Role of brain renin angiotensin system in neurodegeneration: An update

Infectious Causes of Stroke

Stroke is one of the primary causes of mortality and morbidity worldwide. It can be ischemic or hemorrhagic, and the former can be due to an in-situ thrombus or a distant embolus. Despite being a rare cause, stroke can also be caused in the setting of infection. Bacterial agents are the most common cause of stroke, among other infectious agents. Until the antibiotic era, rheumatic heart disease was a predisposing risk factor of infective endocarditis. VZV is the most common cause of strokes in pediatric and adult populations. Cryptococcus and Candida spp are the most common yeasts involved in CNS infections, especially in immunocompromised patients. In COVID-19 patients, ischemic strokes are more common than hemorrhagic strokes. In this review, we will discuss the most common infectious agents, with particular emphasis on COVID-19.

Can SARS-CoV-2 Infection Exacerbate Alzheimer's Disease? An Overview of Shared Risk Factors and Pathogenetic Mechanisms

The current coronavirus disease 2019 (COVID-19) pandemic, caused by severe acute respiratory syndrome coronavirus (SARS-CoV)-2, is affecting every aspect of global society, including public healthcare systems, medical care access, and the economy. Although the respiratory tract is primarily affected by SARS-CoV-2, emerging evidence suggests that the virus may also reach the central nervous system (CNS), leading to several neurological issues. In particular, people with a diagnosis of Alzheimer's disease (AD) are a vulnerable group at high risk of contracting COVID-19, and develop more severe forms and worse outcomes, including death. Therefore, understanding shared links between COVID-19 and AD could aid the development of therapeutic strategies against both. Herein, we reviewed common risk factors and potential pathogenetic mechanisms that might contribute to the acceleration of neurodegenerative processes in AD patients infected by SARS-CoV-2.

[Neurological complications of COVID-19 in elderly people]

Virus SARS-CoV2 (beta-coronavirus) can induce severe pneumonia with acute respiratory distress syndrome, respiratory failure and multiorgan dysfunction. As more we learned about Covid-19, we understand that SARS-CoV-2 have neuroinvasive properties and can cause different neurological complications. In this article we discusses about the features of neurological sequences of Covid-19 in elderly people.

Common Inflammatory Mechanisms in COVID-19 and Parkinson's Diseases: The Role of Microbiome, Pharmabiotics and Postbiotics in Their Prevention

In the last decade, metagenomic studies have shown the key role of the gut microbiome in maintaining immune and neuroendocrine systems. Malfunction of the gut microbiome can induce inflammatory processes, oxidative stress, and cytokine storm. Dysfunction of the gut microbiome can be caused by short-term (virus infection and other infectious diseases) or long-term (environment, nutrition, and stress) factors. Here, we reviewed the inflammation and oxidative stress in neurodegenerative diseases and coronavirus infection (COVID-19). Here, we reviewed the renin-angiotensin-aldosterone system (RAAS) involved in the processes of formation of oxidative stress and inflammation in viral and neurodegenerative diseases. Moreover, the coronavirus uses ACE2 receptors of the RAAS to penetrate human cells. The coronavirus infection can be the trigger for neurodegenerative diseases by dysfunction of the RAAS. Pharmabiotics, postbiotics, and next-generation probiotics, are considered as a means to prevent oxidative stress, inflammatory processes, neurodegenerative and viral diseases through gut microbiome regulation.

Neuroinflammation and Its Impact on the Pathogenesis of COVID-19

Coronavirus disease 2019 (COVID-19) is an infectious disease caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). The clinical manifestations of COVID-19 include dry cough, difficult breathing, fever, fatigue, and may lead to pneumonia and respiratory failure. There are significant gaps in the current understanding of whether SARS-CoV-2 attacks the CNS directly or through activation of the peripheral immune system and immune cell infiltration. Although the modality of neurological impairments associated with COVID-19 has not been thoroughly investigated, the latest studies have observed that SARS-CoV-2 induces neuroinflammation and may have severe long-term consequences. Here we review the literature on possible cellular and molecular mechanisms of SARS-CoV-2 induced-neuroinflammation. Activation of the innate immune system is associated with increased cytokine levels, chemokines, and free radicals in the SARS-CoV-2-induced pathogenic response at the blood-brain barrier (BBB). BBB disruption allows immune/inflammatory cell infiltration into the CNS activating immune resident cells (such as microglia and astrocytes). This review highlights the molecular and cellular mechanisms involved in COVID-19-induced neuroinflammation, which may lead to neuronal death. A better understanding of these mechanisms will help gain substantial knowledge about the potential role of SARS-CoV-2 in neurological changes and plan possible therapeutic intervention strategies.

Molecular Mechanisms of SARS-CoV-2/COVID-19 Pathogenicity on the Central Nervous System: Bridging Experimental Probes to Clinical Evidence and Therapeutic Interventions

The coronavirus disease 2019 (COVID-19) pandemic, induced by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), has dramatically impacted the global healthcare systems, constantly challenging both research and clinical practice. Although it was initially believed that the SARS-CoV-2 infection is limited merely to the respiratory system, emerging evidence indicates that COVID-19 affects multiple other systems including the central nervous system (CNS). Furthermore, most of the published clinical studies indicate that the confirmed CNS inflammatory manifestations in COVID-19 patients are meningitis, encephalitis, acute necrotizing encephalopathy, acute transverse myelitis, and acute disseminated encephalomyelitis. In addition, the neuroinflammation along with accelerated neurosenescence and susceptible genetic signatures in COVID-19 patients might prime the CNS to neurodegeneration and precipitate the occurrence of neurodegenerative diseases, including Alzheimer's and Parkinson's diseases. Thus, this review provides a critical evaluation and interpretive analysis of existing published preclinical as well as clinical studies on the key molecular mechanisms modulating neuroinflammation and neurodegeneration induced by the SARS-CoV-2. In addition, the essential age- and gender-dependent impacts of SARS-CoV-2 on the CNS of COVID-19 patients are also discussed.

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.

Inflammation: A Mediator Between Hypertension and Neurodegenerative Diseases

Hypertension is the most prevalent and modifiable risk factor for stroke, vascular cognitive impairment, and Alzheimer's disease. However, the mechanistic link between hypertension and neurodegenerative diseases remains to be understood. Recent evidence indicates that inflammation is a common pathophysiological trait for both hypertension and neurodegenerative diseases. Low-grade chronic inflammation at the systemic and central nervous system levels is now recognized to contribute to the physiopathology of hypertension. This review speculates that inflammation represents a mediator between hypertension and neurodegenerative diseases, either by a decrease in cerebral blood flow or a disruption of the blood-brain barrier which will, in turn, let inflammatory cells and neurotoxic molecules enter the brain parenchyma. This may impact brain functions including cognition and contribute to neurodegenerative diseases. This review will thus discuss the relationship between hypertension, systemic inflammation, cerebrovascular functions, neuroinflammation, and brain dysfunctions. The potential clinical future of immunotherapies against hypertension and associated cerebrovascular risks will also be presented.

