Multiple sclerosis and central nervous system demyelination

Speech deficits in multiple sclerosis: a narrative review of the existing literature

Multiple sclerosis (MS) is a chronic inflammatory and demyelinating autoimmune disease. MS patients deal with motor and sensory impairments, visual disabilities, cognitive disorders, and speech and language deficits. The study aimed to record, enhance, update, and delve into our present comprehension of speech deficits observed in patients with MS and the methodology (assessment tools) studies followed. The method used was a search of the literature through the databases for May 2015 until June 2022. The reviewed studies offer insight into speech impairments most exhibited by MS patients. Patients with MS face numerous communication changes concerning the phonation system (changes observed concerning speech rate, long pause duration) and lower volume. Moreover, the articulation system was affected by the lack of muscle synchronization and inaccurate pronunciations, mainly of vowels. Finally, there are changes regarding prosody (MS patients exhibited monotonous speech). Findings indicated that MS patients experience communication changes across various domains. Based on the reviewed studies, we concluded that the speech system of MS patients is impaired to some extent, and the patients face many changes that impact their conversational ability and the production of slower and inaccurate speech. These changes can affect MS patients' quality of life.

Promoting remyelination: A case study in regenerative medicine

Therapeutics that modulate regenerative mechanisms by targeting the activity of endogenous (adult) stem cell populations have the potential to revolutionize medicine. In many human disease states, capacity to repair damaged tissue underlies progressive decline and disease progression. Recent insights derived from efforts aimed at promoting remyelination for the treatment of multiple sclerosis (MS) highlight the importance of considering the limiting factors and underlying mechanisms associated with all aspects of disease onset, progression and recovery, during both the discovery and clinical stages of developing a regenerative medicine. This perspective presents general considerations for the development of regenerative therapies, using remyelination as a case study.

TH17 cells promote CNS inflammation by sensing danger signals via Mincle

The C-type lectin receptor Mincle is known for its important role in innate immune cells in recognizing pathogen and damage associated molecular patterns. Here we report a T cell-intrinsic role for Mincle in the pathogenesis of experimental autoimmune encephalomyelitis (EAE). Genomic deletion of Mincle in T cells impairs TH17, but not TH1 cell-mediated EAE, in alignment with significantly higher expression of Mincle in TH17 cells than in TH1 cells. Mechanistically, dying cells release β-glucosylceramide during inflammation, which serves as natural ligand for Mincle. Ligand engagement induces activation of the ASC-NLRP3 inflammasome, which leads to Caspase8-dependent IL-1β production and consequentially TH17 cell proliferation via an autocrine regulatory loop. Chemical inhibition of β-glucosylceramide synthesis greatly reduces inflammatory CD4+ T cells in the central nervous system and inhibits EAE progression in mice. Taken together, this study indicates that sensing of danger signals by Mincle on TH17 cells plays a critical role in promoting CNS inflammation.

Role of Viruses in the Pathogenesis of Multiple Sclerosis

Multiple sclerosis (MS) is an immune inflammatory disease, where the underlying etiological cause remains elusive. Multiple triggering factors have been suggested, including environmental, genetic and gender components. However, underlying infectious triggers to the disease are also suspected. There is an increasing abundance of evidence supporting a viral etiology to MS, including the efficacy of interferon therapy and over-detection of viral antibodies and nucleic acids when compared with healthy patients. Several viruses have been proposed as potential triggering agents, including Epstein-Barr virus, human herpesvirus 6, varicella-zoster virus, cytomegalovirus, John Cunningham virus and human endogenous retroviruses. These viruses are all near ubiquitous and have a high prevalence in adult populations (or in the case of the retroviruses are actually part of the genome). They can establish lifelong infections with periods of reactivation, which may be linked to the relapsing nature of MS. In this review, the evidence for a role for viral infection in MS will be discussed with an emphasis on immune system activation related to MS disease pathogenesis.

