Downregulation Of Angiotensin-converting Enzyme 2 Research Articles

Modeling the Molecular Impact of SARS-CoV-2 Infection on the Renin-Angiotensin System.

SARS-CoV-2 infection is mediated by the binding of its spike protein to the angiotensin-converting enzyme 2 (ACE2), which plays a pivotal role in the renin-angiotensin system (RAS). The study of RAS dysregulation due to SARS-CoV-2 infection is fundamentally important for a better understanding of the pathogenic mechanisms and risk factors associated with COVID-19 coronavirus disease and to design effective therapeutic strategies. In this context, we developed a mathematical model of RAS based on data regarding protein and peptide concentrations; the model was tested on clinical data from healthy normotensive and hypertensive individuals. We used our model to analyze the impact of SARS-CoV-2 infection on RAS, which we modeled through a downregulation of ACE2 as a function of viral load. We also used it to predict the effect of RAS-targeting drugs, such as RAS-blockers, human recombinant ACE2, and angiotensin 1–7 peptide, on COVID-19 patients; the model predicted an improvement of the clinical outcome for some drugs and a worsening for others. Our model and its predictions constitute a valuable framework for in silico testing of hypotheses about the COVID-19 pathogenic mechanisms and the effect of drugs aiming to restore RAS functionality.

Clinically Suspected Myocarditis in the Course of Severe Acute Respiratory Syndrome Novel Coronavirus-2 Infection: Fact or Fiction?

Cardiac complications, including clinically suspected myocarditis, have been described in novel coronavirus disease 2019. Here, we review current data on suspected myocarditis in the course of severe acute respiratory syndrome novel coronavirus-2 (SARS-CoV-2) infection. Hypothetical mechanisms to explain the pathogenesis of troponin release in patients with novel coronavirus disease 2019 include direct virus-induced myocardial injury (ie, viral myocarditis), systemic hyperinflammatory response (ie, cytokine storm), hypoxemia, downregulation of angiotensin-converting enzyme 2, systemic virus-induced endothelialitis, and type 1 and type 2 myocardial infarction. To date, despite the fact that millions of SARS-CoV-2 infections have been diagnosed worldwide, there is no definitive proof that SARS-CoV-2 is a novel cardiotropic virus causing direct cardiomyocyte damage. Diagnosis of viral myocarditis should be based on the molecular assessment of endomyocardial biopsy or autopsy by polymerase chain reaction or in-situ hybridization. Blood, sputum, or nasal and throat swab virology testing are insufficient and do not correlate with the myocardial involvement of a given pathogen. Data from endomyocardial biopsies and autopsies in clinically suspected SARS-CoV-2 myocarditis are scarce. Overall, current clinical epidemiologic data do not support the hypothesis that viral myocarditis is caused by SARS-CoV-2, or that it is common. More endomyocardial biopsy and autopsy data are also needed for a better understanding of pathogenesis of clinically suspected myocarditis in the course of SARS-CoV-2 infection, which may include virus-negative immune-mediated or already established subclinical autoimmune forms, triggered or accelerated by the hyperinflammatory state of severe novel coronavirus disease 2019.

Tissue- and Cell-Specific Dysregulations of ACE2 may put Patients with Diabetes at Higher Risk for COVID-19

Hypertension and diabetes are the major risk factors for patients with Coronavirus disease 2019 (COVID-19). The physiological link between the diseases is still obscure. A growing body of evidence indicates that Angiotensin-converting enzyme 2 (ACE2) could be one of the critical agents linking diabetes with hypertension and COVID-19. Whether an up- or rather a down-regulation of ACE2 is responsible for the higher risk for COVID-19 is not clear. Experimental evidence and theoretical models exist for both. We show here that in addition to the overall up-/down-regulation of ACE2 at the whole-body level, we need to consider the tissue- and cell-specific dysregulations of ACE2, determining the risk of patients with diabetes for COVID-19.

Downregulation of Membrane-bound Angiotensin Converting Enzyme 2 (ACE2) Receptor has a Pivotal Role in COVID-19 Immunopathology.