Valsartan alleviates the blood-brain barrier dysfunction in db/db diabetic mice

Type 2 diabetes (T2D)-related neurological complication is the risk factor for neurodegenerative disorders. The pathological changes from T2D-caused blood–brain barrier (BBB) dysfunction plays a critical role in developing neurodegeneration. The hyper-activation of the Angiotensin II type 1 receptor (AT1R) in the brain is associated with neurovascular impairment. The AT1R antagonist Valsartan is commonly prescribed to control high blood pressure, heart failure, and diabetic kidney diseases. In this study, we investigated the beneficial effects of Valsartan in db/db diabetic mice and isolated brain endothelial cells. We showed that 2 weeks of Valsartan administration (30 mg/Kg body weight) mitigated the increased permeability of the brain-blood barrier and the reduction of gap junction proteins VE-Cadherin and Claudin 2. In human brain microvascular cells (HBMVECs), we found that Valsartan treatment ameliorated high glucose-induced hyperpermeability by measuring Dextran uptake and transendothelial electrical resistance (TEER). Furthermore, Valsartan treatment recovered high glucose-repressed endothelial VE-Cadherin and Claudin 2 expression. Moreover, Valsartan significantly suppressed the expressions of pro-inflammatory cytokines such as macrophage chemoattractant protein-1 (MCP-1) and interleukin-6 (IL-6) against high glucose. Mechanistically, Valsartan ameliorated high glucose-repressed endothelial cAMP-responsive element-binding protein (CREB) signaling activation. The blockage of CREB activation by PKA inhibitor H89 abolished the action of Valsartan, suggesting its dependence on CREB signaling. In conclusion, Valsartan shows a neuroprotective effect in diabetic mice by ameliorating BBB dysfunction. These effects of Valsartan require cellular CREB signaling in brain endothelial cells.

Harpagide alleviate neuronal apoptosis and blood-brain barrier leakage by inhibiting TLR4/MyD88/NF-κB signaling pathway in Angiotensin II-induced microglial activation in vitro

Angiotensin II, the effector peptide of the renin-angiotensin system, is not only a pivotal peptide implicated in the regulation of blood pressure but also a key mediator of the inflammatory processes that play an important role in the pathology of hypertension-related cSVD. Harpagide is the major bioactive constituent of Scrophulariae Radix widely used in traditional Chinese medicine for numerous diseases including hypertension. The present study aimed to investigate the effect of harpagide on Ang II-induced neuroinflammation and the potential mechanism. Pretreated with harpagide or resatorvid (the TLR4 pathway inhibitor), BV2 cells were treated with Ang II or LPS (the TLR4 activator). NO, pro-inflammatory cytokines, the proteins on TLR4/MyD88/NF-κB signaling pathway and the expression of CD86, CD206, TREM2 in BV2 cells were detected respectively. Subsequently, the effects of harpagide on neurotoxicity and BBB destruction triggered by Ang II-induced neuroinflammation were investigated in the co-cultures of BV2 microglia/HT22 hippocampal neurons, BV2 microglia/bEnd.3 endotheliocyte and BV2 microglia/BBB monolayer model. We found that Ang II converted microglia into M1 state and resulted in neuroinflammation through activating TLR4/MyD88/NF-κB signaling pathway. It also triggered the imbalance of TLR4/TREM2 in microglia. Ang II-mediated inflammation microglia further led to neuronal apoptosis and BBB damage. Harpagide showed the effect of alleviating Ang II-mediated neuroinflammation as well as the resulting neurotoxicity and BBB destruction through inhibiting the TLR4/MyD88/NF-κB pathway. The anti-inflammatory and neuroprotective effect of harpagide suggested that it might be a potential therapeutic strategy in hypertensive cSVD.

The Renin-Angiotensin System in the Tumor Microenvironment of Glioblastoma

Simple Summary

Glioblastoma (GB) is the most aggressive brain cancer in humans. Patient survival outcomes have remained dismal despite intensive research over the past 50 years, with a median overall survival of only 14.6 months. We highlight the critical role of the renin–angiotensin system (RAS) on GB cancer stem cells and the tumor microenvironment which, in turn, influences cancer stem cells in driving tumorigenesis and treatment resistance. We present recent developments and underscore the need for further research into the GB tumor microenvironment. We discuss the novel therapeutic targeting of the RAS using existing commonly available medications and utilizing model systems to further this critical investigation.

Abstract

Glioblastoma (GB) is an aggressive primary brain tumor. Despite intensive research over the past 50 years, little advance has been made to improve the poor outcome, with an overall median survival of 14.6 months following standard treatment. Local recurrence is inevitable due to the quiescent cancer stem cells (CSCs) in GB that co-express stemness-associated markers and components of the renin–angiotensin system (RAS). The dynamic and heterogeneous tumor microenvironment (TME) plays a fundamental role in tumor development, progression, invasiveness, and therapy resistance. There is increasing evidence showing the critical role of the RAS in the TME influencing CSCs via its upstream and downstream pathways. Drugs that alter the hallmarks of cancer by modulating the RAS present a potential new therapeutic alternative or adjunct to conventional treatment of GB. Cerebral and GB organoids may offer a cost-effective method for evaluating the efficacy of RAS-modulating drugs on GB. We review the nexus between the GB TME, CSC niche, and the RAS, and propose re-purposed RAS-modulating drugs as a potential therapeutic alternative or adjunct to current standard therapy for GB.

Manifestation of renin angiotensin system modulation in traumatic brain injury

Traumatic brain injury (TBI) alters brain function and is a crucial public health concern worldwide. TBI triggers the release of inflammatory mediators (cytokines) that aggravate cerebral damage, thereby affecting clinical prognosis. The renin angiotensin system (RAS) plays a critical role in TBI pathophysiology. RAS is widely expressed in many organs including the brain. Modulation of the RAS in the brain via angiotensin type 1 (AT₁) and type 2 (AT₂) receptor signaling affects many pathophysiological processes, including TBI. AT₁R is highly expressed in neurons and astrocytes. The upregulation of AT₁R mediates the effects of angiotensin II (ANG II) including release of proinflammatory cytokines, cell death, oxidative stress, and vasoconstriction. The AT₂R, mainly expressed in the fetal brain during development, is also related to cognitive function. Activation of this receptor pathway decreases neuroinflammation and oxidative stress and improves overall cell survival. Numerous studies have illustrated the therapeutic potential of inhibiting AT₁R and activating AT₂R for treatment of TBI with variable outcomes. In this review, we summarize studies that describe the role of brain RAS signaling, through AT₁R and AT₂R in TBI, and its modulation with pharmacological approaches.

[Current issues of treatment and rehabilitation of patients with neurological disorders and the consequences of COVID-19. Resolution of Advisory Board]

Last year the global medical community faced the pandemic of the new coronavirus infection caused by SARS-CoV-2. To date, there is considerable expert experience, which indicates that the brain, along with the corresponding respiratory system, is a target organ for a new coronavirus infection. Moreover, a number of symptoms from the central and peripheral nervous system can persist for several weeks, months, and even tens of months. To designate such protracted clinical conditions, a new definition was introduced: «Post-COVID-19 Condition». Advisory Board of Neurologists and Rehabilitation Therapists met to, discuss of practical experience and taking into account scientific information about COVID-19, which was available at the time of the meeting, to develop unified approaches for the management of patients with neurological complications and the consequences of a new coronavirus infection. The Advisory Board worked out a resolution in which formulated the tactics of managing patients with neurological manifestations of COVID-19. The substantiation of the importance and expediency of the development and implementation of a special program of clinical examination of patients who have undergone COVID-19, which would include a clinical examination with a detailed assessment of cognitive functions to early identification and diagnosis of neurodegeneration and subsequent therapy, is given.

