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This study investigated the effects of nobiletin on cardiorenal changes and the underlying mechanisms involved in two-kidney, one-clip (2K-1C) hypertension. 2K-1C rats were treated with nobiletin (15 or 30 mg/kg/day) or losartan (10 mg/kg/day) for 4 weeks (n = 8/group). Nobiletin (30 mg/kg) reduced high levels of blood pressure and circulating angiotensin II and angiotensin-converting enzyme activity in 2K-1C rats. Left ventricular (LV) dysfunction and remodelling in 2K-1C rats were alleviated in the nobiletin-treated group (P < 0.05). Nobiletin reduced the upregulation of Ang II type I receptor (AT1R)/JAK (Janus kinase)/STAT (signal transducer and activator of transcription) protein expression in cardiac tissue of 2K-1C rats (P < 0.05). The reduction in kidney function, and accumulation of renal fibrosis in 2K-1C rats were alleviated by nobiletin (P < 0.05). Overexpression of AT1R and NADPH oxidase 4 (Nox4) protein in nonclipped kidney tissue was suppressed in the nobiletin-treated group (P < 0.05). The elevations in oxidative stress parameters and the reductions in antioxidant enzymes were attenuated in 2K-1C rats treated with nobiletin (P < 0.05). In summary, nobiletin had renin-angiotensin system inhibitory and antioxidant effects and attenuated LV dysfunction and remodelling via restoration of the AT1R/JAK/STAT pathway. Nobiletin also resolved renal damage that was related to modulation of the AT1R/Nox4 cascade in 2K-1C hypertension. [ABSTRACT FROM AUTHOR]

In malignant hypertension, far more severe kidney injury occurs than in the "benign" form of the disease. The role of high blood pressure and the renin–angiotensin–aldosterone system is well recognized, but the pathogenesis of the renal injury of malignant hypertension (MH) remains incompletely understood. Using the rat model of two-kidney, one-clip renovascular hypertension in which some but not all animals develop MH, we performed a transcriptomic analysis of gene expression by RNA sequencing to identify transcriptional changes in the kidney cortex specific for MH. Differential gene expression was assessed in three groups: MH, non-malignant hypertension (NMH), and normotensive, sham-operated controls. To distinguish MH from NMH, we considered two factors: weight loss and typical renovascular lesions. Mean blood pressure measured intraarterially was elevated in MH (220 ± 6.5 mmHg) as well as in NMH (192 ± 6.4 mmHg), compared to controls (119 ± 1.7 mmHg, p < 0.05). Eight hundred eighty-six genes were exclusively regulated in MH only. Principal component analysis revealed a separated clustering of the three groups. The data pointed to an upregulation of many inflammatory mechanisms in MH including pathways which previously attracted relatively little attention in the setting of hypertensive kidney injury: Transcripts from all three complement activation pathways were upregulated in MH compared to NMH but not in NMH compared with controls; immunohistochemistry confirmed complement deposition in MH exclusively. The expression of chemokines attracting neutrophil granulocytes (CXCL6) and infiltration of myeloperoxidase-positive cells were increased only in MH rats. The data suggest that these pathways, especially complement deposition, may contribute to kidney injury under MH. Key messages: The most severe hypertension-induced kidney injury occurs in malignant hypertension. In a rat model of malignant hypertension, we assessed transcriptional responses in the kidney exposed to high blood pressure. A broad stimulation of inflammatory mechanisms was observed, but a few specific pathways were activated only in the malignant form of the disease, notably activation of the complement cascades. Complement inhibitors may alleviate the thrombotic microangiopathy of malignant hypertension even in the absence of primary complement abnormalities. [ABSTRACT FROM AUTHOR]

Obstructive sleep apnea (OSA) is characterized by recurrent episodes of partial (hypopnea) or complete interruption (apnea) in breathing during sleep due to airway collapse in the pharyngeal region. OSA and its cardiovascular consequences have been widely explored in observational and prospective studies. Most evidence verifies the positive relationship between OSA and hypertension, coronary artery disease, atrial fibrillation, stroke and heart failure. However, more studies are needed to better assess the impact of OSA, and possible benefit of treatment with continuous positive airway pressure (CPAP) on dyslipidemia, type 2 diabetes, insulin resistance and cardiovascular mortality. The leading pathophysiological mechanisms involved in the changes triggered by OSA, include intermittent hypoxemia and re-oxygenation, arousals and changes in intrathoracic pressure. Hypertension is strongly related with activation of the sympathetic nervous system, stimulation of the renin-angiotensin-aldosterone system and impairment of endothelial function. The high prevalence of OSA in the general population, hypertensive patients and especially obese individuals and patients resistant to antihypertensive therapy, highlights the need for effective screening, diagnosis and treatment of OSA to decrease cardiovascular risk. [ABSTRACT FROM AUTHOR]

We investigated the relationship between pulse pressure (PP)-a surrogate marker of arterial stiffness-and activity of the renin-angiotensin-aldosterone system (RAAS) in adult patients with repaired coarctation and normal left ventricular (LV) function. A total of 114 patients (44 (26-74) years, 13 (0.1-40) years at repair) and 20 healthy controls were examined with 24-h ambulatory blood pressure monitoring, echocardiography, vasoactive hormone levels and magnetic resonance of the thoracic aorta. Forty-one patients (36%) were taking antihypertensives (28 RAAS inhibitors). Fifty-one had mean 24-h blood pressures >130/80 mm Hg. Hypertension was not associated with age at repair (P=0.257). Patients had higher PP and LV mass compared with controls (52±11 vs 45±5 mm Hg and 221±71 vs 154±55 g, respectively; both P<0.05). Differences were more pronounced in the presence of recoarctation, but independently of RAA levels. Even normotensive patients had higher LV mass than controls. LV mass and recoarctation were correlated with PP levels. In conclusion, adult patients with repaired coarctation have increased PP and LV mass compared with controls. PP increased with increasing recoarctation. Hypertension was present also in the absence of recoarctation. These changes could not be explained by abnormal activation of the RAAS. [ABSTRACT FROM AUTHOR]

Obesity-related hypertension is associated with increased activity of the renin-angiotensin-aldosterone system (RAAS), increasing arterial stiffness. Aerobic exercise decreases pulse wave velocity (PWV), therefore a treatment option for hypertension and obesity. Assess RAAS activity and PWV before and after 4 weeks of aerobic training in unmedicated, pre-to-stage-1 hypertensives. Ten obese subjects (52±3.2 years, body mass index=33.5±1.4) performed 30 min of aerobic exercise on a treadmill 3 days per week at 65% of peak oxygen consumption (VO2peak). Descriptive characteristics, systolic and diastolic blood pressure (SBP and DBP), PWV, and a blood draw was performed at baseline, following the 4-week control and training interventions. No differences in descriptive characteristics during the control period were observed, however, a significant decrease in plasma aldosterone (ALDO) (255.4±75 to 215.8±66 pg ml−1, P=0.001), SBP (140±12 to 136±10.4 mm Hg; P=0.02), DBP (89±4.2 to 85±6.3 mm Hg; P=0.03) and central PWV (11.2±0.6 to 9.8±0.8 m s−1; P=0.04) was shown pre-to-post exercise training. Four weeks of moderate-intensity aerobic training in obese, hypertensives decreases plasma ALDO independently of body weight and is significantly correlated to decreases in PWV reductions. [ABSTRACT FROM AUTHOR]