The Coronavirus Disease 2019 (COVID-19) is becoming the major health issue in recent human history with thousands of deaths and millions of cases worldwide. Newer research and old experience with other coronaviruses highlighted a probable underlying mechanism of disturbance of the renin-angiotensin system (RAS) that is associated with the intrinsic effects of SARS-CoV-2 infection. In this review, we aimed to describe the intimate connections between the RAS components, the immune system and COVID-19 pathophysiology. This non-systematic review article summarizes recent evidence on the relationship between COVID-19 and the RAS. Several studies have indicated that the downregulation of membrane-bound ACE2 may exert a key role for the impairment of immune functions and for COVID-19 patients' outcomes. The downregulation may occur by distinct mechanisms, particularly: (1) the shedding process induced by the SARS-CoV-2 fusion pathway, which reduces the amount of membrane-bound ACE2, stimulating more shedding by the high levels of Angiotensin II; (2) the endocytosis of ACE2 receptor with the virus itself and (3) by the interferon inhibition caused by SARS-CoV-2 effects on the immune system, which leads to a reduction of ACE2 receptor expression. Recent research provides evidence of a reduction of the components of the alternative RAS axis, including ACE2 and Angiotensin-(1-7). In contrast, increased levels of Angiotensin II can activate the AT1 receptor in several organs. Consequently, increased inflammation, thrombosis and angiogenesis occur in patients infected with SARS-COV-2. Attention should be paid to the interactions of the RAS and COVID-19, mainly in the context of novel vaccines and proposed medications.

Converging pathways in pulmonary fibrosis and Covid-19 - The fibrotic link to disease severity

As Covid-19 affects millions of people worldwide, the global health care will encounter an increasing burden of the aftermaths of the disease. Evidence shows that up to a fifth of the patients develop fibrotic tissue in the lung. The SARS outbreak in the early 2000 resulted in chronic pulmonary fibrosis in a subset (around 4%) of the patients, and correlated to reduced lung function and forced expiratory volume (FEV). The similarities between corona virus infections causing SARS and Covid-19 are striking, except that the novel coronavirus, SARS-CoV-2, has proven to have an even higher communicability. This would translate into a large number of patients seeking care for clinical signs of pulmonary fibrosis, given that the Covid-19 pandemic has up till now (Sept 2020) affected around 30 million people. The SARS-CoV-2 is dependent on binding to the angiotensin converting enzyme 2 (ACE2), which is part of the renin-angiotensin system (RAS). Downregulation of ACE2 upon virus binding disturbs downstream activities of RAS resulting in increased inflammation and development of fibrosis. The poor prognosis and risk of developing pulmonary fibrosis are therefore associated with the increased expression of ACE2 in risk groups, such as obesity, heart disorders and aging, conferring plenty of binding opportunity for the virus and subsequently the internalization of ACE2, thus devoiding the enzyme from acting counter-inflammatory and antifibrotic. Identifying pathways that are associated with Covid-19 severity that result in pulmonary fibrosis may enable early diagnosis and individualized treatment for these patients to prevent or reduce irreversible fibrotic damage to the lung.

Elevated markers of gut leakage and inflammasome activation in COVID-19 patients with cardiac involvement.

BackgroundA high proportion of COVID‐19 patients have cardiac involvement, even those without known cardiac disease. Downregulation of angiotensin converting enzyme 2 (ACE2), a receptor for SARS‐CoV‐2 and the renin‐angiotensin system, as well as inflammatory mechanisms have been suggested to play a role. ACE2 is abundant in the gut and associated with gut microbiota composition. We hypothesized that gut leakage of microbial products, and subsequent inflammasome activation could contribute to cardiac involvement in COVID‐19 patients.MethodsPlasma levels of a gut leakage marker (LPS‐binding protein, LBP), a marker of enterocyte damage (intestinal fatty acid binding protein, IFABP), a gut homing marker (CCL25, ligand for chemokine receptor CCR9) and markers of inflammasome activation (IL‐1β, IL‐18 and their regulatory proteins) were measured at three time points (day 1, 3–5 and 7–10) in 39 hospitalized COVID‐19 patients and related to cardiac involvement.ResultsCompared to controls, COVID‐19 patients had elevated plasma levels of LBP and CCL25 but not IFABP, suggesting impaired gut barrier function and accentuated gut homing of T cells without excessive enterocyte damage. Levels of LBP were twice as high at baseline in patients with elevated cardiac markers compared with those without and remained elevated during hospitalization. Also, markers of inflammasome activation were moderately elevated in patients with cardiac involvement. LBP was associated with higher NT‐pro‐BNP levels, whereas IL‐18, IL‐18BP and IL‐1Ra were associated with higher troponin levels.ConclusionPatients with cardiac involvement had elevated markers of gut leakage and inflammasome activation, suggestive of a potential gut‐heart axis in COVID‐19.

