Hematoma Changes During Clot Resolution After Experimental Intracerebral Hemorrhage

Gas6/Axl signaling promotes hematoma resolution and motivates protective microglial responses after intracerebral hemorrhage in mice

BACKGROUND

Intracerebral hemorrhage (ICH) stands out as the most fatal subtype of stroke, currently devoid of effective therapy. Recent research underscores the significance of Axl and its ligand growth arrest-specific 6 (Gas6) in normal brain function and a spectrum of neurological disorders, including ICH. This study is designed to delve into the role of Gas6/Axl signaling in facilitating hematoma clearance and neuroinflammation resolution following ICH.

METHODS

Adult male C57BL/6 mice were randomly assigned to sham and ICH groups. ICH was induced by intrastriatal injection of autologous arterial blood. Recombinant mouse Gas6 (rmGas6) was administered intracerebroventricularly 30 min after ICH. Virus-induced knockdown of Axl or R428 (a selective inhibitor of Axl) treatment was administrated before ICH induction to investigate the protective mechanisms. Molecular changes were assessed using western blot, enzyme-linked immunosorbent assay and immunohistochemistry. Coronal brain slices, brain water content and neurobehavioral tests were employed to evaluate histological and neurofunctional outcomes, respectively. Primary glia cultures and erythrophagocytosis assays were applied for mechanistic studies.

RESULTS

The expression of Axl increased at 12 h after ICH, peaking on day 3. Gas6 expression did not remarkably changed until day 3 post-ICH. Early administration of rmGas6 following ICH significantly reduced hematoma volume, mitigated brain edema, and restored neurological function. Both Axl-knockdown and Axl inhibitor treatment abolished the neuroprotection of exogenous Gas6 in ICH. In vitro studies demonstrated that microglia exhibited higher capacity for phagocytosing eryptotic erythrocytes compared to normal erythrocytes, a process reversed by blocking the externalized phosphatidylserine on eryptotic erythrocytes. The erythrophagocytosis by microglia was Axl-mediated and Gas6-dependent. Augmentation of Gas6/Axl signaling attenuated neuroinflammation and drove microglia towards pro-resolving phenotype.

CONCLUSIONS

This study demonstrated the beneficial effects of recombinant Gas6 on hematoma resolution, alleviation of neuroinflammation, and neurofunctional recovery in an animal model of ICH. These effects were primarily mediated by the phagocytotic role of Axl expressed on microglia.

The Role of the Complement System in Synaptic Pruning after Stroke

Stroke is a serious disease that can lead to local neurological dysfunction and cause great harm to the patient's health due to blood cerebral circulation disorder. Synaptic pruning is critical for the normal development of the human brain, which makes the synaptic circuit completer and more efficient by removing redundant synapses. The complement system is considered a key player in synaptic loss and cognitive impairment in neurodegenerative disease. After stroke, the complement system is over-activated, and complement proteins can be labeled on synapses. Microglia and astrocytes can recognize and engulf synapses through corresponding complement receptors. Complement-mediated excessive synaptic pruning can cause post-stroke cognitive impairment (PSCI) and secondary brain damage. This review summarizes the latest progress of complement-mediated synaptic pruning after stroke and the potential mechanisms. Targeting complement-mediated synaptic pruning may be essential for exploring therapeutic strategies for secondary brain injury (SBI) and neurological dysfunction after stroke.

Intravenous Administration of Anti-CD47 Antibody Augments Hematoma Clearance, Mitigates Acute Neuropathology, and Improves Cognitive Function in a Rat Model of Penetrating Traumatic Brain Injury

Traumatic brain injury (TBI)-induced intracerebral hematoma is a major driver of secondary injury pathology such as neuroinflammation, cerebral edema, neurotoxicity, and blood-brain barrier dysfunction, which contribute to neuronal loss, motor deficits, and cognitive impairment. Cluster of differentiation 47 (CD47) is an antiphagocytic cell surface protein inhibiting hematoma clearance. This study was designed to evaluate the safety and efficacy of blockade of CD47 via intravenous (i.v.) administration of anti-CD47 antibodies following penetrating ballistic-like brain injury (PBBI) with significant traumatic intracerebral hemorrhage (tICH). The pharmacokinetic (PK) profile of the anti-CD47 antibody elicited that antibody concentration decayed over 7 days post-administration. Blood tests and necropsy analysis indicated no severe adverse events following treatment. Cerebral hemoglobin levels were significantly increased after injury, however, anti-CD47 antibody administration at 0.1 mg/kg resulted in a significant reduction in cerebral hemoglobin levels at 72 h post-administration, indicating augmentation of hematoma clearance. Immunohistochemistry assessment of glial fibrillary acidic protein (GFAP) and ionized calcium-binding adaptor molecule 1 (IBA1) demonstrated a significant reduction of GFAP levels in the lesion core and peri-lesional area. Based on these analyses, the optimal dose was identified as 0.1 mg/kg. Lesion volume showed a reduction following treatment. Rotarod testing revealed significant motor deficits in all injured groups but no significant therapeutic benefits. Spatial learning performance revealed significant deficits in all injured groups, which were significantly improved by the last testing day. Anti-CD47 antibody treated rats showed significantly improved attention deficits, but not retention scores. These results provide preliminary evidence that blockade of CD47 using i.v. administration of anti-CD47 antibodies may serve as a potential therapeutic for TBI with ICH.

Transcriptomic analysis reveals novel hub genes associated with astrocyte autophagy in intracerebral hemorrhage

Introduction

Neuroinflammation serves as a critical local defense mechanism against secondary brain injury following intracerebral hemorrhage (ICH), and astrocytes play a prominent role in this process. In this study, we investigated astrocytic changes during the inflammatory state after ICH to identify new targets for improving the inflammatory response.

Methods

We stimulated mouse astrocytes with lipopolysaccharide (LPS) in vitro and analyzed their transcriptomes via ribonucleic acid sequencing. We created an ICH model in living organisms by injecting autologous blood.

Results

RNA sequencing revealed that 2,717 genes were differentially expressed in the LPS group compared to those in the saline group, with notable enrichment of the autophagic pathway. By intersecting the 2,717 differentially expressed genes (DEGs) with autophagy-related genes, we identified 36 autophagy-related DEGs and seven hub genes. Previous studies and quantitative reverse transcription-polymerase chain reaction results confirmed the increased expression of phosphatidylinositol 3-kinase catalytic subunit type 3 (Pik3c3), AKT serine/threonine kinase 1 (Akt1), and unc-51 like autophagy activating kinase 2 (Ulk2) in astrocytes after ICH. Transcription factors and target miRNAs were identified for the final three DEGs, and 3-methyladenine and leupeptin were identified as potential therapeutic agents for ICH.

Conclusion

Our findings suggest that astrocyte autophagy plays a critical role in ICH complexity, and that Pik3c3, Akt1, and Ulk2 may be potential therapeutic targets.

P2Y6 Receptor Activation Aggravates NLRP3-dependent Microglial Pyroptosis via Downregulation of the PI3K/AKT Pathway in a Mouse Model of Intracerebral Hemorrhage

Pro-inflammatory signals generated after intracerebral hemorrhage (ICH) trigger a form of regulated cell death known as pyroptosis in microglia. White matter injury (WMI) refers to the condition where the white matter area of the brain suffers from mechanical, ischemic, metabolic, or inflammatory damage. Although the p2Y purinoceptor 6 (P2Y6R) plays a significant role in the control of inflammatory reactions in central nervous system diseases, its roles in the development of microglial pyroptosis and WMI following ICH remain unclear. In this study, we sought to clarify the role of P2Y6R in microglial pyroptosis and WMI by using an experimental mouse model of ICH. Type IV collagenase was injected into male C57BL/6 mice to induce ICH. Mice were then treated with MRS2578 and LY294002 to inhibit P2Y6R and phosphatidylinositol 3-kinase (PI3K), respectively. Bio-conductivity analysis was performed to examine PI3K/AKT pathway involvement in microglial pyroptosis. Quantitative Real-Time PCR, immunofluorescence staining, and western blot were conducted to examine microglial pyroptosis and WMI following ICH. A modified Garcia test, corner turning test, and forelimb placement test were used to assess neurobehavior. Hematoxylin-eosin staining (HE) was performed to detect cells damage around hematoma. Increases in the expression of P2Y6R, NLRP3, ASC, Caspase-1, and GSDMD were observed after ICH. P2Y6R was only expressed on microglia. MRS2578, a specific inhibitor of P2Y6R, attenuated short-term neurobehavioral deficits, brain edema and hematoma volume while improving both microglial pyroptosis and WMI. These changes were accompanied by decreases in pyroptosis-related proteins and pro-inflammatory cytokines both in vivo and vitro. Bioinformatic analysis revealed an association between the PI3K/AKT pathway and P2Y6R-mediated microglial pyroptosis. The effects of MRS2578 were partially reversed by treatment with LY294002, a specific PI3K inhibitor. P2Y6R inhibition alleviates microglial pyroptosis and WMI and ameliorates neurological deficits through the PI3K/AKT pathway after ICH. Consequently, targeting P2Y6R might be a promising approach for ICH treatment.

