Aliskiren: a novel renoprotective agent or simply an alternative to ACE inhibitors? Kidney Int. 2009;76:23-31. [PMID: 19367328 DOI: 10.1038/ki.2009.105]

Mathematical modeling of antihypertensive therapy

Hypertension is a multifactorial disease arising from complex pathophysiological pathways. Individual characteristics of patients result in different responses to various classes of antihypertensive medications. Therefore, evaluating the efficacy of therapy based on in silico predictions is an important task. This study is a continuation of research on the modular agent-based model of the cardiovascular and renal systems (presented in the previously published article). In the current work, we included in the model equations simulating the response to antihypertensive therapies with different mechanisms of action. For this, we used the pharmacodynamic effects of the angiotensin II receptor blocker losartan, the calcium channel blocker amlodipine, the angiotensin-converting enzyme inhibitor enalapril, the direct renin inhibitor aliskiren, the thiazide diuretic hydrochlorothiazide, and the β-blocker bisoprolol. We fitted therapy parameters based on known clinical trials for all considered medications, and then tested the model's ability to show reasonable dynamics (expected by clinical observations) after treatment with individual drugs and their dual combinations in a group of virtual patients with hypertension. The extended model paves the way for the next step in personalized medicine that is adapting the model parameters to a real patient and predicting his response to antihypertensive therapy. The model is implemented in the BioUML software and is available at https://gitlab.sirius-web.org/virtual-patient/antihypertensive-treatment-modeling.

Targeting the renin-angiotensin-aldosterone system in fibrosis

Fibrosis is characterized by excessive deposition of extracellular matrix components such as collagen in tissues or organs. Fibrosis can develop in the heart, kidneys, liver, skin or any other body organ in response to injury or maladaptive reparative processes, reducing overall function and leading eventually to organ failure. A variety of cellular and molecular signaling mechanisms are involved in the pathogenesis of fibrosis. The renin-angiotensin-aldosterone system (RAAS) interacts with the potent Transforming Growth Factor β (TGFβ) pro-fibrotic pathway to mediate fibrosis in many cell and tissue types. RAAS consists of both classical and alternative pathways, which act to potentiate or antagonize fibrotic signaling mechanisms, respectively. This review provides an overview of recent literature describing the roles of RAAS in the pathogenesis of fibrosis, particularly in the liver, heart, kidney and skin, and with a focus on RAAS interactions with TGFβ signaling. Targeting RAAS to combat fibrosis represents a promising therapeutic approach, particularly given the lack of strategies for treating fibrosis as its own entity, thus animal and clinical studies to examine the impact of natural and synthetic substances to alter RAAS signaling as a means to treat fibrosis are reviewed as well.

Decades-old renin inhibitors are still struggling to find a niche in antihypertensive therapy. A fleeting look at the old and the promising new molecules

Hypertension is a diverse illness interlinked with cerebral, cardiovascular (CVS) and renal abnormalities. Presently, the malady is being treated by focusing on Renin- angiotensin system (RAS), voltage-gated calcium channels, peripheral vasodilators, renal and sympathetic nervous systems. Cardiovascular and renal abnormalities are associated with the overactivation of RAS, which can be constrained by angiotensin- converting enzyme inhibitors (ACEIs), angiotensin II (Ang-II) -AT1 receptor blockers (ARBs) and renin inhibitors. The latter is a new player in the old system. The renin catalyzes the conversion of angiotensinogen to Angiotensin I (Ang-I). This can be overcome by inhibiting renin, a preliminary step, eventually hinders the occurrence of the cascade of events in the RAS. Various peptidomimetics, the first-generation renin inhibitors developed six decades ago have limited drug-like properties as they suffered from poor intestinal absorption, high liver first-pass metabolism and low oral bioavailability. The development of chemically diverse molecules from peptides to nonpeptides expanded the horizon to achieving direct renin inhibition. Aliskiren, a blockbuster drug that emerged as a clinical candidate and got approved by the US FDA in 2007 was developed by molecular modeling studies. Aliskiren indicated superior to average efficacy and with minor adverse effects relative to other RAS inhibitors. However, its therapeutic use is limited by poor oral bioavailability of less than 2% that is similar to first-generation peptidic compounds. In this review, we present the development of direct renin inhibitors (DRIs) from peptidic to nonpeptidics that lead to the birth of aliskiren, its place in the treatment of cardiovascular diseases and its limitations.

