Loss Of Angiotensin-converting Enzyme 2 Research Articles

Altered kidney distribution and loss of ACE2 into the urine in acute kidney injury.

There are diverse pathophysiological mechanisms involved in acute kidney injury (AKI). Among them, overactivity of the renin-angiotensin system (RAS) has been described. Angiotensin-converting enzyme 2 (ACE2) is a tissue RAS enzyme expressed in the apical border of proximal tubules. Given the important role of ACE2 in the metabolism of angiotensin II, this study aimed to characterize kidney and urinary ACE2 in a mouse model of AKI. Ischemia-reperfusion injury (IRI) was induced in C57BL/6 mice by clamping of the left renal artery followed by removal of the right kidney. In kidneys harvested 48 h after IRI, immunostaining revealed a striking maldistribution of ACE2 including spillage into the tubular lumen and the presence of ACE2-positive luminal casts in the medulla. In cortical membranes, ACE2 protein and enzymatic activity were both markedly reduced (37 ± 4 vs. 100 ± 6 ACE2/β-actin, P = 0.0004, and 96 ± 14 vs. 152 ± 6 RFU/μg protein/h, P = 0.006). In urine, full-length membrane-bound ACE2 protein (100 kDa) was markedly increased (1,120 ± 405 vs. 100 ± 46 ACE2/µg creatinine, P = 0.04), and casts stained for ACE2 were recovered in the urine sediment. In conclusion, in AKI caused by IRI, there is a marked loss of ACE2 from the apical tubular border with deposition of ACE2-positive material in the medulla and increased urinary excretion of full-length membrane-bound ACE2 protein. The deficiency of tubular ACE2 in AKI suggests that provision of this enzyme could have therapeutic applications and that its excretion in the urine may also serve as a diagnostic marker of severe proximal tubular injury.NEW & NOTEWORTHY This study provides novel insights into the distribution of kidney ACE2 in a model of AKI by IRI showing a striking detachment of apical ACE2 from proximal tubules and its loss in urine and urine sediment. The observed deficiency of kidney ACE2 protein and enzymatic activity in severe AKI suggests that administration of forms of this enzyme may mitigate AKI and that urinary ACE2 may serve as a potential biomarker for tubular injury.

Abstract 13505: COVID-19 and Cardiovascular Disease Patient Hearts Harbor Sympathetic Remodeling and Altered Angiotensin Converting Enzyme 2 Localization

Cardiac complications of COVID-19 have been well described and are associated with significant morbidity and mortality. Concomitantly, various pre-existing cardiovascular diseases (CVDs) are established risk factors for developing severe COVID-19 illness and death. The mechanisms of cardiac injury after COVID-19 remain incompletely understood. Further, whether and how SARS-CoV-2 directly infects the heart is unclear. In this study, we investigated cardiac sympathetic innervation and the cellular localization of angiotensin converting enzyme 2 (ACE2) to test the hypothesis that pre-existing or acute changes in these parameters could contribute to cardiac complications of COVID-19. We performed immunohistochemical (IHC) analysis on sections of left ventricular (LV) wall from twenty autopsied human hearts consisting of a control group, a CVD group, and COVID-19 ARDS and COVID-19 non-ARDS groups. Using tyrosine hydroxylase as a noradrenergic marker, we observed substantial sympathetic nerve loss in CVD LVs compared to the control group, which is consistent with previous work suggesting loss of sympathetic activity in severe heart failure. Additionally, we observed mild and heterogeneous nerve loss in both COVID-19 groups. Using an ACE2 antibody, we observed robust transmural staining localized to pericytes in the control group. The CVD hearts displayed significant loss of ACE2 in pericytes and increased ACE2 in cardiomyocytes. Both COVID-19 groups displayed a modest increase in cardiomyocyte ACE2 compared to controls, and pericyte ACE2 staining was generally maintained. We also performed IHC for PDGF receptor β, an established marker for pericytes, and confirmed ACE2 localization to pericytes. The observed sympathetic nerve remodeling could play a key role in arrhythmogenesis in acute or post-acute COVID-19 patients. Further, if SARS-CoV-2 does infect the heart, then our data demonstrate the primary target would be through microvasculature associated pericytes, not cardiomyocytes. Finally, the upregulation of cardiomyocyte ACE2 in both CVD and COVID-19 groups could play a contributing role in COVID-19 associated cardiac injury or a compensatory role in cardiac pathogenesis by attenuating the local effects of angiotensin II.

