Inflammatory mediators and stroke: new opportunities for novel therapeutics

A human neural stem cell line provides neuroprotection and improves neurological performance by early intervention of neuroinflammatory system

A human neural stem cell line, HB1.F3, demonstrated neuroprotective properties in cerebral ischemia animal models. In this study, we have investigated about the mechanisms of such neuroprotection, mainly focusing on the neuroinflammatory system at an earlier time point of the pathology. Cerebral ischemia model was generated by middle cerebral artery occlusion (MCAO) in adult male Wister rats. HB1.F3 cells were transplanted through jugular vein 6h after MCAO. Forty eight hours after MCAO, transplanted rats showed better neurological performance and decreased TUNEL positive apoptotic cell number in the penumbra. However, haematoxylin and eosin staining and immunostaining showed that, HB1.F3 cells did not affect the necrotic cell death. Twenty four hours after MCAO (18h after HB1.F3 transplantation), infiltrated granulocytes and macrophage/microglia number in the core regions were decreased compared to PBS-treated controls. Immunohistochemical analysis further demonstrated that the transplantation decreased inducible nitric oxide synthase (iNOS) and cyclooxygenase (COX)-2 expressing cell number in the core and penumbra, respectively. Double immunofluorescence results revealed that iNOS was mainly expressed in granulocytes and macrophage/microglia in the core region, and COX-2 mainly expressed in neurons, endothelial cells and granulocytes in penumbra. Further analysis showed that although the percentage of iNOS expressing granulocytes and macrophage/microglia was not decreased, COX-2 expressing neurons and vessel number was decreased by the transplantation. In vitro mRNA analysis showed that brain-derived neurotrophic factor (BDNF), basic fibroblast growth factor (βFGF) and bone morphogenic protein (BMP)-4 expression was high in cultured HB1.F3 cells. Thus, our results demonstrated that HB1.F3 cell transplantation provide neuroprotection possibly through the regulation of early inflammatory events in the cerebral ischemia condition.

Neuroimmunomodulatory effects of transcranial laser therapy combined with intravenous tPA administration for acute cerebral ischemic injury

At present, the only FDA approved treatment for ischemic strokes is intravenous administration of tissue plasminogen activator within 4.5 hours of stroke onset. Owing to this brief window only a small percentage of patients receive tissue plasminogen activator. Transcranial laser therapy has been shown to be effective in animal models of acute ischemic stroke, resulting in significant improvement in neurological score and function. NEST-1 and NEST-2 clinical trials in human patients have demonstrated the safety and positive trends in efficacy of transcranial laser therapy for the treatment of ischemic stroke when initiated close to the time of stroke onset. Combining intravenous tissue plasminogen activator treatment with transcranial laser therapy may provide better functional outcomes. Statins given within 4 weeks of stroke onset improve stroke outcomes at 90 days compared to patients not given statins, and giving statins following transcranial laser therapy may provide an effective treatment for patients not able to be given tissue plasminogen activator due to time constraints.

Cinnamaldehyde inhibits inflammation and brain damage in a mouse model of permanent cerebral ischaemia

BACKGROUND AND PURPOSE

Recent findings suggest the importance of inflammation in the pathogenesis of cerebral ischaemia and its potential as a therapeutic target. Cinnamaldehyde is a diterpene with a wide range of anti-inflammatory effects thus may be advantageous in the treatment of cerebral ischaemia. The present study examined the potential therapeutic effects of cinnamaldehyde on cerebral ischaemia using a mouse model with permanent middle cerebral artery occlusion.

EXPERIMENTAL APPROACH

Male CD-1 mice, which had the middle cerebral artery occluded, were treated (i.p.) with cinnamaldehyde. Neuroprotection by cinnamaldehyde was analysed by evaluating neurological deficit scores, brain oedema and infarct volume. Expressions of signal transduction molecules and inflammatory mediators were measured by Western blotting, qRT-PCR and immunohistochemical staining. Activation of NF-κB was assessed by Western blotting, immunohistochemistry and immunofluorescence.

KEY RESULTS

Cinnamaldehyde reduced the neurological deficit scores, brain oedema and infarct volume. Cinnamaldehyde suppressed the activation of signal transduction molecules including toll-like receptor 4, tumour necrosis receptor-associated factor 6 and NF-κB, attenuated the increased levels of TNF-α, IL-1β, CCL2 and endothelial-leukocyte adhesion molecule-1 and ultimately reduced leukocyte infiltration into the ischaemic brain areas after cerebral ischaemia.

CONCLUSIONS AND IMPLICATIONS

Cinnamaldehyde protects against cerebral ischaemia injury by inhibiting inflammation, partly mediated by reducing the expression of toll-like receptor 4, tumour necrosis receptor-associated factor 6 and the nuclear translocation of NF-κB. Our findings suggest that cinnamaldehyde may serve as a new candidate for further development as a treatment for stroke.

Neuroprotection by JM-20 against oxygen-glucose deprivation in rat hippocampal slices: Involvement of the Akt/GSK-3β pathway

Cerebral ischemia is the third most common cause of death and a major cause of disability worldwide. Beyond a shortage of essential metabolites, ischemia triggers many interconnected pathophysiological events, including excitotoxicity, oxidative stress, inflammation and apoptosis. Here, we investigated the neuroprotective mechanisms of JM-20, a novel synthetic molecule, focusing on the phosphoinositide-3-kinase (PI3K)/Akt survival pathway and glial cell response as potential targets of JM-20. For this purpose, we used organotypic hippocampal slice cultures exposed to oxygen-glucose deprivation (OGD) to achieve ischemic/reperfusion damage in vitro. Treatment with JM-20 at 0.1 and 10 μM reduced PI incorporation (indicative of cell death) after OGD. OGD decreased the phosphorylation of Akt (pro-survival) and GSK 3β (pro-apoptotic), resulting in respective inhibition and activation of these proteins. Treatment with JM20 prevented the reduced phosphorylation of these proteins after OGD, representing a shift from pro-apoptotic to pro-survival signaling. The OGD-induced activation of caspase-3 was also attenuated by JM-20 treatment at 10 μM. Moreover, in cultures treated with JM-20 and exposed to OGD conditioning, we observed a decrease in activated microglia, as well as a decrease in interleukin (IL)-1β, IL-6 and tumor necrosis factor (TNF)-α release into the culture medium, while the level of the anti-inflammatory IL-10 increased. GFAP immunostaining and IB4 labeling showed that JM-20 treatment significantly augmented GFAP immunoreactivity after OGD, when compared with cultures exposed to OGD only, suggesting the activation of astroglial cells. Our results confirm that JM-20 has a strong neuroprotective effect against ischemic injury and suggest that the mechanisms involved in this effect may include the modulation of reactive astrogliosis, as well as neuroinflammation and the anti-apoptotic cell signaling pathway.

Association of early inflammatory parameters after subarachnoid hemorrhage with functional outcome: A prospective cohort study

OBJECTIVE

Early brain injury after aneurysmal subarachnoid hemorrhage (aSAH) comprises a pronounced neuroinflammatory reaction. Nevertheless, its relevance for functional outcome and its role as outcome predictor remains uncertain. We evaluated the relationship of various early inflammatory parameters regarding functional outcome according to the modified Rankin Scale score (mRS) at discharge (primary objective) and six months after aSAH.

PATIENTS

A total of 81 patients (63% female) with a mean age of 53.8 ± 13.2 years were included.

