Chemokines and Chemokine Receptors: Potential Therapeutic Targets in Multiple Sclerosis

DAPTA, a C-C Chemokine Receptor 5 (CCR5), Leads to the Downregulation of Notch/NF-κB Signaling and Proinflammatory Mediators in CD40+ Cells in Experimental Autoimmune Encephalomyelitis Model in SJL/J Mice

Multiple sclerosis (MS) is an autoimmune inflammatory disease of the central nervous system characterized by motor deficits, cognitive impairment, fatigue, pain, and sensory and visual dysfunction. CD40, highly expressed in B cells, plays a significant role in MS pathogenesis. The experimental autoimmune encephalomyelitis (EAE) mouse model of MS has been well established, as well as its relevance in MS patients. This study aimed to evaluate the therapeutic potential of DAPTA, a selective C-C chemokine receptor 5 (CCR5) antagonist in the murine model of MS, and to expand the knowledge of its mechanism of action. Following the induction of EAE, DAPTA was administrated (0.01 mg/kg, i.p.) daily from day 14 to day 42. We investigated the effects of DAPTA on NF-κB p65, IκBα, Notch-1, Notch-3, GM-CSF, MCP-1, iNOS, and TNF-α in CD40⁺ spleen B cells using flow cytometry. Furthermore, we also analyzed the effect of DAPTA on NF-κB p65, IκBα, Notch-1, Notch-3, GM-CSF, MCP-1, iNOS, and TNF-α mRNA expression levels using qRT-PCR in brain tissue. EAE mice treated with DAPTA showed substantial reductions in NF-κB p65, Notch-1, Notch-3, GM-CSF, MCP-1, iNOS, and TNF-α but an increase in the IκBα of CD40⁺ B lymphocytes. Moreover, EAE mice treated with DAPTA displayed decreased NF-κB p65, Notch-1, Notch-3, GM-CSF, MCP-1, iNOS, and TNF-α and but showed increased IκBα mRNA expression levels. This study showed that DAPTA has significant neuroprotective potential in EAE via the downregulation of inflammatory mediators and NF-κB/Notch signaling. Collectively, DAPTA might have potential therapeutic targets for use in MS treatment.

Herpes Simplex Virus Type 1 Infection of the Central Nervous System: Insights Into Proposed Interrelationships With Neurodegenerative Disorders

Herpes simplex virus type 1 (HSV-1) is highly prevalent in humans and can reach the brain without evident clinical symptoms. Once in the central nervous system (CNS), the virus can either reside in a quiescent latent state in this tissue, or eventually actively lead to severe acute necrotizing encephalitis, which is characterized by exacerbated neuroinflammation and prolonged neuroimmune activation producing a life-threatening disease. Although HSV-1 encephalitis can be treated with antivirals that limit virus replication, neurological sequelae are common and the virus will nevertheless remain for life in the neural tissue. Importantly, there is accumulating evidence that suggests that HSV-1 infection of the brain both, in symptomatic and asymptomatic individuals could lead to neuronal damage and eventually, neurodegenerative disorders. Here, we review and discuss acute and chronic infection of particular brain regions by HSV-1 and how this may affect neuron and cognitive functions in the host. We review potential cellular and molecular mechanisms leading to neurodegeneration, such as protein aggregation, dysregulation of autophagy, oxidative cell damage and apoptosis, among others. Furthermore, we discuss the impact of HSV-1 infection on brain inflammation and its potential relationship with neurodegenerative diseases.

Extracellular adenosine signaling induces CX3CL1 expression in the brain to promote experimental autoimmune encephalomyelitis

Background

Multiple sclerosis and its animal model experimental autoimmune encephalomyelitis (EAE) are debilitating neuroinflammatory diseases mediated by lymphocyte entry into the central nervous system (CNS). While it is not known what triggers lymphocyte entry into the CNS during neuroinflammation, blockade of lymphocyte migration has been shown to be effective in controlling neuroinflammatory diseases. Since we have previously shown that extracellular adenosine is a key mediator of lymphocyte migration into the CNS during EAE progression, we wanted to determine which factors are regulated by adenosine to modulate EAE development.

Methods

We performed a genetic analysis of wild type and CD73−/− (that are unable to produce extracellular adenosine and are protected from EAE development) to identify factors that are both important for EAE development and controlled by extracellular adenosine signaling.

