Uncovering the interplay between hypertension and the inflammatory response for the patient affected by COVID-19 via mathematical modeling and computer-based analysis

We explore here the systems-based regulatory mechanisms that determine human blood pressure patterns. This in the context of the reported negative association between hypertension and COVID-19 disease. We are particularly interested in the key role that plays angiotensin converting enzyme 2 (ACE2), one of the first identified receptors that enable the entry of the SARS-CoV-2 virus into a cell. Taking into account the two main systems involved in the regulation of blood pressure, that is, the Renin-Angiotensin system and the Kallikrein-Kinin system, we follow a Bottom-Up systems biology modeling approach in order to built the discrete Boolean model of the gene regulatory network that underlies both the typical hypertensive phenotype and the hypotensive/normotensive phenotype. These phenotypes correspond to the dynamic attractors of the regulatory network modeled on the basis of publicly available experimental information. Our model recovers the observed phenotypes and shows the key role played by the inflammatory response in the emergence of hypertension. Source code go to the next url: https://github.com/cxro-cc/red_ras_kks © 2023, EasyChair. All rights reserved.

Role of Angiotensin II in Cardiovascular Diseases: Introducing Bisartans as a Novel Therapy for Coronavirus 2019.

Cardiovascular diseases (CVDs) are the main contributors to global morbidity and mortality. Major pathogenic phenotypes of CVDs include the development of endothelial dysfunction, oxidative stress, and hyper-inflammatory responses. These phenotypes have been found to overlap with the pathophysiological complications of coronavirus disease 2019 (COVID-19). CVDs have been identified as major risk factors for severe and fatal COVID-19 states. The renin-angiotensin system (RAS) is an important regulatory system in cardiovascular homeostasis. However, its dysregulation is observed in CVDs, where upregulation of angiotensin type 1 receptor (AT1R) signaling via angiotensin II (AngII) leads to the AngII-dependent pathogenic development of CVDs. Additionally, the interaction between the spike protein of severe acute respiratory syndrome coronavirus 2 with angiotensin-converting enzyme 2 leads to the downregulation of the latter, resulting in the dysregulation of the RAS. This dysregulation favors AngII/AT1R toxic signaling pathways, providing a mechanical link between cardiovascular pathology and COVID-19. Therefore, inhibiting AngII/AT1R signaling through angiotensin receptor blockers (ARBs) has been indicated as a promising therapeutic approach to the treatment of COVID-19. Herein, we review the role of AngII in CVDs and its upregulation in COVID-19. We also provide a future direction for the potential implication of a novel class of ARBs called bisartans, which are speculated to contain multifunctional targeting towards COVID-19.

Respiratory issues in patients with multiple sclerosis as a risk factor during SARS-CoV-2 infection: a potential role for exercise.

Coronavirus disease-2019 (COVID-19) is associated with cytokine storm and is characterized by acute respiratory distress syndrome (ARDS) and pneumonia problems. The respiratory system is a place of inappropriate activation of the immune system in people with multiple sclerosis (MS), and this may cause damage to the lung and worsen both MS and infections.The concerns for patients with multiple sclerosis are because of an enhance risk of infection with severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). The MS patients pose challenges in this pandemic situation, because of the regulatory defect of autoreactivity of the immune system and neurological and respiratory tract symptoms. In this review, we first indicate respiratory issues associated with both diseases. Then, the main mechanisms inducing lung damages and also impairing the respiratory muscles in individuals with both diseases is discussed. At the end, the leading role of physical exercise on mitigating respiratory issues inducing mechanisms is meticulously evaluated.

Molecular Mimicry of the Viral Spike in the SARS-CoV-2 Vaccine Possibly Triggers Transient Dysregulation of ACE2, Leading to Vascular and Coagulation Dysfunction Similar to SARS-CoV-2 Infection.

