Angiotensin II receptor blockade and ventricular remodelling

The Effects of Aldosterone on Hypertension-Associated Kidney Injury in a Tg-hAS Mouse Model

Hypertension remains a global health challenge due to its high prevalence and association with premature morbidity and mortality. Aldosterone, a mineralocorticoid hormone, and its receptor, the mineralocorticoid receptor (MR), are highly implicated in hypertension pathogenesis. Aldosterone synthase is the sole enzyme responsible for producing aldosterone in humans. We established transgenic mice carrying the human aldosterone synthase gene (cyp11B2) and showed dramatically increased levels of aldosterone in female hemizygotes. High-salt diets persistently increased blood pressure in these mice, and salt-induced hypertension was significantly ameliorated by reducing aldosterone levels via an aldosterone synthase inhibitor or blocking MR via an MR inhibitor. Since both hypertension and hyperaldosteronism specifically induce chronic kidney disease, in this model, we demonstrated that chronic high-salt diets induced hypertension in this mouse line and resulted in kidney inflammation and injury. Both the aldosterone synthase inhibitor and the MR antagonist markedly blocked high-salt-diet-mediated kidney injury. Thus, this transgenic mouse line can be used to study the pathogenic mechanisms underlying aldosterone and its receptor and to screen therapeutic compounds for aldosterone-mediated hypertension and related complications, such as kidney disease, in humans.

Renin-Angiotensin-Aldosterone System and Immunomodulation: A State-of-the-Art Review

The renin–angiotensin system (RAS) has long been described in the field of cardiovascular physiology as the main player in blood pressure homeostasis. However, other effects have since been described, and include proliferation, fibrosis, and inflammation. To illustrate the immunomodulatory properties of the RAS, we chose three distinct fields in which RAS may play a critical role and be the subject of specific treatments. In oncology, RAS hyperactivation has been associated with tumor migration, survival, cell proliferation, and angiogenesis; preliminary data showed promise of the benefit of RAS blockers in patients treated for certain types of cancer. In intensive care medicine, vasoplegic shock has been associated with severe macro- and microcirculatory imbalance. A relative insufficiency in angiotensin II (AngII) was associated to lethal outcomes and synthetic AngII has been suggested as a specific treatment in these cases. Finally, in solid organ transplantation, both AngI and AngII have been associated with increased rejection events, with a regional specificity in the RAS activity. These elements emphasize the complexity of the direct and indirect interactions of RAS with immunomodulatory pathways and warrant further research in the field.

Cardiac fibrosis: Myofibroblast-mediated pathological regulation and drug delivery strategies

Cardiac fibrosis remains an unresolved problem in heart diseases. After initial injury, cardiac fibroblasts (CFs) are activated and subsequently differentiate into myofibroblasts (myoFbs) that are major mediator cells in the pathological remodeling. MyoFbs exhibit proliferative and secretive characteristics, and contribute to extracellular matrix (ECM) turnover, collagen deposition. The persistent functions of myoFbs lead to fibrotic scars and cardiac dysfunction. The anti-fibrotic treatment is hindered by the elusive mechanism of fibrosis and lack of specific targets on myoFbs. In this review, we will outline the progress of cardiac fibrosis and its contributions to the heart failure. We will also shed light on the role of myoFbs in the regulation of adverse remodeling. The communication between myoFbs and other cells that are involved in the heart injury and repair respectively will be reviewed in detail. Then, recently developed therapeutic strategies to treat fibrosis will be summarized such as i) chimeric antigen receptor T cell (CAR-T) therapy with an optimal target on myoFbs, ii) direct reprogramming from stem cells to quiescent CFs, iii) "off-target" small molecular drugs. The application of nano/micro technology will be discussed as well, which is involved in the construction of cell-based biomimic platforms and "pleiotropic" drug delivery systems.

Immunity and Hypertension

Hypertension is the primary cause of cardiovascular mortality. Despite multiple existing treatments, only half of those with the disease achieve adequate control. Therefore, understanding the mechanisms causing hypertension is essential for the development of novel therapies. Many studies demonstrate that immune cell infiltration of the vessel wall, kidney and central nervous system, as well as their counterparts of oxidative stress, the renal renin-angiotensin system (RAS) and sympathetic tone play a critical role in the development of hypertension. Genetically modified mice lacking components of innate and/or adaptive immunity confirm the importance of chronic inflammation in hypertension and its complications. Depletion of immune cells improves endothelial function, decreases oxidative stress, reduces vascular tone and prevents renal interstitial infiltrates, sodium retention and kidney damage. Moreover, the ablation of microglia or central nervous system perivascular macrophages reduces RAS-induced inflammation and prevents sympathetic nervous system activation and hypertension. Therefore, understanding immune cell functioning and their interactions with tissues that regulate hypertensive responses may be the future of novel antihypertensive therapies.