Commentaries on Viewpoint: The interaction between SARS-CoV-2 and ACE2 may have consequences for skeletal muscle viral susceptibility and myopathies.

Commentaries on Viewpoint: The interaction between SARS-CoV-2 and ACE2 may have consequences for skeletal muscle viral susceptibility and myopathies.

Molecular Features of Non-Selective Small Molecule Antagonists of the Bradykinin Receptors.

Angiotensin converting enzyme 2 (ACE2) downregulation is a key negative factor for the severity of lung edema and acute lung failure observed in patients infected with SARS-CoV-2. ACE2 downregulation affects the levels of diverse peptide mediators of the renin-agiotensin-aldestosterone and kallikrein-kinin systems, compromising vascular hemostasis. Increasing evidence suggests that the inflammatory response observed in covid-19 patients is initiated by the action of kinins on the bradykinin receptors. Accordingly, the use of bradykinin antagonists should be considered as a strategy for therapeutic intervention against covid-19 illness progression. Presently, icatibant is the only bradykinin antagonist drug approved. In the present report, we investigated the molecular features characterizing non-selective antagonists targeting the bradykinin receptors and carried out a in silico screening of approved drugs, aimed at the identification of compounds with a non-selective bradykinin antagonist profile that can be evaluated for drug repurposing. The study permitted to identify eight compounds as prospective non-selective antagonists of the bradykinin receptors, including raloxifene; sildenafil; cefepime; cefpirome; imatinib; ponatinib; abemaciclib and entrectinib.

Insights on SARS-CoV-2 Molecular Interactions With the Renin-Angiotensin System.

The emergence of SARS-CoV-2/human/Wuhan/X1/2019, a virus belonging to the species Severe acute respiratory syndrome-related coronavirus, and the recognition of Coronavirus Disease 2019 (COVID-19) as a pandemic have highly increased the scientific research regarding the pathogenesis of COVID-19. The Renin Angiotensin System (RAS) seems to be involved in COVID-19 natural course, since studies suggest the membrane-bound Angiotensin-converting enzyme 2 (ACE2) works as SARS-CoV-2 cellular receptor. Besides the efforts of the scientific community to understand the virus’ molecular interactions with human cells, few studies summarize what has been so far discovered about SARS-CoV-2 signaling mechanisms and its interactions with RAS molecules. This review aims to discuss possible SARS-CoV-2 intracellular signaling pathways, cell entry mechanism and the possible consequences of the interaction with RAS components, including Angiotensin II (Ang II), Angiotensin-(1-7) [Ang-(1-7)], Angiotensin-converting enzyme (ACE), ACE2, Angiotensin II receptor type-1 (AT1), and Mas Receptor. We also discuss ongoing clinical trials and treatment based on RAS cascade intervention. Data were obtained independently by the two authors who carried out a search in the PubMed, Embase, LILACS, Cochrane, Scopus, SciELO and the National Institute of Health databases using Medical Subject Heading terms as “SARS-CoV-2,” “COVID-19,” “Renin Angiotensin System,” “ACE2,” “Angiotensin II,” “Angiotensin-(1-7),” and “AT1 receptor.” Similarly to other members of Coronaviridae family, the molecular interactions between the pathogen and the membrane-bound ACE2 are based on the cleavage of the spike glycoprotein (S) in two subunits. Following the binding of the S1 receptor-binding domain (RBD) to ACE2, transmembrane protease/serine subfamily 2 (TMPRSS2) cleaves the S2 domain to facilitate membrane fusion. It is very likely that SARS-CoV-2 cell entry results in downregulation of membrane-bound ACE2, an enzyme that converts Ang II into Ang-(1-7). This mechanism can result in lung injury and vasoconstriction. In addition, Ang II activates pro-inflammatory cascades when binding to the AT1 Receptor. On the other hand, Ang-(1-7) promotes anti-inflammatory effects through its interactions with the Mas Receptor. These molecules might be possible therapeutic targets for treating COVID-19. Thus, the understanding of SARS-CoV-2 intracellular pathways and interactions with the RAS may clarify COVID-19 physiopathology and open perspectives for new treatments and strategies.

