Comparison of humoral neuroinflammation and adhesion molecule expression in two models of experimental intracerebral hemorrhage

Pathological mechanisms and future therapeutic directions of thrombin in intracerebral hemorrhage: a systematic review

Intracerebral hemorrhage (ICH), a common subtype of hemorrhagic stroke, often causes severe disability or death. ICH induces adverse events that might lead to secondary brain injury (SBI), and there is currently a lack of specific effective treatment strategies. To provide a new direction for SBI treatment post-ICH, the systematic review discussed how thrombin impacts secondary injury after ICH through several potentially deleterious or protective mechanisms. We included 39 studies and evaluated them using SYRCLE's ROB tool. Subsequently, we explored the potential molecular mechanisms of thrombin-mediated effects on SBI post-ICH in terms of inflammation, iron deposition, autophagy, and angiogenesis. Furthermore, we described the effects of thrombin in endothelial cells, astrocytes, pericytes, microglia, and neurons, as well as the harmful and beneficial effects of high and low thrombin concentrations on ICH. Finally, we concluded the current research status of thrombin therapy for ICH, which will provide a basis for the future clinical application of thrombin in the treatment of ICH.

Effect of Early External Ventricular Drainage on Perihemorrhagic Edema and Functional Outcome in Patients with Intraventricular Hemorrhage

OBJECTIVE

External ventricular drainage (EVD) is the most common neurosurgical procedure that allows drainage of cerebrospinal fluid and intraventricular blood. A specific time threshold for insertion of an EVD catheter in patients with spontaneous intracerebral hemorrhage and intraventricular hemorrhage has not been established. This study aimed to evaluate the association of early EVD with functional outcome in patients with intracerebral hemorrhage and intraventricular hemorrhage.

METHODS

Propensity score matching was used to account for baseline imbalances. Modified Rankin Scale score at 3 and 6 months, mortality rates at 3 and 6 months, postoperative complications, time course of edema evolution, and peak perihemorrhagic edema (PHE) were compared in patients who received early EVD versus routine EVD.

RESULTS

The rate of favorable outcome at 3 months was higher in the early EVD group compared with the routine EVD group. There were no differences between groups in modified Rankin Scale score at 6 months or mortality rates at 3 and 6 months. Absolute peak PHE and relative PHE volumes were significantly less in the early EVD group compared with the routine EVD group. The incidence of postoperative infections was lower in the early EVD group compared with the routine EVD group.

CONCLUSIONS

Early EVD was associated with improved functional outcome at 3 months, reduced PHE, and lower rate of infection in intracerebral hemorrhage and intraventricular hemorrhage. However, survival at 3 and 6 months and functional outcome at 6 months were not improved.

Targeted drug delivery to the brain endothelium dominates over passive delivery via vascular leak in experimental intracerebral hemorrhage

Intracerebral hemorrhage (ICH) is one of the most common causes of fatal stroke, yet has no specific drug therapies. Many attempts at passive intravenous (IV) delivery in ICH have failed to deliver drugs to the salvageable area around the hemorrhage. The passive delivery method assumes vascular leak through the ruptured blood-brain barrier will allow drug accumulation in the brain. Here we tested this assumption using intrastriatal injection of collagenase, a well-established experimental model of ICH. Fitting with hematoma expansion in clinical ICH, we showed that collagenase-induced blood leak drops significantly by 4 h after ICH onset and is gone by 24 h. We observed passive-leak brain accumulation also declines rapidly over ∼4 h for 3 model IV therapeutics (non-targeted IgG; a protein therapeutic; PEGylated nanoparticles). We compared these passive leak results with targeted brain delivery by IV monoclonal antibodies (mAbs) that actively bind vascular endothelium (anti-VCAM, anti-PECAM, anti-ICAM). Even at early time points after ICH induction, where there is high vascular leak, brain accumulation via passive leak is dwarfed by brain accumulation of endothelial-targeted agents: At 4 h after injury, anti-PECAM mAbs accumulate at 8-fold higher levels in the brain vs. non-immune IgG; anti-VCAM nanoparticles (NPs) deliver a protein therapeutic (superoxide dismutase, SOD) at 4.5-fold higher levels than the carrier-free therapeutic at 24 h after injury. These data suggest that relying on passive vascular leak provides inefficient delivery of therapeutics even at early time points after ICH, and that a better strategy might be targeted delivery to the brain endothelium, which serves as the gateway for the immune attack on the peri-hemorrhage inflamed brain region.

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.

Mechanism and Regulation of Microglia Polarization in Intracerebral Hemorrhage

Intracerebral hemorrhage (ICH) is the most lethal subtype of stroke, but effective treatments are lacking, and neuroinflammation plays a key role in the pathogenesis. In the innate immune response to cerebral hemorrhage, microglia first appear around the injured tissue and are involved in the inflammatory cascade response. Microglia respond to acute brain injury by being activated and polarized to either a typical M1-like (pro-inflammatory) or an alternative M2-like (anti-inflammatory) phenotype. These two polarization states produce pro-inflammatory or anti-inflammatory. With the discovery of the molecular mechanisms and key signaling molecules related to the polarization of microglia in the brain, some targets that regulate the polarization of microglia to reduce the inflammatory response are considered a treatment for secondary brain tissue after ICH damage effective strategies. Therefore, how to promote the polarization of microglia to the M2 phenotype after ICH has become the focus of attention in recent years. This article reviews the mechanism of action of microglia’s M1 and M2 phenotypes in secondary brain injury after ICH. Moreover, it discusses compounds and natural pharmaceutical ingredients that can polarize the M1 to the M2 phenotype.

