The interleukin-8 (IL-8/CXCL8) receptor inhibitor reparixin improves neurological deficits and reduces long-term inflammation in permanent and transient cerebral ischemia in rats

Inhibition of Neutrophil Extracellular Traps: A Potential Therapeutic Strategy for Hemorrhagic Stroke

Stroke is a major health problem with high mortality and morbidity rates, partly due to limited treatment options. Inflammation has a critical role in the secondary damage that occurs following a stroke event. Neutrophil extracellular traps (NETs) are released by neutrophils and contribute to the progression of neuroinflammation that further worsens brain damage. The prevention of NET formation at sites of brain damage has been reported to prevent neuroinflammation and improve neurological deficits. The aim of this article was to assess the importance of NETs as a treatment target for hemorrhagic stroke in light of the available evidence. NETs are network structures that consist of decondensed DNA strands coated with granule proteins such as citrullinated histones, neutrophile esterase (NE), myeloperoxidase (MPO), and high mobility group protein B1 (HMGB1). Peptidyl arginine deiminase type-IV (PAD4) plays a key role in the formation of NETs. Inhibitors of NET formation, such as the PAD4-specific inhibitor GSK484, are effective at preventing inflammation and thus ultimately reducing brain damage after stroke. In conclusion, inhibition of NETs offers a potential therapeutic strategy for hemorrhagic stroke, although further research is needed to clarify the role of NETs in this condition.

A New Investigation into the Molecular Mechanism of Andrographolide towards Reducing Cytokine Storm

Cytokine storm is a condition in which the immune system produces an excessive number of inflammatory signals, which can result in organ failure and death. It is also known as cytokine release syndrome, CRS, or simply cytokine storm, and it has received a lot of attention recently because of the COVID-19 pandemic. It appears to be one of the reasons why some people experience life-threatening symptoms from COVID-19, a medical condition induced by SARS-CoV-2 infection. In situations where natural substances can be exploited as therapeutics to reduce cytokine storm, the drug development process has come to the rescue. In the present study, we tested the potentiality of Andrographolide, labdane diterpenoid targeting several key cytokines that are secreted as a result of cytokine storm. We used molecular docking analyses, molecular dynamics simulations, and pharmacokinetic properties to test the stability of the complexes. The compound’s binding energy with some cytokines was over −6.5 Kcal/mol. Furthermore, a post-molecular dynamics (MD) study revealed that Andrographolide was extremely stable with these cytokines. The compound’s pharmacokinetic measurements demonstrated excellent properties in terms of adsorption, distribution, metabolism, and excretion. Our research revealed that this compound may be effective in lowering cytokine storm and treating severe symptoms.

Diphtheria toxin induced but not CSF1R inhibitor mediated microglia ablation model leads to the loss of CSF/ventricular spaces in vivo that is independent of cytokine upregulation

Background

Two recently developed novel rodent models have been reported to ablate microglia, either by genetically targeting microglia (via Cx3cr1-creER: iDTR + Dtx) or through pharmacologically targeting the CSF1R receptor with its inhibitor (PLX5622). Both models have been widely used in recent years to define essential functions of microglia and have led to high impact studies that have moved the field forward.

Methods

Using either Cx3cr1-iDTR mice in combination with Dtx or via the PLX5622 diet to pharmacologically ablate microglia, we compared the two models via MRI and histology to study the general anatomy of the brain and the CSF/ventricular systems. Additionally, we analyzed the cytokine profile in both microglia ablation models.

Results

We discovered that the genetic ablation (Cx3cr1-iDTR + Dtx), but not the pharmacological microglia ablation (PLX5622), displays a surprisingly rapid pathological condition in the brain represented by loss of CSF/ventricles without brain parenchymal swelling. This phenotype was observed both in MRI and histological analysis. To our surprise, we discovered that the iDTR allele alone leads to the loss of CSF/ventricles phenotype following diphtheria toxin (Dtx) treatment independent of cre expression. To examine the underlying mechanism for the loss of CSF in the Cx3cr1-iDTR ablation and iDTR models, we additionally investigated the cytokine profile in the Cx3cr1-iDTR + Dtx, iDTR + Dtx and the PLX models. We found increases of multiple cytokines in the Cx3cr1-iDTR + Dtx but not in the pharmacological ablation model nor the iDTR + Dtx mouse brains at the time of CSF loss (3 days after the first Dtx injection). This result suggests that the upregulation of cytokines is not the cause of the loss of CSF, which is supported by our data indicating that brain parenchyma swelling, or edema are not observed in the Cx3cr1-iDTR + Dtx microglia ablation model. Additionally, pharmacological inhibition of the KC/CXCR2 pathway (the most upregulated cytokine in the Cx3cr1-iDTR + Dtx model) did not resolve the CSF/ventricular loss phenotype in the genetic microglia ablation model. Instead, both the Cx3cr1-iDTR + Dtx ablation and iDTR + Dtx models showed increased activated IBA1 + cells in the choroid plexus (CP), suggesting that CP-related pathology might be the contributing factor for the observed CSF/ventricular shrinkage phenotype.

Conclusions

Our data, for the first time, reveal a robust and global CSF/ventricular space shrinkage pathology in the Cx3cr1-iDTR genetic ablation model caused by iDTR allele, but not in the PLX5622 ablation model, and suggest that this pathology is not due to brain edema formation but to CP related pathology. Given the wide utilization of the iDTR allele and the Cx3cr1-iDTR model, it is crucial to fully characterize this pathology to understand the underlying causal mechanisms. Specifically, caution is needed when utilizing this model to interpret subtle neurologic functional changes that are thought to be mediated by microglia but could, instead, be due to CSF/ventricular loss in the genetic ablation model.

Neuroinflammation in Cerebral Ischemia and Ischemia/Reperfusion Injuries: From Pathophysiology to Therapeutic Strategies

Its increasing incidence has led stroke to be the second leading cause of death worldwide. Despite significant advances in recanalization strategies, patients are still at risk for ischemia/reperfusion injuries in this pathophysiology, in which neuroinflammation is significantly involved. Research has shown that in the acute phase, neuroinflammatory cascades lead to apoptosis, disruption of the blood-brain barrier, cerebral edema, and hemorrhagic transformation, while in later stages, these pathways support tissue repair and functional recovery. The present review discusses the various cell types and the mechanisms through which neuroinflammation contributes to parenchymal injury and tissue repair, as well as therapeutic attempts made in vitro, in animal experiments, and in clinical trials which target neuroinflammation, highlighting future therapeutic perspectives.

