Cytokine-induced neutrophil chemoattractant mRNA expressed in cerebral ischemia

Effects of iron oxide nanoparticles on the gene expression profiles of cerebral endotheliocytes and astrocytes

Iron oxide nanoparticles (IONPs) are considered as the most biocompatible magnetic materials suitable for biomedical applications. Nevertheless, there are many evidences of their toxicity for living organisms and partially neurotoxicity. The central nervous system is protected from undesirable substances circulating in the bloodstream by the blood-brain barrier (BBB). And even if being small enough, some nanoparticles could be able to penetrate cell membranes in other cells but will often be delayed by the BBB cells. However, the neurotoxicity of iron oxide is described even in the cases when IONPs should not uptake to the nervous system by experimental design. The aim of this study was to investigate what molecular changes in the cells-components of BBB - endotheliocytes and underlying astrocytes - may be caused by IONPs in the blood vessels of the brain. For this, a two-layer in vitro BBB model was created, consisting of rat cerebral endothelial cells and astrocytes. It was revealed that 100 and 200 mg/L of the nanoparticles induce metabolism alteration in the cells under study. Using RNA-sequencing, the up-regulation of pro-inflammatory chemokines encoding genes and changes in the expression of genes associated with detoxification in the endotheliocytes were demonstrated under the influence of 100 mg/L IONPs.

The Brain-Heart Axis: Neuroinflammatory Interactions in Cardiovascular Disease

PURPOSE OF REVIEW

The role of neuroimmune modulation and inflammation in cardiovascular disease has been historically underappreciated. Physiological connections between the heart and brain, termed the heart-brain axis (HBA), are bidirectional, occur through a complex network of autonomic nerves/hormones and cytokines, and play important roles in common disorders.

RECENT FINDINGS

At the molecular level, advances in the past two decades reveal complex crosstalk mediated by the sympathetic and parasympathetic nervous systems, the renin-angiotensin aldosterone and hypothalamus-pituitary axes, microRNA, and cytokines. Afferent pathways amplify proinflammatory signals via the hypothalamus and brainstem to the periphery, promoting neurogenic inflammation. At the organ level, while stress-mediated cardiomyopathy is the prototypical disorder of the HBA, cardiac dysfunction can result from a myriad of neurologic insults including stroke and spinal injury. Atrial fibrillation is not necessarily a causative factor for cardioembolic stroke, but a manifestation of an abnormal atrial substrate, which can lead to the development of stroke independent of AF. Central and peripheral neurogenic proinflammatory factors have major roles in the HBA, manifesting as complex bi-directional relationships in common conditions such as stroke, arrhythmia, and cardiomyopathy.

Overview of Traumatic Brain Injury: An Immunological Context

Traumatic brain injury (TBI) afflicts people of all ages and genders, and the severity of injury ranges from concussion/mild TBI to severe TBI. Across all spectrums, TBI has wide-ranging, and variable symptomology and outcomes. Treatment options are lacking for the early neuropathology associated with TBIs and for the chronic neuropathological and neurobehavioral deficits. Inflammation and neuroinflammation appear to be major mediators of TBI outcomes. These systems are being intensively studies using animal models and human translational studies, in the hopes of understanding the mechanisms of TBI, and developing therapeutic strategies to improve the outcomes of the millions of people impacted by TBIs each year. This manuscript provides an overview of the epidemiology and outcomes of TBI, and presents data obtained from animal and human studies focusing on an inflammatory and immunological context. Such a context is timely, as recent studies blur the traditional understanding of an “immune-privileged” central nervous system. In presenting the evidence for specific, adaptive immune response after TBI, it is hoped that future studies will be interpreted using a broader perspective that includes the contributions of the peripheral immune system, to central nervous system disorders, notably TBI and post-traumatic syndromes.

Genetic ablation of soluble tumor necrosis factor with preservation of membrane tumor necrosis factor is associated with neuroprotection after focal cerebral ischemia

Microglia respond to focal cerebral ischemia by increasing their production of the neuromodulatory cytokine tumor necrosis factor, which exists both as membrane-anchored tumor necrosis factor and as cleaved soluble tumor necrosis factor forms. We previously demonstrated that tumor necrosis factor knockout mice display increased lesion volume after focal cerebral ischemia, suggesting that tumor necrosis factor is neuroprotective in experimental stroke. Here, we extend our studies to show that mice with intact membrane-anchored tumor necrosis factor, but no soluble tumor necrosis factor, display reduced infarct volumes at one and five days after stroke. This was associated with improved functional outcome after experimental stroke. No changes were found in the mRNA levels of tumor necrosis factor and tumor necrosis factor-related genes (TNFR1, TNFR2, TACE), pro-inflammatory cytokines (IL-1β, IL-6) or chemokines (CXCL1, CXCL10, CCL2); however, protein expression of TNF, IL-1β, IL-6 and CXCL1 was reduced in membrane-anchored tumor necrosis factor(Δ/Δ) compared to membrane-anchored tumor necrosis factor(wt/wt) mice one day after experimental stroke. This was paralleled by reduced MHCII expression and a reduction in macrophage infiltration in the ipsilateral cortex of membrane-anchored tumor necrosis factor(Δ/Δ) mice. Collectively, these findings indicate that membrane-anchored tumor necrosis factor mediates the protective effects of tumor necrosis factor signaling in experimental stroke, and therapeutic strategies specifically targeting soluble tumor necrosis factor could be beneficial in clinical stroke therapy.

Prophylactic Chronic Zinc Administration Increases Neuroinflammation in a Hypoxia-Ischemia Model

Acute and subacute administration of zinc exert neuroprotective effects in hypoxia-ischemia animal models; yet the effect of chronic administration of zinc still remains unknown. We addressed this issue by injecting zinc at a tolerable dose (0.5 mg/kg weight, i.p.) for 14 days before common carotid artery occlusion (CCAO) in a rat. After CCAO, the level of zinc was measured by atomic absorption spectrophotometry, nitrites were determined by Griess method, lipoperoxidation was measured by Gerard-Monnier assay, and mRNA expression of 84 genes coding for cytokines, chemokines, and their receptors was measured by qRT-PCR, whereas nitrotyrosine, chemokines, and their receptors were assessed by ELISA and histopathological changes in the temporoparietal cortex-hippocampus at different time points. Long-term memory was evaluated using Morris water maze. Following CCAO, a significant increase in nitrosative stress, inflammatory chemokines/receptors, and cell death was observed after 8 h, and a 2.5-fold increase in zinc levels was detected after 7 days. Although CXCL12 and FGF2 protein levels were significantly increased, the long-term memory was impaired 12 days after reperfusion in the Zn+CCAO group. Our data suggest that the chronic administration of zinc at tolerable doses causes nitrosative stress, toxic zinc accumulation, and neuroinflammation, which might account for the neuronal death and cerebral dysfunction after CCAO.

Curcuminoids limit neutrophil-mediated reperfusion injury in experimental stroke by targeting the endothelium

OBJECTIVE

We sought to test the hypothesis that turmeric-derived curcuminoids limit reperfusion brain injury in an experimental model of stroke via blockade of early microvascular inflammation during reperfusion.

