Angiotensin-(1-7) dose-dependently inhibits atherosclerotic lesion formation and enhances plaque stability by targeting vascular cells

COVID-19 in the Initiation and Progression of Atherosclerosis: Pathophysiology During and Beyond the Acute Phase

The incidence of atherosclerotic cardiovascular disease is increasing globally, especially in low- and middle-income countries, despite significant efforts to reduce traditional risk factors. Premature subclinical atherosclerosis has been documented in association with several viral infections. The magnitude of the recent COVID-19 pandemic has highlighted the need to understand the association between SARS-CoV-2 and atherosclerosis. This review examines various pathophysiological mechanisms, including endothelial dysfunction, platelet activation, and inflammatory and immune hyperactivation triggered by SARS-CoV-2 infection, with specific attention on their roles in initiating and promoting the progression of atherosclerotic lesions. Additionally, it addresses the various pathogenic mechanisms by which COVID-19 in the post-acute phase may contribute to the development of vascular disease. Understanding the overlap of these syndromes may enable novel therapeutic strategies. We further explore the need for guidelines for closer follow-up for the often-overlooked evidence of atherosclerotic cardiovascular disease among patients with recent COVID-19, particularly those with cardiometabolic risk factors.

Role of SARS-COV-2 and ACE2 in the pathophysiology of peripheral vascular diseases

The occurrence of a novel coronavirus known as severe acute respiratory syndrome-coronavirus-2 (SARS-CoV-2), created a serious challenge worldwide. SARS-CoV-2 has high infectivity, the ability to be transmitted even during the asymptomatic phase, and relatively low virulence, which has resulted in rapid transmission. SARS-CoV-2 can invade epithelial cells, hence, many patients infected with SARS-CoV-2 have suffered from vascular diseases (VDs) in addition to pulmonary manifestations. Accordingly, SARS-CoV-2 may can worsen the clinical condition of the patients with pre-existing VDs. Endothelial cells express angiotensin-converting enzyme 2 (ACE2). ACE2 is a biological enzyme that converts angiotensin (Ang)- 2 to Ang-(1-7). SARS-CoV-2 uses ACE2 as a cell receptor for viral entry. Thus, the SARS-CoV-2 virus promotes downregulation of ACE2, Ang-(1-7), and anti-inflammatory cytokines, as well as, an increase in Ang-2, resulting in pro-inflammatory cytokines. SARS-CoV-2 infection can cause hypertension, and endothelial damage, which can lead to intravascular thrombosis. In this review, we have concentrated on the effect of SARS-CoV-2 in peripheral vascular diseases (PVDs) and ACE2 as an enzyme in Renin-angiotensin aldosterone system (RAAS). A comprehensive search was performed on PubMed, Google Scholar, Scopus, using related keywords. Articles focusing on ("SARS-CoV-2", OR "COVID-19"), AND ("Vascular disease", OR "Peripheral vascular disease", OR interested disease name) with regard to MeSH terms, were selected. According to the studies, it is supposed that vascular diseases may increase susceptibility to severe SARS-CoV-2 infection due to increased thrombotic burden and endothelial dysfunction. Understanding SARS-CoV-2 infection mechanism and vascular system pathogenesis is crucial for effective management and treatment in pre-existing vascular diseases.

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

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

An update on angiotensin-converting enzyme 2 structure/functions, polymorphism, and duplicitous nature in the pathophysiology of coronavirus disease 2019: Implications for vascular and coagulation disease associated with severe acute respiratory syndrome coronavirus infection

It has been known for many years that the angiotensin-converting enzyme 2 (ACE2) is a cell surface enzyme involved in the regulation of blood pressure. More recently, it was proven that the severe acute respiratory syndrome coronavirus (SARS-CoV-2) interacts with ACE2 to enter susceptible human cells. This functional duality of ACE2 tends to explain why this molecule plays such an important role in the clinical manifestations of coronavirus disease 2019 (COVID-19). At the very start of the pandemic, a publication from our Institute (entitled "ACE2 receptor polymorphism: susceptibility to SARS-CoV-2, hypertension, multi-organ failure, and COVID-19 disease outcome"), was one of the first reviews linking COVID-19 to the duplicitous nature of ACE2. However, even given that COVID-19 pathophysiology may be driven by an imbalance in the renin-angiotensin system (RAS), we were still far from understanding the complexity of the mechanisms which are controlled by ACE2 in different cell types. To gain insight into the physiopathology of SARS-CoV-2 infection, it is essential to consider the polymorphism and expression levels of the ACE2 gene (including its alternative isoforms). Over the past 2 years, an impressive amount of new results have come to shed light on the role of ACE2 in the pathophysiology of COVID-19, requiring us to update our analysis. Genetic linkage studies have been reported that highlight a relationship between ACE2 genetic variants and the risk of developing hypertension. Currently, many research efforts are being undertaken to understand the links between ACE2 polymorphism and the severity of COVID-19. In this review, we update the state of knowledge on the polymorphism of ACE2 and its consequences on the susceptibility of individuals to SARS-CoV-2. We also discuss the link between the increase of angiotensin II levels among SARS-CoV-2-infected patients and the development of a cytokine storm associated microvascular injury and obstructive thrombo-inflammatory syndrome, which represent the primary causes of severe forms of COVID-19 and lethality. Finally, we summarize the therapeutic strategies aimed at preventing the severe forms of COVID-19 that target ACE2. Changing paradigms may help improve patients' therapy.

Angiotensin IV attenuates diabetic cardiomyopathy via suppressing FoxO1-induced excessive autophagy, apoptosis and fibrosis

Rationale: The rennin-angiotensin-aldosterone system (RAAS) plays a critical role in the pathogenesis of diabetic cardiomyopathy, but the role of a member of RAAS, angiotensin IV (Ang IV), in this disease and its underlying mechanism are unclear. This study was aimed to clarify the effects of Ang IV and its downstream mediator forkhead box protein O1 (FoxO1) on diabetic cardiomyopathy.

Methods:In vivo, diabetic mice were treated with low-, medium- and high-dose Ang IV, AT₄R antagonist divalinal, FoxO1 inhibitor AS1842856 (AS), or their combinations. In vitro, H9C2 cardiomyocytes and cardiac fibroblasts were treated with different concentrations of glucose, low-, medium- and high-dose Ang IV, divalinal, FoxO1-overexpression plasmid (FoxO1-OE), AS, or their combinations.

Results: Ang IV treatment dose-dependently attenuated left ventricular dysfunction, fibrosis, and myocyte apoptosis in diabetic mice. Besides, enhanced autophagy and FoxO1 protein expression by diabetes were dose-dependently suppressed by Ang IV treatment. However, these cardioprotective effects of Ang IV were completely abolished by divalinal administration. Bioinformatics analysis revealed that the differentially expressed genes were enriched in autophagy, apoptosis, and FoxO signaling pathways among control, diabetes, and diabetes+high-dose Ang IV groups. Similar to Ang IV, AS treatment ameliorated diabetic cardiomyopathy in mice. In vitro, high glucose stimulation increased collagen expression, apoptosis, overactive autophagy flux and FoxO1 nuclear translocation in cardiomyocytes, and upregulated collagen and FoxO1 expression in cardiac fibroblasts, which were substantially attenuated by Ang IV treatment. However, these protective effects of Ang IV were completely blocked by the use of divalinal or FoxO1-OE, and these detrimental effects were reversed by the additional administration of AS.

Conclusions: Ang IV treatment dose-dependently attenuated left ventricular dysfunction and remodeling in a mouse model of diabetic cardiomyopathy, and the mechanisms involved stimulation of AT₄R and suppression of FoxO1-mediated fibrosis, apoptosis, and overactive autophagy.

