Angiotensin-(1-7): cardioprotective effect in myocardial ischemia/reperfusion

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.

Novel Strategies to Improve the Cardioprotective Effects of Cardioplegia

The use of cardioprotective strategies as adjuvants of cardioplegic solutions has become an ideal alternative for the improvement of post-surgery heart recovery. The choice of the optimal cardioplegia, as well as its distribution mechanism, remains controversial in the field of cardiovascular surgery. There is still a need to search for new and better cardioprotective methods during cardioplegic procedures. New techniques for the management of cardiovascular complications during cardioplegia have evolved with new alternatives and additives, and each new strategy provides a tool to neutralize the damage after ischemia/reperfusion events. Researchers and clinicians have committed themselves to studying the effect of new strategies and adjuvant components with the potential to improve the cardioprotective effect of cardioplegic solutions in preventing myocardial ischemia/reperfusion-induced injury during cardiac surgery. The aim of this review is to explore the different types of cardioplegia, their protection mechanisms, and which strategies have been proposed to enhance the function of these solutions in hearts exposed to cardiovascular pathologies that require surgical alternatives for their corrective progression.

The alternative renin-angiotensin system in critically ill patients: pathophysiology and therapeutic implications

The renin-angiotensin system (RAS) plays a crucial role in regulating blood pressure and the cardio-renal system. The classical RAS, mainly mediated by angiotensin I, angiotensin-converting enzyme, and angiotensin II, has been reported to be altered in critically ill patients, such as those in vasodilatory shock. However, recent research has highlighted the role of some components of the counterregulatory axis of the classical RAS, termed the alternative RAS, such as angiotensin-converting Enzyme 2 (ACE2) and angiotensin-(1-7), or peptidases which can modulate the RAS like dipeptidyl-peptidase 3, in many critical situations. In cases of shock, dipeptidyl-peptidase 3, an enzyme involved in the degradation of angiotensin and opioid peptides, has been associated with acute kidney injury and mortality and preclinical studies have tested its neutralization. Angiotensin-(1-7) has been shown to prevent septic shock development and improve outcomes in experimental models of sepsis. In the context of experimental acute lung injury, ACE2 activity has demonstrated a protective role, and its inactivation has been associated with worsened lung function, leading to the use of active recombinant human ACE2, in preclinical and human studies. Angiotensin-(1-7) has been tested in experimental models of acute lung injury and in a recent randomized controlled trial for patients with COVID-19 related hypoxemia. Overall, the alternative RAS appears to have a role in the pathogenesis of disease in critically ill patients, and modulation of the alternative RAS may improve outcomes. Here, we review the available evidence regarding the methods of analysis of the RAS, pathophysiological disturbances of this system, and discuss how therapeutic manipulation may improve outcomes in the critically ill.

Effect of AT1 receptor blockade on cardiovascular outcome after cardiac arrest: an experimental study in rats

Angiotensin II receptor 1(AT1) antagonists are beneficial in focal ischemia/reperfusion (I/R). However, in cases of global I/R, such as cardiac arrest (CA), AT1 blocker's potential benefits are still unknown. Wistar male rats were allocated into four groups: Control group (CG)-animals submitted to CA by ventricular fibrillation induced by direct electrical stimulation for 3 min, and anoxia for 5 min; Group AT1 (GAT1)-animals subjected to CA and treated with 0.2 mg/kg of candesartan diluted in dimethylsulfoxide (DMSO) (0.1%); Vehicle Group (VG): animals subjected to CA and treated with 0.2 ml/kg of DMSO and Sham group (SG)-animals submitted to surgical interventions, without CA. Cardiopulmonary resuscitation consisted of group medications, chest compressions, ventilation, epinephrine (20 mcg/kg) and defibrillation. The animals were observed up to 4 h after spontaneous circulation (ROSC) return, and survival rates, hemodynamic variables, histopathology, and markers of tissue injury were analyzed. GAT1 group had a higher rate of ROSC (62.5% vs. 42.1%, p < 0.0001), survival (100% vs. 62.5%, p = 0.027), lower incidence of arrhythmia after 10 min of ROSC (10% vs. 62.5%, p = 0.000), and lower neuronal and cardiac injury scores on histology evaluation (p = 0.025 and p = 0.0052, respectively) than GC group. The groups did not differ regarding CA duration, number of adrenaline doses, or number of defibrillations. AT1 receptor blockade with candesartan yielded higher rates of ROSC and survival, in addition to neuronal and myocardial protection.

Antioxidants and cardioprotective effects of ethyl acetate fraction of Canavalia rosea leaves in myocardial ischemia-reperfusion injury

Different degrees in the biological activities of Canavalia rosea had been previously reported . In this study, our group assessed the cardioprotective effects of the ethyl acetate fraction (EAcF) of the Canavalia rosea leaves. Firstly, it was confirmed, by in vitro approach, that the EAcF has high antioxidant properties due to the presence of important secondary metabolites, as flavonoids. In order to explore their potential protector against cardiovascular disorders, hearts were previously perfused with EAcF (300 μg.mL-1) and submitted to the global ischemia followed by reperfusion in Langendorff system. The present findings have demonstrated that EAcF restored the left ventricular developed pressure and decreased the arrhythmias severity index. Furthermore, EAcF significantly increased the glutathiones peroxidase activity with decreased malondialdehyde and creatine kinase levels. EAcF was effective upon neither the superoxide dismutase, glutationes reductase nor the catalase activities. In addition, the Western blot analysis revealed that ischemia-reperfusion injury significantly upregulates caspase 3 protein expression, while EAcF abolishes this effect. These results provide evidence that the EAcF reestablishes the cardiac contractility and prevents arrhythmias; it is suggested that EAcF could be used to reduce injury caused by cardiac reperfusion. However more clinical studies should be performed, before applying it in the clinic.

Activation of Mas and pGCA receptor pathways protects renal epithelial cell damage against oxidative-stress-induced injury

Over-activation of the renin-angiotensin-aldosterone system (RAAS) is a leading cause of cardio-renal complications. Oxidative stress is one of the major contributing factors in the over-activation of RAAS. Angiotensin-converting enzyme2/Angiotensin1-7/MasR and natriuretic peptide/particulate guanylyl cyclase receptor-A pathways play a key role in cardiorenal disease protection. Even though individual activation of these pathways possesses cardiorenal protective effects. However, the dual activation of these pathways under stress conditions and the underlying mechanism has not been explored. The study aimed to investigate whether activation of these pathways by dual-acting peptide (DAP) shows a protective effect in-vitro in oxidative stress-induced renal epithelial cells. Oxidative stress was induced in renal epithelial NRK-52E cells with H₂O₂. Co-treatment with Ang 1-7, BNP, and DAP was given for 30 min. AT1, MasR, and pGCA expression were measured by RT-PCR. The markers of oxidative stress and apoptosis were measured by confocal microscopy and FACS analysis. A significant increase in AT1, renin, α-SMA, and NFk-β expression and a significant decrease in MasR and pGCA expression was observed in H₂O₂-induced cells. DAP improved H₂O₂-induced pathological changes in NRK-52E cells. The effect of DAP was superior to that of Ang1-7 and BNP alone. Interestingly, MasR and pGCA inhibitors could block the effect of DAP in H₂O₂-induced cells. DAP shows superior anti-RAAS activity, and it is effective against H₂O₂-induced oxidative stress, apoptosis, fibrosis, and inflammation compared to Ang1-7 and BNP alone. The protective effect is mediated by the dual activation of MasR and pGCA.