The Lipid Paradox is present in ST-elevation but not in non-ST-elevation myocardial infarction patients: Insights from the Singapore Myocardial Infarction Registry

Lowering low-density lipoprotein (LDL-C) and triglyceride (TG) levels form the cornerstone approach of cardiovascular risk reduction, and a higher high-density lipoprotein (HDL-C) is thought to be protective. However, in acute myocardial infarction (AMI) patients, higher admission LDL-C and TG levels have been shown to be associated with better clinical outcomes - termed the 'lipid paradox'. We studied the relationship between lipid profile obtained within 72 hours of presentation, and all-cause mortality (during hospitalization, at 30-days and 12-months), and rehospitalization for heart failure and non-fatal AMI at 12-months in ST-segment elevation myocardial infarction (STEMI) and non-ST-segment elevation myocardial infarction (NSTEMI) patients treated by percutaneous coronary intervention (PCI). We included 11543 STEMI and 8470 NSTEMI patients who underwent PCI in the Singapore Myocardial Infarction Registry between 2008-2015. NSTEMI patients were older (60.3 years vs 57.7 years, p < 0.001) and more likely to be female (22.4% vs 15.0%, p < 0.001). In NSTEMI, a lower LDL-C was paradoxically associated with worse outcomes for death during hospitalization, within 30-days and within 12-months (all p < 0.001), but adjustment eliminated this paradox. In contrast, the paradox for LDL-C persisted for all primary outcomes after adjustment in STEMI. For NSTEMI patients, a lower HDL-C was associated with a higher risk of death during hospitalization but in STEMI patients a lower HDL-C was paradoxically associated with a lower risk of death during hospitalization. For this endpoint, the interaction term for HDL-C and type of MI was significant even after adjustment. An elevated TG level was not protective after adjustment. These observations may be due to differing characteristics and underlying pathophysiological mechanisms in NSTEMI and STEMI.

Tβ4-Ac-SDKP pathway: Any relevance for the cardiovascular system?

The last 20 years witnessed the emergence of the thymosin β4 (Tβ4)-N-acetyl-seryl-aspartyl-lysyl-proline (Ac-SDKP) pathway as a new source of future therapeutic tools to treat cardiovascular and renal diseases. In this review article, we attempted to shed light on the numerous experimental findings pertaining to the many promising cardiovascular therapeutic avenues for Tβ4 and (or) its N-terminal derivative, Ac-SDKP. Specifically, Ac-SDKP is endogenously produced from the 43-amino acid Tβ4 by 2 successive enzymes, meprin α and prolyl oligopeptidase. We also discussed the possible mechanisms involved in the Tβ4-Ac-SDKP-associated cardiovascular biological effects. In infarcted myocardium, Tβ4 and Ac-SDKP facilitate cardiac repair after infarction by promoting endothelial cell migration and myocyte survival. Additionally, Tβ4 and Ac-SDKP have antifibrotic and anti-inflammatory properties in the arteries, heart, lungs, and kidneys, and stimulate both in vitro and in vivo angiogenesis. The effects of Tβ4 can be mediated directly through a putative receptor (Ku80) or via its enzymatically released N-terminal derivative Ac-SDKP. Despite the localization and characterization of Ac-SDKP binding sites in myocardium, more studies are needed to fully identify and clone Ac-SDKP receptors. It remains promising that Ac-SDKP or its degradation-resistant analogs could serve as new therapeutic tools to treat cardiac, vascular, and renal injury and dysfunction to be used alone or in combination with the already established pharmacotherapy for cardiovascular diseases.

Effects of moderate‑intensity endurance exercise on angiotensin II and angiotensin II type I receptors in the rat heart

The current study was aimed at examining the effects of moderate‑intensity endurance exercise on the expression of angiotensin II (AngII) and AngII type 1 receptor (AT1R) in the rat heart. Male Sprague‑Dawley rats were randomly divided into the control group (n=20) and moderate‑intensity endurance exercise group (n=20). Cardiac hypertrophy was induced by treadmill endurance training for 8 weeks. The mRNA expression of AngII and AT1R were assessed by reverse transcription‑quantitative polymerase chain reaction. The immune response positive area and optical density of AngII and AT1R was measured by immunohistochemistry. AngII was primarily expressed in the cytoplasm and membrane, however infrequently in coronary vascular wall smooth muscle cells. AT1R was primarily expressed in the coronary vessel wall smooth muscle, rarely in cardiac cells. The mRNA expression of cardiac AngII was significantly increased after the 8‑week exercise period, while AT1R was significantly decreased. Immunohistochemistry indicated a significant increase in the AngII immune‑positive area and optical density after the 8‑week exercise. The AT1R immune‑positive area and optical density was significantly reduced following the 8‑week exercise. In conclusion, subsequent to 8‑weeks endurance training, the AngII expression was increased and the AT1R expression was decreased. AT1R may expand the coronary artery, thereby increasing coronary blood flow and ensuring the energy supply of heart during exercise. The expression change in AngII does not reflect the character of cardiac hypertrophy. The exercise‑induced change in the expression of AngII and AT1R may be a protective mechanism to avoid cardiac pathological hypertrophy.

