Neuron death and inflammation in a rat model of intracerebral hemorrhage: Effects of delayed minocycline treatment

β2-Integrins Regulate Microglial Responses and the Functional Outcome of Hemorrhagic Stroke In Vivo

Stroke is one of the leading causes of death and long-term disabilities worldwide. In addition to interruption of blood flow, inflammation is widely recognized as an important factor mediating tissue destruction in stroke. Depending on their phenotype, microglia, the main leukocytes in the CNS, are capable of either causing further tissue damage or promoting brain restoration after stroke. β2-integrins are cell adhesion molecules that are constitutively expressed on microglia. The function of β2-integrins has been investigated extensively in animal models of ischemic stroke, but their role in hemorrhagic stroke is currently poorly understood. We show in this study that dysfunction of β2-integrins is associated with improved functional outcome and decreased inflammatory cytokine expression in the brain in a mouse model of hemorrhagic stroke. Furthermore, β2-integrins affect microglial phenotype and cytokine responses in vivo. Therefore, our findings suggest that targeting β2-integrins in hemorrhagic stroke may be beneficial.

Inflammatory regulation by restraining M2 microglial polarization: Neurodestructive effects of Kallikrein-related peptidase 8 activation in intracerebral hemorrhage

Intracerebral hemorrhage (ICH) is a cerebrovascular disease. Kallikrein-related peptidase 8 (KLK8) is a serine peptidase, while its role in ICH remains unclarified. Western blot (WB) showed that KLK8 was upregulated in rat perihematomal tissues 24 h following autologous blood injection. KLK8 overexpression aggravated behavioral deficits and increased water content and Fluoro-Jade B (FJB)-positive neuron numbers in brain tissue of rats. Immunofluorescence (IF) assay showed that overexpressed-KLK8 promoted Iba-1 and iNOS expression in perihematomal tissue of rats. Overexpressed-KLK8 increased COX-2, iNOS, and Arg-1 expression and the content of IL-6, IL-1β, and TNF-α in perihematomal tissue of rats, confirmed by WB and ELISA. IF staining confirmed the expression of CCR5 was co-expressed with Iba-1, and the WB results shown increased CCR5 expression and decreased p-PKA and p-CREB expression in perihematomal tissue. Maraviroc (MVC, CCR5 inhibitor) administration rescued KLK8-induced behavioral deficits and brain injury (decreased water content and FJB-positive neuron numbers) in rats. Additionally, MVC suppressed p-PKA and p-CREB expression and the content of IL-6, IL-1β, and TNF-α in perihematomal tissue, induced by overexpressed-KLK8. Co-IP confirmed the binding of CCR5 and CCL14 in HMC3 cells. Transwell assay shown that KLK8 plus CCL4 promoted the chemotactic activity of cells, which was rescued by MVC. The biological function of KLK8/CCL14/CCR5 axis in ICH injury was also proved by MVC administration in HMC3 cells. Overall, our work revealed that KLK8 overexpression aggravated ICH process and involved in microglial activation. KLK8 might activate CCL14 thereby turning on downstream CCR5/PKA/CREB pathway, providing a theoretical basis for future therapy.

Network Pharmacology Prediction and Experimental Verification for Anti-Ferroptosis of Edaravone After Experimental Intracerebral Hemorrhage

Neuronal ferroptosis plays an important role in secondary brain injuries after intracerebral hemorrhage (ICH). Edaravone (Eda) is a promising free radical scavenger that inhibits ferroptosis in neurological diseases. However, its protective effects and underlying mechanisms in ameliorating post-ICH ferroptosis remain unclear. We employed a network pharmacology approach to determine the core targets of Eda against ICH. Forty-two rats were subjected to successful striatal autologous whole blood injection (n=28) or sham operation (n=14). The 28 blood-injected rats were randomly assigned to either the Eda or vehicle group (n=14) for immediate administration and then for 3 consecutive days. Hemin-induced HT22 cells were used for in vitro studies. The effects of Eda in ICH on ferroptosis and the MEK/ERK pathway were investigated in vivo and in vitro. Network pharmacology-based analysis revealed that candidate targets of Eda-treated ICH might be related to ferroptosis; among which prostaglandin G/H synthase 2 (PTGS2) was a ferroptosis marker. In vivo experiments showed that Eda alleviated sensorimotor deficits and decreased PTGS2 expression (all p<0.05) after ICH. Eda rescued neuron pathological changes after ICH (increased NeuN⁺ cells and decreased FJC⁺ cells, all p<0.01). In vitro experiments showed that Eda reduced intracellular reactive oxygen species and reversed mitochondria damage. Eda repressed ferroptosis by decreasing malondialdehyde and iron deposition and by influencing ferroptosis-related protein expression (all p<0.05) in ICH rats and hemin-induced HT22 cells. Mechanically, Eda significantly suppressed phosphorylated-MEK and phosphorylated-ERK1/2 expression. These results indicate that Eda has protective effects on ICH injury through ferroptosis and MEK/ERK pathway suppression.

Role and Mechanism of Ferroptosis in Neurological Diseases

Background

Ferroptosis, as a new form of cell death, is different from other cell deaths such as autophagy or senescence. Ferroptosis involves in the pathophysiological progress of several diseases, including cancers, cardiovascular diseases, nervous system diseases, and kidney damage. Since oxidative stress and iron deposition are the broad pathological features of neurological diseases, the role of ferroptosis in neurological diseases has been widely explored.

Scope of review

Ferroptosis is mainly characterized by changes in iron homeostasis, iron-dependent lipid peroxidation, and glutamate toxicity accumulation, of which can be specifically reversed by ferroptosis inducers or inhibitors. The ferroptosis is mainly regulated by the metabolism of iron, lipids and amino acids through System Xc⁻, voltage-dependent anion channels, p53, p62-Keap1-Nrf2, mevalonate and other pathways. This review also focus on the regulatory pathways of ferroptosis and its research progress in neurological diseases.

Major conclusions

The current researches of ferroptosis in neurological diseases mostly focus on the key pathways of ferroptosis. At the same time, ferroptosis was found playing a bidirectional regulation role in neurological diseases. Therefore, the specific regulatory mechanisms of ferroptosis in neurological diseases still need to be further explored to provide new perspectives for the application of ferroptosis in the treatment of neurological diseases.

Revisiting Minocycline in Intracerebral Hemorrhage: Mechanisms and Clinical Translation

Intracerebral hemorrhage (ICH) is an important subtype of stroke with an unsatisfactory prognosis of high mortality and disability. Although many pre-clinical studies and clinical trials have been performed in the past decades, effective therapy that meaningfully improve prognosis and outcomes of ICH patients is still lacking. An active area of research is towards alleviating secondary brain injury after ICH through neuroprotective pharmaceuticals and in which minocycline is a promising candidate. Here, we will first discuss new insights into the protective mechanisms of minocycline for ICH including reducing iron-related toxicity, maintenance of blood-brain barrier, and alleviating different types of cell death from preclinical data, then consider its shortcomings. Finally, we will review clinical trial perspectives for minocycline in ICH. We hope that this summary and discussion about updated information on minocycline as a viable treatment for ICH can facilitate further investigations.

