Single-cell RNA sequencing reveals the evolution of the immune landscape during perihematomal edema progression after intracerebral hemorrhage.

BACKGROUND: Perihematomal edema (PHE) after post-intracerebral hemorrhage (ICH) has complex pathophysiological mechanisms that are poorly understood. The complicated immune response in the post-ICH brain constitutes a crucial component of PHE pathophysiology. In this study, we aimed to characterize the transcriptional profiles of immune cell populations in human PHE tissue and explore the microscopic differences between different types of immune cells. METHODS: 9 patients with basal ganglia intracerebral hemorrhage (hematoma volume 50-100 ml) were enrolled in this study. A multi-stage profile was developed, comprising Group1 (n = 3, 0-6 h post-ICH, G1), Group2 (n = 3, 6-24 h post-ICH, G2), and Group3 (n = 3, 24-48 h post-ICH, G3). A minimal quantity of edematous tissue surrounding the hematoma was preserved during hematoma evacuation. Single cell RNA sequencing (scRNA-seq) was used to map immune cell populations within comprehensively resected PHE samples collected from patients at different stages after ICH. RESULTS: We established, for the first time, a comprehensive landscape of diverse immune cell populations in human PHE tissue at a single-cell level. Our study identified 12 microglia subsets and 5 neutrophil subsets in human PHE tissue. What's more, we discovered that the secreted phosphoprotein-1 (SPP1) pathway served as the basis for self-communication between microglia subclusters during the progression of PHE. Additionally, we traced the trajectory branches of different neutrophil subtypes. Finally, we also demonstrated that microglia-produced osteopontin (OPN) could regulate the immune environment in PHE tissue by interacting with CD44-positive cells. CONCLUSIONS: As a result of our research, we have gained valuable insight into the immune-microenvironment within PHE tissue, which could potentially be used to develop novel treatment modalities for ICH.

Genetically predicted hypotaurine levels mediate the relationship between immune cells and intracerebral hemorrhage.

The evidence supports a strong link between immune cells and intracerebral hemorrhage (ICH). Nonetheless, the specific cause-and-effect associations between immune cells and ICH remain indeterminate. Here, our primary investigation compared immune cell infiltration in the ICH and sham groups using the GSE24265 dataset. Afterward, we extensively examined the relationship between immune cells and ICH by applying a two-sample Mendelian randomization (MR) analysis to identify the particular immune cells that may be associated with the initiation and advancement of ICH. Nevertheless, the specific processes that regulate the cause-and-effect connection between immune cells and ICH remain unknown. In this study, our objective was to investigate the connections between immune cell characteristics and plasma metabolites, as well as the links between plasma components and ICH. Our investigation uncovered that the levels of hypotaurine play a key role in the advancement of ICH, influencing the ratio of switched memory B cells among lymphocytes. Thus, our findings provide novel insights into the potential biological mechanisms underlying immune cell-mediated ICH.

CSF1R blockade slows progression of cerebral hemorrhage by reducing microglial proliferation and increasing infiltration of CD8 + CD122+ T cells into the brain.

Microglia play a pivotal role in the neuroinflammatory response after brain injury, and their proliferation is dependent on colony-stimulating factors. In the present study, we investigated the effect of inhibiting microglia proliferation on neurological damage post intracerebral hemorrhage (ICH) in a mouse model, an aspect that has never been studied before. Using a colony-stimulating factor-1 receptor antagonist (GW2580), we observed that inhibition of microglia proliferation significantly ameliorated neurobehavioral deficits, attenuated cerebral edema, and reduced hematoma volume after ICH. This intervention was associated with a decrease in pro-inflammatory factors in microglia and an increased infiltration of peripheral regulatory CD8 + CD122+ T cells into the injured brain tissue. The CXCR3/CXCL10 axis is the mechanism of brain homing of regulatory CD8 + CD122+ T cells, and the high expression of IL-10 is the hallmark of their synergistic anti-inflammatory effect with microglia. And activated astrocytes around the insult site are a prominent source of CXCL10. Thus, inhibition of microglial proliferation offers a new perspective for clinical translation. The cross-talk between multiple cells involved in the regulation of the inflammatory response highlights the comprehensive nature of neuroimmunomodulation.