Dexamethasone attenuates inflammatory-mediated suppression of β2-adrenoceptor expression in rat primary mixed glia

β₂-adrenoceptors are G-protein coupled receptors expressed on both astrocytes and microglia that play a key role in mediating the anti-inflammatory actions of noradrenaline in the CNS. Here the effect of an inflammatory stimulus (LPS + IFN-γ) was examined on glial β₂-adrenoceptor expression and function. Exposure of glia to LPS + IFN-γ decreased β₂-adrenoceptor mRNA and agonist-stimulated production of the intracellular second messenger cAMP. Pre-treatment with the synthetic glucocorticoid and potent anti-inflammatory agent dexamethasone prevented the LPS + IFN-γ-induced suppression of β₂-adrenoceptor mRNA expression. These results raise the possibility that inflammation-mediated β₂-adrenoceptor downregulation in glia may dampen the innate anti-inflammatory properties of noradrenaline in the CNS.

Metabolomics-based discovery of a metabolite that enhances oligodendrocyte maturation

Endogenous metabolites play essential roles in the regulation of cellular identity and activity. Here we have investigated the process of oligodendrocyte precursor cell (OPC) differentiation, a process that becomes limiting during progressive stages of demyelinating diseases, including multiple sclerosis, using mass-spectrometry-based metabolomics. Levels of taurine, an aminosulfonic acid possessing pleotropic biological activities and broad tissue distribution properties, were found to be significantly elevated (∼20-fold) during the course of oligodendrocyte differentiation and maturation. When added exogenously at physiologically relevant concentrations, taurine was found to dramatically enhance the processes of drug-induced in vitro OPC differentiation and maturation. Mechanism of action studies suggest that the oligodendrocyte-differentiation-enhancing activities of taurine are driven primarily by its ability to directly increase available serine pools, which serve as the initial building block required for the synthesis of the glycosphingolipid components of myelin that define the functional oligodendrocyte cell state.

Peripheral sensory neuron injury contributes to neuropathic pain in experimental autoimmune encephalomyelitis

Multiple sclerosis (MS)-induced neuropathic pain deteriorates quality of life in patients but is often refractory to treatment. In experimental autoimmune encephalomyelitis (EAE), a rodent model of MS, animals develop neuropathy and inflammation-induced tissue acidosis, which suggests the involvement of acid-sensing ion channels (ASICs). Also, peripheral neuropathy is reported in MS patients. However, the involvement of the peripheral nervous system (PNS) in MS neuropathic pain remains elusive. This study investigated the contribution of ASICs and peripheral neuropathy in MS-induced neuropathic pain. Elicited pain levels were as high in Asic1a^-/-, Asic2^-/- and Asic3^-/- mice as wild-type mice even though only Asic1a^-/- mice showed reduced EAE disease severity, which indicates that pain in EAE was independent of disease severity. We thus adopted an EAE model without pertussis toxin (EAEnp) to restrain activated immunity in the periphery and evaluate the PNS contribution to pain. Both EAE and EAEnp mice showed similar pain behaviors and peripheral neuropathy in nerve fibers and DRG neurons. Moreover, pregabalin significantly reduced neuropathic pain in both EAE and EAEnp mice. Our findings highlight the essential role of the PNS in neuropathic pain in EAE and pave the way for future development of analgesics without side effects in the CNS.

EBV Infection and Multiple Sclerosis: Lessons from a Marmoset Model

Multiple sclerosis (MS) is thought to be initiated by the interaction of genetic and environmental factors, eliciting an autoimmune attack on the central nervous system. Epstein-Barr virus (EBV) is the strongest infectious risk factor, but an explanation for the paradox between high infection prevalence and low MS incidence remains elusive. We discuss new data using marmosets with experimental autoimmune encephalomyelitis (EAE) - a valid primate model of MS. The findings may help to explain how a common infection can contribute to the pathogenesis of MS. We propose that EBV infection induces citrullination of peptides in conjunction with autophagy during antigen processing, endowing B cells with the capacity to cross-present autoantigen to CD8⁺CD56⁺ T cells, thereby leading to MS progression.

Myelin basic protein induces inflammatory mediators from primary human endothelial cells and blood-brain barrier disruption: implications for the pathogenesis of multiple sclerosis

AIM

Multiple sclerosis (MS) is an autoimmune disease of the central nervous system, characterized by demyelination of white matter, loss of myelin forming oligodendrocytes, changes in the blood-brain barrier (BBB) and leucocyte infiltration. Myelin basic protein (MBP) is a component of the myelin sheath. Degradation of myelin is believed to be an important step that leads to MS pathology. Transmigration of leucocytes across the vasculature, and a compromised BBB participate in the neuroinflammation of MS. We examined the expression and regulation of the chemokine (C-C motif) ligand 2 (CCL2) and the cytokine interleukin-6 (IL-6) in human endothelial cells (EC), a component of the BBB, after treatment with MBP.

