Angiotensin-converting enzyme 2 in the brain: properties and future directions

Neurological consequences of COVID-19 and brain related pathogenic mechanisms: A new challenge for neuroscience

Due to the infection by the SARS-CoV-2 virus (COVID-19) there were also reported neurological symptoms, being the most frequent and best cited those that affect the cerebrovascular, sensorial, cognitive and motor functions, together with the neurological diffuse symptoms as for examples headache or dizziness. Besides, some of them behave high risk of mortality. Consequently, it is crucial to elucidate the mechanisms of action in brain of SARS-CoV-2 virus in order to create new therapeutic targets to fight against this new disease. Since now the mechanisms of arrival to the brain seems to be related with the following processes: blood brain barrier (BBB) disruption together with nervous or axonal transport of the virus by the trigeminal nerve, the vagus nerve, or the brain-gut-axis. Being two the mechanisms of brain affectation most cited: a direct affectation of the virus in the brain through neuroinvasion and an indirect mechanism of action due to the effects of the systemic infection. Both processes include the triggering of inflammation, hypoxia and the increased likelihood of secondary infections. This topic supposes a major novel challenge for neuroscience. Therefore, the aim of this review is to provide summarized information about the neurological symptomatology and the brain pathogenic mechanisms involved and reported in COVID-19.

A Peek into Pandora’s Box: COVID-19 and Neurodegeneration

Ever since it was first reported in Wuhan, China, the coronavirus-induced disease of 2019 (COVID-19) has become an enigma of sorts with ever expanding reports of direct and indirect effects of the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) on almost all the vital organ systems. Along with inciting acute pulmonary complications, the virus attacks the cardiac, renal, hepatic, and gastrointestinal systems as well as the central nervous system (CNS). The person-to-person variability in susceptibility of individuals to disease severity still remains a puzzle, although the comorbidities and the age/gender of a person are believed to play a key role. SARS-CoV-2 needs angiotensin-converting enzyme 2 (ACE2) receptor for its infectivity, and the association between SARS-CoV-2 and ACE2 leads to a decline in ACE2 activity and its neuroprotective effects. Acute respiratory distress may also induce hypoxia, leading to increased oxidative stress and neurodegeneration. Infection of the neurons along with peripheral leukocytes’ activation results in proinflammatory cytokine release, rendering the brain more susceptible to neurodegenerative changes. Due to the advancement in molecular biology techniques and vaccine development programs, the world now has hope to relatively quickly study and combat the deadly virus. On the other side, however, the virus seems to be still evolving with new variants being discovered periodically. In keeping up with the pace of this virus, there has been an avalanche of studies. This review provides an update on the recent progress in adjudicating the CNS-related mechanisms of SARS-CoV-2 infection and its potential to incite or accelerate neurodegeneration in surviving patients. Current as well as emerging therapeutic opportunities and biomarker development are highlighted.

Nutraceuticals in HIV and COVID-19-Related Neurological Complications: Opportunity to Use Extracellular Vesicles as Drug Delivery Modality

Simple Summary

In this review, we discuss the potential use of extracellular vesicles (EVs) to deliver dietary supplements to the brain to reduce brain complications associated with HIV, COVID-19, and other brain disorders. Brain-related complications affect people with HIV and COVID-19 alike. Moreover, since HIV patients are at a higher risk of contracting COVID-19, their neurological problems can be exacerbated by COVID-19. The use of dietary supplements together with available treatment options has been shown to reduce the severity of infections. However, these treatments are not chemically compatible with the body’s blood–brain barrier defense mechanism. Therefore, a viable delivery method is needed to deliver drugs and nutraceuticals to the brain in HIV and COVID-19 comorbid patients.

Abstract

People living with HIV/AIDS (PLWHA) are at an increased risk of severe and critical COVID-19 infection. There is a steady increase in neurological complications associated with COVID-19 infection, exacerbating HIV-associated neurocognitive disorders (HAND) in PLWHA. Nutraceuticals, such as phytochemicals from medicinal plants and dietary supplements, have been used as adjunct therapies for many disease conditions, including viral infections. Appropriate use of these adjunct therapies with antiviral proprieties may be beneficial in treating and/or prophylaxis of neurological complications associated with these co-infections. However, most of these nutraceuticals have poor bioavailability and cannot cross the blood–brain barrier (BBB). To overcome this challenge, extracellular vesicles (EVs), biological nanovesicles, can be used. Due to their intrinsic features of biocompatibility, stability, and their ability to cross BBB, as well as inherent homing capabilities, EVs hold immense promise for therapeutic drug delivery to the brain. Therefore, in this review, we summarize the potential role of different nutraceuticals in reducing HIV- and COVID-19-associated neurological complications and the use of EVs as nutraceutical/drug delivery vehicles to treat HIV, COVID-19, and other brain disorders.

Psychological Symptoms in COVID-19 Patients: Insights into Pathophysiology and Risk Factors of Long COVID-19

There is growing evidence of studies associating COVID-19 survivors with increased mental health consequences. Mental health implications related to a COVID-19 infection include both acute and long-term consequences. Here we discuss COVID-19-associated psychiatric sequelae, particularly anxiety, depression, and post-traumatic stress disorder (PTSD), drawing parallels to past coronavirus outbreaks. A literature search was completed across three databases, using keywords to search for relevant articles. The cause may directly correlate to the infection through both direct and indirect mechanisms, but the underlying etiology appears more complex and multifactorial, involving environmental, psychological, and biological factors. Although most risk factors and prevalence rates vary across various studies, being of the female gender and having a history of psychiatric disorders seem consistent. Several studies will be presented, demonstrating COVID-19 survivors presenting higher rates of mental health consequences than the general population. The possible mechanisms by which the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) enters the brain, affecting the central nervous system (CNS) and causing these psychiatric sequelae, will be discussed, particularly concerning the SARS-CoV-2 entry via the angiotensin-converting enzyme 2 (ACE-2) receptors and the implications of the immune inflammatory signaling on neuropsychiatric disorders. Some possible therapeutic options will also be considered.

COVID-19 and neurologic manifestations: a synthesis from the child neurologist's corner

BACKGROUND

Since December 2019, the SARS-CoV-2 virus has been a global health issue. The main clinical presentation of this virus is a flu-like disease; however, patients with diverse neurologic manifestations have also been reported. In this review, we attempt to summarize, discuss and update the knowledge of the neurologic manifestations in the pediatric population affected by SARS-CoV-2 infection and the pandemic's effects in children with neurologic diseases.

DATA SOURCES

This review analyzes studies found on the PubMed database using the following keywords: Neurologic manifestations COVID-19, Neurological COVID-19, coronavirus, SARS-CoV-2, pediatric COVID-19, COVID-19 in children, MIS-C, Pediatric Inflammatory Multisystem Syndrome, Guillain Barré Syndrome, Stroke, ADEM, and Anti-NMDA encephalitis. All studies cited were published between 2004 and 2022, and represent the most relevant articles in the field. The World Health Organization COVID-19 online dashboard was assessed to obtain updated epidemiological data.

RESULTS

The most common neurologic symptoms in the pediatric population are headache, seizures, encephalopathy, and muscle weakness. These can be present during COVID-19 or weeks after recovering from it. Children who presented with multi-system inflammatory syndrome had a higher incidence of neurologic manifestations, which conferred a greater risk of morbidity and mortality. Several neuro-pathophysiological mechanisms have been proposed, including direct virus invasion, hyper-inflammatory reactions, multi-systemic failure, prothrombotic states, and immune-mediated processes. On the other hand, the COVID-19 pandemic has affected patients with neurologic diseases, making it challenging to access controls, treatment, and therapies.

CONCLUSIONS

Various neurologic manifestations have been associated with children's SARS-CoV-2 infection. It is important to identify and give them proper and opportune treatment because they can be potentially grave and life-threatening; some can lead to long-lasting sequelae. Different neuro-pathophysiological mechanisms have been proposed, however, a causal relationship between SARS-CoV-2 infection and neurologic manifestations remains to be proven. Patients with neurologic diseases are especially affected by COVID-19, not only by the disease itself but also by its complications and pandemic management measures.