METHODS

At admission clinical data and various inflammatory parameters in serum and - wherever applicable - cerebrospinal fluid (CSF) of patients after aSAH were assessed. Outcome was evaluated according to dichotomized mRS at discharge and six months after aSAH (unfavorable outcome: mRS 3-6). Univariate and thereafter multivariate logistic regression analyses were performed using SAS 9.2.

RESULTS

Elevated levels of interleukin 6 (IL-6) and leukemia inhibitory factor (LIF) in serum and CSF were related to unfavorable outcome at discharge (p<0.05; univariate analyses). IL-6 remains the only parameter relevant for outcome applying a multivariate model including the relevant baseline characteristics. Six months after aSAH no significant correlation was found regarding the outcome, most likely due to the high drop-out rate (27%). A pronounced rise of LIF serum and CSF levels after aSAH was observed.

CONCLUSION

Higher early IL-6 serum levels after aSAH are associated with poor outcome at discharge. In addition, involvement of LIF in the early inflammatory reaction after aSAH has been demonstrated.

Hydrogen sulphide and mild hypothermia activate the CREB signaling pathway and prevent ischemia-reperfusion injury

Background

Both hydrogen sulphide (H₂S) and mild hypothermia have been reported to prevent brain damage caused by reperfusion assault through regulating the N-methyl-D-aspartate receptor (NMDAR). However, the relationship between the two treatments and how they exert neuro-protective effects through NMDARs remain to be elucidated.

Methods

Transient cerebral ischemia was induced using the Pulsinelli four-vessel occlusion method. We used sodium hydrosulphide (NaHS) as the H₂S donor. We randomly divided 100 Sprague–Dawley rats into five groups of 20: Sham operation group (Sh), normothermic (36-37 °C) ischemia group (NT), mild hypothermic (32-33 °C) ischemia group (mHT), normothermic ischemia combined with NaHS treatment group (NT + NaHS), and mild hypothermic ischemia combined with NaHS treatment group (mHT + NaHS). After 6 hrs of reperfusion, rats were decapitated and hippocampus samples were immediately collected. We measured NR2A (GluN1), NR2B (GluN2) and p-CREB protein levels using western blotting. We further analyzed BDNF mRNA expression by real-time PCR. Hematoxylin and eosin (HE) staining was used to examine pyramidal cell histology at the CA1 region. All statistical analyses were carried out by ANOVA and LSD t-test as implemented by the SPSS 13.0 software.

Results

In the four test groups with ischemia-reperfusion, hippocampal H₂S concentration increased following treatment, and administration of NaHS further increased H₂S levels. Moreover, administration of both NaHS and mild hypothermia resulted in up-regulation of NR2A and NR2B protein expressions, as well as p-CREB protein and BDNF mRNA levels. At the cellular level, NaHS and mild hypothermia groups exhibited lower damage caused by ischemia-reperfusion in the CA1 region of the hippocampus. The strongest protective effect was observed in rats treated with combined NaHS and mild hypothermia, suggesting their effects were additive.

Conclusion

Our results support previous findings that hydrogen sulphide and mild hypothermia can prevent ischemia-reperfusion injury. Both treatments caused an up-regulation of NMDA receptors, as well as an elevation in p-CREB protein and BDNF mRNA levels. Thus, hydrogen sulphide and mild hypothermia may provide neuro-protective effect through activating the pro-survival CREB signaling pathway.

Organotypic Hippocampal Slices as Models for Stroke and Traumatic Brain Injury

Organotypic hippocampal slice cultures (OHSCs) have been used as a powerful ex vivo model for decades. They have been used successfully in studies of neuronal death, microglial activation, mossy fiber regeneration, neurogenesis, and drug screening. As a pre-animal experimental phase for physiologic and pathologic brain research, OHSCs offer outcomes that are relatively closer to those of whole-animal studies than outcomes obtained from cell culture in vitro. At the same time, mechanisms can be studied more precisely in OHSCs than they can be in vivo. Here, we summarize stroke and traumatic brain injury research that has been carried out in OHSCs and review classic experimental applications of OHSCs and its limitations.

Behavioral assessment of cell transplantation after focal cerebral ischemia in rats

We induced middle cerebral artery occlusion (MCAO) in rats using silicone-coated vascular embolus. We transplanted mouse embryonic stem (mES) cells after MCAO. Rats were tested behaviorally using motor and sensory function with neurological assessment. Functional effectiveness of the transplanted mES cells gradually improved the function of sensory and motor neurons. This study demonstrated that the transplanted cells have synaptic connection in the recipient brain. We suggest that stem cell transplantation can have a positive effect on behavioral recovery and reduction of infarct size in focal ischemic rats. Cell transplantation may induce certain functional recovery of the brain tissue by endogenous cell mediated effect. Our study suggests that intracerebrally injected mES cells survived and migrated into the infarct area from inoculation site and neuroglially differentiated in the ischemic brain area of adult rats. Therefore, mES cells may be a useful tool for the treatment in neurological diseases. In conclusion, cell transplantation therapy represents a novel approach that may enhance the efficacy and effectiveness of stem cell transplantation after ischemic stroke.

Neuroprotection of Early Locomotor Exercise Poststroke: Evidence From Animal Studies

Early locomotor exercise after stroke has attracted a great deal of attention in clinical and animal research in recent years. A series of animal studies showed that early locomotor exercise poststroke could protect against ischemic brain injury and improve functional outcomes through the promotion of angiogenesis, inhibition of acute inflammatory response and neuron apoptosis, and protection of the blood-brain barrier. However, to date, the clinical application of early locomotor exercise poststroke was limited because some clinicians have little confidence in its effectiveness. Here we review the current progress of early locomotor exercise poststroke in animal models. We hope that a comprehensive awareness of the early locomotor exercise poststroke may help to implement early locomotor exercise more appropriately in treatment for ischemic stroke.

Bystander Effect Fuels Human Induced Pluripotent Stem Cell-Derived Neural Stem Cells to Quickly Attenuate Early Stage Neurological Deficits After Stroke

: Present therapies for stroke rest with tissue plasminogen activator (tPA), the sole licensed antithrombotic on the market; however, tPA's effectiveness is limited in that the drug not only must be administered less than 3-5 hours after stroke but often exacerbates blood-brain barrier (BBB) leakage and increases hemorrhagic incidence. A potentially promising therapy for stroke is transplantation of human induced pluripotent stem cell-derived neural stem cells (hiPSC-NSCs). To date, the effects of iPSCs on injuries that take place during early stage ischemic stroke have not been well studied. Consequently, we engrafted iPSC-NSCs into the ipsilesional hippocampus, a natural niche of NSCs, at 24 hours after stroke (prior to secondary BBB opening and when inflammatory signature is abundant). At 48 hours after stroke (24 hours after transplant), hiPSC-NSCs had migrated to the stroke lesion and quickly improved neurological function. Transplanted mice showed reduced expression of proinflammatory factors (tumor necrosis factor-α, interleukin 6 [IL-6], IL-1β, monocyte chemotactic protein 1, macrophage inflammatory protein 1α), microglial activation, and adhesion molecules (intercellular adhesion molecule 1, vascular cell adhesion molecule 1) and attenuated BBB damage. We are the first to report that engrafted hiPSC-NSCs rapidly improved neurological function (less than 24 hours after transplant). Rapid hiPSC-NSC therapeutic activity is mainly due to a bystander effect that elicits reduced inflammation and BBB damage.

