Role In Experimental Autoimmune Encephalomyelitis Research Articles

Osteopontin and multiple sclerosis: An update

Osteopontin (OPN), which was originally identified as a bone matrix protein, is a pro-inflammatory cytokine implicated in autoimmune diseases, such as experimental autoimmune encephalomyelitis (EAE) and multiple sclerosis (MS). Indeed, OPN is highly upregulated in EAE and MS lesions. Recent studies have shown that Th17 cell responses, which are involved in the pathogenesis of EAE and MS, are regulated by OPN. This review provides an overview of the current body of literature on the immunological functions of OPN and its role in EAE and MS. (Clin. Exp. Neuroimmunol. doi: 10.1111/j.1759-1961.2011.00019.x, May 2011)

Recognition of a High Affinity MHC Class I-Restricted Epitope of Myelin Oligodendrocyte Glycoprotein by CD8+ T Cells Derived from Autoantigen-Deficient Mice

CD4+ T cells have a well-defined pathogenic role in experimental autoimmune encephalomyelitis, the rodent model of multiple sclerosis (MS), yet CD8+ T cells are commonly found in MS lesions. To determine whether immunological tolerance might impact differently on CD4+ versus CD8+ T cells, we studied T cell responses in mice genetically deficient for the central nervous system (CNS) autoantigen myelin oligodendrocyte glycoprotein (MOG) versus wild type (WT) C57BL/6 mice. We show that MOG−/− mice have enhanced sensitivity to immunization with the immunodominant peptide of MOG (35–55), as evidenced by increased expansion of both CD4+ and CD8+ T cell subsets. Most strikingly, CD8+ T cells from MOG−/− mice responded to a novel T cell epitope which binds to MHC class I with high affinity. Despite this, MOG-responsive CD8+ T cells sourced from either WT or MOG−/− mice failed to initiate CNS inflammation upon transfer to MOG-sufficient mice. In our hands, this capacity was only found in CD4+ T cells. However, MOG−/− CD4+ cells did not show greater pathogenic activity than their WT counterparts. Our data indicate that, in the presence of endogenous MOG, CD8+ T cells capable of responding to a MHC class I-restricted epitope that can be stably expressed are subject to rigorous control through central and/or peripheral tolerance.

Inhibition of Experimental Autoimmune Encephalomyelitis in Human C-Reactive Protein Transgenic Mice Is FcRIIB Dependent

We showed earlier that experimental autoimmune encephalomyelitis (EAE) in human C-reactive protein (CRP) transgenic mice (CRPtg) has delayed onset and reduced severity compared to wild-type mice. Since human CRP is known to engage Fc receptors and Fc receptors are known to play a role in EAE in the mouse, we sought to determine if FcγRI, FcγRIIb, or FcγRIII was needed to manifest human CRP-mediated protection of CRPtg. We report here that in CRPtg lacking either of the two activating receptors, FcγRI and FcγRIII, the beneficial effects of human CRP are still observed. In contrast, if CRPtg lack expression of the inhibitory receptor FcγRIIB, then the beneficial effect of human CRP is abrogated. Also, subcutaneous administration of purified human CRP stalled progression of ongoing EAE in wild-type mice, but similar treatment failed to impede EAE progression in mice lacking FcγRIIB. The results reveal that a CRP → FcγRIIB axis is responsible for protection against EAE in the CRPtg model.

Erythropoietin enhances endogenous haem oxygenase-1 and represses immune responses to ameliorate experimental autoimmune encephalomyelitis

Both erythropoietin (EPO) and haem oxygenase-1 (HO-1), an anti-oxidative stress protein, have proven protective roles in experimental autoimmune encephalomyelitis (EAE), a reliable animal model of multiple sclerosis. In this study, EPO delivered intraperitoneally could reduce disease severity in myelin oligodendrocyte glycoprotein (MOG)–EAE mice. To assess the effect of EPO on endogenous HO-1 in EAE, we investigated expression of HO-1 mRNA by real-time polymerase chain reaction (RT–PCR), protein expression centrally and peripherally by Western blot and immunohistochemistry and mean fluorescence intensity of splenic HO-1 by flow cytometry. A significantly higher expression of HO-1 in both the central nervous system (CNS) and spleen was shown in EPO-treated MOG–EAE mice than in controls.We further examined the immunomodulatory effect of EPO in EAE, and via RT–PCR demonstrated significantly lower expression of interferon-γ, interleukin (IL)-23, IL-6 and IL-17 mRNA, and significantly higher expression of IL-4 and IL-10 mRNA in CNS of EPO-treated MOG–EAE mice than in controls. Using flow cytometry, we also observed a significantly decreased ratio of both T helper type 1 (Th1) and Th17 lymphocyte subsets isolated from CNS and a significantly increased ratio of splenic regulatory CD4 T cells in EPO-treated MOG–EAE mice. In addition, we demonstrated that MOG-specific T cell proliferation was lower in the EPO-treated group than in controls and showed amelioration of EAE by adoptive transfer of splenocytes from EPO-treated MOG–EAE mice. Together, our data show that in EAE, EPO induction of endogenous HO-1 and modulation of adaptive immunity both centrally and peripherally may involve the repression of inflammatory responses.