Cytokine Storm and Neuropathological Alterations in Patients with Neurological Manifestations of COVID-19

The COVID-19 pandemic is caused by the severe acute respiratory syndrome coronavirus (SARS-CoV-2), a respiratory pathogen with neuroinvasive potential. Neurological COVID-19 manifestations include loss of smell and taste, headache, dizziness, stroke, and potentially fatal encephalitis. Several studies found elevated proinflammatory cytokines, such as TNF-α, IFN-γ, IL-6 IL-8, IL- 10 IL-16, IL-17A, and IL-18 in severely and critically ill COVID-19 patients may persist even after apparent recovery from infection. Biomarker studies on CSF and plasma and serum from COVID-19 patients have also shown a high level of IL-6, intrathecal IgG, neurofilament light chain (NFL), glial fibrillary acidic protein (GFAP), and tau protein. Emerging evidence on the matter has established the concept of COVID-19-associated neuroinflammation, in the context of COVID-19-associated cytokine storm. While the short-term implications of this condition are extensively documented, its longterm implications are yet to be understood. The association of the aforementioned cytokines with the pathogenesis of neurodegenerative diseases, including Alzheimer's disease, Parkinson's disease, Huntington's disease, and amyotrophic lateral sclerosis, may increase COVID-19 patients' risk of developing neurodegenerative diseases. Analysis of proinflammatory cytokines and CSF biomarkers in patients with COVID-19 can contribute to the early detection of the disease's exacerbation, monitoring the neurological implications of the disease and devising risk scales, and identifying treatment targets.

Implications of testicular ACE2 and the renin-angiotensin system for SARS-CoV-2 on testis function

Although many studies have focused on SARS-CoV-2 infection in the lungs, comparatively little is known about the potential effects of the virus on male fertility. SARS-CoV-2 infection of target cells requires the presence of furin, angiotensin-converting enzyme 2 (ACE2) receptors, and transmembrane protease serine 2 (TMPRSS2). Thus, cells in the body that express these proteins might be highly susceptible to viral entry and downstream effects. Currently, reports regarding the expression of the viral entry proteins in the testes are conflicting; however, other members of the SARS-CoV family of viruses - such as SARS-CoV - have been suspected to cause testicular dysfunction and/or orchitis. SARS-CoV-2, which displays many similarities to SARS-CoV, could potentially cause similar adverse effects. Commonalities between SARS family members, taken in combination with sparse reports of testicular discomfort and altered hormone levels in patients with SARS-CoV-2, might indicate possible testicular dysfunction. Thus, SARS-CoV-2 infection has the potential for effects on testis somatic and germline cells and experimental approaches might be required to help identify potential short-term and long-term effects of SARS-CoV-2 on male fertility.

(Pro)renin Receptor and Blood Pressure Regulation: A Focus on the Central Nervous System

The renin-angiotensin system (RAS) is classically described as a hormonal system in which angiotensin II (Ang II) is one of the main active peptides. The action of circulating Ang II on its cognate Ang II type-1 receptor (AT1R) in circumventricular organs has important roles in regulating the autonomic nervous system, blood pressure (BP) and body fluid homeostasis, and has more recently been implicated in cardiovascular metabolism. The presence of a local or tissue RAS in various tissues, including the central nervous system (CNS), is well established. However, because the level of renin, the rate-limiting enzyme in the systemic RAS, is very low in the brain, how endogenous angiotensin peptides are generated in the CNS-the focus of this review-has been the subject of considerable debate. Notable in this context is the identification of the (pro)renin receptor (PRR) as a key component of the brain RAS in the production of Ang II in the CNS. In this review, we highlight cellular and anatomical locations of the PRR in the CNS. We also summarize studies using gain- and loss-of function approaches to elucidate the functional importance of brain PRR-mediated Ang II formation and brain RAS activation, as well as PRR-mediated Ang II-independent signaling pathways, in regulating BP. We further discuss recent developments in PRR involvement in cardiovascular and metabolic diseases and present perspectives for future directions.

Neurological manifestations of coronavirus infections, before and after COVID-19: a review of animal studies

Coronavirus disease 2019 (COVID-19) is an infectious disease caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). This virus, which was first identified in December 2019 in China, has resulted in a yet ongoing viral pandemic. Coronaviridae could potentially cause several disorders in a wide range of hosts such as birds and mammals. Although infections caused by this family of viruses are predominantly limited to the respiratory tract, Betacoronaviruses are potentially able to invade the central nervous system (CNS) as well as many other organs, thereby inducing neurological damage ranging from mild to lethal in both animals and humans. Over the past two decades, three novel CoVs, SARS-CoV-1, MERS-CoV, and SARS-CoV-2, emerging from animal reservoirs have exhibited neurotropic properties causing severe and even fatal neurological diseases. The pathobiology of these neuroinvasive viruses has yet to be fully known. Both clinical features of the previous CoV epidemics (SARS-CoV-1 and MERS-CoV) and lessons from animal models used in studying neurotropic CoVs, especially SARS and MERS, constitute beneficial tools in comprehending the exact mechanisms of virus implantation and in illustrating pathogenesis and virus dissemination pathways in the CNS. Here, we review the animal research which assessed CNS infections with previous more studied neurotropic CoVs to demonstrate how experimental studies with appliable animal models can provide scientists with a roadmap in the CNS impacts of SARS-CoV-2. Indeed, animal studies can finally help us discover the underlying mechanisms of damage to the nervous system in COVID-19 patients and find novel therapeutic agents in order to reduce mortality and morbidity associated with neurological complications of SARS-CoV-2 infection.

Neurological complications and infection mechanism of SARS-COV-2

Currently, SARS-CoV-2 has caused a global pandemic and threatened many lives. Although SARS-CoV-2 mainly causes respiratory diseases, growing data indicate that SARS-CoV-2 can also invade the central nervous system (CNS) and peripheral nervous system (PNS) causing multiple neurological diseases, such as encephalitis, encephalopathy, Guillain-Barré syndrome, meningitis, and skeletal muscular symptoms. Despite the increasing incidences of clinical neurological complications of SARS-CoV-2, the precise neuroinvasion mechanisms of SARS-CoV-2 have not been fully established. In this review, we primarily describe the clinical neurological complications associated with SARS-CoV-2 and discuss the potential mechanisms through which SARS-CoV-2 invades the brain based on the current evidence. Finally, we summarize the experimental models were used to study SARS-CoV-2 neuroinvasion. These data form the basis for studies on the significance of SARS-CoV-2 infection in the brain.

The underlying mechanisms for severe COVID-19 progression in people with diabetes mellitus: a critical review

Diabetes mellitus (DM) has a high incidence of comorbidities among patients with severe coronavirus disease 2019 (COVID-19). The elevated prevalence of DM in the world population makes it a significant risk factor because diabetic individuals appear to be prone to clinical complications and have increased mortality rates. Here, we review the possible underlying mechanisms involved in DM that led to worse outcomes in COVID-19. The impacts of hyperglycemia side effects, secondary comorbidities, weakened innate and adaptive immunity, chronic inflammation, and poor nutritional status, commonly present in DM, are discussed. The role of the SARS-CoV-2 receptor and its polymorphic variations on higher binding affinity to facilitate viral uptake in people with DM were also considered. Clinical differences between individuals with type 1 DM and type 2 DM affected by COVID-19 and the potential diabetogenic effect of SARS-CoV-2 infection were addressed.

PDZ-Containing Proteins Targeted by the ACE2 Receptor

Angiotensin-converting enzyme 2 (ACE2) is a main receptor for SARS-CoV-2 entry to the host cell. Indeed, the first step in viral entry is the binding of the viral trimeric spike (S) protein to ACE2. Abundantly present in human epithelial cells of many organs, ACE2 is also expressed in the human brain. ACE2 is a type I membrane protein with an extracellular N-terminal peptidase domain and a C-terminal collectrin-like domain that ends with a single transmembrane helix and an intracellular 44-residue segment. This C-terminal segment contains a PDZ-binding motif (PBM) targeting protein-interacting domains called PSD-95/Dlg/ZO-1 (PDZ). Here, we identified the human PDZ specificity profile of the ACE2 PBM using the high-throughput holdup assay and measuring the binding intensities of the PBM of ACE2 against the full human PDZome. We discovered 14 human PDZ binders of ACE2 showing significant binding with dissociation constants' values ranging from 3 to 81 μM. NHERF, SHANK, and SNX27 proteins found in this study are involved in protein trafficking. The PDZ/PBM interactions with ACE2 could play a role in ACE2 internalization and recycling that could be of benefit for the virus entry. Interestingly, most of the ACE2 partners we identified are expressed in neuronal cells, such as SHANK and MAST families, and modifications of the interactions between ACE2 and these neuronal proteins may be involved in the neurological symptoms of COVID-19.

