Angiotensin(1-7) in the spontaneously hypertensive rat

JTT-654, an 11-beta hydroxysteroid dehydrogenase type 1 inhibitor, improves hypertension and diabetic kidney injury by suppressing angiotensinogen production

11β-Hydroxysteroid dehydrogenase type 1 (11β-HSD1) plays an important role in regulating the expression of glucocorticoid actions in target tissues. Overexpression of 11β-HSD1 in mouse adipose tissue causes a metabolic syndrome-like phenotype, leading to hypertension. Although, many 11β-HSD1 inhibitors have been studied, few have shown a clear ameliorative effect against hypertension. We investigated whether JTT-654, a novel 11β-HSD1 inhibitor, ameliorated hypertension and elucidated the underlying mechanisms. JTT-654 showed inhibitory effects on angiotensinogen production in cortisone-treated 3T3-L1 adipocytes and in a rat model. JTT-654 improved hypertension not only in cortisone-treated rats and spontaneously hypertensive rats (SHR), but also in SHR/NDmcr-cp rats. In the SHR study, JTT-654 and losartan showed the same degree of antihypertensive efficacy. In addition, JTT-654 ameliorated diabetic nephropathy by suppressing renal angiotensinogen production in SHR/NDmcr-cp rats. These effects of JTT-654 were independent of its insulin-sensitizing effects, and similar effects were not observed for pioglitazone, an insulin sensitizer. Moreover, JTT-654 did not affect normotension or hypothalamus-pituitary-adrenal (HPA) axis function in normal Sprague-Dawley rats. Our results indicate that JTT-654 ameliorates hypertension and diabetic nephropathy by inhibiting 11β-HSD1 in the adipose tissue, liver, and kidney.

Concurrent exercise training potentiates the effects of angiotensin-converting enzyme inhibitor on regulatory systems of blood pressure control in ovariectomized hypertensive rats

OBJECTIVE

Enalapril has shown satisfactory potential in controlling increased and sustained blood pressure (BP). However, multiple dysregulated mechanisms that interact with each other and are involved in the pathophysiology of arterial hypertension may not be affected, contributing to the remaining cardiovascular risk. Using an exercise training protocol, we investigated whether adding both approaches to arterial hypertension management could promote higher modulation of regulatory mechanisms of BP in postmenopausal rats.

METHODS

Spontaneously hypertensive rats were allocated into sedentary (S) and ovariectomized groups: sedentary (OS), sedentary treated with enalapril maleate (OSE) and trained treated with enalapril maleate (OTE). Both the pharmacological and exercise training protocols lasted for 8 weeks. The BP was directly recorded. Inflammation and oxidative stress were evaluated in the cardiac tissue.

RESULTS

Although BP reduction was similar between OSE and OTE, trained group showed lower vasopressor systems outflow after sympathetic ganglion blocking by hexamethonium (mean BP) (OTE: -53.7 ± 9.86 vs. OS: -75.7 ± 19.2 mmHg). Bradycardic and tachycardic response were increased in OTE group (-1.4 ± 0.4 and -2.6 ± 0.4 vs. OS: -0.6 ± 0.3 and -1.3 ± 0.4 bpm/mmHg, respectively), as well as BP variability. In addition, the combination of approaches induced an increase in interleukin 10, antioxidant defense (catalase and glutathione peroxidase) and nitrite levels compared with the OS group.

CONCLUSION

Despite similar BP, the inclusion of exercise training in antihypertensive drug treatment exacerbates the positive adaptations induced by enalapril alone on autonomic, inflammatory and oxidative stress profiles, probably affecting end-organ damage and remaining risk.

Mas receptor: a potential strategy in the management of ischemic cardiovascular diseases

MasR is a critical element in the RAS accessory pathway that protects the heart against myocardial infarction, ischemia-reperfusion injury, and pathological remodeling by counteracting the effects of AT1R. This receptor is mainly stimulated by Ang 1-7, which is a bioactive metabolite of the angiotensin produced by ACE2. MasR activation attenuates ischemia-related myocardial damage by facilitating vasorelaxation, improving cell metabolism, reducing inflammation and oxidative stress, inhibiting thrombosis, and stabilizing atherosclerotic plaque. It also prevents pathological cardiac remodeling by suppressing hypertrophy- and fibrosis-inducing signals. In addition, the potential of MasR in lowering blood pressure, improving blood glucose and lipid profiles, and weight loss has made it effective in modulating risk factors for coronary artery disease including hypertension, diabetes, dyslipidemia, and obesity. Considering these properties, the administration of MasR agonists offers a promising approach to the prevention and treatment of ischemic heart disease.Abbreviations: Acetylcholine (Ach); AMP-activated protein kinase (AMPK); Angiotensin (Ang); Angiotensin receptor (ATR); Angiotensin receptor blocker (ARB); Angiotensin-converting enzyme (ACE); Angiotensin-converting enzyme inhibitor (ACEI); Anti-PRD1-BF1-RIZ1 homologous domain containing 16 (PRDM16); bradykinin (BK); Calcineurin (CaN); cAMP-response element binding protein (CREB); Catalase (CAT); C-C Motif Chemokine Ligand 2 (CCL2); Chloride channel 3 (CIC3); c-Jun N-terminal kinases (JNK); Cluster of differentiation 36 (CD36); Cocaine- and amphetamine-regulated transcript (CART); Connective tissue growth factor (CTGF); Coronary artery disease (CAD); Creatine phosphokinase (CPK); C-X-C motif chemokine ligand 10 (CXCL10); Cystic fibrosis transmembrane conductance regulator (CFTR); Endothelial nitric oxide synthase (eNOS); Extracellular signal-regulated kinase 1/2 (ERK 1/2); Fatty acid transport protein (FATP); Fibroblast growth factor 21 (FGF21); Forkhead box protein O1 (FoxO1); Glucokinase (Gk); Glucose transporter (GLUT); Glycogen synthase kinase 3β (GSK3β); High density lipoprotein (HDL); High sensitive C-reactive protein (hs-CRP); Inositol trisphosphate (IP3); Interleukin (IL); Ischemic heart disease (IHD); Janus kinase (JAK); Kruppel-like factor 4 (KLF4); Lactate dehydrogenase (LDH); Left ventricular end-diastolic pressure (LVEDP); Left ventricular end-systolic pressure (LVESP); Lipoprotein lipase (LPL); L-NG-Nitro arginine methyl ester (L-NAME); Low density lipoprotein (LDL); Mammalian target of rapamycin (mTOR); Mas-related G protein-coupled receptors (Mrgpr); Matrix metalloproteinase (MMP); MAPK phosphatase-1 (MKP-1); Mitogen-activated protein kinase (MAPK); Monocyte chemoattractant protein-1 (MCP-1); NADPH oxidase (NOX); Neuropeptide FF (NPFF); Neutral endopeptidase (NEP); Nitric oxide (NO); Nuclear factor κ-light-chain-enhancer of activated B cells (NF-κB); Nuclear-factor of activated T-cells (NFAT); Pancreatic and duodenal homeobox 1 (Pdx1); Peroxisome proliferator- activated receptor γ (PPARγ); Phosphoinositide 3-kinases (PI3k); Phospholipase C (PLC); Prepro-orexin (PPO); Prolyl-endopeptidase (PEP); Prostacyclin (PGI2); Protein kinase B (Akt); Reactive oxygen species (ROS); Renin-angiotensin system (RAS); Rho-associated protein kinase (ROCK); Serum amyloid A (SAA); Signal transducer and activator of transcription (STAT); Sirtuin 1 (Sirt1); Slit guidance ligand 3 (Slit3); Smooth muscle 22α (SM22α); Sterol regulatory element-binding protein 1 (SREBP-1c); Stromal-derived factor-1a (SDF); Superoxide dismutase (SOD); Thiobarbituric acid reactive substances (TBARS); Tissue factor (TF); Toll-like receptor 4 (TLR4); Transforming growth factor β1 (TGF-β1); Tumor necrosis factor α (TNF-α); Uncoupling protein 1 (UCP1); Ventrolateral medulla (VLM).