Angiotensin-(1-7) and Mas receptor in the brain

The renin-angiotensin system (RAS) is a key regulator of blood pressure and electrolyte homeostasis. Besides its importance as regulator of the cardiovascular function, the RAS has also been associated to the modulation of higher brain functions, including cognition, memory, depression and anxiety. For many years, angiotensin II (Ang II) has been considered the major bioactive component of the RAS. However, the existence of many other biologically active RAS components has currently been recognized, with similar, opposite, or distinct effects to those exerted by Ang II. Today, it is considered that the RAS is primarily constituted by two opposite arms. The pressor arm is composed by Ang II and the Ang II type 1 (AT1) receptor (AT1R), which mediates the vasoconstrictor, proliferative, hypertensive, oxidative and pro-inflammatory effects of the RAS. The depressor arm is mainly composed by Ang-(1-7), its Mas receptor (MasR) which mediates the depressor, vasodilatory, antiproliferative, antioxidant and anti-inflammatory effects of Ang-(1-7) and the AT2 receptor (AT2R), which opposes to the effects mediated by AT1R activation. Central Ang-(1-7) is implicated in the control of the cardiovascular function, thus participating in the regulation of blood pressure. Ang-(1-7) also exerts neuroprotective actions through MasR activation by opposing to the harmful effects of the Ang II/AT1R axis. This review is focused on the expression and regulation of the Ang-(1-7)/MasR axis in the brain, its main neuroprotective effects and the evidence regarding its involvement in the pathophysiology of several diseases at cardiovascular and neurological level.

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.

Putative mechanism of neurological damage in COVID-19 infection

The recent pandemic of the coronavirus infectious disease 2019 (COVID-19) has affected around 192 countries, and projections have shown that around 40% to 70% of world population could be infected in the next months. COVID-19 is caused by the virus SARS- CoV-2, it enters the cells through the ACE2 receptor (angiotensin converting enzyme 2). It is well known that SARS-CoV-2 could develop mild, moderate, and severe respiratory symptoms that could lead to death. The virus receptor is expressed in different organs such as the lungs, kidney, intestine, and brain, among others. In the lung could cause pneumonia and severe acute respiratory syndrome (SARS). The brain can be directly affected by cellular damage due to viral invasion, which can lead to an inflammatory response, by the decrease in the enzymatic activity of ACE2 that regulates neuroprotective, neuro-immunomodulatory and neutralizing functions of oxidative stress. Another severe damage is hypoxemia in patients that do not receive adequate respiratory support. The neurological symptoms that the patient presents, will depend on factors that condition the expression of ACE2 in the brain such as age and sex, as well as the mechanism of neuronal invasion, the immune response and the general state of the patient. Clinical and histopathological studies have described neurological alterations in human patients with COVID-19. These conditions could have a possible contribution to the morbidity and mortality caused by this disease and may even represent the onset of neurodegenerative activity in recovered patients.

The recent pandemic of the coronavirus infectious disease 2019 (COVID-19) has affected around 192 countries, and projections have shown that around 40% to 70% of world population could be infected in the next months. COVID-19 is caused by the virus SARS- CoV-2, it enters the cells through the ACE2 receptor (angiotensin converting enzyme 2). It is well known that SARS-CoV-2 could develop mild, moderate, and severe respiratory symptoms that could lead to death. The virus receptor is expressed in different organs such as the lungs, kidney, intestine, and brain, among others. In the lung could cause pneumonia and severe acute respiratory syndrome (SARS). The brain can be directly affected by cellular damage due to viral invasion, which can lead to an inflammatory response, by the decrease in the enzymatic activity of ACE2 that regulates neuroprotective, neuro-immunomodulatory and neutralizing functions of oxidative stress. Another severe damage is hypoxemia in patients that do not receive adequate respiratory support. The neurological symptoms that the patient presents, will depend on factors that condition the expression of ACE2 in the brain such as age and sex, as well as the mechanism of neuronal invasion, the immune response and the general state of the patient. Clinical and histopathological studies have described neurological alterations in human patients with COVID-19. These conditions could have a possible contribution to the morbidity and mortality caused by this disease and may even represent the onset of neurodegenerative activity in recovered patients.

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.

Insights into Nuclear G-Protein-Coupled Receptors as Therapeutic Targets in Non-Communicable Diseases

G-protein-coupled receptors (GPCRs) comprise a large protein superfamily divided into six classes, rhodopsin-like (A), secretin receptor family (B), metabotropic glutamate (C), fungal mating pheromone receptors (D), cyclic AMP receptors (E) and frizzled (F). Until recently, GPCRs signaling was thought to emanate exclusively from the plasma membrane as a response to extracellular stimuli but several studies have challenged this view demonstrating that GPCRs can be present in intracellular localizations, including in the nuclei. A renewed interest in GPCR receptors' superfamily emerged and intensive research occurred over recent decades, particularly regarding class A GPCRs, but some class B and C have also been explored. Nuclear GPCRs proved to be functional and capable of triggering identical and/or distinct signaling pathways associated with their counterparts on the cell surface bringing new insights into the relevance of nuclear GPCRs and highlighting the nucleus as an autonomous signaling organelle (triggered by GPCRs). Nuclear GPCRs are involved in physiological (namely cell proliferation, transcription, angiogenesis and survival) and disease processes (cancer, cardiovascular diseases, etc.). In this review we summarize emerging evidence on nuclear GPCRs expression/function (with some nuclear GPCRs evidencing atypical/disruptive signaling pathways) in non-communicable disease, thus, bringing nuclear GPCRs as targets to the forefront of debate.

Is SARS-CoV-2 vaccination safe and effective for elderly individuals with neurodegenerative diseases?

Introduction

Coronavirus Disease 2019 (COVID-19) poses a substantial threat to the lives of the elderly, especially those with neurodegenerative diseases, and vaccination against viral infections is recognized as an effective measure to reduce mortality. However, elderly patients with neurodegenerative diseases often suffer from abnormal immune function and take multiple medications, which may complicate the role of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) vaccines. Currently, there is no expert consensus on whether SARS-CoV-2 vaccines are suitable for patients with neurodegenerative diseases.

Areas covered

We searched Pubmed to conduct a systematic review of published studies, case reports, reviews, meta-analyses, and expert guidelines on the impact of SARS-CoV-2 on neurodegenerative diseases and the latest developments in COVID-19 vaccines. We also summarized the interaction between vaccines and age-related neurodegenerative diseases. The compatibility of future SARS-CoV-2 vaccines with neurodegenerative diseases is discussed.

Expert opinion

Vaccines enable the body to produce immunity by activating the body’s immune response. The pathogenesis and treatment of neurodegenerative diseases is complex, and these diseases often involve abnormal immune function, which can substantially affect the safety and effectiveness of vaccines. In short, this article provides recommendations for the use of vaccine candidates in patients with neurodegenerative diseases.