The benefits of SARS-CoV-2 spike mRNA vaccines are well known, including a significant decline in COVID-19 morbidity and a decrease in the mortality rate of SARS-CoV-2 infected persons. However, pharmacovigilance studies have revealed the existence of rare cases of cardiovascular complications after mass vaccination using such formulations. Cases of high blood pressure have also been reported but were rarely documented under perfectly controlled medical supervision. The press release of these warning signals triggered a huge debate over COVID-19 vaccines' safety. Thereby, our attention was quickly focused on issues involving the risk of myocarditis, acute coronary syndrome, hypertension and thrombosis. Rare cases of undesirable post-vaccine pathophysiological phenomena should question us, especially when they occur in young subjects. They are more likely to occur with inappropriate use of mRNA vaccine (e.g., at the time when the immune response is already very active during a low-noise infection in the process of healing), leading to angiotensin II (Ang II) induced inflammation triggering tissue damage. Such harmful effects observed after the COVID-19 vaccine evoke a possible molecular mimicry of the viral spike transiently dysregulating angiotensin converting enzyme 2 (ACE2) function. Although the benefit/risk ratio of SARS-CoV-2 spike mRNA vaccine is very favorable, it seems reasonable to suggest medical surveillance to patients with a history of cardiovascular diseases who receive the COVID-19 vaccine.

Nanoparticle approaches for the renin-angiotensin system

The renin-angiotensin system (RAS) is a hormonal cascade that contributes to several disorders: systemic hypertension, heart failure, kidney disease, and neurodegenerative disease. Activation of the RAS can promote inflammation and fibrosis. Drugs that target the RAS can be classified into 3 categories, AT1 receptor blockers (ARBs), angiotensin-converting enzyme (ACE) inhibitors, and renin inhibitors. The therapeutic efficacy of current RAS-inhibiting drugs is limited by poor penetration across the blood-brain barrier, low bioavailability, and to some extent, short half-lives. Nanoparticle-mediated drug delivery systems (DDSs) are possible emerging alternatives to overcome such limitations. Nanoparticles are ideally 1–100 nm in size and are considered efficient DDSs mainly due to their unique characteristics, including water dispersity, prolonged half-life in blood circulation, smaller size, and biocompatibility. Nano-scale DDSs can reduce the drug dosage frequency and acute toxicity of drugs while enhancing therapeutic success. Different types of nanoparticles, such as chitosan, polymeric, and nanofibers, have been examined in RAS-related studies, especially in hypertension, cardiovascular disease, and COVID-19. In this review article, we summarize the physical and chemical characteristics of each nanoparticle to elaborate on their potential use in RAS-related nano-drug delivery research and clinical application.

The des-Arg9-bradykinin/B1R axis: Hepatic damage in COVID-19.

Patients infected by the SARS-CoV-2 virus are commonly diagnosed with threatening liver conditions associated with drug-induced therapies and systemic viral action. RNA-Seq data from cells in bronchoalveolar lavage fluid from COVID-19 patients have pointed out dysregulation of kallikrein-kinin and renin-angiotensin systems as a possible mechanism that triggers multi-organ damage away from the leading site of virus infection. Therefore, we measured the plasma concentration of biologically active peptides from the kallikrein-kinin system, bradykinin and des-Arg9-bradykinin, and liver expression of its proinflammatory axis, bradykinin 1 receptor (B1R). We measured the plasma concentration of bradykinin and des-Arg9-bradykinin of 20 virologically confirmed COVID-19 patients using a liquid chromatography-tandem mass spectrometry-based methodology. The expression of B1R was evaluated by immunohistochemistry from post-mortem liver specimens of 27 COVID-19 individuals. We found a significantly higher blood level of des-Arg9-bradykinin and a lower bradykinin concentration in patients with COVID-19 compared to a healthy, uninfected control group. We also observed increased B1R expression levels in hepatic tissues of patients with COVID-19 under all hepatic injuries analyzed (liver congestion, portal vein dilation, steatosis, and ischemic necrosis). Our data indicate that des-Arg9-bradykinin/B1R is associated with the acute hepatic dysfunction induced by the SARS-CoV-2 virus infection in the pathogenesis of COVID-19.

