Increase In Plasma Renin Concentration Research Articles

#1437 Renal expression pattern of the relaxin receptor, RXFP1, and effects of the RXFP1 agonist, AZD5462, on renin in non-human primates and humans

Abstract Background and Aims RXFP1 is a G protein-coupled receptor (GPCR) for the pregnancy hormone, relaxin. While preclinical studies, performed primarily in rodent, describe beneficial effects of this pleiotropic peptide across several organ systems, there has been a disappointing lack of success in translating these observations into clinical benefit. To provide a potential pharmacological explanation accounting for this translational gap, the aim of this study was thus to thoroughly evaluate RXFP1 expression across species and tissues as well as to evaluate the renal-intrinsic effects of the RXFP1 agonist, AZD5462. Method Unbiased bioinformatic analysis of several gene expression databases was used as a first approach to compare RXFP1 tissue-level expression between rodent and human. Experimental validation was subsequently performed using scRNAseq, RNAscope and immunohistochemistry on mouse, rat, non-human primate (NHP) and human kidney. The putative renal target engagement effects of RXFP1 agonism were assessed by determining the acute and chronic effects of the RXFP1-selective small molecule agonist, AZD5462, on plasma renin concentrations in both NHPs and in a Phase 1 randomized, single-blind, placebo-controlled study in healthy humans. Results RXFP1 was identified as one of the most highly expressed GPCRs in human and NHP kidney glomeruli. Specifically, by multiple assays, we identified glomerular endothelial cells as the principal cell type expressing RXFP1. This observation is in stark contrast to mouse and rat kidney, where RXFP1 was not readily detected. AZD5462 administered orally to NHPs and healthy human participants elicited an early and sustained dose-dependent increase in plasma renin concentration, and in humans an additional decline in serum creatinine. Conclusion Human RXFP1 kidney glomerular expression is conserved with NHPs but not rodent, thus highlighting the translational and pharmacological challenges in studying RXFP1/relaxin biology across species. The concordant ability of AZD5462 to induce elevations in renin and reduction in serum creatinine, together with relaxin's reported renal-hemodynamic activity in humans, may underlie a previously unappreciated renal-intrinsic RXFP1 target engagement mechanism driving its hemodynamic and renal effects. The potential therapeutic benefits of RXFP1 agonism are the subject of on-going clinical trials in heart failure patients.

Increased plasma renin by vasodilators promotes the progression of abdominal aortic aneurysm.

Background: It is well-accepted that antihypertensive therapy is the cornerstone of treatment for abdominal aortic aneurysm (AAA) patients with hypertension. Direct-acting vasodilators were used in the treatment of hypertension by directly relaxing vascular smooth muscle but may have destructive effects on the aortic wall by activating the renin-angiotensin system axis. Their roles in AAA disease remain to be elucidated. In this study, we used hydralazine and minoxidil, two classical direct-acting vasodilators, to investigate their influence and potential mechanisms on AAA disease. Methods and results: In this study, we investigated the plasma renin level and plasma renin activity in AAA patients. Simultaneously, age and gender ratio-matched patients diagnosed with peripheral artery disease and varicose veins were selected as the control group using a ratio of 1:1:1. Our regression analysis suggested both the plasma renin level and plasma renin activity are positively associated with AAA development. In view of the well-established relationship between direct-acting vasodilators and increased plasma renin concentration, we established a porcine pancreatic elastase-infused AAA mouse model, followed by oral administration of hydralazine (250mg/L) and minoxidil (120mg/L) to investigate effects of direct-acting vasodilators on AAA disease. Our results suggested both hydralazine and minoxidil promoted the progression of AAA with increased aortic degeneration. Mechanistically, the vasodilators aggravated aortic inflammation by increased leukocyte infiltration and inflammatory cytokine secretion. Conclusion and relevance: The plasma renin level and plasma renin activity are positively associated with AAA development. Direct vasodilators aggravated experimental AAA progression, which raised cautionary concerns about their applications in AAA disease.

Inhibition of the Renin-Angiotensin System Fails to Suppress β-Aminopropionitrile-Induced Thoracic Aortopathy in Mice-Brief Report.