E3 ligase Nedd4L promotes macrophage M1 polarization and exacerbates brain damage by TRAF3/TBK1 signaling pathway after ICH in mice.

BACKGROUND: Intracerebral hemorrhage (ICH) is a serious medical problem, and promising strategy is limited. Macrophage initiated brain inflammatory injury following ICH, but the molecular mechanism had not been well identified. E3 ligase Nedd4L is implicated in the pathogenesis of the inflammatory immune response. METHODS: In the present study, we detected the levels of Nedd4L in macrophages following ICH. Furthermore, Macrophage M1 polarization, pro-inflammatory cytokine production, BBB disruption, brain water content and neurological function were examined in ICH mice. RESULTS: Here, we demonstrated that E3 ligase Nedd4L levels of macrophage increased following ICH, promoted M1 polarization inflammation by TRAF3. Nedd4L promoted BBB disruption, as well as neurological deficits. Inhibition of Nedd4L significantly attenuated M1 polarization in vivo. Inhibition of Nedd4L decreased TRAF3 and TBK1 levels, and subsequent phosphorylation of p38 and NF-κB p65 subunit following ICH. CONCLUSIONS: Our data demonstrated that Nedd4L was involved in the pathogenesis of ICH, which promoted inflammatory responses and exacerbated brain damage by TRAF3 following ICH.

Microglial replacement in the aged brain restricts neuroinflammation following intracerebral hemorrhage.

Aged microglia display augmented inflammatory activity after neural injury. Although aging is a risk factor for poor outcome after brain insults, the precise impact of aging-related alterations in microglia on neural injury remains poorly understood. Microglia can be eliminated via pharmacological inhibition of the colony-stimulating factor 1 receptor (CSF1R). Upon withdrawal of CSF1R inhibitors, microglia rapidly repopulate the entire brain, leading to replacement of the microglial compartment. In this study, we investigated the impact of microglial replacement in the aged brain on neural injury using a mouse model of intracerebral hemorrhage (ICH) induced by collagenase injection. We found that replacement of microglia in the aged brain reduced neurological deficits and brain edema after ICH. Microglial replacement-induced attenuation of ICH injury was accompanied with alleviated blood-brain barrier disruption and leukocyte infiltration. Notably, newly repopulated microglia had reduced expression of IL-1ß, TNF-α and CD86, and upregulation of CD206 in response to ICH. Our findings suggest that replacement of microglia in the aged brain restricts neuroinflammation and brain injury following ICH.

Enhanced Cerebral Microbleeds by Long-Term Air Pollution Exposure in Spontaneously Hypertensive Rats.

BACKGROUND: Cerebral microbleeds (CMBs) are associated with a high risk for stroke . The present study determined whether long-term exposure to PM2.5 results in progressive worsening of CMBs and induction of systemic inflammation and microvascular oxidative stress. METHODS: Sixteen male Spontaneously hypertensive rats (SHR) and eight Wistar-Kyoto (WKY) rats were exposed to either filtered air or PM2.5 for 12 months. To detect CMBs, rats were imaged using a 7-T MRI. To determine systemic inflammation and oxidative stress, interleukin-6 (IL-6), tumor necrosis factor-α (TNF-α), monocyte chemoattractant protein-1 (MCP-1), as well as reactive oxygen species (ROS), NADPH activity and its subunits p22/47/67phox & gp91phox were measured. RESULTS: During the exposure period, the mean daily concentration of PM2.5 was 59.2 ± 1.0 µg/m3. PM2.5 exposure significantly increased the incidence of CMBs compared to the PM2.5 (-) group (37.5% vs 12.5% incidence rate, p < 0.001). Animals exposed to PM2.5 also had significantly increased systolic blood pressures (SBPs) at 3 months (173 ± 5 vs 157 ± 5 mmHg, p < 0.05), 6 months (218 ± 6 vs 193 ± 7 mmHg, p < 0.01), 9 months (222 ± 6 vs 203 ± 8 mmHg, p < 0.05), and 12 months (231 ± 4 vs 207 ± 5 mmHg, p = 0.01). Additionally, there were significant elevations in IL-6, MCP-1, and TNF-α in the exposed group. Furthermore, PM2.5 significantly increased NOX activity and protein levels of gp91phox and p22/47/67phox. CONCLUSION: In the SHR model, long-term exposure to PM2.5 worsened CMBs, increased SBPs, induced systemic inflammation and oxidative stress. Therefore, PM2.5 is potentially a controllable risk factor that promotes CMBs in certain patients, such as those with hypertension.