Relationship between site of myocardial infarction, left ventricular function and cytokine levels in patients undergoing coronary artery surgery

BACKGROUND

The purpose of this study was to examine the relationship between left ventricular (LV) function, cytokine levels and site of myocardial infarction (MI) in patients undergoing coronary artery bypass grafting (CABG).

METHODS

Sixty patients undergoing CABG were divided into three groups (n = 20) according to their history of site of myocardial infarction (MI): no previous MI, anterior MI and posterior/inferior MI. In the pre-operative period, detailed analysis of LV function was done by transthoracic echocardiography. The levels of adrenomedullin, interleukin-1-beta, interleukin-6, tumour necrosis factor-alpha (TNF-α) and angiotensin-II in both peripheral blood samples and pericardial fluid were also measured.

RESULTS

Echocardiographic analyses showed that the anterior MI group had significantly worse LV function than both the group with no previous MI and the posterior/inferior MI group (p < 0.05 for LV end-systolic diameter, fractional shortening, LV end-systolic volume, LV end-systolic volume index and ejection fraction). In the anterior MI group, both plasma and pericardial fluid levels of adrenomedullin and and pericardial fluid levels of interleukin-6 and interleukin- 1-beta were significantly higher than those in the group with no previous MI (p < 0.05), and pericardial fluid levels of adrenomedullin, interleukin-6 and interleukin-1-beta were significantly higher than those in the posterior/inferior MI group (p < 0.05).

CONCLUSIONS

The results of this study indicate that (1) patients with an anterior MI had worse LV function than patients with no previous MI and those with a posterior/inferior MI, and (2) cytokine levels in the plasma and pericardial fluid in patients with anterior MI were increased compared to patients with no previous MI.

Radionuclide imaging of neurohormonal system of the heart

Heart failure is one of the growing causes of death especially in developed countries due to longer life expectancy. Although many pharmacological and instrumental therapeutic approaches have been introduced for prevention and treatment of heart failure, there are still limitations and challenges. Nuclear cardiology has experienced rapid growth in the last few decades, in particular the application of single photon emission computed tomography (SPECT) and positron emission tomography (PET), which allow non-invasive functional assessment of cardiac condition including neurohormonal systems involved in heart failure; its application has dramatically improved the capacity for fundamental research and clinical diagnosis. In this article, we review the current status of applying radionuclide technology in non-invasive imaging of neurohormonal system in the heart, especially focusing on the tracers that are currently available. A short discussion about disadvantages and perspectives is also included.

Role of the Carotid Body Chemoreflex in the Pathophysiology of Heart Failure: A Perspective from Animal Studies

The treatment and management of chronic heart failure (CHF) remains an important focus for new and more effective clinical strategies. This important goal, however, is dependent upon advancing our understanding of the underlying pathophysiology. In CHF, sympathetic overactivity plays an important role in the development and progression of the cardiac and renal dysfunction and is often associated with breathing dysregulation, which in turn likely mediates or aggravates the autonomic imbalance. In this review we will summarize evidence that in CHF, the elevation in sympathetic activity and breathing instability that ultimately lead to cardiac and renal failure are driven, at least in part, by maladaptive activation of the carotid body (CB) chemoreflex. This maladaptive change derives from a tonic increase in CB afferent activity. We will focus our discussion on an understanding of mechanisms that alter CB afferent activity in CHF and its consequence on reflex control of autonomic, respiratory, renal, and cardiac function in animal models of CHF. We will also discuss the potential translational impact of targeting the CB in the treatment of CHF in humans, with relevance to other cardio-respiratory diseases.