Modulation of the proteoglycan receptor PTPσ promotes white matter integrity and functional recovery after intracerebral hemorrhage stroke in mice

Background

Intracerebral hemorrhage (ICH) is associated with high morbidity and mortality rates. However, extant investigations have mainly focused on gray matter injury within the primary injury site after ICH rather than on white matter (WM) injury in the brain and spinal cord. This focus partly accounts for the diminished therapeutic discovery. Recent evidence suggests that chondroitin sulphate proteoglycans (CSPG), which can bind to the neural transmembrane protein tyrosine phosphatase-sigma (PTPσ), may facilitate axonal regrowth and remyelination by ameliorating neuroinflammation.

Methods

A clinically relevant ICH model was established using adult C57BL/6 mice. The mice were then treated systemically with intracellular sigma peptide (ISP), which specifically targets PTPσ. Sensorimotor function was assessed by various behavioral tests and electrophysiological assessment. Western blot was used to verify the expression levels of Iba-1 and different inflammatory cytokines. The morphology of white matter tracts of brain and spinal cord was evaluated by immunofluorescence staining and transmission electron microscopy (TEM). Adeno-associated virus (AAV) 2/9 injection was used to assess the ipsilateral axonal compensation after injury. Parallel in vitro studies on the effects of CSPG interference on oligodendrocyte–DRG neuron co-culture explored the molecular mechanism through which ISP treatment promoted myelination capability.

Results

ISP, by targeting PTPσ, improved WM integrity and sensorimotor recovery via immunomodulation. In addition, ISP administration significantly decreased WM injury in the peri-hematomal region as well as cervical spinal cord, enhanced axonal myelination and facilitated neurological restoration, including electrophysiologically assessed sensorimotor functions. Parallel in vitro studies showed that inhibition of PTPσ by ISP fosters myelination by modulating the Erk/CREB signaling pathway.

Conclusions

Our findings revealed for the first time that manipulation of PTPσ signaling by ISP can promote prolonged neurological recovery by restoration of the integrity of neural circuits in the CNS through modulation of Erk/CREB signaling pathway.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12974-022-02561-4.

Microglia Phenotypes in Aging and Neurodegenerative Diseases

Neuroinflammation is a hallmark of many neurodegenerative diseases (NDs) and plays a fundamental role in mediating the onset and progression of disease. Microglia, which function as first-line immune guardians of the central nervous system (CNS), are the central drivers of neuroinflammation. Numerous human postmortem studies and in vivo imaging analyses have shown chronically activated microglia in patients with various acute and chronic neuropathological diseases. While microglial activation is a common feature of many NDs, the exact role of microglia in various pathological states is complex and often contradictory. However, there is a consensus that microglia play a biphasic role in pathological conditions, with detrimental and protective phenotypes, and the overall response of microglia and the activation of different phenotypes depends on the nature and duration of the inflammatory insult, as well as the stage of disease development. This review provides a comprehensive overview of current research on the various microglia phenotypes and inflammatory responses in health, aging, and NDs, with a special emphasis on the heterogeneous phenotypic response of microglia in acute and chronic diseases such as hemorrhagic stroke (HS), Alzheimer's disease (AD), and Parkinson's disease (PD). The primary focus is translational research in preclinical animal models and bulk/single-cell transcriptome studies in human postmortem samples. Additionally, this review covers key microglial receptors and signaling pathways that are potential therapeutic targets to regulate microglial inflammatory responses during aging and in NDs. Additionally, age-, sex-, and species-specific microglial differences will be briefly reviewed.

T-Lymphocyte Interactions with the Neurovascular Unit: Implications in Intracerebral Hemorrhage

In the pathophysiology of hemorrhagic stroke, the perturbation of the neurovascular unit (NVU), a functional group of the microvascular and brain intrinsic cellular components, is implicated in the progression of secondary injury and partially informs the ultimate patient outcome. Given the broad NVU functions in maintaining healthy brain homeostasis through its maintenance of nutrients and energy substrates, partitioning central and peripheral immune components, and expulsion of protein and metabolic waste, intracerebral hemorrhage (ICH)-induced dysregulation of the NVU directly contributes to numerous destructive processes in the post-stroke sequelae. In ICH, the damaged NVU precipitates the emergence and evolution of perihematomal edema as well as the breakdown of the blood–brain barrier structural coherence and function, which are critical facets during secondary ICH injury. As a gateway to the central nervous system, the NVU is among the first components to interact with the peripheral immune cells mobilized toward the injured brain. The release of signaling molecules and direct cellular contact between NVU cells and infiltrating leukocytes is a factor in the dysregulation of NVU functions and further adds to the acute neuroinflammatory environment of the ICH brain. Thus, the interactions between the NVU and immune cells, and their reverberating consequences, are an area of increasing research interest for understanding the complex pathophysiology of post-stroke injury. This review focuses on the interactions of T-lymphocytes, a major cell of the adaptive immunity with expansive effector function, with the NVU in the context of ICH. In cataloging the relevant clinical and experimental studies highlighting the synergistic actions of T-lymphocytes and the NVU in ICH injury, this review aimed to feature emergent knowledge of T cells in the hemorrhagic brain and their diverse involvement with the neurovascular unit in this disease.

Necrosulfonamide Alleviates Acute Brain Injury of Intracerebral Hemorrhage via Inhibiting Inflammation and Necroptosis

Objective

Intracerebral hemorrhage (ICH) is the most lethal subtype of stroke, without effective treatment. Necrosulfonamide (NSA), a specific inhibitor for mixed lineage kinase domain-like protein, has been reported to exert neuroprotective effects in neurological diseases by ameliorating neuroinflammation and necroptosis. We hypothesized that NSA would alleviate acute brain injury and improve behavioral outcomes after ICH.