Neuroprotection of Heme Oxygenase-2 in Mice AfterIntracerebral Hemorrhage

There are few effective preventive or therapeutic strategies to mitigate the effects of catastrophic intracerebral hemorrhage (ICH) in humans. Heme oxygenase is the rate-limiting enzyme in heme metabolism; heme oxygenase-2 (HO-2) is a constitutively expressed heme oxygenase. We explored the involvement of HO-2 in a collagenase-induced mouse model of ICH in C57BL/6 wild-type and HO-2 knockout mice. We assessed oxidative stress injury, blood-brain barrier permeability, neuronal damage, late-stage angiogenesis, and hematoma clearance using immunofluorescence, Western blot, MRI, and special staining methods. Our results show that HO-2 reduces brain injury volume and brain edema, alleviates cytotoxic injury, affects vascular function in the early stage of ICH, and improves hematoma absorbance and angiogenesis in the late stage of ICH in this model. Thus, we found that HO-2 has a protective effect on brain injury after ICH.

Ferroptosis: An emerging therapeutic target in stroke

Stroke is a disastrous neurological disease with high morbidity and mortality. The mechanism of the pathological process is extremely complicated and unclear. Although many basic studies have confirmed molecular mechanism of brain injury after stroke, these studies have not yet translated into treatment and clinical application. Ferroptosis is a form of cell death that is distinct from necrosis, apoptosis, and autophagy morphologically and biochemically and is characterized by iron-dependent accumulation of lipid peroxides. Despite ferroptosis being first identified in cancer cells, it was recently revealed to also be a significant factor in the pathological process of stroke. A better understanding of ferroptosis in stroke may provide us with better therapeutic targets to treat this devastating disease. Here, we systematically summarized the current mechanism of ferroptosis and reviewed the current studies regarding the relationship between ferroptosis and stroke.

Brain injury and repair after intracerebral hemorrhage: The role of microglia and brain-infiltrating macrophages

Intracerebral hemorrhage (ICH) is a major public health problem characterized by cerebral bleeding. Despite recent advances in preclinical studies, there is no effective treatment for ICH making it the deadliest subtype of stroke. The lack of effective treatment options partly attributes to the complexity as well as poorly defined pathophysiology of ICH. The emerging evidence indicates the potential of targeting secondary brain damage and hematoma resolution for improving neurological outcomes after ICH. Herein, we provide an overview of our understanding of the functional roles of activated microglia and brain-infiltrating monocyte-derived macrophages in brain injury and repair after ICH. The clinical and preclinical aspects that we discuss in this manuscript are related to ICH that occurs in adults, but not in infants. Also, we attempt to identify the knowledge gap in the field for future functional studies given the potential of targeting microglia and brain-infiltrating macrophages for therapeutic intervention after ICH.

Angiogenesis-Related Genes in Endothelial Progenitor Cells May Be Involved in Sickle Cell Stroke

Background The clinical aspects of sickle cell anemia (SCA) are heterogeneous, and different patients may present significantly different clinical evolutions. Almost all organs can be affected, particularly the central nervous system. Transient ischemic events, infarcts, and cerebral hemorrhage can be observed and affect ≈25% of the patients with SCA. Differences in the expression of molecules produced by endothelial cells may be associated with the clinical heterogeneity of patients affected by vascular diseases. In this study, we investigated the differential expression of genes involved in endothelial cell biology in SCA patients with and without stroke. Methods and Results Endothelial progenitor cells from 4 SCA patients with stroke and 6 SCA patients without stroke were evaluated through the polymerase chain reaction array technique. The analysis of gene expression profiling identified 29 differentially expressed genes. Eleven of these genes were upregulated, and most were associated with angiogenesis (55%), inflammatory response (18%), and coagulation (18%) pathways. Downregulated expression was observed in 18 genes, with the majority associated with angiogenesis (28%), apoptosis (28%), and cell adhesion (22%) pathways. Remarkable overexpression of the MMP1 (matrix metalloproteinase 1) gene in the endothelial progenitor cells of all SCA patients with stroke (fold change: 204.64; P=0.0004) was observed. Conclusions Our results strongly suggest that angiogenesis is an important process in sickle cell stroke, and differences in the gene expression profile of endothelial cell biology, especially MMP1, may be related to stroke in SCA patients.

Mannitol and Hypertonic Saline Reduce Swelling and Modulate Inflammatory Markers in a Rat Model of Intracerebral Hemorrhage

BACKGROUND

Spontaneous intracerebral hemorrhage (ICH) leaves most survivors dependent at follow-up. The importance of promoting M2-like microglial responses is increasingly recognized as a key element to ameliorate brain injury following ICH. The osmotherapeutic agents, mannitol and hypertonic saline (HTS), which are routinely used to reduce intracranial pressure, have been shown to reduce neuroinflammation in experimental ischemic and traumatic brain injury, but anti-inflammatory effects of osmotherapies have not been investigated in ICH.

METHODS

We studied the effects of iso-osmotic mannitol and HTS in rat models of ICH utilizing high-dose and moderate-dose collagenase injections into the basal ganglia, associated with high and low mortality, respectively. We studied the effects of osmotherapies, first given 5 h after ICH induction, and then administered every 12 h thereafter (4 doses total). Immunohistochemistry was used to quantify microglial activation and polarization.

RESULTS

Compared to controls, mannitol and HTS increased plasma osmolarity 1 h after infusion (301 ± 1.5, 315 ± 4.2 and 310 ± 2.0 mOsm/kg, respectively), reduced mortality at 48 h (82, 36 and 53%, respectively), and reduced hemispheric swelling at 48 h (32, 21, and 17%, respectively). In both perihematomal and contralateral tissues, mannitol and HTS reduced activation of microglia/macrophages (abundance and morphology of Iba1 + cells), and in perihematomal tissues, they reduced markers of the microglia/macrophage M1-like phenotype (nuclear p65, TNF, and NOS2), increased markers of the microglia/macrophage M2-like phenotype (arginase, YM1, and pSTAT3), and reduced infiltration of CD45 + cells.

CONCLUSIONS

Repeated dosing of osmotherapeutics at regular intervals may be a useful adjunct to reduce neuroinflammation following ICH.

Parthenolide ameliorates intracerebral hemorrhage-induced brain injury in rats

Neuroinflammation and oxidative stress are key contributors to intracranial hemorrhage (ICH)-induced brain injury. Parthenolide (PN) is a sesquiterpene lactone that has been observed to have antioxidative, anti-inflammatory, and neuroprotective potentials. However, the role of PN in ICH remains unclear. Therefore, we investigated the neuroprotective effects and underlying mechanisms of PN on an experimental model of ICH in rats. Our results showed that PN treatment improved neurological deficit and brain edema in ICH rats. The ipsilateral hemispheres of the brain were separated and homogenized. The concentrations of TNF-α, interleukin (IL)-6, and IL-17 in the homogenates were detected by enzyme-linked immunosorbent assay. We found that PN inhibited the production of proinflammatory cytokines in an ICH rat model. The ROS and glutathione (GSH) levels, as well as the activity of superoxide dismutase (SOD) in the homogenates were measured. ICH caused an increase in ROS level, and the decreases in GSH level and SOD activity were mitigated by PN treatment. Furthermore, PN significantly suppressed the expressions of active caspase-3 and Bax in ipsilateral hemispheres of the brain at Day 3 after ICH, as well as increased the surviving neurons. Finally, the ICH-induced activation of TLR4/NF-κB pathway was suppressed by PN treatment. These findings suggested that PN could be beneficial in the therapeutic strategy for ICH treatment.