Effects of PM2.5 Exposure on the ACE/ACE2 Pathway: Possible Implication in COVID-19 Pandemic

Particulate matter (PM) is a harmful component of urban air pollution and PM2.5, in particular, can settle in the deep airways. The RAS system plays a crucial role in the pathogenesis of pollution-induced inflammatory diseases: the ACE/AngII/AT1 axis activates a pro-inflammatory pathway counteracted by the ACE2/Ang(1-7)/MAS axis, which in turn triggers an anti-inflammatory and protective pathway. However, ACE2 acts also as a receptor through which SARS-CoV-2 penetrates host cells to replicate. COX-2, HO-1, and iNOS are other crucial proteins involved in ultrafine particles (UFP)-induced inflammation and oxidative stress, but closely related to the course of the COVID-19 disease. BALB/c male mice were subjected to PM2.5 sub-acute exposure to study its effects on ACE2 and ACE, COX-2, HO-1 and iNOS proteins levels, in the main organs concerned with the pathogenesis of COVID-19. The results obtained show that sub-acute exposure to PM2.5 induces organ-specific modifications which might predispose to greater susceptibility to severe symptomatology in the case of SARS-CoV-2 infection. The novelty of this work consists in using a molecular study, carried out in the lung but also in the main organs involved in the disease, to analyze the close relationship between exposure to pollution and the pathogenesis of COVID-19.

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.

Cardioprotective Mechanisms against Reperfusion Injury in Acute Myocardial Infarction: Targeting Angiotensin II Receptors

Ischemia/reperfusion injury is a process associated with cardiologic interventions, such as percutaneous coronary angioplasty after an acute myocardial infarction. Blood flow restoration causes a quick burst of reactive oxygen species (ROS), which generates multiple organelle damage, leading to the activation of cell death pathways. Therefore, the intervention contributes to a greater necrotic zone, thus increasing the risk of cardiovascular complications. A major cardiovascular ROS source in this setting is the activation of multiple NADPH oxidases, which could result via the occupancy of type 1 angiotensin II receptors (AT1R); hence, the renin angiotensin system (RAS) is associated with the generation of ROS during reperfusion. In addition, ROS can promote the expression of NF-κΒ, a proinflammatory transcription factor. Recent studies have described an intracellular RAS pathway that is associated with increased intramitochondrial ROS through the action of isoform NOX4 of NADPH oxidase, thereby contributing to mitochondrial dysfunction. On the other hand, the angiotensin II/ angiotensin type 2 receptor (Ang II/AT2R) axis exerts its effects by counter-modulating the action of AT1R, by activating endothelial nitric oxide synthase (eNOS) and stimulating cardioprotective pathways such as akt. The aim of this review is to discuss the possible use of AT1R blockers to hamper both the Ang II/AT1R axis and the associated ROS burst. Moreover; we suggest that AT1R antagonist drugs should act synergistically with other cardioprotective agents, such as ascorbic acid, N-acetylcysteine and deferoxamine, leading to an enhanced reduction in the reperfusion injury. This therapy is currently being tested in our laboratory and has shown promising outcomes in experimental studies.

Altered heart cytokine profile and action potential modulation in cardiomyocytes from Mas-deficient mice

The renin-angiotensin system (RAS) is a key hormonal system. In recent years, the functional analysis of the novel axis of the RAS (ACE2/Ang-(1-7)/Mas receptor) revealed that its activation can become protective against several pathologies, including cardiovascular diseases. Mas knockout mice (Mas-KO) represent an important tool for new investigations. Indeed, extensive biological research has focused on investigating the functional implications of Mas receptor deletion. However, although the Mas receptor was identified in neonatal cardiomyocytes and also in adult ventricular myocytes, only few reports have explored the Ang-(1-7)/Mas signaling directly in cardiomyocytes to date. This study investigated the implication of Mas receptor knockout to the cytokine profile, energy metabolism, and electrical properties of mice-isolated cardiomyocytes. Here, we demonstrated that Mas-KO mice have modulation in some cytokines, such as G-CSF, IL-6, IL-10, and VEGF in the left ventricle. This model also presents increased mitochondrial number in cardiomyocytes and a reduction in the myocyte diameter. Finally, Mas-KO cardiomyocytes have altered action potential modulation after diazoxide challenge. Such electrical finding was different from the data showed for the TGR(A1-7)3292 (TGR) model, which overexpresses Ang-(1-7) in the plasma by 4.5, used by us as a control. Collectively, our findings exemplify the importance of understanding the ACE2/Ang-(1-7)/Mas pathway in cardiomyocytes and heart tissue. The Mas-KO mice model can be considered an important tool for new RAS investigations.

Diminazene Aceturate, an angiotensin converting enzyme 2 (ACE2) activator, promotes cardioprotection in ischemia/reperfusion-induced cardiac injury

This study aimed to investigate whether the Diminazene Aceturate (DIZE), an angiotensin-converting enzyme 2 (ACE2) activator, can revert cardiac dysfunction in ischemia reperfusion-induced (I/R) injury in animals and examine the mechanism underlying this effect. Wistar rats systemically received DIZE (1 mg/kg) for thirty days. Cardiac function in isolated rat hearts was evaluated using the Langendorff technique. After I/R, ventricular non-I/R and I/R samples were used to evaluate ATP levels. Mitochondrial function was assessed using cardiac permeabilized fibers and isolated cardiac mitochondria. Cardiac cellular electrophysiology was evaluated using the patch clamp technique. DIZE protected the heart after I/R from arrhythmia and cardiac dysfunction by preserving ATP levels, independently of any change in coronary flow and heart rate. DIZE improved mitochondrial function, increasing the capacity for generating ATP and reducing proton leak without changing the specific citrate synthase activity. The activation of the ACE2 remodeled cardiac electrical profiles, shortening the cardiac action potential duration at 90 % repolarization. Additionally, cardiomyocytes from DIZE-treated animals exhibited reduced sensibility to diazoxide (K_ATP agonist) and a higher K_ATP current compared to the controls. DIZE was able to improve mitochondrial function and modulate cardiac electrical variables with a cardio-protective profile, resulting in direct myocardial cell protection from I/R injury.