Brain Immune Interactions-Novel Emerging Options to Treat Acute Ischemic Brain Injury

Ischemic stroke is still among the leading causes of mortality and morbidity worldwide. Despite intensive advancements in medical sciences, the clinical options to treat ischemic stroke are limited to thrombectomy and thrombolysis using tissue plasminogen activator within a narrow time window after stroke. Current state of the art knowledge reveals the critical role of local and systemic inflammation after stroke that can be triggered by interactions taking place at the brain and immune system interface. Here, we discuss different cellular and molecular mechanisms through which brain–immune interactions can take place. Moreover, we discuss the evidence how the brain influence immune system through the release of brain derived antigens, damage-associated molecular patterns (DAMPs), cytokines, chemokines, upregulated adhesion molecules, through infiltration, activation and polarization of immune cells in the CNS. Furthermore, the emerging concept of stemness-induced cellular immunity in the context of neurodevelopment and brain disease, focusing on ischemic implications, is discussed. Finally, we discuss current evidence on brain–immune system interaction through the autonomic nervous system after ischemic stroke. All of these mechanisms represent potential pharmacological targets and promising future research directions for clinically relevant discoveries.

Immune Cells in the BBB Disruption After Acute Ischemic Stroke: Targets for Immune Therapy?

Blood-Brain Barrier (BBB) disruption is an important pathophysiological process of acute ischemic stroke (AIS), resulting in devastating malignant brain edema and hemorrhagic transformation. The rapid activation of immune cells plays a critical role in BBB disruption after ischemic stroke. Infiltrating blood-borne immune cells (neutrophils, monocytes, and T lymphocytes) increase BBB permeability, as they cause microvascular disorder and secrete inflammation-associated molecules. In contrast, they promote BBB repair and angiogenesis in the latter phase of ischemic stroke. The profound immunological effects of cerebral immune cells (microglia, astrocytes, and pericytes) on BBB disruption have been underestimated in ischemic stroke. Post-stroke microglia and astrocytes can adopt both an M1/A1 or M2/A2 phenotype, which influence BBB integrity differently. However, whether pericytes acquire microglia phenotype and exert immunological effects on the BBB remains controversial. Thus, better understanding the inflammatory mechanism underlying BBB disruption can lead to the identification of more promising biological targets to develop treatments that minimize the onset of life-threatening complications and to improve existing treatments in patients. However, early attempts to inhibit the infiltration of circulating immune cells into the brain by blocking adhesion molecules, that were successful in experimental stroke failed in clinical trials. Therefore, new immunoregulatory therapeutic strategies for acute ischemic stroke are desperately warranted. Herein, we highlight the role of circulating and cerebral immune cells in BBB disruption and the crosstalk between them following acute ischemic stroke. Using a robust theoretical background, we discuss potential and effective immunotherapeutic targets to regulate BBB permeability after acute ischemic stroke.

Circulating mRNA and microRNA profiling analysis in patients with ischemic stroke

To provide insight into molecular diagnosis and individualized treatment of ischemic stroke (IS), several available datasets in IS were analyzed to identify the differentially expressed genes and microRNAs (miRNAs). Series matrix files from GSE22255 and GSE16561 (mRNA profiles), a well as GSE110993 (miRNA profile) were downloaded from the Gene Expression Omnibus database. System-level clustering was performed with GeneCluster 3.0 software, and gene annotation and pathway enrichment were performed with gene ontology analysis and Database for Annotation, Visualization and Integrated Discovery software. For a protein-protein interaction (PPI) network, Biological General Repository for Interaction Datasets and IntAct interaction information were integrated to determine the interaction of differentially expressed genes. The selected miRNA candidates were imported into the TargetScan, miRDB and miRecords databases for the prediction of target genes. The present study identified 128 upregulated and 231 downregulated genes in female stroke patients, and 604 upregulated and 337 downregulated genes in male stroke patients compared with sex- and age-matched controls. The construction of a PPI network demonstrated that male stroke patients exhibited YWHAE, CUL3 and JUN as network center nodes, and in female patients CYLD, FOS and PIK3R1 interactions were the strongest. Notably, these interactions are mainly involved in immune inflammatory response, apoptosis and other biological pathways, such as blood coagulation. Female and male upregulated genes were cross-validated with another set of Illumina HumanRef-8 v3.0 expression beadchip (GSE16561). Functional item association networks, gene function networks and transcriptional regulatory networks were successfully constructed, and the relationships between miRNAs and target genes were successfully predicted. The present study identified a number of transcription factors, including DEFA1, PDK4, SDPR, TCN1 and MMP9, and miRNAs, including miRNA (miR)-21, miR-143/145, miR-125-5p and miR-122, which may serve important roles in the development of cerebral stroke and may be important molecular indicators for the treatment of IS.

Biomaterials to Neuroprotect the Stroke Brain: A Large Opportunity for Narrow Time Windows

Ischemic stroke represents one of the most prevalent pathologies in humans and is a leading cause of death and disability. Anti-thrombolytic therapy with tissue plasminogen activator (t-PA) and surgical thrombectomy are the primary treatments to recanalize occluded vessels and normalize the blood flow in ischemic and peri-ischemic regions. A large majority of stroke patients are refractory to treatment or are not eligible due to the narrow time window of therapeutic efficacy. In recent decades, we have significantly increased our knowledge of the molecular and cellular mechanisms that inexorably lead to progressive damage in infarcted and peri-lesional brain areas. As a result, promising neuroprotective targets have been identified and exploited in several stroke models. However, these considerable advances have been unsuccessful in clinical contexts. This lack of clinical translatability and the emerging use of biomaterials in different biomedical disciplines have contributed to developing a new class of biomaterial-based systems for the better control of drug delivery in cerebral disorders. These systems are based on specific polymer formulations structured in nanoparticles and hydrogels that can be administered through different routes and, in general, bring the concentrations of drugs to therapeutic levels for prolonged times. In this review, we first provide the general context of the molecular and cellular mechanisms impaired by cerebral ischemia, highlighting the role of excitotoxicity, inflammation, oxidative stress, and depolarization waves as the main pathways and targets to promote neuroprotection avoiding neuronal dysfunction. In the second part, we discuss the versatile role played by distinct biomaterials and formats to support the sustained administration of particular compounds to neuroprotect the cerebral tissue at risk of damage.