Complement Inhibition Reduces Early Erythrolysis, Attenuates Brain Injury, Hydrocephalus, and Iron Accumulation after Intraventricular Hemorrhage in Aged Rats

Blood components released by erythrolysis play an important role in secondary brain injury and posthemorrhagic hydrocephalus (PHH) after intraventricular hemorrhage (IVH). The current study examined the impact of N-acetylheparin (NAH), a complement inhibitor, on early erythrolysis, PHH and iron accumulation in aged rats following IVH. This study, on 18-months-old male Fischer 344 rats, was in 3 parts. First, rats had an intracerebroventricular injection of autologous blood (IVH) mixed with NAH or saline, or saline alone. After MRI at four hours, Western blot and immunohistochemistry examined complement activation and electron microscopy choroid plexus and periventricular damage. Second, rats had an IVH with NAH or vehicle, or saline. Rats underwent serial MRI at 4 h and 1 day to assess ventricular volume and erythrolysis. Immunohistochemistry and H&E staining examined secondary brain injury. Third, rats had an IVH with NAH or vehicle. Serial MRIs on day 1 and 28 assessed ventricular volume and iron accumulation. H&E staining and immunofluorescence evaluated choroid plexus phagocytes. Complement activation was found 4 h after IVH, and co-injection of NAH inhibited that activation. NAH administration attenuated erythrolysis, reduced ventricular volume, alleviated periventricular and choroid plexus injury at 4 h and 1 day after IVH. NAH decreased iron accumulation, the number of choroid plexus phagocytes, and attenuated hydrocephalus at 28 days after IVH. Inhibiting complement can reduce early erythrolysis, attenuates hydrocephalus and iron accumulation after IVH in aged animals.

Prominent elevation of extracellular matrix molecules in intracerebral hemorrhage

Background

Intracerebral hemorrhage (ICH) is the predominant type of hemorrhagic stroke with high mortality and disability. In other neurological conditions, the deposition of extracellular matrix (ECM) molecules is a prominent obstacle for regenerative processes and an enhancer of neuroinflammation. Whether ECM molecules alter in composition after ICH, and which ECM members may inhibit repair, remain largely unknown in hemorrhagic stroke.

Methods

The collagenase-induced ICH mouse model and an autopsied human ICH specimen were investigated for expression of ECM members by immunofluorescence microscopy. Confocal image z-stacks were analyzed with Imaris 3D to assess the association of immune cells and ECM molecules. Sections from a mouse model of multiple sclerosis were used as disease and staining controls. Tissue culture was employed to examine the roles of ECM members on oligodendrocyte precursor cells (OPCs).

Results

Among the lectican chondroitin sulfate proteoglycan (CSPG) members, neurocan but not aggrecan, versican-V1 and versican-V2 was prominently expressed in perihematomal tissue and lesion core compared to the contralateral area in murine ICH. Fibrinogen, fibronectin and heparan sulfate proteoglycan (HSPG) were also elevated after murine ICH while thrombospondin and tenascin-C was not. Confocal microscopy with Imaris 3D rendering co-localized neurocan, fibrinogen, fibronectin and HSPG molecules to Iba1+ microglia/macrophages or GFAP+ astrocytes. Marked differentiation from the multiple sclerosis model was observed, the latter with high versican-V1 and negligible neurocan. In culture, purified neurocan inhibited adhesion and process outgrowth of OPCs, which are early steps in myelination in vivo. The prominent expression of neurocan in murine ICH was corroborated in human ICH sections.

Conclusion

ICH caused distinct alterations in ECM molecules. Among CSPG members, neurocan was selectively upregulated in both murine and human ICH. In tissue culture, neurocan impeded the properties of oligodendrocyte lineage cells. Alterations to the ECM in ICH may adversely affect reparative outcomes after stroke.

Revisiting the role of the complement system in intracerebral hemorrhage and therapeutic prospects

Intracerebral hemorrhage (ICH) is a stroke subtype characterized by non-traumatic rupture of blood vessels in the brain, resulting in blood pooling in the brain parenchyma. Despite its lower incidence than ischemic stroke, ICH remains a significant contributor to stroke-related mortality, and most survivors experience poor outcomes that significantly impact their quality of life. ICH has been accompanied by various complex pathological damage, including mechanical damage of brain tissue, hematoma mass effect, and then leads to inflammatory response, thrombin activation, erythrocyte lysis, excitatory amino acid toxicity, complement activation, and other pathological changes. Accumulating evidence has demonstrated that activation of complement cascade occurs in the early stage of brain injury, and the excessive complement activation after ICH will affect the occurrence of secondary brain injury (SBI) through multiple complex pathological processes, aggravating brain edema, and pathological brain injury. Therefore, the review summarized the pathological mechanisms of brain injury after ICH, specifically the complement role in ICH, and its related pathological mechanisms, to comprehensively understand the specific mechanism of different complements at different stages after ICH. Furthermore, we systematically reviewed the current state of complement-targeted therapies for ICH, providing a reference and basis for future clinical transformation of complement-targeted therapy for ICH.

Characteristics of activation of monocyte-derived macrophages versus microglia after mouse experimental intracerebral hemorrhage

Both monocyte-derived macrophages (MDMs) and brain resident microglia participate in hematoma resolution after intracerebral hemorrhage (ICH). Here, we utilized a transgenic mouse line with enhanced green fluorescent protein (EGFP) labeled microglia (Tmem119-EGFP mice) combined with a F4/80 immunohistochemistry (a pan-macrophage marker) to visualize changes in MDMs and microglia after ICH. A murine model of ICH was used in which autologous blood was stereotactically injected into the right basal ganglia. The autologous blood was co-injected with CD47 blocking antibodies to enhance phagocytosis or clodronate liposomes for phagocyte depletion. In addition, Tmem119-EGFP mice were injected with the blood components peroxiredoxin 2 (Prx2) or thrombin. MDMs entered the brain and formed a peri-hematoma cell layer by day 3 after ICH and giant phagocytes engulfed red blood cells were found. CD47 blocking antibody increased the number of MDMs around and inside the hematoma and extended MDM phagocytic activity to day 7. Both MDMs and microglia could be diminished by clodronate liposomes. Intracerebral injection of Prx2 but not thrombin attracted MDMs into brain parenchyma. In conclusion, MDMs play an important role in phagocytosis after ICH which can be enhanced by CD47 blocking antibody, suggesting the modulation of MDMs after ICH could be a future therapeutic target.

Regulators of phagocytosis as pharmacologic targets for stroke treatment

Stroke, including ischemic and hemorrhagic stroke, causes massive cell death in the brain, which is followed by secondary inflammatory injury initiated by disease-associated molecular patterns released from dead cells. Phagocytosis, a cellular process of engulfment and digestion of dead cells, promotes the resolution of inflammation and repair following stroke. However, professional or non-professional phagocytes also phagocytose stressed but viable cells in the brain or excessively phagocytose myelin sheaths or prune synapses, consequently exacerbating brain injury and impairing repair following stroke. Phagocytosis includes the smell, eating and digestion phases. Notably, efficient phagocytosis critically depends on phagocyte capacity to take up dead cells continually due to the limited number of phagocytes vs. dead cells after injury. Moreover, phenotypic polarization of phagocytes occurring after phagocytosis is also essential to the proresolving and prorepair properties of phagocytosis. Much has been learned about the molecular signals and regulatory mechanisms governing the sense and recognition of dead cells by phagocytes during the smell and eating phase following stroke. However, some key areas remain extremely understudied, including the mechanisms involved in digestion regulation, continual phagocytosis and phagocytosis-induced phenotypic switching following stroke. Here, we summarize new discoveries related to the molecular mechanisms and multifaceted effects of phagocytosis on brain injury and repair following stroke and highlight the knowledge gaps in poststroke phagocytosis. We suggest that advancing the understanding of poststroke phagocytosis will help identify more biological targets for stroke treatment.

