Induction of glial L-CCR mRNA expression in spinal cord and brain in experimental autoimmune encephalomyelitis

Chemokines and chemokine receptors are important regulators of leukocyte trafficking and immune response. It is well established that chemokines and their receptors are also expressed in the central nervous system (CNS), where their expression has been associated with various neuroinflammatory diseases, such as multiple sclerosis (MS). One of the most important chemokines involved in MS pathology is CCL2 (previously known as MCP-1). CCL2, released by glial cells, activates the chemokine receptor CCR2, causing the infiltration of blood monocytes in tissues affected by MS. There is evidence, however, that CCL2 also has local effects on CNS cells, including induction or modulation of cytokine release and synthesis of matrix metalloproteinases, that might contribute to CNS pathology. These effects are most likely independent of CCR2, since CCR2 expression in glial cells is rarely observed. We have recently provided evidence for the presence of an alternative CCL2 receptor in glial cells called L-CCR and have investigated the expression of L-CCR mRNA in a murine EAE model. It is shown that L-CCR mRNA is expressed in infiltrating macrophages during EAE, but not in infiltrating T cells. Prominent expression of L-CCR mRNA was detected in astrocytes and microglia already at early time points throughout the brain and spinal cord supporting the hypothesis that L-CCR expression in glial cells is related to CNS inflammation.     

Lipocalin 2 is a novel immune mediator of experimental autoimmune encephalomyelitis pathogenesis and is modulated in multiple sclerosis

Experimental autoimmune encephalomyelitis (EAE) is a widely used animal model of multiple sclerosis (MS), an inflammatory, demyelinating disease of the central nervous system (CNS). EAE pathogenesis involves various cell types, cytokines, chemokines, and adhesion molecules. Given the complexity of the inflammatory response in EAE, it is likely that many immune mediators still remain to be discovered. To identify novel immune mediators of EAE pathogenesis, we performed an Affymetrix gene array screen on the spinal cords of mice at the onset stage of disease. This screening identified the gene encoding lipocalin 2 (Lcn2) as being significantly upregulated. Lcn2 is a multi-functional protein that plays a role in glial activation, matrix metalloproteinase (MMP) stabilization, and cellular iron flux. As many of these processes have been implicated in EAE, we characterized the expression and role of Lcn2 in this disease in C57BL/6 mice. We show that Lcn2 is significantly upregulated in the spinal cord throughout EAE and is expressed predominantly by monocytes and reactive astrocytes. The Lcn2 receptor, 24p3R, is also expressed on monocytes, macrophages/microglia, and astrocytes in EAE. In addition, we show that EAE severity is increased in Lcn2(-/-) mice as compared with wild-type controls. Finally, we demonstrate that elevated levels of Lcn2 are detected in the plasma and cerebrospinal fluid (CSF) in MS and in immune cells in CNS lesions in MS tissue sections. These data indicate that Lcn2 is a modulator of EAE pathogenesis and suggest that it may also play a role in MS.     

Selective suppression of chemokine receptor CXCR3 expression by interferon-beta1a in multiple sclerosis

We studied the expression of chemokine receptors CCR1, CCR2, CCR3, CCR5, and CXCR3 on CD4 and CD8 positive T cells, and on CD14 positive monocytes in blood from 10 patients with relapsing-remitting multiple sclerosis (MS) at initiation of interferon (IFN)-beta treatment, after 1 month and after 3 months of treatment. It was found that the expression of CXCR3 on CD4+ and CD8+ T cells was significantly reduced after 3 months of treatment. The expression of other receptors was unaltered. Since CXCR3 cells are enriched in cerebrospinal fluid (CSF), and are detected in lesion material in MS this may represent an important mode of action of interferon-beta in MS.     

