Angiotensin Peptide Levels Research Articles

Dysregulation of the renin-angiotensin system in vascular dementia.

The renin-angiotensin system (RAS) regulates systemic and cerebral blood flow and is dysregulated in dementia. The major aim of this study was to determine if RAS signalling is dysregulated in vascular dementia. We measured markers of RAS signalling in white matter underlying the frontal and occipital cortex in neuropathologically confirmed cases of vascular dementia (n = 42), Alzheimer's disease (n = 50), mixed AD/VaD (n = 50) and age-matched controls (n = 50). All cases were stratified according to small vessel disease (SVD) severity across both regions. ACE-1 and ACE-2 protein and activity was measured by ELISA and fluorogenic peptide assays respectively, and angiotensin peptide (Ang-II, Ang-III and Ang-(1-7)) levels were measured by ELISA. ACE-1 protein level and enzyme activity, and Ang-II and Ang-III, were elevated in the white matter in vascular dementia in relation to SVD severity. ACE-1 and Ang-II protein levels were inversely related to MAG:PLP1 ratio, a biochemical marker of brain tissue oxygenation that when reduced indicates cerebral hypoperfusion, in a subset of cases. ACE-2 level was elevated in frontal white matter in vascular dementia. Ang-(1-7) level was elevated across all dementia groups compared to age-matched controls but was not related to SVD severity. RAS signalling was not altered in the white matter in Alzheimer's disease. In the overlying frontal cortex, ACE-1 protein was reduced and ACE-2 protein increased in vascular dementia, whereas angiotensin peptide levels were unchanged. These data indicate that RAS signalling is dysregulated in the white matter in vascular dementia and may contribute to the pathogenesis of small vessel disease.

Levels of Angiotensin and Kinin Metabolite Peptides Related to COVID-19 Severity.

In addition to crucial roles in normal human biology, peptide metabolites of the renin-angiotensin (RAS) and kallikrein-kinin systems (KKS) have been reported to be altered in COVID-19 patients. Here, we evaluate new data on RAS and KKS peptides in COVID-19 patient serum obtained from a recently developed, fully validated, and optimized stable isotope labeling LC-MS peptide assay. We found that the RAS peptides angiotensin (ANG) 1, 2, 1-5, and 1-7 were downregulated compared to COVID-free surrogate controls, while the KKS peptides Brad, Brad 1-8, and Brad 1-7 were upregulated. This paper focuses on uncovering the possible diagnostic value of these peptides using receiver operating characteristic (ROC) analyses of these data. ROC plots confirmed that all of the analyte peptides in 80 serum samples from COVID-19 patients were significantly altered from "normal" values of the control samples. The best diagnostic sensitivities and selectivities for COVID vs no COVID were found in ROC plots for Brad and Brad 1-7 (both 99% sensitivity, 100% selectivity). We then analyzed levels of all the peptides grouped according to preassigned values of the World Health Organization (WHO) COVID-19 Severity Index. ROC plots differentiated patients with a high WHO severity index from those with a low WHO severity index with moderate success, with BRAD (73% sensitivity, 79% selectivity) and Ang 1-7 (75% sensitivity, 65% selectivity) giving the best diagnostic performance. Results suggest the possible diagnostic value of these peptides as biomarkers to help identify moderate and serious COVID-19 cases at relatively early stages.

Development and validation of an LC-MS/MS method for the simultaneous quantitation of angiotensin (1–7), (1–8), (1–9) and (1–10) in human plasma

Cardiovascular diseases have cast a significant negative impact on the lives of millions worldwide. Over the years, extensive efforts have been dedicated to enhancing diagnostic and prognostic tools for these diseases. A growing body of evidence indicates that the angiotensin convertase enzyme (ACE) and the angiotensin convertase enzyme 2 (ACE2), and angiotensin peptide levels could hold a pivotal role in assisting clinicians with the management of cardiovascular conditions, notably hypertension and heart failure. However, despite the considerable body of knowledge in this domain, a void remains in the field of analytical methodologies for these molecules. In this study, we present a fully validated LC-MS/MS method for the precise quantitation of plasma angiotensin (1–7), (1–8), (1–9), and (1–10), following the guidelines set by the Clinical and Laboratory Standards Institute (CLSI). Our method not only enables the accurate quantification of angiotensin peptides but also provides a means to assess ACE and ACE2 activity. Remarkably, our method achieved a Lower Limit of Measurement Interval (LLMI) as low as 5 pg/mL. This has enabled the detection of angiotensin (1–7), (1–8), (1–9) and (1–10) and the accurate quantitation of angiotensin (1–7), (1–8) and (1–10) in all analyzed groups, including healthy controls, patients with high blood pressure, and patients with chronic kidney disease. To our knowledge, our method represents the most sensitive approach allowing for simultaneous quantitation of these four angiotensin peptides. A distinct advantage of our method, when compared to immunoassays, is its high sensitivity combined with comprehensive chromatographic separation of all currently known angiotensin peptides. This combination translates to an exceptional level of selectivity, underscoring the value and potential of our methodology in advancing cardiovascular disease research.

