Aliskiren—mode of action and preclinical data

Normalizing Plasma Renin Activity in Experimental Dilated Cardiomyopathy: Effects on Edema, Cachexia, and Survival

Heart failure (HF) patients frequently have elevated plasma renin activity. We examined the significance of elevated plasma renin activity in a translationally-relevant model of dilated cardiomyopathy (DCM), which replicates the progressive stages (A–D) of human HF. Female mice with DCM and elevated plasma renin activity concentrations were treated with a direct renin inhibitor (aliskiren) in a randomized, blinded fashion beginning at Stage B HF. By comparison to controls, aliskiren treatment normalized pathologically elevated plasma renin activity (p < 0.001) and neprilysin levels (p < 0.001), but did not significantly alter pathological changes in plasma aldosterone, angiotensin II, atrial natriuretic peptide, or corin levels. Aliskiren improved cardiac systolic function (ejection fraction, p < 0.05; cardiac output, p < 0.01) and significantly reduced the longitudinal development of edema (extracellular water, p < 0.0001), retarding the transition from Stage B to Stage C HF. The normalization of elevated plasma renin activity reduced the loss of body fat and lean mass (cachexia/sarcopenia), p < 0.001) and prolonged survival (p < 0.05). In summary, the normalization of plasma renin activity retards the progression of experimental HF by improving cardiac systolic function, reducing the development of systemic edema, cachexia/sarcopenia, and mortality. These data suggest that targeting pathologically elevated plasma renin activity may be beneficial in appropriately selected HF patients.

Renin Activity in Heart Failure with Reduced Systolic Function-New Insights

Regardless of the cause, symptomatic heart failure (HF) with reduced ejection fraction (rEF) is characterized by pathological activation of the renin–angiotensin–aldosterone system (RAAS) with sodium retention and extracellular fluid expansion (edema). Here, we review the role of active renin, a crucial, upstream enzymatic regulator of the RAAS, as a prognostic and diagnostic plasma biomarker of heart failure with reduced ejection fraction (HFrEF) progression; we also discuss its potential as a pharmacological bio-target in HF therapy. Clinical and experimental studies indicate that plasma renin activity is elevated with symptomatic HFrEF with edema in patients, as well as in companion animals and experimental models of HF. Plasma renin activity levels are also reported to be elevated in patients and animals with rEF before the development of symptomatic HF. Modulation of renin activity in experimental HF significantly reduces edema formation and the progression of systolic dysfunction and improves survival. Thus, specific assessment and targeting of elevated renin activity may enhance diagnostic and therapeutic precision to improve outcomes in appropriate patients with HFrEF.

Aliskiren and valsartan in combination is a promising therapy for hypertensive renal injury in rats

Neither ACEI nor ARBs completely repress the RAAS. Aliskiren is a newer agent that inhibits renin. However, it increases the biosynthesis and secretion of renin and prorenin, that might induce renal tissue damage. This study was conducted to investigate the renoprotective effects of aliskiren and valsartan the ARB, either alone or in combination, on hypertensive nephropathy induced by L-NAME. Aliskiren (50 mg/kg/daily i.p.), valsartan (10 mg/kg daily i.p.) alone or in half dose combination were administered with L-NAME (30-40 mg daily in drinking water) for 8 weeks. Aliskiren and valsartan significantly reduced systolic blood pressure, proteinuria, serum creatinine, blood urea nitrogen, oxidative stress, and structural renal injury although not to the same extent. Valsartan reduced systolic blood pressure and proteinuria in L-NAME treated rats more significantly than aliskiren. However, glomerular collapse index and the expansion of interstitial tissue were significantly attenuated by aliskiren than by valsartan. Cotreatment with aliskiren and valsartan markedly reduced the oxidative stress and further reduced the glomerular collapse and the expansion of interstitial tissue compared with aliskiren monotherapy.

CONCLUSION

These results suggest that therapies aimed at different targets within the RAAS may have additional effects in attenuating structural injury in experimental hypertensive nephropathy.