Minocycline Preserves the Integrity and Permeability of BBB by Altering the Activity of DKK1-Wnt Signaling in ICH Model

Disruption of the blood-brain barrier (BBB) and subsequent neurological deficits are the most severe consequence of intracerebral hemorrhage (ICH). Minocycline has been wildly used clinically as a neurological protective agent in clinical practice. However, the underlying mechanisms by which minocycline functions remain unclear. Therefore, we assessed the influence of minocycline on BBB structure, neurological function, and inflammatory responses in a collagenase-induced ICH model, and elucidated underlying molecular mechanisms as well. Following a single injection of collagenase VII-S into the basal ganglia, BBB integrity was assessed by Evans blue extravasation while neurological function was assessed using an established neurologic function scoring system. Minocycline treatment significantly alleviated the severity of BBB disruption, brain edema, and neurological deficits in ICH model. Moreover, minocycline decreased the production of inflammatory mediators including TNF, IL-6, and MMP-9, by microglia. Minocycline treatment decreased DKK1 expression but increased Wnt1, β-catenin and Occludin, a phenomenon mimicked by DKK1 silencing. These data suggest that minocycline improves the consequences of ICH by preserving BBB integrity and attenuating neurologic deficits in a DKK1-related manner that involves enhancement of the Wnt1-β-catenin activity.

Serum lipoprotein-associated phospholipase A2 as a promising prognostic biomarker in association with 90-day outcome of acute intracerebral hemorrhage

BACKGROUND

Lipoprotein-associated phospholipase A2 (Lp-PLA2) is reflective of vascular inflammation and plays a role in the pathophysiology of cerebrovascular disease. We determine usefulness of serum Lp-PLA2 as a prognostic biomarker for intracerebral hemorrhage (ICH).

METHODS

In this prospective, observational study, serum Lp-PLA2 concentrations were detected among 164 patients with acute spontaneous basal ganglia hemorrhage and 164 healthy controls. Using multivariate analysis, we analyzed its association with poor outcome (modified Rankin Scale >2) at poststroke 90 days and hemorrhagic severity indicated by National Institutes of Health Stroke Scale (NIHSS) score and hematoma volume.

RESULTS

Serum Lp-PLA2 concentrations were remarkably higher in patients than in controls. Lp-PLA2 concentrations were independently correlated with NIHSS score (t = 5.095, P < .001) and hematoma volume (t = 2.850, P = .005). At 90-day follow-up, 85 patients (51.8%) had poor outcome. Under receiver operating characteristic curve, serum Lp-PLA2 showed a significant prognostic discriminatory capability (AUC, 0.813; 95% CI, 0.744-0.869). Serum Lp-PLA2 concentrations ≥304 ng/ml was an independent predictor associated with poor outcome (OR 7.052; 95% CI 1.971-25.228).

CONCLUSIONS

Rising serum Lp-PLA2 concentrations are closely hemorrhagic severity and clinical outcomes after ICH, substantializing serum Lp-PLA2 as a potential prognostic biomarker of ICH.

Iron toxicity, lipid peroxidation and ferroptosis after intracerebral haemorrhage

Intracerebral haemorrhage (ICH) is a devastating type of stroke with high mortality and morbidity. However, we have few options for ICH therapy and limited knowledge about post-ICH neuronal death and related mechanisms. In the aftermath of ICH, iron overload within the perihaematomal region can induce lethal reactive oxygen species (ROS) production and lipid peroxidation, which contribute to secondary brain injury. Indeed, iron chelation therapy has shown efficacy in preclinical ICH studies. Recently, an iron-dependent form of non-apoptotic cell death known as ferroptosis was identified. It is characterised by an accumulation of iron-induced lipid ROS, which leads to intracellular oxidative stress. The ROS cause damage to nucleic acids, proteins and lipid membranes, and eventually cell death. Recently, we and others discovered that ferroptosis does occur after haemorrhagic stroke in vitro and in vivo and contributes to neuronal death. Inhibition of ferroptosis is beneficial in several in vivo and in vitro ICH conditions. This minireview summarises current research on iron toxicity, lipid peroxidation and ferroptosis in the pathomechanisms of ICH, the underlying molecular mechanisms of ferroptosis and the potential for combined therapeutic strategies. Understanding the role of ferroptosis after ICH will provide a vital foundation for cell death-based ICH treatment and prevention.

Sheng-Di-Da-Huang Decoction Inhibited Inflammation Expressed in Microglia after Intracerebral Hemorrhage in Rats

Objects

Sheng-Di-Da-Huang Decoction was used as an effective hemostatic agent in ancient China. However, its therapeutic mechanism is still not clear. Inflammatory injury plays a critical role in ICH-induced secondary brain injury. After hemolysis, hematoma components are released, inducing microglial activation via TLR4, which initiates the activation of transcription factors (such as NF-κB) to regulate expression of proinflammatory cytokine genes. This study aimed to verify the anti-inflammatory effects of Sheng-Di-Da-Huang Decoction on ICH rats.

Materials and Methods

Intracerebral hemorrhage was induced by injection of bacterial collagenase (0.2 U) in rats. Neurological deficits, brain water content, Evans blue extravasation, expression of TLR4, NF-κB, Iba-1 positive cells (activated microglia), tumor necrosis factor-α (TNF-α), and interleukin-1β (IL-1β) were examined 1, 3, 7, and 14 days after collagenase injection. MR images were also studied.

Results

Sheng-Di-Da-Huang Decoction remarkably improved neurological function, reduced brain water content as well as Evans blue extravasation, downregulated expression of TLR4, NF-κB, TNF-α, and IL-1β, and inhibited microglial activation.

Conclusions

Sheng-Di-Da-Huang Decoction reduced inflammation reaction after ICH through inhibited inflammation expressed in microglia.

Butin Attenuates Brain Edema in a Rat Model of Intracerebral Hemorrhage by Anti Inflammatory Pathway

Background

This study evaluates the effect of butin against brain edema in intracerebral hemorrhage (ICH).

Methodology

ICH was induced by injecting bacterial collagenase in the brain and all the animals were separated into four groups such as control group, ICH group treated with vehicle, Butin 25 and 50 mg/kg group receives butin (25 and 50 mg/kg, i.p.)60 min after the induction of ICH in all animals. One day after neurological score, hemorrhagic injury and expressions of protein responsible for apoptosis and inflammatory cytokines were assessed in the brain tissue of ICH rats.

Result

Neurological scoring significantly increased and hemorrhagic lesion volume decreased in butin treated group of rats compared to ICH group. However, treatment with butin significantly decreases the ratio of Bax/Bcl-2 and protein expression of Cleaved caspase-3 than ICH group in dose dependent manner. Level of inflammatory mediators such as tumor necrosis factor-α (TNF-α) and interlukin-6 (IL-6) in the brain tissues were significantly decreased in the butin treated group than ICH group. In addition butin attenuates the altered signaling pathway of NF-κB in the brain tissues of ICH rats.