Activation of the Renin-Angiotensin-Aldosterone System Is Attenuated in Hypertensive Compared with Normotensive Pregnancy.

Hypertension during pregnancy increases the risk of adverse maternal and fetal outcomes, but the mechanisms of pregnancy hypertension are not precisely understood. Elevated plasma renin activity and aldosterone concentrations play an important role in the normal physiologic adaptation to pregnancy. These effectors are reduced in patients with pregnancy hypertension, creating an opportunity to define the features of the renin-angiotensin-aldosterone system (RAAS) that are characteristic of this disorder. In the current study, we used a novel LC-MS/MS-based methodology to develop comprehensive profiles of RAAS peptides and effectors over gestation in a cohort of 74 pregnant women followed prospectively for the development of gestational hypertension and pre-eclampsia (HYP, 27 patients) versus those remaining normotensive (NT, 47 patients). In NT pregnancy, the plasma renin activity surrogate, (PRA-S, calculated from the sum of Angiotensin I + Angiotensin II) and aldosterone concentrations significantly increased from the first to the third trimester, accompanied by a modest increase in the concentrations of angiotensin peptide metabolites. In contrast, in HYP pregnancies, PRA-S and angiotensin peptides were largely unchanged over gestation, and third-trimester aldosterone concentrations were significantly lower compared with those in NT pregnancies. The results indicated that the predominant features of pregnancies that develop HYP are stalled or waning activation of the RAAS in the second half of pregnancy (accompanied by unchanging levels of angiotensin peptides) and the attenuated secretion of aldosterone.

Prenatal Morphine Exposure Increases Cardiovascular Disease Risk and Programs Neurogenic Hypertension in the Adult Offspring.

The opioid overdose and opioid use disorder epidemics are concomitant with increased metabolic and CVD risk. Although opioid use disorder causes adverse pregnancy outcomes, the offspring's cardiovascular health is understudied. We hypothesized that offspring exposed to in utero morphine exposure (IUME) would show increased CVD risk factors and endogenous opioid system dysregulation. Sprague Dawley dams were treated with saline (vehicle, n=10) or escalating doses of morphine (5-20 mg/kg per day, SC, n=10) during gestation. Cardiovascular and metabolic parameters were assessed in adult offspring. Litter size and pups' birth weight were not different in response to IUME. Female and male IUME offspring showed reduced body length at birth (P<0.05) and body weight from weeks 1 to 3 of life (P<0.05), followed by a catch-up growth effect. By week 16, female and male IUME rats showed reduced tibia length (P<0.05) and fat mass. IUME increases the mean arterial pressure and the depressor response to mecamylamine (5 mg/kg per day, IP) induced by IUME were abolished by a chronic treatment with an alpha-adrenergic receptor blocker (prazosin; 1 mg/kg per day, IP). Although circulating levels of angiotensin peptides were similar between groups, IUME exacerbated maximal ex vivo Ang (angiotensin) II-induced vasoconstriction (P<0.05) and induced endothelial dysfunction in a sex-specific manner (P<0.05). Proenkephalin, an endogenous opioid peptide that lowers blood pressure and sympathetic-mediated vasoconstriction, showed reduced mRNA expression in the heart, aorta, and kidneys from morphine versus vehicle group (P<0.05). Among the effects of IUME, neurogenic hypertension, vascular dysfunction, and metabolic dysfunction could be associated with the dysregulation of the endogenous opioid system.

