ACE2 expression in the brain during development and susceptibility to brain infection by SARS-COV-2.

The COVID-19 pandemic spread around the world due to the enormous transmission of the SARS-CoV-2 among humans. COVID-19 represents a threat to global public health. The entry of this virus into cells is greatly facilitated by the presence of angiotensin-converting enzyme 2 (ACE2) in the cell membrane. Today we do not have a precise understanding of how this receptor expresses in the brain during human development and, as a consequence, we do not know whether neural cells in the developing brain are susceptible to infection. We review the knowledge about ACE2 expression in the developing human brain, with special attention to the fetal stage. This stage corresponds to the period of the cerebral cortex formation. Therefore, SARS-CoV-2 infection during the fetal period may alter the normal development of the cerebral cortex. Although few cases have been published demonstrating vertical transmission of SARS-CoV-2 infection, the large number of infected young people may represent a problem which requires health surveillance, due to the possibility of cognitive alterations and abnormalities in the development of cortical circuits that may represent a predisposition to mental problems later in life.Copyright © 2023, Instituto de Investigaciones Medicas. All rights reserved.

Comorbidity between lung cancer and COVID-19 pneumonia: role of immunoregulatory gene transcripts in high ACE2-expressing normal lung.

Background: SARS-CoV-2 (COVID-19) elicits a T-cell antigen-mediated immune response of variable efficacy. To understand this variability, we explored transcriptomic expression of angiotensin-converting enzyme 2 (ACE2, the SARS-CoV-2 receptor) and of immunoregulatory genes in normal lung tissues from patients with non-small cell lung cancer (NSCLC). Methods: This study used the transcriptomic and the clinical data for NSCLC patients generated during the CHEMORES study [n = 123 primary resected (early-stage) NSCLC] and the WINTHER clinical trial (n = 32 metastatic NSCLC). Results: We identified patient subgroups with high and low ACE2 expression (p = 1.55 × 10-19) in normal lung tissue, presumed to be at higher and lower risk, respectively, of developing severe COVID-19 should they become infected. ACE2 transcript expression in normal lung tissues (but not in tumor tissue) of patients with NSCLC was higher in individuals with more advanced disease. High-ACE2 expressors had significantly higher levels of CD8+ cytotoxic T lymphocytes and natural killer cells but with presumably impaired function by high Thymocyte Selection-Associated High Mobility Group Box Protein TOX (TOX) expression. In addition, immune checkpoint-related molecules - PD-L1, CTLA-4, PD-1, and TIGIT - are more highly expressed in normal (but not tumor) lung tissues; these molecules might dampen immune response to either viruses or cancer. Importantly, however, high inducible T-cell co-stimulator (ICOS), which can amplify immune and cytokine reactivity, significantly correlated with high ACE2 expression in univariable analysis of normal lung (but not lung tumor tissue). Conclusions: We report a normal lung immune-tolerant state that may explain a potential comorbidity risk between two diseases - NSCLC and susceptibility to COVID-19 pneumonia. Further, a NSCLC patient subgroup has normal lung tissue expressing high ACE2 and high ICOS transcripts, the latter potentially promoting a hyperimmune response, and possibly leading to severe COVID-19 pulmonary compromise.

Increased circulating microparticles contribute to severe infection and adverse outcomes of COVID-19 in patients with diabetes.

Patients with diabetes infected with COVID-19 have greater mortality than those without comorbidities, but the underlying mechanisms remain unknown. This study aims to identify the mechanistic interactions between diabetes and severe COVID-19. Microparticles (MPs), the cell membrane-derived vesicles released on cell activation, are largely increased in patients with diabetes. To date, many mechanisms have been postulated for increased severity of COVID-19 in patients with underlying conditions, but the contributions of excessive MPs in patients with diabetes have been overlooked. This study characterizes plasma MPs from normal human subjects and patients with type 2 diabetes in terms of amount, cell origins, surface adhesive properties, ACE2 expression, spike protein binding capacity, and their roles in SARS-CoV-2 infection. Results showed that over 90% of plasma MPs express ACE2 that binds the spike protein of SARS-CoV-2. MPs in patients with diabetes increase 13-fold in quantity and 11-fold in adhesiveness when compared with normal subjects. Perfusion of human plasma with pseudo-typed SARS-CoV-2 virus or spike protein-bound MPs into human endothelial cell-formed microvessels-on-a chip demonstrated that MPs from patients with diabetes, not normal subjects, interact with endothelium and carry SARS-CoV-2 into cells through endocytosis, providing additional virus entry pathways and enhanced infection. Results also showed a large percentage of platelet-derived tissue factor-bearing MPs in diabetic plasma, which could contribute to thrombotic complications with SARS-CoV-2 infection. This study reveals a dual role of diabetic MPs in promoting SARS-CoV-2 entry and propagating vascular inflammation. These findings provide novel mechanistic insight into the high prevalence of COVID-19 in patients with diabetes and their propensity to develop severe vascular complications.NEW & NOTEWORTHY This study provides the first evidence that over 90% of human plasma microparticles express ACE2 that binds SARS-CoV-2 S protein with high affinity. Thus, the highly elevated adhesive circulating microparticles identified in patients with diabetes not only have greater SARS-CoV-2 binding capacity but also enable additional viral entry through virus-bound microparticle-endothelium interactions and enhanced infection. These findings reveal a novel mechanistic insight into the adverse outcomes of COVID-19 in patients with diabetes.

