Early Erythrolysis in the Hematoma 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 Complement C1qa in Experimental Intracerebral Hemorrhage

Evidence indicates that the complement system is activated and plays a role in brain injury after intracerebral hemorrhage (ICH). Most studies have focused on the role of C3, C5 and the membrane attack complex. The purpose of this study was to investigate the potential impact of complement C1q, a key upstream component of the classical pathway, on ICH-induced brain injury. Wild-type (WT) and C1qa knock out (KO) mice were compared using an autologous blood injection ICH model. Magnetic resonance imaging (MRI) was performed on days 1, 3 and 7 and brains harvested on days 3 and 7 for immunohistochemistry to examine brain injury mechanisms. WT and C1qa KO mice also received an intracerebral injection of thrombin, a key factor in ICH-induced brain injury. Following MRI scans, brains were harvested for immunohistochemistry on day 1. In comparison to WT mice, C1qa KO mice had reduced hematoma erythrolysis and neutrophil infiltration after ICH. However, they also had delayed hematoma clearance, which was associated with reduced induction of phagocytic multinuclear giant cells, and increased perihematomal neuronal damage. After thrombin injection, C1qa KO mice had smaller lesion volumes, less neuronal loss, reduced neutrophil infiltration, and less BBB damage. C1qa knockout has beneficial and detrimental effects on ICH-induced brain injury mechanisms, but a consistent beneficial effect after thrombin injection. Strategies to balance the roles of C1q after ICH may represent a promising therapeutic direction.

Neuroprotective effect of Naochuxue prescription on intracerebral hemorrhage: inhibition of autophagy downregulating high mobility group box-1

OBJECTIVE

To determine the molecular mechanisms underlying the neuroprotective effects of Naochuxue prescription (,NCXP) in rats with intracerebral hemorrhage (ICH).

METHODS

Sprague-Dawley rats were injected with collagenase to generate ICH models, which were then randomly divided into six groups, including control, sham, model, and three intervention groups. The intervention groups received different doses of NCXP (0.13, 0.26, and 0.52 g/kg) daily for 10 d. High-performance liquid chromatography (HPLC) was used to analyze the chemical characteristics of NCXP. The neurobehavioral outcomes of the rats were evaluated using neurological deficit scores (Zea Longa 5) and the corner turn test. Pathomorphological changes in perihematomal tissues after ICH were observed using hematoxylin and eosin staining. Immunohistochemistry (IHC) was used to detect the inflammation expression of interleukin 6 (IL-6) and toll-like receptor 4 (TLR4). High mobility group box-1 (HMGB1), Beclin1, microtubule-associated protein 1 light chain 3 beta (LC3), and sequestosome 1 (p62) were detected using real-time quantitative polymerase chain reaction and Western blotting in perihematomal tissues.

RESULTS

HPLC showed that the NCXP had good stability. Rats with ICH had severe neurological function deficits compared to the control group. IHC results showed that NCXP significantly downregulated the expression of the inflammatory proteins IL-6 and TLR4. ICH rats treated with NCXP showed less neurological injury than the model group, accompanied by a significantly decreased expression of HMGB1, Beclin1, and LC3 and an increased expression of p62.

CONCLUSIONS

The neuroprotective effect of NCXP alleviated inflammation and autophagy possibly by downregulating HMGB1 expression. However, further research on the signaling pathways is required to verify this hypothesis.

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.

MR Imaging-based Biomarker Development in Hemorrhagic Stroke Patients Including Brain Iron Quantification, Diffusion Tensor Imaging, and Phenomenon of Ultra-early Erythrolysis

This review article discusses the role of MR imaging-based biomarkers in understanding and managing hemorrhagic strokes, focusing on intracerebral hemorrhage (ICH) and aneurysmal subarachnoid hemorrhage. ICH is a severe type of stroke with high mortality and morbidity rates, primarily caused by the rupture of small blood vessels in the brain, resulting in hematoma formation. MR imaging-based biomarkers, including brain iron quantification, ultra-early erythrolysis detection, and diffusion tensor imaging, offer valuable insights for hemorrhagic stroke management. These biomarkers could improve early diagnosis, risk stratification, treatment monitoring, and patient outcomes in the future, revolutionizing our approach to hemorrhagic strokes.

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.

Role of mass effect on neuronal iron deposition after intracerebral hemorrhage

Mass effect after intracerebral hemorrhage (ICH) not only mechanically induces the brain damage, but also influences the progress of secondary brain damage. However, the influence of mass effect on the iron overload after ICH is still unclear. Here, a fixed volume of ferrous chloride solution and different volumes of poly(N-isopropylacrylamide) (PNIPAM) hydrogel were co-injected into the right basal ganglia of rats to establish the ICH model with certain degree of iron deposition but different degrees of mass effect. We found that mass effect significantly increased the iron deposition on neuronal cells at 6 h after ICH in a volume-dependent manner. Furthermore, the upregulation of Piezo-2, divalent metal transporter 1 (DMT1), transferrin receptor (TfR), and ferroptosis expressions were noted as the increase of mass effect. In addition, the pERK1/2 inhibitor PD98059 treated ICH rats reversed the upregulation of iron uptake protein and ferroptosis. Our findings revealed the relationship between mass effect and the iron uptake and ferroptosis, which are benefit to understand the brain damage process after ICH.

Pathophysiology, Management, and Therapeutics in Subarachnoid Hemorrhage and Delayed Cerebral Ischemia: An Overview

Subarachnoid hemorrhage (SAH) is a type of hemorrhagic stroke resulting from the rupture of an arterial vessel within the brain. Unlike other stroke types, SAH affects both young adults (mid-40s) and the geriatric population. Patients with SAH often experience significant neurological deficits, leading to a substantial societal burden in terms of lost potential years of life. This review provides a comprehensive overview of SAH, examining its development across different stages (early, intermediate, and late) and highlighting the pathophysiological and pathohistological processes specific to each phase. The clinical management of SAH is also explored, focusing on tailored treatments and interventions to address the unique pathological changes that occur during each stage. Additionally, the paper reviews current treatment modalities and pharmacological interventions based on the evolving guidelines provided by the American Heart Association (AHA). Recent advances in our understanding of SAH will facilitate clinicians' improved management of SAH to reduce the incidence of delayed cerebral ischemia in patients.

BCL-3 Promotes Intracerebral Hemorrhage Progression by Increasing Blood-Brain Barrier Permeability, Inflammation, and Cell Apoptosis via Endoplasmic Reticulum Stress

Background

Intracerebral hemorrhage (ICH) is among the common types of stroke with high mortality and morbidity. Molecular biomarker selection is crucial for ICH diagnosis and treatment. However, the identification of ICH-related biomarkers remains inadequate.