Conclusion

Our study concludes that butin attenuates the altered behavior and neuronal condition in ICH rats by reducing apoptosis and inflammatory response.

Comparing Effects of Transforming Growth Factor β1 on Microglia From Rat and Mouse: Transcriptional Profiles and Potassium Channels

The cytokine, transforming growth factor β1 (TGFβ1), is up-regulated after central nervous system (CNS) injuries or diseases involving microglial activation, and it has been proposed as a therapeutic agent for treating neuroinflammation. Microglia can produce and respond to TGFβ1. While rats and mice are commonly used for studying neuroinflammation, very few reports directly compare them. Such studies are important for improving pre-clinical studies and furthering translational progress in developing therapeutic interventions. After intracerebral hemorrhage (ICH) in the rat striatum, the TGFβ1 receptor was highly expressed on microglia/macrophages within the hematoma. We recently found species similarities and differences in response to either a pro-inflammatory (interferon-γ, IFN-γ, +tumor necrosis factor, TNF-α) or anti-inflammatory interleukin-4 (IL-4) stimulus. Here, we assessed whether rat and mouse microglia differ in their responses to TGFβ1. Microglia were isolated from Sprague-Dawley rats and C57BL/6 mice and treated with TGFβ1. We quantified changes in expression of >50 genes, in their morphology, proliferation, apoptosis and in three potassium channels that are considered therapeutic targets. Many inflammatory mediators, immune receptors and modulators showed species similarities, but notable differences included that, for some genes, only one species responded (e.g., Il4r, Il10, Tgfbr2, colony-stimulating factor receptor (Csf1r), Itgam, suppressor of cytokine signaling 1 (Socs1), toll-like receptors 4 (Tlr4), P2rx7, P2ry12), and opposite responses were seen for others (Tgfb1, Myc, Ifngr1). In rat only, TGFβ1 affected microglial morphology and proliferation, but there was no apoptosis in either species. In both species, TGFβ1 dramatically increased Kv1.3 channel expression and current (no effects on Kir2.1). KCa3.1 showed opposite species responses: the current was low in unstimulated rat microglia and greatly increased by TGFβ1 but higher in control mouse cells and decreased by TGFβ1. Finally, we compared TGFβ1 and IL10 (often considered similar anti-inflammatory stimuli) and found many different responses in both species. Overall, the numerous species differences should be considered when characterizing neuroinflammation and microglial activation in vitro and in vivo, and when targeting potassium channels.

Gene Expression Profile of Peripheral Blood Mononuclear Cells in Response to Intracerebral Hemorrhage

RNA-sequencing, a powerful tool, yields a comprehensive view of whole transcriptome. Intracerebral hemorrhage (ICH) is a devastating form of stroke. To date, RNA-sequencing analysis of ICH has not been reported. Peripheral blood mononuclear cells (PBMCs) were used as a source of mRNA for gene expression profile analysis in stroke. In this study, we performed transcriptome analyses for PBMCs from four ICH patients and four healthy volunteers on Illumina platform. We identified 4040 significantly differentially expressed genes (DEGs). Functional annotation of DEGs with DAVID Bioinformatics Resources indicated that genes associated with cell apoptosis, autophagy, cell-cell adhesion, inflammatory response, protein binding, positive regulation of gene expression, and signal transduction were most significantly enriched by DEGs. Gene set enrichment analysis identified 40 significant Kyoto Encyclopedia of Genes and Genomes (KEGG) pathways, including chemokine signaling, cytokine-cytokine receptor interaction, oxidative phosphorylation, and glutathione metabolism processes. These data point to a complex mechanism for ICH pathogenesis. Overall, the present study demonstrated an altered gene expression profile of PBMCs in response to acute ICH. Our study provided important information for understanding the molecular mechanisms of ICH pathogenesis at system-wide levels.

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.

NG2 glial cells regulate neuroimmunological responses to maintain neuronal function and survival

NG2-expressing neural progenitor cells (i.e., NG2 glial cells) maintain their proliferative and migratory activities even in the adult mammalian central nervous system (CNS) and produce myelinating oligodendrocytes and astrocytes. Although NG2 glial cells have been observed in close proximity to neuronal cell bodies in order to receive synaptic inputs, substantive non-proliferative roles of NG2 glial cells in the adult CNS remain unclear. In the present study, we generated NG2-HSVtk transgenic rats and selectively ablated NG2 glial cells in the adult CNS. Ablation of NG2 glial cells produced defects in hippocampal neurons due to excessive neuroinflammation via activation of the interleukin-1 beta (IL-1β) pro-inflammatory pathway, resulting in hippocampal atrophy. Furthermore, we revealed that the loss of NG2 glial cell-derived hepatocyte growth factor (HGF) exacerbated these abnormalities. Our findings suggest that NG2 glial cells maintain neuronal function and survival via the control of neuroimmunological function.

Brain iron overload following intracranial haemorrhage

Intracranial haemorrhages, including intracerebral haemorrhage (ICH), intraventricular haemorrhage (IVH) and subarachnoid haemorrhage (SAH), are leading causes of morbidity and mortality worldwide. In addition, haemorrhage contributes to tissue damage in traumatic brain injury (TBI). To date, efforts to treat the long-term consequences of cerebral haemorrhage have been unsatisfactory. Incident rates and mortality have not showed significant improvement in recent years. In terms of secondary damage following haemorrhage, it is becoming increasingly apparent that blood components are of integral importance, with haemoglobin-derived iron playing a major role. However, the damage caused by iron is complex and varied, and therefore, increased investigation into the mechanisms by which iron causes brain injury is required. As ICH, IVH, SAH and TBI are related, this review will discuss the role of iron in each, so that similarities in injury pathologies can be more easily identified. It summarises important components of normal brain iron homeostasis and analyses the existing evidence on iron-related brain injury mechanisms. It further discusses treatment options of particular promise.

IL-17A promotes microglial activation and neuroinflammation in mouse models of intracerebral haemorrhage

Microglial activation is an important contributor to neuroinflammation in intracerebral haemorrhage (ICH). IL-17A has been demonstrated to be involved in neuroinflammatory diseases such as multiple sclerosis. However, the exact mechanism of IL-17A mediated microglial activation in ICH has not been well identified. The purpose of this experiment is to investigate the role of IL-17A in ICH induced microglial activation and neuroinflammation. ICH mice were made by injection of autologous blood model. IL-17A expression and inflammatory factors in perihematomal region, and neurological function of mice were examined after ICH. In addition, IL-17A-neutralizing antibody was utilized to potentially prevent microglial activation and neuroinflammation in ICH mice. The expression of IL-17A, inflammatory factors and microglial activation in perihematomal region were significantly increased, and neurological function of mice was impaired after ICH. In addition, IL-17A Ab prevented ICH-induced cytokine expression, including TNF-α, IL-1β and IL-6, and downstream signaling molecules, including MyD88, TRIF, IκBα, and NF-κBp65 expression, and attenuated microglial activation. IL-17A Ab significantly reduced brain water content and improved neurological function of ICH mice. In conclusion, our results demonstrated that IL-17A was involved in ICH-induced microglial activation and neuroinflammation. IL-17A Ab might also provide a promising therapeutic strategy in ICH.