The Inflammatory Cytokine Imbalance for Miscarriage, Pregnancy Loss and COVID-19 Pneumonia

Pregnancy can be defined a vascular event upon endocrine control. In the human hemo-chorial placentation the chorionic villi penetrate the wall of the uterine spiral arteries, to provide increasing amounts of nutrients and oxygen for optimal fetal growth. In any physiological pregnancy the natural maternal response is of a Th1 inflammatory type, aimed at avoiding blood loss through the arteriolar wall openings. The control of the vascular function, during gestation as in any other condition, is achieved through the action of two main types of prostanoids: prostaglandin E2 and thromboxane on the one hand (for vasoconstriction and coagulation), prostacyclin on the other (for vasodilation and blood fluidification). The control of the maternal immune response is upon the responsibility of the fetus itself. Indeed, the chorionic villi are able to counteract the natural maternal response, thus changing the inflammatory Th1 type into the anti-inflammatory Th2. Clinical and experimental research in the past half century address to inflammation as the leading cause of abortion, pregnancy loss, premature delivery and related pulmonary, cerebral, intestinal fetal syndromes. Increased level of Interleukin 6, Interleukin 1-beta, Tumor Necrosis Factor-alfa, Interferon-gamma, are some among the well-known markers of gestational inflammation. On the other side, COVID-19 pneumonia is a result of extensive inflammation induced by viral replication within the cells of the respiratory tract. As it may happen in the uterine arteries in the absence of an effective fetal control, viral pneumonia triggers pulmonary vascular coagulation. The cytokines involved in the process are the same as those in gestational inflammation. As the fetus breathes throughout the placenta, fetal death from placental thrombosis is similar to adult death from pulmonary thrombosis. Preventing and counteracting inflammation is mandatory in both conditions. The most relevant literature dealing with the above-mentioned concepts is reviewed in the present article.

Design and rationale for a comparison study of Olmesartan and Valsartan On myocardial metabolism In patients with Dilated cardiomyopathy (OVOID) trial: study protocol for a randomized controlled trial

BACKGROUND

Dilated cardiomyopathy (DCMP) is characterized by ventricular chamber enlargement and systolic dysfunction which may cause heart failure. Patients with DCMP have overactivation of the renin-angiotensin-aldosterone systems, which can also adversely affect myocardial metabolism in heart failure. The impairment of myocardial metabolism can contribute to the progression of left ventricular remodeling and contractile dysfunction in heart failure. Although angiotensin II receptor blockers (ARBs) have been used to treat patients with DCMP, there has been no direct comparison of the efficacy of these agents. The objective of this study is to compare the effects of olmesartan and valsartan on myocardial metabolism in patients with DCMP.

METHODS/DESIGN

The OVOID study (a comparison study of Olmesartan and Valsartan On myocardial metabolism In patients with Dilated cardiomyopathy) is designed as a non-blinded, open-label, parallel-group, prospective, randomized, controlled, multicenter clinical trial. A total of 40 DCMP patients aged between 20 and 85 years will be randomly allocated into the olmesartan or the valsartan group. ¹⁸F-fluoro-2-deoxyglucose (FDG) cardiac positron emission tomography (PET) will be performed at baseline and six months after receiving the study agent. The primary endpoint is myocardial glucose consumption per square meter, measured using ¹⁸F-FDG PET 6 months after receiving the study agent.

DISCUSSION

The purpose of this trial is to compare the efficacy between olmesartan and valsartan in improving myocardial metabolism in DCMP patients. This will be the first randomized comparative study investigating the differential effects of ARBs on heart failure.

TRIAL REGISTRATION

ClinicalTrials.gov NCT04174456 . Registered on 18 November 2019.

Female fertility under the impact of COVID-19 pandemic: a narrative review

Coronavirus disease 2019 (COVID-19) is a serious respiratory disease mediated by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection. The worldwide spread of COVID-19 has caused millions of confirmed cases and morbidity, and the crisis has greatly affected global economy and daily life and changed our attitudes towards life. The reproductive system, as a potential target, is at a high risk of SARS-CoV-2 infection, and females are more vulnerable to viral infection compared with males. Therefore, female fertility and associated reproductive health care in the COVID-19 era need more attention. This review summarises the mechanism of SARS-CoV-2 infection in the female reproductive system and discusses the impact of the COVID-19 crisis on female fertility. Studies have proven that COVID-19 might affect female fertility and interfere with assisted reproductive technology procedures. The side effects of vaccines against the virus on ovarian reserve and pregnancy have not yet been well investigated. In the future, the female fertility after SARS-CoV-2 infection and vaccination needs more attention because of the uncertainty of COVID-19.

Classical and Counter-Regulatory Renin-Angiotensin System: Potential Key Roles in COVID-19 Pathophysiology

In the current COVID-19 pandemic, severe acute respiratory syndrome coronavirus 2 uses angiotensin-converting enzyme-2 (ACE-2) receptors for cell entry, leading to ACE-2 dysfunction and downregulation, which disturb the balance between the classical and counter-regulatory renin-angiotensin system (RAS) in favor of the classical RAS. RAS dysregulation is one of the major characteristics of several cardiovascular diseases; thus, adjustment of this system is the main therapeutic target. RAS inhibitors-particularly angiotensin-converting enzyme inhibitors (ACEIs) and angiotensin II type 1 receptor blockers (ARBs)-are commonly used for treatment of hypertension and cardiovascular disease. Patients with cardiovascular diseases are the group most commonly seen among those with COVID-19 comorbidity. At the beginning of this pandemic, a dilemma occurred regarding the use of ACEIs and ARBs, potentially aggravating cardiovascular and pulmonary dysfunction in COVID-19 patients. Urgent clinical trials from different countries and hospitals reported that there is no association between RAS inhibitor treatment and COVID-19 infection or comorbidity complication. Nevertheless, the disturbance of the RAS that is associated with COVID-19 infection and the potential treatment targeting this area have yet to be resolved. In this review, the link between the dysregulation of classical RAS and counter-regulatory RAS activities in COVID-19 patients with cardiovascular metabolic diseases is investigated. In addition, the latest findings based on ACEI and ARB administration and ACE-2 availability in relation to COVID-19, which may provide a better understanding of the RAS contribution to COVID-19 pathology, are discussed, as they are of the utmost importance amid the current pandemic.

Current and emerging drug targets in heart failure treatment

After initial strategies targeting inotropism and congestion, the neurohormonal interpretative model of heart failure (HF) pathophysiology has set the basis for current pharmacological management of HF, as most of guideline recommended drug classes, including beta-blockers, angiotensin-converting enzyme inhibitors, angiotensin receptor blockers, and mineralocorticoid receptor antagonists, blunt the activation of detrimental neurohormonal axes, namely sympathetic and renin–angiotensin–aldosterone (RAAS) systems. More recently, sacubitril/valsartan, a first-in-class angiotensin receptor neprilysin inhibitor, combining inhibition of RAAS and potentiation of the counter-regulatory natriuretic peptide system, has been consistently demonstrated to reduce mortality and HF-related hospitalization. A number of novel pharmacological approaches have been tested during the latest years, leading to mixed results. Among them, drugs acting directly at a second messenger level, such as the soluble guanylate cyclase stimulator vericiguat, or other addressing myocardial energetics and mitochondrial function, such as elamipretide or omecamtiv-mecarbil, will likely change the therapeutic management of patients with HF. Sodium glucose cotransporter 2 inhibitors, initially designed for the management of type 2 diabetes mellitus, have been recently demonstrated to improve outcome in HF, although mechanisms of their action on cardiovascular system are yet to be elucidated. Most of these emerging approaches have shifted the therapeutic target from neurohormonal systems to the heart, by improving cardiac contractility, metabolism, fibrosis, inflammation, and remodeling. In the present paper, we review from a pathophysiological perspective current and novel therapeutic strategies in chronic HF.

