Study of the mechanisms of aldosterone prothrombotic effect in rats

The Mineralocorticoid Receptor in the Vasculature: Friend or Foe?

Originally described as the renal aldosterone receptor that regulates sodium homeostasis, it is now clear that mineralocorticoid receptors (MRs) are widely expressed, including in vascular endothelial and smooth muscle cells. Ample data demonstrate that endothelial and smooth muscle cell MRs contribute to cardiovascular disease in response to risk factors (aging, obesity, hypertension, atherosclerosis) by inducing vasoconstriction, vascular remodeling, inflammation, and oxidative stress. Extrapolating from its role in disease, evidence supports beneficial roles of vascular MRs in the context of hypotension by promoting inflammation, wound healing, and vasoconstriction to enhance survival from bleeding or sepsis. Advances in understanding how vascular MRs become activated are also reviewed, describing transcriptional, ligand-dependent, and ligand-independent mechanisms. By synthesizing evidence describing how vascular MRs convert cardiovascular risk factors into disease (the vascular MR as a foe), we postulate that the teleological role of the MR is to coordinate responses to hypotension (the MR as a friend).

Aldosterone and cardiovascular diseases

Aldosterone's role in the kidney and its pathophysiologic actions in hypertension are well known. However, its role or that of its receptor [minieralocorticoid receptor (MR)] in other cardiovascular (CV) disease are less well described. To identify their potential roles in six CV conditions (heart failure, myocardial infarction, atrial fibrillation, stroke, atherosclerosis, and thrombosis), we assessed these associations in the following four areas: (i) mechanistic studies in rodents and humans; (ii) pre-clinical studies of MR antagonists; (iii) clinical trials of MR antagonists; and (iv) genetics. The data were acquired from an online search of the National Library of Medicine using the PubMed search engine from January 2011 through June 2021. There were 3702 publications identified with 200 publications meeting our inclusion and exclusion criteria. Data strongly supported an association between heart failure and dysregulated aldosterone/MR. This association is not surprising given aldosterone/MR's prominent role in regulating sodium/volume homeostasis. Atrial fibrillation and myocardial infarction are also associated with dysregulated aldosterone/MR, but less strongly. For the most part, the data were insufficient to determine whether there was a relationship between atherosclerosis, stroke, or thrombosis and aldosterone/MR dysregulation. This review clearly documented an expanding role for aldosterone/MR's dysregulation in CV diseases beyond hypertension. How expansive it might be is limited by the currently available data. It is anticipated that with an increased focus on aldosterone/MR's potential roles in these diseases, additional clinical and pre-clinical data will clarify these relationships, thereby, opening approaches to use modulators of aldosterone/MR's action to more precisely treat these CV conditions.

The Effect of Aldosterone on Cardiorenal and Metabolic Systems

Aldosterone, a vital hormone of the human body, has various pathophysiological roles. The excess of aldosterone, also known as primary aldosteronism, is the most common secondary cause of hypertension. Primary aldosteronism is associated with an increased risk of cardiovascular disease and kidney dysfunction compared to essential hypertension. Excess aldosterone can lead to harmful metabolic and other pathophysiological alterations, as well as cause inflammatory, oxidative, and fibrotic effects in the heart, kidney, and blood vessels. These alterations can result in coronary artery disease, including ischemia and myocardial infarction, left ventricular hypertrophy, heart failure, arterial fibrillation, intracarotid intima thickening, cerebrovascular disease, and chronic kidney disease. Thus, aldosterone affects several tissues, especially in the cardiovascular system, and the metabolic and pathophysiological alterations are related to severe diseases. Therefore, understanding the effects of aldosterone on the body is important for health maintenance in hypertensive patients. In this review, we focus on currently available evidence regarding the role of aldosterone in alterations of the cardiovascular and renal systems. We also describe the risk of cardiovascular events and renal dysfunction in hyperaldosteronism.

Aldosterone Increases Vascular Permeability in Rat Skin

The aim of this study was to evaluate the effect of acute aldosterone (ALDO) administration on the vascular permeability of skin. ALDO was injected intradermally into rats, and vascular permeability was measured. Eplerenone (EPL), a selective mineralocorticoid receptor (MR) antagonist, was used. Skin biopsies were carried out for immunohistochemical (IHC) staining, and polymerase chain reactions were performed to analyze the expression of MR, 11β-hydroxysteroid dehydrogenase type 2, von Willebrand factor (vWF), vascular endothelial growth factor (VEGF), and zonula occludens 1. Our study showed the presence of MR in the rat skin vasculature for the first time. It was found that ALDO injection resulted in a more than 30% increase in vascular permeability and enhanced the endothelial exocytosis of vWF. The effect of ALDO diminished after EPL administration. An accumulation of vWF and a reduction in VEGF IHC staining were observed following chronic EPL administration. No effect of ALDO or EPL on the mRNA expression of the studied genes or skin structure was observed. The results suggest that ALDO increases vascular permeability in the skin via an MR-dependent mechanism. This effect of ALDO on skin microcirculation may have important therapeutic implications for diseases characterized by increased levels of ALDO and coexisting skin microangiopathy.

