Potential predictors of severe course and outcome of community-acquired pneumonia.

Severe pneumonia is a condition with a high risk of death and mandatory hospitalization in the intensive care unit. The incidence of severe pneumonia has increased dramatically during the pandemic of new coronavirus infection. Timely diagnosis and early initiation of adequate treatment of severe pneumonia are crucial for improving survival of critically ill patients. The aim of this review was to analyze published scientific research on molecular markers that allow to objectively assess the severity of pneumonia and to determine treatment tactics based on the predicted outcome upon admission to the hospital. A systematic search was conducted in the electronic databases PubMed, Medline, Web of Science for the period 2019 - 2022. Conclusion. The review focuses on the prognostic role of a number of markers of immune response, vascular transformation, as well as angiotensin II and angiotensin converting enzyme-2. Further prospective studies of potential predictors of severe pneumonia will enable using marker molecules in a comprehensive clinical and laboratory diagnosis for early prediction of the hospitalized patient's condition and expected outcome.Copyright © Volchkova E.V. et al., 2023.

Increases in expression of carbohydrate sulfotransferases CHST11 and CHST15 and decline in N-acetylgalactosamine-4-sulfatase (Arylsulfatase B, ARSB) require phospho-p38-MAPK following exposure to SARS-CoV-2 spike protein receptor binding domain in human a

Objective: Immunohistochemistry of post-mortem lung tissue from Covid-19 patients with diffuse alveolar damage demonstrated marked increases in chondroitin sulfate and CHST15 and decline in N-acetylgalactosamine-4-sulfatase. Studies were undertaken to identify the mechanisms involved in these effects. Method(s): Human primary small airway epithelial cells (PCS 301-010;ATCC) were cultured and exposed to the SARSCoV- 2 spike protein receptor binding domain (SPRBD;AA: Lys310-Leu560;Amsbio). Expression of the spike protein receptor, angiotensin converting enzyme 2 (ACE2), was enhanced by treatment with Interferon-beta. Promoter activation, DNA-binding, RNA silencing, QPCR, Western blots, ELISAs, and specific enzyme inhibitors were used to elucidate the underlying molecular mechanisms. Result(s): Treatment of the cultured cells by the SPRBD led to increased CHST15 and CHST11 expression and decline in ARSB expression. Sulfotransferase activity, total chondroitin sulfate, and sulfated glycosaminoglycan (GAG) content were increased. Phospho-T180/T182-p38-MAPK and phospho- S423/S425-Smad3 were required for the activation of the CHST15 and CHST11 promoters. Inhibition by SB203580, a phospho-p38 MAPK inhibitor, and by SIS3, a Smad3 inhibitor, blocked the CHST15 and CHST11 promoter activation. SB203580 reversed the SPRBD-induced decline in ARSB expression, but SIS3 had no effect on ARSB expression or promoter activation. Phospho-p38 MAPK was shown to reduce retinoblastoma protein (RB) S807/S811 phosphorylation and increase RB S249/T252 phosphorylation. E2F-DNA binding declined following exposure to SPRBD, and SB203580 reversed this effect. This indicates a mechanism by which SPRBD, phospho-p38 MAPK, E2F, and RB can regulate ARSB expression and thereby impact on chondroitin 4-sulfate and dermatan sulfate and molecules that bind to these sulfated GAGs, including Interleukin-8, bone morphogenetic protein-4, galectin-3 and SHP-2 (Src homology region 2-containing protein tyrosine phosphatase 2). Conclusion(s): The enzyme ARSB is required for the degradation of chondroitin 4-sulfate and dermatan sulfate, and accumulation of these sulfated GAGs can contribute to lung pathophysiology, as evident in Covid-19. Some effects of the SPRBD may be attributable to unopposed Angiotensin II, when Ang1-7 counter effects are diminished due to binding of ACE2 with the SARS-CoV-2 spike protein and reduced production of Ang1-7. Aberrant cell signaling and activation of the phospho-p38 MAPK and Smad3 pathways increase CHST15 and CHST11 production, which can contribute to increased chondroitin sulfate in infected cells. Decline in ARSB may occur as a consequence of effects of phospho-p38 MAPK on RB phosphorylation and E2F1 availability. Decline in ARSB and the resulting impaired degradation of sulfated GAGs have profound consequences on cellular metabolic, signaling, and transcriptional events. Funding is VA Merit Award.Copyright © 2023 The American Society for Biochemistry and Molecular Biology, Inc.