Complement Drives Chronic Inflammation and Progressive Hydrocephalus in Murine Neonatal Germinal Matrix Hemorrhage

Germinal matrix hemorrhage (GMH) is a pathology that occurs in infancy, with often devastating long-term consequences. Posthemorrhagic hydrocephalus (PHH) can develop acutely, while periventricular leukomalacia (PVL) is a chronic sequala. There are no pharmacological therapies to treat PHH and PVL. We investigated different aspects of the complement pathway in acute and chronic outcomes after murine neonatal GMH induced at postnatal day 4 (P4). Following GMH-induction, the cytolytic complement membrane attack complex (MAC) colocalized with infiltrating red blood cells (RBCs) acutely but not in animals treated with the complement inhibitor CR2-Crry. Acute MAC deposition on RBCs was associated with heme oxygenase-1 expression and heme and iron deposition, which was reduced with CR2-Crry treatment. Complement inhibition also reduced hydrocephalus and improved survival. Following GMH, there were structural alterations in specific brain regions linked to motor and cognitive functions, and these changes were ameliorated by CR2-Crry, as measured at various timepoints through P90. Astrocytosis was reduced in CR2-Crry-treated animals at chronic, but not acute, timepoints. At P90, myelin basic protein and LAMP-1 colocalized, indicating chronic ongoing phagocytosis of white matter, which was reduced by CR2-Crry treatment. Data indicate acute MAC-mediated iron-related toxicity and inflammation exacerbated the chronic effects of GMH.

Research progress of endogenous hematoma absorption after intracerebral hemorrhage

Non-traumatic intraparenchymal brain hemorrhage is referred to as intracerebral hemorrhage (ICH). Although ICH is associated with a high rate of disability and case fatality, active intervention can significantly lower the rate of severe disability. Studies have shown that the speed of hematoma clearance after ICH determines the patient's prognosis. Following ICH, depending on the hematoma volume and mass effect, either surgical- or medication-only conservative treatment is chosen. The goal of promoting endogenous hematoma absorption is more relevant because surgery is only appropriate for a small percentage of patients, and open surgery can cause additional trauma to patients. The primary method of removing hematoma after ICH in the future will involve understanding how to produce and manage macrophage/microglial endogenous phagocytic hematomas. Therefore, it is necessary to elucidate the regulatory mechanisms and key targets for clinical purposes.

Combination of Hematoma Volume and Perihematoma Radiomics Analysis on Baseline CT Scan Predicts the Growth of Perihematomal Edema

PURPOSE

The aim is to explore the potential value of CT-based radiomics in predicting perihematomal edema (PHE) volumes after acute intracerebral hemorrhage (ICH) from admission to 24 h.

METHODS

A total of 231 patients newly diagnosed with acute ICH at two institutes were analyzed retrospectively. The patients were randomly divided into training (N = 117) and internal validation cohort (N = 45) from institute 1 with a ratio of 7:3. According to radiomics features extracted from baseline CT, the radiomics signatures were constructed. Multiple logistic regression analysis was used for clinical radiological factors and then the nomogram model was generated to predict the extent of PHE according to the optimal radiomics signature and the clinical radiological factors. The receiver operating characteristic (ROC) curve was used to evaluate the discrimination performance. The calibration curve and Hosmer-Lemeshow test were used to evaluate the consistency between the predicted and actual probability. The support vector regression (SVR) model was constructed to predict the overall value of follow-up PHE. The performance of the models was evaluated on the internal and independent validation cohorts.

RESULTS

The perihematoma 5 mm radiomics signature (AUC: 0.875) showed good ability to discriminate the small relative PHE(rPHE) from large rPHE volumes, comparing to intrahematoma radiomics signature (AUC: 0.711) or perihematoma 10 mm radiomics signature (AUC: 0.692) on the training cohort. The AUC of the combined nomogram model was 0.922 for the training cohort, 0.945 and 0.902 for the internal and independent validation cohorts, respectively. The calibration curves and Hosmer-Lemeshow test of the nomogram model suggested that the predictive performance and actual outcome were in favorable agreement. The SVR model also predicted the overall value of follow-up rPHE (root mean squared error, 0.60 and 0.45; Pearson correlation coefficient, 0.73 and 0.68; P < 0.001).

CONCLUSION

Among patients with acute ICH, the established nomogram and SVR model with favorable performance can offer a noninvasive tool for the prediction of PHE after ICH.

The Critical Role of Erythrolysis and Microglia/Macrophages in Clot Resolution After Intracerebral Hemorrhage: A Review of the Mechanisms and Potential Therapeutic Targets

Intracerebral hemorrhage (ICH) is a common cerebrovascular disorder with high morbidity and mortality. Secondary brain injury after ICH, which is initiated by multiple hemolytic products during erythrolysis, has been identified as a critical factor accounting for the poor prognosis of ICH patients. Clot resolution and hematoma clearance occur immediately after ICH via erythrolysis and erythrophagocytosis. During this process, erythrolysis after ICH results in the release of hemoglobin and products of degradation along with rapid morphological changes in red blood cells (RBCs). Phagocytosis of deformed erythrocytes and products of degradation by microglia/macrophages accelerates hematoma clearance, which turns out to be neuroprotective. Thus, a better understanding of the mechanism of erythrolysis and the role of microglia/macrophages after ICH is urgently needed. In this review, the current research progresses on the underlying mechanism of erythrolysis and erythrophagocytosis, as well as several useful tools for the quantification of erythrolysis-induced brain injury, are summarized, providing potential intervention targets and possible treatment strategies for ICH patients.

Animal models for the study of intracranial hematomas (Review)

Intracranial hematomas (ICH) are a frequent condition in neurosurgical and neurological practices, with several mechanisms of primary and secondary injury. Experimental research has been fundamental for the understanding of the pathophysiology implicated with ICH and the development of therapeutic interventions. To date, a variety of different animal approaches have been described that consider, for example, the ICH evolutive phase, molecular implications and hemodynamic changes. Therefore, choosing a test protocol should consider the scope of each particular study. The present review summarized investigational protocols in experimental research on the subject of ICH. With this subject, injection of autologous blood or bacterial collagenase, inflation of intracranial balloon and avulsion of cerebral vessels were the models identified. Rodents (mice) and swine were the most frequent species used. These different models allowed improvements on the understanding of intracranial hypertension establishment, neuroinflammation, immunology, brain hemodynamics and served to the development of therapeutic strategies.

The Fate of Erythrocytes after Cerebral Hemorrhage

After a cerebral hemorrhage (intracerebral, subarachnoid, and intraventricular), extravasated blood contributes to both initial brain injury, via physical disruption and mass effect, and secondary injury, through the release of potentially neurotoxic and pro-inflammatory factors such as hemoglobin, iron, and peroxiredoxin-2. Erythrocytes are a major blood component and are a source of such damaging factors. Erythrolysis after cerebral hemorrhage releases potential neurotoxins, contributing to brain injury and edema. Alternatively, erythrocyte phagocytosis via microglia or macrophages may limit the spill of neurotoxins therefore limiting subsequent brain injury. The aim of this review is to discuss the process of phagocytosis of erythrocytes by microglia or macrophages after cerebral hemorrhage, the effect of erythrolysis on brain injury, novel mechanisms of erythrocyte and phagocyte egress from the brain, and exciting new targets in this pathway to attenuate brain injury. Understanding the fate of erythrocytes after cerebral hemorrhage may uncover additional potential interventions for clinical translational research.

Role of complement C1q/C3-CR3 signaling in brain injury after experimental intracerebral hemorrhage and the effect of minocycline treatment

Aim

The complement cascade is activated and may play an important pathophysiologic role in brain injury after experimental intracerebral hemorrhage (ICH). However, the exact mechanism of specific complement components has not been well studied. This study determined the role of complement C1q/C3-CR3 signaling in brain injury after ICH in mice. The effect of minocycline on C1q/C3-CR3 signaling-induced brain damage was also examined.

Methods

There were three parts to the study. First, the natural time course of C1q and CR3 expression was determined within 7 days after ICH. Second, mice had an ICH with CR3 agonists, LA-1 or vehicle. Behavioral score, neuronal cell death, hematoma volume, and oxidative stress response were assessed at 7 days after ICH. Third, the effect of minocycline on C1q/C3-CR3 signaling and brain damage was examined.

Results

There were increased numbers of C1q-positive and CR3-positive cells after ICH. Almost all perihematomal C1q-positive and CR3-positive cells were microglia/macrophages. CR3 agonist LA-1 aggravated neurological dysfunction, neuronal cell death, and oxidative stress response on day 7 after ICH, as well as enhancing the expression of the CD163/HO-1 pathway and accelerating hematoma resolution. Minocycline treatment exerted neuroprotective effects on brain injury following ICH, partly due to the inhibition of C1q/C3-CR3 signaling, and that could be reversed by LA-1.

Conclusions

The complement C1q/C3-CR3 signaling is upregulated after ICH. The activation of C1q/C3-CR3 signaling by LA-1 aggravates brain injury following ICH. The neuroprotection of minocycline, at least partly, is involved with the repression of the C1q/C3-CR3 signaling pathway.