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.

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.

Successful treatment of hypertension in anuric hemodialysis patients with a direct Renin inhibitor, aliskiren

OBJECTIVE

A direct renin-inhibitor (DRI), aliskiren, was administered to anuric patients to investigate whether it can be a new optional therapy against hypertension in hemodialysis (HD) patients.

PATIENTS

The patients that received aliskiren comprised 8 males and 2 females with a mean ± SD age of 63 ± 8 years (43-72 years). They were exposed to dialysis therapy for 118 ± 73 months (8-251 months), with diabetes mellitus in 4 cases, chronic glomerulonephritis in 4 cases, and other diagnoses in 2 cases.

METHODS

After the plasma renin activity (PRA) and plasma aldosterone concentration (PAC) were measured before an HD session, aliskiren, 150 mg as an initial dose, was administered to the patients. PRA and PAC were also examined a week after initiating aliskiren. The blood pressure (BP) levels at the start of each HD session for a period of 2 weeks (6 HD sessions) were compared between before and after administration of aliskiren. The change of doses in other antihypertensive agents was also counted.

RESULTS

The averaged reduction of mean blood pressure was 4 ± 5 mmHg, and doses of antihypertensives other than aliskiren were reduced in 4 patients. Of the examined parameters, only the reduction rate of PRA x PAC seemed correlated with the BP lowering effect of aliskiren, which was calculated as the sum of the mean BP reduction in mmHg and drug reduction with 1 tablet (capsule)/day considered to be 10 mmHg.

CONCLUSION

A DRI, aliskiren, was effective even in anuric dialysis patients, and monitoring of PRA and PAC was valuable for selecting cases responsive to aliskiren.

Peri-operative kidney injury and long-term chronic kidney disease following orthotopic heart transplantation in children

Significant advances in cardiac intensive care including extracorporeal life support have enabled children with complex congenital heart disease and end-stage heart failure to be supported while awaiting transplantation. With an increasing number of survivors after heart transplantation in children, the complications from long-term immunosuppression, including renal insufficiency, are becoming more apparent. Severe renal dysfunction after heart transplant is defined by a serum creatinine level >2.5 mg/dL (221 μmol/L), and/or need for dialysis or renal transplant. The degree of renal dysfunction is variable and is progressive over time. About 3-10 % of heart transplant recipients will go on to develop severe renal dysfunction within the first 10 years post-transplantation. Multiple risk factors for chronic kidney disease post-transplant have been identified, which include pre-transplant worsening renal function, recipient demographics and morbidity, peri-transplant haemodynamics and long-term exposure to calcineurin inhibitors. Renal insufficiency increases the risk of post-transplant morbidity and mortality. Hence, screening for renal dysfunction pre-, peri- and post-transplantation is important. Early and timely detection of renal insufficiency may help minimize renal insults, and allow prompt implementation of renoprotective strategies. Close monitoring and pre-emptive management of renal dysfunction is an integral aspect of peri-transplant and subsequent post-transplant long-term care.

Protective effects of aliskiren and valsartan in mice with diabetic nephropathy

AIM

We investigated whether aliskiren, a direct renin inhibitor, provided protection in a model of diabetic nephropathy in mice and compared its protective effects to valsartan, an angiotensin II type 1 receptor blocker.

MATERIALS AND METHODS

Hyperglycemia was induced with streptozotocin (STZ, 40 mg/kg/day × 5 days) injection in DBA/2J mice fed on a high fat diet. Mice were treated with either aliskiren (25 mg/kg/day) or valsartan (8 mg/kg/day) for 6 weeks.