Kidney damage represents a frequent event in the course of hypertension, ranging from a benign to a malignant form of nephropathy depending on several factors, that is, individual susceptibility, degree of hypertension, type of etiology and underlying kidney disease. Multiple mechanisms are involved in determination of kidney glomerular, tubular and interstitial injuries in hypertension. The present review article discusses relevant contributory molecular mechanisms underpinning the promotion of hypertensive renal damage, such as the renin-angiotensin-aldosterone system (RAAS), oxidative stress, endothelial dysfunction, and genetic and epigenetic determinants. We highlighted major pathways involved in the progression of inflammation and fibrosis leading to glomerular sclerosis, tubular atrophy and interstitial fibrosis, thus providing a state of the art review of the pathogenetic background useful for a better understanding of current and future therapeutic strategies toward hypertensive nephropathy. An adequate control of high blood pressure, obtained through an appropriate therapeutic intervention, still represents the key strategy to achieve a satisfactory control of renal damage in hypertension. In this regard, we reviewed the impact of currently available antihypertensive pharmacological treatment on kidney damage, with particular regard to RAAS inhibitors. Notably, recent findings underscored the ability of the kidneys to regenerate and to repair tissue injuries through the differentiation of resident embryonic stem cells. Pharmacological modulation of the renal endogenous reparative process (that is, with angiotensin-converting enzyme inhibitors and AT1 angiotensin II receptor blockers), as well as future therapeutic strategies targeted to the renopoietic system, offers interesting perspectives for the management of hypertensive nephropathy. [ABSTRACT FROM AUTHOR]

Hypertension secondary to hydronephrosis is not commonly reported in the medical literature. Tubuloglomerular feedback and the renin-angiotensin-aldosterone axis are thought to mediate this process. We describe a patient presenting with acute kidney injury and bilateral hydronephrosis secondary to pelvic malignancy in which peripheral venous renin and aldosterone were elevated. Her blood pressure improved rapidly following insertion of bilateral nephrostomies. The speed of resolution of hypertension following relief of obstruction suggests that humorally mediated vasoconstriction can play an important role in the mechanism by which hydronephrosis causes hypertension. We also discuss other causes of renal parenchymal compression that may lead to the development of hypertension. [ABSTRACT FROM AUTHOR]

The renin-angiotensin-aldosterone system (RAAS) is not the sole, but perhaps the most important volume regulator in vertebrates. To gain insights into the function and evolution of its components, we conducted a phylogenetic analysis of its main related genes. We found that important parts of the system began to appear with primitive chordates and tunicates and that all major components were present at the divergence of bony fish, with the exception of the Mas receptor. The Mas receptor first appears after the bony-fish/tetrapod divergence. This phase of evolutionary innovation happened about 400 million years ago. We found solid evidence that angiotensinogen made its appearance in cartilage fish. The presence of several RAAS genes in organisms that lack all the components shows that these genes have had other ancestral functions outside of their current role. Our analysis underscores the utility of sequence comparisons in the study of evolution. Such analyses may provide new hypotheses as to how and why in today's population an increased activity of the RAAS frequently leads to faulty salt and volume regulation, hypertension, and cardiovascular diseases, opening up new and clinically important research areas for evolutionary medicine. [ABSTRACT FROM AUTHOR]

Obesity and vitamin D deficiency have both been linked to augmented activity of the tissue renin-angiotensin system (RAS). We investigated whether obesity status influenced the relationship between 25-hydroxyvitamin D (25(OH)D) and vascular RAS activity. The levels of 25(OH)D were measured in hypertensive obese (n=39) and non-obese (n=58) Caucasian individuals. RAS activity was assessed by plasma renin activity, and evaluation of the vascular sensitivity to angiotensin II (AngII) using the mean arterial pressure (MAP) response to an infusion of AngII. Among obese subjects, 25(OH)D was an independent positive predictor of the MAP response to AngII (β=0.70, r=0.41, P<0.01); lower 25(OH)D concentrations were associated with a blunted MAP response to AngII. In contrast, 25(OH)D did not significantly predict the vascular sensitivity to AngII in non-obese subjects (β=0.10, r=0.07, P=0.62). A multivariable-adjusted interaction model confirmed that the positive relationship between 25(OH)D and the vascular sensitivity to AngII strengthened with obesity (P-interaction=0.03). These findings demonstrate a positive association between 25(OH)D and the vascular sensitivity to AngII in obese hypertensives, and further suggest that vascular RAS activity may progressively increase when 25(OH)D deficiency occurs in obesity. Future studies to evaluate the effect of vitamin D supplementation on vascular RAS activity in obesity are needed. [ABSTRACT FROM AUTHOR]

Metabolic syndrome, a cluster of risk factors that increase the risk of cardiovascular morbidity and mortality, is common in patients with hypertension. Chronic renin-angiotensin-aldosterone system (RAAS) activation, shown by elevated plasma renin activity (PRA), is implicated in many of the features of metabolic syndrome. The direct renin inhibitor aliskiren may be of benefit in this patient group as aliskiren targets the RAAS at the rate-limiting step. In this double-blind study, 141 patients with hypertension (mean baseline BP 155/93 mm Hg) and metabolic syndrome (modified National Cholesterol Education Program ATP III criteria) were randomized to aliskiren 300 mg or irbesartan 300 mg once daily. Patients treated with aliskiren 300 mg had their mean sitting blood pressure (BP) lowered by 13.8/7.1 mm Hg after 12 weeks, significantly greater (P0.001) than the 5.8/2.8 mm Hg reduction observed in patients treated with irbesartan 300 mg. A significantly greater proportion of patients treated with aliskiren achieved BP control to <135/85 mm Hg (29.2 vs 16.7% with irbesartan; P=0.019). Aliskiren treatment led to a 60% decrease in PRA from baseline, whereas irbesartan increased PRA by 99% (both P<0.001). Aliskiren and irbesartan had similar effects on glucose and lipid profiles and on a panel of biomarkers of inflammation and cardiovascular risk. Both aliskiren and irbesartan were well tolerated. Collectively, these results suggest that aliskiren 300 mg may offer treatment benefits compared with irbesartan 300 mg for BP reduction in patients with hypertension and metabolic syndrome. [ABSTRACT FROM AUTHOR]

A retrospective analysis of the database from A Coronary Disease Trial Investigating Outcome with Nifedipine (ACTION) evaluated the effectiveness of nifedipine gastrointestinal therapeutic system (GITS) (i) in combination with renin angiotensin system (RAS) blockers and (ii) in patients with isolated systolic hypertension (ISH). Analysed on an intention-to-treat basis, treatment groups were compared by the log-rank test without adjustment for covariates and hazard ratios with 95% CIs were obtained using Cox proportional hazards models. Of 7665 randomized patients, 1732 patients were receiving RAS blockade at baseline, the addition of nifedipine GITS significantly reduced any cardiovascular (CV) event (−20%; P<0.05), the composite of death, any CV event and revascularization (−16%; P<0.05) and coronary angiography (−22%; P<0.01). These benefits were achieved with relatively small differences in systolic (3.2 mm Hg) and diastolic blood pressure (BP) (2.3 mm Hg). In 2303 patients (30.0%) who had ISH at baseline (1145 nifedipine GITS and 1158 placebo), nifedipine significantly reduced the primary efficacy end point (−18%; P<0.03), any CV event (−22%; P<0.01) and new heart failure (−40%; P<0.01). The benefits were associated with between-group differences in achieved BP of 4.7 and 3.3 mm Hg for systolic and diastolic BP, respectively. In summary, the lowest CV event rates were seen in those receiving (i) the combination of RAS blockade and nifedipine GITS and (ii) in those specifically treated for ISH. [ABSTRACT FROM AUTHOR]

This longitudinal study examined the relationship between 2-year change in white matter hyperintense lesion (WML) volume and polymorphisms in genes coding for the angiotensin-II type 1 and type 2 receptors, AGTR1 A1166C and AGTR2 C3123A, respectively. 137 depressed and 94 non-depressed participants aged 60 years were enrolled. Standard clinical evaluations were performed on all participants and blood samples obtained for genotyping. 1.5-T MRI (magnetic resonance imaging) data were obtained at baseline and approximately 2 years later. These scans were processed using a semi-automated segmentation process, which allowed for the calculation of WML volume at each time point. Statistical models were tested for the relationship between change in WML volume and genotype, while also controlling for age, sex, diagnostic strata, baseline WML volume and comorbid cerebrovascular risk factors. In men, AGTR1 1166A allele homozygotes exhibited significantly less change in WML volume than 1166C carriers. We also found that men reporting hypertension (HTN) with the AGTR2 3123C allele exhibit less change in WML volume than hypertensive men with the 3123A allele, or men without HTN. There were no significant relationships between these polymorphisms and change in WML volume in women. No significant gene–gene or gene–depression interactions were observed. Our results parallel earlier observed gender differences of the relationship between other renin–angiotensin system polymorphisms and HTN. Further work is needed to determine whether these observed relationships are secondary to polymorphisms affecting response to antihypertensive medication, and whether antihypertensive medications can slow WML progression and lower the risk of morbidity associated with WMLs. [ABSTRACT FROM AUTHOR]

The article reports that monotherapy with renin-angiotensin system blocker may not be suitable for patients with low-renin hypertension. It states that pretreatment plasma renin activity levels with ambulatory blood pressure responses to angiotension receptor blockers in essential hypertension. It adds that the effectiveness of antihypertensive medications is based from the blood pressure-lowering effect rather than the characteristic actions of hypertensive drugs.