Characterization of CD8-positive macrophages infiltrating the central nervous system of rats with chronic autoimmune encephalomyelitis

CD8+ macrophages appear in the central nervous system (CNS) under various pathological conditions such as trauma and ischemia. Furthermore, macrophages expressing CD8 were found in CNS lesions of chronic, but not acute, experimental autoimmune encephalomyelitis (EAE). To further characterize cells with this phenotype, we examined CD8+ macrophages/monocytes in the CNS and peripheral organs during the course of acute and chronic EAE that had been induced by immunization of rats with myelin basic protein and myelin oligodendrocyte glycoprotein, respectively. Counting CD8+ macrophages in CNS lesions revealed that their numbers increased reaching about 60% of total infiltrating macrophages in chronic EAE, while CD8+ macrophages remained less than 5% throughout the course of acute EAE. Unexpectedly, however, higher abundance of CD8+ monocytes/macrophages in the peripheral blood was found in both acute and chronic EAE. Real-time polymerase chain reaction analysis revealed no significant difference in the levels of chemokines and chemokine receptors of blood CD8+ monocytes between acute and chronic EAE. mRNA expression of perforin, a cytotoxic substance, was up-regulated in CD8+ monocytes compared with that of CD8- monocytes in both acute and chronic EAE. These findings suggest that activated CD8+ macrophages may play a cytotoxic role in chronic EAE lesions and that cells other than CD8+ monocytes/macrophages determined the difference in CNS pathology between acute and chronic EAE. Analysis of CD8+ monocytes/macrophages may provide useful information to permit further dissect the pathomechanisms of multiple sclerosis and to develop effective immunotherapies against autoimmune diseases in the CNS.     

Enhanced expression of the CXCl12/SDF-1 chemokine receptor CXCR7 after cerebral ischemia in the rat brain

Expression patterns of the second SDF-1 receptor RDC1/CXCR7 were examined after focal ischemia in rats using in situ hybridization. CXCR7 mRNA was identified in the ventricle walls as well as neuronal, astroglial, and vascular cells. After ischemia, intact cortical regions showed a rapid, 4 days-lasting increase in neuronal CXCR7 expression. In the ischemic tissue CXCR7 expression was scarce and associated with blood vessels. Between days 2 and 10 after ischemia-onset, SDF-1 expression increased strongly in the peri-infarct and infarct region, which was accompanied by the appearance of numerous CXCR4-expressing but not CXCR7-expressing cells. These patterns suggest that SDF-1 may influence vascular, astroglial, and neuronal functions via CXCR7 and mediate cell recruitment to ischemic brain areas via CXCR4.     

Low dose dextromethorphan attenuates moderate experimental autoimmune encephalomyelitis by inhibiting NOX2 and reducing peripheral immune cells infiltration in the spinal cord

Dextromethorphan (DM) is a dextrorotary morphinan and a widely used component of cough medicine. Relatively high doses of DM in combination with quinidine are used for the treatment of mood disorders for patients with multiple sclerosis (MS). However, at lower doses, morphinans exert anti-inflammatory activities through the inhibition of NOX2-dependent superoxide production in activated microglia. Here we investigated the effects of high (10 mg/kg, i.p., "DM-10") and low (0.1 mg/kg, i.p., "DM-0.1") doses of DM on the development and progression of mouse experimental autoimmune encephalomyelitis (EAE), an animal model of MS. We found no protection by high dose DM treatment. Interestingly, a minor late attenuation by low dose DM treatment was seen in severe EAE that was characterized by a chronic disease course and a massive spinal cord infiltration of CD45(+) cells including T-lymphocytes, macrophages and neutrophils. Furthermore, in a less severe form of EAE, where lower levels of CD4(+) and CD8(+) T-cells, Iba1(+) microglia/macrophages and no significant infiltration of neutrophils were seen in the spinal cord, the treatment with DM-0.1 was remarkably more beneficial. The effect was the most significant at the peak of disease and was associated with an inhibition of NOX2 expression and a decrease in infiltration of monocytes and lymphocytes into the spinal cord. In addition, chronic treatment with low dose DM resulted in decreased demyelination and reduced axonal loss in the lumbar spinal cord. Our study is the first report to show that low dose DM is effective in treating EAE of moderate severity. Our findings reveal that low dose morphinan DM treatment may represent a new promising protective strategy for treating MS.     