SIGNIFICANCE

Clinically, cerebral vessel occlusion is rarely permanent because of spontaneous or thrombolytic therapy-mediated reperfusion. These results have clinical implications indicating a much extended therapeutic window for transplantation of human induced pluripotent stem cell-derived neural stem cells (hiPSC-NSCs; 24 hours after stroke as opposed to the 5-hour window with tissue plasminogen activator [tPA]). In addition, there is potential for a synergistic effect by combining hiPSC-NSC transplantation with tPA to attenuate stroke's adverse effects.

Ligustrazine monomer against cerebral ischemia/reperfusion injury

Ligustrazine (2,3,5,6-tetramethylpyrazine) is a major active ingredient of the Szechwan lovage rhizome and is extensively used in treatment of ischemic cerebrovascular disease. The mechanism of action of ligustrazine use against ischemic cerebrovascular diseases remains unclear at present. This study summarizes its protective effect, the optimum time window of administration, and the most effective mode of administration for clinical treatment of cerebral ischemia/reperfusion injury. We examine the effects of ligustrazine on suppressing excitatory amino acid release, promoting migration, differentiation and proliferation of endogenous neural stem cells. We also looked at its effects on angiogenesis and how it inhibits thrombosis, the inflammatory response, and apoptosis after cerebral ischemia. We consider that ligustrazine gives noticeable protection from cerebral ischemia/reperfusion injury. The time window of ligustrazine administration is limited. The protective effect and time window of a series of derivative monomers of ligustrazine such as 2-[(1,1-dimethylethyl)oxidoimino]methyl]-3,5,6-trimethylpyrazine, CXC137 and CXC195 after cerebral ischemia were better than ligustrazine.

Neuroprotective effects of pioglitazone against transient cerebral ischemic reperfusion injury in diabetic rats: Modulation of antioxidant, anti-inflammatory, and anti-apoptotic biomarkers

BACKGROUND

Recent growing consensus introduced thiazolidinediones, agonists of the nuclear receptor peroxisome proliferator-activated receptor gamma as promising candidates in the management of ischemia in various organs. Thereby, interest was raised to investigate the neuroprotective effects of pioglitazone against transient ischemia/reperfusion (I/R) injury in diabetic rats targeting mainly the oxidative-inflammatory-apoptotic cascades which are involved in this insult.

METHODS

Forebrain ischemia was induced in streptozotocin-diabetic rats by occlusion of the bilateral common carotid arteries for 15min followed by 1h reperfusion. Pioglitazone (10mg/kg; po) was administered daily for 2 weeks prior to I/R.

RESULTS

The drug alleviated hippocampal injury inflicted by diabetes and/or I/R injury where it suppressed nuclear factor kappa (NFκB), and consequently the downstream inflammatory cytokines tumor necrosis factor-α and interleukin-6. In parallel, the anti-inflammatory cytokine interleukin-10 was elevated. Antioxidant potential of pioglitazone was depicted, where it reduced neutrophil infiltration, lipid peroxides, nitric oxide associated with replenished reduced glutathione. Decline of excitatory amino acid glutamate content is a main finding which is probably mediated by the NFκB signaling pathway as well as improved oxidant status. Pioglitazone exerted an anti-apoptotic effect as reflected by the reduction of the cytosolic cytochrome c and the key downstream executioner caspase-3.

CONCLUSIONS

Pioglitazone is endowed with neuroprotective properties which are probably mediated by its antioxidant, anti-inflammatory, and anti-apoptotic mechanisms hence may provide a successful agent for the management of ischemic stroke.

TLR2-induced astrocyte MMP9 activation compromises the blood brain barrier and exacerbates intracerebral hemorrhage in animal models

BACKGROUND

The innate immune response plays an important role in the pathogenesis of intracerebral hemorrhage (ICH). Recent studies have shown that Toll-like receptor 2 (TLR2) is involved in the innate immune response in various neurological diseases, yet neither its role in ICH nor the mechanisms by which it functions have yet been elucidated. We examined these in this study using a collagenase-induced mouse ICH model with TLR2 knock-out (KO) mice.

RESULTS

TLR2 expression was upregulated in the ipsilateral hemorrhagic tissues of the collagenase-injected mice. Brain injury volume and neurological deficits following ICH were reduced in TLR2 KO mice compared to wild-type (WT) control mice. Heterologous blood-transfer experiments show that TLR2 signaling in brain-resident cells, but not leukocytes, contributes to the injury. In our study to elucidate underlying mechanisms, we found that damage to blood-brain barrier (BBB) integrity following ICH was attenuated in TLR2 KO mice compared to WT mice, which may be due to reduced matrix metalloproteinase-9 (MMP9) activation in astrocytes. The reduced BBB damage accompanies decreased neutrophil infiltration and proinflammatory gene expression in the injured brain parenchyma, which may account for the attenuated brain damage in TLR2 KO mice after ICH.

CONCLUSIONS

TLR2 plays a detrimental role in ICH-induced brain damage by activating MMP9 in astrocytes, compromising BBB, and enhancing neutrophils infiltration and proinflammatory gene expression.

Comparison of the effects of human dental pulp stem cells and human bone marrow-derived mesenchymal stem cells on ischemic human astrocytes in vitro

This study assesses the cytoprotective effects of human dental pulp stem cells (hDPSCs) and conditioned medium from hDPSCs (CM-hDPSCs) on ischemic human astrocytes (hAs) in vitro compared with human bone marrow-derived mesenchymal stem cells (hMSCs). Ischemia of hAs was induced by oxygen-glucose deprivation (OGD). CM-hDPSCs and hMSCs were collected after 48 hr of culture. Cell death was determined by 3-[4,5-dimethylthialzol-2-yl]-2,5-diphenyltetrazolium bromide and cellular ATP assays. The expression of glial fibrillary acidic protein (GFAP) and musashi-1 as markers of reactive astrogliosis was examined with immunochemical staining. mRNA expression and reactive oxygen species (ROS) were analyzed by RT-PCR and flow cytometry, respectively. OGD increased cytotoxicity in a time-dependent manner and decreased cellular ATP content concomitantly in hAs. Pretreatment and posttreatment with hDPSCs were associated with greater recovery from OGD-induced cytotoxicity in hAs compared with hMSCs. Similarly, CM-hDPSCs had a greater effect on OGD-induced cytotoxicity in a dose-dependent manner. Pre- and posttreatment with CM-hDPSCs or CM-hMSCs attenuated OGD-induced GFAP, nestin, and musashi-1 expression in hAs. Furthermore, treatment of cells with CM-hDPSCs and hMSCs blocked OGD-induced ROS production and interleukin-1ß upregulation. This study demonstrates for the first time that hDPSCs and CM-hDPSCs confer superior cytoprotection against cell death in an in vitro OGD model compared with hMSCs as shown by cell viability assay. Reactive gliosis, ROS production, and inflammatory mediators might contribute to this protective effect. Therefore, hDPSCs could represent an alternative source of cell therapy for ischemic stroke.

Expression of interleukin-9 and its upstream stimulating factors in rats with ischemic stroke

To investigate the temporal expressions of IL-9 and its related cytokines after middle cerebral artery occlusion in rats. IL-9 and its related cytokines in ischemia brain and blood were tested after rats were subjected to transient focal ischemia. Comparing with sham-operated group, the levels of IL-4, TGF-β, PU.1, IRF4, OX40, NIK, RelB-p52 and IL-9 in experimental groups were significantly higher after middle cerebral artery occlusion. The results showed that expressions of IL-9 and its upstream stimulating factors increased in experimental stroke, and whether they play a role or just a secondary change is awaiting further research.