It remains to be determined whether the evidence in Western countries for blockade of the renin–angiotensin System in cardiovascular diseases could be directly applied to East Asian races including the Japanese population as a long-term strategy. The KYOTO HEART Study (KHS) is designed to investigate the add-on effect of valsartan versus conventional anti-hypertensive treatment on cardiovascular morbidity and mortality in Japanese hypertensive patients with uncontrolled blood pressure and with high cardiovascular risk. Over 3000 high-risk Japanese patients with uncontrolled hypertension were randomised to receive either additional treatment with valsartan or conventional non-angiotensin receptor blocker therapies, and the follow-up period will be at least 3 years. The primary end point is a composite of defined cardio- or cerebro-vascular events. Secondary end points include all causes of mortality, worsening of cardiac function, new onset or worsening of arrhythmias or diabetes mellitus. The KHS will provide new evidence for the management of blood pressure in hypertensive patients with high risk.Journal of Human Hypertension (2009) 23, 188–195; doi:10.1038/jhh.2008.116; published online 18 September 2008 [ABSTRACT FROM AUTHOR]

Renin–angiotensin (RAS) genes, a group of promising candidate genes involved in essential hypertension (EH), play a key role in blood pressure regulation. Recently, a series of novel RAS gene polymorphisms were reported, which significantly influence the rate of the gene transcription. This study was designed to explore the association between the RAS gene polymorphisms and EH in a remote countryside population. We examined six polymorphisms in the main component genes of RAS: angiotensin-converting enzyme (ACE) (I/D), angiotensinogen (AGT) (A-6G, A-20C, G-217A and T174 M) and angiotensin type 1 receptor (AT1R) (A1166C). Six polymorphisms were genotyped by gene chip technology. Association studies were performed in 220 EH patients and 235 normotensives. Our results revealed that AGT A-6G, T174 M and ACE-I/D were significantly associated with EH (AGT A-6G: AG+GG vs AA; OR=1.36; 95% CI=1.04–1.77. T174M: CT+TT vs CC; OR=1.45; 95% CI=1.15–1.90. ACE I/D: ID+DD vs II; OR=1.171; 95% CI=1.00–1.37). Moreover the logistic regression analysis suggested that the haplotype of AGT −6A, 174C, −217G and −20A might decrease the risk of EH (OR=0.64; 95% CI=0.49–0.83), after adjusting the confounding factors of gender, age and BMI. In conclusion, the AGT A-6G, T174 M and ACE I/D polymorphisms are associated with EH and the AGT haplotype −6A, 174C, −217G and −20A decrease the risk of EH in the southern Chinese population.Journal of Human Hypertension (2009) 23, 176–181; doi:10.1038/jhh.2008.123; published online 2 October 2008 [ABSTRACT FROM AUTHOR]

The aim of this study was to assess whether the association between angiotensin-converting enzyme (ACE) inhibitor use and the incidence of treated diabetes mellitus is modified by genetic polymorphisms in the renin-angiotensin system (RAS).In a nested case–control study, treated hypertensive patients were genotyped for ACE (insertion (I)/deletion (D)), angiotensinogen (AGT; M235T) and angiotensin II type 1 receptor (AGTR1; A1166C). Cases of newly treated diabetes were identified based on pharmacy records and controls were not yet drug treated for diabetes (case:control ratio 1:10). Self-administered questionnaires and physical examinations were used to assess risk factors for diabetes mellitus. Logistic regression was used to calculate the relative risk of diabetes associated with ACE inhibitor use relative to other antihypertensive treatment, stratified by the RAS genotypes. Among 205 cases and 2050 controls, homozygous 1166A carriers of the AGTR1 gene had a significantly decreased incidence of diabetes associated with current use of ACE inhibitors (odds ratio, OR: 0.47; 95% CI: 0.26–0.84), whereas this incidence was increased among 1166C allele carriers (OR: 1.32; 95% CI: 0.81–2.14). The interaction OR was 3.21 (95% CI: 1.53–6.75). ACE I allele carriers had a significantly reduced incidence of diabetes associated with ACE inhibitors use (OR: 0.63; 95% CI: 0.41–0.98), whereas DD homozygotes had no reduced risk (OR: 0.95; 95% CI: 0.46–1.96). The risk of diabetes associated with ACE inhibitor use was not significantly modified by the AGT-M235T polymorphism. Treatment with ACE inhibitors in hypertensive subjects significantly reduces the occurrence of diabetes in homozygous 1166A carriers of the AGTR1 gene and carriers of the ACE I allele, but not in 1166C allele carriers of the AGTR1 gene and in homozygous ACE D allele carriers.Journal of Human Hypertension (2008) 22, 774–780; doi:10.1038/jhh.2008.62; published online 19 June 2008 [ABSTRACT FROM AUTHOR]

The inhibition of the renin–angiotensin system is one of the most commonly utilized ways to lower blood pressure in patients with arterial hypertension. Up till now, angiotensin-converting enzyme inhibitors as well as angiotensin receptor blockers are the established inhibitors of this system, and both classes are used in clinical routine. There is a wealth of information about those classes, which are known not only to lower blood pressure, but also to prevent end-organ damage and, ultimately, reduce mortality in patients. Direct renin inhibition was already targeted 30 years ago to inhibit the renin–angiotensin system, but low bioavailability and short duration of action of the first generations of renin inhibitors withheld their clinical success. With the new generation of non-peptide orally available renin inhibitors, a third substance to inhibit the renin–angiotensin system is on the market, and the prototype of this class, aliskiren, has now been tested in various clinical trials in arterial hypertension. We review the studies of aliskiren and discuss its current role in the contemporary treatment of arterial hypertension as well as the possible new fields of action for aliskiren in treating heart failure and diabetic nephropathy. [ABSTRACT FROM AUTHOR]

Pre-eclampsia is a common, pregnancy-induced disorder, consisting of hypertension and proteinuria. The condition is one of the leading causes for maternal and perinatal morbidity and mortality. Nonetheless, the underlying molecular mechanisms remain unclear. Immunological mechanisms and the renin–angiotensin system have been implicated in the development of pre-eclampsia. Agonistic autoantibodies to the angiotensin II type I receptor (AT1-AA) have been identified in pre-eclamptic patients, unifying the two hypothesis. Evidence has also accumulated for the existence and importance of a local, utroplacental renin–angiotensin system. We summarize recent data emphasizing the pathophysiological role for the autoantibodies and the uteroplacental renin–angiotensin system. [ABSTRACT FROM AUTHOR]

Hypertension is one of the major health care problems worldwide since it markedly increases the risk for development of heart disease, stroke, generalized vascular disease, and renal failure. The renin–angiotensin system (RAS) with its major end-product angiotensin II (Ang II) plays a fundamental role in blood pressure regulation through direct and indirect mechanisms. Pharmacologically, we can inhibit the RAS using angiotensin-converting enzyme inhibitors and AT1 receptor blocker. Inhibiting renin directly with a clinically useful drug eluded pharmacologists until recently. However, the once-daily, orally effective, small-molecule, direct renin inhibitor aliskiren has recently changed this state of affairs. Aliskiren, with its 40-h half-life and ideal pharmacokinetics, can now address angiotensin production directly at its rate-limiting step. A novel transgenic rat model outfitted with the human renin and angiotensinogen genes allowed the testing of aliskiren in an animal model. Preclinical data demonstrated that aliskiren prolonged survival, decreased cardiac hypertrophy and the inducibility of arrhythmias, proteinuria, and attenuated inflammation. All these features might result in improved target-organ damage. Studies in humans attest to an effective blood pressure-lowering action, a largely side effect-free profile, and the option of several combination therapies. Aliskiren is the first of a novel antihypertensive drug class. The preclinical data is very promising. Nevertheless, for the evaluation of its potency in humans, we have to wait for more clinical data. [ABSTRACT FROM AUTHOR]