METHODS

EC were treated with full-length MBP. CCL2 and IL-6 protein were determined by ELISA. Western blot analysis was used to determine signalling pathways. A BBB model was treated with MBP and permeability was assayed using albumin conjugated to Evan's blue dye. The levels of the tight junction proteins occludin and claudin-1, and matrix metalloprotease (MMP)-2 were assayed by Western blot.

RESULTS

MBP significantly induced CCL2 and IL-6 protein from EC. This induction was partially mediated by the p38 MAPK pathway as there was phosphorylation after MBP treatment. MBP treatment of a BBB model caused an increase in permeability that correlated with a decrease in occludin and claudin-1, and an induction of MMP2.

CONCLUSION

These data demonstrate that MBP induces chemotactic and inflammatory mediators. MBP also alters BBB permeability and tight junction expression, indicating additional factors that may contribute to the BBB breakdown characteristic of MS.

Combination treatment of mice with CRx-153 (nortriptyline and desloratadine) decreases the severity of experimental autoimmune encephalomyelitis

Pro-inflammatory CD4(+) T cell-mediated autoimmune diseases, such as multiple sclerosis, are hypothesized to be initiated and maintained by self-reactive interferon-gamma (IFN-γ) and interleukin-17 (IL-17) producing CD4(+) T cells. Previous studies have shown moderate to significant alterations in inflammatory T cell responses and potentially treatment of autoimmune disease by administration of antihistamine or tricyclic antidepressants alone. The goal of the present study was to determine if treatment of PLP(139-151)-induced relapsing-remitting experimental autoimmune encephalomyelitis (R-EAE) in SJL/J mice with a combination of two FDA approved drugs for other indications could decrease R-EAE disease. The findings show that combination treatment with desloratadine and nortriptyline decreases the mean clinical score, disease relapse frequency, and number of CD4(+) T cells infiltrating into the CNS. In addition, combination treatment of PLP(139-151) primed mice decreases the level of IFN-γ and IL-17 secreted via a decrease in both the number of cells secreting and the amount of cytokine secreted per cell following PLP(139-151) reactivation ex vivo. This is in contrast to an increase in the level of IL-4 produced and the number of IL-4 secreting cells. The data also show that combination treatment with desloratadine and nortriptyline inhibits the production of IFN-γ and IL-17 produced by naive CD4(+) T cells activated in the presence of Th1 cell- and Th17 cell-promoting conditions, while increasing the level of IL-4 produced by naive CD4(+) T cells activated in the presence of Th2 cell-promoting conditions. The present findings suggest a novel method for the development of a putative autoimmune therapy.

γδ T cells and multiple sclerosis: Friends, foes, or both?

Multiple sclerosis (MS) is a debilitating CNS disease characterized by demyelination and neuro-axonal loss. Though the exact etiology is still unknown, accumulated evidence points to the immune system being involved in the MS disease-process. Both ill-fated adaptive and innate immune responses can potentially contribute to the etiopathogenesis. We have been interested in deciphering how innate immunity might be involved; in particular, the role of γδ T cells. In this review, we discuss the current understanding about γδ T cells and describe the evidence implicating them in myelin injury, neurotoxicity, and immunoregulation in the development of MS.

Cleavage of transaldolase by granzyme B causes the loss of enzymatic activity with retention of antigenicity for multiple sclerosis patients

Multiple sclerosis (MS) is an autoimmune demyelinating disease of the CNS resulting from a progressive loss of oligodendrocytes. Transaldolase (TAL) is expressed at selectively high levels in oligodendrocytes of the brain, and postmortem sections show concurrent loss of myelin basic protein and TAL from sites of demyelination. Infiltrating CD8(+) CTLs are thought to play a key role in oligodendrocyte cell death. Cleavage by granzyme B (GrB) is predictive for autoantigenicity of self-proteins, thereby further implicating CTL-induced death in the initiation and propagation of autoimmunity. The precursor frequency and CTL activity of HLA-A2-restricted TAL 168-176-specific CD8(+) T cells is increased in MS patients. In this paper, we show that TAL, but not myelin basic protein, is specifically cleaved by human GrB. The recognition site of GrB that resulted in the cleavage of a dominant TAL fragment was mapped to a VVAD motif at aa residue 27 by N-terminal sequencing and confirmed by site-directed mutagenesis. The major C-terminal GrB cleavage product, residues 28-337, had no enzymatic activity but retained the antigenicity of full-length TAL, effectively stimulating the proliferation and CTL activity of PBMCs and of CD8(+) T cell lines from patients with MS. Sera of MS patients exhibited similar binding affinity to wild-type and GrB-cleaved TAL. Because GrB mediates the killing of target cells and cleavage by GrB is predictive of autoantigen status of self proteins, GrB-cleaved TAL-specific T cell-mediated cytotoxicity may contribute to the progressive destruction of oligodendrocytes in patients with MS.

