Role of aliskiren on arterial stiffness and endothelial function in patients with primary hypertension

Aliskiren Improved the Endothelial Repair Capacity of Endothelial Progenitor Cells from Patients with Hypertension via the Tie2/PI3k/Akt/eNOS Signalling Pathway

Background

Studies show that aliskiren exerts favourable effects not only on endothelial progenitor cells (EPCs) but also on endothelial function. However, the mechanism of the favourable effect of aliskiren on EPCs from patients with hypertension is unclear and remains to be further studied.

Methods

The object of this study was to investigate and assess the in vitro function of EPCs pretreated with aliskiren. After treated with aliskiren, the human EPCs were transplanted into a nude mouse model of carotid artery injury, and the in vivo reendothelialization of injured artery was estimated by staining denuded areas with Evans blue dye via tail vein injection.

Results

We found that aliskiren increased the in vitro migration, proliferation, and adhesion of EPCs from patients with hypertension in a dose-dependent manner and improved the reendothelialization capability of these EPCs. Furthermore, aliskiren increased the phosphorylation of Tie2, Akt, and eNOS. After the blockade of the Tie2 signalling pathway, the favourable effects of aliskiren on the in vitro function and in vivo reendothelialization capability of EPCs were suppressed.

Conclusions

This study demonstrates that aliskiren can improve the in vitro function and in vivo reendothelialization capability of EPCs from patients with hypertension via the activation of the Tie2/PI3k/Akt/eNOS signalling pathway. These findings further indicate that aliskiren is an effective pharmacological treatment for cell-based repair in hypertension-related vascular injury.

Attenuation of atrial remodeling by aliskiren via affecting oxidative stress, inflammation and PI3K/Akt signaling pathway

INTRODUCTION

Atrial fibrillation (AF) is the most common type of arrhythmia. Atrial remodeling is a major factor to the AF substrate. The purpose of the study is to explore whether aliskiren (ALS) has a cardioprotective effect and its potential molecular mechanisms on atrial remodeling.

METHODS

In acute experiments, dogs were randomly assigned to Sham, Paced and Paced+aliskiren (10 mg kg^-1) (Paced+ALS) groups, with 7 dogs in each group. Rapid atrial pacing (RAP) was maintained at 600 bpm for 2 h for paced and Paced+ALS groups and atrial effective refractory periods (AERPs), inducibility of AF (AFi) and average duration time (ADT) were measured. In chronic experiments, there were 5 groups: Sham, Sham+ALS, Paced, Paced+ALS and Paced+ALS+PI3K antagonist wortmannin (WM) (70 μg kg^-1 day^-1). RAP at 500 beats/min was maintained for 2 weeks. Inflammation and oxidative stress indicators were measured by ELISA assay, echocardiogram and pathology were used to assess atrial structural remodeling, phosphatidylinositol 3-hydroxy kinase/protein kinase B (PI3K/Akt) signaling pathways were studied by RT-PCR and western blotting to evaluate whether the cardioprotective effect of ALS works through PI3K/Akt signaling pathway.

RESULTS

The electrophysiological changes were observed after 2-h pacing. The AERP shortened with increased AFi and ADT, which was attenuated by ALS (P < 0.05). After pacing for 2 weeks, oxidative stress and inflammation markers in the Paced group were significantly higher than those in the Sham group (P < 0.01) and were reduced by ALS treatment (P < 0.01). The reduced level of antioxidant enzymes caused by RAP was also found to be elevated in ALS-treated group (P < 0.01). The results of pathology and echocardiography showed that RAP can cause atrial enlargement, fibrosis (P < 0.01), and were attenuated in ALS treatment group. The PI3K/Akt signaling pathway were downregulated induced by RAP. ALS could upregulate the PI3K/Akt pathway expression (P < 0.05). Furthermore, the cardioprotective effects in structural remodeling of ALS were suppressed by WM.

CONCLUSIONS

ALS may offer cardioprotection in RAP-induced atrial remodeling, which may partly be ascribed to its anti-inflammatory and anti-oxidative stress action and the regulation of PI3K/Akt signaling pathway.