Results

We show that extracellular adenosine triggered lymphocyte migration into the CNS by inducing the expression of the specialized chemokine/adhesion molecule CX3CL1 at the choroid plexus. In wild type mice, CX3CL1 is upregulated in the brain on Day 10 post EAE induction, which corresponds with initial CNS lymphocyte infiltration and the acute stage of EAE. Conversely, mice that cannot synthesize extracellular adenosine (CD73−/− mice) do not upregulate CX3CL1 in the brain following EAE induction and are protected from EAE development and its associated lymphocyte infiltration. Additionally, blockade of the A2A adenosine receptor following EAE induction prevents disease development and the induction of brain CX3CL1 expression. The CX3CL1 induced during EAE is found on the choroid plexus, which is the barrier between the blood and cerebral spinal fluid in the brain and is a prime entry point into the CNS for immune cells. Furthermore, CX3CL1 expression can be induced in the brains of mice and in choroid plexus cell line following A2A adenosine receptor agonist administration. Most importantly, we show that CX3CL1 blockade protects against EAE development and inhibits lymphocyte entry into the CNS.

Conclusions

We conclude that extracellular adenosine is an endogenous modulator of neuroinflammation during EAE that induces CX3CL1 at the choroid plexus to trigger lymphocyte entry into the brain.

Evaluation of serum levels of chemokines during interferon-β treatment in multiple sclerosis patients: a 1-year, observational cohort study

BACKGROUND

The molecules that provide access to activated T cells in the CNS, including chemokines, have been considered to be a crucial step in the pathogenesis of multiple sclerosis (MS).

AIMS

In this study, we investigated serial serum chemokine levels in patients with relapsing-remitting MS over 1 year and the association of these chemokine levels with treatment regimens, lesions on MRI and patients' characteristics.

METHODS

Serum CXCL9, CXCL10, CCL2, CCL4 and CCL5 levels were evaluated using ELISA every 2 months for a year in 28 healthy controls and 28 MS patients during their treatment with interferon (IFN)-β. Patients underwent MRI and were evaluated using the Expanded Disability Status Scale (EDSS) at the first and final evaluations.

RESULTS

CXCL10 serum levels were higher in MS patients compared with controls, were positively correlated with T2 lesions on MRI and were slightly increased during relapses. Treatment with IFNβ-1a or IFNβ-1b was associated with increased CXCL10 levels when evaluated more than 36 hours after subcutaneous injection. The CXCL9 levels were higher after MS relapse. There was significant variability in CCL4 and CCL5 levels in the serial evaluations, associated with gender and treatment. CCL2 levels were higher in treated MS patients than healthy controls, particularly among those patients with a stable form of the disease.

CONCLUSION

Serum is a feasible resource for searching for an immunological marker in MS. Peripheral chemokine levels correlated in different ways with IFNβ therapy and with disease and patient characteristics.

CLINICAL TRIAL REGISTRATION NUMBER

ISRCTN45526724.

PPAR Regulation of Inflammatory Signaling in CNS Diseases

Central nervous system (CNS) is an immune privileged site, nevertheless inflammation associates with many CNS diseases. Peroxisome proliferator-activated receptors (PPARs) are a family of nuclear hormone receptors that regulate immune and inflammatory responses. Specific ligands for PPARα, γ, and δ isoforms have proven effective in the animal models of multiple sclerosis (MS), Alzheimer's disease, Parkinson's disease, and trauma/stroke, suggesting their use in the treatment of neuroinflammatory diseases. The activation of NF-κB and Jak-Stat signaling pathways and secretion of inflammatory cytokines are critical in the pathogenesis of CNS diseases. Interestingly, PPAR agonists mitigate CNS disease by modulating inflammatory signaling network in immune cells. In this manuscript, we review the current knowledge on how PPARs regulate neuroinflammatory signaling networks in CNS diseases.