Potential implications of angiotensin-converting enzyme 2 blockades on neuroinflammation in SARS-CoV-2 infection

BACKGROUND

Angiotensin-converting enzyme 2 (ACE2) has been reported as a portal for the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection. Consequently, scientific strategies to combat coronavirus disease of 2019 (COVID-19) were targeted to arrest SARS-CoV-2 invasion by blocking ACE2. While blocking ACE2 appears a beneficial approach to treat COVID-19, clinical concerns have been raised primarily due to the various intrinsic roles of ACE2 in neurological functions. Selective reports indicate that angiotensin receptor blockers (ARBs) and angiotensin-converting enzyme inhibitors (ACEIs) upregulate ACE2 levels. ACE2 metabolizes angiotensin II and several peptides, including apelin-13, neurotensin, kinetensin, dynorphin, [des-Arg9] bradykinin, and [Lys-des-Arg9]-bradykinin, which may elicit neuroprotective effects. Since ARBs and ACEIs upregulate ACE2, it may be hypothesized that patients with hypertension receiving ARBs and ACEIs may have higher expression of ACE2 and thus be at a greater risk of severe disease from the SARS-CoV-2 infections. However, recent clinical reports indicate the beneficial role of ARBs/ACEIs in reducing COVID-19 severity. Together, this warrants a further study of the effects of ACE2 blockades in hypertensive patients medicated with ARBs/ACEIs, and their consequential impact on neuronal health. However, the associations between their blockade and any neuroinflammation also warrant further research.

OBJECTIVE

This review collates mechanistic insights into the dichotomous roles of ACE2 in SARS-CoV-2 invasion and neurometabolic functions and the possible impact of ACE2 blockade on neuroinflammation.

CONCLUSION

It has been concluded that ACE2 blockade imposes neuroinflammation.

Evidence of Coronavirus (CoV) Pathogenesis and Emerging Pathogen SARS-CoV-2 in the Nervous System: A Review on Neurological Impairments and Manifestations

The coronavirus disease 2019 (COVID-19) pandemic is an issue of global significance that has taken the lives of many across the world. Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) is the virus responsible for its pathogenesis. The pulmonary manifestations of COVID-19 have been well described in the literature. Initially, it was thought to be limited to the respiratory system; however, we now recognize that COVID-19 also affects several other organs, including the nervous system. Two similar human coronaviruses (CoV) that cause severe acute respiratory syndrome (SARS-CoV-1) and Middle East respiratory syndrome (MERS-CoV) are also known to cause disease in the nervous system. The neurological manifestations of SARS-CoV-2 infection are growing rapidly, as evidenced by several reports. There are several mechanisms responsible for such manifestations in the nervous system. For instance, post-infectious immune-mediated processes, direct virus infection of the central nervous system (CNS), and virus-induced hyperinflammatory and hypercoagulable states are commonly involved. Guillain-Barré syndrome (GBS) and its variants, dysfunction of taste and smell, and muscle injury are numerous examples of COVID-19 PNS (peripheral nervous system) disease. Likewise, hemorrhagic and ischemic stroke, encephalitis, meningitis, encephalopathy acute disseminated encephalomyelitis, endothelialitis, and venous sinus thrombosis are some instances of COVID-19 CNS disease. Due to multifactorial and complicated pathogenic mechanisms, COVID-19 poses a large-scale threat to the whole nervous system. A complete understanding of SARS-CoV-2 neurological impairments is still lacking, but our knowledge base is rapidly expanding. Therefore, we anticipate that this comprehensive review will provide valuable insights and facilitate the work of neuroscientists in unfolding different neurological dimensions of COVID-19 and other CoV associated abnormalities.

Neurobiology of COVID-19: how can the virus affect the brain?

Severe acute respiratory syndrome-related coronavirus-2 (SARS-CoV-2) causes the coronavirus disease 2019 (COVID-19), which has been declared a public health emergency of international interest, with confirmed cases in most countries. COVID-19 presents manifestations that can range from asymptomatic or mild infections up to severe manifestations that lead to hospitalization and death. A growing amount of evidence indicates that the virus may cause neuroinvasion. Postmortem brain study findings have included edema, hemorrhage, hydrocephalus, atrophy, encephalitis, infarcts, swollen axons, myelin loss, gliosis, neuronal satellitosis, hypoxic-ischemic damage, arteriolosclerosis, leptomeningeal inflammation, neuronal loss, and axon degeneration. In addition, the COVID-19 pandemic is causing dangerous effects on the mental health of the world population, some of which can be attributed to its social impact (social distancing, financial issues, and quarantine). There is also a concern that environmental stressors, enhanced by psychological factors, are contributing to the emergence of psychiatric outcomes during the pandemic. Although clinical studies and diagnosing SARS-CoV-2-related neurological disease can be challenging, they are necessary to help define the manifestations and burden of COVID-19 in neurological and psychiatric symptoms during and after the pandemic. This review aims to present the neurobiology of coronavirus and postmortem neuropathological hallmarks.

Renin-Angiotensin System Alterations in the Human Alzheimer's Disease Brain

BACKGROUND

Understanding Alzheimer's disease (AD) in terms of its various pathophysiological pathways is essential to unravel the complex nature of the disease process and identify potential therapeutic targets. The renin-angiotensin system (RAS) has been implicated in several brain diseases, including traumatic brain injury, ischemic stroke, and AD.

OBJECTIVE

This study was designed to evaluate the protein expression levels of RAS components in postmortem cortical and hippocampal brain samples obtained from AD versus non-AD individuals.

METHODS

We analyzed RAS components in the cortex and hippocampus of postmortem human brain samples by western blotting and immunohistochemical techniques in comparison with age-matched non-demented controls.

RESULTS

The expression of AT1R increased in the hippocampus, whereas AT2R expression remained almost unchanged in the cortical and hippocampal regions of AD compared to non-AD brains. The Mas receptor was downregulated in the hippocampus. We also detected slight reductions in ACE-1 protein levels in both the cortex and hippocampus of AD brains, with minor elevations in ACE-2 in the cortex. We did not find remarkable differences in the protein levels of angiotensinogen and Ang II in either the cortex or hippocampus of AD brains, whereas we observed a considerable increase in the expression of brain-derived neurotrophic factor in the hippocampus.

CONCLUSION

The current findings support the significant contribution of RAS components in AD pathogenesis, further suggesting that strategies focusing on the AT1R and AT2R pathways may lead to novel therapies for the management of AD.

SARS-CoV-2 Spike Protein Disrupts Blood-Brain Barrier Integrity via RhoA Activation

The SARS-CoV-2 spike protein has been shown to disrupt blood–brain barrier (BBB) function, but its pathogenic mechanism of action is unknown. Whether angiotensin converting enzyme 2 (ACE2), the viral binding site for SARS-CoV-2, contributes to the spike protein-induced barrier disruption also remains unclear. Here, a 3D-BBB microfluidic model was used to interrogate mechanisms by which the spike protein may facilitate barrier dysfunction. The spike protein upregulated the expression of ACE2 in response to laminar shear stress. Moreover, interrogating the role of ACE2 showed that knock-down affected endothelial barrier properties. These results identify a possible role of ACE2 in barrier homeostasis. Analysis of RhoA, a key molecule in regulating endothelial cytoskeleton and tight junction complex dynamics, reveals that the spike protein triggers RhoA activation. Inhibition of RhoA with C3 transferase rescues its effect on tight junction disassembly. Overall, these results indicate a possible means by which the engagement of SARS-CoV-2 with ACE2 facilitates disruption of the BBB via RhoA activation. Understanding how SARS-CoV-2 dysregulates the BBB may lead to strategies to prevent the neurological deficits seen in COVID-19 patients.