A Bitter Experience That Enlightens the Future: COVID-19 Neurological Affection and Perspectives on the Orexigenic System

The history of coronaviruses revealed that these viruses caused multiple outbreaks in the past, including a previous severe acute respiratory syndrome (SARS) outbreak in 2003. In 2019, a novel SARS virus, SARS-CoV-2, started a drastic pandemic that, up till now, keeps peaking in successive waves owing to the mutational ability of the virus versus the short-term immunity against it. Although the angiotensin-converting enzyme 2 (ACE2) is the gate through which the virus gets access to human cells, yet ACE2 is deemed protective in lung injury yielding vasodilator, anti-fibrotic, and anti-inflammatory peptides. The viral-provoked ACE2 downregulation aggravated a subsequent potentially lethal cytokine storm. Both the tumor necrosis factor-alpha (TNF-α) receptor (TNFR), activated by the proinflammatory cytokine, TNF-α, released during coronavirus disease 2019 (COVID-19), and ACE2 are cleaved by tumor necrosis convertase enzyme (TACE) to render respective soluble decoy mediators. Several risk factors were linked to COVID-19 morbidity and neurological affection, including obesity and diabetes mellitus (DM), attributed toACE2 overexpression in obesity, a low-grade inflammatory state with both obesity and DM, and defective lung reparative machinery, added to low tissue-to-lung ACE2 expression in DM. The ACE2 shedding by SARS-CoV-2 upon its entry into the brain, together with the inflammatory cytokines invading the brain, predispose to such neurological affection. However, ACE2 was not sufficient to justify the occurrence of neurological disorders with COVID-19, owing to its lower brain expression, relative to other tissues. Other mediators should have contributed to such neurological disorders, of which, orexins (OXs) are discussed, owing to multiple functional similarities to ACE2. Eventually, this review highlights such similarities selected according to their possible relevance to COVID-19 symptomatology and pathology. Both ACE2 and OXs confer anti-inflammatory benefits, reduce cerebral endothelial dysfunction, promote neuronal survival and neurogenesis, and add to their therapeutic potentiality in sepsis. Both ACE2 and OXs assist in moderating the stress responses and the stress-activated hypothalamic-pituitary-adrenal axis. Both ACE2 and OXs are affected by obesity and DM. The loss of ACE2 and OXs signaling was suggested in neuro-inflammatory and neurodegenerative diseases. Of interest is the abundance of OXs in the dissemination routes to the brain, namely, the peripheral olfactory and the enteric systems. The presumptive role of OXs as analgesics and antipyretics might add to their favorable profile. Advantageously, the availability of OXs agonists and antagonists makes it applicable to corroborate or abrogate the future utility of targeting the orexigenic system in terms of COVID-19 neurological affection. Elaborative work, exploring in vitro and in vivo models, is recommended to identify or deny such perspective involvement.

Diminazen Aceturate Protects Pulmonary Ischemia-Reperfusion Injury via Inhibition of ADAM17-Mediated Angiotensin-Converting Enzyme 2 Shedding.

Lung ischemia-reperfusion (IR) injury is induced by pulmonary artery occlusion and reperfusion. Lung IR injury commonly happens after weaning from extracorporeal circulation, lung transplantation, and pulmonary thromboendarterectomy; it is a lethal perioperative complication. A definite therapeutic intervention remains to be determined. It is known that the enzyme activity of angiotensin-converting enzyme 2 (ACE2) is critical in maintaining pulmonary vascular tone and epithelial integrity. In a noxious environment to the lungs, inactivation of ACE2 is mainly due to a disintegrin and metalloprotease 17 (ADAM17) protein-mediated ACE2 shedding. Thus, we assumed that protection of local ACE2 in the lung against ADAM17-mediated shedding would be a therapeutic target for lung IR injury. In this study, we established both in vivo and in vitro models to demonstrate that the damage degree of lung IR injury depends on the loss of ACE2 and ACE2 enzyme dysfunction in lung tissue. Treatment with ACE2 protectant diminazen aceturate (DIZE) maintained higher ACE2 enzyme activity and reduced angiotensin II, angiotensin type 1 receptor, and ADAM17 levels in the lung tissue. Concurrently, DIZE-inhibited oxidative stress and nitrosative stress via p38MAPK and NF-κB pathways consequently reduced release of pro-inflammatory cytokines such as TNF-α, IL-6, and IL-1β. The underlying molecular mechanism of DIZE contributed to its protective effect against lung IR injury and resulted in the improvement of oxygenation index and ameliorating pulmonary pathological damage. We concluded that DIZE protects the lungs from IR injury via inhibition of ADAM17-mediated ACE2 shedding.

Elabela prevents angiotensin II-induced apoptosis and inflammation in rat aortic adventitial fibroblasts via the activation of FGF21-ACE2 signaling.