Thrombophilia and hormonal therapy in transgender persons: A literature review and case series

Background: Venous thromboembolism (VTE) is a rare side effect of hormonal therapy in transgender persons. Prothrombotic genetic variants can increase this risk. For this reason, previous VTE and/or genetic thrombophilia may be considered by some as contraindications to hormonal treatment. Aim: To formulate directions for clinical practice about the indications for thrombophilia screening and when to consider combination therapy of therapeutic anticoagulation and hormonal treatment as a safe alternative to withholding hormonal treatment. Methods: We conducted a literature search and describe a case series. All adult patients with gender dysphoria and a known prothrombotic genetic variant or history of VTE were invited by letter to participate in this study. Results: In our center, thrombophilia screening before start of hormonal treatment was restricted to those with a personal or family history of VTE. Sixteen individuals with a history of VTE and/or an underlying prothrombogenic condition were described. The time of follow up varied from 4 months to 20 years. Seven trans women had a positive thrombophilia screening (2 Factor V Leiden (FVL), 1 FVL + anticardiolipin antibodies, 1 FVL + high Factor VIII coagulant activity, 1 protein C deficiency, 1 prothrombin mutation, 1 positive lupus anticoagulant). Three trans women experienced an unprovoked VTE after start of hormonal therapy of which one lead to a positive thrombophilia screening. One VTE event in a trans woman was assumed to be provoked by surgery. Five trans men were identified with a prothrombogenic mutation (3 FVL, 1 protein C deficiency, 1 prothrombin mutation). One trans man, with a negative thrombophilia screen, experienced multiple provoked VTE events before start of hormonal therapy. Conclusion: Based on our literature review and case series we offer guidance when confronted with patients with previous VTE and/or genetic thrombophilia requesting hormonal interventions.

Posttranslational Modifications of the Mineralocorticoid Receptor and Cardiovascular Aging

During aging, the cardiovascular system is especially prone to a decline in function and to life-expectancy limiting diseases. Cardiovascular aging is associated with increased arterial stiffness and vasoconstriction as well as left ventricular hypertrophy and reduced diastolic function. Pathological changes include endothelial dysfunction, atherosclerosis, fibrosis, hypertrophy, inflammation, and changes in micromilieu with increased production of reactive oxygen and nitrogen species. The renin-angiotensin-aldosterone-system is an important mediator of electrolyte and blood pressure homeostasis and a key contributor to pathological remodeling processes of the cardiovascular system. Its effects are partially conveyed by the mineralocorticoid receptor (MR), a ligand-dependent transcription factor, whose activity increases during aging and cardiovascular diseases without correlating changes of its ligand aldosterone. There is growing evidence that the MR can be enzymatically and non-enzymatically modified and that these modifications contribute to ligand-independent modulation of MR activity. Modifications reported so far include phosphorylation, acetylation, ubiquitination, sumoylation and changes induced by nitrosative and oxidative stress. This review focuses on the different posttranslational modifications of the MR, their impact on MR function and degradation and the possible implications for cardiovascular aging and diseases.

Hyperglycemia Potentiates Prothrombotic Effect of Aldosterone in a Rat Arterial Thrombosis Model

We investigated the role of aldosterone (ALDO) in the development of arterial thrombosis in streptozotocin-induced diabetic rats. To evaluate the effect of endogenous ALDO, the rats underwent adrenalectomy (ADX). ADX reduced the development of arterial thrombosis. A 1 h infusion of ALDO (30 μg/kg/h) enhanced thrombosis in adrenalectomized rats, while this effect was potentiated in diabetic rats. ALDO shortened bleeding time, increased plasma levels of tissue factor (TF) and plasminogen activator inhibitor, decreased plasma level of nitric oxide (NO) metabolites, and increased oxidative stress. Moreover, 2 h incubation of human umbilical vein endothelial cells (HUVECs) with ALDO (10^-7 M) disrupted hemostatic balance in endothelial cells in normoglycemia (glucose 5.5 mM), and this effect was more pronounced in hyperglycemia (glucose 30 mM). We demonstrated that the acute ALDO infusion enhances arterial thrombosis in rats and hyperglycemia potentiates this prothrombotic effect. The mechanism of ALDO action was partially mediated by mineralocorticoid (MR) and glucocorticoid (GR) receptors and related to impact of the hormone on primary hemostasis, TF-dependent coagulation cascade, fibrinolysis, NO bioavailability, and oxidative stress balance. Our in vitro study confirmed that ALDO induces prothrombotic phenotype in the endothelium, particularly under hyperglycemic conditions.

