Role of angiotensin-converting enzyme 2 and pericytes in cardiac complications of COVID-19 infection

The fate and role of the pericytes in myocardial diseases

The adult mammalian heart contains a large population of pericytes that play important roles in homeostasis and disease. In the normal heart, pericytes regulate microvascular permeability and flow. Myocardial diseases are associated with marked alterations in pericyte phenotype and function. This review manuscript discusses the role of pericytes in cardiac homeostasis and disease. Following myocardial infarction (MI), cardiac pericytes participate in all phases of cardiac repair. During the inflammatory phase, pericytes may secrete cytokines and chemokines and may regulate leukocyte trafficking, through formation of intercellular gaps that serve as exit points for inflammatory cells. Moreover, pericyte contraction induces microvascular constriction, contributing to the pathogenesis of 'no-reflow' in ischemia and reperfusion. During the proliferative phase, pericytes are activated by growth factors, such as transforming growth factor (TGF)-β and contribute to fibrosis, predominantly through secretion of fibrogenic mediators. A fraction of pericytes acquires fibroblast identity but contributes only to a small percentage of infarct fibroblasts and myofibroblasts. As the scar matures, pericytes form a coat around infarct neovessels, promoting stabilization of the vasculature. Pericytes may also be involved in the pathogenesis of chronic heart failure, by regulating inflammation, fibrosis, angiogenesis and myocardial perfusion. Pericytes are also important targets of viral infections (such as SARS-CoV2) and may be implicated in the pathogenesis of cardiac complications of COVID19. Considering their role in myocardial inflammation, fibrosis and angiogenesis, pericytes may be promising therapeutic targets in myocardial disease.

The Impact of Cardiovascular Antecedents on the Prognosis of COVID-19 Critically Ill Patients

Background/Objectives: The objective of the study is to analyze the impact of cardiovascular history on mortality in COVID-19 patients, hospitalized in the intensive care unit with indications for continuous positive airway pressure (CPAP) and subsequently mechanical ventilation, without oncological disease. Methods: A retrospective observational study was carried out on a group of 108 critical COVID-19 patients. We compared demographic data, paraclinical and clinical parameters, days of hospitalization, and mortality rate between two groups of patients, one group with a history of cardiovascular disease (81 patients) and a group without a history of cardiovascular disease (27 patients). Results: Patients with cardiovascular antecedents had a higher mortality rate than those without cardiovascular antecedents, presenting severe forms with shorter survival time in the intensive care unit and increased inflammatory evidence. Compared to patients without a history of cardiovascular illness, those with cardiovascular disease had a lower average age, and developed a severe form of COVID-19. Conclusions: Cardiovascular antecedents can worsen the prognosis of patients with COVID-19, requiring a careful screening and multidisciplinary approach.

Sympathetic remodeling and altered angiotensin-converting enzyme 2 localization occur in patients with cardiac disease but are not exacerbated by severe COVID-19

PURPOSE

Remodeling of sympathetic nerves and ACE2 has been implicated in cardiac pathology, and ACE2 also serves as a receptor for SARS-CoV-2. However, there is limited histological knowledge about the transmural distribution of sympathetic nerves and the cellular localization and distribution of ACE2 in human left ventricles from normal or diseased hearts. Goals of this study were to establish the normal pattern for these parameters and determine changes that occurred in decedents with cardiovascular disease alone compared to those with cardiac pathology and severe COVID-19.

METHODS

We performed immunohistochemical analysis on sections of left ventricular wall from twenty autopsied human hearts consisting of a control group, a cardiovascular disease group, and COVID-19 ARDS, and COVID-19 non-ARDS groups.

RESULTS

Using tyrosine hydroxylase as a noradrenergic marker, we found substantial sympathetic nerve loss in cardiovascular disease samples compared to controls. Additionally, we found heterogeneous nerve loss in both COVID-19 groups. Using an ACE2 antibody, we observed robust transmural staining localized to pericytes in the control group. The cardiovascular disease hearts displayed regional loss of ACE2 in pericytes and regional increases in staining of cardiomyocytes for ACE2. Similar changes were observed in both COVID-19 groups.

CONCLUSIONS

Heterogeneity of sympathetic innervation, which occurs in cardiac disease and is not increased by severe COVID-19, could contribute to arrhythmogenesis. The dominant localization of ACE2 to pericytes suggests that these cells would be the primary target for potential cardiac infection by SARS-CoV-2. Regional changes in ACE2 staining by myocytes and pericytes could have complex effects on cardiac pathophysiology.

Evidence of autoinflammation as a principal mechanism of myocardial injury in SARS-CoV-2 PCR-positive medical examiner cases

BACKGROUND

Disease from Severe Acute Respiratory Syndrome Coronavirus-2 (SARS-CoV-2) remains the seventh leading cause of death in the United States. Many patients infected with this virus develop later cardiovascular complications including myocardial infarctions, stroke, arrhythmia, heart failure, and sudden cardiac death (20-28%). The purpose of this study is to understand the primary mechanism of myocardial injury in patients infected with SARS-CoV-2.