Circulating ACE2 level and zinc/albumin ratio as potential biomarkers for a precision medicine approach to COVID-19.

Highly mutable influenza is successfully countered based on individual susceptibility and similar precision-like medicine approach should be effective against SARS-COV-2. Among predictive markers to bring precision medicine to COVID-19, circulating ACE2 has potential features being upregulated in both severe COVID-19 and predisposing comorbidities. Spike SARS-CoVs were shown to induce ADAM17-mediated shedding of enzymatic active ACE2, thus accounting for its increased activity that has also been suggested to induce positive feedback loops leading to COVID-19-like manifestations. For this reason, pre-existing ACE2 activity and inhibition of ACE2/ADAM17 zinc-metalloproteases through zinc chelating agents have been proposed to predict COVID-19 outcome before infection and to protect from COVID-19, respectively. Since most diagnostic laboratories are not equipped for enzymatic activity determination, other potential predictive markers of disease progression exploitable by diagnostic laboratories were explored. Concentrations of circulating albumin, zinc, ACE2 protein and its activity were investigated in healthy, diabetic (COVID-19-susceptible) and SARS-CoV-2-negative COVID-19 individuals. ACE2 both protein levels and activity significantly increased in COVID-19 and diabetic patients. Abnormal high levels of ACE2 characterised a subgroup (16-19%) of diabetics, while COVID-19 patients were characterised by significantly higher zinc/albumin ratios, pointing to a relative increase of albumin-unbound zinc species, such as free zinc ones. Data on circulating ACE2 levels are in line with the hypothesis that they can drive susceptibility to COVID-19 and elevated zinc/albumin ratios support the therapeutic use of zinc chelating inhibitors of ACE2/ADAM17 zinc-metalloproteases in a targeted therapy for COVID-19.

Ras and Sars-Cov-2 Interaction: Short Review of the Latest Evidence

Coronavirus SARS-CoV-2 is responsible for the coronavirus disease (COVID-19) cause of the recent global pandemic, which is causing thousands of deaths worldwide and represents a health challenge with few precedents in human history. The angiotensin 2 conversion enzyme (ACE-2) has been identified as the receptor that facilitates access to SARSCoV-2 in cells;evidence shows that its concentration varies during the various stages of viral infection. Therapeutic agents modifying the renin-angiotensin system (RAS) may be able to modulate the concentration of ACE-2 and the various components of the system. In this article we examine the latest evidence on the association between the use of RAS modifying agents and coronavirus 2019 (COVID-19) disease caused by SARS-CoV-2. Our investigation and critical literature research does not suggest discontinuation of ACEIs/ARBs treatment in clinical practice as there is a lack of robust evidence. However, we recommend further well-structured epidemiological studies investigating this sensitive issue that may provide important new suggestions for implementing guidelines.Copyright © Vitiello A., Ferrara F., 2023.

Renin-Angiotensin System and Sex Differences in COVID-19: A Critical Assessment.

The current epidemic of corona virus disease (COVID-19) has resulted in an immense health burden that became the third leading cause of death and potentially contributed to a decline in life expectancy in the United States. The severe acute respiratory syndrome-related coronavirus-2 binds to the surface-bound peptidase angiotensin-converting enzyme 2 (ACE2, EC 3.4.17.23) leading to tissue infection and viral replication. ACE2 is an important enzymatic component of the renin-angiotensin system (RAS) expressed in the lung and other organs. The peptidase regulates the levels of the peptide hormones Ang II and Ang-(1-7), which have distinct and opposing actions to one another, as well as other cardiovascular peptides. A potential consequence of severe acute respiratory syndrome-related coronavirus-2 infection is reduced ACE2 activity by internalization of the viral-ACE2 complex and subsequent activation of the RAS (higher ratio of Ang II:Ang-[1-7]) that may exacerbate the acute inflammatory events in COVID-19 patients and possibly contribute to the effects of long COVID-19. Moreover, COVID-19 patients present with an array of autoantibodies to various components of the RAS including the peptide Ang II, the enzyme ACE2, and the AT1 AT2 and Mas receptors. Greater disease severity is also evident in male COVID-19 patients, which may reflect underlying sex differences in the regulation of the 2 distinct functional arms of the RAS. The current review provides a critical evaluation of the evidence for an activated RAS in COVID-19 subjects and whether this system contributes to the greater severity of severe acute respiratory syndrome-related coronavirus-2 infection in males as compared with females.