Antihypertensive drugs based on the blockade of the renin–angiotensin system (RAS) target classical components of this system, i.e., angiotensin-converting enzyme (ACE) and angiotensin (Ang) II type 1 receptor. These antihypertensives are well-recognized and successful, if prescribed properly, in reducing high blood pressure, but much less effective in preventing and reverting end-organ damage induced by cardiovascular disease (CVD) and hypertension. Thus, new strategies and new drug targets that are more effective must be discovered. Recent identification of a counterregulatory axis of the RAS [ACE2, Ang-(1–7), and Mas receptor] that is potentially important in promoting vasoprotective effects offers a novel target for CVD therapeutics. In this brief review, we will highlight the functional characteristics of this axis with special emphasis on ACE2 and its possible involvement in the pathophysiology of the CVD. In addition, we will present our views on the potential of ACE2 as a new target for the development of innovative antihypertensives by highlighting the development and functional findings obtained with small molecules ACE2 activators. [ABSTRACT FROM AUTHOR]

The genes coding for the renin angiotensin system have been extensively studied. During the last 15 years, informative markers and functional polymorphisms have been identified, and numerous linkage and association studies have been performed in cardiovascular diseases, especially human hypertension. This mini-review aims to summarize the main findings observed for each component of this enzymatic cascade taken alone or in combination, with an emphasis on the most recent or innovative studies. [ABSTRACT FROM AUTHOR]

Two (pro)renin receptors have been characterized so far, the mannose-6-phosphate receptor (M6P-R) and a specific receptor called (P)RR for ( pro) renin receptor. Each receptor controls a different aspect of renin and prorenin metabolism. The M6P-R is a clearance receptor, whereas (P)RR mediates their cellular effects by activating intracellular signaling and up-regulating gene expression. Moreover, binding to (P)RR increases renin enzymatic activity and fully activates prorenin, the inactive proenzyme form of renin. Experimental models suggest that increased (P)RR synthesis and/or activation may be relevant to diseases, especially to high blood pressure, to cardiac fibrosis associated with hypertension, and to diabetic nephropathy. [ABSTRACT FROM AUTHOR]

Accumulation of a large body of evidence during the past two decades testifies to the complexity of the renin–angiotensin system (RAS). The incorporation of novel enzymatic pathways, resulting peptides, and their corresponding receptors into the biochemical cascade of the RAS provides a better understanding of its role in the regulation of cardiovascular and renal function. Hence, in recent years, it became apparent that the balance between the two opposing effector peptides, angiotensin II and angiotensin-(1-7), may have a pivotal role in determining different cardiovascular pathophysiologies. Furthermore, our recent studies provide evidence for the functional relevance of a newly discovered rat peptide, containing two additional amino acid residues compared to angiotensin I, first defined as proangiotensin-12 [angiotensin-(1-12)]. This review focuses on angiotensin-(1-7) and its important contribution to cardiovascular function and growth, while introducing angiotensin-(1-12) as a potential novel angiotensin precursor. [ABSTRACT FROM AUTHOR]

Angiotensin II (Ang II) is considered the main final mediator of the renin–angiotensin–aldosterone system (RAAS). The actions of Ang II have been implicated in many cardiovascular conditions, such as hypertension, atherosclerosis, coronary heart disease, restenosis after injury, and heart failure. The Ang II type 1 receptor (AT1R), a G-protein-coupled receptor, mediates most of the physiological and pathophysiological actions of Ang II. This receptor is predominantly expressed in cardiovascular cells, such as vascular smooth muscle cells where it activates various signaling cascades leading to vascular remodeling and inflammation. Besides Ang II, aldosterone has emerged as an important component and mediator of the effects of the RAAS. Aldosterone-induced genomic effects mediated through binding to the mineralocorticoid receptor (MR), a member of the steroid hormone receptor superfamily, which functions as a ligand-dependent transcription factor, are characterized by a delay of minutes to hours corresponding to a long series of subcellular events that include gene activation and protein synthesis. Besides its well-known genomic actions, there is evidence of aldosterone-mediated rapid effects which lead to the activation of ion channels and other signaling pathways. Some of the effects of aldosterone occur through similar pathways as Ang II-induced signaling events. Indeed, recent studies suggest complex interactions between Ang II and aldosterone: it has become evident that aldosterone may influence the signaling or trafficking of the AT1R. Thus, growing evidence demonstrates the existence of cross-talk between Ang II and aldosterone which could potentially modulate Ang II signal transduction. These interactions between Ang II and aldosterone activate specific signaling pathways, sometimes in ways distinct from those that they induce on their own, one which may lead to pathogenic effects on target organs. Here we focus on recent findings and concepts that suggest the existence of novel signaling mechanisms whereby the cross-talk between Ang II and aldosterone plays a role in cardiovascular disease. We also discuss the importance of investigating Ang II/aldosterone cross-talk as a mean of developing new therapeutic strategies to combat cardiovascular disease. [ABSTRACT FROM AUTHOR]

A brain renin angiotensin system (RAS) and its role in cardiovascular control and fluid homeostasis was at first controversial. This was because a circulating kidney-derived renin angiotensin system was so similar and well established. But, the pursuit of brain RAS has proven to be correct. In the course of accepting brain RAS, high standards of proof attracted state of the art techniques in all the new developments of biolo1gy. Consequently, brain RAS is a robust concept that has enlightened neuroscience as well as cardiovascular physiology and is a model neuropeptide system. Molecular biology confirmed the components of brain RAS and their location in the brain. Transgenic mice and rats bearing renin and extra copies of angiotensinogen genes revealed the importance of brain RAS. Cre-lox delivery in vectors has enabled pinpoint gene deletion of brain RAS in discrete brain nuclei. The new concept of brain RAS includes ACE-2, Ang1–7, and prorenin and Mas receptors. Angiotensin II (ANG II) generated in the brain by brain renin has many neural effects. It activates behavioral effects by selective activation of ANG II receptor subtypes in different locations. It regulates sympathetic activity and baroreflexes and contributes to neurogenic hypertension. New findings implicate brain RAS in a much wider range of neural effects. We review brain RAS involvement in Alzheimer’s disease, stroke memory, and learning alcoholism stress depression. There is growing evidence to consider developing treatment strategies for a variety of neurological disease states based on brain RAS. [ABSTRACT FROM AUTHOR]

