Reporter mouse strain provides a novel look at angiotensin type-2 receptor distribution in the central nervous system

Angiotensin-II acts at its type-1 receptor (AT1R) in the brain to regulate body fluid homeostasis, sympathetic outflow and blood pressure. However, the role of the angiotensin type-2 receptor (AT2R) in the neural control of these processes has received far less attention, largely because of limited ability to effectively localize these receptors at a cellular level in the brain. The present studies combine the use of a bacterial artificial chromosome transgenic AT2R-enhanced green fluorescent protein (eGFP) reporter mouse with recent advances in in situ hybridization (ISH) to circumvent this obstacle. Dual immunohistochemistry (IHC)/ISH studies conducted in AT2R-eGFP reporter mice found that eGFP and AT2R mRNA were highly co-localized within the brain. Qualitative analysis of eGFP immunoreactivity in the brain then revealed localization to neurons within nuclei that regulate blood pressure, metabolism, and fluid balance (e.g., NTS and median preoptic nucleus [MnPO]), as well as limbic and cortical areas known to impact stress responding and mood. Subsequently, dual IHC/ISH studies uncovered the phenotype of specific populations of AT2R-eGFP cells. For example, within the NTS, AT2R-eGFP neurons primarily express glutamic acid decarboxylase-1 (80.3 ± 2.8 %), while a smaller subset express vesicular glutamate transporter-2 (18.2 ± 2.9 %) or AT1R (8.7 ± 1.0 %). No co-localization was observed with tyrosine hydroxylase in the NTS. Although AT2R-eGFP neurons were not observed within the paraventricular nucleus (PVN) of the hypothalamus, eGFP immunoreactivity is localized to efferents terminating in the PVN and within GABAergic neurons surrounding this nucleus. These studies demonstrate that central AT2R are positioned to regulate blood pressure, metabolism, and stress responses.

Biomarkers of activation of renin-angiotensin-aldosterone system in heart failure: how useful, how feasible?

Renin-angiotensin-aldosterone system (RAAS), participated by kidney, liver, vascular endothelium, and adrenal cortex, and counter-regulated by cardiac endocrine function, is a complex endocrine system regulating systemic functions, such as body salt and water homeostasis and vasomotion, in order to allow the accomplishment of physiological tasks, such as orthostasis, physical and emotional stimuli, and to react towards the hemorrhagic insult, in tight conjunction with other neurohormonal axes, namely the sympathetic nervous system, the endothelin and vasopressin systems. The systemic as well as the tissue RAAS are also dedicated to promote tissue remodeling, particularly relevant after damage, when chronic activation may configure as a maladaptive response, leading to fibrosis, hypertrophy and apoptosis, and organ dysfunction. RAAS activation is a fingerprint of systemic arterial hypertension, kidney dysfunction, vascular atherosclerotic disease, and is definitely an hallmark of heart failure, which rapidly shifts from organ disease to a disorder of neurohormonal regulatory systems. Chronic RAAS activation is an indirect or direct target of most effective pharmacological treatments in heart failure, such as beta-blockers, inhibitors of angiotensin converting enzyme, angiotensin receptor blockers, direct renin inhibitors, and mineralocorticoid receptor blockers. Biomarkers of RAAS activation are available, with different feasibility and accuracy, such as plasma renin activity, renin, angiotensin II, and aldosterone, which all accompany the increasing clinical severity of heart failure disease, and are well recognized prognostic factors, even in patients with optimal therapy. Polymorphisms influencing the expression and activity of RAAS pathways have been recognized as clinically relevant biomarkers, likely influencing either the individual clinical phenotype, or the response to drugs. This solid, growing evidence strongly suggests the rationale for the use of biomarkers of the RAAS activation, as a guide to tailor individual therapy in the current practice, and their implementation as a rule-in marker for future trials on novel drugs in the heart failure setting.