Differential expression of SOCS1 in macrophages in relapsing‐remitting and chronic EAE and its role in disease severity

Experimental autoimmune encephalomyelitis (EAE) is a T cell-mediated neuroinflammatory disease that is often used as a model of multiple sclerosis. EAE can follow either relapsing-remitting (RR) or chronic (CH) courses, yet the factors responsible for differentially inducing these forms of disease remain largely unknown. Proinflammatory cytokines play an important role in EAE, and signaling by these cytokines can be negatively regulated by the suppressor of cytokine signaling 1 protein (SOCS1). We assessed if differential expression of SOCS1 could contribute to the clinical course of RR and CH forms of EAE induced in the same mouse strain (C57BL/6) using the same myelin antigen (myelin oligodendrocyte glycoprotein). We show that SOCS1 mRNA levels are significantly elevated in the spinal cord in early stages of both RR- and CH-EAE. SOCS1 protein is highly expressed in immune cells in EAE lesions in the spinal cord, with expression predominantly localized within macrophages. Importantly, the number of Mac-1(+) macrophages expressing SOCS1 at the peak stage of RR disease is three-fold greater than in CH-EAE. Furthermore, the macrophage effector molecule iNOS, whose expression is regulated by SOCS1, is significantly reduced at the peak of RR- versus CH-EAE. Finally, the administration of a SOCS1-mimetic peptide reduces disease severity in the CH-EAE model. Thus, the differential expression of SOCS1 may contribute to the development of RR and CH forms of EAE.

Targeted lipidomics reveals mPGES-1-PGE2 as a therapeutic target for multiple sclerosis

The arachidonic acid (AA) cascade produces eicosanoids, such as prostaglandins (PGs), that regulate physiological and pathological functions. Although various nonsteroidal anti-inflammatory drugs have been developed, blocking upstream components (cyclooxygenase-1 and -2) of the AA cascade leads to severe side effects, including gastrointestinal ulcers and cardiovascular events, respectively, due to the complexity of the AA cascade. Here, using an AA cascade-targeted lipidomics approach, we report that microsomal PGE synthase 1 (mPGES-1) plays a key role in experimental autoimmune encephalomyelitis (EAE). Eicosanoids (mainly PGD(2)) are produced constitutively in the spinal cord of naive mice. However, in EAE lesions, the PGE(2) pathway is favored and the PGD(2), PGI(2), and 5-lipoxygenase pathways are attenuated. Furthermore, mPGES-1(-/-) mice showed less severe symptoms of EAE and lower production of IL-17 and IFN-gamma than mPGES-1(+/+) mice. Expression of PGE(2) receptors (EP1, EP2, and EP4) was elevated in EAE lesions and correlated with clinical symptoms. Immunohistochemistry on central nervous systems of EAE mice and multiple sclerosis (MS) patients revealed overt expression of mPGES-1 protein in microglia/macrophages. Thus, the mPGES-1-PGE(2)-EPs axis of the AA cascade may exacerbate EAE pathology. Our findings have important implications for the design of therapies for MS.