It Ain't Over 'Til It's Over: SARS CoV-2 and Post-infectious Gastrointestinal Dysmotility

The ongoing pandemic resulting from severe acute respiratory syndrome-caused by coronavirus 2 (SARS-CoV-2)-has posed a multitude of healthcare challenges of unprecedented proportions. Intestinal enterocytes have the highest expression of angiotensin-converting enzyme-2 (ACE2), which functions as the key receptor for SARS-CoV-2 entry into cells. As such, particular interest has been accorded to SARS-CoV-2 and how it manifests within the gastrointestinal system. The acute and chronic alimentary clinical implications of infection are yet to be fully elucidated, however, the gastrointestinal consequences from non-SARS-CoV-2 viral GI tract infections, coupled with the generalized nature of late sequelae following COVID-19 disease, would predict that motility disorders are likely to be seen in these patients. Determination of the chronic effects of COVID-19 disease, herein defined as GI disease which is persistent or recurrent more than 3 months following recovery from the acute respiratory illness, will require comprehensive investigations comprising combined endoscopic- and motility-based evaluation. It will be fascinating to ascertain whether the specific post-COVID-19 phenotype is hypotonic or hypertonic in nature and to identify the most vulnerable target portions of the gut. A specific biological hypothesis is that motility disorders may result from SARS-CoV-2-induced angiotensin-converting enzyme 2 (ACE2) depletion. Since SARS-CoV-2 is known to exhibit direct neuronal tropism, the potential also exists for the development of neurogenic motility disorders. This review aims to explore some of the potential pathophysiologic mechanisms underlying motility dysfunction as it relates to ACE2 and thereby aims to provide the foundation for mechanism-based potential therapeutic options.

Phosphoproteomic studies of alamandine signaling in CHO-MrgD and human pancreatic carcinoma cells: An antiproliferative effect is unveiled

Alamandine is a heptapeptide from the renin-angiotensin system (RAS) with similar structure/function to angiotensin-(1-7) [ang-(1-7)], but they act via different receptors. It remains elusive whether alamandine is an antiproliferative agent like ang-(1-7). The goal of this study was to evaluate the potential antiproliferative activity of alamandine and the underlying cellular signaling. We evaluated alamandine effect in the tumoral cell lines Mia PaCa-2 and A549, and in the nontumoral cell lines HaCaT, CHO and CHO transfected with the alamandine receptor MrgD (CHO-MrgD). Alamandine was able to reduce the proliferation of the tumoral cell lines in a MrgD-dependent fashion. We did not observe any effect in the nontumoral cell lines tested. We also performed proteomics and phosphoproteomics to study the alamandine signaling in Mia PaCa-2 and CHO-MrgD. Data suggest that alamandine induces a shift from anaerobic to aerobic metabolism in the tumoral cells, induces a negative regulation of PI3K/AKT/mTOR pathway and activates the transcriptional factor FoxO1; events that could explain, at least partially, the observed antiproliferative effect of alamandine. This study provides for the first time a comprehensive investigation of the alamandine signaling in tumoral (Mia PaCa-2) and nontumoral (CHO-MrgD) cells, highlighting the antiproliferative activity of alamandine/MrgD and its possible antitumoral effect.

Interactions between the intrarenal dopaminergic and the renin-angiotensin systems in the control of systemic arterial pressure

Systemic arterial hypertension is one of the leading causes of morbidity and mortality in the general population, being a risk factor for many cardiovascular diseases. Although its pathogenesis is complex and still poorly understood, some systems appear to play major roles in its development. This review aims to update the current knowledge on the interaction of the intrarenal renin-angiotensin system (RAS) and dopaminergic system in the development of hypertension, focusing on recent scientific hallmarks in the field. The intrarenal RAS, composed of several peptides and receptors, has a critical role in the regulation of blood pressure (BP) and, consequently, the development of hypertension. The RAS is divided into two main intercommunicating axes: the classical axis, composed of angiotensin-converting enzyme, angiotensin II, and angiotensin type 1 receptor, and the ACE2/angiotensin-(1-7)/Mas axis, which appears to modulate the effects of the classical axis. Dopamine and its receptors are also increasingly showing an important role in the pathogenesis of hypertension, as abnormalities in the intrarenal dopaminergic system impair the regulation of renal sodium transport, regardless of the affected dopamine receptor subtype. There are five dopamine receptors, which are divided into two major subtypes: the D1-like (D1R and D5R) and D2-like (D2R, D3R, and D4R) receptors. Mice deficient in any of the five dopamine receptor subtypes have increased BP. Intrarenal RAS and the dopaminergic system have complex interactions. The balance between both systems is essential to regulate the BP homeostasis, as alterations in the control of both can lead to hypertension.

Involvement of the Renin-Angiotensin System in Stress: State of the Art and Research Perspectives

BACKGROUND

Along with other canonical systems, the renin-angiotensin system (RAS) has shown important roles in stress. This system is a complex regulatory proteolytic cascade composed of various enzymes, peptides, and receptors. Besides the classical (ACE/Ang II/AT1 receptor) and the counter-regulatory (ACE2/Ang-(1-7)/Mas receptor) RAS axes, evidence indicates that nonclassical components, including Ang III, Ang IV, AT₂ and AT₄, can also be involved in stress.

OBJECTIVE AND METHODS

This comprehensive review summarizes the current knowledge on the participation of RAS components in different adverse environmental stimuli stressors, including air jet stress, cage switch stress, restraint stress, chronic unpredictable stress, neonatal isolation stress, and post-traumatic stress disorder.

RESULTS AND CONCLUSION

In general, activation of the classical RAS axis potentiates stress-related cardiovascular, endocrine, and behavioral responses, while the stimulation of the counter-regulatory axis attenuates these effects. Pharmacological modulation in both axes is optimistic, offering promising perspectives for stress-related disorders treatment. In this regard, angiotensin-converting enzyme inhibitors and angiotensin receptor blockers are potential candidates already available since they block the classical axis, activate the counter-regulatory axis, and are safe and efficient drugs.

Effects of hydrogen-rich water and ascorbic acid treatment on spontaneously hypertensive rats

Hydrogen-rich water (HW) has been suggested to possess antioxidant properties of value in treatments of lifestyle diseases and for prevention of latent pathologies. To date, the potential benefits of HW against the deleterious effects of excessive salt intake and hypertension have not been investigated. Here, we first examined the effects of HW or HW supplemented with 0.1% ascorbic acid (HWA) on spontaneously hypertensive rats (SHR) that had been fed a normal diet. In comparison to control rats given distilled water (DW), we found that HW did not significantly influence systolic blood pressure (SBP) or diastolic blood pressure (DBP) in SHR; however, the increase in SBP and DBP were inhibited in the HWA group. Next, four groups of SHR were given DW, 0.1% ascorbic acid-added DW (DWA), HW, or HWA in combination with a 4% NaCl-added diet. SHR fed the 4% NaCl-added diet showed increased hypertension; HWA treatment resulted in a significant reduction in blood pressure. The HWA group tended to have lower plasma angiotensin II levels than the DW group. In addition, urinary volumes and urinary sodium levels were significantly lower in the HWA group than the DW group. Urinary isoprostane, an oxidative stress marker, was also significantly lower in the HWA group, suggesting that the inhibitory effect of HWA on blood pressure elevation was caused by a reduction in oxidative stress. These findings suggest a synergistic interaction between HW and ascorbic acid, and also suggest that HWA ingestion has potential for prevention of hypertension.

Retinal Protein O-GlcNAcylation and the Ocular Renin-angiotensin System: Signaling Cross-roads in Diabetic Retinopathy

It is well established that diabetes and its associated hyperglycemia negatively impact retinal function, yet we know little about the role played by augmented flux through the Hexosamine Biosynthetic Pathway (HBP). This offshoot of the glycolytic pathway produces UDP-Nacetyl- glucosamine, which serves as the substrate for post-translational O-linked modification of proteins in a process referred to as O-GlcNAcylation. HBP flux and subsequent protein O-GlcNAcylation serve as nutrient sensors, enabling cells to integrate metabolic information to appropriately modulate fundamental cellular processes including gene expression. Here we summarize the impact of diabetes on retinal physiology, highlighting recent studies that explore the role of O-GlcNAcylation- induced variation in mRNA translation in retinal dysfunction and the pathogenesis of Diabetic Retinopathy (DR). Augmented O-GlcNAcylation results in wide variation in the selection of mRNAs for translation, in part, due to O-GlcNAcylation of the translational repressor 4E-BP1. Recent studies demonstrate that 4E-BP1 plays a critical role in regulating O-GlcNAcylation-induced changes in the translation of the mRNAs encoding Vascular Endothelial Growth Factor (VEGF), a number of important mitochondrial proteins, and CD40, a key costimulatory molecule involved in diabetes-induced retinal inflammation. Remarkably, 4E-BP1/2 ablation delays the onset of diabetes- induced visual dysfunction in mice. Thus, pharmacological interventions to prevent the impact of O-GlcNAcylation on 4E-BP1 may represent promising therapeutics to address the development and progression of DR. In this regard, we discuss the potential interplay between retinal O-GlcNAcylation and the ocular renin-angiotensin system as a potential therapeutic target of future interventions.

