Journal of Biomedical Science

BackgroundMyocarditis has emerged as a rare but lethal Immune checkpoint inhibitor (ICI)-associated toxicity. However, the exact mechanism for ICI related myocarditis remains underexplored; and the specific therapeutic targets is still lacking. In this study, we used scRNA-seq to characterize the transcriptomic profiles of single cells from the peripheral blood mononuclear cell (PBMC) of ICI related myocarditis during fulminant myocarditis and disease recovery. MethodsPBMC samples were taken from the patient during fulminant ICI related myocarditis and after disease remission. Cells were isolated from blood samples by density gradient centrifugation over Ficoll-Paque. Single-cell RNA sequencing with 10X genomics was performed. Subpopulation determination, functional analysis, single-cell trajectory and cell-cell interaction analysis were carried out afterwards. ResultsWe presented the altered landscape of immune cells and differential genes in ICI related myocarditis during the disease activity and remission using scRNA-seq. Substantial immune cell composition and intercellular communication were found to be altered. Monocyte, NK cell as well as B cell subpopulations contributed to the regulation of innate immunity and inflammation in ICI related myocarditis. T cell subpopulations highly expressed genes associated with PD-1 inhibitor resistance and hyper-progressor. At last, the intercellular communication in ICI related myocarditis was significantly dysregulated. ConclusionBy identifying altered pathways and highlighting a catalog of marker genes, this study has revealed the diversity of cellular populations in ICI related myocarditis, marked by their distinct transcriptional profiles and biological functions. Our investigation would shed light on the pathophysiological mechanism and potential therapeutic targets of ICI related myocarditis in continuous exploration.

BackgroundSubarachnoid hemorrhage (SAH) is a severe stroke and the advanced treatment for SAH is still limited. Recent studies have shown that microglia-mediated neuroinflammation plays a critical role in the pathogenesis of SAH. Microglia can transform their states in response to central nervous system injury. However, the transcriptomic features of microglia remained unknown in SAH. Recent developed single-cell RNA sequencing (scRNA-seq) provides a possible way to solve this problem. MethodsEndovascular perforation (EVP) murine SAH model was established to reproduce experimental SAH. Microglia states are examined with immune staining and quantitate analysis. Post-SAH microglial single-cell suspension were harvest and sequenced using 10X scRNA-seq platform. Then, the detailed single-cell transcriptomic characterization of post-SAH microglia were analyzed with bioinformatics. ResultsTranscriptional analysis revealed at least ten diverse microglial subgroups, including SAH-associated microglia (SAM), inflammatory-associated microglia (IAM) and proliferation-associated microglia (PAM), which all exhibit distinct marker gene expression patterns. Microglia subsets interaction reveals the functional relationship between elevated signaling pathways and microglial sub-populations in SAH. Receptor-ligand pair analysis revealed that complex inter-cellular interactions exist between the microglia subsets and other cell types, and indicated that microglia are important mediators of neuroinflammation after SAH. Integrated analysis with normal microglia further proved the existence of these microglia subpopulations and different gene markers associated with SAH were clarified. ConclusionsCollectively, we first report the single-cell transcriptome of post-SAH microglia and found specific biomarkers related to the neuroinflammation in SAH. These results enhanced our understanding of the pathological mechanisms of microglial response to SAH, and may guide future development of SAH monitoring methods and therapeutics.

Secondary brain injury following subarachnoid hemorrhage (SAH) is the critical contributor to the mortality of SAH patients. The underlying mechanisms are poorly understood. In this study, we utilized a mice model of SAH to investigate whether FoxO4 is related to the brain injury after SAH and identified its upstream regulator Akt. Experimental SAH was induced in adult male mice by prechiasmatic cistern injection. Brain FoxO4 protein levels in cytoplasm and nucleaus were examined in the sham-operated controls, and in mice 1h, 6h, 12h, 24h, 3d, and 5d after SAH induction. The Akt inhibitor LY294002 was administered by intracerebroventricular infusion to determine its effects on FoxO4. Moreover, the expression of FoxO4 was also investigated in neurons incubated with hemoglobin in vitro, which was also dertermined after inhibition of Akt. FoxO4 protein expression in the nuclei increased remarkably after SAH. The Akt inhibitor LY294002 induced more FoxO4 nuclear localization after SAH in vivo and in vitro. Our results suggest the activation of FoxO4 after SAH and which was inhibited by the increased phosphorylated Akt (p-Akt).