Pathology of Aldosterone Biosynthesis and its Action

Aldosterone plays pivotal roles in renin-angiotensin-aldosterone system in order to maintain the equilibrium of liquid volume and electrolyte metabolism. Aldosterone action is mediated by both mineralocorticoid receptor and 11β-hydroxysteroid dehydrogenase type 2 (11β-HSD2). Its excessive actions directly induced tissue injuries in its target organs such as myocardial and vascular fibrosis in addition to chronic kidney diseases. Excessive aldosterone actions were also reported to be involved in unbalanced electrolyte metabolism in inflammatory bowel disease and development of pulmonary diseases. Hyperaldosteronism is tentatively classified into primary and secondary types. Primary aldosteronism is more frequent and has been well known to result in secondary hypertension with subsequent cardiovascular damages. Primary aldosteronism is also further classified into distinctive subtypes and among those, aldosterone-producing adenoma is the most frequent one accounting for the great majority of unilateral primary aldosteronism cases. In bilateral hyperaldosteronism, aldosterone-producing diffuse hyperplasia and aldosterone-producing micronodules or nodules are the major subtypes. All these aldosterone-producing lesions were reported to harbor somatic mutations including KCNJ5, CACNA1D, ATP1A1 and ATP2B3, which were all related to excessive aldosterone production. Among those mutations above, somatic mutation of KCNJ5 is the most frequent in aldosterone-producing adenoma and mostly composed of clear cells harboring abundant aldosterone synthase expression. In contrast, CACNA1D-mutated aldosterone-producing micronodules or aldosterone-producing nodules were frequently detected not only in primary aldosteronism patients but also in the zona glomerulosa of normal adrenal glands, which could eventually lead to an autonomous aldosterone production resulting in normotensive or overt primary aldosteronism, but their details have remained unknown.

Cannabidiol Ameliorates Monocrotaline-Induced Pulmonary Hypertension in Rats

Cannabidiol (CBD) is known for its vasorelaxant (including in the human pulmonary artery), anti-proliferative and anti-inflammatory properties. The aim of our study was to examine the potential preventive effect of chronic CBD administration (10 mg/kg/day for three weeks) on monocrotaline (MCT)-induced pulmonary hypertension (PH) rats. PH was connected with elevation of right ventricular systolic pressure; right ventricle hypertrophy; lung edema; pulmonary artery remodeling; enhancement of the vasoconstrictor and decreasing vasodilatory responses; increases in plasma concentrations of tissue plasminogen activator, plasminogen activator inhibitor type 1 and leukocyte count; and a decrease in blood oxygen saturation. CBD improved all abovementioned changes induced by PH except right ventricle hypertrophy and lung edema. In addition, CBD increased lung levels of some endocannabinoids (anandamide, N-arachidonoyl glycine, linolenoyl ethanolamide, palmitoleoyl ethanolamide and eicosapentaenoyl ethanolamide but not 2-arachidonoylglycerol). CBD did not affect the cardiopulmonary system of control rats or other parameters of blood morphology in PH. Our data suggest that CBD ameliorates MCT-induced PH in rats by improving endothelial efficiency and function, normalization of hemostatic alterations and reduction of enhanced leukocyte count determined in PH. In conclusion, CBD may be a safe, promising therapeutic or adjuvant therapy agent for the treatment of human pulmonary artery hypertension.

Aldosterone and the mineralocorticoid receptor in renal injury: A potential therapeutic target in feline chronic kidney disease

There is a growing body of experimental and clinical evidence supporting mineralocorticoid receptor (MR) activation as a powerful mediator of renal damage in laboratory animals and humans. Multiple pathophysiological mechanisms are proposed, with the strongest evidence supporting aldosterone-induced vasculopathy, exacerbation of oxidative stress and inflammation, and increased growth factor signalling promoting fibroblast proliferation and deranged extracellular matrix homeostasis. Further involvement of the MR is supported by extensive animal model experiments where MR antagonists (such as spironolactone and eplerenone) abrogate renal injury, including ischaemia-induced damage. Additionally, clinical trials have shown MR antagonists to be beneficial in human chronic kidney disease (CKD) in terms of reducing proteinuria and cardiovascular events, though current studies have not evaluated primary end points which allow conclusions to made about whether MR antagonists reduce mortality or slow CKD progression. Although differences between human and feline CKD exist, feline CKD shares many characteristics with human disease including tubulointerstitial fibrosis. This review evaluates the evidence for the role of the MR in renal injury and summarizes the literature concerning aldosterone in feline CKD. MR antagonists may represent a promising therapeutic strategy in feline CKD.

Rapid effects of aldosterone on platelets, coagulation, and fibrinolysis lead to experimental thrombosis augmentation

An increase in aldosterone levels positively correlates with an increased risk of acute cardiovascular thrombotic events. The aim of the study was to determine the mechanism of action of prothrombotic aldosterone focusing on the rapid effects of the hormone on platelets, coagulation, and fibrinolysis. A wide panel of advanced ex vivo and in vitro techniques was used for the evaluation of coagulation and fibrinolysis in aldosterone-treated rats. Additionally, two experimental mice models of thrombosis, which allowed for the intravital observation of the first stage of thrombus formation in real time, were used. Acute administration of aldosterone in rats increased the density of fibrin net and platelet aggregates in clots as well as reduced fibrinolysis. These effects were observed within 10 min and were partially suppressed by eplerenone. Moreover, acute administration of aldosterone in mice enhanced platelet accumulation at the site of endothelial injury induced by laser and increased the area of irreversibly activated platelets in FeCl₃-induced thrombus. These results demonstrate that aldosterone acutely affects platelets, coagulation, and fibrinolysis, leading to an enhanced thrombosis. The aldosterone effects were mediated partially via a mineralocorticoid receptor. The mechanism seems to involve non-genomic signaling since the effects were observed within a few minutes of aldosterone administration.