Materials and Methods

Male adult C57BL/6 mice were assigned randomly into three groups. In vehicle and treatment groups, animals were injected with collagenase VII to induce ICH. The solvent (0.25% DMSO) and NSA (5 mg/kg) were administrated intraperitoneally twice a day, respectively. The sham group was injected with saline and administrated with DMSO. The brain hematoma volume, inflammatory factors, and blood-brain barrier permeability were measured on day 3 after the operation. Fluorescent double immunostaining was performed to evaluate the neuronal death. Neurological functions were assessed.

Results

In the NSA group, the hematoma size was significantly reduced, inflammatory cells and cytokines were suppressed, and the blood-brain barrier was protected compared to vehicle controls. NSA dramatically reduced the death of neurons and improved the performance of neurological functions after ICH.

Conclusion

Necrosulfonamide has a neuroprotective role in alleviating acute brain injury in a mouse ICH model, and this is associated with reduced neuroinflammation and necroptosis.

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.

Application of Programmable Tetrahedral Framework Nucleic Acid-Based Nanomaterials in Neurological Disorders: Progress and Prospects

Tetrahedral framework nucleic acid (tFNA), a special DNA nanodevice, is widely applied in diverse biomedical fields. Due to its high programmability, biocompatibility, tissue permeability as well as its capacity for cell proliferation and differentiation, tFNA presents a powerful tool that could overcome potential barriers in the treatment of neurological disorders. This review evaluates recent studies on the use and progress of tFNA-based nanomaterials in neurological disorders.

Innate Immune Anti-Inflammatory Response in Human Spontaneous Intracerebral Hemorrhage

Background and Purpose

Spontaneous intracerebral hemorrhage (sICH) is a common form of hemorrhagic stroke, with high mortality and morbidity. Pathophysiological mechanisms in sICH are poorly understood and treatments limited. Neuroinflammation driven by microglial-macrophage activation contributes to brain damage post-sICH. We aim to test the hypothesis that an anti-inflammatory (repair) process occurs in parallel with neuroinflammation in clinical sICH.

Methods

We performed quantitative analysis of immunohistochemical markers for microglia and macrophages (Iba1, CD68, TMEM119, CD163, and CD206) in brain tissue biospecimens 1 to 12 days post-sICH and matched control cases. In a parallel, prospective group of patients, we assayed circulating inflammatory markers (CRP [C-reactive protein], total white cell, and monocyte count) over 1 to 12 days following sICH.

Results

In 27 supratentorial sICH cases (n=27, median [interquartile range] age: 59 [52–80.5], 14F/13M) all microglia-macrophage markers increased post-sICH, relative to control brains. Anti-inflammatory markers (CD163 and CD206) were elevated alongside proinflammatory markers (CD68 and TMEM119). CD163 increased progressively post-sICH (15.0-fold increase at 7–12 days, P<0.001). CD206 increased at 3 to 5 days (5.2-fold, P<0.001) then returned to control levels at 7 to 12 days. The parenchymal immune response combined brain-derived microglia (TMEM119 positive) and invading monocyte-derived macrophages (CD206 positive). In a prospective sICH patient cohort (n=26, age 74 [66–79], National Institutes of Health Stroke Scale on admission: 8 [4–17]; 14F/12M) blood CRP concentration and monocyte density (but not white blood cell) increased post-sICH. CRP increased from 0 to 2 to 3 to 5 days (8.3-fold, P=0.020) then declined at 7 to 12 days. Monocytes increased from 0 to 2 to 3 to 5 days (1.8-fold, P<0.001) then declined at 7 to 12 days.

Conclusions

An anti-inflammatory pathway, enlisting native microglia and blood monocytes, occurs alongside neuroinflammation post-sICH. This novel pathway offers therapeutic targets and a window of opportunity (3–5 days post-sICH) for delivery of therapeutics via invading monocytes.

Profiling of Blood-Brain Barrier Disruption in Mouse Intracerebral Hemorrhage Models: Collagenase Injection vs. Autologous Arterial Whole Blood Infusion

Disruption of the blood-brain barrier (BBB) and the subsequent formation of brain edema is the most severe consequence of intracerebral hemorrhage (ICH), leading to drastic neuroinflammatory responses and neuronal cell death. A better understanding of ICH pathophysiology to develop effective therapy relies on selecting appropriate animal models. The collagenase injection ICH model and the autologous arterial whole blood infusion ICH model have been developed to investigate the pathophysiology of ICH. However, it remains unclear whether the temporal progression and the underlying mechanism of BBB breakdown are similar between these two ICH models. In this study, we aimed to determine the progression and the mechanism of BBB disruption via the two commonly used murine ICH models: the collagenase-induced ICH model (c-ICH) and the double autologous whole blood ICH model (b-ICH). Intrastriatal injection of 0.05 U collagenase or 20 μL autologous blood was used for a comparable hematoma volume in these two ICH models. Then we analyzed BBB permeability using Evan’s blue and IgG extravasation, evaluated tight junction (TJ) damage by transmission electron microscope (TEM) and Western blotting, and assessed matrix metalloproteinase-9 (MMP-9) activity and aquaporin 4 (AQP4) mRNA expression by Gelatin gel zymography and RT-PCR, respectively. The results showed that the BBB leakage was associated with a decrease in TJ protein expression and an increase in MMP-9 activity and AQP4 expression on day 3 in the c-ICH model compared with that on day 5 in the b-ICH model. Additionally, using TEM, we found that the TJ was markedly damaged on day 3 in the c-ICH model compared with that on day 5 in the b-ICH model. In conclusion, the BBB was disrupted in the two ICH models; compared to the b-ICH model, the c-ICH model presented with a more pronounced disruption of BBB at earlier time points, suggesting that the c-ICH model might be a more suitable model for studying early BBB damage and protection after ICH.