Longitudinal assessment of imatinib's effect on the blood-brain barrier after ischemia/reperfusion injury with permeability MRI

Acute ischemic stroke (AIS) often results in degeneration of the blood-brain barrier (BBB), which can lead to vasogenic edema and an increased risk of intracerebral hemorrhage. Imatinib is an agent that may be able to protect the BBB and reduce the risk of the harmful consequences of BBB degeneration. We sought to measure the effect of Imatinib on the BBB after experimental stroke longitudinally in vivo with permeability dynamic contrast-enhanced MRI. Ischemia/reperfusion injury was induced with a transient middle cerebral artery occlusion surgery. Rats were given Imatinib at 2 and 20 h after stroke onset. Post-assessment included neurologic functioning, MR imaging, Evans Blue extravasation, Western blot, and immunohistology assay. Imatinib protected the BBB by 24 h but failed to decrease BBB permeability at an earlier time-point. Imatinib also reduced infarct volume, edema, and improved neurologic functioning by 24 h. Rats treated with Imatinib also had a higher expression of the BBB structural protein Zona ocludens-1 and a reduction in nuclear factor-kappa beta (NF-κβ) activation. Imatinib is a promising agent to protect the BBB after AIS, but its effect on the BBB may not become prominent until 24 h after the onset of ischemia. This finding may help elucidate Imatinib's role in the clinical management of AIS and influence future study designs.

Acute neuroinflammation in a clinically relevant focal cortical ischemic stroke model in rat: longitudinal positron emission tomography and immunofluorescent tracking

Adequate estimation of neuroinflammatory processes following ischemic stroke is essential for better understanding of disease mechanisms, and for the development of treatment strategies. With the TSPO (18 kDa translocator protein) positron emission tomography (PET) radioligand [(11)C]PBR28, we monitored longitudinally the inflammatory response post-transient cerebral ischemia in rats, using a recently developed rat stroke model that produces isolated focal cortical infarcts with clinical relevance in size and pathophysiology. Six Sprague-Dawley rats were subjected to 90 min transient endovascular occlusion of the M2 segment of the middle cerebral artery (M2CAO). Animals were imaged with a nanoScan(®) PET/MRI system at 1, 4, 7 and 14 days after M2CAO with a bolus injection of [(11)C]PBR28. In the infarct region, we found a significantly increased uptake of [(11)C]PBR28 on day 4, 7 and 14 compared to day 1 as well as compared to the contralateral cortex. No significant increase was detected in the contralateral cortex during the 14 days of imaging. The activation in the infarct region gradually decreased between day 4 and day 14. In an additional group of animals (n = 26), immunofluorescence studies were performed with antibodies for activated microglia/monocytes (Cd11b), phagocytes (Cd68), astrocytes (glial fibrillary acidic protein) and TSPO. The TSPO immunofluorescence signal indicated reactive microgliosis post injury, corresponding to PET findings. The present clinically relevant animal model and TSPO PET ligand appear to be well suited for studies on neuroinflammation after ischemic stroke.

Human neural stem cells rapidly ameliorate symptomatic inflammation in early-stage ischemic-reperfusion cerebral injury

Introduction

Clinically, a good deal of injury from stroke results from ischemic-reperfusion. There is a loss of cerebral parenchyma and its associated cells, disruption of neuronal connections, compromise of the blood-brain barrier, and inflammation. We tested whether exogenously engrafted human neural stem cells could migrate rapidly and extensively to damaged regions, following transplantation into a neurogenic site where migration cues are already underway during stroke onset, then counteract a number of these pathological processes.

Methods

One day post-injury, we injected human neural stem cells (hNSCs) into the ipsilesional hippocampus of a mouse model of stroke with middle cerebral artery occlusion to induce focal ischemia followed by reperfusion (MCAO/R). The time frame for hNSC transplantation corresponded to upregulation of endogenous proinflammatory cytokines. We examined the effect of hNSC transplantation on pathological processes and behavioral dysfunction 48 hours post-injury.

Results

Twenty-four hours after transplantation, engrafted hNSCs had migrated extensively to the lesion, and infarct volume was reduced relative to MCAO/R controls. The behavioral deficits seen in MCAO/R controls were also significantly improved. Given this rapid response, we hypothesized that the mechanisms underlying therapeutic activity were anti-inflammatory rather than due to cell replacement. In support of this idea, in hNSC-transplanted mice we observed reduced microglial activation, decreased expression of proinflammatory factors (tumor necrosis factor-α, interleukin (IL)-6, IL-1β, monocyte chemotactic protein-1, macrophage inflammatory protein-1α) and adhesion molecules (intercellular adhesion molecule-1, vascular cell adhesion molecule-1), and amelioration of blood-brain barrier damage.

Conclusions

While long-term effects of engrafted hNSCs on the amelioration of ischemic stroke-induced behavioral dysfunction in a rodent model have been reported, our study is the first to show rapid, beneficial impacts on behavioral function (within 24 hours) upon early delivery of hNSCs into the hippocampus.

Electronic supplementary material

The online version of this article (doi:10.1186/scrt519) contains supplementary material, which is available to authorized users.

A novel treatment strategy for glioblastoma multiforme and glioma associated seizures: increasing glutamate uptake with PPARγ agonists

The established role of glutamate in the pathogenesis of glioma-associated seizures (GAS) led us to investigate a novel treatment method using an established drug class, peroxisome proliferator activated receptor (PPAR) gamma agonists. Previously, sulfasalazine has been shown to prevent release of glutamate from glioma cells and prevent GAS in rodent models. However, raising protein mediated glutamate transport via excitatory amino acid transporter 2 (EAAT2) has not been investigated previously to our knowledge. PPAR gamma agonists are known to upregulate functional EAAT2 expression in astrocytes and prevent excitotoxicity caused by glutamate excess. These agents are also known to have anti-neoplastic mechanisms. Herein we discuss and review the potential mechanisms of these drugs and highlight a novel potential treatment for GAS.

Silencing phosphodiesterase 7B gene by lentiviral-shRNA interference attenuates neurodegeneration and motor deficits in hemiparkinsonian mice

Different studies have suggested that the nucleotide cyclic adenosine 3', 5'-monophosphate can actively play an important role as a neuroprotective and anti-inflammatory agent after a brain injury. The phosphodiesterase 7 (PDE7) enzyme is one of the enzymes responsible for controlling specifically the intracellular levels of cyclic adenosine 3', 5'-monophosphate in the immune and central nervous systems. Therefore, this enzyme could play an important role in brain inflammation and neurodegeneration. In this regard, using different chemical inhibitors of PDE7 we have demonstrated their neuroprotective and anti-inflammatory activity in different models of neurodegenerative disorders, including Parkinson's disease (PD). In the present study, we have used the toxin 6-hydroxydopamine and lipopolysaccharide to model PD and explore the protective effects of PDE7B deficiency in dopaminergic neurons cell death. Lentivirus-mediated PDE7B deprivation conferred marked in vitro and in vivo neuroprotection against 6-hydroxydopamine and lipopolysaccharide toxicity in dopaminergic neurons and preserved motor function involving the dopamine system in mouse. Our results substantiate previous data and provide a validation of PDE7B enzyme as a valuable new target for therapeutic development in the treatment of PD.