After Intracerebral Hemorrhage, Oligodendrocyte Precursors Proliferate and Differentiate Inside White-Matter Tracts in the Rat Striatum

Damage to myelinated axons contributes to neurological deficits after acute CNS injury, including ischemic and hemorrhagic stroke. Potential treatments to promote re-myelination will require fully differentiated oligodendrocytes, but almost nothing is known about their fate following intracerebral hemorrhage (ICH). Using a rat model of ICH in the striatum, we quantified survival, proliferation, and differentiation of oligodendrocyte precursor cells (OPCs) (at 1, 3, 7, 14, and 28 days) in the peri-hematoma region, surrounding striatum, and contralateral striatum. In the peri-hematoma, the density of Olig2⁺ cells increased dramatically over the first 7 days, and this coincided with disorganization and fragmentation of myelinated axon bundles. Very little proliferation (Ki67⁺) of Olig2⁺ cells was seen in the anterior subventricular zone from 1 to 28 days. However, by 3 days, many were proliferating in the peri-hematoma region, suggesting that local proliferation expands their population. By 14 days, the density of Olig2⁺ cells declined in the peri-hematoma region, and, by 28 days, it reached the low level seen in the contralateral striatum. At these later times, many surviving axons were aligned into white-matter bundles, which appeared less swollen or fragmented. Oligodendrocyte cell maturation was prevalent over the 28-day period. Densities of immature OPCs (NG2⁺Olig2⁺) and mature (CC-1⁺Olig2⁺) oligodendrocytes in the peri-hematoma increased dramatically over the first week. Regardless of the maturation state, they increased preferentially inside the white-matter bundles. These results provide evidence that endogenous oligodendrocyte precursors proliferate and differentiate in the peri-hematoma region and have the potential to re-myelinate axon tracts after hemorrhagic stroke.

The role of aquaporin 4 in apoptosis after intracerebral hemorrhage

Background

We previously reported that aquaporin-4 deletion (AQP4^−/−) in mice increased edema and altered blood-brain barrier integrity following intracerebral hemorrhage (ICH). To date, little is known about the role of AQP4 in apoptosis after ICH. The purpose of this study was to examine the role of AQP4 in apoptosis and its mechanisms after ICH using AQP4^−/− mice.

Methods

We compared the survival rate and neurological deficits in wild-type (AQP4^+/+) mice with those in AQP4^−/− mice following ICH. Histological changes were detected with terminal deoxynucleotidyl transferase-mediated dUTP-biotin nick end labeling (TUNEL) staining and Hoechst staining. The cell types involved were determined by immunocytochemical studies. We also measured activated caspase-3, caspase-9, caspase-8, Bax, and Bcl-2 with Western blotting at 1, 3, and 7 days after ICH. A cytokine protein assay was used to detect cytokines in AQP4^+/+ and AQP4^−/− mice following ICH, and the results were verified by ELISA.

Results

We found more apoptotic cells in AQP4^−/− mice following ICH; the cell types involved were predominantly neurons and astrocytes. Western blotting showed that the expression of activated caspase-3 and caspase-8 was significantly increased (P <0.05). Moreover, we demonstrated a greater enhancement in the release of TNF-α and IL-1β, as well as their receptors, in AQP4^−/− mice following ICH than in AQP4^+/+ mice by cytokine protein assay and Western blotting (P <0.05). The inhibitors of TNF-α and IL-1β reduced apoptotic cells after ICH in AQP4^−/− mice compared with wild-type mice (P <0.05).

Conclusions

AQP4 deletion increases apoptosis following ICH, and the underlying mechanism may be through cytokines, especially TNF-α and IL-1β, initiating the apoptotic cascade, as well as activation of caspase-3 and caspase-8.

Polymorphonuclear neutrophil in brain parenchyma after experimental intracerebral hemorrhage

Polymorphonuclear neutrophils (PMNs) infiltration into brain parenchyma after cerebrovascular accidents is viewed as a key component of secondary brain injury. Interestingly, a recent study of ischemic stroke suggests that after ischemic stroke, PMNs do not enter brain parenchyma and as such may cause no harm to the brain. Thus, the present study was designed to determine PMNs' behavior after intracerebral hemorrhage (ICH). Using the autologous blood injection model of ICH in rats and immunohistochemistry for PMNs and vascular components, we evaluated the temporal and spatial PMNs distribution in the ICH-affected brain. We found that, similar to ischemia, there is a robust increase in presence of PMNs in the ICH-injured tissue that lasts for at least 1 to 2 weeks. However, in contrast to what was suggested for ischemia, besides PMNs that stay in association with the vasculature, after ICH, we found abundance of intraparenchymal PMNs (with no obvious association with vessels) in the ICH core and hematoma border, especially between 1 and 7 days after the ictus. Interestingly, the increased presence of intraparenchymal PMNs after ICH coincided with the massive loss of microvascular integrity, suggesting vascular disruption as a potential cause of PMNs presence in the brain parenchyma. Our study indicates that in contrast to ischemic stroke, after ICH, PMNs target not only vascular compartment but also brain parenchyma in the affected brain. As such, it is possible that the pathogenic role and therapeutic implications of targeting PMNs after ICH could be different from these after ischemic stroke. Our work suggests the needs for more studies addressing the role of PMNs in ICH.

Profile of minocycline and its potential in the treatment of schizophrenia

Accumulating evidence suggests that neuroinflammation affecting microglia plays an important role in the etiology of schizophrenia, and appropriate control of microglial activation may be a promising therapeutic strategy for schizophrenia. Minocycline, a second-generation tetracycline that inhibits microglial activation, has been shown to have a neuroprotective effect in various models of neurodegenerative disease, including anti-inflammatory, antioxidant, and antiapoptotic properties, and an ability to modulate glutamate-induced excitotoxicity. Given that these mechanisms overlap with neuropathologic pathways, minocycline may have a potential role in the adjuvant treatment of schizophrenia, and improve its negative symptoms. Here, we review the relevant studies of minocycline, ranging from preclinical research to human clinical trials.

Emerging experimental therapies for intracerebral hemorrhage: targeting mechanisms of secondary brain injury

Intracerebral hemorrhage (ICH) is associated with a higher degree of morbidity and mortality than other stroke subtypes. Despite this burden, currently approved treatments have demonstrated limited efficacy. To date, therapeutic strategies have principally targeted hematoma expansion and resultant mass effect. However, secondary mechanisms of brain injury are believed to be critical effectors of cell death and neurological outcome following ICH. This article reviews the pathophysiology of secondary brain injury relevant to ICH, examines pertinent experimental models, and highlights emerging therapeutic strategies. Treatment paradigms discussed include thrombin inhibitors, deferoxamine, minocycline, statins, granulocyte-colony stimulating factors, and therapeutic hypothermia. Despite promising experimental and preliminary human data, further studies are warranted prior to effective clinical translation.

