ACE2 Cell Biology, Regulation, and Physiological Functions

Pathogenesis and virulence of coronavirus disease: Comparative pathology of animal models for COVID-19

Animal models that can replicate clinical and pathologic features of severe human coronavirus infections have been instrumental in the development of novel vaccines and therapeutics. The goal of this review is to summarize our current understanding of the pathogenesis of coronavirus disease 2019 (COVID-19) and the pathologic features that can be observed in several currently available animal models. Knowledge gained from studying these animal models of SARS-CoV-2 infection can help inform appropriate model selection for disease modelling as well as for vaccine and therapeutic developments.

Pulmonary hypertension associated to left heart disease: Phenotypes and treatment

Pulmonary hypertension associated to left heart disease (PH-LHD) refers to a clinical and haemodynamic condition of pulmonary hypertension associated with a heterogeneous group of diseases affecting any of the compartments that form the left ventricle and left atrium. PH-LHD is the most common cause of PH, accounting for 65-80 % of diagnoses. Based on the haemodynamic phase of the disease, PH-LDH is classified into three subgroups: postcapillary PH, isolated postcapillary PH and combined pre-postcapillary PH (CpcPH). Several signaling pathways involved in the regulation of vascular tone are dysfunctional in PH-LHD, including nitric oxide, MAP kinase and endothelin-1 pathways. These pathways are the same as those altered in PH group 1, however PH-LHD can heardly be treated by specific drugs that act on the pulmonary circulation. In this manuscript we provide a state of the art of the available clinical trials investigating the safety and efficacy of PAH-specific drugs, as well as drugs active in patients with heart failure and PH-LHD. We also discuss the different phenotypes of PH-LHD, as well as molecular targets and signaling pathways potentially involved in the pathophysiology of the disease. Finally we will mention some new emerging therapies that can be used to treat this form of PH.

Development of a mutant aerosolized ACE2 that neutralizes SARS-CoV-2 in vivo

The rapid evolution of SARS-CoV-2 variants highlights the need for new therapies to prevent disease spread. SARS-CoV-2, like SARS-CoV-1, uses the human cell surface protein angiotensin-converting enzyme 2 (ACE2) as its native receptor. Here, we design and characterize a mutant ACE2 that enables rapid affinity purification of a dimeric protein by altering the active site to prevent autoproteolytic digestion of a C-terminal His10 epitope tag. In cultured cells, mutant ACE2 competitively inhibits lentiviral vectors pseudotyped with spikes from multiple SARS-CoV-2 variants and infectious SARS-CoV-2. Moreover, the protein can be nebulized and retains virus-binding properties. We developed a system for the delivery of aerosolized ACE2 to K18-hACE2 mice and demonstrated protection by our modified ACE2 when delivered as a prophylactic agent. These results show proof-of-concept for an aerosolized delivery method to evaluate anti-SARS-CoV-2 agents in vivo and suggest a new tool in the ongoing fight against SARS-CoV-2 and other ACE2-dependent viruses.

IMPORTANCE

The rapid evolution of SARS-CoV-2 variants poses a challenge for immune recognition and antibody therapies. However, the virus is constrained by the requirement that it recognizes a human host receptor protein. A recombinant ACE2 could protect against SARS-CoV-2 infection by functioning as a soluble decoy receptor. We designed a mutant version of ACE2 with impaired catalytic activity to enable the purification of the protein using a single affinity purification step. This protein can be nebulized and retains the ability to bind the relevant domains from SARS-CoV-1 and SARS-CoV-2. Moreover, this protein inhibits viral infection against a panel of coronaviruses in cells. Finally, we developed an aerosolized delivery system for animal studies and show the modified ACE2 offers protection in an animal model of COVID-19. These results show proof-of-concept for an aerosolized delivery method to evaluate anti-SARS-CoV-2 agents in vivo and suggest a new tool in the ongoing fight against SARS-CoV-2.

Analytical Methods and Effects of Bioactive Peptides Derived from Animal Products: A Mini-Review

Peptides with bioactive effects are being researched for various purposes. However, there is a lack of overall research on pork-derived peptides. In this study, we reviewed the process of obtaining bioactive peptides, available analytical methods, and the study of bioactive peptides derived from pork. Pepsin and trypsin, two representative protein digestive enzymes in the body, are hydrolyzed by other cofactors to produce peptides. Bicinchoninic acid assay, sodium dodecyl sulfate-polyacrylamide gel electrophoresis, chromatography, and in vitro digestion simulation systems are utilized to analyze bioactive peptides for protein digestibility and molecular weight distribution. Pork-derived peptides mainly exhibit antioxidant and antihypertensive activities. The antioxidant activity of bioactive peptides increases the accessibility of amino acid residues by disrupting the three-dimensional structure of proteins, affecting free radical scavenging, reactive oxygen species inactivation, and metal ion chelating. In addition, the antihypertensive activity decreases angiotensin II production by inhibiting angiotensin converting enzyme and suppresses blood pressure by blocking the AT1 receptor. Pork-derived bioactive peptides, primarily obtained using papain and pepsin, exhibit significant antioxidant and antihypertensive activities, with most having low molecular weights below 1 kDa. This study may aid in the future development of bioactive peptides and serve as a valuable reference for pork-derived peptides.

ACE2 acts as a novel regulator of TMPRSS2-catalyzed proteolytic activation of influenza A virus in airway cells

The transmembrane serine protease 2 (TMPRSS2) activates the outer structural proteins of a number of respiratory viruses including influenza A virus (IAV), parainfluenza viruses, and various coronaviruses for membrane fusion. Previous studies showed that TMPRSS2 interacts with the carboxypeptidase angiotensin-converting enzyme 2 (ACE2), a cell surface protein that serves as an entry receptor for some coronaviruses. Here, by using protease activity assays, we determine that ACE2 increases the enzymatic activity of TMPRSS2 in a non-catalytic manner. Furthermore, we demonstrate that ACE2 knockdown inhibits TMPRSS2-mediated cleavage of IAV hemagglutinin (HA) in Calu-3 human airway cells and suppresses virus titers 100- to 1.000-fold. Transient expression of ACE2 in ACE2-deficient cells increased TMPRSS2-mediated HA cleavage and IAV replication. ACE2 knockdown also reduced titers of MERS-CoV and prevented S cleavage by TMPRSS2 in Calu-3 cells. By contrast, proteolytic activation and multicycle replication of IAV with multibasic HA cleavage site typically cleaved by furin were not affected by ACE2 knockdown. Co-immunoprecipitation analysis revealed that ACE2-TMPRSS2 interaction requires the enzymatic activity of TMPRSS2 and the carboxypeptidase domain of ACE2. Together, our data identify ACE2 as a new co-factor or stabilizer of TMPRSS2 activity and as a novel host cell factor involved in proteolytic activation and spread of IAV in human airway cells. Furthermore, our data indicate that ACE2 is involved in the TMPRSS2-catalyzed activation of additional respiratory viruses including MERS-CoV.IMPORTANCEProteolytic cleavage of viral envelope proteins by host cell proteases is essential for the infectivity of many viruses and relevant proteases provide promising drug targets. The transmembrane serine protease 2 (TMPRSS2) has been identified as a major activating protease of several respiratory viruses, including influenza A virus. TMPRSS2 was previously shown to interact with angiotensin-converting enzyme 2 (ACE2). Here, we report the mechanistic details of this interaction. We demonstrate that ACE2 increases or stabilizes the enzymatic activity of TMPRSS2. Furthermore, we describe ACE2 involvement in TMPRSS2-catalyzed cleavage of the influenza A virus hemagglutinin and MERS-CoV spike protein in human airway cells. These findings expand our knowledge of the activation of respiratory viruses by TMPRSS2 and the host cell factors involved. In addition, our results could help to elucidate a physiological role for TMPRSS2.

Utilizing noncatalytic ACE2 protein mutant as a competitive inhibitor to treat SARS-CoV-2 infection

Introduction

Angiotensin converting-enzyme 2 (ACE2) is an enzyme catalyzing the conversion of angiotensin 2 into angiotensin 1-7. ACE2 also serves as the receptor of several coronaviruses, including SARS-CoV-1 and SARS-CoV-2. Therefore, ACE2 could be utilized as a therapeutic target for treating these coronaviruses, ideally lacking enzymatic function.

Methods

Based on structural analysis, specific mutations were introduced to generate mutants of ACE2 and ACE2-Fc (fusion protein of ACE2 and Fc region of IgG1). The enzyme activity, binding affinity, and neutralization abilities were measured.