Distinct Disease Severity Between Children and Older Adults With Coronavirus Disease 2019 (COVID-19): Impacts of ACE2 Expression, Distribution, and Lung Progenitor Cells.

BACKGROUND: Children and older adults with coronavirus disease 2019 (COVID-19) display a distinct spectrum of disease severity yet the risk factors aren't well understood. We sought to examine the expression pattern of angiotensin-converting enzyme 2 (ACE2), the cell-entry receptor for severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), and the role of lung progenitor cells in children and older patients. METHODS: We retrospectively analyzed clinical features in a cohort of 299 patients with COVID-19. The expression and distribution of ACE2 and lung progenitor cells were systematically examined using a combination of public single-cell RNA-seq data sets, lung biopsies, and ex vivo infection of lung tissues with SARS-CoV-2 pseudovirus in children and older adults. We also followed up patients who had recovered from COVID-19. RESULTS: Compared with children, older patients (>50 years.) were more likely to develop into serious pneumonia with reduced lymphocytes and aberrant inflammatory response (P = .001). The expression level of ACE2 and lung progenitor cell markers were generally decreased in older patients. Notably, ACE2 positive cells were mainly distributed in the alveolar region, including SFTPC positive cells, but rarely in airway regions in the older adults (P < .01). The follow-up of discharged patients revealed a prolonged recovery from pneumonia in the older (P < .025). CONCLUSIONS: Compared to children, ACE2 positive cells are generally decreased in older adults and mainly presented in the lower pulmonary tract. The lung progenitor cells are also decreased. These risk factors may impact disease severity and recovery from pneumonia caused by SARS-Cov-2 infection in older patients.

Role of ACE2-Ang (1-7)-Mas axis in post-COVID-19 complications and its dietary modulation.

Severe acute respiratory syndrome-coronavirus-2 (COVID-19) virus uses Angiotensin-Converting Enzyme 2 (ACE2) as a gateway for their entry into the human body. The ACE2 with cleaved products have emerged as major contributing factors to multiple physiological functions and pathogenic complications leading to the clinical consequences of the COVID-19 infection Decreased ACE2 expression restricts the viral entry into the human cells and reduces the viral load. COVID-19 infection reduces the ACE2 expression and induces post-COVID-19 complications like pneumonia and lung injury. The modulation of the ACE2-Ang (1-7)-Mas (AAM) axis is also being explored as a modality to treat post-COVID-19 complications. Evidence indicates that specific food components may modulate the AAM axis. The variations in the susceptibility to COVID-19 infection and the post-COVID its complications are being correlated with varied dietary habits. Some of the food substances have emerged to have supportive roles in treating post-COVID-19 complications and are being considered as adjuvants to the COVID-19 therapy. It is possible that some of their active ingredients may emerge as the direct treatment for the COVID-19.

Oral Mucosa Could Be an Infectious Target of SARS-CoV-2.

The World Health Organization reported that severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) transmission is caused by respiratory droplets and aerosols from the oral cavity of infected patients. The angiotensin-converting enzyme 2 (ACE2) is considered the host functional protein for SARS-CoV-2 infection. In this article, we first revealed that the positive proportion of ACE2 expression in gingival cells collected from the gingival sulcus was increased to the same level as the tongue. Our data demonstrate that cells in the gingival sulcus may be a new entry point for the SARS-CoV-2 virus via a high expression of ACE2. In addition, we first evaluated the expression of ACE2 in various sites of the oral cavity with noninvasive, convenient liquid-based cytology. The liquid-based cytology evaluation of oral tissue may provide a novel preventive medical avenue against COVID-19.