The use of aliskiren as an antifibrotic drug in experimental models: A systematic review

Aliskiren is an oral antihypertensive medication that acts by directly inhibiting renin. High levels of circulating renin and prorenin activate the pathological signaling pathway of fibrosis. This drug also reduces oxidative stress. Thus, the aim of this systematic review is to analyze experimental studies that show the actions of aliskiren on fibrosis. PubMed and LILACS databases were consulted using the keywords aliskiren and fibrosis within the period between 2005 and 2017. Fifty-three articles were analyzed. In the heart, aliskiren attenuated remodeling, hypertrophy, inflammatory cytokines, collagen deposition, and oxidative stress. In the kidneys, there was a reduction in interstitial fibrosis, the infiltration of inflammatory cells, apoptosis, proteinuria, and in the recruitment of macrophages. In diabetic models, an improvement in the albumin/creatinine relationship and in the insulin pathway in skeletal muscles was observed; aliskiren was beneficial to pancreatic function and glucose tolerance. In the liver, aliskiren reduced fibrosis, steatosis, inflammatory cytokines, and collagen deposition. In the lung and peritoneal tissues, there was a reduction in fibrosis. Many studies have reported on the beneficial effects of aliskiren on endothelial function and arterial rigidity. A reduction in fibrosis in different organs is cited by many authors, which complies with the results found in this review. However, studies diverge on the use of the drug in diabetic patients. Aliskiren has antifibrotic potential in several experimental models, interfering with the levels of fibrogenic cytokines and oxidative stress. Therefore, its use in diseases in which fibrosis plays an important pathophysiological role is suggested.

Lysyl Oxidase Induces Vascular Oxidative Stress and Contributes to Arterial Stiffness and Abnormal Elastin Structure in Hypertension: Role of p38MAPK

AIMS

Vascular stiffness, structural elastin abnormalities, and increased oxidative stress are hallmarks of hypertension. Lysyl oxidase (LOX) is an elastin crosslinking enzyme that produces H2O2 as a by-product. We addressed the interplay between LOX, oxidative stress, vessel stiffness, and elastin.

RESULTS

Angiotensin II (Ang II)-infused hypertensive mice and spontaneously hypertensive rats (SHR) showed increased vascular LOX expression and stiffness and an abnormal elastin structure. Mice over-expressing LOX in vascular smooth muscle cells (TgLOX) exhibited similar mechanical and elastin alterations to those of hypertensive models. LOX inhibition with β-aminopropionitrile (BAPN) attenuated mechanical and elastin alterations in TgLOX mice, Ang II-infused mice, and SHR. Arteries from TgLOX mice, Ang II-infused mice, and/or SHR exhibited increased vascular H2O2 and O2.- levels, NADPH oxidase activity, and/or mitochondrial dysfunction. BAPN prevented the higher oxidative stress in hypertensive models. Treatment of TgLOX and Ang II-infused mice and SHR with the mitochondrial-targeted superoxide dismutase mimetic mito-TEMPO, the antioxidant apocynin, or the H2O2 scavenger polyethylene glycol-conjugated catalase (PEG-catalase) reduced oxidative stress, vascular stiffness, and elastin alterations. Vascular p38 mitogen-activated protein kinase (p38MAPK) activation was increased in Ang II-infused and TgLOX mice and this effect was prevented by BAPN, mito-TEMPO, or PEG-catalase. SB203580, the p38MAPK inhibitor, normalized vessel stiffness and elastin structure in TgLOX mice.

INNOVATION

We identify LOX as a novel source of vascular reactive oxygen species and a new pathway involved in vascular stiffness and elastin remodeling in hypertension.

CONCLUSION

LOX up-regulation is associated with enhanced oxidative stress that promotes p38MAPK activation, elastin structural alterations, and vascular stiffness. This pathway contributes to vascular abnormalities in hypertension. Antioxid. Redox Signal. 27, 379-397.

Renin Inhibition with Aliskiren: A Decade of Clinical Experience

The renin-angiotensin-aldosterone system (RAAS) plays a key role in the pathophysiology of arterial hypertension as well as in more complex mechanisms of cardiovascular and renal diseases. RAAS-blocking agents like angiotensin-converting enzyme (ACE) inhibitors and angiotensin II receptor blockers, have long been key components in the treatment of essential hypertension, heart failure, diabetic nephropathy, and chronic kidney disease, showing benefits well beyond blood pressure reduction. Renin blockade as the first step of the RAAS cascade finally became possible in 2007 with the approval of aliskiren, the first orally active direct renin inhibitor available for clinical use and the newest antihypertensive agent on the market. In the last decade, many clinical trials and meta-analyses have been conducted concerning the efficacy and safety of aliskiren in comparison to other antihypertensive agents, as well as the efficacy and potential clinical use of various combinations. Large trials with cardiovascular and renal endpoints attempted to show potential benefits of aliskiren beyond blood pressure lowering, as well as morbidity and mortality outcomes in specific populations such as diabetics, heart failure patients, and post-myocardial infarction individuals. The purpose of this review is to present the currently available data regarding established and future potential clinical uses of aliskiren.