The renal excretory responses to acute renal interstitial angiotensin (1-7) infusion in anaesthetised spontaneously hypertensive rats

This study investigated the impact of intrarenal angiotensin 1-7 (Ang [1-7]) infusion on renal excretory function in a rat model of hypertension. Eleven-week-old spontaneously hypertensive rats (SHRs, n = 7) and Han Wistar controls (NCR, n = 7) were anaesthetised with sodium pentobarbital (60 mg/kg i.p.) and prepared for the measurement of mean arterial pressure (MAP) and left renal function during renal interstitial infusion of Ang (1-7) (50 ng/min). The kidneys were harvested, the renal cortex and medulla separated, prepared for measurement of Ang II and Ang (1-7) and Western blot determination of AT1 and Mas receptor protein expression. MAP, glomerular filtration rate (GFR), urine flow (UF) and absolute sodium excretion (UNaV) were 109 ± 16 mmHg, 4.4 ± 1.0 mL/min/kg, 102 ± 16 µL/min/kg and 16 ± 3 µmol/min/kg, respectively in the NCR and 172 ± 24 mmHg, 3.4 ± 0.7 mL/min/kg, 58 ± 30 μL/min/kg and 8.6 ± 4.8 μmol/min/kg respectively in the SHR. Ang (1-7) increased UF (31%), UNa V (50%) and fractional sodium excretion (FENa+ ) (22%) in the NCR group (all p < 0.05) but had no effect on GFR in either group. The magnitudes of the Ang (1-7)-induced increases in UF and UNa V were significantly blunted in the SHR group (model × drug p < 0.05). The renal cortical AT1: Mas receptor expression ratio was significantly higher in the SHR group (p < 0.05) but renal Ang II and Ang (1-7) levels were not statistically different between groups. The Ang (1-7)-induced increases in sodium and water excretion were impaired in the SHR group in the context of an unstimulated RAS. The decrease in responsiveness of the SHR kidney to Ang (1-7) appears to be associated with higher levels of AT1 receptor expression in the renal cortex.

Aerobic training-mediated DNA hypermethylation of Agtr1a and Mas1 genes ameliorate mesenteric arterial function in spontaneously hypertensive rats

BACKGROUND

The imbalance of vasoconstrictor and vasodilator axes of the renin-angiotensin system (RAS) is observed in hypertension. Exercise regulates RAS level and improves vascular function. This study focused on the contribution of RAS axes in vascular function of mesenteric arteries and exercise-induced DNA methylation of the Agtr1a (AT_1aR) and Mas1 (MasR) genes in hypertension.

METHODS

Spontaneously hypertensive rats (SHRs) and Wistar-Kyoto rats were randomized into exercise or sedentary group. Levels of plasma RAS components, vascular tone, and DNA methylation markers were measured.

RESULTS

Blood pressure of SHR was markedly reduced after 12 weeks of aerobic exercise. RAS peptides in plasma were all increased with an imbalanced upregulation of Ang II and Ang-(1-7) in SHR, exercise revised the level of RAS and increased Ang-(1-7)/Ang II. The vasoconstriction response induced by Ang II was mainly via type 1 receptors (AT₁R), while this contraction was inhibited by Mas receptor (MasR). mRNA and protein of AT₁R and MasR were both upregulated in SHR, whereas exercise significantly suppressed this imbalanced increase and increased MasR/AT₁R ratio. Exercise hypermethylated Agtr1a and Mas1 genes, associating with increased DNMT1 and DNMT3b and SAM/SAH.

CONCLUSIONS

Aerobic exercise ameliorates vascular function via hypermethylation of the Agtr1a and Mas1 genes and restores the vasoconstrictor and vasodilator axes balance.

ASTHMA: ROLE OF THE ANGIOTENSIN-(1-7)/MAS PATHWAY IN PATHOPHYSIOLOGY AND THERAPY

The incidence of asthma is a global health problem, requiring studies aimed at developing new treatments to improve clinical management, thereby reducing personal and economic burdens on the health system. Therefore, the discovery of mediators that promote anti-inflammatory and pro-resolutive events are highly desirable to improve lung function and quality of life in asthmatic patients. In that regard, experimental studies have shown that the Angiotensin-(1-7)/Mas receptor of the renin-angiotensin system (RAS) is a potential candidate for the treatment of asthma. Therefore, we reviewed findings related to the function of the Angiotensin-(1-7)/Mas pathway in regulating the processes associated with inflammation and exacerbations in asthma, including leukocyte influx, fibrogenesis, pulmonary dysfunction and resolution of inflammation. Thus, knowledge of the role of the Angiotensin-(1-7)/Mas can help pave the way for the development of new treatments for this disease with high morbidity and mortality through new experimental and clinical trials.

Anthracycline-induced cardiotoxicity and renin-angiotensin-aldosterone system-from molecular mechanisms to therapeutic applications

Few millions of new cancer cases are diagnosed worldwide every year. Due to significant progress in understanding cancer biology and developing new therapies, the mortality rates are decreasing with many of patients that can be completely cured. However, vast majority of them require chemotherapy which comes with high medical costs in terms of adverse events, of which cardiotoxicity is one of the most serious and challenging. Anthracyclines (doxorubicin, epirubicin) are a class of cytotoxic agents used in treatment of breast cancer, sarcomas, or hematological malignancies that are associated with high risk of cardiotoxicity that is observed in even up to 30% of patients and can be diagnosed years after the therapy. The mechanism, in which anthracyclines cause cardiotoxicity are not well known, but it is proposed that dysregulation of renin-angiotensin-aldosterone system (RAAS), one of main humoral regulators of cardiovascular system, may play a significant role. There is increasing evidence that drugs targeting this system can be effective in the prevention and treatment of anthracycline-induced cardiotoxicity what has recently found reflection in the recommendation of some scientific societies. In this review, we comprehensively describe possible mechanisms how anthracyclines affect RAAS and lead to cardiotoxicity. Moreover, we critically review available preclinical and clinical data on use of RAAS inhibitors in the primary and secondary prevention and treatment of cardiac adverse events associated with anthracycline-based chemotherapy.

Angiotensin-(1-7) Attenuates Protein O-GlcNAcylation in the Retina by EPAC/Rap1-Dependent Inhibition of O-GlcNAc Transferase

Purpose

O-GlcNAcylation of cellular proteins contributes to the pathophysiology of diabetes and evidence supports a role for augmented O-GlcNAcylation in diabetic retinopathy. The aim of this study was to investigate the impact of the renin-angiotensin system on retinal protein O-GlcNAcylation.

Methods

Mice fed a high-fat diet were treated chronically with the angiotensin-converting enzyme inhibitor captopril or captopril plus the angiotensin-(1-7) Mas receptor antagonist A779. Western blotting and quantitative polymerase chain reaction were used to analyze retinal homogenates. Similar analyses were performed on lysates from human MIO-M1 retinal Müller cell cultures exposed to media supplemented with angiotensin-(1-7). Culture conditions were manipulated to influence the hexosamine biosynthetic pathway and/or signaling downstream of the Mas receptor.

Results

In the retina of mice fed a high-fat diet, captopril attenuated protein O-GlcNAcylation in a manner dependent on Mas receptor activation. In MIO-M1 cells, angiotensin-(1-7) or adenylate cyclase activation were sufficient to enhance cyclic AMP (cAMP) levels and inhibit O-GlcNAcylation. The repressive effect of cAMP on O-GlcNAcylation was dependent on exchange protein activated by cAMP (EPAC), but not protein kinase A, and was recapitulated by a constitutively active variant of the small GTPase Rap1. We provide evidence that cAMP and angiotensin-(1-7) act to suppress O-GlcNAcylation by inhibition of O-GlcNAc transferase (OGT) activity. In cells exposed to an O-GlcNAcase inhibitor or hyperglycemic culture conditions, mitochondrial superoxide levels were elevated; however, angiotensin-(1-7) signaling prevented the effect.

Conclusions

Angiotensin-(1-7) inhibits retinal protein O-GlcNAcylation via an EPAC/Rap1/OGT signaling axis.