Adrenal adrenoceptors in heart failure

Heart failure (HF) is a chronic clinical syndrome characterized by the reduction in left ventricular (LV) function and it represents one of the most important causes of morbidity and mortality worldwide. Despite considerable advances in pharmacological treatment, HF represents a severe clinical and social burden. Sympathetic outflow, characterized by increased circulating catecholamines (CA) biosynthesis and secretion, is peculiar in HF and sympatholytic treatments (as β-blockers) are presently being used for the treatment of this disease. Adrenal gland secretes Epinephrine (80%) and Norepinephrine (20%) in response to acetylcholine stimulation of nicotinic cholinergic receptors on the chromaffin cell membranes. This process is regulated by adrenergic receptors (ARs): α2ARs inhibit CA release through coupling to inhibitory Gi-proteins, and β ARs (mainly β2ARs) stimulate CA release through coupling to stimulatory Gs-proteins. All ARs are G-protein-coupled receptors (GPCRs) and GPCR kinases (GRKs) regulate their signaling and function. Adrenal GRK2-mediated α2AR desensitization and downregulation are increased in HF and seem to be a fundamental regulator of CA secretion from the adrenal gland. Consequently, restoration of adrenal α2AR signaling through the inhibition of GRK2 is a fascinating sympatholytic therapeutic strategy for chronic HF. This strategy could have several significant advantages over existing HF pharmacotherapies minimizing side-effects on extra-cardiac tissues and reducing the chronic activation of the renin–angiotensin–aldosterone and endothelin systems. The role of adrenal ARs in regulation of sympathetic hyperactivity opens interesting perspectives in understanding HF pathophysiology and in the identification of new therapeutic targets.

An orally active angiotensin-(1-7) inclusion compound and exercise training produce similar cardiovascular effects in spontaneously hypertensive rats

Low angiotensin-(1-7) (Ang-(1-7)) concentration is observed in some cardiovascular diseases and exercise training seems to restore its concentration in the heart. Recently, a novel formulation of an orally active Ang-(1-7) included in hydroxy-propyl-beta-cyclodextrin (HPB-CD) was developed and chronically administered in experimental models of cardiovascular diseases. The present study examined whether chronic administration of HPB-CD/Ang-(1-7) produces beneficial cardiovascular effects in spontaneously hypertensive rats (SHR), as well as to compare the results obtained with those produced by exercise training. Male SHR (15-week old) were divided in control (tap water) or treated with HPB-CD/Ang-(1-7) (corresponding to 30μgkg(-1)day(-1) of Ang-(1-7)) by gavage, concomitantly or not to exercise training (treadmill, 10 weeks). After chronic treatment, hemodynamic, morphometric and molecular analysis in the heart were performed. Chronic HPB-CD/Ang-(1-7) decreased arterial blood pressure (BP) and heart rate in SHR. The inclusion compound significantly improved left ventricular (LV) end-diastolic pressure, restored the maximum and minimum derivatives (dP/dT) and decreased cardiac hypertrophy index in SHR. Chronic treatment improved autonomic control by attenuating sympathetic modulation on heart and vessels and the SAP variability, as well as increasing parasympathetic modulation and HR variability. Overall results were similar to those obtained with exercise training. These results show that chronic treatment with the HPB-CD/Ang-(1-7) inclusion compound produced beneficial effects in SHR resembling the ones produced by exercise training. This observation reinforces the potential cardiovascular therapeutic effect of this novel peptide formulation.

Molecular hybrid positron emission tomography/computed tomography imaging of cardiac angiotensin II type 1 receptors

OBJECTIVES

The goal of this study was to explore the feasibility of targeted imaging of the angiotensin II type 1 receptor (AT1R) in cardiac tissue, using clinical hybrid positron emission tomography/computed tomography (PET/CT).

BACKGROUND

AT1R is an attractive imaging target due to its key role in various cardiac pathologies, including post-infarct left ventricular remodeling.

METHODS

Using the novel AT1R ligand [(11)C]-KR31173, dynamic PET/CT was performed in young farm pigs under healthy conditions (n = 4) and 3 to 4 weeks after experimental myocardial infarction (n = 5). Ex vivo validation was carried out by immunohistochemistry and polymerase chain reaction. First-in-man application was performed in 4 healthy volunteers at baseline and under AT1R blocking.

RESULTS

In healthy pigs, myocardial KR31173 retention was detectable, regionally homogeneous, and specific for AT1R, as confirmed by blocking experiments. Metabolism in plasma was low (85 ± 2% of intact tracer after 60 min). After myocardial infarction, KR31173 retention, corrected for regional perfusion, revealed AT1R up-regulation in the infarct area relative to remote myocardium, whereas retention was elevated in both regions when compared with myocardium of healthy controls (8.7 ± 0.8% and 7.1 ± 0.3%/min vs. 5.8 ± 0.4%/min for infarct and remote, respectively, vs. healthy controls; p < 0.01 each). Postmortem analysis confirmed AT1R up-regulation in remote and infarct tissue. First-in-man application was safe, and showed detectable and specific myocardial KR31173 retention, albeit at a lower level than pigs (left ventricular average retention: 1.2 ± 0.1%/min vs. 4.4 ± 1.2%/min for humans vs. pigs; p = 0.04).