Targeting Oxidative Stress and Inflammation to Prevent Ischemia-Reperfusion Injury

The cerebral ischemia injury can result in neuronal death and/or functional impairment, which leads to further damage and dysfunction after recovery of blood supply. Cerebral ischemia/reperfusion injury (CIRI) often causes irreversible brain damage and neuronal injury and death, which involves many complex pathological processes including oxidative stress, amino acid toxicity, the release of endogenous substances, inflammation and apoptosis. Oxidative stress and inflammation are interactive and play critical roles in ischemia/reperfusion injury in the brain. Oxidative stress is important in the pathological process of ischemic stroke and is critical for the cascade development of ischemic injury. Oxidative stress is caused by reactive oxygen species (ROS) during cerebral ischemia and is more likely to lead to cell death and ultimately brain death after reperfusion. During reperfusion especially, superoxide anion free radicals, hydroxyl free radicals, and nitric oxide (NO) are produced, which can cause lipid peroxidation, inflammation and cell apoptosis. Inflammation alters the balance between pro-inflammatory and anti-inflammatory factors in cerebral ischemic injury. Inflammatory factors can therefore stimulate or exacerbate inflammation and aggravate ischemic injury. Neuroprotective therapies for various stages of the cerebral ischemia cascade response have received widespread attention. At present, neuroprotective drugs mainly include free radical scavengers, anti-inflammatory agents, and anti-apoptotic agents. However, the molecular mechanisms of the interaction between oxidative stress and inflammation, and their interplay with different types of programmed cell death in ischemia/reperfusion injury are unclear. The development of a suitable method for combination therapy has become a hot topic.

Glutaminase 1 Regulates Neuroinflammation After Cerebral Ischemia Through Enhancing Microglial Activation and Pro-Inflammatory Exosome Release

Cerebral ischemia induces a robust neuroinflammatory response that is largely mediated by the activation of CNS resident microglia. Activated microglia produce pro-inflammatory molecules to cause neuronal damage. Identifying regulators of microglial activation bears great potential in discovering promising candidates for neuroprotection post cerebral ischemia. Previous studies demonstrate abnormal elevation of glutaminase 1 (GLS1) in microglia in chronic CNS disorders including Alzheimer's disease and HIV-associated neurocognitive disorders. Ectopic expression of GLS1 induced microglia polarization into pro-inflammatory phenotype and exosome release in vitro. However, whether GLS1 is involved in neuroinflammation in acute brain injury remains unknown. Here, we observed activation of microglia, elevation of GLS1 expression, and accumulation of pro-inflammatory exosomes in rat brains 72 h post focal cerebral ischemia. Treatment with CB839, a glutaminase inhibitor, reversed ischemia-induced microglial activation, inflammatory response, and exosome release. Furthermore, we found that the application of exosome secretion inhibitor, GW4869, displayed similar anti-inflammatory effects to that of CB839, suggesting GLS1-mediated exosome release may play an important role in the formation of neuroinflammatory microenvironment. Therefore, GLS1 may serve as a key mediator and promising target of neuroinflammatory response in cerebral ischemia.

Intracerebral Hemorrhage Induces Inflammatory Gene Expression in Peripheral Blood: Global Transcriptional Profiling in Intracerebral Hemorrhage Patients

To perform global transcriptome profiling using RNA-seq in the peripheral blood of intracerebral hemorrhage (ICH) patients. In 11 patients with ICH, peripheral blood was collected within 24 h of symptom onset or last known well, and a second blood draw occurred 72 h (±6) after the first. RNA-seq identified differentially expressed genes (DEGs) between the first and second samples. Biological pathway enrichment analysis was performed with Ingenuity® Pathway Analysis (IPA). A total of 16,640 genes were identified and 218 were significant DEGs after ICH (false discovery rate <0.1). IPA identified 97 disease and functional categories that were significantly upregulated (z-score >2) post-ICH; 46 categories were specifically related to immune cell activation, 22 to general cellular activation processes, and 4 to other inflammation-related responses. In the canonical pathway and network analysis, inflammatory mediators of particular importance included interleukin-8, NF-κB, ERK1/2, and members of the integrin class. ICH induced peripheral blood gene expression at 72 to 96 h compared with 0 to 24 h from symptom onset. DEGs that were highly expressed included those related to inflammation and activation of the immune response. Further research is needed to determine whether these changes affect outcomes and may represent new therapeutic targets.

Intracerebral hemorrhage induces monocyte-related gene expression within six hours: Global transcriptional profiling in swine ICH

Intracerebral hemorrhage (ICH) is a severe neurological disorder with no proven treatment. Our prior research identified a significant association with monocyte level and ICH mortality. To advance our understanding, we sought to identify gene expression after ICH using a swine model to test the hypothesis that ICH would induce peripheral blood mononuclear cell (PBMC) gene expression. In 10 pigs with ICH, two PBMC samples were drawn from each with the first immediately prior to ICH induction and the second six hours later. RNA-seq was performed with subsequent bioinformatics analysis using Gene Ontology (GO), Kyoto Encyclopedia of Genes and Genomes (KEGG), and Ingenuity® Pathway Analysis (IPA). There were 182 significantly upregulated and 153 significantly down-regulated differentially expressed genes (DEGs) after ICH. Consistent with findings in humans, significant GO and KEGG pathways were primarily related to inflammation and the immune response. Five genes, all upregulated post-ICH and known to be associated with monocyte activation, were repeatedly DEGs in the significant KEGG pathways: CD14, TLR4, CXCL8, IL-18, and CXCL2. In IPA, the majority of upregulated disease/function categories were related to inflammation and immune cell activation. TNF and LPS were the most significantly activated upstream regulators, and ERK was the most highly connected node in the top network. ICH induced changes in PBMC gene expression within 6 h of onset related to inflammation, the immune response, and, more specifically, monocyte activation. Further research is needed to determine if these changes affect outcomes and may represent new therapeutic targets.

Innate Immunity Cells and the Neurovascular Unit

Recent studies have clarified many still unknown aspects related to innate immunity and the blood-brain barrier relationship. They have also confirmed the close links between effector immune system cells, such as granulocytes, macrophages, microglia, natural killer cells and mast cells, and barrier functionality. The latter, in turn, is able to influence not only the entry of the cells of the immune system into the nervous tissue, but also their own activation. Interestingly, these two components and their interactions play a role of great importance not only in infectious diseases, but in almost all the pathologies of the central nervous system. In this paper, we review the main aspects in the field of vascular diseases (cerebral ischemia), of primitive and secondary neoplasms of Central Nervous System CNS, of CNS infectious diseases, of most common neurodegenerative diseases, in epilepsy and in demyelinating diseases (multiple sclerosis). Neuroinflammation phenomena are constantly present in all diseases; in every different pathological state, a variety of innate immunity cells responds to specific stimuli, differentiating their action, which can influence the blood-brain barrier permeability. This, in turn, undergoes anatomical and functional modifications, allowing the stabilization or the progression of the pathological processes.

Myeloid cells as therapeutic targets in neuroinflammation after stroke: Specific roles of neutrophils and neutrophil-platelet interactions

Ischemic brain injury causes a local inflammatory response, involving the activation of resident brain cells such as microglia and the recruitment of infiltrating immune cells. Increasing evidence supports that plasticity of the myeloid cell lineage is determinant for the specific role of these cells on stroke outcome, from initiation and maintenance to resolution of post-ischemic inflammation. The aim of this review is to summarize some of the key characteristics of these cells and the mechanisms for their recruitment into the injured brain through interactions with platelets, endothelial cells and other leukocytes. Also, we discuss the existence of different leukocyte subsets in the ischemic tissue and, specifically, the impact of different myeloid phenotypes on stroke outcome, with special emphasis on neutrophils and their interplay with platelets. Knowledge of these cellular phenotypes and interactions may pave the way to new therapies able to promote protective immune responses and tissue repair after cerebral ischemia.