Cross-linking of lysine residues in elastic and collagen fibers is a vital process in aortic development. Inhibition of lysyl oxidase by BAPN (β-aminopropionitrile) leads to thoracic aortopathies in mice. Although the renin-angiotensin system contributes to several types of thoracic aortopathies, it remains unclear whether inhibition of the renin-angiotensin system protects against aortopathy caused by the impairment of elastic fiber/collagen crosslinking. BAPN (0.5% wt/vol) was started in drinking water to induce aortopathies in male C57BL/6J mice at 4 weeks of age for 4 weeks. Five approaches were used to investigate the impact of the renin-angiotensin system. Bulk RNA sequencing was performed to explore potential molecular mechanisms of BAPN-induced thoracic aortopathies. Losartan increased plasma renin concentrations significantly, compared with vehicle-infused mice, indicating effective angiotensin II type 1 receptor inhibition. However, losartan did not suppress BAPN-induced aortic rupture and dilatation. Since losartan is a surmountable inhibitor of the renin-angiotensin system, irbesartan, an insurmountable inhibitor, was also tested. Although increased plasma renin concentrations indicated effective inhibition, irbesartan did not ameliorate aortic rupture and dilatation in BAPN-administered mice. Thus, BAPN-induced thoracic aortopathies were refractory to angiotensin II type 1 receptor blockade. Next, we inhibited angiotensin II production by pharmacological or genetic depletion of AGT (angiotensinogen), the unique precursor of angiotensin II. However, neither suppressed BAPN-induced thoracic aortic rupture and dilatation. Aortic RNA sequencing revealed molecular changes during BAPN administration that were distinct from other types of aortopathies in which angiotensin II type 1 receptor inhibition protects against aneurysm formation. Inhibition of either angiotensin II action or production of the renin-angiotensin system does not attenuate BAPN-induced thoracic aortopathies in mice.

Abstract 543: Inhibition Of Renin-angiotensin System Failed To Suppress Beta-aminopropionitrile-induced Thoracic Aortopathies In Mice

Objective: Cross-linking of elastin and collagen fibers is a vital process in aortic development. Pharmacological inhibition of aortic cross-linking by β-aminopropionitrile (BAPN) leads to thoracic aortopathies, such as thoracic aortic aneurysm and dissection, in mice. Although the renin angiotensin system (RAS) contributes to several types of thoracic aortopathies, it remains unclear whether inhibition of the RAS protects against aortopathy formation caused by the impairment of elastin and collagen cross-linking in mice. Approach and Results: Either vehicle or losartan (15 mg/kg/d, AT1 receptor blocker) were administered through osmotic pumps for 4 weeks in male C57BL/6J mice (3-4-weeks-old, n=30/group). BAPN (0.5% wt/vol) was given through drinking water to induce aortopathies. Losartan increased plasma renin concentrations significantly compared to vehicle-infused mice, indicating effective blockade of at1 receptors. However, losartan did not suppress BAPN-induced aortic rupture and dilatation. Since losartan is a surmountable inhibitor, we also tested the effects of irbesartan, an insurmountable inhibitor of AT1 receptor blocker, on BAPN-induced aortopathy formation (50 mg/kg/day, diet, n=30/group). Despite the significant increase of plasma renin concentrations, irbesartan did not ameliorate aortic rupture and dilatation in BAPN-administered mice. Thus, BAPN-induced thoracic aortopathies were refractory to angiotensin receptor blockade. We next inhibited angiotensinogen, the unique substrate for angiotensin II, using an antisense oligonucleotide targeting angiotensinogen (AGT-ASO). AGT-ASO decreased plasma angiotensinogen concentrations, while aortic death and dilatations were not attenuated. Since hepatocytes are the major source of angiotensinogen, BAPN-induced thoracic aortopathy formation was also examined in mice with hepatocyte-specific angiotensinogen deletion. Although plasma angiotensinogen concentrations displayed 90% reduction compared to wild type littermates, aortic rupture and aneurysm formation were not suppressed. Conclusion: Inhibition of the RAS does not attenuate BAPN-induced thoracic aortopathy formation in mice.

Science, Medicine, and the Anesthesiologist

Science, Medicine, and the Anesthesiologist

Protein Kinase G Is Involved in Acute but Not in Long-Term Regulation of Renin Secretion.