Angiotensin-converting enzyme 2 (ACE2) in COVID-19 and other diseases.

The coronavirus SARS-CoV-2 was detected in isolates of pneumonia patients in January 2020. The virus cannot multiply extracellularly but requires access to the cells of a host organism. SARS-CoV-2 uses angiotensin-converting enzyme 2 (ACE2) as a receptor, to which it docks with its spikes. ACE2 belongs to the renin angiotensin system (RAS), whose inhibitors have been used for years against high blood pressure. Renin is an endopeptidase that is predominantly formed in the juxtaglomerular apparatus of the kidney and cleaves the decapeptide angiotensin I (Ang I) from angiotensinogen. Through the angiotensin-converting enzyme (ACE), another 2 C-terminal amino acids are removed from Ang I, so that finally the active octapeptide angiotensin II (Ang II) is formed. The biological effect of Ang II via the angiotensin II receptor subtype 1 (AT1-R) consists of vasoconstriction, fibrosis, proliferation, inflammation, and thrombosis formation. ACE2 is a peptidase that is a homolog of ACE. ACE2 is predominantly expressed by pulmonary alveolar epithelial cells in humans and has been detected in arterial and venous endothelial cells. In contrast to the dicarboxy-peptidase ACE, ACE2 is a monocarboxypeptidase that cleaves only one amino acid from the C-terminal end of the peptides. ACE2 can hydrolyze the nonapeptide Ang-(1-9) from the decapeptide Ang I and the heptapeptide Ang-(1-7) from the octapeptide Ang II. Ang-(1-7) acts predominantly antagonistically (vasodilatory, anti-fibrotic, anti-proliferative, anti-inflammatory, anti-thrombogenetically) via the G protein-coupled Mas receptor to the AT1-R-mediated effects of Ang II. In the pathogenesis of COVID-19 infection, it is therefore assumed that there is an imbalance due to overstimulation of the AT1 receptor in conjunction with a weakening of the biological effects of the Mas receptor.Copyright © 2022 Dustri-Verlag Dr. K. Feistle.

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

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

Potential predictors of severe course and outcome of community-acquired pneumonia

Severe pneumonia is a condition with a high risk of death and mandatory hospitalization in the intensive care unit. The incidence of severe pneumonia has increased dramatically during the pandemic of new coronavirus infection. Timely diagnosis and early initiation of adequate treatment of severe pneumonia are crucial for improving survival of critically ill patients. The aim of this review was to analyze published scientific research on molecular markers that allow to objectively assess the severity of pneumonia and to determine treatment tactics based on the predicted outcome upon admission to the hospital. A systematic search was conducted in the electronic databases PubMed, Medline, Web of Science for the period 2019 – 2022. Conclusion. The review focuses on the prognostic role of a number of markers of immune response, vascular transformation, as well as angiotensin II and angiotensin converting enzyme-2. Further prospective studies of potential predictors of severe pneumonia will enable using marker molecules in a comprehensive clinical and laboratory diagnosis for early prediction of the hospitalized patient's condition and expected outcome. © Volchkova E.V. et al., 2023.

Potential predictors of severe course and outcome of community-acquired pneumonia.

Severe pneumonia is a condition with a high risk of death and mandatory hospitalization in the intensive care unit. The incidence of severe pneumonia has increased dramatically during the pandemic of new coronavirus infection. Timely diagnosis and early initiation of adequate treatment of severe pneumonia are crucial for improving survival of critically ill patients. The aim of this review was to analyze published scientific research on molecular markers that allow to objectively assess the severity of pneumonia and to determine treatment tactics based on the predicted outcome upon admission to the hospital. A systematic search was conducted in the electronic databases PubMed, Medline, Web of Science for the period 2019 - 2022. Conclusion. The review focuses on the prognostic role of a number of markers of immune response, vascular transformation, as well as angiotensin II and angiotensin converting enzyme-2. Further prospective studies of potential predictors of severe pneumonia will enable using marker molecules in a comprehensive clinical and laboratory diagnosis for early prediction of the hospitalized patient's condition and expected outcome.Copyright © Volchkova E.V. et al., 2023.