Targeting the Angiotensin II Type 1 Receptor in Cerebrovascular Diseases: Biased Signaling Raises New Hopes

The physiological and pathophysiological relevance of the angiotensin II type 1 (AT₁) G protein-coupled receptor no longer needs to be proven in the cardiovascular system. The renin–angiotensin system and the AT₁ receptor are the targets of several classes of therapeutics (such as angiotensin converting enzyme inhibitors or angiotensin receptor blockers, ARBs) used as first-line treatments in cardiovascular diseases. The importance of AT₁ in the regulation of the cerebrovascular system is also acknowledged. However, despite numerous beneficial effects in preclinical experiments, ARBs do not induce satisfactory curative results in clinical stroke studies. A better understanding of AT₁ signaling and the development of biased AT₁ agonists, able to selectively activate the β-arrestin transduction pathway rather than the G_q pathway, have led to new therapeutic strategies to target detrimental effects of AT₁ activation. In this paper, we review the involvement of AT₁ in cerebrovascular diseases as well as recent advances in the understanding of its molecular dynamics and biased or non-biased signaling. We also describe why these alternative signaling pathways induced by β-arrestin biased AT₁ agonists could be considered as new therapeutic avenues for cerebrovascular diseases.

The Genetic Dissection of Ace2 Expression Variation in the Heart of Murine Genetic Reference Population

Background: A high inflammatory and cytokine burden that induces vascular inflammation, myocarditis, cardiac arrhythmias, and myocardial injury is associated with a lethal outcome in COVID-19. The SARS-CoV-2 virus utilizes the ACE2 receptor for cell entry in a similar way to SARS-CoV. This study investigates the regulation, gene network, and associated pathways of ACE2 that may be involved in inflammatory and cardiovascular complications of COVID-19.

Methods: Cardiovascular traits were determined in the one of the largest mouse genetic reference populations: BXD recombinant inbred strains using blood pressure, electrocardiography, and echocardiography measurements. Expression quantitative trait locus (eQTL) mapping, genetic correlation, and functional enrichment analysis were used to identify Ace2 regulation, gene pathway, and co-expression networks.

Results: A wide range of variation was found in expression of Ace2 among the BXD strains. Levels of Ace2 expression are negatively correlated with cardiovascular traits, including systolic and diastolic blood pressure and P wave duration and amplitude. Ace2 co-expressed genes are significantly involved in cardiac- and inflammatory-related pathways. The eQTL mapping revealed that Cyld is a candidate upstream regulator for Ace2. Moreover, the protein–protein interaction (PPI) network analysis inferred several potential key regulators (Cul3, Atf2, Vcp, Jun, Ppp1cc, Npm1, Mapk8, Set, Dlg1, Mapk14, and Hspa1b) for Ace2 co-expressed genes in the heart.

Conclusions:Ace2 is associated with blood pressure, atrial morphology, and sinoatrial conduction in BXD mice. Ace2 co-varies with Atf2, Cyld, Jun, Mapk8, and Mapk14 and is enriched in the RAS, TGFβ, TNFα, and p38α signaling pathways, involved in inflammation and cardiac damage. We suggest that all these novel Ace2-associated genes and pathways may be targeted for preventive, diagnostic, and therapeutic purposes in cardiovascular damage in patients with systemic inflammation, including COVID-19 patients.

Inclusion complex with β-cyclodextrin is a key determining factor for the cardioprotection induced by usnic acid

Ischemia-reperfusion (I/R) injury causes oxidative stress, leading to severe cardiac dysfunction. Thus, biologically active compounds with antioxidant properties may be viewed as a promising therapeutic strategy against oxidative-related cardiac disorders. Usnic acid (UA), a natural antioxidant, was complexed with β-cyclodextrin (βCD) to improve its bioavailability. Wistar male rats were orally treated with the free form of UA (50 mg/kg) or the inclusion complex UA/βCD (50 mg/kg) for seven consecutive days. Afterward, hearts were subjected to I/R injury, and the cardiac contractility, rhythmicity, infarct size, and antioxidant enzyme activities were evaluated. Here, we show that neither UA nor UA/βCD treatments developed signs of toxicity. After I/R injury, animals treated with UA/βCD showed improved post-ischemic cardiac functional recovery while the release of cell injury biomarkers decreased. Following reduced cardiac damage, a lower incidence of ventricular arrhythmias and smaller myocardial infarct size were associated with reduced lipid peroxidation, along with preserved activity of antioxidant enzymes compared to untreated rats. Surprisingly, uncomplexed UA did not protect hearts against IR injury. Altogether, our results indicate that the inclusion complex UA/βCD is a critical determining factor responsible for the cardioprotection action of UA, suggesting the involvement of an antioxidant-dependent mechanisms. Moreover, our findings support that UA/βCD is a structurally engineered compound with active cardioprotective properties.

ACE2 in the Era of SARS-CoV-2: Controversies and Novel Perspectives

Angiotensin-converting enzyme 2 (ACE2) is related to ACE but turned out to counteract several pathophysiological actions of ACE. ACE2 exerts antihypertensive and cardioprotective effects and reduces lung inflammation. ACE2 is subjected to extensive transcriptional and post-transcriptional modulation by epigenetic mechanisms and microRNAs. Also, ACE2 expression is regulated post-translationally by glycosylation, phosphorylation, and shedding from the plasma membrane. ACE2 protein is ubiquitous across mammalian tissues, prominently in the cardiovascular system, kidney, and intestine. ACE2 expression in the respiratory tract is of particular interest, in light of the discovery that ACE2 serves as the initial cellular target of severe acute respiratory syndrome (SARS)-coronaviruses, including the recent SARS-CoV2, responsible of the COronaVIrus Disease 2019 (COVID-19). Since the onset of the COVID-19 pandemic, an intense effort has been made to elucidate the biochemical determinants of SARS-CoV2-ACE2 interaction. It has been determined that SARS-CoV2 engages with ACE2 through its spike (S) protein, which consists of two subunits: S1, that mediates binding to the host receptor; S2, that induces fusion of the viral envelope with the host cell membrane and delivery of the viral genome. Owing to the role of ACE2 in SARS-CoV2 pathogenicity, it has been speculated that medical conditions, i.e., hypertension, and/or drugs, i.e., ACE inhibitors and angiotensin receptor blockers, known to influence ACE2 density could alter the fate of SARS-CoV-2 infection. The debate is still open and will only be solved when results of properly designed experimental and clinical investigations will be made public. An interesting observation is, however that, upon infection, ACE2 activity is reduced either by downregulation or by shedding. These events might precipitate the so-called "cytokine storm" that characterizes the most severe COVID-19 forms. As evidence accumulates, ACE2 appears a druggable target in the attempt to limit virus entry and replication. Strategies aimed at blocking ACE2 with antibodies, small molecules or peptides, or at neutralizing the virus by competitive binding with exogenously administered ACE2, are currently under investigations. In this review, we will present an overview of the state-of-the-art knowledge on ACE2 biochemistry and pathophysiology, outlining open issues in the context of COVID-19 disease and potential experimental and clinical developments.