Inflammation in intracerebral hemorrhage: from mechanisms to clinical translation

Intracerebral hemorrhage (ICH) accounts for 10-15% of all strokes and is associated with high mortality and morbidity. Currently, no effective medical treatment is available to improve functional outcomes in patients with ICH. Potential therapies targeting secondary brain injury are arousing a great deal of interest in translational studies. Increasing evidence has shown that inflammation is the key contributor of ICH-induced secondary brain injury. Inflammation progresses in response to various stimuli produced after ICH. Hematoma components initiate inflammatory signaling via activation of microglia, subsequently releasing proinflammatory cytokines and chemokines to attract peripheral inflammatory infiltration. Hemoglobin (Hb), heme, and iron released after red blood cell lysis aggravate ICH-induced inflammatory injury. Danger associated molecular patterns such as high mobility group box 1 protein, released from damaged or dead cells, trigger inflammation in the late stage of ICH. Preclinical studies have identified inflammatory signaling pathways that are involved in microglial activation, leukocyte infiltration, toll-like receptor (TLR) activation, and danger associated molecular pattern regulation in ICH. Recent advances in understanding the pathogenesis of ICH-induced inflammatory injury have facilitated the identification of several novel therapeutic targets for the treatment of ICH. This review summarizes recent progress concerning the mechanisms underlying ICH-induced inflammation. We focus on the inflammatory signaling pathways involved in microglial activation and TLR signaling, and explore potential therapeutic interventions by targeting the removal of hematoma components and inhibition of TLR signaling.

Development and pharmacological verification of a new mouse model of central post-stroke pain

Central post-stroke pain (CPSP) including thalamic pain is one of the most troublesome sequelae that can occur after a cerebrovascular accident. Although the prevalence of CPSP among stroke patients is relatively low, the persistent, often treatment-refractory, painful sensations can be a major problem and decrease the affected patient's quality of life. To better understand of the pathophysiological basis of CPSP, we developed and characterized a new mouse model of thalamic CPSP. This model is based on a hemorrhagic stroke lesion with collagenase in the ventral posterolateral nucleus of the thalamus. Histopathological analysis indicated that the thalamic hemorrhage produced a relatively confined lesion that destroys the tissue within the initial bleed, and also showed the presence of activated microglia adjacent to the core of hemorrhagic lesions. Behavioral analysis demonstrated that the animals displayed diclofenac-, morphine- or pregabalin-resistant mechanical allodynia and thermal hyperalgesia of the hind paw contralateral to the lesion for over 112 days. However, we found that minocycline, a microglial inhibitor, significantly ameliorated mechanical allodynia and thermal hyperalgesia. These results suggest that this model might be proved as a useful animal model for studying the neuropathology of thalamic syndrome, and developing improved therapeutics for CPSP.

Role of PGE₂ EP1 receptor in intracerebral hemorrhage-induced brain injury

Prostaglandin E₂ (PGE₂) has been described to exert beneficial and detrimental effects in various neurologic disorders. These conflicting roles of PGE₂ could be attributed to its diverse receptor subtypes, EP1-EP4. At present, the precise role of EP1 in intracerebral hemorrhage (ICH) is unknown. Therefore, to elucidate its possible role in ICH, intrastriatal injection of collagenase was given in randomized groups of adult male wildtype (WT) and EP1 receptor knockout (EP1⁻/⁻)C57BL/6 mice. Functional outcomes including neurologic deficits, rotarod performance, open field activity, and adhesive removal performance were evaluated at 24, 48, and 72 h post-ICH. Lesion volume, cell survival and death, were assessed using Cresyl Violet, and Fluoro-Jade staining, respectively. Microglial activation and phagocytosis were estimated using Iba1 immunoreactivity and fluorescently-labeled microspheres. Following 72 h post-ICH, EP1⁻/⁻ mice showed deteriorated outcomes compared to the WT control mice. These outcomes were demonstrated by elevated neurological deficits, exacerbated lesion volume, and significantly worsened sensorimotor functions. Fluoro-Jade staining showed significantly increased numbers of degenerating neurons and reduced neuronal survival in EP1⁻/⁻ compared to WT mice. To assess in vivo phagocytosis, the number of microspheres phagocytosed by Iba1-positive cells was 145.4 ± 15.4 % greater in WT compared to EP1⁻/⁻ mice. These data demonstrate that EP1 deletion exacerbates neuro-behavioral impairments following ICH, potentially by slowing down/impairing microglial phagocytosis. A better understanding of this EP1 mechanism could lead to improved intervention strategies for hemorrhagic stroke.

Effects of minocycline on the expression of NGF and HSP70 and its neuroprotection role following intracerebral hemorrhage in rats

The present study was aimed to investigate the effects of minocycline (MC) on the expression of nerve growth factor (NGF) and heat shock protein 70 (HSP70) following intracerebral hemorrhage (ICH) in rats, and explore the neuroprotective function of MC. Seventy-eight male SD rats were randomly assigned to three groups: the ICH control group (n = 36), ICH intervention group (n = 36) and sham operation group (n = 6). The ICH control group and ICH intervention group were subdivided into 6 subgroups at 1, 2, 4, 5, 7 and 14 d after ICH with 6 rats in each subgroup. Type IV collagenase was injected into the basal nuclei to establish the ICH model. All rats showed symptoms of the nervous system after the model was established, and the sympotsm in the ICH control group were more serious than the ICH intervention group. The number of NGF-positive cells and HSP70-positive cells in the ICH intervention group was higher than that of the ICH control group. MC administration by intraperitoneal injection can increase the expression of NGF and HSP70. MC may inhibit the activation of microglia, the inflammatory reaction and factors, matrix metalloproteinases and apoptosis, thus protecting neurons. The change of the expression of NGF and HSP70 may be involved in the pathway of neuroprotection by MC.

Minocycline reduces reactive gliosis in the rat model of hydrocephalus

Background

Reactive gliosis had been implicated in injury and recovery patterns associated with hydrocephalus. Our aim is to determine the efficacy of minocycline, an antibiotic known for its anti-inflammatory properties, to reduce reactive gliosis and inhibit the development of hydrocephalus.

Results

The ventricular dilatation were evaluated by MRI at 1-week post drugs treated, while GFAP and Iba-1were detected by RT-PCR, Immunohistochemistry and Western blot. The expression of GFAP and Iba-1 was significantly higher in hydrocephalic group compared with saline control group (p < 0.05). Minocycline treatment of hydrocephalic animals reduced the expression of GFAP and Iba-1 significantly (p < 0.05). Likewise, the severity of ventricular dilatation is lower in minocycline treated hydrocephalic animals compared with the no minocycline group (p < 0.05).

Conclusion

Minocycline treatment is effective in reducing the gliosis and delaying the development of hydrocephalus with prospective to be the auxiliary therapeutic method of hydrocephalus.

What is behind the non-antibiotic properties of minocycline?

Minocycline is a second-generation, semi-synthetic tetracycline that has been in use in therapy for over 30 years for its antibiotic properties against both Gram-positive and Gram-negative bacteria. It displays antibiotic activity due to its ability to bind to the 30S ribosomal subunit of bacteria and thus inhibit protein synthesis. More recently, it has been described to exert a variety of biological actions beyond its antimicrobial activity, including anti-inflammatory and anti-apoptotic activities, inhibition of proteolysis, as well as suppression of angiogenesis and tumor metastasis, which have been confirmed in different experimental models of non-infectious diseases. There are also many studies that have focused on the mechanisms involved in these non-antibiotic properties of minocycline, including anti-oxidant activity, inhibition of several enzyme activities, inhibition of apoptosis and regulation of immune cell activation and proliferation. This review summarizes the current findings in this topic, mainly focusing on the mechanisms underlying the immunomodulatory and anti-inflammatory activities of minocycline.

