Astrocyte tissue factor controls CNS hemostasis and autoimmune inflammation

Tissue factor as a potential coagulative/vascular marker in relapsing-remitting multiple sclerosis

Objectives

Recent studies supported coagulation involvement in multiple sclerosis, an inflammatory-demyelinating and degenerative disease of the central nervous system. The main objectives of this observational study were to identify the most specific pro-coagulative/vascular factors for multiple sclerosis pathogenesis and to correlate them with brain hemodynamic abnormalities.

Methods

We compared i) serum/plasma levels of complement(C)/coagulation/vascular factors, viral/microbiological assays, fat-soluble vitamins and lymphocyte count among people with multiple sclerosis sampled in a clinical remission (n=30; 23F/7M, 40 ± 8.14 years) or a relapse (n=30; 24F/6M, age 41 ± 10.74 years) and age/sex-matched controls (n=30; 23F/7M, 40 ± 8.38 years); ii) brain hemodynamic metrics at dynamic susceptibility contrast-enhanced 3T-MRI during relapse and remission, and iii) laboratory data with MRI perfusion metrics and clinical features of people with multiple sclerosis. Two models by Partial Least Squares Discriminant Analysis were performed using two groups as input: (1) multiple sclerosis vs. controls, and (2) relapsing vs. remitting multiple sclerosis.

Results

Compared to controls, multiple sclerosis patients had a higher Body-Mass-Index, Protein-C and activated-C9; and a lower activated-C4. Levels of Tissue-Factor, Tie-2 and P-Selectin/CD62P were lower in relapse compared to remission and HC, whereas Angiopoietin-I was higher in relapsing vs. remitting multiple sclerosis. A lower number of total lymphocytes was found in relapsing multiple sclerosis vs. remitting multiple sclerosis and controls. Cerebral-Blood-Volume was lower in normal-appearing white matter and left caudatum while Cerebral-Blood-Flow was inferior in bilateral putamen in relapsing versus remitting multiple sclerosis. The mean-transit-time of gadolinium-enhancing lesions negatively correlated with Tissue-Factor. The top-5 discriminating variables for model (1) were: EBV-EBNA-1 IgG, Body-Mass-Index, Protein-C, activated-C4 and Tissue-Factor whereas for model (2) were: Tissue-Factor, Angiopoietin-I, MCHC, Vitamin A and T-CD3.

Conclusion

Tissue-factor was one of the top-5 variables in the models discriminating either multiple sclerosis from controls or multiple sclerosis relapse from remission and correlated with mean-transit-time of gadolinium-enhancing lesions. Tissue-factor appears a promising pro-coagulative/vascular biomarker and a possible therapeutic target in relapsing-remitting multiple sclerosis.

Clinical trial registration

ClinicalTrials.gov, identifier NCT04380220.

CNS-peripheral immune interactions in hemorrhagic stroke

Stroke is a sudden and rapidly progressing ischemic or hemorrhagic cerebrovascular disease. When stroke damages the brain, the immune system becomes hyperactive, leading to systemic inflammatory response and immunomodulatory disorders, which could significantly impact brain damage, recovery, and prognosis of stroke. Emerging researches suggest that ischemic stroke-induced spleen contraction could activate a peripheral immune response, which may further aggravate brain injury. This review focuses on hemorrhagic strokes including intracerebral hemorrhage (ICH) and subarachnoid hemorrhage (SAH) and discusses the central nervous system-peripheral immune interactions after hemorrhagic stroke induction. First, inflammatory progression after ICH and SAH is investigated. As a part of this review, we summarize the various kinds of inflammatory cell infiltration to aggravate brain injury after blood-brain barrier interruption induced by hemorrhagic stroke. Then, we explore hemorrhagic stroke-induced systemic inflammatory response syndrome (SIRS) and discuss the interactions of CNS and peripheral inflammatory response. In addition, potential targets related to inflammatory response for ICH and SAH are discussed in this review, which may lead to novel therapeutic strategies for hemorrhagic stroke.

