The ACE2-Ang (1-7)-Mas receptor axis attenuates cardiac remodeling and fibrosis in post-myocardial infarction

Research progress on the natural products in the intervention of myocardial infarction

Coronary heart disease is a prevalent cardiovascular ailment globally, with myocardial infarction (MI) being one of its most severe manifestations. The morbidity and mortality of MI are escalating, showing an increasing trend among younger, highly educated individuals, thereby posing a serious threat to public health. Currently, thrombolysis, percutaneous coronary intervention, and coronary artery bypass grafting are the primary clinical treatments for MI. Although these methods significantly reduce patient mortality, complications often result in poor prognoses. Due to limitations in chemical synthetic drug research, the focus has shifted towards developing herbs based on natural substances. Natural medicines represent a novel approach for safer and more effective MI management and treatment. They can control multiple pathogenic variables by targeting various pathways and systems. This paper investigates the molecular mechanisms of MI and evaluates the application of natural products and medicinal plants in MI treatment over the past 5 years, demonstrating their specific good therapeutic potential and superior tolerance. These natural therapies have been shown to mitigate myocardial cell damage caused by MI through mechanisms such as oxidative stress, inflammation, apoptosis, angiogenesis, myocardial fibrosis, autophagy, endoplasmic reticulum stress, mitophagy, and pyroptosis. This review offers the latest insights into the application of natural products and medicinal plants in MI treatment, elucidating their mechanisms of action and serving as an important reference for MI prevention.

Lnc PVT1 facilitates TGF-β1-induced human cardiac fibroblast activation in vitro and ISO-induced myocardial fibrosis in vivo through regulating MYC

Cardiac fibrosis is a commonly seen pathophysiological process in various cardiovascular disorders, such as coronary heart disorder, hypertension, and cardiomyopathy. Cardiac fibroblast trans-differentiation into myofibroblasts (MFs) is a key link in myocardial fibrosis. LncRNA PVT1 participates in fibrotic diseases in multiple organs; however, its role and mechanism in cardiac fibrosis remain largely unknown. Human cardiac fibroblasts (HCFs) were stimulated with TGF-β1 to induce myofibroblast; Immunofluorescent staining, Immunoblotting, and fluorescence in situ hybridization were used to detect the myofibroblasts phenotypes and lnc PVT1 expression. Cell biological phenotypes induced by lnc PVT1 knockdown or overexpression were detected by CCK-8, flow cytometry, and Immunoblotting. A mouse model of myocardial fibrosis was induced using isoproterenol (ISO), and the cardiac functions were examined by echocardiography measurements, cardiac tissues by H&E, and Masson trichrome staining. In this study, TGF-β1 induced HCF transformation into myofibroblasts, as manifested as significantly increased levels of α-SMA, vimentin, collagen I, and collagen III; the expression level of lnc PVT1 expression showed to be significantly increased by TGF-β1 stimulation. The protein levels of TGF-β1, TGFBR1, and TGFBR2 were also decreased by lnc PVT1 knockdown. Under TGF-β1 stimulation, lnc PVT1 knockdown decreased FN1, α-SMA, collagen I, and collagen III protein contents, inhibited HCF cell viability and enhanced cell apoptosis, and inhibited Smad2/3 phosphorylation. Lnc PVT1 positively regulated MYC expression with or without TGF-β1 stimulation; MYC overexpression in TGF-β1-stimulated HCFs significantly attenuated the effects of lnc PVT1 knockdown on HCF proliferation and trans-differentiation to MFs. In the ISO-induced myocardial fibrosis model, lnc PVT1 knockdown partially reduced fibrotic area, improved cardiac functions, and decreased the levels of fibrotic markers. In addition, lnc PVT1 knockdown decreased MYC and CDK4 levels but increased E-cadherin in mice heart tissues. lnc PVT1 is up-regulated in cardiac fibrosis and TGF-β1-stimulated HCFs. Lnc PVT1 knockdown partially ameliorates TGF-β1-induced HCF activation and trans-differentiation into MFs in vitro and ISO-induced myocardial fibrosis in vivo, potentially through interacting with MYC and up-regulating MYC.

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.

Myocardial Angiotensin-Converting Enzyme 2 Protein Expression in Ischemic Heart Failure

The angiotensin-converting enzyme 2 (ACE2)-angiotensin-(1-7)-Mas receptor axis plays a significant role in regulating myocardial remodeling and the development of heart failure (HF), with ACE2 being the primary focus. However, contemporary understanding of the membrane-bound form of the human ACE2 protein remains insufficient. The purpose of this study was to determine the expression of ACE2 protein in different cells of the left ventricular myocardium in non-diseased hearts and at various stages of ischemic HF. A total of 103 myocardial tissue samples from the left ventricle underwent quantitative and semi-quantitative immunohistochemical analysis. Upon assessing ACE2 immunostaining in all myocardial cells through unselective digital image analysis, there was no change in the stage A HF group. Nevertheless, the expression of ACE2 membrane protein in cardiomyocytes showed a tendency to increase, while non-cardiomyocyte ACE2 expression decreased significantly (p < 0.001). In the stage B HF group, the intensity of ACE2 immunostaining continued to increase with rising cardiomyocyte ACE2 expression (p < 0.001). Non-cardiomyocyte expression, in contrast, remained similar to that observed in the stage A HF group. In the stages C/D HF group, ACE2 expression reached its highest level in cardiomyocytes (p < 0.001), while ACE2 expression in non-cardiomyocytes was the lowest (p < 0.001). These changes in ACE2 protein levels are associated with left ventricular remodeling in ischemic HF.

PDZK1 improves ventricular remodeling in hypertensive rats by regulating the stability of the Mas receptor

Ventricular remodeling is one of the main causes of mortality from heart failure due to hypertension. Exploring its mechanism and finding therapeutic targets have become urgent scientific problems to be solved. A number of studies have shown that Mas, as an Ang-(1-7) specific receptor, was significantly reduced in myocardial tissue of rats undergoing hypertensive ventricular remodeling. It has been reported that Mas receptor levels are significantly downregulated in myocardium undergoing ventricular remodeling, but studies focused on intracellular and post-translational modifications of Mas are lacking. The results of this research are as follows: (1) PDZK1 interacts with the carboxyl terminus of Mas through its PDZ1 domain; (2) the expression of PDZK1 and Mas is decreased in rats undergoing hypertensive ventricular remodeling, and PDZK1 upregulation can ameliorate hypertensive myocardial fibrosis and myocardial hypertrophy; (3) PDZK1 enhances the stability of Mas protein through the proteasome pathway, and the proteasome inhibitor MG132 promotes hypertensive ventricular remodeling. PDZK1 improves ventricular remodeling in hypertensive rats by regulating Mas receptor stability. This study provides a scientific basis for the prevention and treatment of ventricular remodeling.

Ameliorative effect of mussel-derived ACE inhibitory peptides on spontaneous hypertension rats

PURPOSE

The purpose of this study was to prepare the novel mussel-derived ACE inhibitory peptides (MEPs) by enzymatic hydrolysis of Mytilus edulis and investigate their antihypertensive effects in vivo.

METHODS

After assessing the stability of MEPs in vitro, we investigated the effect of MEPs on hypertension using spontaneously hypertensive rats (SHRs). Subsequently, MEPs were purified and identified by ultrafiltration, gel filtration chromatography and liquid chromatography-tandem mass spectrometry (LC-MS/MS).