Patients with severe hypertension (>180/110 mm Hg) require large blood pressure (BP) reductions to reach recommended treatment goals (<140/90 mm Hg) and usually require combination therapy to do so. This 8-week, multicenter, randomized, double-blind, parallel-group study compared the tolerability and antihypertensive efficacy of the novel direct renin inhibitor aliskiren with the angiotensin converting enzyme inhibitor lisinopril in patients with severe hypertension (mean sitting diastolic blood pressure (msDBP)105 mm Hg and <120 mm Hg). In all, 183 patients were randomized (2:1) to aliskiren 150 mg (n=125) or lisinopril 20 mg (n=58) with dose titration (to aliskiren 300 mg or lisinopril 40 mg) and subsequent addition of hydrochlorothiazide (HCTZ) if additional BP control was required. Aliskiren-based treatment (ALI) was similar to lisinopril-based treatment (LIS) with respect to the proportion of patients reporting an adverse event (AE; ALI 32.8%; LIS 29.3%) or discontinuing treatment due to AEs (ALI 3.2%; LIS 3.4%). The most frequently reported AEs in both groups were headache, nasopharyngitis and dizziness. At end point, ALI showed similar mean reductions from baseline to LIS in msDBP (ALI −18.5 mm Hg vs LIS −20.1 mm Hg; mean treatment difference 1.7 mm Hg (95% confidence interval (CI) −1.0, 4.4)) and mean sitting systolic blood pressure (ALI −20.0 mm Hg vs LIS −22.3 mm Hg; mean treatment difference 2.8 mm Hg (95% CI −1.7, 7.4)). Responder rates (msDBP<90 mm Hg and/or reduction from baseline10 mm Hg) were 81.5% with ALI and 87.9% with LIS. Approximately half of patients required the addition of HCTZ to achieve BP control (ALI 53.6%; LIS 44.8%). In conclusion, ALI alone, or in combination with HCTZ, exhibits similar tolerability and antihypertensive efficacy to LIS alone, or in combination with HCTZ, in patients with severe hypertension.Journal of Human Hypertension (2007) 21, 780–787; doi:10.1038/sj.jhh.1002220; published online 31 May 2007 [ABSTRACT FROM AUTHOR]

The article focuses on the inhibition of the renin angiotensin system (RAS) as a way to intervene in the progression of cardiovascular and renal disorders. The system can be initiated at various points with resulting reduction in blood pressure. Beta blockers, ACE inhibitors and angiotensin receptor blockers inhibit renin.

The acute effects of the renin-angiotensin system (RAS) blockers may be important in some clinical settings. To assess the acute impact of such drugs on arterial function, we studied the effects of captopril 25 mg, quinapril 20 mg and telmisartan 80 mg on 100 hypertensive patients, according to a randomized, double-blind, placebo-controlled study. Central (aortic) blood pressure (BP) and augmentation index (AIx, a measure of wave reflections), as well as flow-mediated dilatation (FMD) of the brachial artery and forearm blood flow (FBF) (measures of conduit and resistance artery endothelial function, respectively), were evaluated before and 2 h after oral drug administration. Compared to placebo, captopril and quinapril decreased central systolic (by 7.5 mm Hg, P<0.05 and by 12.3 mm Hg, P<0.001) and diastolic BP (by 4.9 mm Hg, P<0.01 and by 8.4 mm Hg, P<0.001), whereas telmisartan had no significant effect (P=NS). Additionally, AIx was reduced after quinapril (absolute decrease of 7.2%, P<0.01) and marginally after captopril (decrease of 4.7%, P=0.07). Only quinapril led to a beneficial change of FMD (absolute increase of 2.7%, P<0.001). No treatment was related to significant changes of peak hyperaemic or 3-min hyperaemic FBF. In adjusted analyses, all the favourable alterations induced by quinapril were independent of potential confounding haemodynamic factors. Our data show that acute RAS inhibition with quinapril (20 mg) may be more beneficial in terms of arterial function and central haemodynamics compared to captopril (25 mg) or telmisartan (80 mg). Further studies are needed to investigate whether these acute arterial effects of quinapril are clinically significant.Journal of Human Hypertension (2007) 21, 654–663; doi:10.1038/sj.jhh.1002211; published online 26 April 2007 [ABSTRACT FROM AUTHOR]

The effects of 24 weeks losartan and ramipril treatment, both alone and in combination, on left ventricular mass (LVM), circulating transforming growth factor β1 (TGFβ1), procollagen type I (PIP) and III (PIIIP), have been evaluated in hypertensive (HT) patients. A total of 57 HT with stage 1 and 2 essential hypertension were included. After 4 weeks run in, a randomized double-blind, three arms, double dummy, independent trial was used. All HT patients were randomly allocated to three treatment arms consisting of losartan (50 mg/daily), ramipril (5 mg/ daily) and combined (losartan 50 mg/daily + ramipril 5 mg/daily) for 24 weeks. TGFβ1, PIP and PIIIP, LVM, LVM/h2.7 and other echocardiographic measurements, blood urea nitrogen, creatinine and clearance and potassium were determined after run in and after 24 weeks. All groups were comparable for gender, age, body mass index, blood pressure and LVM. The prevalence of baseline left ventricular hypertrophy (LVH) was not significantly different among three groups. At the end of treatment, a significant (P<0.05) reduction in systolic blood pressure (SBP), diastolic blood pressure (DBP), mean blood pressure (MBP), TGFβ1, PIP, PIIIP, LVM and LVM/h2.7 was observed in all groups. The absolute and percent reduction in TGFβ1 and LVM/h2.7 were significantly higher in combined than losartan or ramipril groups and also in HT patients with LVH. No significant change in absolute and percent reduction of SBP, DBP and MBP were found. Our data indicate an additional cardioprotective effect of dual blockade of renin–angiotensin in HT patients.Journal of Human Hypertension (2007) 21, 307–315. doi:10.1038/sj.jhh.1002161; published online 15 February 2007 [ABSTRACT FROM AUTHOR]

High rates of uncontrolled hypertensives have been reported in France as well as in other countries, partly owing to an inadequate management of hypertension by clinicians. The objectives of the study were (1) to describe the therapeutic decisions faced by general practitioners (GP) in hypertensives not controlled by fixed-dose combination antihypertensive therapy with a renin–angiotensin system (RAS) inhibitor and a diuretic (D) and (2) to evaluate the frequency with which ambulatory blood pressure monitoring (ABPM) is used in these patients. Each GP had to include five uncontrolled hypertensives on fixed-dose RAS inhibitor and D combination. A total of 2118 GPs included 9551 patients; 8643 patients were receiving at least one of the two drugs at a low dose (group 1) and the remaining 908 patients were receiving high doses of both drugs (group 2). The most common therapeutic choice was that of a new combination, either a fixed-dose in one pill or with separate preparations: 65% (n=5621) in group 1 and 56% (n=505) in group 2. An increase in dose was chosen in 28% of patients in group 1 (n=2467) and continuation of treatment without modification in 27% of patients in group 2 (n=242). A third active principle was only added in 2.5% of patients in group 1 (n=219) and 11% in group 2 (n=103). Ambulatory blood pressure monitoring was employed in 25% of patients (n=2413). An improvement in hypertension management should be expected from the implementation of the 2005 French guidelines.Journal of Human Hypertension (2006) 20, 407–418. doi:10.1038/sj.jhh.1002000; published online 30 March 2006 [ABSTRACT FROM AUTHOR]

The incidence of end-stage renal disease (ESRD) is rising worldwide, accompanied by corresponding increases in the risk of morbidity and mortality. Underlying this trend are increasing rates of hypertension and diabetes mellitus, the two most common causes of ESRD. In addition to the adverse haemodynamic effects of hypertension on the kidney, elevated blood pressure (BP) can activate components of the renin–angiotensin–aldosterone system (RAAS), which, in turn, activate mediators of inflammation, oxidative stress, cell growth, and matrix accumulation. Lowering BP reduces the risk of cardiovascular events and renal damage. Accumulating evidence from clinical and laboratory studies suggests that interrupting the RAAS with therapies such as angiotensin-converting enzyme inhibitors, angiotensin II receptor blockers, and aldosterone receptor blockers can interfere with the mechanisms that promote diabetic and non-diabetic renal damage. Moreover, clinical trials of RAAS blockade have demonstrated reductions in microalbuminuria, a predictor of increased cardiorenal risk and overt nephropathy in patients with and without diabetes and/or hypertension. In this way, agents that block the RAAS should be considered the drugs of first choice as they provide enhanced renoprotection compared with other classes of antihypertensive agents such as calcium channel blockers and β-blockers.Journal of Human Hypertension (2006) 20, 239–253. doi:10.1038/sj.jhh.1001982; published online 2 February 2006 [ABSTRACT FROM AUTHOR]

