An oral formulation of angiotensin-(1-7) produces cardioprotective effects in infarcted and isoproterenol-treated rats

Angiotensin 1-7 increases cardiac tolerance to ischemia/reperfusion and mitigates adverse remodeling of the heart-The signaling mechanism

BACKGROUND

The high mortality rate of patients with acute myocardial infarction (AMI) remains the most pressing issue of modern cardiology. Over the past 10 years, there has been no significant reduction in mortality among patients with AMI. It is quite obvious that there is an urgent need to develop fundamentally new drugs for the treatment of AMI. Angiotensin 1-7 has some promise in this regard.

OBJECTIVE

The objective of this article is analysis of published data on the cardioprotective properties of angiotensin 1-7.

METHODS

PubMed, Scopus, Science Direct, and Google Scholar were used to search articles for this study.

RESULTS

Angiotensin 1-7 increases cardiac tolerance to ischemia/reperfusion and mitigates adverse remodeling of the heart. Angiotensin 1-7 can prevent not only ischemic but also reperfusion cardiac injury. The activation of the Mas receptor plays a key role in these effects of angiotensin 1-7. Angiotensin 1-7 alleviates Ca2+ overload of cardiomyocytes and reactive oxygen species production in ischemia/reperfusion (I/R) of the myocardium. It is possible that both effects are involved in angiotensin 1-7-triggered cardiac tolerance to I/R. Furthermore, angiotensin 1-7 inhibits apoptosis of cardiomyocytes and stimulates autophagy of cells. There is also indirect evidence suggesting that angiotensin 1-7 inhibits ferroptosis in cardiomyocytes. Moreover, angiotensin 1-7 possesses anti-inflammatory properties, possibly achieved through NF-kB activity inhibition. Phosphoinositide 3-kinase, Akt, and NO synthase are involved in the infarct-reducing effect of angiotensin 1-7. However, the specific end-effector of the cardioprotective impact of angiotensin 1-7 remains unknown.

CONCLUSION

The molecular nature of the end-effector of the infarct-limiting effect of angiotensin 1-7 has not been elucidated. Perhaps, this end-effector is the sarcolemmal KATP channel or the mitochondrial KATP channel.

The Renin-Angiotensin System in Liver Disease

The renin-angiotensin system (RAS) is a complex homeostatic entity with multiorgan systemic and local effects. Traditionally, RAS works in conjunction with the kidney to control effective arterial circulation, systemic vascular resistance, and electrolyte balance. However, chronic hepatic injury and resulting splanchnic dilation may disrupt this delicate balance. The role of RAS in liver disease, however, is even more extensive, modulating hepatic fibrosis and portal hypertension. Recognition of an alternative RAS pathway in the past few decades has changed our understanding of RAS in liver disease, and the concept of opposing vs. "rebalanced" forces is an ongoing focus of research. Whether RAS inhibition is beneficial in patients with chronic liver disease appears to be context-dependent, but further study is needed to optimize clinical management and reduce organ-specific morbidity and mortality. This review presents the current understanding of RAS in liver disease, acknowledges areas of uncertainty, and describes potential areas of future investigation.

The Mas agonist CGEN-856S prevents Ang II induced cardiomyocyte hypertrophy via nitric oxide production

With the previous knowledge of the cardioprotective effects of the Angiotensin-(1-7) axis, a agonist of Mas receptor has been described, the CGEN-856S. This peptide is more stable than Ang-(1-7), and has a low binding affinity to Angiotensin II receptors. Although the cardioprotective effects of CGEN-856S were previously shown in vivo, the mechanisms behind its effects are still unknown. Here, we employed a combination of molecular biology, confocal microscopy, and genetically modified mouse with Mas deletion to investigate the CGEN-856S protective signaling in cardiomyocytes. In isolated adult ventricular myocytes, CGEN-856S induced an increase in nitric oxide (NO) production which was absent in cells from Mas knockout mice. Using western blot, we observed a significant increase in phosphorylation of AKT after treatment with CGEN-856S. In addition, CGEN-856S prevented the Ang II induced hypertrophy and the nuclear translocation of GRK5 in a culture model of rat neonatal cardiomyocytes. Blockage of Mas receptor and inhibition of the NO synthase abolished the effects of CGEN-856S on Ang II treated cardiomyocytes. In conclusion, we show that CGEN-856S acting via receptor Mas induces NO raise to block Ang II induced cardiomyocyte hypertrophy. These results indicate that CGEN-856S acts very similarly to Ang-(1-7) in cardiac myocytes, highlighting its therapeutic potential for treating cardiovascular diseases.

Effects of oral HPΒCD-angiotensin-(1-7) supplementation on recreational mountain bike athletes: a crossover study

BACKGROUND

Supplementation with Angiotensin-(1-7) [(Ang-1-7)] has received considerable attention due to its possible ergogenic effects on physical performance. The effects of a single dose of Ang-(1-7) on the performance of mountain bike (MTB) athletes during progressive load tests performed until the onset of voluntary fatigue have previously been demonstrated. This study tested the effects of Ang-(1-7) in two different exercise protocols with different metabolic demands: aerobic (time trial) and anaerobic (repeated sprint).

METHODS

Twenty one male recreational athletes were given capsules containing an oral formulation of HPβCD-Ang-(1-7) (0.8 mg) and HPβCD-placebo (only HPβCD) over a 7-day interval; a double-blind randomized crossover design was used. Physical performance was examined using two protocols: a 20-km cycling time trial or 4 × 30-s repeated all-out sprints on a leg cycle ergometer. Data were collected before and after physical tests to assess fatigue parameters, and included lactate levels, and muscle activation during the sprint protocol as evaluated by electromyography (EMG); cardiovascular parameters: diastolic and systolic blood pressure and heart rate; and performance parameters, time to complete (time trial), maximum power and mean power (repeated sprint).

RESULTS

Supplementation with an oral formulation of HPβCD-Ang-(1-7) reduced basal plasma lactate levels and promoted the maintenance of plasma glucose levels after repeated sprints. Supplementation with HPβCD-Ang-(1-7) also increased baseline plasma nitrite levels and reduced resting diastolic blood pressure in a time trial protocol. HPβCD-Ang-(1-7) had no effect on the time trial or repeat sprint performance, or on the EMG recordings of the vastus lateralis and vastus medialis.

CONCLUSIONS

Supplementation with HPβCD-Ang-(1-7) did not improve physical performance in time trial or in repeated sprints; however, it promoted the maintenance of plasma glucose and lactate levels after the sprint protocol and at rest, respectively. In addition, HPβCD-Ang-(1-7) also increased resting plasma nitrite levels and reduced diastolic blood pressure in the time trial protocol.

TRIAL REGISTRATION

RBR-2nbmpbc, registered January 6th, 2023. The study was prospectively registered.

Vascular smooth muscle cell-specific miRNA-214 deficiency alleviates simulated microgravity-induced vascular remodeling

The human cardiovascular system has evolved to accommodate the gravity of Earth. Microgravity during spaceflight has been shown to induce vascular remodeling, leading to a decline in vascular function. The underlying mechanisms are not yet fully understood. Our previous study demonstrated that miR-214 plays a critical role in angiotensin II-induced vascular remodeling by reducing the levels of Smad7 and increasing the phosphorylation of Smad3. However, its role in vascular remodeling evoked by microgravity is not yet known. This study aimed to determine the contribution of miR-214 to the regulation of microgravity-induced vascular remodeling. The results of our study revealed that miR-214 expression was increased in the forebody arteries of both mice and monkeys after simulated microgravity treatment. In vitro, rotation-simulated microgravity-induced VSMC migration, hypertrophy, fibrosis, and inflammation were repressed by miR-214 knockout (KO) in VSMCs. Additionally, miR-214 KO increased the level of Smad7 and decreased the phosphorylation of Smad3, leading to a decrease in downstream gene expression. Furthermore, miR-214 cKO protected against simulated microgravity induced the decline in aorta function and the increase in stiffness. Histological analysis showed that miR-214 cKO inhibited the increases in vascular medial thickness that occurred after simulated microgravity treatment. Altogether, these results demonstrate that miR-214 has potential as a therapeutic target for the treatment of vascular remodeling caused by simulated microgravity.

Rat Model of Isoproterenol-Induced Myocardial Injury

Isoproterenol (ISO) administration produces significant biochemical and histological changes including oxidative stress, reactive oxygen species (ROS) overproduction, and inflammation that leads to aggravation of myocardial injury. Subcutaneous or intraperitoneal ISO injection into rats can replicate several features of human heart disease, making it a useful tool for comprehending the underlying mechanisms and evaluating potential therapeutic strategies. In the present chapter, we elaborate on how depending on the precise experimental goals and the intended level of severity, different dosages and regimens are employed to induce myocardial injury.