RESULTS

Our study demonstrated that MEPs could keep stable ACE inhibitory activity after treatment with heat, acid, alkali, metal ions and simulated gastrointestinal digestive fluid. Additionally, the animal experiments showed that both short-term and long-term treatment with MEPs resulted in a significant reduction in systolic and diastolic blood pressure in SHRs. Mechanistically, the results suggested that MEPs could reduce vascular remodeling, regulate renin-angiotensin system (RAS), and inhibit kidney and myocardial fibrosis. Finally, we isolated and identified five peptides from MEPs, with the peptide Ile-Leu-Thr-Glu-Arg showed the highest ACE inhibition rate.

CONCLUSION

Our findings demonstrate the potential use of MEPs as active components in functional foods designed to lower blood pressure.

Inappropriate activation of the renin-angiotensin system improves cardiac tolerance to ischemia/reperfusion injury in rats with late angiotensin II-dependent hypertension

The aim of the study was to clarify the role of the interplay between hypertension and the renin-angiotensin system (RAS) in the pathophysiology of myocardial ischemia/reperfusion (I/R) injury. We hypothesized that in the late phase of hypertension with already developed signs of end-organ damage, inappropriate RAS activation could impair cardiac tolerance to I/R injury. Experiments were performed in male Cyp1a1-Ren-2 transgenic rats with inducible hypertension. The early phase of ANG II-dependent hypertension was induced by 5 days and the late phase by the 13 days dietary indole-3-carbinol (I3C) administration. Noninduced rats served as controls. Echocardiography and pressure-volume analysis were performed, angiotensins' levels were measured and cardiac tolerance to ischemia/reperfusion injury was studied. The infarct size was significantly reduced (by 50%) in 13 days I3C-induced hypertensive rats with marked cardiac hypertrophy, this reduction was abolished by losartan treatment. In the late phase of hypertension there are indications of a failing heart, mainly in reduced preload recruitable stroke work (PRSW), but only nonsignificant trends in worsening of some other parameters, showing that the myocardium is in a compensated phase. The influence of the RAS depends on the balance between the vasoconstrictive and the opposed vasodilatory axis. In the initial stage of hypertension, the vasodilatory axis of the RAS prevails, and with the development of hypertension the vasoconstrictive axis of the RAS becomes stronger. We observed a clear effect of AT1 receptor blockade on maximum pressure in left ventricle, cardiac hypertrophy and ANG II levels. In conclusion, we confirmed improved cardiac tolerance to I/R injury in hypertensive hypertrophied rats and showed that, in the late phase of hypertension, the myocardium is in a compensated phase.

COVID-19-Induced Myocarditis: Pathophysiological Roles of ACE2 and Toll-like Receptors

The clinical manifestations of the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection responsible for coronavirus disease 2019 (COVID-19) commonly include dyspnoea and fatigue, and they primarily involve the lungs. However, extra-pulmonary organ dysfunctions, particularly affecting the cardiovascular system, have also been observed following COVID-19 infection. In this context, several cardiac complications have been reported, including hypertension, thromboembolism, arrythmia and heart failure, with myocardial injury and myocarditis being the most frequent. These secondary myocardial inflammatory responses appear to be associated with a poorer disease course and increased mortality in patients with severe COVID-19. In addition, numerous episodes of myocarditis have been reported as a complication of COVID-19 mRNA vaccinations, especially in young adult males. Changes in the cell surface expression of angiotensin-converting enzyme 2 (ACE2) and direct injury to cardiomyocytes resulting from exaggerated immune responses to COVID-19 are just some of the mechanisms that may explain the pathogenesis of COVID-19-induced myocarditis. Here, we review the pathophysiological mechanisms underlying myocarditis associated with COVID-19 infection, with a particular focus on the involvement of ACE2 and Toll-like receptors (TLRs).

Angiotensin II Type 1 Receptor Blocker Prevents Abdominal Aortic Aneurysm Progression in Osteoprotegerin-Deficient Mice via Upregulation of Angiotensin (1-7)

Background Angiotensin II type 1 receptor blockers (ARBs) have been shown to limit the growth of abdominal aortic aneurysm (AAA), but their efficacy is controversial. This study aimed to investigate the molecular mechanism underlying the protective effect of ARBs against AAA progression. Methods and Results Olmesartan, an ARB, was administered to wild-type and osteoprotegerin-knockout (Opg-KO) mice starting 2 weeks before direct application of CaCl₂ to aortas to induce AAA. The protective effect of olmesartan against AAA in wild-type and Opg-KO mice was compared at 6 weeks after AAA induction. Olmesartan prevented AAA progression in Opg-KO mice, including excessive aortic dilatation and collapse of tunica media, but not in wild-type mice. Deficiency of the Opg gene is known to cause excessive activation of the tumor necrosis factor-related apoptosis-inducing ligand-induced c-Jun N-terminal kinase/matrix metalloproteinase 9 pathway, resulting in prolonged AAA progression. Olmesartan attenuated the upregulation of phosphorylated c-Jun N-terminal kinase and matrix metalloproteinase 9 expression in the aortic wall of Opg-KO mice. In cultured vascular smooth muscle cells, tumor necrosis factor-related apoptosis-inducing ligand-induced c-Jun N-terminal kinase phosphorylation and matrix metalloproteinase 9 expression were inhibited by angiotensin (1-7), the circulating levels of which are increased by ARBs. Furthermore, administering an angiotensin (1-7) antagonist to Opg-KO mice diminished the protective effect of olmesartan against AAA progression. Conclusions Olmesartan prevented AAA progression in Opg-KO mice by upregulating angiotensin (1-7), suggesting that angiotensin (1-7) may be a key factor that mediates the protective effect of ARBs.

Signaling Pathways and Potential Therapeutic Strategies in Cardiac Fibrosis

Cardiac fibrosis constitutes irreversible necrosis of the heart muscle as a consequence of different acute (myocardial infarction) or chronic (diabetes, hypertension, …) diseases but also due to genetic alterations or aging. Currently, there is no curative treatment that is able to prevent or attenuate this phenomenon that leads to progressive cardiac dysfunction and life-threatening outcomes. This review summarizes the different targets identified and the new strategies proposed to fight cardiac fibrosis. Future directions, including the use of exosomes or nanoparticles, will also be discussed.

Serum levels of angiotensin-converting enzyme 2 in children with Kawasaki disease

Kawasaki disease (KD) has replaced rheumatic fever as the main cause of acquired heart disease in Japanese, American, and Chinese children. Polymorphisms in angiotensin-converting enzyme may be associated with susceptibility to KD, but the association of angiotensin-converting enzyme 2 (ACE2) with vascular endothelial injury in KD and the possibility for prognosis of vascular injury in KD by evaluating changes in serum ACE2 have not yet been assessed. Thus, this study aimed to investigate ACE2 levels in patients with KD to further explore the relationship between ACE2 and vascular injury in KD. Blood samples were collected from 49 children with KD before intravenous immunoglobulin treatment and 28 healthy children in the same period as the control group. Clinical data were collected from the patients and serum ACE2 levels of all participants were measured using an enzyme-linked immunosorbent assay. Serum ACE2 levels were significantly higher in the KD group than in the control group, and were negatively correlated with platelet levels in patients with KD. Serum ACE2 levels are related to the pathogenesis of KD and may be used as a potential serum marker for KD diagnosis.