RESULTS

Aliskiren and/or valsartan treatment significantly attenuated albuminuria, urinary nephrin excretion and glomerulosclerosis. Aliskiren and/or valsartan prevented reduction of podocin and WT1 protein abundance in diabetic mice. Aliskiren and/or valsartan significantly prevented increased expression of profibrotic growth factors (TGFβ, CTGF and PAI-1), proinflammatory cytokines (MCP-1, TNFα and IL-1β), endoplasmic reticulum (ER) stress markers (CHOP and XBP-1) and lipid accumulation in the kidney of diabetic animals. Aliskiren showed similar efficacy compared to valsartan therapy and dual treatment in some aspects has synergistic protective effects.

CONCLUSION

Our study indicates that aliskiren and/or valsartan protects against diabetic kidney disease through multiple mechanisms, including decreasing podocyte injury, activation of profibrotic growth factors and proinflammatory cytokines, ER stress and accumulation of lipids.

A retrospective Aliskiren and Losartan study in non-diabetic chronic kidney disease

AIM: To assess the efficacy of combined Aliskiren and Losartan vs high dose Losartan and Aliskiren alone in chronic kidney disease (CKD).

METHODS: This is a retrospective study of 143 patients with non-diabetic CKD comparing combined Aliskiren (150 mg/d) with Losartan (100 mg/d) therapy vs High dose Angiotensin receptor blockers (ARB) (Losartan 200 mg/d) and the third group Aliskiren (150 mg/d) alone. This study involved only patient medical records. Entry criteria included those patients who had been treated with the above drugs for at least 36 mo within the 5 years period; other criteria included proteinuria of 1 g or more and or CKD Stage 3 at the start of the 36 mo period. The study utilised primary renal end points of estimated Glomerular Filtration Rate (eGFR) < 15 mL/min or end stage renal failure.

RESULTS: Patients treated with high dose ARB compared to the other two treatment groups had significantly less proteinuria at the end of 36 mo (P < 0.007). All 3 groups had significant reduction of proteinuria (P < 0.043, P < 0.001). Total urinary protein was significantly different between the 3 groups over the 3-year study period (P = 0.008), but not eGFR. The changes in eGFR from baseline to each year were not significantly different between the 3 therapeutic groups (P < 0.119). There were no significant differences in the systolic and diastolic blood pressure between the 3 drug groups throughout the 3 years. The incidence of hyperkalemia (> 5.5 mmol/L) was 14.2% (7/49) in the Combined Aliskiren and ARB group, 8.7% (4/46) in the Aliskiren alone group and 6.3% (3/48) in the High dose ARB group (P < 0.001).

CONCLUSION: This study in non-diabetic CKD patients showed that Combination therapy with Aliskiren and ARB was effective but was not safe as it was associated with a high prevalence of hyperkalaemia.

Aliskiren, exendin-4, and insulin: their impact on endothelin receptor subtype(s) regulation/binding in type 1 diabetic rat hearts

This study focuses on the impact of aliskiren and (or) glucagon-like peptide-1 analogue on the binding affinity/regulation of endothelin-1 (ET-1) to its receptor subtypes A (ETAR) and B (ETBR) at the level of the coronary endothelium and the cardiomyocytes in a type-1 diabetic rat model. Seven groups were used: (i) normal rats, (ii) rats with induced diabetes, (iii) rats with induced diabetes that were treated with insulin, (iv) rats with induced diabetes that were treated with exendin-4, (v) rats with induced diabetes that were treated with aliskiren, (vi) rats with induced diabetes that were co-treated with insulin plus aliskiren, and (vii) rats with induced diabetes that were co-treated with exendin-4 plus aliskiren. Heart perfusion with [125I]-ET-1 was employed to estimate ET-1 binding affinity (τ = 1/K–n) to ETAR and ETBR at the level of the coronary endothelium and the cardiomyocytes. Plasma ET-1 levels were measured using enzyme immunoassay, whereas densities of ETAR and ETBR were detected using Western blot. No significance differences were detected in the τ of ETAR and ETBR between normal and diabetic in cardiomyocytes and the coronary endothelium. Exendin-4 normalized the τ value for ETAR and ETBR on coronary endothelium, while aliskiren normalized it on cardiomyocytes. Furthermore, ETAR and ETBR densities were normalized with monotreatments of aliskiren and exendin-4, compared with up-regulated ETAR and down-regulated ETBR band densities in the diabetic animals. Our data indicate that aliskiren alleviates diabetes-associated hypertrophy in type 1 diabetes mellitus.