Counter-regulatory renin-angiotensin system in hypertension: Review and update in the era of COVID-19 pandemic

Cardiovascular disease is the major cause of mortality and disability, with hypertension being the most prevalent risk factor. Excessive activation of the renin-angiotensin system (RAS) under pathological conditions, leading to vascular remodeling and inflammation, is closely related to cardiovascular dysfunction. The counter-regulatory axis of the RAS consists of angiotensin-converting enzyme 2 (ACE2), angiotensin (1-7), angiotensin (1-9), alamandine, proto-oncogene Mas receptor, angiotensin II type-2 receptor and Mas-related G protein-coupled receptor member D. Each of these components has been shown to counteract the effects of the overactivated RAS. In this review, we summarize the latest insights into the complexity and interplay of the counter-regulatory RAS axis in hypertension, highlight the pathophysiological functions of ACE2, a multifunctional molecule linking hypertension and COVID-19, and discuss the function and therapeutic potential of targeting this counter-regulatory RAS axis to prevent and treat hypertension in the context of the current COVID-19 pandemic.

Reshaping the Preterm Heart: Shifting Cardiac Renin-Angiotensin System Towards Cardioprotection in Rats Exposed to Neonatal High-Oxygen Stress

BACKGROUND

Approximately 10% of infants are born preterm. Preterm birth leads to short and long-term changes in cardiac shape and function. By using a rat model of neonatal high-oxygen (80%O₂) exposure, mimicking the premature hyperoxic transition to the extrauterine environment, we revealed a major role of the renin-angiotensin system peptide Angio II (angiotensin II) and its receptor AT1 (angiotensin receptor type 1) on neonatal O₂-induced cardiomyopathy. Here, we tested whether treatment with either orally active compounds of the peptides Angio-(1-7) or alamandine included in cyclodextrin could prevent postnatal cardiac remodeling and the programming of cardiomyopathy induced by neonatal high-O₂ exposure.

METHODS

Sprague-Dawley pups were exposed to room air or 80% O₂ from postnatal day 3 (P3) to P10. Neonatal rats were treated orally from P3 to P10 and assessed at P10 and P28. Left ventricular (LV) shapes were characterized by tridimensional computational atlases of ultrasound images in addition to histomorphometry.

RESULTS

At P10, high O₂-exposed rats presented a smaller, globular and hypertrophied LV shape versus controls. Treatment with cyclodextrin-Angio-(1-7) significantly improved LV function in the O₂-exposed neonatal rats and slightly changed LV shape. Cyclodextrin-alamandine and cyclodextrin-Angio-(1-7) treatments similarly reduced hypertrophy at P10 as well as LV remodeling and dysfunction at P28. Both treatments upregulated cardiac angiotensin-converting enzyme 2 in O₂-exposed rats at P10 and P28.

CONCLUSIONS

Our findings demonstrate LV remodeling changes induced by O₂-stress and the potential benefits of treatments targeting the cardioprotective renin-angiotensin system axis, supporting the neonatal period as an important window for interventions aiming at preventing cardiomyopathy in people born preterm.

Alamandine Induces Neuroprotection in Ischemic Stroke Models

Background and Objective:

Stroke, a leading cause of mortality and disability, characterized by neuronal death, can be induced by a reduction or interruption of blood flow. In this study, the role of Alamandine, a new peptide of the renin-angiotensin system, was evaluated in in-vitro and in-vivo brain ischemia models.

Method:

In the in-vitro model, hippocampal slices from male C57/Bl6 mice were placed in a glucose-free aCSF solution and bubbled with 95% N2 and 5% CO2 to mimic brain ischemia. An Alamandine concentration-response curve was generated to evaluate cell damage, glutamatergic excitotoxicity, and cell death. In the in-vivo model, cerebral ischemia/reperfusion was induced by bilateral occlusion of common carotid arteries (BCCAo-untreated) in SD rats. An intracerebroventricular injection of Alamandine was given 20–30 min before BCCAo. Animals were subjected to neurological tests 24 h and 72 h after BCCAo. Cytokine levels, oxidative stress markers, and immunofluorescence were assessed in the brain 72 h after BCCAo.

Results:

Alamandine was able to protect brain slices from cellular damage, excitotoxicity and cell death. When the Alamandine receptor was blocked, protective effects were lost. ICV injection of Alamandine attenuated neurological deficits of animals subjected to BCCAo and reduced the number of apoptotic neurons/cells. Furthermore, Alamandine induced anti-inflammatory effects in BCCAo animals as shown by reductions in TNFα, IL-1β, IL-6, and antioxidant effects through attenuation of the decreased SOD, catalase, and GSH activities in the brain.

Conclusion:

This study showed, for the first time, a neuroprotective role for Alamandine in different ischemic stroke models.

Pro-resolving therapies as potential adjunct treatment for infectious diseases: Evidence from studies with annexin A1 and angiotensin-(1-7)

Infectious diseases, once believed to be an eradicable public health threat, still represent a leading cause of death worldwide. Environmental and social changes continuously favor the emergence of new pathogens and rapid dissemination around the world. The limited availability of anti-viral therapies and increased antibiotic resistance has made the therapeutic management of infectious disease a major challenge. Inflammation is a primordial defense to protect the host against invading microorganisms. However, dysfunctional inflammatory responses contribute to disease severity and mortality during infections. In recent years, a few studies have examined the relevance of resolution of inflammation in the context of infections. Inflammation resolution is an active integrated process transduced by several pro-resolving mediators, including Annexin A1 and Angiotensin-(1-7). Here, we examine some of the cellular and molecular circuits triggered by pro-resolving molecules and that may be beneficial in the context of infectious diseases.

Research Progress on Pulmonary Arterial Hypertension and the Role of the Angiotensin Converting Enzyme 2-Angiotensin-(1-7)-Mas Axis in Pulmonary Arterial Hypertension

Pulmonary arterial hypertension (PAH) is a progressive disease with a complex aetiology and high mortality. Functional and structural changes in the small pulmonary arteries lead to elevated pulmonary arterial pressure, resulting in right heart failure. The pathobiology of PAH is not fully understood, and novel treatment targets in PAH are desperately needed. The renin-angiotensin system is critical for maintaining homeostasis of the cardiovascular system. The system consists of the angiotensin converting enzyme (ACE)-angiotensin (Ang) II-angiotensin type 1 receptor (AT₁R) axis and the ACE2-Ang-(1-7)-Mas receptor axis. The former, the ACE-Ang II-AT₁R axis, is involved in vasoconstrictive and hypertensive actions along with cardiac and vascular remodelling. The latter, the ACE2-Ang-(1-7)-Mas axis, generally mediates counterbalancing effects against those mediated by the ACE-Ang II-AT₁R axis. Based on established functions, the ACE2-Ang-(1-7)-Mas axis may represent a novel target for the treatment of PAH. This review focuses on recent advances in pulmonary circulation science and the role of the ACE2-Ang-(1-7)-Mas axis in PAH.

Oral Treatment with Angiotensin-(1-7) Attenuates the Kidney Injury Induced by Gentamicin in Wistar Rats

BACKGROUND

Acute Kidney Injury (AKI), a common disease of the urinary system, can be induced by high doses of gentamicin (GM). The Renin-Angiotensin System exerts a key role in the progression of the AKI since elevated intrarenal levels of Ang II, and ACE activity is found in this condition. However, it is unknown whether oral administration of Ang-(1-7), a heptapeptide that evokes opposite effects of Ang II, may attenuate the renal injuries induced by gentamicin.

OBJECTIVES

To evaluate the effects of Ang (1-7) on GM-induced renal dysfunction in rats.

METHODS

AKI was induced by subcutaneous administration of GM (80 mg/Kg) for 5 days. Simultaneously, Ang-(1-7) included in hydroxypropyl β-cyclodextrin (HPβCD) was administered by gavage [46 μg/kg HPβCD + 30 μg/kg Ang- (1-7)]. At the end of the treatment period (sixth day), the rats were housed in metabolic cages for renal function evaluation. Thereafter, blood and kidney samples were collected.

RESULTS

The Ang-(1-7) attenuated the increase of the plasmatic creatinine and proteinuria caused by GM but did not change the glomerular filtration rate nor tubular necrosis. Ang-(1-7) attenuated the increased urinary flow and the fractional excretion of H2O and potassium observed in GM rats but intensified the elevated excretion of sodium in these animals. Morphological analysis showed that Ang-(1-7) also reduced the tubular vacuolization in kidneys from GM rats.

CONCLUSION

Ang-(1-7) promotes selective beneficial effects in renal injuries induced by GM.

Crosstalk between the renin-angiotensin, complement and kallikrein-kinin systems in inflammation

During severe inflammatory and infectious diseases, various mediators modulate the equilibrium of vascular tone, inflammation, coagulation and thrombosis. This Review describes the interactive roles of the renin–angiotensin system, the complement system, and the closely linked kallikrein–kinin and contact systems in cell biological functions such as vascular tone and leakage, inflammation, chemotaxis, thrombosis and cell proliferation. Specific attention is given to the role of these systems in systemic inflammation in the vasculature and tissues during hereditary angioedema, cardiovascular and renal glomerular disease, vasculitides and COVID-19. Moreover, we discuss the therapeutic implications of these complex interactions, given that modulation of one system may affect the other systems, with beneficial or deleterious consequences.

The renin–angiotensin, complement and kallikrein–kinin systems comprise a multitude of mediators that modulate physiological responses during inflammatory and infectious diseases. This Review investigates the complex interactions between these systems and how these are dysregulated in various conditions, including cardiovascular diseases and COVID-19, as well as their therapeutic implications.