Alamandine alleviated heart failure and fibrosis in myocardial infarction mice

Alamandine (Ala) is the newest identified peptide of the renin-angiotensin system and has protective effect on myocyte hypertrophy. However, it is still unclear whether Ala can alleviate heart failure (HF). The aim of this study was to explore the effects of Ala on HF and the related cardiac fibrosis, and to probe the mechanism. HF model was induced by myocardial infarction (MI) in mice. Four weeks after MI, Ala was administrated by intraperitoneal injection for two weeks. Ala injection significantly improved cardiac dysfunction of MI mice in vivo. The cardiac fibrosis and the related biomarkers were attenuated after Ala administration in HF mice in vivo. The increases of collagen I, alpha-smooth muscle actin and transforming growth factor-beta induced by oxygen–glucose deprivation (OGD) in neonatal rat cardiac fibroblasts (NRCFs) were inhibited by Ala treatment in vitro. The biomarkers of apoptosis were elevated in NRCFs induced by OGD, which were attenuated after treating with Ala in vitro. The enhancement of oxidative stress in the heart of MI mice or in the NRCFs treated with OGD was suppressed by treating with Ala in vivo and in vitro. These effects of Ala were reversed by tBHP, an exogenous inducer of oxidative stress in vitro. These results demonstrated that Ala could alleviate cardiac dysfunction and attenuate cardiac fibrosis via inhibition of oxidative stress.

Insights into Cardiovascular Defects and Cardiac Epigenome in the Context of COVID-19

Although few in number, studies on epigenome of the heart of COVID-19 patients show that epigenetic signatures such as DNA methylation are significantly altered, leading to changes in expression of several genes. It contributes to pathogenic cardiac phenotypes of COVID-19, e.g., low heart rate, myocardial edema, and myofibrillar disarray. DNA methylation studies reveal changes which likely contribute to cardiac disease through unknown mechanisms. The incidence of severe COVID-19 disease, including hospitalization, requiring respiratory support, morbidity, and mortality, is disproportionately higher in individuals with co-morbidities. This poses unprecedented strains on the global healthcare system. While their underlying conditions make patients more susceptible to severe COVID-19 disease, strained healthcare systems, lack of adequate support, or sedentary lifestyles from ongoing lockdowns have proved detrimental to their underlying health conditions, thus pushing them to severe risk of congenital heart disease (CHD) itself. Prophylactic vaccines against COVID-19 have ushered new hope for CHD. A common connection between COVID-19 and CHD is SARS-CoV-2’s host receptor ACE2, because ACE2 regulates and protects organs, including the heart, in various ways. ACE2 is a common therapeutic target against cardiovascular disease and COVID-19 which damages organs. Hence, this review explores the above regarding CHDs, cardiovascular damage, and cardiac epigenetics, in COVID-19 patients.

New Insights Into the Role of Inflammation in the Brain in Heart Failure

Heart failure is a growing medical problem. Although the underlying aetiology of heart failure differs according to the phenotype, there are some common characteristics observed in patients with heart failure. These include an increased sympathetic nerve activity, an activated renin–angiotensin system, and inflammation. The mechanisms mediating the increased sympathetic activity are not completely understood but the central nervous system plays a major role. Activation of the renin–angiotensin system plays an active role in the remodelling of the heart and in fluid and electrolyte imbalance. The presence of a central renin–angiotensin system means that locally produced angiotensin in the brain may also play a key role in autonomic dysfunction seen in heart failure. Markers of inflammation in the heart and in the circulation are observed in patients diagnosed with heart failure. Circulating pro-inflammatory cytokines can also influence cardiac function further afield than just locally in the heart including actions within the brain to activate the sympathetic nervous system. Preclinical evidence suggests that targeting the pro-inflammatory cytokines would be a useful therapy to treat heart failure. Most clinical studies have been disappointing. This mini-review suggests that pro-inflammatory cytokines in the brain play a key role and there is a problem associated with access of effective doses of the drugs to the site of action in the brain. The recent advances in nanotechnology delivery techniques may provide exciting future technology to investigate the role of specific pro-inflammatory mediators as novel targets within the brain in the treatment of heart failure.

The miR-214-3p/c-Ski axis modulates endothelial-mesenchymal transition in human coronary artery endothelial cells in vitro and in mice model in vivo

Cardiovascular disease (CVD) is a leading non-communicable disease with a high fatality rate worldwide. Hypertension, a common cardiovascular condition, is a significant risk factor for the development of heart failure because the activation of the renin-angiotensin system (RAS) is considered to be the major promoting reason behind myocardial fibrosis (MF). In this study, Angiotensin II (Ang II) stimulation-induced endothelial to mesenchymal transition (End-MT) in HCAECs, including the decrease of CD31 level, the increase of α-SMA, collagen I, slug, snail, and TGF-β1 levels, and the promotion of Smad2/3 phosphorylation. Meanwhile, the c-Ski level was reduced in Ang II-stimulated HCAECs. In HCAECs, Ang II-induced changes could be partially attenuated by c-Ski overexpression. miR-214-3p directly targeted c-Ski and inhibited c-Ski expression. Moreover, miR-214-3p inhibition reduced Ang II-caused End-MT in HCAECs. miR-214-3p overexpression further enhanced Ang II-induced End-MT, while c-Ski overexpression could markedly reverse the effects of miR-214-3p overexpression. In the Ang II-induced mouse cardiac hypertrophic model, Ang II-caused increase of cellular cross-sectional area and cardiac fibrosis were partially ameliorated by LV-c-Ski; when mice were co-treated with LV-c-Ski and agomir-214-3p, the beneficial effects of LV-c-Ski were reversed. In conclusion, the miR-214-3p/c-Ski axis modulated Ang II-induced End-MT in HCAECs and cardiac hypertrophy and fibrosis in the mice model.

Alternative RAS in Various Hypoxic Conditions: From Myocardial Infarction to COVID-19

Alternative branches of the classical renin–angiotensin–aldosterone system (RAS) represent an important cascade in which angiotensin 2 (AngII) undergoes cleavage via the action of the angiotensin-converting enzyme 2 (ACE2) with subsequent production of Ang(1-7) and other related metabolites eliciting its effects via Mas receptor activation. Generally, this branch of the RAS system is described as its non-canonical alternative arm with counterbalancing actions to the classical RAS, conveying vasodilation, anti-inflammatory, anti-remodeling and anti-proliferative effects. The implication of this branch was proposed for many different diseases, ranging from acute cardiovascular conditions, through chronic respiratory diseases to cancer, nonetheless, hypoxia is one of the most prominent common factors discussed in conjugation with the changes in the activity of alternative RAS branches. The aim of this review is to bring complex insights into the mechanisms behind the various forms of hypoxic insults on the activity of alternative RAS branches based on the different duration of stimuli and causes (acute vs. intermittent vs. chronic), localization and tissue (heart vs. vessels vs. lungs) and clinical relevance of studied phenomenon (experimental vs. clinical condition). Moreover, we provide novel insights into the future strategies utilizing the alternative RAS as a diagnostic tool as well as a promising pharmacological target in serious hypoxia-associated cardiovascular and cardiopulmonary diseases.

Angiotensin II receptor blocker and statin combination therapy associated with higher skeletal muscle index in patients with cardiovascular disease: A retrospective study

WHAT IS KNOWN AND OBJECTIVE

Reduction in skeletal muscle mass is the most important component in diagnosing sarcopenia. Ageing and chronic heart failure due to cardiovascular diseases (CVDs) accelerate the reduction of skeletal muscles. However, there are no currently available drugs that are effective for sarcopenia. The purpose of this study was to explore the association between prescribed medications and skeletal muscle mass in patients with CVD.

METHODS

This was a single-centre, retrospective, cross-sectional study. The subjects were 636 inpatients with CVD who took prescribed medicines for at least 4 weeks at the time of admission. Skeletal muscle volume was assessed using a bioelectrical impedance assay.