METHODS

Male Sprague Dawley rats subjected to MCAO/R were treated with turmeric-derived curcuminoids (vs. vehicle) 1 hour prior to reperfusion (300 mg/kg ip). Neutrophil adhesion to the cerebral microcirculation and measures of neutrophil and endothelial activation were assayed during early reperfusion (0-4 hours); cerebral infarct size, edema, and neurological function were assessed at 24 hours. Curcuminoid effects on TNFα-stimulated human brain microvascular endothelial cell (HBMVEC) were assessed.

RESULTS

Early during reperfusion following MCAO, curcuminoid treatment decreased neutrophil rolling and adhesion to the cerebrovascular endothelium by 76% and 67% and prevented >50% of the fall in shear rate. The increased number and activation state (CD11b and ROS) of neutrophils were unchanged by curcuminoid treatment, while increased cerebral expression of TNFα and ICAM-1, a marker of endothelial activation, were blocked by >30%. Curcuminoids inhibited NF-κB activation and subsequent ICAM-1 gene expression in HBMVEC.

CONCLUSION

Turmeric-derived curcuminoids limit reperfusion injury in stroke by preventing neutrophil adhesion to the cerebrovascular microcirculation and improving shear rate by targeting the endothelium.

Different actions of endothelin-1 on chemokine production in rat cultured astrocytes: reduction of CX3CL1/fractalkine and an increase in CCL2/MCP-1 and CXCL1/CINC-1

Background

Chemokines are involved in many pathological responses of the brain. Astrocytes produce various chemokines in brain disorders, but little is known about the factors that regulate astrocytic chemokine production. Endothelins (ETs) have been shown to regulate astrocytic functions through ET_B receptors. In this study, the effects of ETs on chemokine production were examined in rat cerebral cultured astrocytes.

Methods

Astrocytes were prepared from the cerebra of one- to two-day-old Wistar rats and cultured in serum-containing medium. After serum-starvation for 48 hours, astrocytes were treated with ETs. Total RNA was extracted using an acid-phenol method and expression of chemokine mRNAs was determined by quantitative RT-PCR. The release of chemokines was measured by ELISA.

Results

Treatment of cultured astrocytes with ET-1 and Ala^1,3,11,15-ET-1, an ET_B agonist, increased mRNA levels of CCL2/MCP1 and CXCL1/CINC-1. In contrast, CX3CL1/fractalkine mRNA expression decreased in the presence of ET-1 and Ala^1,3,11,15-ET-1. The effect of ET-1 on chemokine mRNA expression was inhibited by BQ788, an ET_B antagonist. ET-1 increased CCL2 and CXCL1 release from cultured astrocytes, but decreased that of CX3CL1. The increase in CCL2 and CXCL1 expression by ET-1 was inhibited by actinomycin D, pyrrolidine dithiocarbamate, SN50, mithramycin, SB203580 and SP600125. The decrease in CX3CL1 expression by ET-1 was inhibited by cycloheximide, Ca²⁺ chelation and staurosporine.

Conclusion

These findings suggest that ETs are one of the factors regulating astrocytic chemokine production. Astrocyte-derived chemokines are involved in pathophysiological responses of neurons and microglia. Therefore, the ET-induced alterations of astrocytic chemokine production are of pathophysiological significance in damaged brains.

Effects of heat shock protein 72 (Hsp72) on evolution of astrocyte activation following stroke in the mouse

Astrocyte activation is a hallmark of the response to brain ischemia consisting of changes in gene expression and morphology. Heat shock protein 72 (Hsp72) protects from cerebral ischemia, and although several protective mechanisms have been investigated, effects on astrocyte activation have not been studied. To identify potential mechanisms of protection, microarray analysis was used to assess gene expression in the ischemic hemispheres of wild-type (WT) and Hsp72-overexpressing (Hsp72Tg) mice 24 h after middle cerebral artery occlusion or sham surgery. After stroke both genotypes exhibited changes in genes related to apoptosis, inflammation, and stress, with more downregulated genes in Hsp72Tg and more inflammation-related genes increased in WT mice. Genes indicative of astrocyte activation were also upregulated in both genotypes. To measure the extent and time course of astrocyte activation after stroke, detailed histological and morphological analyses were performed in the cortical penumbra. We observed a marked and persistent increase in glial fibrillary acidic protein (GFAP) and a transient increase in vimentin. No change in overall astrocyte number was observed based on glutamine synthetase immunoreactivity. Hsp72Tg and WT mice were compared for density of astrocytes expressing activation markers and astrocytic morphology. In animals with comparable infarct size, overexpression of Hsp72 reduced the density of GFAP- and vimentin-expressing cells, and decreased astrocyte morphological complexity 72 h following stroke. However, by 30 days astrocyte activation was similar between genotypes. These data indicate that early modulation of astrocyte activation provides an additional novel mechanism associated with Hsp72 overexpression in the setting of ischemia.

Inhibition of CXCR2 signaling promotes recovery in models of multiple sclerosis

Multiple sclerosis (MS) is a neurodegenerative disease characterized by demyelination/remyelination episodes that ultimately fail. Chemokines and their receptors have been implicated in both myelination and remyelination failure. Chemokines regulate migration, proliferation and differentiation of immune and neural cells during development and pathology. Previous studies have demonstrated that the absence of the chemokine receptor CXCR2 results in both disruption of early oligodendrocyte development and long-term structural alterations in myelination. Histological studies suggest that CXCL1, the primary ligand for CXCR2, is upregulated around the peripheral areas of demyelination suggesting that this receptor/ligand combination modulates responses to injury. Here we show that in focal LPC-induced demyelinating lesions, localized inhibition of CXCR2 signaling reduced lesion size and enhanced remyelination while systemic treatments were relatively less effective. Treatment of spinal cord cultures with CXCR2 antagonists reduced CXCL1 induced A2B5+ cell proliferation and increased differentiation of myelin producing cells. More critically, treatment of myelin oligodendrocyte glycoprotein peptide 35-55-induced EAE mice, an animal model of multiple sclerosis, with small molecule antagonists against CXCR2 results in increased functionality, decreased lesion load, and enhanced remyelination. Our findings demonstrate the importance of antagonizing CXCR2 in enhancing myelin repair by reducing lesion load and functionality in models of multiple sclerosis and thus providing a therapeutic target for demyelinating diseases.

Brain cytokines as neuromodulators in cardiovascular control

1. The role of cytokines in cardiovascular control, especially in neurogenic hypertension, has received considerable attention during the past few years. Brain cytokines have been shown to exert profound effects on neuronal activity. Recently, a number of studies have shown that administration of pro-inflammatory cytokines or anti-inflammatory cytokines into the central nervous system has a significant impact on sympathetic outflow, arterial pressure and cardiac remodelling in experimental models of hypertension and heart failure. 2. Our objective in this review is to present a succinct account of the effect of cytokines on neuronal activity and their role in cardiovascular disease. Furthermore, we propose a hypothesis for a neuromodulatory role of cytokines in the neural control of cardiovascular function.