Vascular smooth muscle cell-specific miRNA-214 knockout inhibits angiotensin II-induced hypertension through upregulation of Smad7

Vascular remodeling is a prominent trait during the development of hypertension, attributable to the phenotypic transition of vascular smooth muscle cells (VSMCs). Increasing studies demonstrate that microRNA plays an important role in this process. Here, we surprisingly found that smooth muscle cell-specific miR-214 knockout (miR-214 cKO) significantly alleviates angiotensin II (Ang II)-induced hypertension, which has the same effect as that of miR-214 global knockout mice in response to Ang II stimulation. Under the treatment of Ang II, miR-214 cKO mice exhibit substantially reduced systolic blood pressure. The vascular medial thickness and area in miR-214 cKO blood vessels were obviously reduced, the expression of collagen I and proinflammatory factors were also inhibited. VSMC-specific deletion of miR-214 blunts the response of blood vessels to the stimulation of endothelium-dependent and -independent vasorelaxation and phenylephrine and 5-HT induced vasocontraction. In vitro, Ang II-induced VSMC proliferation, migration, contraction, hypertrophy, and stiffness were all repressed with miR-214 KO in VSMC. To further explore the mechanism of miR-214 in the regulation of the VSMC function, it is very interesting to find that the TGF-β signaling pathway is mostly enriched in miR-214 KO VSMC. Smad7, the potent negative regulator of the TGF-β/Smad pathway, is identified to be the target of miR-214 in VSMC. By which, miR-214 KO sharply enhances Smad7 levels and decreases the phosphorylation of Smad3, and accordingly alleviates the downstream gene expression. Further, Ang II-induced hypertension and vascular dysfunction were reversed by antagomir-214. These results indicate that miR-214 in VSMC established a crosstalk between Ang II-induced AT1R signaling and TGF-β induced TβRI /Smad signaling, by which it exerts a pivotal role in vascular remodeling and hypertension and imply that miR-214 has the potential as a therapeutic target for the treatment of hypertension.

Renin angiotensin aldosterone system in pulmonary fibrosis: Pathogenesis to therapeutic possibilities

Pulmonary fibrosis is a devastating lung disease with multifactorial etiology characterized by alveolar injury, fibroblast proliferation and excessive deposition of extracellular matrix proteins, which progressively results in respiratory failure and death. Accumulating evidence from experimental and clinical studies supports a central role of the renin angiotensin aldosterone system (RAAS) in the pathogenesis and progression of idiopathic pulmonary fibrosis. Angiotensin II (Ang II), a key vasoactive peptide of the RAAS mediates pro-inflammatory and pro-fibrotic effects on the lungs, adversely affecting organ function. Recent years have witnessed seminal discoveries in the field of RAAS. Identification of new enzymes, peptides and receptors has led to the development of several novel concepts. Of particular interest is the establishment of a protective axis of the RAAS comprising of Angiotensin converting enzyme 2 (ACE2), Angiotensin-(1-7) [Ang-(1-7)], and the Mas receptor (the ACE2/Ang-(1-7)/Mas axis), and the discovery of a functional role for the Angiotensin type 2 (AT₂) receptor. Herein, we will review our current understanding of the role of RAAS in lung fibrogenesis, provide evidence on the anti-fibrotic actions of the newly recognized RAAS components (the ACE2/Ang-(1-7)/Mas axis and AT₂ receptor), discuss potential strategies and translational efforts to convert this new knowledge into effective therapeutics for PF.

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.

Oral administration of angiotensin-(1-7) decreases muscle damage and prevents the fibrosis in rats after eccentric exercise

NEW FINDINGS

What is the central question of this study? Eccentric contraction exercises cause damage to muscle fibres and induce inflammatory responses. The exacerbation of this process can induce deposition of fibrous connective tissue, leading to decreased muscle function. The aim of this study was to examine the role of angiotensin-(1-7) in this context. What is the main finding and its importance? Our results show that oral treatment with angiotensin-(1-7) decreases muscle damage induced by eccentric exercise, reducing inflammation and fibrosis in the gastrocnemius and soleus muscles. This study shows a potential effect of angiotensin-(1-7) for the prevention of muscle injuries induced by physical exercise.

ABSTRACT

Eccentric contraction exercises cause damage to the muscle fibres and induce an inflammatory reaction. The protective effect of angiotensin-(1-7) [Ang-(1-7)] in skeletal muscle has led us to examine the role of this peptide in modifying processes associated with inflammation and fibrogenesis induced by eccentric exercise. In this study, we sought to investigate the effects of oral administration of Ang-(1-7) formulated in hydroxypropyl β-cyclodextrin (HPβ-CD) in prevention and treatment of muscle damage after downhill running. Male Wistar rats were divided into three groups: control (untreated and not exercised; n = 10); treated/exercised HPβ-CD Ang-(1-7) (n = 40); and treated/exercised HPβ-CD (n = 40). Exercised groups were subjected to a single eccentric contraction exercise session on a treadmill inclined to -13° at a constant speed of 20 m/min, for 60 min. Oral administration of HPβ-CD Ang-(1-7) and HPβ-CD was performed 3 h before the exercise protocol and daily as a single dose, until the end of the experiment. Samples were collected 4, 12, 24, 48 and 72 h after the exercise session. The animals treated with the Ang-(1-7) showed lower levels of creatine kinase, lower levels of tumor necrosis factor-α in soleus muscle and increased levels of interleukin-10 cytokines. The inflammatory cells and deposition of fibrous connective tissue in soleus and gastrocnemius muscles were lower in the group treated with Ang-(1-7). The results of this study show that treatment with an oral formulation of Ang-(1-7) enhances the process of repair of muscle injury induced by eccentric exercise.

SARS-CoV-2, Endothelial Dysfunction, and the Renin-Angiotensin System (RAS): A Potentially Dangerous Triad for the Development of Pre-Eclampsia

SARS-CoV-2 represents the greatest epidemiological, clinical, and social challenge the human being has had to face in this century. SARS-CoV-2 is not merely a respiratory virus, as its target cells range from upper airway respiratory cells to pulmonary cells but also and above all to the cardiovascular cells, such as pericytes and endothelial cells. Indeed, the pathology related to SARS-CoV-2, COVID-19, may be defined as a thromboinflammatory syndrome in its most severe form, characterized by sepsis-induced coagulopathy (SIC) and disseminated intravascular coagulopathy (DIC), which is prevalent in individuals already presenting a chronic level of inflammation (e.g., obese individuals, elderly) and hypertension. Pregnancy is not only an inflammatory-prone condition but is characterized by a consistent rearrangement of the blood circulation and coagulation profile. Cardiac output increases while arterial systolic and diastolic pressure decrease, regardless of the activation of the RAS system. ACE2, the SARS-CoV-2 entry receptor into the host cells, which transforms Ang II in Ang 1–7, is highly expressed in endothelial, smooth muscle cells and pericytes of placental villi, regulating blood pressure and fetal development. Pre-eclampsia is a pregnancy disorder characterized by hypertension and low levels of ACE2, endothelial dysfunction, and a high production of pro-inflammatory cytokines, resembling COVID-19 manifestations. Whereas pre-eclampsia and COVID-19 have overlapping clinical features, a role for SARS-CoV-2 as a leading cause of pre-eclampsia in COVID-19 positive pregnant women has not been clarified yet. In this mini-review, we will explore the possibility of the existence of such a link, focusing on the role of endothelial dysfunction and RAS in both pre-eclampsia and SARS-CoV-2-induced COVID-19 pathogenesis.

Angiotensin-(1-7) oral formulation improves physical performance in mountain bike athletes: a double-blinded crossover study

Background

The ECA2/Ang-(1–7)/Mas axis is shown to be involved in effects mediated by physical exercise, as it can induce the release of nitric oxide (ON) and bradykinin (BK), which are potent vasodilators. The vasodilating action the NO/BK can contribute to increased metabolic efficiency in muscle tissue and central nervous system. The formulation HPβ-CD-Ang-(1–7) through its mechanisms of action can be a promising supplement to aid in the maintenance and improvement of performance and may also favor recovery during competitions. The premise of this study was to investigate the effects of acute oral supplementation HPβ-CD-Ang-(1–7) on the performance of mountain bike (MTB) practitioners.

Methods

Fourteen recreational athletes, involved in training programs for at least one year, participated in this crossover design study. Subjects underwent two days of testing with a seven-day interval. HPβ-CD-Ang-(1–7) (1.75 mg) and HPβCD-Placebo were provided in capsules three hours prior to tests. To determine the safety of the HPβ-CD-Ang-(1–7) formulation associated with physical effort, cardiovascular parameters heart rate (HR) and blood pressure (BP) were analyzed. Physical performance was measured using maximal oxygen uptake (VO₂), total exercise time (TET), mechanical work (MW), mechanical efficiency (ME), and rating of perceived exertion (RPE). Respiratory exchange coefficient (REC), lactate and non-esterified fatty acids (NEFAs) were measured. Maximal incremental tests were performed on a progressively loaded leg cycle ergometer.