Role of Angiotensin Converting Enzyme-2 and its modulation in disease: exploring new frontiers.

Angiotensin Converting Enzyme-2 (ACE2), an important enzyme in the Renin Angiotensin Aldosterone System, degrades Angiotensin II (Ang II) into Angiotensin-(1-7) (Ang-(1-7)), whose actions are opposite to that of Ang II. Interestingly, SARS CoV-2 virus entry into human cells is mediated by ACE2. ACE2 receptors that are widely expressed in lungs and various other organs. Ang-(1-7) seems to have favorable effects on lungs, by preventing fibrosis in lung inflammation models, and exerts a similar action in cardiac and renal pathologies as well. Thus, modulation of Ang-(1-7) can be of potential benefit in chronic as well as acute inflammatory diseases affecting lungs and other organs. Upregulation of ACE2 by statins in different organs, and its consequent beneficial effects, have been demonstrated in many experimental studies, and also in a few clinical ones. This review aims at probing the role of ACE2 and its therapeutic modulation in pulmonary and extra pulmonary diseases, including COVID-19.

The renin-angiotensin system in the eye

The renin–angiotensin system is major endocrine, paracrine, and autocrine system that has a notorious role in regulating hemodynamics and electrolyte balance, thus controlling blood pressure. Nonetheless, the functions of RAS are multiple and continue to expand, as its receptors, enzymes, and peptides have been identified in different organs/tissues, implying novel local effects of RAS and participation in the pathogenesis of different diseases in multiple organs, including the eyes. Vascularized, fibrous, and nervous structures of the eyes and their fluids express several RAS components including angiotensinogen, prorenin, renin, (P)RR, ACE, Ang II, AT1R, AT2R, ACE2, Ang 1-7, and Mas. Additionally, abundant RAS hormones are present in intraocular tissues implicating local production. Ocular RAS functions seem to be diverse;first, RAS is proposed to modulate aqueous humor biosynthesis and drainage, consequently regulating IOP. Exacerbation of ACE/ Ang II/ AT1R actions is observed in glaucoma, and blockage of this axis with ACEIs and ARBs is a feature that can be explored to reduce IOP and treat glaucoma. Second, impairment of RAS with exacerbation of ACE/ Ang II/ AT1R and depletion of ACE2/ Ang 1-7/ Mas culminate in an angiogenic, inflammatory, proliferative, and oxidative phenotype, which is tightly related to retinal vascular disorders such as diabetic retinopathy, age-related macular degeneration, and retinopathy of prematurity. Indeed, treatments blocking ACE/ Ang II/ AT1R or enhancing ACE2/ Ang 1-7/ Mas are reported to be beneficial to prevent or restrain the progression of these diseases. Finally, clinical manifestations of COVID-19 include ocular disorders such as conjunctivitis, dry eyes, eye pain, discharge, and blurred vision. ACE2 expression in ocular tissues may define ophthalmic susceptibility to SARS-CoV-2 infection. Moreover, SARS-CoV-2 entry mechanisms may cause depletion of ACE2 biological effects, which can contribute to RAS dysregulation and the ocular disorders observed in COVID-19. This chapter focuses on reviewing the components and functions of the ocular RAS, its implications for eye homeostasis, and the potential of RAS as a therapeutic target to treat ocular disorders, including glaucoma, diabetic retinopathy, age-related macular degeneration, and retinopathy of prematurity. © 2023 Elsevier Inc. All rights reserved.