Apoptosis, inflammation, and fibrosis contribute to vascular remodeling and injury. Elabela (ELA) serves as a crucial regulator to maintain vascular function and has been implicated in the pathogenesis of hypertensive vascular remodeling. This study aims to explore regulatory roles and underlying mechanisms of ELA in rat aortic adventitial fibroblasts (AFs) in response to angiotensin II (ATII). In cultured AFs, exposure to ATII resulted in marked decreases in mRNA and protein levels of ELA, fibroblast growth factor 21 (FGF21), and angiotensin-converting enzyme 2 (ACE2) as well as increases in apoptosis, inflammation, oxidative stress, and cellular migration, which were partially blocked by the exogenous replenishment of ELA and recombinant FGF21, respectively. Moreover, treatment with ELA strikingly reversed ATII-mediated the loss of FGF21 and ACE2 levels in rat aortic AFs. FGF21 knockdown with small interfering RNA (siRNA) significantly counterbalanced protective effects of ELA on ATII-mediated the promotion of cell migration, apoptosis, inflammatory, and oxidative injury in rat aortic AFs. More importantly, pretreatment with recombinant FGF21 strikingly inhibited ATII-mediated the loss of ACE2 and the augmentation of cell apoptosis, oxidative stress, and inflammatory injury in rat aortic AFs, which were partially prevented by the knockdown of ACE2 with siRNA. In summary, ELA exerts its anti-apoptotic, anti-inflammatory, and anti-oxidant effects in rat aortic AFs via activation of the FGF21–ACE2 signaling. ELA may represent a potential candidate to predict vascular damage and targeting the FGF21–ACE2 signaling may be a promising therapeutic intervention for vascular adventitial remodeling and related disorders.

Linking ACE2 and angiotensin II to pulmonary immunovascular dysregulation in SARS-CoV-2 infection

Angiotensin-converting enzyme 2 (ACE2) is the receptor of the novel coronavirus, severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), the causative agent of the coronavirus disease 2019 (COVID-19) pandemic. ACE2 has been shown to be down-regulated during coronaviral infection, with implications for circulatory homeostasis. In COVID-19, pulmonary vascular dysregulation has been observed resulting in ventilation perfusion mismatches in lung tissue, causing profound hypoxemia. Despite the loss of ACE2 and raised circulating vasoconstrictor angiotensin II (AngII), COVID-19 patients experience a vasodilative vasculopathy. This article discusses the interplay between the immune system and pulmonary vasculature and how SARS-CoV-2-mediated ACE2 disruption and AngII may contribute to the novel vascular pathophysiology of COVID-19.

COVID-19 as a viral functional ACE2 deficiency disorder with ACE2 related multi-organ disease

SARS-CoV-2, the agent of COVID-19, shares a lineage with SARS-CoV-1, and a common fatal pulmonary profile but with striking differences in presentation, clinical course, and response to treatment. In contrast to SARS-CoV-1 (SARS), COVID-19 has presented as an often bi-phasic, multi-organ pathology, with a proclivity for severe disease in the elderly and those with hypertension, diabetes and cardiovascular disease. Whilst death is usually related to respiratory collapse, autopsy reveals multi-organ pathology. Chronic pulmonary disease is underrepresented in the group with severe COVID-19. A commonality of aberrant renin angiotensin system (RAS) is suggested in the at-risk group. The identification of angiotensin-converting-enzyme 2 (ACE2) as the receptor allowing viral entry to cells precipitated our interest in the role of ACE2 in COVID-19 pathogenesis.We propose that COVID-19 is a viral multisystem disease, with dominant vascular pathology, mediated by global reduction in ACE2 function, pronounced in disease conditions with RAS bias toward angiotensin-converting-enzyme (ACE) over ACE2. It is further complicated by organ specific pathology related to loss of ACE2 expressing cells particularly affecting the endothelium, alveolus, glomerulus and cardiac microvasculature. The possible upregulation in ACE2 receptor expression may predispose individuals with aberrant RAS status to higher viral load on infection and relatively more cell loss. Relative ACE2 deficiency leads to enhanced and protracted tissue, and vessel exposure to angiotensin II, characterised by vasoconstriction, enhanced thrombosis, cell proliferation and recruitment, increased tissue permeability, and cytokine production (including IL-6) resulting in inflammation. Additionally, there is a profound loss of the “protective” angiotensin (1–7), a vasodilator with anti-inflammatory, anti-thrombotic, antiproliferative, antifibrotic, anti-arrhythmic, and antioxidant activity. Our model predicts global vascular insult related to direct endothelial cell damage, vasoconstriction and thrombosis with a disease specific cytokine profile related to angiotensin II rather than “cytokine storm”. Our proposed mechanism of lung injury provides an explanation for early hypoxia without reduction in lung compliance and suggests a need for revision of treatment protocols to address vasoconstriction, thromboprophylaxis, and to minimize additional small airways and alveolar trauma via ventilation choice. Our model predicts long term sequelae of scarring/fibrosis in vessels, lungs, renal and cardiac tissue with protracted illness in at-risk individuals. It is hoped that our model stimulates review of current diagnostic and therapeutic intervention protocols, particularly with respect to early anticoagulation, vasodilatation and revision of ventilatory support choices.