Cabbage and fermented vegetables: From death rate heterogeneity in countries to candidates for mitigation strategies of severe COVID-19.

Large differences in COVID‐19 death rates exist between countries and between regions of the same country. Some very low death rate countries such as Eastern Asia, Central Europe, or the Balkans have a common feature of eating large quantities of fermented foods. Although biases exist when examining ecological studies, fermented vegetables or cabbage have been associated with low death rates in European countries. SARS‐CoV‐2 binds to its receptor, the angiotensin‐converting enzyme 2 (ACE2). As a result of SARS‐CoV‐2 binding, ACE2 downregulation enhances the angiotensin II receptor type 1 (AT1R) axis associated with oxidative stress. This leads to insulin resistance as well as lung and endothelial damage, two severe outcomes of COVID‐19. The nuclear factor (erythroid‐derived 2)‐like 2 (Nrf2) is the most potent antioxidant in humans and can block in particular the AT1R axis. Cabbage contains precursors of sulforaphane, the most active natural activator of Nrf2. Fermented vegetables contain many lactobacilli, which are also potent Nrf2 activators. Three examples are: kimchi in Korea, westernized foods, and the slum paradox. It is proposed that fermented cabbage is a proof‐of‐concept of dietary manipulations that may enhance Nrf2‐associated antioxidant effects, helpful in mitigating COVID‐19 severity.

Should ACE2 be given a chance in COVID-19 therapeutics: A semi-systematic review of strategies enhancing ACE2

The severe acute respiratory syndrome corona virus-2 (SARS-CoV-2) has resulted in almost 28 million cases of COVID-19 (Corona virus disease-2019) and more than 900000 deaths worldwide since December 2019. In the absence of effective antiviral therapy and vaccine, treatment of COVID-19 is largely symptomatic. By making use of its spike (S) protein, the virus binds to its primary human cell receptor, angiotensin converting enzyme 2 (ACE2) which is present in the pulmonary epithelial cells as well as other organs. SARS-CoV-2 may cause a downregulation of ACE2. ACE2 plays a protective role in the pulmonary system through its Mas-receptor and alamandine-MrgD-TGR7 pathways. Loss of this protective effect could be a major component of COVID-19 pathogenesis. An attractive strategy in SARS-CoV-2 therapeutics would be to augment ACE2 either directly by supplementation or indirectly through drugs which increase its levels or stimulate its downstream players. In this semi-systematic review, we have analysed the pathophysiological interplay between ACE and ACE2 in the cardiopulmonary system, the modulation of these two proteins by SARS-CoV-2, and potential therapeutic avenues targeting ACE-Ang II and ACE2-Ang (1–7) axes, that can be utilized against COVID-19 disease progression.

"Mosaic Perfusion Pattern" on Dual-Energy CT in COVID-19 Pneumonia: Pulmonary Vasoplegia or Vasoconstriction?