The Immune Response to Acute Focal Cerebral Ischemia and Associated Post-stroke Immunodepression: A Focused Review

It is currently well established that the immune system is activated in response to transient or focal cerebral ischemia. This acute immune activation occurs in response to damage, and injury, to components of the neurovascular unit and is mediated by the innate and adaptive arms of the immune response. The initial immune activation is rapid, occurs via the innate immune response and leads to inflammation. The inflammatory mediators produced during the innate immune response in turn lead to recruitment of inflammatory cells and the production of more inflammatory mediators that result in activation of the adaptive immune response. Under ideal conditions, this inflammation gives way to tissue repair and attempts at regeneration. However, for reasons that are just being understood, immunosuppression occurs following acute stroke leading to post-stroke immunodepression. This review focuses on the current state of knowledge regarding innate and adaptive immune activation in response to focal cerebral ischemia as well as the immunodepression that can occur following stroke. A better understanding of the intricate and complex events that take place following immune response activation, to acute cerebral ischemia, is imperative for the development of effective novel immunomodulatory therapies for the treatment of acute stroke.

Anti-inflammatory activity of iridoid and catechol derivatives from Eucommia ulmoides Oliver

Neuroinflammation and pro-inflammatory mediators play key roles in the pathogenesis of neurodegenerative diseases including stroke, which account for a significant burden of morbidity and mortality worldwide. Recently, the unsatisfactory pharmacotherapy and side effects of the drugs led to the development of alternative medicine for treating these diseases. Du Zhong (DZ), Eucommia ulmoides Oliver leaves, is a commonly used herb in the therapy of stroke in China. We hypothesize that the components from DZ inhibit neuroinflammation. In this study, DZ was extracted and the bioactive fractions with inhibitory effect on lipopolysaccharide (LPS)-stimulated nitric oxide (NO) production in BV-2 microglial cells were further separated using chromatography. Two purified bioactive compounds, genipin (compound C) and 4-(1,2-dimethoxyethyl)benzene-1,2-diol (compound F), were isolated and identified after spectroscopic analysis. The results showed that they inhibited LPS-stimulated NO and tumor necrosis factor-alpha (TNF-α) production. Genipin exerted its anti-inflammatory effects through PI3K/Akt signaling pathway, whereas compound F inhibited phosphorylation of p38 mitogen-activated protein kinase (MAPK). In conclusion, genipin and compound F have potential for developing into new drugs for treating neurodegenerative diseases.

Bosentan protects the spinal cord from ischemia reperfusion injury in rats through vascular endothelial growth factor receptors

STUDY DESIGN

Experimental study.

OBJECTIVES

To investigate whether Bosentan, an endothelin-A/-B dual receptor antagonist, could protect neurons after spinal cord ischemia reperfusion (SCIR) injury in rats and its underlying signaling pathway.

SETTING

Department of Neurosurgery, the Second Affiliated Hospital, Xi'an Jiaotong University School of Medicine, Xi'an, Shaanxi Province, China.

METHODS

Sprague-Dawley rats were randomly divided into two groups, saline group (IRS, n=48) and Bosentan group (IRB, 5 mg kg(-1), n=48). After ischemia for 1 h with occlusion of the infrarenal aorta, spinal cord were reperfused for 6h, 12h, 24h, 3d, 5d, and 7d separately. Enzyme-linked immunosorbent assay was used to detect vascular endothelial growth factor (VEGF) in serum. Immunohistochemistry was performed to detect protein expression of VEGF, VEGF receptor 1 (FLT-1) and VEGF receptor 2 (FLK-1). Gene expressions of VEGF and its receptors were evaluated using the quantitative reverse transcription polymerase chain reaction.

RESULTS

Compared with the IRS group, gene and protein expressions of VEGF, FLT-1 and FLK-1 were significantly increased (P<0.05), so was the concentration of VEGF in plasma (P<0.05). FLK-1 was expressed on spinal cord neurons.

Neurobiology of microglial action in CNS injuries: receptor-mediated signaling mechanisms and functional roles

Microglia are the first line of immune defense against central nervous system (CNS) injuries and disorders. These highly plastic cells play dualistic roles in neuronal injury and recovery and are known for their ability to assume diverse phenotypes. A broad range of surface receptors are expressed on microglia and mediate microglial 'On' or 'Off' responses to signals from other host cells as well as invading microorganisms. The integrated actions of these receptors result in tightly regulated biological functions, including cell mobility, phagocytosis, the induction of acquired immunity, and trophic factor/inflammatory mediator release. Over the last few years, significant advances have been made toward deciphering the signaling mechanisms related to these receptors and their specific cellular functions. In this review, we describe the current state of knowledge of the surface receptors involved in microglial activation, with an emphasis on their engagement of distinct functional programs and their roles in CNS injuries. It will become evident from this review that microglial homeostasis is carefully maintained by multiple counterbalanced strategies, including, but not limited to, 'On' and 'Off' receptor signaling. Specific regulation of theses microglial receptors may be a promising therapeutic strategy against CNS injuries.

Anti-apoptotic and anti-oxidative roles of quercetin after traumatic brain injury

Experimental studies have demonstrated significant secondary damage (including cell apoptosis, blood-brain barrier disruption, inflammatory responses, excitotoxic damage, and free radical production) after traumatic brain injury (TBI). Quercetin is a natural flavonoid found in high quantities in fruits and vegetables, and may be a potential antioxidant and free radical scavenger. The purpose of this study was to determine the effects of quercetin on TBI-induced upregulation of oxidative stress, inflammation, and apoptosis in adult Sprague-Dawley rats. Animals were subjected to Feeney's weight-drop injury, thus inducing the parietal contusion brain injury model. Quercetin was administered (30 mg/kg intraperitoneal injection) 0, 24, 48, and 72 h after TBI. Quercetin reduced cognitive deficits, the number of TUNEL- and ED-1-positive cells, the protein expressions of Bax and cleaved-caspase-3 proteins, and the levels of TBARS and proinflammatory cytokines, and increased the activity of antioxidant enzymes (GSH-Px, SOD, and CAT) at 1 week after TBI. Our results suggest that in TBI rats, quercetin improves cognitive function owing to its neuroprotective action via the inhibition of oxidative stress, leading to a reduced inflammatory response, thereby reducing neuronal death.

Ischemic tolerance modulates TRAIL expression and its receptors and generates a neuroprotected phenotype

TNF-related apoptosis inducing ligand (TRAIL), a member of the TNF superfamily released by microglia, appears to be involved in the induction of apoptosis following focal brain ischemia. Indeed, brain ischemia is associated with progressive enlargement of damaged areas and prominent inflammation. As ischemic preconditioning reduces inflammatory response to brain ischemia and ameliorates brain damage, the purpose of the present study was to evaluate the role of TRAIL and its receptors in stroke and ischemic preconditioning and to propose, by modulating TRAIL pathway, a new therapeutic strategy in stroke. In order to achieve this aim a rat model of harmful focal ischemia, obtained by subjecting animals to 100 min of transient occlusion of middle cerebral artery followed by 24 h of reperfusion and a rat model of ischemic preconditioning in which the harmful ischemia was preceded by 30 mins of tMCAO, which represents the preconditioning protective stimulus, were used. Results show that the neuroprotection elicited by ischemic preconditioning occurs through both upregulation of TRAIL decoy receptors and downregulation of TRAIL itself and of its death receptors. As a counterproof, immunoneutralization of TRAIL in tMCAO animals resulted in significant restraint of tissue damage and in a marked functional recovery. Our data shed new light on the mechanisms that propagate ongoing neuronal damage after ischemia in the adult mammalian brain and provide new molecular targets for therapeutic intervention. Strategies aimed to repress the death-inducing ligands TRAIL, to antagonize the death receptors, or to activate the decoy receptors open new perspectives for the treatment of stroke.