Results

There were no significant differences in terms of HR or BP at rest and maximum effort between the HPβ-CD-Ang-(1–7) and placebo groups. The VO₂max showed significant differences (p = 0.04). It was higher in the Ang-(1–7)condition (66.15 mlO₂.kg^− 1.min^− 1) compared to the placebo (60.72 mlO₂.kg^− 1.min^− 1). This was also observed for TET (Ang-(1–7) 39.10 min vs. placebo 38.14 min; p = 0.04), MW (Ang-(1–7) 156.7 vs. placebo 148.2; p = 0.04), and at the lowest RPE (Ang-(1–7) vs. placebo; p = 0.009). No significant differences were observed for REC, NEFAs, or Lactate.

Conclusions

These results suggest that HPβ-CD-Ang-(1–7) improves the physical performance of MTB recreational athletes and could be a promising supplement.

Trial registration

RBR-2 × 56pw8, registered January 15th, 2021. The study was prospectively registered.

Brain ACE2 activation following brain aminopeptidase A blockade by firibastat in salt-dependent hypertension

In the brain, aminopeptidase A (APA), a membrane-bound zinc metalloprotease, generates angiotensin III from angiotensin II. Brain angiotensin III exerts a tonic stimulatory effect on the control of blood pressure (BP) in hypertensive rats and increases vasopressin release. Blocking brain angiotensin III formation by the APA inhibitor prodrug RB150/firibastat normalizes arterial BP in hypertensive deoxycorticosterone acetate (DOCA)-salt rats without inducing angiotensin II accumulation. We therefore hypothesized that another metabolic pathway of brain angiotensin II, such as the conversion of angiotensin II into angiotensin 1-7 (Ang 1-7) by angiotensin-converting enzyme 2 (ACE2) might be activated following brain APA inhibition. We found that the intracerebroventricular (icv) administration of RB150/firibastat in conscious DOCA-salt rats both inhibited brain APA activity and induced an increase in brain ACE2 activity. Then, we showed that the decreases in BP and vasopressin release resulting from brain APA inhibition with RB150/firibastat were reduced if ACE2 was concomitantly inhibited by MLN4760, a potent ACE2 inhibitor, or if the Mas receptor (MasR) was blocked by A779, a MasR antagonist. Our findings suggest that in the brain, the increase in ACE2 activity resulting from APA inhibition by RB150/firibastat treatment, subsequently increasing Ang 1-7 and activating the MasR while blocking angiotensin III formation, contributes to the antihypertensive effect and the decrease in vasopressin release induced by RB150/firibastat. RB150/firibastat treatment constitutes an interesting therapeutic approach to improve BP control in hypertensive patients by inducing in the brain renin-angiotensin system, hyperactivity of the beneficial ACE2/Ang 1-7/MasR axis while decreasing that of the deleterious APA/Ang II/Ang III/ATI receptor axis.

Combination of Angiotensin (1-7) Agonists and Convalescent Plasma as a New Strategy to Overcome Angiotensin Converting Enzyme 2 (ACE2) Inhibition for the Treatment of COVID-19

Coronavirus disease-2019 (COVID-19) pandemic caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) is currently the most concerning health problem worldwide. SARS-CoV-2 infects cells by binding to angiotensin-converting enzyme 2 (ACE2). It is believed that the differential response to SARS-CoV-2 is correlated with the differential expression of ACE2. Several reports proposed the use of ACE2 pharmacological inhibitors and ACE2 antibodies to block viral entry. However, ACE2 inhibition is associated with lung and cardiovascular pathology and would probably increase the pathogenesis of COVID-19. Therefore, utilizing ACE2 soluble analogs to block viral entry while rescuing ACE2 activity has been proposed. Despite their protective effects, such analogs can form a circulating reservoir of the virus, thus accelerating its spread in the body. Levels of ACE2 are reduced following viral infection, possibly due to increased viral entry and lysis of ACE2 positive cells. Downregulation of ACE2/Ang (1-7) axis is associated with Ang II upregulation. Of note, while Ang (1-7) exerts protective effects on the lung and cardiovasculature, Ang II elicits pro-inflammatory and pro-fibrotic detrimental effects by binding to the angiotensin type 1 receptor (AT1R). Indeed, AT1R blockers (ARBs) can alleviate the harmful effects associated with Ang II upregulation while increasing ACE2 expression and thus the risk of viral infection. Therefore, Ang (1-7) agonists seem to be a better treatment option. Another approach is the transfusion of convalescent plasma from recovered patients with deteriorated symptoms. Indeed, this appears to be promising due to the neutralizing capacity of anti-COVID-19 antibodies. In light of these considerations, we encourage the adoption of Ang (1-7) agonists and convalescent plasma conjugated therapy for the treatment of COVID-19 patients. This therapeutic regimen is expected to be a safer choice since it possesses the proven ability to neutralize the virus while ensuring lung and cardiovascular protection through modulation of the inflammatory response.

Angiotensin (1-7) and Apelin co-therapy: New strategy for heart failure treatment of rats

Objective:

Isoproterenol (ISO)–induced heart failure is a standardized model for the study of beneficial effects of various drugs. Both apelin and angiotensin 1–7 have a cardiac protective effect. We assumed that co–therapy with apelin and angiotensin 1–7 [Ang (1–7)] may have synergistic cardioprotective effects against isoproterenol-induced heart failure.

Methods:

The rats were randomly assigned to one of eight groups, 7 animals in each, as follows: (1) Control I (saline; IP injection), (2) Control II (saline; via mini-osmotic pump), (3) ISO (5 mg/kg; IP), (4) Apelin (20 μg/kg; IP), (5) Ang (1–7) (30 μg/kg/day; via mini-osmotic pump), (6) Apelin+ISO, (7) Ang (1–7)+ISO, and (8) Apelin+Ang (1–7)+ISO. Rat myocardial injury was induced by intraperitoneal injection of 5 mg/kg of ISO for 10 days. Apelin and Ang (1–7) were administered 30 minutes before the ISO injection.

Results:

A decrease in the systolic blood pressure [SBP (p<0.001)], diastolic blood pressure [DBP (p=0.024)], left ventricular systolic pressure [LVSP (p<0.001)], left ventricular contractility [dP/dt max. (p<0.001)], relaxation [dP/dt min. (p<0.001)], and an increase in left ventricular end-diastolic pressure [LVEDP, (p<0.001)] were observed in ISO-treated rats. Plasma LDH and myocardial and plasma MDA were higher in the ISO heart than in controls (p<0.001). Histopathological examination of the cardiac tissue showed myocardial fibrosis and leukocyte infiltration in ISO-treated rats as compared to control. Co-therapy with apelin and Ang (1–7) was more effective than either agent used alone in restoring these parameters to that of control rats.

Conclusion:

The results of this study showed that the combination of apelin and Ang (1–7) had a more cardioprotective effect than either used alone against ISO-induced heart failure, and co–therapy may be a useful treatment option for myocardial injuries and heart failure.

Pathological cardiac remodeling seen by the eyes of proteomics

Cardiac remodeling involves cellular and structural changes that occur as consequence of multifactorial events to maintain the homeostasis. The progression of pathological cardiac remodeling involves a transition from adaptive to maladaptive changes that eventually leads to impairment of ventricular function and heart failure. In this scenario, proteins are key elements that orchestrate molecular events as increased expression of fetal genes, neurohormonal and second messengers' activation, contractile dysfunction, rearrangement of the extracellular matrix and alterations in heart geometry. Mass spectrometry based-proteomics has emerged as a sound method to study protein dysregulation and identification of cardiac diseases biomarkers in plasma. In this review, we summarize the main findings related to large-scale proteome modulation of cardiac cells and extracellular matrix occurred during pathological cardiac remodeling. We describe the recent proteomic progresses in the selection of protein targets and introduce the renin-angiotensin system as an interesting target for the treatment of pathological cardiac remodeling.

ACE2 and energy metabolism: the connection between COVID-19 and chronic metabolic disorders

The renin-angiotensin system (RAS) has currently attracted increasing attention due to its potential function in regulating energy homeostasis, other than the actions on cellular growth, blood pressure, fluid, and electrolyte balance. The existence of RAS is well established in metabolic organs, including pancreas, liver, skeletal muscle, and adipose tissue, where activation of angiotensin-converting enzyme (ACE) - angiotensin II pathway contributes to the impairment of insulin secretion, glucose transport, fat distribution, and adipokines production. However, the activation of angiotensin-converting enzyme 2 (ACE2) - angiotensin (1-7) pathway, a novel branch of the RAS, plays an opposite role in the ACE pathway, which could reverse these consequences by improving local microcirculation, inflammation, stress state, structure remolding, and insulin signaling pathway. In addition, new studies indicate the protective RAS arm possesses extraordinary ability to enhance brown adipose tissue (BAT) activity and induces browning of white adipose tissue, and consequently, it leads to increased energy expenditure in the form of heat instead of ATP synthesis. Interestingly, ACE2 is the receptor of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), which is threating public health worldwide. The main complications of SARS-CoV-2 infected death patients include many energy metabolism-related chronic diseases, such as diabetes. The specific mechanism leading to this phenomenon is largely unknown. Here, we summarize the latest pharmacological and genetic tools on regulating ACE/ACE2 balance and highlight the beneficial effects of the ACE2 pathway axis hyperactivity on glycolipid metabolism, as well as the thermogenic modulation.