Acute adriamycin-induced cardiotoxicity is exacerbated by angiotension II

Adriamycin (ADR) increases the production of reactive oxygen species (ROS), which diminishes mitochondrial function. Angiotensin-II stimulates mitochondrial ROS generation. The aim of the study was to examine whether angiotensin converting enzyme (ACE) or renin inhibitors protect against ADR-induced mitochondrial function impairment. Rats were divided into five groups as control, ADR, co-treatment ADR with captopril, co-treatment ADR with aliskiren, co-treatment ADR with both captopril and aliskiren. Left ventricular function and blood pressures were assessed at the end of treatment period. Mitochondrial membrane potential (MMP) and ATP levels were determined. ADR treatment decreased the left ventricular pressure and increased the left ventricular end-diastolic pressure. ADR decreased MMP and ATP levels in myocyte mitochondria due to increasing oxidative stress. ADR decreased MMP and ATP levels due to increased oxidative stress in the heart. Inhibitors of ACE and renin caused the elevation of the decreased of MMP and ATP levels. The pathologic changes in electrocardiogram, blood pressure and left ventricular function were decreased by inhibition of Ang-II production. We concluded that inhibitors of angiotensin II are effective against ADR cardiotoxicity via the restoration of MMP and ATP production and prevention of mitochondrial damage in vivo.

Aliskiren and valsartan mediate left ventricular remodeling post-myocardial infarction in mice through MMP-9 effects

We evaluated whether aliskiren, valsartan, or a combination of both was protective following myocardial infarction (MI) through effects on matrix metalloproteinase (MMP)-9. C57BL/6J wild type (WT, n=94) and MMP-9 null (null, n=85) mice were divided into 4 groups at 3h post-MI: saline (S), aliskiren (A; 50mg/kg/day), valsartan (V; 40mg/kg/day), or A+V and compared to no MI controls at 28days post-MI. All groups had similar infarct areas, and survival rates were higher in the null mice. The treatments influenced systolic function and hypertrophy index, as well as extracellular matrix (ECM) and inflammatory genes in the remote region, indicating that primary effects were on the viable myocardium. Saline treated WT mice showed increased end systolic and diastolic volumes and hypertrophy index, along with reduced ejection fraction. MMP-9 deletion improved LV function post-MI. Aliskiren attenuated the increase in end systolic volume and hypertrophy index, while valsartan improved end diastolic volumes and aliskiren+valsartan improved the hypertrophy index only when MMP-9 was absent. Extracellular matrix and inflammatory gene expression showed distinct patterns among the treatment groups, indicating a divergence in mechanisms of remodeling. This study shows that MMP-9 regulates aliskiren and valsartan effects in mice. These results in mice provide mechanistic insight to help translate these findings to post-MI patients.

The restoration of kidney mitochondria function by inhibition of angiotensin-II production in rats with acute adriamycin-induced nephrotoxicity

Adriamycin (ADR) is commonly used for many solid tumor treatments. Its clinical utility is, however, largely limited by the adverse reactions, are known to be nephrotoxic. The mechanism by which it induces kidney damage is still not completely understood, but its nephrotoxicity might relate to increase reactive oxidant status (ROS), mitochondrial dysfunction. Until now, neurohormonal activation of it is unclear. ADR might activate the renin angiotensin system. Angiotensin-II also induced ROS and mitochondrial dysfunction. The aim of this study was to investigate whether angiotensin-II production inhibition has the protective effect on attenuation of mitochondrial function in rats with acute ADR-nephrotoxicity or not. Rats were divided into five groups as a control, ADR, co-treated ADR with captopril (CAP), co-treated ADR with Aliskren, co-treated ADR with both CAP and Aliskren groups. Creatinine kinase (CK) levels were measured at the end of treatment period. The kidneys were homogenized and biochemical measurements were made in mitochondria, cytosol. Mitochondria membrane potential (MMP) and ATP levels were determined. ADR increased CK levels and oxidative stress in mitochondria too (p<0.05). ADR significantly decreased MMP and ATP level in kidney mitochondria (p<0.05). Co-administration with ADR and Aliskren and CAP improved the dissipation of MMP (p<0.05). The decrease in ATP level was restored by treatment with inhibitors of ACE and renin. We concluded that inhibitors of angiotensin-II are effective against acute ADR induced nephrotoxicity via the restoration of MMP and ATP production and prevention of mitochondrial damage in vivo.

Beneficial effects of pioglitazone against cardiovascular injury are enhanced by combination with aliskiren in a rat model of diabetic nephropathy

OBJECTIVES

Aliskiren is the first in a new class of orally active direct renin inhibitors, approved for the treatment of hypertension. However, the efficacy of aliskiren in diabetic cardiovascular complications remains to be defined. This study aimed to test the hypothesis that aliskiren may enhance the beneficial effects of pioglitazone against cardiovascular injury associated with diabetic nephropathy.