Neutrophils in traumatic brain injury (TBI): friend or foe?

Our knowledge of the pathophysiology about traumatic brain injury (TBI) is still limited. Neutrophils, as the most abundant leukocytes in circulation and the first-line transmigrated immune cells at the sites of injury, are highly involved in the initiation, development, and recovery of TBI. Nonetheless, our understanding about neutrophils in TBI is obsolete, and mounting evidences from recent studies have challenged the conventional views. This review summarizes what is known about the relationships between neutrophils and pathophysiology of TBI. In addition, discussions are made on the complex roles as well as the controversial views of neutrophils in TBI.

Stress-Induced Alterations of Immune Profile in Animals Suffering by Tau Protein-Driven Neurodegeneration

Alzheimer's disease (AD) is a multifactorial disorder; neurofibrillary pathology composed of tau protein is found side by side with amyloid-β deposits and extensive neuroinflammation. The immune system of the brain is considered as one of the factors that could influence the speed of the progression of AD neuropathology as a potential mediator of the damage induced by AD protein deposits. Alzheimer's disease pathology can be impacted by psychological stress; however, signalling pathways in background are not well known. We have explored possible avenues of how stress could influence the brain's immune system in a rat model of AD. Animals were subjected either to a single or multiple instances of immobilization stress. The analysis of a panel of immunity-related genes was used to evaluate the impact of stress on the immune response in the brain. We have identified 19 stress-responsive genes that are involved in neuroinflammation accompanying tau pathology: Nos2, Ptgs2, IL-8rb, C5, Mmp9, Cx3cr1, CD40lg, Adrb2, IL-6, IL-6r, IL-1r2, Ccl2, Ccl3, Ccl4, Ccl12, TNF-α, IL-1α, IL-1β, IL-10. Most of them are deregulated under the stress conditions also in control animals; however, the magnitude of the response to either acute or chronic stress differs. This can lead to serious influence, most probably to acceleration of neurodegenerative phenotype in diseased animals. Several of the genes (IL-1β, Casp1, Cx3cr1 and C5) are deregulated solely in tauopathic animals. The stress-induced changes in the inflammatory picture of the brain highlight the fact that the brain's immune response is highly responsive to environmental stimuli. The pattern of changes is indicative of an attempt to protect the brain in the short term, while being potentially detrimental to the response against a long-term pathological process such as neurofibrillary degeneration.

Ladarixin, a dual CXCR1/2 inhibitor, attenuates experimental melanomas harboring different molecular defects by affecting malignant cells and tumor microenvironment

CXCR1 and CXCR2 chemokine receptors and their ligands (CXCL1/2/3/7/8) play an important role in tumor progression. Tested to date CXCR1/2 antagonists and chemokine-targeted antibodies were reported to affect malignant cells in vitro and in animal models. Yet, redundancy of chemotactic signals and toxicity hinder further clinical development of these approaches. In this pre-clinical study we investigated the capacity of a novel small molecule dual CXCR1/2 inhibitor, Ladarixin (LDX), to attenuate progression of experimental human melanomas. Our data showed that LDX-mediated inhibition of CXCR1/2 abrogated motility and induced apoptosis in cultured cutaneous and uveal melanoma cells and xenografts independently of the molecular defects associated with the malignant phenotype. These effects were mediated by the inhibition of AKT and NF-kB signaling pathways. Moreover, systemic treatment of melanoma-bearing mice with LDX also polarized intratumoral macrophages to M1 phenotype, abrogated intratumoral de novo angiogenesis and inhibited melanoma self-renewal. Collectively, these studies outlined the pre-requisites of the successful CXCR1/2 inhibition on malignant cells and demonstrated multifactorial effects of Ladarixin on cutaneous and uveal melanomas, suggesting therapeutic utility of LDX in treatment of various melanoma types.

Leukocyte response is regulated by microRNA let7i in patients with acute ischemic stroke

OBJECTIVE

To evaluate microRNA let7i in ischemic stroke and its regulation of leukocytes.

METHODS

A total of 212 patients were studied: 106 with acute ischemic stroke and 106 controls matched for risk factors. RNA from circulating leukocytes was isolated from blood collected in PAXgene tubes. Let7i microRNA expression was assessed using TaqMan quantitative reverse transcription PCR. To assess let7i regulation of gene expression in stroke, messenger RNA (mRNA) from leukocytes was measured by whole-genome Human Transcriptome Array Affymetrix microarray. Given microRNAs act to destabilize and degrade their target mRNA, mRNAs that inversely correlated with let7i were identified. To demonstrate let7i posttranscriptional regulation of target genes, a 3' untranslated region luciferase assay was performed. Target protein expression was assessed using ELISA.

RESULTS

Let7i was decreased in patients with acute ischemic stroke (fold change -1.70, p < 0.00001). A modest inverse correlation between let7i and NIH Stroke Scale score at admission (r = -0.32, p = 0.02), infarct volume (r = -0.21, p = 0.04), and plasma MMP9 (r = -0.46, p = 0.01) was identified. The decrease in let7i was associated with increased expression of several of its mRNA targets, including CD86, CXCL8, and HMGB1. In vitro studies confirm let7i posttranscriptional regulation of target genes CD86, CXCL8, and HMGB1. Functional analysis predicted let7i regulates pathways involved in leukocyte activation, recruitment, and proliferation including canonical pathways of CD86 signaling in T helper cells, HMGB1 signaling, and CXCL8 signaling.

CONCLUSIONS

Let7i is decreased in circulating leukocytes of patients with acute ischemic stroke. Mechanisms by which let7i regulates inflammatory response post stroke include targeting CD86, CXCL8, and HMGB1.

Inflammation after Ischemic Stroke: The Role of Leukocytes and Glial Cells

The immune response after stroke is known to play a major role in ischemic brain pathobiology. The inflammatory signals released by immune mediators activated by brain injury sets off a complex series of biochemical and molecular events which have been increasingly recognized as a key contributor to neuronal cell death. The primary immune mediators involved are glial cells and infiltrating leukocytes, including neutrophils, monocytes and lymphocyte. After ischemic stroke, activation of glial cells and subsequent release of pro- and anti-inflammatory signals are important for modulating both neuronal cell damage and wound healing. Infiltrated leukocytes release inflammatory mediators into the site of the lesion, thereby exacerbating brain injury. This review describes how the roles of glial cells and circulating leukocytes are a double-edged sword for neuroinflammation by focusing on their detrimental and protective effects in ischemic stroke. Here, we will focus on underlying characterize of glial cells and leukocytes under inflammation after ischemic stroke.

