitric oxide synthase (eNOS), endothelin-1 (ET-1), endothelin A receptor (ETA) receptor, and alpha estrogen receptor was assessed using immunohistochemistry. Intramyocardial capillaries and the aorta were investigated by morphometric methods.

RESULTS

L(V) (mm/mm(3)) was significantly lower (2421 +/- 500) and MID (microm) significantly higher (22.2 +/- 2.33) in vehicle-treated uninephrectomized/ovariectomized compared to uninephrectomized/sham-ovariectomized controls (L(V) 3629 +/- 960, MID 12.7 +/- 2.7) as well as estradiol (L(V) 3340 +/- 739, MID 12.1 +/- 4.96) and estriol (L(V) 4655 +/- 618, MID 14.2 +/- 2.89) treated uninephrectomized/ovariectomized animals. The volume density of the cardiac interstitium was higher in vehicle-treated uninephrectomized/ovariectomized animals compared to uninephrectomized/sham-ovariectomized, estradiol and estriol treated uninephrectomized/ovariectomized rats. The protein level expression of TGF-beta was higher in vehicle treated uninephrectomized/ovariectomized compared to uninephrectomized/sham and all treatment groups.

CONCLUSION

In ovariectomized SHRsp rats with moderate renal failure cardiac lesions were strikingly less after estradiol or estriol treatment. The results document a beneficial role of estrogens on cardiac abnormalities in a model of moderate renal dysfunction.