Results and discussion

As predicted, five mutants (AMI081, AMI082, AMI083, AMI084, AMI090) have completely depleted ACE2 enzymatic activities. More importantly, enzyme-linked receptor-ligand assay (ELRLA) and surface plasmon resonance (SPR) results showed that 2 mutants (AMI082, AMI090) maintained binding activity to the viral spike proteins of SARS-CoV-1 and SARS-CoV-2. In An in vitro neutralization experiment using a pseudovirus, SARS-CoV-2 S1 spike protein-packed lentivirus particles, was also performed, showing that AMI082 and AMI090 significantly reduced GFP transgene expression. Further, in vitro virulent neutralization assays using SARS-CoV-2 (strain name: USA-WA1/2020) showed that AMI082 and AMI090 had remarkable inhibitory effects, indicated by comparable IC50 to wildtype ACE2 (5.33 µg/mL). In addition to the direct administration of mutant proteins, an alternative strategy for treating COVID-19 is through AAV delivery to achieve long-lasting effects. Therefore, AAV5 encoding AMI082 and AMI090 were packaged and transgene expression was assessed. In summary, these ACE2 mutants represent a novel approach to prevent or treat COVID-19 and other viruses with the same spike protein.

Molecular changes in the testes of COVID-19 patients

After the sudden outbreak of the COVID-19 pandemic, scientists and clinicians around the world have significantly expanded understanding of the pathogenesis of the disease as well as the impact of SARS-CoV-2 on various organs and tissues. To date, it is accepted to consider the new coronavirus infection as a multisystem disease, but the data on the effect on fertility remains unclear. Previous works by other authors have presented controversial results, and there is no evidence of a direct effect of the new coronavirus on the male gonads. Thus, further studies are needed to verify the hypothesis that the testicles are the target organ for SARS-CoV-2. Groups were formed: Group I (n = 109; age from 25 to 75 years, Median (IQR) - 60 (23) years), cause of death - new coronavirus infection; Group II (n = 21, age from 25 to 75 years, Median (IQR) - 55 (29.5) years) - autopsy testicular material obtained outside the pandemic. We used RT-PCR to detect the presence of viral RNA in testicular tissue. In addition, we investigated the levels of proteins that provide viral invasion, such as ACE-2 and Furin. In the present study, we detected genetic material of a new coronavirus and increased proteins required for viral invasion in testicular tissue of patients with COVID-19 by RT-PCR. Thus, based on our findings, we assume that testicular tissue is potentially vulnerable to SARS-CoV-2.Communicated by Ramaswamy H. Sarma.

Comprehensive mapping of the AOP-Wiki database: identifying biological and disease gaps

Introduction: The Adverse Outcome Pathway (AOP) concept facilitates rapid hazard assessment for human health risks. AOPs are constantly evolving, their number is growing, and they are referenced in the AOP-Wiki database, which is supported by the OECD. Here, we present a study that aims at identifying well-defined biological areas, as well as gaps within the AOP-Wiki for future research needs. It does not intend to provide a systematic and comprehensive summary of the available literature on AOPs but summarizes and maps biological knowledge and diseases represented by the already developed AOPs (with OECD endorsed status or under validation). Methods: Knowledge from the AOP-Wiki database were extracted and prepared for analysis using a multi-step procedure. An automatic mapping of the existing information on AOPs (i.e., genes/proteins and diseases) was performed using bioinformatics tools (i.e., overrepresentation analysis using Gene Ontology and DisGeNET), allowing both the classification of AOPs and the development of AOP networks (AOPN). Results: AOPs related to diseases of the genitourinary system, neoplasms and developmental anomalies are the most frequently investigated on the AOP-Wiki. An evaluation of the three priority cases (i.e., immunotoxicity and non-genotoxic carcinogenesis, endocrine and metabolic disruption, and developmental and adult neurotoxicity) of the EU-funded PARC project (Partnership for the Risk Assessment of Chemicals) are presented. These were used to highlight under- and over-represented adverse outcomes and to identify and prioritize gaps for further research. Discussion: These results contribute to a more comprehensive understanding of the adverse effects associated with the molecular events in AOPs, and aid in refining risk assessment for stressors and mitigation strategies. Moreover, the FAIRness (i.e., data which meets principles of findability, accessibility, interoperability, and reusability (FAIR)) of the AOPs appears to be an important consideration for further development.

Using a targeted metabolomics approach to explore differences in ARDS associated with COVID-19 compared to ARDS caused by H1N1 influenza and bacterial pneumonia

RATIONALE

Acute respiratory distress syndrome (ARDS) is a life-threatening critical care syndrome commonly associated with infections such as COVID-19, influenza, and bacterial pneumonia. Ongoing research aims to improve our understanding of ARDS, including its molecular mechanisms, individualized treatment options, and potential interventions to reduce inflammation and promote lung repair.

OBJECTIVE

To map and compare metabolic phenotypes of different infectious causes of ARDS to better understand the metabolic pathways involved in the underlying pathogenesis.

METHODS

We analyzed metabolic phenotypes of 3 ARDS cohorts caused by COVID-19, H1N1 influenza, and bacterial pneumonia compared to non-ARDS COVID-19-infected patients and ICU-ventilated controls. Targeted metabolomics was performed on plasma samples from a total of 150 patients using quantitative LC-MS/MS and DI-MS/MS analytical platforms.

RESULTS

Distinct metabolic phenotypes were detected between different infectious causes of ARDS. There were metabolomics differences between ARDSs associated with COVID-19 and H1N1, which include metabolic pathways involving taurine and hypotaurine, pyruvate, TCA cycle metabolites, lysine, and glycerophospholipids. ARDSs associated with bacterial pneumonia and COVID-19 differed in the metabolism of D-glutamine and D-glutamate, arginine, proline, histidine, and pyruvate. The metabolic profile of COVID-19 ARDS (C19/A) patients admitted to the ICU differed from COVID-19 pneumonia (C19/P) patients who were not admitted to the ICU in metabolisms of phenylalanine, tryptophan, lysine, and tyrosine. Metabolomics analysis revealed significant differences between C19/A, H1N1/A, and PNA/A vs ICU-ventilated controls, reflecting potentially different disease mechanisms.

CONCLUSION

Different metabolic phenotypes characterize ARDS associated with different viral and bacterial infections.

Affinity selection-mass spectrometry in the discovery of anti-SARS-CoV-2 compounds

Small molecule therapeutic agents are needed to treat or prevent infections by severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2), which is the cause of the COVID-19 pandemic. To expedite the discovery of lead compounds for development, assays have been developed based on affinity selection-mass spectrometry (AS-MS), which enables the rapid screening of mixtures such as combinatorial libraries and extracts of botanicals or other sources of natural products. AS-MS assays have been used to find ligands to the SARS-CoV-2 spike protein for inhibition of cell entry as well as to the 3-chymotrypsin-like cysteine protease (3CLpro) and the RNA-dependent RNA polymerase complex constituent Nsp9, which are targets for inhibition of viral replication. The AS-MS approach of magnetic microbead affinity selection screening has been used to discover high-affinity peptide ligands to the spike protein as well as the hemp cannabinoids cannabidiolic acid and cannabigerolic acid, which can prevent cell infection by SARS-CoV-2. Another AS-MS method, native mass spectrometry, has been used to discover that the flavonoids baicalein, scutellarein, and ganhuangenin, can inhibit the SARS-CoV-2 protease 3CLpro. Native mass spectrometry has also been used to find an ent-kaurane natural product, oridonin, that can bind to the viral protein Nsp9 and interfere with RNA replication. These natural lead compounds are under investigation for the development of therapeutic agents to prevent or treat SARS-CoV-2 infection.

ACE2 knockout hinders SARS-CoV-2 propagation in iPS cell-derived airway and alveolar epithelial cells

Severe Acute Respiratory Syndrome Coronavirus 2 (SARS-CoV-2), the causative agent of COVID-19, continues to spread around the world with serious cases and deaths. It has also been suggested that different genetic variants in the human genome affect both the susceptibility to infection and severity of disease in COVID-19 patients. Angiotensin-converting enzyme 2 (ACE2) has been identified as a cell surface receptor for SARS-CoV and SARS-CoV-2 entry into cells. The construction of an experimental model system using human iPS cells would enable further studies of the association between viral characteristics and genetic variants. Airway and alveolar epithelial cells are cell types of the lung that express high levels of ACE2 and are suitable for in vitro infection experiments. Here, we show that human iPS cell-derived airway and alveolar epithelial cells are highly susceptible to viral infection of SARS-CoV-2. Using gene knockout with CRISPR-Cas9 in human iPS cells we demonstrate that ACE2 plays an essential role in the airway and alveolar epithelial cell entry of SARS-CoV-2 in vitro. Replication of SARS-CoV-2 was strongly suppressed in ACE2 knockout (KO) lung cells. Our model system based on human iPS cell-derived lung cells may be applied to understand the molecular biology regulating viral respiratory infection leading to potential therapeutic developments for COVID-19 and the prevention of future pandemics.