Novel approaches to detect serum biomarkers for clinical response to interferon-beta treatment in multiple sclerosis

Interferon beta (IFNβ) is the most common immunomodulatory treatment for relapsing-remitting multiple sclerosis (RRMS). However, some patients fail to respond to treatment. In this study, we identified putative clinical response markers in the serum and plasma of people with multiple sclerosis (MS) treated with IFNβ. In a discovery-driven approach, we use 2D-difference gel electrophoresis (DIGE) to identify putative clinical response markers and apply power calculations to identify the sample size required to further validate those markers. In the process we have optimized a DIGE protocol for plasma to obtain cost effective and high resolution gels for effective spot comparison. APOA1, A2M, and FIBB were identified as putative clinical response markers. Power calculations showed that the current DIGE experiment requires a minimum of 10 samples from each group to be confident of 1.5 fold difference at the p<0.05 significance level. In a complementary targeted approach, Cytometric Beadarray (CBA) analysis showed no significant difference in the serum concentration of IL-6, IL-8, MIG, Eotaxin, IP-10, MCP-1, and MIP-1α, between clinical responders and non-responders, despite the association of these proteins with IFNβ treatment in MS.

The chemokine receptor antagonist, TAK-779, decreased experimental autoimmune encephalomyelitis by reducing inflammatory cell migration into the central nervous system, without affecting T cell function

BACKGROUND AND PURPOSE

The C-C chemokine receptor CCR5, and the C-X-C chemokine receptor CXCR3 are involved in the regulation of T cell-mediated immune responses, and in the migration and activation of these cells. To determine whether blockade of these chemokine receptors modulated inflammatory responses in the central nervous sytem (CNS), we investigated the effect of a non-peptide chemokine receptor antagonist, TAK-779, in mice with experimental autoimmune encephalomyelitis (EAE).

EXPERIMENTAL APPROACH

EAE was induced by immunization of C57BL/6 mice with myelin oligodendrocyte glycoprotein (MOG) 35-55. TAK-779 was injected s.c. once a day after immunization. Disease incidence and severity (over 3 weeks) were monitored by histopathological evaluation and FACS assay of inflammatory cells infiltrating into the spinal cord, polymerase chain reaction quantification of mRNA expression, assay of T cell proliferation, by [3H]-thymidine incorporation and cytokine production by enzyme-linked immunosorbent assay.

KEY RESULTS

Treatment with TAK-779 reduced incidence and severity of EAE. It strongly inhibited migration of CXCR3/CCR5 bearing CD4+, CD8+ and CD11b+ leukocytes to the CNS. TAK-779 did not reduce proliferation of anti-MOG T cells, the production of IFN-gamma by T cells or CXCR3 expression on T cells. In addition, TAK-779 did not affect production of IL-12 by antigen-presenting cells, CCR5 induction on T cells and the potential of MOG-specific T cells to transfer EAE.

CONCLUSIONS AND IMPLICATIONS

TAK-779 restricted the development of MOG-induced EAE. This effect involved reduced migration of inflammatory cells into the CNS without affecting responses of anti-MOG T cells or the ability of MOG-specific T cells to transfer EAE.

Administration of a monomeric CCL2 variant to EAE mice inhibits inflammatory cell recruitment and protects from demyelination and axonal loss

Based on gene expression data, we tested the P8A-CCL2 variant of the chemokine CCL2, able to interfere with the chemotactic properties of the parental molecule, in relapsing-remitting (RR)-EAE SJL. Only preventive treatment significantly delayed disease onset in a dose dependent manner. P8A-CCL2 administration, however, decreased demyelination, axonal loss and number of CNS infiltrating T cells and macrophages. Immunological analysis revealed that P8A-CCL2 does not act on Ag-specific T cell proliferation and does not interfere with the differentiation of IFNgamma-releasing effectors T cells. These results suggest that the therapeutic mechanism of P8A-CCL2 may rely on interference with immune cell recruitment.

Cloning and characterization of the murine claudin-5 promoter

Claudin-5, an integral tight junction protein component, plays a critical role in permeability of the endothelial cell barrier. Recently, we have shown that claudin-5 protein is down-regulated by the proinflammatory cytokine TNF alpha and its levels restored by dexamethasone treatment. In order to investigate the regulation of claudin-5 at the transcriptional level, we have cloned the murine claudin-5 promoter. The claudin-5 promoter sequence (1131 bp) showed no consensus TATA-box. We identified putative transcription factor binding sites, including six full and two half sites degenerated glucocorticoid-response elements (GREs), two NFkappaB, three Sp1, one Sp2, one Ap2, as well as three E-boxes. Serially deleted promoter constructs showed high basal activity. TNF alpha significantly reduced the promoter activity and mRNA levels of claudin-5 in brain cEND and myocardial MyEND endothelial cells. Dexamethasone treatment led to a significant increase of the murine claudin-5 promoter activity and mRNA levels in cEND cells. However, no claudin-5 induction could be observed in MyEND cells in response to dexamethasone. Our studies suggest tissue-specific regulation of the claudin-5 gene via glucocorticoids and a high vulnerability of claudin-5 to TNF alpha. This could be an important mechanism in diseases accompanied by the release of proinflammatory cytokines, for example in patients with chronic heart failure or multiple sclerosis.

