Mechanism of Angiotensin II Type 1 Receptor Blocker Action in the Regression of Left Ventricular Hypertrophy

Aqueous extract of Solanum nigrum attenuates Angiotensin-II induced cardiac hypertrophy and improves cardiac function by repressing protein kinase C-ζ to restore HSF2 deSUMOlyation and Mel-18-IGF-IIR signaling suppression

ETHNOPHARMACOLOGICAL RELEVANCE

Solanum nigrum, commonly known as Makoi or black shade has been traditionally used in Asian countries and other regions of world to treat liver disorders, diarrhoea, inflammatory conditions, chronic skin ailments (psoriasis and ringworm), fever, hydrophobia, painful periods, eye diseases, etc. It has been observed that S. nigrum contains substances, like steroidal saponins, total alkaloid, steroid alkaloid, and glycoprotein, which show anti-tumor activity. However; there is no scientific evidence of the efficacy of S. nigrum in the treatment of cardiac hypertrophy.

AIM

To investigate the ability of S. nigrum to attenuate Angiotensin II - induced cardiac hypertrophy and improve cardiac function through the suppression of protein kinase PKC-ζ and Mel-18-IGF-IIR signaling leading to the restoration of HSF2 desumolyation.

MATERIALS AND METHODS

Cardiomyoblast cells (H9c2) were challenged with 100 nM Angiotensin-II (AngII) for 24 h and were then treated with different concentration of S.nigrum or Calphostin C for 24 h. The hypertrophic effect in cardiomyoblast cells were determined by immunofluorescence staining and the modulations in hypertrophic protein marker along with Protein Kinase C-ζ, MEL18, HSF2, and Insulin like growth factor II (IGFIIR), markers were analyzed by western blotting. In vivo experiments were performed using 12 week old male Wistar Kyoto rats (WKY) and Spontaneously hypertensive rats (SHR) separated into five groups. [1]Control WKY, [2] WKY -100 mg/kg of S.nigrum treatment, [3] SHR, [4] SHR-100 mg/kg of S.nigrum treatment, [5] SHR-300 mg/kg of S.nigrum treatment. S. nigrum was administered intraperitoneally for 8 week time interval.

RESULTS

Western blotting results indicate that S. nigrum significantly attenuates AngII induced cardiac hypertrophy. Furthermore, actin staining confirmed the ability of S. nigrum to ameliorate AngII induced cardiac hypertrophy. Moreover, S. nigrum administration suppressed the hypertrophic signaling mediators like Protein Kinase C-ζ, Mel-18, and IGFIIR in a dose-dependent manner and HSF2 activation (restore deSUMOlyation) that leads to downregulation of IGF-IIR expression. Additionally in vivo experiments demonstrate the reduced heart sizes of S. nigrum treated SHRs rats when compared to control WKY rats.

CONCLUSION

Collectively, the data reveals the cardioprotective effect of S. nigrum inhibiting PKC-ζ with alleviated IGF IIR level in the heart that profoundly remits cardiac hypertrophy for hypertension-induced heart failure.

Effect of allisartan on blood pressure and left ventricular hypertrophy through Kv1.5 channels in hypertensive rats

BACKGROUND

The objective of the present work was to study the anti-hypertensive effect of allisartan on blood pressure (BP) and in facilitating left ventricular remodeling through voltage-gated potassium channels (Kv) 1.5 channels.

METHODS

A total of 30 SD rats were randomly divided into sham operation group, hypertension control group, and allisartan treatment group. Hypertension was induced by renal artery stenosis. The animals of treatment group were administered with allisartan once a day at a dose of 30 mg/kg body weight through an oral gavage for 4 weeks. The heart function of animals post 4 weeks of treatment was evaluated by echocardiography, and the degree of ventricular hypertrophy and cardiomyocyte hypertrophy were evaluated by histomorphology. The expression of Kv1.5 is detected by real-time quantitative polymerase chain reaction while Western blotting was used to detect the protein expression.

RESULTS

Four weeks after renal artery stenosis, a significant difference was observed in the whole heart ratio, left heart ratio, and cardiomyocyte area between allisartan treatment group and the hypertension control group (P< .01). A significant decrease in BP of allisartan treatment group compared to hypertension control group (P< .01) was observed. The expression of Kv1.5 mRNA was increased significantly (P< .01) in allisartan treatment group compared to hypertension control group. Western blot analysis also confirmed the increased expression of Kv1.5 channel.

CONCLUSION

The results showed that allisartan lowers BP and improves left ventricular remodeling through increased expression of Kv1.5 mRNA.

Effects of Angiotensin II Receptor Blockers on Ventricular Hypertrophy in Hypertrophic Cardiomyopathy: A Meta-Analysis of Randomized Controlled Trials

PURPOSE

Animal studies have suggested that angiotensin II receptor blockers (ARBs) can attenuate or reverse the progression of hypertrophic cardiomyopathy, while clinical studies yielded conflicting results. We sought to conduct a meta-analysis to investigate the effect of ARBs in patients with hypertrophic cardiomyopathy.