Development of a mutant aerosolized ACE2 that neutralizes SARS-CoV-2 in vivo

The rapid evolution of SARS-CoV-2 variants highlights the need for new therapies to prevent disease spread. SARS-CoV-2, like SARS-CoV-1, uses the human cell surface protein angiotensin-converting enzyme 2 (ACE2) as its native receptor. Here, we design and characterize a mutant ACE2 that enables rapid affinity purification of a dimeric protein by altering the active site to prevent autoproteolytic digestion of a C-terminal His10 epitope tag. In cultured cells, mutant ACE2 competitively inhibits lentiviral vectors pseudotyped with spike from multiple SARS-CoV-2 variants, and infectious SARS-CoV-2. Moreover, the protein can be nebulized and retains virus-binding properties. We developed a system for delivery of aerosolized ACE2 to K18-hACE2 mice and demonstrate protection by our modified ACE2 when delivered as a prophylactic agent. These results show proof-of-concept for an aerosolized delivery method to evaluate anti-SARS-CoV-2 agents in vivo and suggest a new tool in the ongoing fight against SARS-CoV-2 and other ACE2-dependent viruses.

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.

Angiotensin-Converting Enzyme and Hypertension: A Systemic Analysis of Various ACE Inhibitors, Their Side Effects, and Bioactive Peptides as a Putative Therapy for Hypertension

Hypertension is a major risk factor for heart attack, produce atherosclerosis (hardening of the arteries), congestive heart failure, stroke, kidney infection, blindness, end-stage renal infection, and cardiovascular diseases. Many mechanisms are involved in causing hypertension, i.e., via calcium channels, alpha and beta receptors, and the renin-angiotensin system (RAS). RAS has an important role in blood pressure control and is also involved in the metabolism of glucose, homeostasis, and balance of electrolytes in the body. The components of RAS that are involved in the regulation of blood pressure are angiotensinogen, Ang I (angiotensin I), Ang II (angiotensin II), ACE (angiotensin-converting enzyme), and ACE 2 (angiotensin-converting enzyme 2). These components provide for relevant therapeutic targets for the treatment of hypertension, and various drugs are commercially available that target individual components of RAS. Angiotensin receptor blockers (ARBs) and ACE inhibitors are the most popular among these drugs. ACE is chosen in this review as it makes an important target for blood pressure control because it converts Ang I into Ang II and also acts on the vasodilator, bradykinin, to degrade it into inactive peptides. This review highlights various aspects of blood pressure regulation in the body with a focus on ACE, drugs targeting the components involved in regulation, their associated side effects, and a need to shift to alternative therapy for putative hypertension treatment in the form of bioactive peptides from food.

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

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

Interaction of hemorphins with ACE homologs

Hemorphins, short bioactive peptides produced by enzymatic cleavage of β-hemoglobin, exhibit antihypertensive properties by inhibiting angiotensin-1 converting enzyme (ACE1). ACE1 is a key player in the renin-angiotensin system (RAS) and regulates blood pressure. ACE1 and its homolog, ACE2, which exhibit opposing activities in the RAS, share considerable similarity in their catalytic domains. The primary objective of this study was to identify and contrast the molecular mechanisms underlying the interaction of hemorphins of camels and that of other mammals with the two ACE homologs. In silico docking and molecular dynamics simulations were performed for ACE1 and ACE2, along with in vitro confirmatory assays for ACE1. The C-domain of ACE1, primarily involved in regulating blood pressure, was used along with the N-terminal peptidase domain of ACE2. The findings revealed conserved hemorphin interactions with equivalent regions of the two ACE homologs and differential residue-level interactions reflecting the substrate preferences of ACE1 and ACE2 considering their opposing functions. Therefore, conserved residue-level associations and implications of poorly conserved regions between the two ACE receptors may potentially guide the discovery of selective domain-specific inhibitors. The findings of this study can provide a basis for the treatment of related disorders in the future.

Activation of the Mas receptors by AVE0991 and MrgD receptor using alamandine to limit the deleterious effects of Ang II-induced hypertension

The MrgD receptor agonist, alamandine (ALA) and Mas receptor agonist, AVE0991 have recently been identified as protective components of the renin-angiotensin system. We evaluated the effects of ALA and AVE0991 on cardiovascular function and remodeling in angiotensin (Ang) II-induced hypertension in rats. Sprague Dawley rats were subject to 4-week subcutaneous infusions of Ang II (80 ng/kg/min) or saline after which they were treated with ALA (50 μg/kg), AVE0991 (576 μg/kg), or ALA+AVE0991 during the last 2 weeks. Systolic blood pressure (SBP) and heart rate (HR) values were recorded with tail-cuff plethysmography at 1, 15, and 29 days post-treatment. After euthanization, the heart and thoracic aorta were removed for further analysis and vascular responses. SBP significantly increased in the Ang II group when compared to the control group. Furthermore, Ang II also caused an increase in cardiac and aortic cyclophilin-A (CYP-A), monocyte chemoattractant protein-1 (MCP-1), and cardiomyocyte degeneration but produced a decrease in vascular relaxation. HR, matrix metalloproteinase-2 and -9, NADPH oxidase-4, and lysyl oxidase levels were comparable among groups. ALA, AVE0991, and the drug combination produced antihypertensive effects and alleviated vascular responses. The inflammatory and oxidative stress related to cardiac MCP-1 and CYP-A levels decreased in the Ang II+ALA+AVE0991 group. Vascular but not cardiac angiotensin-converting enzyme-2 levels decreased with Ang II administration but were similar to the Ang II+ALA+AVE0991 group. Our experimental data showed the combination of ALA and AVE0991 was found beneficial in Ang II-induced hypertension in rats by reducing SBP, oxidative stress, inflammation, and improving vascular responses.

Relation of ACE2 with co-morbidity factors in SARS-CoV-2 pathogenicity

In the last 3 years of the pandemic situation, SARS-CoV-2 caused a significant number of deaths. Infection rates for symptomatic and asymptomatic patients are higher than that for death. Eventually, researchers explored that the major deaths are attributed to several comorbidity factors. The confounding factors and gender-associated infection/death rate are observed globally. This suggests that SARS-CoV-2 selects the human system recognizing the internal comorbid environment. This article explored the influences of hypertension, diabetes, cardiovascular, and renovascular disorders in COVID-19 severity and mortality. Brief mechanistic layouts have been presented here, indicating some of the comorbidity as the critical determinant in the COVID-19 pathogenesis and related mortality.

Pathophysiology of SARS-CoV-2 Infection of Nasal Respiratory and Olfactory Epithelia and Its Clinical Impact

PURPOSE OF REVIEW

While the predominant cause for morbidity and mortality with SARS-CoV-2 infection is the lower respiratory tract manifestations of the disease, the effects of SARS-CoV-2 infection on the sinonasal tract have also come to the forefront especially with the increased recognition of olfactory symptom. This review presents a comprehensive summary of the mechanisms of action of the SARS-CoV-2 virus, sinonasal pathophysiology of COVID-19, and the correlation with the clinical and epidemiological impact on olfactory dysfunction.

RECENT FINDINGS

ACE2 and TMPRSS2 receptors are key players in the mechanism of infection of SARS-CoV-2. They are present within both the nasal respiratory as well as olfactory epithelia. There are however differences in susceptibility between different groups of individuals, as well as between the different SARS-CoV-2 variants. The sinonasal cavity is an important route for SARS-CoV-2 infection. While the mechanism of infection of SARS-CoV-2 in nasal respiratory and olfactory epithelia is similar, there exist small but significant differences in the susceptibility of these epithelia and consequently clinical manifestations of the disease. Understanding the differences and nuances in sinonasal pathophysiology in COVID-19 would allow the clinician to predict and counsel patients suffering from COVID-19. Future research into molecular pathways and cytokine responses at different stages of infection and different variants of SARS-CoV-2 would evaluate the individual clinical phenotype, prognosis, and possibly response to vaccines and therapeutics.