Renin inhibition reverses renal disease in transgenic mice by shifting the balance between profibrotic and antifibrotic agents

Aliskiren, a direct renin inhibitor, is a novel antihypertensive drug. To study whether aliskiren can reverse chronic kidney disease, we administered it to renin transgenic mice, a strain characterized by elevated blood pressure and a slow decline of renal function, mimicking well the progression of hypertensive chronic kidney disease. Ten-month-old transgenic mice were treated either with aliskiren or placebo for 28 days. Age-matched wild-type mice treated or not with aliskiren were considered as normotensive controls. Aliskiren reduced blood pressure to wild-type levels from as early as day 14. Proteinuria and cardiac hypertrophy and fibrosis were also normalized. Renal interstitial fibrosis and inflammation were significantly ameliorated in aliskiren-treated mice (shown by the decrease of proinflammatory and profibrotic markers), and the phenotypes of tubular epithelial cells and podocytes were restored as evidenced by the reappearance of cellular proteins characteristic of normal phenotype of these cells. Profibrotic p38 and Erk mitogen-activated protein kinases were highly activated in placebo-treated transgenic animals. Aliskiren treatment cancelled this activation. This nephroprotection was not attributed to the antihypertensive activity of aliskiren, because blood pressure normalization after treatment with hydralazine failed to induce the regression of renal fibrosis. Direct inhibition of renin can restore renal function and structure in aged hypertensive animals with existing proteinuria. This finding suggests that, in addition to antihypertensive action, aliskiren can be also used to treat chronic kidney disease.

The effect of antihypertensive drugs on chronic kidney disease: a comprehensive review

Data from randomized clinical trials and epidemiological evidence identify systemic hypertension as the second most common modifiable risk factor for chronic kidney disease (CKD) progression after diabetes mellitus. CKD may progress silently over the years and early diagnosis and control of hypertension is of major importance in delaying renal function decline. Recent guidelines for the treatment of hypertension suggest the use of a variety of antihypertensive drugs in order to achieve the desired blood pressure levels. Renin-angiotensin system inhibitors have been undoubtedly studied the most and are suggested by guidelines and experts as first choice in patients with hypertension and renal injury, particularly in those with diabetes, as they have repeatedly shown to significantly reduce proteinuria. Other classes of antihypertensive drugs have been studied to a lesser extent and they have their own unique properties and effects. However, it is now common knowledge that adequate blood pressure control is the most important factor for the preservation of renal function, so every drug that effectively lowers hypertension is believed to be renoprotective. The present article will review the latest data on the role and properties of each class of antihypertensive drugs on CKD.

Comparative effects of different modes of renin angiotensin system inhibition on hypercholesterolaemia-induced atherosclerosis

BACKGROUND AND PURPOSE

Inhibition of the renin angiotensin system (RAS) has been consistently demonstrated to reduce atherosclerosis. However, there has been no direct comparison among the three available pharmacological modes of inhibiting the RAS, which are inhibitors of renin, ACE and angiotensin II type 1 receptor. The purpose of this study was to determine the relative effects of these three modes of pharmacological RAS inhibition in reducing atherosclerosis by determining the dose-response relationships.

EXPERIMENTAL APPROACH

Male LDL receptor -/- mice were administered either vehicle or any of three doses of aliskiren, enalapril or losartan through s.c. infusion for 12 weeks. All mice were fed a saturated fat-enriched diet during drug infusions. Systolic and diastolic BPs were measured during the study using a non-invasive tail-cuff system. Plasma cholesterol and renin concentrations, atherosclerotic lesions, and renal angiotensin II concentrations were determined at the termination of the study.