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

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

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

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

Role of angiotensin II in SARS-CoV-2 pathophysiology in a hamster model of COVID-19

OBJECTIVES/GOALS: Hamsters develop COVID-19 similarly to people because the SARS-CoV-2 spike protein binds with high affinity to hamster ACE2 resulting in host cell entry and replication. Our goal was to establish a hamster model that mirrors the lung and brain pathophysiology observed in COVID-19. METHODS/STUDY POPULATION: Hamsters infected with SARS CoV-2 are sacrificed on day 1 and day 6 postinfection. Lung histopathology scoring model was implemented for assessment all pathological relevant changes in the lungs of infected animals on tissue sections stained with hematoxylin and eosin. To quantify the extent and severity of lung pathology, two scoring systems were used: the first evaluated all relevant changes in the lungs of the infected animals and the second evaluated only the pathology associated with the pulmonary vasculature. Percentage of airway affected, airway severity, bronchiolar epithelial hyperplasia, alveoli affected, alveolar severity, type II pneumocyte hyperplasia and vessels affected were analyzed. Total airway score plus total lung alveolar score give lung histopathology score. RESULTS/ANTICIPATED RESULTS: Compared to the control hamster, the hamsters day 1 postinfection, exhibited a higher total airway score [9.00 ± 1.35 vs. 0.25 ± 0.1;p DISCUSSION/SIGNIFICANCE: Establishing this outstanding small animal model of COVID-19 will facilitate studies investigating diagnostics, prognosis and response to treatment in COVID-19 disease. These studies will provide insights that will complement on-going clinical trials on angiotensin type 1 receptor (AT1R) blockers (ARBs) in COVID-19.

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

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

Efficacy of defensins as neutralizing agents against the deadly SARS-CoV-2.

SARS-CoV-2 infection causes asymptomatic to severe human respiratory diseases. Vaccinations are effective only to a certain extent, and the disease recurs with milder symptoms even after booster doses. Hence, we hypothesize that antiviral therapy in conjunction with vaccination is the need of the hour for containing the disease. SARS-CoV-2 enters the host cell through interaction between viral spike (S) protein and human Angiotensin II converting enzyme2 (ACE2). So, any S-protein neutralizing molecule could be a potential antiviral moiety. The interaction-interface architecture indicates that cationic peptides effectively bind to anionic interface residues of S protein-receptor binding domain (S-RBD). Subsequently, we adopted molecular docking and simulation approaches to examine the binding affinity of cationic human α and ß defensins, HNP1 and HBD2 with S-RBD. We observed strong hydrogen bonds, electrostatic, salt bridge, and hydrophobic interactions between these defensins and S-RBD with binding energy (BE) of -10.7 kcal/mol. Interestingly, defensins from Zea mays (ZmD32), Solanum lycopersicum (TPP3), and Sorghum bicolor (DEF1_SORBI) exhibited approximately similar BE of -11.1 kcal/mol, -11.9 kcal/mol, and -12.6 kcal/mol respectively, comparable to ACE2 (BE= -11.9 kcal/mol). Molecular dynamics simulation of S-RBD complexes formed with HBD2, ZmD32 and TPP3, showed stable associations for 100 ns. Results of in-silico studies demonstrated higher binding affinity of more positively-charged peptides with S-RBD, suggesting the potential of plant defensins to block ACE2 binding of S-RBD. These results warrant experimental validation. However these findings indicate the usefulness of plant defensin homologues as neutralizing antiviral agents for use as ideal prophylactic and therapeutic drugs for COVID-19.Communicated by Ramaswamy H. Sarma.

Comparing the mortality of COPD and non-COPD patients with COVID-19 in a UK hospital

Rationale: Initial reports during the pandemic have shown that COPD patients with COVID-19 have a poorer prognosis due to an increased risk of respiratory failure. It is well known that in COPD, there is an increased expression of angiotensin converting enzyme-2 (ACE2), the receptor which plays a role in SARS-CoV-2 entry into cells. In the absence of infection, ACE2 converts angiotensin-2 (AngII) to angiotensin-1-7- helping regulate inflammation. During COVID-19 infection, ACE2 activity is reduced due to receptor occupancy, resulting in greater levels of AngII- leading to a pro-inflammatory state. We aim to investigate the impact of COPD and COVID-19 on mortality, length of in-patient stay and gender. Method(s): A retrospective study of all in-patients aged >= 18 years with a confirmed diagnosis of COVID-19 during the first wave of the pandemic. Statistical analysis was performed using the Chi-Squared Test for independence. Result(s): 445 COVID-19 patients were included in the study, out of whom 52 (12%) had COPD. Mortality in COPD patients (65%) was found to be significantly higher than non-COPD patients (49%) (P=0.03) There were no significant differences in mortality between COPD and non-COPD patients when grouped for male and female (P=0.68). Furthermore, there were no significant differences in length of in-patient stays of >7 days between COPD and non-COPD patients (P=0.79). Conclusion(s): Our study demonstrated how COPD increases mortality in COVID-19. This data should be considered when highlighting at risk groups- prioritising them for treatment, isolation, and preventative public health measures such as the COVID-19 vaccination programme.