METHODS

We investigated a consecutive cohort of 48 medical examiner cases who died with PCR-positive SARS-CoV-2 (COVpos) infection in 2020. We compared them to a consecutive cohort of 46 age- and sex-matched controls who were PCR-negative for SARS-CoV-2 (COVneg). Clinical information available at postmortem examination was reviewed on each patient. Formalin-fixed sections were examined using antibodies directed against CD42 (platelets), CD15 (myeloid cells), CD68 (monocytes), C4d, fibrin, CD34 (stem cell antigen), CD56 (natural killer cells), and myeloperoxidase (MPO) (neutrophils and neutrophil extracellular traps(NETs)). We used a Welch 2-sample T-test to determine significance. A cluster analysis of marker distribution was also done.

RESULTS

We found a significant difference between COVpos and COVneg samples for CD42, CD15, CD68, C4d, fibrin, and MPO, all of which were significant at p < 0.001. The most prominent features were neutrophils (CD15, MPO) and MPO-positive debris suggestive of NETs. A similar distribution of platelets, monocytes, fibrin and C4d was seen in COVpos cases. Clinical features were similar in COVpos and COVneg cases for age, sex, and body mass index (BMI).

CONCLUSION

These findings suggest an autoinflammatory process is likely involved in cardiac damage during SARS-CoV-2 infection. No information about clinical cardiac disease was available.

Management of Infective Endocarditis and Tibioperoneal Mycotic Aneurysm Following COVID-19 Infection

Introduction

Infective endocarditis and mycotic tibioperoneal aneurysms are rare complications of COVID-19 infection. Medical therapy may not always be sufficient to reduce the high morbidity and mortality associated with these cardiovascular complications. Surgical treatment may need to be considered in such patients.

Report

A 56 year old male patient with diabetes, hypertension, and hyperlipidaemia developed severe pneumonia from COVID-19 infection. He was admitted to the intensive care unit (ICU) at another facility where he was ventilated for a period of six weeks. Blood culture isolated coagulase-negative Staphylococcus and an echocardiogram showed a 1.4 × 1.5 cm mitral valve vegetation. He was treated for a period of 12 weeks with various antibiotic combinations including meropenem, levofloxacin, and teicoplanin with no improvement. On presentation at the current centre, he complained of painful right calf swelling. Computed tomography angiography showed a 7 cm right tibioperoneal trunk aneurysm. He underwent lung and cardiac assessment, following which it was decided to proceed with one stage synchronous surgery. Cardiac surgery was started through a median sternotomy and Guiraudon transeptal approach, with mitral valve replacement using a bioprosthesis (Edwards Magna, size 29). This was immediately followed by a medial lower limb approach with ligation of the aneurysm, followed by arterial reconstruction using a reversed saphenous vein graft from the superficial femoral artery to the posterior tibial artery. He was placed on intravenous vancomycin and ceftriaxone for a period of six weeks. He was discharged home after day 31 on 75 mg aspirin daily. At six month follow up, he was symptom free with a palpable posterior tibial pulse.

Discussion

Increased awareness and close surveillance are necessary for patients with severe COVID-19 infection. In those who develop unusual cardiovascular complications, one stage cardiac and vascular surgery may be feasible, as described in this case.

Immunopathogenesis and immunomodulatory therapy for myocarditis

Myocarditis is an inflammatory cardiac disease characterized by the destruction of myocardial cells, infiltration of interstitial inflammatory cells, and fibrosis, and is becoming a major public health concern. The aetiology of myocarditis continues to broaden as new pathogens and drugs emerge. The relationship between immune checkpoint inhibitors, severe acute respiratory syndrome coronavirus 2, vaccines against coronavirus disease-2019, and myocarditis has attracted increased attention. Immunopathological processes play an important role in the different phases of myocarditis, affecting disease occurrence, development, and prognosis. Excessive immune activation can induce severe myocardial injury and lead to fulminant myocarditis, whereas chronic inflammation can lead to cardiac remodelling and inflammatory dilated cardiomyopathy. The use of immunosuppressive treatments, particularly cytotoxic agents, for myocarditis, remains controversial. While reasonable and effective immunomodulatory therapy is the general trend. This review focuses on the current understanding of the aetiology and immunopathogenesis of myocarditis and offers new perspectives on immunomodulatory therapies.

Pericyte Loss in Diseases

Pericytes are specialized cells located in close proximity to endothelial cells within the microvasculature. They play a crucial role in regulating blood flow, stabilizing vessel walls, and maintaining the integrity of the blood-brain barrier. The loss of pericytes has been associated with the development and progression of various diseases, such as diabetes, Alzheimer's disease, sepsis, stroke, and traumatic brain injury. This review examines the detection of pericyte loss in different diseases, explores the methods employed to assess pericyte coverage, and elucidates the potential mechanisms contributing to pericyte loss in these pathological conditions. Additionally, current therapeutic strategies targeting pericytes are discussed, along with potential future interventions aimed at preserving pericyte function and promoting disease mitigation.