RESULTS AND DISCUSSION

Single regression analysis showed that 10 and 3 medications were positively and negatively associated with skeletal muscle index (SMI), respectively. Stepwise multivariate regression analysis revealed that angiotensin II receptor blocker (ARB)/statin combination, dipeptidyl peptidase-4 inhibitor, and antihyperuricemic agents were positively associated with SMI while diuretics and antiarrhythmic agents were negatively associated with SMI. After adjustment using propensity score matching, the SMI was found to be significantly higher in ARB/statin combination users than in non-users.

WHAT IS NEW AND CONCLUSION

Combination use of ARB/statin was associated with a higher SMI in patients with CVD. A future randomised, controlled trial is warranted to determine whether the ARB/statin combination will increase the SMI and prevent sarcopenia in patients with CVD.

Angiotensin-converting enzyme 2 alleviates pulmonary artery hypertension through inhibition of focal adhesion kinase expression

Focal adhesion kinase (FAK) is an important therapeutic target in pulmonary artery hypertension (PAH); however, the mechanism of its activation remains unknown. The present study aimed to investigate whether angiotensin-converting enzyme 2 (ACE2) could regulate FAK and alleviate PAH in a rat model of PAH established with a single administration of monocrotaline followed by continuous hypoxia treatment. In the current study, right ventricular pressure, body weight and the right ventricular hypertrophy index were measured, and hematoxylin-eosin staining was performed on lung tissues to determine whether the modeling was successful. Changes in the serum levels of FAK were measured using an ELISA kit to evaluate the association between ACE2 and FAK. The mRNA expression levels of ACE2, FAK, caspase-3 and survivin were determined using reverse transcription-quantitative PCR (RT-qPCR). The protein expression levels of ACE2, phosphorylated FAK/FAK, cleaved caspase-3/pro-caspase-3 and survivin were determined via western blotting. Immunohistochemistry was applied to detect the expression of FAK around the pulmonary arterioles. Apoptosis of smooth muscle cells around pulmonary arterioles was observed by TUNEL staining. After treatment with the ACE2 activator DIZE or inhibitor DX-600, the results demonstrated that ACE2 reduced PAH-induced changes in arteriole morphology compared with the control. It also inhibited FAK expression in serum. WB and RT-qPCR results suggested that ACE2 inhibited the expression of FAK and pathway-related proteins, and promoted caspase-3 expression. Additionally, ACE2 reduced FAK expression around the pulmonary arterioles and promoted smooth muscle cell apoptosis. The results indicated that ACE2 activation inhibited FAK expression, leading to alleviation of the symptoms of PAH.

Overexpression of angiotensin-converting enzyme 2 by renin-angiotensin system inhibitors. Truth or myth? A systematic review of animal studies

Angiotensin-converting enzyme 2 (ACE2) protects against organ damage in hypertension and cardiovascular diseases by counter regulating the renin-angiotensin system (RAS). ACE2 is also the receptor for severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). Based on the claim that RAS inhibitors (RASIs) cause ACE2 overexpression in some animal experiments, concerns have arisen that RASIs may aggravate SARS-CoV-2 infection and coronavirus disease-2019 severity in RASI-treated patients. To achieve a comprehensive review, a systematic search of MEDLINE/PubMed was conducted regarding the effects of RASIs on tissue ACE2 mRNA/protein expression in healthy animals and animal models of human diseases. We identified 88 eligible articles involving 168 experiments in the heart, kidneys, lungs, and other organs. Three of 38 experiments involving healthy animals showed ACE2 expression greater than twice that of the control (overexpression). Among 102 disease models (130 experiments), baseline ACE2 was overexpressed in 16 models (18 experiments) and less than half the control level (repression) in 28 models (40 experiments). In 72 experiments, RASIs did not change ACE2 levels from the baseline levels of disease models. RASIs caused ACE2 overexpression compared to control levels in seven experiments, some of which were unsupported by other experiments under similar conditions. In 36 experiments, RASIs reversed or prevented disease-induced ACE2 repression, yielding no or marginal changes. Therefore, ACE2 overexpression appears to be a rare rather than common consequence of RASI treatment in healthy animals and disease models. Future studies should clarify the pathophysiological significance of RASI-induced reversal or prevention of ACE2 repression in disease models.

RAAS: A Convergent Player in Ischemic Heart Failure and Cancer

The current global prevalence of heart failure is estimated at 64.34 million cases, and it is expected to increase in the coming years, especially in countries with a medium-low sociodemographic index where the prevalence of risk factors is increasing alarmingly. Heart failure is associated with many comorbidities and among them, cancer has stood out as a contributor of death in these patients. This connection points out new challenges both in the context of the pathophysiological mechanisms involved, as well as in the quality of life of affected individuals. A hallmark of heart failure is chronic activation of the renin-angiotensin-aldosterone system, especially marked by a systemic increase in levels of angiotensin-II, a peptide with pleiotropic activities. Drugs that target the renin-angiotensin-aldosterone system have shown promising results both in the prevention of secondary cardiovascular events in myocardial infarction and heart failure, including a lower risk of certain cancers in these patients, as well as in current cancer therapies; therefore, understanding the mechanisms involved in this complex relationship will provide tools for a better diagnosis and treatment and to improve the prognosis and quality of life of people suffering from these two deadly diseases.

Resveratrol Confers Protection Against Ischemia/Reperfusion Injury by Increase of Angiotensin (1-7) Expression in a Rat Model of Myocardial Hypertrophy

ABSTRACT

Left ventricular hypertrophy (LVH) makes the heart vulnerable to ischemia/reperfusion (IR) injury. Angiotensin (Ang) (1-7) is recognized as a cardioprotective peptide. We investigated the effect of polyphenol resveratrol on myocardial IR injury after hypertrophy and examined cardiac content of Ang (1-7) and transcription of its receptor (MasR). Rats were divided into sham-operated, LVH, IR, LVH + IR, and resveratrol + LVH + IR groups. Myocardial hypertrophy and IR models were created by abdominal aortic banding and left coronary artery occlusion, respectively. To evaluate the electrocardiogram parameters and incidence of arrhythmias, electrocardiogram was recorded by subcutaneous leads (lead II). Blood pressure was measured through the left carotid artery. Infarct size was determined by the triphenyl tetrazolium chloride staining. The Ang (1-7) level was evaluated by immunohistochemistry. The Mas receptor mRNA level was assessed by the real-time real time reverse transcription polymerase chain reaction technique. QT-interval duration, infarct size, and incidence of ischemia-induced arrhythmia were significantly higher in the LVH + IR group. However, in the resveratrol-treated group, these parameters were decreased significantly. The cardiac level of Ang (1-7) was decreased in untreated hypertrophied hearts (LVH and LVH + IR groups). Pretreatment with resveratrol normalized the cardiac level of Ang (1-7). The mRNA level of Mas receptor was increased in all of hypertrophied hearts in the presence or absence of resveratrol. Resveratrol can decrease IR injury in rats with LVH. The anti-ischemic effect of resveratrol may be related to the enhancement of Ang (1-7)/MasR axis.

Chronic Intermittent Hypobaric Hypoxia Decreases High Blood Pressure by Stabilizing the Vascular Renin-Angiotensin System in Spontaneously Hypertensive Rats

Background and Aims

Previous studies have demonstrated the anti-hypertensive effect of chronic intermittent hypobaric hypoxia (CIHH) in hypertensive rats. The present study investigated the anti-hypertensive effect of CIHH in spontaneously hypertensive rats (SHR) and the role of the renin-angiotensin system (RAS) in anti-hypertensive effect of CIHH.