Vascular mineralocorticoid receptor activation and disease

Mineralocorticoid receptor activation in endothelial and smooth muscle cells can promote vascular disease by increasing oxidative stress, promoting inflammation, accelerating vascular stiffness, remodeling, and calcification, altering vessel responsiveness to various vasoactive factors, thus altering vascular tone and blood pressure, and by altering angiogenesis. Here, we review the recent evidence highlighting the impact of vascular mineralocorticoid receptor activation in pathological situations, including kidney injury, vascular injury associated with metabolic diseases, atherosclerosis, cerebral vascular injury during hypertension, vascular stiffening and aging, pulmonary hypertension, vascular calcification, cardiac remodeling, wound healing, inflammation, thrombosis, and disorders related to angiogenic defects in the eye. The possible mechanisms implicating mineralocorticoid receptor activation in various vascular disorders are discussed. Altogether, recent evidence points towards pharmacological mineralocorticoid receptor inhibition as a strategy to treat diseases in which overactivation of the mineralocorticoid receptor in endothelial and/or smooth muscle cells may play a pivotal role.

Whey protein concentrate limits venous thrombosis in rats

To study the influence of whey protein concentrate (WPC-80) on the development of thrombosis, rats were supplemented with 2 doses of WPC-80 (0.3 or 0.5 g/kg) for 7, 14, or 21 days. Then, a 1-h venous thrombosis model was performed in half of the animals. Coagulation parameters, platelet count, and thrombus weight were assessed. Thrombus weight was decreased in rats obtaining WPC-80 and that was significant only for 14- and 21-day supplementation. There were slight differences between groups in coagulation parameters and platelet count but without evident direction. Further research is needed to clarify the observed effects.

Vascular Mineralocorticoid Receptor: Evolutionary Mediator of Wound Healing Turned Harmful by Our Modern Lifestyle

The mineralocorticoid receptor (MR) is indispensable for survival through its critical role in maintaining blood pressure in response to sodium scarcity or bleeding. Activation of MR by aldosterone in the kidney controls water and electrolyte homeostasis. This review summarizes recent advances in our understanding of MR function, specifically in vascular endothelial and smooth muscle cells. The evolving roles for vascular MR are summarized in the areas of (i) vascular tone regulation, (ii) thrombosis, (iii) inflammation, and (iv) vascular remodeling/fibrosis. Synthesis of the data supports the concept that vascular MR does not contribute substantially to basal homeostasis but rather, MR is poised to be activated when the vasculature is damaged to coordinate blood pressure maintenance and wound healing. Specifically, MR activation in the vascular wall promotes vasoconstriction, inflammation, and exuberant vascular remodeling with fibrosis. A teleological model is proposed in which these functions of vascular MR may have provided a critical evolutionary survival advantage in the face of mechanical vascular injury with bleeding. However, modern lifestyle is characterized by physical inactivity and high fat/high sodium diet resulting in diffuse vascular damage. Under these modern conditions, diffuse, persistent and unregulated activation of vascular MR contributes to post-reproductive cardiovascular disease in growing populations with hypertension, obesity, and advanced age.

The endothelial mineralocorticoid receptor: mediator of the switch from vascular health to disease

PURPOSE OF REVIEW

Endothelial dysfunction is an early feature of vascular disease induced by cardiovascular risk factors (CRFs). In growing populations with obesity, diabetes, hypertension, and heart failure, mineralocorticoid receptor antagonism improves endothelial function. This review summarizes recent advances in our understanding of the specific role of endothelial cell mineralocorticoid receptor in vascular function in health and disease.

RECENT FINDINGS

Using transgenic mice with mineralocorticoid receptor expression specifically modulated in endothelial cells, recent studies support the emerging concept that while endothelial cell mineralocorticoid receptor may be protective in health, in the presence of CRFs, endothelial cell mineralocorticoid receptor activity contributes to endothelial dysfunction and progression of vascular disease. Proposed mechanisms include a role for endothelial cell mineralocorticoid receptor in decreased nitric oxide production and bioavailability, increased vascular oxidative stress, regulation of epithelial sodium channels that enhance vascular stiffness, and increased endothelial cell adhesion molecules promoting inflammation. The role of endothelial cell mineralocorticoid receptor may also depend on the sex, race, or vascular bed involved.

SUMMARY

Recent advances support the idea that endothelial cell mineralocorticoid receptor is a mediator of the switch from vascular health to disease in response to CRFs. Further investigation of the molecular mechanism is underway to identify therapeutic interventions that will limit the detrimental effects of endothelial cell mineralocorticoid receptor in patients at cardiovascular risk.

Aldosterone modulates blood homocysteine and cholesterol in coronary artery disease patients - a possible impact on atherothrombosis?

Aldosterone plays a key role in maintaining the homeostasis of the whole organism. Under some circumstances, aldosterone can contribute to the progression of cardiovascular diseases, including coronary artery disease. This study demonstrates that aldosterone associates negatively with some lipidogram parameters and positively with the concentration of homocysteine. These associations are characteristic for coronary artery disease and are not present in control subjects. The findings also indicate that in vitro aldosterone stimulates homocysteine production by rat adrenal glands, which may explain the associations observed with coronary artery disease. Moreover, we have found that aldosterone significantly modulates in vitro platelet reactivity to arachidonate and collagen - aldosterone increases the pro-aggregatory action of collagen, but decreases the pro-aggregatory potential of arachidonate. Therefore, the findings of these in vitro and ex vivo experiments indicate the existence of new pathways by which aldosterone modulates lipid- homocysteine- and platelet-dependent atherogenesis.