Injury mechanism of COVID-19-induced cardiac complications

Heart dysfunction is one of the most life-threatening organ dysfunctions caused by coronavirus disease 2019 (COVID-19). Myocardial or cardiovascular damage is the most common extrapulmonary organ complication in critically ill patients. Understanding the pathogenesis and pathological characteristics of myocardial and vascular injury is important for improving clinical diagnosis and treatment approach. Herein, the mechanism of direct damage caused by severe acute respiratory syndrome coronavirus 2 to the heart and secondary damage caused by virus-driven inflammation was reviewed. The pathological mechanism of ischemia and hypoxia due to microthrombosis and inflammatory injury as well as the injury mechanism of tissue inflammation and single myocardial cell necrosis triggered by the viral infection of pericytes or macrophages, hypoxia, and energy metabolism disorders were described. The latter can provide a novel diagnosis, treatment, and investigation strategy for heart dysfunctions caused by COVID-19 or the Omicron variant.

Morphological Changes in the Myocardium of Patients with Post-Acute Coronavirus Syndrome: A Study of Endomyocardial Biopsies

The clinical manifestation study of post-acute sequelae of SARS-CoV-2 infection (PASC) has shown a lack of knowledge regarding its morphology and pathogenesis. The aim of this research was to investigate morphological manifestations of PASC in the myocardium.

MATERIALS AND METHODS

The study included 38 patients requiring endomyocardial biopsy (EMB) during the post-acute phase of coronavirus infection and a control group including patients requiring EMB prior to the SARS-CoV-2 pandemic. The patients' clinical and laboratory data were analyzed. Histological examination and immunohistochemistry (IHC) of the myocardial tissue was conducted with antibodies to CD3, CD68, HLA-DR, MHC1, C1q, VP1 enteroviruses, spike protein SARS-CoV-2, Ang1, von Willebrand factor (VWF), and VEGF. The morphometric analysis included counting the mean number of inflammatory infiltrate cells per mm² and evaluating the expression of SARS-CoV-2 spike protein, HLA-DR, MHC1, C1q, Ang1, VWF, and VEGF using a scoring system. If the expression of SARS-CoV-2 spike protein was >3 points, an additional IHC test with antibodies to ACE2, CD16 as well as RT-PCR testing of the myocardial tissue were performed. For two patients, immunofluorescence tests of the myocardial tissue were performed using antibody cocktails to SARS-CoV-2 spike protein/CD16, SARS-CoV-2 spike protein/CD68, CD80/CD163. The statistical data analysis was carried out using the Python programming language and libraries such as NumPy, SciPy, Pandas, and Matplotlib.

RESULTS

The study demonstrated a significant increase in the number of CD68+ macrophages in the myocardium of PASC patients compared to patients who did not have a history of COVID-19 (p = 0.014 and p = 0.007 for patients with and without myocarditis, respectively), predominantly due to M2 macrophages. An increase in the number of CD68+ macrophages was more frequently observed in patients with shorter intervals between the most recent positive SARS-CoV-2 PCR test and the time of performing the EMB (r = -0.33 and r = -0.61 for patients with and without myocarditis, respectively). The expression scores of Ang1, VEGF, VWF, and C1q in PASC patients did not significantly differ from those in EMB samples taken before 2019.

CONCLUSION

The myocardium of PASC patients demonstrated a significant increase in the number of CD68+ macrophages and a decrease in the expression of markers associated with angiopathy. No evidence of coronavirus-associated myocarditis was observed in any PASC patient.

Human Cardiac Pericytes Are Susceptible to SARS-CoV-2 Infection

COVID-19 is associated with serious cardiovascular complications, with incompletely understood mechanism(s). Pericytes have key functions in supporting endothelial cells and maintaining vascular integrity. We demonstrate that human cardiac pericytes are permissive to SARS-CoV-2 infection in organotypic slice and primary cell cultures. Viral entry into pericytes is mediated by endosomal proteases, and infection leads to up-regulation of inflammatory markers, vasoactive mediators, and nuclear factor kappa-B-dependent cell death. Furthermore, we present evidence of cardiac pericyte infection in COVID-19 myocarditis patients. These data demonstrate that human cardiac pericytes are susceptible to SARS-CoV-2 infection and suggest a role for pericyte infection in COVID-19.