The coronavirus disease 2019 (COVID-19) pandemic is caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2); host cell entry by this virus relies on the interaction between the receptor-binding domain (RBD) of its spike glycoprotein and the angiotensin-converting enzyme 2 (ACE2) receptor on cell membranes. In addition to serving as a receptor for SARS-CoV-2, ACE2 was originally discovered as a protective factor in the renin-angiotensin system (RAS) that catalyses the degradation of angiotensin II (Ang II) to Ang 1-7, which is involved in multiple organ pathology. Recent genetic and clinical studies reported that ApoE4 expression is associated with increased susceptibility to SARS-CoV-2 infection and the development of severe COVID-19, but the underlying mechanism is currently unclear. In the present study, by using immunofluorescence staining, molecular dynamics simulations, proximity ligation assay (PLA) and coimmunoprecipitation (Co-IP) combined with a biolayer interferometry (BLI) assay, we found that ApoE interacts with both the spike protein and ACE2 but does not show obvious isoform-dependent binding effects. These data suggest that ApoE4 increases SARS-CoV-2 infectivity in a manner that may not depend on differential interactions with the spike protein or ACE2. Importantly, further immunoblotting and immunofluorescence staining results showed that ApoE4 significantly downregulates ACE2 protein expression in vitro and in vivo and subsequently decreases the conversion of Ang II to Ang 1-7, which could worsen tissue lesions; these findings provide a possible explain by which ApoE4 exacerbates COVID-19 disease.

A large number of hospitalized COVID-19 patients show neurological symptoms such as ischemic- and hemorrhagic stroke as well as encephalitis, and SARS-CoV-2 can directly infect endothelial cells leading to endotheliitis across multiple vascular beds. These findings suggest an involvement of the brain- and peripheral vasculature in COVID-19, but the underlying molecular mechanisms remain obscure. To understand the potential mechanisms underlying SARS-CoV-2 tropism for brain vasculature, we constructed a molecular atlas of the expression patterns of SARS-CoV-2 viral entry-associated genes (receptors and proteases) and SARS-CoV-2 interaction partners in human (and mouse) adult and fetal brain as well as in multiple non-CNS tissues in single-cell RNA-sequencing data across various datasets. We observed a distinct expression pattern of the cathepsins B (CTSB) and -L (CTSL) - which are able to substitute for the ACE2 co-receptor TMPRSS2 - in the human vasculature with CTSB being mainly expressed in the brain vasculature and CTSL predominantly in the peripheral vasculature, and these observations were confirmed at the protein level in the Human Protein Atlas and using immunofluorescence stainings. This expression pattern of SARS-CoV-2 viral-entry associated proteases and SARS-CoV-2 interaction partners was also present in endothelial cells and microglia in the fetal brain, suggesting a developmentally established SARS-CoV-2 entry machinery in the human vasculature. At both the adult and fetal stages, we detected a distinct pattern of SARS-CoV-2 entry associated genes transcripts in brain vascular endothelial cells and microglia, providing a potential explanation for an inflammatory response in the brain endothelium upon SARS-CoV-2 infection. Moreover, CTSB was co-expressed in adult and fetal brain endothelial cells with genes and pathways involved in innate immunity and inflammation, angiogenesis, blood-brain-barrier permeability, vascular metabolism, and coagulation, providing a potential explanation for the role of brain endothelial cells in clinically observed (neuro)vascular symptoms in COVID-19 patients. Our study serves as a publicly available single-cell atlas of SARS-CoV-2 related entry factors and interaction partners in human and mouse brain endothelial- and perivascular cells, which can be employed for future studies in clinical samples of COVID-19 patients.

Immigration and activation of immune cells play a significant role in damage progression after ischemic stroke. It has been shown that the nuclear receptor NR4A1 exerts a crucial role within the inflammatory response of various immune diseases via regulating immune cell activation. In this study, we investigated the role of NR4A1 on the activation and recruitment of brain resident and peripheral immune cells after cerebral ischemia. Here, we show that NR4A1 mediates an anti-inflammatory and damage limiting effect after ischemic stroke through immigrating neutrophil granulocytes. Importantly, NR4A1-activation with its ligand Cytosporone-B improves functional outcome and diminishes brain damage. Therefore, modulation of NR4A1 is a promising therapeutic target in the treatment of stroke.