Screening for primary hyperaldosteronism (PHA) is often indicated in individuals with resistant hypertension or hypokalaemia. However, in the far larger subset of the hypertensive population who do not fit into these criteria, the evidence for screening is conflicting and dependent on the disease prevalence. The purpose of this study was to examine the prevalence of PHA in a large population with mild to moderate hypertension and without hypokalaemia using a carefully controlled study protocol including a normotensive control population. Hypertensive subjects underwent medication washout and both hypertensive and normotensive subjects placed on a high-sodium diet prior to biochemical and haemodynamic testing. Study specific cutoff values were based on results from the normotensive population studied under identical conditions. A screening test (serum aldosterone/PRA ratio [ARR]>25 with a serum aldosterone level >8 ng/dl) was followed by a confirmatory test (urine aldosterone excretion rate [AER] >17 μg/24 h) to demonstrate evidence of PHA. An elevated ARR with a concomitant elevated serum aldosterone was present in 26 (7.5%) individuals. Of these, 11 (3.2%) had an elevated AER, consistent with evidence of PHA. Individuals with PHA had higher blood pressure and lower serum potassium levels while on a high-sodium diet. Sodium restriction neutralized these differences between PHA and essential hypertensives. The prevalence of PHA in this mild to moderate hypertensive population without hypokalaemia is at most 3.2%, a rate that might lead to excessive false positives with random screening in comparable populations. Hyperaldosteronism, when present, is responsive to sodium restriction.Journal of Human Hypertension (2006) 20, 129–136. doi:10.1038/sj.jhh.1001948; published online 17 November 2005 [ABSTRACT FROM AUTHOR]

Drugs that inhibit the renin–angiotensin system (RAS), namely angiotensin-converting enzyme inhibitors (ACE-I) and angiotensin receptor antagonists (ARA) are gaining increasing popularity as initial medications for the management of hypertensive patients. In the year 2002, ACE-I were the most commonly prescribed drugs for the treatment of hypertension in USA. Although their antihypertensive efficacy as monotherapy is similar to other antihypertensive agents, they have the advantage of better tolerability, limited side effects and a favorable metabolic profile. When compared to other antihypertensive agents (diuretics, beta-adrenergic blockers and calcium antagonists) in large clinical trials, ACE-I and ARA provided no additional advantages regarding improvement in cardiovascular and total mortality. With the exception of the superiority of ARA in prevention of stroke, RAS inhibitors have no advantage over other agents in prevention of other cardiovascular morbid events, namely, heart failure (though ACE-I are superior to calcium antagonists), coronary heart disease and total cardiovascular events. However, there is the possibility that these agents have other benefits beyond blood pressure lowering. At equal degrees of blood pressure reduction, RAS inhibitors prevent or delay the development of diabetes mellitus and provide better end-organ protection, kidneys, blood vessels and the heart when compared with other antihypertensive agents. The combined use of ACE-I and ARA is particularly useful in organ protection. RAS inhibitors are specifically indicated in the treatment of hypertension in patients with impaired left ventricular systolic function, diabetes, proteinuria, impaired kidney function, myocardial infarction, multiple cardiovascular risk factors and possibly elderly patients. The main limitation of the ACE-I is cough and rarely angioedema. Elderly patients or those who are volume depleted or receiving large doses of diuretics or in heart failure are liable to develop hypotensive reaction and/or deterioration in kidney function.Journal of Human Hypertension (2006) 20, 101–108. doi:10.1038/sj.jhh.1001960; published online 5 January 2006 [ABSTRACT FROM AUTHOR]

We investigated the interplay of dietary sodium and renin-angiotensin-aldosterone system (RAAS) activity with the prevalence of left ventricular hypertrophy (LVH) in essential hypertension. Electrocardiograms (EKG) were reviewed for the presence of LVH in 160 hypertensive patients. We then compared the rate of LVH to levels of plasma renin activity (PRA) and serum aldosterone under high and low sodium diet conditions. On high sodium diet, serum aldosterone was significantly higher (7.7±0.93 vs 5.7±0.35?ng/dl, P=0.02) in participants with LVH. With low sodium diet and upright posture, PRA was significantly lower in subjects with LVH vs those without (5.6±1.1 vs 7.6±0.56?ng/ml/h, P=0.026). Aldosterone levels on low sodium diet were not different between those with and those without LVH. PRA was then dichotomized at the lowest quartile under low sodium/upright posture conditions to define a‘low renin’group. In a multivariate logistic regression containing renin status (low renin vs normal/high renin), aldosterone on a high sodium diet, age, body mass index, gender, race, duration of hypertension, systolic and diastolic blood pressure and salt-sensitivity only low-renin status on a low sodium diet (P=0.019) and serum aldosterone on a high sodium diet (P=0.04) were significant predictors of LVH. Thus, reduced modulation of renin activity in response to sodium restriction and an increased aldosterone on a high sodium diet appear to identify characteristics of hypertensive patients predisposed to abnormal cardiac remodelling.Journal of Human Hypertension (2005) 19, 133-138. doi:10.1038/sj.jhh.1001784 Published online 9 September 2004 [ABSTRACT FROM AUTHOR]

This study analyzed the relationship between four renin-angiotensin system (RAS) gene polymorphisms and the response to blood pressure lowering and development of microalbuminuria in 206 patients with essential hypertension treated once daily for 12 months with telmisartan 80?mg. Seated cuff blood pressure and urinary albumin excretion (UAE) were measured throughout the study. Patients were screened for the presence of the A-6G variant of the angiotensinogen gene, angiotensin-converting enzyme insertion/deletion polymorphism, and the A1166C and C573T polymorphisms of the angiotensin II type 1 receptor gene. No significant association was found between the presence of any gene polymorphism and the reduction of blood or UAE following telmisartan treatment. The results indicate that these RAS gene polymorphisms do not affect the antihypertensive activity and renoprotection in mild-to-moderate hypertensive patients treated with telmisartan.The Pharmacogenomics Journal (2005) 5, 14-20. doi:10.1038/sj.tpj.6500280 Published online 26 October 2004 [ABSTRACT FROM AUTHOR]

Systolic blood pressure is a major cardiovascular risk factor which is often associated with arterial stiffness. Markers of arterial stiffness, such as pulse pressure and carotid-femoral pulse wave velocity, have been proved independent predictors of cardiovascular risk. Recent evidence suggests that the renin-angiotensin system is involved in the pathogenesis of systolic hypertension and arterial stiffness. Outcome trials have shown impressive cardiovascular protection by reducing systolic blood pressure (BP) with drug treatment. However, in clinical practice systolic hypertension remains largely uncontrolled, first, because systolic BP goal is more difficult to be reached than diastolic and, second, because physicians are often reluctant to intensify treatment in patients with systolic BP close to 150?mmHg. Recent trials have focused on the effects of antihypertensive drugs not only on blood pressure, but also on pulse pressure and pulse-wave velocity. Blockade of the renin-angiotensin-aldosterone system, using angiotensin-converting enzyme inhibitors and more recently angiotensin receptor blockers, has been shown to provide beneficial effects on arterial stiffness that appear to be independent of their antihypertensive effects. Recent outcome trials have shown significant cardiovascular protection with angiotensin receptor blockers. These drugs have an excellent placebolike profile of adverse effects which is maintained when these drugs are combined with low-dose diuretics. Therefore, an angiotensin receptor blocker-based treatment strategy appears to be an attractive and evidence-based approach for the management of systolic hypertension, the reduction of arterial stiffness and the prevention of cardiovascular disease.Journal of Human Hypertension (2004) 18, 837-847. doi:10.1038/sj.jhh.1001762 Published online 19 August 2004 [ABSTRACT FROM AUTHOR]