Mid- and Long-Term Atrio-Ventricular Functional Changes in Children after Recovery from COVID-19

Background: Although most children may experience mild to moderate symptoms and do not require hospitalization, there are little data on cardiac involvement in COVID-19. However, cardiac involvement is accurately demonstrated in children with MISC. The objective of this study was to evaluate cardiac mechanics in previously healthy children who recovered from severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2) infection in a long-term follow-up by means of two-dimensional speckle-tracking echocardiography (STE). Methods: We analyzed a cohort of 157 paediatric patients, mean age 7.7 ± 4.5 years (age range 0.3−18 years), who had a laboratory-confirmed diagnosis of SARS-CoV-2 infection and were asymptomatic or mildly symptomatic for COVID-19. Patients underwent a standard transthoracic echocardiogram and STE at an average time of 148 ± 68 days after diagnosis and were divided in three follow-up groups (<180 days, 180−240 days, >240 days). Patients were compared with 107 (41 females—38%) age- and BSA-comparable healthy controls (CTRL). Results: Left ventricular (LV) global longitudinal strain (post-COVID-19: −20.5 ± 2.9%; CTRL: −21.8 ± 1.7%; p < 0.001) was significantly reduced in cases compared with CTRLs. No significant differences were seen among the three follow-up groups (p = NS). Moreover, regional longitudinal strain was significantly reduced in LV apical-wall segments of children with disease onset during the second wave of the COVID-19 pandemic compared to the first wave (second wave: −20.2 ± 2.6%; first wave: −21.2 ± 3.4%; p = 0.048). Finally, peak left atrial systolic strain was within the normal range in the post-COVID-19 group with no significant differences compared to CTRLs. Conclusions: Our study demonstrated for the first time the persistence of LV myocardial deformation abnormalities in previously healthy children with an asymptomatic or mildly symptomatic (WHO stages 0 or 1) COVID-19 course after an average follow-up of 148 ± 68 days. A more significant involvement was found in children affected during the second wave. These findings imply that subclinical LV dysfunction may also be a typical characteristic of COVID-19 infection in children and are concerning given the predictive value of LV longitudinal strain in the general population.

Bibliometric and visual analysis of cardiovascular diseases and COVID-19 research

Background

The global community has been affected by the coronavirus disease 2019 (COVID-19), which emerged in December 2019. Since then, many studies have been conducted on cardiovascular diseases (CVDs) and COVID-19. The aim of this study was to perform a bibliometric and visual analysis of the published relationship between CVDs and COVID-19.

Methods

1,890 publications were retrieved from the Web of Science Core Collection database on January 5, 2022. Microsoft Office Excel and CiteSpace were then used to carry out scientometric analysis on the relevant literature according to seven aspects: document type, countries/regions, institutions, authors, journals, references, and keywords.

Results

The research on CVDs and COVID-19 is currently in a period of rapid development, with China, USA, England, and Italy leading the field. There is active cooperation between most countries and institutions. Harvard Medical School stands out among the many institutions not only for the largest number of publications, but also for their high quality. Banerjee A, Solomon SD and Narula J are three representative authors in this field. Frontiers in Cardiovascular Medicine was the journal with the highest number of published studies, and The Lancet was the most cited journal. Two documents with a high degree of significance in this field were identified. Popular research topics in this field are specific diseases, such as acute coronary syndrome and heart failure; pathogenesis related to ACE2, insulin resistance and pericyte; the specific therapeutic drug chloroquine; and clinical characteristics, physical activity, and mental health. ACE2 and NF-κB will be the focus of future research.

Conclusions

This study provides useful information for the research of CVDs and COVID-19, including potential collaborators, popular research topics, and a reference for more extensive and in-depth research in the future.

An update on angiotensin-converting enzyme 2 structure/functions, polymorphism, and duplicitous nature in the pathophysiology of coronavirus disease 2019: Implications for vascular and coagulation disease associated with severe acute respiratory syndrome coronavirus infection

It has been known for many years that the angiotensin-converting enzyme 2 (ACE2) is a cell surface enzyme involved in the regulation of blood pressure. More recently, it was proven that the severe acute respiratory syndrome coronavirus (SARS-CoV-2) interacts with ACE2 to enter susceptible human cells. This functional duality of ACE2 tends to explain why this molecule plays such an important role in the clinical manifestations of coronavirus disease 2019 (COVID-19). At the very start of the pandemic, a publication from our Institute (entitled "ACE2 receptor polymorphism: susceptibility to SARS-CoV-2, hypertension, multi-organ failure, and COVID-19 disease outcome"), was one of the first reviews linking COVID-19 to the duplicitous nature of ACE2. However, even given that COVID-19 pathophysiology may be driven by an imbalance in the renin-angiotensin system (RAS), we were still far from understanding the complexity of the mechanisms which are controlled by ACE2 in different cell types. To gain insight into the physiopathology of SARS-CoV-2 infection, it is essential to consider the polymorphism and expression levels of the ACE2 gene (including its alternative isoforms). Over the past 2 years, an impressive amount of new results have come to shed light on the role of ACE2 in the pathophysiology of COVID-19, requiring us to update our analysis. Genetic linkage studies have been reported that highlight a relationship between ACE2 genetic variants and the risk of developing hypertension. Currently, many research efforts are being undertaken to understand the links between ACE2 polymorphism and the severity of COVID-19. In this review, we update the state of knowledge on the polymorphism of ACE2 and its consequences on the susceptibility of individuals to SARS-CoV-2. We also discuss the link between the increase of angiotensin II levels among SARS-CoV-2-infected patients and the development of a cytokine storm associated microvascular injury and obstructive thrombo-inflammatory syndrome, which represent the primary causes of severe forms of COVID-19 and lethality. Finally, we summarize the therapeutic strategies aimed at preventing the severe forms of COVID-19 that target ACE2. Changing paradigms may help improve patients' therapy.