SC1/hevin identifies early white matter injury after ischemia and intracerebral hemorrhage in young and aged rats

The progression of white matter damage after ischemic and hemorrhagic strokes can exacerbate the initial injury, but little is known about the processes involved. We show that the antiadhesive matricellular glycoprotein SC1 is a novel early marker of white matter damage in 3 models of acute injury in the rat striatum: transient focal ischemia, intracerebral hemorrhage, and a needle penetration wound. SC1 was restricted to the damaged portions of axon bundles that bordered stroke lesions in young-adult and aged rats. SC1 peaked at 1 and 3 days after intracerebral hemorrhage and at 7 days after ischemia. The SC1-positive bundles usually expressed degraded myelin basic protein and amyloid precursor protein, a marker of axonal injury. At the hematoma edge, SC1 was seen in a few axon bundles that retained myelin basic protein staining. In these bundles, punctate SC1 staining filled individual axons, extended beyond a core of pan-axonal neurofilament and NF200 and was inside or overlapped with myelin basic protein staining when it was present. Aged rats had less SC1 (and amyloid precursor protein) after both types of stroke, suggesting a reduced axonal response. SC1 also labeled amyloid precursor protein-positive axon bundles along the needle penetration tract of saline-injected rats; thus, SC1 appears to characterize damaged striatal white matter damage after multiple types of injury.

Intra-parenchymal ferrous iron infusion causes neuronal atrophy, cell death and progressive tissue loss: implications for intracerebral hemorrhage

Intracerebral hemorrhage (ICH) is a devastating stroke causing considerable tissue destruction from mechanical trauma and secondary degeneration. Free iron, released over days from degrading erythrocytes, causes free radicals that likely contribute to delayed injury. Indeed, an intracerebral injection of iron rapidly kills cells and causes cerebral edema. We expanded upon these observations by: determining a dose-response relationship of iron infusion, examining the structural appearance of surviving striatal neurons, and evaluating injury over months. First, we measured 24-h edema in rats given 3.8, 19.0 or 38.0 μg infusions of FeCl₂ (i.e., 30 μL of a 1, 5 or 10 mmol/L solution). Second, rats were given these infusions (vs. saline controls) followed by behavioral assessment and histology at 7 days. Third, dendritic structure was measured in Golgi-Cox stained neurons at 7 days after a 0.95-μg dose (30 μL of a 0.25 mmol/L solution). Last, rats survived 7 or 60 days post-injection (19.0 μg) for histological assessment. Larger doses of iron caused greater injury, but this was generally not reflected in behavior that indicated similar deficits among the 3.8-38.0 μg groups. Similarly, edema occurred but was not linearly related to dose. Even after a low iron dose the surviving neurons in the peri-injury zone were considerably atrophied (vs. contralateral side and controls). Finally, continuing tissue loss occurred over weeks with prominent neuronal death and iron-positive cells (e.g., macrophages) at 60 days. Iron alone may account for the chronic degeneration found after ICH in rodent models.

Intracerebral hemorrhage: clinical overview and pathophysiologic concepts

Intracerebral hemorrhage is by far the most destructive form of stroke. Apart from the management in a specialized stroke or neurological intensive care unit (NICU), no specific therapies have been shown to consistently improve outcomes after ICH. Current guidelines endorse early aggressive optimization of physiologic derangements with ventilatory support when indicated, blood pressure control, reversal of any preexisting coagulopathy, intracranial pressure monitoring for certain cases, osmotherapy, temperature modulation, seizure prophylaxis, treatment of hyerglycemia, and nutritional support in the stroke unit or NICU. Ventriculostomy is the cornerstone of therapy for control of intracranial pressure patients with intraventricular hemorrhage. Surgical hematoma evacuation does not improve outcome for more patients, but is a reasonable option for patients with early worsening due to mass effect due to large cerebellar or lobar hemorrhages. Promising experimental treatments currently include ultra-early hemostatic therapy, intraventricular clot lysis with thrombolytics, pioglitazone, temperature modulation, and deferoxamine to reduce iron-mediated perihematomal inflammation and tissue injury.

Attenuation of microglial activation with minocycline is not associated with changes in neurogenesis after focal traumatic brain injury in adult mice

Neurogenesis is stimulated following injury to the adult brain and could potentially contribute to tissue repair. However, evidence suggests that microglia activated in response to injury are detrimental to the survival of new neurons, thus limiting the neurogenic response. The aim of this study was to determine the effect of the anti-inflammatory drug minocycline on neurogenesis and functional recovery after a closed head injury model of focal traumatic brain injury (TBI). Beginning 30 min after trauma, minocycline was administered for up to 2 weeks and bromodeoxyuridine was given on days 1-4 to label proliferating cells. Neurological outcome and motor function were evaluated over 6 weeks using the Neurological Severity Score (NSS) and ledged beam task. Microglial activation was assessed in the pericontusional cortex and hippocampus at 1 week post-trauma, using immunohistochemistry to detect F4/80. Following immunolabeling of bromodeoxyuridine, double-cortin, and NeuN, cells undergoing distinct stages of neurogenesis, including proliferation, neuronal differentiation, neuroblast migration, and long-term survival, were quantified at 1 and 6 weeks in the hippocampal dentate gyrus, as well as in the subventricular zone of the lateral ventricles and the pericontusional cortex. Our results show that minocycline successfully reduced microglial activation and promoted early neurological recovery that was sustained over 6 weeks. We also show for the first time in the closed head injury model, that early stages of neurogenesis were stimulated in the hippocampus and subventricular zone; however, no increase in new mature neurons occurred. Contrary to our hypothesis, despite the attenuation of activated microglia, minocycline did not support neurogenesis in the hippocampus, lateral ventricles, or pericontusional cortex, with none of the neurogenic stages being affected by treatment. These data provide evidence that a general suppression of microglial activation is insufficient to enhance neuronal production, suggesting that further work is required to elucidate the relationship between microglia and neurogenesis after TBI.

Chemokines and their receptors in intracerebral hemorrhage

Intracerebral hemorrhage (ICH) is a devastating clinical event which results in a high rate of disability and death. At present, no effective treatment is available for ICH. Accumulating evidence suggests that inflammatory responses contribute significantly to the ICH-induced secondary brain outcomes. During ICH, inflammatory cells accumulate at the ICH site attracted by gradients of chemokines. This review summarizes recent progress in ICH studies and the chemoattractants that act during the injury and focuses on and introduces the basic biology of the chemokine monocyte chemoattractant protein-1 (MCP1) and its role in the progression of ICH. Better understanding of MCP1 signaling cascade and the compensation after its inhibition could shed light on the development of effective treatments for ICH.