CONCLUSIONS

Noninvasive imaging of cardiac AT1R expression is feasible using clinical PET/CT technology. Results provide a rationale for broader clinical testing of AT1R-targeted molecular imaging.

Cardiovascular and cerebrovascular outcomes in elderly hypertensive patients treated with either ARB or ACEI

Background

Although angiotensin converting enzyme inhibitors (ACEI) and angiotensin receptor blockers (ARB) are equally important in the treatment of hypertension, there is less evidence whether they have equal cardiovascular and cerebrovascular protective effects, especially in elder hypertensive patients. This study aims to clarify this unresolved issue.

Methods

This cross-sectional study included clinical data on 933 aged male patients with hypertension who received either an ARB or ACEI for more than two months between January 2007 and May 2011. The primary outcome was the composite of cardiovascular death, non-fatal myocardial infarction, and non-fatal stroke. The secondary endpoints were unstable angina, new atrial fibrillation, and transient ischemic attack.

Results

The median follow-up time was 24 months. Age, drug types, cerebral infarction history, renal dysfunction history were the independent predictors of the primary endpoint. The risk of an occurrence of a primary endpoint event was higher in the ARB group than the ACEI group [P = 0.037, hazard ratios (HR): 2.124, 95% confidence interval (95% CI): 1.048–4.306]. The Kaplan-Meier method also suggests that the rate of primary endpoint occurrence was higher in the ARB group than the ACEI group (P = 0.04). In regard to the secondary endpoints, there were no significant differences between the two treatment arms (P = 0.137, HR: 1.454, 95% CI: 0.888–2.380). Patient age and coronary heart disease history were independent predictors of the secondary endpoint.

Conclusion

ACEI were more effective than ARB in reducing cardiovascular and cerebrovascular morbidity and mortality in aged patients with hypertension.

Moderate cardiac-selective overexpression of angiotensin II type 2 receptor protects cardiac functions from ischaemic injury

We hypothesized that moderate cardiac-selective overexpression of the angiotensin II type 2 receptor (AT2R) would protect the myocardium from ischaemic injury after a myocardial infarction (MI) induced by coronary artery ligation. For in vitro studies, adenoviral vector expressing genomic DNA of AT2R and enhanced green fluorescence protein (EGFP) was used to overexpress AT2R in rat neonatal cardiac myocytes. Expression of AT2R, measured by real-time PCR and immunostaining, demonstrated efficient transduction of AT2R in a dose-dependent pattern. The AT2R constitutively induced apoptosis in rat neonatal cardiac myocytes in dose-dependent patterns. For in vivo studies, 4 × 10(10) vector genomes (vg) of recombinant adeno-associated virus serotype 9 (rAAV9)-chicken β actin promoter-AT2R was injected into the left ventricle of 5-day-old Sprague-Dawley rats. At 6 weeks of age, hearts were harvested and expression of AT2R determined by real-time PCR and Western blotting. Expression was increased onefold over control hearts, and no apoptosis was detected. Two subsequent in vivo studies were performed. In a prevention study, 4 × 10(10) vg of rAAV9-CBA-AT2R was injected into the left ventricle of 5-day-old Sprague-Dawley rats and MI was induced at 6 weeks of age. For a post-treatment study, 4 × 10(10) vg of rAAV9-CBA-AT2R was administrated to the peri-infarcted myocardium area immediately after MI in 6-week-old animals. For both in vivo studies, cardiac functions were assessed using echocardiography and haemodynamic measurements 4 weeks after coronary artery ligation. In the in vivo studies, the rats subjected to MI showed significant decreases in fractional shortening and rate of change of left ventricular pressure, with increased left ventricular end-diastolic pressure and ventricular hypertrophy. For the prevention study, the moderate cardiac-selective overexpression of AT2R attenuated these MI-induced impairments and also caused a decrease in ventricular wall thinning. In the post-treatment study, the overexpression of AT2R partly reversed the MI-induced cardiac dysfunction. Myocardial infarction also induced the upregulation of angiotensin II type 1 receptor, angiotensin-converting enzyme and collagen I mRNA expression, all of which were attenuated by the overexpression of AT2R. It is concluded that moderate cardiac-selective overexpression of AT2R protects heart function from ischaemic injury, which may be mediated, at least in part, through modulation of components of the cardiac renin-angiotensin system and collagen levels in the myocardium.