The Renin-Angiotensin-Aldosterone System in Coronavirus-19 Disease Pathogenesis: Extracting the Devil in the Details.

Coronavirus 2019 disease (COVID-19) was first recognised as an acute febrile respiratory syndrome. Soon, it was realised that acute kidney injury, myocarditis, cytokine activation and prothrombotic disseminated intravascular coagulation are also part of the syndrome complex. Currently, it is being recognised as causing microangiopathy as well as thrombo-embolic complications. The SARS-CoV-2 coronavirus enters cells via the ACE2 (Angiotensin converting enzyme-2) receptor and leads to its downregulation. The loss of ACE2 is postulated to cause activation of the Renin Angiotensin Aldosterone System (RAAS) that contributes to cardiac and renal pathology. Supporting the hypothesis that ACE2 loss can explain the entire pathology, we have reviewed the available literature to determine mechanistic associations between RAAS and the various manifestations of COVID-19. ACE2 dependent protective pathways include the Angiotensin(1-7)/Mas receptor and Alamandine/MrgD receptor pathways. These are anti-hypertensive, anti-inflammatory, and anti-thrombotic. Loss of ACE2 leads to Angiotensin II and aldosterone accumulation that causes thrombosis via release of Plasminogen Activator Inhibitor-1(PAI-1). Altered ACE1/ACE2 balance can activate immune cells and cause polarization of macrophages into M2-inflammatory phenotype. Animal models of various viral pneumonias have previously shown that ACE2 loss is associated with severe lung injury. Angiotensin II and aldosterone are known causes of cardiomyopathy and also potentiate acute kidney injury. There is some emerging evidence that inhibitors of canonical RAAS such as ACE inhibitors, Angiotensin receptor blockers, and statins may have mortality benefit in COVID-19. Heparin inhibits both thrombosis and RAAS, and has definite mortality benefit at least in a subset of COVID-19 patients. Activated Protein C may be helpful for the microangiopathic thrombosis. We strongly advocate that treatment strategies for COVID-19 should include synergistic targeting of the RAAS and coagulation systems.

P38 MAPK inhibition: A promising therapeutic approach for COVID-19

COVID-19, caused by the SARS-CoV-2 virus, is a major source of morbidity and mortality due to its inflammatory effects in the lungs and heart. The p38 MAPK pathway plays a crucial role in the release of pro-inflammatory cytokines such as IL-6 and has been implicated in acute lung injury and myocardial dysfunction. The overwhelming inflammatory response in COVID-19 infection may be caused by disproportionately upregulated p38 activity, explained by two mechanisms. First, angiotensin-converting enzyme 2 (ACE2) activity is lost during SARS-CoV-2 viral entry. ACE2 is highly expressed in the lungs and heart and converts Angiotensin II into Angiotensin 1–7. Angiotensin II signals proinflammatory, pro-vasoconstrictive, pro-thrombotic activity through p38 MAPK activation, which is countered by Angiotensin 1–7 downregulation of p38 activity. Loss of ACE2 upon viral entry may tip the balance towards destructive p38 signaling through Angiotensin II. Second, SARS-CoV was previously shown to directly upregulate p38 activity via a viral protein, similar to other RNA respiratory viruses that may hijack p38 activity to promote replication. Given the homology between SARS-CoV and SARS-CoV-2, the latter may employ a similar mechanism. Thus, SARS-CoV-2 may induce overwhelming inflammation by directly activating p38 and downregulating a key inhibitory pathway, while simultaneously taking advantage of p38 activity to replicate. Therapeutic inhibition of p38 could therefore attenuate COVID-19 infection. Interestingly, a prior preclinical study showed protective effects of p38 inhibition in a SARS-CoV mouse model. A number of p38 inhibitors are in the clinical stage and should be considered for clinical trials in serious COVID-19 infection.

Coronavirus Disease 2019 (COVID-19) and Cardiovascular Disease: A Viewpoint on the Potential Influence of Angiotensin-Converting Enzyme Inhibitors/Angiotensin Receptor Blockers on Onset and Severity of Severe Acute Respiratory Syndrome Coronavirus 2 Infection.