KEY RESULTS

Plasma renin concentrations were increased by all three drugs. None of the drugs changed plasma cholesterol concentrations. All drugs produced a dose-related decrease in BP. All three drugs also profoundly reduced atherosclerosis in a dose-dependent manner. The highest dose of each drug markedly attenuated lesion size, with no significant differences between the different drugs. The highest dose of each drug also similarly reduced renal angiotensin II concentrations.

CONCLUSION AND IMPLICATIONS

Drugs that inhibit the RAS, irrespective of their mode of inhibition, profoundly affect atherosclerotic lesion development in a dose-dependent manner.

Combination of direct renin inhibition with angiotensin type 1 receptor blockade improves aldosterone but does not improve kidney injury in the transgenic Ren2 rat

Enhanced renin-angiotensin-aldosterone system (RAAS) activation contributes to proteinuria and chronic kidney disease by increasing glomerular and tubulointerstitial oxidative stress, promotion of fibrosis. Renin activation is the rate limiting step in angiotensin (Ang II) and aldosterone generation, and recent work suggests direct renin inhibition improves proteinuria comparable to that seen with Ang type 1 receptor (AT(1)R) blockade. This is important as, even with contemporary use of AT(1)R blockade, the burden of kidney disease remains high. Thereby, we sought to determine if combination of direct renin inhibition with AT(1)R blockade in vivo, via greater attenuation of kidney oxidative stress, would attenuate glomerular and proximal tubule injury to a greater extent than either intervention alone. We utilized the transgenic Ren2 rat with increased tissue RAS activity and higher serum levels of aldosterone, which manifests hypertension and proteinuria. Ren2 rats were treated with renin inhibition (aliskiren), AT(1)R blockade (valsartan), the combination (aliskiren+valsartan), or vehicle for 21days. Compared to Sprague-Dawley controls, Ren2 rats displayed increased systolic pressure (SBP), circulating aldosterone, proteinuria and greater urine levels of the proximal tubule protein excretory marker beta-N-acetylglucosaminidase (β-NAG). These functional and biochemical alterations were accompanied by increases in kidney tissue NADPH oxidase subunit Rac1 and 3-nitrotyrosine (3-NT) content as well as fibronectin and collagen type III. These findings occurred in conjunction with reductions in the podocyte-specific protein podocin as well as the proximal tubule-specific megalin. Further, in transgenic animals there was increased tubulointerstitial fibrosis on light microscopy as well as ultrastructural findings of glomerular podocyte foot-process effacement and reduced tubular apical endosomal/lysosomal activity. Combination therapy led to greater reductions in SBP and serum aldosterone, but did not result in greater improvement in markers of glomerular and tubular injury (i.e. β-NAG) compared to either intervention alone. Further, combination therapy did not improve markers of oxidative stress and podocyte and proximal tubule integrity in this transgenic model of RAAS-mediated kidney damage despite greater reductions in serum aldosterone and BP levels.

Efficacy of aliskiren in Japanese chronic kidney disease patients with hypertension

BACKGROUND

Aliskiren, a novel direct renin inhibitor, is hypothesized to inhibit the renin-angiotensin- system. This study attempted to provide insight into this mechanism by examining the antihypertensive and renoprotective effects of aliskiren in hypertensive chronic kidney disease (CKD) patients.

METHODS

After recruitment, 43 hypertensive CKD patients (mean age, 53.7 years) began treatment of aliskiren. The patients were classified into high (over 30 mL/min/1.73 m(2)) estimated glomerular filtration rate (eGFR) group or low (under 30 mL/min/1.73 m(2)) eGFR group for comparison of measurements of various parameters over the 6-month observation period.