Gut Microbiota Dynamics in Relation to Long-COVID-19 Syndrome: Role of Probiotics to Combat Psychiatric Complications

Increasing numbers of patients who recover from COVID-19 report lasting symptoms, such as fatigue, muscle weakness, dementia, and insomnia, known collectively as post-acute COVID syndrome or long COVID. These lasting symptoms have been examined in different studies and found to influence multiple organs, sometimes resulting in life-threating conditions. In this review, these symptoms are discussed in connection to the COVID-19 and long-COVID-19 immune changes, highlighting oral and psychiatric health, as this work focuses on the gut microbiota’s link to long-COVID-19 manifestations in the liver, heart, kidney, brain, and spleen. A model of this is presented to show the biological and clinical implications of gut microbiota in SARS-CoV-2 infection and how they could possibly affect the therapeutic aspects of the disease. Probiotics can support the body’s systems in fighting viral infections. This review focuses on current knowledge about the use of probiotics as adjuvant therapies for COVID-19 patients that might help to prevent long-COVID-19 complications.

COVID-19 and Long-Term Outcomes: Lessons from Other Critical Care Illnesses and Potential Mechanisms

Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) is a novel coronavirus that is currently causing a pandemic and has been termed coronavirus disease (COVID-19). The elderly or those with preexisting conditions like diabetes, hypertension, coronary heart disease, chronic obstructive pulmonary disease, cerebrovascular disease, or kidney dysfunction are more likely to develop severe cases when infected. Patients with COVID-19 admitted to the ICU have higher mortality than non-ICU patients. Critical illness has consistently posed a challenge not only in terms of mortality but also in regard to long-term outcomes of survivors. Patients who survive acute critical illness including, but not limited to, pulmonary and systemic insults associated with acute respiratory distress syndrome, pneumonia, systemic inflammation, and mechanical ventilation, will likely suffer from post-ICU syndrome, a phenomenon of cognitive, psychiatric, and/or physical disability after treatment in the ICU. Post-ICU morbidity and mortality continue to be a cause for concern when considering large-scale studies showing 12-month mortality risks of 11.8-21%. Previous studies have demonstrated that multiple mechanisms, including cytokine release, mitochondrial dysfunction, and even amyloids, may lead to end-organ dysfunction in patients. We hypothesize that COVID-19 infection will lead to post-ICU syndrome via potentially similar mechanisms as other chronic critical illnesses and cause long-term morbidity and mortality in patients. We consider a variety of mechanisms and questions that not only consider the short-term impact of the COVID-19 pandemic but its long-term effects that may not yet be imagined.

Protective and therapeutic potentials of HDL and ApoA1 in COVID-19 elderly and chronic illness patients

BACKGROUND

Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) is responsible for coronavirus disease-2019 (COVID-19). Elderly subjects, obese, and patients with chronic illnesses, are the most affected group. HDL has pleiotropic physiological functions that are affected with alteration(s) in its structure.

MAIN TEXT

Inflammation whether septic, immune, or other affects HDL structure and function. COVID-19 is associated with systemic immune-inflammation due to cytokine surge. Viral interaction with erythrocytes and hemoglobin-related compounds (may cause anemia and hypoxia) and other factors may affect HDL function. Trials have been conducted to resume HDL functions using peptide preparation, nutritional, and herbal elements.

CONCLUSIONS

In this review article, I'll discuss the use of reconstituted HDL (rHDL), Apo-A1 mimetic peptide D-4F, ω-3 polyunsaturated fatty acids, and the powdered roots and/or extract of Saussurea lappa (costus) to avoid comorbidity and mortality of COVID-19 in patients with chronic illness or elderly-age mortality.

Mechanisms of COVID-19 Pathogenesis in Diabetes

Coronavirus disease 2019 (COVID-19), caused by the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) virus, is a global pandemic impacting 254 million people in 190 countries. Comorbidities, particularly cardiovascular disease, diabetes, and hypertension, increase the risk of infection and poor outcomes. SARS-CoV-2 enters host cells through the angiotensin-converting enzyme-2 receptor, generating inflammation and cytokine storm, often resulting in multiorgan failure. The mechanisms and effects of COVID-19 on patients with high-risk diabetes are not yet completely understood. In this review, we discuss the variety of coronaviruses, structure of SARS-CoV-2, mutations in SARS-CoV-2 spike proteins, receptors associated with viral host entry, and disease progression. Furthermore, we focus on possible mechanisms of SARS-CoV-2 in diabetes, leading to inflammation and heart failure. Finally, we discuss existing therapeutic approaches, unanswered questions, and future directions.