Angiotensin IV protects against angiotensin II-induced cardiac injury via AT4 receptor

Angiotensin II (Ang II) is an important regulator of cardiac function and injury in hypertension. The novel Ang IV peptide/AT4 receptor system has been implicated in several physiological functions and has some effects opposite to those of Ang II. However, little is known about the role of this system in Ang II-induced cardiac injury. Here we studied the effect of Ang IV on Ang II-induced cardiac dysfunction and injury using isolated rat hearts, neonatal cardiomyocytes and cardiac fibroblasts. We found that Ang IV significantly improved Ang II-induced cardiac dysfunction and injury in the isolated heart in response to ischemia/reperfusion (I/R). Moreover, Ang IV inhibited Ang II-induced cardiac cell apoptosis, cardiomyocyte hypertrophy, and proliferation and collagen synthesis of cardiac fibroblasts; these effects were mediated through the AT4 receptor as confirmed by siRNA knockdown. These findings suggest that Ang IV may have a protective effect on Ang II-induced cardiac injury and dysfunction and may be a novel therapeutic target for hypertensive heart disease.

Role of prolylcarboxypeptidase in angiotensin II type 2 receptor-mediated bradykinin release in mouse coronary artery endothelial cells

Activation of angiotensin II type 2 receptors (AT(2)R) causes the release of kinins, which have beneficial effects on the cardiovascular system. However, it is not clear how AT(2)R interact with the kallikrein-kinin system to generate kinins. Prolylcarboxypeptidase is an endothelial membrane-bound plasma prekallikrein activator that converts plasma prekallikrein to kallikrein, leading to generation of bradykinin from high-molecular-weight kininogen. We hypothesized that AT(2)R-induced bradykinin release is at least in part mediated by activation of prolylcarboxypeptidase. Cultures of mouse coronary artery endothelial cells were transfected with an adenoviral vector containing the AT(2)R gene (Ad-AT(2)R) or green fluorescent protein only (Ad-GFP) as control. We found that overexpression of AT(2)R increased prolylcarboxypeptidase mRNA by 1.7-fold and protein 2.5-fold compared with Ad-GFP controls. AT(2)R overexpression had no effect on angiotensin II type 1 receptor mRNA. Bradykinin release was increased 2.2-fold in AT(2)R-transfected cells. Activation of AT(2)R by CGP42112A, a specific AT(2)R agonist, increased bradykinin further in AT(2)R-transfected cells. These effects were diminished or abolished by AT(2)R blockade or a plasma kallikrein inhibitor. Furthermore, blocking prolylcarboxypeptidase with a small interfering RNA partially but significantly reduced bradykinin release by transfected AT(2)R cells either at the basal condition or when stimulated by the AT(2)R agonist CGP42112A. These findings suggest that overexpression of AT(2)R in mouse coronary artery endothelial cells increases expression of prolylcarboxypeptidase, which may contribute to kinin release.

Synergism of simvastatin with losartan prevents angiotensin II-induced cardiomyocyte apoptosis in vitro

Objectives

Increasing evidence suggests that cardiomyocyte apoptosis has an important role in the transition from compensatory cardiac remodelling to heart failure. The synergistic effect of statins (3-hydroxy-3-methylglutaryl-coenzyme A reductase inhibitors) and angiotensin II (Ang II) type 1 receptor antagonists reduces the incidence of cardiovascular events. However, the anti-apoptotic potential of the synergism between losartan and simvastatin in heart failure remains unexplored. Here, we demonstrate that Ang II-induced apoptosis is prevented by losartan and simvastatin in neonatal cardiomyocytes.

Methods

The in-vitro cardiomyocyte apoptosis model was established by co-culturing neonate rat cardiomyocytes with Ang II. Cell viability was analysed by the MTT assay. Cell apoptosis was evaluated using fluorescence microscopy and flow cytometry. Apoptosis-related proteins Bax and Bcl-2 expressions were measured by flow cytometry detection.

Key findings

Incubation with 10−7  m Ang II for 48 h increased cardiomyocyte apoptosis and decreased cell viability. Losartan (10−5  m) and simvastatin (10−5  m), either alone or in combination, significantly decreased Ang II-induced cardiomyocyte apoptosis and increased cell viability. The q values calculated by the probability sum test were 1.31 for cardiomyocyte apoptosis and 1.21 for cell viability. Ang II induced a significant increase in Bax protein expression, whereas Bcl-2 protein expression was decreased. Losartan alone or in combination with simvastatin blocked the increased Bax expression and increased Bcl-2 expression. However, simvastatin had no such effect.