Update on New Aspects of the Renin-Angiotensin System in Hepatic Fibrosis and Portal Hypertension: Implications for Novel Therapeutic Options

There is considerable experimental evidence that the renin angiotensin system (RAS) plays a central role in both hepatic fibrogenesis and portal hypertension. Angiotensin converting enzyme (ACE), a key enzyme of the classical RAS, converts angiotensin I (Ang I) to angiotensin II (Ang II), which acts via the Ang II type 1 receptor (AT1R) to stimulate hepatic fibrosis and increase intrahepatic vascular tone and portal pressure. Inhibitors of the classical RAS, drugs which are widely used in clinical practice in patients with hypertension, have been shown to inhibit liver fibrosis in animal models but their efficacy in human liver disease is yet to be tested in adequately powered clinical trials. Small trials in cirrhotic patients have demonstrated that these drugs may lower portal pressure but produce off-target complications such as systemic hypotension and renal failure. More recently, the alternate RAS, comprising its key enzyme, ACE2, the effector peptide angiotensin-(1–7) (Ang-(1–7)) which mediates its effects via the putative receptor Mas (MasR), has also been implicated in the pathogenesis of liver fibrosis and portal hypertension. This system is activated in both preclinical animal models and human chronic liver disease and it is now well established that the alternate RAS counter-regulates many of the deleterious effects of the ACE-dependent classical RAS. Work from our laboratory has demonstrated that liver-specific ACE2 overexpression reduces hepatic fibrosis and liver perfusion pressure without producing off-target effects. In addition, recent studies suggest that the blockers of the receptors of alternate RAS, such as the MasR and Mas related G protein-coupled receptor type-D (MrgD), increase splanchnic vascular resistance in cirrhotic animals, and thus drugs targeting the alternate RAS may be useful in the treatment of portal hypertension. This review outlines the role of the RAS in liver fibrosis and portal hypertension with a special emphasis on the possible new therapeutic approaches targeting the ACE2-driven alternate RAS.

Targeting the Protective Arm of the Renin-Angiotensin System: Focused on Angiotensin-(1-7)

The in vivo application and efficacy of many therapeutic peptides is limited because of their instability and proteolytic degradation. Novel strategies for developing therapeutic peptides with higher stability toward proteolytic degradation would be extremely valuable. Such approaches could improve systemic bioavailability and enhance therapeutic effects. The renin-angiotensin system (RAS) is a hormonal system within the body essential for the regulation of blood pressure and fluid balance. The RAS is composed of two opposing classic and protective arms. The balance between these two arms is critical for the homeostasis of the body's physiologic function. Activation of the RAS results in the suppression of its protective arm, which has been reported in inflammatory and pathologic conditions such as arthritis, cardiovascular diseases, diabetes, and cancer. Clinical application of angiotensin-(1-7) [Ang-(1-7)], a RAS critical regulatory peptide, augments the protective arm and restores balance hampered by its enzymatic and chemical instability. Several attempts to increase the half-life and efficacy of this heptapeptide using more stable analogs and different drug delivery approaches have been made. This review article provides an overview of efforts targeting the RAS protective arm. It provides a critical analysis of Ang-(1-7) or its homologs' novel drug delivery systems using different administration routes, their pharmacological characterization, and therapeutic potential in various clinical settings. SIGNIFICANCE STATEMENT: Ang-(1-7) is a unique peptide component of the renin-angiotensin system with vast potential for clinical applications that modulate various inflammatory diseases. Novel Ang-(1-7) peptide drug delivery could compensate its lack of stability for effective clinical application.

Association of ACE inhibitors and angiotensin type II blockers with ACE2 overexpression in COVID-19 comorbidities: A pathway-based analytical study

Severe Acute Respiratory Syndrome Corona Virus 2 (SARS-CoV-2) outbreak is a major public health concern, which has accounted for >1.7 million deaths across the world. A surge in the case fatality ratio as compared with the infection ratio has been observed in most of the countries. The novel Coronavirus SARS-CoV-2 shares the most common sequence with SARS-CoV, but it has a higher rate of transmission. The SARS-CoV-2 pathogenesis is initiated by the binding of viral spike protein with the target receptor Angiotensin-Converting Enzyme 2 (ACE2) facilitating virus internalization within host cells. SARS-CoV-2 mainly causes alveolar damage ranging from mild to severe clinical respiratory manifestations. Most of the cases have revealed the association of Coronavirus disease with patients having earlier comorbidities like Hypertension, Diabetes mellitus, and Cerebrovascular diseases. Pharmacological investigation of the SARS-Cov-2 patients has revealed the frequent use of drugs belongs to Angiotensin-converting enzyme inhibitors (ACEi) and/or Angiotensin II type I receptor blockers (ARBs). Interestingly, a significant increase in ACE2 expression was noticed in patients routinely treated with the above group of drugs were also reported. To date, the association of ACEi and/or ARBs with the up-regulation of ACE2 expression has not been defined distinctively. The proposed review will focus on the pathways which are responsible for the upregulation of ACE2 and its impact on gravity of SARS-CoV-2 disease.

Relevance of angiotensin-(1-7) and its receptor Mas in pneumonia caused by influenza virus and post-influenza pneumococcal infection

Resolution failure of exacerbated inflammation triggered by Influenza A virus (IAV) prevents return of pulmonary homeostasis and survival, especially when associated with secondary pneumococcal infection. Therapeutic strategies based on pro-resolving molecules have great potential against acute inflammatory diseases. Angiotensin-(1-7) [Ang-(1-7)] is a pro-resolving mediator that acts on its Mas receptor (MasR) to promote resolution of inflammation. We investigated the effects of Ang-(1-7) and the role of MasR in the context of primary IAV infection and secondary pneumococcal infection and evaluated pulmonary inflammation, virus titers and bacteria counts, and pulmonary damage. Therapeutic treatment with Ang-(1-7) decreased neutrophil recruitment, lung injury, viral load and morbidity after a primary IAV infection. Ang-(1-7) induced apoptosis of neutrophils and efferocytosis of these cells by alveolar macrophages, but had no direct effect on IAV replication in vitro. MasR-deficient (MasR-/-) mice were highly susceptible to IAV infection, displaying uncontrolled inflammation, increased viral load and greater lethality rate, as compared to WT animals. Ang-(1-7) was not protective in MasR-/- mice. Interestingly, Ang-(1-7) given during a sublethal dose of IAV infection greatly reduced morbidity associated with a subsequent S. pneumoniae infection, as seen by decrease in the magnitude of neutrophil influx, number of bacteria in the blood leading to a lower lethality. Altogether, these results show that Ang-(1-7) is highly protective against severe primary IAV infection and protects against secondary bacterial infection of the lung. These effects are MasR-dependent. Mediators of resolution of inflammation, such as Ang-(1-7), should be considered for the treatment of pulmonary viral infections.

ACE2: from protection of liver disease to propagation of COVID-19

Twenty years ago, the discovery of angiotensin-converting enzyme 2 (ACE2) was an important breakthrough dramatically enhancing our understanding of the renin-angiotensin system (RAS). The classical RAS is driven by its key enzyme ACE and is pivotal in the regulation of blood pressure and fluid homeostasis. More recently, it has been recognised that the protective RAS regulated by ACE2 counterbalances many of the deleterious effects of the classical RAS. Studies in murine models demonstrated that manipulating the protective RAS can dramatically alter many diseases including liver disease. Liver-specific overexpression of ACE2 in mice with liver fibrosis has proved to be highly effective in antagonising liver injury and fibrosis progression. Importantly, despite its highly protective role in disease pathogenesis, ACE2 is hijacked by SARS-CoV-2 as a cellular receptor to gain entry to alveolar epithelial cells, causing COVID-19, a severe respiratory disease in humans. COVID-19 is frequently life-threatening especially in elderly or people with other medical conditions. As an unprecedented number of COVID-19 patients have been affected globally, there is an urgent need to discover novel therapeutics targeting the interaction between the SARS-CoV-2 spike protein and ACE2. Understanding the role of ACE2 in physiology, pathobiology and as a cellular receptor for SARS-CoV-2 infection provides insight into potential new therapeutic strategies aiming to prevent SARS-CoV-2 infection related tissue injury. This review outlines the role of the RAS with a strong focus on ACE2-driven protective RAS in liver disease and provides therapeutic approaches to develop strategies to prevent SARS-CoV-2 infection in humans.

[6]-Gingerol Ameliorates ISO-Induced Myocardial Fibrosis by Reducing Oxidative Stress, Inflammation, and Apoptosis through Inhibition of TLR4/MAPKs/NF-κB Pathway

SCOPE

[6]-Gingerol is one of the primary pungent constituents of ginger. While [6]-gingerol has many pharmacological effects, its benefits for myocardial fibrosis, including its exact role and underlying mechanisms, remain largely unexplored. The present study is designed to characterize the cardio-protective effects of [6]-gingerol in myocardial fibrosis mice and possible underlying mechanisms.