Longitudinal study of chemokine receptor expression on peripheral lymphocytes in multiple sclerosis: CXCR3 upregulation is associated with relapse

The interaction between chemokines and their receptors leads to selective recruitment of cells to foci of inflammation. Cross-sectional studies have reported significantly different expression of chemokine receptors CXCR3, CCR5 and CCR2 on peripheral blood lymphocytes in multiple sclerosis (MS) compared with controls. Cells expressing these receptors are likely to play a pathogenic role as suggested by studies of experimental autoimmune encephalomyelitis. Also, immunogenetic studies of nonfunctional CCR5 receptors in MS patients, due to 32delta deletion, demonstrated a delay in time to next relapse. The aims of this study were to detect any changes in the serial expression of chemokine receptors CCR2, CCR3, CCR5 and CXCR3 on peripheral blood CD4+ lymphocytes from patients with MS and to correlate the changes with relapses. Upregulation of CXCR3 expression on peripheral blood CD4+ lymphocytes was associated with all relapses and CCR5 expression was significantly affected with all relapses. Clinical recovery, with or without intravenous methylprednisolone treatment, coincided with the return of CXCR3 towards baseline in all but one case. Fluctuation in the expression of CXCR3 and CCR5 was also significantly greater in clinically stable patients with MS compared with controls, which may be due to subclinical disease activity. These findings provide further support for the view that CXCR3 and CCR5 antagonists could have a therapeutic value in MS.     

Multiple sclerosis: a study of chemokine receptors and regulatory T cells in relation to MRI variables

Magnetic resonance imaging (MRI) remains the most valuable tool for monitoring disease activity and progression in patients with multiple sclerosis (MS), a chronic demyelinating disease of the central nervous system (CNS) with presumably autoimmune etiology. Chemokine receptors have been implicated in MS as key molecules directing inflammatory cells into the CNS. Regulatory (CD4+CD25+) T cells (Tr cells) are important in suppressing autoimmunity, and their absolute or functional deficit could be expected in MS. In the present study, venous blood was obtained from MS patients concurrent with MRI examination of the brain, and expression of chemokine receptors CCR1, CCR2, CCR5, CXCR3 and CXCR4 by CD4 T cells and monocytes, proportions of Tr cells, as well as expression of CD45RO, CD95, CTLA-4, HLA-DR and interleukin (IL)-10 by Tr cells and non-Tr (CD25-) CD4 T cells was analyzed by flow cytometry. Surface expression of CXCR3 by CD4 T cells was downregulated in the group of patients with high lesion load (LL) on T2-weighted images and gadolinium (Gd)-enhancing lesions on T1-weighted images, compared to the group with high LL and no Gd-enhancing lesions, and to the group with low LL, suggesting internalization of CXCR3 due to the release of its chemokine ligand (IP-10/CXCL10) from active MS lesions. Proportions of Tr cells amongst all CD4 T cells, and expression of IL-10 by Tr cells were increased in the patients with high LL and Gd-enhancing lesions. These results suggest that there is correlation between MRI parameters, chemokine receptor expression and the status of circulating Tr cells in MS, but further studies need to discriminate between pathogenetically relevant and bystander phenomena.     

Regional and temporal expression patterns of interleukin-10, interleukin-10 receptor and adhesion molecules in the rat spinal cord during chronic relapsing EAE

Adhesion molecules intercellular adhesion molecule-1 (ICAM-1) and vascular cell adhesion molecule-1 (VCAM-1) mediate leukocyte infiltration into the CNS, in experimental autoimmune encephalomyelitis (EAE) and multiple sclerosis (MS). Because exogenous interleukin-10 (IL-10) inhibits ICAM-1 and VCAM-1 expression and clinical EAE, we hypothesize that endogenous IL-10 signaling may suppress expression of adhesion molecules. In a rat model of chronic relapsing EAE, expression levels of IL-10 and its receptor (IL-10R1), ICAM-1 and VCAM-1 mRNA in the spinal cord are markedly increased, whereas levels of IL-10 mRNA remain relatively low. The temporal pattern of mRNA and protein expression showed marked differences between spinal cord levels. During relapse, IL-10, IL-10R1, ICAM-1, VCAM-1 mRNA levels and neurological scores show positive correlations. We conclude that endogenous IL-10 is not a crucial factor inhibiting adhesion molecule expression in this model.     