IgG autoantibodies against ACE2 in SARS-CoV-2 infected patients

How frequently autoantibodies against angiotensin-converting enzyme 2 (ACE2) occur in patients infected by SARS-CoV-2 is understudied and limited to investigations on a small sample size. The presence of these antibodies may contribute to the long-lasting effects of COVID-19 observed in some individuals, particularly if IgG-class antibodies would emerge in patients. This study assessed the prevalence of IgG autoantibodies against ACE2 in 1139 patients infected with SARS-CoV-2 and examined their relationship with severity, demographic characteristics, and status of vaccination against influenza. The overall prevalence of anti-ACE IgG antibodies in our cohort was 1.5%. Most of these individuals were men (76.5%) and underwent mild COVID-19, but some severe and asymptomatic cases were also observed. Patients with severe infection had twofold higher titers than mild and asymptomatic cases. Age, comorbidities, and influenza vaccination status were not related to antibody prevalence. The prevalence of IgG anti-SARS-CoV-2 antibodies (against nucleocapsid protein and S2 subunit, but not against receptor-binding domain) was higher in the subset with ACE2 autoantibodies. Further research is required to understand the potential spectrum and duration of effects of IgG autoantibodies against ACE2 in patients after SARS-CoV-2 infection, particularly concerning long COVID-19.

Evolution of Stronger SARS-CoV-2 Variants as Revealed Through the Lens of Molecular Dynamics Simulations

Using molecular dynamics simulations, the protein–protein interactions of the receptor-binding domain of the wild-type and seven variants of the severe acute respiratory syndrome coronavirus 2 spike protein and the peptidase domain of human angiotensin-converting enzyme 2 were investigated. These variants are alpha, beta, gamma, delta, eta, kappa, and omicron. Using 100 ns simulation data, the residue interaction networks at the protein–protein interface were identified. Also, the impact of mutations on essential protein dynamics, backbone flexibility, and interaction energy of the simulated protein–protein complexes were studied. The protein–protein interface for the wild-type, delta, and omicron variants contained several stronger interactions, while the alpha, beta, gamma, eta, and kappa variants exhibited an opposite scenario as evident from the analysis of the inter-residue interaction distances and pair-wise interaction energies. The study reveals that two distinct residue networks at the central and right contact regions forge stronger binding affinity between the protein partners. The study provides a molecular-level insight into how enhanced transmissibility and infectivity by delta and omicron variants are most likely tied to a handful of interacting residues at the binding interface, which could potentially be utilized for future antibody constructs and structure-based antiviral drug design.

Características clínicas, imagenológicas y de laboratorio de pacientes con COVID-19 según requerimiento de ingreso a UCI en Cali, Colombia

Introducción. Actualmente, hay pocos estudios en Latinoamérica sobre las características demográficas, clínicas y de laboratorio de pacientes con COVID-19 y con requerimiento de ingreso a unidad de cuidados intensivos (UCI). Objetivo. Comparar las características sociodemográficas, clínicas, imagenológicas y de laboratorio de pacientes diagnosticados con COVID-19 atendidos en el servicio de urgencias de una clínica en Cali, Colombia, según requerimiento de ingreso a UCI. Materiales y métodos. Estudio retrospectivo descriptivo de cohorte única realizado en 49 adultos con COVID-19 atendidos en el servicio de urgencias de un hospital de cuarto nivel de atención en Cali, Colombia, en marzo y abril de 2020, los cuales se dividieron en dos grupos: requerimiento de UCI (n=24) y no requerimiento de UCI (n=25). Se realizaron análisis bivariados para determinar las diferencias entre ambos grupos (pruebas de chi-2, exacta de Fisher, t de Student y U de Mann-Whitney), con un nivel de significancia de p<0.05. Resultados. La edad promedio fue 53 años (DE=13) y 29 pacientes fueron hombres. Se encontraron diferencias significativas entre ambos grupos en las siguientes variables: edad promedio (UCI x̅=58 vs. No UCI x̅=49; p=0.020), presencia de diabetes (8 vs. 1; p=0.010), presencia de dificultad respiratoria (20 vs. 11; p=0.007), presencia uni o bilateral de áreas de consolidación (12 vs. 3; p=0.005), mediana del conteo de leucocitos (Med=7570/mm3 vs. Med=5130/mm3; p=0.0013), de neutrófilos (Med=5980/mm3 vs. Med=3450/mm3; p=0,0001) y linfocitos (Med=865/mm3 vs. Med=1400/mm3; p<0,0001), mediana de proteína C reactiva (Med=141,25mg/L vs. Med=27,95mg/L; p<0,001), ferritina (Med=1038ng/L vs. Med=542,5ng/L; p=0.0073) y lactato-deshidrogenasa (Med=391U/L vs, Med=248,5U/L, p=0,0014). Finalmente, 15 pacientes requirieron ventilación mecánica invasiva, 2 presentaron extubación fallida, y en total, 5 fallecieron. Conclusiones. Se observaron diferencias significativas en los valores de varios marcadores inflamatorios, daño celular y parámetros del hemograma entre los pacientes que requirieron admisión a la UCI y los que no, por lo que estas variables podrían emplearse para desarrollar herramientas que contribuyan a establecer el pronóstico de esta enfermedad.

Investigation of pituitary functions after acute coronavirus disease 2019

Although coronavirus disease 2019 (COVID-19) mainly involves the lungs, it also affects many systems. The hypothalamic/pituitary axis is vulnerable to hypoxia, hypercoagulation, endothelial dysfunction and autoimmune changes induced by COVID-19 infection. Given that there is no extensive investigation on this issue, we investigated the pituitary functions three to seven months after acute COVID-19 infection. Forty-three patients after diagnosis of COVID-19 infection and 11 healthy volunteers were included in the study. In addition to the basal pituitary hormone levels, growth hormone (GH) and hypothalamo-pituitary adrenal (HPA) axes were evaluated by glucagon stimulation test (GST) and low-dose adrenocorticotropic hormone (ACTH) stimulation test, respectively. The peak cortisol responses to low-dose ACTH test were insufficient in seven (16.2%) patients. Twenty (46.5%) and four (9.3%) patients had inadequate GH and cortisol responses to GST, respectively. Serum insulin-like growth factor-1 (IGF-1) values were also lower than age and sex-matched references in four (9.3%) patients. The peak GH responses to GST were lower in the patient group when compared to the control group. Other abnormalities were mild thyroid-stimulating hormone elevation in four (9.3%) patients, mild prolactin elevation in two (4.6%) patients and central hypogonadism in four (9.3%) patients. Mean total testosterone values were lower in male patients when compared to male controls; however, the difference was not significant. These findings suggest that COVID-19 infection may affect pituitary functions, particularly the HPA and GH axes. These insufficiencies should be kept in mind in post-COVID follow-up. Long-term data are needed to determine whether these deficiencies are permanent or not.

Will the Use of Pharmacogenetics Improve Treatment Efficiency in COVID-19?

The COVID-19 pandemic is associated with a global health crisis and the greatest challenge for scientists and doctors. The virus causes severe acute respiratory syndrome with an outcome that is fatal in more vulnerable populations. Due to the need to find an efficient treatment in a short time, there were several drugs that were repurposed or repositioned for COVID-19. There are many types of available COVID-19 therapies, including antiviral agents (remdesivir, lopinavir/ritonavir, oseltamivir), antibiotics (azithromycin), antiparasitics (chloroquine, hydroxychloroquine, ivermectin), and corticosteroids (dexamethasone). A combination of antivirals with various mechanisms of action may be more efficient. However, the use of some of these medicines can be related to the occurrence of adverse effects. Some promising drug candidates have been found to be ineffective in clinical trials. The knowledge of pharmacogenetic issues, which translate into variability in drug conversion from prodrug into drug, metabolism as well as transport, could help to predict treatment efficiency and the occurrence of adverse effects in patients. However, many drugs used for the treatment of COVID-19 have not undergone pharmacogenetic studies, perhaps as a result of the lack of time.