COVID-19 is a respiratory disease caused by severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2). COVID-19 pathogenesis causes vascular-mediated neurological disorders via still elusive mechanisms. SARS-CoV-2 infects host cells by binding to angiotensin-converting enzyme 2 (ACE2), a transmembrane receptor that recognizes the viral spike (S) protein. Brain pericytes were recently shown to express ACE2 at the neurovascular interface, outlining their possible implication in microvasculature injury in COVID-19. Yet, pericyte responses to SARS-CoV-2 is still to be fully elucidated. Using cell-based assays, we report that ACE2 expression in human brain vascular pericytes is highly dynamic and is increased upon S protein stimulation. Pericytes exposed to S protein underwent profound phenotypic changes translated by increased expression of contractile and myofibrogenic proteins, namely -smooth muscle actin (-SMA), fibronectin, collagen I, and neurogenic locus notch homolog protein-3 (NOTCH3). These changes were associated to an altered intracellular calcium (Ca2+) dynamic. Furthermore, S protein induced lipid peroxidation, oxidative and nitrosative stress in pericytes as well as triggered an immune reaction translated by activation of nuclear factor-kappa-B (NF-{kappa}B) signalling pathway, which was potentiated by hypoxia, a condition associated to vascular comorbidities, which exacerbate COVID-19 pathogenesis. S protein exposure combined to hypoxia enhanced the production of pro-inflammatory cytokines involved in immune cell activation and trafficking, namely interleukin-8 (IL-8), IL-18, macrophage migration inhibitory factor (MIF), and stromal cell-derived factor-1 (SDF-1). Finally, we found that S protein could reach the mouse brain via the intranasal route and that reactive ACE2-expressing pericytes are recruited to the damaged tissue undergoing fibrotic scarring in a mouse model of cerebral multifocal micro-occlusions, a main reported vascular-mediated neurological condition associated to COVID-19. Our data demonstrate that the released S protein is sufficient to mediate pericyte immunoreactivity, which may contribute to microvasculature injury in absence of a productive viral infection. Our study provides a better understanding for the possible mechanisms underlying cerebrovascular disorders in COVID-19, paving the way to develop new therapeutic interventions.

Mutations of EFHC1 gene have been identified in patients with epilepsies including juvenile myoclonic epilepsy (JME), and mice with Efhc1 deficiency exhibit epileptic phenotypes. Myoclonin1 protein encoded by EFHC1 is not expressed in neurons but in cells with motile cilia including those of choroid plexus and ependymal cells which form an epithelial layer lining brain ventricles. Detailed molecular basis of epilepsies caused by EFHC1 mutations, however, remain unclear. Here we report that myoclonin1 is well co-expressed with inositol 1,4,5-trisphosphate receptor type 1 (IP3R1) at choroid plexus and ependymal cells and these two proteins bind each other. Endoplasmic reticulum (ER) of Efhc1-deficient mouse (Efhc1-/-) cells contains larger levels of calcium ions (Ca2+) than that of wild-type (WT) mice, and IP3-induced Ca2+ release (IICR) from ER is higher in Efhc1-/- cells than that of WT. Furthermore, myoclonin1 revealed to interact with PRKCSH, also known as a protein kinase C substrate 80K-H which interacts with IP3R1. Myoclonin1 further binds to IP3R2 and IP3R3. Thus, our results indicate that myoclonin1 modulates ER-Ca2+ homeostasis through interactions with IP3Rs and PRKCSH, and suggest that myoclonin1 dysfunctions cause impaired intracellular Ca2+ mobilization. Its relevance to the epileptic phenotypes of patients with EFHC1 mutations is now of interest.