Deletion of both the C3a and C5a receptors fails to protect against experimental autoimmune encephalomyelitis

Multiple sclerosis (MS) is an autoimmune disease in which inflammation, leukocyte infiltration, and ultimately, demyelination occur as a result of innate and adaptive immune-mediated mechanisms. The pathophysiological role of the complement system, a major component of innate immunity, in the development and progression of experimental autoimmune encephalomyelitis (EAE), the animal model for MS has been extensively examined. Previous studies from our lab have shown that the complement receptor for the anaphylatoxin C3a, but not for C5a plays an important role in EAE. Based on the important contributions of the complement anaphylatoxin receptors to other inflammatory conditions in the CNS, we reasoned that deletion of both receptors may reveal underlying interactions between them that are important to EAE pathology. We performed EAE in C3aR/C5aR double knockout mice (C3aR/C5aR −/−) and observed delayed onset of disease but no attenuation of disease severity compared to wild type mice. Interestingly there was trend toward greater infiltration of CD4 +, but not CD8 + T cells, in C3aR/C5aR −/− mice with EAE, suggesting altered trafficking of these cells. Antigen-specific T cells isolated from C3aR/C5aR −/− mice during acute EAE produced elevated levels of TNF-α, but markedly reduced levels of IFN-γ and IL-12 compared to wild type mice. It remains unclear how the changes in these disease parameters contribute to the loss of the protective effect seen in C3aR −/− mice, however our data indicate a level of cross-modulation between the C3aR and C5aR during EAE.

Galectin-3 Deficiency Reduces the Severity of Experimental Autoimmune Encephalomyelitis

Galectin-3 (Gal-3) is a member of the beta-galactoside-binding lectin family and plays an important role in inflammation. However, the precise role of Gal-3 in autoimmune diseases remains obscure. We have investigated the functional role of Gal-3 in experimental autoimmune encephalomyelitis (EAE) following immunization with myelin oligodendrocyte glycoprotein (MOG)35-55 peptide. Gal-3 deficient (Gal-3-/-) mice developed significantly milder EAE and markedly reduced leukocyte infiltration in the CNS compared with similarly treated wild-type (WT) mice. Gal-3-/- mice also contained fewer monocytes and macrophages but more apoptotic cells in the CNS than did WT mice. Following Ag stimulation in vitro, lymph node cells from the immunized Gal-3-/- mice produced less IL-17 and IFN-gamma than did those of the WT mice. In contrast, Gal-3-/- mice produced more serum IL-10, IL-5, and IL-13 and contained higher frequency of Foxp3+ regulatory T cells in the CNS than did the WT mice. Furthermore, bone marrow-derived dendritic cells from Gal-3-/- mice produced more IL-10 in response to LPS or bacterial lipoprotein than did WT marrow-derived dendritic cells. Moreover, Gal-3-/- dendritic cells induced Ag-specific T cells to produce more IL-10, IL-5, and IL-12, but less IL-17, than did WT dendritic cells. Taken together, our data demonstrate that Gal-3 plays an important disease-exacerbating role in EAE through its multifunctional roles in preventing cell apoptosis and increasing IL-17 and IFN-gamma synthesis, but decreasing IL-10 production.

Effector and suppressor roles for LFA-1 during the development of experimental autoimmune encephalomyelitis

LFA-1 (CD11a/CD18) is a member of the β 2-integrin family of adhesion molecules important in leukocyte trafficking and activation. Although LFA-1 is thought to contribute to the development of experimental autoimmune encephalomyelitis (EAE) primarily through its functions on effector T cells, its importance on other leukocyte populations remains unexplored. To address this question, we performed both adoptive transfer EAE experiments involving CD11a −/− mice and trafficking studies using bioluminescent T cells expressing luciferase under the control of a CD2 promoter (T-lux cells). Transfer of encephalitogenic CD11a −/− T cells to wild type mice resulted in a significant reduction in overall EAE severity compared to control transfers. We also observed, using in vivo imaging techniques, that CD11a −/− T-lux cells readily infiltrated lymph nodes and the CNS of wild type recipients with kinetics comparable to CD11a +/+ transfers, although their overall numbers in these organs were reduced. Surprisingly, transfer of encephalitogenic wild type T cells to CD11a −/− mice induced a severe and sometimes fatal EAE disease course, associated with massive T cell infiltration and proliferation in the CNS. These data indicate that LFA-1 expression on leukocytes in recipient mice plays an important immunomodulatory role in EAE. Thus, LFA-1 acts as a key regulatory adhesion molecule during the development of EAE, serving both pro- and anti-inflammatory roles in disease pathogenesis.