Pharmacological inhibition of the renin–angiotensin–aldosterone system (RAAS) is, in combination with diuretics, the first-choice treatment for hypertension, although 10–20% of patients do not respond adequately. Next to the RAAS, the nitric oxide/cGMP/protein kinase G (PKG) system is the second fundamental blood pressure regulator. Whether both systems influence each other is not well-studied. It has been shown that nitric oxide (NO) supports renin recruitment via activation of soluble guanylate cyclase (sGC) and subsequent generation of cGMP. Whether this leads to an ensuing activation of PKGs in this context is not known. PKGIα, as well as PKGII, is expressed in renin-producing cells. Hence, we analyzed whether these enzymes play a role regarding renin synthesis, secretion, or recruitment. We generated renin-cell-specific PKGI-knockout mice and either stimulated or inhibited the renin system in these mice by salt diets. To exclude the possibility that one kinase isoform can compensate the lack of the other, we also studied double-knockout animals with a conditional knockout of PKGI in juxtaglomerular cells (JG cells) and a ubiquitous knockout of PKGII. We analyzed blood pressure, renin mRNA and renal renin protein content as well as plasma renin concentration. Furthermore, we stimulated the cGMP system in these mice using BAY 41-8543, an sGC stimulator, and examined renin regulation either after acute administration or after 7 days (application once daily). We did not reveal any striking differences regarding long-term renin regulation in the studied mouse models. Yet, when we studied the acute effect of BAY 41-8543 on renin secretion in isolated perfused kidneys as well as in living animals, we found that the administration of the substance led to a significant increase in plasma renin concentration in control animals. This effect was completely abolished in double-knockout animals. However, after 7 days of once daily application, we did not detect a persistent increase in renin mRNA or protein in any studied genotype. Therefore, we conclude that in mice, cGMP and PKG are involved in the acute regulation of renin release but have no influence on long-term renin adjustment.

The renal vasodilatory effect of prostaglandins is ameliorated in isolated-perfused kidneys of endotoxemic mice.

Endotoxemia-related acute kidney injury (AKI) is associated with increased formation of prostaglandins, which may serve as a compensatory mechanism to maintain renal function. We hypothesized that an increase of renal EP2 or EP4 receptors and/or a downregulation of renal EP1 and EP3 receptors enhances PGE2-induced renal vasodilatation. Injection of lipopolysaccharide (LPS; 3mg/kg i.p.) increased microsomal prostaglandin E synthase (mPGES)-1 and prostacyclin synthase expression, whereas mPGES-2 expression was unaltered. Further, LPS increased the mRNA abundance for the prostaglandin EP4 receptor, whereas the expressions of the EP1 and EP3 receptors were decreased. In isolated-perfused kidneys from control mice, PGE2 exerted a dual effect on renal vascular tone, inducing vasodilatation at lower concentrations and vasoconstriction at higher concentrations. In kidneys from endotoxemic mice, the vasodilatory component was more pronounced, whereas the vasoconstriction at higher PGE2 concentrations was absent. Similarly, prostacyclin (PGI2)-induced vasodilatation was more pronounced in endotoxemic kidneys. The enhanced vasodilatory effect was paralleled by an increase in renal vascular EP4 and prostacyclin IP receptor mRNA expression. Further, stimulation of renin secretion rate by PGE2 and PGI2 was enhanced in endotoxemic kidneys. Pretreatment with the cyclooxygenase (COX)-2 inhibitor SC-236 (10mg/kg) did not alter the basal GFR, but augmented the LPS-induced decline in GFR, and attenuated the LPS-induced increase in plasma renin concentration in vivo. Our data suggest that an activation of the COX-2/mPGES-1 synthetic pathway is responsible for the increased renal formation of PGE2 in response to LPS and that the vasodilatory effect of PGE2 and PGI2 is enhanced during endotoxemia.

Effects of Vitamin D Supplementation on Renin and Aldosterone Concentrations in Patients with Advanced Heart Failure: The EVITA Trial

Objective 1,25-Dihydroxyvitamin D (1,25([OH]2D) is considered to be a negative endogenous regulator of the renin-angiotensin-aldosterone system (RAAS), but the effect of vitamin D supplementation on the RAAS is inconclusive. Design In this prespecified secondary analysis of a randomized controlled trial, we assessed in 165 patients with heart failure (vitamin D group: n = 83; placebo group: n = 82) the effect of three years of vitamin D supplementation with 4000 IU daily on parameters of the RAAS (renin and aldosterone) and on circulating 1,25(OH)2D, plasma phosphate, and fibroblast growth factor (FGF)-23. We assessed age- and baseline-adjusted between-group differences at study termination. Results Almost all patients were under treatment with beta-blockers, inhibitors of the RAAS, and diuretics. Initially, the frequency of concentrations above the laboratory-specific reference range (renin: >23.9 mIU/L; aldosterone: >232 ng/L) in the vitamin D and placebo group was 87.7% and 92.7%, respectively (renin), and 24.1% and 32.5%, respectively (aldosterone). Vitamin D increased adjusted 1,25(OH)2D concentrations significantly (mean treatment effect and 95% CI: 18.3 pmol/L,7.3 to 29.3 pmol/L; P < 0.001) but had no significant effects on phosphate (0.18 mmol/L, −0.00 to 0.35 mmol/L; P = 0.051), FGF-23 (685 RU/mL, −213 to 1585 RU/mL; P = 0.134), renin (312 mIU/L, −279 to 902 ng/L; P = 0.298), or aldosterone (−0.19 ng/L, −5.09 to 4.70 ng/L; P = 0.938). Vitamin D supplementation was, however, associated with an increase in renin concentrations in the subgroup with baseline 25-hydroxyvitamin D below 30 nmol/L (n = 67; 1365 mIU/, 343 to 2386 mIU/L; P = 0.010). Conclusions In patients with advanced heart failure treated according to evidence-based guidelines, vitamin D supplementation did not significantly influence parameters of the RAAS in the entire study cohort but was associated with an increase in plasma renin concentrations in the subgroup with low baseline 25-hydroxyvitamin D concentrations.