Saccharomyces boulardii exerts renoprotection by modulating oxidative stress, renin angiotensin system and uropathogenic microbiota in a murine model of diabetes

AimsWe aimed to investigate whether Saccharomyces boulardii strain might exert renoprotective effects by modulating renal renin angiotensin system, oxidative stress and intestinal microbiota in streptozotocin-diabetic mice. Main methodsThirty-six C57BL/6 male mice were divided into four groups: control (C), control + probiotic (CP), diabetes (D), diabetes + probiotic (DP). Diabetes was induced by one intraperitoneal injection of streptozotocin and Saccharomyces boulardii was administered by oral gavage for 8 weeks. Blood glucose, albuminuria and urinary volume were measured. Renal levels of angiotensin peptides (angiotensin I, II and 1–7) and the activities of angiotensin-converting enzyme (ACE) and ACE2 were determined, besides that, renal morphology, serotonin and dopamine levels and also microbiota composition were analyzed. Key findingsProbiotics significantly increased C-peptide secretion and reduced blood glucose of diabetic animals. Saccharomyces boulardii also improved renal antioxidant defense, restored serotonin and dopamine concentration, and activated the renin-angiotensin system (RAS) vasodilator and antifibrotic axis. The modulation of these markers was associated with a beneficial impact on glomerular structure and renal function of diabetic treated animals. The phenotypic changes induced by Saccharomyces boulardii were also related to modulation of intestinal microbiota, evidenced by the decreased abundance of Proteus and Escherichia-Shigella, considered diabetic nephropathy biomarkers. SignificanceTherefore, probiotic administration to streptozotocin-induced diabetic mice improves kidney structure and function in a murine model and might represent a reasonable strategy to counteract nephropathy-associated maladaptive responses in diabetes.

Probiotic Releasing Angiotensin (1-7) in a Drosophila Model of Alzheimer's Disease Produces Sex-Specific Effects on Cognitive Function.

While extensive research on the brain has failed to identify effective therapies, using probiotics to target the gut microbiome has shown therapeutic potential in Alzheimer's disease (AD). Genetically modified probiotics (GMP) are a promising strategy to deliver key therapeutic peptides with high efficacy and tissue specificity. Angiotensin (Ang)-(1-7) levels inversely correlate to AD severity, but its administration is challenging. Our group has successfully established a GMP-based method of Ang-(1-7) delivery. Since Drosophila represents an excellent model to study the effect of probiotics on complex disorders in a high throughput manner, we tested whether oral supplementation with Lactobacillus paracasei releasing Ang-(1-7) (LP-A) delays memory loss in a Drosophila AD model. Flies overexpressing the human amyloid-β protein precursor and its β-site cleaving enzyme in neurons were randomized to receive four 24-h doses of Lactobacillus paracasei alone (LP), LP-A or sucrose over 14 days. Memory was assessed via an aversive phototaxic suppression assay. Optimal dilution,1:2, was determined based on palatability. LP-A improved memory in trained AD males but worsened cognition in AD females. LP-supplementation experiments confirmed that Ang-(1-7) conferred additional cognitive benefits in males and was responsible for the deleterious cognitive effects in females. Sex-specific differences in the levels of angiotensin peptides and differential activation of the kynurenine pathway of tryptophan metabolism in response to supplementation may underlie this male-only therapeutic response. In summary, LP-A ameliorated the memory deficits of a Drosophila AD model, but effects were sex-specific. Dosage optimization may be required to address this differential response.

Resistance exercise shifts the balance of renin-angiotensin system toward ACE2/Ang 1–7 axis and reduces inflammation in the kidney of diabetic rats

AimsWe aimed to determine whether resistance training (RT) regulates renal renin-angiotensin system (RAS) components and inflammatory mediators in diabetic rats. Main methodsMale Wistar rats (3 months old) were randomly assigned into four groups: non-trained (NT), trained (T), non-trained + diabetes (NTD) and trained +diabetes (TD). Diabetes was induced by streptozotocin (50 mg/kg, Sigma Chemical Co., St. Louis, MO, USA), before RT protocol. Trained rats performed RT protocol on a 110-cm ladder (8 ladder climbs, once/day, 5 days/week, 8 weeks), carrying a load corresponding to 50–80% of maximum carrying capacity. Blood glucose, albuminuria and urinary volume were measured. Renal levels of angiotensin peptides (angiotensin I, II and 1–7), inflammatory markers, and also the activities of angiotensin-converting enzyme (ACE) and ACE2 were determined. Key findingsBlood glucose and urinary volume were elevated in diabetic animals, and RT decreased albuminuria, renal Ang I and Ang II levels in diabetic rats. RT shifted the balance of renal RAS toward ACE2/Ang 1–7 axis in TD group, and mitigated the high levels of interleukin (IL)-10, IL-1β and cytokine-induced neutrophil chemoattractant 1 (CINC) in the context of diabetes. Strong positive correlations were found between albuminuria and Ang II, IL-10 and IL-1β. On the other hand, intrarenal Ang 1–7 levels were negatively correlated with IL-10 and IL-1β levels. SignificanceRT improved kidney function by modulating intrarenal RAS toward ACE2/Ang 1–7 axis and inflammatory cytokines. RT represents a reasonable strategy to improve the renal complications induced by diabetes, counteracting nephropathy-associated maladaptive responses.