Antithrombotic effect and mechanism of Rubus spp. Blackberry

The compounds of Rubus spp. Blackberry (RSB) were isolated and identified by a bioassay-guided method, and their antithrombotic effects and mechanism were investigated with the acute blood stasis rat model. The RSB extract was evaluated by activated partial thromboplastin time (APTT), thrombin time (TT), prothrombin time (PT), and fibrinogen (FIB) assays in vitro. Results indicated that RSB extract exhibited anticoagulant activity. In addition to compounds 1 and 6, the other compounds also exhibited anticoagulant activity in vitro. Therefore, the in vivo antithrombosis effects of RSB extract were investigated by measuring whole blood viscosity (WBV), plasma viscosity (PV), APTT, PT, TT, and FIB. Meanwhile, the levels of thromboxane B2 (TXB₂), 6-keto prostaglandin F1α (6-keto-PGF1α), endothelial nitric oxide synthase (eNOS) and ET-1 (endothelin-1) were measured. Results suggested that RSB extract had inhibitory effects on thrombus formation, and its antithrombotic effects were associated with the regulation of vascular endothelium active substance, activation of blood flow and an anticoagulation effect.

Angiotensin-converting enzyme inhibitors attenuate propofol-induced pro-oxidative and antifibrinolytic effect in human endothelial cells

Introduction:

The aim of this study was to investigate the effects of plasma and tissue angiotensin-converting enzyme inhibitors (ACE-Is) against propofol-induced endothelial dysfunction and to elucidate the involved mechanisms in vitro.

Materials and methods:

We examined the effects of propofol (50 μM), quinaprilat and enalaprilat (10⁻⁵ M) on fibrinolysis (t-PA, PAI-1, TAFI antigen levels), oxidative stress parameters (H₂O₂ and MDA antigen levels and SOD and NADPH oxidase mRNA levels) and nitric oxide bioavailability (NO₂/NO₃ concentration and NOS expression at the level of mRNA) in human umbilical vein endothelial cells (HUVECs).

Results:

We found that both ACE-Is promoted similar endothelial fibrinolytic properties and decreased oxidative stress in vitro. Propofol alone increased the release of antifibrinolytic and pro-oxidative factors from the endothelium and increased mRNA iNOS expression. We also found that the incubation of HUVECs in the presence of propofol following ACE-Is pre-incubation caused weakness of the antifibrinolytic and pro-oxidative potential of propofol and this effect was similar after both ACE-Is.

Conclusions:

This observation suggests that the studied ACE-Is exerted protective effects against endothelial cell dysfunction caused by propofol, independently of hemodynamics.

Antithrombotic Effect and Mechanism of Radix Paeoniae Rubra

The compounds of Radix Paeoniae Rubra (RPR) were isolated and identified by bioassay-guided method, and antithrombotic effects and mechanism were investigated by the acute blood stasis rat model. The RPR extract was evaluated by APTT, TT, PT, and FIB assays in vitro. Results indicated that RPR extract exhibited the anticoagulant activity. In order to find active compounds, six compounds were isolated and identified, and four compounds, paeoniflorin (Pae), pentagalloylglucose (Pen), albiflorin (Ali), and protocatechuic acid (Pro), exhibited the anticoagulant activity in vitro. Therefore, the antithrombosis effects of RPR extract and four active compounds were investigated in vivo by measuring whole blood viscosity (WBV), plasma viscosity (PV), APTT, PT, TT, and FIB. Meanwhile, the levels of TXB₂, 6-Keto-PGF_1α, eNOS, and ET-1 were detected. Results suggested that RPR extract and four active compounds had the inhibition effect on thrombus formation, and the antithrombotic effects were associated with the regulation of vascular endothelium active substance, activating blood flow and anticoagulation effect.

Preparation and antithrombotic activity identification of Perinereis aibuhitensis extract: a high temperature and wide pH range stable biological agent

In this work, a thermal and wide pH range stable biological agent was extracted from Perinereis aibuhitensis, whose antithrombotic activity was investigated.

New agents modulating the renin-angiotensin-aldosterone system-Will there be a new therapeutic option?

The renin-angiotensin-aldosterone system (RAAS) is more complex than it was originally regarded. According to the current subject knowledge, there are two main axes of the RAAS: (1) angiotensin-converting enzyme (ACE)-angiotensin II-AT₁ receptor axis and (2) ACE2-angiotensin-(1-7)-Mas receptor axis. The activation of the first axis leads to deleterious effects, including vasoconstriction, endothelial dysfunction, thrombosis, inflammation, and fibrosis; therefore, blocking the components of this axis is a highly rational and commonly used therapeutic procedure. The ACE2-Ang-(1-7)-Mas receptor axis has a different role, since it often opposes the effects induced by the classical ACE-Ang II-AT₁ axis. Once the positive effects of the ACE2-Ang-(1-7)-Mas axis were discovered, the alternative ways of pharmacotherapy activating this axis of RAAS appeared. This article briefly describes new molecules affecting the RAAS, namely: recombinant human ACE2, ACE2 activators, angiotensin-(1-7) peptide and non-peptide analogs, aldosterone synthase inhibitors, and the third and fourth generation of mineralocorticoid receptor antagonists. The results of the experimental and clinical studies are encouraging, which leads us to believe that these new molecules can support the treatment of cardiovascular diseases as well as cardiometabolic disorders.