METHODS

Diabetic nephropathy was induced in rats by unilateral nephrectomy followed by streptozotocin injection. Diabetic nephropathic rats were orally given vehicle, pioglitazone, aliskiren, or combined pioglitazone and aliskiren for four weeks to compare their effects on cardiovascular injury, particularly myocardial fibrosis.

KEY FINDINGS

Pioglitazone treatment significantly attenuated cardiac lipid peroxidation, oxidative injury and myocardial fibrosis in diabetic nephropathic rats. This was associated with up-regulation of transforming growth factor-β1 and matrix metalloproteinase-2 genes, along with down-regulation of tissue inhibitor of metalloproteinase-2 gene in cardiac tissue. The combination of aliskiren with pioglitazone exerted greater beneficial effect than monotherapy with either drug, on all the aforementioned parameters.

CONCLUSIONS

Our findings suggested that aliskiren enhanced the protective effects of pioglitazone against myocardial fibrosis, in experimental diabetic nephropathy. Thus, the combination of aliskiren and pioglitazone may be a potential therapeutic strategy for cardiovascular injury associated with diabetic nephropathy.

Merits of non-invasive rat models of left ventricular heart failure

Heart failure (HF) is characterized as a limitation to cardiac output that prevents the heart from supplying tissues with adequate oxygen and predisposes individuals to pulmonary edema. Impaired cardiac function is secondary to either decreased contractility reducing ejection (systolic failure), diminished ventricular compliance preventing filling (diastolic failure), or both. To study HF etiology, many different techniques have been developed to elicit this condition in experimental animals, with varying degrees of success. Among rats, surgically induced HF models are the most prevalent, but they bear several shortcomings, including high mortality rates and limited recapitulation of the pathophysiology, etiology, and progression of human HF. Alternatively, a number of non-invasive HF induction methods avoid many of these pitfalls, and their merits in technical simplicity, reliability, survivability, and comparability to the pathophysiologic and pathogenic characteristics of HF are reviewed herein. In particular, this review focuses on the primary pathogenic mechanisms common to genetic strains (spontaneously hypertensive and spontaneously hypertensive heart failure), pharmacological models of toxic cardiomyopathy (doxorubicin and isoproterenol), and dietary salt models, all of which have been shown to induce left ventricular HF in the rat. Additional non-invasive techniques that may potentially enable the development of new HF models are also discussed.

Renin-angiotensin system dual blockade using angiotensin receptor plus aliskiren decreases severe proteinuria in kidney transplant recipients

BACKGROUND

Renin-angiotensin system (RAS) blockade has cardioprotective and renoprotective effects in the general population; however, whether dual blockade using angiotensin-receptor blockade (ARB) plus a renin inhibitor, aliskiren, can minimize severe proteinuria in kidney transplant recipients remains undetermined.

OBJECTIVE

To analyze the efficacy and safety of dual blockade of the RAS with an ARB and aliskiren in kidney transplant recipients with severe proteinuria and creatinine concentration 2.5 mg/dL or less.

PATIENTS AND METHODS

This prospective study included 16 patients (mean age 56 years; 10 men [62%] who had undergone cadaveric renal transplantation between 1992 and 2004. Immunosuppression therapy included a calcineurin inhibitor in 9 patients (56%) or mammalian target of rapamycin inhibitor in 7 (44%), and mycophenolate mofetil in 15 (94%). All received high-dose ARB II (1.0-3.5 g/24 h) because of marked proteinuria, with poor response. Accordingly, 11 patients also received aliskiren, and in 5 who were receiving an angiotensin-converting enzyme inhibitor, therapy was changed to aliskiren. Mean (range) follow-up was 11 (3-18) months.

RESULTS

At 3 months, proteinuria decreased by 40%, and at 6 months by 60%. In addition, mean blood pressure was decreased significantly. Renal function remained stable, as did the serum potassium concentration. A slight but significant decrease in hemoglobin concentration was observed, with no clinical repercussions.

CONCLUSIONS

Dual blockade of the RAS with ARB II plus aliskiren therapy demonstrated an additive effect to decrease severe proteinuria and blood pressure in kidney transplant recipients. Neither relevant adverse effects in renal function nor anemia or hyperkalemia were observed. These findings might contribute to prolonging long-term kidney graft survival.