METHODS AND RESULTS

Mice are subcutaneously injected with isoproterenol (ISO, 10 mg kg^-1 ) and gavaged with [6]-gingerol (10, 20 mg kg^-1 day^-1 ) for 14 days. Pathological alterations, fibrosis, oxidative stress, inflammation response, and apoptosis are examined. In ISO-induced myocardial fibrosis, [6]-gingerol treatment decreases the J-point, heart rate, cardiac weight index, left ventricle weight index, creatine kinase (CK), and lactate dehydrogenase serum levels, calcium concentration, reactive oxygen species, malondialdehyde, and glutathione disulfide (GSSG), and increases levels of superoxide dismutase, catalase, glutathione, and GSH/GSSG. Further, [6]-gingerol improved ISO-induced morphological pathologies, inhibited inflammation and apoptosis, and suppressed the toll-like receptor-4 (TLR4)/mitogen-activated protein kinases (MAPKs)/nuclear factor κB (NF-κB) signaling pathways.

CONCLUSION

The protective effect of [6]-gingerol in mice with ISO-induced myocardial fibrosis may be related to the inhibition of oxidative stress, inflammation, and apoptosis, potentially through the TLR4/MAPKs/NF-κB signaling pathway.

The Role of Angiotensin-(1-7)/Mas Axis and Angiotensin Type 2 Receptors in the Central Nervous System in Cardiovascular Disease and Therapeutics: A Riddle to be Solved

In recent years, the Angiotensin-(1-7)/Mas receptor [Ang-(1-7)/Mas] sub-branch of the Renin-Angiotensin System (RAS) in the brain, and Angiotensin Type 2 Receptors (AT2R), have attracted scientific interest, as there is evidence that they constitute an essential pathway in cardiovascular regulation, in health and in disease. By acting centrally, the Ang-(1-7)/Mas axis - that has been termed 'the axis of good'- can exert blood pressure-lowering effects, while also favourably altering baroreflex sensitivity and noradrenergic neurotransmission. Thus, research has focused on the possible neuro- and cardioprotective effects of this pathway in the setting of cardiovascular disease, ultimately aiming to evaluate the potential for development of novel therapeutic strategies based on its modulation. We summarize the available evidence from experimental studies in this context, aiming to assess current limits of scientific knowledge relevant to this newly-described 'player' in haemodynamic regulation, that may become a potential therapeutic target.

The Vasoactive Mas Receptor in Essential Hypertension

The renin–angiotensin–aldosterone system (RAAS) has been studied extensively, and with the inclusion of novel components, it has become evident that the system is much more complex than originally anticipated. According to current knowledge, there are two main axes of the RAAS, which counteract each other in terms of vascular control: The classical vasoconstrictive axis, renin/angiotensin-converting enzyme/angiotensin II/angiotensin II receptor type 1 (AT₁R), and the opposing vasorelaxant axis, angiotensin-converting enzyme 2/angiotensin-(1-7)/Mas receptor (MasR). An abnormal activity within the system constitutes a hallmark in hypertension, which is a global health problem that predisposes cardiovascular and renal morbidities. In particular, essential hypertension predominates in the hypertensive population of more than 1.3 billion humans worldwide, and yet, the pathophysiology behind this multifactorial condition needs clarification. While commonly applied pharmacological strategies target the classical axis of the RAAS, discovery of the vasoprotective effects of the opposing, vasorelaxant axis has presented encouraging experimental evidence for a new potential direction in RAAS-targeted therapy based on the G protein-coupled MasR. In addition, the endogenous MasR agonist angiotensin-(1-7), peptide analogues, and related molecules have become the subject of recent studies within this field. Nevertheless, the clinical potential of MasR remains unclear due to indications of physiological-biased activities of the RAAS and interacting signaling pathways.

Counter-regulatory renin-angiotensin system in cardiovascular disease

The renin-angiotensin system is an important component of the cardiovascular system. Mounting evidence suggests that the metabolic products of angiotensin I and II - initially thought to be biologically inactive - have key roles in cardiovascular physiology and pathophysiology. This non-canonical axis of the renin-angiotensin system consists of angiotensin 1-7, angiotensin 1-9, angiotensin-converting enzyme 2, the type 2 angiotensin II receptor (AT₂R), the proto-oncogene Mas receptor and the Mas-related G protein-coupled receptor member D. Each of these components has been shown to counteract the effects of the classical renin-angiotensin system. This counter-regulatory renin-angiotensin system has a central role in the pathogenesis and development of various cardiovascular diseases and, therefore, represents a potential therapeutic target. In this Review, we provide the latest insights into the complexity and interplay of the components of the non-canonical renin-angiotensin system, and discuss the function and therapeutic potential of targeting this system to treat cardiovascular disease.

Neuroprotection by post-stroke administration of an oral formulation of angiotensin-(1-7) in ischaemic stroke

NEW FINDINGS

What is the central question of this study? Angiotensin-(1-7) decreases cerebral infarct volume and improves neurological function when delivered centrally before and during ischaemic stroke. Here, we assessed the neuroprotective effects of angiotensin-(1-7) when delivered orally post-stroke. What is the main finding and its importance? We show that oral delivery of angiotensin-(1-7) attenuates cerebral damage induced by middle cerebral artery occlusion in rats, without affecting blood pressure or cerebral blood flow. Importantly, these treatments begin post-stroke at times coincident with the treatment window for tissue plasminogen activator, providing supporting evidence for clinical translation of this new therapeutic strategy.

ABSTRACT

As a target for stroke therapies, the angiotensin-converting enzyme 2-angiotensin-(1-7)-Mas [ACE2/Ang-(1-7)/Mas] axis of the renin-angiotensin system can be activated chronically to induce neuroprotective effects, in opposition to the deleterious effects of angiotensin II via its type 1 receptor. However, more clinically relevant treatment protocols with Ang-(1-7) that involve its systemic administration beginning after the onset of ischaemia have not been tested. In this study, we tested systemic post-stroke treatments using a molecule where Ang-(1-7) is included within hydroxypropyl-β-cyclodextrin [HPβCD-Ang-(1-7)] as an orally bioavailable treatment. In three separate protocols, HPβCD-Ang-(1-7) was administered orally to Sprague-Dawley rats after induction of ischaemic stroke by endothelin-1-induced middle cerebral artery occlusion: (i) to assess its effects on cerebral damage and behavioural deficits; (ii) to determine its effects on cardiovascular parameters; and (iii) to determine whether it altered cerebral blood flow. The results indicate that post-stroke oral administration of HPβCD-Ang-(1-7) resulted in 25% reductions in cerebral infarct volumes and improvement in neurological functions (P < 0.05), without inducing any alterations in blood pressure, heart rate or cerebral blood flow. In conclusion, Ang-(1-7) treatment using an oral formulation after the onset of ischaemia induces significant neuroprotection in stroke and might represent a viable approach for taking advantage of the protective ACE2/Ang-(1-7)/Mas axis in this disease.

Alamandine attenuates arterial remodelling induced by transverse aortic constriction in mice

Aims: The renin-angiotensin system (RAS) plays an important role in the pathophysiology of vascular diseases, especially as a mediator of inflammation and tissue remodelling. Alamandine (Ala¹-angiotensin-(1-7)) is a new biologically active peptide from the RAS, interacting with Mas-related G-protein-coupled receptor member D. Although a growing number of studies reveal the cardioprotective effects of alamandine, there is a paucity of data on its participation in vascular remodelling associated events. In the present study, we investigated the effects of alamandine on ascending aorta remodelling after transverse aortic constriction (TAC) in mice. Methods and results: C57BL/6J male mice were divided into the following groups: Sham (sham-operated), TAC (operated) and TAC+ALA (operated and treated with alamandine-HPβCD (2-Hydroxypropyl-β-cyclodextrin), 30 μg/kg/day, by gavage). Oral administration of alamandine for 14 days attenuated arterial remodelling by decreasing ascending aorta media layer thickness and the cells density in the adventitia induced by TAC. Alamandine administration attenuated ascending aorta fibrosis induced by TAC, through a reduction in the following parameters; total collagen deposition, expression collagen III and transforming growth factor-β (TGF-β) transcripts, matrix metalloproteinases (MMPs) activity and vascular expression of MMP-2. Importantly, alamandine decreased vascular expression of proinflammatory genes as CCL2, tumour necrosis factor α (TNF-α) and interleukin-1β (IL-1β), and was able to increase expression of MRC1 and FIZZ1, pro-resolution markers, after TAC surgery. Conclusion: Alamandine treatment attenuates vascular remodelling after TAC, at least in part, through anti-fibrotic and anti-inflammatory effects. Hence, this work opens new avenues for the use of this heptapeptide also as a therapeutic target for vascular disease.