Involvement of cytokine-induced neutrophil chemoattractant in hypothalamic thermoregulation of luteinizing hormone-releasing hormone

We demonstrated in a previous study that serum IL-8 concentrations were significantly higher in women with hot flashes than without hot flashes. To clarify the role of IL-8 in the pathoetiology of menopausal hot flashes, we examined the effect of rat cytokine-induced neutrophil chemoattractant (CINC), a member of the IL-8 family, on thermoregulation using ovariectomized (OVX) rats treated with intracerebroventricular (i.c.v.) injection of LHRH agonist (LHRHa) as a model of hot flashes. We found that: 1) expression of CINC mRNA was increased around the periventricular area in the hypothalamus at 1 h, and the serum CINC concentration was increased at 2 h after i.c.v. injection of LHRHa; 2) the increase in serum CINC concentration in hypophysectomized rats was significantly lower than that in sham-operated rats; 3) i.c.v. but not iv injection of CINC elevated the rectal temperature of OVX rats; 4) i.c.v. injection of LHRHa into OVX rats produced a rapid rise (maximal increase: 10-25 min) in tail skin temperature, and the elevation was augmented by injection of an anti-CINC antibody; and 5) changes in serum CINC concentration and skin temperature after i.c.v. injection of LHRHa were reversed by replacement of estradiol. In conclusion, the production of CINC in the hypothalamus due to LHRHa injection in OVX rats was increased after elevation of skin temperature, suggesting that CINC plays a key role in the homeostasis of body temperature. Disturbance of the thermoregulatory mechanism involving LHRH and CINC may be related to the pathoetiology of hot flashes.

Production of monocyte chemoattractant protein-1 and cytokine-induced neutrophil chemoattractant-1 in rat brain is stimulated by intracerebroventricular administration of an endothelin ETB receptor agonist

The role of endothelin (ET)B receptors in chemokine production in the brain of rats was examined. Intracerebroventricular administration of 500 pmol/day of Ala(1,3,11,15)-ET-1, a selective ETB agonist, for 3 or 7 days increased monocyte chemoattractant protein (MCP)-1 and cytokine-induced neutrophil chemoattractant (CINC)-1 mRNA in the caudate-putamen and cerebrum, whereas it had no effects on regulated on activation normal T-cell expressed and secreted (RANTES), fractalkine and stromal cell-derived factor (SDF)-1alpha mRNA expression. Immunoreactive MCP-1 and CINC-1 in the caudate-putamen and the cerebrum were increased by the ETB agonist. Immunohistochemical observations on the Ala(1,3,11,15)-ET-1-infused rats showed that glial fibrillary acidic protein-positive astrocytes had immunoreactivity for MCP-1 and CINC-1. These findings indicate that the activation of brain ETB receptors causes the production of MCP-1 and CINC-1, and suggest a pathophysiological role for brain ETB receptors in nervous system damage.

Inflammation in stroke and focal cerebral ischemia

BACKGROUND

A growing number of recent investigations have established a critical role for leukocytes in propagating tissue damage after ischemia and reperfusion in stroke. Experimental data obtained from animal models of middle cerebral artery occlusion implicate inflammatory cell adhesion molecules, chemokines, and cytokines in the pathogenesis of this ischemic damage.

METHODS

Data from recent animal and human studies were reviewed to demonstrate that inflammatory events occurring at the blood-endothelium interface of the cerebral capillaries underlie the resultant ischemic tissue damage.

RESULTS

After arterial occlusion, the up-regulated expression of cytokines including IL-1, and IL-6 act upon the vascular endothelium to increase the expression of intercellular adhesion molecule-1, P-selectin, and E-selectin, which promote leukocyte adherence and accumulation. Integrins then serve to structurally modify the basal lamina and extracellular matrix. These inflammatory signals then promote leukocyte transmigration across the endothelium and mediate inflammatory cascades leading to further cerebral infarction.

CONCLUSIONS

Inflammatory interactions that occur at the blood-endothelium interface, involving cytokines, adhesion molecules, chemokines and leukocytes, are critical to the pathogenesis of tissue damage in cerebral infarction. Exploring these pathophysiological mechanisms underlying ischemic tissue damage may direct rational drug design in the therapeutic treatment of stroke.

The therapeutic potential of CXC chemokine blockade in acute inflammation in the brain

Mammalian neurones of the central nervous system (CNS) are terminally differentiated, and there is little endogenous capacity of the CNS to repair itself. Peripheral tissue injury, disease or infection results in a stereotypical inflammatory response to protect the host from pathogens and to promote tissue repair. However, collateral or 'bystander' damage is characteristic of any inflammatory response. Thus, it is apparent that the CNS has evolved mechanisms to regulate tightly the acute inflammatory response, and in particular to restrict the recruitment of neutrophils, in an attempt to protect itself from the potentially damaging consequences of inflammation in the brain. However, neutrophils are not always excluded from the brain. Indeed, they are found in large numbers in the brain parenchyma following traumatic lesions, stroke lesions, and in rodents, during the 'window of susceptibility'. Therapy targeted at blocking excitotoxic cell death has not successfully transferred from rodent models of stroke to human stroke patients. Restricting leukocyte entry to the brain, thereby inhibiting the inflammatory response, may prove to be a more practical therapeutic approach. The evidence presented in this review suggests that antagonising the effects of CXC chemokines may represent one route to achieve this goal.

Angiogenesis and stem cell transplantation as potential treatments of cerebral ischemic stroke

Ischemic stroke is a leading cause of human death and disability. Although stroke survivors may gain spontaneous partial functional recovery, they often suffer from sensory-motor dysfunctions, behavioral/neurological alterations, and various degrees of paralysis. Currently, limited clinical intervention is available to prevent ischemic damage and restore lost function in stroke victims. In addition to the extensive research on protective maneuvers against ischemia-induced cell death, increasing attention has been focused on potential strategies of promoting tissue repair and functional recovery in the damaged post-ischemic brain. Angiogenesis, or the growth of new blood vessels, may contribute to cell survival and functional recovery of the area of insult. The study of angiogenesis will increase the understanding of the mechanism underlying post-ischemia neurovascular plasticity and regeneration. Additionally, stem cell transplantation has emerged in the last few years as a potential therapy for ischemic stroke, because of their capability to differentiate into multiple cell types and the possibility that they may provide trophic support for cell survival, tissue repair, and functional recovery.

Differential regulation of type I and type II interleukin-1 receptors in focal brain inflammation

Most pathologies of the brain have an inflammatory component, associated with the release of cytokines such as interleukin-1beta (IL-1beta) from resident and infiltrating cells. The IL-1 type I receptor (IL-1RI) initiates a signalling cascade but the type II receptor (IL-1RII) acts as a decoy receptor. Here we have investigated the expression of IL-1beta, IL-1RI and IL-1RII in distinct inflammatory lesions in the rat brain. IL-1beta was injected into the brain to generate an inflammatory lesion in the absence of neuronal cell death whereas neuronal death was specifically induced by the microinjection of N-methyl-D-aspartate (NMDA). Using TaqMan RT-PCR and ELISA, we observed elevated de novo IL-1beta synthesis 2 h after the intracerebral microinjection of IL-1beta; this de novo IL-1beta remained elevated 24 h later. There was a concomitant increase in IL-1RI mRNA but a much greater increase in IL-1RII mRNA. Immunostaining revealed that IL-1RII was expressed on brain endothelial cells and on infiltrating neutrophils. In contrast, although IL-1beta and IL-1RI were elevated to similar levels in response to NMDA challenge, the response was delayed and IL-1RII mRNA expression was unchanged. The lesion-specific expression of IL-1 receptors suggests that the receptors are differentially regulated in a manner not directly related to the endogenous level of IL-1 in the CNS.

