Interaction of SARS-CoV-2 and Other Coronavirus With ACE (Angiotensin-Converting Enzyme)-2 as Their Main Receptor: Therapeutic Implications

A Novel Soluble ACE2 Variant with Prolonged Duration of Action Neutralizes SARS-CoV-2 Infection in Human Kidney Organoids

BACKGROUND

There is an urgent need for approaches to prevent and treat SARS-CoV-2 infection. Administration of soluble ACE2 protein acting as a decoy to bind to SARS-CoV-2 should limit viral uptake mediated by binding to membrane-bound full-length ACE2, and further therapeutic benefit should result from ensuring enzymatic ACE2 activity to affected organs in patients with COVID-19.

METHODS

A short variant of human soluble ACE2 protein consisting of 618 amino acids (hACE2 1-618) was generated and fused with an albumin binding domain (ABD) using an artificial gene encoding ABDCon, with improved albumin binding affinity. Human kidney organoids were used for infectivity studies of SARS-CoV-2 in a BSL-3 facility to examine the neutralizing effect of these novel ACE2 variants.

RESULTS

Whereas plasma ACE2 activity of the naked ACE2 1-618 and ACE2 1-740 lasted about 8 hours, the ACE2 1-618-ABD resulted in substantial activity at 96 hours, and it was still biologically active 3 days after injection. Human kidney organoids express ACE2 and TMPRSS2, and when infected with SARS-CoV-2, our modified long-acting ACE2 variant neutralized infection.

CONCLUSIONS

This novel ACE2 1-618-ABD can neutralize SARS-CoV-2 infectivity in human kidney organoids, and its prolonged duration of action should ensure improved efficacy to prevent viral escape and dosing convenience.

Targeting ACE2 for COVID-19 Therapy: Opportunities and Challenges

The coronavirus disease (COVID-19) pandemic is sweeping the globe. Even with a number of effective vaccines being approved and available to the public, new cases and escalating mortality are climbing every day. ACE2 (angiotensin-converting enzyme 2) is the primary receptor for the COVID-19 causative virus, severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), and its complexation with spike proteins plays a crucial role in viral entry into host cells and the subsequent infection. Blocking this binding event or reducing the accessibility of the virus to the ACE2 receptor, represents an alternative strategy to prevent COVID-19. In addition, the biological significance of ACE2 in modulating the innate immune system and tissue repair cascades and anchors its therapeutic potential for treating the infected patients. In this viewpoint article, we review the current efforts of exploiting ACE2 as a therapeutic target to address this dire medical need. We also provide a holistic view of the pros and cons of each treatment strategy. We highlight the fundamental and translational challenges in moving these research endeavors to clinical applications.

Multifunctional angiotensin converting enzyme 2, the SARS-CoV-2 entry receptor, and critical appraisal of its role in acute lung injury

The recent emergence of coronavirus disease-2019 (COVID-19) as a pandemic affecting millions of individuals has raised great concern throughout the world, and the severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2) was identified as the causative agent for COVID-19. The multifunctional protein angiotensin converting enzyme 2 (ACE2) is accepted as its primary target for entry into host cells. In its enzymatic function, ACE2, like its homologue ACE, regulates the renin-angiotensin system (RAS) critical for cardiovascular and renal homeostasis in mammals. Unlike ACE, however, ACE2 drives an alternative RAS pathway by degrading Ang-II and thus operates to balance RAS homeostasis in the context of hypertension, heart failure, and cardiovascular as well as renal complications of diabetes. Outside the RAS, ACE2 hydrolyzes key peptides, such as amyloid-β, apelin, and [des-Arg9]-bradykinin. In addition to its enzymatic functions, ACE2 is found to regulate intestinal amino acid homeostasis and the gut microbiome. Although the non-enzymatic function of ACE2 as the entry receptor for SARS-CoV-2 has been well established, the contribution of enzymatic functions of ACE2 to the pathogenesis of COVID-19-related lung injury has been a matter of debate. A complete understanding of this central enzyme may begin to explain the various symptoms and pathologies seen in SARS-CoV-2 infected individuals, and may aid in the development of novel treatments for COVID-19.