Mendelian randomization analysis provides causality of smoking on the expression of ACE2, a putative SARS-CoV-2 receptor.

Background: To understand a causal role of modifiable lifestyle factors in angiotensin-converting enzyme 2 (ACE2) expression (a putative severe acute respiratory syndrome coronavirus 2 [SARS-CoV-2] receptor) across 44 human tissues/organs, and in coronavirus disease 2019 (COVID-19) susceptibility and severity, we conducted a phenome-wide two-sample Mendelian randomization (MR) study. Methods: More than 500 genetic variants were used as instrumental variables to predict smoking and alcohol consumption. Inverse-variance weighted approach was adopted as the primary method to estimate a causal association, while MR-Egger regression, weighted median, and MR pleiotropy residual sum and outlier (MR-PRESSO) were performed to identify potential horizontal pleiotropy. Results: We found that genetically predicted smoking intensity significantly increased ACE2 expression in thyroid (ß=1.468, p=1.8×10-8), and increased ACE2 expression in adipose, brain, colon, and liver with nominal significance. Additionally, genetically predicted smoking initiation significantly increased the risk of COVID-19 onset (odds ratio=1.14, p=8.7×10-5). No statistically significant result was observed for alcohol consumption. Conclusions: Our work demonstrates an important role of smoking, measured by both status and intensity, in the susceptibility to COVID-19. Funding: XJ is supported by research grants from the Swedish Research Council (VR-2018-02247) and Swedish Research Council for Health, Working Life and Welfare (FORTE-2020-00884).

Dodging COVID-19 infection: low expression and localization of ACE2 and TMPRSS2 in multiple donor-derived lines of human umbilical cord-derived mesenchymal stem cells.

BACKGROUND: Mesenchymal stem cells derived from human umbilical cord (hUC-MSCs) have immunomodulatory properties that are of interest to treat novel coronavirus disease 2019 (COVID-19). Leng et al. recently reported that hUC-MSCs derived from one donor negatively expressed Angiotensin-Converting Enzyme 2 (ACE2), a key protein for viral infection along with Transmembrane Serine Protease 2 (TMPRSS2). The purpose of this study was to quantify the expression of ACE2 and TMPRSS2 in hUC-MSCs lots derived from multiple donors using molecular-based techniques in order to demonstrate their inability to be a host to SARS-CoV-2. METHODS: Expression of ACE2 and TMPRSS2 was analyzed in 24 lots of hUC-MSCs derived from Wharton's jelly via quantitative polymerase chain reaction (qPCR), Western Blot, immunofluorescence and flow cytometry using 24 different donors. RESULTS: hUC-MSCs had significantly lower ACE2 (p = 0.002) and TMPRSS2 (p = 0.008) expression compared with human lung tissue homogenates in Western blot analyses. Little to no expression of ACE2 was observed in hUC-MSC by qPCR, and they were not observable with immunofluorescence in hUC-MSCs cell membranes. A negative ACE2 and TMPRSS2 population percentage of 95.3% ± 15.55 was obtained for hUC-MSCs via flow cytometry, with only 4.6% ACE2 and 29.5% TMPRSS2 observable positive populations. CONCLUSIONS: We have demonstrated negative expression of ACE2 and low expression of TMPRSS2 in 24 lots of hUC-MSCs. This has crucial implications for the design of future therapeutic options for COVID-19, since hUC-MSCs would have the ability to "dodge" viral infection to exert their immunomodulatory effects.

The SARS-CoV-2 host cell receptor ACE2 correlates positively with immunotherapy response and is a potential protective factor for cancer progression.

The severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) has infected more than 29 million people and has caused more than 900,000 deaths worldwide as of September 14, 2020. The SARS-CoV-2 human cell receptor ACE2 has recently received extensive attention for its role in SARS-CoV-2 infection. Many studies have also explored the association between ACE2 and cancer. However, a systemic investigation into associations between ACE2 and oncogenic pathways, tumor progression, and clinical outcomes in pan-cancer remains lacking. Using cancer genomics datasets from the Cancer Genome Atlas (TCGA) program, we performed computational analyses of associations between ACE2 expression and antitumor immunity, immunotherapy response, oncogenic pathways, tumor progression phenotypes, and clinical outcomes in 13 cancer cohorts. We found that ACE2 upregulation was associated with increased antitumor immune signatures and PD-L1 expression, and favorable anti-PD-1/PD-L1/CTLA-4 immunotherapy response. ACE2 expression levels inversely correlated with the activity of cell cycle, mismatch repair, TGF-ß, Wnt, VEGF, and Notch signaling pathways. Moreover, ACE2 expression levels had significant inverse correlations with tumor proliferation, stemness, and epithelial-mesenchymal transition. ACE2 upregulation was associated with favorable survival in pan-cancer and in multiple individual cancer types. These results suggest that ACE2 is a potential protective factor for cancer progression. Our data may provide potential clinical implications for treating cancer patients infected with SARS-CoV-2.

In vitro and in vivo identification of clinically approved drugs that modify ACE2 expression.

The COVID-19 pandemic caused by SARS-CoV-2 has is a global health challenge. Angiotensin-converting enzyme 2 (ACE2) is the host receptor for SARS-CoV-2 entry. Recent studies have suggested that patients with hypertension and diabetes treated with ACE inhibitors (ACEIs) or angiotensin receptor blockers have a higher risk of COVID-19 infection as these drugs could upregulate ACE2, motivating the study of ACE2 modulation by drugs in current clinical use. Here, we mined published datasets to determine the effects of hundreds of clinically approved drugs on ACE2 expression. We find that ACEIs are enriched for ACE2-upregulating drugs, while antineoplastic agents are enriched for ACE2-downregulating drugs. Vorinostat and isotretinoin are the top ACE2 up/downregulators, respectively, in cell lines. Dexamethasone, a corticosteroid used in treating severe acute respiratory syndrome and COVID-19, significantly upregulates ACE2 both in vitro and in vivo. Further top ACE2 regulators in vivo or in primary cells include erlotinib and bleomycin in the lung and vancomycin, cisplatin, and probenecid in the kidney. Our study provides leads for future work studying ACE2 expression modulators.

Expression of the SARS-CoV-2 Entry Proteins, ACE2 and TMPRSS2, in Cells of the Olfactory Epithelium: Identification of Cell Types and Trends with Age.

The COVID-19 pandemic revealed that there is a loss of smell in many patients, including in infected but otherwise asymptomatic individuals. The underlying mechanisms for the olfactory symptoms are unclear. Using a mouse model, we determined whether cells in the olfactory epithelium express the obligatory receptors for entry of the SARS-CoV-2 virus by using RNAseq, RT-PCR, in situ hybridization, Western blot, and immunocytochemistry. We show that the cell surface protein ACE2 and the protease TMPRSS2 are expressed in sustentacular cells of the olfactory epithelium but not, or much less, in most olfactory receptor neurons. These data suggest that sustentacular cells are involved in SARS-CoV-2 virus entry and impairment of the sense of smell in COVID-19 patients. We also show that expression of the entry proteins increases in animals of old age. This may explain, if true also in humans, why individuals of older age are more susceptible to the SARS-CoV-2 infection.

SARS-CoV-2: Olfaction, Brain Infection, and the Urgent Need for Clinical Samples Allowing Earlier Virus Detection.

The novel SARS-CoV-2 virus has very high infectivity, which allows it to spread rapidly around the world. Attempts at slowing the pandemic at this stage depend on the number and quality of diagnostic tests performed. We propose that the olfactory epithelium from the nasal cavity may be a more appropriate tissue for detection of SARS-CoV-2 virus at the earliest stages, prior to onset of symptoms or even in asymptomatic people, as compared to commonly used sputum or nasopharyngeal swabs. Here we emphasize that the nasal cavity olfactory epithelium is the likely site of enhanced binding of SARS-CoV-2. Multiple non-neuronal cell types present in the olfactory epithelium express two host receptors, ACE2 and TMPRSS2 proteases, that facilitate SARS-CoV-2 binding, replication, and accumulation. This may be the underlying mechanism for the recently reported cases of smell dysfunction in patients with COVID-19. Moreover, the possibility of subsequent brain infection should be considered which begins in olfactory neurons. In addition, we discuss the possibility that olfactory receptor neurons may initiate rapid immune responses at early stages of the disease. We emphasize the need to undertake research focused on additional aspects of SARS-CoV-2 actions in the nervous system, especially in the olfactory pathway.