Endogenous H2S targets mitochondria to promote continual phagocytosis of erythrocytes by microglia after intracerebral hemorrhage

Hematoma clearance, which is achieved largely by phagocytosis of erythrocytes in the hemorrhagic brain, limits injury and facilitates recovery following intracerebral hemorrhage (ICH). Efficient phagocytosis critically depends on the capacity of a single phagocyte to phagocytize dead cells continually. However, the mechanism underlying continual phagocytosis following ICH remains unclear. We aimed to investigate the mechanism in this study. By using ICH models, we found that the gasotransmitter hydrogen sulfide (H₂S) is an endogenous modulator of continual phagocytosis following ICH. The expression of the H₂S synthase cystathionine β-synthase (CBS) and CBS-derived H₂S were elevated in brain-resident phagocytic microglia following ICH, which consequently promoted continual phagocytosis of erythrocytes by microglia. Microglia-specific deletion of CBS delayed spontaneous hematoma clearance via an H₂S-mediated mechanism following ICH. Mechanistically, oxidation of CBS-derived endogenous H₂S by sulfide-quinone oxidoreductase initiated reverse electron transfer at mitochondrial complex I, leading to superoxide production. Complex I-derived superoxide, in turn, activated uncoupling protein 2 (UCP2) to promote microglial phagocytosis of erythrocytes. Functionally, complex I and UCP2 were required for spontaneous hematoma clearance following ICH. Moreover, hyperhomocysteinemia, an established risk factor for stroke, impaired ICH-enhanced CBS expression and delayed hematoma resolution, while supplementing exogenous H₂S accelerated hematoma clearance in mice with hyperhomocysteinemia. The results suggest that the microglial CBS-H₂S-complex I axis is critical to continual phagocytosis following ICH and can be targeted to treat ICH.

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CBS-derived H₂S is elevated in brain-resident phagocytic microglia following ICH.

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CBS-derived H₂S promotes continual erythrophagocytosis and hematoma clearance.

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CBS-derived H₂S promotes microglial phagocytosis via complex I-derived ROS.

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Hyperhomocysteinemia inhibits CBS expression to delay hematoma resolution.

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The CBS-H₂S-complex I axis can be targeted to treat ICH.

Role of Eryptosis in Hemorrhagic Stroke

Erythrocytes undergo certain morphological changes resembling apoptosis during senescence or in an abnormal state/site, which is termed eryptosis. This process is characterized by phosphatidylserine (PS) exposure, membrane blebbing, and cell shrinkage. Eryptotic erythrocytes are subsequently removed via macrophage-mediated efferocytosis. In hemorrhagic stroke (HS), blood within an artery rapidly bleeds into the brain tissue or the subarachnoid space, resulting in severe neurological deficits. A hypoxic, over-oxidative, and pro-inflammatory microenvironment in the hematoma leads to oxidative stress, hyperosmotic shock, energy depletion, and Cl^– removal in erythrocytes, which eventually triggers eryptosis. In addition, eryptosis following intracerebral hemorrhage favors hematoma clearance, which sheds light on a common mechanism of intrinsic phagocytosis. In this review, we summarized the canonical mechanisms of eryptosis and discussed its pathological conditions associated with HS. Understanding the role of eryptosis in HS may uncover additional potential interventions for further translational clinical research.

Effect of exercise from a very early stage after intracerebral hemorrhage on microglial and macrophage reactivity states in rats

OBJECTIVE

This study investigated the effects of exercise, starting very early after intracerebral hemorrhage (ICH), on microglia and macrophages in a rat model. Collagenase solution was injected into the left striatum to induce ICH.

METHODS

Rats were randomly assigned to receive placebo surgery without exercise (sham surgery), ICH without exercise (ICH), or ICH with very early exercise (ICH + VET). The ICH + VET group was subjected to treadmill running 6 h, 24 h, and days 2-6 after ICH. Motor function assessment was performed using the ladder test and rotarod test 3 h, 25 h, and 7 days after ICH. Postexercise brain tissue was collected on day 8 after surgery to investigate the lesion volume. Very early exercise temporarily worsened motor dysfunction. The protein expression levels of the macrophage and microglial markers CD80, CD163, and TMEM119 were analyzed 6 h, 24 h, and 8 days after ICH. Protein analysis of NeuN, GFAP, and PSD95 was also performed on day 8 after ICH.

RESULTS

There was no significant difference in lesion volume between the ICH and ICH + VET groups on day 8 after ICH. Exercise from very early stage prevented elevated CD163 protein expression.

CONCLUSION

Very early exercise may inhibit the activation of anti-inflammatory-associated macrophages/microglia.

Potential application of intranasal insulin delivery for treatment of intracerebral hemorrhage: A review of the literature

Intracerebral hemorrhage (ICH) is a devastating subtype of stroke associated with high morbidity and mortality that is considered a medical emergency, mainly managed with adequate blood pressure control and creating a favorable hemostatic condition. However, to date, none of the randomized clinical trials have led to an effective treatment for ICH. It is vital to better understand the mechanisms underlying brain injury to effectively decrease ICH-associated morbidity and mortality. It is well known that initial hematoma formation and its expansion have detrimental consequences. The literature has recently focused on other pathological processes, including oxidative stress, neuroinflammation, blood-brain barrier disruption, edema formation, and neurotoxicity, that constitute secondary brain injury. Since conventional management has failed to improve clinical outcomes significantly, various neuroprotective therapies are tested in preclinical and clinical settings. Unlike intravenous administration, intranasal insulin can reach a higher concentration in the cerebrospinal fluid without causing systemic side effects. Intranasal insulin delivery has been introduced as a novel neuroprotective agent for certain neurological diseases, including ischemic stroke, subarachnoid hemorrhage, and traumatic brain injury. Since there is an overlap of mechanisms causing neuroinflammation in these neurological diseases and ICH, we believe that preclinical studies testing the role of intranasal insulin therapy in ICH are warranted.

Hemin-Induced Death Models Hemorrhagic Stroke and Is a Variant of Classical Neuronal Ferroptosis

Ferroptosis is a caspase-independent, iron-dependent form of regulated necrosis extant in traumatic brain injury, Huntington disease, and hemorrhagic stroke. It can be activated by cystine deprivation leading to glutathione depletion, the insufficiency of the antioxidant glutathione peroxidase-4, and the hemolysis products hemoglobin and hemin. A cardinal feature of ferroptosis is extracellular signal-regulated kinase (ERK)1/2 activation culminating in its translocation to the nucleus. We have previously confirmed that the mitogen-activated protein (MAP) kinase kinase (MEK) inhibitor U0126 inhibits persistent ERK1/2 phosphorylation and ferroptosis. Here, we show that hemin exposure, a model of secondary injury in brain hemorrhage and ferroptosis, activated ERK1/2 in mouse neurons. Accordingly, MEK inhibitor U0126 protected against hemin-induced ferroptosis. Unexpectedly, U0126 prevented hemin-induced ferroptosis independent of its ability to inhibit ERK1/2 signaling. In contrast to classical ferroptosis in neurons or cancer cells, chemically diverse inhibitors of MEK did not block hemin-induced ferroptosis, nor did the forced expression of the ERK-selective MAP kinase phosphatase (MKP)3. We conclude that hemin or hemoglobin-induced ferroptosis, unlike glutathione depletion, is ERK1/2-independent. Together with recent studies, our findings suggest the existence of a novel subtype of neuronal ferroptosis relevant to bleeding in the brain that is 5-lipoxygenase-dependent, ERK-independent, and transcription-independent. Remarkably, our unbiased phosphoproteome analysis revealed dramatic differences in phosphorylation induced by two ferroptosis subtypes. As U0126 also reduced cell death and improved functional recovery after hemorrhagic stroke in male mice, our analysis also provides a template on which to build a search for U0126's effects in a variant of neuronal ferroptosis.SIGNIFICANCE STATEMENT Ferroptosis is an iron-dependent mechanism of regulated necrosis that has been linked to hemorrhagic stroke. Common features of ferroptotic death induced by diverse stimuli are the depletion of the antioxidant glutathione, production of lipoxygenase-dependent reactive lipids, sensitivity to iron chelation, and persistent activation of extracellular signal-regulated kinase (ERK) signaling. Unlike classical ferroptosis induced in neurons or cancer cells, here we show that ferroptosis induced by hemin is ERK-independent. Paradoxically, the canonical MAP kinase kinase (MEK) inhibitor U0126 blocks brain hemorrhage-induced death. Altogether, these data suggest that a variant of ferroptosis is unleashed in hemorrhagic stroke. We present the first, unbiased phosphoproteomic analysis of ferroptosis as a template on which to understand distinct paths to cell death that meet the definition of ferroptosis.

CD47 Blockade Accelerates Blood Clearance and Alleviates Early Brain Injury After Experimental Subarachnoid Hemorrhage

Aims

Subarachnoid hemorrhage (SAH) is a devastating stroke subtype. Following SAH, erythrocyte lysis contributes to cell death and brain injuries. Blockage of the anti-phagocytic receptor Cluster of Differentiation 47 (CD47) enhances phagocyte clearance of erythrocytes, though it has not been well-studied post-SAH. The current study aims to determine whether anti-CD47 treatment can enhance blood clearance after experimental SAH.