Patterns of Recovery of Kidney Function in Patients with Covid-19 and Acute Kidney Injury in a Reference Center in Mexico

Introduction: La enfermedad renal por COVID-19 es clara, sin embargo, hay pocos datos sobre los resultados renales en pacientes que desarrollaron esta enfermedad. Method(s): El objetivo del estudio fue identificar los factores asociados con la lesion renal aguda, los patrones de recuperacion de la funcion renal, la enfermedad renal aguda, la enfermedad renal cronica post-COVID-19 y la muerte. Cohorte retrospectiva realizada en el Hospital de Especialidades del Centro Medico Nacional ''La Raza" en Mexico. Se incluyeron 204 pacientes hospitalizados de marzo a junio de 2020 por COVID-19. Las variables cuantitativas se expresan como media +/- desviacion estandar. Se calcularon razones de momios para identificar factores asociados, con un intervalo de confianza del 95%. Result(s): La edad media fue de 57,83+/-15,42 anos. La incidencia de FRA fue del 42,2% (86 casos). En general, el 31,4% (27 casos) y el 12,8% (11 casos) tuvieron un patron de recuperacion de la funcion renal temprana y tardia, respectivamente, y el 55,8% (48 casos) no se recupero. AKD desarrollo en el 19,8% (17 casos), de los cuales los estadios 0, 1, 2 y 3 se observaron en el 4,7% (4 casos), 1,2% (1 casos), 3,5% (3 casos) y 12,8% (11 casos) respectivamente. Se completo un seguimiento de al menos 12 meses de 98 casos, de los cuales el 9,2% (9 casos) desarrollaron algun estadio de ERC. En estadio G3a, G4, G5 con terapia de reemplazo renal en 4,1% (4 casos), 1% (1 caso), 4,1% (4 casos) respectivamente. Los factores asociados a FRA fueron edad > 60 anos (OR: 3,48;IC: 1,94 - 6,26), hipertension arterial (OR: 2,56;IC: 1,44 - 4,54), uso de vasopresor (OR: 6,68;IC: 3,40 - 13,13), uso de ventilacion mecanica (OR: 6,71;IC: 3,61 - 12,45), forma grave de COVID-19 (OR: 3,95;IC: 1,72 - 9,05), trombocitopenia leve (OR: 3,07;IC: 1,10 - 8,54), SOFA > 4 puntos (OR: 6,22;IC: 3,32 - 11,62), uso de lopinavir/ritonavir en hospitalizacion (OR: 3,94;IC: 1,46 - 10,64), uso de antagonista del receptor de angiotensina II en hospitalizacion (OR: 3,13;IC: 1,49 - 6,58). Los factores asociados con la ERCA fueron el uso de vasopresores (OR: 9,68, IC: 3,01 - 31,14), ventilacion mecanica (OR: 4,85, IC: 1,52 - 15,45), trombocitopenia leve (OR: 5,55, IC: 1,69 - 18,15) y uso de antagonista del receptor de angiotensina II (OR: 3,66;IC: 1,29 - 10-38). Los factores asociados a la ERC fueron el uso de vasopresores (OR: 1,81, IC: 1,50 - 2,19) y el uso de lopinavir/ritonavir (OR: 1,13, IC: 1,04 - 1,21). En pacientes con LRA asociada a COVID-19 se observo una mortalidad del 65,1%. Se concedio terapia de reemplazo renal a 10. Conclusion(s): La insuficiencia renal aguda es una complicacion frecuente en pacientes con COVID-19, con factores de riesgo implicados en su desarrollo, asi como en su evolucion a enfermedad renal aguda o enfermedad renal cronica. La severidad de la LRA con necesidad de TRS es un factor de riesgo de mortalidad como ha sido reportado en otra bibliografia. No conflict of interestCopyright © 2023

Potential use of renin-angiotensin-aldosterone system inhibitors to reduce COVID-19 severity.