Methods

Fifteen-week-old male SHR and WKY rats were divided into four groups: the SHR without CIHH treatment (SHR-CON), the SHR with CIHH treatment (SHR-CIHH), the WKY without CIHH treatment (WKY-CON), and the WKY with CIHH treatment (WKY-CIHH) groups. The SHR-CIHH and WKY-CIHH rats underwent 35-days of hypobaric hypoxia simulating an altitude of 4,000 m, 5 h per day. Arterial blood pressure and heart rate were recorded by biotelemetry, and angiotensin (Ang) II, Ang1–7, interleukin (IL)-6, tumor necrosis factor-alpha (TNF)-α, and IL-10 in serum and the mesenteric arteries were measured by enzyme-linked immunosorbent assay (ELISA) and immunohistochemistry, respectively. The microvessel tension recording technique was used to determine the contraction and relaxation of the mesenteric arteries. Hematoxylin and eosin and Masson’s staining were used to observe vascular morphology and fibrosis. Western blot was employed to detect the expression of the angiotensin-converting enzyme (ACE), ACE2, AT1, and Mas proteins in the mesenteric artery.

Results

The biotelemetry result showed that CIHH decreased arterial blood pressure in SHR for 3–4 weeks (P < 0.01). The ELISA and immunohistochemistry results showed that CIHH decreased Ang II, but increased Ang1–7 in serum and the mesenteric arteries of SHR. In the CIHH-treated SHR, IL-6 and TNF-α decreased in serum and the mesenteric arteries, and IL-10 increased in serum (P < 0.05–0.01). The microvessel tension results revealed that CIHH inhibited vascular contraction with decreased Ang1–7 in the mesenteric arteries of SHR (P < 0.05–0.01). The staining results revealed that CIHH significantly improved vascular remodeling and fibrosis in SHR. The western blot results demonstrated that CIHH upregulated expression of the ACE2 and Mas proteins, and downregulated expression of the ACE and AT1 proteins (P < 0.05–0.01).

Conclusion

CIHH decreased high blood pressure in SHR, possibly by inhibiting RAS activity, downregulating the ACE-Ang II-AT1 axis and upregulating the ACE2-(Ang1-7)-Mas axis, which resulted in antagonized vascular remodeling and fibrosis, reduced inflammation, and enhanced vascular relaxation.

Angiotensin-converting enzyme 2: a double-edged sword in COVID-19 patients with an increased risk of heart failure

The coronavirus disease (COVID-19) pandemic is a global health priority. Given that cardiovascular diseases (CVD) are the leading cause of morbidity around the world and that several trials have reported severe cardiovascular damage in patients infected with SARS-CoV-2, a substantial number of COVID-19 patients with underlying cardiovascular diseases need to continue their medications in order to improve myocardial contractility and to prevent the onset of major adverse cardiovascular events (MACEs), including heart failure. Some of the current life-saving medications may actually simultaneously expose patients to a higher risk of severe COVID-19. Angiotensin-converting enzyme 2 (ACE2), a key counter regulator of the renin-angiotensin system (RAS), is the main entry gate of SARS-CoV-2 into human host cells and an established drug target to prevent heart failure. In fact, ACE inhibitors, angiotensin II receptor blockers, and mineralocorticoid antagonists may augment ACE2 levels to protect organs from angiotensin II overload. Elevated ACE2 expression on the host cell surface might facilitate viral entrance, at the same time sudden nonadherence to these medications triggers MACEs. Hence, safety issues in the use of RAS inhibitors in COVID-19 patients with cardiac dysfunction remain an unsolved dilemma and need paramount attention. Although ACE2 generally plays an adaptive role in both healthy subjects and patients with systolic and/or diastolic dysfunction, we conducted a literature appraisal on its maladaptive role. Understanding the exact role of ACE2 in COVID-19 patients at risk of heart failure is needed to safely manage RAS inhibitors in frail and non-frail critically ill patients.

Angiotensin-Converting-Enzyme 2 and Renin-Angiotensin System Inhibitors in COVID-19: An Update

Ever since its outbreak, Corona Virus Disease 2019(COVID-19) caused by SARS-CoV-2 has affected more than 26 million individuals in more than 200 countries. Although the mortality rate of COVID-19 is low, but several clinical studies showed, patients with diabetes mellitus (DM) or other major complication at high risk of COVID-19 and reported more severe disease and increased fatality. The angiotensin-converting-enzyme 2 (ACE2), a component of renin-angiotensin-system (RAS); acts on ACE/Ang-II/AT1recptor axis, and regulates pathological processes like hypertension, cardiac dysfunction, Acute Respiratory Distress Syndrome (ARDS) etc. The progression of T2DM and hypertension show decreased expression and activity of ACE2. There are several treatment strategies for controlling diabetes, hypertension, etc; like ACE2 gene therapies, endogenous ACE2 activators, human recombinant ACE2 (hrACE2), Angiotensin-II receptor blockers (ARBs) and ACE inhibitors (ACEi) medications. ACE2, the receptors for SARS-CoV2, facilitates virus entry inside host cell. Clinicians are using two classes of medications for the treatment of COVID-19; one targets the SARS-CoV-2-ACE2 interaction, while other targets human immune system. The aim of this review is to discuss the role of ACE2 in diabetes and in COVID-19 and to provide an analysis of data proposing harm and benefit of RAS inhibitor treatment in COVID-19 infection as well as showing no association whatsoever. This review also highlights some candidate vaccines which are undergoing clinical trials.

The role of SARS-CoV-2 target ACE2 in cardiovascular diseases

SARS-CoV-2, the virus responsible for the global coronavirus disease (COVID-19) pandemic, attacks multiple organs of the human body by binding to angiotensin-converting enzyme 2 (ACE2) to enter cells. More than 20 million people have already been infected by the virus. ACE2 is not only a functional receptor of COVID-19 but also an important endogenous antagonist of the renin-angiotensin system (RAS). A large number of studies have shown that ACE2 can reverse myocardial injury in various cardiovascular diseases (CVDs) as well as is exert anti-inflammatory, antioxidant, anti-apoptotic and anticardiomyocyte fibrosis effects by regulating transforming growth factor beta, mitogen-activated protein kinases, calcium ions in cells and other major pathways. The ACE2/angiotensin-(1-7)/Mas receptor axis plays a decisive role in the cardiovascular system to combat the negative effects of the ACE/angiotensin II/angiotensin II type 1 receptor axis. However, the underlying mechanism of ACE2 in cardiac protection remains unclear. Some approaches for enhancing ACE2 expression in CVDs have been suggested, which may provide targets for the development of novel clinical therapies. In this review, we aimed to identify and summarize the role of ACE2 in CVDs.

Impact of renin-angiotensin system inhibitors use on mortality in severe COVID-19 patients with hypertension: a retrospective observational study

OBJECTIVE

Association of angiotensin-converting enzyme inhibitors (ACEI) or angiotensin receptor blockers (ARB) use with coronavirus disease 2019 (COVID-19) remains controversial. We aimed to investigate the impact of ACEI/ARB use on all-cause mortality in severe COVID-19 patients with hypertension.

METHODS

We enrolled 650 COVID-19 patients from Changsha and Wuhan city between 17 January 2020 and 8 March 2020. Demographic, clinical characteristics, and outcomes were collected. Multivariable analysis and propensity-score matching were performed to assess the impact of ACEI/ARB therapy on mortality.

RESULTS

Among the 650 patients, 126 who had severe COVID-19 concomitant with hypertension were analyzed. The average age was 66 years and 56 (44.4%) were men. There were 37 ACEI/ARB users and 21 in-hospital deaths (mortality rate, 16.7%). Male sex (odds ratio [OR], 5.13; 95% confidence interval [CI], 1.75 to 17.8), but not ACEI/ARB use (OR, 1.09; 95%CI, 0.31 to 3.43), was an independent risk factor for mortality in severe COVID-19 patients with hypertension. After propensity-score matching, 60 severe COVID-19 patients were included and no significant correlation between use of ACEI/ARB and mortality was observed.