Reparixin, a CXCR1/2 inhibitor in islet allotransplantation

Quality of life in Type 1 diabetic patients may be improved with islet transplantation, but lifelong immunosuppression is required to prevent rejection. Allo-immune response is a key player in graft dysfunction and although the adaptive immune response is well characterized, the effect of the innate immune reaction after transplantation is only recently becoming appreciated. In this study, we address how the innate response affects long-term outcomes in a murine islet allotransplant model. CTLA-4 Ig treatment is known to significantly prolong kidney subcapsular islet allograft survival and enhance glucose tolerance. The combination of CTLA-4 Ig with reparixin, which blocks against inflammatory neutrophil infiltration, yielded no long-term graft survival in an intrahepatic allotransplant model but had similar long-term graft survival in the kidney subcapsular model. Seven days after transplant, serum blood IFN-γ levels were significantly lower in the CTLA-4 Ig with reparixin treatment group compared to controls. IL-12p70 cytokine levels were increased with combination treatment, a positive modulation of the inflammatory response to the allograft. Furthermore, KC GRO, also known as CXCL1, was decreased in serum 7 d after transplant. Histologically, we found that immune cell infiltrate, CD4+ and CD8+ T cell populations along with both CXCR1+ and CXCR2+ cell populations were decreased within the CTLA-4 Ig and reparixin islet transplant graft. Overall these data provide insight into the down regulation of T-cell recruitment by CTLA-4 Ig and decreased neutrophil activation and recruitment with reparixin after long-term islet graft survival.

Distinct Contributions of Astrocytes and Pericytes to Neuroinflammation Identified in a 3D Human Blood-Brain Barrier on a Chip

Neurovascular inflammation is a major contributor to many neurological disorders, but modeling these processes in vitro has proven to be difficult. Here, we microengineered a three-dimensional (3D) model of the human blood-brain barrier (BBB) within a microfluidic chip by creating a cylindrical collagen gel containing a central hollow lumen inside a microchannel, culturing primary human brain microvascular endothelial cells on the gel’s inner surface, and flowing medium through the lumen. Studies were carried out with the engineered microvessel containing endothelium in the presence or absence of either primary human brain pericytes beneath the endothelium or primary human brain astrocytes within the surrounding collagen gel to explore the ability of this simplified model to identify distinct contributions of these supporting cells to the neuroinflammatory response. This human 3D BBB-on-a-chip exhibited barrier permeability similar to that observed in other in vitro BBB models created with non-human cells, and when stimulated with the inflammatory trigger, tumor necrosis factor-alpha (TNF-α), different secretion profiles for granulocyte colony-stimulating factor (G-CSF) and interleukin-6 (IL-6) were observed depending on the presence of astrocytes or pericytes. Importantly, the levels of these responses detected in the 3D BBB chip were significantly greater than when the same cells were co-cultured in static Transwell plates. Thus, as G-CSF and IL-6 have been reported to play important roles in neuroprotection and neuroactivation in vivo, this 3D BBB chip potentially offers a new method to study human neurovascular function and inflammation in vitro, and to identify physiological contributions of individual cell types.

Matrix-derived inflammatory mediator N-acetyl proline-glycine-proline is neurotoxic and upregulated in brain after ischemic stroke

Background

N-acetyl proline-glycine-proline (ac-PGP) is a matrix-derived chemokine produced through the proteolytic destruction of collagen by matrix metalloproteinases (MMPs). While upregulation and activation of MMPs and concomitant degradation of the extracellular matrix are known to be associated with neurological injury in ischemic stroke, the production of ac-PGP in stroke brain and its effects on neurons have not been investigated.

Findings

We examined the effects of ac-PGP on primary cortical neurons and found that it binds neuronal CXCR2 receptors, activates extracellular signal-regulated kinase 1/2 (ERK1/2), and induces apoptosis associated with caspase-3 cleavage in a dose-dependent manner. After transient ischemic stroke in rats, ac-PGP was significantly upregulated in infarcted brain tissue.

Conclusions

The production of ac-PGP in brain in ischemia/reperfusion injury and its propensity to induce apoptosis in neurons may link MMP-mediated destruction of the extracellular matrix and opening of the blood-brain barrier to progressive neurodegeneration associated with the initiation and propagation of inflammation. Ac-PGP may be a novel neurotoxic inflammatory mediator involved in sustained inflammation and neurodegeneration in stroke and other neurological disorders associated with activation of MMPs.

Systematic Review of the Neurobiological Relevance of Chemokines to Psychiatric Disorders

Psychiatric disorders are highly prevalent and disabling conditions of increasing public health relevance. Much recent research has focused on the role of cytokines in the pathophysiology of psychiatric disorders; however, the related family of immune proteins designated chemokines has been relatively neglected. Chemokines were originally identified as having chemotactic function on immune cells; however, recent evidence has begun to elucidate novel, brain-specific functions of these proteins of relevance to the mechanisms of psychiatric disorders. A systematic review of both human and animal literature in the PubMed and Google Scholar databases was undertaken. After application of all inclusion and exclusion criteria, 157 references were remained for the review. Some early mechanistic evidence does associate select chemokines with the neurobiological processes, including neurogenesis, modulation of the neuroinflammatory response, regulation of the hypothalamus–pituitary–adrenal axis, and modulation of neurotransmitter systems. This early evidence however does not clearly demonstrate any specificity for a certain psychiatric disorder, but is primarily relevant to mechanisms which are shared across disorders. Notable exceptions include CCL11 that has recently been shown to impair hippocampal function in aging – of distinct relevance to Alzheimer’s disease and depression in the elderly, and pre-natal exposure to CXCL8 that may disrupt early neurodevelopmental periods predisposing to schizophrenia. Pro-inflammatory chemokines, such as CCL2, CCL7, CCL8, CCL12, and CCL13, have been shown to drive chemotaxis of pro-inflammatory cells to the inflamed or injured CNS. Likewise, CX3CL has been implicated in promoting glial cells activation, pro-inflammatory cytokines secretion, expression of ICAM-1, and recruitment of CD4+ T-cells into the CNS during neuroinflammatory processes. With further translational research, chemokines may present novel diagnostic and/or therapeutic targets in psychiatric disorders.