Brain angiotensin system: a new promise in the management of epilepsy?

Epilepsy is a highly prevalent neurological disease and anti-epileptic drugs (AED) are almost the unique clinical treatment option. A disbalanced brain renin-angiotensin system (RAS) has been proposed in epilepsy and several reports have shown that angiotensin II (Ang II) receptor-1 (ATR1) activation is pro-inflammatory and pro-epileptogenic. In agreement, ATR1 blockage with the repurposed drug losartan has shown benefits in animal models of epilepsy. Processing of Ang II by ACE2 enzyme renders Ang-(1-7), a metabolite that activates the mitochondrial assembly (Mas) receptor (MasR) pathway. MasR activation presents beneficial effects, facilitating vasodilatation, increasing anti-inflammatory and antioxidative responses. In a recent paper published in Clinical Science, Gomes and colleagues (Clin. Sci. (Lond.) (2020) 134, 2263-2277) performed intracerebroventricular (icv) infusion of Ang-(1-7) in animals subjected to the pilocarpine model of epilepsy, starting after the first spontaneous motor seizure (SMS). They showed that this approach reduced the frequency of SMS, restored animal anxiety, increased exploration, and augmented the hippocampal expression of protective catalase enzyme and antiapoptotic protein B-cell lymphoma 2 (Bcl-2). Interestingly, but surprisingly, Gomes and colleagues showed that MasR expression and mTor activity were reduced in the hippocampus of the epileptic Ang-(1-7) treated animals. These results show that Ang-(1-7) administration could represent a new avenue for developing strategies for the management of epilepsy in clinical settings. However, future work is necessary to evaluate the levels of RAS metabolites and the activity of key enzymes in these experimental interventions to completely understand the therapeutic potential of the brain RAS manipulation in epilepsy.

Antiepileptic effects of long-term intracerebroventricular infusion of angiotensin-(1-7) in an animal model of temporal lobe epilepsy

Temporal lobe epilepsy (TLE) is the most frequent type of epilepsy and is often refractory to pharmacological treatment. In this scenario, extensive research has identified components of the renin-angiotensin system (RAS) as potential therapeutic targets. Therefore, the aim of the present study was to evaluate the effects of long-term treatment with angiotensin-(1-7) [Ang-(1-7)] in male Wistar rats with TLE induced by pilocarpine (PILO). Rats with TLE were submitted to intracerebroventricular (icv) infusion of Ang-(1-7) (200 ng/kg/h) for 28 days, starting at the first spontaneous motor seizure (SMS). Body weight, food intake, and SMS were evaluated daily. Behavioral tests and hippocampal protein levels were also evaluated at the end of the treatment. Ang-(1-7) treatment reduced the frequency of SMS and attenuated low anxiety levels, increased locomotion/exploration, and reduced body weight gain that was induced by TLE. Moreover, Ang-(1-7) positively regulated the hippocampal levels of antioxidant protein catalase and antiapoptotic protein B-cell lymphoma 2 (Bcl-2), as well as mammalian target of rapamycin (mTOR) phosphorylation, which were reduced by TLE. The hippocampal up-regulation of angiotensin type 1 receptor induced by TLE was also attenuated by Ang-(1-7), while the Mas receptor (MasR) was down-regulated compared with epilepsy. These data show that Ang-(1-7) presents an antiepileptic effect, increasing neuroprotection markers and reducing SMS frequency, body weight, and behavior impairments found in TLE. Therefore, Ang-(1-7) is a promising coadjutant therapeutic option for the treatment of TLE.

Olfactory function and findings on chest computed tomography in COVID-19: is there any correlation?

BACKGROUND

Olfactory dysfunction is frequent in COVID-19 and it might occur along with pulmonary involvement. These manifestations do not seem to share pathophysiological mechanisms, but clinical data on the subject is lacking. Aims/Objectives: This study aims to correlate the olfactory function (OF) and the radiological pulmonary involvement among in-hospital patients with COVID-19.

MATERIALS AND METHODS

Patients hospitalized with severe COVID-19 were consecutively recruited. They had their objective OF evaluated by the Alcohol Sniff Test and underwent a chest computed tomography (cCT). Qualitative and quantitative analyses of the cCT scans were performed by a blinded radiologist. The quantitative assessment included both the grade of involved parenchyma and the CT severity score (CT-SS). Data obtained were then compared.

RESULTS

57 patients were included. There was no correlation between the OF and the grade of lung involvement (p-value: .884) or the CT-SS (Pearson's coefficient: -.111). Yet, patients with radiological findings on the cCT typical for COVID-19 did not present significantly different OF from the remaining (p-value: .193). Conclusions: Olfactory dysfunction does not correlate with the radiological lung involvement in patients hospitalized with COVID-19.

SIGNIFICANCE

There is also clinical evidence that the olfactory disorder and the pulmonary disease in COVID-19 have distinct mechanisms.

Supplemental data for this article is available online at here.

Alzheimer's-like remodeling of neuronal ryanodine receptor in COVID-19

COVID-19, caused by SARS-CoV-2 involves multiple organs including cardiovascular, pulmonary and central nervous system. Understanding how SARS-CoV-2 infection afflicts diverse organ systems remains challenging ^1,2 . Particularly vexing has been the problem posed by persistent organ dysfunction known as "long COVID," which includes cognitive impairment ³ . Here we provide evidence linking SARS-CoV-2 infection to activation of TGF-ß signaling and oxidative overload. One consequence is oxidation of the ryanodine receptor/calcium (Ca ²⁺ ) release channels (RyR) on the endo/sarcoplasmic (ER/SR) reticuli in heart, lung and brains of patients who succumbed to COVID-19. This depletes the channels of the stabilizing subunit calstabin2 causing them to leak Ca ²⁺ which can promote heart failure ^4,5 , pulmonary insufficiency ⁶ and cognitive and behavioral defects ^7-9 . Ex-vivo treatment of heart, lung, and brain tissues from COVID-19 patients using a Rycal drug (ARM210) ¹⁰ prevented calstabin2 loss and fixed the channel leak. Of particular interest is that neuropathological pathways activated downstream of leaky RyR2 channels in Alzheimer's Disease (AD) patients were activated in COVID-19 patients. Thus, leaky RyR2 Ca ²⁺ channels may play a role in COVID-19 pathophysiology and could be a therapeutic target for amelioration of some comorbidities associated with SARS-CoV-2 infection.

[The renin-angiotensin system and the brain]

The renin-angiotensin-aldosterone (RAAS) system and its effects on blood pressure and the regulation of water and electrolyte balance have been studied focusing on the cardiovascular and renal system. The activation of RAAS in other organs has local and systemic repercussions by modeling the macro- and microvasculture of peripheral organs. The brain RAAS influence on systemic blood pressure through the sympathetic nervous system. The angiotensin converting enzyme/angiotensin II/angiotensin 1 receptor axis (ACE/AngII/AT1), classical pathway, and angiotensin converting enzyme type 2/angiotensin (1-7)/Mas receptor (ACE2/Ang (1-7)/MasR), non-classical pathway, are involved in the modulation of the sympathetic response. The imbalance of these two axes with subsequently Ang II accumulation promote neurogenic hypertension and other vascular pathologies. The aminopeptidase/angiotensin IV/angiotensin 4 receptor (AMN/Ang IV/AT4) axis, which is exclusive of the brain, acts on cerebral microvasculature and participates in cognition, memory, and learning. The aim of this review is to decipher the major central RAAS mechanisms involved in blood pressure regulation. In addition, paracrine functions of brain RAAS and its role in neuroprotection and cognition are also described in this review.