Materials and Methods

In vivo and in vitro ICH models were generated and transfected with silenced B-cell lymphoma-3 (BCL-3 and siRNA BCL-3), overexpressed BCL-3, and endoplasmic reticulum stress (ERS) agonist (2-CLHA). Hematoxylin-eosin staining and transmission electron microscopy were used to observe the transfected cells. RNA sequencing was performed in vivo on the sham and ICH groups. The blood-brain barrier (BBB) permeability was evaluated by determining Evans blue dye extravasation, transendothelial electrical resistance, and paracellular permeability. Moreover, tight junction-, cell apoptosis-, and endoplasmic reticulum stress- (ERS-) related proteins were evaluated through real-time quantitative PCR, western blotting, immunohistochemistry, and TUNEL staining. The levels of inflammatory cytokines were measured through the enzyme-linked immunosorbent assay.

Results

RNA-seq revealed that BCL-3 acts as a key player. BCL-3 promotes ICH progression by increasing BBB permeability, ERS, inflammation, and cell apoptosis. Silencing of BCL-3 slows ICH progression by reducing BBB permeability and inflammation and terminating cell apoptosis and ERS in vitro and in vivo.

Conclusion

Our study identified ICH biomarkers and elucidated the role of BCL-3 in ICH for the first time.

Intracerebral Hemorrhage Models and Behavioral Tests in Rodents

Intracerebral hemorrhage (ICH) is one of the common types of stroke, which can cause neurological dysfunction. In preclinical ICH studies, researchers often established rodent models by donor/autologous whole blood or a collagenase injection. White matter injury (WMI) can result from primary and secondary injuries after ICH. WMI can lead to short- and long-term neurological impairment, and functional recovery can assess the effect of drug therapy after ICH. Therefore, researchers have devised various behavioral tests to assess dysfunction. This review compares the two ICH modeling methods in rodents and summarizes the pathological mechanisms underlying dysfunction after ICH. We also summarize the functions and characteristics of various behavioral methods, including sensation, motion, emotion, and cognition, to assist researchers in selecting the appropriate tests for preclinical ICH research.

Intracranial hemorrhage management in the multi-omics era

Intracranial hemorrhage (ICH) is a devastating disorder. Neuroprotective strategies that prevent tissue injury and improve functional outcomes have been identified in multiple animal models of ICH. However, these potential interventions in clinical trials produced generally disappointing results. With progress in omics, studies of omics data, including genomics, transcriptomics, epigenetics, proteomics, metabolomics, and the gut microbiome, may help promote precision medicine. In this review, we focused on introducing the applications of all omics in ICH and shed light on all of the considerable advantages to systematically analyze the necessity and importance of multiple omics technology in ICH.

Exploring the pharmacological mechanism of Naoxueshu oral liquid in the treatment of intracerebral hemorrhage through weighted gene co-expression network analysis, network pharmacological and experimental validation

BACKGROUND

Intracerebral hemorrhage (ICH) is a life-threatening stroke subtype with high rates of disability and mortality. Naoxueshu oral liquid is a proprietary Chinese medicine that absorbs hematoma and exhibits neuroprotective effects in patients with ICH. However, the underlying mechanisms remain obscure.

PURPOSE

Exploring and elucidating the pharmacological mechanism of Naoxueshu oral liquid in the treatment of ICH.

STUDY DESIGN AND METHODS

The Gene Expression Omnibus (GEO) database was used to download the gene expression data on ICH. ICH-related hub modules were obtained by weighted gene co-expression network analysis (WGCNA) of differentially co-expressed genes (DEGs). The Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) enrichment analyses were conducted using the obtained key modules to identify the ICH-related signaling pathways. Network pharmacology technology was applied to forecast the targets of Naoxueshu oral liquid and to establish a protein-protein interaction (PPI) network of overlapping targets between Naoxueshu oral liquid and ICH. Functional annotation and enrichment pathway analyses of the intersectional targets were performed using the omicsbean database. Finally, we verified the therapeutic role and mechanism of Naoxueshu oral liquid in ICH through molecular docking and experiments.

RESULTS

Through the WGCNA analysis, combined with network pharmacology, it was found that immune inflammation was closely related to the early pathological mechanism of ICH. Naoxueshu oral liquid suppressed the inflammatory response; hence, it could be a potential drug for ICH treatment. Molecular docking further confirmed that the effective components of Naoxueshu oral liquid docked well with CD163. Finally, the experimental results showed that Naoxueshu oral liquid treatment in the ICH rat model attenuated neurological deficits and neuronal injury, decreased hematoma volume, and promoted hematoma absorption. In addition, Naoxueshu oral liquid treatment also significantly increased the levels of Arg-1, CD163, Nrf2, and HO-1 around hematoma after ICH.

CONCLUSION

This study demonstrated that Naoxueshu oral liquid attenuated neurological deficits and accelerated hematoma absorption, possibly by suppressing inflammatory responses, which might be related to the regulation of Nrf2/CD163/HO-1 that interfered with the activation of M2 microglia, thus accelerating the clearance and decomposition of hemoglobin in the hematoma.

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.

Orexin-A exerts neuroprotective effect in experimental intracerebral hemorrhage by suppressing autophagy via OXR1-mediated ERK/mTOR signaling pathway

Background

Orexin-A (OXA) is a polypeptide produced in the hypothalamus, which binds to specific receptors and exerts multiple physiological effects. Autophagy plays a vital role in early brain injury (EBI) after intracerebral hemorrhage (ICH). However, the relationship between OXA and autophagy after ICH has not been confirmed.

Methods

In this study, the protective role of OXA was investigated in a model of hemin-induced injury in PC12 cells and blood-injection ICH model in rats, and its potential molecular mechanism was clarified. Neurobehavioral tests, brain water content, and pathologic morphology were assessed after ICH. Cell survival rate was determined using Cell Counting Kit-8 (CCK-8), while apoptosis was detected using flow cytometry. The autophagy protein LC3 that was originally identified as microtubule-associated protein 1 light 3 was evaluated by immunohistochemistry. The ultrastructural changes of cells following ICH were observed by transmission electron microscopy. Western blotting was performed to determine the expression levels of LC3, p62/SQSTM1 (p62), phosphorylated extracellular signal-regulated kinase 1/2 (p-ERK_1/2), total extracellular signal-regulated kinase 1/2 (t-ERK_1/2), mammalian target of rapamycin (mTOR), and phosphorylated mammalian target of rapamycin (p-mTOR).

Results

OXA treatment significantly improved neurofunctional outcomes, reduced brain edema, and alleviated neuronal apoptosis. OXA administration upregulated p-mTOR and p62, while it downregulated p-ERK_1/2 and LC3; this effect was reversed by the orexin receptor 1 (OXR1) antagonist SB-334867.