Quinapril decreases antifibrinolytic and prooxidative potential of propofol in arterial thrombosis in hypertensive rats

Angiotensin converting enzyme inhibitors and propofol both exert hypotensive action and may affect hemostasis. We investigated the influence of quinapril and propofol on hemodynamics and hemostasis in renal-hypertensive rats with induced arterial thrombosis. Two-kidney, one clip hypertensive rats were treated with quinapril (3.0 mg/kg for 10 days), and then received propofol infusion (15 mg/kg/h) during ongoing arterial thrombosis. The hemodynamic and hemostatic parameters were assayed. Quinapril exerted a hypotensive effect increasing after propofol infusion. Quinapril showed an antithrombotic effect with the platelet adhesion reduction, fibrinolysis enhancement and oxidative stress reduction. Propofol did not influence thrombosis; however, it inhibited fibrinolysis and showed prooxidative action. The effect of propofol on fibrinolysis and oxidative stress was significantly lower in quinapril-pretreated rats. Mortality was increased among rats treated with both drugs together. Our study demonstrates that pretreatment with quinapril reduced the adverse effects of propofol on hemostasis. Unfortunately, co-administration of both drugs potentiated hypotension in rats, which corresponds to higher mortality.

The acute prothrombotic effect of aldosterone in rats is partially mediated via angiotensin II receptor type 1

INTRODUCTION

We showed previously that the prothrombotic effect of one hour aldosterone (ALDO) infusion in rats was only partially mediated by the mineralocorticoid receptor (MR). Bearing in mind that ALDO potentiates the effects of angiotensin II (Ang II), in the present study we investigated the role of Ang II receptor type 1 - AT1 in acute ALDO prothrombotic action.

MATERIALS AND METHODS

The experiments were performed in a stasis-induced venous thrombosis model in male Wistar, normotensive rats. ALDO (30μg/kg) was infused for 1h. Valsartan (VAL; 10mg/kg), a selective AT1 receptor antagonist, was administered in a single bolus injection before ALDO infusion. Eplerenone (EPL, 100mg/kg), a selective MR receptor antagonist, was administered per os before ALDO. Thrombus weight and incidences of thrombosis were assayed. Bleeding time and platelet adhesion to collagen were evaluated as primary hemostasis parameters. The plasma levels of some coagulation and fibrinolysis parameters, and plasma NO metabolite levels were assayed.

RESULTS

AT1 blockade with valsartan significantly reduced ALDO-induced thrombosis expressed as a reduced thrombus mass (p<0.05 vs ALDO) and diminished the incidence of thrombosis. Valsartan reduced the ALDO-induced changes in bleeding time and platelet adhesion, as well as in coagulation, fibrinolysis, and NO metabolite levels. The effect of AT1 blockade in ALDO-induced thrombosis was similar to the effect of MR blockade. However, dual blockade of AT1 and MR showed no additional benefit.

CONCLUSIONS

ALDO prothrombotic action is partially mediated via AT1 receptor in the mechanism involving enhanced platelet activation, induced coagulation, impaired fibrinolysis and reduced NO bioavailability.

Acute effect of mineralocorticoid receptor antagonism on vascular function in healthy older adults

Mineralocorticoid receptor (MR) activation by aldosterone may regulate vascular function in health or contribute to vascular dysfunction in cardiovascular disease. Whether the effects are beneficial or detrimental to vascular function appear to be dependent on the integrity of the vascular endothelium and whether the responses are short-term or chronic. Acute modulation of MR activation has resulted in conflicting outcomes on vascular function in young healthy adults. Little is known about the vascular role of aldosterone and MR activation in healthy human aging. The primary objective of this study was to examine whether acute inhibition of MR by the selective antagonist eplerenone, influences vascular function in healthy older adults. We performed a randomized, double-blind, placebo-controlled crossover study in 22 adults (61±1 years; mean±SE, 53-79 years) who were free from overt clinical cardiovascular disease. We measured brachial artery flow-mediated endothelium-dependent dilation and endothelium-independent dilation to sublingual nitroglycerin (0.4 mg) following eplerenone (100 mg/dose, 2 doses, 24h between doses) or placebo. In response to acute MR antagonism, flow-mediated dilation decreased by 19% (from 6.9±0.5 to 5.6±0.6%, P=0.02; placebo vs. eplerenone). Endothelial nitric oxide synthase (eNOS) activity also decreased following MR antagonism based on the ratio of phosphorylated eNOS(Ser1177) to total eNOS (1.53±0.08 vs. 1.29±0.06, P=0.02). Nitroglycerin-induced dilation and blood pressure were unaffected (nitroglycerin-induced dilation: 21.9±1.9 vs. 21.0±1.5%, P=0.5 and systolic/diastolic blood pressure: 135/77±4/2 vs. 134/77±4/2 mmHg, P≥0.6). In conclusion, acute MR antagonism impairs vascular endothelial function in healthy older adults without influencing vascular smooth muscle responsiveness to exogenous nitric oxide or blood pressure.