Early Vascular Ageing - A Concept in Development

Cardiovascular disease (CVD) is a prevalent condition in the elderly, often associated with metabolic disturbance and type 2 diabetes. For a number of years, research dedicated to understand atherosclerosis dominated, and for many good reasons, this pathophysiological process being proximal to the CVD events. In recent years, research has been devoted to an earlier stage of vascular pathology named arteriosclerosis (arterial stiffness) and the new concept of early vascular ageing (EVA), developed by a group of mostly European researchers. This overview describes recent developments in research dedicated to EVA and new emerging aspects found in studies of families at high cardiovascular risk. There are new aspects related to genetics, telomere biology and the role of gut microbiota. However, there is still no unifying definition available of EVA and no direct treatment, but rather only recommendations for conventional cardiovascular risk factor control. New interventions are being developed - not only new antihypertensive drugs, but also new drugs for vascular protection - the selective angiotensin-II (AT2) agonist Compound 21 (C21). Human studies are eagerly awaited. Even new functional food products could have the potential to positively influence cardiometabolic regulation, to be confirmed.

Effect of aliskiren on circulating endothelial progenitor cells and vascular function in patients with type 2 diabetes and essential hypertension

BACKGROUND

The aim of this study was to investigate the effects of aliskiren on vascular function and endothelial progenitor cells (EPCs) in patients with type 2 diabetes and essential hypertension.

METHODS

The study enrolled type 2 diabetic patients aged >50 years under stable glycemic control and first diagnosed mild essential hypertension. In phase A (n = 20), patients received aliskiren 150-300 mg daily for 3 months. In phase B (n = 12), hydrochlorothiazide (HCTZ) 12.5-25mg daily substituted for aliskiren for 3 more months. At baseline and at the end of each phase, we assessed (i) brachial blood pressure (BBP); (ii) central aortic systolic pressure (CSP), aortic augmentation index (Aix), and pulse wave velocity (PWV) as markers of arterial stiffness; (iii) brachial artery flow-mediated dilatation (FMD) as a marker of endothelial function; (iv) left ventricular (LV) twisting and untwisting as markers of LV function and (v) EPC numbers in culture of peripheral blood mononuclear cells.

RESULTS

Aliskiren similarly reduced BBP and CSP, increased FMD (P < 0.001) and EPC numbers (P < 0.001), decreased PWV and Aix (P < 0.05), and improved LV twisting and untwisting (P < 0.05). Although substitution of HCTZ sustained BBP at similar levels, CSP and echocardiographic indices nearly returned at baseline levels, and the improvement of FMD, PWV, Aix, and EPC numbers was abolished.

CONCLUSIONS

Aliskiren had a favorable effect on endothelial function and EPCs, reduced arterial stiffness, and improved LV twisting and untwisting. These effects were independent of BBP lowering, as they were not observed after the achievement of similar values of BBP with HCTZ.

Vascular stiffening in pulmonary hypertension: cause or consequence? (2013 Grover Conference series)

Recent studies have indicated that systemic arterial stiffening is a precursor to hypertension and that hypertension, in turn, can perpetuate arterial stiffening. Pulmonary artery (PA) stiffening is also well documented to occur in pulmonary hypertension (PH), and there is evidence that pulmonary vascular stiffness (PVS) may be a better predictor of outcome than pulmonary vascular resistance (PVR). We have hypothesized that the decreased flow-damping function of elastic PAs in PH likely initiates and/or perpetuates dysfunction of pulmonary microvasculature. Recent studies have shown that large-vessel stiffening increases flow pulsatility in the distal pulmonary vasculature, leading to endothelial dysfunction within a proinflammatory, vasoconstricting, and profibrogenic environment. The intricate role of stiffening-stimulated high pulsatile flow in endothelial cell dysfunction includes stepwise molecular events underlying PA hypertrophy, inflammation, endothelial-mesenchymal transition, and fibrosis. In addition to contributing to microenvironmental alterations of the distal vasculature, disordered proximal-distal PA coupling likely also plays a role in increasing ventricular afterload, ultimately causing right ventricle (RV) dysfunction and death. Current therapeutic treatments do not provide a realistic approach to destiffening arteries and, thus, to potentially abrogating the effects of high pulsatile flow on the distal pulmonary vasculature or the increased work imposed by stiffening on the RV. Scrutinizing the effect of PA stiffening on high pulsatile flow-induced cellular and molecular changes, and vice versa, might lead to important new therapeutic options that abrogate PA remodeling and PH development. With a clear understanding that PA stiffening may contribute to the progression of PH to an irreversible state by contributing to chronic microvascular damage in lungs, future studies should be aimed first at defining the underlying mechanisms leading to PA stiffening and then at improved treatment approaches based on these findings.