Renin-Angiotensin System in Pathogenesis of Atherosclerosis and Treatment of CVD

Atherosclerosis has complex pathogenesis, which involves at least three serious aspects: inflammation, lipid metabolism alterations, and endothelial injury. There are no effective treatment options, as well as preventive measures for atherosclerosis. However, this disease has various severe complications, the most severe of which is cardiovascular disease (CVD). It is important to note, that CVD is among the leading causes of death worldwide. The renin–angiotensin–aldosterone system (RAAS) is an important part of inflammatory response regulation. This system contributes to the recruitment of inflammatory cells to the injured site and stimulates the production of various cytokines, such as IL-6, TNF-a, and COX-2. There is also an association between RAAS and oxidative stress, which is also an important player in atherogenesis. Angiotensin-II induces plaque formation at early stages, and this is one of the most crucial impacts on atherogenesis from the RAAS. Importantly, while stimulating the production of ROS, Angiotensin-II at the same time decreases the generation of NO. The endothelium is known as a major contributor to vascular function. Oxidative stress is the main trigger of endothelial dysfunction, and, once again, links RAAS to the pathogenesis of atherosclerosis. All these implications of RAAS in atherogenesis lead to an explicable conclusion that elements of RAAS can be promising targets for atherosclerosis treatment. In this review, we also summarize the data on treatment approaches involving cytokine targeting in CVD, which can contribute to a better understanding of atherogenesis and even its prevention.

Vigilance on New-Onset Atherosclerosis Following SARS-CoV-2 Infection

The pandemic of coronavirus disease 2019 (COVID-19), caused by SARS-CoV-2, has become a global challenge to public health. While its typical clinical manifestations are respiratory disorders, emerging evidence of cardiovascular complications indicates the adverse interaction between SARS-CoV-2 infection and cardiovascular outcomes. Given that viral infection has emerged as an additional risk factor for atherosclerosis, in this paper, we attempt to clarify the susceptibility to new-onset atherosclerosis in individuals infected with SARS-CoV-2. Mechanistically, serving as functional receptors for SARS-CoV-2, angiotensin-converting enzyme 2 (ACE2) mediates SARS-CoV-2 infection of endothelial cells (ECs) directly, leading to endothelial dysfunction and dysregulation of the renin-angiotensin system (RAS). In addition, high expression of CD147, an alternative receptor, and activation of the NLRP3 inflammasome may also contribute to atherosclerosis in the context of COVID-19. More importantly, SARS-CoV-2 attacks the immune system, which results in excessive inflammation and perpetuates a vicious cycle of deteriorated endothelial dysfunction that further promotes inflammation. The alterations in the blood lipid profile induced by COVID-19 should not be ignored in assessing the predisposition toward atherosclerosis in victims of COVID-19. A better understanding of the underlying mechanisms of SARS-CoV-2 infection and the long-term monitoring of inflammatory factors and endothelial function should be considered in the follow-up of patients who have recovered from COVID-19 for early detection and prevention of atherosclerosis.

Cardiovascular disease in patients with COVID-19: evidence from cardiovascular pathology to treatment

The coronavirus disease-2019 (COVID-19) caused by the novel coronavirus severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2) has rapidly developed into a global pneumonia pandemic. Cardiovascular disease is the major comorbidity of COVID-19 patients and is closely related to the severity of COVID-19. SARS-CoV-2 infection can directly or indirectly cause a series of cardiac complications, including acute myocardial injury and myocarditis, heart failure and cardiac arrest, arrhythmia, acute myocardial infarction, cardiogenic shock, Takotsubo cardiomyopathy, and coagulation abnormalities. Intensive research on the SARS-CoV-2-associated cardiovascular complications is urgently needed to elucidate its exact mechanism and to identify potential drug targets, which will help to formulate effective prevention and treatment strategies. Hence, this review will summarize recent progress regarding the effects of COVID-19 on the cardiovascular system and describe the underlying mechanism of cardiovascular injury caused by SARS-CoV-2.

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.

Chronic Angiotensin 1-7 Infusion Prevents Angiotensin-II-Induced Cognitive Dysfunction and Skeletal Muscle Injury in a Mouse Model of Alzheimer's Disease

Alzheimer's disease (AD) is increasingly viewed as a neurological disease accompanied by a systemic disorder. Accumulating evidence supports that angiotensin II and angiotensin 1-7 exert opposite effects on various organs including the brain. However, the interaction between angiotensin II and angiotensin 1-7 in AD remains to be defined. The present study was undertaken to examine the interaction between these peptides in AD. 5XFAD mice, a useful model of AD, were separated into three groups: 1) saline-infused, 2) angiotensin II-infused, and 3) angiotensin II-infused and angiotensin 1-7-co-infused. These peptides were systemically given to 5XFAD mice via osmotic minipump for 4 weeks. Systemic angiotensin II infusion for 4 weeks induced significant hypertension in both wild-type and 5XFAD mice. Angiotensin II induced cognitive abnormality in 5XFAD mice as estimated by the Morris water maze test and the nest building test, and this effect was associated with cerebral blood flow reduction, cortical arterial amyloid-β deposition, hippocampal inflammation, and neuron loss in 5XFAD mice. In addition, angiotensin II infusion led to gastrocnemius muscle atrophy in 5XFAD mice. Co-infusion of angiotensin 1-7 prevented the above mentioned detrimental effects of angiotensin II in the brain and gastrocnemius muscle in 5XFAD mice, without significant influence on blood pressure. The left ventricular hypertrophic response to angiotensin II was attenuated in 5XFAD mice compared with wild-type mice, which was not significantly altered by co-administration of angiotensin 1-7. Our results show that angiotensin 1-7 counteracts angiotensin II-induced cognitive impairment, brain injury, and skeletal muscle injury in AD mice.

Role of Renin-Angiotensin System Components in Atherosclerosis: Focus on Ang-II, ACE2, and Ang-1-7

Atherosclerosis is the leading cause of vascular disease worldwide and contributes significantly to deaths from cardiovascular complications. There is a remarkably close relationship between atherosclerotic plaque formation and the activation of renin-angiotensin system (RAS). However, depending on which RAS pathway is activated, pro- or anti-atherogenic outcomes may be observed. This brief review focuses on the role of three of the most important pieces of RAS axis, angiotensin II (Ang-II), angiotensin converting enzyme type 2 (ACE2), and angiotensin 1-7 (Ang-1-7) and their involvement in atherosclerosis. We focused on the effects of these molecules on vascular function and inflammation, which are important determinants of atherogenesis. Furthermore, we highlighted potential pharmacological approaches to treat this disorder.

Angiotensin-Ⅱ and angiotensin-(1-7) imbalance affects comorbidity of depression and coronary heart disease

A large body of evidence suggests a relationship between depression and coronary heart disease (CHD). Angiotensin-Ⅱ (Ang-Ⅱ) and angiotensin-(1-7) [Ang-(1-7)] are considered to exert biological effects in both conditions. Here, we aimed to determine the role of Ang-Ⅱ and Ang-(1-7) in the occurrence of comorbid depression in patients with CHD. Our study included 214 CHD patients and 100 matched healthy controls. Serum Ang-Ⅱ and Ang-(1-7) levels were assessed by ELISA, and the depression symptoms were evaluated by the nine-item Patient Health Questionnaire (PHQ-9). Linear regression and correlation analyses were used to estimate the associations between PHQ-9 scores and Ang-Ⅱ and Ang-(1-7) serum levels. Six single-nucleotide polymorphisms (SNPs) spanning the angiotensin converting enzyme 2 (ACE2) and MAS1 genes were genotyped. The associations between SNPs and depression risk in CHD patients were examined using logistic regression analysis with adjustment for age and gender. Decreased Ang-(1-7) (P < 0.05) and an elevated Ang-Ⅱ/Ang-(1-7) ratio (P < 0.01) were observed in CHD patients with depression compared to CHD patients without depression. PHQ-9 scores were negatively correlated with Ang-(1-7) level (r=-0.44, P < 0.01) and positively correlated with the Ang-Ⅱ/Ang-(1-7) ratio (r = 0.33, P < 0.05). Furthermore, carriers of risk allele T for CHD with depression had significantly higher PHQ-9 scores (P < 0.05), lower Ang-(1-7) level (P < 0.01), and higher Ang-Ⅱ/Ang-(1-7) ratio (P < 0.05) than those CC carriers. Collectively, our results firstly showed that Ang-(1-7) serum level in CHD patients may protect against comorbid depression. Moreover, the imbalance between Ang-Ⅱ and Ang-(1-7) may contribute to depression in CHD patients.