Traumatic brain injury and hemorrhage in a juvenile rat model of polytrauma leads to immunosuppression and splenic alterations.

BACKGROUND: Traumatic brain injury (TBI) is a common cause of morbidity and mortality. We have previously shown that TBI with a concurrent extra-cranial injury reliably leads to post-injury suppression of the innate immune system, but the impact of this injury on the adaptive immune system is unknown. We present data showing that combined injury reduced immune response as assayed in both blood and spleen samples and that these changes parallel apoptosis in the spleen. To assess the clinical relevance of these changes, we examined lungs for spontaneous bacterial colonization. METHODS: For these studies, prepubescent (28 day old) rats were injured using a controlled cortical impact model and then 25% blood volume removal by arteriotomy, and injured animals were compared with sham injured animals. Blood and spleen samples at post-injury day 1 were incubated with or without immunostimulant and examined for IFN-γ production using an Eli-Spot assay. Spleen samples were also examined for apoptosis using Annexin V staining, and lungs were harvested and plated on blood agar to examine for spontaneous bacterial colonization. RESULTS: Stimulations of whole blood and spleen samples with phorbol 12-myristate 13-acetate/ionomycin (PMA/I) at post-injury day 1 were associated with significant decreases in IFN-γ-positive cells/million in injured animals. Stimulation of whole blood with either PMA/I or pokeweed mitogen led to reduced tumor necrosis factor alpha production. Spleen from injured animals showed a marked increase in apoptosis. Lung samples showed a 300% increase in colonies per plate in injured animals. CONCLUSIONS: These data suggest that the combined injury can lead to adaptive immunosuppression, and our findings further suggest a potential role for the spleen in altering leukocyte function following injury.

Y-2 reduces oxidative stress and inflammation and improves neurological function of collagenase-induced intracerebral hemorrhage rats.

Intracerebral hemorrhage (ICH) is a devastating disease, and there is currently no specific pharmacological treatment that can improve clinical outcomes. Y-2 sublingual tablets, each containing 30 mg edaravone and 6 mg (+)-borneol, is undergoing a phase III clinical trial for treatment of ischemic stroke in China. The purpose of the present study is to investigate the efficacy and potential mechanism of Y-2 in a rat model of collagenase IV injection induced ICH. Sublingual administration of Y-2 at the dose of 1, 3 and 6 mg/kg improved ICH-induced sensorimotor dysfunction, alleviated cell death and histopathological change, restored the hippocampal long-term potentiation (LTP), reduced brain edema and maintained blood-brain barrier (BBB) integrality in ICH rats. Further study demonstrated that Y-2 could reduce inflammatory response and oxidative stress by decreasing the levels of myeloperoxidase (MPO), ionized calcium-binding adaptor protein-1 (Iba-1), inflammatory cytokines and oxidative products, inhibit transcription factor nuclear factor-κB (NF-κB) activation, cyclooxygenase-2 (COX-2) and matrix metallopeptidase 9 (MMP-9) expression in brain tissue around in the core regions of hematoma. Importantly, the protective efficacy of Y-2 from ICH-induced injury was superior to edaravone. In conclusion, Y-2 sublingual tablets might be a promising therapeutic agent for the treatment of ICH.

Prognostic Utility of Serum Biomarkers in Intracerebral Hemorrhage: A Systematic Review.