Angiotensin-(1-7) contributes to insulin-sensitizing effects of angiotensin-converting enzyme inhibition in obese mice

Angiotensin-converting enzyme (ACE) inhibitors reduce body weight, lower blood pressure (BP), and improve insulin sensitivity in animal models of cardiometabolic syndrome. These effects are generally attributed to reduced angiotensin (ANG) II formation; however, these therapies also increase levels of ANG-(1-7), a beneficial hormone opposing ANG II actions. We hypothesized that this ANG-(1-7) generation contributes to the insulin-sensitizing effects of ACE inhibition in obese mice. Adult male C57BL/6J mice were placed on a 60% high-fat diet for 11 wk. During the last 3 wk of diet, mice received normal water or water containing the ACE inhibitor captopril (50 mg/l) as well as the ANG-(1-7) mas receptor antagonist A779 (400 or 800 ng·kg^-1·min^-1) or saline vehicle via subcutaneous osmotic minipumps. At the end of treatment, arterial BP was measured, and hyperinsulinemic-euglycemic clamps were performed in conscious obese mice receiving vehicle, captopril, captopril plus A779, or A779 ( n = 6-13/group). Captopril reduced body weight (28 ± 2 vs. 41 ± 2 g saline; P = 0.001), lowered systolic BP (109 ± 6 vs. 144 ± 7 mmHg saline; P = 0.041), and improved whole-body insulin sensitivity (steady-state glucose infusion rate: 31 ± 4 vs. 16 ± 2 mg·kg^-1·min^-1 saline; P = 0.001) in obese mice. A779 attenuated captopril-mediated improvements in insulin sensitivity (23 ± 2 mg·kg^-1·min^-1; P = 0.042), with no effect on body weight (32 ± 2 g; P = 0.441) or BP (111 ± 7 mmHg; P = 0.788). There was no effect of A779 alone on cardiometabolic outcomes. These data suggest that insulin-sensitizing effects of ACE inhibition are in part due to activation of ANG-(1-7)/ mas receptor pathways and provide new insight into mechanisms underlying the positive metabolic effects of these therapies.

The depressor axis of the renin–angiotensin system and brain disorders: a translational approach

All the components of the classic renin–angiotensin system (RAS) have been identified in the brain. Today, the RAS is considered to be composed mainly of two axes: the pressor axis, represented by angiotensin (Ang) II/angiotensin-converting enzyme/AT1 receptors, and the depressor and protective one, represented by Ang-(1–7)/ angiotensin-converting enzyme 2/Mas receptors. Although the RAS exerts a pivotal role on electrolyte homeostasis and blood pressure regulation, their components are also implicated in higher brain functions, including cognition, memory, anxiety and depression, and several neurological disorders. Overactivity of the pressor axis of the RAS has been implicated in stroke and several brain disorders, such as cognitive impairment, dementia, and Alzheimer or Parkinson’s disease. The present review is focused on the role of the protective axis of the RAS in brain disorders beyond its effects on blood pressure regulation. Furthermore, the use of drugs targeting centrally RAS and its beneficial effects on brain disorders are also discussed.

Renin angiotensin system deregulation as renal cancer risk factor

For numerous years, the non-cardiovascular role of the renin-angiotensin system (RAS) was underestimated, but recent studies have advanced the understanding of its function in various processes, including carcinogenesis. Numerous evidence comes from preclinical and clinical studies on the use of antihypertensive agents targeting the RAS, including angiotensin-converting enzyme inhibitors (ACEIs) and angiotensin receptor blockers. It has been demonstrated that the use of ACEIs can alter the incidence of renal cell carcinoma (RCC) and may have a positive effect by prolonging patient survival. It has an effect on the complex action of ACEI, resulting in decreased angiotensin II (Ang-II) production and altered levels of bradykinin or Ang 1-7. The present review discusses the existing knowledge on the effects of ACE and its inhibitors on RCC cell lines, xenograft models, and patient survival in clinical studies. A brief introduction to molecular pathways aids in understanding the non-cardiovascular effects of RAS inhibitors and enables the conduction of studies on combined cancer treatment with the application of ACEIs. Recent evidence regarding the treatment of hypertension associated with tyrosine kinase inhibitors, one of the most pronounced and common side effects in modern RCC treatment, are also outlined. Captopril, an ACEI, may be used to lower blood pressure in patients, particularly due to its additional renoprotective actions.

A Brief Introduction into the Renin-Angiotensin-Aldosterone System: New and Old Techniques

The renin-angiotensin-aldosterone system (RAAS) is a complex system of enzymes, receptors, and peptides that help to control blood pressure and fluid homeostasis. Techniques in studying the RAAS can be difficult due to such factors as peptide/enzyme stability and receptor localization. This paper gives a brief account of the different components of the RAAS and current methods in measuring each component. There is also a discussion of different methods in measuring stem and immune cells by flow cytometry, hypertension, atherosclerosis, oxidative stress, energy balance, and other RAAS-activated phenotypes. While studies on the RAAS have been performed for over 100 years, new techniques have allowed scientists to come up with new insights into this system. These techniques are detailed in this Methods in Molecular Biology Series and give students new to studying the RAAS the proper controls and technical details needed to perform each procedure.

Measurement of Angiotensin Peptides: HPLC-RIA

The renin-angiotensin system (RAS) is a complex circulating and tissue-based system. There are multiple pathways for the formation and degradation of peptides. In order to understand the functions of the system, characterization of angiotensin peptides (products and substrates) is important. Radioimmunoassays with the requisite specificity and sensitivity have been developed to allow for the characterization and quantification of circulating and tissue angiotensins. Here, we describe the appropriate methods for collecting the tissue and blood, the extractions steps required to partially purify and remove larger molecular weight-interfering proteins from tissue and plasma, and the radioimmunoassay of three of the peptides of this system (Ang I, Ang II, and Ang-(1-7)), as well as the verification of immunoreactive identity for Ang II and Ang-(1-7) by combined high-performance liquid chromatography-RIA analysis.

The role of Ang (1-7) in mediating the chronic hypotensive effects of losartan in normal rats

Hypothesis

The following studies were designed to test the hypothesis that Ang (1-7) contributes to the chronic hypotensive effects of the angiotensin II AT1-receptor antagonist, losartan, in normal rats.

Introduction

We have previously shown a chronic, hypotensive response to the AT1-receptor antagonist, losartan, in normotensive rats. The mechanism of this response is not completely understood. Previous studies by others have demonstrated a role for Ang (1-7) in the beneficial antihypertensive effects of angiotensin-converting enzyme (ACE) inhibition. This is thought to be due to vasodilatory effects of increased levels of Ang (1-7) during ACE inhibition. Since it has now been shown that Ang (1-7) levels are also increased during AT1 antagonism, we designed experiments to test the hypothesis above.

Materials and methods

Sprague-Dawley rats were instrumented with venous catheters and radiotelemetric pressure transducers and commenced on a normal (0.4%) NaCl diet. Arterial pressure responses were measured in rats treated with losartan (10 mg/kg/day) (LOS rats, n=8) and compared with those treated with losartan and the Ang (1-7) antagonist, A779 (24 µg/kg/hour) (A779/LOS rats, n=11) for 10 days.

Results

By day 7 of treatment, mean arterial pressure had dropped by 27±1 mmHg in LOS rats, in contrast with a decrease of only 21±2 mmHg in A779/LOS rats. This attenuated response in rats treated with A779 became more prominent and continued through day 10 of losartan treatment.

Conclusion

These results support the hypothesis that the chronic hypotensive effects of losartan in normal rats are mediated in part through the actions of Ang (1-7).

Anxiolytic- and antidepressant-like effects of angiotensin-(1–7) in hypertensive transgenic (mRen2)27 rats

Angiotensin-(1–7) [Ang-(1–7)], a counter-regulatory peptide of the renin–angiotensin system (RAS) exerts its effects through the G-protein-coupled receptor Mas, which is expressed in different tissues, including the brain. Ang-(1–7) has a broad range of effects beyond the well-described cardiovascular and renal actions, including the modulation of emotional and behavioural responses. In the present study we tested the hypothesis that Ang-(1–7) could attenuate the anxiety- and depression-like behaviours observed in transgenic hypertensive (mRen2)27 rats (TGRs). We also hypothesized that Ang-(1–7) could be involved in the anxiolytic-like effect induced by ACE (angiotensin-converting enzyme) treatment in these hypertensive rats. Therefore, TGRs and Sprague–Dawley rats were subjected to the Elevated Plus Maze (EPM) test, Forced Swimming Test (FST) and Novelty Suppressed Feeding (NSF). TGRs presented a decreased percentage of entries in the open arms of the EPM test, a phenotype reversed by systemic treatment with enalapril or intracerebroventricular infusion of Ang-(1–7). It is interesting that pre-treatment with A779, a selective Mas receptor antagonist, prevented the anxiolytic-like effect induced by the ACE inhibitor. In the NSF test, TGRs showed increased latency to eating, an indicative of a higher aversion in response to a new environment. These animals also showed increased immobility in the FST. Again, Ang-(1–7) reversed this phenotype. Thus, our data showed that Ang-(1–7) can modulate anxiety- and depression-like behaviours in TGRs and warrant further investigation as a new therapy for certain psychiatric disorders.

Vascular Actions of Angiotensin 1-7 in the Human Microcirculation: Novel Role for Telomerase

OBJECTIVE

This study examined vascular actions of angiotensin 1-7 (ANG 1-7) in human atrial and adipose arterioles.