Coronavirus Disease 2019 (COVID-19) and Cardiovascular Disease: A Viewpoint on the Potential Influence of Angiotensin-Converting Enzyme Inhibitors/Angiotensin Receptor Blockers on Onset and Severity of Severe Acute Respiratory Syndrome Coronavirus 2 Infection.

Plasma ACE2 Activity Predicts Mortality in Aortic Stenosis and Is Associated With Severe Myocardial Fibrosis

ObjectivesThis study investigated the relationship between plasma angiotensin-converting enzyme 2 (ACE2) activity levels and the severity of stenosis and myocardial remodeling in patients with aortic stenosis (AS) and determined if plasma ACE2 levels offered incremental prognostic usefulness to predict all-cause mortality. BackgroundACE2 is an integral membrane protein that degrades angiotensin II and has an emerging role as a circulating biomarker of cardiovascular disease. MethodsPlasma ACE2 activity was measured in 127 patients with AS; a subgroup had myocardial tissue collected at the time of aortic valve replacement. ResultsThe median plasma ACE2 activity was 34.0 pmol/ml/min, and levels correlated with increased valvular calcification (p = 0.023) and the left ventricular (LV) mass index (r = 0.34; p < 0.001). Patients with above-median plasma ACE2 had higher LV end-diastolic volume (57 ml/m2 vs. 48 ml/m2; p = 0.021). Over a median follow-up of 5 years, elevated plasma ACE2 activity was an independent predictor of all-cause mortality after adjustment for relevant clinical, imaging, and biochemical parameters (HR: 2.28; 95% CI: 1.03 to 5.06; p = 0.042), including brain natriuretic peptide activation (integrated discrimination improvement: 0.08; p < 0.001). In 22 patients with plasma and tissue, increased circulating ACE2 was associated with reduced myocardial ACE2 gene expression (0.7-fold; p = 0.033) and severe myocardial fibrosis (p = 0.027). ConclusionsIn patients with AS, elevated plasma ACE2 was a marker of myocardial structural abnormalities and an independent predictor of mortality with incremental value over traditional prognostic markers. Loss of ACE2 from the myocardium was associated with increased fibrosis and higher circulating ACE2 levels.

48-OR: Gut Dysbiosis Promotes Diabetic Retinopathy (DR) through TLR-2 Activation by Peptidoglycan (PGN) in Angiotensin Converting Enzyme 2 (ACE2) Deficient Type 1 Diabetic (T1D) Mice

Purpose: Previously, we demonstrated that ACE2 deficiency increases the severity of DR in Akita mice. In this study, we sought to determine the mechanism where by the gut microbiome, which is typically altered in T1D, contributes to the pathogenesis of DR in ACE2-/-Akita mice. Methods: Wild type (WT), Akita and ACE2-/-Akita mice were studied at 9 months of diabetes and the gut microbiota was examined using 16S rRNA sequencing and metatranscriptomic analysis. Microbial load in the circulation was assessed by measuring circulating PGN levels along with markers of the gut vascular barrier (GVB). Next, human retinal endothelial cells (HREC) were treated with PGN, a known Toll-like receptor (TLR)-2 agonist, to determine whether PGN enhances permeability. Results: 16S rRNA sequencing revealed a shift in beta diversity of the gut microbiota with an increase in Firmicutes and Bacteroidetes within the gut of ACE2-/-Akita mice. Metatranscriptomic analysis showed increases in PGN synthesis. Loss of ACE2 promoted gut barrier permeability through decreasing the turnover of VE-cadherin expression (41%, p&amp;lt;0.0001) in the intestine of ACE2-/-Akita mice. Increased vascular permeability was associated with barrier dysfunction, microbial translocation and increase PGN in the circulation (2.5 fold, p&amp;lt;0.007) in ACE2-/-Akita mice compared with Akita mice. Acellular capillaries (2 fold, p&amp;lt;0.05) were significantly higher in ACE2-/-Akita mice compared with Akita mice. PGN treatment caused dissociation of VE-cadherin junctional complexes in HRECs through a MyD88/ARNO/ARF6-mediated signaling pathway. This occurred by depleting p120-catenin (51%. p&amp;lt;0.004) and internalization of VE-cadherin. Conclusions: These data suggest that microbiota-derived PGN has deleterious effects on retinal endothelial cells to increasing permeability. Strategies aimed at resorting gut health may serve to prevent development of DR. Disclosure R. Prasad: None. Y. Duan: None. J.L. Floyd: None. M.B. Grant: None. Funding National Eye Institute (EY028858)

Angiotensin-Converting Enzyme 2 Deficiency Increases Translocation of Gut Bacteria by Depletion of Bone Marrow-Derived Circulating Angiogenic Cells

