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1.
Am J Respir Cell Mol Biol ; 65(4): 403-412, 2021 10.
Article in English | MEDLINE | ID: covidwho-1237350

ABSTRACT

Mechanical ventilation is a known risk factor for delirium, a cognitive impairment characterized by dysfunction of the frontal cortex and hippocampus. Although IL-6 is upregulated in mechanical ventilation-induced lung injury (VILI) and may contribute to delirium, it is not known whether the inhibition of systemic IL-6 mitigates delirium-relevant neuropathology. To histologically define neuropathological effects of IL-6 inhibition in an experimental VILI model, VILI was simulated in anesthetized adult mice using a 35 cc/kg tidal volume mechanical ventilation model. There were two control groups, as follow: 1) spontaneously breathing or 2) anesthetized and mechanically ventilated with 10 cc/kg tidal volume to distinguish effects of anesthesia from VILI. Two hours before inducing VILI, mice were treated with either anti-IL-6 antibody, anti-IL-6 receptor antibody, or saline. Neuronal injury, stress, and inflammation were assessed using immunohistochemistry. CC3 (cleaved caspase-3), a neuronal apoptosis marker, was significantly increased in the frontal (P < 0.001) and hippocampal (P < 0.0001) brain regions and accompanied by significant increases in c-Fos and heat shock protein-90 in the frontal cortices of VILI mice compared with control mice (P < 0.001). These findings were not related to cerebral hypoxia, and there was no evidence of irreversible neuronal death. Frontal and hippocampal neuronal CC3 were significantly reduced with anti-IL-6 antibody (P < 0.01 and P < 0.0001, respectively) and anti-IL-6 receptor antibody (P < 0.05 and P < 0.0001, respectively) compared with saline VILI mice. In summary, VILI induces potentially reversible neuronal injury and inflammation in the frontal cortex and hippocampus, which is mitigated with systemic IL-6 inhibition. These data suggest a potentially novel neuroprotective role of systemic IL-6 inhibition that justifies further investigation.


Subject(s)
Antibodies/pharmacology , Apoptosis/drug effects , Delirium/metabolism , Interleukin-6/antagonists & inhibitors , Neurons/metabolism , Ventilator-Induced Lung Injury/metabolism , Animals , Delirium/drug therapy , Delirium/pathology , Disease Models, Animal , Female , Frontal Lobe/injuries , Frontal Lobe/metabolism , Frontal Lobe/pathology , HSP90 Heat-Shock Proteins/metabolism , Hippocampus/injuries , Hippocampus/metabolism , Hippocampus/pathology , Inflammation/drug therapy , Inflammation/metabolism , Inflammation/pathology , Interleukin-6/metabolism , Mice , Neurons/pathology , Proto-Oncogene Proteins c-fos/metabolism , Repressor Proteins/metabolism , Tumor Suppressor Proteins/metabolism , Ventilator-Induced Lung Injury/drug therapy , Ventilator-Induced Lung Injury/pathology
2.
Neurobiol Dis ; 146: 105131, 2020 12.
Article in English | MEDLINE | ID: covidwho-872391

ABSTRACT

As researchers across the globe have focused their attention on understanding SARS-CoV-2, the picture that is emerging is that of a virus that has serious effects on the vasculature in multiple organ systems including the cerebral vasculature. Observed effects on the central nervous system include neurological symptoms (headache, nausea, dizziness), fatal microclot formation and in rare cases encephalitis. However, our understanding of how the virus causes these mild to severe neurological symptoms and how the cerebral vasculature is impacted remains unclear. Thus, the results presented in this report explored whether deleterious outcomes from the SARS-CoV-2 viral spike protein on primary human brain microvascular endothelial cells (hBMVECs) could be observed. The spike protein, which plays a key role in receptor recognition, is formed by the S1 subunit containing a receptor binding domain (RBD) and the S2 subunit. First, using postmortem brain tissue, we show that the angiotensin converting enzyme 2 or ACE2 (a known binding target for the SARS-CoV-2 spike protein), is ubiquitously expressed throughout various vessel calibers in the frontal cortex. Moreover, ACE2 expression was upregulated in cases of hypertension and dementia. ACE2 was also detectable in primary hBMVECs maintained under cell culture conditions. Analysis of cell viability revealed that neither the S1, S2 or a truncated form of the S1 containing only the RBD had minimal effects on hBMVEC viability within a 48 h exposure window. Introduction of spike proteins to invitro models of the blood-brain barrier (BBB) showed significant changes to barrier properties. Key to our findings is the demonstration that S1 promotes loss of barrier integrity in an advanced 3D microfluidic model of the human BBB, a platform that more closely resembles the physiological conditions at this CNS interface. Evidence provided suggests that the SARS-CoV-2 spike proteins trigger a pro-inflammatory response on brain endothelial cells that may contribute to an altered state of BBB function. Together, these results are the first to show the direct impact that the SARS-CoV-2 spike protein could have on brain endothelial cells; thereby offering a plausible explanation for the neurological consequences seen in COVID-19 patients.


Subject(s)
Angiotensin-Converting Enzyme 2/metabolism , Blood-Brain Barrier/metabolism , Capillary Permeability/physiology , Endothelial Cells/metabolism , Inflammation/metabolism , Matrix Metalloproteinases/metabolism , SARS-CoV-2/pathogenicity , Spike Glycoprotein, Coronavirus/physiology , Blood-Brain Barrier/drug effects , COVID-19 , Capillary Permeability/drug effects , Cell Adhesion Molecules/drug effects , Cell Adhesion Molecules/metabolism , Cell Survival/drug effects , Dementia/metabolism , Electric Impedance , Endothelial Cells/drug effects , Frontal Lobe/metabolism , Humans , Hypertension/metabolism , In Vitro Techniques , Intercellular Junctions/metabolism , Interleukin-6/genetics , Interleukin-6/metabolism , Lab-On-A-Chip Devices , Matrix Metalloproteinases/drug effects , Primary Cell Culture , Protein Domains , Protein Subunits/metabolism , Protein Subunits/pharmacology , RNA, Messenger/drug effects , RNA, Messenger/metabolism , Spike Glycoprotein, Coronavirus/pharmacology
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