Angiotensin-[1-7] attenuates kidney injury in experimental Alport syndrome

Angiotensin-[1–7] (Ang-[1–7]) antagonize the actions of the renin-angiotensin-system via the Mas receptor and thereby exert renoprotective effects. Murine recombinant angiotensin-converting enzyme (ACE)2 was reported to show renoprotective effects in an experimental Alport syndrome model; however, the protective effect of direct administration of Ang-[1–7] is unknown. Here, we used Col4a3^−/− mice as a model of Alport syndrome, which were treated with saline or Ang- [1–7]; saline-treated wild-type mice were used as a control group. The mice were continuously infused with saline or Ang-[1–7] (25 μg/kg/h) using osmotic mini-pumps. Col4a3^−/− mice showed increased α-smooth muscle actin (SMA), collagen, and fibronectin expression levels, which were attenuated by Ang-[1–7] treatment. Moreover, Ang-[1–7] alleviated activation of transforming growth factor-β/Smad signaling, and attenuated the protein expression of ED-1 and heme oxygenase-1, indicating reduction of renal inflammation. Ang-[1–7] treatment further reduced the expression levels of inflammatory cytokines and adhesion molecules and attenuated apoptosis in human kidney cells. Finally, Ang-[1–7] downregulated TNF-α converting enzyme and upregulated ACE2 expression. Thus, treatment with Ang-[1–7] altered the ACE2-Ang-[1–7]-Mas receptor axis in the kidneys of Col4a3^−/− mice to attenuate the nephropathy progression of Alport syndrome.

Angiotensin-(1-7) mitigated angiotensin II-induced abdominal aortic aneurysms in apolipoprotein E-knockout mice

BACKGROUND AND PURPOSE

To test the hypothesis that angiotensin-(1-7) [Ang-(1-7)] may attenuate abdominal aortic aneurysm (AAA) via inhibiting vascular inflammation, extracellular matrix degradation, and smooth muscle cell (SMC) apoptosis, an animal model of AAA was established by angiotensin II (Ang II) infusion to apolipoprotein E-knockout (ApoE^-/- ) mice.

EXPERIMENTAL APPROACH

All mice and cultured SMCs or macrophages were divided into control, Ang II-treated, Ang II + Ang-(1-7)-treated, Ang II + Ang-(1-7) + A779-treated and Ang II + Ang-(1-7) + PD123319-treated groups respectively. In vivo, aortic mechanics and serum lipids were assessed. Ex vivo, AAA were examined by histology, immunohistochemistry and zymography. Cultured cells were analysed by RT-PCR, western blots and TUNEL assays.

KEY RESULTS

In vivo, Ang-(1-7) reduced the incidence and severity of AAA induced by Ang II infusion, by inhibiting macrophage infiltration, attenuating expression of IL-6, TNF-α, CCL2 and MMP2, and decreasing SMC apoptosis in abdominal aortic tissues. Addition of A779 or PD123319 reversed Ang-(1-7)-mediated beneficial effects on AAA. In vitro, Ang-(1-7) decreased expression of mRNA for IL-6, TNF-α, and CCL2 induced by Ang II in macrophages. In addition, Ang-(1-7) suppressed apoptosis and MMP2 expression and activity in Ang II-treated SMCs. These effects were accompanied by inhibition of the ERK1/2 signalling pathways via Ang-(1-7) stimulation of Mas and AT₂ receptors.

CONCLUSION AND IMPLICATIONS

Ang-(1-7) treatment attenuated Ang II-induced AAA via inhibiting vascular inflammation, extracellular matrix degradation, and SMC apoptosis. Ang-(1-7) may provide a novel and promising approach to the prevention and treatment of AAA.

AVE0991, a nonpeptide angiotensin-(1-7) mimic, inhibits angiotensin II-induced abdominal aortic aneurysm formation in apolipoprotein E knockout mice

AVE0991, a nonpeptide angiotensin-(1-7) mimic, has similar protective effects for cardiovascular system to Ang-(1-7). In this article, we aimed to explore the effects of AVE0991 and Ang-(1-7) on abdominal aortic aneurysm (AAA) induced by Ang II in apolipoprotein E knockout mice. The mice AAA model was established by Ang II infusion, and then mice received different treatment with saline, Ang II (1.44 mg/kg/day), different dose AVE0991 (0.58 or 1.16 μmol/kg/day), or Ang-(1-7) (400 ng/kg/min). The incidence of AAA was 76%, 48%, 28%, and 24% in the vehicle, the low-dose AVE0991, high-dose AVE0991, and the Ang-(1-7) group, respectively. In comparison with control group, AVE0991 and Ang-(1-7) treatment significantly increased smooth muscle cells and decreased macrophage accumulation, the expression levels of monocyte chemoattractant protein-1 (MCP-1) and tumor necrosis factor α (TNF-α), and the expression and activity of metalloproteinases 2 and 9 in mice AAA model or in human smooth muscle cells (hVSMCs). The therapeutic effects may be contributed to reduction of oxidative stress and downregulation of P38 and ERK1/2 signal pathways via Mas receptor activation, whereas the positive impacts were reversed by co-administration with the Mas antagonist A779 (400 ng/kg/min) and AVE0991 in Ang II-infused mice or in hVSMCs. Therefore, AVE0991 and Ang-(1-7) might be novel and promising interventions in the prevention and treatment of AAA. KEY MESSAGES: • AVE0991 dose-dependently inhibited Ang II-induced AAA formation in Apoe^-/- mice. • Ang-(1-7) played the same protective role as high-dose AVE0991. • Inhibition of Mas receptor with A779 could reverse the protective effect of AVE0991. • The therapeutic effects may be contributed to reduction of oxidative stress and downregulation of P38 and ERK1/2 signal pathways via Mas receptor activation.

Relationship between circulating levels of angiotensin-converting enzyme 2-angiotensin-(1-7)-MAS axis and coronary heart disease

As a counter-regulatory arm of the renin angiotensin system (RAS), the angiotensin-converting enzyme 2-angiotensin-(1–7)-MAS axis (ACE2-Ang-(1–7)-MAS axis) plays a protective role in cardiovascular diseases. However, the link between circulating levels of ACE2-Ang-(1–7)-Mas axis and coronary atherosclerosis in humans is not determined. The object of present study was to investigate the association of circulating levels of ACE2, Ang-(1–7) and Ang-(1–9) with coronary heart disease (CHD) defined by coronary angiography (CAG). 275 patients who were referred to CAG for the evaluation of suspected CHD were enrolled and divided into two groups: CHD group (diameter narrowing ≥ 50%, n = 218) and non-CHD group (diameter narrowing < 50%, n = 57). Circulating ACE2, Ang-(1–7) and Ang-(1–9) levels were detected by enzyme-linked immunosorbent assay (ELISA). In females, circulating ACE2 levels were higher in the CHD group than in the non-CHD group (5617.16 ± 5206.67 vs. 3124.06 ± 3005.36 pg/ml, P = 0.009), and subgroup analysis showed the significant differences in ACE2 levels between the two groups only exist in patients with multi-vessel lesions (P = 0.009). In multivariate logistic regression, compared with the people in the lowest ACE2 quartile, those in the highest quartile had an OR of 4.33 (95% CI 1.20–15.61) for the CHD (P for trend = 0.025), the OR was 5.94 (95% CI 1.08–32.51) for the third ACE2 quartile and 9.58 (95% CI 1.61–56.95) for the highest ACE2 quartile after adjusting for potential confounders (P for trend = 0.022). However, circulating Ang-(1–7) and Ang-(1–9) levels had no significant differences between the two groups. In males, there were no significant differences in the levels of ACE2-Ang-(1–7)-MAS axis between two groups. Together, circulating ACE2 levels, but not Ang-(1–7) and Ang-(1–9) levels, significantly increased in female CHD group when compared with non-CHD group, increased ACE2 was independently associated with CHD in female and in patients with multi-vessel lesions even after adjusting for the confounding factors, indicating that ACE2 may participate as a compensatory mechanism in CHD.

Silencing of junctional adhesion molecule-like protein attenuates atherogenesis and enhances plaque stability in ApoE-/- mice

Background: Although junctional adhesion molecule-like protein (JAML) has recently been implicated in leukocyte recruitment during inflammation and wound repair, its role in atherosclerosis remains to be elucidated. Methods and results: First, we showed that JAML was strongly expressed in atherosclerotic plaques of cardiovascular patients. Similar results were obtained with atherosclerotic plaques of ApoE^-/- mice. Co-immunofluorescence staining showed that JAML was mainly expressed in macrophages. Enhanced expression of JAML in cultured macrophages was observed following exposure of the cells to oxLDL. The functional role of JAML in atherosclerosis and macrophages function was assessed by interference of JAML with shRNA in vivo and siRNA in vitro Silencing of JAML in mice significantly attenuated atherosclerotic lesion formation, reduced necrotic core area, increased plaque fibrous cap thickness, decreased macrophages content and inflammation. In addition, histological staining showed that JAML deficiency promoted plaques to stable phenotype. In vitro, JAML siRNA treatment lowered the expression of inflammatory cytokines in macrophages treated with oxLDL. The mechanism by which JAML mediated the inflammatory responses may be related to the ERK/NF-κB activation. Conclusions: Our results demonstrated that therapeutic drugs which antagonize the function of JAML may be a potentially effective approach to attenuate atherogenesis and enhance plaque stability.