A review of ischemic stroke in COVID-19: currently known pathophysiological mechanisms

Coronavirus disease 2019 (COVID-19), the third type of coronavirus pneumonia after severe acute respiratory syndrome (SARS) and Middle East respiratory syndrome (MERS), is spreading widely worldwide now. This pneumonia causes not only respiratory symptoms but also multiple organ dysfunction, including thrombotic diseases such as ischemic stroke. The purpose of this review is to explore whether COVID-19 is a risk factor for ischemic stroke and its related pathophysiological mechanisms. Based on the high thrombosis rate and frequent strokes of COVID-19 patients, combined with related laboratory indicators and pathological results, the discussion is mainly from two aspects: nerve invasion and endothelial dysfunction. SARS-CoV-2 can directly invade the CNS through blood-borne and neuronal retrograde pathways, causing cerebrovascular diseases. In addition, the endothelial dysfunction in COVID-19 is almost certain. Cytokine storm causes thromboinflammation, and downregulation of ACE2 leads to RAS imbalance, which eventually lead to ischemic stroke.

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.

Neuropsychiatric manifestations of COVID-19, potential neurotropic mechanisms, and therapeutic interventions

The coronavirus disease 2019 (COVID-19) pandemic has caused large-scale economic and social losses and worldwide deaths. Although most COVID-19 patients have initially complained of respiratory insufficiency, the presence of neuropsychiatric manifestations is also reported frequently, ranging from headache, hyposmia/anosmia, and neuromuscular dysfunction to stroke, seizure, encephalopathy, altered mental status, and psychiatric disorders, both in the acute phase and in the long term. These neuropsychiatric complications have emerged as a potential indicator of worsened clinical outcomes and poor prognosis, thus contributing to mortality in COVID-19 patients. Their etiology remains largely unclear and probably involves multiple neuroinvasive pathways. Here, we summarize recent animal and human studies for neurotrophic properties of severe acute respiratory syndrome coronavirus (SARS-CoV-2) and elucidate potential neuropathogenic mechanisms involved in the viral invasion of the central nervous system as a cause for brain damage and neurological impairments. We then discuss the potential therapeutic strategy for intervening and preventing neuropsychiatric complications associated with SARS-CoV-2 infection. Time-series monitoring of clinical-neurochemical-radiological progress of neuropsychiatric and neuroimmune complications need implementation in individuals exposed to SARS-CoV-2. The development of a screening, intervention, and therapeutic framework to prevent and reduce neuropsychiatric sequela is urgently needed and crucial for the short- and long-term recovery of COVID-19 patients.

Design and Development of Nanomaterial-Based Drug Carriers to Overcome the Blood-Brain Barrier by Using Different Transport Mechanisms

Central nervous system (CNS) diseases are the leading causes of death and disabilities in the world. It is quite challenging to treat CNS diseases efficiently because of the blood-brain barrier (BBB). It is a physical barrier with tight junction proteins and high selectivity to limit the substance transportation between the blood and neural tissues. Thus, it is important to understand BBB transport mechanisms for developing novel drug carriers to overcome the BBB. This paper introduces the structure of the BBB and its physiological transport mechanisms. Meanwhile, different strategies for crossing the BBB by using nanomaterial-based drug carriers are reviewed, including carrier-mediated, adsorptive-mediated, and receptor-mediated transcytosis. Since the viral-induced CNS diseases are associated with BBB breakdown, various neurotropic viruses and their mechanisms on BBB disruption are reviewed and discussed, which are considered as an alternative solution to overcome the BBB. Therefore, most recent studies on virus-mimicking nanocarriers for drug delivery to cross the BBB are also reviewed and discussed. On the other hand, the routes of administration of drug-loaded nanocarriers to the CNS have been reviewed. In sum, this paper reviews and discusses various strategies and routes of nano-formulated drug delivery systems across the BBB to the brain, which will contribute to the advanced diagnosis and treatment of CNS diseases.

COVID-19 Infection in Children, Infants and Pregnant Subjects: An Overview of Recent Insights and Therapies

BACKGROUND

The SARS-CoV-2 pandemic has involved a severe increase of cases worldwide in a wide range of populations. The aim of the present investigation was to evaluate recent insights about COVID-19 infection in children, infants and pregnant subjects.

METHODS

a literature overview was performed including clinical trials, in vitro studies, reviews and published guidelines regarding the present paper topic. A descriptive synthesis was performed to evaluate recent insights and the effectiveness of therapies for SARS-CoV-2 infection in children, infants and pregnant subjects.

RESULTS

Insufficient data are available regarding the relationship between COVID-19 and the clinical risk of spontaneous abortion and premature foetus death. A decrease in the incidence of COVID-19 could be correlated to a minor expression of ACE2 in childrens' lungs. At present, a modulation of the dose-effect posology for children and infants is necessary.

CONCLUSIONS

Pregnant vertical transmission has been hypothesised for SARS-CoV-2 infection. Vaccines are necessary to achieve mass immunity for children and also pregnant subjects.

Novel Insights into the Antagonistic Effects of Losartan against Angiotensin II/AGTR1 Signaling in Glioblastoma Cells

Simple Summary

Patients with high-grade glioma (HGG) such as glioblastoma (GBM) who undergo surgical resection with adjuvant therapy have a mean overall survival of 14.6 months and 100% of recurrence. Thus, these disappointing outcomes in terms of glioblastoma life expectancy require seeking novel pharmacological tools, including drug repurposing. In the present study, we identify a novel molecular mechanism through which Losartan antagonizes Angiotensin II (Ang II)/Angiotensin II type I receptor (AGTR1) signaling, overexpressed in GBM cells. For instance, we demonstrate how Losartan drastically inhibits the stimulatory effects of Ang II on aromatase activity and consequently reduces local estrogen production, sustaining cancer progression. Thus, it is reasonable to repurpose Losartan as an adjuvant pharmacological tool to be implemented prospectively in the novel therapeutic strategies adopted in GBM patients.

Abstract

New avenues for glioblastoma therapy are required due to the limited mortality benefit of the current treatments. The renin-angiotensin system (RAS) exhibits local actions and works as a paracrine system in different tissues and tumors, including glioma. The glioblastoma cell lines U-87 MG and T98G overexpresses Angiotensin II (Ang II)/Angiotensin II type I receptor (AGTR1) signaling, which enhances in vitro and in vivo local estrogen production through a direct up-regulation of the aromatase gene promoters p I.f and p I.4. In addition, Ang II/AGTR1 signaling transactivates estrogen receptor-α in a ligand-independent manner through mitogen-activated protein kinase (MAPK) activation. The higher aromatase mRNA expression in patients with glioblastoma was associated with the worst survival prognostic, according to The Cancer Genome Atlas (TCGA). An intrinsic immunosuppressive glioblastoma tumor milieu has been previously documented. We demonstrate how Ang II treatment in glioblastoma cells increases programmed death-ligand 1 (PD-L1) expression reversed by combined exposure to Losartan (LOS) in vitro and in vivo. Our findings highlight how LOS, in addition, antagonizes the previously documented neoangiogenetic, profibrotic, and immunosuppressive effects of Ang II and drastically inhibits its stimulatory effects on local estrogen production, sustaining glioblastoma cell growth. Thus, Losartan may represent an adjuvant pharmacological tool to be repurposed prospectively for glioblastoma treatment.

Stroke Associated with SARS-CoV-2 Infection and its Pathogenesis: A Systematic Review

INTRODUCTION

The change of stroke incidence during the COVID-19 pandemic period and the proposed mechanisms of the relationship between SARS-CoV-2 and stroke is reviewed.

METHODS

Web of Science, PMC/Medline, and Scopus databases were searched until July 2020 without time and language limitations. After quality assessment, 22 articles were included in this study.

RESULTS

Based on the results, it is impossible to conclude any definite relationship between the rising or decreasing stroke frequency or the shift in the ischemic and hemorrhagic ratio and SARS-CoV-2 infection. However, it appears that SARS-CoV-2 infection has some correlation with stroke. The supposed mechanisms for the SARS-CoV-2-related hemorrhagic stroke include 1) SARS-CoV-2-related vasculopathy with the endothelial damage of small vessels, 2) viral infection-induced platelet dysfunction or thrombocytopenia, and 3) activation of the proinflammatory cascade leading to coagulopathy. The helpful strategies are receiving therapeutic anticoagulation for high D-dimer or a known thrombus due to SARS-CoV-2 infection, as well as using extracorporeal membrane oxygenation (ECMO) in some patients. Furthermore, the possible mechanisms for the SARS-CoV-2-related ischemic stroke include 1) dysregulation of angiotensin-converting enzyme 2 (a key host cellular receptor for SARSCoV-2)-related physiologic functions, 2) endothelial cell damages, 3) thrombo-inflammation, and 4) coagulopathy and coagulation abnormalities related to SARS-CoV-2 infection.