IFNbeta-1a therapy for multiple sclerosis expands regulatory CD8+ T cells and decreases memory CD8+ subset: a longitudinal 1-year study

The beneficial effects of interferon beta-1a (IFNbeta-1a) in multiple sclerosis (MS) remain only partially understood. CD8(+) T cells are key cells in MS pathogenesis that contribute to axonal damage in MS, whereas CD4(+) regulatory T cells (T(Reg)) and CD8(+) regulatory/suppressor T cells (Ts) play an important role in protecting against subsequent MS activity. We analysed ex vivo changes on T(Reg) and on the different subsets of CD4(+) and CD8(+) T lymphocytes, before IFNbeta-1a (Rebif) therapy and at 3, 6, and 12 months after treatment, in 23 MS patients and in 26 healthy controls. IFNbeta-1a significantly increased the proportions of CD4(+) T(Reg) and regulatory CD8(+) T cells (Tr). Memory CD8(+) T cells were significantly decreased after 1 year of treatment, maybe reflecting down-regulation of abnormally persistent systemic activation in MS patients. After 1 year of IFNbeta-1a, a direct correlation was observed between plasmacytoid dendritic cells and effector CD8(+) T cells.

Intracellular versus extracellular granzyme B in immunity and disease: challenging the dogma

The cytotoxic granzyme B (GrB)/perforin pathway has been traditionally viewed as a primary mechanism that is used by cytotoxic lymphocytes to eliminate allogeneic, virally infected and/or transformed cells. Although originally proposed to have intracellular and extracellular functions, upon the discovery that perforin, in combination with GrB, could induce apoptosis, other potential functions for this protease were, for the most part, disregarded. As there are 5 granzymes in humans and 11 granzymes in mice, many studies used perforin knockout mice as an initial screen to evaluate the role of granzymes in disease. However, in recent years, emerging clinical and biochemical evidence has shown that the latter approach may have overlooked a critical perforin-independent, pathogenic role for these proteases in disease. This review focuses on GrB, the most characterized of the granzyme family, in disease. Long known to be a pro-apoptotic protease expressed by cytotoxic lymphocytes and natural killer cells, it is now accepted that GrB can be expressed in other cell types of immune and nonimmune origin. To the latter, an emerging immune-independent role for GrB has been forwarded due to recent discoveries that GrB may be expressed in nonimmune cells such as smooth muscle cells, keratinocytes, and chondrocytes in certain disease states. Given that GrB retains its activity in the blood, can cleave extracellular matrix, and its levels are often elevated in chronic inflammatory diseases, this protease may be an important contributor to certain pathologies. The implications of sustained elevations of intracellular and extracellular GrB in chronic vascular, dermatological, and neurological diseases, among others, are developing. This review examines, for the first time, the multiple roles of GrB in disease pathogenesis.

The role of CD8 suppressors versus destructors in autoimmune central nervous system inflammation

Multiple sclerosis (MS) is an inflammatory demyelinating disease of the central nervous system (CNS) of putative autoimmune origin. Recent evidence indicates that MS autoimmunity is linked to defects in regulatory T-cell function, which normally regulates immune responses to self-antigens and prevents autoimmune diseases. MS and its animal model, experimental autoimmune encephalomyelitis (EAE), have long been regarded as a CD4(+) T-cell-mediated autoimmune disease. Studies addressing the role of CD8(+) T cells, however, have only recently begun to emerge. Pathogenic function was attributed to CD8(+) T cells because of their abundant presence or oligoclonal repertoire within MS lesions. However, CD8(+) T cells appeared to have important regulatory functions, as demonstrated in EAE or human MS studies. We here review the contribution of CD8(+) T cells to inflammation and immune regulation in CNS autoimmunity. The knowledge of distinct CD8(+) T-cell populations exerting destructive versus beneficial functions is summarized. The long-term goal is to delineate the exact phenotypic and functional characteristics of regulatory CD8(+) T-cell populations (natural as well as inducible) in humans. This knowledge may help to further develop concepts of reconstituting or enhancing endogenous mechanisms of immune tolerance in future therapeutic concepts for MS.