Egg White-Derived Antihypertensive Peptide IRW (Ile-Arg-Trp) Reduces Blood Pressure in Spontaneously Hypertensive Rats via the ACE2/Ang (1-7)/Mas Receptor Axis

Scope

It is found in the previous study that egg‐white‐derived antihypertensive peptide Ile‐Arg‐Trp (IRW) upregulated angiotensin converting enzyme 2 (ACE2) in spontaneously hypertensive rats (SHRs). The objective of this study is to evaluate the contribution of ACE2 activation by IRW to blood‐pressure‐lowering activity in vivo.

Methods and results

Adult male SHRs (13–15 week old) are assigned into four groups: 1) untreated with saline infusion; 2) IRW administration (15 mg per kg body weight) with saline infusion; 3) Mas receptor (MasR) antagonist A779 (48 µg per kg body weight per h) infusion; 4) A779 infusion and IRW. Animals are implanted with telemetry transmitter first, and then an osmotic pump filled with saline or A779 is implanted. A779/saline is infused for 7 days, continued with an additional 7 days of treatments. Results indicate that blocking MasR abolished the blood‐pressure‐lowering effect of IRW. Akt/eNOS signaling in aorta is upregulated by IRW treatment but deactivated by A779 infusion. Circulating levels of interleukin 6 and monocyte chemoattractant protein 1, along with cyclooxygenase 2 in aorta are reduced by IRW but restored by A779 infusion.

Conclusion

IRW reduces blood pressure of SHR via the ACE2/Ang (1‐7)/MasR axis. Mechanisms pertaining to IRW as an ACE2 activator in vivo include enhanced endothelium‐dependent vasorelaxation and reduced vascular inflammation.

Decreased circulating catestatin levels are associated with coronary artery disease: The emerging anti-inflammatory role

BACKGROUND AND AIMS

The neuropeptide catestatin (CST) is an endogenous nicotinic cholinergic antagonist that acts as pleiotropic cardiac protective hormone. This study investigated the association between CST and coronary artery disease (CAD) and the underlying mechanisms.

METHODS AND RESULTS

The serum concentration of CST among 224 CAD patients and 204 healthy controls was compared, and its association with atherosclerosis severity in 921 CAD patients was further analyzed. Compared to healthy subjects, serum CST concentration was lower in patients with CAD [1.14 (1.05-1.24) ng/mL vs. 2.15 (1.92-2.39) ng/mL, p < 0.001] and was inversely correlated with disease severity (r = -0.208, p < 0.001). In cultured endothelial cells, CST suppressed TNF-α-elicited expression of inflammatory cytokines and adhesion molecules by activating angiotensin-converting enzyme-2 (ACE2). Administration of CST reduced leukocyte-endothelium interactions in vitro and in vivo, and attenuated the development of atherosclerotic in ApoE^-/- mice fed a high-fat diet. These protective effects by CST were blocked by an ACE2 inhibitor.

CONCLUSIONS

Serum CST concentration is lower in CAD patients and is inversely associated with the severity of atherosclerosis. CST acts as a novel anti-atherogenic peptide that inhibits inflammatory response and EC-leukocyte interactions via an ACE2-dependent mechanism.

Angiotensin-(1-7) and Alamandine on Experimental Models of Hypertension and Atherosclerosis

PURPOSE OF REVIEW

The purpose of this review was to summarize the current knowledge on the role of angiotensin-(1-7) [Ang-(1-7)] and alamandine in experimental hypertension and atherosclerosis.

RECENT FINDINGS

The renin-angiotensin system (RAS) is a very complex system, composed of a cascade of enzymes, peptides, and receptors, known to be involved in the pathogenesis of hypertension and atherosclerosis. Ang-(1-7), identified and characterized in 1987, and alamandine, discovered 16 years after, are the newest two main effector molecules from the RAS, protecting the vascular system against hypertension and atherosclerosis. While the beneficial effects of Ang-(1-7) have been widely studied in several experimental models of hypertension, much less studies were performed in experimental models of atherosclerosis. Alamandine has shown similar vascular effects to Ang-(1-7), namely, endothelial-dependent vasorelaxation mediated by nitric oxide and hypotensive effects in experimental hypertension. There are few studies on the effects of alamandine on atherosclerosis.

Angiotensin-(1-7)-induced Mas receptor activation attenuates atherosclerosis through a nitric oxide-dependent mechanism in apolipoproteinE-KO mice

Angiotensin (Ang)-(1-7) ameliorates vascular injury by increasing nitric oxide (NO) bioavailability. Evidence that Ang-(1-7) attenuates the development of atherosclerosis through a NO-dependent mechanism is still missing. Moreover, it has been postulated that Ang-(1-7) may mediate its effects by other mechanisms than Mas receptor activation. To investigate Ang-(1-7)-dependent Mas receptor function, we treated apoE-KO and apoE/Mas-KO mice chronically with Ang-(1-7) (82 μg/kg per hour) or saline for 6 weeks. Flow-mediated dilation (FMD), a measure for NO-dependent vasodilation and the most accepted prognostic marker for the development of atherosclerosis, was measured in vivo. Chronic Ang-(1-7) treatment improved FMD and attenuated the development of atherosclerosis in apolipoproteinE (apoE)-KO but not in apoE/Mas-KO mice. These effects were accompanied by increased aortic nitrite and cGMP levels. To test whether Ang-(1-7) modulates atherosclerosis through a NO-dependent mechanism, apoE-KO mice were treated with the NO synthase inhibitor L-NAME (20 mg/kg/day) in the presence or absence of Ang-(1-7). L-NAME treatment reduced aortic nitrite content and increased blood pressure and exaggerated atherosclerosis compared to untreated apoE-KO mice. In L-NAME-treated apoE-KO mice, chronic Ang-(1-7) treatment did not increase aortic nitrite content and consequently showed no effect on blood pressure and the development of atherosclerosis. The present study proves that Ang-(1-7) mediates its protective vascular effects through Mas receptor activation. Moreover, Ang-(1-7)-mediated NO generation is essential for improving vascular function and prevents atherosclerosis in apoE-KO mice.

Oleanolic acid protects against pathogenesis of atherosclerosis, possibly via FXR-mediated angiotensin (Ang)-(1-7) upregulation

Atherosclerosis, the leading cause of cardiovascular diseases in the world, is a chronic inflammatory disorder characterized by the dysfunction of arteries. Oleanolic acid (OA) is a bioactive nature product which exists in various plants and herbs. Previous studies have demonstrated that OA was involved in numerous of biological processes, including atherosclerosis. However, the exact mechanisms of the anti-atherosclerosis effects of OA remain unknown. Here, in our study, we analyzed the effects and possible underlying mechanisms of OA in atherosclerosis depending a cell model and an animal model of atherosclerosis. Human umbilical vein endothelial cells (HUVECs) were treated with oxidized low-density lipoprotein (ox-LDL, 100 μg/mL) for 24 h to establish an atherosclerotic cell model. New Zealand white (NZW) rabbits were fed with high-fat (HF) diets for three months to establish an atherosclerotic animal model. Then, cell viability and expression of cytokines (ANG, NO, eNOS, IL-1β, TNF-α, and IL-6) were measured with CCK-8 assay and ELISA kits, cell apoptosis and cell cycle distribution were analyzed by flow cytometry in the atherosclerotic cell model. Results showed that ox-LDL induced effects of anti-proliferation, cytokines alterations, and cell apoptosis were abolished by the application of OA or Ang (1-7). Further study indicated that OA increased the expression of ANG by upregulating the FXR expression in the ox-LDL induced HUVECs arthrosclerosis model. And the in vivo experiment in the HF diet induced animal model suggested that OA may inhibit the development of atherosclerosis. The atherosclerosis of aortas was assessed by Hematoxylin Eosin (HE), Oil Red O and Picrosirius Red staining; the expression levels of total cholesterol (TC), triglycerides (TG), low density lipoprotein cholesterol (LDL-C), and high density lipoprotein cholesterol (HDL-C) were determined by the fully automatic biochemical analyzer, in the atherosclerotic animal model. All the results showed that OA treatment improved the cell viability in the cell model, inhibited the atherosclerosis development in the animal model. OA play as an anti-atherosclerosis agent in both the cell model and animal model by upregulating the production of Angiotensin (Ang)-(1-7) through FXR.