RESULTS

Systolic blood pressure/diastolic blood pressure of 150 mg/day group decreased to an average of 126.8 ± 21.6 mmHg/69.3 ± 15.1 mmHg (average decrease: -7.4/-8.3 mmHg) over the 6-month observation period, while that of 300 mg/day group significantly decreased to an average of 133.5 ± 14.0 mmHg/71.5 ± 11.7 mmHg (average decrease: -21.1/-14.6 mmHg). Urinary protein of all patients decreased slightly and insignificantly to 1.1 ± 1.7 g/gCr from 1.4 ± 2.5 g/gCr. The serum creatinine (Cr) level of all patients decreased from 1.81 ± 1.10 mg/dL to 1.78 ± 0.82 mg/dL. Although the serum Cr level of the high eGFR group decreased from 1.28 ± 0.45 mg/dL to 1.27 ± 0.57 mg/dL, that of the low eGFR group slightly but insignificantly increased from 2.49 ± 0.64 mg/dL to 2.69 ± 1.11 mg/dL.

CONCLUSION

Administration of aliskiren exerts an antihypertensive effect on hypertensive CKD patients that may lead to a decrease in urinary protein and an improvement in renal functioning.

Renal protective effects of aliskiren beyond its antihypertensive property in a mouse model of progressive fibrosis

BACKGROUND

The direct renin inhibitor aliskiren is known to exhibit a strong antihypertensive effect. However, the organoprotective potential of aliskiren beyond its antihypertensive properties is less clear. This study investigates the antifibrotic nephroprotective effects of aliskiren in a nonhypertensive mouse model for progressive renal fibrosis.

METHODS

COL4A3(-/-) mice received aliskiren via osmotic minipumps. Placebo-treated animals served as controls. Therapy was initiated in 6-week-old animals already showing renal damage (proteinuria ~1 g/l, starting renal fibrosis) and lasted for 4 weeks. Six animals were sacrificed after 9.5 weeks; serum urea and proteinuria were measured. Kidneys were further investigated using histological, immunohistological, and western blot techniques. Survival until end-stage renal failure was monitored in the remaining animals.

RESULTS

COL4A3(-/-) mice did not develop hypertension. Aliskiren serum levels were in the therapeutic range (288 ± 44 ng/ml). Therapy significantly prolonged lifespan until death from renal failure by 18% compared with placebo-treated controls (78.6 ± 8.2 vs. 66.6 ± 4.9 days, P < 0.05). Similarly, therapy reduced the amount of proteinuria and serum urea. Compared with placebo-treated controls, the accumulation of extracellular matrix and renal scarring and the levels of transforming growth factor-β (TGFβ) and connective tissue growth factor (CTGF) were decreased in treated mice.

CONCLUSIONS

Despite the late onset of therapy, our results indicate nephroprotective effects of the renin inhibitor aliskiren beyond its antihypertensive property in this animal model of progressive renal fibrosis. In addition to the recognized antihypertensive action of aliskiren, its antifibrotic, antiproteinuric effects demonstrated in the present study indicate that aliskiren may have potential as an important therapeutic option for chronic fibrotic diseases in humans.

Challenges in pediatric transplantation: the impact of chronic kidney disease and cardiovascular risk factors on long-term outcomes and recommended management strategies

Barriers to successful outcomes following pediatric transplantation have shifted from ischemic reperfusion injury and rejection to more long-term complications. Of particular concern is the high prevalence of CKD owing to preexisting damage and nephrotoxicity, as well as other CV complications such as hypertension and cardiomyopathy. All of these contribute to graft loss and shortened life expectancy, thereby limiting the success story of solid-organ transplantation. Managing CKD and related CV morbidity should be integral to the care of pediatric transplant patients, and timely detection of any irregularities would increase the chances of restoring lost kidney function. GFR is still the widely accepted indicator of renal function, and nuclear medicine techniques are the gold standard measurement methods. These methods are limited by costs, radiation exposure and substrate injection, and current practice still uses the Schwartz estimate, despite its well-documented limitations. Newer endogenous markers of GFR, such as cystatin C clearance, give a more accurate measure of true GFR but have not been embraced in the management of pediatric transplant recipients. Furthermore, indirect markers (e.g., microalbuminuria and hypertension) could also aid early detection of renal damage. The effects of mainstay immunosuppressants on kidney and heart function are varied, with available data indicating favorable outcomes with tacrolimus compared with ciclosporin. There is a need for appropriately designed and powered randomized controlled trials to validate innovative concepts for tailored immunosuppression in the pediatric population. To date, very few studies have generated long-term data in pediatric renal transplant patients - results of 1-4-yr study favored tacrolimus over ciclosporin, but other immunosuppressive agents also need to be evaluated.