Mesenchymal stem cells transplantation for neuroprotection in preterm infants with severe intraventricular hemorrhage

Severe intraventricular hemorrhaging (IVH) in premature infants and subsequent posthemorrhagic hydrocephalus (PHH) causes significant mortality and life-long neurological complications, including seizures, cerebral palsy, and developmental retardation. However, there are currently no effective therapies for neonatal IVH. The pathogenesis of PHH has been mainly explained by inflammation within the subarachnoid spaces due to the hemolysis of extravasated blood after IVH. Obliterative arachnoiditis, induced by inflammatory responses, impairs cerebrospinal fluid (CSF) resorption and subsequently leads to the development of PHH with ensuing brain damage. Increasing evidence has demonstrated potent immunomodulating abilities of mesenchymal stem cells (MSCs) in various brain injury models. Recent reports of MSC transplantation in an IVH model of newborn rats demonstrated that intraventricular transplantation of MSCs downregulated the inflammatory cytokines in CSF and attenuated progressive PHH. In addition, MSC transplantation mitigated the brain damages that ensue after IVH and PHH, including reactive gliosis, cell death, delayed myelination, and impaired behavioral functions. These findings suggest that MSCs are promising therapeutic agents for neuroprotection in preterm infants with severe IVH.

A Decade of Research on TLR2 Discovering Its Pivotal Role in Glial Activation and Neuroinflammation in Neurodegenerative Diseases

Toll-like receptors (TLRs) belong to a class of pattern recognition receptors that play an important role in host defense against pathogens. TLRs on innate immune cells recognize a wide variety of pathogen-associated molecular patterns (PAMPs) and trigger innate immune responses. Later, it was revealed that the same receptors are also utilized to detect tissue damage to trigger inflammatory responses in the context of non-infectious inflammation. In the nervous system, different members of the TLR family are expressed on glial cells including astrocytes, microglia, oligodendrocytes, and Schwann cells, implicating their putative role in innate/inflammatory responses in the nervous system. In this regard, we have investigated the function of TLRs in neuroinflammation. We discovered that a specific member of the TLR family, namely TLR2, functions as a master sentry receptor to detect neuronal cell death and tissue damage in many different neurological conditions including nerve transection injury, intracerebral hemorrhage, traumatic brain injury, and hippocampal excitotoxicity. In this review, we have summarized our research for the last decade on the role of TLR2 in neuroinflammation in the above neurological disorders. Our data suggest that TLR2 can be an efficient target to regulate unwanted inflammatory response in these neurological conditions.

Human umbilical cord blood mesenchymal stem cell transplantation suppresses inflammatory responses and neuronal apoptosis during early stage of focal cerebral ischemia in rabbits

AIM

Human umbilical cord blood mesenchymal stem cells (hUCB-MSCs) have been shown to ameliorate cerebral ischemia in animal models. In this study we investigated the effects of hUCB-MSCs on inflammatory responses and neuronal apoptosis during the early stage of focal cerebral ischemia in rabbits.

METHODS

Focal cerebral ischemia was induced in male New Zealand rabbits by occlusion of MCA for 2 h. The blood samples were collected at different time points prior and during MCAO-reperfusion. The animals were euthanized 3 d after MCAO, and the protein levels of IL-1β, IL-6, IL-10 and TNF-α in the serum and peri-ischemic brain tissues were detected using Western blot and ELISA, respectively. Inflammatory cell infiltration, neuronal apoptosis and neuronal density were measured morphologically. hUCB-MSCs (5 × 10(6)) were iv injected a few minutes after MCAO.

RESULTS

The serum levels of IL-1β, IL-6 and TNF-α were rapidly increased, and peaked at 2 h after the start of MCAO. hUCB-MSC transplantation markedly and progressively suppressed the ischemia-induced increases of serum IL-1β, IL-6 and TNF-α levels within 6 h MCAO-reperfusion. Focal cerebral ischemia decreased the serum level of IL-10, which was prevented by hUCB-MSC transplantation. The expression of IL-1β, IL-6, IL-10 and TNF-α in the peri-ischemic brain tissues showed similar changes as in the serum. hUCB-MSC transplantation markedly suppressed the infiltration of inflammatory cells, and increased the neuronal density around the ischemic region. Furthermore, hUCB-MSC transplantation significantly decreased the percentage of apoptosis around the ischemic region.

CONCLUSION

hUCB-MSCs transplantation suppresses inflammatory responses and neuronal apoptosis during the early stage focal cerebral ischemia in rabbits.

The effects of exercise preconditioning on cerebral blood flow change and endothelin-1 expression after cerebral ischemia in rats

Stroke is an acute cerebrovascular disease with high incidence, morbidity, and mortality. Preischemic treadmill training has been shown to be effective in improving behavioral and neuropathologic indices after cerebral ischemia. However, the exact neuroprotective mechanism of preischemic treadmill training against ischemic injury has not been elucidated clearly. The present study investigated whether preischemic treadmill training could protect the brain from ischemic injury via regulating cerebral blood flow (CBF) and endothelin 1 (ET-1). We analyzed the CBF by laser speckle imaging and ET-1 expression by an enzyme-linked immunosorbent assay using an ischemic rat model with preischemic treadmill training. Generally speaking, ET-1 expression decreased and CBF increased significantly in the pretreadmill group. It is worth noting that ET-1 expression is increased at 24 hours of reperfusion in the pretreadmill group compared with the level of the time after middle cerebral artery occlusion. These changes were followed by significant changes in neurologic deficits and cerebral infarct volume. This study indicated that preconditioning exercise protected brain from ischemic injury through the improvement of CBF and regulation of ET-1 expression, which may be a novel component of the neuroprotective mechanism of preischemic treadmill training against brain injury.

Preconditioning provides neuroprotection in models of CNS disease: paradigms and clinical significance

Preconditioning is a phenomenon in which brief episodes of a sublethal insult induce robust protection against subsequent lethal injuries. Preconditioning has been observed in multiple organisms and can occur in the brain as well as other tissues. Extensive animal studies suggest that the brain can be preconditioned to resist acute injuries, such as ischemic stroke, neonatal hypoxia/ischemia, surgical brain injury, trauma, and agents that are used in models of neurodegenerative diseases, such as Parkinson's disease and Alzheimer's disease. Effective preconditioning stimuli are numerous and diverse, ranging from transient ischemia, hypoxia, hyperbaric oxygen, hypothermia and hyperthermia, to exposure to neurotoxins and pharmacological agents. The phenomenon of "cross-tolerance," in which a sublethal stress protects against a different type of injury, suggests that different preconditioning stimuli may confer protection against a wide range of injuries. Research conducted over the past few decades indicates that brain preconditioning is complex, involving multiple effectors such as metabolic inhibition, activation of extra- and intracellular defense mechanisms, a shift in the neuronal excitatory/inhibitory balance, and reduction in inflammatory sequelae. An improved understanding of brain preconditioning should help us identify innovative therapeutic strategies that prevent or at least reduce neuronal damage in susceptible patients. In this review, we focus on the experimental evidence of preconditioning in the brain and systematically survey the models used to develop paradigms for neuroprotection, and then discuss the clinical potential of brain preconditioning.