Genetic analysis of hypertension has yielded inconsistent results, making it difficult to draw clear conclusions regarding the impact of specific variants on blood pressure regulation. Among the most studied of the candidate genes for blood pressure regulation is angiotensinogen (AGT), but as with other candidate loci associations with blood pressure have been inconsistent. We examined the contributions of two AGT polymorphisms (T174M and M235T) to detect the effects of each on blood pressure variation, using single-site and two-site analyses. We analysed data from a study of 177 subjects from Accra, Ghana. We observed significant single-locus associations of the T174M polymorphism with average systolic (SBP) and diastolic blood pressure (DBP) when age was used as a covariate (P<0.001 and P=0.010, respectively). Also, we observed a significant association of the M235T polymorphism with SBPs and DBPs (P<0.001 and P=0.014, respectively). Finally, we observed a simultaneous significant association of the two polymorphisms with SBP and DBP (P<0.001 and P=0.026, respectively), although the two-loci model is not significantly better than either single-locus model. However, for SBP the two-loci model is marginally better (P=0.08 in comparison to both single-locus models). These results suggest that variants at these two AGT sites together, in conjunction with age, may be significantly associated with elevated SBP, whereas the single-site models are as good models of DBP. It is possible that earlier inconsistent results with these AGT polymorphisms with hypertension in African-derived populations may have resulted from an‘incomplete’model in the different study populations. Given the inconclusive nature of our two-loci results, this possibility requires further investigation.Journal of Human Hypertension (2004) 18, 865-869. doi:10.1038/sj.jhh.1001768 Published online 2 September 2004 [ABSTRACT FROM AUTHOR]

Generation of angiotensin II (Ang II) contributes to the pathogenesis of cardiovascular diseases. Owing to the existence of high levels of Ang II within the kidney, blockade of the intrarenal Ang II levels may be important since long term outcome seems not only to be related to blood pressure per se. This was a prospective, randomized, double-blind, placebo-controlled study, with crossover design. We examined in 13 patients with mild to moderate hypertension the specific systemic and renal blocking properties of two different Ang II receptor blockers during a wide range of Ang II concentrations, 24?h post dose. The effects were evaluated after 4 weeks treatment with candesartan cilexetil (16?mg OD), losartan (50?mg OD) and placebo using clearance techniques. Candesartan reduced the 24?h blood pressure better than losartan (138*/87±12/8 vs 145/89±12/7?mmHg,*P<0.05 vs losartan) and placebo. Despite the lower blood pressure, candesartan attenuated the Ang II-induced response on ERPF and RVR markedly better than losartan or placebo. The GFR decreased, as expected, with placebo, but remained stable with candesartan. The present study demonstrates that in hypertensive patients candesartan and to a lesser degree losartan are effective in blocking the systemic and renal effects of Ang II during a wide range of Ang II infusion rates. Interestingly, 24?h post dose, candesartan effectively diminished the change in ERPF as well as GFR. This sustained renal effect of candesartan may be of importance, especially in pathophysiological circumstances in which (high renal levels of) Ang II contributes to cardiovascular damage.Journal of Human Hypertension (2004) 18, 857-863. doi:10.1038/sj.jhh.1001769 Published online 9 September 2004 [ABSTRACT FROM AUTHOR]

Angiotensin-converting enzyme 2 (ACE2) is a recently discovered homologue of the key enzyme of the renin-angiotensin system, the angiotensin-converting enzyme. The ACE2 enzyme is mainly expressed in cardiac blood vessels and tubular epithelia of the kidneys. Together with ACE2’s unique metallocarboxypeptidase activity, the restricted tissue distribution suggests a distinctive physiological function in blood pressure, blood flow and fluid regulation. Theace2gene was mapped to quantitative trait loci affecting susceptibility to hypertension in rats. Furthermore, ACE2 appears to be a negative regulator of ACE in the heart. ACE2 messenger RNA and protein levels are substantially regulated in the kidney of diabetic and pregnant rats. The mechanism of ACE2 function and its physiologic significance are not yet fully understood; however, as ACE2 differs in its specificity and physiological role from ACE, this opens a new potential venue for drug discovery aimed at cardiovascular disease, hypertension and diabetic complications. [ABSTRACT FROM AUTHOR]

Investigates the role of renin-angiotensin-aldosterone system (RAAS) in atrial fibrillation and its potential as a therapeutic target. Overview of atrial fibrillation; Usefulness of the blockade of the RAAS in several cardiovascular disorders; Beneficial effect of losartan in the Losartan Intervention for Endpoint reduction in hypertension trial; Left ventricular hypertrophy; Role of RAAS on thrombogenesis.

Population blood pressure variation is most likely due to multiple genes. This is likely the reason why monogenic testing with the angiotensinogen (AGT) gene polymorphisms on chromosome 1 (1q42-43), especially M235T, has met with negative results, especially in those of African descent. The RH blood group system, also on chromosome 1 (1 p36.2-34), has likewise been associated with blood pressure variation in African-Americans and with the rise in blood pressure with age in whites. Using a random sample of the population, we investigated the combined effects of single and combined variation of the AGTN M235T and RH genotypes on blood pressure, lipids, and lipoprotein concentrations in Afro-Caribbeans aged 18-60 years from the island nation of Dominica. In monogenic analysis, AGT M235T was not associated with blood pressure. However, it was associated with HDL (MM 42±23, MT 44±12, TT 52±14 (P=0.002)). RH genotype was significantly associated with systolic blood pressure (P=0.006) and Apo-A (P=0.003). These effects remained after adjustment for age, gender, weight, and BMI. In the polygenetic analysis, AGT M235T and RH were significantly associated with systolic blood pressure (P=0.037; interaction effects, P=0.068). The association of the AGT M235T with blood pressure across RH blood group haplotypes was then tested. Of the five RH haplotypes available for analysis, the AGT M235T was significantly associated with blood pressure within the “D” haplotype (P=0.01). The RH blood group and gender were significantly associated with systolic blood pressure and Apo-A levels (P=0.005 and 0.012, respectively). All interactions were independent of age and weight. In conclusion, we demonstrate a significant association of AGT M235T with blood pressure and cholesterol metabolism in an Afro-Caribbean population in the “genetic context” of the RH blood group system. Further investigation of these interactions may help understand the effects of genetic factors on cardiovascular risk in African-derived and other populations.Journal of Human Hypertension (2004) 18, 351-363. doi:10.1038/sj.jhh.1001679 Published online 12 February 2004 [ABSTRACT FROM AUTHOR]

OBJECTIVE:: The objectives were two-fold: (1) determine whether the use of hydralazine as antihypertensive therapy during obesity development exacerbated obesity-related cardioacceleration and hormonal abnormalities; (2) determine whether the absence of hypertension in obesity attenuated obesity-related abnormalities in hemodynamics, cardiac hypertrophy, and hormonal profile. DESIGN:: Female New Zealand White rabbits were divided into lean control (n=12), lean hydralazine-treated (n=9), obese control (n=11), and obese hydralazine-treated (n=8) groups. Pretreatment mean blood pressure (BP) and heart rate (HR) were determined using telemetry. Pretreatment BP was maintained during 12 weeks of obesity development using hydralazine. MEASUREMENTS:: Chronically measured BP and HR; plasma/blood volume; wet and dry ventricular weights; body fat/water; and hormonal profile (plasma renin activity, aldosterone, cortisol, atrial natriuretic peptide, adrenaline, and noradrenaline). RESULTS:: Hydralazine treatment in obese animals attenuated obesity-related renin-angiotensin system (RAS) activation. In contrast, RAS was activated in lean hydralazine, as indicated by increased plasma aldosterone. The absence of hypertension in obese hydralazine did not result in attenuation of cardioacceleration, cardiac hypertrophy, or intravascular volumes. CONCLUSIONS:: Hydralazine treatment in obese rabbits did not exacerbate obesity-related cardiovascular and hormonal alterations. Cardioacceleration and cardiac hypertrophy persisted in obese hydralazine despite BP control, suggesting hypertension-independent effects of obesity on these variables. Hydralazine's effects on RAS activation differed in lean and obese rabbits, suggesting that the systemic effects of hydralazine as a control therapy in evaluation of antihypertensive medications may differ depending on the underlying pathology.International Journal of Obesity (2004) 28, 384-390. doi:10.1038/sj.ijo.0802573 [ABSTRACT FROM AUTHOR]