An Atypical Case of Aphasia: Transitory Ischemic Attack in a 13-Year-Old Patient with Asymptomatic SARS-CoV-2 Infection

We report the case of a 13-year-old patient, female, born in Northern Italy, who presented with an acute episode of aphasia, lasting about 15 min, accompanied by left arm dysesthesia. The state of consciousness remained preserved throughout the episode. After a first clinical evaluation at second-level hospital, the patient was sent to our institute for further investigations. Brain MRI performed at admission showed no noteworthy structural alterations. Electroencephalogram was not significant, as was the echocardiographic examination. ECG was normal, except for a corrected-QT at the upper limits of the normal range for age and gender. The neurological examination was substantially normal for the entire duration of the hospital stay. The symptomatology initially described has never reappeared. Blood tests were substantially negative, in particular thrombophilic screening excluded hereditary-familial thrombophilic diseases. Color doppler ultrasound of the supra-aortic trunks, splanchnic vessels and lower limbs were also normal. Only positivity to SARS-CoV-2 serology is reported. In the recent clinical history there were no symptoms attributable to symptomatic coronavirus infection.

Protection by metformin against severe Covid-19: an in-depth mechanistic analysis

Since the outbreak of Covid-19, several observational studies on diabetes and Covid-19 have reported a favourable association between metformin and Covid-19-related outcomes in patients with type 2 diabetes mellitus (T2DM). This is not surprising since metformin affects many of the pathophysiological mechanisms implicated in SARS-CoV-2 immune response, systemic spread and sequelae. A comparison of the multifactorial pathophysiological mechanisms of Covid-19 progression with metformin's well-known pleiotropic properties suggests that the treatment of patients with this drug might be particularly beneficial. Indeed, metformin could alleviate the cytokine storm, diminish virus entry into cells, protect against microvascular damage as well as prevent secondary fibrosis. Although our in-depth analysis covers many potential metformin mechanisms of action, we want to highlight more particularly its unique microcirculatory protective effects since worsening of Covid-19 disease clearly appears as largely due to severe defects in the structure and functioning of microvessels. Overall, these observations confirm that metformin is a unique, pleiotropic drug that targets many of Covid-19′s pathophysiology processes in a diabetes-independent manner.

ACE2 and TMPRSS2 Immunolocalization and COVID-19-Related Thyroid Disorder

Thyroid dysfunction has been reported to be an extrapulmonary symptom of COVID-19. It is important to identify the tissue subset that expresses angiotensin-converting enzyme 2 (ACE2) and transmembrane protease serine 2 (TMPRSS2), which are essential for host infection with severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), in order to understand the viral pathogenesis of COVID-19-related thyroid dysfunction. We investigated the expression and distribution of ACE2- and TMPRSS2-expressing cells in the thyroid gland. RT-PCR and Western blotting were performed on human thyroid follicular cells (Nthy-ori3-1) and rat thyroid tissues to detect the expression levels of ACE and TMPRSS2 mRNA and proteins. We also analyzed the expression patterns of ACE2 and TMPRSS2 in 9 Sprague-Dawley rats and 15 human thyroid tissues, including 5 normal, 5 with Hashimoto's thyroiditis, and 5 with Graves' disease, by immunohistochemistry (IHC) and immunofluorescence. Both ACE2 and TMPRSS2 mRNAs and proteins were detected in the thyroid tissue. However, ACE2 and TMPRSS2 proteins were not expressed in thyroid follicular cells. In IHC, ACE2 and TMPRSS2 were not stained in the follicular cells. No cells co-expressed ACE2 and TMPRSS2. ACE2 was expressed in pericytes between follicles, and TMPRSS2 was mainly stained in the colloid inside the follicle. There was no difference in expression between the normal thyroid, Hashimoto's thyroiditis, and Graves' disease. SARS-CoV-2 does not directly invade the thyroid follicular cells. Whether SARS-CoV-2 infection of pericytes can affect COVID-19-related thyroid dysfunction warrants further study.

Long COVID: post-acute sequelae of COVID-19 with a cardiovascular focus

Emerging as a new epidemic, long COVID or post-acute sequelae of coronavirus disease 2019 (COVID-19), a condition characterized by the persistence of COVID-19 symptoms beyond 3 months, is anticipated to substantially alter the lives of millions of people globally. Cardiopulmonary symptoms including chest pain, shortness of breath, fatigue, and autonomic manifestations such as postural orthostatic tachycardia are common and associated with significant disability, heightened anxiety, and public awareness. A range of cardiovascular (CV) abnormalities has been reported among patients beyond the acute phase and include myocardial inflammation, myocardial infarction, right ventricular dysfunction, and arrhythmias. Pathophysiological mechanisms for delayed complications are still poorly understood, with a dissociation seen between ongoing symptoms and objective measures of cardiopulmonary health. COVID-19 is anticipated to alter the long-term trajectory of many chronic cardiac diseases which are abundant in those at risk of severe disease. In this review, we discuss the definition of long COVID and its epidemiology, with an emphasis on cardiopulmonary symptoms. We further review the pathophysiological mechanisms underlying acute and chronic CV injury, the range of post-acute CV sequelae, and impact of COVID-19 on multiorgan health. We propose a possible model for referral of post-COVID-19 patients to cardiac services and discuss future directions including research priorities and clinical trials that are currently underway to evaluate the efficacy of treatment strategies for long COVID and associated CV sequelae.