Myocardial Infarction (MI), commonly known as a heart attack, stands as a formidable global health challenge, responsible for a substantial burden of morbidity and mortality. This study embarked on a comprehensive exploration of the genetic underpinnings of MI, recognizing the pivotal role of genetic factors in determining an individuals susceptibility to this life-threatening condition. The objective of our research was to investigate missense single nucleotide polymorphisms (SNP) associated with MI to determine whether the changes in amino acid sequences have potential implications for the risk of MI. Employing a multifaceted approach, we leveraged an array of computational tools and databases to scrutinize specific missense SNP and meticulously analyzed their potential effects on protein structure stability and function. Our analysis has confirmed a total of 4 missense SNP in ALDH2, APOE, IGFBP1, and PCSK1 genes to be damaging to protein structure and hence, the function. An extensive literature review was then performed to determine the functional roles of these genes in the regulation of the cardiac system-related pathways. Our analysis confirmed that all 2 of these genes are directly involved in pathways related to the cardiac system, while the other 2 genes play other roles. We have further analyzed their interactions and underlying biological processes to determine their potential role in the incidence of MI. These findings collectively offer a profound understanding of the intricate genetic landscape underlying MI. They not only enhance our comprehension of the multifaceted genetic factors influencing MI susceptibility but also set the stage for future experimental investigations. Importantly, these insights hold the potential to guide future research and the development of therapeutic strategies, to improve the prevention and management of this critical cardiovascular condition.

Respiratory disease caused by the 2019 novel coronavirus (2019-nCoV) pneumonia first emerged in Wuhan, Hubei Province, China, in December 2019 and spread rapidly to other provinces and other countries. Angiotensin-converting enzyme 2 (ACE2) is the receptor for SARS-CoV and has been suggested to be also the receptor for 2019-nCoV. Paradoxically, ACE2 expression in the lung protects mice from SARS-CoV spike protein induced lung injury by attenuating the renin-angiotensin system. In the intestine, ACE2 also suppresses intestinal inflammation by maintaining amino acid homeostasis, antimicrobial peptide expression and ecology of the gut microbiome. Upon analysis of single cell-RNA sequencing data from control subjects and those with colitis or inflammatory bowel disease (IBD), we found that ACE2 expression in the colonocytes was positively associated with genes regulating viral infection, innate and cellular immunity, but was negatively associated with viral transcription, protein translation, humoral immunity, phagocytosis and complement activation. In summary, we suggest that ACE2 may play dual roles in mediating the susceptibility and immunity of 2019-nCoV infection.

Initial symptoms of COVID-19 infection depend on viral replication, while hyperinflammation is a hallmark of critical illness and may drive severe pneumonia and death. Among the mechanisms potentially involved in the hyperinflammatory state, we focused on the unfolded protein response, because the IRE1-XBP1 branch can be activated as result of the endoplasmic reticulum stress produced by the overwhelming synthesis of viral components and synergizes with Toll-like receptor signaling to induce cytokine expression. Viral RNA may trigger the IRE1-XBP1 branch via TLR7/8 activation and like TLR2 and TLR4 may underpin cytokine expression trough XBP1 splicing (sXBP1). The expression of IL1B, IL6, and TNF mRNA in bronchoalveolar aspirates (BAAs) were higher in COVID-19 patients under mechanical ventilation and intubation who showed sXBP1. The scrutiny of monocytic/macrophagic markers during active infection showed a reduction of those involved in antigen presentation and survival, as well as the IFN stimulated gene MX1. These changes reverted after infection tests turned negative. In contrast, the expression of the mRNA of the serine protease TMPRSS2 involved in S protein priming showed a high expression during active infection. TLR8 mRNA showed an overwhelming expression as compared to TLR7 mRNA, which suggests the presence of monocyte-derived dendritic cells (MDDCs). In vitro experiments in MDDCs activated with ssRNA40, a positive-sense, single-stranded RNA (+ssRNA) like SARS-CoV-2 RNA, induced sXBP1 and the expression of IL-1{beta}, IL-6, and TNF at mRNA and protein levels. These responses were blunted by the IRE1 ribonuclease inhibitor MKC8866. Given the analogies between the results observed in BAAs and the effects induced by +ssRNA in MDDCs, IRE1 ribonuclease inhibition might be a druggable target in severe COVID-19 disease. O_FIG O_LINKSMALLFIG WIDTH=180 HEIGHT=200 SRC="FIGDIR/small/22269752v1_ufig1.gif" ALT="Figure 1"> View larger version (53K): org.highwire.dtl.DTLVardef@13b04b3org.highwire.dtl.DTLVardef@1b1af7corg.highwire.dtl.DTLVardef@780104org.highwire.dtl.DTLVardef@8ad0ba_HPS_FORMAT_FIGEXP M_FIG C_FIG Author summaryCOVID-19 pandemics put an unprecedented pressure on health systems. The need of new therapies urged research on the mechanisms triggered by the interaction of SARS-CoV-2 virus with host cells and the ensuing pathophysiology driving pneumonia and multiorgan failure. Hyperinflammation soon appeared as a mechanism involved in mortality that could even proceed after viral infection comes to an end. Hyperinflammation is supported by an inappropriate production of cytokines, and this explains the use of the term cytokine storm to refer to this phase of the disease. Given that insight into the molecular mechanisms driving cytokine storm should focus on the interaction of viral components with immune cells, experiments addressing the effect of viral components on its cognate receptors were carried out. It was observed that viral RNA induces a cytokine pattern like the one observed in bronchoalveolar aspirates of COVID-19 patients with critical disease. Overall, the study revealed that both cell organelle overload and receptors involved in the recognition of viral RNA may team up to induce proinflammatory cytokines. This mechanism can be exploited to develop new treatments for COVID-19 disease.