Inhibition of caspase-1-mediated inflammasome activation reduced blood coagulation in cerebrospinal fluid after subarachnoid haemorrhage

Background

Neuroinflammation and blood coagulation responses in cerebrospinal fluid (CSF) contribute to the poor outcome associated with subarachnoid haemorrhage (SAH). We explored the role of caspase-1-mediated inflammasome activation on extrinsic blood coagulation in CSF after SAH.

Methods

Post-SAH proteomic changes and correlation between caspase-1 with extrinsic coagulation factors in human CSF after SAH were analysed. Time course and cell localisation of brain inflammasome and extrinsic coagulation proteins after SAH were explored in a rat SAH model. Pharmacological inhibition of caspase-1 via VX-765 was used to explore the role of caspase-1 in blood clearance and CSF circulation after SAH in rats. Primary astrocytes were used to evaluate the role of caspase-1 in haemoglobin-induced pyroptosis and tissue factor (TF) production/release.

Findings

Neuroinflammation and blood coagulation activated after SAH in human CSF. The caspase-1 levels significantly correlated with the extrinsic coagulation factors. The activated caspase-1 and extrinsic coagulation initiator TF was increased on astrocytes after SAH in rats. VX-765 attenuated neurological deficits by accelerating CSF circulation and blood clearance through inhibiting pyroptotic neuroinflammation and TF-induced fibrin deposition in the short-term, and improved learning and memory capacity by preventing hippocampal neuronal loss and hydrocephalus in the long-term after SAH in rats. VX-765 reduced haemoglobin-induced pyroptosis and TF production/release in primary astrocytes.

Interpretation

Inhibition of caspase-1 by VX-765 appears to be a potential treatment against neuroinflammation and blood coagulation in CSF after SAH.

Funding

This study was supported by National Institutes of Health of United States of America, and National Natural Science Foundation of China.

Astrocyte responses to nanomaterials: Functional changes, pathological changes and potential applications

Astrocytes are responsible for regulating and optimizing the functional environment of neurons in the brain and can reduce the adverse impacts of external factors by protecting neurons. However, excessive astrocyte activation upon stimulation may alter their initial protective effect and actually lead to aggravation of injury. Similar to the dual effects of astrocytes in the response to injury within the central nervous system (CNS), nanomaterials (NMs) can have either toxic or beneficial effects on astrocytes, serving to promote injury or inhibit tumors. As the important physiological functions of astrocytes have been gradually revealed, the effects of NMs on astrocytes and the underlying mechanisms have become a new frontier in nanomedicine and neuroscience. This review summarizes the in vitro and in vivo findings regarding the effects of various NMs on astrocytes, focusing on functional alterations and pathological processes in astrocytes, as well as the possible underlying mechanisms. We also emphasize the importance of co-culture models in studying the interaction between NMs and cells of the CNS. Finally, we discuss NMs that have shown promise for application in astrocyte-related diseases and propose some challenges and suggestions for further investigations, with the aim of providing guidance for the widespread application of NMs in the CNS.

Hematoma location and morphology of anticoagulation-associated intracerebral hemorrhage

OBJECTIVE

To study hematoma location and morphology of intracerebral hemorrhage (ICH) associated with oral anticoagulants (OAC) and delineate causes and mechanism.

METHODS

We performed a systematic literature research and meta-analysis of studies comparing neuroimaging findings in patients with OAC-ICH compared to those with ICH not associated with OAC (non-OAC ICH). We calculated pooled risk ratios (RRs) for ICH location using the Mantel-Haenszel random-effects method and corresponding 95% confidence intervals (95% CI).