Conclusions

This study demonstrates that OXA suppresses autophagy via the OXR1-mediated ERK/mTOR signaling pathway to exert neuroprotective effects, and it might provide a novel therapeutic approach in patients suffering from ICH.

Melatonin as an Antioxidant Agent in Stroke: An Updated Review

Stroke is a devastating disease associated with high mortality and disability worldwide, and is generally classified as ischemic or hemorrhagic, which share certain similar pathophysiological processes. Oxidative stress is a critical factor involved in stroke-induced injury, which not only directly damages brain tissue, but also enhances a series of pathological signaling cascades, contributing to inflammation, brain edema, and neuronal death. To alleviate these serious secondary brain injuries, neuroprotective agents targeting oxidative stress inhibition may serve as a promising treatment strategy. Melatonin is a hormone secreted by the pineal gland, and has various properties, such as antioxidation, anti-inflammation, circadian rhythm modulation, and promotion of tissue regeneration. Numerous animal experiments studying stroke have confirmed that melatonin exerts considerable neuroprotective effects, partially via anti-oxidative stress. In this review, we introduce the possible role of melatonin as an antioxidant in the treatment of stroke based on the latest published studies of animal experiments and clinical research.

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.

Molecular, Pathological, Clinical, and Therapeutic Aspects of Perihematomal Edema in Different Stages of Intracerebral Hemorrhage

Acute intracerebral hemorrhage (ICH) is a devastating type of stroke worldwide. Neuronal destruction involved in the brain damage process caused by ICH includes a primary injury formed by the mass effect of the hematoma and a secondary injury induced by the degradation products of a blood clot. Additionally, factors in the coagulation cascade and complement activation process also contribute to secondary brain injury by promoting the disruption of the blood-brain barrier and neuronal cell degeneration by enhancing the inflammatory response, oxidative stress, etc. Although treatment options for direct damage are limited, various strategies have been proposed to treat secondary injury post-ICH. Perihematomal edema (PHE) is a potential surrogate marker for secondary injury and may contribute to poor outcomes after ICH. Therefore, it is essential to investigate the underlying pathological mechanism, evolution, and potential therapeutic strategies to treat PHE. Here, we review the pathophysiology and imaging characteristics of PHE at different stages after acute ICH. As illustrated in preclinical and clinical studies, we discussed the merits and limitations of varying PHE quantification protocols, including absolute PHE volume, relative PHE volume, and extension distance calculated with images and other techniques. Importantly, this review summarizes the factors that affect PHE by focusing on traditional variables, the cerebral venous drainage system, and the brain lymphatic drainage system. Finally, to facilitate translational research, we analyze why the relationship between PHE and the functional outcome of ICH is currently controversial. We also emphasize promising therapeutic approaches that modulate multiple targets to alleviate PHE and promote neurologic recovery after acute ICH.

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.

Secondary brain injury after polystyrene microplastic-induced intracerebral hemorrhage is associated with inflammation and pyroptosis

Unlike regular environmental pollutants, microplastics cannot dissolve in liquids. Physical contact of microplastic (MPs) with tissue can damage tissue structure, and it is unclear how this physical secondary injury affects brain tissue. Through CTD database analysis, it was determined that cerebral ischemia may be one of the main ways of brain tissue damage caused by MPs, and inflammatory response may play a key role in it. In the present study, PS-MPs (L-PS group:1 mg/L, M - PS group:10 mg/L, H-PS group: 100 mg/L in water) were assessed to brain tissue damage in chicken after six weeks of continuous exposure. Exposure to PS-MPs caused cerebral hemorrhage as well as generation of microthrombi and loss of Purkinje cells. Intracerebral hemorrhage caused a strong infiltration of inflammatory cells and activated the ASC-NLRP3-GSDMD signaling pathway to induce pyroptosis. Disruption of mitochondrial dynamics by PS-MPs exposure disrupts mitochondrial function and activates AMPK signaling. In conclusion, this study explored the mechanism regulation of subsequent brain injury from the perspective of physical injury (cerebral hemorrhage) of PS-MPs. To provide a reference for elucidating the neurotoxicity induced by microplastic exposure.

Perspectives on the mechanism of pyroptosis after intracerebral hemorrhage

Intracerebral hemorrhage (ICH) is a highly harmful neurological disorder with high rates of mortality, disability, and recurrence. However, effective therapies are not currently available. Secondary immune injury and cell death are the leading causes of brain injury and a poor prognosis. Pyroptosis is a recently discovered form of programmed cell death that differs from apoptosis and necrosis and is mediated by gasdermin proteins. Pyroptosis is caused by multiple pathways that eventually form pores in the cell membrane, facilitating the release of inflammatory substances and causing the cell to rupture and die. Pyroptosis occurs in neurons, glial cells, and endothelial cells after ICH. Furthermore, pyroptosis causes cell death and releases inflammatory factors such as interleukin (IL)-1β and IL-18, leading to a secondary immune-inflammatory response and further brain damage. The NOD-like receptor protein 3 (NLRP3)/caspase-1/gasdermin D (GSDMD) pathway plays the most critical role in pyroptosis after ICH. Pyroptosis can be inhibited by directly targeting NLRP3 or its upstream molecules, or directly interfering with caspase-1 expression and GSDMD formation, thus significantly improving the prognosis of ICH. The present review discusses key pathological pathways and regulatory mechanisms of pyroptosis after ICH and suggests possible intervention strategies to mitigate pyroptosis and brain dysfunction after ICH.

Intracerebral hemorrhage and thrombin-induced alterations in cerebral microvessel matrix

Four phase III clinical trials of oral direct factor Xa or thrombin inhibitors demonstrated significantly lower intracranial hemorrhage compared to warfarin in patients with nonvalvular-atrial fibrillation. This is counter-intuitive to the principle that inhibiting thrombosis should increase hemorrhagic risk. We tested the novel hypothesis that anti-thrombin activity decreases the risk of intracerebral hemorrhage by directly inhibiting thrombin-mediated degradation of cerebral microvessel basal lamina matrix, responsible for preventing hemorrhage. Collagen IV, laminin, and perlecan each contain one or more copies of the unique α-thrombin cleavage site consensus sequence. In blinded controlled experiments, α-thrombin significantly degraded each matrix protein in vitro and in vivo in a concentration-dependent fashion. In vivo stereotaxic injection of α-thrombin significantly increased permeability, local IgG extravasation, and hemoglobin (Hgb) deposition together with microvessel matrix degradation in a mouse model. In all formats the direct anti-thrombin dabigatran completely inhibited matrix degradation by α-thrombin. Fourteen-day oral exposure to dabigatran etexilate-containing chow completely inhibited matrix degradation, the permeability to large molecules, and cerebral hemorrhage associated with α-thrombin. These experiments demonstrate that thrombin can degrade microvessel matrix, leading to hemorrhage, and that inhibition of microvessel matrix degradation by α-thrombin decreases cerebral hemorrhage. Implications for focal ischemia and other conditions are discussed.