A healthy microbiome is central to good nutrition and efficient metabolism both of which can be altered in diabetes. Disruption of gut-vascular integrity may lead to translocation of microbial antigens and bacteria into the circulation. Bone marrow-derived circulating angiogenic cells (CACs) are essential to maintain vascular integrity. We tested the hypothesis that angiotensin-converting enzyme 2 (ACE2), the key enzyme in the vasoprotective axis of renin-angiotensin system (RAS), acts to regulate the infiltration of bone marrow-derived CACs in the gut and to maintain gut-vascular integrity in diabetes and could influence the systemic translocation of pathogenic antigens and bacteria from the gut. Diabetic ACE2 knockout (ACE2-/y)/C57BL/6-Ins2WT/C96Y (Akita) mice were examined at 9 months after the onset of diabetes and compared to age-matched controls. Beta diversity analysis of the gut microbiome revealed a distinct bacterial profile among the different genotypes (n=9-17 per group, p=0.002). The fecal samples from ACE2-/y-Akita group compared to Akita group were enriched with a great diversity of bacterial taxa that have been reported to contribute to the pathogenesis of diabetes and showed activation of peptidoglycan biosynthesis pathways by metatranscriptome analysis (n=4 per group, p=0.005). Flow cytometry analysis showed that loss of ACE2 led to reduced infiltration of bone marrow-derived CACs (CD45+Flk-1+CD31+) into the gut (n=8-14 per group, p&amp;lt;0.0001), without modifying levels of proinflammatory or immune cell phenotypes. The CAC depletion mediated by ACE2 deficiency was associated with increased levels of gut bacteria in the blood as assessed by SourceTracker analysis (n=9 per group). These data suggested a loss of the protective arm of RAS contributes to the depletion of CACs and disruption of gut-vascular barrier that may promote bacterial translocation in diabetes. Disclosure Y. Duan: None. D. Feng: None. E. Beli: None. S. Li Calzi: None. A.F. Longhini: None. R. Lamendella: None. J.R. Wright: None. T.A. Markel: None. A.G. Obukhov: None. M.B. Grant: None.

Deletion of Angiotensin-Converting Enzyme-2 Promotes Hypertensive Nephropathy by Targeting Smad7 for Ubiquitin Degradation.

Angiotensin-converting enzyme-2 (ACE2) is downregulated in hypertensive nephropathy. The present study investigated the mechanisms whereby loss of ACE2 promoted angiotensin II-induced hypertensive nephropathy in ACE2 gene knockout mice. We found that compared with wild-type animals, mice lacking ACE2 developed much more severe hypertensive nephropathy in response to chronic angiotensin II infusion, including higher levels of blood pressure, urinary protein excretion, serum creatinine, and progressive renal fibrosis and inflammation. Mechanistic studies revealed that worsening kidney injury in ACE2 knockout mice was associated with an increase in Smurf2 (Smad-specific E3 ubiquitin protein ligase 2), a decrease in renal Smad7, and marked activation of TGF-β (transforming growth factor β)/Smad3 and NF-κB (nuclear factor κ-light-chain-enhancer of activated B cells) signaling, suggesting that Smurf2-dependent Smad7 ubiquitin degradation may be a key mechanism whereby loss of ACE2 promotes angiotensin II-induced TGF-β/Smad3 and NF-κB-mediated hypertensive nephropathy. This was validated by restoring Smad7 locally in the kidneys of ACE2 knockout mice to block angiotensin II-induced TGF-β/Smad3-mediated renal fibrosis and NF-κB-driven renal inflammation. Moreover, we found that angiotensin II could induce microRNA-21 in the mouse kidney and in cultured mesangial cells via a Smad3-dependent mechanism, which was enhanced by deleting ACE2 but inhibited by overexpressing renal Smad7. In conclusion, loss of ACE2 promotes angiotensin II-induced renal injury by targeting Smad7 for degradation via a Smurf2-dependent mechanism. Overexpression of renal Smad7 protects against hypertensive nephropathy by inactivating angiotensin II-induced TGF-β/Smad3 and NF-κB pathways and by targeting the Smad3-dependent microRNA-21 axis.

Angiotensin converting enzyme 2 and diminazene: role in cardiovascular and blood pressure regulation.