Direct renin inhibitors as antihypertensive agents

Hypertension, a serious disease affecting almost a billion people (25% of adults) worldwide, is a major modifiable risk factor for cardiovascular (CV) and renal disease. Despite numerous advances in the pharmacologic treatment of high blood pressure (BP) and availability of several antihypertensive drugs to treat hypertension, a significant proportion of treated hypertensive patients still have uncontrolled high BP, and thus, face serious morbidity and mortality. Furthermore, it is not sufficient to aim for optimum BP control, but to treat all CV risk factors, protect end-organ damage, prevent progression of disease, and prevent long-range adverse effects of the drugs. Therefore, new therapeutic modalities have to be developed to achieve the above objectives. Some years ago, investigators identified renin inhibition as the preferred pharmacologic approach to blockade of the renin-angiotensin system. Renin is a monospecific enzyme that catalyzes the rate-limiting step in the synthesis of angiotensin II. Amplified enzymatic activity and additional physiologic effects occur when renin and prorenin bind to the (pro)renin receptor. Until very recently, development of clinically effective renin inhibitors remained elusive but molecular modeling was used to develop aliskiren and other renin inhibitors that produce sustained suppression of plasma renin activity after oral administration with a dose-dependent BP. Additional studies will ultimately determine the place of renin inhibition in the treatment of hypertension and related CV disorders.

A reduction of unilateral ureteral obstruction-induced renal fibrosis by a therapy combining valsartan with aliskiren

The protective effect of combination therapy with valsartan and aliskiren against renal fibrosis remains to be defined. This study was undertaken to examine the protective effects of the combination of valsartan and aliskiren against renal fibrosis induced by unilateral ureteral obstruction (UUO). Combination therapy with valsartan (15 mg·kg(-1)·day(-1)) and aliskiren (10 mg·kg(-1)·day(-1)), valsartan monotherapy (30 mg·kg(-1)·day(-1)), and aliskiren monotherapy (20 mg·kg(-1)·day(-1)) all significantly ameliorated the increase in blood urea nitrogen and the degree of hydronephrosis determined by the increase in weight and length of the obstructed kidney. The dose titration study and blood pressure measurement confirmed that the combination therapy provided a greater benefit independent of the vasodilatory effect. There were no significant changes in serum levels of creatinine, sodium, and potassium in UUO rats and any treatment groups. Combination therapy also attenuated UUO-related increases in the scores of tubular dilatation, interstitial volume, interstitial collagen deposition, α-smooth muscle actin, the activation of ERK 1/2, the infiltration of monocytes/macrophages, the mRNA expression of snail-1, and transforming growth factor-β1 to a greater extent compared with aliskiren or valsartan used alone. The mRNA expression of renin and the (pro)renin receptor significantly increased after UUO. Combination therapy and monotherapy of valsartan and aliskiren had a comparable enhancing effect on the mRNA expression of renin, whereas all these treatments did not affect the expression of the (pro)renin receptor. In conclusion, a direct renin inhibitor in conjunction with an angiotensin II receptor blocker exerts increased renal protection against renal fibrosis and inflammation during obstruction over either agent alone.