Neurological Complications Associated with the Blood-Brain Barrier Damage Induced by the Inflammatory Response During SARS-CoV-2 Infection

The main discussion above of the novel pathogenic severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection has focused substantially on the immediate risks and impact on the respiratory system; however, the effects induced to the central nervous system are currently unknown. Some authors have suggested that SARS-CoV-2 infection can dramatically affect brain function and exacerbate neurodegenerative diseases in patients, but the mechanisms have not been entirely described. In this review, we gather information from past and actual studies on coronaviruses that informed neurological dysfunction and brain damage. Then, we analyzed and described the possible mechanisms causative of brain injury after SARS-CoV-2 infection. We proposed that potential routes of SARS-CoV-2 neuro-invasion are determinant factors in the process. We considered that the hematogenous route of infection can directly affect the brain microvascular endothelium cells that integrate the blood-brain barrier and be fundamental in initiation of brain damage. Additionally, activation of the inflammatory response against the infection represents a critical step on injury induction of the brain tissue. Consequently, the virus' ability to infect brain cells and induce the inflammatory response can promote or increase the risk to acquire central nervous system diseases. Here, we contribute to the understanding of the neurological conditions found in patients with SARS-CoV-2 infection and its association with the blood-brain barrier integrity.

COVID-19 associated central nervous system manifestations, mental and neurological symptoms: a systematic review and meta-analysis

The ongoing pandemic of Coronavirus disease 2019 (COVID-19) has infected more than 27 million confirmed cases and 8,90,000 deaths all around the world. Verity of viral infections can infect the nervous system; these viral infections can present a wide range of manifestation. The aim of the current study was to systematically review the COVID-19 associated central nervous system manifestations, mental and neurological symptoms. For that we conducted a comprehensive systematic literature review of four online databases, including Web of Science, PubMed, Scopus and Embase. All relevant articles that reported psychiatric/psychological symptoms or disorders in COVID-19 without considering time and language restrictions were assessed. All the study procedures were performed based on the PRISMA criteria. Due to the screening, 14 studies were included. The current study result indicated that, the pooled prevalence of CNS or mental associated disorders with 95% CI was 50.68% (6.68-93.88). The most prevalence symptoms were hyposmia/anosmia/olfactory dysfunction (number of study: 10) with 36.20% (14.99-60.51). Only one study reported numbness/paresthesia and dysphonia. Pooled prevalence of numbness/paresthesia and dysphonia was 5.83% (2.17-12.25) and 2.39% (10.75-14.22). The pooled prevalence of depression and anxiety was 3.52% (2.62-4.54) and 13.92% (9.44-19.08). Our findings demonstrate that COVID-19 has a certain relation with neurological symptoms. The hypsomia, anosmia or olfactory dysfunction was most frequent symptom. Other symptoms were headache or dizziness, dysgeusia or ageusia, dysphonia and fatigue. Depression, anxiety, and confusion were less frequent symptoms.

Pathophysiological Clues to How the Emergent SARS-CoV-2 Can Potentially Increase the Susceptibility to Neurodegeneration

Along with emergence of the novel severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) in late 2019, a myriad of neurologic symptoms, associated with structural brain changes, were reported. In this paper, we provide evidence to critically discuss the claim that the survived patients could possibly be at increased risk for neurodegenerative diseases via various mechanisms. This virus can directly invade the brain through olfactory bulb, retrograde axonal transport from peripheral nerve endings, or via hematogenous or lymphatic routes. Infection of the neurons along with peripheral leukocytes activation results in pro-inflammatory cytokine increment, rendering the brain to neurodegenerative changes. Also, occupation of the angiotensin-converting enzyme 2 (ACE-2) with the virus may lead to a decline in ACE-2 activity, which acts as a neuroprotective factor. Furthermore, acute respiratory distress syndrome (ARDS) and septicemia induce hypoxemia and hypoperfusion, which are locally exacerbated due to the hypercoagulable state and micro-thrombosis in brain vessels, leading to oxidative stress and neurodegeneration. Common risk factors for COVID-19 and neurodegenerative diseases, such as metabolic risk factors, genetic predispositions, and even gut microbiota dysbiosis, can contribute to higher occurrence of neurodegenerative diseases in COVID-19 survivors. However, it should be considered that severity of the infection, the extent of neurologic symptoms, and the persistence of viral infection consequences are major determinants of this association. Importantly, whether this pandemic will increase the overall incidence of neurodegeneration is not clear, as a high percentage of patients with severe form of COVID-19 might probably not survive enough to develop neurodegenerative diseases.

Quantum binding energy features of the drug olmesartan bound to angiotensin type-1 receptors in the therapeutics of stroke

We investigated the binding energies of 105 residues within a 10 Å pocket radius, predicted the energetic relevance of olmesartan regions, and the influence of individual protein segments on OLM -AT1 binding.

Blood Biomarkers for Detection of Brain Injury in COVID-19 Patients

The severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) virus attacks multiple organs of coronavirus disease 2019 (COVID-19) patients, including the brain. There are worldwide descriptions of neurological deficits in COVID-19 patients. Central nervous system (CNS) symptoms can be present early in the course of the disease. As many as 55% of hospitalized COVID-19 patients have been reported to have neurological disturbances three months after infection by SARS-CoV-2. The mutability of the SARS-COV-2 virus and its potential to directly affect the CNS highlight the urgency of developing technology to diagnose, manage, and treat brain injury in COVID-19 patients. The pathobiology of CNS infection by SARS-CoV-2 and the associated neurological sequelae of this infection remain poorly understood. In this review, we outline the rationale for the use of blood biomarkers (BBs) for diagnosis of brain injury in COVID-19 patients, the research needed to incorporate their use into clinical practice, and the improvements in patient management and outcomes that can result. BBs of brain injury could potentially provide tools for detection of brain injury in COVID-19 patients. Elevations of BBs have been reported in cerebrospinal fluid (CSF) and blood of COVID-19 patients. BB proteins have been analyzed in CSF to detect CNS involvement in patients with infectious diseases, including human immunodeficiency virus and tuberculous meningitis. BBs are approved by the U.S. Food and Drug Administration for diagnosis of mild versus moderate traumatic brain injury and have identified brain injury after stroke, cardiac arrest, hypoxia, and epilepsy. BBs, integrated with other diagnostic tools, could enhance understanding of viral mechanisms of brain injury, predict severity of neurological deficits, guide triage of patients and assignment to appropriate medical pathways, and assess efficacy of therapeutic interventions in COVID-19 patients.