Inhibition of tumour necrosis factor-alpha by antisense targeting produces immunophenotypical and morphological changes in injury-activated microglia and macrophages

Microglia respond in a stereotypical pattern to a diverse array of pathological states. These changes are coupled to morphological and immunophenotypical alterations and the release of a variety of reactive species, trophic factors and cytokines that modify both microglia and their cellular environment. We examined whether a microglial-produced cytokine, tumour necrosis factor-alpha (TNF-alpha), was involved in the maintenance of microglial activation after spinal cord injury by selective inhibition using TNF-alpha antisense deoxyoligonucleotides (ASOs). Microglia and macrophages harvested from 3 d post-contused rat spinal cord were large and rounded (86.3 +/- 9.6%). They were GSA-IB4-positive (GSA-IB4(+)) (Griffonia simplicifolia lectin, microglia specific; 94.8 +/- 5.1%), strongly OX-42 positive (raised against a type 3 complement/integrin receptor, CD11b; 78.9 +/- 9.1%), ED-1 positive (a lysosomal marker shown to correlate well with immune cell activation; 97.2 +/- 2.6%) and IIA positive (antibody recognizes major histocompatibility complex II; 57.2 +/- 5.6%), indicative of fully activated cells, for up to 48 h after plating. These cells also secreted significant amounts of TNF-alpha (up to 436 pg/microg total protein, 16 h). Fluoroscein isothiocyanate-labelled TNF-alpha ASOs (5, 50 and 200 nm) added to the culture medium were taken up very efficiently into the cells (> 90% cells) and significantly reduced TNF-alpha production by up to 92% (26.5 pg/microg total protein, 16 h, 200 nm TNF-alpha ASOs). Furthermore, few of the treated cells at this time were round (5.4 +/- 2.7%), having become predominantly spindle shaped (74.9 +/- 6.3%) or stellate (21.4 +/- 2.7%); immunophenotypically, although all of them remained GSA-IB4 positive (91.6 +/- 6.2%), many were weakly OX-42 positive and few expressed either ED-1 (12.9 +/- 2.5%) or IIA (19.8 +/- 7.4%). Thus, the secretion of TNF-alpha early in spinal cord injury may be involved in autoactivating microglia/macrophages. However, at the peak of microglial activation after injury, the activation state of microglia/macrophages is not stable and this process may still be reversible by blocking TNF-alpha.

Chemokine receptors in the central nervous system: role in brain inflammation and neurodegenerative diseases

Chemokines were originally described as chemotactic cytokines involved in leukocyte trafficking. Research over the last decade, however, has shown that chemokine receptors are not restricted to leukocytes. In the brain, chemokine receptors are not only found in microglia (a brain macrophage), but also in astrocytes, oligodendrocytes and neurons. In this review, we describe the spatial and cellular distribution of chemokine receptors in the brain, distinguishing between constitutively and inducibly expressed receptors. We then discuss possible physiological functions, including neuronal migration, cell proliferation and synaptic activity. Evidence is emerging that chemokine receptors are also involved in neuronal death and hence neurodegenerative diseases. Chemokines may induce neuronal death either indirectly (e.g. through activation of microglia killing mechanisms) or directly through activation of neuronal chemokine receptors. Disease processes in which chemokines and their receptors are likely to be involved include multiple sclerosis (MS), Alzheimer's disease (AD), HIV-associated dementia (HAD) and cerebral ischemic disease. The study of chemokines and their receptors in the central nervous system (CNS) is not only relevant for the understanding of brain physiology and pathophysiology, but may also lead to the development of targeted treatments for neurodegenerative diseases.

Screening anti-inflammatory compounds in injured spinal cord with microarrays: a comparison of bioinformatics analysis approaches

Inflammatory responses contribute to secondary tissue damage following spinal cord injury (SCI). A potent anti-inflammatory glucocorticoid, methylprednisolone (MP), is the only currently accepted therapy for acute SCI but its efficacy has been questioned. To search for additional anti-inflammatory compounds, we combined microarray analysis with an explanted spinal cord slice culture injury model. We compared gene expression profiles after treatment with MP, acetaminophen, indomethacin, NS398, and combined cytokine inhibitors (IL-1ra and soluble TNFR). Multiple gene filtering methods and statistical clustering analyses were applied to the multi-dimensional data set and results were compared. Our analysis showed a consistent and unique gene expression profile associated with NS398, the selective cyclooxygenase-2 (COX-2) inhibitor, in which the overall effect of these upregulated genes could be interpreted as neuroprotective. In vivo testing demonstrated that NS398 reduced lesion volumes, unlike MP or acetaminophen, consistent with a predicted physiological effect in spinal cord. Combining explanted spinal cultures, microarrays, and flexible clustering algorithms allows us to accelerate selection of compounds for in vivo testing.

CXC chemokine receptors in the central nervous system: Role in cerebellar neuromodulation and development

Chemokines and their receptors are constitutively present in the central nervous system (CNS), expressed in neurons and glial cells. Much evidence suggests that, beyond their involvement in neuroinflammation, these proteins play a role in neurodevelopment and neurophysiological signaling. The goal of this review is to summarize recent information concerning expression, signaling, and function of CXC chemokine receptor in the CNS, with the main focus on the developmental and neuromodulatory actions of chemokines in the cerebellum.

TAK-779, a nonpeptide CC chemokine receptor antagonist, protects the brain against focal cerebral ischemia in mice

The effect of a nonpeptide CC chemokine receptor antagonist, TAK-779, on ischemic brain injury resulting from 1-hour middle cerebral artery occlusion followed by 48-hour reperfusion was examined in ddY mice. On intracerebroventricular injection of vehicle or TAK-779, infarct volume in the vehicle-treated group was 44.2 +/- 13.2% of the contralateral hemispheric volume, and TAK-779 (25 and 250 ng/mouse) dose-dependently reduced the infarct volume to 35.0 +/- 12.2% and 31.1 +/- 12.9%, respectively. On intravenous injection, infarct volume in the vehicle-treated group was 32.0 +/- 16.1%, and TAK-779 (5 microg per 20 g body weight) significantly reduced this to 22.0 +/- 10.5%. The results showed for the first time that a nonpeptide chemokine receptor antagonist is protective against ischemic brain injury.

Chemokine GRO1 and the spatial and temporal regulation of oligodendrocyte precursor proliferation

Oligodendrocyte precursor proliferation is precisely regulated spatially and temporally during development to allow optimal myelination of the central nervous system (CNS). We propose that a paracrine regulatory pathway involving the chemokine GRO1 and platelet-derived growth factor (PDGF) permit local control of precursor proliferation in the brain. GRO1, PDGF, and their receptors act synergistically to precisely regulate oligodendrocyte precursor proliferation in vitro and in vivo in the rat CNS. The nature of the paracrine regulatory loop with astrocyte and neuronal GRO1 expression in a pattern that is closely correlated with PDGF alpha R(+) oligodendrocyte precursors suggests that the GRO1/PDGF regulatory mechanism provides local control of oligodendrocyte precursor proliferation during development.