Alpha 1-antitrypsin therapy mitigated ischemic stroke damage in rats

Our objective is to develop a new therapy for the treatment of stroke. Currently, the only effective therapy for acute ischemic stroke is the thrombolytic agent recombinant tissue plasminogen activator. α1-Antitrypsin (AAT), a serine proteinase inhibitor with potent anti-inflammatory, anti-apoptotic, antimicrobial, and cytoprotective activities, could be beneficial in stroke. The goal of this study is to test whether AAT can improve ischemic stroke outcome in an established rat model. Middle cerebral artery occlusion was induced in male rats via intracranial (i.c.) microinjection of endothelin-1. Five to 10 minutes after stroke induction, rats received either i.c. or intravenous delivery of human AAT. Cylinder and vibrissae tests were used to evaluate sensorimotor function before and 72 hours after middle cerebral artery occlusion. Infarct volumes were examined via either 2,3,5-triphenyltetrazolium chloride assay or magnetic resonance imaging 72 hours after middle cerebral artery occlusion. Despite equivalent initial strokes, at 72 hours, the infarct volumes of the human AAT treatment groups (local and systemic injection) were statistically significantly reduced by 83% and 63% (P < .0001 and P < .05, respectively) compared with control rats. Human AAT significantly limited sensory motor system deficits. Human AAT could be a potential novel therapeutic drug for the protection against neurodegeneration after ischemic stroke, but more studies are needed to investigate the protective mechanisms and efficacy in other animal models.

Delayed, long-term administration of the caspase inhibitor Q-VD-OPh reduced brain injury induced by neonatal hypoxia-ischemia

Apoptosis contributes greatly to the morphological and biochemical features of cell death after neonatal cerebral hypoxia-ischemia (HI), making this mode of cell death a promising therapeutic target. We previously showed that 10 mg/kg of the caspase inhibitor Q-VD-OPh at the onset of and immediately after HI on postnatal day 9 reduced brain infarct volume. In this study, delayed administration of Q-VD-OPh, 12 and 36 h after HI, decreased HI-induced caspase-3 activity (DEVD cleavage) by 23% and diminished the levels of the proinflammatory chemokines CCL2 (MCP-1) and CCL3 (MIP-1α) by 29.3 and 29.1%, respectively, but not the levels of the anti-inflammatory cytokines IL-4 and IL-10. Long-term administration of Q-VD-OPh initiated at 12 h after HI, and continued at 24-hour intervals for 2 weeks, reduced total brain tissue loss by 31.3% from 41.5±3.1 mm3 in the vehicle group to 28.5±3.0 mm3 in the Q-VD-OPh group when evaluated 16 weeks after HI (p=0.004). Q-VD-OPh treatment also ameliorated the loss of sensorimotor function, as evaluated by a cylinder rearing test (Q-VD-OPh: 30.8±4.3% vs. vehicle: 59.7±6.3% in nonimpaired forepaw preference) 3 weeks after HI, and reduced HI-induced hyperactivity, as measured in an open field test (Q-VD-OPh: 4,062±198 cm vs. vehicle: 4,792±205 cm in distance moved) 7 weeks after the insult. However, the functional protection was no longer observed when analyzed again at later time points. The mechanisms underlying the discrepancy between sustained morphological protection and transient functional protection remain to be elucidated.

Neamine induces neuroprotection after acute ischemic stroke in type one diabetic rats

INTRODUCTION

Angiogenin is a member of the ribonuclease superfamily and promotes degradation of the basement membrane and the extracellular matrix. After stroke in type one diabetes (T1DM) rats, Angiogenin is significantly increased and the Angiogenin is inversely correlated with functional outcome. Neamine, an aminoglycoside antibiotic, blocks nuclear translocation of Angiogenin, thereby abolishing the biological activity of Angiogenin. In this study, we therefore investigated the effect and underlying protective mechanisms of Neamine treatment of stroke in T1DM.

METHODS

T1DM was induced in male Wistar rats by streptozotocin (60mg/kg, ip), and T1DM rats were subjected to embolic middle cerebral artery occlusion (MCAo). Neamine (10mg/kg ip) was administered at 2, 24 and 48h after the induction of embolic MCAo. A battery of functional outcome tests was performed. Blood-brain barrier (BBB) leakage, and lesion volume were evaluated and immunostaining, and Western blot were performed.

RESULTS

Neamine treatment of stroke in T1DM rats significantly decreased BBB leakage and lesion volume as well as improved functional outcome compared to T1DM-control. Neamine also significantly decreased apoptosis and cleaved caspase-3 in the ischemic brain. Using immunostaining, we found that Neamine treatment significantly decreased nuclear Angiogenin, nuclear factor kappa-light-chain-enhancer of activated B cells (NFκB) activity, advanced glycation endproducts receptor (RAGE) number, the positive area of toll-like receptor 4 (TLR4) and increased Angeopoietin-1 expression compared to T1DM-MCAo control rats. Western blot results are consistent with the immunostaining.

CONCLUSION

Neamine treatment of stroke is neuroprotective in T1DM rats. Inhibition of neuroinflammatory factor expression and decrease of BBB leakage may contribute to Neamine-induced neuroprotective effects after stroke in T1DM rats.

NLRP3 inflammasome contributes to inflammation after intracerebral hemorrhage

OBJECTIVE

The NLRP3 (NALP3, cryopyrin) inflammasome, a key component of the innate immune system, facilitates caspase-1 and interleukin (IL)-1β processing, which amplifies the inflammatory response. Here, we investigated whether NLRP3 knockdown decreases neutrophil infiltration, reduces brain edema, and improves neurological function in an intracerebral hemorrhage (ICH) mouse model. We also determined whether mitochondrial reactive oxygen species (ROS) governed by mitochondrial permeability transition pores (mPTPs) would trigger NLRP3 inflammasome activation following ICH.

METHODS

ICH was induced by injecting autologous arterial blood (30μl) into a mouse brain. NLRP3 small interfering RNAs were administered 24 hours before ICH. A mPTP inhibitor (TRO-19622) or a specific mitochondria ROS scavenger (Mito-TEMPO) was coinjected with the blood. In naive animals, rotenone, which is a respiration chain complex I inhibitor, was applied to induce mitochondrial ROS production, and followed by TRO-19622 or Mito-TEMPO treatment. Neurological deficits, brain edema, enzyme-linked immunosorbent assay, Western blot, in vivo chemical cross-linking, ROS assay, and immunofluorescence were evaluated.

RESULTS

ICH activated the NLRP3 inflammasome. NLRP3 knockdown reduced brain edema and decreased myeloperoxidase (MPO) levels at 24 hours, and improved neurological functions from 24 to 72 hours following ICH. TRO-19622 or Mito-TEMPO reduced ROS, NLRP3 inflammasome components, and MPO levels following ICH. In naive animals, rotenone administration induced mPTP formation, ROS generation, and NLRP3 inflammasome activation, which were then reduced by TRO-19622 or Mito-TEMPO.