Conclusions

Our data provide the first evidence that synergism of simvastatin with losartan prevents angiotensin II-induced cardiomyocyte apoptosis in vitro. Synergism between simvastatin and losartan may provide a new therapeutic approach to the prevention of cardiac remodelling.

Effects of Telmisartan, Ramipril, and Their Combination on Left Ventricular Hypertrophy in Individuals at High Vascular Risk in the Ongoing Telmisartan Alone and in Combination With Ramipril Global End Point Trial and the Telmisartan Randomized Assessment Study in ACE Intolerant Subjects With Cardiovascular Disease

Background— Angiotensin-converting enzyme (ACE) inhibitors and angiotensin receptor blockers reduce left ventricular hypertrophy (LVH). The effect of these drugs on LVH in high-risk patients without heart failure is unknown.

Methods and Results— In the Ongoing Telmisartan Alone and in Combination With Ramipril Global End Point Trial (ONTARGET), patients at high vascular risk and tolerant of ACE inhibitors were randomly assigned to ramipril, telmisartan, or their combination (n=23 165). In the Telmisartan Randomized Assessment Study in ACE Intolerant Subjects With Cardiovascular Disease (TRANSCEND), patients intolerant of ACE inhibitors were randomized to telmisartan or placebo (n=5343). Prevalence of LVH at entry in TRANSCEND was 12.7%. It was reduced by telmisartan (10.5% and 9.9% after 2 and 5 years) compared with placebo (12.7% and 12.8% after 2 and 5 years) (overall odds ratio, 0.79; 95% confidence interval [CI], 0.68 to 0.91; P =0.0017). New-onset LVH occurred less frequently with telmisartan compared with placebo (overall odds ratio, 0.63; 95% CI, 0.51 to 0.79; P =0.0001). LVH regression was similar in the 2 groups. In ONTARGET, prevalence of LVH at entry was 12.4%. At follow-up, it occurred slightly less frequently with telmisartan (odds ratio, 0.92; 95% CI, 0.83 to 1.01; P =0.07) and the combination (odds ratio, 0.93; 95% CI, 0.84 to 1.02; P =0.12) than with ramipril, but differences between the groups were not significant. New-onset LVH was associated with a higher risk of primary outcome during follow-up (hazard ratio, 1.77; 95% CI, 1.50 to 2.07).

Conclusions— In patients at high vascular risk, telmisartan is more effective than placebo in reducing LVH. New-onset LVH is reduced by 37%. The effect of combination of the 2 drugs on LVH is similar to that of ramipril alone.

Effects of chronic PPAR-agonist treatment on cardiac structure and function, blood pressure, and kidney in healthy sprague-dawley rats

PPAR-γ agonists have been associated with heart failure (HF) in diabetic patients. These incidences have been reported mostly in patient populations who were at high risk for HF or had pre-existing impaired cardiovascular function. However, whether there are similar effects of these agents in subjects with no or reduced cardiovascular pathophysiology is not clear. In this study, the effects of chronic treatment with PD168, a potent peroxisome proliferator activated receptor (PPAR) subtype-γ agonist with weak activity at PPAR-α, and rosiglitazone (RGZ), a less potent PPAR-γ agonist with no PPAR-α activity, were evaluated on the cardiovascular-renal system in healthy male Sprague-Dawley (SD) rats by serial echocardiography and radiotelemetry. Rats were treated with vehicle (VEH), PD168, @ 10 or 50 mg/kg.bw/day (PD-10 or PD-50, resp.) or RGZ @ 180 mg/kg.bw/day for 28 days (n = 10/group). Relative to VEH, RGZ, and both doses of PD168 resulted in a significant fall in blood pressure. Furthermore, RGZ and PD168 increased plasma volume (% increase from baseline) 18%, 22%, and 48% for RGZ, PD-10, and PD-50, respectively. PD168 and RGZ significantly increased urinary aldosterone excretion and heart-to-body weight ratio relative to VEH. In addition, PD168 significantly decreased (10-16%) cardiac ejection fraction (EF) and increased left ventricular area (LVA) in systole (s) and diastole (d) in PD-10 and -50 rats. RGZ significantly increased LVAd; however, it did not affect EF relative to VEH. In conclusion, chronic PPAR-γ therapy may predispose the cardiorenal system to a potential sequela of structural and/or functional changes that may be deleterious with regard to morbidity and mortality.