Lipocalin‐2 deficiency prevents hypertension in dietary obese mice

Objectives Lipocalin-2 is a pro-inflammatory adipokine up-regulated in obese animals and human subjects. Mice without lipocalin-2 (LKO) are protected from dietary or genetic obesity-induced metabolic dysfunctions and vascular abnormalities. The present study aimed to investigate the role of lipocalin-2 and the mechanisms underlying its actions in dietary obesity-induced hypertension. Methods Wild-type (WT) and LKO, as well as mice with tissue-specific deletion of lipocalin-2 were subjected to 20-weeks high-fat diet treatment. Blood pressure was monitored with implantable radio telemetry. Wire myography was performed to evaluate the vascular responses in mesenteric arteries without or with the attached perivascular adipose tissue (PVAT). Enzyme-linked immunosorbent assay (ELISA), Western blotting and quantitative PCR were performed to measure the levels of angiotensin peptides and angiotensin-converting enzymes. Results Deletion of LCN2 alleles prevented the development of hypertension induced by dietary obesity. Lipocalin-2 deficiency inhibited obesity-associated arterial remodeling and promoted the anti-contractile function of PVAT. The data demonstrated that lipocalin-2 was involved in the local production of angiotensin peptides via modulating the expression of angiotensin-converting enzymes. Conclusion Lipocalin-2 plays a causal role in blood pressure elevation. The source of the pathological form of lipocalin-2 contributing to obesity-induced hypertension needs to be further investigated.

PHARMACOLOGIC ACTIVATION OF THE ALTERNATIVE RAS ATTENUATES DEVELOPMENT OF PULMONARY ARTERIAL HYPERTENSION IN MONOCROTALINE TREATED RATS

Objective: Pulmonary arterial hypertension (PAH) is a rare, chronic and debilitating disease characterized by increased pulmonary arterial pressure leading to right heart failure and – eventually death. Several drugs are approved for the treatment of PAH, but due to ongoing disease progression only half of the patients survive more than 7 years after diagnosis. A novel therapeutic approach based on pharmacologic activation of the alternative RAS was investigated in monocrotaline induced PAH in rats. Design and method: PAH was induced in 12 week-old Wistar rats by an injection of monocrotaline (60 mg/kg). Immediately after PAH induction, the rats (n = 11-12 in each group) were treated for 4 weeks with either a) vehicle, b) the novel peptidase inhibitor ALT001, or c) the endothelin receptor antagonist bosentan – representing the standard of care. Vehicle-treated sham rats served as healthy controls. Analysis included tissue and plasma equilibrium levels of angiotensin metabolites, echocardiography determined right ventricular function and structure, pulmonary arterial pressure, systemic blood pressure and histomorphometrical evaluations. Results: Ang II was significantly increased in lungs of monocrotaline treated animals concomitant with a profound increase in pulmonary arterial pressure (mPAP), reduced fractional shortening, dilated pulmonary valve diameter and a thickened and enlarged right ventricle. ALT001 treatment resulted in increased Ang 1–7 levels while Ang II levels were normalized. Bosentan treatment did not affect angiotensin peptide levels. The PAH induced increase in mPAP was almost completely abolished by ALT001 treatment, while systemic blood pressure remained unaffected. Right ventricular structure and function was effectively preserved under ALT001 treatment and pathological changes in fractional shortening (FS) were significantly reduced. Conclusions: Small molecule based modulation of the RAS might represent a promising novel therapeutic approach in treating RAS-related diseases, including PAH. (Partly supported by VEGA 1/0127/17, FFG 872313)

Role of angiotensin peptides in risk stratification and prognostication for heart failure: focus on plasma Ang 1–7/Ang II ratio