Renin-angiotensin-aldosterone system inhibition: overview of the therapeutic use of angiotensin-converting enzyme inhibitors, angiotensin receptor blockers, mineralocorticoid receptor antagonists, and direct renin inhibitors

Angiotensin-converting enzyme (ACE) inhibitor or angiotensin receptor blocker (ARB) therapy in hypertensive diabetic patients with macroalbuminuria, microalbuminuria, or normoalbuminuria has been repeatedly shown to improve cardiovascular mortality and reduce the decline in glomerular filtration rate. Renin-angiotensin-aldosterone system (RAAS) blockade in normotensive diabetic patients with normoalbuminuria or microalbuminuria cannot be advocated at present. Dual RAAS inhibition with ACE inhibitors plus ARBs or ACE inhibitors plus direct renin inhibitors has failed to improve cardiovascular or renal outcomes but has predisposed patients to serious adverse events.

African Americans, hypertension and the renin angiotensin system

African Americans have exceptionally high rates of hypertension and hypertension related complications. It is commonly reported that the blood pressure lowering efficacy of renin angiotensin system (RAS) inhibitors is attenuated in African Americans due to a greater likelihood of having a low renin profile. Therefore these agents are often not recommended as initial therapy in African Americans with hypertension. However, the high prevalence of comorbid conditions, such as diabetes, cardiovascular and chronic kidney disease makes treatment with RAS inhibitors more compelling. Despite lower circulating renin levels and a less significant fall in blood pressure in response to RAS inhibitors in African Americans, numerous clinical trials support the efficacy of RAS inhibitors to improve clinical outcomes in this population, especially in those with hypertension and risk factors for cardiovascular and related diseases. Here, we discuss the rationale of RAS blockade as part of a comprehensive approach to attenuate the high rates of premature morbidity and mortality associated with hypertension among African Americans.

Urinary sodium excretion has positive correlation with activation of urinary renin angiotensin system and reactive oxygen species in hypertensive chronic kidney disease

It is not well described the pathophysiology of renal injuries caused by a high salt intake in humans. The authors analyzed the relationship between the 24-hr urine sodium-to-creatinine ratio (24HUna/cr) and renal injury parameters such as urine angiotensinogen (uAGT/cr), monocyte chemoattractant peptide-1 (uMCP1/cr), and malondialdehyde-to-creatinine ratio (uMDA/cr) by using the data derived from 226 hypertensive chronic kidney disease patients. At baseline, the 24HUna/cr group or levels had a positive correlation with uAGT/cr and uMDA/cr adjusted for related factors (P<0.001 for each analysis). When we estimated uAGT/cr in the 24HUna/cr groups by ANCOVA, the uAGT/cr in patients with ≥200 mEq/g cr was higher than in patients with <100 mEq/g cr (708 [95% CI, 448-967] vs. 334 [95% CI, 184-483] pg/mg cr, P=0.014). Similarly, uMDA/cr was estimated as 0.17 (95% CI, 0.14-0.21) pM/mg cr in patients with <100 mEq/g cr and 0.27 (95% CI, 0.20-0.33) pM/mg cr in patients with ≥200 mEq/g cr (P=0.016). During the 16-week follow-up period, an increase in urinary sodium excretion predicted an increase in urinary angiotensinogen excretion. In conclusion, high salt intake increases renal renin-angiotensin-system (RAS) activation, primarily, and directly or indirectly affects the production of reactive oxygen species through renal RAS activation.

Telmisartan in combination with hydrochlorothiazide 12.5 mg for the management of patients with hypertension

OBJECTIVE

To compare the efficacy and safety of telmisartan 40 mg (T40) or 80 mg (T80) plus hydrochlorothiazide 12.5 mg (H12.5) single-pill combinations (SPCs) with telmisartan monotherapies, in a pooled analysis of patients with mild to moderate hypertension.

METHODS

Six phase 3, double-blind studies of 8 weeks' duration that assessed the T/H12.5 SPC and T40 or T80 monotherapy, were included in the analysis. Data was pooled separately for the two T40 non-responder studies (T40 NR group, two T80 non-responder studies (T80 NR group), and the two factorial design dose-response studies (FD-DR group).