CONCLUSION

A better understanding of the SARS-CoV-2 pathogenesis and its relation to neurologic abnormalities such as stroke can help to design new therapeutic approaches.

Blood-Brain Barrier Crossing Renin-Angiotensin Drugs and Cognition in the Elderly: A Meta-Analysis

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Analysis of COVID-19 vaccines: Types, thoughts, and application

OBJECTIVE

To deal with COVID-19, various countries have made many efforts, including the research and development of vaccines. The purpose of this manuscript was to summarize the development, application, and problems of COVID-19 vaccines.

METHODS

This article reviewed the existing literature to see the development of the COVID-19 vaccine.

RESULTS

We found that different types of vaccines had their own advantages and disadvantages. At the same time, the side effects of the vaccine, the dose of vaccination, the evaluation of the efficacy, and the application of the vaccine were all things worth studying.

CONCLUSION

The successful development of the COVID-19 vaccine concerns almost all countries and people in the world. We must do an excellent job of researching the immunogenicity and immune reactivity of the vaccines. We hope this review can help colleagues at home and abroad.

Correlation of Neuroimaging Findings with Clinical Presentation and Laboratory Data in Patients with COVID-19: A Single-Center Study

Background

This study was aimed at revealing neuroimaging findings in COVID-19 patients and at discussing their relationship with epidemiological data and some laboratory parameters. Materials and Method. This study included 436 cases of COVID-19 and 40 cases of non-COVID-19 acute/subacute thromboembolism who underwent at least one neuroimaging procedure due to neurological symptoms between April 2020 and December 2020. The group of COVID-19-positive acute/subacute thromboembolism cases was compared with both the group of normal brain imaging cases and the non-COVID-19 acute/subacute thromboembolism group in terms of demographic data and laboratory parameters.

Results

When the acute/subacute thromboembolism group and neuroimaging findings were compared in terms of negative group, presence of comorbid disease, D-dimer level, and lymphocyte count in COVID-19 patients, a statistically significant difference was found (p = 0.047, 0.014, and <0.001, respectively). COVID-19-positive and COVID-19-negative acute/subacute thromboembolism cases that were compared in terms of gender, neuroimaging reason, C-reactive protein, D-dimer level and lymphocyte count, a statistically significant difference was found (p = 0.003, <0.001, 0.005, 0.02, and <0.001, respectively).

Conclusion

Acute thromboembolic events are common in patients with COVID-19 due to a potentially increased procoagulant process. Neurological evaluation and, if necessary, detailed neuroimaging should be performed, especially in cases with high D-dimer levels.

What can the neurological manifestations of COVID-19 tell us: a meta-analysis

Background

Covid-19 became a global pandemic in 2019. Studies have shown that coronavirus can cause neurological symptoms, but clinical studies on its neurological symptoms are limited. In this meta-analysis, we aimed to summarize the various neurological manifestations that occurred in COVID-19 patients and calculate the incidence of various neurological manifestations. At the same time, we further explored the mechanism of nervous system injury and prognosis in COVID-19 patients in combination with their nervous system manifestations. This study provides a reference for early clinical identification of COVID-19 nervous system injury in the future, so as to achieve early treatment and reduce neurological sequelae.

Methods

We systematically searched all published English literature related to the neurological manifestations of COVID-19 from January 1, 2020, to April 30, 2021, in Pubmed, Embase, and Cochrane Library. The keywords used were COVID-19 and terminology related to the nervous system performance. All included studies were selected by two independent reviewers using EndNote and NoteExpress software, any disagreement was resolved by consensus or by a third reviewer, and the selected data were then collected for meta-analysis using a random-effects model.

Results

A total of 168 articles (n = 292,693) were included in the study, and the meta-analysis showed that the most common neurological manifestations of COVID-19 were myalgia(33%; 95%CI 0.30–0.37; I² = 99.17%), smell impairment(33%; 95%CI 0.28–0.38; I² = 99.40%), taste dysfunction(33%; 95%CI 0.27–0.39; I² = 99.09%), altered mental status(32%; 95%CI 0.22–0.43; I² = 99.06%), headache(29%; 95%CI 0.25–0.33; I² = 99.42%), encephalopathy(26%; 95%CI 0.16–0.38; I² = 99.31%), alteration of consciousness(13%; 95%CI 0.08–0.19; I² = 98.10%), stroke(12%; 95%CI 0.08–0.16; I² = 98.95%), dizziness(10%; 95%CI 0.08–0.13; I² = 96.45%), vision impairment(6%; 95%CI 0.03–0.09; I² = 86.82%), intracerebral haemorrhage(5%; 95%CI 0.03–0.09; I² = 95.60%), seizure(4%; 95%CI 0.02 -0.05; I² = 98.15%), encephalitis(2%; 95%CI 0.01–0.03; I² = 90.36%), Guillan-Barré Syndrome (GBS) (1%; 95%CI 0.00–0.03; I² = 89.48%).

Conclusions

Neurological symptoms are common and varied in Covid-19 infections, and a growing number of reports suggest that the prevalence of neurological symptoms may be increasing. In the future, the role of COVID-19 neurological symptoms in the progression of COVID-19 should be further studied, and its pathogenesis and assessment methods should be explored, to detect and treat early neurological complications of COVID-19 and reduce mortality.

Microbiota-Gut-Brain Communication in the SARS-CoV-2 Infection

The coronavirus disease of 2019 (COVID-19) is an infectious disease caused by severe acute respiratory syndrome 2 (SARS-CoV-2). In addition to pneumonia, individuals affected by the disease have neurological symptoms. Indeed, SARS-CoV-2 has a neuroinvasive capacity. It is known that the infection caused by SARS-CoV-2 leads to a cytokine storm. An exacerbated inflammatory state can lead to the blood-brain barrier (BBB) damage as well as to intestinal dysbiosis. These changes, in turn, are associated with microglial activation and reactivity of astrocytes that can promote the degeneration of neurons and be associated with the development of psychiatric disorders and neurodegenerative diseases. Studies also have been shown that SARS-CoV-2 alters the composition and functional activity of the gut microbiota. The microbiota-gut-brain axis provides a bidirectional homeostatic communication pathway. Thus, this review focuses on studies that show the relationship between inflammation and the gut microbiota-brain axis in SARS-CoV-2 infection.

Neuropathophysiology of coronavirus disease 2019: neuroinflammation and blood brain barrier disruption are critical pathophysiological processes that contribute to the clinical symptoms of SARS-CoV-2 infection

Coronavirus disease 2019 (COVID-19) is caused by the novel SARS-CoV-2 (severe acute respiratory syndrome coronavirus 2) first discovered in Wuhan, Hubei province, China in December 2019. SARS-CoV-2 has infected several millions of people, resulting in a huge socioeconomic cost and over 2.5 million deaths worldwide. Though the pathogenesis of COVID-19 is not fully understood, data have consistently shown that SARS-CoV-2 mainly affects the respiratory and gastrointestinal tracts. Nevertheless, accumulating evidence has implicated the central nervous system in the pathogenesis of SARS-CoV-2 infection. Unfortunately, however, the mechanisms of SARS-CoV-2 induced impairment of the central nervous system are not completely known. Here, we review the literature on possible neuropathogenic mechanisms of SARS-CoV-2 induced cerebral damage. The results suggest that downregulation of angiotensin converting enzyme 2 (ACE2) with increased activity of the transmembrane protease serine 2 (TMPRSS2) and cathepsin L in SARS-CoV-2 neuroinvasion may result in upregulation of proinflammatory mediators and reactive species that trigger neuroinflammatory response and blood brain barrier disruption. Furthermore, dysregulation of hormone and neurotransmitter signalling may constitute a fundamental mechanism involved in the neuropathogenic sequelae of SARS-CoV-2 infection. The viral RNA or antigenic peptides also activate or interact with molecular signalling pathways mediated by pattern recognition receptors (e.g., toll-like receptors), nuclear factor kappa B, Janus kinase/signal transducer and activator of transcription, complement cascades, and cell suicide molecules. Potential molecular targets and therapeutics of SARS-CoV-2 induced neurologic damage are also discussed.