Early Inflammatory Cytokine Expression in Cerebrospinal Fluid of Patients with Spontaneous Intraventricular Hemorrhage

We investigated cerebrospinal fluid (CSF) expression of inflammatory cytokines and their relationship with spontaneous intracerebral and intraventricular hemorrhage (ICH, IVH) and perihematomal edema (PHE) volumes in patients with acute IVH. Twenty-eight adults with IVH requiring external ventricular drainage for obstructive hydrocephalus had cerebrospinal fluid (CSF) collected for up to 10 days and had levels of interleukin-1α (IL-1α), IL-1β, IL-6, IL-8, IL-10, tumor necrosis factor-α (TNFα), and C-C motif chemokine ligand CCL2 measured using enzyme-linked immunosorbent assay. Median [IQR] ICH and IVH volumes at baseline (T0) were 19.8 [5.8–48.8] and 14.3 [5.3–38] mL respectively. Mean levels of IL-1β, IL-6, IL-10, TNF-α, and CCL2 peaked early compared to day 9–10 (p < 0.05) and decreased across subsequent time periods. Levels of IL-1β, IL-6, IL-8, IL-10, and CCL2 had positive correlations with IVH volume at days 3–8 whereas positive correlations with ICH volume occurred earlier at day 1–2. Significant correlations were found with PHE volume for IL-6, IL-10 and CCL2 at day 1–2 and with relative PHE at days 7–8 or 9–10 for IL-1β, IL-6, IL-8, and IL-10. Time trends of CSF cytokines support experimental data suggesting association of cerebral inflammatory responses with ICH/IVH severity. Pro-inflammatory markers are potential targets for injury reduction.

The Glymphatic System: A Novel Therapeutic Target for Stroke Treatment

The glymphatic system (GS) is a novel defined brain-wide perivascular transit network between cerebrospinal fluid (CSF) and interstitial solutes that facilitates the clearance of brain metabolic wastes. The complicated network of the GS consists of the periarterial CSF influx pathway, astrocytes-mediated convective transport of fluid and solutes supported by AQP4 water channels, and perivenous efflux pathway. Recent researches indicate that the GS dysfunction is associated with various neurological disorders, including traumatic brain injury, hydrocephalus, epilepsy, migraine, and Alzheimer’s disease (AD). Meanwhile, the GS also plays a pivotal role in the pathophysiological process of stroke, including brain edema, blood–brain barrier (BBB) disruption, immune cell infiltration, neuroinflammation, and neuronal apoptosis. In this review, we illustrated the key anatomical structures of the GS, the relationship between the GS and the meningeal lymphatic system, the interaction between the GS and the BBB, and the crosstalk between astrocytes and other GS cellular components. In addition, we contributed to the current knowledge about the role of the GS in the pathology of stroke and the role of AQP4 in stroke. We further discussed the potential use of the GS in early risk assessment, diagnostics, prognostics, and therapeutics of stroke.

Intracerebral Injection of Heme Induces Lipid Peroxidation, Neuroinflammation, and Sensorimotor Deficits

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Characterization of a novel model of global forebrain ischaemia-reperfusion injury in mice and comparison with focal ischaemic and haemorrhagic stroke

Stroke is caused by obstructed blood flow (ischaemia) or unrestricted bleeding in the brain (haemorrhage). Global brain ischaemia occurs after restricted cerebral blood flow e.g. during cardiac arrest. Following ischaemic injury, restoration of blood flow causes ischaemia-reperfusion (I/R) injury which worsens outcome. Secondary injury mechanisms after any stroke are similar, and encompass inflammation, endothelial dysfunction, blood-brain barrier (BBB) damage and apoptosis. We developed a new model of transient global forebrain I/R injury (dual carotid artery ligation; DCAL) and compared the manifestations of this injury with those in a conventional I/R injury model (middle-cerebral artery occlusion; MCAo) and with intracerebral haemorrhage (ICH; collagenase model). MRI revealed that DCAL produced smaller bilateral lesions predominantly localised to the striatum, whereas MCAo produced larger focal corticostriatal lesions. After global forebrain ischaemia mice had worse overall neurological scores, although quantitative locomotor assessment showed MCAo and ICH had significantly worsened mobility. BBB breakdown was highest in the DCAL model while apoptotic activity was highest after ICH. VCAM-1 upregulation was specific to ischaemic models only. Differential transcriptional upregulation of pro-inflammatory chemokines and cytokines and TLRs was seen in the three models. Our findings offer a unique insight into the similarities and differences in how biological processes are regulated after different types of stroke. They also establish a platform for analysis of therapies such as endothelial protective and anti-inflammatory agents that can be applied to all types of stroke.