Angiotensin-(1-7) Inhibits Thrombin-Induced Endothelial Phenotypic Changes and Reactive Oxygen Species Production via NADPH Oxidase 5 Downregulation

Background and Aims: The angiotensin-(1-7)/angiotensin-converting enzyme 2/Mas receptor axis counter-regulates the detrimental effects of angiotensin II. Beneficial effects of angiotensin-(1-7), including anti-inflammation, oxidative stress reduction, and anti-thrombosis, have been reported. Previous studies documented that ramipril decreased thrombin generation in human hypertension and that the anti-thrombotic effects of captopril and losartan were angiotensin-(1-7)-dependent, suggesting an interaction between thrombin and angiotensin-(1-7). However, it is not clear whether angiotensin-(1-7) can alleviate the endothelial phenotypic changes induced by thrombin. We have previously documented cytoskeleton remodeling, cell adhesion, and cell migration as dominant altered phenotypes in thrombin-stimulated human aortic endothelial cells (HAECs). In this study, we investigated whether angiotensin-(1-7) can modulate thrombin-induced phenotypic changes. Furthermore, we investigated whether NAPDH oxidase 5 (Nox5)-produced reactive oxygen species (ROS) play a significant role in angiotensin-(1-7)-mediated phenotypic changes.

Methods: HAECs were pretreated with 100 nM angiotensin-(1-7) for 1 h, followed by stimulation with 2 units/mL thrombin for different times. Immunofluorescent assay, monocyte adhesion assay, wound-healing assay, ROS assay, real-time PCR, Western blotting, and Nox5 siRNA transfection were conducted. HAECs were pretreated with the ROS scavenger N-acetylcysteine (NAC) to determine whether thrombin-induced phenotypic changes depended on ROS production.

Results: Angiotensin-(1-7) prevented thrombin-induced actin cytoskeleton derangements, monocyte adhesion, and migratory impairment. Nox5 siRNA transfection confirmed that thrombin-induced Nox5 expression stimulated ROS production and increased HO-1/NQO-1/ICAM-1/VCAM-1 gene expression, all of which were decreased by angiotensin-(1-7). Phenotypic changes induced by thrombin were prevented by NAC pretreatment.

Conclusion: Angiotensin-(1-7) prevents actin cytoskeleton derangement, monocyte adhesion, and migration impairment induced by thrombin via downregulation of ROS production. In addition, thrombin-induced Nox5 expression is involved in the production of ROS, and angiotensin-(1-7) decreases ROS through its inhibitory effect on Nox5 expression.

ACE2 and the Homolog Collectrin in the Modulation of Nitric Oxide and Oxidative Stress in Blood Pressure Homeostasis and Vascular Injury

SIGNIFICANCE

Hypertension is the leading risk factor causing mortality and morbidity worldwide. Angiotensin (Ang) II, the most active metabolite of the renin-angiotensin system, plays an outstanding role in the pathogenesis of hypertension and vascular injury. Activation of angiotensin converting enzyme 2 (ACE2) has shown to attenuate devastating effects of Ang II in the cardiovascular system by reducing Ang II degradation and increasing Ang-(1-7) generation leading to Mas receptor activation. Recent Advances: Activation of the ACE2/Ang-(1-7)/Mas receptor axis reduces hypertension and improves vascular injury mainly through an increased nitric oxide (NO) bioavailability and decreased reactive oxygen species production. Recent studies reported that shedding of the enzymatically active ectodomain of ACE2 from the cell surface seems to regulate its activity and serves as an interorgan communicator in cardiovascular disease. In addition, collectrin, an ACE2 homolog with no catalytic activity, regulates blood pressure through an NO-dependent mechanism.

CRITICAL ISSUES

Large body of experimental data confirmed sustained beneficial effects of ACE2/Ang-(1-7)/Mas receptor axis activation on hypertension and vascular injury. Experimental studies also suggest that activation of collectrin might be beneficial in hypertension and endothelial dysfunction. Their role in clinical hypertension is unclear as selective and reliable activators of both axes are not yet available.

FUTURE DIRECTIONS

This review will highlight the results of recent research progress that illustrate the role of both ACE and collectrin in the modulation of NO and oxidative stress in blood pressure homeostasis and vascular injury, providing evidence for the potential therapeutic application of ACE2 and collectrin in hypertension and vascular disease. Antioxid. Redox Signal. 26, 645-659.

Angiotensin-(1-7) regulates angiotensin II-induced matrix metalloproteinase-8 in vascular smooth muscle cells

BACKGROUND AND AIMS

Angiotensin II (Ang II) is a bioactive peptide that is related to cardiovascular disease such as atherosclerosis, whereas angiotensin-(1-7) (Ang-(1-7)) is a counter-regulator of angiotensin II, which protects against cardiovascular disease. Matrix metalloproteinase 8 (MMP-8) is thought to participate in plaque destabilization though degradation of extracellular matrix, improving the development of atherosclerosis. Whether Ang-(1-7) modulates Ang II-induced MMP-8 remains unclear. In this study, we investigated the effect of Ang-(1-7) on Ang II-induced MMP-8 expression in smooth muscle cells.

METHODS

Smooth muscle cells were treated with Ang II, Ang-(1-7) and their antagonists. In addition, ApoE knockout mice were fed a high fat diet and subcutaneously injected with Ang II, Ang-(1-7), Ang II+Ang-(1-7) (±A779).

RESULTS

We found that Ang II increased MMP-8 mRNA and protein expression in vascular smooth muscle cells, while Ang-(1-7) alone had no effect. However, Ang-(1-7) inhibited Ang II-induced MMP-8 expression. The inhibitory effect of Ang-(1-7) could be abolished by the competitive antagonist of Ang-(1-7) at the MAS receptor. Furthermore, Ang II induced p38 MAPK activation, and this was inhibited by the treatment of Ang-(1-7). Ang II-induced MMP-8 expression could be attenuated by the p38 MAPK inhibitor SB203580. Ang-(1-7) also significantly suppressed Ang II-induced MMP-8 in both atherosclerotic plaques and serum in ApoE^-/- mice. The atherosclerotic plaques in mice treated with Ang-(1-7) and Ang II appeared to be more stable with more type I collagen contents than those in mice treated with Ang II.

CONCLUSIONS

Our results suggest that Ang-(1-7) plays an important role in protecting against atherosclerosis via counter-regulation of Ang II-induced MMP-8.

p-Cresyl sulfate promotes the formation of atherosclerotic lesions and induces plaque instability by targeting vascular smooth muscle cells

Coronary atherosclerosis is a major complication of chronic kidney disease. This condition contributes to the increased mortality in dialysis patients. p-Cresyl sulfate (PCS) is a prototype of protein-bound uremic toxins that cannot be efficiently removed through routine dialysis procedures. In the present study, ApoE(-/-) mice that underwent 5/6 nephrectomy were randomly divided into two groups, namely, vehicle-treated group (n = 20) and PCS-treated group (n = 20). Mice were sacrificed for en face and immunohistological analyses after 8 or 24 weeks of high-fat diet. Rat aortic vascular smooth muscle cells (VSMCs) were treated with phosphate buffer solution or 500 μmol/L PCS for in vitro evaluation. PCS-treated mice were observed to suffer increased atherosclerotic lesions after eight weeks of PCS administration. Moreover, 24 weeks of PCS administration also markedly increased the vulnerability index of aortic plaques. PCS was also observed to facilitate the migration and proliferation of VSMCs during the progression of the disease. Moreover, PCS disturbed the balance between matrix metalloproteinases and tissue inhibitor of metalloproteinases within the plaques. Thus, PCS played a vital role in promoting atherogenesis and disturbing the stability of formed plaques probably by targeting VSMCs.

Imbalance between angiotensin II and angiotensin-(1-7) in human coronary atherosclerosis

Objective:

Our previous studies found that angiotensin-(1–7) (Ang-(1–7)) is an endogenous counter-factor of angiotensin II (Ang-II). However, the balance between Ang-II and Ang-(1–7) in the development of human coronary atherosclerosis is not determined.