The Effect of COVID-19 on NF-κB and Neurological Manifestations of Disease

The coronavirus disease that presumably began in 2019 (COVID-19) is a highly infectious disease caused by the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) and has resulted in a pandemic. Initially, COVID-19 was thought to only affect respiration. However, accumulating evidence shows a wide range of neurological symptoms are also associated with COVID-19, such as anosmia/ageusia, headaches, seizures, demyelination, mental confusion, delirium, and coma. Neurological symptoms in COVID-19 patients may arise due to a cytokine storm and a heighten state of inflammation. The nuclear factor kappa-light-chain enhancer of activated B cells (NF-κB) is a central pathway involved with inflammation and is shown to be elevated in a dose-dependent matter in response to coronaviruses. NF-κB has a role in cytokine storm syndrome, which is associated with greater severity in COVID-19-related symptoms. Therefore, therapeutics that reduce the NF-κB pathway should be considered in the treatment of COVID-19. Neuro-COVID-19 units have been established across the world to examine the neurological symptoms associated with COVID-19. Neuro-COVID-19 is increasingly becoming an accepted term among scientists and clinicians, and interdisciplinary teams should be created to implement strategies for treating the wide range of neurological symptoms observed in COVID-19 patients.

Demyelination as a result of an immune response in patients with COVID-19

The coronavirus disease of 2019 (COVID-19) is caused by the severe acute respiratory syndrome coronavirus-2 (SARS CoV-2), that already appeared as a global pandemic. Presentation of the disease often includes upper respiratory symptoms like dry cough, dyspnea, chest pain, and rhinorrhea that can develop to respiratory failure, needing intubation. Furthermore, the occurrence of acute and subacute neurological manifestations such as stroke, encephalitis, headache, and seizures are frequently stated in patients with COVID-19. One of the reported neurological complications of severe COVID-19 is the demolition of the myelin sheath. Indeed, the complex immunological dysfunction provides a substrate for the development of demyelination. Nevertheless, few published reports in the literature describe demyelination in subjects with COVID-19. In this short narrative review, we discuss probable pathological mechanisms that may trigger demyelination in patients with SARS-CoV-2 infection and summarize the clinical evidence, confirming SARS-CoV-2 condition as a risk factor for the destruction of myelin.

SARS-CoV-2 Infected Pediatric Cerebral Cortical Neurons: Transcriptomic Analysis and Potential Role of Toll-like Receptors in Pathogenesis

Different mechanisms were proposed as responsible for COVID-19 neurological symptoms but a clear one has not been established yet. In this work we aimed to study SARS-CoV-2 capacity to infect pediatric human cortical neuronal HCN-2 cells, studying the changes in the transcriptomic profile by next generation sequencing. SARS-CoV-2 was able to replicate in HCN-2 cells, that did not express ACE2, confirmed also with Western blot, and TMPRSS2. Looking for pattern recognition receptor expression, we found the deregulation of scavenger receptors, such as SR-B1, and the downregulation of genes encoding for Nod-like receptors. On the other hand, TLR1, TLR4 and TLR6 encoding for Toll-like receptors (TLRs) were upregulated. We also found the upregulation of genes encoding for ERK, JNK, NF-κB and Caspase 8 in our transcriptomic analysis. Regarding the expression of known receptors for viral RNA, only RIG-1 showed an increased expression; downstream RIG-1, the genes encoding for TRAF3, IKKε and IRF3 were downregulated. We also found the upregulation of genes encoding for chemokines and accordingly we found an increase in cytokine/chemokine levels in the medium. According to our results, it is possible to speculate that additionally to ACE2 and TMPRSS2, also other receptors may interact with SARS-CoV-2 proteins and mediate its entry or pathogenesis in pediatric cortical neurons infected with SARS-CoV-2. In particular, TLRs signaling could be crucial for the neurological involvement related to SARS-CoV-2 infection.

The Impact of the COVID-19 Pandemic on Dementia Risk: Potential Pathways to Cognitive Decline

BACKGROUND

Coronavirus disease 2019 (COVID-19), the far-reaching pandemic, has infected approximately 185 million of the world's population to date. After infection, certain groups, including older adults, men, and people of color, are more likely to have adverse medical outcomes. COVID-19 can affect multiple organ systems, even among asymptomatic/mild severity individuals, with progressively worse damage for those with higher severity infections.

SUMMARY

The COVID-19 virus, severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), primarily attaches to cells through the angiotensin-converting enzyme 2 (ACE2) receptor, a universal receptor present in most major organ systems. As SARS-CoV-2 binds to the ACE2 receptor, its bioavailability becomes limited, thus disrupting homeostatic organ function and inducing an injury cascade. Organ damage can then arise from multiple sources including direct cellular infection, overactive detrimental systemic immune response, and ischemia/hypoxia through thromboembolisms or disruption of perfusion. In the brain, SARS-CoV-2 has neuroinvasive and neurotropic characteristics with acute and chronic neurovirulent potential. In the cardiovascular system, COVID-19 can induce myocardial and systemic vascular damage along with thrombosis. Other organ systems such as the lungs, kidney, and liver are all at risk for infection damage. Key Messages: Our hypothesis is that each injury consequence has the independent potential to contribute to long-term cognitive deficits with the possibility of progressing to or worsening pre-existing dementia. Already, reports from recovered COVID-19 patients indicate that cognitive alterations and long-term symptoms are prevalent. This critical review highlights the injury pathways possible through SARS-CoV-2 infection that have the potential to increase and contribute to cognitive impairment and dementia.

Intracranial Hemorrhage in COVID-19 patients: A Case Series

Background

The coronavirus disease 2019 (COVID-19) pandemic is an ongoing public health emergency. While most cases end in asymptomatic or minor illness, there is growing evidence that some COVID-19 infections result in nonconventional dire consequences. We sought to describe the characteristics of patients with intracranial hemorrhage who were infected with severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). Also, with the existing literature, we raise the idea of a possible association between SARS-CoV-2 infection and intracranial hemorrhage and propose possible pathophysiological mechanisms connecting the two.

Methods

We retrospectively collected and analyzed intracranial hemorrhage cases who were also positive for SARS-CoV-2 from 4 tertiary-care cerebrovascular centers.

Results

We identified a total of 19 patients consisting of 11 males (58%) and 8 females (42%). Mean age was 52.2, with 95% younger than 75 years of age. With respect to COVID-19 illness, 50% had mild-to-moderate disease, 21% had severe disease, and 20% had critical disease requiring intubation. Of the 19 cases, 12 patients had intraparenchymal hemorrhage (63%), 6 had subarachnoid hemorrhage (32%), and 1 patient had a subdural hematoma (5%). A total of 43% had an intracerebral hemorrhage score of 0–2 and 57% a score of 3–6. Modified Rankin Scale cores at discharge were 0–2 in 23% and 3–6 in 77%. The mortality rate was 59%.

Conclusions

Our series sheds light on a distinct pattern of intracerebral hemorrhage in COVID-19–positive cases compared with typical non–COVID-19 cases, namely the severity of hemorrhage, high mortality rate, and the young age of patients. Further research is warranted to delineate a potential association between SARS-CoV-2 infection and intracranial hemorrhage.

Anti-inflammatory Therapy by Cholinergic and Purinergic Modulation in Multiple Sclerosis Associated with SARS-CoV-2 Infection

The virus "acute respiratory syndrome coronavirus 2" (SARS-CoV-2) is the etiologic agent of coronavirus disease 2019 (COVID-19), initially responsible for an outbreak of pneumonia in Wuhan, China, which, due to the high level of contagion and dissemination, has become a pandemic. The clinical picture varies from mild to critical cases; however, all of these signs already show neurological problems, from sensory loss to neurological diseases. Thus, patients with multiple sclerosis (MS) infected with the new coronavirus are more likely to develop severe conditions; in addition to worsening the disease, this is due to the high level of pro-inflammatory cytokines, which is closely associated with increased mortality both in COVID-19 and MS. This increase is uncontrolled and exaggerated, characterizing the cytokine storm, so a possible therapy for this neuronal inflammation is the modulation of the cholinergic anti-inflammatory pathway, since acetylcholine (ACh) acts to reduce pro-inflammatory cytokines and acts directly on the brain for being released by cholinergic neurons, as well as acting on other cells such as immune and blood cells. In addition, due to tissue damage, there is an exacerbated release of adenosine triphosphate (ATP), potentiating the inflammatory process and activating purinergic receptors which act directly on neuroinflammation and positively modulate the inflammatory cycle. Associated with this, in neurological pathologies, there is greater expression of P2X7 in the cells of the microglia, which positively activates the immune inflammatory response. Thus, the administration of blockers of this receptor can act in conjunction with the action of ACh in the anticholinergic inflammatory pathway. Finally, there will be a reduction in the cytokine storm and triggered hyperinflammation, as well as the level of mortality in patients with multiple sclerosis infected with SARS-CoV-2 and the development of possible neurological damage.