Prevalence of Symptoms in Patients Discharged from COVID Care Facility of NIMS Hospital: Is RT PCR Negativity Truly Reflecting Recovery? A Single-Centre Observational Study

PURPOSE

To assess the prevalence of post-COVID symptoms in patients with recovered COVID-19 (nasopharyngeal RT PCR negative) who were discharged from an acute COVID care facility at a tertiary care teaching hospital in North India.

METHODS

This study was an observational study with retrospective data collection, conducted in the COVID follow-up clinic, a combined clinic of medicine and endocrinology. Patients discharged from the acute COVID care facility were recruited after 14 days of discharge if they fulfilled inclusion and exclusion criteria. The retrospective data was collected from the hospital records/EMR and analysed by the SPSSv23.

RESULTS

Fifty patients, who fulfilled the inclusion and exclusion criteria, were included in the study. The Mean age of patients was 53.4±13.8 years (range 28-77). Seventy six percent were male, and 38% had type 2 diabetes. Fever (94%), cough (78%) and breathlessness (68%), were the most common symptoms at presentation to acute care facility. Oxygen saturation at presentation had a negative correlation with D-Dimer, age, and C reactive protein. When patients were evaluated clinically, after 14 days (range 15 to 50 days) of the discharge, 82% of patients had at least one persistent symptom. Fatigue (74%) was the most common symptoms in follow-up followed by breathlessness (44%), and muscle weakness (36%). Two patients had persistent fever, even after negative RT PCR status.

CONCLUSION

Patients discharged from the acute COVID care facility had a high prevalence of post-COVID symptoms even after 14 days.

Could SARS-CoV-2 blocking of ACE2 in endothelial cells result in upregulation of CX3CL1, promoting thrombosis in COVID-19 patients?

SARS-CoV-2 is the causal agent of COVID-19 disease. Currently, infection with SARS-CoV-2 has been the cause of death of over 2.5 million people globally, and there is still no effective curative treatment. Clinically, the severe symptoms caused by COVID-19, in addition to pneumonia, are associated with the development of hyperinflammatory syndrome and thrombosis. It is urgent to expand our understanding of the molecular mechanisms involved in the pathophysiology of COVID-19. This article discusses the potential role that the chemokine CX3CL1 could have in the development of COVID-19-associated thrombosis. CX3CL1 is abundantly expressed by activated endothelium and is an important regulator of many aspects of endothelial function and dysfunction, including thrombosis. The generation of hypotheses about molecules that could be relevant in well-defined aspects of the pathophysiology of COVID-19 encourages the development of basic and clinical studies, that could help find effective and much needed treatments.

In-Silico Drug Designing of Spike Receptor with Its ACE2 Receptor and Nsp10/Nsp16 MTase Complex Against SARS-CoV-2

The realm Riboviria constitutes Coronaviruses, which led to the emergence of the pandemic COVID 19 in the twenty-first century affected millions of lives. At present, the management of COVID 19 largely depends on antiviral therapeutics along with the anti-inflammatory drug. The vaccine is under the final clinical phase, and emergency use is available. We aim at ACE2 and Nsp10/Nsp16 MTase as potential drug candidate in COVID 19 management in the present work. For drug designing, various computational simulation strategies have been employed like Swiss-Model, Hawk Dock, HDOCK, py Dock, and PockDrug for homology modeling, binding energies of the molecule with a target, simulate the conformation and binding poses, statistics of protein lock with target key and drug ability, respectively. The current in-silico screening depicts that the spike protein receptor is complementary to the target when bound to each other and forms a stable complex. The MMGBSA free energy binding property of receptor and ligand is critical. The intermolecular Statistics with the target Nsp10/Nsp16 MTase complex are plausible. We have also observed a high-affinity pocket binding site with the target. Therefore, the favorable intermolecular interactions and Physico-chemical properties emanate as a drug candidate treating COVID-19. This study has approached computational tools to analyze the conformation, binding affinity, and drug ability of receptor-ligand. Thus, the spike receptor with its ACE2 receptor with Nsp10/Nsp16 MTase complex would be a potent drug against SARS CoV-2 and can cure the infection as per consensus scoring.