CD16+ gammadelta T cells mediate antibody dependent cellular cytotoxicity: potential mechanism in the pathogenesis of multiple sclerosis

Our overall objective is to understand the role of gammadelta T cells in the pathogenesis of the central nervous system (CNS) autoimmune disease multiple sclerosis (MS). We have demonstrated that gammadelta T cells are directly cytotoxic to CNS cells in vitro. Although the exact mechanism of damage in MS is unknown, recent evidence suggests a role for B cells and antibodies to myelin. We were therefore interested in examining whether gammadelta T cells can injure CNS cells via an indirect mechanism involving antibody dependent cellular cytotoxicity. To study this we developed an in vitro flow cytometric cellular cytotoxicity assay (called "FC(3)A") to quantitate the amount of cytotoxicity. We utilized known target cells (Burkitt's B lymphoma) that express CD20, together with a monoclonal antibody (mAb) to CD20, rituximab, that is being studied as a potential treatment for MS. Target cells are first coated with rituximab followed by co-culture with gammadelta T cells derived from patients with MS. Specific lysis of target cells was determined by quantitation of 7-AAD (which increases only upon nuclear disruption indicating cell death). We determined that this lysis was due to gammadelta T cells that express CD16 (Fc gamma receptor) and were therefore capable of binding the rituximab and mediating cytolysis via ADCC. This specific cell lysis correlated with rituximab concentration, E:T ratio, and the surface expression of CD16 on gammadelta T cells. These findings provide a new perspective with regards to the role of gammadelta T cells in the immunopathogenesis of MS and an insight into one of the potential therapeutic effects of rituximab in the treatment of MS. In addition, this new FC(3)A method we developed could readily be adapted to study other types of immune cells suspected of ADCC-type killing.

Correlation of specialized CD16(+) gammadelta T cells with disease course and severity in multiple sclerosis

gammadelta T cells may be important innate immune system contributors to the immunopathogenesis of multiple sclerosis (MS), though the mechanisms are not yet fully understood. CD16 is a low affinity Fcgamma receptor, an activation receptor for gammadelta T cells, and a mediator of cytotoxicity. In this study, we found that the percentage of CD16(+) gammadelta T cells is elevated in MS patients compared with healthy controls. The increase is especially pronounced in patients with a progressive course of the disease, and the extent of this elevation shows a positive correlation with the time of disease progression and severity. In vitro cultured gammadelta T cells can be shown to upregulate the expression of CD16 in response to inflammatory cytokines such as IL-2 and -15, that have been shown to be elevated in progressive disease. These results suggest that CD16 expressing gammadelta T cells are somehow involved in the process of disease progression. Understanding more about these cells and their particular function in progressive vs. non-progressive disease could provide important clues to the mechanism of immune-mediated MS disease progression.

A cytokine immunosensor for multiple sclerosis detection based upon label-free electrochemical impedance spectroscopy

A biosensor for the serum cytokine, interleukin-12 (IL-12), based upon a label-free electrochemical impedance spectroscopy monitoring is described. Overexpression of IL-12 has been correlated to the diagnosis of multiple sclerosis (MS). The prototype biosensor was fabricated on a disposable gold-coated silver ribbon electrode by immobilizing anti-IL-12 monoclonal antibodies (mAbs) onto the surface of the electrode. This technique was advantageous as the silver electrodes provided a more rigid and conductive substrate than thin gold foil electrodes and helped in obtaining more reproducible data when used with the electrode holder. Results indicate that IL-12 can be detected at physiological levels, <100 fM with p<0.05 in a label-free and real-time manner. The cost-effective approach described here can be used for diagnosis of diseases (like MS) with known biomarkers in body fluids and for monitoring physiological levels of biomolecules with healthcare, food, and environmental relevance.