Can SARS-CoV-2 infect the central nervous system via the olfactory bulb or the blood-brain barrier?

Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) emerged in Wuhan, China in December 2019. On February 11, the World Health Organization (WHO) announced the name for the new illness caused by SARS-CoV-2: COVID-19. By March 11, the outbreak of COVID-19 was declared a pandemic by the WHO. This virus has extensively altered daily life for many across the globe, while claiming hundreds of thousands of lives. While fundamentally a respiratory illness, many infected individuals experience symptoms that involve the central nervous system (CNS). It is likely that many of these symptoms are the result of the virus residing outside of the CNS. However, the current evidence does indicate that the SARS-CoV-2 virus can use olfactory neurons (or other nerve tracts) to travel from the periphery into the CNS, and that the virus may also enter the brain through the blood-brain barrier (BBB). We discuss how the virus may use established infection mechanisms (ACE2, NRP1, TMPRSS2, furin and Cathepsin L), as well mechanisms still under consideration (BASIGIN) to infect and spread throughout the CNS. Confirming the impact of the virus on the CNS will be crucial in dealing with the long-term consequences of the epidemic.

The unfolding palette of COVID-19 multisystemic syndrome and its neurological manifestations

Although our current knowledge of the pathophysiology of COVID-19 is still fragmentary, the information so far accrued on the tropism and life cycle of its etiological agent SARS-CoV-2, together with the emerging clinical data, suffice to indicate that the severe acute pulmonary syndrome is the main, but not the only manifestation of COVID-19. Necropsy studies are increasingly revealing underlying endothelial vasculopathies in the form of micro-haemorrhages and micro-thrombi. Intertwined with defective antiviral responses, dysregulated coagulation mechanisms, abnormal hyper-inflammatory reactions and responses, COVID-19 is disclosing a wide pathophysiological palette. An additional property in categorising the disease is the combination of tissue (e.g. neuro- and vasculo-tropism) with organ tropism, whereby the virus preferentially attacks certain organs with highly developed capillary beds, such as the lungs, gastrointestinal tract, kidney and brain. These multiple clinical presentations confirm that the acute respiratory syndrome as described initially is increasingly unfolding as a more complex nosological entity, a multiorgan syndrome of systemic breadth. The neurological manifestations of COVID-19, the focus of this review, reflect this manifold nature of the disease.

Neurological Effects of Sars-Cov-2 And Neurotoxicity of Antiviral Drugs Against Covid-19

Severe Acute Respiratory Syndrome (SARS) is caused by different SARS viruses. In 2020, novel coronavirus (SARS-CoV-2) led to an ongoing pandemic, known as "Coronavirus Disease 2019 (COVID-19)". The disease can spread among individuals through direct (via saliva, respiratory secretions or secretion droplets) or indirect (through contaminated objects or surfaces) contact. The pandemic has spread rapidly from Asia to Europe and later to America. It continues to affect all parts of the world at an increasing rate. There have been over 92 million confirmed cases of COVID-19 by mid-January 2021. The similarity of homological sequences between SARS-CoV-2 and other SARS-CoVs is high. In addition, clinical symptoms of SARS-CoV-2 and other SARS viruses show similarities. However, some COVID-19 cases show neurologic signs like headache, loss of smell, hiccups and encephalopathy. The drugs used in the palliative treatment of the disease also have some neurotoxic effects. Currently, there are approved vaccines for COVID-19. However, there is a need for specific therapeutics against COVID-19. This review will describe the neurological effects of SARS-CoV-2 and the neurotoxicity of COVID-19 drugs used in clinics. Drugs used in the treatment of COVID-19 will be evaluated by their mechanism of action and their toxicological effects.

SARS-CoV-2 Neuronal Invasion and Complications: Potential Mechanisms and Therapeutic Approaches

Clinical reports suggest that the coronavirus disease-19 (COVID-19) pandemic caused by severe acute respiratory syndrome (SARS)-coronavirus-2 (CoV-2) has not only taken millions of lives, but has also created a major crisis of neurologic complications that persist even after recovery from the disease. Autopsies of patients confirm the presence of the coronaviruses in the CNS, especially in the brain. The invasion and transmission of SARS-CoV-2 in the CNS is not clearly defined, but, because the endocytic pathway has become an important target for the development of therapeutic strategies for COVID-19, it is necessary to understand endocytic processes in the CNS. In addition, mitochondria and mechanistic target of rapamycin (mTOR) signaling pathways play a critical role in the antiviral immune response, and may also be critical for endocytic activity. Furthermore, dysfunctions of mitochondria and mTOR signaling pathways have been associated with some high-risk conditions such as diabetes and immunodeficiency for developing severe complications observed in COVID-19 patients. However, the role of these pathways in SARS-CoV-2 infection and spread are largely unknown. In this review, we discuss the potential mechanisms of SARS-CoV-2 entry into the CNS and how mitochondria and mTOR pathways might regulate endocytic vesicle-mitochondria interactions and dynamics during SARS-CoV-2 infection. The mechanisms that plausibly account for severe neurologic complications with COVID-19 and potential treatments with Food and Drug Administration-approved drugs targeting mitochondria and the mTOR pathways are also addressed.

Inflammatory Response Leads to Neuronal Death in Human Post-Mortem Cerebral Cortex in Patients with COVID-19

The recent coronavirus disease of 2019 (COVID-19) pandemic has adversely affected people worldwide. A growing body of literature suggests the neurological complications and manifestations in response to COVID-19 infection. Herein, we explored the inflammatory and immune responses in the post-mortem cerebral cortex of patients with severe COVID-19. The participants comprised three patients diagnosed with severe COVID-19 from March 26, 2020, to April 17, 2020, and three control patients. Our findings demonstrated a surge in the number of reactive astrocytes and activated microglia, as well as low levels of glutathione along with the upregulation of inflammation- and immune-related genes IL1B, IL6, IFITM, MX1, and OAS2 in the COVID-19 group. Overall, the data imply that oxidative stress may invoke a glial-mediated neuroinflammation, which ultimately leads to neuronal cell death in the cerebral cortex of COVID-19 patients.

Association between angiotensin-converting enzyme inhibitors, angiotensin receptor blockers, and major psychiatric disorders

OBJECTIVE

To exam the association between major psychiatry illness and angiotensin-converting enzyme inhibitor (ACEI) versus angiotensin receptor blocker (ARB) users in a head-to-head comparison manner.

METHODS

Study design is a retrospective cohort study utilizing available data through the National Health Insurance database. 13,974 ACEI users and 13,974 propensity score matching ARB users were included to look at the future incident psychiatry illness. The Kaplan-Meier method was used to assess the cumulative curves and were tested by the Log-rank test. The crude hazard ratio (HR) and adjusted HR were estimated by univariable and multivariable Cox proportional hazard model.

RESULTS

After controlling for the confounders, ACEI users had a higher risk of major psychiatric disorders than ARB users, (adjusted HR = 1.07; 95% CI = 1.02, 1.13). The cumulative incidence of major psychiatric disorders for ACEI cohort was significantly higher than that of ARB cohort (p-value = 0.001).

CONCLUSIONS

Compared to ARB users, ACEI users are prone to major psychiatry illness development.

Regulated Intramembrane Proteolysis of ACE2: A Potential Mechanism Contributing to COVID-19 Pathogenesis?