A critical appraisal of experimental intracerebral hemorrhage research

The likelihood of translating therapeutic interventions for stroke rests on the quality of preclinical science. Given the limited success of putative treatments for ischemic stroke and the reasons put forth to explain it, we sought to determine whether such problems hamper progress for intracerebral hemorrhage (ICH). Approximately 10% to 20% of strokes result from an ICH, which results in considerable disability and high mortality. Several animal models reproduce ICH and its underlying pathophysiology, and these models have been widely used to evaluate treatments. As yet, however, none has successfully translated. In this review, we focus on rodent models of ICH, highlighting differences among them (e.g., pathophysiology), issues with experimental design and analysis, and choice of end points. A Pub Med search for experimental ICH (years: 2007 to 31 July 2011) found 121 papers. Of these, 84% tested neuroprotectants, 11% tested stem cell therapies, and 5% tested rehabilitation therapies. We reviewed these to examine study quality (e.g., use of blinding procedures) and choice of end points (e.g., behavioral testing). Not surprisingly, the problems that have plagued the ischemia field are also prevalent in ICH literature. Based on these data, several recommendations are put forth to facilitate progress in identifying effective treatments for ICH.

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.

Effects of minocycline on apoptosis and angiogenesis-related protein expression in a rat model of intracerebral hemorrhage

In the present study, a rat model of non-traumatic intracerebral hemorrhage was established by type IV collagenase injection into the right globus pallidus. Bax and Bcl-2 expression in tissues surrounding hematomas was significantly increased within 14 days after injury, and it then gradually decreased. Vascular endothelial growth factor, Flk-1 and Flt-1 mRNA expression gradually increased over time. After intraperitoneal injection with minocycline, Bax expression was decreased 1 day after intracerebral hemorrhage. Flk-1 and Flt-1 mRNA expression was decreased after minocycline injection, but Bcl-2 expression was increased, and vascular endothelial growth factor mRNA expression was decreased between 4-14 days. These results indicated that protective effects of minocycline on nerve tissues were associated with increased Bcl-2 expression and decreased Bax expression in the early stage after intracerebral hemorrhage. In the late stage, minocycline downregulated vascular endothelial growth factor and its receptor expression to inhibit brain tissue self-repair.

Toll-like receptor 4 contributes to poor outcome after intracerebral hemorrhage

OBJECTIVE

Intracerebral hemorrhage (ICH) is a devastating stroke subtype in which perihematomal inflammation contributes to neuronal injury and functional disability. Histologically, the region becomes infiltrated with neutrophils and activated microglia followed by neuronal loss, but little is known about the immune signals that coordinate these events. This study aimed to determine the role of Toll-like receptor 4 (TLR4) in the innate immune response after ICH and its impact on neurobehavioral outcome.

METHODS

Transgenic mice incapable of TLR4 signaling and wild-type controls were subjected to striatal blood injection to model ICH. The perihematomal inflammatory response was then quantified by immunohistochemistry, whole brain flow cytometry, and polymerase chain reaction. The critical location of TLR4 signaling was determined by blood transfer experiments between genotypes. Functional outcomes were quantified in all cohorts using the cylinder and open field tests.

RESULTS

TLR4-deficient mice had markedly decreased perihematomal inflammation, associated with reduced recruitment of neutrophils and monocytes, fewer microglia, and improved functional outcome by day 3 after ICH. Moreover, blood transfer experiments revealed that TLR4 on leukocytes or platelets within the hemorrhage contributes to perihematomal leukocyte infiltration and the neurological deficit.

INTERPRETATION

Together, these data identify a critical role for TLR4 signaling in perihematomal inflammation and injury and indicate this pathway may be a target for therapeutic intervention.

SC1/hevin and reactive gliosis after transient ischemic stroke in young and aged rats

SC1 is a member of the SPARC family of glycoproteins that regulate cell-matrix interactions in the developing brain. SC1 is expressed in astrocytes, but nothing is known about the expression in the aged or after stroke. We found that after focal striatal ischemic infarction in adult rats, SC1 increased in astrocytes surrounding the infarct and in the glial scar, but in aged rats, SC1 was lower at the lesion edge. Glial fibrillary acidic protein (GFAP) also increased, but it was less prominent in reactive astrocytes further from the lesion in the aged rats. On the basis of their differential expression of several molecules, 2 types of reactive astrocytes with differing spatiotemporal distributions were identified. On Days 3 and 7, SC1 was prevalent in cells expressing markers of classic reactive astrocytes (GFAP, vimentin, nestin, S100β), as well as apoliprotein E (ApoE), interleukin 1β, aggrecanase 1 (ADAMTS4), and heat shock protein 25 (Hsp25). Adjacent to the lesion on Days 1 and 3, astrocytes with low GFAP levels and a "starburst" SC1 pattern expressed S100β, ApoE, and Hsp32 but not vimentin, nestin, interleukin 1β, ADAMTS4, or Hsp25. Neither cell type was immunoreactive for NG2,CC-1, CD11b, or ionized calcium-binding adapter-1. Their differing expression of inflammation-related and putatively protective molecules suggests different roles for starburst and classic reactive astrocytes in the early glial responses to ischemia.

Minocycline attenuates photoreceptor degeneration in a mouse model of subretinal hemorrhage microglial: inhibition as a potential therapeutic strategy

Hemorrhage under the neural retina (subretinal hemorrhage) can occur in the context of age-related macular degeneration and induce subsequent photoreceptor cell death and permanent vision loss. Current treatments with the objective of removing or displacing the hemorrhage are invasive and of mixed efficacy. We created a mouse model of subretinal hemorrhage to characterize the inflammatory responses and photoreceptor degeneration that occur in the acute aftermath of hemorrhage. It was observed that microglial infiltration into the outer retina commences as early as 6 hours after hemorrhage. Inflammatory cells progressively accumulate in the outer nuclear layer concurrently with photoreceptor degeneration and apoptosis. Administration of minocycline, an inhibitor of microglial activation, decreased microglial expression of chemotactic cytokines in vitro and reduced microglial infiltration and photoreceptor cell loss after subretinal hemorrhage in vivo. Inflammatory responses and photoreceptor atrophy occurred after subretinal hemorrhage, however, the degree of response and atrophy were similar between C3-deficient and C3-sufficient mice, indicating a limited role for complement-mediated processes. Our data indicate a role for inflammatory responses in driving photoreceptor cell loss in subretinal hemorrhage, and it is proposed that microglial inhibition may be beneficial in the treatment of subretinal hemorrhage.

Therapeutic time window for the neuroprotective effects of NGF when administered after focal cerebral ischemia

In the present study, we evaluated the neuroprotection time window for nerve growth factor (NGF) after ischemia/reperfusion brain injury in rabbits as related to this anti-apoptosis mechanism. Male New Zealand rabbits were subjected to 2 h of middle cerebral artery occlusion (MCAO), followed by 70 h of reperfusion. NGF was administered after injury to evaluate the time window. Neurological deficits, infarct volume, neural cell apoptosis and expressions of caspase-3 and Bcl-2 were measured. Compared to saline-treated control, NGF treatment at 2, 3 and 5 h after MCAO significantly reduced infarct volume, neural cell apoptosis and expression of caspase-3 (P < 0.01), up-regulated the expression of Bcl-2 and improved functional recovery (P < 0.01). However, treatment at latter time points did not produce significant neuroprotection. Neuroprotection treatment with NGF provides an extended time window of up to 5 h after ischemia/reperfusion brain injury, in part by attenuating the apoptosis.