GROalpha/KC, a chemokine receptor CXCR2 ligand, can be a potent trigger for neuronal ERK1/2 and PI-3 kinase pathways and for tau hyperphosphorylation-a role in Alzheimer's disease?

Inflammation has been implicated in the pathogenesis of Alzheimer's disease (AD) and other neurodegenerative diseases. We have examined the potential role of some chemokine/chemokine receptors in this process. It is known that CXCR2 is a strongly expressed chemokine receptor on neurons and is strongly upregulated in AD in a subpopulation of neuritic plaques. Here, we show that one of the CXCR2 ligand GROalpha/KC can be a potent trigger for the ERK1/2 and PI-3 kinase pathways, as well as tau hyperphosphorylation in the mouse primary cortical neurons. GROalpha immunoreactivity can be detected in a subpopulation of neurons in normal and AD. Therefore, the CXCR2-ligand pair may have a potent pathophysiological role in neurodegenerative diseases.

[Cytokines and chemokines: mediators for intercellular communication in the brain]

The brain includes glial cells (astrocytes, microglia and oligodendrocytes) and endothelial cells in addition to neurons. Under some pathological conditions, it is invaded by leukocytes such as neutrophils, monocytes/macrophages and lymphocytes. Intercellular communication across these cell species is supposed to play crucial roles both in the brain functions and dysfunctions. However, the molecular basis of such intercellular communication remains unclear. We have studied the roles of cytokines and chemokines, which have been investigated as essential mediators in the immune and inflammatory systems, in intercellular communication across neurons, glial cells, endothelial cells and leukocytes. Messenger RNA expression of cytokines such as interleukin-1 beta was induced in brain microglia by i.p. injection of excitotoxin and neurostimulant, at least, partly via catecholaminergic systems. Messenger RNA of other cytokines such as leukemia inhibitory factor was induced in astrocytes. This cytokine specifically induced nociceptin mRNA in the cultured cortical neurons. Constitutive expression of some chemokines such as fractalkine and stromal cell derived factor-1 alpha was observed in the brain, suggesting that they play important roles in maintenance of brain homeostasis or determination of the patterning of neurons and/or glial cells in the developing and adult brains. Cytokines such as interleukin-1 beta and chemokines such as monocyte chemoattractant protein-1 and macrophage inflammatory protein-1 alpha were produced in ischemic brain and implicated in ischemic brain injury. In addition to ischemia, cytokines, chemokines and their receptors have been shown to be involved in various neurodegenerative diseases such as multiple sclerosis, Alzheimer's disease and AIDS dementia syndrome. They are potential targets for therapeutic intervention for neurodegenerative diseases.

Chemokine receptor antagonist peptide, viral MIP-II, protects the brain against focal cerebral ischemia in mice

The authors previously reported that mRNA for macrophage inflammatory protein-1alpha (MIP-1 alpha), a member of the CC chemokines, was expressed in glial cells after focal cerebral ischemia in rats. However, the function of chemokines in the ischemic brain remains unclear. Recently, viral macrophage inflammatory protein-II (vMIP-II), a chemokine analogue encoded by human herpesvirus-8 DNA, has been demonstrated to have antagonistic activity at several chemokine receptors. In the present study, the effects of vMIP-II and MIP-1alpha on ischemic brain injury were examined in mice to elucidate the roles of chemokines endogenously produced in the ischemic brain. Intracerebroventricular injection of vMIP-II (0.01-1 microg) reduced infarct volume in a dose-dependent manner when examined 48 hours after 1-hour middle cerebral artery occlusion followed by reperfusion. However, 1 microg MIP-1alpha increased infarct volume in the cortical region. These results supported the possibility that chemokines endogenously produced in the brain are involved in ischemic injury, and that chemokine receptors are potential targets for therapeutic intervention of stroke.

Stroke genomics: approaches to identify, validate, and understand ischemic stroke gene expression

Sequencing of the human genome is nearing completion and biologists, molecular biologists, and bioinformatics specialists have teamed up to develop global genomic technologies to help decipher the complex nature of pathophysiologic gene function. This review will focus on differential gene expression in ischemic stroke. It will discuss inheritance in the broader stroke population, how experimental models of spontaneous stroke might be applied to humans to identify chromosomal loci of increased risk and ischemic sensitivity, and also how the gene expression induced by stroke is related to the poststroke processes of brain injury, repair, and recovery. In addition, we discuss and summarise the literature of experimental stroke genomics and compare several approaches of differential gene expression analyzes. These include a comparison of representational difference analysis we have provided using an experimental stroke model that is representative of stroke evolution observed most often in man, and a summary of available data on stroke differential gene expression. Issues regarding validation of potential genes as stroke targets, the verification of message translation to protein products, the relevance of the expression of neuroprotective and neurodestructive genes and their specific timings, and the emerging problems of handling novel genes that may be discovered during differential gene expression analyses will also be addressed.

Chemokines and their receptors in the central nervous system

Chemokines are a family of proteins associated with the trafficking of leukocytes in physiological immune surveillance and inflammatory cell recruitment in host defence. They are classified into four classes based on the positions of key cystiene residues: C, CC, CXC, and CX3C. Chemokines act through both specific and shared receptors that all belong to the superfamily of G-protein-coupled receptors. Besides their well-established role in the immune system, several recent reports have demonstrated that these proteins also play a role in the central nervous system (CNS). In the CNS, chemokines are constitutively expressed by microglial cells, astrocytes, and neurons, and their expression can be increased after induction with inflammatory mediators. Constitutive expression of chemokines and chemokine receptors has been observed in both developing and adult brains, and the role played by these proteins in the normal brain is the object of intense study by many research groups. Chemokines are involved in brain development and in the maintenance of normal brain homeostasis; these proteins play a role in the migration, differentiation, and proliferation of glial and neuronal cells. The chemokine stromal cell-derived factor 1 and its receptor, CXCR4, are essential for life during development, and this ligand-receptor pair has been shown to have a fundamental role in neuron migration during cerebellar formation. Chemokine and chemokine receptor expression can be increased by inflammatory mediators, and this has in turn been associated with several acute and chronic inflammatory conditions. In the CNS, chemokines play an essential role in neuroinflammation as mediators of leukocyte infiltration. Their overexpression has been implicated in different neurological disorders, such as multiple sclerosis, trauma, stroke, Alzheimer's disease, tumor progression, and acquired immunodeficiency syndrome-associated dementia. An emerging area of interest for chemokine action is represented by the communication between the neuroendocrine and the immune system. Chemokines have hormone-like actions, specifically regulating the key host physiopathological responses of fever and appetite. It is now evident that chemokines and their receptors represent a plurifunctional family of proteins whose actions on the CNS are not restricted to neuroinflammation. These molecules constitute crucial regulators of cellular communication in physiological and developmental processes.