Effects of IFN-beta, leptin and simvastatin on LIF secretion by T lymphocytes of MS patients and healthy controls

In multiple sclerosis (MS), oligodendrocyte injury is believed to be caused by an aberrant immune response initiated by autoreactive T cells. Increasing evidence indicates that inflammatory responses in the central nervous system are not exclusively detrimental, but may also exert protective effects. Such protective effects are potentially mediated by the local secretion of neurotrophic factors by immune cells. We previously reported that T cells and monocytes in vitro and in inflammatory MS lesions produce leukaemia inhibitory factor (LIF), a member of the neuropoietic family of neurotrophins. In the present study, we report a reduced LIF production by CD4+ T cells of relapsing remitting MS patients as compared to healthy controls. Furthermore, immunomodulatory agents such as leptin, IFN-beta and simvastatin were studied for their potential to alter LIF and secretion of other cytokines by T cells and monocytes of relapsing remitting MS patients and healthy controls. Low doses of simvastatin, but not IFN-beta or leptin enhanced LIF secretion by CD4+ T cells of RR-MS patients. We further demonstrated that LIF did not influence viability, proliferation and cytokine secretion of T cells. Together these data provide new information on the regulation of LIF secretion by immune cells. Further insights into the complex regulation of neurotrophic factors such as LIF may prove useful for treatment of MS.

The pathology of multiple sclerosis is the result of focal inflammatory demyelination with axonal damage

Multiple sclerosis is a chronic inflammatory demyelinating disease of the central nervous system manifested morphologically by inflammation, demyelination, axonal loss and gliosis. The inflammatory lesions are characterized by massive infiltration by a heterogeneous population of cellular and soluble mediators of the immune system, including T cells, B cells, macrophages and mi croglia, as well as a broad range of cytokines, chemokines, antibodies, complement and other toxic substances. The appearance of such lesions is associated with clinical relapses. Recent detailed immunopathological studies of early, acute lesions revealed profound heterogeneity in the patterns of demyelination and the factors of the immune system involved. During remission, resolution of inflammation is the main factor which leads to clinical improvement of patients. However, the immune system can play a beneficial role at this stage, promoting remyelination perhaps by production of growth factors such as BDNF. In contrast, the progressive irreversible neurological deficit in multiple sclerosis is associated with neurodegenerative processes resulting in axonal and neuronal loss. The mechanisms behind damage to axons in multiple sclerosis lesions are poorly understood. However, the close proximity of areas with prominent axonal loss and areas containing inflammatory infiltrates (e. g., T cells, macrophages) suggest that axonal damage is closely associated with inflammation. Different soluble or cellular mediators of the immune response have been shown to damage axons in experimental systems, and these may be responsible for neurodegeneration in human disease.

Oligodendrocyte/myelin injury and repair as a function of the central nervous system environment

Multiple sclerosis is a chronic neurologic disorder considered to result from relatively selective immune mediated injury of central nervous system (CNS) myelin and/or its cell of origin, the oligodendrocyte (OGC). Constituents of both the innate and adaptive immune systems are potential contributors to this process. Endogenous (microglia) and infiltrating (macrophages, dendritic cells) constituents of the innate immune system serve as sensors of events occurring within the CNS; their response to such events underlies the extent of their interaction (chemoattraction, antigen presentation) with the components of the adaptive immune system (alphabeta T cells, B cells) and ultimately the extent of the resultant inflammatory response. Constituents of both the innate and adaptive immune system can serve as effectors of tissue injury. The susceptibility of specific types of neural cells to injury further reflects the extent to which immune mediators modulate expression of crucial molecules (adhesion molecules, receptors) involved in effector-target interactions. Ongoing interactions between the constituents of the immune system themselves and between these constituents and neural cells are important determinants of disease recurrence and/or progression. Conversely, these interactions also impact on the mechanisms involved in target protection and repair.

The mechanism of action of methylprednisolone in the treatment of multiple sclerosis

Methylprednisolone plays an important role in the current treatment of multiple sclerosis (MS), particularly in the acute phase of relapse. It acts in various ways to decrease the inflammatory cycle including: dampening the inflammatory cytokine cascade, inhibiting the activation of T cells, decreasing the extravasation of immune cells into the central nervous system, facilitating the apoptosis of activated immune cells, and indirectly decreasing the cytotoxic effects of nitric oxide and tumor necrosis factor alpha. This paper reviews the most recent observations on these mechanisms both to understand the disease mechanism and its treatment. As more becomes known about these mechanisms, it may become possible to design treatment regimes that are more specific towards both the individual and the disease state.

