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1.
Crit Care ; 25(1): 236, 2021 07 06.
Article in English | MEDLINE | ID: covidwho-1854835

ABSTRACT

Infectious diseases may affect brain function and cause encephalopathy even when the pathogen does not directly infect the central nervous system, known as infectious disease-associated encephalopathy. The systemic inflammatory process may result in neuroinflammation, with glial cell activation and increased levels of cytokines, reduced neurotrophic factors, blood-brain barrier dysfunction, neurotransmitter metabolism imbalances, and neurotoxicity, and behavioral and cognitive impairments often occur in the late course. Even though infectious disease-associated encephalopathies may cause devastating neurologic and cognitive deficits, the concept of infectious disease-associated encephalopathies is still under-investigated; knowledge of the underlying mechanisms, which may be distinct from those of encephalopathies of non-infectious cause, is still limited. In this review, we focus on the pathophysiology of encephalopathies associated with peripheral (sepsis, malaria, influenza, and COVID-19), emerging therapeutic strategies, and the role of neuroinflammation.


Subject(s)
Brain Diseases/immunology , COVID-19/complications , Cytokines/immunology , Influenza, Human/complications , Malaria/complications , Sepsis/complications , Blood-Brain Barrier/immunology , Brain Diseases/prevention & control , COVID-19/immunology , Humans , Influenza, Human/immunology , Malaria/immunology , Sepsis/immunology
2.
J Gen Virol ; 102(10)2021 10.
Article in English | MEDLINE | ID: covidwho-1490495

ABSTRACT

The highly pathogenic Middle East Respiratory Syndrome Coronavirus (MERS-CoV) is a severe respiratory virus. Recent reports indicate additional central nervous system (CNS) involvement. In this study, human DPP4 transgenic mice were infected with MERS-CoV, and viral antigens were first detected in the midbrain-hindbrain 4 days post-infection, suggesting the virus may enter the brainstem via peripheral nerves. Neurons and astrocytes throughout the brain were infected, followed by damage of the blood brain barrier (BBB), as well as microglial activation and inflammatory cell infiltration, which may be caused by complement activation based on the observation of deposition of complement activation product C3 and high expression of C3a receptor (C3aR) and C5a receptor (C5aR1) in neurons and glial cells. It may be concluded that these effects were mediated by complement activation in the brain, because of their reduction resulted from the treatment with mouse C5aR1-specific mAb. Such mAb significantly reduced nucleoprotein expression, suppressed microglial activation and decreased activation of caspase-3 in neurons and p38 phosphorylation in the brain. Collectively, these results suggest that MERS-CoV infection of CNS triggers complement activation, leading to inflammation-mediated damage of brain tissue, and regulating of complement activation could be a promising intervention and adjunctive treatment for CNS injury by MERS-CoV and other coronaviruses.


Subject(s)
Brain/pathology , Complement System Proteins/immunology , Coronavirus Infections/pathology , Dipeptidyl Peptidase 4/genetics , Middle East Respiratory Syndrome Coronavirus/pathogenicity , Animals , Blood-Brain Barrier/immunology , Blood-Brain Barrier/pathology , Brain/blood supply , Brain/immunology , Brain/virology , Complement Activation/drug effects , Complement Inactivating Agents/therapeutic use , Coronavirus Infections/drug therapy , Coronavirus Infections/immunology , Coronavirus Infections/virology , Disease Models, Animal , Humans , Inflammation , Mice , Mice, Transgenic , Microglia/immunology , Microglia/pathology
3.
CNS Neurosci Ther ; 27(1): 36-47, 2021 01.
Article in English | MEDLINE | ID: covidwho-1388231

ABSTRACT

The blood-brain barrier (BBB) is an important physiological barrier that separates the central nervous system (CNS) from the peripheral circulation, which contains inflammatory mediators and immune cells. The BBB regulates cellular and molecular exchange between the blood vessels and brain parenchyma. Normal functioning of the BBB is crucial for the homeostasis and proper function of the brain. It has been demonstrated that peripheral inflammation can disrupt the BBB by various pathways, resulting in different CNS diseases. Recently, clinical research also showed CNS complications following SARS-CoV-2 infection and chimeric antigen receptor (CAR)-T cell therapy, which both lead to a cytokine storm in the circulation. Therefore, elucidation of the mechanisms underlying the BBB disruption induced by peripheral inflammation will provide an important basis for protecting the CNS in the context of exacerbated peripheral inflammatory diseases. In the present review, we first summarize the physiological properties of the BBB that makes the CNS an immune-privileged organ. We then discuss the relevance of peripheral inflammation-induced BBB disruption to various CNS diseases. Finally, we elaborate various factors and mechanisms of peripheral inflammation that disrupt the BBB.