First-line treatment of hypertension: critical appraisal of potential role of aliskiren and hydrochlorothiazide in a fixed combination

Arterial hypertension is one of the major diseases in the Western world. It is an independent cardiovascular risk factor and is associated with increased morbidity and mortality. Several drug classes have been shown to be effective in the treatment of hypertension. Aliskiren is a direct renin inhibitor and belongs to the class of renin-angiotensin-aldosterone system inhibitors. Several large studies have shown that aliskiren is effective in lowering blood pressure, and equivalent in this respect to the angiotensin-converting enzyme (ACE) inhibitors and the angiotensin receptor-1 blockers (ARBs). Furthermore, aliskiren has a safety and tolerability profile comparable with that of the ARBs and slightly better than that of the ACE inhibitors. From a pathophysiologic perspective, it can be combined with hydrochlorothiazide successfully, because it can block the diuretic-induced increase in plasma renin activity. Its combination with hydrochlorothiazide in a single pill has been investigated and shown to be superior to monotherapy with respect to blood pressure control and improvement in patient compliance with therapy. Further studies are needed to show whether aliskiren and its combination with hydrochlorothiazide is effective in preventing cardiovascular events and mortality when end organ damage is present.

Effects of aliskiren on stroke in rats expressing human renin and angiotensinogen genes

OBJECTIVE

Pre-treatment with angiotensin receptor blockers is known to improve neurological outcome after stroke. This study investigated for the first time, whether the renin inhibitor aliskiren has similar neuroprotective effects.

METHODS

Since aliskiren specifically blocks human renin, double transgenic rats expressing human renin and angiotensinogen genes were used. To achieve a systolic blood pressure of 150 or 130 mmHg animals were treated with aliskiren (7.5 or 12.5 mg/kg*d) or candesartan (1.5 or 10 mg/kg*d) via osmotic minipump starting five days before middle cerebral artery occlusion with reperfusion. Infarct size was determined by magnetic resonance imaging. mRNA of inflammatory marker genes was studied in different brain regions.

RESULTS

The mortality of 33.3% (7 of 21 animals) in the vehicle group was reduced to below 10% by treatment with candesartan or aliskiren (p<0.05). Aliskiren-treated animals had a better neurological outcome 7 days post-ischemia, compared to candesartan (Garcia scale: 9.9±0.7 vs. 7.3±0.7; p<0.05). The reduction of infarct size in the aliskiren group did not reach statistical significance compared to candesartan and vehicle (24 h post-ischemia: 314±81 vs. 377±70 and 403±70 mm(3) respectively). Only aliskiren was able to significantly reduce stroke-induced gene expression of CXC chemokine ligand 1, interleukin-6 and tumor necrosis factor-alpha in the ischemic core.

CONCLUSIONS

Head-to-head comparison suggests that treatment with aliskiren before and during cerebral ischemia is at least as effective as candesartan in double transgenic rats. The improved neurological outcome in the aliskiren group was blood pressure independent. Whether this effect is due to primary anti-inflammatory mechanisms has to be investigated further.

Left ventricular hypertrophy and renin-angiotensin system blockade

The renin-angiotensin system (RAS), an important control system for blood pressure and intravascular volume, also causes left ventricular hypertrophy (LVH) and fibrosis. The main causal mechanism is the increase in blood pressure, which leads to increased left ventricular wall stress; however, aldosterone release from the adrenals and (more controversially) the direct action of angiotensin II on the cardiomyocytes also play a role. Large clinical trials evaluating the blockade of the RAS with angiotensin-converting enzyme inhibitors or angiotensin receptor blockers have demonstrated an ability to prevent progression and induce regression of left ventricular mass, thereby reducing the significant and independent cardiovascular risk conferred by LVH. Regression of left ventricular mass is also achieved by other medication classes, but the RAS blockers have an additional beneficial effect for the same blood pressure reduction, for which the mechanism is not entirely clear. Studies comparing the efficacy of angiotensin-converting enzyme inhibitors versus angiotensin receptor blockers to achieve LVH regression have not demonstrated any clear benefit of one class over the other.