Use of dual-flow bioreactor to develop a simplified model of nervous-cardiovascular systems crosstalk: A preliminary assessment

Chronic conditions requiring long-term rehabilitation therapies, such as hypertension, stroke, or cancer, involve complex interactions between various systems/organs of the body and mutual influences, thus implicating a multiorgan approach. The dual-flow IVTech LiveBox2 bioreactor is a recently developed inter-connected dynamic cell culture model able to mimic organ crosstalk, since cells belonging to different organs can be connected and grown under flow conditions in a more physiological environment. This study aims to setup for the first time a 2-way connected culture of human neuroblastoma cells, SH-SY5Y, and Human Coronary Artery Smooth Muscle Cells, HCASMC through a dual-flow IVTech LiveBox2 bioreactor, in order to represent a simplified model of nervous-cardiovascular systems crosstalk, possibly relevant for the above-mentioned diseases. The system was tested by treating the cells with 10nM angiotensin II (AngII) inducing PKCβII/HuR/VEGF pathway activation, since AngII and PKCβII/HuR/VEGF pathway are relevant in cardiovascular and neuroscience research. Three different conditions were applied: 1- HCASMC and SH-SY5Y separately seeded in petri dishes (static condition); 2- the two cell lines separately seeded under flow (dynamic condition); 3- the two lines, seeded in dynamic conditions, connected, each maintaining its own medium, with a membrane as interface for biohumoral changes between the two mediums, and then treated. We detected that only in condition 3 there was a synergic AngII-dependent VEGF production in SH-SY5Y cells coupled to an AngII-dependent PKCβII/HuR/VEGF pathway activation in HCASMC, consistent with the observed physiological response in vivo. HCASMC response to AngII seems therefore to be generated by/derived from the reciprocal cell crosstalk under the dynamic inter-connection ensured by the dual flow LiveBox 2 bioreactor. This system can represent a useful tool for studying the crosstalk between organs, helpful for instance in rehabilitation research or when investigating chronic diseases; further, it offers the advantageous opportunity of cultivating each cell line in its own medium, thus mimicking, at least in part, distinct tissue milieu.

Oxidative stress and diabetic retinopathy: Molecular mechanisms, pathogenetic role and therapeutic implications

Oxidative stress, a cytopathic outcome of excessive generation of ROS and the repression of antioxidant defense system for ROS elimination, is involved in the pathogenesis of multiple diseases, including diabetes and its complications. Retinopathy, a microvascular complication of diabetes, is the primary cause of acquired blindness in diabetic patients. Oxidative stress has been verified as one critical contributor to the pathogenesis of diabetic retinopathy. Oxidative stress can both contribute to and result from the metabolic abnormalities induced by hyperglycemia, mainly including the increased flux of the polyol pathway and hexosamine pathway, the hyper-activation of protein kinase C (PKC) isoforms, and the accumulation of advanced glycation end products (AGEs). Moreover, the repression of the antioxidant defense system by hyperglycemia-mediated epigenetic modification also leads to the imbalance between the scavenging and production of ROS. Excessive accumulation of ROS induces mitochondrial damage, cellular apoptosis, inflammation, lipid peroxidation, and structural and functional alterations in retina. Therefore, it is important to understand and elucidate the oxidative stress-related mechanisms underlying the progress of diabetic retinopathy. In addition, the abnormalities correlated with oxidative stress provide multiple potential therapeutic targets to develop safe and effective treatments for diabetic retinopathy. Here, we also summarized the main antioxidant therapeutic strategies to control this disease.

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Oxidative stress can both contribute to and result from hyperglycemia-induced metabolic abnormalities in retina.

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Genes important in regulation of ROS are epigenetically modified, increasing ROS accumulation in retina.

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Oxidative stress is closely associated with the pathological changes in the progress of diabetic retinopathy.

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Antioxidants ameliorate retinopathy through targeting multiple steps of oxidative stress.

COVID-19 in age-related neurodegenerative diseases: is there a role for vitamin D3 as a possible therapeutic strategy?

The coronavirus disease (COVID-19), identified in Wuhan, China, on December 2019, was declared a pandemic by the World Health Organization, on March, 2020. Since then, efforts have been gathered to describe its clinical course and to determine preventive measures and treatment strategies. Adults older than 65 years of age are more susceptible to serious clinical symptoms and present higher mortality rates. Angiotensin-converting enzyme 2 (ACE2) is a major receptor for some coronavirus infection, including SARS-COV-2, but is also a crucial determinant in anti-inflammation processes during the renin-angiotensin system (RAS) functioning - converting angiotensin II to angiotensin 1-7. The decline in ACE2 expression that occurs with aging has been associated to the higher morbidity and mortality rates in older adults. These observations highlight the importance of investigating the association between COVID-19 and age-related neurodegenerative disorders, i.e., Parkinson's and Alzheimer's diseases. A possible option to reduce the risk of COVID-19 is vitamin D supplementation, due to its anti-inflammatory and immune-system-modulating effects. It has also been suggested that vitamin D supplementation plays a role in slowing progression of Parkinson and Alzheimer. The present study is a literature review of articles published on the theme COVID-19, Parkinson and Alzheimer's diseases, and the role played by vitamin D. PUBMED, MEDLINE, and EMBASE databases were consulted. Results confirm neurodegenerative and neuroinflammatory effects of COVID-19, aggravated in Parkinson's and Alzheimer's patients, and the important role of vitamin D as a possible therapeutic strategy. Nevertheless, randomized controlled trials and large population studies are still warranted.

Research Progress of Alzheimer's Disease Therapeutic Drugs: Based on Renin-Angiotensin System Axis

It is widely recognized that Alzheimer's disease (AD) has a complicate link to renin-angiotensin system (RAS). It is known that cerebrovascular disease has some connections with AD, but most of the studies are still conducted in parallel or independently. Although previous research came up with large number of hypotheses about the pathogenesis of AD, it does not include the mechanism of RAS-related regulation of AD. It has been found that many components of RAS have been changed in AD. For example, the multifunctional and high-efficiency vasoconstrictor Ang II and Ang III with similar effects are changed under the action of other RAS signal peptides; these signal peptides are believed to help improve nerve injury and cognitive function. These changes may lead to neuropathological changes of AD, and progressive defects of cognitive function, which are association with some hypotheses of AD. The role of RAS in AD gradually attracts our attention, and RAS deserved to be considered carefully in the pathogenesis of AD. This review discusses the mechanisms of RAS participating in the three current hypotheses of AD: neuroinflammation, oxidative stress and amyloid-β protein (Aβ) hypothesis, as well as the drugs that regulate RAS systems already in clinical or in clinical trials. It further demonstrates the importance of RAS in the pathogenesis of AD, not only because of its multiple aspects of participation, which may be accidental, but also because of the availability of RAS drugs, which can be reused as therapies of AD.

Care for Patients with Stroke During the COVID-19 Pandemic: Physical Therapy and Rehabilitation Suggestions for Preventing Secondary Stroke

Infection with the novel severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) causes the development of the novel 2019 coronavirus disease (COVID-19) and associated clinical symptoms, which typically presents as an upper respiratory syndrome such as pneumonia. Growing evidence indicates an increased prevalence of neurological involvement (e.g., in the form of stroke) during virus infection. COVID-19 has been suggested to be more than a lung infection because it affects the vasculature of the lungs and other organs and increases the risk of thrombosis. Patients with stroke are vulnerable to secondary events as a result not only of their poor vascular condition but also of their lack of access to rehabilitation resources. Herein, we review current knowledge regarding the pathophysiology of COVID-19, its possible association with neurological involvement, and current drug therapies. Suggestions are also offered regarding the potential for current neurorehabilitation therapies to be taught and practiced at home.