Raritná kombinácia Turnerovho syndrómu a kongenitálnej adrenálnej hyperplázie s deficitom 21-hydroxylázy: kazuistika

Combination of Turner syndrome (TS) and classic congenital adrenal hyperplasia (CAH) is rare. Globally, the incidence of CAH, autosomal recessive disorder caused by enzyme defect of steroidogenic pathway, is very low (1 : 10 000-16 000). 90 % of CAH cases are caused by 21-hydroxylase gene mutation (CYP21A2). Globally, the incidencie of Turner syndrome reaches 1 : 2 500. Phenotypically, females with TS may render wide spectrum of clinical features. Dominant symptoms are lowered terminal height and gonadal dysgenesia, ultimately leading to absence of puberty and infertility. Virilisation may be evident among TS women with chromosome Y 45, X/46, XY. We present a 57 year old woman suffering from both TS 45, X/46, XX and 21-hydroxylase deficiency. Based on the intersex, she was misdiagnosed as a male after the birth. Dominant signs were intrauterine growth retardation and Prader 5 virilisation of the external genitalia. Testes were not palpable. Laparoscopy at the age of 6 showed uterus and ovaries. After this examination, clitoroplasty and vaginoplasty was performed. Karyotyping revealed a 45, X/46, XX pattern. The presence of virilising features at the time of puberty however could not be explained with the diagnosis of Turner syndrome. Laboratory tests revealed elevated level of 17-hydroxyprogesterone, dehydroepiandrosterone with low cortisol concentration and elevated ACTH. With the genomic analysis CYP21A2 gene, namely IN2G (IVS 2-13 A/C>G), large deletion/conversion was detected. Glucocorticoid treatment was initiated. Due to increased plasma renin concentration, fludrocortisone therapy was also initiated. Within this therapy, patient´s state improved significantly.Key words: congenital adrenal hyperplasia - CYP21A2 - Turner syndrome - 21-hydroxylase deficiency.

Significant natriuretic and antihypertensive action of the epithelial sodium channel blocker amiloride in diabetic patients with and without nephropathy.

Diabetic nephropathy is associated with aberrant glomerular filtration of serine proteases. The study was designed to test the hypothesis that the epithelial sodium channel is activated proteolytically by urine plasmin in diabetic nephropathy and mediates renal sodium retention. In an open-label intervention study on type 1 diabetes patients on standardized NaCl intake (200 mmol/day) with (n = 15) and without diabetic nephropathy (control, n = 12), urinary Na excretion in response to oral amiloride (20 or 40 mg/day for 2 days) was compared. A total of 27 patients completed the study and nine diabetic nephropathy and eight control study participants were compliant (24-h urine Na excretion of 200 mmol ± 30%). Amiloride increased significantly total and fractional Na excretion in both groups. Total natriuresis and weight loss were significantly larger in the control group compared with diabetic nephropathy at day 1 of amiloride, whereas fractional Na excretion did not differ. Amiloride intervention increased plasma renin concentration only in diabetic nephropathy group; it reduced SBP in both groups, whereas DBP was reduced in diabetic nephropathy group only. Albuminuria was reduced significantly by amiloride in diabetic nephropathy group. Urine total amiloride concentration was not different between groups (12 ± 1 and 16 ± 1 μmol/l, respectively). Urine total plasminogen and active plasmin were reduced after amiloride in diabetic nephropathy. Amiloride increased renal Na excretion, reduced blood pressure, albuminuria, and total and active plasmin in urine. It is concluded that epithelial sodium channel is an attractive target to attain blood pressure control in long-term type I diabetes with no enhanced activity associated with nephropathy.

Higher plasma prorenin concentration plays a role in the development of coronary artery disease.