APPROACH AND RESULTS

The endothelium-derived hyperpolarizing factor of flow-mediated dilation (FMD) switches from antiproliferative nitric oxide (NO) to proatherosclerotic hydrogen peroxide in arterioles from humans with coronary artery disease (CAD). Given the known vasoprotective properties of ANG 1-7, we tested the hypothesis that overnight ANG 1-7 treatment restores the NO component of FMD in arterioles from patients with CAD. Endothelial telomerase activity is essential for preserving the NO component of vasodilation in the human microcirculation; thus, we also tested whether telomerase activity was necessary for ANG 1-7-mediated vasoprotection by treating separate arterioles with ANG 1-7±the telomerase inhibitor 2-[[(2E)-3-(2-naphthalenyl)-1-oxo-2-butenyl1-yl]amino]benzoic acid. ANG 1-7 dilated arterioles from patients without CAD, whereas dilation was significantly reduced in arterioles from patients with CAD. In atrial arterioles from patients with CAD incubated with ANG 1-7 overnight, the NO synthase inhibitor NG-nitro-l-arginine methyl ester abolished FMD, whereas the hydrogen peroxide scavenger polyethylene glycol catalase had no effect. Conversely, in vessels incubated with ANG 1-7+2-[[(2E)-3-(2-naphthalenyl)-1-oxo-2-butenyl1-yl]amino]benzoic acid, NG-nitro-l-arginine methyl ester had no effect on FMD, but polyethylene glycol catalase abolished dilation. In cultured human coronary artery endothelial cells, ANG 1-7 significantly increased telomerase activity. These results indicate that ANG 1-7 dilates human microvessels, and dilation is abrogated in the presence of CAD. Furthermore, ANG 1-7 treatment is sufficient to restore the NO component of FMD in arterioles from patients with CAD in a telomerase-dependent manner.

CONCLUSIONS

ANG 1-7 exerts vasoprotection in the human microvasculature via modulation of telomerase activity.

Ang-(1-7) promotes the migration and invasion of human renal cell carcinoma cells via Mas-mediated AKT signaling pathway

Ang-(1-7) is an active peptide component of renin-angiotensin system and endogenous ligand for Mas receptor. In the current study, we showed that Ang-(1-7) enhanced migratory and invasive abilities of renal cell carcinoma cells 786-O and Caki-1 by wound-healing, transwell migration and transwell invasion assays. Mas antagonist A779 pretreatment or shRNA-mediated Mas knockdown abolished the stimulatory effect of Ang-(1-7). Furthermore, Ang-(1-7)-stimulated AKT activation was inhibited by either A779 pretreatment or Mas knockdown. Blockage of AKT signaling by AKT inhibitor VIII inhibited Ang-(1-7)-induced migration and invasion in 786-O cells. Taken together, our results provided the first evidence for the pro-metastatic role of Ang-(1-7) in RCC, which may help to better understand the molecular mechanism underlying the progression of this tumor.

Hemodynamic responses to angiotensin-(1-7) in women in their third trimester of pregnancy

BACKGROUND

To understand the role of Angiotensin-(1-7) (Ang-(1-7)) in vasculature of pregnant women, we compared cardiac output (CO), total peripheral resistance (TPR) and forearm blood flow (FBF) responses to Ang-(1-7) infusion between normotensive pregnant women in their third trimester and healthy age matched non-pregnant women. The responses of skin microcirculation to Ang-(1-7) were tested in preeclamptic, normotensive pregnant and non-pregnant women. Responses to Angiotensin II (Ang II) were also determined.

METHODS

Non-invasive methods for systemic (bioimpedance and VascuMAP), FBF (venous occlusion strain gauge plethysmography), and skin (laser Doppler) hemodynamics assessments were used.

RESULTS

Compared to non-pregnant women, systemic infusion of Ang-(1-7) (2000 pmol/min) resulted in a greater increase in CO (9.4 ± 6.4 versus -3.3 ± 2.1%, n = 9-10) in normotensive pregnant women. Brachial local infusion of Ang-(1-7) had no effect on FBF in either group. In non-pregnant and normotensive pregnant women, local Ang II induced a dose-dependent decrease in FBF and increase in forearm resistance at 50 and 100 pmol/min (p < 0.05 versus corresponding baseline, n = 7-10). Following iontophoretic application of 5 mmol/l dose of Ang-(1-7), the change in skin flow was higher in normotensive pregnant versus preeclamptic women (182.5 ± 93 versus 15.76 ± 19.46%, n = 14-15). Skin flow was lower in normotensive pregnant versus preeclamptic women (-46.5 ± 48.7 versus 108.7 ± 49.1%, n = 14-15) following Ang II infusion at 1.0 pmol/min.

CONCLUSION

In the third trimester of pregnancy, Ang-(1-7) induces alterations in CO and differentially regulates micro- and macro-circulations, depending on the dose. Dysregulation in skin vasculature may contribute to the development of vascular dysfunction and hypertension in preeclampsia.

Origin of the Y chromosome influences intrarenal vascular responsiveness to angiotensin I and angiotensin (1-7) in stroke-prone spontaneously hypertensive rats

The lineage of the Y chromosome accounts for up to 15 to 20 mm Hg in arterial pressure. Genes located on the Y chromosome from the spontaneously hypertensive rat (SHR) are associated with the renin-angiotensin system. Given the important role of the renin-angiotensin system in the renal regulation of fluid homeostasis and arterial pressure, we hypothesized that the origin of the Y chromosome influences arterial pressure via interaction between the intrarenal vasculature and the renin-angiotensin system. Sixteen-week-old normotensive rats (Wistar Kyoto [WKY]), spontaneously hypertensive stroke-prone rat (SHRSP), and 2 reciprocal Y consomic rat strains, 1 comprising the WKY autosomes and X chromosome with the Y chromosome from the hypertensive rat strain (WKY.SPGlaY) and vice versa (SP.WKYGlaY), were examined. SP.WKYGlaY had lower systolic blood pressure than SHRSP (195±5 versus 227±8 mm Hg; P<0.03), whereas WKY.SPGlaY had higher systolic blood pressure compared with WKY (157±3 versus 148±3 mm Hg; P<0.05), measured by radiotelemetry. Compared with WKY rats, SHRSP had higher plasma angiotensin(1-7) (Ang (1-7)):Ang II ratio (WKY: 0.13±0.01 versus SHRSP: 1.33±0.4; P<0.005), greater angiotensin II receptor type 2 and Mas receptor mRNA expression, and a blunted renal constrictor response to intrarenal Ang I and Ang(1-7) infusions. Introgression of the normotensive Y chromosome into the SHRSP background (SP.WKYGlaY) restored responses in the SHRSP to WKY levels, evidenced by a reduction in plasma Ang(1-7):Ang II ratio (SP.WKYGlaY: 0.24±0.02; P<0.01), angiotensin II receptor type 2, and Mas receptor mRNA expression and an increased vasoconstrictor response to intrarenal Ang I and Ang(1-7) infusion. This study demonstrates that the origin of the Y chromosome significantly impacts the renal vascular responsiveness and therefore may influence the long-term renal regulation of blood pressure.

Contribution of renin-angiotensin system to exercise-induced attenuation of aortic remodeling and improvement of endothelial function in spontaneously hypertensive rats

INTRODUCTION

It is well known that exercise alleviates aortic remodeling and preserves endothelial function in spontaneously hypertensive rats (SHRs). However, the underlying molecular mechanism remains unclear. This study aimed to investigate the role of renin-angiotensin system (RAS) components in exercise-induced attenuation of aortic remodeling and improvement of endothelial function in an animal model of human essential hypertension.

METHODS

The 10-week-old male SHR and age-matched normotensive Wistar-Kyoto rats were given moderate-intensity exercise for 12weeks (four groups, n=80-86 in each group).

RESULTS

In this work, exercise training reduced blood pressure and effectively attenuated aortic remodeling, marked by a reduction in aortic weight/length, wall thickness, and aortic levels of elastin and hydroxyproline, and improved endothelium-mediated vascular relaxations of aortas in response to acetylcholine. Exercise training in SHR reduced angiotensin II (AngII) levels and enhanced Ang-(1-7) levels in aortas. Exercise training in SHR suppressed aortic angiotensin-converting enzyme (ACE) and AngII type 1 receptor (AT1R) messenger RNA (mRNA) levels and protein expression and up-regulated ACE2, AngII type 2 receptor, and Mas mRNA levels and protein expression. In addition, exercise training in SHR increased levels of microRNA-27a (targeting ACE) and microRNA-155 (targeting AT1R) and decreased levels of microRNA-143 (targeting ACE2) in the aortas.