CONCLUSIONS

There was no significant association of ACEI/ARB use with mortality in severe COVID-19 patients with hypertension. These findings support the continuation of ACEI/ARB therapy for such patients.

COVID-19: Case fatality and ACE2 inhibitors treatment concerns in patients with comorbidities

The Corona Virus Disease 2019 (COVID-19) outbreak is becoming pandemic with the highest mortality in patients with associated comorbidities. These RNA viruses containing 4 structural proteins usually use spike protein to enter the host cell. Angiotensin-converting enzyme 2 (ACE2) acts as a host receptor for the virus. Therefore, medications acting on renin-angiotensin-aldosterone system can lead to serious complications, especially in patients with diabetes and hypertension. To avoid this, other potential treatment modalities should be used in COVID-19 patients with associated comorbidities.

Cirrhotic portal hypertension: From pathophysiology to novel therapeutics

Portal hypertension and bleeding from gastroesophageal varices is the major cause of morbidity and mortality in patients with cirrhosis. Portal hypertension is initiated by increased intrahepatic vascular resistance and a hyperdynamic circulatory state. The latter is characterized by a high cardiac output, increased total blood volume and splanchnic vasodilatation, resulting in increased mesenteric blood flow. Pharmacological manipulation of cirrhotic portal hypertension targets both the splanchnic and hepatic vascular beds. Drugs such as angiotensin converting enzyme inhibitors and angiotensin II type receptor 1 blockers, which target the components of the classical renin angiotensin system (RAS), are expected to reduce intrahepatic vascular tone by reducing extracellular matrix deposition and vasoactivity of contractile cells and thereby improve portal hypertension. However, these drugs have been shown to produce significant off-target effects such as systemic hypotension and renal failure. Therefore, the current pharmacological mainstay in clinical practice to prevent variceal bleeding and improving patient survival by reducing portal pressure is non-selective -blockers (NSBBs). These NSBBs work by reducing cardiac output and splanchnic vasodilatation but most patients do not achieve an optimal therapeutic response and a significant proportion of patients are unable to tolerate these drugs. Although statins, used alone or in combination with NSBBs, have been shown to improve portal pressure and overall mortality in cirrhotic patients, further randomized clinical trials are warranted involving larger patient populations with clear clinical end points. On the other hand, recent findings from studies that have investigated the potential use of the blockers of the components of the alternate RAS provided compelling evidence that could lead to the development of drugs targeting the splanchnic vascular bed to inhibit splanchnic vasodilatation in portal hypertension. This review outlines the mechanisms related to the pathogenesis of portal hypertension and attempts to provide an update on currently available therapeutic approaches in the management of portal hypertension with special emphasis on how the alternate RAS could be manipulated in our search for development of safe, specific and effective novel therapies to treat portal hypertension in cirrhosis.

Twenty years of progress in angiotensin converting enzyme 2 and its link to SARS-CoV-2 disease

The virulence of the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection and the aggressive nature of the disease has transformed the universal pace of research in the desperate attempt to seek effective therapies to halt the morbidity and mortality of this pandemic. The rapid sequencing of the SARS-CoV-2 virus facilitated identification of the receptor for angiotensin converting enzyme 2 (ACE2) as the high affinity binding site that allows virus endocytosis. Parallel evidence that coronavirus disease 2019 (COVID-19) disease evolution shows greater lethality in patients with antecedent cardiovascular disease, diabetes, or even obesity questioned the potential unfavorable contribution of angiotensin converting enzyme (ACE) inhibitors or angiotensin II (Ang II) receptor blockers as facilitators of adverse outcomes due to the ability of these therapies to augment the transcription of Ace2 with consequent increase in protein formation and enzymatic activity. We review, here, the specific studies that support a role of these agents in altering the expression and activity of ACE2 and underscore that the robustness of the experimental data is associated with weak clinical long-term studies of the existence of a similar regulation of tissue or plasma ACE2 in human subjects.

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.

Differential role of specific cardiovascular neuropeptides in pain regulation: Relevance to cardiovascular diseases

In many instances, the perception of pain is disproportionate to the strength of the algesic stimulus. Excessive or inadequate pain sensation is frequently observed in cardiovascular diseases, especially in coronary ischemia. The mechanisms responsible for individual differences in the perception of cardiovascular pain are not well recognized. Cardiovascular disorders may provoke pain in multiple ways engaging molecules released locally in the heart due to tissue ischemia, inflammation or cellular stress, and through neurogenic and endocrine mechanisms brought into action by hemodynamic disturbances. Cardiovascular neuropeptides, namely angiotensin II (Ang II), angiotensin-(1-7) [Ang-(1-7)], vasopressin, oxytocin, and orexins belong to this group. Although participation of these peptides in the regulation of circulation and pain has been firmly established, their mutual interaction in the regulation of pain in cardiovascular diseases has not been profoundly analyzed. In the present review we discuss the regulation of the release, and mechanisms of the central and systemic actions of these peptides on the cardiovascular system in the context of their central and peripheral nociceptive (Ang II) and antinociceptive [Ang-(1-7), vasopressin, oxytocin, orexins] properties. We also consider the possibility that they may play a significant role in the modulation of pain in cardiovascular diseases. The rationale for focusing attention on these very compounds was based on the following premises (1) cardiovascular disturbances influence the release of these peptides (2) they regulate vascular tone and cardiac function and can influence the intensity of ischemia - the factor initiating pain signals in the cardiovascular system, (3) they differentially modulate nociception through peripheral and central mechanisms, and their effect strongly depends on specific receptors and site of action. Accordingly, an altered release of these peptides and/or pharmacological blockade of their receptors may have a significant but different impact on individual sensation of pain and comfort of an individual patient.

Clinical Implications of SARS-CoV-2 Interaction With Renin Angiotensin System: JACC Review Topic of the Week

Severe acute respiratory-syndrome coronavirus-2 (SARS-CoV-2) host cell infection is mediated by binding to angiotensin-converting enzyme 2 (ACE2). Systemic dysregulation observed in SARS-CoV was previously postulated to be due to ACE2/angiotensin 1-7 (Ang1-7)/Mas axis downregulation; increased ACE2 activity was shown to mediate disease protection. Because angiotensin II receptor blockers, ACE inhibitors, and mineralocorticoid receptor antagonists increase ACE2 receptor expression, it has been tacitly believed that the use of these agents may facilitate viral disease; thus, they should not be used in high-risk patients with cardiovascular disease. Based on the anti-inflammatory benefits of the upregulation of the ACE2/Ang1-7/Mas axis and previously demonstrated benefits of lung function improvement in SARS-CoV infections, it has been hypothesized that the benefits of treatment with renin-angiotensin system inhibitors in SARS-CoV-2 may outweigh the risks and at the very least should not be withheld.

Tsantan Sumtang attenuated chronic hypoxia-induced right ventricular structure remodeling and fibrosis by equilibrating local ACE-AngII-AT1R/ACE2-Ang1-7-Mas axis in rat

ETHNOPHARMACOLOGICAL RELEVANCE

Tsantan Sumtang, which consists of Choerospondias axillaris (Roxb.) Burtt et Hill, Myristica fragrans Houtt and Santalum album L, is a traditional and common prescription of Tibetan medicine. Tsantan Sumtang originates from Four Tantra with properties of nourishing heart and has been used as a folk medicine for cardiovascular diseases and heart failure in Qinghai, Tibet and Inner Mongolia. Our previous studies found that Tsantan Sumtang showed beneficial effects on right ventricular structure in hypoxia rats, while the underling mechanism remains unclear.