Angiotensin and COVID-19

Coronavirus disease 2019 (COVID-19) is a highly contagious illness caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). COVID-19 has spread rapidly worldwide since 2019, causing a high rate of deaths and disabilities. This virus exerts its pathogenicity through angiotensin-converting enzyme 2 (ACE2) receptor, expressed on a wide array of human cells. The infectious process starts with the engagement of ACE2 by protein S of the virus, which leads to the entry of viral genetic material within the host cell. COVID-19 induces imbalances of the renin–angiotensin system (RAS) manifesting with ACE upregulation and ACE2 downregulation. ACE converts angiotensin I into the peptide angiotensin (Ang) II, which binds to and activates Ang II type 1 (AT1) and Ang II type 2 (AT2) receptors. The upregulation of the ACE/Ang II/AT1 signaling induces a series of deleterious effects in tissue and organs along with direct viral damage and proinflammatory cytokines. In general, Ang II mediates proliferation, inflammation, endothelial dysfunction, oxidative stress, and apoptosis. However, the negative effect of ACE signaling tends to be specific for all the organs (lungs, endothelium, kidneys, brain, and bowel) mainly affected by the virus. Given the key role of angiotensin in COVID-19, numerous experimental treatments have been tested to dampen the severe consequences of this unbalanced activation of RAS. © 2023 Elsevier Inc. All rights reserved.

Hematopoietic bone marrow renin-angiotensin system in health and disease

A locally active renin–angiotensin system (RAS) present in the bone marrow, which controls the growth, production, proliferation, and differentiation of hematopoietic cells. Local bone marrow RAS has also a role in neoplastic hematopoiesis such as genesis of leukemia and other malignancies. The local RAS in bone marrow plays important roles in atherosclerosis. The "bone marrow response-to-lipid” hypothesis integrates the knowledge that proatherogenic features of hematopoietic and nonhematopoietic progenitors are determined by the local actions of modified LDL on the expression of local RAS genes. There is a relationship between the autonomic nervous system and bone marrow cells. This association between bone marrow stromal cells, hematopoietic stem cell, and nerve terminals has been described as the "neuroreticular complex.” A characteristic feature of early hypertension is endothelial dysfunction. Bone marrow–related endothelial progenitor cells contribute in the healing of injured endothelium. Relationship between autonomous nervous system and bone marrow vasculature could be an important mechanism of the pathophysiology of hypertension. Local bone marrow RAS has important role in COVID-19 syndrome. ACE2 receptor is presented on the surface of hematopoietic stem/progenitor cells within the context of local bone marrow RAS that characterizes a target for the SARS-CoV-2 attack on bone marrow hematopoiesis. Bone marrow and lung tissue are in a harmony in hematopoiesis under the control of tissue RAS. RAS genes are critical at the initiation of the infections initiated by coronavirus family members and can have an important association with the exchange of immune genes in due clinical course following the infection. The aim of this chapter is to focus on the impacts of the local bone marrow RAS on definitive and neoplastic hematopoiesis, as well as its interrelationships among atherosclerosis, hypertension, and COVID-19 syndrome. © 2023 Elsevier Inc. All rights reserved.

Exploration of multifaceted molecular mechanism of angiotensin-converting enzyme 2 (ACE2) in pathogenesis of various diseases.

Angiotensin converting enzyme 2 (ACE2) is a homolog of ACE (a transmembrane bound dipeptidyl peptidase enzyme). ACE2 converts angiotensinogen to the heptapeptide angiotensin-(1-7). ACE2 and its product, angiotensin-(1-7), have counteracting effects against the adverse actions of other members of renin-angiotensin system (RAS). ACE2 and its principal product, angiotensin-(1-7), were considered an under recognized arm of the RAS. The COVID-19 pandemic brought to light this arm of RAS with special focus on ACE2. Membrane bound ACE2 serves as a receptor for SARS-CoV-2 viral entry through spike proteins. Apart from that, ACE2 is also involved in the pathogenesis of various other diseases like cardiovascular disease, cancer, respiratory diseases, neurodegenerative diseases and infertility. The present review focuses on the molecular mechanism of ACE2 in neurodegenerative diseases, cancer, cardiovascular disease, infertility and respiratory diseases, including SARS-CoV-2. This review summarizes unveiled roles of ACE2 in the pathogenesis of various diseases which further provides intriguing possibilities for the use of ACE2 activators and RAS modulating agents for various diseases.