BackgroundProrenin and renin are both involved in atherosclerosis. However, the role of plasma prorenin and renin in the development and progression of coronary artery disease (CAD) is still not clear. Thus, we aimed to examine the relationships among plasma prorenin concentration, CAD and clinical parameters.MethodsWe measured plasma prorenin and renin concentrations and other parameters in 85 patients who underwent coronary angiography. Patients were divided into a CAD group (≥75 % stenosis in one or more coronary arteries) and a non-CAD group.ResultsThere was a weak correlation between prorenin and plasma renin concentration (r =0.35, p =0.001), and plasma renin activity (r =0.34, p =0.001). There was no significant difference in the plasma prorenin concentration between the CAD group and non-CAD group. However, patients with a high plasma prorenin concentration frequently suffered CAD. Receiver-operating-characteristic curve analysis showed that the optimal cutoff value of plasma prorenin concentration to detect CAD was 1,100 pg/ml, with a positive predictive value of 94 % and a negative predictive value of 36 %.ConclusionThe plasma prorenin concentration increases with increases in plasma renin concentration. Higher plasma prorenin concentration (>1,100 pg/ml) plays a role in the development of CAD.

Efficacy and Safety Profile of Aliskiren: Practical Implications for Clinicians

Renin-angiotensin-system (RAS) is an enzymatic cascade that plays a pivotal role in the development of arterial hypertension, kidney disease and cardiovascular disease. Inhibition of the RAS with angiotensin converting enzyme (ACE) inhibitors (ACE-Is) or angiotensin receptor blockers (ARBs) has proved to be a successful strategy for the treatment of hypertension and related cardiovascular disorders. However, by reducing feedback inhibition of renin release, the effects of ACE-Is and ARBs lead to an increase in plasma renin concentration (PRC) and activity (PRA), limiting a complete inhibition of the RAS. Consequently the effects of a different pharmacological strategy that completely blocks the RAS upstream has been assessed in the last years. In this context, aliskiren is the first representative of a new class of non-peptide orally active renin inhibitor that blocks the RAS at its rate-limiting step and induces a net reduction in PRA, angiotensin II and aldosterone levels. Aliskiren effectively reduces blood pressure as a monotherapy as well in combination therapy. In addition, aliskiren has a placebo-like tolerability profile at the licensed doses of 150 mg and 300 mg. Aliskiren also exhibits additive effects on blood pressure reduction when combined with drugs that lead to a reactive increase in the PRA, such as diuretics, ACE-Is or ARBs. In previous studies, aliskiren showed beneficial effects in patients with arterial hypertension and associated clinical conditions. However, later trials indicated that the use of aliskiren should be avoided in patients with renal failure or receiving ACE-Is or ARBs. The main aim of this review is to summarize the available data on its efficacy and safety profile, highlighting clinical implications from recent trials.

Effect of Contrasted Sodium Diets on the Pharmacokinetics and Pharmacodynamic Effects of Renin–Angiotensin System Blockers

Dietary sodium, the main determinant of the pharmacodynamic response to renin-angiotensin system blockade, influences the pharmacokinetics of various cardiovascular drugs. We compared the effect of contrasted sodium diets on the pharmacokinetics of single oral doses of 8 mg candesartan cilexetil, 160 mg valsartan, 10 mg ramipril, and 50 mg atenolol administered to 64 (16 per group) normotensive male subjects randomly assigned to sodium depletion (SD) or sodium repletion (SR) in a crossover study. Pharmacodynamic response was assessed as the increase in plasma renin concentration for renin-angiotensin system blockers and electrocardiographic changes in PR interval duration for atenolol. The area under the curve (AUC) for plasma candesartan and atenolol concentrations was significantly lower for SR than for SD (respective ratios of AUC0-∞: 0.74; [90% CI, 0.66-0.82] and 0.69 [90% CI, 0.54-0.88], respectively), indicating a lack of bioequivalence between SR and SD. SR did not affect the pharmacokinetics of valsartan or ramipril. The increase in plasma renin concentration with the 3 renin-angiotensin system blockers was 10 times lower during the SR than the SD period. In the multiple regression analysis, the AUC0-24 of plasma drug concentration explained <1% and 21% of the variance of the AUC0-24 of delta plasma renin concentration for candesartan (P=0.8882/P=0.0368) during the SR and SD periods, respectively. The atenolol-induced lengthening of PR interval was fully reversed by SR. Thus, sodium balance modulates the pharmacokinetics of candesartan cilexetil and atenolol, with measurable effects on the selected pharmacodynamic end points.