Subject(s)
Blood-Brain Barrier/metabolism , Brain/metabolism , COVID-19/metabolism , Inflammation Mediators/metabolism , Animals , Blood-Brain Barrier/immunology , Blood-Brain Barrier/pathology , Brain/immunology , Brain/pathology , COVID-19/immunology , COVID-19/pathology , Endothelial Cells/immunology , Endothelial Cells/metabolism , Humans , Inflammation/immunology , Inflammation/metabolism , Inflammation/pathology , Inflammation Mediators/immunology
4.
Front Immunol ; 11: 565521, 2020.
Article in English | MEDLINE | ID: covidwho-1389164

ABSTRACT

Neurological disorders caused by neuroviral infections are an obvious pathogenic manifestation. However, non-neurotropic viruses or peripheral viral infections pose a considerable challenge as their neuropathological manifestations do not emerge because of primary infection. Their secondary or bystander pathologies develop much later, like a syndrome, during and after the recovery of patients from the primary disease. Massive inflammation caused by peripheral viral infections can trigger multiple neurological anomalies. These neurological damages may range from a general cognitive and motor dysfunction up to a wide spectrum of CNS anomalies, such as Acute Necrotizing Hemorrhagic Encephalopathy, Guillain-Barré syndrome, Encephalitis, Meningitis, anxiety, and other audio-visual disabilities. Peripheral viruses like Measles virus, Enteroviruses, Influenza viruses (HIN1 series), SARS-CoV-1, MERS-CoV, and, recently, SARS-CoV-2 are reported to cause various neurological manifestations in patients and are proven to be neuropathogenic even in cellular and animal model systems. This review presents a comprehensive picture of CNS susceptibilities toward these peripheral viral infections and explains some common underlying themes of their neuropathology in the human brain.


Subject(s)
Betacoronavirus/immunology , Coronavirus Infections/complications , Coronavirus Infections/immunology , Middle East Respiratory Syndrome Coronavirus/immunology , Neurogenic Inflammation/complications , Neurogenic Inflammation/immunology , Pneumonia, Viral/complications , Pneumonia, Viral/immunology , SARS Virus/immunology , Severe Acute Respiratory Syndrome/complications , Animals , Blood-Brain Barrier/immunology , Blood-Brain Barrier/virology , COVID-19 , Coronavirus Infections/virology , Cytokines/blood , Disease Models, Animal , Humans , Microglia/immunology , Microglia/virology , Neurogenic Inflammation/virology , Pandemics , Pneumonia, Viral/virology , SARS-CoV-2 , Severe Acute Respiratory Syndrome/immunology , Severe Acute Respiratory Syndrome/virology
5.
Brain ; 144(12): 3576-3588, 2021 12 31.
Article in English | MEDLINE | ID: covidwho-1358432

ABSTRACT

Coronavirus disease 2019 (COVID-19) is a global pandemic caused by SARS-CoV-2 infection and is associated with both acute and chronic disorders affecting the nervous system. Acute neurological disorders affecting patients with COVID-19 range widely from anosmia, stroke, encephalopathy/encephalitis, and seizures to Guillain-Barré syndrome. Chronic neurological sequelae are less well defined although exercise intolerance, dysautonomia, pain, as well as neurocognitive and psychiatric dysfunctions are commonly reported. Molecular analyses of CSF and neuropathological studies highlight both vascular and immunologic perturbations. Low levels of viral RNA have been detected in the brains of few acutely ill individuals. Potential pathogenic mechanisms in the acute phase include coagulopathies with associated cerebral hypoxic-ischaemic injury, blood-brain barrier abnormalities with endotheliopathy and possibly viral neuroinvasion accompanied by neuro-immune responses. Established diagnostic tools are limited by a lack of clearly defined COVID-19 specific neurological syndromes. Future interventions will require delineation of specific neurological syndromes, diagnostic algorithm development and uncovering the underlying disease mechanisms that will guide effective therapies.


Subject(s)
Brain/immunology , COVID-19/epidemiology , COVID-19/immunology , Nervous System Diseases/epidemiology , Nervous System Diseases/immunology , Neuroimmunomodulation/physiology , Blood-Brain Barrier/immunology , Blood-Brain Barrier/pathology , Brain/pathology , COVID-19/complications , COVID-19/diagnostic imaging , Humans , Nervous System Diseases/diagnostic imaging
6.
Crit Care ; 25(1): 236, 2021 07 06.
Article in English | MEDLINE | ID: covidwho-1298056