Mechanisms Modified by (-)-Epicatechin and Taxifolin Relevant for the Treatment of Hypertension and Viral Infection: Knowledge from Preclinical Studies

Various studies have shown that certain flavonoids, flavonoid-containing plant extracts, and foods can improve human health. Experimental studies showed that flavonoids have the capacity to alter physiological processes as well as cellular and molecular mechanisms associated with their antioxidant properties. An important function of flavonoids was determined in the cardiovascular system, namely their capacity to lower blood pressure and to improve endothelial function. (-)-Epicatechin and taxifolin are two flavonoids with notable antihypertensive effects and multiple beneficial actions in the cardiovascular system, but they also possess antiviral effects, which may be of particular importance in the ongoing pandemic situation. Thus, this review is focused on the current knowledge of (-)-epicatechin as well as (+)-taxifolin and/or (-)-taxifolin-modified biological action and underlining molecular mechanisms determined in preclinical studies, which are relevant not only to the treatment of hypertension per se but may provide additional antiviral benefits that could be relevant to the treatment of hypertensive subjects with SARS-CoV-2 infection.

A novel soluble ACE2 protein totally protects from lethal disease caused by SARS-CoV-2 infection

Severe acute respiratory syndrome coronavirus type 2 (SARS-CoV-2) uses full-length angiotensin converting enzyme 2 (ACE2), which is membrane bound, as its initial cell contact receptor preceding viral entry. Here we report a human soluble ACE2 variant fused with a 5kD albumin binding domain (ABD) and bridged via a dimerization motif hinge-like 4-cysteine dodecapeptide, which we term ACE2 1-618-DDC-ABD. This protein is enzymatically active, has increased duration of action in vivo conferred by the ABD-tag, and displays 20-30-fold higher binding affinity to the SARS-CoV-2 receptor binding domain than its des-DDC monomeric form (ACE2 1-618-ABD) due to DDC-linked dimerization. ACE2 1-618-DDC-ABD was administered for 3 consecutive days to transgenic k18-hACE2 mice, a model that develops lethal SARS-CoV-2 infection, to evaluate the preclinical preventative/ therapeutic value for COVID-19. Mice treated with ACE2 1-618-DDC-ABD developed a mild to moderate disease for the first few days assessed by a clinical score and modest weight loss. The untreated control animals, by contrast, became severely ill and had to be sacrificed by day 6/7 and lung histology revealed extensive pulmonary alveolar hemorrhage and mononuclear infiltrates. At 6 days, mortality was totally prevented in the treated group, lung histopathology was improved and viral titers markedly reduced. This demonstrates for the first time in vivo the preventative/ therapeutic potential of a novel soluble ACE2 protein in a preclinical animal model.

Endothelial Cells in Emerging Viral Infections

There are several reasons to consider the role of endothelial cells in COVID-19 and other emerging viral infections. First, severe cases of COVID-19 show a common breakdown of central vascular functions. Second, SARS-CoV-2 replicates in endothelial cells. Third, prior deterioration of vascular function exacerbates disease, as the most common comorbidities of COVID-19 (obesity, hypertension, and diabetes) are all associated with endothelial dysfunction. Importantly, SARS-CoV-2's ability to infect endothelium is shared by many emerging viruses, including henipaviruses, hantavirus, and highly pathogenic avian influenza virus, all specifically targeting endothelial cells. The ability to infect endothelium appears to support generalised dissemination of infection and facilitate the access to certain tissues. The disturbed vascular function observed in severe COVID-19 is also a prominent feature of many other life-threatening viral diseases, underscoring the need to understand how viruses modulate endothelial function. We here review the role of vascular endothelial cells in emerging viral infections, starting with a summary of endothelial cells as key mediators and regulators of vascular and immune responses in health and infection. Next, we discuss endotheliotropism as a possible virulence factor and detail features that regulate viruses' ability to attach to and enter endothelial cells. We move on to review how endothelial cells detect invading viruses and respond to infection, with particular focus on pathways that may influence vascular function and the host immune system. Finally, we discuss how endothelial cell function can be dysregulated in viral disease, either by viral components or as bystander victims of overshooting or detrimental inflammatory and immune responses. Many aspects of how viruses interact with the endothelium remain poorly understood. Considering the diversity of such mechanisms among different emerging viruses allows us to highlight common features that may be of general validity and point out important challenges.