Cardiovascular disturbances in COVID-19: an updated review of the pathophysiology and clinical evidence of cardiovascular damage induced by SARS-CoV-2

Severe acute respiratory coronavirus-2 (SARS-Co-2) is the causative agent of coronavirus disease-2019 (COVID-19). COVID-19 is a disease with highly variable phenotypes, being asymptomatic in most patients. In symptomatic patients, disease manifestation is variable, ranging from mild disease to severe and critical illness requiring treatment in the intensive care unit. The presence of underlying cardiovascular morbidities was identified early in the evolution of the disease to be a critical determinant of the severe disease phenotype. SARS-CoV-2, though a primarily respiratory virus, also causes severe damage to the cardiovascular system, contributing significantly to morbidity and mortality seen in COVID-19. Evidence on the impact of cardiovascular disorders in disease manifestation and outcome of treatment is rapidly emerging. The cardiovascular system expresses the angiotensin-converting enzyme-2, the receptor used by SARS-CoV-2 for binding, making it vulnerable to infection by the virus. Systemic perturbations including the so-called cytokine storm also impact on the normal functioning of the cardiovascular system. Imaging plays a prominent role not only in the detection of cardiovascular damage induced by SARS-CoV-2 infection but in the follow-up of patients' clinical progress while on treatment and in identifying long-term sequelae of the disease.

ACE2, the Counter-Regulatory Renin-Angiotensin System Axis and COVID-19 Severity

Angiotensin (ANG)-converting enzyme (ACE2) is an entry receptor of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) that causes coronavirus disease 2019 (COVID-19). ACE2 also contributes to a deviation of the lung renin-angiotensin system (RAS) towards its counter-regulatory axis, thus transforming harmful ANG II to protective ANG (1-7). Based on this purported ACE2 double function, it has been put forward that the benefit from ACE2 upregulation with renin-angiotensin-aldosterone system inhibitors (RAASi) counterbalances COVID-19 risks due to counter-regulatory RAS axis amplification. In this manuscript we discuss the relationship between ACE2 expression and function in the lungs and other organs and COVID-19 severity. Recent data suggested that the involvement of ACE2 in the lung counter-regulatory RAS axis is limited. In this setting, an augmentation of ACE2 expression and/or a dissociation of ACE2 from the ANG (1-7)/Mas pathways that leaves unopposed the ACE2 function, the SARS-CoV-2 entry receptor, predisposes to more severe disease and it appears to often occur in the relevant risk factors. Further, the effect of RAASi on ACE2 expression and on COVID-19 severity and the overall clinical implications are discussed.

Pericytes: Intrinsic Transportation Engineers of the CNS Microcirculation

Pericytes in the brain are candidate regulators of microcirculatory blood flow because they are strategically positioned along the microvasculature, contain contractile proteins, respond rapidly to neuronal activation, and synchronize microvascular dynamics and neurovascular coupling within the capillary network. Analyses of mice with defects in pericyte generation demonstrate that pericytes are necessary for the formation of the blood-brain barrier, development of the glymphatic system, immune homeostasis, and white matter function. The development, identity, specialization, and progeny of different subtypes of pericytes, however, remain unclear. Pericytes perform brain-wide 'transportation engineering' functions in the capillary network, instructing, integrating, and coordinating signals within the cellular communicome in the neurovascular unit to efficiently distribute oxygen and nutrients ('goods and services') throughout the microvasculature ('transportation grid'). In this review, we identify emerging challenges in pericyte biology and shed light on potential pericyte-targeted therapeutic strategies.

Expression of SARS-CoV-2-related receptors in cells of the neurovascular unit: implications for HIV-1 infection

BACKGROUND

Neurological complications are common in patients affected by COVID-19 due to the ability of SARS-CoV-2 to infect brains. While the mechanisms of this process are not fully understood, it has been proposed that SARS-CoV-2 can infect the cells of the neurovascular unit (NVU), which form the blood-brain barrier (BBB). The aim of the current study was to analyze the expression pattern of the main SARS-CoV-2 receptors in naïve and HIV-1-infected cells of the NVU in order to elucidate a possible pathway of the virus entry into the brain and a potential modulatory impact of HIV-1 in this process.

METHODS

The gene and protein expression profile of ACE2, TMPRSS2, ADAM17, BSG, DPP4, AGTR2, ANPEP, cathepsin B, and cathepsin L was assessed by qPCR, immunoblotting, and immunostaining, respectively. In addition, we investigated if brain endothelial cells can be affected by the exposure to the S1 subunit of the S protein, the domain responsible for the direct binding of SARS-CoV-2 to the ACE2 receptors.