ABSTRACT

Infectious diseases may affect brain function and cause encephalopathy even when the pathogen does not directly infect the central nervous system, known as infectious disease-associated encephalopathy. The systemic inflammatory process may result in neuroinflammation, with glial cell activation and increased levels of cytokines, reduced neurotrophic factors, blood-brain barrier dysfunction, neurotransmitter metabolism imbalances, and neurotoxicity, and behavioral and cognitive impairments often occur in the late course. Even though infectious disease-associated encephalopathies may cause devastating neurologic and cognitive deficits, the concept of infectious disease-associated encephalopathies is still under-investigated; knowledge of the underlying mechanisms, which may be distinct from those of encephalopathies of non-infectious cause, is still limited. In this review, we focus on the pathophysiology of encephalopathies associated with peripheral (sepsis, malaria, influenza, and COVID-19), emerging therapeutic strategies, and the role of neuroinflammation.


Subject(s)
Brain Diseases/immunology , COVID-19/complications , Cytokines/immunology , Influenza, Human/complications , Malaria/complications , Sepsis/complications , Blood-Brain Barrier/immunology , Brain Diseases/prevention & control , COVID-19/immunology , Humans , Influenza, Human/immunology , Malaria/immunology , Sepsis/immunology
7.
Immunity ; 54(7): 1594-1610.e11, 2021 07 13.
Article in English | MEDLINE | ID: covidwho-1281436

ABSTRACT

COVID-19 can cause severe neurological symptoms, but the underlying pathophysiological mechanisms are unclear. Here, we interrogated the brain stems and olfactory bulbs in postmortem patients who had COVID-19 using imaging mass cytometry to understand the local immune response at a spatially resolved, high-dimensional, single-cell level and compared their immune map to non-COVID respiratory failure, multiple sclerosis, and control patients. We observed substantial immune activation in the central nervous system with pronounced neuropathology (astrocytosis, axonal damage, and blood-brain-barrier leakage) and detected viral antigen in ACE2-receptor-positive cells enriched in the vascular compartment. Microglial nodules and the perivascular compartment represented COVID-19-specific, microanatomic-immune niches with context-specific cellular interactions enriched for activated CD8+ T cells. Altered brain T-cell-microglial interactions were linked to clinical measures of systemic inflammation and disturbed hemostasis. This study identifies profound neuroinflammation with activation of innate and adaptive immune cells as correlates of COVID-19 neuropathology, with implications for potential therapeutic strategies.


Subject(s)
Brain/immunology , CD8-Positive T-Lymphocytes/immunology , COVID-19/immunology , Microglia/immunology , Blood-Brain Barrier/immunology , Blood-Brain Barrier/metabolism , Blood-Brain Barrier/pathology , Brain/metabolism , Brain/pathology , CD8-Positive T-Lymphocytes/metabolism , COVID-19/pathology , Cell Communication , Central Nervous System/immunology , Central Nervous System/metabolism , Central Nervous System/pathology , Humans , Immune Checkpoint Proteins/metabolism , Inflammation , Lymphocyte Activation , Multiple Sclerosis/immunology , Multiple Sclerosis/pathology , Olfactory Bulb/immunology , Olfactory Bulb/metabolism , Olfactory Bulb/pathology , Respiratory Insufficiency/immunology , Respiratory Insufficiency/pathology , SARS-CoV-2 , Spike Glycoprotein, Coronavirus/metabolism , T-Lymphocyte Subsets/immunology , T-Lymphocyte Subsets/metabolism
8.
Inflammopharmacology ; 29(4): 939-963, 2021 Aug.
Article in English | MEDLINE | ID: covidwho-1169006

ABSTRACT

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.


Subject(s)
Blood-Brain Barrier/metabolism , Brain/metabolism , COVID-19/metabolism , Inflammation Mediators/metabolism , SARS-CoV-2/metabolism , Blood-Brain Barrier/immunology , Blood-Brain Barrier/pathology , Brain/immunology , Brain/pathology , COVID-19/immunology , COVID-19/pathology , Cytokine Release Syndrome/immunology , Cytokine Release Syndrome/metabolism , Cytokine Release Syndrome/pathology , Humans , Inflammation Mediators/immunology , SARS-CoV-2/immunology , Signal Transduction/physiology
9.
CNS Neurosci Ther ; 27(1): 36-47, 2021 01.
Article in English | MEDLINE | ID: covidwho-1003961

ABSTRACT

The blood-brain barrier (BBB) is an important physiological barrier that separates the central nervous system (CNS) from the peripheral circulation, which contains inflammatory mediators and immune cells. The BBB regulates cellular and molecular exchange between the blood vessels and brain parenchyma. Normal functioning of the BBB is crucial for the homeostasis and proper function of the brain. It has been demonstrated that peripheral inflammation can disrupt the BBB by various pathways, resulting in different CNS diseases. Recently, clinical research also showed CNS complications following SARS-CoV-2 infection and chimeric antigen receptor (CAR)-T cell therapy, which both lead to a cytokine storm in the circulation. Therefore, elucidation of the mechanisms underlying the BBB disruption induced by peripheral inflammation will provide an important basis for protecting the CNS in the context of exacerbated peripheral inflammatory diseases. In the present review, we first summarize the physiological properties of the BBB that makes the CNS an immune-privileged organ. We then discuss the relevance of peripheral inflammation-induced BBB disruption to various CNS diseases. Finally, we elaborate various factors and mechanisms of peripheral inflammation that disrupt the BBB.