Targeting neutrophils in ischemic stroke: translational insights from experimental studies

Neutrophils have key roles in ischemic brain injury, thrombosis, and atherosclerosis. As such, neutrophils are of great interest as targets to treat and prevent ischemic stroke. After stroke, neutrophils respond rapidly promoting blood-brain barrier disruption, cerebral edema, and brain injury. A surge of neutrophil-derived reactive oxygen species, proteases, and cytokines are released as neutrophils interact with cerebral endothelium. Neutrophils also are linked to the major processes that cause ischemic stroke, thrombosis, and atherosclerosis. Thrombosis is promoted through interactions with platelets, clotting factors, and release of prothrombotic molecules. In atherosclerosis, neutrophils promote plaque formation and rupture by generating oxidized-low density lipoprotein, enhancing monocyte infiltration, and degrading the fibrous cap. In experimental studies targeting neutrophils can improve stroke. However, early human studies have been met with challenges, and suggest that selective targeting of neutrophils may be required. Several properties of neutrophil are beneficial and thus may important to preserve in patients with stroke including antimicrobial, antiinflammatory, and neuroprotective functions.

The role of PPAR activation during the systemic response to brain injury

Background

Fenofibrate, a PPAR-α activator, has shown promising results as a neuroprotective therapy, with proposed anti-inflammatory and anti-oxidant effects. However, it displays poor blood-brain barrier permeability leading to some ambiguity over its mechanism of action. Experimentally induced brain injury has been shown to elicit a hepatic acute phase response that modulates leukocyte recruitment to the injured brain. Here, we sought to discover whether one effect of fenofibrate might include the suppression of the acute phase response (APR) following brain injury.

Methods

A 1-h intraluminal thread middle cerebral artery occlusion (MCAO) model followed by a 6-h reperfusion was performed in C57/BL6 mice. Quantitative reverse transcriptase-polymerase chain reaction was then used to measure hepatic expression of chemokine (C-X-C motif) ligand 1 (CXCL1), chemokine ligand 10 (CXCL10) and serum amyloid A-1 (SAA-1), and immunohistochemical analysis was used to quantify brain and hepatic neutrophil infiltration following stroke.

Results

The MCAO and sham surgery induced the expression of all three acute phase reactants. A 14-day fenofibrate pre-treatment decreased reactant production, infarct volume, and neutrophil recruitment to the brain and liver, which is a hallmark of the APR.

Conclusions

The data highlight a novel mechanism of action for fenofibrate and lend further evidence towards the promotion of its use as a prophylactic therapy in patients at risk of cerebral ischaemia. Further research is required to elucidate the mechanistic explanation underlying its actions.

Microglia is a key player in the reduction of stroke damage promoted by the new antithrombotic agent ticagrelor

The ADP-responsive P2Y12 receptor is expressed on both platelets and microglia. Clinical data show that ticagrelor, a direct-acting, reversibly binding P2Y12-receptor antagonist, reduces total cardiovascular events, including stroke. In our present study, we investigated the expression of P2Y12 receptors and the effects of ticagrelor on brain injury in Sprague-Dawley rats subjected to a permanent middle cerebral artery occlusion (MCAo). Rats were treated per os with ticagrelor 3 mg/kg or vehicle at 10 minutes, 22, and 36 hours after MCAo and killed after 48 hours. Immunofluorescence analysis showed an ischemia-related modulation of the P2Y12 receptor, which is constitutively expressed in Iba1(+) resting microglia. After MCAo, activated microglia was mainly concentrated around the lesion, with fewer cells present inside the ischemic core. Ticagrelor significantly attenuated the evolution of ischemic damage-evaluated by magnetic resonance imaging (MRI) at 2, 24, and 48 hours after MCAo-, the number of infiltrating cells expressing the microglia/monocyte marker ED-1, the cerebral expression of proinflammatory mediators (interleukin 1 (IL-1), monocyte chemoattractant protein 1 (MCP-1), nitric oxide synthase (iNOS)) and the associated neurologic impairment. In transgenic fluorescent reporter CX3CR1-green fluorescent protein (GFP) mice, 72 hours after MCAo, ticagrelor markedly reduced GFP(+) microglia and both early and late infiltrating blood-borne cells. Finally, in primary cultured microglia, ticagrelor fully inhibited ADP-induced chemotaxis (P<0.01). Our results show that ticagrelor is protective against ischemia-induced cerebral injury and this effect is mediated, at least partly, by inhibition of P2Y12-mediated microglia activation and chemotaxis.

Molecular dialogs between the ischemic brain and the peripheral immune system: dualistic roles in injury and repair

Immune and inflammatory responses actively modulate the pathophysiological processes of acute brain injuries such as stroke. Soon after the onset of stroke, signals such as brain-derived antigens, danger-associated molecular patterns (DAMPs), cytokines, and chemokines are released from the injured brain into the systemic circulation. The injured brain also communicates with peripheral organs through the parasympathetic and sympathetic branches of the autonomic nervous system. Many of these diverse signals not only activate resident immune cells in the brain, but also trigger robust immune responses in the periphery. Peripheral immune cells then migrate toward the site of injury and release additional cytokines, chemokines, and other molecules, causing further disruptive or protective effects in the ischemic brain. Bidirectional communication between the injured brain and the peripheral immune system is now known to regulate the progression of stroke pathology as well as tissue repair. In the end, this exquisitely coordinated crosstalk helps determine the fate of animals after stroke. This article reviews the literature on ischemic brain-derived signals through which peripheral immune responses are triggered, and the potential impact of these peripheral responses on brain injury and repair. Pharmacological strategies and cell-based therapies that target the dialog between the brain and peripheral immune system show promise as potential novel treatments for stroke.

Effect of the +781C/T polymorphism in the interleukin-8 gene on atherosclerotic cerebral infarction, and its interaction with smoking and drinking

OBJECTIVE

The aims of this study were to investigate the association between the +781C/T polymorphism of interleukin-8 (IL-8) and atherosclerotic cerebral infarction and the interaction between the +781C/T polymorphism and smoking or drinking in cerebral infarction in the Han Chinese population.

METHODS

We investigated the +781C/T polymorphism of IL-8 in 308 consecutive Han Chinese patients who were diagnosed with atherosclerotic cerebral infarction and in 294 age- and gender-matched healthy control subjects. The patients were classified using the Oxfordshire Community Stroke Project (OCSP) classification. The patients and subjects' histories of smoking and drinking were recorded, and atherosclerosis (AS) of the internal carotid artery (ICA) was evaluated in the patients. The +781C/T polymorphism was determined by polymerase chain reaction and restriction fragment length polymorphism (PCR-RFLP) analysis.

RESULTS

The +781C/T polymorphism and allele frequencies were not significantly different between the patients and controls and were not significantly associated with the OCSP classifications. We found that the 781C allele was significantly associated with AS of the ICA in the patients (p = 0.017), and the CT genotype was more prevalent in patients without AS of the ICA (p = 0.035). No interactions were observed between the +781C/T polymorphism and smoking or drinking.

CONCLUSION

Our results demonstrated that the +781C/T polymorphism of IL-8 did not play a role and had no interaction with smoking or drinking in the occurrence of cerebral infarction in the Han Chinese population. However, the C allele and the CT genotype might be associated with AS of the ICA in patients with ischemic stroke.