SARS-COV-2 (COVID-19): Cellular and biochemical properties and pharmacological insights into new therapeutic developments

COVID‐19 caused by SARS‐COV‐2 first appeared in the Wuhan City of China and began to spread rapidly among people. Rapid progression of the outbreak has led to a major global public health problem of a potentially fatal disease. On January 30, 2020, WHO declared the pandemic as the sixth public health emergency of the world. Upon this, the whole country has started to take the necessary precautions. The new coronavirus uses membrane‐bound angiotensin‐converting enzyme 2 (ACE2) to enter into the cells, such as SARS‐CoV, and mostly affects the respiratory tract. Symptoms of COVID‐19 patients include fever (93%), fatigue (70%), cough (70%), anorexia (40%) and dyspnoea (34.5%). The elderly and people with underlying chronic diseases are more susceptible to infection and higher mortality. Currently, a large number of drugs and vaccines studies are ongoing. In this review, we discussed the virology, epidemiological data, the replication of the virus, and its relationship with cardiovascular diseases on COVID‐19 pandemics, treatment and vaccines. Thereby, this study aims to neatly present scientific data in light of many regarding literature that can be a clue for readers who research this disease prevention and treatment.

Could Mesenchymal Stem Cell-Derived Exosomes Be a Therapeutic Option for Critically Ill COVID-19 Patients?

Coronavirus disease 2019 (COVID-19) is a pandemic viral disease originated in Wuhan, China, in December 2019, caused by the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). The severe form of the disease is often associated with acute respiratory distress syndrome (ARDS), and most critically ill patients require mechanical ventilation and support in intensive care units. A significant portion of COVID-19 patients also develop complications of the cardiovascular system, primarily acute myocardial injury, arrhythmia, or heart failure. To date, no specific antiviral therapy is available for patients with SARS-CoV-2 infection. Exosomes derived from mesenchymal stem cells (MSCs) are being explored for the management of a number of diseases that currently have limited or no therapeutic options, thanks to their anti-inflammatory, immunomodulatory, and pro-angiogenic properties. Here, we briefly introduce the pathogenesis of SARS-CoV-2 and its implications in the heart and lungs. Next, we describe some of the most significant clinical evidence of the successful use of MSC-derived exosomes in animal models of lung and heart injuries, which might strengthen our hypothesis in terms of their utility for also treating critically ill COVID-19 patients.

Antioxidant Solution in Combination with Angiotensin-(1-7) Provides Myocardial Protection in Langendorff-Perfused Rat Hearts

As progressive organ shortage in cardiac transplantation demands extension of donor criteria, effort is needed to optimize graft survival. Reactive oxygen and nitrogen species, generated during organ procurement, transplantation, and reperfusion, contribute to acute and late graft dysfunction. The combined application of diverse substances acting via different molecular pathways appears to be a reasonable approach to face the complex mechanism of ischemia reperfusion injury. Thus, an antioxidant solution containing α-ketoglutaric acid, 5-hydroxymethylfurfural, N-acetyl-L-methionine, and N-acetyl-selenium-L-methionine was combined with endogenous angiotensin-(1-7). Its capacity of myocardial protection was investigated in isolated Langendorff-perfused rat hearts subjected to warm and cold ischemia. The physiological cardiac parameters were assessed throughout the experiments. Effects were evaluated via determination of the oxidative stress parameters malondialdehyde and carbonyl proteins as well as immunohistochemical and ultrastructural tissue analyses. It was shown that a combination of 20% (v/v) antioxidant solution and 220 pM angiotensin-(1-7) led to the best results with a preservation of heart tissue against oxidative stress and morphological alteration. Additionally, immediate cardiac recovery (after warm ischemia) and normal physiological performance (after cold ischemia) were recorded. Overall, the results of this study indicate substantial cardioprotection of the novel combination with promising prospective for future clinical use.

Potential influence of COVID-19/ACE2 on the female reproductive system

The 2019 novel coronavirus (2019-nCoV) appeared in December 2019 and then spread throughout the world rapidly. The virus invades the target cell by binding to angiotensin-converting enzyme (ACE) 2 and modulates the expression of ACE2 in host cells. ACE2, a pivotal component of the renin-angiotensin system, exerts its physiological functions by modulating the levels of angiotensin II (Ang II) and Ang-(1-7). We reviewed the literature that reported the distribution and function of ACE2 in the female reproductive system, hoping to clarify the potential harm of 2019-nCoV to female fertility. The available evidence suggests that ACE2 is widely expressed in the ovary, uterus, vagina and placenta. Therefore, we believe that apart from droplets and contact transmission, the possibility of mother-to-child and sexual transmission also exists. Ang II, ACE2 and Ang-(1-7) regulate follicle development and ovulation, modulate luteal angiogenesis and degeneration, and also influence the regular changes in endometrial tissue and embryo development. Taking these functions into account, 2019-nCoV may disturb the female reproductive functions through regulating ACE2.

Angiotensin-Converting Enzyme Inhibitors and Angiotensin Receptor Blockers in Patients With Coronavirus Disease 2019: Friend or Foe?

When the coronavirus disease 2019 (COVID-19) wreaked an unprecedented havoc of an escalating number of deaths and hospitalization in the United States, clinicians were faced with a myriad of unanswered questions, one of the them being the implication of the renin-angiotensin-aldosterone system in patients with COVID-19. Animal data and human studies have shown that angiotensin-converting enzyme (ACE) inhibitors and angiotensin receptor blockers (ARBs) increase the expression of ACE2. ACE2 is an enzyme found in the heart, kidney, gastrointestinal tract, and lung and is a coreceptor for severe acute respiratory syndrome-related coronavirus-2 (SARS-CoV2), the virus responsible for COVID-19. Therefore, one can speculate that discontinuing ACE inhibitor or ARB therapy may lead to decreased ACE2 expression, thereby attenuating the infectivity of SARS-CoV-2, and mitigating the disease progression of COVID-19. However, several studies have also shown that ACE2 exhibits reno- and cardioprotection and preserves lung function in acute respiratory distress syndrome, which would favor ACE inhibitor or ARB therapy. This article is to examine and summarize the 2 opposing viewpoints and provide guideline recommendations to support the use or discontinuation of ACE inhibitors and ARBs in patients with COVID-19.

An Overview of the Potential Use of Ethno-Medicinal Plants Targeting the Renin-Angiotensin System in the Treatment of Hypertension

The development of risk factors associated with cardiovascular disorders present a major public health challenge in both developed countries and countries with emerging economies. Hypertension and associated complications including stroke and myocardial infarction have reached pandemic levels. Current management strategies of hypertension predominantly include the utilization of pharmaceutical drugs which are often associated with undesirable side effects. Moreover, the drugs are often too expensive for populations from resource-limited Southern African rural, and some urban, communities. As a result, most patients rely on ethno-medicinal plants for the treatment of a variety of diseases including cardiovascular and metabolic disorders. The effectiveness of these plants in managing several cardiovascular diseases has been attributed to the presence of bioactive phytochemical constituents. In this review, the treatment options that target the renin-angiotensin system (RAS) in the management of hypertension were summarized, with special emphasis on ethno-medicinal plants and their influence on the ACE1 RAS pathway. The dearth of knowledge regarding the effect of ethno-medicinal plants on the ACE2 pathway was also highlighted.