Background. Intracerebral hemorrhage (ICH) accounts for 10-20% of all strokes and is associated with high morbidity and mortality. Recent studies have identified serum biomarkers as a means to improve outcome prognostication in poor grade ICH patients. Poor prognosis of ICH patients and complex pathophysiology of the disease necessitate prognostic serum biomarkers to help guide treatment recommendations. Objective. The objective is to systematically review all biomarkers used to predict long-term functional outcome in patients with spontaneous intracerebral hemorrhage. Results. We identified 36 studies investigating the predictive utility of 50 discrete biomarkers. Data from 4865 ICH patients were reviewed. Inflammatory biomarkers (11/50) were most often studied, followed by oxidative (8/50), then neuron and astrocyte-specific (7/50). S100 calcium binding protein B, white blood cell count, and copeptin were the most often studied individual biomarkers. The prognostic utility of 23 biomarkers was analyzed using receiver operating characteristic curves. Area under the curve (AUC) values for all available biomarkers except neutrophil/lymphocyte ratio were acceptable. Twenty of the 23 biomarkers were characterized by at least one excellent AUC value. Vascular endothelial growth factor, glial fibrillary astrocyte protein, and S100 calcium binding protein B were characterized by outstanding AUC. Conclusions. We identified the inflammatory and neuron and astrocyte-specific biomarker categories as having the greatest number of significant individual biomarker predictors of long-term outcome. Further investigation utilizing cross-validation of prediction models in a second independent group and blinded assessment of outcomes for the predictive utility of biomarkers in patients with ICH is warranted.

The neuroprotective effect of phillyrin in intracerebral hemorrhagic mice is produced by activation of the Nrf2 signaling pathway.

Phillyrin, a natural plant extract, has significant antioxidant and anti-apoptotic effects. However, its effect on intracerebral hemorrhage (ICH) remains unclear. In this study, we investigated a potential role for phillyrin in the regulation of the oxidative stress and apoptosis induced by ICH. A model of ICH was induced by collagenase IV (0.2 U in 1 µl sterile normal saline) in male C57BL/6J (B6) mice and different doses of phillyrin (5, 15, or 30 mg/kg) were intraperitoneally (i.p.) injected at 30 min, 6 h, and 22 h after modeling. We found that phillyrin significantly reduced neural function and lesion volume, improved injury of white and grey matter around the lesion, decreased apoptosis and oxidative stress, increased the expression of nuclear factor-erythroid 2-related factor 2 (Nrf2), heme oxygenase 1(HO-1), NADPH quinone oxidoreductase 1 (NQO1) and Superoxide Dismutase-1(SOD-1) in vitro and in vivo, and protected neurons from the stimulation of hemin by promoting Nrf2 nuclear translocation. Treatment with ML385 (Nrf2 inhibitor) completely reversed the protective effects of phillyrin in vivo after ICH injury. Based on our findings, we conclude that phillyrin treatment alleviates ICH injury-induced apoptosis and oxidative stress via activation of the Nrf2 signaling pathway, highlighting a potential role for phillyrin as an ICH therapeutic.

Activation of GPR40 attenuates neuroinflammation and improves neurological function via PAK4/CREB/KDM6B pathway in an experimental GMH rat model.