Genistein down-modulates pro-inflammatory cytokines and reverses clinical signs of experimental autoimmune encephalomyelitis

Multiple sclerosis (MS) is the most common non-traumatic, disabling neurological human inflammatory demyelinating disease of the central nervous system (CNS). Experimental autoimmune encephalomyelitis (EAE) models MS and is characterized as a CD4+ T-helper type 1 (Th1) cell-mediated autoimmune disease. It is characterized by an influx of activated leukocytes into the CNS. Genistein, occurring abundantly in soy products, has apoptotic, antioxidant, and anti-inflammatory properties. In the present report, we investigated the use of genistein for the treatment of the murine model of MS. After induction of EAE with myelin oligodendrocyte glycoprotein 35-55 peptide (MOG(35-55)), we observed that genistein treatment ameliorated significantly the clinical symptoms, modulating pro- and anti-inflammatory cytokines. Moreover, we analyzed the leukocyte rolling and adherence in the CNS by performing intravital microscopy. Genistein treatment resulted in decreased rolling and adhering of leukocytes as compared to the untreated group. Our data suggest that genistein might be a potential therapy for MS.

Angiocidin promotes pro-inflammatory cytokine production and antigen presentation in multiple sclerosis

Angiocidin was originally identified as a potent inhibitor of angiogenesis and tumor growth in vivo. In addition to its involvement in the regulation of carcinogenesis, recent studies indicate that angiocidin may also play a significant role in immune system modulation. This report describes the expression and potential function of angiocidin in multiple sclerosis (MS), a severe demyelinating, inflammatory and autoimmune disease of the central nervous system (CNS). We demonstrated that angiocidin and interleukin-7 (IL-7) are over-expressed in brain lesions of MS patients. Angiocidin-treated monocytes, peripheral blood T cells and primary astrocytes secreted various cytokines and chemokines including, IL-6, IL-7, GM-CSF, and MCP-1. Addition of recombinant angiocidin to cell cultures was able to promote differentiation of monocytes into a macrophage-like cell, induce MHC class I and class II gene expression and activate CD4(+) and CD8(+) T lymphocytes. Consistent with these findings, angiocidin induced mononuclear phagocyte migration and adhesion as well as increased the IL-2 response by antigen-specific T cells to myelin basic protein peptide presented to them by autologous mononuclear phagocytes. Furthermore, we examined STAT3 expression in angiocidin stimulated mononuclear phagocytes, T cells, and primary astrocytes. We found that angiocidin markedly stimulates STAT3 expression in these cell populations. Angiocidin, therefore appears to play a previously unappreciated and potentially important role in the regulation of immune response during the clinical course of MS.

Human mesenchymal stem cells constitutively express chemokines and chemokine receptors that can be upregulated by cytokines, IFN-beta, and Copaxone

The factors associated with the migration of marrow-derived mesenchymal stem cells (MSCs) when transplanted into the diseased central nervous system (CNS) are unclear. Chemokines are key mediators of selective cell migration in neurodegenerative diseases and related inflammatory processes. We hypothesized that chemokines are likely to be the chief determinants of MSC migration. We, therefore, systematically assessed the expression and modulating factors for chemokines and chemokine receptors in human MSCs (HuMSCs). The present study demonstrates that unstimulated HuMSCs express a broad range of mRNAs encoding cytokines, chemokines, and their receptors. Using chemotaxis assays, we also assessed the functionality of the receptor expression in HuMSC and we show that CXCL12/stromal cell-derived factor-lalpha (SDF-lalpha), CX3CL1/fractalkine, and CXCL10/interferon-gamma (IFN-gamma)-inducible protein (IP-10) lead to significant HuMSC migration. Moreover, we provide evidence that tumor necrosis factor-alpha (TNF-alpha) and IFN-gamma act as major regulators of the expression of chemokines and their receptors in HuMSCs. Correspondingly, we demonstrate for the first time that current multiple sclerosis (MS) therapies, namely, IFN-beta and Copaxone, influence the expression of chemokines and their receptors in HuMSCs at both mRNA and protein levels. Administration of cytokines, including IFN-beta and Copaxone, may be important in stem cell transplantation therapies and perhaps important in the efficacy of existing MS therapies.