HomeRadiology: Cardiothoracic ImagingVol. 2, No. 5 PreviousNext Letters to the EditorFree Access“Mosaic Perfusion Pattern” on Dual-Energy CT in COVID-19 Pneumonia: Pulmonary Vasoplegia or Vasoconstriction?Amit Jain* , D. John Doyle*, Ramesh Mangal†Amit Jain* , D. John Doyle*, Ramesh Mangal†Author AffiliationsAnesthesiology Institute, Cleveland Clinic Abu Dhabi, Al Maryah Island, Abu Dhabi, United Arab Emirates*Radiology Institute, Mednext, Ahmedabad, India†e-mail: [email protected]Amit Jain* D. John Doyle*Ramesh Mangal†Published Online:Sep 10 2020https://doi.org/10.1148/ryct.2020200433MoreSectionsPDF ToolsImage ViewerAdd to favoritesCiteTrack Citations ShareShare onFacebookTwitterLinked In Editor:Finding dilated subsegmental vessels at dual-energy CT (DECT), Dr Lang and colleagues (1) proposed inflammatory-mediated impaired hypoxic pulmonary vasoconstriction (HPV) with overactive regional vasodilation to explain coronavirus disease 2019 (COVID-19) hypoxemia in their article in the June issue of Radiology: Cardiothoracic Imaging. However, this was not associated with increased pulmonary blood volume (PBV) in consolidated areas; instead, most (96%) patients had decreased peripheral perfusion corresponding to peripheral lung opacities, and only one-third demonstrated a halo of increased perfusion surrounding peripheral opacities. If HPV loss occurs in consolidated regions, PBV should have increased, producing hyperemia rather than oligemia. We instead propose an angiotensin II–mediated, nonimmune, noninflammatory mechanism to explain the mosaic perfusion pattern.Severe acute respiratory syndrome coronavirus 2 (SARS-Cov-2) infection of alveolar epithelium results in downregulation of angiotensin-converting enzyme 2 (ACE-2) and ACE-angiotensin II-angiotensin II type 1 receptor pathway overactivity, producing heterogeneous small vessel vasoconstriction (2) and recruitment of segmental/subsegmental vessels with relatively less vasoconstriction, causing regional overperfusion, reduced diffusion capacity, increased shunt and hypoxia, even in the absence of radiologically evident lesions. Where precapillary constriction is intense (due to high local concentration of angiotensin II), PBV would decrease, reducing perfusion even in normal lung or may produce wedge-shaped areas of pulmonary deficit on DECT (3). In areas of ineffective constriction due to lower concentrations of angiotensin II, capillary filtration pressure would increase, resulting in capillary stress failure and hydrostatic interstitial edema with patchy ground-glass opacities (GGOs) on CT. Disruption of the alveolocapillary membrane develops, with SARS-CoV-2 directly infecting endothelial cells. Endothelialitis with intracapillary fibrin-microthrombi blocks alveolar capillaries and further decreases perfusion within the areas of GGOs and consolidation but, with dilatation of proximal subsegmental arterioles, along with a halo of increased perfusion surrounding regions of consolidation. Thus, in COVID-19 pneumonia as the GGOs worsens to consolidation, oligemia or hyperemia in the area of consolidation is largely determined by the balance between the endothelialitis-mediated capillary obstruction (in consolidation regions) versus angiotensin II-mediated regional vasoconstriction (in healthy lung regions) (3,4).Our theory is supported by high incidence of raised PVR and right ventricular dysfunction in early COVID-19 disease (5) and reports of lung perfusion deficits that do not overlap with GGOs or consolidation and are not associated with major vessel occlusion (3). We believe determining the predominant pathophysiology—heterogeneous pulmonary vasoconstriction versus pulmonary vasoplegia—has treatment implications: pulmonary vasoconstrictors versus vasodilators.Disclosures of Conflicts of Interest: A.J. disclosed no relevant relationships. D.J.D. disclosed no relevant relationships. R.M. disclosed no relevant relationships.

Cancer progression in COVID-19: integrating the roles of renin angiotensin aldosterone system, angiopoietin-2, heat shock protein-27 and epithelial mesenchymal transition.