SARS-CoV-2 infection and its clinical manifestations (COVID-19) quickly evolved to a pandemic and a global public health emergency. The limited effectivity of available treatments aimed at reducing virus replication and the lessons learned from other coronavirus infections (SARS-CoV-1 or NL63) that share the internalization process of SARS-CoV-2, led us to revisit the COVID-19 pathogenesis and potential treatments. Virus protein S binds to the angiotensin-converting enzyme 2 (ACE2) initiating the internalization process. Endosome formation removes ACE2 from the cellular membrane preventing its counter-regulative effect mediated by the metabolism of angiotensin II to angiotensin (1-7). Internalized virus-ACE2 complexes have been identified for these coronaviruses. SARS-CoV-2 presents the highest affinity for ACE2 and produces the most severe symptoms. Assuming ACE2 internalization is the trigger for COVID-19 pathogenesis, accumulation of angiotensin II can be viewed as the potential cause of symptoms. Angiotensin II is a strong vasoconstrictor, but has also important roles in hypertrophy, inflammation, remodeling, and apoptosis. Higher levels of ACE2 in the lungs explain the acute respiratory distress syndrome as primary symptoms. Most of the described findings and clinical manifestations of COVID-19, including increased interleukin levels, endothelial inflammation, hypercoagulability, myocarditis, dysgeusia, inflammatory neuropathies, epileptic seizures and memory disorders can be explained by excessive angiotensin II levels. Several meta-analyses have demonstrated that previous use of angiotensin-converting enzyme inhibitors or angiotensin receptor blockers were associated with better prognosis for COVID-19. Therefore, pragmatic trials to assess the potential therapeutic benefits of renin-angiotensin-aldosterone system inhibitors should be urgently promoted by health authorities to widen the therapeutic options for COVID-19.

An Unexpected Enzyme in Vascular Smooth Muscle Cells: Angiotensin II Upregulates Cholesterol-25-Hydroxylase Gene Expression.

Angiotensin II (AngII) is a vasoactive peptide hormone, which, under pathological conditions, contributes to the development of cardiovascular diseases. Oxysterols, including 25-hydroxycholesterol (25-HC), the product of cholesterol-25-hydroxylase (CH25H), also have detrimental effects on vascular health by affecting vascular smooth muscle cells (VSMCs). We investigated AngII-induced gene expression changes in VSMCs to explore whether AngII stimulus and 25-HC production have a connection in the vasculature. RNA-sequencing revealed that Ch25h is significantly upregulated in response to AngII stimulus. The Ch25h mRNA levels were elevated robustly (~50-fold) 1 h after AngII (100 nM) stimulation compared to baseline levels. Using inhibitors, we specified that the AngII-induced Ch25h upregulation is type 1 angiotensin II receptor- and Gq/11 activity-dependent. Furthermore, p38 MAPK has a crucial role in the upregulation of Ch25h. We performed LC-MS/MS to identify 25-HC in the supernatant of AngII-stimulated VSMCs. In the supernatants, 25-HC concentration peaked 4 h after AngII stimulation. Our findings provide insight into the pathways mediating AngII-induced Ch25h upregulation. Our study elucidates a connection between AngII stimulus and 25-HC production in primary rat VSMCs. These results potentially lead to the identification and understanding of new mechanisms in the pathogenesis of vascular impairments.

Unraveling the Underlying Molecular Mechanism of 'Silent Hypoxia' in COVID-19 Patients Suggests a Central Role for Angiotensin II Modulation of the AT1R-Hypoxia-Inducible Factor Signaling Pathway.

A few days after being infected with SARS-CoV-2, a fraction of people remain asymptomatic but suffer from a decrease in arterial oxygen saturation in the absence of apparent dyspnea. In light of our clinical investigation on the modulation of molecules belonging to the renin angiotensin system (RAS) in COVID-19 patients, we propose a model that explains 'silent hypoxia'. The RAS imbalance caused by SARS-CoV-2 results in an accumulation of angiotensin 2 (Ang II), which activates the angiotensin 2 type 1 receptor (AT1R) and triggers a harmful cascade of intracellular signals leading to the nuclear translocation of the hypoxia-inducible factor (HIF)-1α. HIF-1α transactivates many genes including the angiotensin-converting enzyme 1 (ACE1), while at the same time, ACE2 is downregulated. A growing number of cells is maintained in a hypoxic condition that is self-sustained by the presence of the virus and the ACE1/ACE2 ratio imbalance. This is associated with a progressive worsening of the patient's biological parameters including decreased oxygen saturation, without further clinical manifestations. When too many cells activate the Ang II-AT1R-HIF-1α axis, there is a 'hypoxic spillover', which marks the tipping point between 'silent' and symptomatic hypoxia in the patient. Immediate ventilation is required to prevent the 'hypoxic spillover'.