RESULTS

We identified 8 studies including 6,259 patients (OAC-ICH n = 1,107, pooled OAC-ICH population 17.7%). There was some evidence for deep ICH location (defined as ICH in the thalamus, basal ganglia, internal capsule, or brainstem) being less frequent in patients with OAC-ICH (OAC-ICH: 450 of 1,102/40.8% vs non-OAC ICH: 2,656 of 4,819/55.1%; RR 0.94, 95% CI 0.88-1.00, p = 0.05, I ² = 0%) while cerebellar ICH location was significantly more common in OAC-ICH (OAC-ICH: 111 of 1,069/10.4% vs non-OAC ICH: 326 of 4,787/6.8%; RR 1.45, 95% CI 1.12-1.89, p = 0.005, I ² = 21%) compared to non-OAC ICH. There was no statistically significant relationship to OAC use for lobar (OAC-ICH: 423 of 1,107/38.2% vs non-OAC ICH: 1,884 of 5,152/36.6%; RR 1.02, 95% CI 0.89-1.17, p = 0.75, I ² = 53%, p for heterogeneity = 0.04) or brainstem ICH (OAC-ICH: 36 of 546/6.6% vs non-OAC ICH: 172 of 2,626/6.5%; RR 1.04, 95% CI 0.58-1.87, p = 0.89, I ² = 59%, p for heterogeneity = 0.04). The risk for intraventricular extension (OAC-ICH: 436 of 840/51.9% vs non-OAC ICH: 1,429 of 3,508/40.7%; RR 1.26, 95% CI 1.16-1.36, p < 0.001, I ² = 0%) was significantly increased in patients with OAC-ICH. We found few data on ICH morphology in OAC-ICH vs non-OAC ICH.

CONCLUSION

The overrepresentation of cerebellar ICH location and intraventricular extension in OAC-ICH might have mechanistic relevance for the underlying arteriopathy, pathophysiology, or bleeding pattern of OAC-ICH, and should be investigated further.

YAP and MRTF-A, transcriptional co-activators of RhoA-mediated gene expression, are critical for glioblastoma tumorigenicity

The role of YAP (Yes-associated protein 1) and MRTF-A (myocardin-related transcription factor A), two transcriptional co-activators regulated downstream of GPCRs (G protein-coupled receptors) and RhoA, in the growth of glioblastoma cells and in vivo glioblastoma multiforme (GBM) tumor development was explored using human glioblastoma cell lines and tumor-initiating cells derived from patient-derived xenografts (PDX). Knockdown of these co-activators in GSC-23 PDX cells using short hairpin RNA significantly attenuated in vitro self-renewal capability assessed by limiting dilution, oncogene expression, and neurosphere formation. Orthotopic xenografts of the MRTF-A and YAP knockdown PDX cells formed significantly smaller tumors and were of lower morbidity than wild-type cells. In vitro studies used PDX and 1321N1 glioblastoma cells to examine functional responses to sphingosine 1-phosphate (S1P), a GPCR agonist that activates RhoA signaling, demonstrated that YAP signaling was required for cell migration and invasion, whereas MRTF-A was required for cell adhesion; both YAP and MRTF-A were required for proliferation. Gene expression analysis by RNA-sequencing of S1P-treated MRTF-A or YAP knockout cells identified 44 genes that were induced through RhoA and highly dependent on YAP, MRTF-A, or both. Knockdown of F3 (tissue factor (TF)), a target gene regulated selectively through YAP, blocked cell invasion and migration, whereas knockdown of HBEGF (heparin-binding epidermal growth factor-like growth factor), a gene selectively induced through MRTF-A, prevented cell adhesion in response to S1P. Proliferation was sensitive to knockdown of target genes regulated through either or both YAP and MRTF-A. Expression of TF and HBEGF was also selectively decreased in tumors from PDX cells lacking YAP or MRTF-A, indicating that these transcriptional pathways are regulated in preclinical GBM models and suggesting that their activation through GPCRs and RhoA contributes to growth and maintenance of human GBM.

Hemostasis biomarkers in multiple sclerosis

BACKGROUND AND PURPOSE

The aim was to investigate the plasma levels of hemostasis components in multiple sclerosis (MS) and their association with clinical and magnetic resonance imaging (MRI) outcomes.