BACKGROUND: Germinal matrix hemorrhage (GMH) is defined by the rupture of immature blood vessels in the germinal matrix, where subsequent hemorrhage enters the subependymal zone and the cerebral lateral ventricles. The consequent blood clot has been identified as the causative factor of secondary brain injury, which triggers a series of complex parallel and sequential harmful mechanisms, including neuroinflammation. The orphan G-protein-coupled receptor 40 (GPR40), a free fatty acid (FFA) receptor 1, has been shown to exert anti-inflammatory effects when activated and improved outcomes in animal models of stroke. We aimed to investigate the anti-inflammatory effects of GPR40 and its underlying mechanisms after GMH. METHODS: GMH model was induced in 7-day-old rat pups by an intraparenchymal injection of bacterial collagenase. GPR40 agonist, GW9508, was administered intranasally 1 h, 25 h, and 49 h after GMH induction. CRISPR targeting GPR40, PAK4, and KDM6B were administered through intracerebroventricular injection 48 h before GMH induction. Neurologic scores, microglia polarization, and brain morphology were evaluated by negative geotaxis, right reflex, rotarod test, foot fault test, Morris water maze, immunofluorescence staining, Western blots, and nissl staining respectfully. RESULTS: The results demonstrated that GW9508 improved neurological and morphological outcomes after GMH in the short (24 h, 48 h, 72h) and long-term (days 21-27). However, the neuroprotective effects of treatment were abolished by GW1100, a selective GPR40 antagonist. GW9508 treatment increased populations of M2 microglia and decreased M1 microglia in periventricular areas 24 h after GMH induction. GW9508 upregulated the phosphorylation of PAK4, CREB, and protein level of KDM6B, CD206, IL-10, which was also met with the downregulation of inflammatory markers IL-1ß and TNF-α. The mechanism study demonstrated that the knockdown of GPR40, PAK4, and KDM6B reversed the neuroprotective effects brought on by GW9508. This evidence suggests that GPR40/PAK4/CREB/KDM6B signaling pathway in microglia plays a role in the attenuation of neuroinflammation after GMH. CONCLUSIONS: In conclusion, the present study demonstrates that the activation of GPR40 attenuated GMH-induced neuroinflammation through the activation of the PAK4/CREB/KDM6B signaling pathway, and M2 microglia may be a major mediator of this effect. Thus, GPR40 may serve as a potential target in the reduction of the inflammatory response following GMH, thereby improving neurological outcomes in the short- and long-term.

Innate Immune Anti-Inflammatory Response in Human Spontaneous Intracerebral Hemorrhage.

Background and Purpose: Spontaneous intracerebral hemorrhage (sICH) is a common form of hemorrhagic stroke, with high mortality and morbidity. Pathophysiological mechanisms in sICH are poorly understood and treatments limited. Neuroinflammation driven by microglial-macrophage activation contributes to brain damage post-sICH. We aim to test the hypothesis that an anti-inflammatory (repair) process occurs in parallel with neuroinflammation in clinical sICH. Methods: We performed quantitative analysis of immunohistochemical markers for microglia and macrophages (Iba1, CD68, TMEM119, CD163, and CD206) in brain tissue biospecimens 1 to 12 days post-sICH and matched control cases. In a parallel, prospective group of patients, we assayed circulating inflammatory markers (CRP [C-reactive protein], total white cell, and monocyte count) over 1 to 12 days following sICH. Results: In 27 supratentorial sICH cases (n=27, median [interquartile range] age: 59 [52­80.5], 14F/13M) all microglia-macrophage markers increased post-sICH, relative to control brains. Anti-inflammatory markers (CD163 and CD206) were elevated alongside proinflammatory markers (CD68 and TMEM119). CD163 increased progressively post-sICH (15.0-fold increase at 7­12 days, P<0.001). CD206 increased at 3 to 5 days (5.2-fold, P<0.001) then returned to control levels at 7 to 12 days. The parenchymal immune response combined brain-derived microglia (TMEM119 positive) and invading monocyte-derived macrophages (CD206 positive). In a prospective sICH patient cohort (n=26, age 74 [66­79], National Institutes of Health Stroke Scale on admission: 8 [4­17]; 14F/12M) blood CRP concentration and monocyte density (but not white blood cell) increased post-sICH. CRP increased from 0 to 2 to 3 to 5 days (8.3-fold, P=0.020) then declined at 7 to 12 days. Monocytes increased from 0 to 2 to 3 to 5 days (1.8-fold, P<0.001) then declined at 7 to 12 days. Conclusions: An anti-inflammatory pathway, enlisting native microglia and blood monocytes, occurs alongside neuroinflammation post-sICH. This novel pathway offers therapeutic targets and a window of opportunity (3­5 days post-sICH) for delivery of therapeutics via invading monocytes.