COVID-19 and RAS: Unravelling an Unclear Relationship

The renin-angiotensin system (RAS) plays a main role in regulating blood pressure and electrolyte and liquid balance. Previous evidence suggests that RAS may represent an important target for the treatment of lung pathologies, especially for acute respiratory distress syndrome and chronic fibrotic disease. The scientific community has recently focused its attention on angiotensin-converting enzyme (ACE) inhibitors and angiotensin receptor 1 (AT1R) inhibitors and their possible benefit/harms for patients infected by Coronavirus disease (COVID-19) who experience pneumonia, but there are still some doubts about the effects of these drugs in this setting.

Angiotensin peptide synthesis and cyclic nucleotide modulation in sympathetic stellate ganglia

Chronically elevated angiotensin II is a widely-established contributor to hypertension and heart failure via its action on the kidneys and vasculature. It also augments the activity of peripheral sympathetic nerves through activation of presynaptic angiotensin II receptors, thus contributing to sympathetic over-activity. Although some cells can synthesise angiotensin II locally, it is not known if this machinery is present in neurons closely coupled to the heart. Using a combination of RNA sequencing and quantitative real-time polymerase chain reaction, we demonstrate evidence for a renin-angiotensin synthesis pathway within human and rat sympathetic stellate ganglia, where significant alterations were observed in the spontaneously hypertensive rat stellate ganglia compared with Wistar stellates. We also used Förster Resonance Energy Transfer to demonstrate that administration of angiotensin II and angiotensin 1-7 peptides significantly elevate cyclic guanosine monophosphate in the rat stellate ganglia. Whether the release of angiotensin peptides from the sympathetic stellate ganglia alters neurotransmission and/or exacerbates cardiac dysfunction in states associated with sympathetic over activity remains to be established.

Stimulation of the ACE2/Ang-(1-7)/Mas axis in hypertensive pregnant rats attenuates cardiovascular dysfunction in adult male offspring

The aim of this study was to investigate whether treatment with diminazene aceturate (DIZE), a putative ACE2 activator, or with angiotensin-(1-7) during pregnancy could attenuate the development of cardiovascular dysfunction in the adult offspring of spontaneously hypertensive rats (SHRs). For this, pregnant SHRs received DIZE or Ang-(1-7) throughout gestation. The systolic blood pressure (SBP) was measured in the male offspring from the 6th to16th weeks of age by tail-cuff plethysmography. Thereafter, the left ventricular contractile function and coronary reactivity were evaluated by the Langendorff technique. Samples of the left ventricles (LVs) and kidneys were collected for histology and western blot assay in another batch of adult rat offspring. Maternal treatment with DIZE or Ang-(1-7) during pregnancy attenuated the increase in SBP in adult offspring. In addition, both DIZE and Ang-(1-7) treatments reduced the cardiomyocyte diameter and fibrosis deposition in the LV, and treatment with Ang-(1-7) also reduced the fibrosis deposition in the kidneys. Maternal treatment with DIZE, as well as Ang-(1-7), improved the coronary vasodilation induced by bradykinin in isolated hearts from adult offspring. However, no difference was observed in the contractile function of the LVs of these animals. The expression levels of AT1 and Mas receptors, ACE, ACE2, SOD, and catalase in the LV were not modified by maternal treatment with Ang-(1-7), but this treatment elicited a reduction in AT2 expression. These data show that treatment with DIZE or Ang-(1-7) during gestation promoted beneficial effects of attenuating hypertension and cardiac remodeling in adult offspring.

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.

Investigation of antioxidative effects of a cardioprotective solution in heart tissue

A multi-component solution, containing α-ketoglutaric acid (α-KG), 5-hydroxymethylfurfural (5-HMF), N-acetyl-seleno-L-methionine (NASeLM), and N-acetyl-L-methionine (NALM) as active ingredients, has been tested considering its supposed antioxidative effect with respect to heart transplantations. Oxidative stress was induced on isolated rat hearts through occlusion of a coronary artery and in chicken heart tissue through hydrogen peroxide. Both heart types were analyzed and the oxidative stress markers malondialdehyde (MDA) and carbonyl proteins (CPs) were determined via HPLC/UV-Vis. In both approaches, it was found that treatment with the multi-component solution led to a lower amount of MDA and CPs compared to a negative control treated with Krebs-Ringer solution (KRS). Further investigation on chicken heart tissue identified α-KG as antioxidative component in these experiments. However, numerous factors like arrhythmia, vessel dilatation, and minimization of oxidative stress effects play an important role for successful transplantation. Therefore, the investigated multi-component solution might be a novel approach against oxidative stress situations, for example at ischemia reperfusion injury during heart transplantations.

Participation of Gαi-Adenylate Cyclase and ERK1/2 in Mas Receptor Signaling Pathways

The MasR receptor (MasR) is an orphan G protein-coupled receptor proposed as a candidate for mediating the angiotensin (Ang)-converting enzyme 2-Ang-(1–7) protective axis of renin-angiotensin system. This receptor has been suggested to participate in several physiological processes including cardio- and reno-protection and regulation of the central nervous system function. Although the knowledge of the signaling mechanisms associated with MasR is essential for therapeutic purposes, these are still poorly understood. Accordingly, in the current study we aimed to characterize the signaling pathways triggered by the MasR. To do that, we measured cAMP and Ca²⁺ levels in both naïve and MasR transfected cells in basal conditions and upon incubation with putative MasR ligands. Besides, we evaluated activation of ERK1/2 by Ang-(1–7) in MasR transfected cells. Results indicated the existence of a high degree of MasR constitutive activity toward cAMP modulation. This effect was not mediated by the PDZ-binding motif of the MasR but by receptor coupling to Gαi-adenylyl cyclase signaling pathway. Incubation of MasR transfected cells with Ang-(1–7) or the synthetic ligand AVE 0991 amplified MasR negative modulation of cAMP levels. On the other hand, we provided evidence for lack of MasR-associated modulation of Ca²⁺ levels by Ang-(1–7). Finally, it was determined that the MasR attenuated Ang-(1–7)-induced ERK1/2 phosphorylation mediated by AT1R. We provided further characterization of MasR signaling mechanisms regarding its constitutive activity and response to putative ligands. This information could prove useful to better describe MasR physiological role and development of therapeutic agents that could modulate its action.

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.

Alamandine Protects the Heart Against Reperfusion Injury via the MrgD Receptor

BACKGROUND

Alamandine differs from angiotensin-(1-7) in a single N-terminal alanine residue. The aim of this study was to investigate whether alamandine protects the heart against reperfusion injury. Methods and Results: After euthanizing Sprague-Dawley rats, hearts were perfused with Krebs-Henseleit buffer for a 20-min pre-ischemic period with or without alamandine, followed by 20 min global ischemia and 50 min reperfusion. Alamandine (0.1 mg/kg) improved the postischemic left ventricular developed pressure and ±dP/dt, decreased the infarct size, and decreased the lactate dehydrogenase levels in the effluent. Alamandine increased the coronary flow and the amount of atrial natriuretic peptide (ANP) in the coronary effluent, and it decreased the expression of apoptotic proteins and increased the expression of antioxidative proteins. Pretreatment with the MrgD receptor antagonist or PD123319, but not the angiotensin type 1 receptor antagonist, attenuated the cardioprotective effects of alamandine. A similar cardioprotective effect with alamandine was also observed with high plasma ANP levels in an in vivo study. Alamandine directly stimulated ANP secretion from isolated atria, which was completely blocked by pretreatment with the MrgD receptor antagonist and was partially blocked by PD123319.