The ongoing coronavirus disease 2019 (COVID-19) pandemic has affected millions worldwide and has been found to cause severe disease in patients with underlying comorbidities. In patients with known malignancies, in addition to constraints in routine healthcare, the risk of being susceptible to developing severe forms of the disease is of grave concern.While follow-up studies on survivors of the severe acute respiratory syndrome (SARS) 2003 outbreak revealed increased susceptibility to infections, tumours and cardiovascular abnormalities, recent studies implicating angiopoietin 2 in induction of inflammatory intussusceptive angiogenesis and diffuse alveolar damage in COVID-19 patients raises the possibility of progression of carcinogenetic processes in patients with known malignancies. Angiotensin converting enzyme-2 (ACE-2) mediated cellular entry of SARS-Cov2 leads to receptor shedding of ACE-2 and disrupts the renin angiotensin aldosterone axis (RAAS). This augments the pro-inflammatory and proliferative effects of RAAS, while attenuating the anti-inflammatory and anti-proliferative angiotensin 1-7 /Mas pathway. Angiopoietin-2, a molecule responsible for angiogenesis and cancer progression which corelates with tumour load in certain cancers, is upregulated by angiotensin 2-AT1 Receptor axis. Tumour microenvironment—comprising of various cells, blood vessels and extra cellular matrix which express the RAAS peptides—plays a key role in cancer initiation, progression and metastasis. Angiotensin 2 induces the formation of a desmoplastic environment, favouring cancer cell growth. ACE-2 downregulation causes bradykinin accumulation which may exert its proliferative action via mitogen activated protein kinase pathways which has established roles in cancers of breast and kidney.In addition to cytokine storm causing organ damage, acute inflammation in COVID-19 may also cause epithelial mesenchymal transition and heat shock protein 27 phosphorylation, both of which are key mediators in cancer signalling pathways.We hypothesise that SARS-Cov2, by impacting the RAAS and immune system, has the potential to cause tumour cell proliferation, apoptosis evasion and metastasis, thereby increasing the possibility of cancer progression in patients with known malignancies.

Renin-angiotensin system inhibitors and the severity of coronavirus disease 2019 in Kanagawa, Japan: a retrospective cohort study.

Since the beginning of the coronavirus disease 2019 (COVID-19) outbreak initiated on the Diamond Princess Cruise Ship at Yokohama harbor in February 2020, we have been doing our best to treat COVID-19 patients. In animal experiments, angiotensin converting enzyme inhibitors (ACEIs) and angiotensin II type-1 receptor blockers (ARBs) are reported to suppress the downregulation of angiotensin converting enzyme 2 (ACE2), and they may inhibit the worsening of pathological conditions. We aimed to examine whether preceding use of ACEIs and ARBs affected the clinical manifestations and prognosis of COVID-19 patients. One hundred fifty-one consecutive patients (mean age 60 ± 19 years) with polymerase-chain-reaction proven severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection who were admitted to six hospitals in Kanagawa Prefecture, Japan, were analyzed in this multicenter retrospective observational study. Among all COVID-19 patients, in the multiple regression analysis, older age (age ≥ 65 years) was significantly associated with the primary composite outcome (odds ratio (OR) 6.63, 95% confidence interval (CI) 2.28-22.78, P < 0.001), which consisted of (i) in-hospital death, (ii) extracorporeal membrane oxygenation, (iii) mechanical ventilation, including invasive and noninvasive methods, and (iv) admission to the intensive care unit. In COVID-19 patients with hypertension, preceding ACEI/ARB use was significantly associated with a lower occurrence of new-onset or worsening mental confusion (OR 0.06, 95% CI 0.002-0.69, P = 0.02), which was defined by the confusion criterion, which included mild disorientation or hallucination with an estimation of medical history of mental status, after adjustment for age, sex, and diabetes. In conclusion, older age was a significant contributor to a worse prognosis in COVID-19 patients, and ACEIs/ARBs could be beneficial for the prevention of confusion in COVID-19 patients with hypertension.

Cross-Talk Between Key Players in Patients with COVID-19 and Ischemic Stroke: AReview on Neurobiological Insight of the Pandemic.