METHODS

PubMed and EMBASE databases were searched through June 2020. Only randomized controlled trials (RCTs) were included, and each study's quality was assessed using the Jadad scale. The primary outcome was left ventricular mass reduction, and the secondary outcome was the change in left ventricular ejection fraction (LVEF). Data were pooled using the random effects model.

RESULTS

A total of 1294 articles were screened. Five RCTs were included in the final analysis, enrolling 209 patients with hypertrophic cardiomyopathy (101 patients were in the ARB arm). ARB treatment was not associated with either significant left ventricular mass reduction (standardized mean difference: - 0.25; 95% CI: - 0.73, 0.22; p = 0.29) or change in LVEF (weighted mean difference: 0.73%; 95% CI: - 1.10%, 2.56%; p = 0.43). Subgroup analysis showed that losartan, one of the most investigated and commonly used ARBs, was also not associated with significant decreases of left ventricular mass (standardized mean difference: - 0.13; 95% CI: - 0.61, 0.36; p = 0.61).

CONCLUSION

This meta-analysis showed that ARB treatment is not associated with reduced left ventricular mass nor remarkable LVEF change among patients with hypertrophic cardiomyopathy. Further studies with a larger number of patients will be required to confirm these findings.

Is left ventricular hypertrophy a friend or foe of patients with aortic stenosis?

Left ventricular hypertrophy (LVH) is traditionally considered a physiological compensatory response to LV pressure overload, such as hypertension and aortic stenosis (AS), in an effort to maintain LV systolic function in the face of an increased afterload. According to the Laplace law, LV wall thickening lowers LV wall stress, which in turn would be helpful to preserve LV systolic performance. However, numerous studies have challenged the notion of LVH as a putative beneficial adaptive mechanism. In fact, the magnitude of LVH is associated with higher cardiovascular morbidity and mortality, especially when LVH is disproportionate to LV afterload. We have briefly reviewed: first, the importance of non-valvular factors, beyond AS severity, for total LV afterload and symptomatic status in AS patients; second, associations of excessive LVH with LV dysfunction and adverse outcome in AS; third, prognostic relevance of the presence or absence of pre-operative LVH in patients referred for aortic valve surgery; fourth, time course, determinants and prognostic implications of LVH regression and LV function recovery after surgical valve replacement and transcatheter aortic valve implantation (TAVI) with a focus on TAVI-specific effects; fifth, the potential of medical therapy to modulate LVH before and after surgical or interventional treatment for severe AS, a condition perceived as a relative contraindication to renin-angiotensin system blockade.

Comparison of the effect of combination therapy with an angiotensin II receptor blocker and either a low-dose diuretic or calcium channel blocker on cardiac hypertrophy in patients with hypertension

Left ventricular hypertrophy (LVH) regression is an important issue in hypertensive patients. Patients with LVH who had received the angiotensin receptor blocker (ARB) treatment for 8 weeks and had not reached the target blood pressure level were enrolled in the study. Patients were assigned to either losartan (50 mg)/hydrochlorothiazide (HCTZ, 12.5 mg) group or ARB + CCB group (usual dose of ARB and calcium channel blocker, CCB). After 48 weeks, LV mass index was found to be reduced significantly in the losartan/HCTZ group but not in the ARB + CCB group. These results suggest that combination therapy of an ARB and diuretic has greater potential to cause regression compared with an ARB and CCB.

Association of blood pressure with left ventricular mass in untreated hypertensives in rural Yunnan Province

BACKGROUND

Chinese rural residents make up one-eighth of the world's population. Hypertension (HTN) and its resultant cardiovascular complications are rapidly increasing in this vast segment of humanity, while its treatment and control remain unacceptably low. HTN is associated with increased left ventricular mass (LVM), but the magnitude and characteristics of this relationship in persons not undergoing treatment are unknown.

METHODS

We studied 344 randomly selected adults who were not being treated for HTN and who had ages between 50 and 70 years (mean age 57.8, 51.7% female) using a questionnaire, height, weight, blood pressure (BP), and ultrasonic measurements of LVM. We performed bivariate and multivariable regression analysis to examine the relation of BP with LVM index (LVMI).

RESULTS

We found a HTN prevalence of 30%. There was a significant (P < 0.0001) linear relationship between BP and LVMI in this untreated population. Diastolic (DBP) compared to systolic BP (SBP) was more strongly associated with LVMI (beta = 0.714 vs. 0.379, both P = 0.02). Persons with vs. without HTN had higher LVMI (102.5 g vs. 84.9 g, P < 0.0001).

CONCLUSIONS

The LVMI of hypertensives, not undergoing treatment in rural Yunnan province is strongly related to BP, especially DBP.