The ACE rs1799752 Variant Is Associated with COVID-19 Severity but Is Independent of Serum ACE Activity in Hospitalized and Recovered Patients.

This paper assesses the association of the insertion/deletion ACE (angiotensin-converting enzyme) variant (rs1799752 I/D) and the serum ACE activity with the severity of COVID-19 as well as its impact on post-COVID-19, and we compare these associations with those for patients with non-COVID-19 respiratory disorders. We studied 1252 patients with COVID-19, 104 subjects recovered from COVID-19, and 74 patients hospitalized with a respiratory disease different from COVID-19. The rs1799752 ACE variant was assessed using TaqMan® Assays. The serum ACE activity was determined using a colorimetric assay. The DD genotype was related to risk for invasive mechanical ventilation (IMV) requirement as an indicator of COVID-19 severity when compared to the frequencies of II + ID genotypes (p = 0.025, OR = 1.428, 95% CI = 1.046-1.949). In addition, this genotype was significantly higher in COVID-19 and post-COVID-19 groups than in the non-COVID-19 subjects. The serum ACE activity levels were lower in the COVID-19 group (22.30 U/L (13.84-32.23 U/L)), which was followed by the non-COVID-19 (27.94 U/L (20.32-53.36 U/L)) and post-COVID-19 subjects (50.00 U/L (42.16-62.25 U/L)). The DD genotype of the rs1799752 ACE variant was associated with the IMV requirement in patients with COVID-19, and low serum ACE activity levels could be related to patients with severe disease.

Association of RASis and HMG-CoA reductase inhibitors with clinical manifestations in coronavirus disease 2019 patients: Results from the Khorshid Coronavirus Disease Cohort Study.

Background: Angiotensin II receptor blockers (ARBs) and angiotensin-converting enzyme inhibitors (ACEinhs) may deteriorate or improve the clinical manifestations in severe acute respiratory syndrome coronavirus 2 infection. A comparative, cross-sectional study was conducted to evaluate the association of ARBs/ACEinhs and hydroxy-3-methyl-glutaryl-CoA reductase inhibitors (HMGRis) with clinical outcomes in coronavirus disease 2019 (COVID-19). Materials and Methods: From April 4 to June 2, 2020, 659 patients were categorized according to whether they were taking ARB, ACEinh, or HMGRi drugs or none of them. Demographic variables, clinical and laboratory tests, chest computed tomography findings, and intensive care unit-related data were analyzed and compared between the groups. Results: The ARB, ACEinh, and HMGRi groups significantly had lower heart rate (P < 0.05). Furthermore, a lower percent of O2 saturation (89.34 ± 7.17% vs. 84.25 ± 7.00%; P = 0.04) was observed in the ACEis group than non-ACEinhs. Mortality rate and the number of intubated patients were lower in patients taking ARBs, ACEinhs, and HMGRis, although these differences failed to reach statistical significance. Conclusion: Our findings present clinical data on the association between ARBs, ACEinhs, and HMGRis and outcomes in hospitalized, hypertensive COVID-19 patients, implying that ARBs/ACEinhs are not associated with the severity or mortality of COVID-19 in such patients.

ACE2 enhance viral infection or viral infection aggravate the underlying diseases.

ACE2 plays a critical role in SARS-CoV-2 infection to cause COVID-19 and SARS-CoV-2 spike protein binds to ACE2 and probably functionally inhibits ACE2 to aggravate the underlying diseases of COVID-19. The important factors that affect the severity and fatality of COVID-19 include patients' underlying diseases and ages. Therefore, particular care to the patients with underlying diseases is needed during the treatment of COVID-19 patients.