Monocyte chemoattractant protein-1 expressed in neurons and astrocytes during focal ischemia in mice

Focal cerebral ischemia elicits an inflammatory response characterized by the infiltration and accumulation of leukocytes, as well as the secretion of inflammatory mediators (Clark et al., Brain Res. Bull., 35 (1994) 387-392; Garcia et al., Am. J. Pathol., 144 (1994) 188-199; Wang et al., J. Neurochem. 71 (1998) 1194-1204). Leukocytes eliminate microbial invaders and necrotizing tissue debris, and can also turn against surrounding healthy tissue and exacerbate tissue injury (Furie and Randolph, Am. J. Pathol., 146 (1995) 1287-1301; Kochanek and Hallenbeck, Stroke 23 (1992) 1367-1379). Inflammatory mediators are considered to play an important role in attracting and stimulating leukocytes (Weiss, N. Engl. J. Med., 320 (1989) 365-376). Monocyte chemoattractant protein-1 (MCP-1) functions as an inflammatory mediator, whose source and role in focal cerebral ischemia is worth studying. MCP-1, a potent chemoattractant factor, may play an important role in ischemia-induced inflammatory response. The aim of the present study is to determine the time course and cell type of MCP-1 protein expression after permanent focal ischemia in mice. ELISA and immunohistochemical staining were used to detect the expression of MCP-1 protein after 0 h, 2 h, 4 h, 12 h, 1 day, 2 days, 3 days, 5 days and 7 days of middle cerebral artery occlusion (n=3-5 in each group). Double-labeled fluorescent staining was used to examine the cellular localization of MCP-1. The results demonstrated that MCP-1 expression was mainly observed in the ischemic core after 12 h of middle cerebral artery occlusion, then gradually increased and extended to the ischemic perifocal area. MCP-1 expression peaked at 2 days and 3 days, and gradually decreased after 5 days of MCAO. Double-labeled immunostaining for MCP-1 and neuron specific enolase (NSE) or glial fibrillary acidic protein (GFAP) showed that MCP-1 positive neurons were observed as early as 12 h of ischemia, while MCP-1 positive astrocytes were observed after 2 days of ischemia. These results support the functional role of MCP-1 in ischemic brain injury and reveal a distinct temporal and spatial expression of MCP-1 in cells believed to be neurons and astrocytes.

Changing the chemokine gradient: CINC1 crosses the blood-brain barrier

Chemokines are a large family of small, inducible, secreted, chemoattractant cytokines that are involved in inflammatory processes. It is well known that systemic and CNS infections cause disruption of the blood-brain barrier (BBB); however, it is not clear how chemokines are involved in this process. We studied the pharmacokinetics of the passage of the chemokine cytokine-induced neutrophil chemoattractant-1 (CINC1) from blood to brain after i.v. bolus injection and its efflux out of the brain after i.c.v. injection. Radiolabeled CINC1 was injected i.v. into mice, and the results were determined by multiple-time regression analysis. Using HPLC, we detected intact CINC1 in brain homogenate and blood after i.v. administration. CINC1 accumulated in the cerebral vasculature but also crossed the BBB completely and rapidly. No saturation of the influx was found, suggesting that either CINC1 crossed the BBB by simple diffusion or the dynamic interactions of binding and internalization precluded the self-inhibition typical of a transport system. Furthermore, there was no efflux system, with CINC1 exiting the brain at the same rate as reabsorption of CSF. The CINC1 injected into blood or CSF did not cause any breakdown of the BBB during the course of the experiments. Thus, the influx of CINC1 may alter the "chemokine gradient" across the BBB and therefore affect inflammatory reactions involving the CNS.

Expression of the anaphylatoxin C5a receptor in the oligodendrocyte lineage

Expression of the C5a receptor in the central nervous system has been demonstrated on microglia, astrocytes and neurons. In the present study, we demonstrate C5aR expression in vitro by rat and murine O2-A progenitor cells and oligodendrocytes. We also observed that in vitro differentiation of O2-A progenitors into mature oligodendrocytes is accompanied by down-regulation of C5aR mRNA expression. These results suggest that the C5aR may be a marker for oligodendroglial differentiation and play a role in oligodendrocyte function.

Potential of anticytokine therapies in central nervous system ischaemia

Central nervous system (CNS) ischaemia is associated with an acute inflammatory response which appears to potentiate CNS injury, especially following reperfusion. This response includes the release of inflammatory mediators called cytokines including IL-1 and TNF-alpha, which triggers the production of additional cytokines including IL-6 and activates leukocytes which infiltrate into the CNS. Increased expression of cytokines has been demonstrated to occur in the first few hours after CNS ischaemia. Preliminary clinical studies suggest that plasma levels of IL-6 are correlated with functional recovery while brain levels of cytokines have been demonstrated to increase following experimental ischaemia. Although there are no current clinical 'anti-cytokine' treatment studies for stroke, experimental studies modulating IL-1 and TNF-alpha have shown neuroprotection.

Therapeutic potential of anti-inflammatory drugs in focal stroke

The importance of cytokines, especially TNF-alpha and IL-1beta, are emphasised in the propagation and maintenance of the brain inflammatory response to injury. Much data supports the case that ischaemia and trauma elicit an inflammatory response in the injured brain. This inflammatory response consists of mediators (cytokines, chemokines and adhesion molecules) followed by cells (neutrophils early after the onset of brain injury and then a later monocyte infiltration). De novo upregulation of pro-inflammatory cytokines, chemokines and endothelial-leukocyte adhesion molecules occurs soon after focal ischaemia and trauma, as well as at the time when the tissue injury is evolving. The significance of this brain inflammatory response and its contribution to brain injury is now becoming more understood. In this review, we discuss the role of TNF-alpha and IL-1beta in traumatic and ischaemic brain injury and associated inflammation and the co-operative actions of chemokines and adhesion molecules in this process. We also address novel approaches to target cytokines and reduce the brain inflammatory response and thus brain injury, in stroke and neurotrauma. The mitogen-activated protein kinase (MAPK), p38, has been linked to inflammatory cytokine production and cell death following cellular stress. Stroke-induced p38 enzyme activation in the brain has been demonstrated and treatment with a second generation p38 MAPK inhibitor, SB-239063, provides a significant reduction in infarct size, neurological deficits and inflammatory cytokine expression produced by focal stroke. SB-239063 can also provide direct protection of cultured brain tissue to in vitro ischaemia. This robust SB-239063-induced neuroprotection emphasises a significant opportunity for targeting MAPK pathways in ischaemic stroke injury and also suggests that p38 inhibition should be evaluated for protective effects in other experimental models of nervous system injury and neurodegeneration.