Since being identified as a key receptor for SARS-CoV-2, Angiotensin converting enzyme 2 (ACE2) has been studied as one of the potential targets for the development of preventative and/or treatment options. Tissue expression of ACE2 and the amino acids interacting with the spike protein of SARS-CoV-2 have been mapped. Furthermore, the recombinant soluble extracellular domain of ACE2 is already in phase 2 trials as a treatment for SARS-CoV-2 infection. Most studies have continued to focus on the ACE2 extracellular domain, which is known to play key roles in the renin angiotensin system and in amino acid uptake. However, few also found ACE2 to have an immune-modulatory function and its intracellular tail may be one of the signaling molecules in regulating cellular activation. The implication of its immune-modulatory role in preventing the cytokine-storm, observed in severe COVID-19 disease outcomes requires further investigation. This review focuses on the regulated proteolytic cleavage of ACE2 upon binding to inducer(s), such as the spike protein of SARS-CoV, the potential of cleaved ACE2 intracellular subdomain in regulating cellular function, and the ACE2's immune-modulatory function. This knowledge is critical for targeting ACE2 levels for developing prophylactic treatment or preventative measures in SARS-CoV infections.

The impact of COVID-19 on diagnostic biomarkers in neuropsychiatric and neuroimmunological diseases: a review

Coronavirus disease 2019 (COVID-19) is an infectious respiratory disease, caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). Evidence-based emerging reports of neurological manifestations show that SARS-CoV-2 can attack the nervous system. However, little is known about the biomarkers in disease in neuropsychiatric and neuroimmunological disorders. One of the important keys in the management of COVID-19 is an accurate diagnosis. Biomarkers could provide valuable information in the early detection of disease etiology, diagnosis, further treatment, and prognosis. Moreover, ongoing investigations on hematologic, biochemical, and immunologic biomarkers in nonsevere, severe, or fatal forms of COVID-19 patients provide an urgent need for the identification of clinical and laboratory predictors. In addition, several cytokines acting through mechanisms to emerge immune response against SARS-CoV-2 infection are known to play a major role in neuroinflammation. Considering the neuroinvasive potential of SARS-CoV-2, which can be capable of triggering a cytokine storm, the current evidence on inflammation in psychiatry and neurodegenerative by emerging neuroinflammation is discussed in this review. We also highlighted the hematologic, biochemical, and immunologic biomarkers in COVID-19 diagnosis. COVID-19 prognostic biomarkers in patients with neuropsychiatric and neuroimmunological diseases are also explained.

Immune mediating molecules and pathogenesis of COVID-19-associated neurological disease

Background

Long period of SARS-CoV-2 infection has been associated with psychiatric and cognitive disorders in adolescents and children. SARS-CoV-2 remains dormant in the CNS leading to neurological complications. The wide expression of ACE2 in the brain raises concern for its involvement in SARS-CoV-2 infection. Though, the mechanistic insights about blood-brain barriers (BBB) crossing by SARS-CoV-2 and further brain infection are still not clear. Moreover, the mechanism behind dormant SARS-CoV-2 infections leading to chronic neurological disorders needs to be unveiled. There is an urgent need to find out the risk factor involved in COVID-19-associated neurological disease. Therefore, the role of immune-associated genes in the pathogenesis of COVID-19 associated neurological diseases is presented which could contribute to finding associated genetic risk factors.

Method

The search utilizing multiple databases, specifically, EMBASE, PubMed (Medline), and Google Scholar was performed. Moreover, the literature survey on the involvement of COVID-19, neuropathogenesis, and its consequences was done.

Description

Persistent inflammatory stimuli may promote the progression of neurodegenerative diseases. An increased expression level of cytokine, chemokine, and decreased expression level of immune cells has been associated with the COVID-19 patient. Cytokine storm was observed in severe COVID-19 patients. The nature of SARS-CoV-2 infection can be neuroinflammatory. Genes of immune response could be associated with neurodegenerative diseases.

Conclusion

The present review will provide a useful framework and help in understanding COVID-19-associated neuropathogenesis. Experimental studies on immune-associated genes in COVID-19 patients with neurological manifestations could be helpful to establish its neuropathogenesis.

SARS-CoV-2 Infection in the Central and Peripheral Nervous System-Associated Morbidities and Their Potential Mechanism

The recent outbreak of SARS-CoV-2 infections that causes coronavirus-induced disease of 2019 (COVID-19) is the defining and unprecedented global health crisis of our time in both the scale and magnitude. Although the respiratory tract is the primary target of SARS-CoV-2, accumulating evidence suggests that the virus may also invade both the central nervous system (CNS) and the peripheral nervous system (PNS) leading to numerous neurological issues including some serious complications such as seizures, encephalitis, and loss of consciousness. Here, we present a comprehensive review of the currently known role of SARS-CoV-2 and identify all the neurological problems reported among the COVID-19 case reports throughout the world. The virus might gain entry into the CNS either through the trans-synaptic route via the olfactory neurons or through the damaged endothelium in the brain microvasculature using the ACE2 receptor potentiated by neuropilin-1 (NRP-1). The most critical of all symptoms appear to be the spontaneous loss of breathing in some COVID-19 patients. This might be indicative of a dysfunction within the cardiopulmonary regulatory centers in the brainstem. These pioneering studies, thus, lay a strong foundation for more in-depth basic and clinical research required to confirm the role of SARS-CoV-2 infection in neurodegeneration of critical brain regulatory centers.

Autoimmune Processes Involved in Organ System Failure Following Infection with SARS-CoV-2

During the COVID-19 pandemic associated with high incidence, transmissibility, and mortality, this chapter focuses on three phases of the disease: initial exposure, initiation of the immune response to the agent, and finally, an inflammatory/autoimmune-like presentation with pulmonary, neurological, and renal failure and disseminated intravascular coagulation which occurs in a small proportion of the patients. The elegant demonstration of the site of interaction between the spike (S) protein of the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), which is the causative agent of COVID-19, and the ACE (angiotensin-converting enzyme) 2 receptor of cells distributed throughout the body has enabled research efforts to develop pharmacological and immune countermeasures to the viral phase of the disease. This chapter rapidly reviews the molecular and structural organization of SARS-CoV-2 and its interaction with ACE2. It is followed by a discussion over the role of the major histocompatibility complex (MHC) in recognition of the virus. The importance of rapid compartmentation of the viral genome into the target cells as opposed to the binding constant of the virus for the ACE receptor is discussed. Host factors affecting the immune response to the virus are examined, and the subsequent inflammatory dysregulation enabling the cytokine storm leading to system organ failure is described. Finally, the similarities of the clinical effects of the murine hepatitis virus-JHM (a coronavirus) on multi-organ systems (liver, brain, clotting cascade) as described by Perlman and colleagues permit insights regarding the role of the interaction between the host and the virus in developing the clinical presentation of the inflammatory/autoimmune disorders that occur in multiple sclerosis, neuromyelitis optica, and more interestingly, during the third phase of COVID-19.

Cerebral Vasoreactivity Evaluated by Transcranial Color Doppler and Breath-Holding Test in Patients after SARS-CoV-2 Infection

From the beginning of the SARS-CoV-2 virus pandemic, it was clear that the virus is highly neurotrophic. Neurological manifestations can range from nonspecific symptoms such as dizziness, headaches and olfactory disturbances to severe forms of neurological dysfunction. Some neurological complication can occur even after mild forms of respiratory disease. This study’s aims were to assess cerebrovascular reactivity in patients with nonspecific neurological symptoms after SARS-CoV-2 infection. A total of 25 patients, aged 33–62 years, who had nonspecific neurological symptoms after SARS-CoV-2 infection, as well as 25 healthy participants in the control group, were assessed for cerebrovascular reactivity according to transcranial color Doppler (TCCD) which we combined with a breath-holding test (BHT). In subjects after SARS-CoV-2 infection, there were statistically significantly lower flow velocities through the middle cerebral artery at rest period, lower maximum velocities at the end of the breath-holding period and lower breath holding index (BHI) in relation to the control group. Changes in cerebral artery flow rate velocities indicate poor cerebral vasoreactivity in the group after SARS-CoV-2 infection in regard to the control group and suggest vascular endothelial damage by the SARS-CoV-2 virus.

Neurological manifestations of COVID-19: a clinical approach

Coronavirus disease 2019 (COVID-19) is an emerging infectious disease caused by SARS-CoV-2 which attacks the respiratory tract and has been declared a global pandemic by the World Health Organization. The disease has a very wide clinical spectrum which can be manifested as asymptomatic to critical conditions. SARS-CoV-2 shows a neurotropism proven by its identification in the cerebrospinal fluid and brain vascular endothelial. The complete mechanism of how the virus invades the human nervous system is yet to be identified. Thus, every neurologist needs to follow the progressivity of COVID-19 symptoms involving the nervous system.