Pharmacological modulation of fibrinolytic response - In vivo and in vitro studies

Fibrinolysis is an action of converting plasminogen by its activators, like tissue- or urokinase-type plasminogen activators (t-PA, u-PA), to plasmin, which in turn cleaves fibrin, thereby causing clot dissolution and restoration of blood flow. Endothelial cells release t-PA, prostacyclin (PGI2) and nitric oxide (NO), the potent factors playing a crucial role in regulation of the fibrinolytic system. Since blood platelets can release not only prothrombotic, but also antifibrinolytic factors, like plasminogen activator inhibitor type-1 (PAI-1), they are involved in fibrynolysis regulation. Therefore agents enhancing fibrinolysis can be preferred pharmacologicals in many cardiovascular diseases. This review describes mechanisms by which major cardiovascular drugs (renin-angiotensin-aldosterone system inhibitors, statins, adrenergic receptors and calcium channel blockers, aspirin and 1-methylnicotinamide) influence fibrinolysis. The presented data indicate, that the influence of these drugs on endothelium-blood platelets interactions via NO/PGI2 pathway is fundamental for its antithrombotic and profibrinolytic action. We also described new approaches for intravital confocal real-time imaging as a tool useful to investigate mechanisms of thrombus formation and the effects of drugs affecting haemostasis and mechanisms of their action in the circulation.

Mineralocorticoid Receptors in the Pathophysiology of Vascular Inflammation and Atherosclerosis

Atherosclerosis is a chronic inflammatory disease of the vasculature that causes significant morbidity and mortality from myocardial infarction, stroke, and peripheral vascular disease. Landmark clinical trials revealed that mineralocorticoid receptor (MR) antagonists improve outcomes in cardiovascular patients. Conversely, enhanced MR activation by the hormone aldosterone is associated with increased risk of MI, stroke, and cardiovascular death. This review summarizes recent advances in our understanding of the role of aldosterone and the MR in the pathogenesis of vascular inflammation and atherosclerosis as it proceeds from risk factor-induced endothelial dysfunction and inflammation to plaque formation, progression, and ultimately rupture with thrombosis, the cause of acute ischemia. The role of the MR in converting cardiac risk factors into endothelial dysfunction, in enhancing leukocyte adhesion and infiltration into the vasculature, in promoting systemic inflammation and vascular oxidative stress, and in plaque destabilization and thrombosis are discussed. A greater understanding of the mechanisms by which the MR promotes atherosclerosis has substantial potential to identify novel treatment targets to improve cardiovascular health and decrease mortality.

Eplerenone reduces arterial thrombosis in diabetic rats

INTRODUCTION

Clinical studies demonstrated the benefits of eplerenone (EPL) in reduction of cardiovascular events in diabetic patients. Since acute myocardial infarction (AMI) and stroke are related to acute intravascular thrombosis, we postulate that the beneficial effects of EPL may result from its antithrombotic action.

MATERIALS AND METHODS

Streptozotocin (STZ)-induced diabetic rats were treated with EPL (100 mg/kg/day) for 10 days. Thrombosis in the carotid artery was stimulated electrically.

RESULTS

Thrombosis development was enhanced in STZ-induced diabetic rats as compared to normoglycaemic controls. EPL caused prolongation of the time to artery occlusion, reduction in the incidence of occlusion and decrease in thrombus weight. Changes in the thrombi structure and the inhibition of hypertrophy of the tunica media in the artery wall were also observed. EPL caused reduction in tissue factor, plasminogen activator inhibitor type 1 and interleukin-1β plasma levels.

CONCLUSIONS

Our study demonstrated the antithrombotic effect of EPL manifested by a decrease in the dynamics of thrombus formation and changes in its structure. The changes in thrombosis process were accompanied by antihaemostatic, profibrinolytic and anti-inflammatory effects. The aldosterone blockade with EPL seems to be an additional pharmacological strategy for the prevention and treatment of thrombotic disorders in diabetes.

Endothelial mineralocorticoid receptor activation enhances endothelial protein C receptor and decreases vascular thrombosis in mice

Previous studies have shown that aldosterone, which activates the mineralocorticoid receptor (MR), promotes thrombosis in animal models. Our objective was to determine whether MR activation/expression in the vascular endothelium could modify thrombotic risk in vivo and to examine thrombin generation at the surface of aortic endothelial cells (HAECs). MR was conditionally overexpressed in vivo in vascular endothelial cells in mice (MR-EC mice) or stimulated with aldosterone in HAECs. Thrombosis after ferric chloride injury was delayed in MR-EC mice compared with controls as well as in wild-type FVB/NRj mice treated with aldosterone (60 μg/kg/d for 21 d). Thrombin generation in platelet-poor plasma did not differ between MR-EC mice and controls. In MR-EC mice, aortic endothelial cell protein C receptor (EPCR) expression was increased. Aldosterone (10(-8) M) attenuated thrombin generation at the surface of cultured HAECs, and this effect was associated with up-regulation of expression of EPCR, which promotes formation of activated protein C. Aldosterone increases EPCR expression via a transcriptional mechanism involving interaction of MR with the specificity protein 1 site. These findings demonstrate that MR activation acts on endothelial cells to protect against thrombosis in physiological conditions and that MR-mediated EPCR overexpression drives this antithrombotic property through enhancing protein C activation.