Mycobacterium bovisBacille Calmette-Guérin Infection in the CNS Suppresses Experimental Autoimmune Encephalomyelitis and Th17 Responses in an IFN-γ-Independent Manner

Multiple sclerosis and an animal model resembling multiple sclerosis, experimental autoimmune encephalomyelitis (EAE), are inflammatory demyelinating diseases of the CNS that are suppressed by systemic mycobacterial infection in mice and BCG vaccination in humans. Host defense responses against Mycobacterium in mice are influenced by T lymphocytes and their cytokine products, particularly IFN-gamma, which plays a protective regulatory role in EAE. To analyze the counter-regulatory role of mycobacterial infection-induced IFN-gamma in the CNS on the function of the pathological Th17 cells and the clinical outcome of EAE, we induced EAE in mice that were intracerebrally infected with Mycobacterium bovis bacille Calmette-Guerin (BCG). In this study, we demonstrate that intracerebral (i.c.) BCG infection prevented inflammatory cell recruitment to the spinal cord and suppressed the development of EAE. Concomitantly, there was a significant decrease in the frequency of myelin oligodendrocyte glycoprotein-specific IFN-gamma-producing CD4(+) T cells in the CNS. IL-17(+)CD4(+) T cell responses were significantly suppressed in i.c. BCG-infected mice following EAE induction regardless of T cell specificity. The frequency of Foxp3(+)CD4(+) T cells in these mice was equivalent to that of control mice. Intracerebral BCG infection-induced protection of EAE and suppression of myelin oligodendrocyte glycoprotein-specific IL-17(+)CD4(+) T cell responses were similar in both wild-type and IFN-gamma-deficient mice. These data show that live BCG infection in the brain suppresses CNS autoimmunity. These findings also reveal that the regulation of Th17-mediated autoimmunity in the CNS can be independent of IFN-gamma-mediated mechanisms.

Repeated 0.5-Gy γ Irradiation Attenuates Experimental Autoimmune Encephalomyelitis with Up-regulation of Regulatory T Cells and Suppression of IL17 Production

We recently reported attenuation of autoimmune disease by low-dose gamma irradiation (repeated doses of 0.5 Gy) in MRL-lpr/ lpr mice. Here we studied the effect of low-dose gamma irradiation on experimental autoimmune encephalomyelitis (EAE), which is a rodent model of multiple sclerosis. SJL/J mice were immunized with myelin basic protein for the induction of EAE and were exposed to 0.5 Gy gamma rays once a week for 4 weeks. Radiation suppressed incidence and disease severity scores and delayed the onset of pathological changes. Pro-inflammatory cytokines (IFN-gamma and IL6), autoantibody and CD8+ cytotoxic T cells are involved in the appearance of EAE. Radiation suppressed the increases in these cytokines and the autoantibody production and blocked the increase in the population of CD8+ cytotoxic T cells. Production of IL17 by Th17 cells and/or gammadelta T cells, which plays a crucial role in EAE, was also significantly suppressed by radiation. Furthermore, a significant increase in regulatory T cells, which are involved in suppression of autoimmune disease, was found in irradiated EAE mice. These data suggest that low-dose gamma irradiation attenuates EAE through suppression of pro-inflammatory cytokines, reduction of cytotoxic T cells and induction of regulatory T cells.

Gender-specific influence of the chromosome 16 chemokine gene cluster on the susceptibility to Multiple Sclerosis

Macrophage-derived chemokine (MDC/CCL22) plays a role in Experimental Autoimmune Encephalomyelitis (EAE), the animal model of Multiple Sclerosis (MS). MDC/CCL22 gene is part of a chemokine cluster, which includes also thymus and Activation-Regulated Chemokine (TARC/CCL17). The frequency of the C/T and C/A Single Nucleotide Polymorphisms (SNPs) in the promoter and coding sequence of CCL22 as well as the C/T SNP in the promoter of CCL17 were determined in 370 patients with Multiple Sclerosis (MS) compared with 380 controls. A trend towards a decreased allelic frequency of the A allele of the CCL22 C/A SNP as well as of the T allele of the CCL17 C/T SNP was found in patients compared with controls. The frequency of the AT haplotype was significantly decreased in MS patients (P=0.017, OR: 0.49, CI: 0.28-0.87). Stratifying patients according to gender, the observed association was even more pronounced in male patients compared with male controls (P=0.004, OR=0.18, 95% CI: 0.06-0.50), whereas no significant differences were observed in females. Therefore, the presence of the AT haplotype in chromosome 16 chemokine cluster is likely to confer a decreased risk of developing MS, particularly in males.