Methods and results:

The plasma levels of Ang-II and Ang-(1–7) were detected by enzyme-linked immunosorbent assay (ELISA) in 112 patients with known or suspected coronary artery disease (CAD) undergoing coronary angiography. Patients were divided into three groups based on the coronary angiography as follows: (1) normal (n = 13); (2) noncritical CAD (<50% stenosis, n = 17); and (3) critical CAD (⩾50% stenosis, n = 82). The plasma levels of Ang-II, Ang-(1–7) and the ratio of Ang-II and Ang-(1–7) (Ang-II/Ang-(1–7) were comparable between the normal and noncritical CAD groups. However, Ang-II, Ang-(1–7), and especially Ang-II/Ang-(1–7), were elevated in patients with critical CAD, compared with patients with normal or noncritical CAD. The level of Ang-II/Ang-(1–7) was positively associated with serious coronary stenosis, and correlated with tumor necrosis factor-alpha (TNF-α) level.

Conclusion:

Both Ang-II and Ang-(1–7) expression are significantly increased in patients with critical CAD. However, increased Ang-II/Ang-(1–7) ratios may lead to Ang-II over-activation and aggravate atherosclerosis progression.

Indoxyl Sulfate Downregulates Mas Receptor via Aryl Hydrocarbon Receptor/Nuclear Factor-kappa B, and Induces Cell Proliferation and Tissue Factor Expression in Vascular Smooth Muscle Cells

BACKGROUND/AIM

Angiotensin converting enzyme-related carboxypeptidase 2/angiotensin (Ang)-(1-7)/Mas receptor axis is protective in the development of chronic kidney disease and cardiovascular disease. This study is aimed at investigating whether indoxyl sulfate (IS) affects Mas receptor expression, cell proliferation and tissue factor expression in vascular smooth muscle cells, and if Ang-(1-7), an activator of Mas receptor, counteracts the IS-induced effects.

METHODS

IS was administered to normotensive and hypertensive rats. Human aortic smooth muscle cells (HASMCs) were cultured with IS.

RESULTS

IS reduced the expression of Mas receptor in the aorta of normotensive and hypertensive rats. IS downregulated the Mas receptor expression in a time- and dose-dependent manner in HASMCs. Knockdown of aryl hydrocarbon receptor (AhR) and nuclear factor-kappa B (NF-x03BA;B) inhibited IS-induced downregulation of Mas receptor. Further, IS stimulated cell proliferation and tissue factor expression in HASMCs. Ang-(1-7) attenuated IS-induced cell proliferation and tissue factor expression in HASMCs. Ang-(1-7) suppressed phosphorylation of extracellular signal-regulated kinase 1/2 (ERK1/2) and NF-x03BA;B in HASMCs.

CONCLUSION

IS downregulated the expression of Mas receptor via AhR/NF-x03BA;B, and induced cell proliferation and tissue factor expression in HASMCs. Ang-(1-7) inhibited IS-induced cell proliferation and tissue factor expression by suppressing the phosphorylation of ERK1/2 and NF-x03BA;B p65.

Angiotensin-(1-7): new perspectives in atherosclerosis treatment

Angiotensin (Ang)-(1-7) is recognized as a new bioactive peptide in renin-angiotensin system (RAS). Ang-(1-7) is a counter-regulatory mediator of Ang-II which appears to be protective against cardiovascular disease. Recent studies have found that Ang-(1-7) played an important role in reducing smooth muscle cell proliferation and migration, improving endothelial function and regulating lipid metabolism, leading to inhibition of atherosclerotic lesions and increase of plaque stability. Although clinical application of Ang-(1-7) is restricted due to its pharmacokinetic properties, identification of stabilized compounds, including more stable analogues and specific delivery compounds, has enabled clinical application of Ang-(1-7). In this review, we discussed recent findings concerning the biological role of Ang-(1-7) and related mechanism during atherosclerosis development. In addition, we highlighted the perspective to develop therapeutic strategies using Ang-(1-7) to treat atherosclerosis.

Atherosclerotic Plaque Destabilization in Mice: A Comparative Study

Atherosclerosis-associated diseases are the main cause of mortality and morbidity in western societies. The progression of atherosclerosis is a dynamic process evolving from early to advanced lesions that may become rupture-prone vulnerable plaques. Acute coronary syndromes are the clinical manifestation of life-threatening thrombotic events associated with high-risk vulnerable plaques. Hyperlipidemic mouse models have been extensively used in studying the mechanisms controlling initiation and progression of atherosclerosis. However, the understanding of mechanisms leading to atherosclerotic plaque destabilization has been hampered by the lack of proper animal models mimicking this process. Although various mouse models generate atherosclerotic plaques with histological features of human advanced lesions, a consensus model to study atherosclerotic plaque destabilization is still lacking. Hence, we studied the degree and features of plaque vulnerability in different mouse models of atherosclerotic plaque destabilization and find that the model based on the placement of a shear stress modifier in combination with hypercholesterolemia represent with high incidence the most human like lesions compared to the other models.

Angiotensin-(1-7) counteracts the effects of Ang II on vascular smooth muscle cells, vascular remodeling and hemorrhagic stroke: Role of the NFкB inflammatory pathway

Angiotensin (Ang)-(1-7) is a potential vasoprotective peptide. In the present study, we investigated its counteractive effects to Ang II on vascular smooth muscle cells (VSMCs) and intracerebral hemorrhagic stroke (ICH) through inflammatory mechanism. In in vitro experiments, human brain VSMCs (HBVSMCs) were treated with vehicle, Ang II, Ang II+Ang-(1-7), Ang II+A-779 or Ang II+Ang-(1-7)+A-779 (Mas receptor antagonist). HBVSMC proliferation, migration and apoptosis were determined by methyl thiazolyltetrazolium, wound healing assay and flow cytometry, respectively. In in vivo experiments, C57BL/6 mice were divided into vehicle, Ang II, Ang II+Ang-(1-7), Ang II+A-779 or Ang II+Ang-(1-7)+A-779 groups before they were subjected to collagenase-induced ICH or sham surgery. Hemorrhage volume and middle cerebral artery (MCA) remodeling were determined by histological analyses. Levels of NFκB, inhibitor of κBα (IκBα), tumor necrosis factor-α (TNF-α), monocyte chemoattractant protein 1 (MCP-1) and interleukin (IL-8) were measured by western blot or ELISA. We found that 1) Ang II increased HBVSMC migration, proliferation and apoptosis, and increased the blood pressure (BP), neurological deficit score, MCA remodeling and hemorrhage volume in ICH mice. 2) Ang-(1-7) counteracted these effects of Ang II, which was independent of BP, with the down-regulation of NFκB, up-regulation of IκBα, and decreased levels of TNF-α, MCP-1 and IL-8. 3) The beneficial effects of Ang-(1-7) could be abolished by A-779. In conclusion, Ang-(1-7) counteracts the effects of Ang II on ICH via modulating NFκB inflammation pathway in HBVSMCs and cerebral microvessels.

Dose-Dependent Bidirectional Effect of Angiotensin IV on Abdominal Aortic Aneurysm via Variable Angiotensin Receptor Stimulation

Angiotensin IV (Ang IV), as an effector peptide of the rennin-angiotensin system, possesses many biological properties yet not completely known. In this study, we aimed to investigate the role of Ang IV in the development of Ang II-induced abdominal aortic aneurysm (AAA) in apolipoprotein E-knockout mice. We used Ang II infusion to induce AAA, and animals were treated with Ang II (1.44 mg/kg per day) plus no treatment, Ang II (1.44 mg/kg per day) plus low-, medium-, and high-dose Ang IV (0.72, 1.44, and 2.88 mg/kg per day, respectively). The incidence of AAA was 87.5%, 66.7%, 37.5%, and 83.3% in the no treatment, the low-, medium-, or high-dose Ang IV group, respectively. Compared with the no treatment group, medium-dose Ang IV treatment markedly reduced macrophage infiltration; levels of proinflammatory cytokines, including monocyte chemoattractant protein 1, interleukin 6, and intercellular adhesion molecule 1; the expression and activity of metalloproteinases 2 and 9; but increased smooth muscle cells, and collagen content in AAA. However, high-dose Ang IV treatment did not have obvious protective effect. The beneficial effect of medium-dose Ang IV may be contributed to the stimulation of type 4 angiotensin receptor (AT4R) and AT2R with suppression of AT1R, activation of Akt, and inhibition of nuclear factor-κB, as these beneficial effects were largely reversed by cotreatment with the AT4R antagonist divalinal-Ang IV in Ang II-infused mice or with the Akt inhibitor A6730 in Ang II-stimulated human smooth muscle cells. Therefore, medium dose of Ang IV may provide a novel and promising approach to the treatment of AAA.