Methods

The prechiasmatic blood injection model of SAH was used in mice. Mice were either treated with the CD47-blocking antibody or IgG as control. The effect of the anti-CD47 antibody on blood clearance and neurological function following SAH was determined. Neuroinflammation and neuronal injury were compared between the treatment and control samples on day 1 and day 7 after SAH using flow cytometry, immunofluorescence, Fluoro-Jade C, and Nissl staining, RT-PCR, and Western blot analysis.

Results

CD47-blocking antibody sped-up blood clearance after SAH, and resulted in less neuronal injury and neurological deficits than control samples. Microglia played a role in the anti-CD47 blockade. Following SAH Following SAH, CD47 antibody-treated mice had less neuroinflammation and lower levels of apoptosis compared to controls and both one and 7 days.

Conclusions

CD47 antibody treatment has a neuroprotective effect following SAH, by increasing blood clearance rate and reducing brain injury. These findings suggest CD47 antibody treatment may improve SAH patient outcomes.

Erythrophagocytosis by Microglia/Macrophage in Intracerebral Hemorrhage: From Mechanisms to Translation

Intracerebral hemorrhage (ICH) is a devastating condition characterized by hematoma related mass effect. Microglia/macrophage (M φ) are rapidly recruited in order to remove the red blood cells through erythrophagocytosis. Efficient erythrophagocytosis can detoxify hemolytic products and facilitate neurological recovery after ICH. The underlying mechanisms include modulation of inflammatory response and oxidative stress, among others. It is a dynamic process mediated by a cascade of signal transduction, including “find-me” signals, “eat-me” signals and a set of phagocytotic receptors-ligand pairs that may be exploited as therapeutic targets. This review summarizes mechanistic signaling pathways of erythrophagocytosis and highlights the potential of harnessing M φ-mediated phagocytosis for ICH treatment.

Novel targets, treatments, and advanced models for intracerebral haemorrhage

Intracerebral haemorrhage (ICH) is the second most common type of stroke and a major cause of mortality and disability worldwide. Despite advances in surgical interventions and acute ICH management, there is currently no effective therapy to improve functional outcomes in patients. Recently, there has been tremendous progress uncovering new pathophysiological mechanisms underlying ICH that may pave the way for the development of therapeutic interventions. Here, we highlight emerging targets, but also existing gaps in preclinical animal modelling that prevent their exploitation. We particularly focus on (1) ICH aetiology, (2) the haematoma, (3) inflammation, and (4) post-ICH pathology. It is important to recognize that beyond neurons and the brain, other cell types and organs are crucially involved in ICH pathophysiology and successful interventions likely will need to address the entire organism. This review will spur the development of successful therapeutic interventions for ICH and advanced animal models that better reflect its aetiology and pathophysiology.

Assessing the Evolution of Intracranial Hematomas by using Animal Models: A Review of the Progress and the Challenges

Stroke has become the second leading cause of death in people aged higher than 60 years, with cancer being the first. Intracerebral hemorrhage (ICH) is the most lethal type of stroke. Using imaging techniques to evaluate the evolution of intracranial hematomas in patients with hemorrhagic stroke is worthy of ongoing research. The difficulty in obtaining ultra-early imaging data and conducting intensive dynamic radiographic imaging in actual clinical settings has led to the application of experimental animal models to assess the evolution of intracranial hematomas. Herein, we review the current knowledge on primary intracerebral hemorrhage mechanisms, focus on the progress of animal studies related to hematoma development and secondary brain injury, introduce preclinical therapies, and summarize related challenges and future directions.

Iron toxicity in intracerebral hemorrhage: Physiopathological and therapeutic implications

Intracerebral hemorrhage (ICH)-induced brain injury is a continuous pathological process that involves the deterioration of neurological functions, such as sensory, cognitive or motor functions. Cytotoxic byproducts of red blood cell lysis, especially free iron, appear to be a significant pathophysiologic mechanism leading to ICH-induced injury. Free iron has a crucial role in secondary brain injury after ICH. Chelating iron may attenuate iron-induced neurotoxicity and may be developed as a therapeutic candidate for ICH treatment. In this review, we focused on the potential role of iron toxicity in ICH-induced injury and iron chelation therapy in the management of ICH. It will hopefully advance our understanding of the pathogenesis of ICH and lead to new approaches for treatment.

Microglia Phenotype and Intracerebral Hemorrhage: A Balance of Yin and Yang

Intracerebral hemorrhage (ICH) features extremely high rates of morbidity and mortality, with no specific and effective therapy. And local inflammation caused by the over-activated immune cells seriously damages the recovery of neurological function after ICH. Fortunately, immune intervention to microglia has provided new methods and ideas for ICH treatment. Microglia, as the resident immune cells in the brain, play vital roles in both tissue damage and repair processes after ICH. The perihematomal activated microglia not only arouse acute inflammatory responses, oxidative stress, excitotoxicity, and cytotoxicity to cause neuron death, but also show another phenotype that inhibit inflammation, clear hematoma and promote tissue regeneration. The proportion of microglia phenotypes determines the progression of brain tissue damage or repair after ICH. Therefore, microglia may be a promising and imperative therapeutic target for ICH. In this review, we discuss the dual functions of microglia in the brain after an ICH from immunological perspective, elaborate on the activation mechanism of perihematomal microglia, and summarize related therapeutic drugs researches.

Exploring scraping therapy: Contemporary views on an ancient healing - A review

Gua sha is a traditional healing technique that aims to create petechiae on the skin for a believed therapeutic benefit. Natural healings are mostly based on repeated observations and anecdotal information. Hypothetical model for healing does not always fit the modern understanding. Yet, the mechanisms underlying Gua Sha have not been empirically established. Contemporary scientific research can now explain some events of traditional therapies that were once a mystery. It is assumed that Gua Sha therapy can serve as a mechanical signal to enhance the immune surveillance function of the skin during the natural resolving of the petechiae, through which scraping may result in therapeutic benefits. The current review, without judging the past hypothetical model, attempts to interpret the experience of the ancient healings in terms of contemporary views and concepts.

Neuroprotective Therapies for Spontaneous Intracerebral Hemorrhage

Patients who survive the initial ictus of spontaneous intracerebral hemorrhage (ICH) remain vulnerable to subsequent injury of the perilesional parenchyma by molecular and cellular responses to the hematoma. Secondary brain injury after ICH, which contributes to long-term functional impairment and mortality, has emerged as an attractive therapeutic target. This review summarizes preclinical and clinical evidence for neuroprotective therapies targeting secondary injury pathways following ICH. A focus on therapies with pleiotropic antiinflammatory effects that target thrombin-mediated chemotaxis and inflammatory cell migration has led to studies investigating statins, anticholinergics, sphingosine-1-phosphate receptor modulators, peroxisome proliferator activated receptor gamma agonists, and magnesium. Attempts to modulate ICH-induced blood-brain barrier breakdown and perihematomal edema formation has prompted studies of nonsteroidal antiinflammatory agents, matrix metalloproteinase inhibitors, and complement inhibitors. Iron chelators, such as deferoxamine and albumin, have been used to reduce the free radical injury that ensues from erythrocyte lysis. Stem cell transplantation has been assessed for its potential to enhance subacute neurogenesis and functional recovery. Despite promising preclinical results of numerous agents, their outcomes have not yet translated into positive clinical trials in patients with ICH. Further studies are necessary to improve our understanding of the molecular events that promote damage and inflammation of the perihematomal parenchyma after ICH. Elucidating the temporal and pathophysiologic features of this secondary brain injury could enhance the clinical efficacy of neuroprotective therapies for ICH.

Anti-CD47 antibody administration via cisterna magna in proper dosage can reduce perihematomal cell death following intracerebral hemorrhage in rats

OBJECTIVE

The secondary injury caused by RBC autolysis after intracerebral hemorrhage (ICH) can be reduced by increasing the efficiency of microglia (MG)/macrophages (Mø) phagocytizing red blood cells (RBCs). CD47 is an important regulator of MG/Mø phagocytosis. This study aims to clarify whether anti-CD47 antibody administrated into the cisterna magna after ICH can transfer to the hematoma site, promote MG/Mø gathering to phagocytize RBCs and ultimately reduce cell death.

METHODS

Forty male Wistar rats were divided into sham, ICH, low-dosage (group A, 0.3 μg), medium-dosage (group B, 0.9 μg) and high-dosage (group C, 1.8 μg) anti-CD47 antibody groups. For the rats in group A, B and C, anti-CD47 antibody solution was administrated into the cisterna magna at 10 min after ICH. Brain tissue was harvested 3 days after the operation. Western blotting was performed to detect the expression of Caspase-3 and Bcl-2. Immunofluorescence was performed to detect the CD68 expression. TUNEL was performed to detect the cell death.