The role of Tenascin C in intracerebral hemorrhage-induced secondary brain injury in rats via induction of neuronal cell death and neuroinflammation

BACKGROUND

Spontaneous intracerebral hemorrhage (ICH) is a major cause of stroke that causes high rates of disability and mortality in adults. Tenascin C (TNC) protein, one of the matricellular proteins associated with platelet-derived growth factor receptor (PDGFR) activation, has been reported to induce neuronal apoptosis. However, the role and underlying mechanisms of TNC in ICH-induced secondary brain injury (SBI) have not yet been fully explained. The main purpose of this study was to explore the role of TNC and its potential mechanisms in ICH.

METHODS

An ICH model was established by injecting autologous blood into the right basal ganglia in male Sprague Dawley (SD) rats, and imatinib, an inhibitor of PDGFR, was used to inhibit the release of TNC.

RESULTS

We found that TNC protein was significantly increased in the brain tissues after ICH and expressed in both neurons and microglia. We also found that the TNC level was elevated in the cerebrospinal fluid (CSF) after ICH. Additionally, we observed that the infiltration of activated microglia and the release of TNFα and IL-1β induced by ICH were decreased after inhibition of the protein levels of TNC and cleaved-TNC by a chemical inhibitor (imatinib). Furthermore, imatinib improved neuronal cell death and neurobehavioral abnormalities induced by ICH.

CONCLUSION

In summary, our study revealed that TNC protein plays an important role in ICH-induced SBI, and inhibition of TNC could alleviate ICH-induced neuroinflammation, neuronal cell death, and neurobehaviour. Therefore, TNC may be a potential therapeutic target for ICH-induced SBI.

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.

Intracerebral Hemorrhage-Induced Cognitive Impairment in Rats Is Associated With Brain Atrophy, Hypometabolism, and Network Dysconnectivity

The mechanisms underlying intracerebral hemorrhage (ICH)-related cognitive impairment (CI) remain unclear. Long-term structural and functional changes were investigated in the brains of healthy male and female Wistar rats after experimental ICH. Following double injection of autologous blood, rats underwent short-term (onset, 3 and 7 days) and long-term (3 and 6 months) radiological assessment and behavioral tests exploring spontaneous locomotion, anxiety-like behavior and working memory, spatial recognition memory and visual recognition memory. Volumetric and metabolic changes in brain areas were examined by 7Tesla-MRI and [18F] FDG-PET, respectively. Brain connectomic disorders and maladaptive processes were seeked through brain metabolic connectivity analysis and atrophy-related network analysis. From an initial hematoma mean volume of 23.35 ± 9.50 mm³, we found early spontaneous locomotor recovery and significant spontaneous blood resorption (≈ 40% of the initial lesion) from days 0 to 7. After 3 and 6 months, ICH rats exhibited CI in several domains as compared to the sham group (working memory: 58.1 ± 1.2 vs. 70.7 ± 1.2%, p < 0.001; spatial recognition memory: 48.7 ± 1.9 vs. 64 ± 1.8%, p < 0.001 and visual recognition memory: 0.14 ± 0.05 vs. 0.33 ± 0.04, p = 0.013, in female only). Rats that experienced ICH had remote and concomitant cerebral atrophy and hypometabolism of ipsilateral striatum, thalamus, limbic system and cortical areas (temporal and parietal lobes). Interestingly, both structural and metabolic deterioration was found in the limbic system connected to the affected site, but remotely from the initial insult. On the other hand, increased activity and functional connectivity occurred in the contralateral hemisphere. These connectomics results showed that both maladaptative and compensation processes coexist in the rat brain following ICH, even at young age and in a disease-free setting. These radiological findings deepen our understanding of ICH-related CI and may serve as biomarkers in the view of future therapeutic intervention.

Reduction of lactoferrin aggravates neuronal ferroptosis after intracerebral hemorrhagic stroke in hyperglycemic mice

Diabetic hyperglycemia aggravates the prognosis of intracerebral hemorrhagic stroke (ICH) in the clinic. In addition to hematoma expansion and increased inflammation, how diabetic hyperglycemia affects the outcomes of ICH is still unclear. We found that streptozotocin-induced diabetic hyperglycemia not only increased neutrophil infiltration, but also changed the gene expression profile of neutrophils, including lactoferrin (Ltf) encoding gene Ltf. Peroxisome proliferator-activated receptor γ (PPARγ) transcribed Ltf and the lack of neutrophilic Ltf transcription and secretion exacerbated neuronal ferroptosis by accumulating intraneuronal iron. Furthermore, the administration of recombinant Ltf protected against neuronal ferroptosis and improved neurobehavior in hyperglycemic ICH mice, and vice versa. These results indicate that supplementing Ltf or inhibiting neuronal ferroptosis are promising potential strategies to improve the acute outcomes of diabetic ICH in the clinic.

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Neutrophil infiltration and ICH prognosis are aggravated in hyperglycemic mice.

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Hyperglycemia impairs PPAR-γ activity and decreases Ltf expression in neutrophils.

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The lack of neutrophilic Ltf fails to decrease intraneuronal iron and ferroptosis.

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rLtf eases neuronal ferroptosis and neurologic deficits in hyperglycemic ICH mice.

Traditional Chinese medicine use in the pathophysiological processes of intracerebral hemorrhage and comparison with conventional therapy

Intracerebral hemorrhage (ICH) refers to hemorrhage caused by non-traumatic vascular rupture in the brain parenchyma, which is characterized by acute onset, severe illness, and high mortality and disability. The influx of blood into the brain tissue after cerebrovascular rupture causes severe brain damage, including primary injury caused by persistent hemorrhage and secondary brain injury (SBI) induced by hematoma. The mechanism of brain injury is complicated and is a significant cause of disability after ICH. Therefore, it is essential to understand the mechanism of brain injury after ICH to develop drugs to prevent and treat ICH. Studies have confirmed that many traditional Chinese medicines (TCM) can reduce brain injury by improving neurotoxicity, inflammation, oxidative stress (OS), blood-brain barrier (BBB), apoptosis, and neurological dysfunction after ICH. Starting from the pathophysiological process of brain injury after ICH, this paper summarizes the mechanisms by which TCM improves cerebral injury after ICH and its comparison with conventional western medicine, so as to provide clues and a reference for the clinical application of TCM in the prevention and treatment of hemorrhagic stroke and further research and development of new drugs.

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.