Extracellular vesicles derived from bone marrow mesenchymal stem cells alleviate neuroinflammation after diabetic intracerebral hemorrhage via the miR-183-5p/PDCD4/NLRP3 pathway.

OBJECTIVES: Intracerebral hemorrhage (ICH) induced by diabetes results in further brain injury and nerve cell death. Bone marrow mesenchymal stem cell (BMSC) transplantation contributes to attenuating neurological deficits after ICH. This study investigated the mechanism of extracellular vesicles (EVs) derived from BMSCs in reducing neuroinflammation after diabetic ICH. METHODS: BMSC-EVs were isolated and identified. The rat model of db/db-ICH was established and the model rats were administered with EVs. miR-183-5p expression in brain tissues of db/db-ICH rats was detected. The brain injury of db/db-ICH rats was evaluated by measuring neurobehavioral score, brain water content and inflammatory factors. BV2 cells were cultured in vitro to establish high-glucose (HG)-Hemin-BV2 cell model. The levels of reactive oxygen species (ROS) and inflammatory factors in BV2 cells were measured, and BV2 cell viability and apoptosis were assessed. The targeting relationship between miR-183-5p and PDCD4 was predicted and verified. The activation of PDCD4/NLRP3 pathway in rat brain tissues and BV2 cells was detected. RESULTS: miR-183-5p expression was reduced in db/db-ICH rats brain tissues. BMSC-EVs ameliorated cranial nerve function, decreased brain water content and repressed inflammatory response by carrying miR-183-5p. BMSC-EVs mitigated HG-Hemin-BV2 cell injury, reduced ROS level and suppressed inflammatory response. miR-183-5p targeted PDCD4. PDCD4 promoted BV2 cell inflammation by activating the NLRP3 pathway. BMSC-EVs inhibited HG-Hemin-BV2 cell inflammation through the miR-183-5p/PDCD4/NLRP3 pathway, and inhibition of miR-183-5p reversed the protective effect of EVs. CONCLUSION: BMSC-EVs carried miR-183-5p into db/db-ICH rat brain tissues and repressed the NLRP3 pathway by targeting PDCD4, thus alleviating neuroinflammation after diabetic ICH.

Microglia: A Double-Edged Sword in Intracerebral Hemorrhage From Basic Mechanisms to Clinical Research.

Microglia are the resident immune cells of the central nervous system (CNS). It is well established that microglia are activated and polarized to acquire different inflammatory phenotypes, either pro-inflammatory or anti-inflammatory phenotypes, which act as a critical component in the neuroinflammation following intracerebral hemorrhage (ICH). Microglia produce pro-inflammatory mediators at the early stages after ICH onset, anti-inflammatory microglia with neuroprotective effects appear to be suppressed. Previous research found that driving microglia towards an anti-inflammatory phenotype could restrict inflammation and engulf cellular debris. The principal objective of this review is to analyze the phenotypes and dynamic profiles of microglia as well as their shift in functional response following ICH. The results may further the understanding of the body's self-regulatory functions involving microglia following ICH. On this basis, suggestions for future clinical development and research are provided.

Blood-brain barrier dysfunction in hemorrhagic transformation: a therapeutic opportunity for nanoparticles and melatonin.

Stroke is the second leading cause of death worldwide, estimated that one-sixth of the world population will suffer it once in their life. The most common type of this medical condition is the ischemic stroke (IS), produced by a thrombotic or embolic occlusion of a major cerebral artery or its branches, leading to the formation of a complex infarct region caused by oxidative stress, excitotoxicity, and endothelial dysfunction. Nowadays, the immediate treatment for IS involves thrombolytic agents or mechanical thrombectomy, depending on the integrity of the blood-brain barrier (BBB). A common stroke complication is the hemorrhagic transformation (HT), which consists of bleeding into the ischemic brain area. Currently, better treatments for IS are urgently needed. As such, the neurohormone melatonin has been proposed as a good candidate due to its antioxidant, anti-inflammatory, and neuroprotective effects, particularly against lipid peroxidation and oxidative stress during brain ischemia. Here, we proposed to develop intravenous or intranasal melatonin nanoformulation to specifically target the brain in patients with stroke. Nowadays, the challenge is to find a formulation able to cross the barriers and reach the target organ in an effective dose to generate the pharmacological effect. In this review, we discuss the current literature about stroke pathophysiology, melatonin properties, and its potential use in nanoformulations as a novel therapeutic approach for ischemic stroke.