RESULTS

The hematoma of the ICH rats was located in the basal ganglia, with a good homogeneity of hematoma volume. Low-dosage anti-CD47 antibody in group A had no effects on the perihematomal CD68 (P = 0.338), Caspase-3 (P = 0.769), Bcl-2 (P = 0.176) expression and cell death (P = 0.698), compared with the ICH group. CD68 and Bcl-2 expression increased and Caspase-3 expression decreased significantly in group B (P < 0.001 for all) and group C (P < 0.001 for all). The increase of CD68 expression in group C was greater than that in group B (P < 0.01) by a large margin, while there was no difference for Bcl-2 (P = 0.908) and Caspase-3 (P = 0.913) expression between the 2 groups. Compared with the ICH group, medium-dosage of anti-CD47 antibody in group B significantly reduced the number of TUNEL-positive cells (P < 0.005), but not for group C (P = 0.311).

CONCLUSION

The results suggested that anti-CD47 antibody administration into the cisterna magna in proper dosage (0.9 μg) can effectively reach the hematoma, induce more MG/Møs to gather around the hematoma, and reduce cell death in perihematomal brain tissue. The results of this study has provided a basic theory for improving the efficiency of MG/Mø phagocytizing RBCs and hematoma clearance after ICH by administrating anti-CD47 antibody via the cisterna magna.

Role of Complement Component 3 in Early Erythrolysis in the Hematoma After Experimental Intracerebral Hemorrhage

[Figure: see text].

The combination of deferoxamine and minocycline strengthens neuroprotective effect on acute intracerebral hemorrhage in rats

Objectives: Intracerebral hemorrhage (ICH) is a devastating type of strokes that carries high mortality rates, but effective therapeutic options are still lacking. Here, the adult rat model of ICH was used to investigate the efficacy of a combinational therapy of deferoxamine (DFX) and minocycline.Methods: The ICH was induced by stereotaxic infusion of collagenase into striatum of adult rats. After the induction of ICH, rats were treated with intraperitoneal injection of deferoxamine (50 mg/kg), minocycline (45 mg/kg), or both agents, at 2 hours after ICH and then every 12 hours for up to 3 days. The vehicle group were treated with phosphate-buffered saline (PBS) only. Rats were killed at 1, 2, and 3 day(s) for examination of iron deposition, neuronal death, neurological deficits, the area of brain damage, activation of microglia/macrophages.Results: Our data revealed that the systemic administration of DFX and/or minocycline decreased iron accumulation. And immunofluorescence staining results indicated that drug-treated group significantly decreased the neuronal degeneration, the number of activated microglia/macrophages and the amount of cell death after ICH. In addition, neurological deficits caused by ICH were improved in the presence of DFX and/or minocycline compare with vehicle group. Furthermore, the combination treatment showed better effects in neuroprotection and anti-inflammation when compared to the monotherapy groups.Conclusions: The combination therapy significantly reduces the number of neuronal deaths, suppresses of the activation of microglia/macrophages, decreases iron accumulation in the area around the hematoma, lessening the brain damage area, and improving neurological deficits in ICH.

White Matter Injury After Intracerebral Hemorrhage

Spontaneous intracerebral hemorrhage (ICH) accounts for 15% of all stroke cases. ICH is a devastating form of stroke associated with high morbidity, mortality, and disability. Preclinical studies have explored the mechanisms of neuronal death and gray matter damage after ICH. However, few studies have examined the development of white matter injury (WMI) following ICH. Research on WMI indicates that its pathophysiological presentation involves axonal damage, demyelination, and mature oligodendrocyte loss. However, the detailed relationship and mechanism between WMI and ICH remain unclear. Studies of other acute brain insults have indicated that WMI is strongly correlated with cognitive deficits, neurological deficits, and depression. The degree of WMI determines the short- and long-term prognosis of patients with ICH. This review demonstrates the structure and functions of the white matter in the healthy brain and discusses the pathophysiological mechanism of WMI following ICH. Our review reveals that the development of WMI after ICH is complex; therefore, comprehensive treatment is essential. Understanding the relationship between WMI and other brain cells may reveal therapeutic targets for the treatment of ICH.

Deferoxamine B: A Natural, Excellent and Versatile Metal Chelator

Deferoxamine B is an outstanding molecule which has been widely studied in the past decade for its ability to bind iron and many other metal ions. The versatility of this metal chelator makes it suitable for a number of medicinal and analytical applications, from the well-known iron chelation therapy to the most recent use in sensor devices. The three bidentate hydroxamic functional groups of deferoxamine B are the centerpiece of its metal binding ability, which allows the formation of stable complexes with many transition, lanthanoid and actinoid metal ions. In addition to the ferric ion, in fact, more than 20 different metal complexes of deferoxamine b have been characterized in terms of their chemical speciation in solution. In addition, the availability of a terminal amino group, most often not involved in complexation, opens the way to deferoxamine B modification and functionalization. This review aims to collect and summarize the available data concerning the complex-formation equilibria in solutions of deferoxamine B with different metal ions. A general overview of the progress of its applications over the past decade is also discussed, including the treatment of iron overload-associated diseases, its clinical use against cancer and neurodegenerative disorders and its role as a diagnostic tool.

When the Blood Hits Your Brain: The Neurotoxicity of Extravasated Blood

Hemorrhage in the central nervous system (CNS), including intracerebral hemorrhage (ICH), intraventricular hemorrhage (IVH), and aneurysmal subarachnoid hemorrhage (aSAH), remains highly morbid. Trials of medical management for these conditions over recent decades have been largely unsuccessful in improving outcome and reducing mortality. Beyond its role in creating mass effect, the presence of extravasated blood in patients with CNS hemorrhage is generally overlooked. Since trials of surgical intervention to remove CNS hemorrhage have been generally unsuccessful, the potent neurotoxicity of blood is generally viewed as a basic scientific curiosity rather than a clinically meaningful factor. In this review, we evaluate the direct role of blood as a neurotoxin and its subsequent clinical relevance. We first describe the molecular mechanisms of blood neurotoxicity. We then evaluate the clinical literature that directly relates to the evacuation of CNS hemorrhage. We posit that the efficacy of clot removal is a critical factor in outcome following surgical intervention. Future interventions for CNS hemorrhage should be guided by the principle that blood is exquisitely toxic to the brain.

Neutrophil extracellular traps (NETs) infiltrate haematoma and surrounding brain tissue after intracerebral haemorrhage: A post-mortem study

AIMS

Because of their prothrombotic and neuroinflammatory effects, neutrophils and neutrophil extracellular traps (NETs) represent interesting therapeutic targets for spontaneous intracerebral haemorrhage (sICH). We investigated the presence, spatial and temporal distribution of NETs in a human sICH post-mortem study.

METHODS

From 2005 to 2019, all sICH patients who came to autopsy within the first month after stroke were included and grouped according to the timing of death: 72 h, 4-7 days, 8-15 days and >15 days after ICH onset. Paraffin-embedded tissue was extracted from four strategic areas: haematoma, peri-haematomal area, ipsilateral surrounding brain tissue and a control contralateral area. Myeloperoxidase and histone H3 citrulline were immunolabelled to detect neutrophils and NETs respectively.

RESULTS

Neutrophils were present in the brains of the 14 cases (4 men, median age: 78 years) and NETs were found in 7/14 cases. Both neutrophils and NETs were detected within the haematoma but also in the surrounding tissue. The appearance of neutrophils and NETs was time-dependent, following a two-wave pattern: during the first 72 h and between 8 and 15 days after ICH onset. Qualitative examination showed that neutrophils and NETs were mainly located around dense fibrin fibres within the haematoma.

CONCLUSIONS

These observations provide evidence for NETs infiltration in the brain of patients who die from sICH. NETs might interact with early haemostasis within the haematoma core, and with the surrounding neuroinflammatory response. These findings open research perspectives for NETs in the treatment of sICH injuries.

Hydrocephalus Following Experimental Subarachnoid Hemorrhage in Rats with Different Aerobic Capacity

Low aerobic capacity is considered to be a risk factor for stroke, while the mechanisms underlying the phenomenon are still unclear. The current study looked into the impacts of different aerobic capacities on early brain injury in a subarachnoid hemorrhage (SAH) model using rats bred for high and low aerobic capacity (high-capacity runners, HCR; low-capacity runners, LCR). SAH was modeled with endovascular perforation in HCR and LCR rats. Twenty-four hours after SAH, the rats underwent behavioral testing and MRI, and were then euthanized. The brains were used to investigate ventricular wall damage, blood-brain barrier breakdown, oxidative stress, and hemoglobin scavenging. The LCR rats had worse SAH grades (p < 0.01), ventricular dilatation (p < 0.01), ventricular wall damage (p < 0.01), and behavioral scores (p < 0.01). The periventricular expression of HO-1 and CD163 was significantly increased in LCR rats (p < 0.01 each). CD163-positive cells were co-localized with HO-1-positive cells. The LCR rats had greater early brain injuries than HCR rats. The LCR rats had more serious SAH and extensive ventricular wall damage that evolved more frequently into hydrocephalus. This may reflect changes in iron handling and neuroinflammation.