Predominance of AT1 Blockade Over Mas–Mediated Angiotensin-(1–7) Mechanisms in the Regulation of Blood Pressure and Renin–Angiotensin System in mRen2.Lewis Rats

We investigated whether the antihypertensive actions of the angiotensin II (Ang II) receptor (AT(1)-R) blocker, olmesartan medoxomil, may in part be mediated by increased Ang-(1-7) in the absence of significant changes in plasma Ang II. mRen2.Lewis congenic hypertensive rats were administered either a vehicle (n = 14) or olmesartan (0.5 mg/kg/day; n = 14) by osmotic minipumps. Two weeks later, rats from both groups were further randomized to receive either the mas receptor antagonist A-779 (0.5 mg/kg/day; n = 7 per group) or its vehicle (n = 7 per group) for the next 4 weeks. Blood pressure was monitored by telemetry, and circulating and tissue components of the renin-angiotensin system (RAS) were measured at the completion of the experiments. Antihypertensive effects of olmesartan were associated with an increase in plasma renin concentration, plasma Ang I, Ang II, and Ang-(1-7), whereas serum aldosterone levels and kidney Ang II content were reduced. Preserved Ang-(1-7) content in kidneys was associated with increases of ACE2 protein but not activity and no changes on serum and kidney ACE activity. There was no change in cardiac peptide levels after olmesartan treatment. The antihypertensive effects of olmesartan were not altered by concomitant administration of the Ang-(1-7) receptor antagonist except for a mild further increase in plasma renin concentration. Our study highlights the independent regulation of RAS among plasma, heart, and kidney tissue in response to AT(1)-R blockade. Ang-(1-7) through the mas receptor does not mediate long-term effects of olmesartan besides counterbalancing renin release in response to AT(1)-R blockade.

Sequential comparison of aldosterone synthase inhibition and mineralocorticoid blockade in patients with primary aldosteronism

We compared the effects of aldosterone synthase inhibition with LCI699 with those of mineralocorticoid receptor blockade in patients with primary aldosteronism. After a 2-week placebo run-in, 14 patients with primary aldosteronism received oral LCI699 (0.5 mg b.i.d.) from day 1 to 14, LCI699 (1 mg b.i.d.) from day 15 to 29, and placebo from day 29 to 36. From day 36 to day 66, patients were treated with eplerenone (50 mg b.i.d., up-titrated to 100 mg b.i.d. in 12/14 patients), in addition to their previous antihypertensive treatment, which was maintained unchanged. Eplerenone significantly decreased more 24-h ambulatory SBP on day 66 than LCI699 on day 29 and the difference between the two treatment was -5.34 [95% confidence interval (CI) -10.30; -0.38)] mmHg (P = 0.027). Plasma potassium concentration achieved on eplerenone (4.30 ± 0.45 mmol/l) was significantly greater than on LCI699 (3.89 ± 0.35 mmol/l; P = 0.009). The increase in plasma renin concentration was significantly greater after eplerenone [+131% (range 61; 231)] than on LCI699 on day 29 [+39% (range 5; 86); P = 0.023]. LCI699 markedly decreased plasma aldosterone concentration by 75% (range -84;-63), whereas eplerenone markedly increased this concentration, from day 36, by 89% (range 40;154; P < 0.0001 vs. day 29). In patients with primary aldosteronism, the effects on blood pressure and plasma potassium and renin concentrations of 4 weeks of eplerenone treatment (50-100 mg b.i.d.) were more marked than those of 4 weeks of LCI699 treatment (0.5-1 mg b.i.d.). These two drugs had opposite effects on plasma aldosterone concentration.