Angiotensin-(1-7) protects against the development of aneurysmal subarachnoid hemorrhage in mice

Angiotensin-(1-7) (Ang-(1-7)) can regulate vascular inflammation and remodeling, which are processes that have important roles in the pathophysiology of intracranial aneurysms. In this study, we assessed the effects of Ang-(1-7) in the development of intracranial aneurysm rupture using a mouse model of intracranial aneurysms in which aneurysmal rupture (i.e., aneurysmal subarachnoid hemorrhage) occurs spontaneously and causes neurologic symptoms. Treatment with Ang-(1-7) (0.5 mg/kg/day), Mas receptor antagonist (A779 0.5 mg/kg/day or 2.5 mg/kg/day), or angiotensin II type 2 receptor (AT2R) antagonist (PD 123319, 10 mg/kg/day) was started 6 days after aneurysm induction and continued for 2 weeks. Angiotensin-(1-7) significantly reduced the rupture rate of intracranial aneurysms without affecting the overall incidence of aneurysms. The protective effect of Ang-(1-7) was blocked by the AT2R antagonist, but not by the Mas receptor antagonist. In AT2R knockout mice, the protective effect of Ang-(1-7) was absent. While AT2R mRNA was abundantly expressed in the cerebral arteries and aneurysms, Mas receptor mRNA expression was very scarce in these tissues. Angiotensin-(1-7) reduced the expression of tumor necrosis factor-α and interleukin-1β in cerebral arteries. These findings indicate that Ang-(1-7) can protect against the development of aneurysmal rupture in an AT2R-dependent manner.

Perinatally administered losartan augments renal ACE2 expression but not cardiac or renal Mas receptor in spontaneously hypertensive rats

Since the identification of the alternative angiotensin converting enzyme (ACE)2/Ang-(1-7)/Mas receptor axis, renin-angiotensin system (RAS) is a new complex target for a pharmacological intervention. We investigated the expression of RAS components in the heart and kidney during the development of hypertension and its perinatal treatment with losartan in young spontaneously hypertensive rats (SHR). Expressions of RAS genes were studied by the RT-PCR in the left ventricle and kidney of rats: normotensive Wistar, untreated SHR, SHR treated with losartan since perinatal period until week 9 of age (20 mg/kg/day) and SHR treated with losartan only until week 4 of age and discontinued until week 9. In the hypertrophied left ventricle of SHR, cardiac expressions of Ace and Mas were decreased while those of AT1 receptor (Agtr1a) and Ace2 were unchanged. Continuous losartan administration reduced LV weight (0.43 ± 0.02; P < 0.05 versus SHR) but did not influence altered cardiac RAS expression. Increased blood pressure in SHR (149 ± 2 in SHR versus 109 ± 2 mmHg in Wistar; P < 0.05) was associated with a lower renal expressions of renin, Agtr1a and Mas and with an increase in ACE2. Continuous losartan administration lowered blood pressure to control levels (105 ± 3 mmHg; P < 0.05 versus SHR), however, only renal renin and ACE2 were significantly up-regulated (for both P < 0.05 versus SHR). Conclusively, prevention of hypertension and LV hypertrophy development by losartan was unrelated to cardiac or renal expression of Mas. Increased renal Ace2, and its further increase by losartan suggests the influence of locally generated Ang-(1-7) in organ response to the developing hypertension in SHRs.

Comparison of angiotensin-(1-7), losartan and their combination on atherosclerotic plaque formation in apolipoprotein E knockout mice

AIMS

Inhibition of the classical renin-angiotensin system (RAS) has been proved to reduce atherosclerosis. Recently, angiotensin-(1-7) [Ang-(1-7)], a new component of RAS, has been shown to attenuate atherosclerosis formation. However, direct comparison of Ang-(1-7) and angiotensin II type 1 receptor blocker (ARB) on atherogenesis is sparse. Here, we investigated whether large dose of Ang-(1-7) and losartan are equivalent or the combination of both is superior in reducing atherosclerotic plaque formation.

METHODS AND RESULTS

In vivo, we established an atherosclerosis model in ApoE-/- mice. All mice were fed a high fat diet during experiments. Mice were divided into control, Ang-(1-7), losartan, Ang-(1-7)+losartan groups for 4 weeks treatment. Ang-(1-7) did not change the blood pressure (BP) levels, while losartan produced a significant decrease in systolic BP. The attenuation of Ang-(1-7) and losartan in atherosclerosis plaque formation was similar. However, the decrease of atherosclerosis in mice with combination of Ang-(1-7) and losartan was more remarkable relative to that of Ang-(1-7) or losartan alone. The decreases of macrophages infiltration, superoxide production and improvement of endothelium function in aortic lesions were more significant in combination group. In vitro study, we found that combination of Ang-(1-7) and losartan notably inhibited VSMCs proliferation and migration.

CONCLUSIONS

The anti-atherosclerosis effects of Ang-(1-7) and losartan in early lesion formation were equivalent. Combination use of both agents further enhanced the beneficial effects. Ang-(1-7) might add additional beneficial effect for patients with adequate ARB treatment.

External ultrasound for carotid atherosclerotic plaque treatment

OBJECTIVES

The purpose of this study was to evaluate the efficacy of external ultrasound in the treatment of carotid atherosclerotic plaques.

METHODS

In the prospective study, 357 patients with 363 carotid atherosclerotic plaques were divided into an ultrasound treatment group and a control group. For 30 days, conventional medical treatment was conducted on 54 plaques in the control group, whereas irradiation therapy in addition to conventional medical treatment was conducted on 309 plaques in the ultrasound group. Carotid sonography was conducted before and after treatment, and the maximum plaque thickness and area were measured in a longitudinal section.

RESULTS

No patients withdrew from the treatment because of related side effects. After treatment, the maximum thickness and area of 79.94% of the plaques in the ultrasound group were reduced, whereas in the control group, the thickness and area of 18.52% were reduced. The mean changes in plaque thickness and area ± SD in the ultrasound and control groups were 0.22 ± 0.19 mm (7.61% ± 5.67%) versus 0.02 ± 0.05 mm (0.74% ± 1.64%) and 0.047 ± 0.039 cm(2) (13.28% ± 9.8%) versus 0.0044 ± 0.0102 cm(2) (1.1% ± 2.46%), respectively. Changes in both plaque thickness and area in the ultrasound group were significantly greater than those in the control group (P< .0001). Furthermore, the plaque echo type was another prognostic factor affecting efficacy (P < .05).

CONCLUSIONS

External ultrasound treatment is safe and effective for carotid atherosclerotic plaques and is worthy of further research and applications. The efficacy in anechoic/hypoechoic plaques is significantly higher than that in mixed echoic and calcified echoic plaques.

Update on the role of angiotensin in the pathophysiology of coronary atherothrombosis

BACKGROUND

Coronary atherothrombosis due to atherosclerotic plaque rupture or erosion is frequently associated with acute coronary syndromes (ACS). Significant efforts have been made to elucidate the pathophysiological mechanisms underlying acute coronary events.

MATERIALS AND METHODS

This narrative review is based on the material searched for and obtained via PubMed up to August 2014. The search terms we used were as follows: 'angiotensin, acute coronary syndromes, acute myocardial infarction' in combination with 'atherosclerosis, vulnerability, clinical trial, ACE inhibitors, inflammation'.

RESULTS

Among several regulatory components, the renin-angiotensin system (RAS) was shown as a key pathway modulating coronary atherosclerotic plaque vulnerability. Indeed, these molecules are involved in all stages of atherogenesis. Classically, the RAS is composed by a series of enzymatic reactions leading to the angiotensin (Ang) II generation and activity. However, the knowledge of RAS has expanded and become more complex. The discovery of novel components and their functions has revealed additional pathways that contribute to or counterbalance the actions of Ang II. In this review, we discussed on recent findings concerning the role of different angiotensin peptides in the pathophysiology of ACS and coronary atherothrombosis, exploring the link between these molecules and atherosclerotic plaque vulnerability.