Containing the spread of COVID-19 virus facing to its high mutation rate: approach to intervention using a nonspecific way of blocking its entry into the cells

Viruses have multiple mutation rates that are higher than any other member of the kingdom of life. This gives them the ability to evolve, even within the course of a single infection, and to evade multiple host defenses, thereby impacting pathogenesis. Additionally, there are also interplays between mutation and recombination and the high multiplicity of infection (MOI) that enhance viral adaptability and increase levels of recombination leading to complex and conflicting effects on genome selection, and the net results is difficult to predict. Recently, the outbreak of COVID-19 virus represents a pandemic threat that has been declared a public health emergency of international concern. Up to present, however, due to the high mutation rate of COVID-19 virus, there are no effective procedures to contain the spread of this virus across the globe. For such a purpose, there is then an urgent need to explore new approaches. As an opinion, the present approach emphasizes on (a) the use of a nonspecific way of blocking the entry of COVID-19 virus as well as its variants into the cells via a therapeutic biocompatible compound (ideally, "in a pill") targeting its spike (S) glycoprotein; and (b) the construction of expression vectors via the glycosyl-phosphatidylinositol, GPI, anchor for studying intermolecular interactions between the spike S of COVID-19 virus as well as its variants and the angiotensin-converting enzyme 2 (ACE2) of its host receptor for checking the efficacy of any therapeutic biocompatible compound of the nonspecific way of blocking. Such antiviral drug would be safer than the ACE1 and ACE2 inhibitors/angiotensin receptor blockers, and recombinant human ACE2 as well as nucleoside analogs or protease inhibitors used for fighting the spread of the virus inside the cells, and it would also be used as a universal one for any eventual future pandemic related to viruses, especially the RNA viruses with high mutation rates.

Inhibitory mechanism of Ambroxol and Bromhexine Hydrochlorides as potent blockers of molecular interaction between SARS-CoV-2 spike protein and human angiotensin-converting Enzyme-2

Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infects the host cells through interaction of its spike protein with human angiotensin-converting enzyme 2 (hACE-2). High binding affinity between the viral spike protein and host cells hACE-2 receptor has been reported to enhance the viral infection. Thus, the disruption of this molecular interaction will lead to reduction in viral infectivity. This study, therefore, aimed to analyze the inhibitory potentials of two mucolytic drugs; Ambroxol hydrochlorides (AMB) and Bromhexine hydrochlorides (BHH), to serve as potent blockers of these molecular interactions and alters the binding affinity/efficiency between the proteins employing computational techniques. The study examined the effects of binding of each drug at the receptor binding domain (RBD) of the spike protein and the exopeptidase site of hACE-2 on the binding affinity (ΔG_bind) and molecular interactions between the two proteins. Binding affinity revealed that the binding of the two drugs at the RBD-ACE-2 site does not alter the binding affinity and molecular interaction between the proteins. However, the binding of AMB (−56.931 kcal/mol) and BHH (−46.354 kcal/mol) at the exopeptidase site of hACE-2, significantly reduced the binding affinities between the proteins compared to the unbound, ACE-2-RBD complex (−64.856 kcal/mol). The result further showed the two compounds have good affinity at the hACE-2 site, inferring they might be potent inhibitors of hACE-2. Residue interaction networks analysis further revealed the binding of the two drugs at the exopeptidase site of hACE-2 reduced the number of interacting amino residues, subsequently leading to loss of interactions between the two proteins, with BHH showing better reduction in the molecular interaction and binding affinity than AMB. The result of the structural analyses additionally, revealed that the binding of the drugs considerably influences the dynamic of the complexes when compared to the unbound complex. The findings from this study suggest the binding of the two drugs at the exopeptidase site reduces the binding effectiveness of the proteins than their binding at the RBD site, and consequently might inhibit viral attachment and entry.

Review of non-invasive detection of SARS-CoV-2 and other respiratory pathogens in exhaled breath condensate

In 2019, severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) emerged to cause high viral infectivity and severe respiratory illness in humans (COVID-19). Worldwide, limited pandemic mitigation strategies, including lack of diagnostic test availability, resulted in COVID-19 overrunning health systems and spreading throughout the global population. Currently, proximal respiratory tract (PRT) specimens such as nasopharyngeal swabs are used to diagnose COVID-19 because of their relative ease of collection and applicability in large scale screening. However, localization of SARS-CoV-2 in the distal respiratory tract (DRT) is associated with more severe infection and symptoms. Exhaled breath condensate (EBC) is a sample matrix comprising aerosolized droplets originating from alveolar lining fluid that are further diluted in the DRT and then PRT and collected via condensation during tidal breathing. The COVID-19 pandemic has resulted in recent resurgence of interest in EBC collection as an alternative, non-invasive sampling method for the staging and accurate detection of SARS-CoV-2 infections. Herein, we review the potential utility of EBC collection for detection of SARS-CoV-2 and other respiratory infections. While much remains to be discovered in fundamental EBC physiology, pathogen-airway interactions, and optimal sampling protocols, EBC, combined with emerging detection methods, presents a promising non-invasive sample matrix for detection of SARS-CoV-2.

mRNA expression of the severe acute respiratory syndrome-coronavirus 2 angiotensin-converting enzyme 2 receptor in the lung tissue of Wistar rats according to age

Background and Aim:

Angiotensin-converting enzyme 2 (ACE2) is expressed and plays functional and physiological roles in different tissues of the body. This study aimed to distinguish the levels of expression of ACE2 in the lung tissue at different ages of rats.

Materials and Methods:

In this study, 18 male rats were used and divided into three groups according to age. Real-time quantitative polymerase chain reaction (RT-qPCR) was conducted to determine the levels of the quantification of eosinophil cationic protein mRNA transcript. In addition, tissue specimens of the lung were stained with routine hematoxylin and eosin stains.

Results:

This study confirmed that RT-qPCR amplification plots of ACE2 gene exhibited clearly expression of the lung tissue of rats in the different groups and there are strong different threshold cycles numbers according to the age at 2 weeks, 2 months, and 6-8 months. Consequently, the expression of ACE2 was completely different between groups depending on the age of the rats. The RT-qPCR results showed that the older animal group (age of 6-8 months) had a significantly higher expression of ACE2 than the other animal groups (ages of 2 weeks and 2 months). In the same way, the second group (age of 2 months) had a significantly higher expression of ACE2 than the first group (age of 2 weeks). This study confirmed that the ACE2 expression is influenced by the age of rats.

Conclusion:

This study concluded that the expression of the ACE2 receptor of coronavirus disease 2019 would be different according to the age of rats, and this result suggested that expression of ACE2 in lung tissue could determine infection and pathogenesis of COVID-19 during different ages of rats or some individual differences.

Known Cellular and Receptor Interactions of Animal and Human Coronaviruses: A Review

This article aims to review all currently known interactions between animal and human coronaviruses and their cellular receptors. Over the past 20 years, three novel coronaviruses have emerged that have caused severe disease in humans, including SARS-CoV-2 (severe acute respiratory syndrome virus 2); therefore, a deeper understanding of coronavirus host-cell interactions is essential. Receptor-binding is the first stage in coronavirus entry prior to replication and can be altered by minor changes within the spike protein-the coronavirus surface glycoprotein responsible for the recognition of cell-surface receptors. The recognition of receptors by coronaviruses is also a major determinant in infection, tropism, and pathogenesis and acts as a key target for host-immune surveillance and other potential intervention strategies. We aim to highlight the need for a continued in-depth understanding of this subject area following on from the SARS-CoV-2 pandemic, with the possibility for more zoonotic transmission events. We also acknowledge the need for more targeted research towards glycan-coronavirus interactions as zoonotic spillover events from animals to humans, following an alteration in glycan-binding capability, have been well-documented for other viruses such as Influenza A.

Cannabinoids Block Cellular Entry of SARS-CoV-2 and the Emerging Variants

As a complement to vaccines, small-molecule therapeutic agents are needed to treat or prevent infections by severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2) and its variants, which cause COVID-19. Affinity selection-mass spectrometry was used for the discovery of botanical ligands to the SARS-CoV-2 spike protein. Cannabinoid acids from hemp (Cannabis sativa) were found to be allosteric as well as orthosteric ligands with micromolar affinity for the spike protein. In follow-up virus neutralization assays, cannabigerolic acid and cannabidiolic acid prevented infection of human epithelial cells by a pseudovirus expressing the SARS-CoV-2 spike protein and prevented entry of live SARS-CoV-2 into cells. Importantly, cannabigerolic acid and cannabidiolic acid were equally effective against the SARS-CoV-2 alpha variant B.1.1.7 and the beta variant B.1.351. Orally bioavailable and with a long history of safe human use, these cannabinoids, isolated or in hemp extracts, have the potential to prevent as well as treat infection by SARS-CoV-2.