Longitudinal Observation of Asymmetric Iron Deposition in an Intracerebral Hemorrhage Model Using Quantitative Susceptibility Mapping

Quantitative susceptibility mapping (QSM) is used to obtain quantitative magnetic susceptibility maps of materials from magnitude and phase images acquired by three-dimensional gradient-echo using inverse problem-solving. Few preclinical studies have evaluated the intracerebral hemorrhage (ICH) model and asymmetric iron deposition. We created a rat model of ICH and compared QSM and conventional magnetic resonance imaging (MRI) during the longitudinal evaluation of ICH. Collagenase was injected in the right striatum of 12-week-old Wistar rats. QSM and conventional MRI were performed on days 0, 1, 7, and 28 after surgery using 7-Tesla MRI. Susceptibility, normalized signal value, and area of the hemorrhage site were statistically compared during image analysis. Susceptibility decreased monotonically up to day 7 but increased on day 28. Other imaging methods showed a significant increase in signal from day 0 to day 1 but a decreasing trend after day 1. During the area evaluation, conventional MRI methods showed an increase from day 0 to day 1; however, decreases were observed thereafter. QSM showed a significant increase from day 0 to day 1. The temporal evaluation of ICH by QSM suggested the possibility of detecting of asymmetric iron deposition for normal brain site.

Acute T2*-Weighted Magnetic Resonance Imaging Detectable Cerebral Thrombosis in a Rat Model of Subarachnoid Hemorrhage

Subarachnoid hemorrhage (SAH) is associated with a high incidence of morbidity and mortality, particularly within the first 72 h after aneurysm rupture. We recently found ultra-early cerebral thrombosis, detectable on T2* magnetic resonance imaging (MRI), in a mouse SAH model at 4 h after onset. The current study examined whether such changes also occur in rat at 24 h after SAH, the vessels involved, whether the degree of thrombosis varied with SAH severity and brain injury, and if it differed between male and female rats. Adult Sprague Dawley rats were subjected to an endovascular perforation SAH model or sham surgery and underwent T2 and T2* MRI 24 h later. Following SAH, increased numbers of T2* hypointense vessels were detected on MRI. The number of such vessels correlated with SAH severity, as assessed by MRI-based grading of bleeding. Histologically, thrombotic vessels were found on hematoxylin and eosin staining, had a single layer of smooth muscle cells on alpha-smooth muscle actin immunostaining, and had laminin 2α/fibrinogen double labeling, suggesting venule thrombosis underlies the T2*-positive vessels on MRI. Capillary thrombosis was also detected which may follow the venous thrombosis. In both male and female rats, the number of T2*-positive thrombotic vessels correlated with T2 lesion volume and neurological function, and the number of such vessels was significantly greater in female rats. In summary, this study identified cerebral venous thrombosis 24 h following SAH in rats that could be detected with T2* MRI imaging and may contribute to SAH-induced brain injury.

Ferroptosis in Intracerebral Hemorrhage: A Panoramic Perspective of the Metabolism, Mechanism and Theranostics

Iron is one of the most crucial elements in the human body. In recent years, a kind of programmed, non-apoptotic cell death closely related to iron metabolism-called ferroptosis- has aroused much interest among many scientists. Ferroptosis also interacts with other pathways involved in cell death including iron abnormality, the cystine/glutamate antiporter and lipid peroxidation. Together these pathological pathways exert great impacts on intracerebral hemorrhage (ICH), a lethal cerebrovascular disease with a high incidence rate and mortality rate. Furthermore, the ferroptosis also affects different brain cells (neurons and neuroglial cells) and different organelles (mitochondria and endoplasmic reticulum). Clinical treatments for ferroptosis in ICH have been closely investigated recently. This perspective provides a comprehensive summary of ferroptosis mechanisms after ICH and its interaction with other cell death patterns. Understanding the role of ferroptosis in ICH will open new windows for the future treatments and preventions for ICH and other intracerebral diseases.

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.

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.

The role of cell-free DNA in fibrinolysis for intraventricular hemorrhage

OBJECTIVE

Tissue plasminogen activator (tPA) fibrinolysis did not improve functional outcomes of patients with intraventricular hemorrhage (IVH), largely because of the unsatisfactory clot clearance. The presence of neutrophil extracellular traps (NETs) within the clot has been confirmed to impair tPA fibrinolysis, but the mechanism has been unclear. The authors hypothesized that cell-free DNA (cfDNA), the main framework of NETs, might be the important reason for the fibrinolysis resistance, and they validated the hypothesis, hoping to provide a new target to promote intraventricular fibrinolysis.

METHODS

First, cfDNA was detected in IVH clots by immunofluorescence staining in a rat model of IVH. Second, after blood (with or without exogenous cfDNA) intraventricular injection, IVH rats were given intraventricular infusion of 2 μl of saline, tPA, or tPA + DNase1 randomly. Then, the ventricular volume, animal behavior, and reactive astrocyte proliferation were assessed. Third, the IVH clots were collected for fibrinolysis assay in vitro. Finally, the effects of exogenous cfDNA in IVH were evaluated.

RESULTS

The presence of cfDNA in clots was observed as early as 1 hour after IVH. Compared with the whole-blood model, blood + cfDNA caused more severe ventricular dilation (day 7: blood 32.47 ± 2.096 mm3 vs blood + DNA 40.09 ± 2.787 mm3, p < 0.05), increased fibrinolysis resistance to tPA (day 7: tPA + DNA 26.04 ± 1.318 mm3 vs tPA 22.15 ± 1.706 mm3, p < 0.05), and further deteriorated the functional defects in rats (blood vs blood + DNA, p < 0.05). Degradation of cfDNA by DNase1 further enhanced the fibrinolysis effects on relieving the ventricular dilation (day 7: tPA + DNase1 11.67 ± 2.023 mm3 vs tPA, p < 0.05), improving the functional outcome (tPA vs tPA + DNase1, p < 0.05) and reducing periventricular astrocyte proliferation.

CONCLUSIONS

cfDNA impaired tPA fibrinolysis for IVH, and degradation of cfDNA may be a new target to improve this condition.

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

[Figure: see text].

Assessing early erythrolysis and the relationship to perihematomal iron overload and white matter survival in human intracerebral hemorrhage

AIMS

Iron released from lysed red blood cells within the hematoma plays a role in intracerebral hemorrhage (ICH)-related neurotoxicity. This study utilizes magnetic resonance imaging (MRI) to examine the time course, extent of erythrolysis, and its correlation with perihematomal iron accumulation and white matter loss.

METHODS

The feasibility of assessing proportional erythrolysis using T2* MRI was examined using pig blood phantoms with specified degrees of erythrolysis. Fifteen prospectively enrolled ICH patients had MRIs (3-Tesla) at days 1-3, 14, and 30 (termed early, subacute, and late periods, respectively). Measurement was performed on T2*, 1/T2*, and fractional anisotropy (FA) maps.