CONCLUSION

Chronic aerobic exercise training improved RAS balance in the aortas, which may in part explain the protective effect of exercise on aortic function and structure.

SUMMARY

Chronic aerobic exercise training improved RAS balance in the aortas, which may explain the protective effect of exercise on aortic function and structure, at least in part.

Angiotensin converting enzyme 2: a new important player in the regulation of glycemia

In spite of the novel antidiabetic drugs available on the market, type 2 diabetes mellitus (T2DM) affects nearly 25 million people in the USA and causes about 5% of all deaths globally each year. Given the rate and proportion by which T2DM is affecting human beings, it is indispensable to identify new therapeutic targets that can control the disease. Recent preclinical and clinical studies suggest that attenuating the activity of the renin-angiotensin system (RAS) could improve glycemia in diabetic patients. Angiotensin-converting enzyme 2 (ACE2) counteracts RAS overactivity by degrading angiotensin-II (Ang-II), a vasoconstrictor, to Ang-(1-7) which is a vasodilator. A decrease in ACE2 and an increase in A disintegrin and metalloproteinase (ADAM17)-mediated shedding activity have been observed with the progression of T2DM, suggesting the importance of this mechanism in the disease. Indeed, restoration of ACE2 improves glycemia in db/db and Ang-II-infused mice. The beneficial effects of ACE2 can be attributed to reduced oxidative stress and ADAM17 expression in the islets of Langerhans in addition to the improvement of blood flow to the β-cells. The advantage of ACE2 over other RAS blockers is that ACE2 not only counteracts the negative effects of Ang-II but also increases Ang-(1-7)/Mas receptor (MasR) [a receptor through which Ang-(1-7) produces its actions] signaling in the cells. Increased Ang-(1-7)/MasR signaling has been reported to improve insulin sensitivity and glycemia in diabetic animals. Altogether, ACE2/Ang-(1-7)/MasR axis of the RAS appears to be protective in T2DM and strategies to restore ACE2 levels in the disease seem to be a promising therapy for Ang-II-mediated T2DM.

Differential effect of low dose thiazides on the Renin Angiotensin system in genetically hypertensive and normotensive rats

Fifty years since their introduction, thiazide diuretics are established as first-line therapy in the treatment of hypertension. Because the dosing profile for thiazide agents lessened, the mechanism responsible for the blood pressure lowering effect may lie outside their diuretic properties. We evaluated the mechanism driving blood pressure reductions in spontaneously hypertensive rats (SHR) and normotensive WKY by examining the effects of low-dose hydrochlorothiazide (HCTZ) administration on renin-angiotensin system (RAS) components. The 7-day, 1.5 mg/kg/day HCTZ did not change systolic pressure in WKY, but decreased SBP by 41 +/- 2 mm Hg (p < 0.0001) in SHR. This reduction was independent of increases in water intake, urine output, or alterations in electrolyte excretion. HCTZ significantly increased the plasma concentrations of angiotensin I (Ang I) and angiotensin II (Ang II) in both WKY and SHR while reducing angiotensin converting enzyme (ACE) activity and the Ang II/Ang I ratio (17.1 +/- 2.9 before versus 10.3 +/- 2.9 after, p < 0.05) only in SHR. HCTZ increased cardiac ACE2 mRNA and activity, and neprilysin mRNA in WKY, but not SHR. Conversely in SHR, ACE2 activity was decreased and aside from a 75% increase in AT(1) mRNA in the HCTZ-treated SHR, the expression of the other variables remained unaltered. Measures of cardiac mas receptor mRNA showed no changes in response to treatment in both strains, although cardiac mas mRNA was significantly lower in untreated SHR. These data, which document for the first time the effect of low-dose thiazide on the activity of the ACE2/Ang-(1-7)/mas-receptor axis, suggest that the opposing arm of the system does not substantially contribute to the antihypertensive effect of low-dose thiazides in SHR.

The renin-angiotensin-aldosterone system in 2011: role in hypertension and chronic kidney disease

Over the past two decades, considerable advances have been made in our understanding of the renin-angiotensin-aldosterone system (RAAS) and its roles in various disease states. In this review, we will discuss the current state of knowledge of the many components of the RAAS, including new data on prorenin and its receptors, and important angiotensin fragments. The roles of these components of the RAAS in the pathogenesis of primary hypertension and the progression of chronic kidney disease (CKD) will also be highlighted. Given the new understanding of the many components and roles of the RAAS, it may be possible to develop improved therapies for hypertension and CKD.

Angiotensin-converting enzyme inhibition, but not AT(1) receptor blockade, in the solitary tract nucleus improves baroreflex sensitivity in anesthetized transgenic hypertensive (mRen2)27 rats

Transgenic hypertensive (mRen2)27 rats overexpress the murine Ren2 gene and have impaired baroreflex sensitivity (BRS) for control of the heart rate. Removal of endogenous angiotensin (Ang)-(1-7) tone using a receptor blocker does not further lower BRS. Therefore, we assessed whether blockade of Ang II with a receptor antagonist or combined reduction in Ang II and restoration of endogenous Ang-(1-7) levels with Ang-converting enzyme (ACE) inhibition will improve BRS in these animals. Bilateral solitary tract nucleus (nTS) microinjections of the AT(1) receptor blocker, candesartan (CAN, 24 pmol in 120 nl, n=9), or a peptidic ACE inhibitor, bradykinin (BK) potentiating nonapeptide (Pyr-Trp-Pro-Arg-Pro-Gln-Ile-Pro-Pro; BPP9α, 9 nmol in 60 nl, n=12), in anesthetized male (mRen2)27 rats (15-25 weeks of age) show that AT(1) receptor blockade had no significant effect on BRS, whereas microinjection of BPP9α improved BRS over 60-120 min. To determine whether Ang-(1-7) or BK contribute to the increase in BRS, separate experiments using the Ang-(1-7) receptor antagonist D-Ala(7)-Ang-(1-7) or the BK antagonist HOE-140 showed that only the Ang-(1-7) receptor blocker completely reversed the BRS improvement. Thus, acute AT(1) blockade is unable to reverse the effects of long-term Ang II overexpression on BRS, whereas ACE inhibition restores BRS over this same time frame. As the BPP9α potentiation of BK actions is a rapid phenomenon, the likely mechanism for the observed delayed increase in BRS is through ACE inhibition and elevation of endogenous Ang-(1-7).

Biosynthetic pathways and the role of the MAS receptor in the effects of Angiotensin-(1-7) in smooth muscles

Ang-(1–7) is produced via degradation of Ang II by the human angiotensin converting enzyme, also known as ACE2. In the cardiovascular system, Ang-(1–7) has been shown to produce effects that are opposite to those of Ang II. These include smooth muscle relaxation and cardioprotection. While the roles of Ang-(1–7) in other systems are currently topic of intense research, functional data suggest a relaxation action in gastrointestinal smooth muscles in a way that corroborates the results obtained from vascular tissues. However, more studies are necessary to determine a relevant role for Ang-(1–7) in the gastrointestinal system. The Ang-(1–7) actions are mediated by a distinct, functional, Ang-(1–7) receptor: the Mas receptor as shown by diverse studies involving site-specific binding techniques, selective antagonists, and targeted gene deletion. This paper provides an overview of the functional role and the molecular pathways involved in the biosynthesis and activity of Ang-(1–7) in diverse systems.

Swimming training improves the vasodilator effect of angiotensin-(1–7) in the aorta of spontaneously hypertensive rat

Introduction: endothelial dysfunction plays a critical role in the pathogenesis of hypertension. It is well established that physical training has beneficial effects on the cardiovascular system. We recently reported that angiotensin-(1–7) [Ang-(1–7)] concentration and the Mas receptor expression is increased in the left ventricle of trained spontaneous hypertensive rats (SHR). The vascular effects of Ang-(1–7) in trained animals remain so far unknown. In the present study we investigated the effects of physical training on the vasodilator effect of Ang-(1–7) in the aorta of SHR. Methodology: normotensive Wistar rats and SHR were subjected to an 8-wk period of 5% overload of body weight swimming training. Changes in isometric tension were recorded on myograph. Western blot was used to investigate Ang-(1–7) receptors expression. Results: in aortas from normotensive rats Ang-(1–7) and ACh induced a concentration-dependent vasodilator effect, which was not modified by the physical training. Vessels from SHR had an impaired vasodilator response to Ang-(1–7) and ACh. The swimming training strongly potentiated the vasodilator effect induced by Ang-(1–7) in SHR, but did not modify the effect of ACh. Interestingly, Mas receptor protein expression was substantially increased by physical training in SHR. In trained SHR, the vasodilator effect of Ang-(1–7) was abrogated by removal of the endothelium and by the selective Ang-(1–7) receptor antagonists A-779 and d-Pro7-Ang-(1–7). l-NAME decreased Ang-(1–7) vasodilator response and indomethacin abolished the remaining dilatory response. Conclusion: physical training increased Mas receptors expression in SHR aortas, thereby improving the vasodilator effect of Ang-(1–7) through an endothelium-dependent mechanism involving nitric oxide and prostacyclin.