RESULTS

After 8 weeks' treatment, the adjusted mean reduction in systolic blood pressure (SBP) and diastolic blood pressure (DBP), and the SBP, DBP, and blood pressure (BP) goal rates were significantly higher with the T40/H12.5 SPC than T40 in the T40 NR group and with the T80/H12.5 SPC than T80 in the T80 NR group. In the FD-DR group, the adjusted mean reduction in SBP and DBP, and DBP goal rates were significantly higher for T40/H12.5 versus T40. The percentage of patients with an adverse event was numerically higher with T40/H12.5 versus T40 in the T40 NR group, and was similar in telmisartan monotherapies and the T/H12.5 SPCs in the T80 NR group and FD-DR group. A limitation of this study is the retrospective and pooled nature of the analysis. Also, >75% of patients were <65 years of age, which limits the applicability of the results to older patients.

CONCLUSIONS

In patients with mild to moderate hypertension, 8 weeks' treatment with the T/H12.5 SPC is significantly more efficacious than telmisartan monotherapies. The safety and tolerability of the T/H12.5 SPC are comparable to that of telmisartan monotherapy and consistent with that reported in previous studies.

Regulation of cell volume and water transport--an old fundamental role of the renin angiotensin aldosterone system components at the cellular level

The expression and the role of renin angiotensin aldosterone system (RAAS) components on regulation of cell volume and water transport on vertebrates and invertebrates were reviewed. The presence of these components even in simple organisms like leeches and their relevance for the control of cellular volume and water transport supports the view that the expression of these components, at cellular level, is an acquisition which was preserved throughout evolution.

Elevated plasma levels of soluble (pro)renin receptor in patients with obstructive sleep apnea syndrome: association with polysomnographic parameters

(Pro)renin receptor ((P)RR) is a specific receptor for both renin and its precursor prorenin. (P)RR was shown to be involved in pathophysiology of cardiovascular and renal diseases. Soluble (pro)renin receptor (s(P)RR), which is generated by furin from full length (P)RR, is present in blood. The aim of the present study is to clarify the association of plasma s(P)RR levels and the severity of OSAS. Plasma levels of s(P)RR were measured by ELISA in 58 male patients diagnosed as OSAS based on polysomnography, and 14 age-matched male control subjects. Blood samples were obtained at 6:00 a.m. just after overnight polysomnography. Plasma s(P)RR levels were significantly higher in patients with OSAS (9.0±2.0 ng/mL, mean ± SD) than in control subjects (7.4±1.5 ng/mL) (P=0.0026). Plasma s(P)RR levels showed a significant negative correlation with % stage rapid eye movement (REM) sleep (r=-0.377, p<0.005), and significant positive correlations with % stage 1 (r=0.374, p<0.005), arousal index (r=0.341, p<0.01), apnea hypopnea index (AHI) (r=0.352, p<0.01) and desaturation index (r=0.302, p<0. 05). In 12 OSAS patients with AHI ≥20, plasma levels of s(P)RR were studied after 3-month treatment with nasal continuous positive airway pressure (nCPAP). Plasma s(P)RR levels were significantly decreased after the nCPAP treatment (p=0.0016). The present study has shown for the first time elevated plasma s(P)RR levels in patients with OSAS. Plasma s(P)RR levels were associated with the severity of OSAS. Soluble (P)RR may serve as a plasma marker reflecting the severity of OSAS.

A case of reninoma with variant angina

Reninoma is a tumor of the renal juxtaglomerular cell apparatus that causes hypertension and hypokalemia because of hypersecretion of renin. We present a case of a 29-year-old female patient with reninoma and concomitant variant angina. The patient had uncontrolled hypertension and elevated plasma renin activity and aldosterone levels. Imaging studies revealed a mass in the left kidney, which was further confirmed as a renin-producing lesion via selective venous catheterization. During the evaluation, the patient had acute-onset chest pain that was diagnosed as variant angina after a provocation test. After partial nephrectomy, the plasma renin activity and plasma aldosterone levels decreased and blood pressure normalized. We report a case of reninoma with variant angina.