RESULTS

Pig blood phantoms showed a linear relationship between 1/T2* signal and percent erythrolysis. MRI on patients showed an increase in erythrolysis within the hematoma between the early and subacute phases after ICH, almost completing by day 14. Although perihematomal iron overload (IO) correlated with the erythrolysis extent and hematoma volume at days 14 and 30, perihematomal white matter (WM) loss significantly correlated with both, only at day 14.

CONCLUSION

MRI may reliably assess the portion of the hematoma that lyses over time after ICH. Perihematomal IO and WM loss correlate with both the erythrolysis extent and hematoma volume in the early and subacute periods following ICH.

Rapid hematoma growth triggers spreading depolarizations in experimental intracortical hemorrhage

Recurrent waves of spreading depolarization (SD) occur in brain injury and are thought to affect outcomes. What triggers SD in intracerebral hemorrhage is poorly understood. We employed intrinsic optical signaling, laser speckle flowmetry, and electrocorticography to elucidate the mechanisms triggering SD in a collagenase model of intracortical hemorrhage in mice. Hematoma growth, SD occurrence, and cortical blood flow changes were tracked. During early hemorrhage (0-4 h), 17 out of 38 mice developed SDs, which always originated from the hematoma. No SD was detected at late time points (8-52 h). Neither hematoma size, nor peri-hematoma perfusion were associated with SD occurrence. Further, arguing against ischemia as a trigger factor, normobaric hyperoxia did not inhibit SD occurrence. Instead, SDs always occurred during periods of rapid hematoma growth, which was two-fold faster immediately preceding an SD compared with the peak growth rates in animals that did not develop any SDs. Induced hypertension accelerated hematoma growth and resulted in a four-fold increase in SD occurrence compared with normotensive animals. Altogether, our data suggest that spontaneous SDs in this intracortical hemorrhage model are triggered by the mechanical distortion of tissue by rapidly growing hematomas.

The Role of NLRP3 Inflammasome in Cerebrovascular Diseases Pathology and Possible Therapeutic Targets

Cerebrovascular diseases are pathological conditions involving impaired blood flow in the brain, primarily including ischaemic stroke, intracranial haemorrhage, and subarachnoid haemorrhage. The nucleotide-binding and oligomerisation (NOD) domain-like receptor (NLR) family pyrin domain (PYD)-containing 3 (NLRP3) inflammasome is a protein complex and a vital component of the immune system. Emerging evidence has indicated that the NLRP3 inflammasome plays an important role in cerebrovascular diseases. The function of the NLRP3 inflammasome in the pathogenesis of cerebrovascular diseases remains an interesting field of research. In this review, we first summarised the pathological mechanism of cerebrovascular diseases and the pathological mechanism of the NLRP3 inflammasome in aggravating atherosclerosis and cerebrovascular diseases. Second, we outlined signalling pathways through which the NLRP3 inflammasome participates in aggravating or mitigating cerebrovascular diseases. Reactive oxygen species (ROS)/nuclear factor kappa-light-chain-enhancer of activated B cells (NF-κB), ROS/thioredoxin-interacting protein (TXNIP) and purinergic receptor-7 (P2X7R) signalling pathways can activate the NLRP3 inflammasome; activation of the NLRP3 inflammasome can aggravate cerebrovascular diseases by mediating apoptosis and pyroptosis. Autophagy/mitochondrial autophagy, nuclear factor E2-related factor-2 (Nrf2), interferon (IFN)-β, sirtuin (SIRT), and phosphoinositide 3-kinase (PI3K)/protein kinase B (AKT) reportedly alleviate cerebrovascular diseases by inhibiting NLRP3 inflammasome activation. Finally, we explored specific inhibitors of the NLRP3 inflammasome based on the two-step activation of the NLRP3 inflammasome, which can be developed as new drugs to treat cerebrovascular diseases.

CD47 blocking antibody accelerates hematoma clearance and alleviates hydrocephalus after experimental intraventricular hemorrhage

Background CD47, a glycoprotein on red blood cell membranes, inhibits phagocytosis via interaction with signal regulatory protein α on phagocytes. Our previous research has demonstrated that blocking CD47 accelerates hematoma clearance and reduces brain injury after intracerebral hemorrhage. The current study investigated whether phagocytosis or erythrocyte CD47 impacts hematoma resolution and hydrocephalus development after intraventricular hemorrhage (IVH). Methods Adult (3-month-old) male Fischer 344 rats were intraventricularly injected with 200 μl autologous blood, mixed with either CD47 blocking antibody or isotype IgG, or 200 μl saline as control. In subgroups of CD47 blocking antibody treated rats, clodronate liposomes (to deplete microglia/monocyte-derived macrophages) or control liposomes were co-injected. Magnetic resonance imaging (MRI) was used to evaluate ventricular volume and intraventricular T2* lesion volume (estimating hematoma volume). The brains were harvested after 4 or 72 h for histology to evaluate phagocytosis. Results In adult male rats, CD47 blocking antibody alleviated hydrocephalus development by day 3. In addition, the CD47 blocking antibody reduced intraventricular T2* lesion and T2* non-hypointense lesion size after IVH through day 1 to day 3. Erythrophagocytosis was observed as soon as 4 h after IVH and was enhanced on day 3. Furthermore, intra-hematoma infiltration of CD68, heme oxygenase-1 and ferritin positive phagocytes were upregulated by CD47 blockade by day 3. Clodronate liposomes co-injection caused more severe hydrocephalus and weight loss. Conclusion Blocking CD47 in the hematoma accelerated hematoma clearance and alleviated hemolysis and hydrocephalus development after IVH, suggesting CD47 might be valuable in the future treatment for IVH.

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.

Neurovascular Units and Neural-Glia Networks in Intracerebral Hemorrhage: from Mechanisms to Translation

Intracerebral hemorrhage (ICH), the most lethal type of stroke, often leads to poor outcomes in the clinic. Due to the complex mechanisms and cell-cell crosstalk during ICH, the neurovascular unit (NVU) was proposed to serve as a promising therapeutic target for ICH research. This review aims to summarize the development of pathophysiological shifts in the NVU and neural-glia networks after ICH. In addition, potential targets for ICH therapy are discussed in this review. Beyond cerebral blood flow, the NVU also plays an important role in protecting neurons, maintaining central nervous system (CNS) homeostasis, coordinating neuronal activity among supporting cells, forming and maintaining the blood-brain barrier (BBB), and regulating neuroimmune responses. During ICH, NVU dysfunction is induced, along with neuronal cell death, microglia and astrocyte activation, endothelial cell (EC) and tight junction (TJ) protein damage, and BBB disruption. In addition, it has been shown that certain targets and candidates can improve ICH-induced secondary brain injury based on an NVU and neural-glia framework. Moreover, therapeutic approaches and strategies for ICH are discussed.