Multiple molecular penumbras after focal cerebral ischemia

Though the ischemic penumbra has been classically described on the basis of blood flow and physiologic parameters, a variety of ischemic penumbras can be described in molecular terms. Apoptosis-related genes induced after focal ischemia may contribute to cell death in the core and the selective cell death adjacent to an infarct. The HSP70 heat shock protein is induced in glia at the edges of an infarct and in neurons often at some distance from the infarct. HSP70 proteins are induced in cells in response to denatured proteins that occur as a result of temporary energy failure. Hypoxia-inducible factor (HIF) is also induced after focal ischemia in regions that can extend beyond the HSP70 induction. The region of HIF induction is proposed to represent the areas of decreased cerebral blood flow and decreased oxygen delivery. Immediate early genes are induced in cortex, hippocampus, thalamus, and other brain regions. These distant changes in gene expression occur because of ischemia-induced spreading depression or depolarization and could contribute to plastic changes in brain after stroke.

Matrix remodeling after stroke. De novo expression of matrix proteins and integrin receptors

Following an ischemic insult to the central nervous system a reorganization of cells and tissue takes place as the surrounding cells attempt to limit the injury, repair the damage, and restore normal architecture of the brain. This tissue remodeling requires de novo synthesis of genes and proteins which enables cells to actively change their relationship with the existing extracellular matrix and with other cells to reorganize the damaged tissue. We have identified two key molecular components of the matrix remodeling process after focal ischemia: osteopontin (OPN) and its integrin receptor alpha v beta 3 (alpha v beta 3). OPN is initially expressed by activated macrophages and microglia in the periinfarct region (24-48 hr) and at later times (5-15 days) in the core infarct. After focal stroke the alpha v beta 3 was upregulated by astrocytes in the periinfarct region. Spatial and temporal analyses demonstrated that at 5 days after injury the alpha v beta 3-positive astrocytes were at a distance from the osteopontin-expressing macrophages; by 15 days the alpha v beta 3-expressing astrocytes were localized within an osteopontin-rich matrix. In vitro OPN was shown to induce migration of astrocytes in a Boyden chamber system. These data suggest that OPN derived from microglia at the infarct border zone (and possible macrophages in the infarct core) may serve as an "astrokine" (suggested term for astrocyte chemoattractant) to organize the astrocyte scar after focal stroke. Our data demonstrate profound changes in brain matrix remodeling after focal ischemic stroke, including the synthesis and release of matrix proteins alien to the normal brain, the expression of integrin receptors that ligate these proteins, and possibly a novel function for microglial-derived OPN in astrocyte migration after focal ischemia that may drive glial activation, organization, and repair functions.

Expression of receptors for complement anaphylatoxins C3a and C5a following permanent focal cerebral ischemia in the mouse

In the present study, we have examined the expression of anaphylatoxin C3a and C5a receptors (C3aR and C5aR) at the mRNA and protein levels in ischemic brain tissues following permanent middle cerebral artery (MCA) occlusion in the mouse. C3aR and C5aR mRNAs were both detected by semiquantitative reverse transcription and polymerase chain reaction (RT-PCR) and the cellular distribution of each receptor was analyzed by immunohistochemistry. Significant increases in the expression of C3aR and C5aR mRNAs in the ischemic cortex were observed; the expression of both reached a peak at 2 days after MCA occlusion (4.3- and 3.4-fold increases, respectively, compared with nonoperated control cortical samples; P < 0.00625 with Bonferroni's correction, n = 3). C3aR and C5aR stainings were found constitutively on neurons and astrocytes. In ischemic tissues, we observed that C3aR and C5aR were expressed de novo on endothelial cells of blood vessels, at 6 h and 2 days after MCA occlusion, respectively. C3aR and C5aR immunostaining was increased in macrophage-like cells and reactive astrocytes 7 days postocclusion. C3a and C5a may play an important role in promoting inflammatory and/or repair processes in the ischemic brain by regulating glial cell activation and chemotaxis.

Increased expression of bioactive chemokines in human cerebromicrovascular endothelial cells and astrocytes subjected to simulated ischemia in vitro

Leukocyte infiltration into the brain has been implicated in the development of ischemic brain damage. In this study, simulated in vitro ischemia/reperfusion and IL-1beta were found to up-regulate both the expression of intercellular adhesion molecule- (ICAM-1) in cultured human cerebromicrovascular endothelial cells (HCEC) and the adhesion of allogenic neutrophils to HCEC. Both HCEC and human fetal astrocytes (FHAS) also responded to IL-1beta and to in vitro ischemia/reperfusion by a pronounced up-regulation of IL-8 and MCP-1 mRNA and by increased release of IL-8 and MCP-1 in cell culture media. FHAS were found to release 30-times higher levels of MCP-1 than HCEC under both basal and ischemic conditions. However, 100 u/ml IL-1beta induced greater stimulation of both IL-8 and MCP-1 secretion in HCEC (50 and 20 times above controls, respectively) than in FHAS (three and two times above controls, respectively). IL-8 was the principal neutrophil chemoattractant released from IL-1beta-treated HCEC, since IL-8 antibody completely inhibited neutrophil chemotaxis enticed by HCEC media. However, the IL-8 antibody neutralized only 50% of IL-1beta-stimulated neutrophil chemoattractants released from FHAS, and 40%-60% of ischemia-stimulated chemotactic activity released by either HCEC or FHAS. These results suggest that simulated in vitro ischemia, in addition to IL-8 and MCP-1, stimulates secretion of other bioactive chemokines from HCEC and FHAS.

Molecular cloning and expression of the rat monocyte chemotactic protein-3 gene: a possible role in stroke

Using the suppression subtractive hybridization (SSH) strategy for differential gene cloning, we identified the induced expression of a rat homologue to murine and human monocyte chemotactic protein-3 (MCP-3) in ischemic brain. The 2.4-kilobase rat MCP-3 gene features high homology in gene structure and sequence to murine MCP-3. The temporal expression of MCP-3 mRNA was examined in brain tissue rendered ischemia by permanent or temporary occlusion of the middle cerebral artery (MCAO). A marked increase in MCP-3 mRNA was observed 12 h post-ischemia, with 49-fold and 17-fold increase (n=4, p<0.01) over control in the permanent or temporary MCAO, respectively. Significant induction of MCP-3 in the ischemic cortex was sustained up to 5 days after ischemic injury. The profile of MCP-3 mRNA induction paralleled leukocyte infiltration and accumulation that occur after focal stroke, suggesting a role for MCP-3 in recruiting these inflammatory cells into the ischemic tissue. Molecular cloning of rat MCP-3 should provide a valuable tool, as demonstrated in the present work, for the investigation of MCP-3 expression and function in rat disease models.

Inflammatory mediators and stroke: new opportunities for novel therapeutics

Contrary to previous dogmas, it is now well established that brain cells can produce cytokines and chemokines, and can express adhesion molecules that enable an in situ inflammatory reaction. The accumulation of neutrophils early after brain injury is believed to contribute to the degree of brain tissue loss. Support for this hypothesis has been drawn from many studies where neutrophil-depletion blockade of endothelial-leukocyte interactions has been achieved by various techniques. The inflammation reaction is an attractive pharmacologic opportunity, considering its rapid initiation and progression over many hours after stroke and its contribution to evolution of tissue injury. While the expression of inflammatory cytokines that may contribute to ischemic injury has been repeatedly demonstrated, cytokines may also provide "neuroprotection" in certain conditions by promoting growth, repair, and ultimately, enhanced functional recovery. Significant additional basic work is required to understand the dynamic, complex, and time-dependent destructive and protective processes associated with inflammation mediators produced after brain injury. The realization that brain ischemia and trauma elicit robust inflammation in the brain provides fertile ground for discovery of novel therapeutic agents for stroke and neurotrauma. Inhibition of the mitogen-activated protein kinase (MAPK) cascade via cytokine suppressive anti-inflammatory drugs, which block p38 MAPK and hence the production of interleukin-1 and tumor necrosis factor-alpha, are most promising new opportunities. However, spatial and temporal considerations need to be exercised to elucidate the best opportunities for selective inhibitors for specific inflammatory mediators.