Neurological effects of COVID-19 and long-COVID-19 as well as neuroinvasion by SARS-CoV-2 still pose several questions and are of both clinical and scientific relevance. We described the cellular and molecular effects of the human brain microvascular endothelial cells (HBMECs) in vitro infection by SARS-CoV-2 to understand the underlying mechanisms of viral transmigration through the Blood-Brain Barrier. Despite the low to non-productive viral replication, SARS-CoV-2-infected cultures displayed increased apoptotic cell death and tight junction protein expression and immunolocalization. Transcriptomic profiling of infected cultures revealed endothelial activation via NF-{kappa}B non-canonical pathway, including RELB overexpression, and mitochondrial dysfunction. Additionally, SARS-CoV-2 led to altered secretion of key angiogenic factors and to significant changes in mitochondrial dynamics, with increased mitofusin-2 expression and increased mitochondrial networks. Endothelial activation and remodeling can further contribute to neuroinflammatory processes and lead to further BBB permeability in COVID-19.

Cerebral ischemia reperfusion injury (CIRI) is a complex pathophysiological process involving multiple mechanisms. Piezo1, a stretch-activated ion channel, has recently emerged as a potential regulator of cellular responses to ischemic conditions. However, its role in specific cells during ischemic events is not well elucidated. Here, we showed that after experimentally induced CIRI, Piezo1 channel was highly expressed in peri-infarct area, where is upregulated and activated mainly in microglia. Behavioral tests, and infarct volume measurements demonstrated that conditional Piezo1 deficient in microglia markedly ameliorated the neurological deficits and reduced the infarct volumes. Flow cytometry and immunofluorescence staining showed decreased peripheral immune cells, especially T lymphocytes infiltration into the brain in microglia Piezo1 deficient mice after stroke. Multiplex chemokine immunoassay and T cell migration assays screened that Piezo1 deficient microglia blocked the CXC chemokine ligand 10 (CXCL10) release from astrocyte, which lead to the inhibited T cell recruitment in transwell co-cultured system. Furthermore, RNA-Sequencing analysis showed that defective Piezo1 in microglia lead to its polarization towards an anti-inflammatory phenotype in response to cerebral ischemia and reduced the secretion of tumor necrosis factor- (TNF-) and interferon-{gamma} (IFN-{gamma}). Collectively, Piezo1 deficiency inhibited the secretion of TNF- and IFN-{gamma} in microglia. The reduction of these inflammatory cytokines further blocked the CXCL10 release from astrocyte, and ultimately ameliorated the infiltration of peripheral T lymphocytes after stroke. Our results therefore highlight the critical role of Piezo1 in microglia-orchestrated neuroinflammation and suggest a potential means for reducing stroke-induced neurological injury.