Covid-19, the thyroid and the pituitary - the real state of play

Thyroid and pituitary disorders linked to the coronavirus SARS-CoV-2, responsible for the COVID-19 epidemic, are mainly due to direct infection of the endocrine glands by the virus and to cell damage induced by the immune response. The two most frequent thyroid complications of COVID-19 are low T3 syndrome, or “non-thyroidal illness syndrome” (NTIS), and thyroiditis. Studies among in-patients with COVID-19 have shown that between one out of six and half of them have a low TSH level, related to NTIS and thyroiditis, respectively, sometimes found in the same patient. In NTIS, the decrease in free T3 concentration correlates with the severity of the infection and with a poor prognosis. Assessment of thyroid function in patients after a COVID-19 infection, shows normalization of thyroid function tests. Thyroiditis linked to COVID-19 can be divided into two groups, which probably differ in their pathophysiology. One is “destructive” thyroiditis occurring early in infection with SARS-CoV-2, with a severe form of COVID-19, usually observed in men. It is often asymptomatic and associated with lymphopenia. The other is subacute thyroiditis occurring, on average, one month after the COVID-19 episode, usually in clinically symptomatic women and associated with moderate hyperleukocytosis. Post-infection, one quarter to one third of patients remain hypothyroid. An Italian study demonstrated that low TSH in patients hospitalized for COVID-19 was associated with prolonged hospitalization and a higher mortality risk. Pituitary diseases associated with SARS-CoV-2 infection are much rarer and the causal relationship more difficult to ascertain. Several cases of pituitary apoplexy and diabetes insipidus during COVID-19 infection have been reported. Hyponatremia occurs in 20–50% of patients admitted to hospital for COVID-19. The prevalence of the syndrome of inappropriate antidiuretic hormone secretion (SIADH) amongst these hyponatremic cases is difficult to determine. These endocrine complications may influence the prognosis of infection with SARS-CoV-2. Although they rarely require specific treatment, it is important that endocrinologists recognize them to ensure appropriate management, particularly in the acute phase.

Perspectives and potential approaches for targeting neuropilin 1 in SARS-CoV-2 infection

Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) is a novel type b coronavirus responsible for the COVID-19 pandemic. With over 224 million confirmed infections with this virus and more than 4.6 million people dead because of it, it is critically important to define the immunological processes occurring in the human response to this virus and pathogenetic mechanisms of its deadly manifestation. This perspective focuses on the contribution of the recently discovered interaction of SARS-CoV-2 Spike protein with neuropilin 1 (NRP1) receptor, NRP1 as a virus entry receptor for SARS-CoV-2, its role in different physiologic and pathologic conditions, and the potential to target the Spike-NRP1 interaction to combat virus infectivity and severe disease manifestations.

Impact of air pollution and smoking on COVID-19: a review

Background

The 21st century already witnessed many deadly epidemics and pandemics. The major ones were respiratory tract infections like SARS (2003), H1N1 (2009), MERS (2012) and the most recent pandemic COVID-19 (2019). The COVID-19 story begins when pneumonia of unknown cause was reported in the WHO country office of China at the end of 2019. SARS-CoV-2 is the causative agent that enters the host through the receptor ACE2, a component of the renin–angiotensin system.

Main body of the abstract

Symptoms of COVID-19 varies from patient to patient. It is all about the immunity and health status of the individual that decides the severity of the disease. The review focuses on the significant and often prevailing factors, those that influence the lung function. The factors that compromise the lung functions which may prepare the ground for severe COVID-19 infection are interestingly looked into. Focus was more on air pollution and cigarette smoke.

Short conclusion

The fact that the forested areas across the world show very low COVID-19 infection rate suggests that we are in need of the “Clean Air” on the fiftieth anniversary of World Earth Day. As many policies are implemented worldwide to protect from SARS-CoV-2, one simple remedy that we forgot was clean air can save lives. SARS-CoV-2 infects our lungs, and air pollution makes us more susceptible. In this crucial situation, the focus is only on the main threat; all other conditions are only in words to console the situation.

COVID-19: Zinc and Angiotensin-Converting Enzyme 2 (ACE2) Deficiencies as Determinants of Risk and Severity of Disease: A Narrative Review

A growing body of evidence supports the premise that deficiencies of zinc and angiotensin-converting enzyme 2 (ACE2, a zinc enzyme) determine severity of coronavirus disease 2019 (COVID-19). ACE2 is part of the renin-angiotensin system (RAS) and acts as a feedback control system moderating blood pressure, keeping blood pressure within normal limits. For a virus to infect a person, the virus has to get inside the person's cells. The virus that causes COVID-19 uses ACE2 to get into the cell. Think of this like an invader from outer space attacking your car by getting in through your cruise control; the RAS is like the cruise control of your car. What happens next depends on how robust your cruise control is. If your cruise control is young and healthy perhaps very little happens; your car may slow down or speed up a bit. But if your cruise control is in poor condition the attack might disrupt the entire speed control system; your car may brake suddenly or speed out of control and crash. Feedback control systems (natural or man-made) are designed to keep dynamic systems in control, but under certain situations can drive the system completely out of control. The RAS is composed of two feedback loops: the ACE loop provides amplification, increasing pro-inflammatory cytokines and blood pressure; the ACE2 loop provides fine control and mitigates the vasoconstrictive, pro-inflammatory, and thrombotic actions of the ACE loop. Usually, there is balance, but in the setting of COVID-19, underlying deficiencies of zinc and ACE2 can lead to an imbalance. Exacerbated by the severe downregulation of ACE2 seen with viral entry, a "tipping point" is reached with loss of control of the RAS system resulting in increased angiotensin II (Ang II) causing downstream vasoconstriction, inflammation, and thromboses. These, in turn, lead to complications often seen in "severe COVID-19" such as acute respiratory distress syndrome (ARDS) or cytokine storm, often seen in high-risk patients in the second week of illness. This model suggests that supplemental zinc could replenish zinc in ACE2, stabilize the ACE2 axis, and prevent disruption of the RAS. This would prevent the vasoconstrictive, inflammatory, and thrombotic actions of Ang II, thus preventing the severe COVID-19 complications which cause the high morbidity and mortality seen in high-risk patients with underlying zinc deficiency. Zinc supplements are available, easy to use, and relatively safe. Randomized clinical trials are needed to confirm safety and efficacy of zinc supplementation to decrease severity of and morality from COVID-19 in high-risk patients. Since replenishment of zinc and active ACE2 in patients in whom these are deficient may take weeks, supplementation in high-risk populations prior to COVID infection may be required. Such supplementation should not replace vaccination but may be useful in populations for whom vaccination is not available or for populations exposed to viral variants to which available vaccines have insufficient coverage.

Low-cost biosensor for rapid detection of SARS-CoV-2 at the point of care

SARS-CoV-2, the virus that causes COVID-19, has killed over 3 million people worldwide. Despite the urgency of the current pandemic, most available diagnostic methods for COVID-19 use RT-PCR to detect nucleic acid sequences specific to SARS-CoV-2. These tests are limited by their requirement of a large laboratory space, high reagent costs, multistep sample preparation, and the potential for cross-contamination. Moreover, results usually take hours to days to become available. Therefore, fast, reliable, inexpensive, and scalable point-of-care diagnostics are urgently needed. Here, we describe RAPID 1.0, a simple, handheld, and highly sensitive miniaturized biosensor modified with human receptor angiotensin-converting enzyme-2. RAPID 1.0 can detect SARS-CoV-2 using 10 μL of sample within 4 min through its increased resistance to charge transfer of a redox probe measured by electrochemical impedance spectroscopy. The sensitivity and specificity of RAPID for nasopharyngeal/oropharyngeal swab and saliva samples are 85.3% and 100% and 100% and 86.5%, respectively.

Triangle of cytokine storm, central nervous system involvement, and viral infection in COVID-19: the role of sFasL and neuropilin-1

Severe acute respiratory syndrome coronavirus 2 (SARS-CoV2) is identified as the cause of coronavirus disease 2019 (COVID-19), and is often linked to extreme inflammatory responses by over activation of neutrophil extracellular traps (NETs), cytokine storm, and sepsis. These are robust causes for multi-organ damage. In particular, potential routes of SARS-CoV2 entry, such as angiotensin-converting enzyme 2 (ACE2), have been linked to central nervous system (CNS) involvement. CNS has been recognized as one of the most susceptible compartments to cytokine storm, which can be affected by neuropilin-1 (NRP-1). ACE2 is widely-recognized as a SARS-CoV2 entry pathway; However, NRP-1 has been recently introduced as a novel path of viral entry. Apoptosis of cells invaded by this virus involves Fas receptor-Fas ligand (FasL) signaling; moreover, Fas receptor may function as a controller of inflammation. Furthermore, NRP-1 may influence FasL and modulate cytokine profile. The neuroimmunological insult by SARS-CoV2 infection may be inhibited by therapeutic approaches targeting soluble Fas ligand (sFasL), cytokine storm elements, or related viral entry pathways. In the current review, we explain pivotal players behind the activation of cytokine storm that are associated with vast CNS injury. We also hypothesize that sFasL may affect neuroinflammatory processes and trigger the cytokine storm in COVID-19.