Potential pathophysiological role for the vitamin D deficiency in essential hypertension

Vitamin D deficiency has been indicated as a pandemic emerging public health problem. In addition to the well-known role on calcium-phosphorus homeostasis in the bone, vitamin D-mediated processes have been recently investigated on other diseases, such as infections, cancer and cardiovascular diseases. Recently, both the discovery of paracrine actions of vitamin D (recognized as “local vitamin D system”) and the link of vitamin D with renin-angiotensin-aldosterone system and the fibroblast growth factor 23/klotho pathways highlighted its active cardiovascular activity. Focusing on hypertension, this review summarizes the more recent experimental evidence involving the vitamin D system and deficiency in the cardiovascular pathophysiology. In particular, we updated the vascular synthesis/catabolism of vitamin D and its complex interactions between the various endocrine networks involved in the regulation of blood pressure in humans. On the other hand, the conflicting results emerged from the comparison between observational and interventional studies emphasize the fragmentary nature of our knowledge in the field of vitamin D and hypertension, strongly suggesting the need of further researches in this field.

Renin angiotensin system modulates mTOR pathway through AT2R in HIVAN

Mammalian target of rapamycin (mTOR) has been reported to contribute to the development of HIV-associated nephropathy (HIVAN). We hypothesized that HIV may be activating renal tissue mTOR pathway through renin angiotensin system (RAS) via Angiotensin Receptor Type II receptor (AT2R). Renal tissues of Vpr transgenic and Tg26 (HIVAN) mice displayed enhanced phosphorylation of mTOR and p70S6K. Aliskiren, a renin inhibitor attenuated phosphorylation of both mTOR and p70S6K in renal tissues of HIVAN mice. Interestingly, Angiotensin Receptor Type I (AT1R) blockade did not modulate renal tissue phosphorylation of mTOR in HIVAN mice; on the other hand, AT2R blockade attenuated renal tissue phosphorylation of mTOR in HIVAN mice. In vitro studies, both renin and Ang II displayed enhanced mouse tubular cell (MTC) phosphorylation of p70S6K in a dose dependent manner. HIV/MTC also displayed enhanced phosphorylation of both mTOR and p70S6K; interestingly this effect of HIV was further enhanced by losartan (an AT1R blocker). On the other hand, AT2R blockade attenuated HIV-induced tubular cell phosphorylation of mTOR and p70S6K, whereas, AT2R agonist enhanced phosphorylation of mTOR and p70S6K. These findings indicate that HIV stimulates mTOR pathway in HIVAN through the activation of renin angiotensin system via AT2R.

A reduction of 3 g/day from a usual 9 g/day salt diet improves endothelial function and decreases endothelin-1 in a randomised cross_over study in normotensive overweight and obese subjects

BACKGROUND AND AIM

It is unclear if a modest reduction in dietary salt intake has beneficial effects on vascular function. The aim was to compare the effects of 9 g salt/day with 6 g salt/day intake on measures of vascular function and explore mechanisms of effect in overweight and obese adults.

METHODS

Twenty-five overweight/obese subjects (BMI 27-40 kg/m(2)) completed a randomised cross-over study of 6 weeks each on a reduced salt (RS) (6 g/day) and usual salt diet (US) (9 g/day). Flow-mediated-dilatation (FMD), 24 h blood pressure (BP), augmentation index (AIx), pulse wave velocity (PWV), plasma and urinary nitrate/nitrite, asymmetric dimethylarginine (ADMA), renin, aldosterone and endothelin-1 and vascular adhesion molecules were measured after 2 days and 6 weeks. Adherence to the diets was determined from two 24 h urine collections.

RESULTS

Urinary sodium excretion was 155 ± 58 mmol/24 h US vs 113 ± 45 mmol/24 h RS (p = 0.002). Following the RS diet there was a significant improvement in FMD from 3.5 ± 2.8% to 5.6 ± 2.8% (P < 0.001) and decrease in serum endothelin-1 from 1.45 ± 0.38 pg/ml to 1.25 ± 0.39 pg/ml (P < 0.05). Endothelium-independent vasodilatation was also significantly different between treatments (P < 0.05). AIx, PWV, serum ADMA and plasma and urinary nitrate/nitrite concentrations were not different between treatments. Change in FMD was related to the urinary sodium: creatinine ratio (r = -0.47, P < 0.05) and was independent of blood pressure. Aldosterone and renin were unchanged.

CONCLUSIONS

A small reduction in dietary salt intake of 3 g/day improves endothelial function in normotensive overweight and obese subjects. This response may be mediated by serum endothelin-1. This small reduction in salt had no effect on aldosterone and renin concentrations. This trial was registered with the Australian and New Zealand Clinical Trials Registry Unique Identifier: ACTRN12609000321246 http://www.anzctr.org.au/ACTRN12609000321246.aspx.