Suppressive Effect of IL-27 on Encephalitogenic Th17 Cells and the Effector Phase of Experimental Autoimmune Encephalomyelitis

IL-27 has been shown to play a suppressive role in experimental autoimmune encephalomyelitis (EAE) as demonstrated by more severe disease in IL-27R-deficient (WSX-1(-/-)) mice. However, whether IL-27 influences the induction or effector phase of EAE is unknown. This is an important question as therapies for autoimmune diseases are generally started after autoreactive T cells have been primed. In this study, we demonstrate maximal gene expression of IL-27 subunits and its receptor in the CNS at the effector phases of relapsing-remitting EAE including disease peak and onset of relapse. We also show that activated astrocyte cultures secrete IL-27p28 protein which is augmented by the endogenous factor, IFN-gamma. To investigate functional significance of a correlation between gene expression and disease activity, we examined the effect of IL-27 at the effector phase of disease using adoptive transfer EAE. Exogenous IL-27 potently suppressed the ability of encephalitogenic lymph node and spleen cells to transfer EAE. IL-27 significantly inhibited both nonpolarized and IL-23-driven IL-17 production by myelin-reactive T cells thereby suppressing their encephalitogenicity in adoptive transfer EAE. Furthermore, we demonstrate a strong suppressive effect of IL-27 on active EAE in vivo when delivered by s.c. osmotic pump. IL-27-treated mice had reduced CNS inflammatory infiltration and, notably, a lower proportion of Th17 cells. Together, these data demonstrate the suppressive effect of IL-27 on primed, autoreactive T cells, particularly, cells of the Th17 lineage. IL-27 can potently suppress the effector phase of EAE in vivo and, thus, may have therapeutic potential in autoimmune diseases such as multiple sclerosis.

Targeting the CB2 receptor for immune modulation

Early work on the biology of the components of Cannabis sativa showed evidence for a potential influence on immune regulation. With the discovery of a peripheral cannabinoid receptor associated with immune cells, many laboratories have sought to link the immunoregulatory activities of cannabinoid compounds with this receptor, hoping that such compounds would lack the psychoactive effects of marijuana and other nonspecific cannabinoid agonists. In this report, the authors investigate the role of the cannabinoid CB2 receptor in immune regulation, with particular emphasis on compounds shown to regulate immune cell recruitment. The authors conclude by using the immune cell recruitment model to rationalise cannabinoid CB2 receptor-specific effects in modulating immune disease, particularly the increasing evidence for its role in experimental autoimmune encephalomyelitis and in influencing bone density.