IMMUNE STATUS AND CYTOKINE SPECTRUM AS PREDICTORS OF THE RISK OF SEVERE DISEASE AND PERFORMANCE INDICATORS OF INTENSIVE THERAPY IN PATIENTS WITH CORONAVIRUS INFECTION COVID-19

The pandemic caused by a new strain of the SARS-CoV-2 coronavirus has swept the whole world but effective methods for treating this severe pathology have not yet been created. It has now been established that a risk of a severe course of COVID-19 is not so much a patient's age itself, but so-called age-related diseases;the renin-angiotensin system (RAS) is directly or indirectly involved into their development. The SARS-CoV-19 virus interacts with one of the main regulatory elements of this system, ACE2, and disrupts the balance between the two RAS branches. This ultimately manifests itself in an increase in levels of angiotensin II, which, through binding to the angiotensin type 1 receptor (AT1R), causes a number of pathological conditions, including hypertension, atherosclerosis, and cardiovascular diseases, enhances cell proliferation, apoptosis, death of vascular endothelial cells, etc. This process has been described in many reviews by Russian and foreign authors. However, cells of innate and adaptive immunity are another less well-described but no less important target of angiotensin II. The consequences of this interaction are analyzed in detail in this review. With COVID-19, dendritic cells are activated, macrophage proliferation and neutrophil infiltration increase with further involvement of CD4-lymphocytes and other cellular elements of the adaptive immunity in this process. Hyperactivation of the immune system is accompanied with the release of a large amount of pro-inflammatory cytokines, which can lead to the occurrence of a cytokine storm. The picture is aggravated by the inhibitory effect produced by the virus itself on the synthesis of signaling interferons at initial stages in its internalization into the cell. A separate section in the review addresses the problem how to predict a risk of a developing serious condition and search for its predictors by analyzing the state of the RAS and ratios of key cellular elements in the immune system. This is extremely important for making decisions concerning the amount of necessary medical care and strategies for subsequent treatment. © Sadykov V.F., Poltavtseva R.A., Chaplygina A.V., Bobkova N.V., 2022

The Significance of Angiotensin-Converting Enzyme-2 (ACE2) in SARS-Cov-2 Infection and COVID-19

The new coronavirus was first reported in 2019 (China) and officially announced by the World Health Organization as a pandemic in March 2020. Severe acute respiratory syndrome coro-navirus 2 (SARS-CoV-2) is the causative agent of the pneumonia-associated illnesses and shares structural homology with the related Severe acute respiratory syndrome coronavirus-1 (SARS-CoV--1). One of the mechanisms for SARS-Cov-1 and-2 infection is mediated by the angiotensin-con-verting enzyme-2 (ACE2) cell receptor, enabling the virus to enter the host cells. ACE2 is an iso-form of the angiotensin-converting enzyme 1 (ACE). The actions of ACE2 counterbalance the clas-sic renin-angiotensin system (RAS) axis through the production of Ang 1-7, which promotes car-diovascular, renal, and lung-protective effects. The ACE2 is not the only route for SARS-CoV-2 to enter the host cells. However, due to its roles in the RAS and its participation in the SARS-CoV-2 virulence, ACE2 has gained attention regarding viral mechanisms of pathogenesis, effects of drugs that interfere with the RAS, and as a potential target for therapeutic strategies for the damages caused by SARS-CoV-2 infection. Among other tissues, ACE2 gene expression seems to be in-creased in the lungs upon SARS-CoV-2 infection;however, amid other variables, expression and/or activity of ACE2 is shown as a disease, sex, and age-dependent. The present review covers critical aspects for a comprehensive understanding of ACE2 and its current involvement in SARS-CoV-2 infection and the development of COVID-19.Copyright © 2021 Bentham Science Publishers.