Potential roles of melatonin and chronotherapy among the new trends in hypertension treatment

The number of well-controlled hypertensives is unacceptably low worldwide. Respecting the circadian variation of blood pressure, nontraditional antihypertensives, and treatment in early stages of hypertension are potential ways to improve hypertension therapy. First, prominent variations in circadian rhythm are characteristic for blood pressure. The revolutionary MAPEC (Ambulatory Blood Pressure Monitoring and Cardiovascular Events) study, in 3000 adult hypertensives investigates, whether chronotherapy influences the cardiovascular prognosis beyond blood pressure reduction per se. Second, melatonin, statins and aliskiren are hopeful drugs for hypertension treatment. Melatonin, through its scavenging and antioxidant effects, preservation of NO availability, sympatholytic effect or specific melatonin receptor activation exerts antihypertensive and anti-remodeling effects and may be useful especially in patients with nondipping nighttime blood pressure pattern or with nocturnal hypertension and in hypertensives with left ventricular hypertrophy (LVH). Owing to its multifunctional physiological actions, this indolamine may offer cardiovascular protection far beyond its hemodynamic benefit. Statins exert several pleiotropic effects through inhibition of small guanosine triphosphate-binding proteins such as Ras and Rho. Remarkably, statins reduce blood pressure in hypertensive patients and more importantly they attenuate LVH. Addition of statins should be considered for high-risk hypertensives, for hypertensives with LVH, and possibly for high-risk prehypertensive patients. The direct renin inhibitor, aliskiren, inhibits catalytic activity of renin molecules in circulation and in the kidney, thus lowering angiotensin II levels. Furthermore, aliskiren by modifying the prorenin conformation may prevent prorenin activation. At present, aliskiren should be considered in hypertensive patients not sufficiently controlled or intolerant to other inhibitors of renin-angiotensin system. Third, TROPHY (Trial of Preventing Hypertension) is the first pharmacological intervention for prehypertensive patients revealing that treatment with angiotensin II type 1 receptor blocker attenuates hypertension development and thus decreases the risk of cardiovascular events.

Role of the renin-angiotensin system in autoimmune inflammation of the central nervous system

Angiotensin II is the principle effector molecule of the renin angiotensin system (RAS). It exerts its various actions on the cardiovascular and renal system, mainly via interaction with the angiotensin II type-1 receptor (AT1R), which contributes to blood pressure regulation and development of hypertension but may also mediate effects on the immune system. Here we study the role of the RAS in myelin-oligodendrocyte glycoprotein-induced experimental autoimmune encephalomyelitis (MOG-EAE), a model mimicking many aspects of multiple sclerosis. Quantitative RT-PCR analyses showed an up-regulation of renin, angiotensin-converting enzyme, as well as AT1R in the inflamed spinal cord and the immune system, including antigen presenting cells (APC). Treatment with the renin inhibitor aliskiren, the angiotensin II converting-enzyme inhibitor enalapril, as well as preventive or therapeutic application of the AT1R antagonist losartan, resulted in a significantly ameliorated course of MOG-EAE. Blockade of AT1R did not directly impact on T-cell responses, but significantly reduced numbers of CD11b+ or CD11c+ APC in immune organs and in the inflamed spinal cord. Additionally, AT1R blockade impaired the expression of CCL2, CCL3, and CXCL10, and reduced CCL2-induced APC migration. Our findings suggest a pivotal role of the RAS in autoimmune inflammation of the central nervous system and identify RAS blockade as a potential new target for multiple sclerosis therapy.

The renin-angiotensin system modulates inflammatory processes in atherosclerosis: evidence from basic research and clinical studies

Recent evidence shows that the renin-angiotensin system is a crucial player in atherosclerotic processes. The regulation of arterial blood pressure was considered from its first description of the main mechanism involved. Vasoconstriction (mediated by angiotensin II) and salt and water retention (mainly due to aldosterone) were classically considered as pivotal proatherosclerotic activities. However, basic research and animal studies strongly support angiotensin II as a proinflammatory mediator, which directly induces atherosclerotic plaque development and heart remodeling. Furthermore, angiotensin II induces proatherosclerotic cytokine and chemokine secretion and increases endothelial dysfunction. Accordingly, the pharmacological inhibition of the renin-angiotensin system improves prognosis of patients with cardiovascular disease even in settings of normal baseline blood pressure. In the present review, we focused on angiotensin-convertingenzyme (ACE) inhibitors, angiotensin II receptor blockers (ARBs), and renin inhibitors to update the direct activities of the renin-angiotensin system in inflammatory processes governing atherosclerosis.