The renin-angiotensin system: going beyond the classical paradigms

Thirty years ago, a novel axis of the renin-angiotensin system (RAS) was unveiled by the discovery of angiotensin-(1−7) [ANG-(1−7)] generation in vivo. Later, angiotensin-converting enzyme 2 (ACE2) was shown to be the main mediator of this reaction, and Mas was found to be the receptor for the heptapeptide. The functional analysis of this novel axis of the RAS that followed its discovery revealed numerous protective actions in particular for cardiovascular diseases. In parallel, similar protective actions were also described for one of the two receptors of ANG II, the ANG II type 2 receptor (AT₂R), in contrast to the other, the ANG II type 1 receptor (AT₁R), which mediates deleterious actions of this peptide, e.g., in the setting of cardiovascular disease. Very recently, another branch of the RAS was discovered, based on angiotensin peptides in which the amino-terminal aspartate was replaced by alanine, the alatensins. Ala-ANG-(1−7) or alamandine was shown to interact with Mas-related G protein-coupled receptor D, and the first functional data indicated that this peptide also exerts protective effects in the cardiovascular system. This review summarizes the presentations given at the International Union of Physiological Sciences Congress in Rio de Janeiro, Brazil, in 2017, during the symposium entitled “The Renin-Angiotensin System: Going Beyond the Classical Paradigms,” in which the signaling and physiological actions of ANG-(1−7), ACE2, AT₂R, and alatensins were reported (with a focus on noncentral nervous system-related tissues) and the therapeutic opportunities based on these findings were discussed.

Current therapies and novel approaches for biliary diseases

Chronic liver diseases that inevitably lead to hepatic fibrosis, cirrhosis and/or hepatocellular carcinoma have become a major cause of illness and death worldwide. Among them, cholangiopathies or cholestatic liver diseases comprise a large group of conditions in which injury is primarily focused on the biliary system. These include congenital diseases (such as biliary atresia and cystic fibrosis), acquired diseases (such as primary sclerosing cholangitis and primary biliary cirrhosis), and those that arise from secondary damage to the biliary tree from obstruction, cholangitis or ischaemia. These conditions are associated with a specific pattern of chronic liver injury centered on damaged bile ducts that drive the development of peribiliary fibrosis and, ultimately, biliary cirrhosis and liver failure. For most, there is no established medical therapy and, hence, these diseases remain one of the most important indications for liver transplantation. As a result, there is a major need to develop new therapies that can prevent the development of chronic biliary injury and fibrosis. This mini-review briefly discusses the pathophysiology of liver fibrosis and its progression to cirrhosis. We make a special emphasis on biliary fibrosis and current therapeutic options, such as angiotensin converting enzyme-2 (known as ACE2) over-expression in the diseased liver as a novel potential therapy to treat this condition.

Modulation of leucocytic angiotensin-converting enzymes expression in patients maintained on high-permeable haemodialysis

Background

High mortality of haemodialysis patients is associated with systemic chronic inflammation and overactivation of the renin-angiotensin system (RAS). Insufficient elimination of pro-inflammatory immune mediators, especially in the molecular weight range of 15-45 kDa, may be one of the reasons for this. Employment of haemodialysis membranes with increased permeability was shown to ameliorate the inflammatory response and might modulate the effects of local RAS. In this study, we tested the impact of high cut-off (HCO), medium cut-off (MCO) and high-flux (HF) dialysis on leucocytic transcripts of angiotensin-converting enzymes (ACE and ACE2). Additionally, the impact of HCO, MCO and HF sera and dialysates on local ACEs and inflammation markers was tested in THP-1 monocytes.

Methods

Patients' leucocytes were obtained from our recent clinical studies comparing HCO and MCO dialysers with HF. The cells were subjected to quantitaive polymerase chain reaction (qPCR) analyses with TaqMan probes specific for ACE, ACE2 and angiotensin II (AngII) and Ang1-7 receptors. Sera and dialysates from the clinical trials as well as samples from in vitro dialysis were tested on THP-1 monocytic cells. The cells were subjected to qPCR analyses with TaqMan probes specific for ACE, ACE2, interleukin-6 and tumour necrosis factor α and immunocytochemistry with ACE and ACE2 antibodies.

Results

Leucocytes obtained from patients treated with HCO or MCO demonstrated decreased transcript expression of ACE, while ACE2 was significantly upregulated as compared with HF. Receptors for AngII and Ang1-7 remained unchanged. THP-1 monocytes preconditioned with HCO and MCO patients' or in vitro dialysis sera reflected the same expressional regulation of ACE and ACE2 as those observed in HCO and MCO leucocytes. As a complementary finding, treatment with HCO and MCO in vitro dialysates induced a pro-inflammatory response of the cells as demonstrated by elevated messenger RNA expression of tumour necrosis factor α and interleukin-6, as well as upregulation of ACE and decreased levels of ACE2.

Conclusions

Taken together, these data demonstrate that employment of membranes with high permeability eliminates a spectrum of mediators from circulation that affect the RAS components in leucocytes, especially ACE/ACE2.

Beneficial Effects of Angiotensin-(1-7) on CD34+ Cells From Patients With Heart Failure

The dysfunctional nature of CD34 cells from patients with heart failure (HF) may make them unsuitable for autologous stem-cell therapy. In view of evidence that the vasoprotective axis of the renin-angiotensin system (RAS) improves CD34 cell functions, we hypothesized that CD34 cells from patients with HF will be dysfunctional and that angiotensin-(1-7) [Ang-(1-7)] would improve their function. Peripheral blood was collected from New York Heart Association class II-IV patients with HF (n = 31) and reference subjects (n = 16). CD34 cell numbers from patients with HF were reduced by 47% (P < 0.05) and also displayed 76% reduction in migratory capacity and 56% (P < 0.05) lower production of nitric oxide. These alterations were associated with increases in RAS genes angiotensin-converting enzyme and AT2R (595%, P < 0.05) mRNA levels and 80% and 85% decreases in angiotensin-converting enzyme 2 and Mas mRNA levels, respectively. Treatment with Ang-(1-7) enhanced CD34 cell function through increased migratory potential and nitric oxide production, and reduced reactive oxygen species generation. These data show that HF CD34 cells are dysfunctional, and Ang-(1-7) improves their functions. This suggests that activation of the vasoprotective axis of the RAS may hold therapeutic potential for autologous stem-cell therapy in patients with HF.

Angiotensin-(1-7) Promotes Resolution of Eosinophilic Inflammation in an Experimental Model of Asthma

Defective apoptosis of eosinophils, the main leukocyte in the pathogenesis of asthma, and delay in its removal lead to lung damage and loss of pulmonary function due to failure in the resolution of inflammation. Here, we investigated the ability of angiotensin-(1-7) [Ang-(1-7)], a pivotal peptide of the renin-angiotensin system, to promote resolution of an allergic lung inflammatory response. Balb/c mice were sensitized and challenged with ovalbumin and treated with Ang-(1-7) at the peak of the inflammatory process. Bronchoalveolar lavage (BAL) fluid and lungs were collected 24 h after treatment. Different lung lobes were processed for histology to evaluate inflammatory cell infiltration, airway and pulmonary remodeling, total collagen staining, and measurements of (i) collagen I and III mRNA expression by qRT-PCR; (ii) ERK1/2, IκB-α, and GATA3 protein levels by Western blotting; and (iii) eosinophilic peroxidase activity. Total number of inflammatory cells, proportion of apoptotic eosinophils and immunofluorescence for caspase 3 and NF-κB in leukocytes were evaluated in the BAL. Mas receptor immunostaining was evaluated in mouse and human eosinophils. Engulfment of human polimorphonuclear cells by macrophages, efferocytosis, was evaluated in vivo. Ang-(1-7) reduced eosinophils in the lung and in the BAL, increased the number of apoptotic eosinophils, shown by histology criteria and by increase in caspase 3 immunostaining. Furthermore, Ang-(1-7) decreased NF-kB immunostaining in eosinophils, reduced GATA3, ERK1/2, and IκB-α expression in the lung and decreased pulmonary remodeling and collagen deposition. Importantly, Ang-(1-7) increased efferocytosis. Our results demonstrate, for the first time, Ang-(1-7) activates events that are crucial for resolution of the inflammatory process of asthma and promotion of the return of lung homeostasis, indicating Ang-(1-7) as novel endogenous inflammation-resolving mediator.

The ACE2/Angiotensin-(1-7)/MAS Axis of the Renin-Angiotensin System: Focus on Angiotensin-(1-7)

The renin-angiotensin system (RAS) is a key player in the control of the cardiovascular system and hydroelectrolyte balance, with an influence on organs and functions throughout the body. The classical view of this system saw it as a sequence of many enzymatic steps that culminate in the production of a single biologically active metabolite, the octapeptide angiotensin (ANG) II, by the angiotensin converting enzyme (ACE). The past two decades have revealed new functions for some of the intermediate products, beyond their roles as substrates along the classical route. They may be processed in alternative ways by enzymes such as the ACE homolog ACE2. One effect is to establish a second axis through ACE2/ANG-(1-7)/MAS, whose end point is the metabolite ANG-(1-7). ACE2 and other enzymes can form ANG-(1-7) directly or indirectly from either the decapeptide ANG I or from ANG II. In many cases, this second axis appears to counteract or modulate the effects of the classical axis. ANG-(1-7) itself acts on the receptor MAS to influence a range of mechanisms in the heart, kidney, brain, and other tissues. This review highlights the current knowledge about the roles of ANG-(1-7) in physiology and disease, with particular emphasis on the brain.