SAMHD1 as the Potential Link Between SARS-CoV-2 Infection and Neurological Complications

The recent pandemic of coronavirus infectious illness 2019 (COVID19) triggered by SARS-CoV-2 has rapidly spread around the globe, generating in severe events an acute, highly lethal pneumonia and death. In the past two hitherto similar CoVs, the severe acute respiratory syndrome CoV (SARS-CoV-1) and Middle East respiratory syndrome CoV (MERS-CoV) also gained universal attention as they produced clinical symptoms similar to those of SARS-CoV-2 utilizing angiotensin-converting enzyme 2 (ACE2) receptor and dipeptidyl peptidase 4 (DPP4) to go into the cells. COVID-19 may also present with overtly neurological symptoms. The proper understanding of the expression and dissemination of ACE2 in central and peripheral nerve systems is crucial to understand better the neurological morbidity caused by COVID-19. Using the STRING bioinformatic tool and references through text mining tools associated to Coronaviruses, we identified SAMHD1 as the probable link to neurological symptoms. Paralleled to the response to influenza A virus and, specifically, respiratory syncytial virus, SARS-CoV-2 evokes a response that needs robust induction of a subclass of cytokines, including the Type I and, obviously, Type III interferons as well as a few chemokines. We correlate ACE2 to the pathogenesis and neurologic complications of COVID-19 and found that SAMHD1 links to NF-κB pathway. No correlation was found with other molecules associated with Coronavirus infection, including ADAR, BST2, IRF3, IFITM3, ISG15, MX1, MX2, RNASEL, RSAD2, and VPRBP. We suggest that SAMHD1 is the molecule that may be behind the mechanisms of the neurological complications associated with COVID-19.

Modulatory action of environmental enrichment on hormonal and behavioral responses induced by chronic stress in rats: Hypothalamic renin-angiotensin system components

Environmental enrichment (EE) has been studied as a protocol that can improve brain plasticity and may protect against negative insults such as chronic stress. The aim of this study was to evaluate the effects of EE on the hormonal and behavioral responses induced by chronic mild unpredictable stress (CMS) in rats, considering the involvement of the renin-angiotensin system. Male adult rats were divided into 4 groups: control, CMS, EE, and CMS + EE, and the experimental protocol lasted for 7 weeks. EE was performed during 7 weeks, 5 days per week, 2 h per day. CMS was applied during weeks 3, 4, and 5. After the CMS (week 6), depression-like behavior was evaluated by forced swimming and sucrose consumption tests, anxiety level was evaluated using the elevated plus-maze test, and memory was evaluated using the Y-maze test. On week 7, the animals were euthanized and basal plasma levels of corticosterone and catecholamines were determined. The hypothalamus was isolated and tissue levels of angiotensin peptides were evaluated. CMS increased plasma corticosterone, norepinephrine, and epinephrine basal concentrations, induced depression-like behaviors, impaired memory, and increased hypothalamic angiotensin I, II, and IV concentrations. EE decreased stress hormones secretion, depression-like behaviors, memory impairment, and hypothalamic angiotensin II induced by stress. Reductions of anxiety-like behavior and norepinephrine secretion were observed in both stressed and unstressed groups. The results indicated that EE seemed to protect adult rats against hormonal and behavioral CMS effects, and that the reduction of angiotensin II could contribute to these effects.

Severe Acute Respiratory Syndrome Coronavirus 2 Impact on the Central Nervous System: Are Astrocytes and Microglia Main Players or Merely Bystanders?

With confirmed coronavirus disease 2019 (COVID-19) cases surpassing the 18 million mark around the globe, there is an imperative need to gain comprehensive understanding of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). Although the main clinical manifestations of COVID-19 are associated with respiratory or intestinal symptoms, reports of neurological signs and symptoms are increasing. The etiology of these neurological manifestations remains obscure, and probably involves several direct pathways, not excluding the direct entry of the virus to the central nervous system (CNS) through the olfactory epithelium, circumventricular organs, or disrupted blood–brain barrier. Furthermore, neuroinflammation might occur in response to the strong systemic cytokine storm described for COVID-19, or due to dysregulation of the CNS rennin-angiotensin system. Descriptions of neurological manifestations in patients in the previous coronavirus (CoV) outbreaks have been numerous for the SARS-CoV and lesser for Middle East respiratory syndrome coronavirus (MERS-CoV). Strong evidence from patients and experimental models suggests that some human variants of CoV have the ability to reach the CNS and that neurons, astrocytes, and/or microglia can be target cells for CoV. A growing body of evidence shows that astrocytes and microglia have a major role in neuroinflammation, responding to local CNS inflammation and/or to disbalanced peripheral inflammation. This is another potential mechanism for SARS-CoV-2 damage to the CNS. In this comprehensive review, we will summarize the known neurological manifestations of SARS-CoV-2, SARS-CoV and MERS-CoV; explore the potential role for astrocytes and microglia in the infection and neuroinflammation; and compare them with the previously described human and animal CoV that showed neurotropism to propose possible underlying mechanisms.

Renal Contributions in the Pathophysiology and Neuropathological Substrates Shared by Chronic Kidney Disease and Alzheimer's Disease

Chronic kidney disease and Alzheimer's disease are chronic conditions highly prevalent in elderly communities and societies, and a diagnosis of them is devastating and life changing. Demanding therapies and changes, such as non-compliance, cognitive impairment, and non-cognitive anomalies, may lead to supplementary symptoms and subsequent worsening of well-being and quality of life, impacting the socio-economic status of both patient and family. In recent decades, additional hypotheses have attempted to clarify the connection between these two diseases, multifactorial in their nature, but even so, the mechanisms behind this link are still elusive. In this paper, we sought to highlight the current understanding of the mechanisms for cognitive decline in patients with these concurrent pathologies and provide insight into the relationship between markers related to these disease entities and whether the potential biomarkers for renal function may be used for the diagnosis of Alzheimer's disease. Exploring detailed knowledge of etiologies, heterogeneity of risk factors, and neuropathological processes associated with these conditions opens opportunities for the development of new therapies and biomarkers to delay or slow their progression and validation of whether the setting of chronic kidney disease could be a potential determinant for cognitive damage in Alzheimer's disease.