The global pandemic of novel coronavirus disease 2019 (COVID-19) has taken the entire human race by surprise and led to an unprecedented number of mortalities worldwide so far. Current clinical studies have interpreted that angiotensin-converting enzyme 2 (ACE2) is the host receptor for severe acute respiratory syndrome-coronavirus 2 (SARS-CoV-2). In addition, ACE2 is the major component of the renin-angiotensin system. ACE2 deteriorates angiotensin II, a peptide that is responsible for the promotion of stroke. The downregulation of ACE2 further activates an immunological cascade. Thus, researchers need to explore and examine the possible links between COVID-19 and ischemic stroke (IS). Human ACE2 expression level and pattern in various tissues might be decisive for the vulnerability, symptoms, and treatment outcomes of the SARS-CoV-2 infection. The swift increase in the knowledge of SARS-CoV-2 has given creditable evidence that SARS-CoV-2 infected patients also encounter neurological deficits. As the SARS-CoV-2 binds to ACE2, it will hamper the activity of ACE2 in providing neuroprotection, especially in the case of stroke patients. Due to the downregulation of ACE2, the inflammatory response is activated in the ischemic penumbra. The COVID-19 pandemic has affected people with various pre-existing diseases, including IS, in such a way that these patients need special care and attention for their survival. Several clinical trials are currently ongoing worldwide as well as many other projects are in different stages of conceptualization and planning to facilitate the effective management of stroke patients with COVID-19 infection.

Coronavirus 2019 Disease (COVID-19), Systemic Inflammation, and Cardiovascular Disease.

Acute respiratory failure associated with the Severe Acute Respiratory Syndrome coronavirus 2 (SARS-CoV-2), has rapidly spread worldwide and presents critical challenges for the public health and medical communities The World Health Organization (WHO) has declared SARS-CoV-2 a public health emergency of international concern, with a global estimate of over 7 million human infections and more than 400000 deaths worldwide as of June 12, 2020 A 2020 report by the China Medical Treatment Expert Group for Coronavirus disease 2010 (COVID-19) (2) showed that the clinical spectrum of the viral infection is dominated by fever (up to 88 7% of patients during hospitalization) and cough (67 8% of patients) followed by symptoms such as headache, fatigue, or shortness of breath

Renin-Angiotensin System and Coronavirus Disease 2019: A Narrative Review.

Although clinical manifestations of the 2019 novel coronavirus disease pandemic (COVID-19), caused by the novel severe acute respiratory syndrome coronavirus 2 (SARS-COV-2), are mainly respiratory symptoms, patients can also develop severe cardiovascular damage. Therefore, understanding the damage caused by SARS-COV-2 to the cardiovascular system and the underlying mechanisms is fundamental. The cardiovascular damage may be related to the imbalance of the renin-angiotensin-system (RAS) as this virus binds the Angiotensin-Converting-Enzyme 2 (ACE2), expressed on the lung alveolar epithelial cells, to enter into cells. Virus internalization may cause a downregulation of ACE2 on host cell surface that could lead to a local increased level of angiotensin II (AII) and a reduced level of angiotensin 1-7 (A1-7). An imbalance between these angiotensins may be responsible for the lung and heart damage. Pharmacological strategies that interfere with the viral attachment to ACE2 (umifenovir and hydroxychloroquine/chloroquine) or that modulate the RAS (analogous of A1-7 and ACE2, losartan) are in clinical development for COVID-19. The use of RAS inhibitors has also become a matter of public concern as these drugs may increase the mRNA expression and levels of ACE2 and impact the virulence and transmission of SARS-COV-2. Data on the effect of RAS inhibitors on ACE2 mRNA expression are scarce. Scientific societies expressed their opinion on continuing the therapy with RAS inhibitors in patients with COVID-19 and underlying cardiovascular diseases. In conclusion, RAS may play a role in SARS-COV-2-induced cardiac and pulmonary damage. Further studies are needed to better understand the role of RAS in COVID-19 and to guide decision on the use of RAS inhibitors.

Severe Acute Respiratory Syndrome-coronavirus 2 Infection: Role of Angiotensin-converting Enzyme 2