Review of Sertoli cell dysfunction caused by COVID-19 that could affect male fertility

Spermatogenesis is a complex and elaborate differentiation process and is vital for male fertility. Sertoli cells play a major role in fertility and induce spermatogenesis by protecting, nourishing, and supporting germ cells. It has been speculated that severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) could directly affect the male reproductive system, and therefore heredity and fertility. The similarity of SARS-CoV-2 to SARS-CoV could confirm this hypothesis because both viruses use angiotensin-converting enzyme (ACE2) as the receptor to enter human cells. ACE2 is expressed by Sertoli cells and other testicular cells, therefore COVID-19 has the potential to impair fertility by destroying Sertoli cells. This hypothesis should be evaluated and confirmed by monitoring fertility in patients with COVID-19.

Regulated Intramembrane Proteolysis of ACE2: A Potential Mechanism Contributing to COVID-19 Pathogenesis?

Since being identified as a key receptor for SARS-CoV-2, Angiotensin converting enzyme 2 (ACE2) has been studied as one of the potential targets for the development of preventative and/or treatment options. Tissue expression of ACE2 and the amino acids interacting with the spike protein of SARS-CoV-2 have been mapped. Furthermore, the recombinant soluble extracellular domain of ACE2 is already in phase 2 trials as a treatment for SARS-CoV-2 infection. Most studies have continued to focus on the ACE2 extracellular domain, which is known to play key roles in the renin angiotensin system and in amino acid uptake. However, few also found ACE2 to have an immune-modulatory function and its intracellular tail may be one of the signaling molecules in regulating cellular activation. The implication of its immune-modulatory role in preventing the cytokine-storm, observed in severe COVID-19 disease outcomes requires further investigation. This review focuses on the regulated proteolytic cleavage of ACE2 upon binding to inducer(s), such as the spike protein of SARS-CoV, the potential of cleaved ACE2 intracellular subdomain in regulating cellular function, and the ACE2's immune-modulatory function. This knowledge is critical for targeting ACE2 levels for developing prophylactic treatment or preventative measures in SARS-CoV infections.

Mechanistic Investigations of Metallo-β-lactamase Inhibitors: Strong Zinc Binding Is Not Required for Potent Enzyme Inhibition*

Metallo-β-lactamases (MBLs) are zinc-dependent bacterial enzymes that inactivate essentially all classes of β-lactam antibiotics including last-resort carbapenems. At present there are no clinically approved MBL inhibitors, and in order to develop such agents it is essential to understand their inhibitory mechanisms. Herein, we describe a comprehensive mechanistic study of a panel of structurally distinct MBL inhibitors reported in both the scientific and patent literature. Specifically, we determined the half-maximal inhibitory concentration (IC50 ) for each inhibitor against MBLs belonging to the NDM and IMP families. In addition, the binding affinities of the inhibitors for Zn2+ , Ca2+  and Mg2+  were assessed by using isothermal titration calorimetry (ITC). We also compared the ability of the different inhibitors to resensitize a highly resistant MBL-expressing Escherichia coli strain to meropenem. These investigations reveal clear differences between the MBL inhibitors studied in terms of their IC50 value, metal binding ability, and capacity to synergize with meropenem. Notably, our studies demonstrate that potent MBL inhibition and synergy with meropenem are not explicitly dependent on the capacity of an inhibitor to strongly chelate zinc.

Molecules in pathogenesis: angiotensin converting enzyme 2 (ACE2)

The renin-angiotensin system is mainly associated with the regulation of blood pressure, but recently many other functions of this system have been described. ACE2, an 805-amino acid monocarboxypeptidase type I transmembrane glycoprotein, was discovered in 2000 and has sequence similarity to two other proteins, namely ACE and collectrin. The ACE2 gene is located on Xp22 and is highly polymorphic. ACE2 is expressed in numerous tissues especially the lung alveolar epithelial cells, heart, kidney and gastrointestinal tract. Animal studies have found that ACE2 is central in diseases affecting almost all organ systems, among other cardiac, respiratory, renal and endocrine functions. ACE2 was identified as the cellular contact point for severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), the cause of the global pandemic (COVID-19), and is a potential drug target. SARS-CoV-2 infection has several effects on the renin-angiotensin system and conversely, regulation of this receptor may affect the progress of infection. We describe the genetics and functions of ACE2, explore its various physiological functions in the renin-angiotensin system and discuss its role in the pathophysiology of disease. ACE2 opposes the vasopressor ACE pathway of the renin-angiotensin system by converting angiotensin (Ang) I to Ang (1-9) and Ang II to Ang (1-7) which initiates the vasodilatory pathway. ACE2 may have a protective effect in the lung and kidney as knockout mice display susceptibility to acute respiratory distress and hypertensive nephropathy. Binding of SARS-CoV-2 and the subsequent fusion and downregulation of this pathway during SARS-CoV-2 infection may explain some of the unusual sequelae seen in COVID-19.

Dual role for angiotensin-converting enzyme 2 in Severe Acute Respiratory Syndrome Coronavirus 2 infection and cardiac fat

Angiotensin-converting enzyme 2 (ACE2) has been an increasingly prevalent target for investigation since its discovery 20 years ago. The finding that it serves a counterregulatory function within the traditional renin-angiotensin system, implicating it in cardiometabolic health, has increased its clinical relevance. Focus on ACE2's role in cardiometabolic health has largely centered on its apparent functions in the context of obesity. Interest in ACE2 has become even greater with the discovery that it serves as the cell receptor for severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), opening up numerous mechanisms for deleterious effects of infection. The proliferation of ACE2 within the literature coupled with its dual role in SARS-CoV-2 infection and obesity necessitates review of the current understanding of ACE2's physiological, pathophysiological, and potential therapeutic functions. This review highlights the roles of ACE2 in cardiac dysfunction and obesity, with focus on epicardial adipose tissue, to reconcile the data in the context of SARS-CoV-2 infection.

Potential combination therapy using twenty phytochemicals from twenty plants to prevent SARS- CoV-2 infection: An in silico Approach

Covid 19 caused by novel strain SARS- CoV-2 has become a pandemic due to its contagious nature of infection. It enters by binding with ACE2 receptor present on the outer surface of a cell by cleaving S1/S2 with proteolytic protein Furin. Further viral replication or transcription then takes place with the help of main protease 3CLpro and polymerase RdRp. This in silco study was carried out to block ACE2, Furin, 3CLpro and RdRP with various phytochemicals to prevent SARS- CoV-2 entry and replication or transcription. Twenty different phytochemicals were screened to understand the drug-likeliness obeying Lipinski’s rule 5 and further, molecular docking was performed using these phytochemicals to block their respective target proteins. All the phytochemicals follow Lipinski’s rule of five and molecular docking result shows best binding affinity of Podofilox − 7.54 kcal/mol with ACE2, Psoralidin − 8.04 kcal/mol with Furin, Ursolic acid − 8.88 kcal/mol with 3CLpro and Epiafzelechin − 8.26 kcal/mol with RdRp. Thus, blocking two human receptors ACE2 and Furin with Podofilox and Psoralidin respectively may prevent the viral entry into the cells. Also blocking viral proteins 3CLpro and RdRp with Ursolic acid and Epiafzelechin may prevent viral replication or transcription. Using this combination therapy of blocking the receptors responsible for viral entry and viral proteins responsible for replication or transcription may prevent SARS- CoV-2 infection.

TMPRSS2 inhibitor discovery facilitated through an in silico and biochemical screening platform

The COVID-19 pandemic has highlighted the need for new antiviral targets, as many of the currently approved drugs have proven ineffective against mitigating SARS-CoV-2 infections. The host transmembrane serine protease TMPRSS2 is a highly promising antiviral target, as it plays a direct role in priming the spike protein before viral entry occurs. Further, unlike other targets such as ACE2, TMPRSS2 has no known biological role. Here we utilize virtual screening to curate large libraries into a focused collection of potential inhibitors. Optimization of a recombinant expression and purification protocol for the TMPRSS2 peptidase domain facilitates subsequent biochemical screening and characterization of selected compounds from the curated collection in a kinetic assay. In doing so, we demonstrate that serine protease inhibitors camostat, nafamostat, and gabexate inhibit through a covalent mechanism. We further identify new non-covalent compounds as TMPRSS2 protease inhibitors, demonstrating the utility of a combined virtual and experimental screening campaign in rapid drug discovery efforts.