Blockade of CXCR1/2 chemokine receptors protects against brain damage in ischemic stroke in mice

OBJECTIVE

Ischemic stroke may result from transient or permanent reductions of regional cerebral blood flow. Polymorphonuclear neutrophils have been described as the earliest inflammatory cells to arrive in ischemic tissue. CXCR1/2 receptors are involved in the recruitment of these cells. However, the contribution of these chemokine receptors during transient brain ischemia in mice remains poorly understood. In this work, we investigated the effects of reparixin, an allosteric antagonist of CXCR1/2 receptors, in a model of middle cerebral artery occlusion and reperfusion in mice.

METHODS

C57BL/6J male mice treated with reparixin or vehicle were subjected to a middle cerebral artery occlusion procedure 1 h after the treatment. Ninety minutes after ischemia induction, the monofilament that prevented blood flow was removed. Twenty-four hours after the reperfusion procedure, behavioral changes, including motor signs, were analyzed with the SmithKline/Harwell/lmperial College/Royal Hospital/Phenotype Assessment (SHIRPA) battery. The animals were sacrificed, and brain tissue was removed for histological and biochemical analyses. Histological sections were stained with hematoxylin and eosin, neutrophil infiltration was estimated by myeloperoxidase activity and the inflammatory cytokine IL-iβ was measured by ELISA.

RESULTS

Pre-treatment with reparixin reduced the motor deficits observed in this model of ischemia and reperfusion. Myeloperoxidase activity and IL-iβ were reduced in the reparixin-treated group. Histological analysis revealed that ischemic injury was also attenuated by reparixin pre-treatment.

CONCLUSIONS

Our results suggest that the blockade of the CXCR1/2 receptors by reparixin promotes neuroprotective effects by reducing the levels of polymorphonuclear infiltration in the brain and the tissue damage associated with middle cerebral artery occlusion and reperfusion.

Effect of vagus nerve stimulation during transient focal cerebral ischemia on chronic outcome in rats

The aim of this study was to investigate the effect of vagus nerve stimulation (VNS) on infarct volume and neurological recovery up to 3 weeks following transient focal cerebral ischemia. Transient ischemia was produced by filament occlusion of the proximal middle cerebral artery (MCA) in rats. The right vagus nerve was stimulated starting 30 min after MCA occlusion and consisted of 30-sec pulse trains (20 Hz) delivered to the animal's right vagus nerve every 5 min for a total period of 60 min (n = 10). All the procedures were duplicated, but no stimulus was delivered, in a control group (n = 10). Neurological evaluations were performed in all animals at 24 hr, 48 hr, 1 week, 2 weeks, and 3 weeks after MCA occlusion; animals were euthanized; and neuronal damage was evaluated in hematoxylin-eosin-stained sections. The ischemic lesion volume was smaller in the VNS-treated animals in comparison with the nonstimulated group (P < 0.02). Although the functional score in both treated and untreated groups improved over the 3-week observation period (P < 0.001), there was still a statistically significant improvement reszulting from VNS treatment compared with control animals (P < 0.05). Cerebral blood flow changes in the MCA territory during ischemia did not differ between the VNS-treated animals (31.9% ± 10.4% of baseline) and control animals (29.9% ± 9.1%; P = 0.6). Stimulation of the vagus nerve for only a brief period early in ischemia provides neuroprotection in transient ischemia, with neuroprotection persisting for at least 3 weeks.

CX3CL1 is neuroprotective in permanent focal cerebral ischemia in rodents

The chemokine CX3CL1 and its receptor CX3CR1 are constitutively expressed in the nervous system. In this study, we used in vivo murine models of permanent middle cerebral artery occlusion (pMCAO) to investigate the protective potential of CX3CL1. We report that exogenous CX3CL1 reduced ischemia-induced cerebral infarct size, neurological deficits, and caspase-3 activation. CX3CL1-induced neuroprotective effects were long lasting, being observed up to 50 d after pMCAO in rats. The neuroprotective action of CX3CL1 in different models of brain injuries is mediated by its inhibitory activity on microglia and, in vitro, requires the activation of adenosine receptor 1 (A₁R). We show that, in the presence of the A₁R antagonist 1,3-dipropyl-8-cyclopentylxanthine and in A₁R⁻/⁻ mice, the neuroprotective effect of CX3CL1 on pMCAO was abolished, indicating the critical importance of the adenosine system in CX3CL1 protection also in vivo. In apparent contrast with the above reported data but in agreement with previous findings, cx3cl1⁻/⁻ and cx3cr1(GFP/GFP) mice, respectively, deficient in CX3CL1 or CX3CR1, had less severe brain injury on pMCAO, and the administration of exogenous CX3CL1 increased brain damage in cx3cl1⁻/⁻ ischemic mice. We also report that CX3CL1 induced a different phagocytic activity in wild type and cx3cl1⁻/⁻ microglia in vitro during cotreatment with the medium conditioned by neurons damaged by oxygen-glucose deprivation. Together, these data suggest that acute administration of CX3CL1 reduces ischemic damage via an adenosine-dependent mechanism and that the absence of constitutive CX3CL1-CX3CR1 signaling changes the outcome of microglia-mediated effects during CX3CL1 administration to ischemic brain.

Maxadilan, the Lutzomyia longipalpis vasodilator, drives plasma leakage via PAC1-CXCR1/2-pathway

Experiments were designed to determine if the vasodilatory peptides maxadilan and pituitary adenylate cyclase-activating peptide (PACAP-38) may cause plasma leakage through activation of leukocytes and to what extent these effects could be due to PAC1 and CXCR1/2 receptor stimulation. Intravital microscopy of hamster cheek pouches utilizing FITC-dextran and rhodamine, respectively, as plasma and leukocyte markers was used to measure arteriolar diameter, plasma leakage and leukocyte accumulation in a selected area (5mm(2)) representative of the hamster cheek pouch microcirculation. Our studies showed that the sand fly vasodilator maxadilan and PACAP-38 induced arteriolar dilation, leukocyte accumulation and plasma leakage in postcapillary venules. The recombinant mutant of maxadilan M65 and an antagonist of CXCR1/2 receptors, reparixin, and an inhibitor of CD11b/CD18 up-regulation, ropivacaine, inhibited all these effects as induced by maxadilan. Dextran sulfate, a complement inhibitor with heparin-like anti-inflammatory effects, inhibited plasma leakage and leukocyte accumulation but not arteriolar dilation as induced by maxadilan and PACAP-38. In vitro studies with isolated human neutrophils showed that maxadilan is a potent stimulator of neutrophil migration comparable with fMLP and leukotriene B(4) and that M65 and reparixin inhibited such migration. The data suggest that leukocyte accumulation and plasma leakage induced by maxadilan involves a mechanism related to PAC1- and CXCR1/2-receptors on leukocytes and endothelial cells.