Interaction of Microglia and Astrocytes in the Neurovascular Unit

The interaction between microglia and astrocytes significantly influences neuroinflammation. Microglia/astrocytes, part of the neurovascular unit (NVU), are activated by various brain insults. The local extracellular and intracellular signals determine their characteristics and switch of phenotypes. Microglia and astrocytes are activated into two polarization states: the pro-inflammatory phenotype (M1 and A1) and the anti-inflammatory phenotype (M2 and A2). During neuroinflammation, induced by stroke or lipopolysaccharides, microglia are more sensitive to pathogens, or damage; they are thus initially activated into the M1 phenotype and produce common inflammatory signals such as IL-1 and TNF-α to trigger reactive astrocytes into the A1 phenotype. These inflammatory signals can be amplified not only by the self-feedback loop of microglial activation but also by the unique anatomy structure of astrocytes. As the pathology further progresses, resulting in local environmental changes, M1-like microglia switch to the M2 phenotype, and M2 crosstalk with A2. While astrocytes communicate simultaneously with neurons and blood vessels to maintain the function of neurons and the blood-brain barrier (BBB), their subtle changes may be identified and responded by astrocytes, and possibly transferred to microglia. Although both microglia and astrocytes have different functional characteristics, they can achieve immune "optimization" through their mutual communication and cooperation in the NVU and build a cascaded immune network of amplification.

Activation of PPAR-β/δ Attenuates Brain Injury by Suppressing Inflammation and Apoptosis in a Collagenase-Induced Intracerebral Hemorrhage Mouse Model

Brain injury has been proposed as the major cause of the poor outcomes associated with intracerebral hemorrhage (ICH). Emerging evidence indicates that the nuclear receptor, peroxisome proliferator-activated receptor β/δ (PPAR-β/δ), plays a crucial role in the pathological process of central nervous impairment. The present study was undertaken to evaluate the protective effects of PPAR-β/δ activation using a selective PPAR-β/δ agonist, GW0742, against brain injury after ICH in a mouse model. ICH was induced by intravenous injection of collagenase into the right caudate putamen. To examine the protective effect of PPAR-β/δ activation against ICH-induced brain injury, mice were either intraperitoneally injected with GW0742 (3 mg/kg, body weight) or saline (control group) 30 min before inducing ICH. Behavioral dysfunction was evaluated 24 and 72 h after injury. Then, all mice were killed to assess hematoma volume, brain water content, and blood-brain barrier (BBB) permeability. TUNEL and Nissl staining were performed to quantify the brain injury. The expression of PPAR-β/δ, interleukin (IL)-1β, tumor necrosis factor (TNF)-α, Bcl-2-related X-protein (Bax), and B-cell lymphoma 2 (Bcl-2) in the perihematomal area was examined by immunohistochemistry and western blotting analysis. Mice treated with GW0742 showed significantly less severe behavioral deficits compared to the control group, accompanied by increased expression of PPAR-β/δ and Bcl-2, and increased expression of IL-1β, TNF-α, and Bax decreased simultaneously in the GW0742-treated group. Furthermore, the GW0742-pretreated group showed significantly less brain edema and BBB leakage. Neuronal loss was attenuated, and the number of apoptotic neuronal cells in perihematomal tissues reduced, in the GW0742-pretreated group compared to the control group. However, the hematoma volume did not decrease significantly on day 3 after ICH. These results suggest that the activation of PPAR-β/δ exerts a neuroprotective effect on ICH-induced brain injury, possibly through anti-inflammatory and anti-apoptotic pathways.

Interactions between rat cortico-striatal slice cultures and neutrophil-like HL60 cells under thrombin challenge: Toward elucidation of pathological events in intracerebral hemorrhage

Neutrophils constitute the major population of infiltrating leukocytes after stroke including intracerebral hemorrhage (ICH), and these cells may exhibit pro-inflammatory and anti-inflammatory phenotypes depending on the external stimuli. Here we constructed an experimental system to evaluate how the properties of neutrophils were influenced by the injured brain tissues. HL60 cells differentiated into neutrophils were added to the culture medium of neonatal rat cortico-striatal slices maintained at liquid-air interface. Thrombin was applied to the cultures to mimic the pathogenic events associated with ICH. HL60 cells responded to thrombin by increasing mRNA expression of pro-inflammatory IL-1β and anti-inflammatory IL-10 with a different time course. Co-presence of cortico-striatal slice cultures significantly enhanced IL-1β mRNA expression, whereas attenuated IL-10 mRNA expression, in HL60 cells. Toll-like receptor 4 (TLR4) agonist lipopolysaccharide synergistically enhanced IL-1β mRNA expression with thrombin, and TLR4 inhibitor TAK-242 abolished thrombin-induced IL-1β mRNA expression in the presence of slice cultures. On the other hand, thrombin-induced cell death in cortico-striatal cultures was attenuated by the presence of HL60 cells. This experimental system may provide a unique platform to elucidate complex cell-to-tissue interactions during ICH pathogenesis.

Role and mechanisms of cytokines in the secondary brain injury after intracerebral hemorrhage

Intracerebral hemorrhage (ICH) is a common and severe cerebrovascular disease that has high mortality. Few survivors achieve self-care. Currently, patients receive only symptomatic treatment for ICH and benefit poorly from this regimen. Inflammatory cytokines are important participants in secondary injury after ICH. Increases in proinflammatory cytokines may aggravate the tissue injury, whereas increases in anti-inflammatory cytokines might be protective in the ICH brain. Inflammatory cytokines have been studied as therapeutic targets in a variety of acute and chronic brain diseases; however, studies on ICH are limited. This review summarizes the roles and functions of various pro- and anti-inflammatory cytokines in secondary brain injury after ICH and discusses pathogenic mechanisms and emerging therapeutic strategies and directions for treatment of ICH.