The effect of angiotensin-converting enzyme levels on COVID-19 susceptibility and severity: a Mendelian randomization study

Background

There has been uncertainty about the safety or benefit of angiotensin-converting enzyme (ACE) inhibitors during the COVID-19 pandemic. We used Mendelian randomization using genetic determinants of serum-ACE levels to test whether decreased ACE levels increase susceptibility to SARS-CoV-2 infection or COVID-19 severity, while reducing potential bias from confounding and reverse causation in observational studies.

Methods

Genetic variants strongly associated with ACE levels, which were nearby the ACE gene, were identified from the ORIGIN trial and a separate genome-wide association study (GWAS) of ACE levels from the AGES cohort. The ORIGIN trial included 4147 individuals of European and Latino ancestries. Sensitivity analyses were performed using a study of 3200 Icelanders. Cohorts from the COVID-19 Host Genetics Initiative GWAS of up to 960 186 individuals of European ancestry were used for COVID-19 susceptibility, hospitalization and severe-disease outcome.

Results

Genetic variants were identified that explain between 18% and 37% of variance in ACE levels. Using genetic variants from the ORIGIN trial, a standard-deviation decrease in ACE levels was not associated with an increase in COVID-19 susceptibility [odds ratio (OR): 1.02, 95% confidence interval (CI): 0.90, 1.15], hospitalization (OR: 0.86, 95% CI: 0.68, 1.08) or severe disease (OR: 0.74, 95% CI: 0.51, 1.06). Using genetic variants from the AGES cohort, the result was similar for susceptibility (OR: 0.98, 95% CI: 0.89, 1.09), hospitalization (OR: 0.86, 95% CI: 0.66, 1.11) and severity (OR: 0.75, 95% CI: 0.50, 1.14). Multiple-sensitivity analyses led to similar results.

Conclusion

Genetically decreased serum ACE levels were not associated with susceptibility to, or severity of, COVID-19 disease. These data suggest that individuals taking ACE inhibitors should not discontinue therapy during the COVID-19 pandemic.

The Physiological Mechanisms of the Sex-Based Difference in Outcomes of COVID19 Infection

The scale of the SARS-CoV-2 pandemic has thrust a spotlight on the sex-based differences in response to viral diseases; morbidity and mortality are greater in men than women. We outline the mechanisms by which being female offers a degree of protection from COVID19, that persists even when confounders such as comorbidities are considered. The physiological and immunological mechanisms are fascinating and range from incomplete X chromosome inactivation of immune genes, a crucial role for angiotensin converting enzyme 2 (ACE2), and regulation of both immune activity and ACE2 by sex steroids. From this flows understanding of why lung and other organs are more susceptible to COVID19 damage in men, and how their distinct immunological landscapes need to be acknowledged to guide prognosis and treatment. Pregnancy, menopause, and hormone replacement therapy bring changed hormonal environments and the need for better stratification in COVID19 studies. We end by noting clinical trials based on increasing estrogens or progesterone or anti-testosterone drugs; excellent examples of translational physiology.

Predicting Potential SARS-COV-2 Drugs-In Depth Drug Database Screening Using Deep Neural Network Framework SSnet, Classical Virtual Screening and Docking

Severe Acute Respiratory Syndrome Corona Virus 2 has altered life on a global scale. A concerted effort from research labs around the world resulted in the identification of potential pharmaceutical treatments for CoVID-19 using existing drugs, as well as the discovery of multiple vaccines. During an urgent crisis, rapidly identifying potential new treatments requires global and cross-discipline cooperation, together with an enhanced open-access research model to distribute new ideas and leads. Herein, we introduce an application of a deep neural network based drug screening method, validating it using a docking algorithm on approved drugs for drug repurposing efforts, and extending the screen to a large library of 750,000 compounds for de novo drug discovery effort. The results of large library screens are incorporated into an open-access web interface to allow researchers from diverse fields to target molecules of interest. Our combined approach allows for both the identification of existing drugs that may be able to be repurposed and de novo design of ACE2-regulatory compounds. Through these efforts we demonstrate the utility of a new machine learning algorithm for drug discovery, SSnet, that can function as a tool to triage large molecular libraries to identify classes of molecules with possible efficacy.

Association of ACE inhibitors and angiotensin type II blockers with ACE2 overexpression in COVID-19 comorbidities: A pathway-based analytical study

Severe Acute Respiratory Syndrome Corona Virus 2 (SARS-CoV-2) outbreak is a major public health concern, which has accounted for >1.7 million deaths across the world. A surge in the case fatality ratio as compared with the infection ratio has been observed in most of the countries. The novel Coronavirus SARS-CoV-2 shares the most common sequence with SARS-CoV, but it has a higher rate of transmission. The SARS-CoV-2 pathogenesis is initiated by the binding of viral spike protein with the target receptor Angiotensin-Converting Enzyme 2 (ACE2) facilitating virus internalization within host cells. SARS-CoV-2 mainly causes alveolar damage ranging from mild to severe clinical respiratory manifestations. Most of the cases have revealed the association of Coronavirus disease with patients having earlier comorbidities like Hypertension, Diabetes mellitus, and Cerebrovascular diseases. Pharmacological investigation of the SARS-Cov-2 patients has revealed the frequent use of drugs belongs to Angiotensin-converting enzyme inhibitors (ACEi) and/or Angiotensin II type I receptor blockers (ARBs). Interestingly, a significant increase in ACE2 expression was noticed in patients routinely treated with the above group of drugs were also reported. To date, the association of ACEi and/or ARBs with the up-regulation of ACE2 expression has not been defined distinctively. The proposed review will focus on the pathways which are responsible for the upregulation of ACE2 and its impact on gravity of SARS-CoV-2 disease.

High expression of ACE2 in HER2 subtype of breast cancer is a marker of poor prognosis

Background

ACE2 a key molecule of the Renin-Angiotensin system has been identified as the receptor for SARS-CoV-2 entry into human cells. In the context of human cancers, there is evidence that ACE2 might function as a tumor suppressor. The expression levels of ACE2 among the different subtypes of breast cancer has not been investigated.

Methods

We have examined the differential expression of ACE2 and its correlation with prognosis in breast cancer subtypes using the METABRIC (n = 1898) and TCGA (n = 832) cohorts. Correlations were evaluated by Pearsons's correlation co-efficient and Kaplan-Meier analysis was used to estimate differences in disease-free survival between the ACE2 high and ACE2 low groups.

Results

There is minimal expression of ACE2 in the luminal classes, but significantly higher levels in the Basal-like and HER2-enriched subclasses. Metastatic biopsies of these tumor types also show enhanced expression of ACE2. High levels of ACE2 correlated with decreased disease-free survival in the HER2-enriched subtype, and it was positively correlated with EGFR expression.

Conclusion

These observations suggest ACE2 might function as a context dependent factor driving tumor progression in breast cancer and permit new opportunities for targeted therapy.

Potential detrimental role of soluble ACE2 in severe COVID-19 comorbid patients

Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) enters the host cell by binding to angiotensin-converting enzyme 2 (ACE2) receptor. Other important proteins involved in this process include disintegrin and metalloproteinase domain-containing protein 17 (ADAM17) also known as tumour necrosis factor-α-converting enzyme and transmembrane serine protease 2. ACE2 converts angiotensin II (Ang II) to angiotensin (1-7), to balance the renin angiotensin system. Membrane-bound ACE2 ectodomain shedding is mediated by ADAM17 upon viral spike binding, Ang II overproduction and in several diseases. The shed soluble ACE2 (sACE2) retains its catalytic activity, but its precise role in viral entry is still unclear. Therapeutic sACE2 is claimed to exert dual effects; reduction of excess Ang II and blocking viral entry by masking the spike protein. Nevertheless, the paradox is why SARS-CoV-2 comorbid patients struggle to attain such benefit in viral infection despite having a high amount of sACE2. In this review, we discuss the possible detrimental role of sACE2 and speculate on a series of events where protease primed or non-primed virus-sACE2 complex might enter the host cell. As extracellular virus can bind many sACE2 molecules, sACE2 level could be reduced drastically upon endocytosis by the host cell. A consequential rapid rise in Ang II level could potentially aggravate disease severity through Ang II-angiotensin II receptor type 1 (AT1R) axis in comorbid patients. Hence, monitoring sACE2 and Ang II level in coronavirus disease 2019 comorbid patients are crucial to ensure safe and efficient intervention using therapeutic sACE2 and vaccines.