Blood pressure and renal hemodynamic effects of angiotensin fragments

Angiotensin (Ang) II, the main effector peptide of the renin-Ang system, increases arterial blood pressure through Ang II type 1A (AT(1a)) receptor-dependent arterial vasoconstriction and by decreasing renal salt and water excretion through extrarenal and intrarenal mechanisms. AT(2) receptors are assumed to oppose these responses mediated by AT(1) receptors, thereby attenuating the pressor effects of Ang II. Nevertheless, a possible role of AT(2) receptors in the regulation of renal hemodynamics and sodium homeostasis remains to be unclear. Several other Ang fragments such as Ang III, Ang IV, Ang-(1-7) and Ang A have also been shown to display biological activity. In this review, we focus on the effects of these Ang on blood pressure, renal hemodynamics and sodium water handling, and discuss the receptors involved in these actions.

Altered cardiovascular reflexes responses in conscious Angiotensin-(1-7) receptor Mas-knockout mice

This study evaluated the physiological importance of Angiotensin-(1-7) receptor Mas on reflex control of circulation. Experiments were performed in male Mas-knockout (Mas-KO) and Wild Type (WT) conscious mice (12-20 wk of age). Baroreceptor reflex was evaluated by the bradycardic response induced by phenylephrine (0.25 μg/5 μl, i.v.). Bezold-Jarisch reflex was evaluated by phenylbiguanide (0.5 μg/5 μl, i.v.) and chemoreflex by potassium cyanide (2.5 μg/5 μl, i.v.). Baseline mean arterial pressure was higher in Mas-KO (n=14) as compared with WT mice (n=18) (118±1 mmHg vs. 109±2 mmHg); however, heart rate was similar in both strains (615±30 bpm vs. 648±13 bpm). Baroreflex bradycardia was lower (0.78±0.44 ms/mmHg vs. 1.30±0.14 ms/mmHg) in Mas-KO compared with WT mice. The depressor (-17±5 mmHg vs. -45±6 mmHg) and bradycardic (-212±36 bpm vs. -391±29 bpm) components of the Bezold-Jarisch reflex were also lower in Mas-KO mice. In addition, chemoreflex pressor response (+20±3 mmHg vs. +12±0.8 mmHg) and bradycardic response (-250±74 bpm vs. -52±26 bpm) were significantly higher in Mas-KO. These results further advances previous studies by showing that the lack of Mas receptor induced important imbalance in the neural control of blood pressure, altering not only the baroreflex but also the chemo- and Bezold-Jarisch reflexes.

The exenatide analogue AC3174 attenuates hypertension, insulin resistance, and renal dysfunction in Dahl salt-sensitive rats

Background

Activation of glucagon-like peptide-1 (GLP-1) receptors improves insulin sensitivity and induces vasodilatation and diuresis. AC3174 is a peptide analogue with pharmacologic properties similar to the GLP-1 receptor agonist, exenatide. Hypothetically, chronic AC3174 treatment could attenuate salt-induced hypertension, cardiac morbidity, insulin resistance, and renal dysfunction in Dahl salt-sensitive (DSS) rats.

Methods

DSS rats were fed low salt (LS, 0.3% NaCl) or high salt (HS, 8% NaCl) diets. HS rats were treated with vehicle, AC3174 (1.7 pmol/kg/min), or GLP-1 (25 pmol/kg/min) for 4 weeks via subcutaneous infusion. Other HS rats received captopril (150 mg/kg/day) or AC3174 plus captopril.

Results

HS rat survival was improved by all treatments except GLP-1. Systolic blood pressure (SBP) was lower in LS rats and in GLP-1, AC3174, captopril, or AC3174 plus captopril HS rats than in vehicle HS rats (p < 0.05). AC3174 plus captopril attenuated the deleterious effects of high salt on posterior wall thickness, LV mass, and the ratio of LV mass to body weight (P ≤ 0.05). In contrast, GLP-1 had no effect on these cardiovascular parameters. All treatments reduced LV wall stress. GLP-1, AC3174, captopril, or AC3174 plus captopril normalized fasting insulin and HOMA-IR (P ≤ 0.05). AC3174, captopril, or AC3174 plus captopril improved renal function (P ≤ 0.05). Renal morphology in HS rats was associated with extensive sclerosis. Monotherapy with AC3174, captopril, or GLP-1 attenuated renal damage. However, AC3174 plus captopril produced the most effective improvement.

Conclusions

Thus, AC3174 had antihypertensive, cardioprotective, insulin-sensitizing, and renoprotective effects in the DSS hypertensive rat model. Furthermore, AC3174 improved animal survival, an effect not observed with GLP-1.

ACE inhibition reduces infarction in normotensive but not hypertensive rats: correlation with cortical ACE activity

Angiotensin-converting enzyme (ACE) inhibition can reduce stroke risk by up to 43% in humans and reduce the associated disability, and hence understanding the mechanism of improvement is important. In animals and humans, these effects may be independent of the blood pressure-lowering effects of ACE inhibition. Normotensive (Wistar-Kyoto (WKY)) and hypertensive (spontaneously hypertensive rat (SHR)) animals were treated with the ACE inhibitors ramipril or lisinopril for 7 or 42 days before 2 hours of transient middle cerebral artery occlusion (MCAo). Blood pressure, serum ACE, and blood glucose levels were measured and stroke infarct volume was recorded 24 hours after stroke. Despite greater reductions in blood pressure, infarct size was not improved by ACE inhibition in hypertensive animals. Short-term ACE inhibition produced only a modest reduction in blood pressure, but WKY rats showed marked reductions in infarct volume. Long-term ACE inhibition had additional reductions in blood pressure; however, infarct volumes in WKY rats did not improve further but worsened. WKY rats differed from SHR in having marked cortical ACE activity that was highly sensitive to ACE inhibition. The beneficial effects of ACE inhibition on infarct volume in normotensive rats do not correlate with changes in blood pressure. However, WKY rats have ACE inhibitor-sensitive cortical ACE activity that is lacking in the SHR.

Vasoprotective and atheroprotective effects of angiotensin (1-7) in apolipoprotein E-deficient mice

OBJECTIVE

To evaluate the effectiveness of long-term angiotensin (Ang) (1-7) treatment to inhibit the progression of atherosclerosis in apolipoprotein E-deficient (ApoE(-/-)) mice.

METHODS AND RESULTS

Ang (1-7) is a heptapeptide fragment that has been proposed to counterregulate the Ang II proatherogenic effects. The effect of long-term 4-week Ang (1-7) treatment on both inhibition of atherosclerotic lesion development and improvement of endothelial function was examined in apolipoprotein E(-/-) mice that had been fed an atherogenic high-fat (21%) diet for 16 weeks. Chronic Ang (1-7) treatment significantly improved endothelial function, an effect reversed with either angiotensin type 2 (AT(2)) or Mas receptor blockade. In these vessels, Ang (1-7) treatment significantly decreased superoxide production and increased endothelial nitric oxide synthase immunoreactivity when compared with vehicle treatment. These effects were blocked by both AT(2) and Mas receptor antagonists. Lesion development, assessed as both fatty deposits (oil red O) and intima to media ratio, was also significantly decreased with Ang (1-7) treatment compared with respective controls. Cotreatment with either AT(2) or Mas receptor antagonists reversed Ang (1-7)-mediated reduction in lesion development.

CONCLUSIONS

Long-term Ang (1-7) treatment caused both vasoprotection, via improvement in endothelial function, and atheroprotection, with a reduction in lesion progression in a model of atherosclerosis. These effects appear to be mediated by the restoration of nitric oxide bioavailability and involve a complex interaction of both Mas and AT(2) receptors.

The ANG-(1-7)/ACE2/mas axis in the regulation of nephron function

The study of experimental hypertension and the development of drugs with selective inhibitory effects on the enzymes and receptors constituting the components of the circulating and tissue renin-angiotensin systems have led to newer concepts of how this system participates in both physiology and pathology. Over the last decade, a renewed emphasis on understanding the role of angiotensin-(1-7) and angiotensin-converting enzyme 2 in the regulation of blood pressure and renal function has shed new light on the complexity of the mechanisms by which these components of the renin angiotensin system act in the heart and in the kidneys to exert a negative regulatory influence on angiotensin converting enzyme and angiotensin II. The vasodepressor axis composed of angiotensin-(1-7)/angiotensin-converting enzyme 2/mas receptor emerges as a site for therapeutic interventions within the renin-angiotensin system. This review summarizes the evolving knowledge of the counterregulatory arm of the renin-angiotensin system in the control of nephron function and renal disease.