Role of lipocalin-2 in extracellular peroxiredoxin 2-induced brain swelling, inflammation and neuronal death

Peroxiredoxin-2 (PRX-2) is known to be released from erythrocytes and induce brain damage after intracerebral hemorrhage (ICH); lipocalin-2 (LCN-2) is involved in neuroinflammation following ICH. This study examined the role of LCN-2 in PRX-2 induced brain injury and involved three parts. In the first part, adult male C57BL/6 wild-type (WT), LCN-2 heterozygous (LCN-2 HET), and LCN-2 knockout (LCN-2 KO) mice received either an intracaudate injection of recombinant PRX-2 or saline. In the second part, adult male C57BL/6 WT and male LCN-2 KO mice received recombinant PRX-2 with either recombinant mouse LCN-2 protein or control. In the third part, adult female C57BL/6 WT, LCN-2 HET, and LCN-2 KO mice received recombinant PRX-2. Behavioral tests, and T2- and T2*- weighted magnetic resonance imaging was obtained for all mice. Mice were then euthanized, and their brains used for Western blotting, histology and immunohistochemistry. Intracerebral PRX-2 injections resulted in increased expression of LCN-2 protein. PRX-2-induced brain swelling, neutrophil infiltration, microglia/macrophage activation, neuronal cell death, and neurological deficits were reduced in male LCN-2 HET and LCN-2 KO mice (P < 0.01) compared to WT and were exacerbated by exogenous LCN-2 co-injection. Additionally, intracerebral PRX-2 injections caused brain injury and neurological deficits in female WT mice; effects reduced in female LCN-2 KO mice. In conclusion, intracerebral injection of PRX-2 upregulates LCN-2, and LCN-2 is crucial in the effects of PRX-2 on neutrophil infiltration and microglia/macrophage activation, and ultimately brain damage.

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.

IL-4/STAT6 signaling facilitates innate hematoma resolution and neurological recovery after hemorrhagic stroke in mice

Intracerebral hemorrhage (ICH) is a devastating form of stroke affecting millions of people worldwide. Parenchymal hematoma triggers a series of reactions leading to primary and secondary brain injuries and permanent neurological deficits. Microglia and macrophages carry out hematoma clearance, thereby facilitating functional recovery after ICH. Here, we elucidate a pivotal role for the interleukin (IL)-4)/signal transducer and activator of transcription 6 (STAT6) axis in promoting long-term recovery in both blood- and collagenase-injection mouse models of ICH, through modulation of microglia/macrophage functions. In both ICH models, STAT6 was activated in microglia/macrophages (i.e., enhanced expression of phospho-STAT6 in Iba1⁺ cells). Intranasal delivery of IL-4 nanoparticles after ICH hastened STAT6 activation and facilitated hematoma resolution. IL-4 treatment improved long-term functional recovery in young and aged male and young female mice. In contrast, STAT6 knockout (KO) mice exhibited worse outcomes than WT mice in both ICH models and were less responsive to IL-4 treatment. The construction of bone marrow chimera mice demonstrated that STAT6 KO in either the CNS or periphery exacerbated ICH outcomes. STAT6 KO impaired the capacity of phagocytes to engulf red blood cells in the ICH brain and in primary cultures. Transcriptional analyses identified lower level of IL-1 receptor-like 1 (ST2) expression in microglia/macrophages of STAT6 KO mice after ICH. ST2 KO diminished the beneficial effects of IL-4 after ICH. Collectively, these data confirm the importance of IL-4/STAT6/ST2 signaling in hematoma resolution and functional recovery after ICH. Intranasal IL-4 treatment warrants further investigation as a clinically feasible therapy for ICH.

Wogonin Accelerates Hematoma Clearance and Improves Neurological Outcome via the PPAR-γ Pathway After Intracerebral Hemorrhage

Intracerebral hemorrhage (ICH) is a cerebrovascular disease with high mortality and morbidity for which effective treatments are currently lacking. Wogonin is a major flavonoid compound isolated from Scutellaria radix. Accumulating evidence suggests that wogonin plays a crucial role in anti-inflammatory and anti-oxidative stress. Treatment of microglia with nuclear receptor agonists augments the expression of phagocytosis-related genes. However, the neuroprotective effects of wogonin in ICH remain obscure. In this study, we elucidated an innovative mechanism by which wogonin acts to enhance phagocytosis in a murine model of ICH. Wogonin promoted hematoma clearance and improved neurological recovery after ICH by upregulating the expression of Axl, MerTK, CD36, and LAMP2 in perihematomal microglia and BV2 cells. Treatment of a murine model of ICH with wogonin stimulated microglial phagocytosis in vitro. Further, we demonstrated that wogonin dramatically attenuated inflammatory and oxidative stress responses in a murine model of ICH by reducing the expression of pro-inflammatory cytokines and pro-oxidant enzymes such as TNF-α, IL-1β, and inducible nitric oxide synthase (iNOS) after ICH. The effects of wogonin were abolished by administration of the PPAR-γ inhibitor GW9662. In conclusion, our data suggest that wogonin facilitates hematoma clearance and neurobehavioral recovery by targeting PPAR-γ.

Rh-relaxin-2 attenuates degranulation of mast cells by inhibiting NF-κB through PI3K-AKT/TNFAIP3 pathway in an experimental germinal matrix hemorrhage rat model

BACKGROUND

Mast cells play an important role in early immune reactions in the brain by degranulation and the consequent inflammatory response. Our aim of the study is to investigate the effects of rh-relaxin-2 on mast cells and the underlying mechanisms in a germinal matrix hemorrhage (GMH) rat model.

METHODS

One hundred seventy-three P7 rat pups were subjected to GMH by an intraparenchymal injection of bacterial collagenase. Clodronate liposome was administered through intracerebroventricular (i.c.v.) injections 24 h prior to GMH to inhibit microglia. Rh-relaxin-2 was administered intraperitoneally at 1 h and 13 h after GMH. Small interfering RNA of RXFP1 and PI3K inhibitor LY294002 were given by i.c.v. injection. Post-GMH evaluation included neurobehavioral function, Western blot analysis, immunofluorescence, Nissl staining, and toluidine blue staining.

RESULTS

Our results demonstrated that endogenous relaxin-2 was downregulated and that RXFP1 level peaked on the first day after GMH. Administration of rh-relaxin-2 improved neurological functions, attenuated degranulation of mast cells and neuroinflammation, and ameliorated post-hemorrhagic hydrocephalus (PHH) after GMH. These effects were associated with RXFP1 activation, increased expression of PI3K, phosphorylated AKT and TNFAIP3, and decreased levels of phosphorylated NF-κB, tryptase, chymase, IL-6, and TNF-α. However, knockdown of RXFP1 and PI3K inhibition abolished the protective effects of rh-relaxin-2.