Angiotensin converting enzyme 2 (ACE2) is an important regulator of the renin-angiotensin system through actions to degrade angiotensin II. Loss of ACE2 can contribute to the development and progression of cardiovascular disease, and experimental studies have highlighted a beneficial role for novel therapeutic approaches that activate or replenish tissue ACE2. This review focuses on experimental studies that have used the off-target effects of the antitrypanosomal agent, diminazene aceturate (DIZE) to activate ACE2. In cardiovascular disease, activation of the classical renin-angiotensin system and depletion of ACE2 leads to pathophysiological changes. One approach to activate ACE2 involves the drug DIZE, which has been shown to have beneficial effects in experimental models of hypertension, pulmonary hypertension, myocardial infarction, stroke, atherosclerosis, type 1 diabetes, and eye disease. The precise mechanism of action of DIZE to activate ACE2 remains under scrutiny. Activation of ACE2 may represent an important therapeutic approach in cardiovascular disease. To date, most studies have focused on the off-target actions of DIZE, in experimental models of disease. More research is required to determine the exact mechanism of action of DIZE and evaluate its therapeutic potential in comparison with currently available clinical interventions. There are no clinical studies of DIZE, and its side-effects, and toxicity make such studies unlikely. Hence, new methods of selectively activating or replenishing ACE2 will be needed in the future if this approach is to be used in a clinical context.

Gonadectomy prevents the increase in blood pressure and glomerular injury in angiotensin-converting enzyme 2 knockout diabetic male mice. Effects on renin-angiotensin system.

Angiotensin-converting enzyme 2 (ACE2) deletion worsens kidney injury, and its amplification ameliorates diabetic nephropathy. Male sex increases the incidence, prevalence, and progression of chronic kidney disease in our environment. Here, we studied the effect of ACE2 deficiency and gonadectomy (GDX) on diabetic nephropathy and its relationship with fibrosis, protein kinase B (Akt) activation, and the expression of several components of the renin-angiotensin system (RAS).Mice were injected with streptozotocin to induce diabetes and followed for 19 weeks. Physiological and renal parameters were studied in wild-type and ACE2 knockout (ACE2KO) male mice with and without GDX. Diabetic ACE2KO showed increased blood pressure (BP), glomerular injury, and renal fibrosis compared with diabetic wild-type. Gonadectomized diabetic ACE2KO presented a decrease in BP. In the absence of ACE2, GDX attenuated albuminuria and renal lesions, such as mesangial matrix expansion and podocyte loss. Both, α-smooth muscle actin accumulation and collagen deposition were significantly decreased in renal cortex of gonadectomized diabetic ACE2KO but not diabetic wild-type mice. GDX also reduced circulating ACE activity in ACE2KO mice. Loss of ACE2 modified the effect of GDX on cortical gene expression of RAS in diabetic mice. Akt phosphorylation in renal cortex was increased by diabetes and loss of ACE2 and decreased by GDX in control and diabetic ACE2KO but not in wild-type mice. Our results suggest that GDX may exert a protective effect within the kidney under pathological conditions of diabetes and ACE2 deficiency. This renoprotection may be ascribed to different mechanisms such as decrease in BP, modulation of RAS, and downregulation of Akt-related pathways.

Role of the ACE2/Angiotensin 1-7 Axis of the Renin-Angiotensin System in Heart Failure.

Heart failure (HF) remains the most common cause of death and disability, and a major economic burden, in industrialized nations. Physiological, pharmacological, and clinical studies have demonstrated that activation of the renin-angiotensin system is a key mediator of HF progression. Angiotensin-converting enzyme 2 (ACE2), a homolog of ACE, is a monocarboxypeptidase that converts angiotensin II into angiotensin 1-7 (Ang 1-7) which, by virtue of its actions on the Mas receptor, opposes the molecular and cellular effects of angiotensin II. ACE2 is widely expressed in cardiomyocytes, cardiofibroblasts, and coronary endothelial cells. Recent preclinical translational studies confirmed a critical counter-regulatory role of ACE2/Ang 1-7 axis on the activated renin-angiotensin system that results in HF with preserved ejection fraction. Although loss of ACE2 enhances susceptibility to HF, increasing ACE2 level prevents and reverses the HF phenotype. ACE2 and Ang 1-7 have emerged as a key protective pathway against HF with reduced and preserved ejection fraction. Recombinant human ACE2 has been tested in phase I and II clinical trials without adverse effects while lowering and increasing plasma angiotensin II and Ang 1-7 levels, respectively. This review discusses the transcriptional and post-transcriptional regulation of ACE2 and the role of the ACE2/Ang 1-7 axis in cardiac physiology and in the pathophysiology of HF. The pharmacological and therapeutic potential of enhancing ACE2/Ang 1-7 action as a novel therapy for HF is highlighted.

Heterozygote loss of ACE2 is sufficient to increase the susceptibility to heart disease.