Soluble ACE2 as a potential therapy for COVID-19

Soluble angiotensin-converting enzyme 2 (sACE2) could be a therapeutic option to treat coronavirus disease 2019 (COVID-19) infection. Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) utilizes ACE2 receptors on cell surfaces to gain intracellular entry, making them an ideal target for therapy. High-affinity variants of sACE2, engineered using high-throughput mutagenesis, are capable of neutralizing COVID-19 infection as decoy receptors. These variants compete with native ACE2 present on cells by binding with spike (S) protein of SARS-CoV-2, making native ACE2 on cell surfaces available to convert angiotensin II to angiotensin-1,7, thus alleviating the exaggerated inflammatory response associated with COVID-19 infection. This article explores the use of sACE2 as potential therapy for COVID-19 infection.

Targeting Neurological Manifestations of Coronaviruses by Candidate Phytochemicals: A Mechanistic Approach

The novel coronavirus 2019 (COVID-19) caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) has made a wide range of manifestations. In this regard, growing evidence is focusing on COVID-19 neurological associations; however, there is a lack of established pathophysiological mechanisms and related treatments. Accordingly, a comprehensive review was conducted, using electronic databases, including PubMed, Scopus, Web of Science, and Cochrane, along with the author's expertize in COVID-19 associated neuronal signaling pathways. Besides, potential phytochemicals have been provided against neurological signs of COVID-19. Considering a high homology among SARS-CoV, Middle East Respiratory Syndrome and SARS-CoV-2, revealing their precise pathophysiological mechanisms seems to pave the road for the treatment of COVID-19 neural manifestations. There is a complex pathophysiological mechanism behind central manifestations of COVID-19, including pain, hypo/anosmia, delirium, impaired consciousness, pyramidal signs, and ischemic stroke. Among those dysregulated neuronal mechanisms, neuroinflammation, angiotensin-converting enzyme 2 (ACE2)/spike proteins, RNA-dependent RNA polymerase and protease are of special attention. So, employing multi-target therapeutic agents with considerable safety and efficacy seems to show a bright future in fighting COVID-19 neurological manifestations. Nowadays, natural secondary metabolites are highlighted as potential multi-target phytochemicals in combating several complications of COVID-19. In this review, central pathophysiological mechanisms and therapeutic targets of SARS-CoV-2 has been provided. Besides, in terms of pharmacological mechanisms, phytochemicals have been introduced as potential multi-target agents in combating COVID-19 central nervous system complications.

Excessive matrix metalloproteinase-1 and hyperactivation of endothelial cells occurred in COVID-19 patients and were associated with the severity of COVID-19

COVID-19 starts as a respiratory disease that can progress to pneumonia, severe acute respiratory syndrome (SARS), and multi-organ failure. Growing evidence suggests that COVID-19 is a systemic illness that primarily injures the vascular endothelium, yet the underlying mechanisms remain unknown. SARS-CoV-2 infection is believed to trigger a cytokine storm that plays a critical role in the pathogenesis of endothelialitis and vascular injury, eventually leading to respiratory and multi-organ failure in COVID-19 patients. We used a multiplex immunoassay to systematically profile and compare 65 inflammatory cytokines/chemokines/growth factors in plasma samples from 24 hospitalized (severe/critical) COVID-19 patients, 14 mild/moderate cases, and 13 healthy controls (HCs). Patients with severe/critical and mild/moderate COVID-19 had significantly higher plasma levels of 20 analytes than HCs. Surprisingly, only one cytokine (MIF) was among these altered analytes, while the rest were chemokines and growth factors. In addition, only MMP-1 and VEGF-A were significantly elevated in hospitalized COVID-19 patients when compared to mild/moderate cases. Given that excessive MMP-1 plays a central role in tissue destruction in a wide variety of vascular diseases and that elevated VEGF-A, an EC activation marker, increases vascular permeability, we further studied MMP-1 enzymatic activity and other EC activation markers such as soluble forms of CD146, ICAM-1, and VCAM-1. We found that plasma MMP-1 enzymatic activity and plasma levels of MMP-1 and EC activation markers were highly dysregulated in COVID-19 patients. Some dysregulations were associated with patients' age or gender, but not with race. Our results demonstrate that COVID-19 patients have distinct inflammatory profiles that are distinguished from the cytokine storms in other human diseases. Excessive MMP-1 and hyperactivation of ECs occur in COVID-19 patients and are associated with the severity of COVID-19.