Genetic Deletion of PGF2α-FP Receptor Exacerbates Brain Injury Following Experimental Intracerebral Hemorrhage

Background: The release of inflammatory molecules such as prostaglandins (e.g., PGF_2α) is associated with brain damage following an intracerebral hemorrhagic (ICH) stroke; however, the role of PGF_2α and its cognate FP receptor in ICH remains unclear. This study focused on investigating the role of the FP receptor as a target for novel neuroprotective drugs in a preclinical model of ICH, aiming to investigate the contribution of the PGF_2α-FP axis in modulating functional recovery and anatomical outcomes following ICH.

Results: Neurological deficit scores in FP^−/− mice were significantly higher compared to WT mice 72 h after ICH (6.1 ± 0.7 vs. 3.1 ± 0.8; P < 0.05). Assessing motor skills, the total time mice stayed on the rotating rod was significantly less in FP^−/−mice compared to WT mice 24 h after ICH (27.0 ± 7.5 vs. 52.4 ± 11.2 s; P < 0.05). Using grip strength to quantify forepaw strength, results showed that the FP^−/− mice had significantly less strength compared to WT mice 72 h after ICH (96.4 ± 17.0 vs. 129.6 ± 5.9 g; P < 0.01). In addition to the behavioral outcomes, histopathological measurements were made. In Cresyl violet stained brain sections, the FP^−/− mice showed a significantly larger lesion volume compared to the WT (15.0 ± 2.2 vs. 3.2 ± 1.7 mm³; P < 0.05 mice.) To estimate the presence of ferric iron in the peri-hematoma area, Perls' staining was performed, which revealed that FP^−/− mice had significantly greater staining than the WT mice (186.3 ± 34.4% vs. 86.9 ± 13.0% total positive pixel counts, P < 0.05). Immunoreactivity experiments on brain sections from FP^−/− and WT mice post-ICH were performed to monitor changes in microgliosis and astrogliosis using antibodies against Iba1 and GFAP respectively. These experiments showed that FP^−/− mice had a trend toward greater astrogliosis than WT mice post-ICH.

Conclusion: We showed that deletion of the PGF_2α FP receptor exacerbates behavioral impairments and increases lesion volumes following ICH compared to WT-matched controls.Detailed mechanisms responsible for these novel results are actively being pursued.

IL-17A induces autophagy and promotes microglial neuroinflammation through ATG5 and ATG7 in intracerebral hemorrhage

Microglial inflammation plays a vital role in intracerebral hemorrhage (ICH)-induced secondary brain injury. IL-17A has been identified to promote microglia activation, but the role in the pathology following ICH remains unclear. Autophagy is involved in modulation of cell metabolism, cell survival, and immune response. However, the role of IL-17A in autophagy following ICH has not been well defined. In this study, we assessed the role of IL-17A in microglial autophagic activity following ICH. The microglia were treated with IL-17A, and then autophagy and inflammation were detected. In addition, RNA interference in essential autophagy genes (ATG5 and ATG7) was also utilized to analyze microglial autophagy in vitro. Furthermore, ICH mice were made by injection of autologous blood model in vivo. And the IL-17A-neutralizing antibody was utilized to assess the neurological scores and brain edema. These data demonstrated that IL-17A promoted microglial autophagy and microglial inflammation. The suppression of autophagy using RNA interference in essential autophagy genes (ATG5 and ATG7) decreased microglial autophagy and inflammation. Moreover, IL-17A Ab significantly reduced brain water content and improved neurological function of ICH mice. Taken together, these data demonstrated that IL-17A promoted microglial autophagy and microglial inflammation, and IL-17A-mediated activation of autophagy might represent novel clues in ICH therapy.

Modulators of microglial activation and polarization after intracerebral haemorrhage

Intracerebral haemorrhage (ICH) is the most lethal subtype of stroke but currently lacks effective treatment. Microglia are among the first non-neuronal cells on the scene during the innate immune response to ICH. Microglia respond to acute brain injury by becoming activated and developing classic M1-like (proinflammatory) or alternative M2-like (anti-inflammatory) phenotypes. This polarization implies as yet unrecognized actions of microglia in ICH pathology and recovery, perhaps involving microglial production of proinflammatory or anti-inflammatory cytokines and chemokines. Furthermore, alternatively activated M2-like microglia might promote phagocytosis of red blood cells and tissue debris, a major contribution to haematoma clearance. Interactions between microglia and other cells modulate microglial activation and function, and are also important in ICH pathology. This Review summarizes key studies on modulators of microglial activation and polarization after ICH, including M1-like and M2-like microglial phenotype markers, transcription factors and key signalling pathways. Microglial phagocytosis, haematoma resolution, and the potential crosstalk between microglia and T lymphocytes, neurons, astrocytes, and oligodendrocytes in the ICH brain are described. Finally, the clinical and translational implications of microglial polarization in ICH are presented, including the evidence that therapeutic approaches aimed at modulating microglial function might mitigate ICH injury and improve brain repair.

Inhibition of neuronal ferroptosis protects hemorrhagic brain

Intracerebral hemorrhage (ICH) causes high mortality and morbidity, but our knowledge of post-ICH neuronal death and related mechanisms is limited. In this study, we first demonstrated that ferroptosis, a newly identified form of cell death, occurs in the collagenase-induced ICH model in mice. We found that administration of ferrostatin-1, a specific inhibitor of ferroptosis, prevented neuronal death and reduced iron deposition induced by hemoglobin in organotypic hippocampal slice cultures (OHSCs). Mice treated with ferrostatin-1 after ICH exhibited marked brain protection and improved neurologic function. Additionally, we found that ferrostatin-1 reduced lipid reactive oxygen species production and attenuated the increased expression level of PTGS2 and its gene product cyclooxygenase-2 ex vivo and in vivo. Moreover, ferrostatin-1 in combination with other inhibitors that target different forms of cell death prevented hemoglobin-induced cell death in OHSCs and human induced pluripotent stem cell-derived neurons better than any inhibitor alone. These results indicate that ferroptosis contributes to neuronal death after ICH, that administration of ferrostatin-1 protects hemorrhagic brain, and that cyclooxygenase-2 could be a biomarker of ferroptosis. The insights gained from this study will advance our knowledge of the post-ICH cell death cascade and be essential for future preclinical studies.