Encephalitic syndrome and anosmia in COVID-19: Do these clinical presentations really reflect SARS-CoV-2 neurotropism? A theory based on the review of 25 COVID-19 cases

Since the discovery of coronavirus disease 2019 (COVID‐19), a disease caused by the new coronavirus severe acute respiratory syndrome coronavirus 2 (SARS‐CoV‐2), the pathology showed different faces. There is an increasing number of cases described as (meningo)encephalitis although evidence often lacks. Anosmia, another atypical form of COVID‐19, has been considered as testimony of the potential of neuroinvasiveness of SARS‐CoV‐2, though this hypothesis remains highly speculative. We did a review of the cases reported as brain injury caused by SARS‐CoV‐2. Over 98 papers found, 21 were analyzed. Only four publications provided evidence of the presence of SARS‐CoV‐2 within the central nervous system (CNS). When facing acute neurological abnormalities during an infectious episode it is often difficult to disentangle neurological symptoms induced by the brain infection and those due to the impact of host immune response on the CNS. Cytokines release can disturb neural cells functioning and can have in the most severe cases vascular and cytotoxic effects. An inappropriate immune response can lead to the production of auto‐antibodies directed toward CNS components. In the case of proven SARS‐CoV‐2 brain invasion, the main hypothesis found in the literature focus on a neural pathway, especially the direct route via the nasal cavity, although the virus is likely to reach the CNS using other routes. Our ability to come up with hypotheses about the mechanisms by which the virus might interact with the CNS may help to keep in mind that all neurological symptoms observed during COVID‐19 do not always rely on CNS viral invasion.

Review of 25 COVID‐19 cases with neurological symptoms.

Evidence of the SARS‐CoV‐2 presence in the brain is often lacking.

Brain magnetic resonance imagery is the most accurate exam to explore brain damages.

SARS‐CoV‐2 can cause anosmia and neurological symptoms without invading the brain.

The routes used by SARS‐CoV‐2 to invade the brain may lead to different symptoms.

Sinonasal pathophysiology of SARS-CoV-2 and COVID-19: A systematic review of the current evidence

OBJECTIVE

The ongoing pandemic of coronavirus disease (2019 coronavirus disease [COVID-19]), caused by the Severe Acute Respiratory Syndrome Coronavirus 2 (SARS-CoV-2) virus, is highly contagious with high morbidity and mortality. The role of the nasal and paranasal sinus cavities is increasingly recognized for COVID-19 symptomatology and transmission. We therefore conducted a systematic review, synthesizing existing scientific evidence about sinonasal pathophysiology in COVID-19.

STUDY DESIGN

Systematic review.

METHODS

Systematic searches were performed of all indexed studies in PubMed/Medline and Cochrane databases through 28 March 2020 and studies searchable on preprints.com (including ArXiv and Scilit repositories) through 30 March 2020. Data extraction focused on sinonasal pathophysiology in COVID-19.

RESULTS

A total of 19 studies were identified. The sinonasal cavity may be a major site of infection by SARS-CoV-2, where susceptibility genes required for infection are expressed at high levels and may be modulated by environmental and host factors. Viral shedding appears to be highest from the nose, therefore reflecting a major source for transmission. This has been highlighted by multiple reports of health care-associated infection (HAI) during rhinologic procedures, which are now consequently considered to be high risk for SARS-CoV-2 transmission to health care workers. While sinonasal symptomatology, such as rhinorrhea or congestion, appears to be a rarer symptom of COVID-19, anosmia without nasal obstruction is reported as highly specific predictor of COVID-19+ patients.

CONCLUSION

Sinonasal pathophysiology is increasingly important in our understanding of COVID-19. The sinonasal tract may be an important site of infection while sinonasal viral shedding may be an important transmission mechanism-including HAI. Anosmia without nasal obstruction may be a highly specific indicator of COVID-19.

LEVEL OF EVIDENCE

2a.

Coronavirus Disease 2019 and Stroke: Clinical Manifestations and Pathophysiological Insights

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Coronavirus disease 2019 (COVID-19) is caused by the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2).

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Some COVID-19 patients have exhibited widespread neurological manifestations including stroke.

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Acute ischemic stroke, intracerebral hemorrhage, and cerebral venous sinus thrombosis have been reported in patients with COVID-19.

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COVID-19-associated coagulopathy is likely caused by inflammation.

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Resultant ACE2 down-regulation causes RAS imbalance, which may lead to stroke.

Coronavirus disease 2019 (COVID-19), caused by the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), is a global health threat. Some COVID-19 patients have exhibited widespread neurological manifestations including stroke. Acute ischemic stroke, intracerebral hemorrhage, and cerebral venous sinus thrombosis have been reported in patients with COVID-19. COVID-19-associated coagulopathy is increasingly recognized as a result of acute infection and is likely caused by inflammation, including inflammatory cytokine storm. Recent studies suggest that axonal transport of SARS-CoV-2 to the brain can occur via the cribriform plate adjacent to the olfactory bulb that may lead to symptomatic anosmia. The internalization of SARS-CoV-2 is mediated by the binding of the spike glycoprotein of the virus to the angiotensin-converting enzyme 2 (ACE2) on cellular membranes. ACE2 is expressed in several tissues including lung alveolar cells, gastrointestinal tissue, and brain. The aim of this review is to provide insights into the clinical manifestations and pathophysiological mechanisms of stroke in COVID-19 patients. SARS-CoV-2 can down-regulate ACE2 and, in turn, overactivate the classical renin-angiotensin system (RAS) axis and decrease the activation of the alternative RAS pathway in the brain. The consequent imbalance in vasodilation, neuroinflammation, oxidative stress, and thrombotic response may contribute to the pathophysiology of stroke during SARS-CoV-2 infection.

Neurological manifestations of patients with COVID-19: potential routes of SARS-CoV-2 neuroinvasion from the periphery to the brain

Coronavirus disease 2019 (COVID-19), caused by severe acute respiratory syndrome Coronavirus 2 (SARS-CoV-2), has caused a global pandemic in only 3 months. In addition to major respiratory distress, characteristic neurological manifestations are also described, indicating that SARS-CoV-2 may be an underestimated opportunistic pathogen of the brain. Based on previous studies of neuroinvasive human respiratory coronaviruses, it is proposed that after physical contact with the nasal mucosa, laryngopharynx, trachea, lower respiratory tract, alveoli epithelium, or gastrointestinal mucosa, SARS-CoV-2 can induce intrinsic and innate immune responses in the host involving increased cytokine release, tissue damage, and high neurosusceptibility to COVID-19, especially in the hypoxic conditions caused by lung injury. In some immune-compromised individuals, the virus may invade the brain through multiple routes, such as the vasculature and peripheral nerves. Therefore, in addition to drug treatments, such as pharmaceuticals and traditional Chinese medicine, non-pharmaceutical precautions, including facemasks and hand hygiene, are critically important.

Towards Neuro-CoViD-19

CoViD-19 is the current pandemic caused by the Severe Acute Respiratory Syndrome Corona Virus-2 (SARS-CoV-2). Infection by SARS-CoV-2 occurs via the binding of its S protein to the angiotensin-converting enzyme-2 receptor (ACE2-R). S binding to ACE2-R leads to a drop in ACE2, a homolog of angiotensin converting enzyme (ACE). In the central nervous system (CNS), ACE mediates neuroinflammation, neurodegeneration and neurotoxicity responsible for several CNS disorders. ACE2 counteracts the damaging effects of ACE on CNS neurons. SARS-CoV-2 can directly access the CNS via the circulation or via cranial nerve I and the olfactory bulb. Inactivation of ACE2 following binding of SARS-CoV-2 S protein to ACE2-R in situ might blunt ACE2-moderating effects upon ACE CNS neurotoxicity and neurodegeneration. Here, we propose a neurobiological mechanism directly involving SARS-CoV-2 binding to ACE2-R in the etiology of putative Neuro-CoViD-19.