Figure - available from: Analytical Cellular Pathology
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Renin–angiotensin system (RAS) components and functions. Angiotensinogen is a plasma protein that is mostly produced in the liver. Renin is synthesized in juxtaglomerular cells in the kidney glomeruli and converts angiotensinogen to Ang I (1–10). Angiotensin-converting enzyme (ACE) located on apical membranes of endothelial cells in different organs, especially in the lungs, catalyzes the conversion of Ang I to a potent vasoconstrictor Ang II (1–8). ACE2 is also a protease that converts Ang I (1–10) to Ang-(1–9) and Ang II (1–8) to Ang-(1–7). The actions of Ang II on target cells are mediated by two types of receptors, AT1R and AT2R, which lead to opposing effects. Ang-(1–7) also binds to AT2R, and another receptor known as the mitochondrial assembly (MAS) receptor, has positive effects on target cells.
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Angiotensin-converting enzyme 2 (ACE2), a key enzyme in the renin–angiotensin system (RAS), is expressed in various tissues and organs, including the central nervous system (CNS). The spike protein of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), the virus responsible for coronavirus disease-2019 (COVID-19), binds to ACE2, which rai...
Citations
... These results are consistent with a previous systematic review that found that peripheral neurological symptoms in patients with COVID-19 were associated to nonsevere outcomes and better long-term disability 42 . These manifestations of the peripherical nervous system could be expressions of the direct virus entry into nerve cells from cranial nerves through angiotensin-converting enzyme 2 and neurolopin-1 receptors 43,44 . However, it is unclear that the SARS-CoV-2 infiltrate the central nervous system using this method 45 . ...
Background: Most of hospitalized patients with COVID-19 have had neurological
manifestations. However, biomarkers for specific neurological manifestations and how these affect clinical outcomes are still unclear. Objective: To describe the frequency of neurological manifestations in patients hospitalized with COVID-19 and analyze their relationship with biomarkers and relevant clinical outcomes. Methods: This retrospective cohort study included adult patients hospitalized due to COVID-19 with at least one neurological manifestation. Headache, anosmia, ageusia, and polyneuromyopathy were classified as nonspecific neurological manifestations, whereas epileptic seizures, decreased level of consciousness, delirium, encephalitis, abnormal movements, ataxia, and cerebrovascular events as specific. Assessed associations: a) clinical and laboratory covariates with the presentation of a specific neurological manifestation; b) the relationship between specific neurological manifestation and COVID-19 severity, mechanical ventilation, and mortality; and c) duration of mechanical ventilation and polyneuromyopathy. Results: Of the 338 patients included in the study, 61,2% had severe COVID-19, 25,2% required mechanical ventilation, and 23,7% died. The most frequent neurological manifestations were headache (68,3%), delirium (41,9%), decreased level
of consciousness (40,8%), and polyneuromyopathy (21,8%). High serum D-dimer levels and lymphopenia were associated with a specific neurological manifestation. At least one specific neurological manifestation was found in 39,9% of patients, and these group was associated with mechanical ventilation and mortality. Finally, a longer duration on mechanical ventilation was associated with a higher frequency of polyneuromyopathy.
Conclusion: Specific neurological manifestations were frequent in hospitalized patients with COVID-19 and are associated with greater clinical and laboratory severity.
... One of the symptoms of COVID-19 is headache, with a frequency of 6-13% [109,[124][125][126][127]. It frequently occurs with other symptoms like fever and cough; thus, it is not an isolated symptom. Hyposmia and hypogeusia were noted as symptoms observed in individuals diagnosed with COVID-19, with reported prevalence rates varying from approximately 5% [28,128] to as high as 70% [129] or even exceeding 79% [130,131]. The data presented in this study indicate that specific findings may possess prognostic relevance in predicting the possibility of serious neurological problems. ...
Respiratory viral infections have been found to have a negative impact on neurological functions, potentially leading to significant neurological impairment. The SARS-CoV-2 virus has precipitated a worldwide pandemic, posing a substantial threat to human lives. Growing evidence suggests that SARS-CoV-2 may severely affect the CNS and respiratory system. The current prevalence of clinical neurological issues associated with SARS-CoV-2 has raised significant concerns. However, there needs to be a more comprehensive understanding of the specific pathways by which SARS-CoV-2 enters the nervous system. Based on the available evidence, this review focuses on the clinical neurological manifestations of SARS-CoV-2 and the possible mechanisms by which SARS-CoV-2 invades the brain.