Chemokine receptor expression on B cells and effect of interferon-beta in multiple sclerosis.

We investigated the B-cell expression of chemokine receptors CXCR3, CXCR5 and CCR5 in the blood and cerebrospinal fluid (CSF) from patients in relapse of multiple sclerosis (MS) and in neurological controls. Chemokine receptor expression was also studied in interferon-beta-treated patients with relapsing-remitting or secondary progressive MS. We observed significantly higher expression of CXCR3 on B cells in the CSF in active MS than in controls. Patients with active MS also had higher B-cell expression of CCR5 in blood. No major differences between RRMS and SPMS patients were detected, and chemokine receptor expression was not affected by interferon-beta treatment.     

Lesional accumulation of RhoA(+) cells in brains of experimental autoimmune encephalomyelitis and multiple sclerosis

Aim: Infiltration of autoantigen-specific T cells and monocytes into the central nervous system is essential for the development of both experimental autoimmune encephalomyelitis (EAE) and multiple sclerosis (MS). RhoA is one of the best-known members of Rho GTPases, and inhibition of RhoA has been shown to attenuate the progression of EAE. The aim of this study was to investigate the expression of RhoA in brains of EAE rats and MS tissue. Methods: EAE was induced by immunization with the synthetic peptide gpMBP68-84 in rats, and clinical severity was scored. RhoA expression pattern was investigated in brains of EAE rats at different time points and in different lesions of brain tissue specimens from six MS brains and five neuropathologically unaffected controls by immunohistochemistry. Methods: In EAE rat brains, accumulation of RhoA⁺ cells reached maximal levels around Day 13, correlating to the clinical severity of EAE, and up-regulation lasted until the recovery stage of the disease. Double-labelling experiments showed that the major cellular sources of RhoA were reactive macrophages/microglia. While RhoA⁺ cells in normal human brain parenchyma were rarely observed, RhoA expression was found to be spatially associated with MS lesions, showing a marked decrease from active lesions via chronic stages to its near absence in normal-appearing white matter. In addition, major RhoA⁺ cells in brain parenchyma of MS were identified to be activated macrophages/microglia. Conclusion: Our present data indicated that RhoA may play an important role during the effector phase of EAE and MS. Therefore, RhoA inhibitors might be a therapeutic option for MS patients.     

Expression of TH1/TH2-related chemokine receptors on peripheral T cells and correlation with clinical disease activity in patients with multiple sclerosis

Th1 cells play an important role in the pathogenesis of multiple sclerosis (MS), a disease likely linked to an autoimmune process. We measured the levels of chemokines in serum or cerebrospinal fluid (CSF) samples by ELISA, and also studied the expression of Th1-related CXCR3/CCR5 chemokine receptors and Th2-related CCR4/CCR3 chemokine receptors on blood cells from MS patients using three-color flow cytometry. The Bonferroni correction was used for the statistical analysis. The levels of CXCL10, CCL3, and CCL5 in the CSF samples for the MS groups were significantly higher than those for the control group. However, the levels of CCL2 in both the CSF and serum samples for the remission group were significantly higher than those for the active group. The percentage of CXCR3-expressing CD4+ T cells in patients with MS was significantly elevated compared with the healthy controls. Moreover, MS patients in an active phase showed a more increased CD4+CXCR3+/CD4+CCR4+ ratio than patients in a remission phase. The increased percentage of CD4+CXCR3+ cells in the blood was associated with relapses in MS. This study suggested that the CD4+CXCR3+/CD4+CCR4+ ratio could be a sensitive maker of immune dysfunction in MS.     