C10 is a novel chemokine expressed in experimental inflammatory demyelinating disorders that promotes recruitment of macrophages to the central nervous system

Chemokines may be important in the control of leukocytosis in inflammatory disorders of the central nervous system. We studied cerebral chemokine expression during the evolution of diverse neuroinflammatory disorders in transgenic mice with astrocyte glial fibrillary acidic protein-targeted expression of the cytokines IL-3, IL-6, or IFN-alpha and in mice with experimental autoimmune encephalomyelitis. Distinct chemokine gene expression patterns were observed in the different central nervous system inflammatory models that may determine the phenotype and perhaps the functions of the leukocytes that traffic into the brain. Notably, high expression of C10 and C10-related genes was found in the cerebellum and spinal cord of GFAP-IL3 mice with inflammatory demyelinating disease and in mice with experimental autoimmune encephalomyelitis. In both these neuroinflammatory models, C10 RNA and protein expressing cells were predominantly macrophage/microglia and foamy macrophages present within demyelinating lesions as well as in perivascular infiltrates and meninges. Intracerebroventricular injection of recombinant C10 protein promoted the recruitment of large numbers of Mac-1(+) cells and, to a much lesser extent, CD4(+) lymphocytes into the meninges, choroid plexus, ventricles, and parenchyma of the brain. Thus, C10 is a prominent chemokine expressed in the central nervous system in experimental inflammatory demyelinating disease that, we show, also acts as a potent chemotactic factor for the migration of these leukocytes to the brain.

Chemokine and inflammatory cell response to hypoxia-ischemia in immature rats

Hypoxia-ischemia induces an inflammatory response in the immature central nervous system that may be important for development of brain injury. Recent data implicate that chemoattractant cytokines, chemokines, are involved in the recruitment of immune cells. The aim was to study alpha- and beta-chemokines in relation to the temporal activation of inflammatory cells after hypoxia-ischemia in immature rats. Hypoxia-ischemia was induced in 7-day-old rats (left carotid artery occlusion + 7.7% oxygen). The pups were decapitated at different times after the insult. Immunohistochemistry was used for evaluation of the inflammatory cell response and RT-PCR to analyze the cytokine mRNA and chemokine mRNA expression. A distinct interleukin-1beta and tumor necrosis factor-alpha cytokine expression was found 0-24 h after hypoxia-ischemia that was accompanied by induction of alpha-chemokines (growth related gene and macrophage inflammatory protein-2). In the next phase, the beta2-integrin expression was increased (12 h and onward) and neutrophils transiently invaded the vessels and tissue in the infarct region. The mRNA induction for the beta-chemokines macrophage inflammatory protein-1alpha, macrophage inflammatory protein-1beta, and RANTES preceded the expression of markers for lymphocytes [cluster of differentiation (CD)4, CD8], microglia/macrophages (MHC I), and natural killer cells in the infarct area. The activation of microglia/macrophages, CD4 lymphocytes, and astroglia persisted up to at least 42 d of postnatal age implicating a chronic component of immunoinflammatory activation. The expression of mRNA for alpha- and beta-chemokines preceded the appearance of immune cells suggesting that these molecules may have a role in the inflammatory response to insults in the immature central nervous system.

Expression of specific chemokines and chemokine receptors in the central nervous system of multiple sclerosis patients

Chemokines direct tissue invasion by specific leukocyte populations. Thus, chemokines may play a role in multiple sclerosis (MS), an idiopathic disorder in which the central nervous system (CNS) inflammatory reaction is largely restricted to mononuclear phagocytes and T cells. We asked whether specific chemokines were expressed in the CNS during acute demyelinating events by analyzing cerebrospinal fluid (CSF), whose composition reflects the CNS extracellular space. During MS attacks, we found elevated CSF levels of three chemokines that act toward T cells and mononuclear phagocytes: interferon-gamma-inducible protein of 10 kDa (IP-10); monokine induced by interferon-gamma (Mig); and regulated on activation, normal T-cell expressed and secreted (RANTES). We then investigated whether specific chemokine receptors were expressed by infiltrating cells in demyelinating MS brain lesions and in CSF. CXCR3, an IP-10/Mig receptor, was expressed on lymphocytic cells in virtually every perivascular inflammatory infiltrate in active MS lesions. CCR5, a RANTES receptor, was detected on lymphocytic cells, macrophages, and microglia in actively demyelinating MS brain lesions. Compared with circulating T cells, CSF T cells were significantly enriched for cells expressing CXCR3 or CCR5. Our results imply pathogenic roles for specific chemokine-chemokine receptor interactions in MS and suggest new molecular targets for therapeutic intervention.

The chemokine growth-regulated oncogene-alpha promotes spinal cord oligodendrocyte precursor proliferation

Chemokines, (chemotactic cytokines) are a family of regulatory molecules involved in modulating inflammatory responses. Here we demonstrate that the chemokine growth-regulated oncogene-alpha (GRO-alpha) is a potent promoter of oligodendrocyte precursor proliferation. The proliferative response of immature spinal cord oligodendrocyte precursors to their major mitogen, platelet derived growth factor (PDGF), is dramatically enhanced by GRO-alpha present in spinal cord conditioned medium. One source of GRO-alpha is a subset of spinal cord astrocytes. Cultures of astrocytes contain GRO-alpha mRNA and protein and secrete biologically active concentrations of GRO-alpha. In postnatal spinal cord white matter the location of GRO-alpha-immunoreactive cells is developmentally regulated: GRO-alpha+ cells first appear in ventral and later in dorsal spinal cord white matter. These results suggest that localized proliferation of oligodendrocytes is mediated by synergy between PDGF and GRO-alpha.

Chemokines and chemokine receptors in the CNS: a possible role in neuroinflammation and patterning

Chemokines constitute a growing family of structurally and functionally related small (8-10 kDa) proteins associated with inflammatory-cell recruitment in host defence. In addition to their well-established role in the immune system, recent data suggest their involvement in the maintenance of CNS homeostasis, in neuronal patterning during ontogeny and as potential mediators of neuroinflammation, playing an essential role in leukocyte infiltration into the brain. Chemokines and their G protein-coupled receptors are constitutively expressed at low-to-negligible levels in various cell types in the brain. Their expression is rapidly induced by various neuroinflammatory stimuli, implicating them in various neurological disorders such as trauma, stroke and Alzheimer's disease, in tumour induction and in neuroimmune diseases such as multiple sclerosis or acquired immunodeficiency syndrome (AIDS). Here, F. Mennicken, R. Maki, E. B. De Souza and R. Quirion briefly summarize recent exciting findings in the field.