Mechanism of White Matter Injury and Promising Therapeutic Strategies of MSCs After Intracerebral Hemorrhage

Intracerebral hemorrhage (ICH) is the most fatal subtype of stroke with high disability and high mortality rates, and there is no effective treatment. The predilection site of ICH is in the area of the basal ganglia and internal capsule (IC), where exist abundant white matter (WM) fiber tracts, such as the corticospinal tract (CST) in the IC. Proximal or distal white matter injury (WMI) caused by intracerebral parenchymal hemorrhage is closely associated with poor prognosis after ICH, especially motor and sensory dysfunction. The pathophysiological mechanisms involved in WMI are quite complex and still far from clear. In recent years, the neuroprotection and repairment capacity of mesenchymal stem cells (MSCs) has been widely investigated after ICH. MSCs exert many unique biological effects, including self-recovery by producing growth factors and cytokines, regenerative repair, immunomodulation, and neuroprotection against oxidative stress, providing a promising cellular therapeutic approach for the treatment of WMI. Taken together, our goal is to discuss the characteristics of WMI following ICH, including the mechanism and potential promising therapeutic targets of MSCs, aiming at providing new clues for future therapeutic strategies.

Timing of diffusion weighted imaging lesions in spontaneous intracerebral hemorrhage

INTRODUCTION

Diffusion weighted imaging (DWI) lesions are common after spontaneous intracerebral hemorrhage (sICH). However, their timing relative to a patient's admission to the hospital is unknown. The purpose of this study is to estimate the timing of new DWI lesions after admission for acute sICH.

MATERIAL AND METHODS

Select patients enrolled in a single center prospective study examining the prevalence DWI lesions in acute primary sICH received two MRI scans of the brain after admission. The presence of a new DWI lesion between MRI scans was defined as a new DWI event. A lognormal parametric model was used to estimate the median time (50% percentile) to develop a new DWI lesion.

RESULTS

Among the 121 participants enrolled in the study, 63 (52%) had two brain MRIs. The median time from admission to 1st MRI was 1 day (IQR 1.2, range 0.1-8.4). The median time between the 2 MRI scans was 2.1 (IQR 2.9, range 0.02-17.4) days. 30.2% (n = 19) of participants developed a new DWI lesion between MRI scans. The estimated median time from 1st MRI to new DWI event was 6.3 days (95% CI, 4.1 to 9.6).

DISCUSSION AND CONCLUSION

Accounting for time from admission to 1st MRI, we found that 50% of new DWI lesions occurred by 7.3 days after sICH admission. Pathophysiologic changes in sICH during this time frame need to be studied in order to elucidate a mechanism for DWI lesions.

Role of mass effect and trehalose on early erythrolysis after experimental intracerebral hemorrhage

The mechanisms of brain injury after intracerebral hemorrhage (ICH) involve mass effect-induced primary injury and secondary injury caused by a pathologic response to the hematoma. Considerable attentions have recently been paid to the mechanisms and therapeutic strategy for secondary brain injury due to no overall benefit from early surgery compared with initial conservative treatment. However, it is unclear whether there is a causal relationship between mass effect and secondary brain injury. Here, the role of mass effect on early erythrolysis after experimental ICH was investigated based on the poly(N-isopropylacrylamide) (PNIPAM) ICH model. Autologous blood and PNIPAM hydrogel were co-injected into the right basal ganglia of rats to induce different degrees of mass effect, but with a constant hematoma. The influences of different mass effect and time courses on erythrolysis and brain damages after ICH were investigated. Furthermore, the protective effect of trehalose against erythrolysis after ICH was evaluated. The results showed that mass effect caused erythrocyte morphological change at 24 hr after ICH. The released hemoglobin was quantitatively evaluated by a polynomial concerning with the mass effect, the volume of hematoma, and the time of ICH. An obvious increase in heme oxygenase-1 (HO-1) and ionized calcium binding adaptor molecule-1 (Iba-1) expression, iron deposition, cell death, and neurological deficits was observed with increasing mass effect. Moreover, trehalose alleviated brain injury by inhibiting erythrolysis after ICH. These data demonstrated that mass effect accelerated the erythrolysis and brain damages after ICH, which could be relieved through trehalose therapy.

Iron Metabolism Disorders for Cognitive Dysfunction After Mild Traumatic Brain Injury

Traumatic brain injury (TBI) is one of the most harmful forms of acute brain injury and predicted to be one of the three major neurological diseases that cause neurological disabilities by 2030. A series of secondary injury cascades often cause cognitive dysfunction of TBI patients leading to poor prognosis. However, there are still no effective intervention measures, which drive us to explore new therapeutic targets. In this process, the most part of mild traumatic brain injury (mTBI) is ignored because its initial symptoms seemed not serious. Unfortunately, the ignored mTBI accounts for 80% of the total TBI, and a large part of the patients have long-term cognitive dysfunction. Iron deposition has been observed in mTBI patients and accompanies the whole pathological process. Iron accumulation may affect long-term cognitive dysfunction from three pathways: local injury, iron deposition induces tau phosphorylation, the formation of neurofibrillary tangles; neural cells death; and neural network damage, iron deposition leads to axonal injury by utilizing the iron sensibility of oligodendrocytes. Thus, iron overload and metabolism dysfunction was thought to play a pivotal role in mTBI pathophysiology. Cerebrospinal fluid-contacting neurons (CSF-cNs) located in the ependyma have bidirectional communication function between cerebral-spinal fluid and brain parenchyma, and may participate in the pathway of iron-induced cognitive dysfunction through projected nerve fibers and transmitted factor, such as 5-hydroxytryptamine, etc. The present review provides an overview of the metabolism and function of iron in mTBI, and to seek a potential new treatment target for mTBI with a novel perspective through combined iron and CSF-cNs.

The role of complement in brain injury following intracerebral hemorrhage: A review

Intracerebral hemorrhage (ICH) is a significant cause of death and disability and current treatment is limited to supportive measures to reduce brain edema and secondary hematoma expansion. Current evidence suggests that the complement cascade is activated early after hemorrhage and contributes to brain edema/injury in multiple ways. The aim of this review is to summarize the most recent literature about the role of the complement cascade after ICH. Primary literature demonstrating complement mediated brain edema and neurologic injury through the membrane attack complex (MAC) as well as C3a and C5a are reviewed. Further, attenuation of brain edema and improved functional outcomes are demonstrated after inhibition of specific components of the complement cascade. Conversely, complement also plays a significant role in neurologic recovery after ICH and in other neurologic disorders. We conclude that the role of complement after ICH is complex. Understanding the role of complement after ICH is essential and may elucidate possible interventions to reduce brain edema and injury.

IL-20R Activation via rIL-19 Enhances Hematoma Resolution through the IL-20R1/ERK/Nrf2 Pathway in an Experimental GMH Rat Pup Model

Aims

Blood clots play the primary role in neurological deficits after germinal matrix hemorrhage (GMH). Previous studies have shown a beneficial effect in blood clot clearance after hemorrhagic stroke. The purpose of this study is to investigate interleukin-19's role in hematoma clearance after GMH and its underlying mechanism of IL-20R1/ERK/Nrf2 signaling pathway.

Methods

A total of 240 Sprague-Dawley P7 rat pups were used. GMH was induced by intraparenchymal injection of bacterial collagenase. rIL-19 was administered intranasally 1 hour post-GMH. IL-20R1 CRISPR was administered intracerebroventricularly, or Nrf2 antagonist ML385 was administered intraperitoneally 48 hours and 1 hour before GMH induction, respectively. Neurobehavior, Western blot, immunohistochemistry, histology, and hemoglobin assay were used to evaluate treatment regiments in the short- and long-term.

Results

Endogenous IL-19, IL-20R1, IL-20R2, and scavenger receptor CD163 were increased after GMH. rIL-19 treatment improved neurological deficits, reduced hematoma volume and hemoglobin content, reduced ventriculomegaly, and attenuated cortical thickness loss. Additionally, treatment increased ERK, Nrf2, and CD163 expression, whereas IL-20R1 CRISPR-knockdown plasmid and ML385 inhibited the effects of rIL-19 on CD163 expression.