The mechanism of distinct diurnal variations of renin-angiotensin system in aorta and heart of spontaneously hypertensive rats

Diurnal variations in plasminogen activator inhibitor-1 mRNA expression are different between the spontaneously hypertensive rats (SHRs) and the Wistar-Kyoto (WKY) rats, and between the aorta and the heart. To elucidate the mechanisms, we examined diurnal changes in the circulating renin-angiotensin system in the SHR and WKY rats. Diurnal variations in plasma renin activity (PRA), plasma angiotensin I, and aldosterone concentrations were similar between the SHR and WKY rats. On the other hand, plasma angiotensin II (Ang II) concentration in the SHR was lower than that in the WKY rats at most time points, but increased to the level of the WKY rats in the late light phase. Treatment with AT1 receptor antagonist candesartan increased plasma Ang II concentration except at ZT 8 and lessened its diurnal variation in the SHR. At the peak in plasma Ang II in the SHR, Ang II regulated genes such as transforming growth factor-beta1 and p22phox were upregulated in the aorta. On the other hand, these genes were upregulated throughout the day in the heart of SHR. Candesartan treatment increased AT1a receptor mRNA expression in the heart but not in the aorta of SHR. These findings suggest that an AT1 receptor-mediated mechanism might cause a surge in plasma Ang II concentration at the late light phase in the SHR. Homologous down-regulation of AT1a receptor by Ang II may dampen the effect of a surge in plasma Ang II concentration in the heart of SHR.

Peptide hormone regulation of angiogenesis

It is now apparent that regulation of blood vessel growth contributes to the classical actions of hormones on development, growth, and reproduction. Endothelial cells are ideally positioned to respond to hormones, which act in concert with locally produced chemical mediators to regulate their growth, motility, function, and survival. Hormones affect angiogenesis either directly through actions on endothelial cells or indirectly by regulating proangiogenic factors like vascular endothelial growth factor. Importantly, the local microenvironment of endothelial cells can determine the outcome of hormone action on angiogenesis. Members of the growth hormone/prolactin/placental lactogen, the renin-angiotensin, and the kallikrein-kinin systems that exert stimulatory effects on angiogenesis can acquire antiangiogenic properties after undergoing proteolytic cleavage. In view of the opposing effects of hormonal fragments and precursor molecules, the regulation of the proteases responsible for specific protein cleavage represents an efficient mechanism for balancing angiogenesis. This review presents an overview of the actions on angiogenesis of the above-mentioned peptide hormonal families and addresses how specific proteolysis alters the final outcome of these actions in the context of health and disease.

Inhibitory effects of angiotensin-(1-7) on the nerve stimulation-induced release of norepinephrine and neuropeptide Y from the mesenteric arterial bed

Neuropeptide Y (NPY) is a cotransmitter with norepinephrine (NE) and ATP in sympathetic nerves. There is evidence for increased activity of the sympathetic nervous system and the renin-angiotensin system (RAS), as well as a role for NPY in the development of hypertension in experimental animal models and in humans. Angiotensin II (ANG II) is known to facilitate sympathetic neurotransmission, an effect greater in spontaneously hypertensive rats (SHR) than normotensive Wistar-Kyoto (WKY) rats. A newly discovered product of the RAS is angiotensin-(1-7) [ANG-(1-7)]. There is evidence suggesting that ANG-(1-7) opposes the actions of ANG II, resulting in hypotensive effects. The objective of this study was to investigate the role of ANG-(1-7) on the nerve-stimulated overflow of NE and NPY from the mesenteric arterial bed of SHR and the mechanisms involved in mediating any effects produced. ANG-(1-7) (0.001, 0.01, 0.1 microM) decreased nerve-stimulated NE and NPY overflow, as well as perfusion pressure in preparations obtained from SHR. This effect was greater in preparations of SHR than WKY controls. In addition, ANG-(1-7) decreased NE overflow to a greater extent than NPY overflow. Administration of the Mas receptor antagonist, D-Ala(7) ANG-(1-7), attenuated the decrease in both NE and NPY overflow due to ANG-(1-7) administration. However, the angiotensin type 2 receptor antagonist, PD-123391, attenuated the effect of ANG-(1-7) on NE overflow without affecting the decrease in NPY overflow. Moreover, in the presence of N(G)-nitro-L-arginine methyl ester, ANG-(1-7) decreased NPY overflow, but not NE overflow. ANG-(1-7) decreases the nerve-stimulated overflow of NE and NPY in preparations of SHR, whereas ANG II enhances it. Therefore, ANG-(1-7) may counteract the effects of ANG II by acting on ANG type 2 and Mas receptors.

Newer Insights into the Biochemical Physiology of the Renin–Angiotensin System: Role of Angiotensin-(1-7), Angiotensin Converting Enzyme 2, and Angiotensin-(1-12)

Knowledge of the mechanisms by which the rennin–angiotensin system contributes to cardiovascular pathology continues to advance at a rapid pace as newer methods and therapies uncover the nature of this complex system and its fundamental role in the regulation of blood pressure and tissue function. The characterization of the biochemical pathways and functions mediated by angiotensin-(1-7) [Ang-(1-7)], angiotensin converting enzyme 2 (ACE2), and the mas receptor has revealed a vasodepressor and antiproliferative axis that within the rennin–angiotensin system opposes the biological actions of angiotensin II (Ang II). In addition, new research expands on this knowledge by demonstrating additional mechanisms for the formation of Ang II and Ang-(1-7) through the existence of an alternate form of the angiotensinogen substrate [angiotensin-(1-12)] which generates Ang II and even Ang-(1-7) through a non-renin dependent action. Altogether, this research paves the way for a better understanding of the intracellular mechanisms involved in the synthesis of angiotensin peptides and its consequences in terms of cell function in both physiology and pathology.

The angiotensin-(1-7) receptor agonist AVE0991 is cardioprotective in diabetic rats

Angiotensin-(1-7) is associated with beneficial effects in cardiovascular diseases. In this study, we determined the effect of AVE0991, a nonpeptide angiotensin-(1-7) receptor agonist, on cardiac function in an animal model of diabetes mellitus type I. Diabetes was induced in Sprague-Dawley rats by a single injection of streptozotocin (70 mg/kg). Diabetic and non-diabetic animals were fed with AVE0991 (20 mg/kg per day) or control chow. Normoglycemic control chow- or AVE0991-fed rats served as controls (n=10/group). After five weeks, metabolic cage experiments were performed to assess metabolic parameters. Six weeks after induction of diabetes, cardiac function was monitored using a Millar-tip catheter system. AVE0991 had no effect on any of the investigated hemodynamic parameters under normoglycemic conditions. Hyperglycemia was comparable in diabetic animals with or without AVE0991 treatment. Diabetic control rats suffered from severe systolic dysfunction, indicated by a significant decrease in heart rate, left ventricular systolic pressure, systolic blood pressure and an impairment of left ventricular contractility. Administration of AVE0991 clearly rescued cardiac function under diabetic conditions as indicated by a normalisation of blood pressure and contractility parameters. Our data demonstrates a dominant beneficial impact of AVE0991 on the diabetic heart, implying a cardioprotective role for angiotensin-(1-7) under hyperglycemic conditions and thus pointing to new therapeutic strategies using angiotensin-(1-7) agonists to treat cardiovascular complications in diabetes mellitus.

Differential regulation of the renin-angiotensin system by nicotine in WKY and SHR glia

Given that (1) the renin-angiotensin system (RAS) is compartmentalized within the central nervous system in neurons and glia (2) the major source of brain angiotensinogen is the glial cells, (3) the importance of RAS in the central control of blood pressure, and (4) nicotine increases the probability of development of hypertension associated to genetic predisposition; the objective of the present study was to evaluate the effects of nicotine on the RAS in cultured glial cells from the brainstem and hypothalamus of Wistar Kyoto (WKY) and spontaneously hypertensive (SHR) rats. Ligand binding, real-time PCR and western blotting assays were used to compare the expression of angiotensinogen, angiotensin converting enzyme, angiotensin converting enzyme 2 and angiotensin II type1 receptors. We demonstrate, for the first time, that there are significant differences in the basal levels of RAS components between WKY and SHR rats in glia from 1-day-old rats. We also observed that nicotine is able to modulate the renin-angiotensin system in glial cells from the brainstem and hypothalamus and that the SHR responses were more pronounced than WKY ones. The present data suggest that nicotine effects on the RAS might collaborate to the development of neurogenic hypertension in SHR through modulation of glial cells.