METHODS

In all, 138 MS patients [85 with relapsing-remitting MS (RR-MS) and 53 with progressive MS (P-MS) with a mean age of 54 years; 72.5% female; median Expanded Disability Status Scale 3.5; mean disease duration 21 years] and 42 age- and sex-matched healthy individuals (HI) were studied. All subjects were examined with 3 T MRI and clinical examinations. Plasma levels of hemostasis factors [procoagulant, factor XII (FXII)] and inhibitors [tissue factor pathway inhibitor (TFPI), thrombomodulin, heparin cofactor II, a disintegrin-like and metalloprotease with thrombospondin type 1 motif 13 (ADAMTS13) and plasminogen activator inhibitor 1 (PAI-1)] were evaluated by magnetic Luminex assays and enzyme-linked immunosorbent assay. Associations between hemostasis plasma levels and clinical and MRI outcomes were assessed.

RESULTS

Lower ADAMTS13 levels were found in MS patients compared to HI (P = 0.008) and in MS patients presenting with cerebral microbleeds compared to those without (P = 0.034). Higher PAI-1 levels were found in MS patients compared to HI (P = 0.02). TFPI levels were higher in the P-MS subgroup compared to RR-MS patients (P = 0.011) and compared to HI (P = 0.002). No significant associations between hemostasis plasma levels and clinical or MRI outcomes were found.

CONCLUSIONS

Decreased ADAMTS13, particularly in MS patients with cerebral microbleeds, which deserves further investigation, and increased PAI-1 and TFPI levels were observed in MS patients, which deserves further investigation. No relationship between hemostasis plasma levels and measures of disease severity was detected.

Adenosine binds predominantly to adenosine receptor A1 subtype in astrocytes and mediates an immunosuppressive effect

The four kinds of adenosine receptor subtypes (ARs), named as ARA1, ARA2A, ARA2B and ARA3, have multiple biological functions. ARs are differently distributed across the body and have distinguished ability of binding adenosine. We try to figure out how these ARs were expressed in astrocytes and which one has the first priority of utilizing adenosine. Firstly, mRNA expressions and membrane localization of all ARs were evaluated by qPCR and western blot. After the membrane localization of all ARs in astrocytes was being confirmed their individual adenosine binding ability was determined by radio-active ligand binding assay respectively. It was revealed that ARA1 had much superior adenosine binding ability than other AR subtypes. Functional study demonstrated that ARA1 potentially mediated an immune suppressive effect in astrocytes. The activation of ARA1 signaling lead to decreased IL-12 and IL-23 production, and decreased chemokine production, including CCL2, CXCL8 and IP-10. When interacted with CD4 cells ARA1 agonist pre-treated astrocytes showed hindered ability of stimulating CD4 cells to secret IL-17 and IFN-γ and inducing CD4 cells' chemo taxi. Finally, in vivo experiment confirmed that local administration of ARA1agonist ameliorated EAE in wild type B6 recipients, but not Ara1-/- recipients. As a conclusion, this paper suggested that adenosine receptor A1 subtype predominantly binds adenosine in astrocytes and mediates an immunosuppressive effect.

Subarachnoid hemorrhage - Induced block of cerebrospinal fluid flow: Role of brain coagulation factor III (tissue factor)

Subarachnoid hemorrhage (SAH) in 95% of cases results in long-term disabilities due to brain damage, pathogenesis of which remains uncertain. Hindrance of cerebrospinal fluid (CSF) circulation along glymphatic pathways is a possible mechanism interrupting drainage of damaging substances from subarachnoid space and parenchyma. We explored changes in CSF circulation at different time following SAH and possible role of brain tissue factor (TF). Fluorescent solute and fluorescent microspheres injected into cisterna magna were used to track CSF flow in mice. SAH induced by perforation of circle of Willis interrupted CSF flow for up to 30 days. Block of CSF flow did not correlate with the size of hemorrhage. Following SAH, fibrin deposits were observed on the brain surface including areas without visible blood. Block of astroglia-associated TF by intracerebroventricular administration of specific antibodies increased size of hemorrhage, decreased fibrin deposition and facilitated spread of fluorophores in sham/naïve animals. We conclude that brain TF plays an important role in localization of hemorrhage and also regulates CSF flow under normal conditions. Targeting of the TF system will allow developing of new therapeutic approaches to the treatment of SAH and pathologies related to CSF flow such as hydrocephalus.