Does treatment of hypertension decrease the incidence of atrial fibrillation and cardioembolic stroke?

Hypertension is the most common disease affecting humans. Statistical surveys indicate that approximately one billion individuals worldwide suffer from this serious condition. The spotlight of the present review is on the cardiac involvement in patients with hypertension and especially on the possibility that treatment of increased blood pressure may abolish the incidence of cardiac arrhythmia and particularly atrial fibrillation. Modern therapeutic approach based on the electrical and structural remodeling process in the hypertensive heart with a consequent administration of ACE inhibitors and AT1 receptor blockers represent new and more efficient option compared to other antihypertensive drugs, such as calcium channel blockers, beta-blockers and thiazide-type diuretics and might be useful in the prevention of atrial fibrillation and incidence of stroke.

Treatment of hypertension in heart failure with preserved ejection fraction: role of the kidney

Heart failure can present clinically as primarily diastolic or systolic dysfunction or both. There is an increasing awareness that heart failure can occur in the presence of a normal left ventricular ejection fraction. Heart failure with normal left ventricular ejection fraction is frequently referred to as diastolic heart failure because of the presence of diastolic left ventricular dysfunction evident from impaired left ventricular relaxation. This article focuses on the treatment of hypertension and the role the kidney plays in selecting appropriate agents.

Evaluation of the renin-angiotensin system in cardiac tissues of cats with pressure-overload cardiac hypertrophy

OBJECTIVE

To clarify regulation of the renin-angiotensin (RA) system in cardiac tissues by measuring angiotensin-converting enzyme (ACE) and chymase activities in cats with pressure-overload cardiac hypertrophy.

ANIMALS

13 adult cats.

PROCEDURES

Pressure-overload cardiac hypertrophy was induced by coarctation of the base of the ascending aorta in 6 cats, and 7 cats served as untreated control animals. Cats were examined before and 3 months and 2 years after surgery. Two years after surgery, cardiac hypertrophy was confirmed by echocardiography, and the blood pressure gradient was measured at the site of constriction. Cats were euthanized, and ACE and chymase activities were measured in cardiac tissues.

RESULTS

Mean +/- SD pressure gradient across the aortic constriction was 63 +/- 6 mm Hg. Chymase activity predominated (75% to 85%) in the RA system of the cardiac tissues of cats. Fibrosis in the wall of the left ventricle was detected in cats with hypertrophy, and fibrosis of the papillary muscle was particularly evident.

CONCLUSIONS AND CLINICAL RELEVANCE

Chronic pressure overload on the heart of cats can activate the RA system in cardiac tissues. A local increase in angiotensin II was one of the factors that sustained myocardial remodeling.

Establishing a new option for target-organ protection: rationale for ARB plus ACE inhibitor combination therapy

Activation of the renin-angiotensin system (RAS) plays an important role in the promotion of cardiovascular disease and target-organ damage, mediated in part by hypertension. Combination therapy targeting RAS activation may reduce target-organ damage and provide superior blood pressure (BP) control; combining angiotensin-converting enzyme (ACE) inhibitors and angiotensin II receptor blockers (ARBs) represents one possible approach. In monotherapy studies, both ACE inhibitors and ARBs have demonstrated similar positive effects on BP and on RAS-related target-organ damage, including nephropathy and congestive heart failure. Studies of combination therapy, most of which involved addition of an ARB to existing ACE inhibitor therapy, have demonstrated benefits among patients with congestive heart failure and renal disease. However, variances in study design and populations, dosing and titration methods, and clinical end points, in addition to inherent differences between agents, limit the ability to reach clinically meaningful conclusions about the value of dual RAS inhibition. Trials designed to document such efficacy are currently underway.

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.

Prevention of new-onset atrial fibrillation and its predictors with angiotensin II-receptor blockers in the treatment of hypertension and heart failure

Atrial fibrillation is the most frequent occurring sustained cardiac arrhythmia and it is related to common cardiac disease conditions. Hypertension increases the risk of atrial fibrillation by approximately two-fold and, because of the high prevalence of hypertension, it accounts for more cases of atrial fibrillation than any other risk factor. In recent years, there are two large hypertension trials (LIFE and VALUE) and two large heart failure trials (CHARM and Val-HeFT) reporting the beneficial effect of angiotensin II-receptor blockers (ARBs) on new-onset atrial fibrillation, beyond the blood pressure-lowering effect. Blockade of the renin-angiotensin system may prevent left atrial dilatation, atrial fibrosis, dysfunction and conduction velocity slowing. Some studies also indicate direct anti-arrhythmic properties. This review aims to consider the preventive effect of ARBs on new-onset atrial fibrillation observed in recent reports from these trials, and to discuss possible mechanisms of the beneficial effect of angiotensin II-receptor blockade.