Treatment with FTY720 has no beneficial effects on short-term outcome in an experimental model of intracerebral hemorrhage

BACKGROUND

No evidence-based therapy is available for patients with acute intracerebral hemorrhage (ICH). In view of the profound inflammatory reaction in the perilesional tissue, we investigated in a well-characterized experimental model whether the administration of the immunomodulator fingolimod (FTY720) is neuroprotective in acute ICH.

METHODS

ICH was induced by means of a stereotactic intrastriatal injection of collagenase type VII-S. FTY720 (1 mg/kg) was administered intraperitoneally 1 h after ICH induction. Hematoma volume was assessed spectrophotometrically at 24 h after ICH induction. The following endpoints were determined at 24 and 72 h, respectively: mortality rate and neurologic outcomes, edema formation, and MMP-9 activity.

RESULTS

Twenty-four hour after ICH induction, hematoma volume was not statistically different between groups. No difference was found in mortality and neurologic outcomes at 24 and 72 h between FTY720 treated mice and controls. Edema formation was present in both groups on the ipsilateral side with no statistical difference between groups at both time points. No difference was found in MMP-9 levels after 24 and 72 h between groups.

CONCLUSIONS

Our results suggest that FTY720 has no beneficial effects in the acute phase of experimental ICH.

α4 integrin is a regulator of leukocyte recruitment after experimental intracerebral hemorrhage

BACKGROUND AND PURPOSE

Intracerebral hemorrhage (ICH) is swiftly followed by an inflammatory response. A key component of this response is the recruitment of leukocytes into the brain, which promotes neurological injury in rodent models. However, the mechanisms by which leukocytes transmigrate across the endothelium into the injured brain are unclear. The present study examines leukocyte adhesion molecules (α4 integrin, L-selectin, and αLβ2 integrin) on 4 leukocyte subtypes to determine which are important for leukocyte recruitment after ICH.

METHODS

We used the blood injection mouse model of ICH, whereby 25 μL of blood was injected into the striatum. Flow cytometry was used to quantify leukocyte populations and adhesion molecule expression in brain and blood. An α4 integrin-blocking antibody was administered to evaluate the contribution of α4 integrin in leukocyte migration and neurological injury.

RESULTS

α4 integrin was elevated on all leukocyte populations in brain after ICH, whereas L-selectin was unchanged and αLβ2 was increased only on T cells. Antagonism of α4 resulted in decreased leukocyte transmigration and lessened neurobehavioral disability.

CONCLUSIONS

α4 integrin is an important cell adhesion molecule involved in neuroinflammation after ICH.

Mechanism of mesenchymal stem cell-induced neuron recovery and anti-inflammation

BACKGROUND AIMS

After ischemic or hemorrhagic stroke, neurons in the penumbra surrounding regions of irreversible injury are vulnerable to delayed but progressive damage as a result of ischemia and hemin-induced neurotoxicity. There is no effective treatment to rescue such dying neurons. Mesenchymal stem cells (MSCs) hold promise for rescue of these damaged neurons. In this study, we evaluated the efficacy and mechanism of MSC-induced neuro-regeneration and immune modulation.

METHODS

Oxygen-glucose deprivation (OGD) was used in our study. M17 neuronal cells were subjected to OGD stress then followed by co-culture with MSCs. Rescue effects were evaluated using proliferation and apoptosis assays. Cytokine assay and quantitative polymerase chain reaction were used to explore the underlying mechanism. Antibody and small molecule blocking experiments were also performed to further understand the mechanism.

RESULTS

We showed that M17 proliferation was significantly decreased and the rate of apoptosis increased after exposure to OGD. These effects could be alleviated via co-culture with MSCs. Tumor necrosis factor-α was found elevated after OGD stress and was back to normal levels after co-culture with MSCs. We believe these effects involve interleukin-6 and vascular endothelial growth factor signaling pathways.

DISCUSSION

Our studies have shown that MSCs have anti-inflammatory properties and the capacity to rescue injured neurons.

Mouse models of intracerebral hemorrhage in ventricle, cortex, and hippocampus by injections of autologous blood or collagenase