Abstract Background ACE2 and Ang 1–7 are endogenous negative regulators of the renin-angiotensin system (RAS) exerting cardioprotective effects in models of heart failure (HF). Recombinant ACE2 markedly increased plasma Ang 1–7 and lowered Ang II levels in clinical trials. Elevated plasma ACE2 activity is associated with adverse outcomes in HF patients. However, the direct effects of systemic and tissue ACE2 activation on angiotensin peptides in relation to long-term HF outcomes has yet to be examined. Purpose To generate insights into the ACE2 mediated cardioprotective arm through the relative levels of its substrates and products using the plasma Ang 1–7/Ang II ratio, and assess its prognostic utility in HF patients. Methods 110 HF patients were prospectively enrolled from outpatient clinics and the emergency department. Comprehensive circulating and equilibrium levels of plasma angiotensin peptides were assessed using novel liquid chromatography-mass spectrometry/mass spectroscopy techniques. Plasma aldosterone, BNP, active renin activity and clinical profiles were captured at baseline. Patients were stratified into above and below median cohorts based on equilibrium and circulating levels of Ang 1–7/Ang II ratio, as a surrogate for ACE2 functionality. During a median follow-up of 5.1±0.8 years, composite clinical outcomes were assessed through all-cause in-patient hospitalizations and mortality. Results Circulating and equilibrium angiotensin peptide levels strongly correlated in our patient cohort. All-cause mortality for HF patients with equilibrium Ang 1–7/Ang II ratios above the median showed higher survival rates compared to below median patients (76.4% vs. 50.9%; p=0.004); similar results were observed for circulating Ang 1–7/Ang II ratios (72.7% vs. 54.5%; p=0.041). Adjusting for covariates, elevated equilibrium (HR: 0.24; 95% CI: 0.09 to 0.69; p=0.008) and circulating (HR: 0.35; 95% CI: 0.13 to 0.94; p=0.036) Ang 1–7/Ang II ratios was associated with improved survival. Lower hospitalization duration was also associated with elevated equilibrium (p&amp;lt;0.001) and circulating (p=0.023) Ang 1–7/Ang II ratios. In nested models, net reclassification analysis showed considerable improvement in risk prediction for all-cause mortality at 5 years provided by both the equilibrium (+45.0% [95% CI: 7.3% to 82.7%]) and circulating Ang 1–7/Ang II ratios (+24.3% [95% CI: 0.4% to 59.6%]) respectively. Conclusions We extensively profiled plasma angiotensin peptides in HF patients and identified elevated ACE2 signature, reflected through the Ang 1–7/Ang II ratio, as an independent and incremental predictor of beneficial outcomes, higher survival rate, and decreased hospitalization duration. These findings provide important clinical evidence supporting strategies aiming to promote the beneficial ACE2/Ang 1–7/Mas receptor axis concurrent with RAS blockade therapies inhibiting the detrimental ACE/Ang II/AT1 receptor axis. Funding Acknowledgement Type of funding source: Public grant(s) – National budget only. Main funding source(s): Alberta Innovates, Canadian Institute of Health Research

Modulatory action of environmental enrichment on hormonal and behavioral responses induced by chronic stress in rats: Hypothalamic renin-angiotensin system components

Environmental enrichment (EE) has been studied as a protocol that can improve brain plasticity and may protect against negative insults such as chronic stress. The aim of this study was to evaluate the effects of EE on the hormonal and behavioral responses induced by chronic mild unpredictable stress (CMS) in rats, considering the involvement of the renin-angiotensin system. Male adult rats were divided into 4 groups: control, CMS, EE, and CMS + EE, and the experimental protocol lasted for 7 weeks. EE was performed during 7 weeks, 5 days per week, 2 h per day. CMS was applied during weeks 3, 4, and 5. After the CMS (week 6), depression-like behavior was evaluated by forced swimming and sucrose consumption tests, anxiety level was evaluated using the elevated plus-maze test, and memory was evaluated using the Y-maze test. On week 7, the animals were euthanized and basal plasma levels of corticosterone and catecholamines were determined. The hypothalamus was isolated and tissue levels of angiotensin peptides were evaluated. CMS increased plasma corticosterone, norepinephrine, and epinephrine basal concentrations, induced depression-like behaviors, impaired memory, and increased hypothalamic angiotensin I, II, and IV concentrations. EE decreased stress hormones secretion, depression-like behaviors, memory impairment, and hypothalamic angiotensin II induced by stress. Reductions of anxiety-like behavior and norepinephrine secretion were observed in both stressed and unstressed groups. The results indicated that EE seemed to protect adult rats against hormonal and behavioral CMS effects, and that the reduction of angiotensin II could contribute to these effects.

Elevated Angiotensin 1-7/Angiotensin II Ratio Predicts Favorable Outcomes in Patients With Heart Failure.