Hypertension and depressed symptomatology: a cluster related to the activation of the renin-angiotensin-aldosterone system (RAAS). Findings from population based KORA F4 study

CONTEXT

Preliminary evidence points to aldosterone being not only prominently involved in the systemic regulation of the blood pressure but also to play a role in the pathophysiology of depression.

OBJECTIVE

We evaluated whether the combination of hypertension and depressed symptomatology is useful to screen for individuals suffering an activation of the renin-angiotensin-aldosterone system (RAAS).

DESIGN

We conducted a cross-sectional analysis in participants from the Cooperative Health Research in the Region of Augsburg (KORA) F4 Study conducted between 2006 and 2008 in Southern Germany. A total of 1805 participants of the F4 study were included in the study.

METHODS

The association between aldosterone and renin levels and the different combinations of hypertension and depressed symptomatology was examined in four different models of multiple linear regression adjusted for age, sex, creatinine levels, potassium levels, body mass index (BMI) and behavioural risk factors.

RESULTS

Individuals suffering both, depressed symptomatology and hypertension exhibited highly significantly increased aldosterone levels (p<0.001) and slightly, not significantly increased renin levels (p=0.08) compared to individuals with no depressed symptomatology and no hypertension. No significant activation of the RAAS was seen in only depressed or only hypertensive individuals.

CONCLUSIONS

The finding of highly significantly increased aldosterone levels and increased renin levels in individuals suffering both, depressed symptomatology and hypertension provides further evidence for the involvement of the RAAS in the pathogenesis of depressed symptomatology. These findings have important implications for future research concerning the pathophysiological pathways that link depression and cardiovascular disease.

(Pro)renin receptor and insulin resistance: possible roles of angiotensin II-dependent and -independent pathways

A growing body of evidence has suggested the potential role of (pro)renin receptor [(P)RR] in the pathogenesis of cardiovascular and renal injuries during the development of hypertension and diabetes. However, there is very little information on the contribution of (P)RR to the pathophysiology of insulin resistance. In this regard, our preliminary data showed that the development of insulin resistance was associated with nonproteolytic activation of prorenin as well as local angiotensin II generation in skeletal muscle and adipose tissues of obese Otsuka Long-Evans Tokushima Fatty rats. In fructose-fed rats, insulin resistance was also associated with nonproteolytic activation of prorenin and skeletal muscle angiotensin II generation. Furthermore, inhibition of (P)RR with handle region decoy peptide (HRP) improved the development of fructose-induced insulin resistance. However, in other animal model, such as transgenic rats overexpressing the human renin gene, HRP failed to ameliorate glucose intolerance. In this review, we will summarized the current knowledge regarding the possible contribution of (P)RR to the pathophysiology of insulin resistance.

Synthesis and optimization of novel (3S,5R)-5-(2,2-dimethyl-5-oxo-4-phenylpiperazin-1-yl)piperidine-3-carboxamides as orally active renin inhibitors

We report synthesis and optimization of a series of (3S,5R)-5-(2,2-dimethyl-5-oxo-4-phenylpiperazin-1-yl)piperidine-3-carboxamides as renin inhibitors. Chemical modification of P1', P2' and P3 portions led to a promising 3,5-disubstituted piperidine 32o showing high renin inhibitory activity and favorable oral exposure in both rats and cynomolgus monkeys with acceptable CYP and hERG current inhibition. Compound 32o exhibited a significant blood pressure lowering effect by oral administration in two hypertensive animal models, double transgenic rats and furosemide pretreated cynomolgus monkeys.

Impaired blood pressure compensation following hemorrhage in conscious obese Zucker rats

AIMS

Hemorrhagic shock leads to a higher risk of mortality and morbidity in obese patients, however the mechanisms for these outcomes are unclear. We hypothesized that following severe hemorrhage, blood pressure control in conscious obese Zucker rats (OZ) is impaired.

MAIN METHODS

Experiments were performed in conscious lean Zucker rats (LZ) and OZ. Blood pressure, heart rate, cardiac output, total peripheral resistance (TPR), plasma renin activity (PRA), plasma antidiuretic hormone (ADH), and blood gasses were measured before and after severe hemorrhage (35% of the total blood volume).