Angiotensin II - A Brief Review and Role in Severe SARS-COV-2 Sepsis.

The renin-angiotensin-aldosterone system (RAAS), whose major vasopressor effector is angiotensin II (ATII), has multiple activities and regulates sodium-water homeostasis and fluid and blood pressure homeostasis. RAAS plays a crucial role in cardiocirculatory shock because it counteracts hypotension and hypovolemia by activating different physiologic responses. Based on the encouraging results of the ATHOS-3 trial, the US Food and Drug Administration and the European Medicines Agency approved the use of ATII for catecholamine-resistant vasodilatory shock. More recently, ATII was used for the compassionate treatment of critically ill patients with COVID-19. Beyond its vasopressor properties, ATII was hypothesized to have antiviral activity because it induces internalization and degradation of angiotensin-converting enzyme 2 receptors used by SARS-Cov-2 to infect cells. Overall, the use of ATII in patients with COVID-19 showed promising results because its administration was associated with the achievement and maintenance of target mean arterial pressure, increased PaO2/FIO2 ratio, and decreased FIO2. The aim of this narrative review is to summarize the available knowledge on the use of ATII in patients with COVID-19.

Myocardial Injury and Altered Gene Expression Associated With SARS-CoV-2 Infection or mRNA Vaccination.

SARS CoV-2 enters host cells via its Spike protein moiety binding to the essential cardiac enzyme angiotensin-converting enzyme (ACE) 2, followed by internalization. COVID-19 mRNA vaccines are RNA sequences that are translated into Spike protein, which follows the same ACE2-binding route as the intact virion. In model systems, isolated Spike protein can produce cell damage and altered gene expression, and myocardial injury or myocarditis can occur during COVID-19 or after mRNA vaccination. We investigated 7 COVID-19 and 6 post-mRNA vaccination patients with myocardial injury and found nearly identical alterations in gene expression that would predispose to inflammation, coagulopathy, and myocardial dysfunction.

ANGIOTENSIN II EXAGGERATES SARS-COV-2 SPECIFIC T-CELL RESPONSE IN CONVALESCENT INDIVIDUALS FOLLOWING COVID-19

Background: Coronavirus disease 2019 (COVID-19) is an emerging respiratory disease caused by severe acute respiratory syndrome coronavirus 2 (SARSCoV- 2). Recent studies have suggested numerous hypotheses that may explain multi-organ dysfunction during a COVID-19 infection. One possible hypothesis posits that the renin-angiotensin system dysregulation before SARS-CoV-2 infection could exacerbate disease symptoms and severity, especially in COVID-19 patients with underlying comorbidities. Objective: This study sought to investigate the effect of exogenous angiotensin II (Ang II) on peripheral blood mononuclear cells (PBMCs) stimulated with SARSCoV- 2 peptide pool. Methods: PBMCs from recovered COVID-19 patients (n = 18) were used in this study. SARS-CoV-2 specific t-cell responses were measured using activation induced cell marker assay and intracellular cytokine staining (ICS) assay, while enzyme-linked immunosorbent assay (ELISA) and ICS assays determined functional capability and polarization. Additionally, the relative level of protein phosphorylation in PBMCs was measured using a phosphokinase array. Results: Our results showed that in vitro Ang II treatment significantly increased the magnitude of SARS-CoV-2 specific t-cell response in stimulated PBMCs with SARS-CoV-2 peptide pool. Moreover, the phosphorylation level of numerous proteins implicated in cardiovascular diseases, inflammation, and viral infection showed significant increase in the presence of Ang II. Mitogenic stimulation of PBMCs after Ang II and SARS-CoV-2 peptide pool stimulation showed functional polarization of CD4+ and CD8+ t-cells toward Th1/Th17 and Th17 phenotypes, respectively. Meanwhile, ELISA showed an increased production of IL-1b and IL-6 in Ang II-stimulated PBMCs without affecting the reduction of IL-10 level resulting from SARS-CoV-2 peptide pool stimulation. Conclusion: To our knowledge, the present study is the first to demonstrate that Ang II exaggerates SARS-CoV-2 specific t-cells response. Therefore, during COVID-19 infection Ang II may aggravate the inflammatory response and change the immune response toward a more inflammatory profile against SARS-CoV-2 infection, leading to serious complications and worse outcomes during COVID-19 infection.