ACE2 (angiotensin-converting enzyme 2) and Ang 1-7 (angiotensin 1-7) are endogenous negative regulators of the renin-angiotensin system exerting cardioprotective effects in models of heart failure. Recombinant human ACE2 markedly increased plasma Ang 1-7 and lowered Ang II levels in phase II clinical trials. We hypothesize that the dynamic state of this renin-angiotensin system protective arm could influence long-term outcomes in patients with heart failure. One hundred ten patients with heart failure were prospectively enrolled from our outpatient clinic and the emergency department. Comprehensive circulating and equilibrium levels of plasma angiotensin peptide profiles were assessed using novel liquid chromatography-mass spectrometry/mass spectroscopy techniques. Plasma aldosterone, B-type natriuretic peptide, active renin concentration, and clinical profiles were captured at baseline. During a median follow-up of 5.1 years (interquartile range, 4.7-5.7 years), composite clinical outcomes were assessed using all-cause in-patient hospitalizations and mortality. Circulating and equilibrium angiotensin peptide levels strongly correlated in our patient cohort. Adjusting for covariates, elevated equilibrium (hazard ratio, 0.38 [95% CI, 0.18-0.81] P=0.012), and circulating (hazard ratio, 0.38 [95% CI, 0.18-0.80] P=0.011) Ang 1-7/Ang II ratios were associated with improved survival. Lower hospitalization duration was also associated with elevated equilibrium (P<0.001) and circulating (P=0.023) Ang 1-7/Ang II ratios. Importantly, individual Ang 1-7 and Ang II peptide levels failed to predict all-cause mortality or hospitalization duration in our patient cohort. We extensively profiled plasma angiotensin peptides in patients with heart failure and identified elevated Ang 1-7/Ang II ratio, as an independent and incremental predictor of beneficial outcomes, higher survival rate, and decreased hospitalization duration. These findings provide important clinical evidence supporting strategies aiming to promote the beneficial Ang 1-7/Mas axis concurrent with renin-angiotensin system blockade therapies inhibiting the detrimental Ang II/AT1 receptor axis.

Levels of angiotensin peptides in healthy and cardiovascular/renal-diseased paediatric population-an investigative review.

The renin-angiotensin-aldosterone system (RAAS) plays a major role in the regulation of blood pressure and homeostasis. Therefore, it is a commonly used target for pharmacotherapy of cardiovascular diseases in adults. However, the efficacy of this pharmacotherapy can only be limitedly derived into children. Comprehensive knowledge of the humoral parameters acting in the paediatric RAAS (e.g. angiotensin I, angiotensin II, angiotensin 1-7, angiotensin III, and angiotensin IV) might facilitate a more effective and rational pharmacotherapy in children. Therefore, this review aims to provide an overview of the maturing RAAS. Out of 925 identified records, 35 publications were classified as relevant. Physiological and pathophysiological concentrations of angiotensin peptides were compiled and categorised according to European Medicines Agency age groups. Age has a major impact on circulating angiotensin I, angiotensin II, and angiotensin 1-7, which is reflected in an age-dependent decrease during childhood. In contrast to data obtained in adults, no gender-related differences in angiotensin levels were identified. The observed increase in peptide concentrations regarding cardiac- and renal-diseased children is influenced by surgical repair, while evidence for a pharmacological impact is conflicting. A comprehensive set of angiotensin I, angiotensin II, and angiotensin 1-7 values from neonates up to adolescents was compiled. Indicating age as a strong effector. However, evidence about potential promising targets of the RAAS like angiotensin III and angiotensin IV is still lacking in children.

Cardiac hypertrophy in mice submitted to a swimming protocol: influence of training volume and intensity on myocardial renin-angiotensin system.

Exercise promotes physiological cardiac hypertrophy and activates the renin-angiotensin system (RAS), which plays an important role in cardiac physiology, both through the classical axis [angiotensin II type 1 receptor (AT1R) activated by angiotensin II (ANG II)] and the alternative axis [proto-oncogene Mas receptor (MASR) activated by angiotensin-(1-7)]. However, very intense exercise could have deleterious effects on the cardiovascular system. We aimed to analyze the cardiac hypertrophy phenotype and the classical and alternative RAS axes in the myocardium of mice submitted to swimming exercises of varying volume and intensity for the development of cardiac hypertrophy. Male Balb/c mice were divided into three groups, sedentary, swimming twice a day without overload (T2), and swimming three times a day with a 2% body weight overload (T3), totaling 6 wk of training. Both training groups developed similar cardiac hypertrophy, but only T3 mice improved their oxidative capacity. We observed that T2 had increased levels of MASR, which was followed by the activation of its main downstream protein AKT; meanwhile, AT1R and its main downstream protein ERK remained unchanged. Furthermore, no change was observed regarding the levels of angiotensin peptides, in either group. In addition, we observed no change in the ratio of expression of the myosin heavy chain β-isoform to that of the α-isoform. Fibrosis was not observed in any of the groups. In conclusion, our results suggest that increasing exercise volume and intensity did not induce a pathological hypertrophy phenotype, but instead improved the oxidative capacity, and this process might have the participation of the RAS alternative axis.