Treating coronary disease and the impact of endothelial dysfunction

Ischemic heart disease is the leading cause of morbidity and mortality throughout the world. Many clinical trials have suggested that lifestyle and pharmacologic interventions are effective in attenuating atherosclerotic disease progression and events development. However, an individualized approach with careful consideration to comprehensive vascular health is necessary to perform successful intervention strategies. Endothelial dysfunction plays a pivotal role in the early stage of atherosclerosis and is also associated with plaque progression and occurrence of atherosclerotic complications. The assessment of endothelial function provides us with important information about individual patient risk, progress and vulnerability of disease, and guidance of therapy. Thus, the application of endothelial function assessment might enable clinicians to innovate ideal individualized medicine. In this review, we summarize the current knowledge on the impact of pharmacological therapies for atherosclerotic cardiovascular disease on endothelial dysfunction, and argue for the utility of non-invasive assessment of endothelial function aiming at individualized medicine.

Arterial stiffness and cardiovascular therapy

The world population is aging and the number of old people is continuously increasing. Arterial structure and function change with age, progressively leading to arterial stiffening. Arterial stiffness is best characterized by measurement of pulse wave velocity (PWV), which is its surrogate marker. It has been shown that PWV could improve cardiovascular event prediction in models that included standard risk factors. Consequently, it might therefore enable better identification of populations at high-risk of cardiovascular morbidity and mortality. The present review is focused on a survey of different pharmacological therapeutic options for decreasing arterial stiffness. The influence of several groups of drugs is described: antihypertensive drugs (angiotensin-converting enzyme inhibitors, angiotensin receptor blockers, calcium channel blockers, beta-blockers, diuretics, and nitrates), statins, peroral antidiabetics, advanced glycation end-products (AGE) cross-link breakers, anti-inflammatory drugs, endothelin-A receptor antagonists, and vasopeptidase inhibitors. All of these have shown some effect in decreasing arterial stiffness. Nevertheless, further studies are needed which should address the influence of arterial stiffness diminishment on major adverse cardiovascular and cerebrovascular events (MACCE).

Effects of aliskiren- and ramipril-based treatment on central aortic blood pressure in elderly with systolic hypertension: a substudy of AGELESS

BACKGROUND

Systolic hypertension is the most common form of hypertension in elderly patients. There is increasing evidence that measurement of central aortic pressure (CAP) better accounts for cardiovascular risk than brachial blood pressure (BP). The Aliskiren for GEriatric LowEring of SyStolic hypertension (AGELESS) study in elderly patients with systolic hypertension showed that aliskiren-based therapy provided greater reductions in peripheral BP than ramipril-based therapy over 12 and 36 weeks of treatment. Here, we present CAP results in a substudy of elderly patients from the AGELESS study.

METHODS

This was a post hoc analysis of a 36-week, randomized, double-blind, parallel-group, active-controlled, optional-titration study in patients ≥65 years of age with systolic BP ≥140 mmHg. Changes in both central and peripheral BP and pulse pressure (PP) and changes in systolic and PP amplification ratios from baseline to the week 36 end point with aliskiren-based versus ramipril-based therapy were analyzed.

RESULTS

Of the 901 patients randomized in the overall study, 154 patients (aliskiren, n=78; ramipril, n=76) had CAP data. Numerically comparable reductions were seen for central aortic systolic pressure (CASP) in aliskiren-based therapy (baseline: 143.7±15.0; week 36: -20.3±16.2) compared with ramipril-based therapy (baseline: 147.9±11.9; week 36: -20.7±14.6). However, for the change in central aortic diastolic pressure, the least squares mean between-treatment difference (-3.6 mmHg [95% confidence interval, -6.76, -0.43; P=0.0263]) was in favor of aliskiren, while the other changes were comparable between the two groups with a trend in favor of aliskiren for CASP as well (-2.6 mmHg [95% confidence interval, -7.38, 2.19; P=0.2855)]. Correlation coefficients for change from baseline between CASP and systolic BP and between central aortic pulse pressure and PP (r=0.8, P<0.0001) were highly significant.

CONCLUSION

Aliskiren-based therapy provides comparable reductions in CASP to ramipril-based therapy. Although the results did not reach statistical significance, these findings, when coupled with those of the main study, suggest that aliskiren may offer effective control of central BP in elderly patients with systolic hypertension and may be a good alternative to ramipril.