Adipokines have not been studied in acute dengue, despite their emerging role in inducing and regulating inflammation. Therefore, we sought to identify adipokine levels in patients with varying severities of acute dengue to understand their role in disease pathogenesis. We determined the levels of leptin, resistin, omentin, adiponectin, as well as IFN{beta}, and NS1 using quantitative ELISA in patients with dengue fever (DF=49) and dengue haemorrhagic fever (DHF=22) at admission (febrile phase) and at the time of discharge (recovery phase). The viral loads and serotypes of all samples were quantified using quantitative real-time RT-PCR. Resistin levels (p =0.04) and omentin (p=0.006) levels were significantly higher in patients who developed DHF. Omentin levels in the febrile phase also correlated with the AST (Spearmans r=0.38, p=0.001) and ALT levels (Spearmans r=0.24, p=0.04); as well as serum leptin levels with both AST (Spearmans r=0.27, p=0.02) and ALT (Spearmans r=0.28, p=0.02). Serum adiponectin levels in the febrile phase did not correlate with any of the other adipokines or with liver enzymes, but inversely correlated with CRP levels (Spearmans r=-0.31, p=0.008). Although not significant (p=0.14) serum IFN{beta} levels were lower in the febrile phase in those who progressed to develop DHF (median 0, IQR 0 to 39.4 pg/ml), compared to those who had DF (median 37.1, IQR 0 to 65.6 pg.ml). The data suggest that adipokines are likely to play a role in the pathogenesis of dengue, which should be further explored for the potential to be used as prognostic markers and as therapeutic targets.

Graves disease (GD) is the leading cause of hyperthyroidism and is often treated with antithyroid drugs (ATDs). Although ATD therapy is effective, it might cause a rare but serious adverse effect called ATD-induced agranulocytosis (TiA), which can lead to severe neutropenia and life-threatening infections. Previous studies have shown that certain human leukocyte antigen (HLA) alleles, including HLA-B*38:02 and HLA-DRB1*08:03 in Asian populations, have been associated with TiA susceptibility. However, the underlying mechanisms remain unclear, highlighting the need to investigate the TiA-related immune alterations to better understand its pathogenesis and mechanisms. In this study, we investigated the immune receptor repertoire in TiA patients. Global repertoire diversity, VJ gene usage, and V-J pairing remained preserved across phenotypes and disease phases. Notably, TiA patients exhibited several upregulated complementarity-determining regions 3 (CDR3) clonotypes compared to GD patients, suggesting their role in disease progression and pathogenesis. Single-cell immune repertoire analysis revealed that TiA-associated risk CDR3 sequences were predominantly expressed on CD8+ effector memory T cells (CD8 TEM) in patients with HLA-B*38:02, while CD4+ central memory T cells (TCM) showed increased expression of risk CDR3 sequences in patients with HLA-DRB1*08:03, suggesting distinct cellular mechanisms underlying HLA-associated TiA pathogenesis. In conclusion, this study sheds light on the adaptive immunoprofile associated with TiA development and provides insights into the adaptive immune profile of TiA and HLA-mediated disease susceptibility.

Following ischemic stroke, Ccl5 mRNA expression increased, while miR-324-5p expression decreased in the peri-infract cortex of middle cerebral artery occlusion (MCAO) mice. However, the roles of CCL5 and miR-324-5p in stroke remain unclear. Here, we show that inhibiting CCL5 using antibodies or miR-324-5p not only reduced infarct area and preserved neurological function in MCAO mice but also attenuated astrocyte and microglia activation, protected dendritic structures, and maintained spine density. In an astrocyte-neuron co-culture system after oxygen-glucose deprivation (OGD), knockdown astrocytic CCL5 expression by antibody or miR-324-5p decreased neuronal apoptosis and preserved dendritic architecture. Importantly, the suppression of CCL5 enhanced the activation of the ERK/CREB pathway both in vivo and in vitro. Consistent with these findings, the application of Maraviroc, a CCR5 antagonist, reduced infarct size, decreased neuronal apoptosis, and upregulated the ERK/CREB pathway in neurons treated with OGD. In conclusion, targeting the CCL5 pathway via miR-324-5p represents a promising therapeutic strategy for alleviating ischemic stroke damage through modulation of neuronal CCR5/ERK/CREB pathway.

Brain injury after intracerebral hemorrhage is extremely complicated, and the exact mechanism remains puzzling. Piezo1, a novel mammalian mechanosensitive ion channel, has been identified to play important roles in several pathologic and physiologic procedures that involve cellular mechanotransduction. However, the role of Piezo1 in hematoma compression after intracerebral hemorrhage is still unclear. In the present study, we established a balloon-inflated rat brain model mimicking the pure mechanical compression of a hematoma and detected balloon compression in the basal ganglia region of the brain, resulting in abnormal behaviors and a significant increase in the expression of Piezo1 and proinflammatory cytokines. These effects were reversed by GsMTx4, an antagonist of Piezo1. Additionally, the balloon deflation time affected behavioral function and the levels of Piezo1 and proinflammatory cytokines. These results establish the first in vivo evidence for the role of Piezo1 in blood-brain neuroinflammation after hematoma compression. Piezo1 may therefore be a potential therapeutic target for the treatment of intracerebral hemorrhage.