A17284 The modulation of angiotensin peptide levels by RAS blockade in spontaneously hypertensive rats

Objectives: There are only sparse data on dual (or single) RAS blockade effect on angiotensin peptides. We aimed to investigate the effects of single/combined RAS blockade on angiotensin peptides in spontaneously hypertensive rats (SHR). Methods: 8 groups of SHR were investigated for 4 weeks: aliskiren (Ali), lisinopril (Lis), olmesartan (Olm) or their dual combinations along with SHR and Wistar-Kyoto (WKY) rats. Instant and equilibrated RAS peptide levels in plasma and equilibrated levels in the kidney and left ventricle (LV) were determined along with blood pressure (BP), LV weight and myocardial echocardiography. Results: Compared to WKY, the SHR had increased BP, LV hypertrophy, reduced renin activity and higher circulatory ACE activity. While Ang II was reduced in the LV, it was increased in the kidneys of SHR. Ali achieved only modest BP reduction, while the reduction by Olm, Lis and Olm + Ali were more pronounced. The combinations Olm + Lis and Lis + Ali achieved highest BP reductions. Hypertrophy correlated with BP. While Ali suppressed the RAS, Olm and Lis led to increased Ang I production, which in case of Olm resulted in increased Ang II levels. Both Lis and Olm increased Ang 1–7 equilibrium levels. A discrepancy between instant and equilibrium levels of Ang II and Ang 1-7 suggested their sequestration/degradation in the periphery. Further, levels of both peptides were increased in the kidneys, which was reduced by Olm. All combination treatments reduced the circulatory levels of Ang 1–7 compared to Lis or Olm monotherapy. Conclusion: The circulatory RAS strongly influences the peripheral RAS levels. Dual RAS blockade compromises the potentially protective Ang 1-7 increase. These results provide rationale for the novel therapeutic strategies, combinations and personalized treatment schemes. (VEGA 1/127/17)

Adverse cardiac effects of exogenous angiotensin 1-7 in rats with subtotal nephrectomy are prevented by ACE inhibition.

We previously reported that exogenous angiotensin (Ang) 1–7 has adverse cardiac effects in experimental kidney failure due to its action to increase cardiac angiotensin converting enzyme (ACE) activity. This study investigated if the addition of an ACE inhibitor (ACEi) to Ang 1–7 infusion would unmask any beneficial effects of Ang 1–7 on the heart in experimental kidney failure. Male Sprague–Dawley rats underwent subtotal nephrectomy (STNx) and were treated with vehicle, the ACEi ramipril (oral 1mg/kg/day), Ang 1–7 (subcutaneous 24 μg/kg/h) or dual therapy (all groups, n = 12). A control group (n = 10) of sham-operated rats were also studied. STNx led to hypertension, renal impairment, cardiac hypertrophy and fibrosis, and increased both left ventricular ACE2 activity and ACE binding. STNx was not associated with changes in plasma levels of ACE, ACE2 or angiotensin peptides. Ramipril reduced blood pressure, improved cardiac hypertrophy and fibrosis and inhibited cardiac ACE. Ang 1–7 infusion increased blood pressure, cardiac interstitial fibrosis and cardiac ACE binding compared to untreated STNx rats. Although in STNx rats, the addition of ACEi to Ang 1–7 prevented any deleterious cardiac effects of Ang 1–7, a limitation of the study is that the large increase in plasma Ang 1–7 with ramipril may have masked any effect of infused Ang 1–7.