BACKGROUND:: The renin-angiotensin-aldosterone (RAA) system regulates blood pressure (BP) levels and influences responses to antihypertensive medications. Variation in RAA system genes has been reported to influence interindividual differences in BP levels and the occurrence of hypertension (HTN). METHODS:: We evaluated the relationship between variation in genes of the RAA system and interindividual differences in BP response to a thiazide diuretic. Analyses were carried out in a race- and gender-specific manner in 255 unrelated hypertensive African-Americans (125 men and 130 women) and 246 unrelated hypertensive non-Hispanic Whites (133 men and 113 women). RESULTS:: The angiotensin II receptor (AT1R) A1166C and angiotensinogen G-6A polymorphisms had a significant effect on systolic BP response to the diuretic in African-American women. Multilocus analyses indicated that the effects of these genes combined additively to influence response. Results of a permutation test to adjust for multiple comparisons and the possible nonindependence among genotypes remained significant at the P=0.003 level. CONCLUSIONS:: Among African-American women, particular gene variations in the RAA system have additive effects on BP response to a thiazide diuretic.The Pharmacogenomics Journal (2004) 4, 17-23. doi:10.1038/sj.tpj.6500215 [ABSTRACT FROM AUTHOR]

Focuses on recent clinical trials on blocking the renin-angiotensin-aldosterone system in cardiovascular disease and the long-term treatment of hypertension as of November 2003. Assessment of reduction in mortality and morbidity in heart failure with candesartan; Clinical trial on reduction of cardiac events with perindopril in stable coronary artery disease; Comparison of antihypertensive treatment with placebo in elderly patients with isolated systolic hypertension.

According to the World Health Organization predictions cardiovascular diseases will be the leading cause of death by the year 2020. High blood pressure is a major risk factor for myocardial infarction, cerebrovascular disease, and stroke. Modulation of the renin-angiotensin system, particularly inhibition of the angiotensin-converting enzyme (ACE), has become a prime strategy in the treatment of hypertension and heart failure. Recently the gene of a new ACE, termed ACE2, has been characterized. The ACE2 gene maps to defined quantitative trait loci on the X chromosome in three different rat models of hypertension, suggesting ACE2 as a candidate gene for hypertension. In mice the targeted disruption of ACE2 resulted in increased systemic angiotensin II levels, impaired cardiac contractility, and upregulation of hypoxia-induced genes in the heart. Since mice deficient in both ACE2 and ACE show completely normal heart function, it appears that ACE and ACE2 negatively regulate each other. The mechanisms and physiological significance of the interplay between ACE and ACE2 are not yet elucidated, but it may involve several new peptides and peptide systems. In view of drug development the increasing complexity of the renin-angiotensin system offers both challenge and opportunity to develop new and refined treatment strategies against cardiovascular diseases. [ABSTRACT FROM AUTHOR]

Limited information exists on the relations between heart rate variability, hypertension, lifestyle factors and renin-angiotensin-aldosterone system. A total of 191 newly diagnosed yet untreated hypertensive men and women, 35-54 years of age, were compared with an age- and gender-stratified random population sample of 105 normotensive men and women to find out independent determinants of heart rate variability. Heart rate variability was computed from 5-min ECG time series using the standard deviation of normal-to-normal RR intervals (SDNN), the square root of the mean of squared differences between adjacent normal RR intervals (RMSSD) and the fast Fourier transform spectral analysis. All absolute measures of heart rate variability were reduced in hypertension (P<0.001 for each, ANOVA). In multivariate regression analyses, reduced heart rate variability was independently associated with higher heart rate (P<0.001 for all absolute measures of heart rate variability), higher age (P=0.001 for SDNN, total and LF powers; P<0.001 for RMSSD and HF power) and higher mean arterial pressure (P<0.05 for total power, P<0.01 for the other absolute measures) but not with sodium and alcohol intakes, body mass index and smoking. Increased plasma renin activity (PRA) was an independent attributor of reduced HF power (P<0.05) and reduced RMSSD (P<0.01). Increased blood pressure and heart rate are associated with decreased heart rate variability without any direct effects on heart rate variability of lifestyle factors. High PRA is an independent determinant of diminished modulation of vagal activity.Journal of Human Hypertension (2003) 17, 171-179. doi:10.1038/sj.jhh.1001529 [ABSTRACT FROM AUTHOR]

Approximately 50% of hypertensive patients are salt sensitive (they increase their Blood Pressure in response to sodium intake or volume expansion). Mechanisms underlying salt sensitivity are not completely elucidated although there is evidence that they may be genetically determined. The aim of this study is to establish the relation among some genetic polymorphisms of the renin-angiotensin system (RAAS) and the beta-3 subunit of the protein G and salt sensitivity. We studied 102 essential hypertensive patients, stage 1-2 and without target organ damage. Salt sensitivity was assessed by the rapid protocol of Weinberger. We determined by polymerase Chain reaction techniques the following polymorphisms: insertion/deletion (I/D) of the angiotensin-converting enzyme (ACE), A1166C of the angiotensin II type 1 receptor (AT1R), -344C/T and intron 2 conversion (IC) of the aldosterone synthase (CYP11B2), and C825T of the beta-3 subunit of the protein G (GNB3). 41 patients (40.19%) were salt sensitive. The distribution of the different polymorphisms was similar in both groups of patients, but subjects carriers of the W allele of the CYP11B2 IC polymorphism had a greater risk for salt sensitivity as compared with no carriers (37 of 41, 90.2% vs 4 of 41, 9.8%, OR 3.02, P<0.05). Although there is no association between salt sensitivity and the different studied genotypes of the RAAS and of the GNB3, our data show a greater risk for salt sensitivity among carriers of the W allele of the CYP11B2 1C polymorphism.Journal of Human Hypertension (2003) 17, 187-191. doi:10.1038/sj.jhh.1001534 [ABSTRACT FROM AUTHOR]

Fibromuscular dysplasia (FMD) is an important cause of renal artery stenosis, particularly in young females. Polymorphisms of the renin-angiotensin (RA) system have been implicated in the pathogenesis of hypertension and atherosclerotic vascular disease, and may play a role in the development of FMD. Examination of polymorphisms by PCR for angiotensin-converting enzyme (ACE) I/D, angiotensin II type 1 receptor AT[SUB1]R) A1166C and angiotensinogen (AGT) M235T and T174M was undertaken in 43 patients with typical multifocal renal arterial FMD (MF-FMD) and in 89 controls. The age of MF-FMD patients at the time of diagnosis of hypertension did not differ (38.6 ± 11.1 years vs 35.5 ± 10.3 years, P = 0.12) from controls and the proportion (95% vs 86%, P = 0.14) of females was similar. Allele frequencies did not differ significantly between groups, except that MF-FMD patients had a significantly higher frequency of the ACE I allele than control subjects (0.62 vs 0.47, P = 0.026). Since the ACE I allele is associated with lower circulating ACE levels and possibly lower tissue levels of angiotensin II (Ang II), and since Ang II modulates vascular smooth muscle cell growth and synthetic activity, the I allele might predispose to defective remodelling of the arterial media, and thus to the development of MF-FMD. This contrasts with atherosclerotic renal artery stenosis, coronary stent restenosis and carotid intimal thickening, which are diseases affecting the arterial intima, and which are associated with increased frequency of the D allele. [ABSTRACT FROM AUTHOR]

Focuses on renin-angiotensin system. Discovery of renin; Physiological and pathological significance of renin-angiotensin system in hypertension; Range of actions of renin-angiotensin system.

Hypertension in organ transplant recipients is associated with several functional modifications of the renin angiotensin system (RAS), which varies according to the type of transplanted organs (kidney, heart, liver or bone marrow) and the immunosuppressive regimen. Before transplantation, chronic organ failure is associated with direct and indirect stimulation of both systemic and local RASs. After transplantation, cyclosporin per se is the major determinant of hypertension. It induces stimulation of both systemic and local RAS via direct and indirect effects within the kidney and peripheral vessels. In kidney transplant recipients, ischaemia from the native kidneys and from the graft, due to acute or chronic rejection, also contributes to RAS stimulation. In cardiac transplant recipients, several haemodynamic parameters, abnormal cardiorenal neuroendocrine reflex mechanism and other hormonal systems (ANF, AVP, cathecholamines) stimulate the RAS. [ABSTRACT FROM AUTHOR]