CONCLUSIONS

Our findings showed that rh-relaxin-2 attenuated degranulation of mast cells and neuroinflammation, improved neurological outcomes, and ameliorated hydrocephalus after GMH through RXFP1/PI3K-AKT/TNFAIP3/NF-κB signaling pathway.

Melatonin Alleviates Neuronal Damage After Intracerebral Hemorrhage in Hyperglycemic Rats

Background

This study sought to investigate a novel effect of melatonin in reducing brain injury in an in vivo hyperglycemic intracerebral hemorrhage (ICH) model and further explore the mechanisms of protection.

Methods

Hyperglycemia ICH was induced in Sprague-Dawley rats by streptozocin injection followed by autologous blood injection into the striatum. A combined approach including RNA-specific depletion, electron microscopy, magnetic resonance, Western blots, and immunohistological staining was applied to quantify the brain injuries after ICH.

Results

Hyperglycemia resulted in enlarged hematoma volume, deteriorated brain edema, and aggravated neuronal mitochondria damage 3 days after ICH. Post-treatment with melatonin 2 hours after ICH dose-dependently improved neurological behavioral performance lasting out to 14 days after ICH. This improved neurological function was associated with enhanced structural and functional integrity of mitochondria. Mechanistic studies revealed that melatonin alleviated mitochondria damage in neurons via activating the PPARδ/PGC-1α pathway. Promisingly, melatonin treatment delayed until 6 hours after ICH still reduced brain edema and improved neurological functions. Melatonin supplementation reduces neuronal damage after hyperglycemic ICH by alleviating mitochondria damage in a PPARδ/PGC-1α-dependent manner.

Conclusion

Melatonin may represent a therapeutic strategy with a wide therapeutic window to reduce brain damage and improve long-term recovery after ICH.

Activated WNK3 induced by intracerebral hemorrhage deteriorates brain injury maybe via WNK3/SPAK/NKCC1 pathway

BACKGROUND

Intracerebral hemorrhage (ICH) is the common brain diseases in middle-aged and elderly people, with high disability and/or mortality rate, and is a serious public health concern. Both WNK3 kinase and the WNK3/SPAK/NKCC1 signaling pathway play an integral role in maintaining normal cell homeostasis. However, their role and underlying mechanisms in ICH-induced secondary brain injury (SBI) have yet to be elucidated.

METHODS

We established an ICH model using male Sprague-Dawley (SD) rats by injecting autologous arterial blood into the unilateral basal ganglia. To establish ICH model in vitro, oxyhemoglobin (OxyHb; 20 μM) and neurons were cultured for 6 h at 37 °C, 5% CO₂ atmosphere. To investigate the role of WNK3 and the WNK3/SPAK/NKCC1 signaling pathway in SBI, after genetic interventions, rotation and water maze test, brain edema and neuroinflammation were detected, and terminal-deoxynucleoitidyl transferase mediated dUTP nick end labeling (TUNEL), Fluoro-Jade C (FJC), and Nissl staining were performed.

RESULTS

Our data showed that WNK3 expression in brain tissue were upregulated after ICH induction. In addition, silencing of WNK3 reduced neuronal apoptosis, and inflammatory responses in rats that underwent ICH. Inhibition of WNK3 expression reduced the damaged blood-brain barrier (BBB), alleviated the impaired degree of cerebral edema, and improved disruptive neurobehavioral cognition caused by ICH. Moreover, overexpression of WNK3 had the opposite effects. Finally, WNK3/SPAK/NKCC1 signaling pathway may be involved in the above-mentioned processes.

CONCLUSIONS

In conclusion, our findings showed that WNK3 and WNK3/SPAK/NKCC1 signaling pathway play a vital biological function in ICH-induced SBI. Depletion of WNK3 attenuated brain injury after ICH both in vivo and in vitro. Thus, WNK3 and WNK3/SPAK/NKCC1 signaling pathway are potential targets for treating SBI after ICH.

Brainstem iron overload and injury in a rat model of brainstem hemorrhage

BACKGROUND AND PURPOSE

Brainstem hemorrhage (BSH) is the most devastating subtype of intracerebral hemorrhage (ICH) with the highest mortality ranging from 56 % to 61.2 %. However, there is no effective medical or surgical therapy to improve its outcomes in clinic to date due to lack of understanding of its injury mechanisms. Herein, we explored the brainstem iron overload and injury in a rat model of BSH.

METHODS

Neurological scores were examined on day 1, 3, and 7 after modeling, and mortality of the rats was recorded to draft a survival curve. Rats were monitored by MRI using T2 and susceptibility weighted imaging (SWI) before sacrifice for examination of histology and immunofluorescence on day 1, 3, and 7.

RESULTS

BSH rats had a high mortality of 56 % and demonstrated the severe neurological deficits mimicking the clinical conditions. SWI showed that the same increasing tendency in change of hypointense area with that in iron deposition by Perls staining from day 1 to 7. Expression of heme oxygenase 1 (HO-1) and generation of reactive oxygen species (ROS) had similar tendency and both peaked on day 3. Neuronal degeneration occurred and stayed elevated from day 1 to 7, while myelin sheath injury was initially observed on day 1 but without significant difference within 7 days.

CONCLUSIONS

The time courses of erythrocyte lysis, HO-1 expression, iron deposition and ROS generation are related to each other after BSH. Besides, brainstem injury including neuronal degeneration and myelin damage were observed and discussed.

Intracerebral Hemorrhage-Induced Brain Injury in Rats: the Role of Extracellular Peroxiredoxin 2

Red blood cell (RBC) lysis within the hematoma causes brain injury following intracerebral hemorrhage. Peroxiredoxin 2 (PRX-2) is the third most abundant protein in RBCs and this study examined the potential role of PRX-2 in inducing brain injury in rats. First, adult male Sprague-Dawley rats had an intracaudate injection of lysed RBCs or saline. Brains were harvested at 1 h to measure PRX-2 levels. Second, rats had an intracaudate injection of either recombinant PRX-2, heat-inactivated PRX-2, or saline. Third, rats had intracaudate co-injection of lysed RBCs with conoidin A, a PRX-2 inhibitor, or vehicle. For the second and third parts of studies, behavioral tests were performed and all rats had magnetic resonance imaging prior to euthanasia for brain immunohistochemistry and Western blotting. We found that brain PRX-2 levels were increased after lysed RBC injection. Intracaudate injection of PRX-2 resulted in blood-brain barrier disruption, brain swelling, neutrophil infiltration, microglia activation, neuronal death, and neurological deficits. Intracerebral injection of lysed RBCs induced brain injury, which was reduced by conoidin A. These results suggest that extracellular PRX-2 released from hematoma can cause brain injury following brain hemorrhage and could be a potential therapeutic target.