Bone morphogenetic proteins 4, 6, and 7 are up-regulated in mouse spinal cord during experimental autoimmune encephalomyelitis

Although spontaneous remyelination occurs in multiple sclerosis (MS), the extent of myelin repair is often inadequate to restore normal function. Oligodendrocyte precursors remaining in nonremyelinating MS plaques may be restricted by an inhibitory signal. Bone morphogenetic proteins (BMPs) have been implicated as repressors of oligodendrocyte development and inducers of astrogliogenesis. We hypothesized that BMPs are up-regulated in MS lesions and play a role in demyelination and astrogliosis. We examined expression of BMPs in an animal model of MS, chronic experimental autoimmune encephalomyelitis (EAE) induced by the myelin oligodendrocyte glycoprotein (MOG) peptide in C57BL/6 mice. By 14 days postimmunization, compared to those of control mice, the lumbar spinal cords of MOG-peptide EAE mice demonstrated prominent astrogliosis, infiltration of inflammatory cells, and disrupted expression of myelin proteins. Quantitative RT-PCR showed that expression of BMP4, BMP6, and BMP7 mRNA increased 2- to 4-fold in the lumbar spinal cords of animals with symptomatic EAE versus in vehicle-treated and untreated controls on days 14, 21, and 42 postimmunization. BMP2 mRNA expression was not altered. BMP4 mRNA was much more abundant in the spinal cords of all animals than was mRNA encoding BMP2, BMP6, and BMP7. Immunoblot analysis confirmed the increased expression of BMP4 in the EAE animals. Immunohistochemistry revealed increased BMP4 immunoreactivity in areas of inflammation in MOG-peptide EAE animals. BMP4 labeling was mostly limited to macrophages but was sometimes associated with astrocytes and oligodendrocytes. These results indicate that members of the BMP family are differentially expressed in adult spinal cord and are up-regulated during EAE. (c) 2007 Wiley-Liss, Inc.     

Microglial cell activation and proliferation precedes the onset of CNS autoimmunity

Microglial cells are central nervous system (CNS) resident cells that are thought to become activated and contribute to the inflammation that occurs in the human autoimmune disease multiple sclerosis (MS). This has never been proven, however, because microglial cells cannot be phenotypically distinguished from peripheral macrophages that accumulate in MS inflammatory lesions. To study the kinetics and nature of microglial cell activation in the CNS, we used the animal model of MS, experimental autoimmune encephalomyelitis (EAE), and induced EAE in bone marrow (BM) chimera mice generated using major histocompatibility complex (MHC)-mismatched donor BM, allowing the separation of microglial cells and peripheral monocytes/macrophages. We found that microglial cell activation was evident before onset of disease symptoms and infiltration of peripheral myeloid cells into the CNS. Activated microglial cells underwent proliferation and upregulated the expression of CD45, MHC class II, CD40, CD86, and the dendritic cell marker CD11c. At the peak of EAE disease, activated microglial cells comprised 37% of the total macrophage and dendritic cell populations and colocalized with infiltrating leukocytes in inflammatory lesions. Our findings thus definitively demonstrate that during EAE, microglial cells become activated early in EAE disease and then differentiate into both macrophages and dendritic-like cells, suggesting they play an active role in the pathogenesis of EAE and MS.     

Involvement of neuropsin in the pathogenesis of experimental autoimmune encephalomyelitis

Inflammation, demyelination, and axonal damage of the central nervous system (CNS) are major pathological features of multiple sclerosis (MS). Proteolytic digestion of the blood-brain barrier and myelin protein by serine proteases is known to contribute to the development and progression of MS. Neuropsin, a serine protease, has a role in neuronal plasticity, and its expression has been shown to be upregulated in response to injury to the CNS. To determine the possible involvement of neuropsin in demyelinating diseases of the CNS, we examined its expression in myelin oligodendrocyte glycoprotein (MOG)-induced experimental autoimmune encephalomyelitis (EAE), a recognized animal model for MS. Neuropsin mRNA expression was induced in the spinal cord white matter of mice with EAE. Combined in situ hybridization and immunohistochemistry demonstrated that most of the cells expressing neuropsin mRNA showed immunoreactivity for CNPase, a cell-specific marker for oligodendrocytes. Mice lacking neuropsin (neuropsin-/-) exhibited an altered EAE progression characterized by delayed onset and progression of clinical symptoms as compared to wild-type mice. Neuropsin-/- mice also showed attenuated demyelination and delayed oligodendroglial death early during the course of EAE. These observations suggest that neuropsin is involved in the pathogenesis of EAE mediated by demyelination and oligodendroglial death.     