Intracerebral hemorrhage (ICH) is a devastating condition. Existing preclinical ICH models focus largely on striatum but neglect other brain areas such as ventricle, cortex, and hippocampus. Clinically, however, hemorrhagic strokes do occur in these other brain regions. In this study, we established mouse hemorrhagic models that utilize stereotactic injections of autologous whole blood or collagenase to produce ventricular, cortical, and hippocampal injury. We validated and characterized these models by histology, immunohistochemistry, and neurobehavioral tests. In the intraventricular hemorrhage (IVH) model, C57BL/6 mice that received unilateral ventricular injections of whole blood demonstrated bilateral ventricular hematomas, ventricular enlargement, and brain edema in the ipsilateral cortex and basal ganglia at 72 h. Unilateral injections of collagenase (150 U/ml) caused reproducible hematomas and brain edema in the frontal cortex in the cortical ICH (c-ICH) model and in the hippocampus in the hippocampal ICH (h-ICH) model. Immunostaining revealed cellular inflammation and neuronal death in the periventricular regions in the IVH brain and in the perihematomal regions in the c-ICH and h-ICH brains. Locomotor abnormalities measured with a 24-point scoring system were present in all three models, especially on days 1, 3, and 7 post-ICH. Locomotor deficits measured by the wire-hanging test were present in models of IVH and c-ICH, but not h-ICH. Interestingly, mice in the c-ICH model demonstrated emotional abnormality, as measured by the tail suspension test and forced swim test, whereas h-ICH mice exhibited memory abnormality, as measured by the novel object recognition test. All three ICH models generated reproducible brain damage, brain edema, inflammation, and consistent locomotor deficits. Additionally, the c-ICH model produced emotional deficits and the h-ICH model produced cognitive deficits. These three models closely mimic human ICH and should be useful for investigating the pathophysiology of ICH in ventricle, cortex, and hippocampus and for evaluating potential therapeutic strategies.

Gr1+ Macrophages and Dendritic Cells Dominate the Inflammatory Infiltrate 12 Hours After Experimental Intracerebral Hemorrhage

Intracerebral hemorrhage (ICH) is a devastating disease lacking an effective treatment. While the initial injury occurs within minutes, an inflammatory response contributes to ongoing tissue damage over hours to days. Relatively little is known about leukocyte trafficking into the brain in the hours after ICH onset. Understanding these events may lead to identification of new therapeutic targets. Using the blood injection mouse model of ICH, the numbers of leukocytes in the ipsilateral and contralateral brain were quantified by flow cytometry 12 hours after surgery. Perihematomal inflammation was confirmed by histology and chemokines and cytokines in the brain quantified by multiplex ELISA. Few neutrophils were detected in the brain 12 hours after ICH. The majority of leukocytes consisted of inflammatory macrophages (CD45.1(hi)CD3(-)Ly6G(-)CD11c(-)CD11b(+)Gr1(+) cells) and inflammatory dendritic cells (CD45.1(hi)CD3(-)Ly6G(-)CD11c(int)CD11b(+)Gr1(+) cells). Microglia numbers did not differ between the hemispheres. These results indicate that blood-derived monocyte populations traffic into brain early after ICH and outnumber neutrophils at 12 hours.

The interaction of leukocytes and adhesion molecules in mesenteric microvessel endothelial cells after internal capsule hemorrhage

OBJECTIVE

To explore the correlation between hemorheological variations and the expression of cell adhesion molecules in mesenteric microvessel endothelial cells after internal capsule hemorrhage.

METHODS

We established an internal capsule hemorrhage model. Then leukocyte-endothelium interaction was observed and hemorheological variations in mesenteric microvessels were evaluated in the following aspects: blood flow volume, diameter of microvessels, blood flow rate, and shear rate. We also measured the expression of vascular cell adhesion molecule-l and intercellular adhesion molecule-1 (ICAM-1) in mesenteric microvessel endothelial cells with immunohistochemistry stain.

RESULTS

Leukocyte-endothelium interaction intensified after internal capsule hemorrhage. Besides, blood flow volume and velocity decreased, diameter narrowed, and shear rate reduced. Immunohistochemical staining of vascular cell adhesion molecule-l and ICAM-1in mesenteric microvessel endothelial cells was stronger.

CONCLUSIONS

VCAM-1 and ICAM-1 expression in mesenteric microvessels increased as a result of decreased wall shear stress in stress state following internal capsule hemorrhage, and then further shear stress change from interaction of enhanced production of CAMs and leukocytes created a vicious cycle of leukocytes margination, adhesion, and transmigration that could ultimately result in stress gastrointestinal ulcer.

Age-related comparisons of evolution of the inflammatory response after intracerebral hemorrhage in rats

In the hours to days after intracerebral hemorrhage (ICH), there is an inflammatory response within the brain characterized by the infiltration of peripheral neutrophils and macrophages and the activation of brain-resident microglia and astrocytes. Despite the strong correlation of aging and ICH incidence, and increasing information about cellular responses, little is known about the temporal- and age-related molecular responses of the brain after ICH. Here, we monitored a panel of 27 genes at 6 h and 1, 3, and 7 days after ICH was induced by injecting collagenase into the striatum of young adult and aged rats. Several molecules (CR3, TLR2, TLR4, IL-1β, TNFα, iNOS, IL-6) were selected to reflect the classical activation of innate immune cells (macrophages, microglia) and the potential to exacerbate inflammation and damage brain cells. Most of the others are associated with the resolution of innate inflammation, alternative pathways of macrophage/microglial activation, and the repair phase after acute injury (TGFβ, IL-1ra, IL-1r2, IL-4, IL-13, IL-4Rα, IL-13Rα1, IL-13Rα2, MRC1, ARG1, CD163, CCL22). In young animals, the up-regulation of 26 in 27 genes (not IL-4) was detected within the first week. Differences in timing or levels between young and aged animals were detected for 18 of 27 genes examined (TLR2, GFAP, IL-1β, IL-1ra, IL-1r2, iNOS, IL-6, TGFβ, MMP9, MMP12, IL-13, IL-4Rα, IL-13Rα1, IL-13Rα2, MRC1, ARG1, CD163, CCL22), with a generally less pronounced or delayed inflammatory response in the aged animals. Importantly, within this complex response to experimental ICH, the induction of pro-inflammatory, potentially harmful mediators often coincided with resolving and beneficial molecules.