CONCLUSIONS

These results suggest that the cardioprotective effects of alamandine against I/R injury are, in part, related to the activation of antioxidant and antiapoptotic enzymes via the MrgD receptor.

Angiotensin-(1–7) reduces cardiac effects of thyroid hormone by GSK3Β/NFATc3 signaling pathway

Patients with hyperthyroidism exhibit increased risk of development and progression of cardiac diseases. The activation of the renin–angiotensin system (RAS) has been indirectly implicated in these cardiac effects observed in hyperthyroidism. Angiotensin-(1–7) (Ang-(1–7)) has previously been shown to counterbalance pathological effects of angiotensin II (Ang II). The aim of the present study was to investigate the effects of elevated circulating Ang-(1–7) levels on cardiac effects promoted by hyperthyroidism in a transgenic rat (TG) model that constitutively overexpresses an Ang-(1–7)-producing fusion protein [TGR(A1-7)3292]. TG and wild-type (WT) rats received daily injections (i.p.) of triiodothyronine (T3; 7 µg/100 g of body weight (BW)) or vehicle for 14 days. In contrast with WT rats, the TG rats did not develop cardiac hypertrophy after T3 treatment. Indeed, TG rats displayed reduced systolic blood pressure (SBP) and cardiac hyperdynamic condition induced by hyperthyroidism. Moreover, increased plasma levels of Ang II observed in hyperthyroid WT rats were prevented in TG rats. TG rats were protected from glycogen synthase kinase 3β (GSK3β) inactivation and nuclear factor of activated T cells (NFAT) nuclear accumulation induced by T3. In vitro studies evidenced that Ang-(1–7) prevented cardiomyocyte hypertrophy and GSK3β inactivation induced by T3. Taken together, these data reveal an important cardioprotective action of Ang-(1–7) in experimental model of hyperthyroidism.

Altered global microRNA expression in hepatic stellate cells LX-2 by angiotensin-(1-7) and miRNA-1914-5p identification as regulator of pro-fibrogenic elements and lipid metabolism

The development of new therapeutic strategies to control or reverse hepatic fibrosis requires thorough knowledge about its molecular and cellular basis. It is known that the heptapeptide angiotensin-(1-7) [ang-(1-7)] can reduce hepatic fibrosis and steatosis in vivo; therefore, it is important to uncover the mechanisms regulating its activity and cellular model of investigation. Ang-(1-7) is a peptide of the renin-angiotensin system (RAS), and here we investigated its modulatory effect on the expression pattern of microRNAs (miRNAs) in hepatic stellate cells (HSCs) LX-2, which transdifferentiate into fibrogenic and proliferative cells. We compared the miRNA profiles between quiesced, activated and ang-(1-7)-treated activated HSCs to identify miRNAs that may regulate their transdifferentiation. Thirteen miRNAs were pointed, and cellular and molecular analyses identified miRNA-1914-5p as a molecule that contributes to the effects of ang-(1-7) on lipid metabolism and on the pro-fibrotic environment control. In our cellular model, we also analyzed the regulators of fatty acid metabolism. Specifically, miRNA-1914-5p regulates the expression of malonyl-CoA decarboxylase (MLYCD) and phosphatidic acid phosphohydrolase (PAP or Lipin-1). Additionally, Lipin-1 was closely correlated with mRNA expression of peroxisome proliferator-activated receptors (PPAR)-α and -γ, which also contribute to lipid homeostasis and to the reduction of TGF-β1 expression. These findings provide a novel link between RAS and lipid metabolism in controlling HSCs activation.

Angiotensin 1-7 modulates electrophysiological characteristics and calcium homoeostasis in pulmonary veins cardiomyocytes via MAS/PI3K/eNOS signalling pathway

BACKGROUND

Atrial fibrillation (AF) is the most common sustained arrhythmia, and pulmonary veins (PVs) play a critical role in triggering AF. Angiotensin (Ang)-(1-7) regulates calcium (Ca²⁺ ) homoeostasis and also plays a critical role in cardiovascular pathophysiology. However, the role of Ang-(1-7) in PV arrhythmogenesis remains unclear.

MATERIALS AND METHODS

Conventional microelectrodes, whole-cell patch-clamp and the fluo-3 fluorimetric ratio technique were used to record ionic currents and intracellular Ca²⁺ in isolated rabbit PV preparations and in single isolated PV cardiomyocytes, before and after administration of Ang-(1-7).

RESULTS

Ang (1-7) concentration dependently (0.1, 1, 10 and 100 nmol/L) decreased PV spontaneous electrical activity. Ang-(1-7) (100 nmol/L) decreased the late sodium (Na⁺ ), L-type Ca²⁺ and Na⁺ -Ca²⁺ exchanger currents, but did not affect the voltage-dependent Na⁺ current in PV cardiomyocytes. In addition, Ang-(1-7) decreased intracellular Ca²⁺ transient and sarcoplasmic reticulum Ca²⁺ content in PV cardiomyocytes. A779 (a Mas receptor blocker, 3 μmol/L), L-NAME (a NO synthesis inhibitor, 100 μmol/L) or wortmannin (a specific PI3K inhibitor, 10 nmol/L) attenuated the effects of Ang-(1-7) (100 nmol/L) on PV spontaneous electric activity.

CONCLUSION

Ang-(1-7) regulates PV electrophysiological characteristics and Ca²⁺ homoeostasis via Mas/PI3K/eNOS signalling pathway.

Myrtenol protects against myocardial ischemia-reperfusion injury through antioxidant and anti-apoptotic dependent mechanisms

Myrtenol is a monoterpene with multiple pharmacological activities. However, although monoterpenes have been proposed to play beneficial roles in a variety of cardiac disorders, pharmacological actions of myrtenol in the heart are not yet reported. Hence, the aim of this study was to evaluate whether myrtenol promotes cardioprotection against myocardial ischemia-reperfusion (IR) injury, and the mechanisms involved in these effects. Male Wistar rats were orally treated for seven consecutive days with myrtenol (50 mg/kg) or N-acetyl cysteine (1.200 mg/kg, NAC). Afterward, hearts were subjected to myocardial IR injury. Here, we show that the severe impairment of contractile performance induced by IR was significantly prevented by myrtenol or NAC. Moreover, myrtenol abolished aberrant electrocardiographic waveform (ST-segment elevation), as well as reduced life-threatening arrhythmias and infarct size induced by IR injury. Importantly, myrtenol fully prevented the massive increase of cardiac reactive oxygen species generation and oxidative stress damage. Accordingly, myrtenol restored the impairment of endogenous antioxidant enzymes (superoxide dismutase, catalase, glutathione peroxidase and reductase) activities and balance of pro- and anti-apoptotic pathways (Bax and Bcl-2), associated with decreased apoptotic cells. Taken together, our data show that myrtenol promotes cardioprotection against IR injury through attenuation of oxidative stress and inhibition of pro-apoptotic pathway.