Comparative effect of direct renin inhibition and AT1R blockade on glomerular filtration barrier injury in the transgenic Ren2 rat

Renin-angiotensin system (RAS) activation contributes to kidney injury through oxidative stress. Renin is the rate-limiting step in angiotensin (ANG II) generation. Recent work suggests renin inhibition improves proteinuria comparable to ANG type 1 receptor (AT1R) blockade (ARB). Thereby, we investigated the relative impact of treatment with a renin inhibitor vs. an ARB on renal oxidative stress and associated glomerular structural and functional changes in the transgenic Ren2 rat, which manifests hypertension, albuminuria, and increased tissue RAS activity. Young Ren2 and age-matched Sprague-Dawley (SD) controls (age 6-9 wk) were treated with a renin inhibitor (aliskiren), an ARB (irbesartan), or vehicle for 21 days. Ren2 rats exhibited increases in systolic pressure (SBP), albuminuria, and renal 3-nitrotyrosine content as well as ultrastructural podocyte foot-process effacement and diminution of the podocyte-specific protein nephrin. Structural and functional alterations were accompanied by increased renal cortical ANG II, AT1R, as well as NADPH oxidase subunit (Nox2) expression compared with SD controls. Abnormalities were attenuated to a similar extent with both aliskiren and irbesartan treatment. Despite the fact the dose of irbesartan used caused a greater reduction in SBP than aliskerin treatment (P < 0.05), the effects on proteinuria, nephrin, and oxidative stress were similar between the two treatments. Our results highlight both the importance of pressor-related reductions on podocyte integrity and albuminuria as well as RAS-mediated oxidant stress largely comparable between ARB and renin inhibition treatment.

Aliskiren: Just a New Drug for Few Selected Patients or an Innovative Molecule Predestinated to Replace Arbs and Ace-Inhibitors?

The renin-angiotensin-aldosterone system (RAAS) plays a dominant role in the pathophysiology of hypertension, diabetes mellitus, chronic kidney disease and chronic heart failure. Therefore, drugs that block key components of the RAAS such as ACE inhibitors (ACEI) and angiotensin receptor blockers (ARBs) have gained wide clinical use for these indications. Despite progress, the morbidity and mortality of patients treated with ACEI or ARBs remain high. Aliskiren (Tekturna, Rasilez) is the first orally active inhibitor of renin approved for clinical use as an antihypertensive agent. The development program has established that at the licensed doses of 150 mg and 300 mg. Aliskiren is effective either as monotherapy or in combination with drugs from the other major classes. In this review we analyze and review the information already gained with Aliskiren, raises questions regarding the advantages of DRIs as monotherapy compared to marketed ACEIs and ARBs, their potential added value in combination with other RAAS modulators and other still unproven benefits in relation to prorenin and renin receptor biology.

Proteinuria and clinical outcomes in hypertensive patients

This narrative review focuses on outcomes related to proteinuria in hypertension (HT), and also examines the role of current and future therapeutic strategies. Proteinuria is an independent marker of renal and cardiovascular (CV) disease in hypertensive populations, particularly in high-risk groups such as diabetic patients. Effective blood pressure (BP) control and proteinuria management are associated with significant improvements in the risk of key adverse outcomes, although a causative relationship needs careful assessment. Available antihypertensives have varying effects on proteinuria reduction. Drugs affecting the renin system offer antiproteinuric and renoprotective effects that are probably at least partially independent of their BP effects. Economic evaluations of these interventions confirm their cost-saving benefits relative to other antihypertensives, but outcomes-based research is needed in some settings.

Is there a role for direct renin inhibitors in chronic kidney disease?

PURPOSE OF REVIEW

To evaluate the evidence supporting the use of renin inhibitors to control hypertension, limit kidney disease progression, and decrease cardiovascular risk in patients with chronic kidney disease (CKD).

RECENT FINDINGS

The literature on the subject is still limited. Most of the studies have used aliskiren as the study drug. Animal models show improved survival and decreased renal injury in animals receiving aliskiren. Human studies in patients with normal renal function show effective blood pressure control alone or in combination with different agents. There are no studies focusing on blood pressure control in patients with CKD, though the drug has been safely used in CKD. In a randomized clinical trial, aliskiren decreased albuminuria when added to losartan in patients with early diabetic nephropathy. Ongoing studies are evaluating the role of renin inhibitors in the prevention of cardiovascular events and slowing of kidney disease progression in CKD.

SUMMARY

Renin inhibitors, specifically aliskiren, effectively decrease albuminuria. Their role in improving hard renal endpoints and decreasing cardiovascular events in CKD still remains to be established.