RESULTS

The receptors involved in SARS-CoV-2 infection are co-expressed in the cells of the NVU, especially in astrocytes and microglial cells. These receptors are functionally active as exposure of endothelial cells to the SARS CoV-2 S1 protein subunit altered the expression pattern of tight junction proteins, such as claudin-5 and ZO-1. Additionally, HIV-1 infection upregulated ACE2 and TMPRSS2 expression in brain astrocytes and microglia cells.

CONCLUSIONS

These findings provide key insight into SARS-CoV-2 recognition by cells of the NVU and may help to develop possible treatment of CNS complications of COVID-19.

Stroke in SARS-CoV-2 Infection: A Pictorial Overview of the Pathoetiology

Since the early days of the pandemic, there have been several reports of cerebrovascular complications during the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection. Numerous studies proposed a role for SARS-CoV-2 in igniting stroke. In this review, we focused on the pathoetiology of stroke among the infected patients. We pictured the results of the SARS-CoV-2 invasion to the central nervous system (CNS) via neuronal and hematogenous routes, in addition to viral infection in peripheral tissues with extensive crosstalk with the CNS. SARS-CoV-2 infection results in pro-inflammatory cytokine and chemokine release and activation of the immune system, COVID-19-associated coagulopathy, endotheliitis and vasculitis, hypoxia, imbalance in the renin-angiotensin system, and cardiovascular complications that all may lead to the incidence of stroke. Critically ill patients, those with pre-existing comorbidities and patients taking certain medications, such as drugs with elevated risk for arrhythmia or thrombophilia, are more susceptible to a stroke after SARS-CoV-2 infection. By providing a pictorial narrative review, we illustrated these associations in detail to broaden the scope of our understanding of stroke in SARS-CoV-2-infected patients. We also discussed the role of antiplatelets and anticoagulants for stroke prevention and the need for a personalized approach among patients with SARS-CoV-2 infection.

Expression of SARS-CoV-2-related Receptors in Cells of the Neurovascular Unit: Implications for HIV-1 Infection

Background. Neurological complications are common in patients affected by COVID-19 due to the ability of SARS-CoV-2 to infect brains. While the mechanisms of this process are not fully understood, it has been proposed that SARS-CoV-2 can infect the cells of the neurovascular units (NVU), which form the blood-brain barrier (BBB). The aim of the current study was to analyze the expression pattern of the main SARS-CoV-2 receptors in naïve and HIV-1-infected cells of the NVU in order to elucidate a possible pathway of the virus entry into the brain and a potential modulatory impact of HIV-1 in this process. Methods. The gene and protein expression profile of ACE2, TMPRSS2, ADAM17, BSG, DPP4, AGTR2, ANPEP, cathepsin B and cathepsin L was assessed by qPCR and immunoblotting, respectively. In addition, we investigated if brain endothelial cells can be affected by the exposure to the S1 subunit of the S protein, the domain responsible for the direct binding of SARS-CoV-2 to the ACE2 receptors. Results. The receptors involved in SARS-CoV-2 infection are coexpressed in the cells of the NVU, especially in astrocytes and microglial cells. These receptors are functionally active as exposure of endothelial cells to the SARS CoV-2 S1 protein subunit altered the expression pattern of tight junction proteins, such as claudin-5 and ZO-1. Additionally, HIV-1 infection upregulated ACE2 and TMPRSS2 expression in brain astrocytes and microglia cells. Conclusions. These findings provide key insight into SARS-CoV-2 recognition by cells of the NVU and may help to develop possible treatment of CNS complications of COVID-19.

COVID-19 and the Pediatric Nervous System: Global Collaboration to Meet a Global Need

The coronavirus disease 2019 (COVID-19) pandemic has affected mortality and morbidity across all ages, including children. It is now known that neurological manifestations of COVID-19, ranging from headaches to stroke, may involve the central and/or peripheral nervous system at any age. Neurologic involvement is also noted in the multisystem inflammatory syndrome in children, a pediatric condition that occurs weeks after infection with the causative virus of COVID-19, severe acute respiratory syndrome coronavirus 2. Knowledge about mechanisms of neurologic disease is scarce but rapidly growing. COVID-19 neurologic manifestations may have particularly adverse impacts on the developing brain. Emerging data suggest a cohort of patients with COVID-19 will have longitudinal illness affecting their cognitive, physical, and emotional health, but little is known about the long-term impact on affected children and their families. Pediatric collaboratives have begun to provide important initial information on neuroimaging manifestations and the incidence of ischemic stroke in children with COVID 19. The Global Consortium Study of Neurologic Dysfunction in COVID-19-Pediatrics, a multinational collaborative, is working to improve understanding of the epidemiology, mechanisms of neurological manifestations, and the long-term implications of COVID-19 in children and their families.