Investigation of CD24 and its expression in Iranian relapsing-remitting multiple sclerosis

CD24 is a glycosylphosphatidylinositol (GPI)-linked cell surface glycoprotein expressed in central nervous system cells. Recent investigations have suggested that CD24 participates in the pathogenesis of experimental autoimmune encephalomyelitis (EAE), an animal model of multiple sclerosis (MS). However, a limited number of studies have been published regarding the contribution of CD24 to the risk and severity of MS in humans. We investigated the contribution of a CD24 single nucleotide polymorphism (SNP) to MS disease risk and severity. We also studied mRNA expression of the CD24 gene in Iranian MS patients using quantitative real-time polymerase chain reaction (PCR). Our findings showed that the CD24(v/v) genotype was significantly more frequent in MS patients compared with controls (p(c) = .004). Moreover, a statistically significant difference in the Multiple Sclerosis Severity Score (MSSS) was found between MS patients carrying CD24(a/a) and CD24(v/v) genotypes (p = .008). The results also indicated that the expression of CD24 mRNA was 1.7 times more in MS patients compared with controls. In conclusion, our results suggest that the CD24(v/v) genotype influences both MS disease risk and severity in Iranian MS patients, and the high disease severity in CD24(v/v) patients may indicate that they require more aggressive treatment than do patients carrying CD24(a/a).     

Upregulation of monocyte chemotactic protein-1 and CC chemokine receptor 2 in the central nervous system is closely associated with relapse of autoimmune encephalomyelitis in Lewis rats

Experimental autoimmune encephalomyelitis (EAE) is a disease model of multiple sclerosis (MS) that is characterized by remittance and relapse of the disease and autoimmune and demyelinating lesions in the central nervous system (CNS). To better understand the mechanism of disease relapse, we induced acute and chronic relapsing (CR)-EAE in Lewis rats and examined the differences between the two groups. An immunohistochemical study revealed that significantly higher numbers of macrophages infiltrated the spinal cord during the first and second attacks of CR-EAE than at the peak of acute EAE, whereas the number of infiltrating T cells was essentially the same in acute and CR-EAE. In accordance with this finding, monocyte chemoattractant protein-1 (MCP-1) mRNA, but not MIP-1alpha and RANTES mRNA, increased significantly in CR-EAE lesions rather than in acute EAE lesions. More importantly, the level of MCP-1 during the remission of CR-EAE was significantly higher than during the recovery phase of acute EAE, suggesting that this high level of MCP-1 in CR-EAE is associated with relapse of the disease. CC chemokine receptor 2 (CCR2), the main receptor for MCP-1, was expressed on astrocytes, macrophages and T cells and the number of positive cells was higher in CR-EAE than in acute EAE. Collectively, these findings suggest that high expression of MCP-1 and its receptor, CCR2, in the CNS play important roles in relapse of EAE.     

Up-regulation of platelet-derived growth factor by peripheral-blood leukocytes during experimental allergic encephalomyelitis

In multiple sclerosis (MS) and its animal model, experimental allergic encephalomyelitis (EAE), clinical disease is associated with infiltration of the central nervous system (CNS) by immune cells. Subsequent remission with remyelination has been linked to an increased occurrence of oligodendrocyte progenitor (O2A) cells. Platelet-derived growth factor (PDGF) and fibroblast growth factor-2 (FGF-2) are key growth factors for O2A cells, yet little is known about their relevance in EAE and MS. We analyzed the expression of PDGF, FGF-2, and their receptors by peripheral-blood leukocytes (PBLs) and lymphocyte subsets during MBP-induced EAE. Strong up-regulation of PDGF, but not FGF-2, was observed in PBLs, with the highest expression after the disease maximum. T, NK, and NKT cells expressed PDGF, which is a novel observation because thus far only monocytes/macrophages have been reported to express PDGF. These results extend the idea that growth factors may contribute to improved CNS tissue repair, including PDGF, which is secreted by lesion-homing immune cells. The production of PDGF by lymphocytes may have potential therapeutic value when activating or modulating T-cell responses in demyelinating diseases.