Roles of Angiotensin Peptides and Recombinant Human ACE2 in Heart Failure

BackgroundThe renin-angiotensin system (RAS) is activated in heart failure (HF) and inhibition of RAS is a mainstay therapy for HF. Angiotensin-converting enzyme 2 (ACE2) and its product, angiotensin 1–7 (Ang-[1–7]), are important negative regulators of the RAS. ObjectivesA comprehensive examination of angiotensin peptide levels and therapeutic effects of recombinant human ACE2 (rhACE2) on peptide metabolism was evaluated in human plasma and explanted heart tissue from patients with HF. MethodsUsing prospective cohorts with chronic (n = 59) and acute (n = 42) HF, plasma angiotensin analysis was performed using a unique liquid chromatography-mass spectrometry/mass spectroscopy method quantifying circulating and equilibrium levels. Angiotensin II (Ang II) metabolism was examined in human explanted hearts with dilated cardiomyopathy (n = 25). ResultsThe dynamic range of the RAS was large, with equilibrium angiotensin levels being 8- to 10-fold higher compared with circulating angiotensin levels. In chronic HF patients receiving ACE inhibition, plasma Ang II was suppressed and plasma Ang-(1–7) was elevated, whereas acute HF and patients receiving angiotensin receptor blocker had higher plasma Ang II with lower Ang-(1–7) levels. Suppressed Ang-(1–7)/Ang II ratio was associated with worsening HF symptoms and longer hospitalization. Recombinant human ACE2 effectively metabolized Ang-(1–10) and Ang II into Ang-(1–9) and Ang-(1–7), respectively. Myocardial Ang II levels in explanted human hearts with dilated cardiomyopathy were elevated despite ACE inhibition with elevated chymase activity, and Ang II was effectively converted to Ang-(1–7) by rhACE2. ConclusionsPlasma angiotensin peptides represent a dynamic network that is altered in HF and in response to rhACE2. An increased plasma Ang-(1–7) level is linked to ACE inhibitor use, whereas acute HF reduced Ang-(1–7) levels and suppressed the Ang-(1–7)/Ang II ratio. Increased chymase activity elevated Ang II levels in failing human hearts. Use of rhACE2 effectively normalized elevated Ang II while increasing Ang-(1–7) and Ang-(1–9) levels.

PS 10-10 KEEPING THE FLOW – NOVEL PERSPECTIVES ON ANGIOTENSIN DYNAMICS

Objective: The renin-mediated formation of Angiotensin I from angiotensinogen is a well-characterized enzymatic reaction providing the input for the RAS. The renin reaction is rate-limiting and resulting Angiotensin I is immediately further metabolized to downstream angiotensin metabolites including Angiotensin II, taking over distinct physiologic functions in human physiology. All molecular components of the RAS are present in the plasma compartment, resulting in a continuous flow of angiotensin metabolites throughout the body, originating in the vascular compartment. Design and Method: Our laboratory investigated the utilization of equilibrium angiotensin peptide levels for the biochemical characterization of the circulating RAS. We extensively compared the correlation between angiotensin levels obtained using state-of the art sampling procedures and equilibrium analysis, which involves a post-sampling equilibration step of a serum or heparin-plasma sample at 37°C. Results: Investigation of healthy volunteers receiving different RAS blockers revealed, that the ratios between metabolically related peptides reflect the activity of the corresponding enzymes. Surprisingly, a strong correlation between equilibrium and stabilized angiotensin levels was observed. The relative differences between stabilized and equilibrium angiotensin levels were peptide specific, with Angiotensin II showing an up to 20-fold increase from “stabilized“ to “equilibrium”, while Angiotensin I changes were limited to a 5-fold increase. Conclusions: The increase of angiotensin levels during ex vivo equilibration of plasma might be caused by the absence of the tissue as angiotensin acceptor. Given that AT1 receptors have been reported to be effectively internalize bound Angiotensin II, the extraordinary strong increase of Angiotensin II in equilibrium suggests that equilibrium levels could serve as a surrogate for Angiotensin II acting on tissues and might represent a diagnostic tool to characterize RAS at the interface between the circulation and the tissue.

The kinetics of angiotensin-I metabolism in human carotid atheroma: An emerging role for angiotensin (1–7)

AimLocal levels of angiotensin peptides depend on their rates of production and degradation, which induce proatherogenic or atheroprotective effects. Here, we reveal the kinetics of Angiotensin-I metabolism in paired early and advanced atherosclerotic lesions. MethodsLesions were spiked with labeled Ang-I* and supernatants withdrawn after 0, 10, 20, 40 and 80min. The concentration of produced Ang-II*, Ang-III*, Ang-IV* and Ang-(1–7)* peptides were measured using multiple reaction monitoring mass spectrometry coupled to ultra-performance liquid chromatography, normalized to tissue weight and initial [Ang-I*]. ResultsAng-(1–7)* was the major angiotensin peptide produced, showing increased levels in both tissue types, with 2–3 fold lower levels in advanced compared to early lesions. In contrast, Ang-II* was 2–3 fold higher in advanced compared to early lesions, showing a decrease between 0 and 40min then an increase at 80min in both tissue types. The levels of Ang-IV were stable in both tissue types across all time points. Finally, Ang-III was non-detectable in both lesions across all time points. ConclusionOur results suggest that progression of atherosclerosis depends on the increased levels of Ang-II along with the decreased levels of Ang-(1–7), which supports the use of Ang-(1–7) along with Angiotensin type-1 receptor (AT1R) blockers.