A role of angiotensin-converting enzyme 2 (ACE2) in the coronavirus disease 2019 pandemic has been suggested, because it is the molecular receptor for severe acute respiratory syndrome-coronavirus 2 (SARS-CoV2). ACE2 is known to provide a protective effect for cardiac and vascular tissues, because it generally counteracts angiotensin II (Ang II) activity. ACE2 downregulation has been implicated in the pathogenesis of cardiovascular disease. ACE inhibitors and angiotensin receptor blockers may enhance ACE2 mRNA expression and enzyme activity. However, this has not been demonstrated in lung tissue. In the lungs, Ang II induces vasoconstriction to prevent ventilation perfusion mismatch, while also increasing vascular permeability (which can precipitate pulmonary edema). ACE2 is expressed in 0.67% of human lung cells, 80% of which are type 2 alveolar cells. Men (of all ethnicities) and Asian individuals have been shown to express higher levels of ACE2 than women and non-Asian individuals, respectively. However, there are no data from human studies indicating that high ACE2 expression increases the likelihood of SARS-CoV2 infection. In animal studies, an increase in Ang II caused by SARS-CoV2 or spike protein interactions, in turn due to ACE2 downregulation, has been identified as the key mechanism underlying lung injury. In human studies of SARS-CoV2 infection, ACE2 overexpression was shown to cause inflammatory apoptosis and a cytokine storm. The actions of ACE2 and Ang II in SARS-CoV2-infected vascular and lung tissues differ between animals and humans. ACE2 expression levels pre- and post-SARS-CoV2 infection should be differentiated.

COVID-19: the role of excessive cytokine release and potential ACE2 down-regulation in promoting hypercoagulable state associated with severe illness.

The novel coronavirus disease (COVID-19) has become a universally prevalent infectious disease. The causative virus of COVID-19 is severe acute respiratory syndrome coronavirus type 2. Recent retrospective clinical studies have established a significant association between the incidence of vascular thrombotic events and the severity of COVID-19. The enhancement in serum levels of markers that reflect a hypercoagulable state has been suggested to indicate a poor prognosis. Therefore, at present, it is crucial to understand the mechanisms that foster the hypercoagulable state in COVID-19. Over-activated inflammatory response, which is manifested as excessive cytokine release in COVID-19 patients, is also associated with COVID-19 severity. This review discusses the immuno-pathological basis of the excessive cytokine release in COVID-19. Besides, this article reviews the role of pro-inflammatory or anti-inflammatory cytokines, whose significant elevations in their serum levels have been consistently detected in multiple different clinical studies, in promoting the hypercoagulable state. Since the expression of angiotensin-converting enzyme 2 (ACE2) is potentially down-regulated in COVID-19, as proposed by a recent bio-informatic analysis, mechanisms through which reduced ACE2 expressions promote vascular thrombosis are summarized. In addition, the reciprocal-enhancing effects of the excessive cytokine release and the downregulated ACE2 expression on their pro-thrombotic activities are further discussed. Here, based on currently available evidence, we review the pathogenic mechanisms of the hypercoagulable state associated with severe cases of COVID-19 to give insights into prevention and treatment of the vascular thrombotic events in COVID-19.Graphic abstract

Disequilibrium between the classic renin-angiotensin system and its opposing arm in SARS-CoV-2-related lung injury.

A dysregulation of the renin-angiotensin system (RAS) has been involved in the genesis of lung injury and acute respiratory distress syndrome from different causes, including several viral infections. The severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection of pneumocytes, the hallmark of the pandemic coronavirus disease 2019 (COVID-19) involving both alveolar interstitium and capillaries, is linked to angiotensin-converting enzyme 2 (ACE2) binding and its functional downregulation. ACE2 is a key enzyme for the balance between the two main arms of the RAS: the ACE/angiotensin (Ang) II/Ang II type 1 receptor axis (“classic RAS”) and the ACE2/Ang(1–7)/Mas receptor (MasR) axis (“anti-RAS”). The ACE2 downregulation, as a result of SARS-coronaviruses binding, enhances the classic RAS, leading to lung damage and inflammation with leaky pulmonary blood vessels and fibrosis, when the attenuation mediated by the anti-RAS arm is reduced. ACE inhibitors (ACE-I) and Ang II type 1 receptor blockers (ARB), effective in cardiovascular diseases, were found to prevent and counteract acute lung injury in several experimental models by restoring the balance between these two opposing arms. The evidence of RAS arm disequilibrium in COVID-19 and the hypothesis of a beneficial role of RAS modulation supported by preclinical and clinical studies are the focus of the present review. Preclinical and clinical studies on drugs balancing RAS arms might be the right way to counter COVID-19.