CNS demyelination during anti–tumor necrosis factor alpha therapy

Sirs: Tumor Necrosis Factor alpha (TNFalpha) is a cytokine released by activated monocytes, macrophages, and T-lymphocytes. It is involved in several processes, but plays an important role particularly in inflammation [1]. Its overproduction is implicated in a wide range of pathological conditions, including rheumatoid arthritis (RA) [2] and multiple sclerosis (MS) [3]. High concentrations of TNFalpha are present in synovial fluid of RA patients [4] and in cerebro-spinal fluid (CSF) of MS patients [5]. Considering its role in inflammatory disease, numerous drugs have been developed to modulate its action on inflammation in recent years [6, 7]. Some are characterized by monoclonal antibodies against TNFalpha (Infliximab, Adalimumab), while others are soluble TNF-receptor fusionproteins (Etanercept, Lenercept), but all inhibit the TNFalpha effect [6, 7]. In the literature the effectiveness of TNFalpha therapy in experimental models and in studies of RA in humans is well known [8]. In addition several studies have shown its preventive role in experimental autoimmune encephalomyelitis (EAE), a well established experimental model of MS [9]. Despite these findings, antiTNFalpha treatment for MS worsens the disease. In a trial of antiTNFalpha-targeted therapy using Lenercept, treated patients had significantly more exacerbations than placebo-treated patients [7]. Moreover, other studies have demonstrated that Etanercept and Infliximab may also worsen preexisting MS and trigger de-novo CNS demyelination [10, 11]. The patient we report experienced CNS demyelination using Adalimumab, a new TNFalpha-blocker. A 40-year old woman with RA on methotrexate (10 mg i. m. once a week) treatment for several months started a therapy with Adalimumab (40 mg s. c. once 15 days), a TNFalpha-blocker. After two months she experienced diplopia, headache, nausea and dizziness with subacute onset. She had no family history of neurological disturbances and there was no evidence of a previous febrile episode or other previous neurological dysfunction. Neurological examination showed VI and VII right cranial nerve palsy, a tetrapyramidal syndrome, bladder voiding disorder, mild leg extremity sensory deficit. Immunological and infection investigations were normal, whereas CSF analysis showed barrier damage and several oligoclonal bands. VEPs, SEPs and BAEPs were abnormal. Brain and spinal cord MRI revealed several T2-hyperintensities in the hemispheric white matter, in the brainstem and in the spinal cord. Following gadolinium-DTPA (Gd) administration, some areas of enhancement were present in both hemispheres and in cervical spinal cord (Fig. 1A, B). Anti-TNFalpha therapy was stopped and methylprednisolone 1 g/day i. v. for five days was administered with a progressive improvement of the clinical picture. After six months brain and spinal MRI showed the persistence of T2-weighted hyperintensities (Fig. 1C), but there was no evidence of enhancement after Gd administration (Fig. 1D). After 6 and 14 months the clinical picture was normal except for mild hyperreflexia in all four limbs. Exacerbation of previously quiescent MS and new-onset demyelinating disease have been reported during Infliximab and Etenarcept therapy for RA. Moreover it has been well documented that another TNF-antagonist, Lenercept, increased the number of attacks of pre-existing MS [7, 10, 11]. The present data – in particular the temporal correlation of neurological symptoms onset with TNFalpha-blocker administration and the monophasic course – suggest that even Adalimumab, like other TNFalpha blockers, may trigger denovo CNS demyelination. Therefore, although a causal relationship between anti-TNFalpha therapy and CNS demyelination has not been well established, all reports make this association more plausible, indicating a possible protective role of TNFalpha in demyelinating diseases. Until further long-term safety data are available, we suggest that anti-TNFalpha therapy should not be administered to patients with MS or to patients with neurological signs or symptoms possibly arising from previous demyelinating episodes. Moreover it would be useful to look for MRI signs of leukoencephalopathy, possibly due to silent CNS demyelination, before starting a therapy with TNF-blockers.

Modulating CCR2 and CCL2 at the blood–brain barrier: relevance for multiple sclerosis pathogenesis

Chemokines and chemokine receptors play a key role in the transmigration of leucocytes across the blood-brain barrier (BBB). CCR2 is the major receptor for CCL2, a potent monocyte and T cell chemoattractant. CCR2 and CCL2 have been consistently associated with a pathogenic role in experimental autoimmune encephalomyelitis, using knockout and transgenic mice, neutralizing antibodies, peptide antagonists and DNA vaccination. However, the significance of CCL2 and CCR2 in multiple sclerosis is enigmatic, because CCL2 levels are consistently decreased in the CSF of patients with this disease and other chronic neuroinflammatory conditions, despite abundant expression within lesional multiple sclerosis tissues. This study used an in vitro BBB model to test the hypothesis that CCL2 is removed from the extracellular fluid by CCR2-positive migrating cells as they cross the BBB, resulting in decreased CSF CCL2 levels. We showed that CCR2-positive T cells and monocytes migrated selectively across the in vitro BBB, and that CCL2 on the abluminal (tissue) side was consumed by migrating T cells and monocytes. Next, we used a new anti-CCR2 antibody to show that CCR2-positive mononuclear inflammatory cells could be readily detected in appropriate positive control tissues, but that CCR2+ cells were very infrequently found in multiple sclerosis lesions. We then showed that CCR2 receptor density on T cells and monocytes was specifically downregulated upon in vitro BBB transmigration in response to CCL2, but not irrelevant chemokines. These findings document a novel strategy for analysing chemokine receptor function in inflammatory CNS disease, and support the hypothesis that CCL2 is consumed by migrating inflammatory cells, which downregulate CCR2, as they cross the BBB.

Mechanism of natural killer (NK) cell regulatory role in experimental autoimmune encephalomyelitis

The mechanism of natural killer (NK) cell regulatory role in experimental autoimmune encephalomyelitis (EAE) was studied in SJL/J mice. In vivo experiments showed that NK cell depletion by anti-NK1.1 monoclonal antibody treatment enhanced EAE in mice. To investigate the mechanism, we cultured proteolipid protein (PLP) 136–150 peptide-specific, encephalitogenic T cell lines, which were used as the NK cell target. Our results show that NK cells exert a direct cytotoxic effect on autoantigen-specific, encephalitogenic T cells. Furthermore, cytotoxicity to PLP-specific, encephalitogenic T line cells was enhanced by using enriched NK cells as effector cells. However, the cytotoxic effect of NK cells to ovalbumin-specific T line cells and ConA-stimulated T cells could also be detected with a lesser efficiency. Our studies indicate that NK cells play a regulatory role in EAE through killing of syngeneic T cells which include myelin antigen-specific, encephalitogenic T cells, and thus ameliorate EAE.