Angiotensin-(1-7) Promotes Resolution of Neutrophilic Inflammation in a Model of Antigen-Induced Arthritis in Mice

Defective resolution of inflammation may be crucial for the initiation and development of chronic inflammatory diseases, such as arthritis. Therefore, it has been suggested that therapeutic strategies based on molecules that facilitate inflammation resolution present great potential for the treatment of chronic inflammatory diseases. In this study, we investigated the effects and role of angiotensin-(1-7) [Ang-(1-7)] in driving resolution of neutrophilic inflammation in a model of arthritis. For this purpose, male C57BL/6 mice were subjected to antigen-induced arthritis and treated with Ang-(1-7) at the peak of the inflammatory process. Analysis of the number of inflammatory cells, apoptosis, and immunofluorescence for NF-κB was performed in the exudate collected from the knee cavity. Neutrophil accumulation in periarticular tissue was measured by assaying myeloperoxidase activity. Apoptosis of human neutrophil after treatment with Ang-(1-7) was evaluated morphologically and by flow cytometry, and NF-κB phosphorylation by immunofluorescence. Efferocytosis was evaluated in vivo. Therapeutic treatment with Ang-(1-7) at the peak of inflammation promoted resolution, an effect associated with caspase-dependent neutrophils apoptosis and NF-κB inhibition. Importantly, Ang-(1-7) was also able to induce apoptosis of human neutrophils, an effect associated with NF-κB inhibition. The pro-resolving effects of Ang-(1-7) were inhibited by the Mas receptor antagonist A779. Finally, we showed that Ang-(1-7) increased the efferocytic ability of murine macrophages. Our results clearly demonstrate that Ang-(1-7) resolves neutrophilic inflammation in vivo acting in two key step of resolution: apoptosis of neutrophils and their removal by efferocytosis. Ang-(1-7) is a novel mediator of resolution of inflammation.

Angiotensin-(1-7) protects cardiomyocytes against high glucose-induced injuries through inhibiting reactive oxygen species-activated leptin-p38 mitogen-activated protein kinase/extracellular signal-regulated protein kinase 1/2 pathways, but not the leptin-c-Jun N-terminal kinase pathway in vitro

Aims/Introduction

Angiotensin‐(1–7) (Ang‐[1–7]), recognized as a new bioactive peptide in the renin–angiotensin system, shows biological and pharmacological properties in diabetic cardiovascular diseases. The leptin‐induced p38 mitogen‐activated protein kinase (MAPK) pathway has been reported to contribute to high glucose (HG)‐induced injury. In the present study, we showed the mechanism of how Ang‐(1–7) can protect against HG‐stimulated injuries in H9c2 cells.

Materials and Methods

H9c2 cells were treated with 35 mmol/L glucose (HG) for 24 h to establish a model of HG‐induced damage. Apoptotic cells were observed by Hoechst 33258 staining. Cell viability was analyzed by cell counter kit‐8. The expression of protein was detected by western blot. Reactive oxygen species was tested by 2′,7′‐dichlorodihydrofluorescein diacetate staining. Mitochondrial membrane potential was measured by 5,5′,6,6′‐Tetrachloro‐1,1′,3,3′‐tetraethyl‐imidacarbocyanine iodide staining.

Results

The present results showed that treating H9c2 cells with HG obviously enhanced the expressions of both the leptin and phosphorylated (p)‐MAPK pathway. However, the overexpression levels of leptin and p‐p38 MAPK/p‐extracellular signal‐regulated protein kinase 1/2 (ERK1/2), but not p‐c‐Jun N‐terminal kinase, were significantly suppressed by treatment of the cells with Ang‐(1–7). Additionally, leptin antagonist also markedly suppressed the overexpressions of p38 and ERK1/2 induced by HG, whereas leptin antagonist had no influence on the overexpression of c‐Jun N‐terminal kinase. More remarkable, Ang‐(1–7), leptin antagonist, SB203580 or SP600125, respectively, significantly inhibited the injuries induced by HG, such as the increased cell viability, decreased apoptotic rate, reduction of ROS production and increased mitochondrial membrane potential. Furthermore, the overexpressions of p38 MAPK, ERK1/2 and leptin were suppressed by N‐actyl‐L‐cystine.

Conclusions

The present findings show that Ang‐(1–7) protects from HG‐stimulated damage as an inhibitor of the reactive oxygen species–leptin–p38 MAPK/ERK1/2 pathways, but not the leptin–c‐Jun N‐terminal kinase pathway in vitro.

Cellular basis of angiotensin-(1-7)-induced augmentation of left ventricular functional performance in heart failure

BACKGROUND

Angiotensin-(1-7) [Ang-(1-7)] exhibits cardiovascular effects opposite those of angiotensin II (Ang II), thus providing protection against heart disease. However, how Ang-(1-7) imparts cardioprotection is unclear, and its direct cardiac effects are controversial. Whether heart failure (HF) alters cardiac contractile responses to Ang-(1-7) remains undetermined. We tested the hypothesis that in HF, Ang-(1-7) may produce positive modulation on [Ca²⁺]_i regulation, enhancing left ventricular (LV) and myocyte contraction and relaxation via Ang-(1-7) Mas receptor coupled with nitric oxide (NO)/bradykinin (BK)-mediated mechanism.

METHODS AND RESULTS

We measured LV contractility changes after Ang-(1-7) (650ng/kg, iv) and compared myocyte functional and [Ca²⁺]_i transient ([Ca²⁺]_iT) responses to Ang-(1-7) superfusion in 24 normal rats and 34 rats with isoproterenol-induced HF (3months after 170mg/kg, s.q. for 2days). To assess the mechanisms of altered HF responses to Ang-(1-7), subsets of HF myocytes were pretreated to inhibit NO synthase (L-NAME), BK (HOE-140), and Mas receptor (A-779) followed with Ang-(1-7). In normal rats, Ang-(1-7) produced no significant changes in LV and myocyte function. In HF rats, Ang-(1-7) significantly augmented LV contractility and relaxation with increased E_ES (51%), but decreased τ compared to baseline. Ang-(1-7) also significantly increased myocyte contraction (dL/dt_max, 30%), relaxation (dR/dt_max, 41%), and [Ca²⁺]_iT. L-NAME increased, HOE-140 decreased, and A-779 prevented HF myocyte contractile responses to Ang-(1-7).

CONCLUSIONS

In a rat model of HF, Ang-(1-7) increases [Ca²⁺]_iT, and produces positive inotropic and lusitropic effects in the LV and myocytes. These effects are mediated by the Mas receptor and involve activation of NO/BK pathways.

Chronic allergic pulmonary inflammation is aggravated in angiotensin-(1-7) Mas receptor knockout mice

The angiotensin-(1-7) [ANG-(1-7)]/Mas receptor pathway is currently recognized as a counterbalancing mechanism of the renin-angiotensin system in different pathophysiological conditions. We have previously described that treatment with ANG-(1-7) attenuates lung inflammation and remodeling in an experimental model of asthma. In the present study, we investigated whether lack of the Mas receptor could alter the inflammatory response in a model of chronic allergic lung inflammation induced by ovalbumin (OVA). Mas receptor wild-type (MasWT) and knockout (MasKO) mice were subjected to four doses of OVA (20 μg/mice ip) with a 14-day interval. At the 21st day, nebulization with OVA (1%) was started, three times per week until the 46th day. Control groups received saline (0.9% ip) and were nebulized with saline (0.9%). MasWT-OVA developed a modest inflammatory response and minor pulmonary remodeling to OVA challenge. Strikingly, MasKO-OVA presented a significant increase in inflammatory cell infiltrate, increase in extracellular matrix deposition, increase in thickening of the alveolar parenchyma, increase in thickening of the smooth muscle layer of the pulmonary arterioles, increase in proinflammatory cytokine and chemokine levels in the lungs, characteristic of chronic asthma. Additionally, MasKO-OVA presented an increase in ERK1/2 phosphorylation compared with MasWT-OVA. Furthermore, MasKO-OVA showed a worse performance in a test of maximum physical exercise compared with MasWT-OVA. Our study shows that effects triggered by the Mas receptor are important to attenuate the inflammatory and remodeling processes in a model of allergic lung inflammation in mice. Our data indicate that impairment of the ANG-(1-7)/Mas receptor pathway may lead to worsening of the pathophysiological changes of asthma.

Therapeutic uses for Angiotensin-(1-7)

INTRODUCTION

Angiotensin-(1-7) is a key component of the Renin-Angiotensin System, which can counter-regulate several deleterious effects caused by angiotensin II. Due to the potential for therapeutic use, several of its actions are specifically described in patents.

AREAS COVERED

In this review, the authors describe a plethora of therapeutic uses for Angiotensin-(1-7), claimed and supported by experimental evidence in patent documents and applications.

EXPERT OPINION

The clinical potential of Angiotensin-(1-7) as a therapeutic agent to treat several pathologies is evidenced by the variety of patents and clinical trials involving this peptide. Cancer treatment is one of the most advanced therapeutic areas, but clinical studies are also available in several other areas, such as cardiovascular, hematological, transplantation, surgical and medical procedures.