Conclusion

rIL-19 treatment improved hematoma clearance and attenuated neurological deficits induced by GMH, which was mediated through the upregulation of the IL-20R1/ERK/Nrf2 pathways. rIL-19 treatment may provide a promising therapeutic strategy for the GMH patient population.

The Chemical Basis of Intracerebral Hemorrhage and Cell Toxicity With Contributions From Eryptosis and Ferroptosis

Intracerebral hemorrhage (ICH) is a particularly devastating event both because of the direct injury from space-occupying blood to the sequelae of the brain exposed to free blood components from which it is normally protected. Not surprisingly, the usual metabolic and energy pathways are overwhelmed in this situation. In this review article, we detail the complexity of red blood cell degradation, the contribution of eryptosis leading to hemoglobin breakdown into its constituents, the participants in that process, and the points at which injury can be propagated such as elaboration of toxic radicals through the metabolism of the breakdown products. Two prominent products of this breakdown sequence, hemin, and iron, induce a variety of pathologies including free radical damage and DNA breakage, which appear to include events independent from typical oxidative DNA injury. As a result of this confluence of damaging elements, multiple pathways of injury, cell death, and survival are likely engaged including ferroptosis (which may be the same as oxytosis but viewed from a different perspective) and senescence, suggesting that targeting any single cause will likely not be a sufficient strategy to maximally improve outcome. Combination therapies in addition to safe methods to reduce blood burden should be pursued.

Mechanism of Ferroptosis and Its Relationships With Other Types of Programmed Cell Death: Insights for Potential Interventions After Intracerebral Hemorrhage

Intracerebral hemorrhage (ICH) is a fatal cerebrovascular disease with high morbidity and mortality, for which no effective therapies are currently available. Brain tissue damage caused by ICH is mediated by a newly identified form of non-apoptotic programmed cell death, called ferroptosis. Ferroptosis is characterized by the iron-induced accumulation of lipid reactive oxygen species (ROS), leading to intracellular oxidative stress. Lipid ROS cause damage to nucleic acids, proteins, and cell membranes, eventually resulting in ferroptosis. Numerous biological processes are involved in ferroptosis, including iron metabolism, lipid peroxidation, and glutathione biosynthesis; therefore, iron chelators, lipophilic antioxidants, and other specific inhibitors can suppress ferroptosis, suggesting that these modulators are beneficial for treating brain injury due to ICH. Accumulating evidence indicates that ferroptosis differs from other types of programmed cell death, such as necroptosis, apoptosis, oxytosis, and pyroptosis, in terms of ultrastructural characteristics, signaling pathways, and outcomes. Although several studies have emphasized the importance of ferroptosis due to ICH, the detailed mechanism underlying ferroptosis remains unclear. This review summarizes the available evidence on the mechanism underlying ferroptosis and its relationship with other types of cell death, with the aim to identify therapeutic targets and potential interventions for ICH.

Targeting connexin 43 provides anti-inflammatory effects after intracerebral hemorrhage injury by regulating YAP signaling

Background

In the central nervous system (CNS), connexin 43 (Cx43) is mainly expressed in astrocytes and regulates astrocytic network homeostasis. Similar to Cx43 overexpression, abnormal excessive opening of Cx43 hemichannels (Cx43Hcs) on reactive astrocytes aggravates the inflammatory response and cell death in CNS pathologies. However, the role of excessive Cx43Hc opening in intracerebral hemorrhage (ICH) injury is not clear.

Methods

Hemin stimulation in primary cells and collagenase IV injection in C57BL/6J (B6) mice were used as ICH models in vitro and in vivo. After ICH injury, the Cx43 mimetic peptide Gap19 was used for treatment. Ethidium bromide (EtBr) uptake assays were used to measure the opening of Cx43Hcs. Western blotting and immunofluorescence were used to measure protein expression. qRT-PCR and ELISA were used to determine the levels of cytokines. Coimmunoprecipitation (Co-IP) and the Duolink in situ proximity ligation assay (PLA) were applied to measure the association between proteins.

Results

In this study, Cx43 expression upregulation and excessive Cx43Hc opening was observed in mice after ICH injury. Delayed treatment with Gap19 significantly alleviated hematoma volume and neurological deficits after ICH injury. In addition, Gap19 decreased inflammatory cytokine levels in the tissue surrounding the hematoma and decreased reactive astrogliosis after ICH injury in vitro and in vivo. Intriguingly, Cx43 transcriptional activity and expression in astrocytes were significantly increased after hemin stimulation in culture. However, Gap19 treatment downregulated astrocytic Cx43 expression through the ubiquitin-proteasome pathway without affecting Cx43 transcription. Additionally, our data showed that Gap19 increased Yes-associated protein (YAP) nuclear translocation. This subsequently upregulated SOCS1 and SOCS3 expression and then inhibited the TLR4-NFκB and JAK2-STAT3 pathways in hemin-stimulated astrocytes. Finally, the YAP inhibitor, verteporfin (VP), reversed the anti-inflammatory effect of Gap19 in vitro and almost completely blocked its protective effects in vivo after ICH injury.

Conclusions

This study provides new insight into potential treatment strategies for ICH injury involving astroglial Cx43 and Cx43Hcs. Suppression of abnormal astroglial Cx43 expression and Cx43Hc opening by Gap19 has anti-inflammatory and neuroprotective effects after ICH injury.

Intra-hematomal White Matter Tracts Act As a Scaffold for Macrophage Infiltration After Intracerebral Hemorrhage

Intracerebral hemorrhage (ICH) is a stroke subtype with high mortality and severe morbidity. Hemorrhages frequently develop within the white matter, but whether white matter fibers within the hematoma survive after ICH has not been well studied. The current study examines whether white matter fibers persist in the hematoma after ICH, fibers that might be impacted by evacuation, and their relationship to macrophage infiltration in a porcine model. Male piglets had 2.5 ml blood with or without CD47 blocking antibody injected into the right frontal lobe. Brains were harvested from 3 days to 2 months after ICH for brain histology. White matter fibers were detected within the hematoma 3 and 7 days after hemorrhage by brain histology and myelin basic protein immunohistochemistry. White matter still remained in the hematoma cavity at 2 months after ICH. Macrophage scavenger receptor-1 positive macrophages/microglia and heme oxygenase-1 positive cells infiltrated into the hematoma along the intra-hematomal white matter fibers at 3 and 7 days after ICH. Treatment with CD47 blocking antibody enhanced the infiltration of these cells. In conclusion, white matter fibers exist within the hematoma after ICH and macrophages/microglia may use such fibers as a scaffold to infiltrate into the hematoma and aid in hematoma clearance.

Recombinant CCL17 Enhances Hematoma Resolution and Activation of CCR4/ERK/Nrf2/CD163 Signaling Pathway After Intracerebral Hemorrhage in Mice

Hematoma is a crucial factor leading to poor prognosis after intracerebral hemorrhage (ICH). Promoting microglial phagocytosis to enhance hematoma resolution may be an important therapeutic target for recovery after ICH. C-C chemokine receptor 4 (CCR4) is important for regulating immune balance in the central nervous system. However, whether CCR4 activation can attenuate hematoma after ICH remains unknown. We aimed to evaluate whether CCL17 (a specific ligand of CCR4) treatment can promote hematoma resolution through CCR4/ERK/Nrf2/CD163 pathway after ICH. A total of 261 adult male CD1 mice were used. Mice were subjected to intrastriatal injection of autologous blood to induce ICH and randomly assigned to receive recombinant CCL17 (rCCL17) or vehicle which was administered intranasally at 1 h after ICH. To elucidate the underlying mechanism, C021, a selective inhibitor of CCR4 and ML385 and a selective inhibitor of Nrf2 were administered 1 h prior to ICH induction. Clustered regularly interspaced short palindromic repeats (CRISPR) knockout for CD163 was administered by intracerebroventricular injection at 48 h before ICH. Brain edema, short- and long-term neurobehavior evaluation, hematoma volume, hemoglobin content, western blot, and immunofluorescence staining were performed. Endogenous CCL17, CCR4, and CD163 expression increased and peaked at 72 h after ICH. CCR4 was expressed by microglia. CCR4 activation with rCCL17 significantly improved neurobehavioral scores and reduced hematoma volume and brain edema compared with vehicle. Moreover, rCCL17 treatment significantly promoted phosphorylation of ERK1/2, increased the expression Nrf2, and upregulated CD163 expression after ICH. The protective effects of rCCL17 were abolished by administration of C021, ML385, and CD163 CRISPR knockout. This study demonstrated that CCR4 activation with rCCL17 promoted hematoma resolution by increasing CD163 expression and CCR4/ERK/Nrf2 pathway activation after ICH, thereby reducing brain edema and improving neurological function. Overall, our study suggests that CCR4 activation may be a potential therapeutic strategy to attenuate hematoma in early brain injury after ICH.