Mineralocorticoid receptors in vascular disease: connecting molecular pathways to clinical implications

The mineralocorticoid receptor (MR), a steroid-hormone-activated transcription factor, plays a substantial role in cardiovascular diseases. MR antagonists (MRAs) have long been appreciated as effective treatments for heart failure and hypertension; however, recent research suggests that additional patient populations may also benefit from MRA therapy. Experimental evidence demonstrates that in addition to its classic role in the regulating sodium handling in the kidney, functional MR is expressed in the blood vessels and contributes to hypertension, vascular inflammation and remodeling, and atherogenesis. MR activation drives pathological phenotypes in smooth muscle cells, endothelial cells, and inflammatory cells, whereas MRAs inhibit these effects. Collectively, these studies demonstrate a new role for extrarenal MR in cardiovascular disease. This review summarizes these new lines of evidence and how they contribute to the mechanisms of atherosclerosis, pulmonary and systemic hypertension, and vein graft failure, and describes new patient populations that may benefit from MRA therapy.

Impact of aldosterone antagonists on the substrate for atrial fibrillation: aldosterone promotes oxidative stress and atrial structural/electrical remodeling

Atrial fibrillation (AF), the most common cardiac arrhythmia, is an electrocardiographic description of a condition with multiple and complex underlying mechanisms. Oxidative stress is an important driver of structural remodeling that creates a substrate for AF. Oxidant radicals may promote increase of atrial oxidative damage, electrical and structural remodeling, and atrial inflammation. AF and other cardiovascular morbidities activate angiotensin (Ang-II)-dependent and independent cascades. A key component of the renin-angiotensin-aldosterone system (RAAS) is the mineralocorticoid aldosterone. Recent studies provide evidence of myocardial aldosterone synthesis. Aldosterone promotes cardiac oxidative stress, inflammation and structural/electrical remodeling via multiple mechanisms. In HF patients, aldosterone production is enhanced. In patients and in experimental HF and AF models, aldosterone receptor antagonists have favorable influences on cardiac remodeling and oxidative stress. Therapeutic approaches that seek to reduce AF burden by modulating the aldosterone system are likely beneficial but underutilized.

Aldosterone affects blood flow and vascular tone regulated by endothelium-derived NO: therapeutic implications

Aldosterone, in doses inappropriate to the salt status, plays an important role in the development of cardiovascular injury, including endothelial dysfunction, independent of its hypertensive effects. Acute non-genomic effects of aldosterone acting on mineralocorticoid receptors are inconsistent in healthy humans: vasoconstriction or forearm blood flow decrease via endothelial dysfunction, vasodilatation mediated by increased NO actions, or no effects. However, in studies with experimental animals, aldosterone mostly enhances vasodilatation mediated by endothelium-derived NO. Chronic exposure to aldosterone, which induces genomic responses, results in impairments of endothelial function through decreased NO synthesis and action in healthy individuals, experimental animals and isolated endothelial cells. Chronic aldosterone reduces NO release from isolated human endothelial cells only when extracellular sodium is raised. Oxidative stress is involved in the impairment of endothelial function by promoting NO degradation. Aldosterone liberates endothelin-1 (ET-1) from endothelial cells, which elicits ET(A) receptor-mediated vasoconstriction by inhibiting endothelial NO synthesis and action and through its own direct vasoconstrictor action. Ca(2+) flux through T-type Ca(2+) channels activates aldosterone synthesis and thus enhances unwanted effects of aldosterone on the endothelium. Mineralocorticoid receptor inhibitors, ET(A) receptor antagonists and T-type Ca(2) + channel blockers appear to diminish the pathophysiological participation of aldosterone in cardiovascular disease and exert beneficial actions on bioavailability of endothelium-derived NO, particularly in resistant hypertension and aldosteronism.

Aldosterone, oxidative stress, and NF-κB activation in hypertension-related cardiovascular and renal diseases

The mineralocorticoid aldosterone regulates electrolyte and fluid balance and is involved in blood pressure homoeostasis. Classically, it binds to its intracellular mineralocorticoid receptor to induce expression of proteins influencing the reabsorption of sodium and water in the distal nephron. Aldosterone gained special attention when large clinical studies showed that blocking its receptor in patients with cardiovascular diseases reduced their mortality. These patients present increased plasma aldosterone levels. The exact mechanisms of the potential toxic effects of aldosterone leading to cardiovascular damage are not known yet. The observation of reduced nitric oxide bioavailability in hyperaldosteronism implied the generation of oxidative stress by aldosterone. Subsequent studies confirmed the increase of oxidative stress markers in patients with chronic heart failure and in animal models of hyperaldosteronism. The effects of reactive oxygen species have been related to the activation of transcription factors, such as NF-κB. This review summarizes the present-day knowledge of aldosterone-induced oxidative stress and NF-κB activation in humans and different experimental models.