Aldosterone synthase inhibition in humans

Aldosterone synthase (CYP11B2) inhibition has emerged as a new option for the treatment of hypertension, heart failure and renal disorders, in addition to mineralocorticoid receptor (MR) blockade. The aim is to decrease aldosterone concentrations in both plasma and tissues, thereby decreasing MR-dependent and MR-independent effects in the cardiac, vascular and renal target organs. LCI699 was the first orally active aldosterone-synthase inhibitor to be developed for human use. Its structure is similar to that of FAD286, the dextroenantiomer of the aromatase inhibitor, fadrozole. It dose-dependently decreases plasma and urine aldosterone concentrations by up to 70 or 80% and increases plasma renin activity in healthy male subjects on a low-sodium diet. LCI699 does not decrease basal plasma cortisol concentrations at doses of 0.5-3 mg q.d., but it blocks the cortisol response to adrenocorticotropic hormone (ACTH) at doses ≥ 3 mg q.d. In a proof-of-concept study in patients with primary aldosteronism (PA), LCI699 (0.5-1 mg b.i.d.) induced a dose-dependent and reversible 70-80% decrease in plasma and urinary aldosterone concentration accompanied by a massive dose-dependent accumulation of deoxycorticosterone (>+700%), the aldosterone precursor, in the plasma, thereby confirming the inhibition of the CYP11B2 gene product. This effect was associated with a rapid correction of hypokalaemia, a modest decrease in blood pressure (BP) and a mild increase in plasma renin concentration in patients with PA. LCI699 administration induced biological signs of partial inhibition of the glucocorticoid axis, such as dose-dependent increases in both plasma ACTH and 11-deoxycortisol (the precursor of cortisol) concentrations, consistent with the inhibition of the CYP11B1 gene product. An 8-week placebo-controlled dose-response study on patients with Stage 1 and 2 essential hypertension reported an optimal decrease in BP with a dose of 1 mg LCI699 q.d., which had an antihypertensive effect similar to that of 50 mg b.i.d. eplerenone. A blunted cortisol response to ACTH was observed in 20% of patients, but the clinical and biological safety and tolerability of LCI699 were similar to those of placebo and eplerenone. The discovery of this first orally active aldosterone synthase inhibitor, LCI699, has provided new opportunities to assess the feasibility and the haemodynamic, biological and safety consequences as well as the limitations of this new approach to block the aldosterone pathway in hypertensive patients. However, as the effects of LCI699 on the glucocorticoid axis limit the use of higher doses range because of the loss of selectivity for CYP11B2, this aldosterone synthase inhibitor cannot replace the MR blockade in patients with hypertension, other cardiovascular or renal disorders. The development of second-generation aldosterone synthase inhibitors with a higher selectivity index for CYP11B2 than LCI699 should make it possible to test this approach at much higher doses in these patients, after the necessary toxicology and Phase I studies.

Abstract 283: Predominance of Angiotensin II Type 1 Receptor Blockade Over Angiotensin-(1-7) Mechanisms in the Regulation of Blood Pressure and Renin Angiotensin System in mRen.Lewis Rats

We investigated the angiotensin-(1-7) [Ang-(1-7)] mediated effects of Ang II receptor (AT 1 -R) blocker -olmesartan medoxomil-on blood pressure, plasma, renal, and cardiac Ang II as well as activities of the enzymes involved in peptide formation or metabolism in mRen2.Lewis congenic hypertensive rats, a model of Ang II tissue-dependent hypertension. mRen2.Lewis rats were treated with either vehicle (n=14) or olmesartan (0.5 mg/kg/day; n=14) by osmotic minipumps. After 2 weeks rats from both groups were further randomized to receive either the mas receptor antagonist A-779 (0.5 mg/kg/day; n=7 per group) or its vehicle (n=7 per group) for the next 4 weeks. Antihypertensive effect of olmesartan monitored by telemetry (Figure) was associated with an increase in plasma renin concentration (PRC), plasma Ang II (513 ± 115 vs. 31 ± 5 fmol/mL; p&lt;0.05) and Ang-(1-7) (60 ± 5 vs. 27 ± 4 fmol/mL; p&lt;0.05) while reduced kidney Ang II content and no changes in kidney Ang-(1-7), angiotensin converting enzyme (ACE), ACE2 and neprilysin activities were noted in olmesartan treated group when compared to the controls (Figure). Olmesartan had no effect on cardiac peptide levels . Concomitant administration of A-779 increased PRC but had no effect on blood pressure or other RAS components. Our study highlights the independent regulation of RAS among plasma, heart, and kidney tissue in response to AT 1 -R blockade. Ang-(1-7) through mas-receptor does not mediate long-term effects of olmesartan besides counterbalancing renal renin release in response to AT 1 -R blockade.

Nebivolol reduces cardiac angiotensin II, associated oxidative stress and fibrosis but not arterial pressure in salt-loaded spontaneously hypertensive rats

Increased sympathetic outflow, renin-angiotensin system (RAS) activity, and oxidative stress are critical mechanisms underlying the adverse cardiovascular effects of dietary salt excess. Nebivolol is a third-generation, highly selective β1-receptor blocker with RAS-reducing effects and additional antioxidant properties. This study evaluated the hypothesis that nebivolol reduces salt-induced cardiac remodeling and dysfunction in spontaneous hypertensive rats (SHRs) by suppressing cardiac RAS and oxidative stress. Male SHRs (8 weeks of age) were given an 8% high salt diet (HSD; n = 22), whereas their age-matched controls (n = 10) received standard chow. In a subgroup of HSD rats (n = 11), nebivolol was given at a dose of 10 mg/kg per day by gastric gavage. After 5 weeks, HSD exacerbated hypertension as well as increased left-ventricular weight and collagen deposition while impairing left-ventricular relaxation. Salt-induced cardiac remodeling and dysfunction were associated with increased plasma renin concentration (PRC), cardiac angiotensin II immunostaining, and angiotensin-converting enzyme (ACE)/ACE2 mRNA and activity ratio. HSD also increased cardiac 3-nitrotyrosine staining indicating enhanced oxidative stress. Nebivolol treatment did not alter the salt-induced increase in arterial pressure, left-ventricular weight, and cardiac dysfunction but reduced PRC, cardiac angiotensin II immunostaining, ACE/ACE2 ratio, oxidative stress, and fibrosis. Our data suggest that nebivolol, in a blood pressure-independent manner, ameliorated cardiac oxidative stress and associated fibrosis in salt-loaded SHRs. The beneficial effects of nebivolol may be attributed, at least in part, to the decreased ACE/ACE2 ratio and consequent reduction of cardiac angiotensin II levels.