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.

Clinical spectrum and outcome of patients visiting coronavirus screening centre in North India and clinical predictors for COVID-19

AIM

The aim of this study is to elucidate the demographics, symptoms and outcome of sick persons visiting coronavirus (COVID) screening OPD of a tertiary institute in North India.

STUDY DESIGN

The present descriptive, prospective study was done on 1030 patients and information about presenting symptoms, demographics (age, sex, nationality, residence), contact and travel history, comorbidities etc., were recorded. On the basis of criteria given by Indian Council of Medical Research, patients were divided into suspected (SARS-CoV-2) and non-suspected group. Of the suspected patients, with RT-PCR test positive were classified as confirmed COVID-19 case and negative RT-PCR symptomatic individual were defined as negative COVID-19 case.

RESULTS

Out of the total patients, 65.6% were male and 34.4% were females. The mean age was 37.04 years. Fever 49.3%, cough 57.1% and sore throat 43.5% were the main symptoms. Comorbidities were seen in 8.5% patients with hypertension (3.5%) and diabetes mellitus (3.4%). Forty patients were positive. Highly significant correlation (P < 0.01) was found between COVID-19 positive status and in patients without any symptoms, between COVID-19 and cough and sore throat, between COVID-19 and comorbidity (diabetes mellitus), between COVID-19 and high-risk exposures (resident of hot spot and history of contact with confirmed case). Our study also found COVID-19 positive status, shortness of breath and tachycardia as independent predictors of mortality (P < 0.05).

CONCLUSIONS

Most of the patients were young adults and males were mainly affected. Main presentation was cough followed by fever. Infectivity was higher in patients who had underlying comorbid diseases, especially diabetes and chronic kidney disease. Critical patients with decreased oxygen saturation, tachypnoea and tachycardia had strong predictability for COVID-19 positivity. COVID-19 positive status, shortness of breath and tachycardia are important predictors of mortality.

ACE2, the kidney and the emergence of COVID-19 two decades after ACE2 discovery

Angiotensin-converting enzyme II (ACE2) is a homologue of angiotensin-converting enzyme discovered in 2000. From the initial discovery, it was recognized that the kidneys were organs very rich on ACE2. Subsequent studies demonstrated the precise localization of ACE2 within the kidney and the importance of this enzyme in the metabolism of Angiotensin II and the formation of Angiotensin 1–7. With the recognition early in 2020 of ACE2 being the main receptor of severe acute respiratory syndrome Coronavirus 2 (SARS-CoV-2), the interest in this protein has dramatically increased. In this review, we will focus on kidney ACE2; its localization, its alterations in hypertension, diabetes, the effect of ACE inhibitors and angiotensin type 1 receptor blockers (ARBs) on ACE2 and the potential use of ACE2 recombinant proteins therapeutically for kidney disease.

We also describe the emerging kidney manifestations of COVID-19, namely the frequent development of acute kidney injury. The possibility that binding of SARS-CoV-2 to kidney ACE2 plays a role in the kidney manifestations is also briefly discussed.

ACE2: The Major Cell Entry Receptor for SARS-CoV-2

Despite the unprecedented effort of the scientific community, the novel SARS-CoV-2 virus has infected more than 46 million people worldwide, killing over one million two hundred thousand. Understanding the mechanisms by which some individuals are more susceptible to SARS-CoV-2 infection and why a subgroup of them are prone to experience severe pneumonia, and death should lead to a better approach and more effective treatments for COVID-19. Here, we focus our attention on ACE2, a primary receptor of SARS-CoV-2. We will discuss its biology, tissue expression, and post-translational regulation that determine its potential to be employed by SARS-CoV-2 for cell entry. Particular attention will be given to how the ACE2 soluble form can have a great impact on disease progression and thus be used in a potential therapeutic strategy. Furthermore, we will discuss repercussions that SARS-CoV-2/ACE2 binding has on the renin–angiotensin system and beyond. Indeed, although mostly neglected, ACE2 can also act on [des-Arg 937]-bradykinin of the kinin–kallikrein system regulating coagulation and inflammation. Thorough comprehension of the role that ACE2 plays in different pathways will be the key to assess the impact that SARS-CoV-2/ACE2 binding has on organismal physiology and will help us to find better therapies and diagnostic tools.