INTERPRETATION

The NLRP3 inflammasome amplified the inflammatory response by releasing IL-1β and promoting neutrophil infiltration following ICH. Mitochondria ROS may be a major trigger of NLRP3 inflammasome activation. The results of our study suggest that the inhibition of the NLRP3 inflammasome may effectively reduce the inflammatory response following ICH.ANN NEUROL 2014;75:209-219.

Neuroinflammation and neuroimmune dysregulation after acute hypoxic-ischemic injury of developing brain

Hypoxic-ischemic (HI) injury to developing brain results from birth asphyxia in neonates and from cardiac arrest in infants and children. It is associated with varying degrees of neurologic sequelae, depending upon the severity and length of HI. Global HI triggers a series of cellular and biochemical pathways that lead to neuronal injury. One of the key cellular pathways of neuronal injury is inflammation. The inflammatory cascade comprises activation and migration of microglia - the so-called "brain macrophages," infiltration of peripheral macrophages into the brain, and release of cytotoxic and proinflammatory cytokines. In this article, we review the inflammatory and immune mechanisms of secondary neuronal injury after global HI injury to developing brain. Specifically, we highlight the current literature on microglial activation in relation to neuronal injury, proinflammatory and anti-inflammatory/restorative pathways, the role of peripheral immune cells, and the potential use of immunomodulators as neuroprotective compounds.

Porcine brain microvessel endothelial cells show pro-inflammatory response to the size and composition of metallic nanoparticles

The purpose of the current studies was to determine if systemic exposure of various metallic nanoparticles differing in size and composition [silver (Ag-NPs, 25, 40 and 80 nm), copper-oxide (Cu-NPs, 40 and 60 nm) or gold (Au-NPs, 3 and 5 nm)] can induce the release of pro-inflammatory mediators that influence the restrictive nature of the blood-brain barrier (BBB) in vitro. Confluent porcine brain microvessel endothelial cells (pBMECs) (8-12 days) were treated with various metallic nanoparticles (15 μg/ml). Extracellular concentrations of pro-inflammatory mediators (IL-1β, TNFα and PGE2) were evaluated using ELISA. pBMECs were cultured in standard 12-well Transwell® inserts, and permeability was evaluated by measuring the transport of fluorescein across the pBMEC monolayers. PGE2 release following Cu-NP exposure was significantly increased when compared to the control. Similar results were observed for Ag-NPs but not Au-NPs. The secretion of TNFα and IL-1β was observed for both Cu-NPs and Ag-NPs but not in response to Au-NPs. The post-treatment time profiles of TNFα and IL-1β revealed that the IL-1β response was more persistent. The permeability ratios (exposure/control) were significantly greater following exposure to Cu-NPs or Ag-NPs, compared to Au-NPs. Together, these data suggest that the composition and size of NPs can cause significant pro-inflammatory response that can influence the integrity of the BBB.

Administration of a Sigma Receptor Agonist Delays MCAO-Induced Neurodegeneration and White Matter Injury

Many pharmacological treatments for stroke have afforded protection in rodent models but failed to show efficacy in clinical trials. This discrepancy may be due to the lack of long-term functional studies. Previously, delayed administration of the sigma receptor agonist 1,3-di-o-tolylguanidine (DTG) reduced infarct volume after middle cerebral artery occlusion (MCAO) in rats. The present study was conducted to determine whether the protective effects of DTG lead to improvements in behavioral functioning. Rats were subjected to MCAO and administered 7.5, 1.5, or 0.75 mg/kg DTG beginning 24 h post-surgery. Histological outcomes (96 h, 2 weeks, and 5 weeks) were compared with performance on a series of behavioral tests (2 and 4 weeks). Fluoro-Jade staining and immunohistochemistry were used to assess infarct volume and immune cell recruitment. All doses significantly reduced infarct volume and perturbation of striatal white matter tracts at 96 h. These reductions were associated with decreased numbers of CD11b-positive amoeboid microglia/macrophages. Despite short-term efficacy, DTG failed to improve behavioral outcomes or reduce infarct volumes after 96 h. While DTG may prove beneficial as a short-term therapy, these data highlight the importance of long-term functional recovery when evaluating novel therapies to treat stroke.

Inflammation after stroke: mechanisms and therapeutic approaches

Reperfusion of ischemic brain can reduce injury and improve outcome, but secondary injury due to inflammatory mechanisms limits the efficacy and time window of such treatments for stroke. This review summarizes the cellular and molecular basis of inflammation in ischemic injury as well as possible therapeutic strategies.

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.

Extracellular proteolytic pathophysiology in the neurovascular unit after stroke

The NINDS Stroke Progress Review Group recommended a shift in emphasis from a purely neurocentric view of cell death towards a more integrative approach whereby responses in all brain cells and matrix are considered. The neurovascular unit (fundamentally comprising endothelium, astrocyte, and neuron) provides a conceptual framework where cell-cell and cell-matrix signaling underlies the overall tissue response to stroke and its treatments. Here, we briefly review recent data on extracellular proteolytic dysfunction in the neurovascular unit after a stroke. The breakdown of neurovascular matrix initiates blood-brain barrier disruption with edema and/or hemorrhage. Endothelial dysfunction amplifies inflammatory responses. Perturbation of cell-matrix homeostasis triggers multiple cell death pathways. Interactions between the major classes of extracellular proteases from the plasminogen and matrix metalloprotease families may underlie processes responsible for some of the hemorrhagic complications of thrombolytic stroke therapy. Targeting the proteolytic imbalance within the neurovascular unit may provide new approaches for improving the safety and efficacy of thrombolytic reperfusion therapy for stroke.

Triggering Receptor Expressed on Myeloid Cells-2 Correlates to Hypothermic Neuroprotection in Ischemic Stroke

Hypothermia is neuroprotective against many acute neurological insults, including ischemic stroke. We and others have previously shown that protection by hypothermia is partially associated with an anti-inflammatory effect. Phagocytes are thought to play an important role in the clearance of necrotic debris, paving the way for endogenous repair mechanisms to commence, but the effect of cooling and phagocytosis has not been extensively studied. Triggering receptor expressed on myeloid cells-2 (TREM2) is a newly identified surface receptor shown to be involved in phagocytosis. In this study, we examined the effect of therapeutic hypothermia on TREM2 expression. Mice underwent permanent middle cerebral artery occlusion (MCAO) and were treated with one of the two cooling paradigms: one where cooling (30°C) began at the onset of MCAO (early hypothermia [eHT]) and another where cooling began 1 hour later (delayed hypothermia [dHT]). In both groups, cooling was maintained for 2 hours. A third group was maintained at normothermia (NT) as a control (37°C). Mice from the NT and dHT groups had similar ischemic lesion sizes and neurological performance, but the eHT group showed marked protection as evidenced by a smaller lesion size and less neurological deficits up to 30 days after the insult. Microglia and macrophages increased after MCAO as early as 3 days, peaked at 7 days, and decreased by 14 days. Both hypothermia paradigms were associated with decreased numbers of microglia and macrophages at 3 and 7 days, with greater decreases in the early paradigm. However, the proportion of the TREM2-positive microglia/macrophages was actually increased among the eHT group at day 7. eHT showed a long-term neurological benefit, but neuroprotection did not correlate to immune suppression. However, hypothermic neuroprotection was associated with a relative increase in TREM2 expression, and suggests that TREM2 may serve a beneficial role in brain ischemia.