Aliskiren and perindopril reduce the levels of transforming growth factor-β in patients with non-diabetic kidney disease

It is highly likely that the rise in plasma prorenin and plasma renin during renin inhibitor treatment is induced at least as much by the fall in blood pressure (BP) as it is by the negative feedback of angiotensin II. This could potentially be harmful because high levels of renin and prorenin may stimulate the (pro)renin receptor, thus inducing profibrotic effects. To further understand this relationship, the influence of aliskiren on the urinary excretion of transforming growth factor-β1 (TGF-β1) and procollagen III N-terminal propeptide (PIIINP) was evaluated in patients with nondiabetic kidney diseases. Aliskiren 300 mg and perindopril 10 mg, were each individually administered for 12 weeks separated by a placebo period in a cross-over, randomized, double-blinded pilot study. A 1,131% (P < 0.001) and 628% (P < 0.001) increase in plasma renin concentration was observed after the aliskiren and perindopril therapies, respectively, as compared to the placebo. Aliskiren and perindopril increased prorenin concentrations as compared to the placebo by 100% (P < 0.01) and 52.4% (P = 0.53), respectively. The TGF-β1 excretion was lower after tested therapies compared to the placebo (55.0 ± 7.56 vs. 56.21 ± 8.56 vs. 85.79 ± 14.11 pg/mg creatinine; P = 0.016); without differences between aliskiren and perindopril. PIIINP excretion did not differ between treatments. The study shows that both aliskiren and perindopril suppress TGF-β1 in patients with chronic kidney diseases. This effect was observed despite significant increases in the renin and prorenin concentrations. Further studies involving histological assessments are required to elucidate the exact impact of these agents on renal fibrosis.

Abstract 331: Angiotensinogen Inhibition by Antisense Oligonucleotides Decreases Atherosclerosis and Obesity in a Dose-Dependent Manner

Background and Objective: The renin-angiotensin system (RAS) exerts profound effects on experimental atherosclerosis. While there is evolving evidence of the complexity of the RAS, angiotensinogen (Agt) remains the single precursor for all known angiotensin peptides. The aim of this study was to determine the dose-dependent effects of inhibiting Agt synthesis on atherosclerosis. Methods and results: Male LDL receptor -/- mice were fed a saturated fat-enriched diet (21% wt/wt milk fat; 0.2% wt/wt cholesterol) for 3 months. Mice were injected weekly i.p. with either an antisense oligonucleotide (ASO) to Agt (ISIS #261333 at 50 mg/kg/week or #487022 at 12.5, 25 and 50 mg/kg/week) or a control ASO (ISIS #141923 at 50 mg/kg/week; n=10 mice per group). Administration of Agt ASO led to ∼90% reduction in plasma Agt concentrations (P&lt;0.001) and a marked reduction in hepatic Agt mRNA abundance (P&lt;0.05). There was also an expected dose-dependent increase in plasma renin concentrations (P&lt;0.001). Agt ASO administration also decreased systolic blood pressure (SBP) in a dose-dependent manner (P&lt;0.05). Inhibition of Agt significantly decreased total plasma cholesterol concentrations in the two highest dose Agt ASO groups. Atherosclerotic lesion areas were markedly decreased by Agt ASO administration in highest dose groups when compared to the PBS group (16.9 ± 1.0 versus 6.0 ± 1.3 and 6.2 ± 1.1 % of intimal area; P&lt;0.001). Unexpectedly, Agt ASO administration also markedly attenuated body weight gain. MRI analyses demonstrated a dose-dependent reduction in fat mass (P&lt;0.001) with no effect on lean mass. Adipose (retroperitoneal, inguinal and subcutaneous) tissue weights were decreased in a dose-dependent manner. Conclusions: Inhibition of Agt synthesis markedly decreases SBP, development of atherosclerosis and body weight gain in a dose-dependent manner.