AIM OF THE STUDY

To elucidate the underlying mechanisms of Tsantan Sumtang attenuated right ventricular (RV) remodeling and fibrosis of chronic hypoxia-induced pulmonary arterial hypertension (HPAH) rats.

MATERIALS AND METHODS

Fifty male Sprague Dawley (SD) rats (170 ± 20 g) were randomly divided into control group, hypoxia group, and hypoxia + Tsantan Sumtang groups (1.0 g· kg^-1·day^-1, 1.25 g· kg^-1·day^-1, 1.5 g ·kg^-1·day^-1). Rats in the hypoxia group and hypoxia + Tsantan Sumtang groups were maintained in a hypobaric chamber by adjusting the inner pressure and oxygen content to simulate an altitude of 4500 m for 28 days. The mean pulmonary arterial pressure (mPAP), right ventricle hypertrophy index (RVHI), the ratio of RV weight to tibia length (TL) (RV/TL), heart rate (HR) and RV systolic pressure (RVSP) was determined. Histomorphological assay of RV structure was evaluated by hematoxylin and eosin (HE) staining. RV tissue fibrosis was assessed by collagen proportion area (CPA), collagen I, collagen III and hydroxyproline content. CPA was obtained by picro-sirius red staining (PSR). The expression of collagen I and collagen III were detected by immunohistochemistry and western blotting. The hydroxyproline content was detected by alkaline hydrolysis. In addition, the level of angiotensin II (AngII) and angiotensin 1-7 (Ang1-7) in RV tissue was tested by enzyme-linked immune sorbent assay (ELISA). Protein expression of angiotensin-converting enzyme (ACE), AngII, AngII type 1 receptor (AT1R), angiotensin-converting enzyme 2 (ACE2), Mas receptor (Mas) were determined by immunohistochemistry and western blotting. mRNA level of ACE, AT1R, ACE2, Mas were tested by qPCR. The chemical profile of Tsantan Sumtang was revealed by UHPLC-Q-Exactive hybrid quadrupole-orbitrap mass analysis.

RESULTS

Our results showed that RVHI, RV/TL and RVSP were significantly increased in HPAH rat. Furthermore, levels of collagen I, collagen III and hydroxyproline were up-regulated in RV tissue under hypoxia. We found that RV hypertrophy and fibrosis were associated with increased expression of ACE, AngII, AT1R as well as decreased expression of ACE2, Ang1-7 and Mas. RV remodeling and fibrosis were attenuated after Tsantan Sumtang administration by up-regulating ACE2 and Mas level as well as down-regulating ACE, AngII and AT1R levels in RV tissue. 35 constituents in Tsantan Sumtang were identified.

CONCLUSION

Tsantan Sumtang attenuated RV remodeling and fibrosis in rat exposed to chronic hypoxia. The pharmacological effect of Tsantan Sumtang was based on equilibrating ACE-AngII-AT1R and ACE2-Ang1-7-Mas axis of RV tissue in HPAH rat.

Angiotensin-(1-7) Receptor Mas Deficiency Does Not Exacerbate Cardiac Atrophy Following High-Level Spinal Cord Injury in Mice

Experimental spinal cord injury (SCI) causes a morphological and functional deterioration of the heart, in which the renin–angiotensin system (RAS) might play a role. The recently discovered non-canonical axis of RAS with angiotensin-(1–7) and its receptor Mas, which is associated with cardioprotection could be essential to prevent damage to the heart following SCI. We investigated the cardiac consequences of SCI and the role of Mas in female wild-type (WT, n = 22) and mice deficient of Mas (Mas^–/–, n = 25) which underwent spinal cord transection at thoracic level T4 (T4-Tx) or sham-operation by echocardiography (0, 7, 21, and 28 days post-SCI), histology and gene expression analysis at 1 or 2 months post-SCI. We found left ventricular mass reduction with preserved ejection fraction (EF) and fractional shortening in WT as well as Mas^–/– mice. Cardiac output was reduced in Mas^–/– mice, whereas stroke volume (SV) was reduced in WT T4-Tx mice. Echocardiographic indices did not differ between the genotypes. Smaller heart weight (HW) and smaller cardiomyocyte diameter at 1 month post-SCI compared to sham mice was independent of genotype. The muscle-specific E3 ubiquitin ligases Atrogin-1/MAFbx and MuRF1 were upregulated or showed a trend for upregulation in WT mice at 2 months post-SCI, respectively. Angiotensinogen gene expression was upregulated at 1 month post-SCI and angiotensin II receptor type 2 downregulated at 2 month post-SCI in Mas^–/– mice. Mas was downregulated post-SCI. Cardiac atrophy following SCI, not exacerbated by lack of Mas, is a physiological reaction as there were no signs of cardiac pathology and dysfunction.

Effects of Angiotensin-(1-7) and Angiotensin II on Acetylcholine-Induced Vascular Relaxation in Spontaneously Hypertensive Rats

Endothelial dysfunction of small arteries occurs in patients with hypertension and in various hypertensive models. Endothelial function is usually evaluated by the degree of acetylcholine- (ACh-) induced vascular relaxation. Our previous study has found that compared to Wistar-Kyoto rats (WKY), ACh-induced vasodilatation was attenuated significantly in the mesenteric artery (MA), coronary artery (CA), and pulmonary artery (PA) of spontaneously hypertensive rats (SHR). This study investigated the influence of angiotensin- (Ang-) (1-7) and Ang II on blood pressure and ACh-induced vascular relaxation, as well as their interactive roles and downstream signal pathways in SHR and WKY. Intravenous injection of Ang II significantly increased, while Ang-(1-7) decreased the mean arterial pressure (MAP) in SHR. Ang-(1-7) improved ACh-induced relaxation in the MA, CA, and PA of SHR, while Ang II further attenuated it, which were inhibited by pretreatment with Mas receptor antagonist A-779 or AT₁ receptor antagonist losartan, respectively. Ang-(1-7) decreased the basal arterial tension, and Ang II induced great vasoconstriction in SHR. Pretreatment with Ang-(1-7) inhibited the Ang II-induced pressor response, vasoconstriction, and the effects on ACh-induced relaxation in SHR. AT₁ receptor expression was higher, while nitric oxide (NO), cGMP, and protein kinase G (PKG) levels of arteries were lower in SHR than in WKY. Ang II decreased, while Ang-(1-7) increased, the levels of NO, cGMP, and PKG of arteries. In addition, pretreatment with Ang-(1-7) inhibited the Ang II-induced reduction of NO, cGMP, and PKG in SHR. These results indicate that the activation of the Mas receptor by Ang-(1-7) can improve endothelial function and decrease MAP in SHR and inhibit the deteriorative effect of Ang II on endothelial function through the NO-cGMP-PKG pathway.