Angiotensin-converting enzyme 2 (ACE2) metabolizes Ang II into Ang 1-7 thereby negatively regulating the renin-angiotensin system. However, heart disease in humans and in animal models is associated with only a partial loss of ACE2. ACE2 is an X-linked gene; and as such, we tested the clinical relevance of a partial loss of ACE2 by using female ACE2(+/+) (wildtype) and ACE2(+/-) (heterozygote) mice. Pressure overload in ACE2(+/-) mice resulted in greater LV dilation and worsening systolic and diastolic dysfunction. These changes were associated with increased myocardial fibrosis, hypertrophy, and upregulation of pathological gene expression. In response to Ang II infusion, there was increased NADPH oxidase activity and myocardial fibrosis resulting in the worsening of Ang II-induced diastolic dysfunction with a preserved systolic function. Ang II-mediated cellular effects in cultured adult ACE2(+/-) cardiomyocytes and cardiofibroblasts were exacerbated. Ang II-mediated pathological signaling worsened in ACE2(+/-) hearts characterized by an increase in the phosphorylation of ERK1/2 and JNK1/2 and STAT-3 pathways. The ACE2(+/-) mice showed an exacerbated pressor response with increased vascular fibrosis and stiffness. Vascular superoxide and nitrotyrosine levels were increased in ACE2(+/-) vessels consistent with increased vascular oxidative stress. These changes occurred with increased renal fibrosis and superoxide production. Partial heterozygote loss of ACE2 is sufficient to increase the susceptibility to heart disease secondary to pressure overload and Ang II infusion. Heart disease in humans with idiopathic dilated cardiomyopathy is associated with a partial loss of ACE2. Heterozygote female ACE2 mutant mice showed enhanced susceptibility to pressure overload-induced heart disease. Heterozygote female ACE2 mutant mice showed enhanced susceptibility to Ang II-induced heart and vascular diseases. Partial loss of ACE2 is sufficient to enhance the susceptibility to heart disease.

Targeting angiotensin-converting enzyme 2 as a new therapeutic target for cardiovascular diseases.

Angiotensin-converting enzyme 2 (ACE2) is a monocarboxypeptidase that metabolizes several vasoactive peptides, including angiotensin II (Ang-II; a vasoconstrictive/proliferative peptide), which it converts to Ang-(1-7). Ang-(1-7) acts through the Mas receptor to mediate vasodilatory/antiproliferative actions. The renin-angiotensin system involving the ACE-Ang-II-Ang-II type-1 receptor (AT1R) axis is antagonized by the ACE2-Ang-(1-7)-Mas receptor axis. Loss of ACE2 enhances adverse remodeling and susceptibility to pressure and volume overload. Human recombinant ACE2 may act to suppress myocardial hypertrophy, fibrosis, inflammation, and diastolic dysfunction in heart failure patients. The ACE2-Ang-(1-7)-Mas axis may present a new therapeutic target for the treatment of heart failure patients. This review is mainly focused on the analysis of ACE2, including its influence and potentially positive effects, as well as the potential use of human recombinant ACE2 as a novel therapy for the treatment cardiovascular diseases, such as hypertension and heart failure.

Role of angiotensin-converting enzyme 2 (ACE2) in diabetic cardiovascular complications

Diabetes mellitus results in severe cardiovascular complications, and heart disease and failure remain the major causes of death in patients with diabetes. Given the increasing global tide of obesity and diabetes, the clinical burden of diabetes-induced cardiovascular disease is reaching epidemic proportions. Therefore urgent actions are needed to stem the tide of diabetes which entails new prevention and treatment tools. Clinical and pharmacological studies have demonstrated that AngII (angiotensin II), the major effector peptide of the RAS (renin-angiotensin system), is a critical promoter of insulin resistance and diabetes mellitus. The role of RAS and AngII has been implicated in the progression of diabetic cardiovascular complications and AT1R (AngII type1 receptor) blockers and ACE (angiotensin-converting enzyme) inhibitors have shown clinical benefits. ACE2, the recently discovered homologue of ACE, is a monocarboxypeptidase which converts AngII into Ang-(1-7) [angiotensin-(1-7)] which, by virtue of its actions on the MasR (Mas receptor), opposes the effects of AngII. In animal models of diabetes, an early increase in ACE2 expression and activity occurs, whereas ACE2 mRNA and protein levels have been found to decrease in older STZ (streptozotocin)-induced diabetic rats. Using the Akita mouse model of Type1 diabetes, we have recently shown that loss of ACE2 disrupts the balance of the RAS in a diabetic state and leads to AngII/AT1R-dependent systolic dysfunction and impaired vascular function. In the present review, we will discuss the role of the RAS in the pathophysiology and treatment of diabetes and its complications with particular emphasis on potential benefits of the ACE2/Ang-(1-7)/MasR axis activation.