Subject(s)
Blood-Brain Barrier/metabolism , Brain/metabolism , COVID-19/metabolism , Inflammation Mediators/metabolism , Animals , Blood-Brain Barrier/immunology , Blood-Brain Barrier/pathology , Brain/immunology , Brain/pathology , COVID-19/immunology , COVID-19/pathology , Endothelial Cells/immunology , Endothelial Cells/metabolism , Humans , Inflammation/immunology , Inflammation/metabolism , Inflammation/pathology , Inflammation Mediators/immunology
10.
Fluids Barriers CNS ; 17(1): 55, 2020 Sep 10.
Article in English | MEDLINE | ID: covidwho-755214

ABSTRACT

Human coronaviruses are highly pathogenic viruses that pose a serious threat to human health. Examples include the severe acute respiratory syndrome outbreak of 2003 (SARS-CoV-1), the Middle East Respiratory Syndrome (MERS-CoV) outbreak of 2012, and the current SARS-CoV-2 (COVID-19) pandemic. Herein, we review the neurological manifestations of coronaviruses and discuss the potential pathogenic role of blood-brain barrier dysfunction. We present the hypothesis that pre-existing vascular damage (due to aging, cardiovascular disease, diabetes, hypertension or other conditions) facilitates infiltration of the virus into the central nervous system (CNS), increasing neuro-inflammation and the likelihood of neurological symptoms. We also discuss the role of a neuroinflammatory cytokine profile in both blood-brain barrier dysfunction and macrovascular disease (e.g. ischemic stroke and thromboembolism). Future studies are needed to better understand the involvement of the microvasculature in coronavirus neuropathology, and to test the diagnostic potential of minimally-invasive screening tools (e.g. serum biomarkers, fluorescein retinal angiography and dynamic-contrast MRI).


Subject(s)
Blood-Brain Barrier/physiopathology , Coronavirus Infections/physiopathology , Inflammation/physiopathology , Microvessels/physiopathology , Nervous System Diseases/physiopathology , Pneumonia, Viral/physiopathology , Betacoronavirus , Blood-Brain Barrier/immunology , Blood-Brain Barrier/virology , COVID-19 , Cardiovascular Diseases/physiopathology , Coronavirus Infections/immunology , Cytokines/immunology , Diabetes Mellitus/physiopathology , Encephalitis/immunology , Encephalitis/physiopathology , Humans , Inflammation/immunology , Microvessels/immunology , Nervous System Diseases/immunology , Pandemics , Pneumonia, Viral/immunology , SARS-CoV-2 , Seizures/immunology , Seizures/physiopathology , Stroke/immunology , Stroke/physiopathology , Thromboembolism/immunology , Thromboembolism/physiopathology
11.
Biochim Biophys Acta Mol Basis Dis ; 1866(10): 165823, 2020 10 01.
Article in English | MEDLINE | ID: covidwho-133265

ABSTRACT

A wide array of molecular pathways has been investigated during the past decade in order to understand the mechanisms by which the practice of physical exercise promotes neuroprotection and reduces the risk of developing communicable and non-communicable chronic diseases. While a single session of physical exercise may represent a challenge for cell homeostasis, repeated physical exercise sessions will improve immunosurveillance and immunocompetence. Additionally, immune cells from the central nervous system will acquire an anti-inflammatory phenotype, protecting central functions from age-induced cognitive decline. This review highlights the exercise-induced anti-inflammatory effect on the prevention or treatment of common chronic clinical and experimental settings. It also suggests the use of pterins in biological fluids as sensitive biomarkers to follow the anti-inflammatory effect of physical exercise.


Subject(s)
Anti-Inflammatory Agents/pharmacology , Exercise/physiology , Immune System/drug effects , Immune System/immunology , Animals , Biomarkers , Blood-Brain Barrier/immunology , Chronic Disease , Communicable Diseases/immunology , Cytokines , Databases, Factual , Humans , Immunity, Innate/immunology , Inflammation/immunology , Neopterin/pharmacology , Neuroprotection/immunology
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