Chemokines, mononuclear cells and the nervous system: heaven (or hell) is in the details

Chemokines and their receptors are essential elements in leukocyte trafficking during health and disease. There are three (or more) distinct routes of leukocyte entry into the central nervous system (CNS), and molecular mechanisms of physiological and neuroinflammatory leukocyte recruitment to the CNS are slowly coming into view. Migration of immune cells into cerebrospinal fluid supports CNS immunosurveillance. Current knowledge of the trafficking determinants that direct the leukocyte recruitment in CNS pathology relies in large part on studies of multiple sclerosis and its models including experimental autoimmune encephalomyelitis. Overlapping molecular signals are responsible for the migration of specific cells into the CNS during pathological inflammation and host defense, raising challenges and opportunities for therapeutic manipulation.

Experimental autoimmune encephalomyelitis develops in CC chemokine receptor 7-deficient mice with altered T-cell responses

CC chemokine receptor 7 (CCR7) is involved in the initiation of immune responses by mediating the migration of naïve T cells and mature dendritic cells to T-cell-rich zones of secondary lymphoid organs where antigen presentation occurs. To address whether CCR7 plays a role in the development of autoimmunity, we induced experimental autoimmune encephalomyelitis in CCR7-deficient mice on a C57BL/6 background (CCR7(-/-)) using the neuroantigen, myelin oligodendrocyte glycoprotein 35-55 amino acid peptide (MOG((35-55))) and Bordetella pertussis toxin (PTX). CCR7(-/-) mice acquired disease with an intensity similar to wild-type littermates. MOG((35-55))-specific lymphocyte responses were dominant in the spleen of CCR7(-/-) mice, rather than in lymph nodes as observed in wild-type mice. These results indicate that effective immune responses (with altered kinetics) can develop in the absence of CCR7 but develop in the spleen rather than lymph nodes as CCR7 is necessary for T and dendritic cells to enter lymph nodes.

Novel immunosuppressive therapy by M2000 in experimental multiple sclerosis

The therapeutic potency of M2000 (beta-D-mannuronic acid), a novel designed nonsteroidal anti-inflammatory drug with immunosuppressive property in T-cell-mediated autoimmune disease, was tested. The influence of M2000 on myelin basic protein (MBP)-induced experimental autoimmune encephalomyelitis (EAE), an animal model of multiple sclerosis, was assessed. M2000 at two doses, 40 and 80 mg/kg/day, was administered intraperitoneally (i.p.) to prevention and treatment groups, respectively. Onset of i.p. injections of M2000 to prophylactic and therapeutic groups was day-1 and day-7 postimmunization. The WEHI-164 cell line was used for assaying the tolerability against M2000. The results of this experiment showed that the treatment of EAE with M2000 could significantly suppress disease development both prophylactically and therapeutically; the onset and symptoms of EAE in Lewis rats could be suppressed following the administration of M2000. Clinical improvement was accompanied by a marked decrease in mean numbers of vessels with perivascular cellular infiltration in M2000-treated rats compared with nontreated control. Disease suppression was associated with a marked suppression of MBP-specific T-cell reactivity in vitro, without any evidence for a generalized impairment of T-cell activity. Moreover, M2000 also showed a very high tolerability compared with certain steroidal and nonsteroidal anti-inflammatory drugs. Collectively, our data suggest that M2000 may provide a novel therapeutic option for T-cell-mediated autoimmune diseases in animal models and possibly in humans.

Differential susceptibility of cerebral and cerebellar murine brain microvascular endothelial cells to loss of barrier properties in response to inflammatory stimuli