Longitudinal transcriptomics define the stages of myeloid activation in the living human brain after intracerebral hemorrhage.

Opportunities to interrogate the immune responses in the injured tissue of living patients suffering from acute sterile injuries such as stroke and heart attack are limited. We leveraged a clinical trial of minimally invasive neurosurgery for patients with intracerebral hemorrhage (ICH), a severely disabling subtype of stroke, to investigate the dynamics of inflammation at the site of brain injury over time. Longitudinal transcriptional profiling of CD14+ monocytes/macrophages and neutrophils from hematomas of patients with ICH revealed that the myeloid response to ICH within the hematoma is distinct from that in the blood and occurs in stages conserved across the patient cohort. Initially, hematoma myeloid cells expressed a robust anabolic proinflammatory profile characterized by activation of hypoxia-inducible factors (HIFs) and expression of genes encoding immune factors and glycolysis. Subsequently, inflammatory gene expression decreased over time, whereas anti-inflammatory circuits were maintained and phagocytic and antioxidative pathways up-regulated. During this transition to immune resolution, glycolysis gene expression and levels of the potent proresolution lipid mediator prostaglandin E2 remained elevated in the hematoma, and unexpectedly, these elevations correlated with positive patient outcomes. Ex vivo activation of human macrophages by ICH-associated stimuli highlighted an important role for HIFs in production of both inflammatory and anti-inflammatory factors, including PGE2, which, in turn, augmented VEGF production. Our findings define the time course of myeloid activation in the human brain after ICH, revealing a conserved progression of immune responses from proinflammatory to proresolution states in humans after brain injury and identifying transcriptional programs associated with neurological recovery.

Very Early Exercise Rehabilitation After Intracerebral Hemorrhage Promotes Inflammation in the Brain.

BACKGROUND: Very early exercise has been reported to exacerbate motor dysfunction; however, its mechanism is largely unknown. OBJECTIVE: This study examined the effect of very early exercise on motor recovery and associated brain damage following intracerebral hemorrhage (ICH) in rats. METHODS: Collagenase solution was injected into the left striatum to induce ICH. Rats were randomly assigned to receive placebo surgery without exercise (SHAM) or ICH without (ICH) or with very early exercise within 24 hours of surgery (ICH+VET). We observed sensorimotor behaviors before surgery, and after surgery preexercise and postexercise. Postexercise brain tissue was collected 27 hours after surgery to investigate the hematoma area, brain edema, and Il1b, Tgfb1, and Igf1 mRNA levels in the striatum and sensorimotor cortex using real-time reverse transcription polymerase chain reaction. NeuN, PSD95, and GFAP protein expression was analyzed by Western blotting. RESULTS: We observed significantly increased skillful sensorimotor impairment in the horizontal ladder test and significantly higher Il1b mRNA levels in the striatum of the ICH+VET group compared with the ICH group. NeuN protein expression was significantly reduced in both brain regions of the ICH+VET group compared with the SHAM group. CONCLUSION: Our results suggest that very early exercise may be associated with an exacerbation of motor dysfunction because of increased neuronal death and region-specific changes in inflammatory factors. These results indicate that implementing exercise within 24 hours after ICH should be performed with caution.

Inhibition of hypoxia inducible factor 1 by YC-1 attenuates tissue plasminogen activator induced hemorrhagic transformation by suppressing HMGB1/TLR4/NF-κB mediated neutrophil infiltration in thromboembolic stroke rats.