CONCLUSIONS

Treatments selectively targeting angiotensins (including Mas and AT2 agonists, ACE2 recombinant, or Ang-(1-7) and almandine in oral formulations) have been tested in animal studies or in small human subgroups, expanding the perspective in the ACS prevention. These novel strategies, especially in the counter-regulatory axis ACE2/Ang-(1-7)/Mas, might be promising to reduce plaque vulnerability and inflammation.

Angiotensin-converting enzyme 2 and angiotensin 1-7: novel therapeutic targets

Angiotensin-converting enzyme (ACE) 2 and its product angiotensin 1–7 are thought to have effects that counteract the adverse actions of other, better-known renin–angiotensin system (RAS) components

Numerous experimental studies have suggested that ACE2 and angiotensin 1–7 have notable protective effects in the heart and blood vessels

ACE2-mediated catabolism of angiotensin II is likely to have a major role in cardiovascular protection, whereas the functional importance and signalling mechanisms of angiotensin-1–7-induced actions remain unclear

New pharmacological interventions targeting ACE2 are expected to be useful in clinical treatment of cardiovascular disease, especially those associated with overactivation of the conventional RAS

More studies, especially randomized controlled clinical trials, are needed to clearly delineate the benefits of therapies targeting angiotensin 1–7 actions

Angiotensin-converting enzyme 2, and its product angiotensin 1–7, are thought to have counteracting effects against the adverse actions of the better-known members of the renin–angiotensin system and might, therefore, be useful therapeutic targets in patients with cardiovascular disease. Professor Jiang and colleagues review the evidence for the potential roles of these proteins in various cardiovascular conditions, including hypertension, atherosclerosis, myocardial remodelling, heart failure, ischaemic stroke, and diabetes.

The renin–angiotensin system (RAS) has pivotal roles in the regulation of normal physiology and the pathogenesis of cardiovascular disease. Angiotensin-converting enzyme (ACE) 2, and its product angiotensin 1–7, are thought to have counteracting effects against the adverse actions of other, better known and understood, members of the RAS. The physiological and pathological importance of ACE2 and angiotensin 1–7 in the cardiovascular system are not completely understood, but numerous experimental studies have indicated that these components have protective effects in the heart and blood vessels. Here, we provide an overview on the basic properties of ACE2 and angiotensin 1–7 and a summary of the evidence from experimental and clinical studies of various pathological conditions, such as hypertension, atherosclerosis, myocardial remodelling, heart failure, ischaemic stroke, and diabetes mellitus. ACE2-mediated catabolism of angiotensin II is likely to have a major role in cardiovascular protection, whereas the relevant functions and signalling mechanisms of actions induced by angiotensin 1–7 have not been conclusively determined. The ACE2–angiotensin 1–7 pathway, however, might provide a useful therapeutic target for the treatment of cardiovascular disease, especially in patients with overactive RAS.

Angiotensin-(1-7) and angiotensin-(1-9): function in cardiac and vascular remodelling

The RAS (renin-angiotensin system) is integral to cardiovascular physiology; however, dysregulation of this system largely contributes to the pathophysiology of CVD (cardiovascular disease). It is well established that AngII (angiotensin II), the main effector of the RAS, engages the AT1R (angiotensin type 1 receptor) and promotes cell growth, proliferation, migration and oxidative stress, all processes which contribute to remodelling of the heart and vasculature, ultimately leading to the development and progression of various CVDs, including heart failure and atherosclerosis. The counter-regulatory axis of the RAS, which is centred on the actions of ACE2 (angiotensin-converting enzyme 2) and the resultant production of Ang-(1-7) [angiotensin-(1-7)] from AngII, antagonizes the actions of AngII via the receptor Mas, thereby providing a protective role in CVD. More recently, another ACE2 metabolite, Ang-(1-9) [angiotensin-(1-9)], has been reported to be a biologically active peptide within the counter-regulatory axis of the RAS. The present review will discuss the role of the counter-regulatory RAS peptides Ang-(1-7) and Ang-(1-9) in the cardiovascular system, with a focus on their effects in remodelling of the heart and vasculature.

Possible Role of Angiotensin-Converting Enzyme 2 and Activation of Angiotensin II Type 2 Receptor by Angiotensin-(1–7) in Improvement of Vascular Remodeling by Angiotensin II Type 1 Receptor Blockade

Cross talk between the angiotensin-converting enzyme (ACE)/angiotensin II (Ang II)/Ang II type 1 (AT 1 ) receptor axis and the ACE2/Ang-(1–7)/Mas axis plays a role in the pathogenesis of cardiovascular remodeling. Furthermore, possible stimulation of the Ang II type 2 (AT 2 ) receptor by Ang-(1–7) has been highlighted as a new pathway. Therefore, we examined the possibility of whether the ACE2/Ang-(1–7)/Mas axis and Ang-(1–7)/AT 2 receptor axis are involved in the inhibitory effects of AT 1 receptor blockers on vascular remodeling. Wild-type, Mas-knockout, and AT 2 receptor knockout mice were used in this study. Vascular injury was induced by polyethylene-cuff placement around the mouse femoral artery. Some mice were treated with azilsartan, an AT 1 receptor blocker, or Ang-(1–7). Neointimal formation 2 weeks after cuff placement was more marked in Mas-knockout mice compared with wild-type mice. Treatment with azilsartan or Ang-(1–7) attenuated neointimal area, vascular smooth muscle cell proliferation, increases in the mRNA levels of monocyte chemoattractant protein-1, tumor necrosis factor-α, and interleukin-1β, and superoxide anion production in the injured artery; however, these inhibitory effects of azilsartan and Ang-(1–7) were less marked in Mas-knockout mice. Administration of azilsartan or Ang-(1–7) attenuated the decrease in ACE2 mRNA and increased AT 2 receptor mRNA but did not affect AT 1 receptor mRNA or the decrease in Mas mRNA. The inhibitory effect of Ang-(1–7) on neointimal formation was less marked in AT 2 receptor knockout mice compared with wild-type mice. These results suggest that blockade of the AT 1 receptor by azilsartan could enhance the activities of the ACE2/Ang-(1–7)/Mas axis and ACE2/Ang-(1–7)/AT 2 receptor axis, thereby inhibiting neointimal formation.

Angiotensin-(1–7) Modulates Renal Vascular Resistance Through Inhibition of p38 Mitogen-Activated Protein Kinase in Apolipoprotein E–Deficient Mice

Apolipoprotein E–deficient (apoE(−/−)) mice fed on Western diet are characterized by increased vascular resistance and atherosclerosis. Previously, we have shown that chronic angiotensin (Ang)-(1–7) treatment ameliorates endothelial dysfunction in apoE(−/−) mice. However, the mechanism of Ang-(1–7) on vasoconstrictor response to Ang II is unknown. To examine Ang-(1–7) function, we used apoE(−/−) and wild-type mice fed on Western diet that were treated via osmotic minipumps either with Ang-(1–7) (82 μg/kg per hour) or saline for 6 weeks. We show that Ang II–induced renal pressor response was significantly increased in apoE(−/−) compared with wild-type mice. This apoE(−/−)-specific response is attributed to reactive oxygen species–mediated p38 mitogen–activated protein kinase activation and subsequent phosphorylation of myosin light chain (MLC 20 ), causing renal vasoconstriction. Here, we provide evidence that chronic Ang-(1–7) treatment attenuated the renal pressor response to Ang II in apoE(−/−) mice to wild-type levels. Ang-(1–7) treatment significantly decreased renal inducible nicotinamide adenine dinucleotide phosphate subunit p47phox levels and, thus, reactive oxygen species production that in turn causes decreased p38 mitogen-activated protein kinase activity. The latter has been confirmed by administration of a specific p38 mitogen-activated protein kinase inhibitor SB203580 (5 μmol/L), causing a reduced renal pressor response to Ang II in apoE(−/−) but not in apoE(−/−) mice treated with Ang-(1–7). Moreover, Ang-(1–7) treatment had no effect in Mas(−/−)/apoE(−/−) double-knockout mice confirming the specificity of Ang-(1–7) action through the Mas-receptor. In summary, Ang-(1–7) modulates vascular function via Mas-receptor activation that attenuates pressor response to Ang II in apoE(−/−) mice by reducing reactive oxygen species–mediated p38 mitogen-activated protein kinase activity.