Epidermal growth factor receptor (EGFR) activates major cell signaling pathways that regulate various cell responses. Its dimerization and clustering coupled with its lateral mobility are critical for EGFR function, but the contribution of the plasma membrane environment to EGFR function is unknown. Here we show, using single-molecule analysis, that EGFR mobility and clustering are altered by the depletion of cholesterol or sphingomyelin, major lipids of membrane subdomains, causing significant changes in EGFR signaling. When cholesterol was depleted, the subdomain boundary in EGFR diffusion disappeared, the fraction of EGFR pre-dimers was increased, and the ligand-induced phosphorylation of EGFR was enhanced. In addition, the depletion of either lipid prevented the formation of immobile clusters after EGF association and decreased the phosphorylation of downstream proteins. Our results revealed that cholesterol plays dichotomous roles in the signaling pathway of EGFR and that clustering in the membrane subdomains is critical for EGFR signal transduction.

While there is clinical evidence of neurological manifestation in coronavirus disease-19, its unclear whether this is due to differential severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) uptake from blood by cells of the cerebrovasculature. SARS-CoV-2 and its spike protein (SP) interact with the endothelium but the roles of extracellular peptidase domain on angiotensin converting enzyme 2 receptors (ACE2) and ACE2 independent pathways (such as glycans) are not fully elucidated. In addition, for SARS-CoV-2 to enter the brain parenchyma from blood it has to cross several cell types, including the endothelium, pericytes and vascular smooth muscle. Since SARS-CoV-2 interacts with host cells via it SP at the entry point of it life cycle, we used fluorescently labelled SP (SP-555) (wild type and mutants) to model viral behaviour, in vitro, for these cell types (endothelial, pericytes and vascular smooth muscle) to explore pathways of viral entry into brain from blood. There was differential SP uptake by these cell types. The endothelial cells had the least uptake, which may limit SP uptake into brain from blood. Uptake was mediated by ACE2, but it was dependent on SP interaction with ganglioside GM1 in the lipid raft. Mutation sites, N501Yand E484K and D614G, as seen in variants of interest, were differentially taken up by these cell types. There was greater uptake but neutralization with anti-ACE2 and anti-GM1antibodies was less effective. Our data suggested that GM1/lipid raft is an important entry point of SARS-CoV-2 into these cells since inhibition of SP uptake with both anti-ACE2 and anti-GM1 together was similar to that with only anti-GM1, and both ACE2 and GM1 are within the lipid raft region of plasma membrane. Thus, GM1 is a potential SARS-CoV-2 and therapeutic target at the cerebrovasculature.

Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) is a positive single-stranded RNA virus that causes a highly contagious Corona Virus Disease (COVID19). Entry of SARS-CoV-2 in human cells depends on binding of the viral spike (S) proteins to cellular receptor Angiotensin-converting enzyme 2 (ACE2) and on S-protein priming by host cell serine protease TMPRSS2. Recently, COVID19 has been declared pandemic by World Health Organization (WHO) yet high differences in disease outcomes across countries have been seen. We provide evidences to explain these population-level differences. One of the key factors of entry of the virus in host cells presumably is because of differential interaction of viral proteins with host cell proteins due to different genetic backgrounds. Based on our findings, we conclude that a higher expression of ACE2 is facilitated by natural variations, acting as Expression quantitative trait loci (eQTLs), with different frequencies in different populations. We suggest that high expression of ACE2 results in homo-dimerization, proving disadvantageous for TMPRSS2 mediated cleavage of ACE2; whereas, the monomeric ACE2 has higher preferential binding with SARS-CoV-2 S-Protein vis-a-vis its dimerized counterpart. Further, eQTLs in TMPRSS2 and natural structural variations in the gene may also result in differential outcomes towards priming of viral S-protein, a critical step for entry of the Virus in host cells. In addition, we suggest that several key host genes, like SLC6A19, ADAM17, RPS6, HNRNPA1, SUMO1, NACA, BTF3 and some other proteases as Cathepsins, might have a critical role. To conclude, understanding population specific differences in these genes may help in developing appropriate management strategies for COVID19 with better therapeutic interventions.