Hemorrhagic transformation (HT) is a frequent complication of ischemic stroke after thrombolytic therapy and seriously affects the prognosis of stroke. Due to the limited therapeutic window and hemorrhagic complications, tissue plasminogen activator (t-PA) is underutilized in acute ischemic stroke. Currently, there are no clinically effective drugs to decrease the incidence of t-PA-induced HT. Hypoxia-inducible factor 1 (HIF-1) is an important transcription factor that maintains oxygen homeostasis and mediates neuroinflammation under hypoxia. However, the effect of HIF-1 on t-PA-induced HT is not clear. The aim of this study was to investigate the role of HIF-1 in t-PA-induced HT by applying YC-1, an inhibitor of HIF-1. In the present study, we found that HIF-1 expression was significantly increased in ischemic brain tissue after delayed t-PA treatment and was mainly localized in neurons and endothelial cells. Inhibition of HIF-1 by YC-1 improved infarct volume and neurological deficits. YC-1 inhibited matrix metalloproteinase protein expression, increased tight junction protein expression, and ameliorated BBB disruption and the occurrence of HT. Furthermore, YC-1 suppressed the release of inflammatory factors, neutrophil infiltration and the activation of the HMGB1/TLR4/NF-κB signaling pathway. These results demonstrated that inhibition of HIF-1 could protect BBB integrity by suppressing HMGB1/TLR4/NF-κB-mediated neutrophil infiltration, thereby reducing the risk of t-PA-induced HT. Thus, HIF-1 may be a potential therapeutic target for t-PA-induced HT.

Impacts of ABO-incompatible platelet transfusions on platelet recovery and outcomes after intracerebral hemorrhage.

Acute platelet transfusion after intracerebral hemorrhage (ICH) given in efforts to reverse antiplatelet medication effects and prevent ongoing bleeding does not appear to improve outcome and may be associated with harm. Although the underlying mechanisms are unclear, the influence of ABO-incompatible platelet transfusions on ICH outcomes has not been investigated. We hypothesized that patients with ICH who receive ABO-incompatible platelet transfusions would have worse platelet recovery (using absolute count increment [ACI]) and neurological outcomes (mortality and poor modified Rankin Scale [mRS 4-6]) than those receiving ABO-compatible transfusions. In a single-center cohort of consecutively admitted patients with ICH, we identified 125 patients receiving acute platelet transfusions, of whom 47 (38%) received an ABO-incompatible transfusion. Using quantile regression, we identified an association of ABO-incompatible platelet transfusion with lower platelet recovery (ACI, 2 × 103cells per µL vs 15 × 103cells per µL; adjusted coefficient ß, -19; 95% confidence interval [CI], -35.55 to -4.44; P = .01). ABO-incompatible platelet transfusion was also associated with increased odds of mortality (adjusted odds ratio [OR], 2.59; 95% CI, 1.00-6.73; P = .05) and poor mRS (adjusted OR, 3.61; 95% CI, 0.97-13.42; P = .06); however, these estimates were imprecise. Together, these findings suggest the importance of ABO compatibility for platelet transfusions for ICH, but further investigation into the mechanism(s) underlying these observations is required.

Clemastine promotes recovery of neural function and suppresses neuronal apoptosis by restoring balance of pro-inflammatory mediators in an experimental model of intracerebral hemorrhage.

Intracerebral hemorrhage (ICH) represents a common acute cerebrovascular event that imparts high rates of disability. The microglia-mediated inflammatory response is a critical factor in determining cerebral damage post-ICH. Clemastine (CLM) is a histamine receptor H1 (HRH1) antagonist that has been shown to modulate the inflammatory response. However, the effects of CLM on ICH and the underlying mechanism remain to be determined. This investigation reveals that CLM resulted in reduction of cerebral hematoma volume, decreased cerebral edema and lower rates of neuronal apoptosis as well as improved behavioral scores in an acute ICH murine model. CLM treatment was noted to decrease pro-inflammatory effectors and increased anti-inflammatory effectors post-ICH. In addition, CLM reduced the deleterious effects of activated microglia on neurons in a transwell co-culture system. Our findings show that CLM likely mediates its therapeutic effect through inhibition of microglia-induced inflammatory response and apoptosis, thereby enhancing restoration of neuronal function.