Multiple sclerosis (MS) is a chronic autoimmune disease whose symptoms are caused by an inflammatory invasion of the central nervous system (CNS). The molecular pathogenesis of MS includes an increased permeability of the blood brain barrier (BBB) along with an inability of the BBB to fulfill its normal function of protecting the CNS. The cerebellar BBB seems to be especially vulnerable, as the development of experimental autoimmune encephalomyelitis (EAE) as an animal model of MS often takes its beginning in the cerebellum. Inflammatory lesion development seems to correlate with increased permeability of the local BBB. Responsible for the BBB are cerebral and cerebellar capillary endothelial cells. We therefore generated an in vitro model of the cerebellar BBB (cerebEND) and compared its response to inflammatory stimuli (TNFalpha administration) with a cerebral BBB in vitro model (cEND) characterised previously [Förster, C., Silwedel, C., Golenhofen, N., Burek, M., Kietz, S., Mankertz, J., Drenckhahn, D., 2005. Occludin as direct target for glucocorticoid-induced improvement of blood brain-barrier properties in a murine in vitro system. J. Physiol. 565(Pt 2), 475-486]. We could demonstrate a faster and more pronounced increase in permeability in the cerebellar BBB manifested by reduced transendothelial electrical resistance and reduced tight junction protein expression. This cell line cerebEND could thus be valuable to identify genes differently expressed within the BBB in the future and therefore be helpful in finding new ways of treatment of MS.

Functional diversity of chemokines and chemokine receptors in response to viral infection of the central nervous system

Encounters with neurotropic viruses result in varied outcomes ranging from encephalitis, paralytic poliomyelitis or other serious consequences to relatively benign infection. One of the principal factors that control the outcome of infection is the localized tissue response and subsequent immune response directed against the invading toxic agent. It is the role of the immune system to contain and control the spread of virus infection in the central nervous system (CNS), and paradoxically, this response may also be pathologic. Chemokines are potent proinflammatory molecules whose expression within virally infected tissues is often associated with protection and/or pathology which correlates with migration and accumulation of immune cells. Indeed, studies with a neurotropic murine coronavirus, mouse hepatitis virus (MHV), have provided important insight into the functional roles of chemokines and chemokine receptors in participating in various aspects of host defense as well as disease development within the CNS. This chapter will highlight recent discoveries that have provided insight into the diverse biologic roles of chemokines and their receptors in coordinating immune responses following viral infection of the CNS.

The expression and function of chemokines involved in CNS inflammation

Chemokines and their receptors have principal roles in leukocyte trafficking under normal physiological and pathological conditions. The differential expression of the chemokine system in different parts of the CNS provides insights into the processes that are required for normal immune surveillance and pathological immune-mediated effector processes. Insights derived from studying multiple sclerosis, an inflammatory disorder of the CNS in humans, and experimental autoimmune encephalomyelitis, an animal model of this disorder, aid in further understanding the complexities of chemokine-mediated inflammation. Knowledge of the molecular biology of chemokines and their receptors, and the roles of specific chemokine ligands and receptors in the CNS in health and in disease have made these proteins targets for therapeutic intervention in neuroinflammation. We also discuss currently proposed and potentially useful chemokine receptor antagonists.

Constitutive expression of CCR2 chemokine receptor and inhibition by MCP-1/CCL2 of GABA-induced currents in spinal cord neurones

In the CNS, immune-like competent cells (microglia and astrocytes) were first described as potential sites of chemokine synthesis, but more recent evidence has indicated that neurones might also express chemokines and their receptors. The aim of the present work was to investigate further, both in vivo and in vitro, CC Chemokine Family Receptor 2 (CCR2) expression and functionality in rat spinal cord neurones. First, we demonstrated by RT-PCR and western blot analysis that CCR2 mRNA and protein were present in spinal extracts. Furthermore, we showed by immunolabelling that CCR2 was exclusively expressed by neurones in spinal sections of healthy rat. Finally, to test the functionality of CCR2, we used primary cultures of rat spinal neurones. In this model, similar to what was observed in vivo, CCR2 mRNA and protein were expressed by neurones. Cultured neurones stimulated with Monocyte Chemoattractant Protein-1 (MCP-1)/CCL2, the best characterized CCR2 agonist, showed activation of the Akt pathway. Finally, patch-clamp recording of cultured spinal neurones was used to investigate whether MCP-1/CCL2 could modulate their electrophysiological properties. MCP-1 alone did not affect the electrical properties of spinal neurones, but potently and efficiently inhibited GABA(A)-mediated GABAergic responses in these neurones. These data constitute the first demonstration of a modulatory role of MCP-1 on GABAergic neurotransmission and contribute to our understanding of the roles of CCR2 and MCP-1/CCL2 in spinal cord physiology, in particular with respect to nociceptive transmission, as well as the implication of this chemokine in neuronal adaptation or dysfunction during neuropathy.