Neural injury following stroke: are Toll-like receptors the link between the immune system and the CNS?

The CNS can exhibit features of inflammation in response to injury, infection or disease, whereby resident cells generate inflammatory mediators, including cytokines, prostaglandins, free radicals and complement, chemokines and adhesion molecules that recruit immune cells, and activate glia and microglia. Cerebral ischaemia triggers acute inflammation, which exacerbates primary brain damage. The regulation of inflammation after stroke is multifaceted and comprises vascular effects, distinct cellular responses, apoptosis and chemotaxis. There are many cell types that are affected including neurons, astrocytes, microglia and endothelial cells, all responding to the resultant neuroinflammation in different ways. Over the past 20 years, researchers examining brain tissue at various time intervals after stroke observed the presence of inflammatory cells, neutrophils and monocytes at the site of injury, as well as the activation of endogenous glia and microglia. This review examines the involvement of these cells in the progression of neural injury and proposes that the Toll-like receptors (TLRs) are likely to be an integral component in the communication between the CNS and the periphery. This receptor system is the archetypal pathogen sensing receptor system and its presence and signalling in the brain following neural injury suggests a more diverse role. We propose that the TLR system presents excellent pharmacological targets for the design of a new generation of therapeutic agents to modulate the inflammation that accompanies neural injury.

Role of chemokines in CNS health and pathology: a focus on the CCL2/CCR2 and CXCL8/CXCR2 networks

Chemokines and their receptors have crucial roles in the trafficking of leukocytes, and are of particular interest in the context of the unique immune responses elicited in the central nervous system (CNS). The chemokine system CC ligand 2 (CCL2) with its receptor CC receptor 2 (CCR2), as well as the receptor CXCR2 and its multiple ligands CXCL1, CXCL2 and CXCL8, have been implicated in a wide range of neuropathologies, including trauma, ischemic injury and multiple sclerosis. This review aims to overview the current understanding of chemokines as mediators of leukocyte migration into the CNS under neuroinflammatory conditions. We will specifically focus on the involvement of two chemokine networks, namely CCL2/CCR2 and CXCL8/CXCR2, in promoting macrophage and neutrophil infiltration, respectively, into the lesioned parenchyma after focal traumatic brain injury. The constitutive brain expression of these chemokines and their receptors, including their recently identified roles in the modulation of neuroprotection, neurogenesis, and neurotransmission, will be discussed. In conclusion, the value of evidence obtained from the use of Ccl2- and Cxcr2-deficient mice will be reported, in the context of potential therapeutics inhibiting chemokine activity which are currently in clinical trial for various inflammatory diseases.

Vulnerability to stroke: implications of perinatal programming of the hypothalamic-pituitary-adrenal axis

Chronic stress is capable of exacerbating each major, modifiable, endogenous risk factor for cerebrovascular and cardiovascular disease. Indeed, exposure to stress can increase both the incidence and severity of stroke, presumably through activation of the hypothalamic-pituitary-adrenal (HPA) axis. Now that characterization of the mechanisms underlying epigenetic programming of the HPA axis is well underway, there has been renewed interest in examining the role of early environment on the evolution of health conditions across the entire lifespan. Indeed, neonatal manipulations in rodents that reduce stress responsivity, and subsequent life-time exposure to glucocorticoids, are associated with a reduction in the development of neuroendocrine, neuroanatomical, and cognitive dysfunctions that typically progress with age. Although improved day to day regulation of the HPA axis also may be accompanied by a decrease in stroke risk, evidence from rodent studies suggest that an associated cost could be increased susceptibility to inflammation and neuronal death in the event that a stroke does occur and the individual is exposed to persistently elevated corticosteroids. Given its importance in regulation of health and disease states, any long-term modulation of the HPA axis is likely to be associated with both benefits and potential risks. The goals of this review article are to examine (1) the clinical and experimental data suggesting that neonatal experiences can shape HPA axis regulation, (2) the influence of stress and the HPA axis on stroke incidence and severity, and (3) the potential for neonatal programming of the HPA axis to impact adult cerebrovascular health.

Chemokine receptor antagonists: overcoming developmental hurdles

Chemokine receptors have a key role in the pathogenesis of autoimmune diseases, inflammation and viral infection. However, with the exception of selective CCR5 antagonists for HIV, the promise of obtaining new therapeutics related to chemokine receptors has not yet been realized. This article highlights some of the recent failures in the clinical trials of chemokine receptor antagonists and explores possible reasons as to why this might have occurred. Such reasons include the lack of predictability of animal models and redundancy of the target. A potential solution could be to develop drugs that target more than one receptor--known as polypharmacology--which could be a novel way to generate effective therapeutics.

Treatment with LXR agonists after focal cerebral ischemia prevents brain damage

Stroke is characterized by massive inflammation in areas surrounding the injury that magnifies damage to the brain. The liver X receptors (LXRs) are nuclear receptors that regulate cholesterol, lipid, and glucose metabolism. Synthetic LXR agonists have potent anti-inflammatory properties in a variety of settings, including neuroinflammation. However, the ability of LXR agonists to suppress stroke-associated inflammation has not been evaluated. Here, we have used time-lapse magnetic resonance imaging (MRI) to show that a single dose of an LXR ligand administered post-injury dramatically reduces brain damage in a model of acute brain ischemia. Neuroprotection was associated with suppression of neuroinflammation.

Role of microglial IKKbeta in kainic acid-induced hippocampal neuronal cell death

Microglial cells are activated during excitotoxin-induced neurodegeneration. However, the in vivo role of microglia activation in neurodegeneration has not yet been fully elucidated. To this end, we used Ikkbeta conditional knockout mice (LysM-Cre/Ikkbeta(F/F)) in which the Ikkbeta gene is specifically deleted in cells of myeloid lineage, including microglia, in the CNS. This deletion reduced IkappaB kinase (IKK) activity in cultured primary microglia by up to 40% compared with wild-type (Ikkbeta(F/F)), and lipopolysaccharide-induced proinflammatory gene expression was also compromised. Kainic acid (KA)-induced hippocampal neuronal cell death was reduced by 30% in LysM-Cre/Ikkbeta(F/F) mice compared with wild-type mice. Reduced neuronal cell death was accompanied by decreased KA-induced glial cell activation and subsequent expression of proinflammatory genes such as tumour necrosis factor (TNF)-alpha and interleukin (IL)-1beta. Similarly, neurons in organotypic hippocampal slice cultures (OHSCs) from LysM-Cre/Ikkbeta(F/F) mouse brain were less susceptible to KA-induced excitotoxicity compared with wild-type OHSCs, due in part to decreased TNF-alpha and IL-1beta expression. Based on these data, we concluded that IKK/nuclear factor-kappaB dependent microglia activation contributes to KA-induced hippocampal neuronal cell death in vivo through induction of inflammatory mediators.