Analysis of Gene Expression in MOG-Induced Experimental Autoimmune Encephalomyelitis After Treatment <SMALL>W</SMALL>ith a Novel Brain-Penetrating Antioxidant

Accumulating data from experimental studies indicate that oxidative stress has a major role in the pathogenesis of multiple sclerosis (MS). It has been suggested that local production of reactive oxygen species, probably by macrophages, mediates axonal damage in both MS patients and the mouse model experimental autoimmune encephalomyelitis (EAE). We have shown previously that our novel brain-penetrating antioxidant, N-acetylcysteine amide (AD4), reduces the clinical and pathological symptoms, including inflammation and axonal damage in myelin oligodendrocyte glycoprotein (MOG)-induced chronic EAE in mice. The aim of this study was to examine the molecular mechanism by which AD4 exerts protection in MOG-induced EAE mice. Therefore, we analyzed gene-expression profile in the spinal cords of MOG-induced chronic EAE mice and compared them with MOG-induced mice treated with AD4, using a cDNA microarray. We found that MOG treatment up-regulated genes encoding growth factors, cytokines, death receptors, proteases, and myelin structure proteins, whereas MOG- and AD4-treated mice demonstrated gene expression profiles similar to that seen in naive healthy mice. In conclusion, our study shows that chronic AD4 administration suppresses the induction of various pathological pathways that play a role in EAE and probably in MS.

Critical roles of CXC chemokine ligand 16/scavenger receptor that binds phosphatidylserine and oxidized lipoprotein in the pathogenesis of both acute and adoptive transfer experimental autoimmune encephalomyelitis.

The scavenger receptor that binds phosphatidylserine and oxidized lipoprotein (SR-PSOX)/CXCL16 is a chemokine expressed on macrophages and dendritic cells, while its receptor expresses on T and NK T cells. We investigated the role of SR-PSOX/CXCL16 on acute and adoptive experimental autoimmune encephalomyelitis (EAE), which is Th1-polarized T cell-mediated autoimmune disease of the CNS. Administration of mAb against SR-PSOX/CXCL16 around the primary immunization decreased disease incidence of acute EAE with associated reduced infiltration of mononuclear cells into the CNS. Its administration was also shown to inhibit elevation of serum IFN-gamma level at primary immune response, as well as subsequent generation of Ag-specific T cells. In adoptive transfer EAE, treatment of recipient mice with anti-SR-PSOX/CXCL16 mAb also induced not only decreased clinical disease incidence, but also diminished traffic of mononuclear cells into the CNS. In addition, histopathological analyses showed that clinical development of EAE correlates well with expression of SR-PSOX/CXCL16 in the CNS. All the results show that SR-PSOX/CXCL16 plays important roles in EAE by supporting generation of Ag-specific T cells, as well as recruitment of inflammatory mononuclear cells into the CNS.

Calcium channel blockers ameliorate disease in a mouse model of multiple sclerosis

Multiple sclerosis (MS) and experimental autoimmune encephalomyelitis (EAE), an animal model of MS, are inflammatory demyelinating diseases of the central nervous system. The inflammatory attacks lead to glial dysfunction and death, axonal damage, and neurological deficits. Numerous studies in rat suggest that extracellular calcium influx, via voltage-gated calcium channels (VGCC), contributes to white matter damage in acute spinal cord injury and stroke. Our immunohistochemical finding that mouse spinal cord axons display subunits of L-type VGCC also supports this hypothesis. Furthermore, we hypothesized that VGCC also play a role in EAE, and possibly, MS. In our study, administration of the calcium channel blockers (CCB) bepridil and nitrendipine significantly ameliorated EAE in mice, compared with vehicle-treated controls. Spinal cord samples showed reduced inflammation and axonal pathology in bepridil-treated animals. Our data support the hypothesis that calcium influx via VGCC plays a significant role in the development of neurological disability and white matter damage in EAE and MS.