KEY FINDINGS

Basal blood pressure, cardiac output, TPR, PRA, and ADH levels were not different between LZ and OZ. Compared to LZ, OZ exhibited impaired baroreflex control of heart rate and showed higher levels of vascular adrenergic tone. One hour after the hemorrhage, LZ and OZ exhibited similar decreases in cardiac output. However, blood pressure, heart rate, TPR, PRA, and ADH levels were lower in OZ than in LZ.

SIGNIFICANCE

These results indicate that conscious OZ has impaired blood pressure compensation after hemorrhage due to a blunted increase in TPR. This is due at least in part to an impaired regulation of vasoconstrictor hormones. To our knowledge, the current study is the first to demonstrate that hemodynamic responses and associated hormone secretion are impaired in a conscious obese model.

Long-term antihypertensive effects of aliskiren, a direct renin inhibitor, in chronic hemodialysis patients

The renin-angiotensin-aldosterone system is not necessarily suppressed in end-stage renal disease patients undergoing dialysis. Of all the inhibitors of this system, the clinical efficacy of the renin inhibitor, aliskiren, has not been well demonstrated in dialysis patients. We evaluated the antihypertensive effect of aliskiren, administered as a single daily dose of 150 mg for 24 weeks, in 23 chronic hemodialysis patients (age 65 ± 12 years, 15 men and eight women) with blood pressure ≥140/90 mm Hg, and assessed the factors relating to blood pressure reduction. At 4 weeks, the average systolic blood pressure before the dialysis session was insignificantly reduced from 163 ± 10 mm Hg to 160 ± 15 mm Hg, while it was significantly lowered at 12 (154 ± 13 mm Hg) and 24 weeks (155 ± 10 mm Hg), although the pulse rate was not significantly altered. Serum K increased at 24 weeks from 4.9 ± 0.6 mEq/L to 5.2 ± 0.8 mEq/L. Only 10 out of 23 patients showed systolic blood pressure reduction by ≥10 mm Hg. Naturally, plasma renin immunoreactivity increased, while plasma renin activity, along with angiotensin II and aldosterone levels decreased. Basal levels of the components of the renin-angiotensin-aldosterone system were not significantly different in patients showing systolic blood pressure reduction by ≥10 mm Hg (n = 10) vs. those with <10 mm Hg changes (n = 13). The reduction in systolic blood pressure in all 23 patients taken as a whole correlated with changes in plasma renin activity (r = -0.432, P < 0.05) and angiotensin II (r = 0.467, P < 0.05). In chronic hemodialysis patients, aliskiren modestly lowers blood pressure over the long term, although the antihypertensive effect seems dependent on the changes, but not on the basal levels of plasma renin activity and angiotensin II.

Severe hypertension and encephalopathy due to Renin-producing hepatoblastoma

Paraneoplastic syndromes result from secretion of hormones, peptides or cytokines by tumor or immune cross-reactivity between malignant and normal tissues. These conditions are rare in children, but when the clinical presentation of patients with a tumor is unusual, these syndromes should be emphasized. Extrarenal tumors with renin-secretion are rare in children. They may be related to paraneoplastic syndromes. We report a 22-month-old infant with hepatoblastoma presented with severe hypertension and related neurologic symptoms due to high plasma renin activity. To the best of our knowledge, this is the second report of renin producing hepatoblastoma in the literature. However, due to lack of laboratory facilities such as immunohistochemical study or polyclonal antibody for human renin activity, we could not prove the secretion of renin just by tumor tissue cells, but this potentiality is very likely. Other intensive investigations did not show any other origin for rennin secretion or hypertension in this patient.