Angiotensin-(1-7): Translational Avenues in Cardiovascular Control

Despite decades of research and numerous treatment approaches, hypertension and cardiovascular disease remain leading global public health problems. A major contributor to regulation of blood pressure, and the development of hypertension, is the renin-angiotensin system. Of particular concern, uncontrolled activation of angiotensin II contributes to hypertension and associated cardiovascular risk, with antihypertensive therapies currently available to block the formation and deleterious actions of this hormone. More recently, angiotensin-(1-7) has emerged as a biologically active intermediate of the vasodilatory arm of the renin-angiotensin system. This hormone antagonizes angiotensin II actions as well as offers antihypertensive, antihypertrophic, antiatherogenic, antiarrhythmogenic, antifibrotic and antithrombotic properties. Angiotensin-(1-7) elicits beneficial cardiovascular actions through mas G protein-coupled receptors, which are found in numerous tissues pivotal to control of blood pressure including the brain, heart, kidneys, and vasculature. Despite accumulating evidence for favorable effects of angiotensin-(1-7) in animal models, there is a paucity of clinical studies and pharmacokinetic limitations, thus limiting the development of therapeutic agents to better understand cardiovascular actions of this vasodilatory peptide hormone in humans. This review highlights current knowledge on the role of angiotensin-(1-7) in cardiovascular control, with an emphasis on significant animal, human, and therapeutic research efforts.

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.

Regulating the Warburg effect on metabolic stress and myocardial fibrosis remodeling and atrial intracardiac waveform activity induced by atrial fibrillation

Atrial fibrillation (AF) is associated with metabolic stress and induces myocardial fibrosis reconstruction by increasing glycolysis. One goal in the treatment of paroxysmal AF (p-AF) is to improve myocardial fibrosis reconstruction and myocardial metabolic stress caused by the Warburg effect. Adopted male canine that rapid right atrial pacing (RAP) for 6 days to establish a p-AF model. The canines were pre-treated with phenylephrine (PE) or dichloroacetic acid (DCA) before exposure to p-AF or non-p-AF. P-wave duration (P_max), minimum P-wave duration (P_min), P wave dispersion (PWD), atrial effective refractory period (AERP) and AERP dispersion (AERPd) were measured in canine atrial cardiomyocytes. Pyruvate dehydrogenase kinase-1 (PDK-1), PDK-4, lactate dehydrogenase A (LDHA), pyruvate dehydrogenase (PDH), citrate synthase (CS), isocitrate dehydrogenase (IDH), and matrix metalloproteinase 9 (MMP-9) were evaluated by western blotting and reverse transcription polymerase chain reaction (RT-PCR), content of adenosine monophosphate (AMP), adenosine triphosphate (ATP), lactic acid and glycogen, and activity of LDHA, PDK-1 and PDK-4 were evaluated by enzyme-linked immunosorbent assay (ELISA), myocardial tissue glycogen content was evaluated by PAS, myocardial fibrosis remodeling was evaluated by hematoxylin and eosin (H&E) and Masson staining. Our findings demonstrated that p-AF increases the Warburg effect-related metabolic stress and myocardial fibrosis remodeling by increasing the expression and activity of PDK-1, PDK-4, and LDHA, content of AMP and lactic acid, and the ratio of AMP/ATP and decreasing the expression of PDH, CS, and IDH, and glycogen content. In addition, p-AF can induce cardiomyocyte fibrosis remodeling and increase MMP-9 expression, and p-AF also increases atrial intracardiac waveform activity by prolonging P_max, P_min, PWD, and AERPd and shortening AERP. PDK isoforms agonists (PE) produce a similar p-AF pathological effect and can produce synergistic effects with p-AF, further increasing Warburg effect-related metabolic stress, myocardial fibrosis remodeling, and atrial intracardiac waveform activity. In contrast, the use of PDK-specific inhibitors (DCA) completely reverses these pathophysiological changes induced by p-AF. We demonstrate that p-AF can induce the Warburg effect in canine atrial cardiomyocytes and significantly improve p-AF-induced metabolic stress, myocardial fibrosis remodeling, and atrial intracardiac waveform activity by inhibiting the Warburg effect.

Angiotensin-(1-7) induced vascular relaxation in spontaneously hypertensive rats

Enhanced vasoconstriction and decreased vasodilatation due to endothelial dysfunction contribute to the progression of hypertension. Angiotensin (Ang)-(1-7) plays important roles in regulating the cardiovascular activity. The current study aimed to investigate the roles of Ang-(1-7) in modulating blood pressure, vascular tension and its signal pathway in spontaneously hypertensive rats (SHR). The effects of intravenous injection of drugs were determined in rats with anesthesia in vivo. Mesenteric artery (MA), coronary artery (CA) and pulmonary artery (PA) were isolated from rats and isometric tension measurements in arteries were performed. Compared with Wistar-Kyoto rats (WKY), the high K⁺ induced vasoconstriction was enhanced and acetylcholine-induced vasodilatation were attenuated in the MA, CA and PA in SHR. Intravenous injection of Ang-(1-7) decreased, while A-779 increased mean arterial pressure and abolished the hypotensive effect of Ang-(1-7) in SHR. Ang-(1-7) caused dose-dependent relaxation in MA, CA and PA in SHR, which was inhibited by pretreatment with Mas receptor antagonist A-779, nitric oxide (NO) synthase inhibitor l-NAME, guanylate cyclase inhibitor ODQ and protein kinase G (PKG) inhibitor DT-2. The Mas receptor expression, NO, cGMP and PKG levels of the three above arteries of SHR were lower than that of WKY. Ang-(1-7) increased the NO, cGMP and PKG levels in arteries from SHR, which was blocked by A-779. Activation of the Mas receptor by Ang-(1-7) relaxes the MA, CA, and PA through the NO-cGMP-PKG pathway, which contributes to the decrease of arterial pressure in SHR.

Unique mechanistic insights into the beneficial effects of angiotensin-(1-7) on the prevention of cardiac fibrosis: A metabolomic analysis of primary cardiac fibroblasts

BACKGROUND

Cell metabolic pathways are highly conserved among species and change rapidly in response to drug stimulation. Therefore, we explore the effects of angiotensin-(1-7) in a primary cell model of cardiac fibrosis established in angiotensin II-stimulated cardiac fibroblasts via metabolomics analysis and further clarify the potential protective mechanism of angiotensin-(1-7).

METHODS AND RESULTS

After exposing cardiac fibroblasts to angiotensin II and/or angiotensin-(1-7), 172 metabolites in these cells were quantified and identified by gas chromatography-mass spectrometry. The data were subsequently analyzed by orthogonal partial least squares discriminant analysis to shortlist biochemically significant metabolites associated with the antifibrotic action of angiotensin-(1-7). Seven significant metabolites were identified: 10,13-dimethyltetradecanoic acid, arachidonic acid, aspartic acid, docosahexaenoic acid (DHA), glutathione, palmitelaidic acid, and pyroglutamic acid. By metabolic network analysis, we found that these metabolites were involved in six metabolic pathways, including arachidonic acid metabolism, leukotriene metabolism, and the γ-glutamyl cycle. Since these metabolic pathways are related to calcium balance and oxidative stress, we further verified that angiotensin-(1-7) suppressed the abnormal extracellular calcium influx and excessive accumulation of intracellular reactive oxygen species (ROS) in angiotensin II-stimulated cardiac fibroblasts. Furthermore, we found that angiotensin-(1-7) suppressed the abnormal calcium- and ROS-dependent activation of calcium/calmodulin-dependent protein kinase II delta (CaMKIIδ), the increased expression of CaMKIIδ-related proteins (NADPH oxidase 4 (Nox4), cellular communication network factor 2 (CTGF), and p-ERK1/2), and excessive collagen deposition in vitro and in vivo.

CONCLUSIONS

Angiotensin-(1-7) can ameliorate the angiotensin II-stimulated metabolic perturbations associated with cardiac fibroblast activation. These metabolic changes indicate that modulation of calcium- and ROS-dependent activation of CaMKIIδ mediates the activity of angiotensin-(1-7) against cardiac fibrosis. Moreover, pyroglutamic acid and arachidonic acid may be potential biomarkers for monitoring the antifibrotic action of angiotensin-(1-7).