Protective effect of diltiazem on myocardial ischemic rats induced by isoproterenol

The aim of the present study was to analyze the effect of diltiazem on myocardial fibrosis and remodeling of connexin43 (Cx43) in myocardial ischemic rats and mechanisms underlying these processes. A total of 36 Sprague‑Dawley rats were randomly allocated into three groups (control, isoproterenol and isoproterenol with diltiazem). The myocardial ischemic model was established by 5 mg/kg/day isoproterenol administration for 7 days, and the diltiazem group received 25 mg/kg/day diltiazem for 4 weeks. Following the treatment, paraffin sections were prepared to observe microstructural changes and to evaluate the concentration of Ca2+ in myocardium. The expression of transforming growth factors‑β1 (TGF‑β1), mothers against decapentaplegic homologues (Smad)2 and 7 and Cx43, were analyzed by reverse transcription-quantitative polymerase chain reaction and western blotting. The percentage Cx43 expression in intercalated disks was evaluated using immunohistochemistry. Fibrosis did not differ significantly between the control and the diltiazem‑treated group. The concentration of Ca2+ increased in the myocardium of model rats. The expression of Smad7 and Cx43 was decreased in the rat model, while the expression of TGF‑β1 and Smad2 was increased. There was a significant decrease in the relative abundance of intercalated disk Cx43 in the model group. The results of the present study suggest that diltiazem may serve a protective role during remodeling of myocardial ischemia, especially in fibrosis and Cx43 remodeling.

Angiotensin II-preconditioning is associated with increased PKCε/PKCδ ratio and prosurvival kinases in mitochondria

Angiotensin II-preconditioning (APC) has been shown to reproduce the cardioprotective effects of ischaemic preconditioning (IPC), however, the molecular mechanisms mediating the effects of APC remain unknown. In this study, Langendorff-perfused rat hearts were subjected to IPC, APC or both (IPC/APC) followed by ischaemia-reperfusion (IR), to determine translocation of PKCε, PKCδ, Akt, Erk1/2, JNK, p38 MAPK and GSK-3β to mitochondria as an indicator of activation of the protein kinases. In agreement with previous observations, IPC, APC and IPC/APC increased the recovery of left ventricular developed pressure (LVDP), reduced infarct size (IS) and lactate dehydrogenase (LDH) release, compared to controls. These effects were associated with increased mitochondrial PKCε/PKCδ ratio, Akt, Erk1/2, JNK, and inhibition of permeability transition pore (mPTP) opening. Chelerythrine, a pan-PKC inhibitor, abolished the enhancements of PKCε but increased PKCδ expression, and inhibited Akt, Erk1/2, and JNK protein levels. The drug had no effect on the APC- and IPC/APC-induced cardioprotection as previously reported, but enhanced the post-ischaemic LVDP in controls. Losartan, an angiotensin II type 1 receptor (AT1-R) blocker, abolished the APC-stimulated increase of LVDP and reduced PKCε, Akt, Erk1/2, JNK, and p38. Both drugs reduced ischaemic contracture and LDH release, and abolished the inhibition of mPTP by the preconditioning. Chelerythrine also prevented the reduction of IS by APC and IPC/APC. These results suggest that the cardioprotection induced by APC and IPC/APC involves an AT1-R-dependent translocation of PKCε and survival kinases to the mitochondria leading to mPTP inhibition. In chelerythrine-treated hearts, however, alternate mechanisms appear to maintain cardiac function.

Role of the ACE2‑Ang‑(1‑7)‑Mas axis in blood pressure regulation and its potential as an antihypertensive in functional foods (Review)

The renin‑angiotensin system (RAS) serves a critical role in blood pressure regulation and prevention of cardiovascular diseases. Efforts to develop functional foods that enhance the RAS have focused on inhibition of angiotensin‑converting enzyme (ACE) activity in the ACE‑angiotensin II (Ang II)‑Ang II type 1 receptor axis. ACE2 and the Mas receptor are important components of this axis. ACE2 catalyzes Ang II into Ang‑(1‑7), which then binds to the G‑protein‑coupled receptor Mas. In addition, it induces nitric oxide release from endothelial cells and exerts antiproliferative, vasodilatory and antihypertensive effects. The present review examined recent findings regarding the physiological and biological roles of the ACE2‑Ang‑(1‑7)‑Mas axis in the cardiovascular system, discussed potential food‑derived ACE2‑activating agents, and highlighted initiatives, based on this axis, that aim to develop functional foods for the treatment of hypertension.

Gene Therapy With Angiotensin-(1-9) Preserves Left Ventricular Systolic Function After Myocardial Infarction

Background

Angiotensin-(1-9) [Ang-(1-9)] is a novel peptide of the counter-regulatory axis of the renin-angiotensin-aldosterone system previously demonstrated to have therapeutic potential in hypertensive cardiomyopathy when administered via osmotic mini-pump. Here, we investigate whether gene transfer of Ang-(1-9) is cardioprotective in a murine model of myocardial infarction (MI).

Objectives

The authors evaluated effects of Ang-(1-9) gene therapy on myocardial structural and functional remodeling post-infarction.

Methods

C57BL/6 mice underwent permanent left anterior descending coronary artery ligation and cardiac function was assessed using echocardiography for 8 weeks followed by a terminal measurement of left ventricular pressure volume loops. Ang-(1-9) was delivered by adeno-associated viral vector via single tail vein injection immediately following induction of MI. Direct effects of Ang-(1-9) on cardiomyocyte excitation/contraction coupling and cardiac contraction were evaluated in isolated mouse and human cardiomyocytes and in an ex vivo Langendorff-perfused whole-heart model.

Results

Gene delivery of Ang-(1-9) reduced sudden cardiac death post-MI. Pressure volume measurements revealed complete restoration of end-systolic pressure, ejection fraction, end-systolic volume, and the end-diastolic pressure volume relationship by Ang-(1-9) treatment. Stroke volume and cardiac output were significantly increased versus sham. Histological analysis revealed only mild effects on cardiac hypertrophy and fibrosis, but a significant increase in scar thickness. Direct assessment of Ang-(1-9) on isolated cardiomyocytes demonstrated a positive inotropic effect via increasing calcium transient amplitude and contractility. Ang-(1-9) increased contraction in the Langendorff model through a protein kinase A–dependent mechanism.

Conclusions

Our novel findings showed that Ang-(1-9) gene therapy preserved left ventricular systolic function post-MI, restoring cardiac function. Furthermore, Ang-(1-9) directly affected cardiomyocyte calcium handling through a protein kinase A–dependent mechanism. These data emphasized Ang-(1-9) gene therapy as a potential new strategy in the context of MI.

Protective roles of bioactive peptides during ischemia-reperfusion injury: From bench to bedside

Ischemia-reperfusion (I/R) is a well-known pathological condition which may lead to disability and mortality. I/R injury remains an unresolved and complicated situation in a number of clinical conditions, such as cardiac arrest with successful reanimation, as well as ischemic events in brain and heart. Peptides have many attractive advantages which make them suitable candidate drugs in treating I/R injury, such as low toxicity and immunogenicity, good solubility property, distinct tissue distribution pattern, and favorable pharmacokinetic profile. An increasing number of studies indicate that peptides could protect against I/R injury in many different organs and tissues. Peptides also face several therapeutic challenges that limit their clinical application. In this review, we present the mechanisms of action of peptides in reducing I/R injury, as well as further discuss modification strategies to improve the functional properties of bioactive peptides.