Multiple roles of angiotensin in colorectal cancer

Colorectal cancer (CRC) cells express renin and chymase through which they can activate angiotensin. Renin expression is induced by hyperglycemic conditions. As angiotensinogen is produced in the liver, CRC cells that can activate angiotensin have an enhanced ability to metastasize to this organ. In human CRC cases, patients with diabetes have higher activities of rennin and angiotensin-II in primary tumors, and on average, have a more progressed disease stage, especially with respect to liver metastasis. These patients exhibit a stronger association with Hemoglobin A1c levels and metastasis compared to patients without diabetes. In a combined diabetes/CRC liver metastasis mouse model, concurrent treatment with anti-angiotensin and hypoglycemic agents shows a synergic effect in terms of reduced liver metastasis and improved survival. The effect of anti-angiotensin treatment and blood sugar control as a baseline management for colon cancer patients with diabetes needs to be examined in clinical trials to establish whether it can prevent liver metastasis.

Discovery of VTP-27999, an Alkyl Amine Renin Inhibitor with Potential for Clinical Utility

Structure guided optimization of a series of nonpeptidic alkyl amine renin inhibitors allowed the rational incorporation of additional polar functionality. Replacement of the cyclohexylmethyl group occupying the S1 pocket with a (R)-(tetrahydropyran-3-yl)methyl group and utilization of a different attachment point led to the identification of clinical candidate 9. This compound demonstrated excellent selectivity over related and unrelated off-targets, >15% oral bioavailability in three species, oral efficacy in a double transgenic rat model of hypertension, and good exposure in humans.

Renin and cardiovascular disease: Worn-out path, or new direction

Inhibition of the renin angiotensin system has beneficial effects in cardiovascular prevention and treatment. The advent of orally active direct renin inhibitors adds a novel approach to antagonism of the renin-angiotensin system. Inhibition of the first and rate-limiting step of the renin angiotensin cascade offers theoretical advantages over downstream blockade. However, the recent discovery of the (pro)renin receptor which binds both renin and prorenin, and which can not only augment catalytic activity of both renin and prorenin in converting angiotensinogen to angiotensin I, but also signal intracellularly via various pathways to modulate gene expression, adds a significant level of complexity to the field. In this review, we will examine the basic and clinical data on renin and its inhibition in the context of cardiovascular pathophysiology.

Comparison of the effect of midodrine versus octreotide on hemodynamic status in cirrhotic patients with ascites

BACKGROUND

In cirrhotic patients peripheral vasodilatation may decrease renal blood flow and subsequently raises plasma renin activity. Octreotide with several mechanisms causes peripheral arterial vasoconstriction. Midodrine is an alpha agonist and acts as a peripheral vasoconstrictor; therefore it may reduce plasma renin activity and improve renal function. In this study the effects of these two agents were compared on cirrhotic patients to determine their ability to reduce plasma renin activity and increase GFR.

METHODS

This study was a randomized clinical trial and was performed in Al-Zahra hospital in 2008-2009; 34 patients with CHILD C cirrhosis enrolled in this study. They were randomly divided into two groups. First group were treated by 3 days of subcutaneous octreotide 50 μg tid (n = 17). For the second group oral midodrine 7.5 mg tid was administrated for 3 days. Plasma renin activity, blood pressure, glomerular filtration rate, and body weight were measured and compared before and after therapy in both groups.

RESULTS

In both groups, plasma rennin activity decreased significantly after treatment. The present study showed that both midodrine and octreotide can reduce plasma renin activity but midodrine can reduce PRA and increase GFR more potently than octreotide.

CONCLUSIONS

Midodrine has a favorable hemodynamic effect in nonazotemic cirrhotic patients by decreasing plasma renin activity and increasing GFR.

Is hyperaldosteronism a pathognomonic feature of conn's syndrome?

A 10-year-old female child presented with resistant hypertension and hypokalaemia. There was no muscle weakness or periodic paralysis. The ratio of plasma aldosterone concentration to plasma renin activity was increased. MRI of the abdomen showed the right adrenal mass. The child underwent open right adrenalectomy. she had natriuresis in the postoperative period. She was normotensive without antihypertensive drugs at discharge and 2 months after surgery.

Hypertension caused by renal arteriovenous fistula

We describe a case of secondary hypertension caused by renal arteriovenous fistula. An 8-year old girl was hospitalized with a severe headache, vomiting, and seizure. Renal angiography demonstrated multiple renal arteriovenous fistula and increased blood renin concentration in the left renal vein. Thus, left renal arteriovenous fistula and renin induced secondary hypertension were diagnosed. Her blood pressure was well controlled by medication with angiotensin converting enzyme inhibitor.