Cardiac fibroblasts: at the heart of myocardial remodeling

Cardiac fibroblasts are the most prevalent cell type in the heart and play a key role in regulating normal myocardial function and in the adverse myocardial remodeling that occurs with hypertension, myocardial infarction and heart failure. Many of the functional effects of cardiac fibroblasts are mediated through differentiation to a myofibroblast phenotype that expresses contractile proteins and exhibits increased migratory, proliferative and secretory properties. Cardiac myofibroblasts respond to proinflammatory cytokines (e.g. TNFalpha, IL-1, IL-6, TGF-beta), vasoactive peptides (e.g. angiotensin II, endothelin-1, natriuretic peptides) and hormones (e.g. noradrenaline), the levels of which are increased in the remodeling heart. Their function is also modulated by mechanical stretch and changes in oxygen availability (e.g. ischaemia-reperfusion). Myofibroblast responses to such stimuli include changes in cell proliferation, cell migration, extracellular matrix metabolism and secretion of various bioactive molecules including cytokines, vasoactive peptides and growth factors. Several classes of commonly prescribed therapeutic agents for cardiovascular disease also exert pleiotropic effects on cardiac fibroblasts that may explain some of their beneficial outcomes on the remodeling heart. These include drugs for reducing hypertension (ACE inhibitors, angiotensin receptor blockers, beta-blockers), cholesterol levels (statins, fibrates) and insulin resistance (thiazolidinediones). In this review, we provide insight into the properties of cardiac fibroblasts that underscores their importance in the remodeling heart, including their origin, electrophysiological properties, role in matrix metabolism, functional responses to environmental stimuli and ability to secrete bioactive molecules. We also review the evidence suggesting that certain cardiovascular drugs can reduce myocardial remodeling specifically via modulatory effects on cardiac fibroblasts.

Adrenal adrenoceptors in heart failure: fine-tuning cardiac stimulation

Chronic heart failure (HF) is characterized by sympathetic hyperactivity reflected by increased circulating catecholamines (CAs), which contributes significantly to its morbidity and mortality. Therefore, sympatholytic treatments, that is, treatments that reduce sympathetic hyperactivity, are being pursued currently for the treatment of HF. Secretion of CAs from the adrenal gland, which is a major source of CAs, is regulated by alpha(2)-adrenoceptors (alpha(2)ARs), which inhibit, and by beta-adrenoceptors (betaARs), which enhance CA secretion. All ARs are G-protein-coupled receptors (GPCRs), whose signaling and function are regulated tightly by the family of GPCR kinases (GRKs). Despite the enormous potential of adrenal ARs for the regulation of sympathetic outflow, elucidation of their properties has only begun recently. Here, recent advances regarding the roles of adrenal ARs in the regulation of sympathetic outflow in HF and the regulatory properties of ARs are discussed, along with the potential benefits and challenges of harnessing their function for HF therapy.

Activation of the ERK1/2 cascade via pulsatile interstitial fluid flow promotes cardiac tissue assembly

Deciphering the cellular signals leading to cardiac muscle assembly is a major challenge in ex vivo tissue regeneration. For the first time, we demonstrate that pulsatile interstitial fluid flow in three-dimensional neonatal cardiac cell constructs can activate ERK1/2 sixfold, as compared to static-cultivated constructs. Activation of ERK1/2 was attained under physiological shear stress conditions, without activating the p38 cell death signal above its basic level. Activation of the ERK1/2 signaling cascade induced synthesis of high levels of contractile and cell-cell contact proteins by the cardiomyocytes, while its inhibition diminished the inducing effects of pulsatile flow. The pulsed medium-induced cardiac cell constructs showed improved cellularity and viability, while the regenerated cardiac tissue demonstrated some ultra-structural features of the adult myocardium. The cardiomyocytes were elongated and aligned into myofibers with defined Z-lines and multiple high-ordered sarcomeres. Numerous intercalated disks were positioned between adjacent cardiomyocytes, and deposits of collagen fibers surrounded the myofibrils. The regenerated cardiac tissue exhibited high density of connexin 43, a major protein involved in electrical cellular connections. Our research thus demonstrates that by judiciously applying fluid shear stress, cell signaling cascades can be augmented with subsequent profound effects on cardiac tissue regeneration.

Complications of hypertension and the role of angiotensin receptor blockers in hypertension trials

Hypertension is a high-prevalence disease that may affect several organs. In recent years, data have accumulated indicating that angiotensin II receptor blockers (ARBs) may have a supplementary effect beyond lowering blood pressure. The aim of this review is to evaluate the impact of ARBs on the most important complications of hypertension--heart, cerebrovascular and renal diseases, and metabolic complications--based on the findings from large clinical hypertension trials. The results may indicate that ARBs have a superior effect compared with placebo or other antihypertensive drugs in order to prevent left ventricular hypertrophy, atrial fibrillation, stroke, renal disease and diabetes mellitus, while there appears to be no blood pressure-independent superior effect of ARBs regarding prevention of myocardial infarction or heart failure.