Protective autoimmunity and neuroprotection in inflammatory and noninflammatory neurodegenerative diseases

Autoimmune diseases are traditionally viewed as an outcome of a malfunctioning of the immune system, in which an individual's immune system reacts against the body's own proteins. In multiple sclerosis (MS), a disease of the white matter of the central nervous system (CNS), the attack is directed against myelin proteins. In this article we summarize a paradigm shift proposed by us in the perception of autoimmune disease. Observations by our group indicating that an autoimmune response is the body's mechanism for coping with CNS damage led us to suggest that all individuals are apparently endowed with a purposeful autoimmune response to CNS injuries, but have only limited inherent ability to control this response so that its effect will be beneficial. In animals susceptible to autoimmune diseases, the same autoimmune T cells are responsible both for neuroprotection and for disease development; the timing and strength of their activity will determine which of these effects is expressed. Individuals with non-inflammatory neurodegenerative diseases need a heightened autoimmunity. We discovered that autoimmunity could be boosted without risk of disease induction, even in susceptible strains, by the use of Copolymer-1 (Copaxone(R)), a weak agonist of a wide range of self-reactive T cells. Here we summarize the basic findings that led us to formulate the concept of protective autoimmunity, the mechanisms underlying its constitutive presence and its on/off regulation, and its therapeutic implications. We also offer an explanation for the commonly observed presence of cells and antibodies directed against self-components in healthy individuals.

Fibrin depletion decreases inflammation and delays the onset of demyelination in a tumor necrosis factor transgenic mouse model for multiple sclerosis

In multiple sclerosis, in which brain tissue becomes permeable to blood proteins, extravascular fibrin deposition correlates with sites of inflammatory demyelination and axonal damage. To examine the role of fibrin in neuroinflammatory demyelination, we depleted fibrin in two tumor necrosis factor transgenic mouse models of multiple sclerosis, transgenic lines TgK21 and Tg6074. In a genetic analysis, we crossed TgK21 mice into a fibrin-deficient background. TgK21fib(-/-) mice had decreased inflammation and expression of major histocompatibility complex class I antigens, reduced demyelination, and a lengthened lifespan compared with TgK21 mice. In a pharmacologic analysis, fibrin depletion, by using the snake venom ancrod, in Tg6074 mice also delayed the onset of inflammatory demyelination. Overall, these results indicate that fibrin regulates the inflammatory response in neuroinflammatory diseases. Design of therapeutic strategies based on fibrin depletion could potentially benefit the clinical course of demyelinating diseases such as multiple sclerosis.

[Determination of autoantibody for myelin antigens in the serum of patients HLA-DQB1*0602 with multiple sclerosis]

Multiple sclerosis (MS) is a chronic inflammatory demyelinating disease of the human central nervous system (CNS) mediated by autoimmune Th1 lymphocytes. We determined the serum levels of autoantibodies for myelin basic protein (MBP), proteolipid (PLP) and myelin oligodendrocyte glycoprotein sequence MOG 92-106 in a group of 54 healthy individuals and 26 MS patients expressing or not HLA-DQB1*0602. Regardless expression of the susceptibility allele DQB1*0602, MS patients presented marked (p<0.0001) IgG antibody production for MBP and MOG92-106. Yet, significant (p<0.0001) IgA antibody levels were mainly observed for PLP and MOG antigens. Our results suggest that other HLA class II alleles may be conferring susceptibility to MS in this population and influencing the pattern of immune recognition of encephalitogen antigens. Furthermore, distinct IgG and/or IgA autoantibody production may be contributing to the control or maintenance of the CNS inflammatory reaction.

A genome-wide German screen for linkage disequilibrium in multiple sclerosis

We report on a genome-wide screen for association with multiple sclerosis (MS) in the German population performed using 6000 microsatellite markers. These markers were typed in four DNA pools consisting of 234 MS patients (cases), 209 unrelated controls, 68 index patients from trio families and their 136 parents (related controls). Stringent analysis identified 11 markers showing apparent evidence for association. Five from regions previously identified in linkage studies and two from the MHC region on chromosome 6p21. These MHC markers are known to be in linkage disequilibrium with HLA class II alleles influencing susceptibility to MS. The identification of these markers serves as an important positive control.

Multiple sclerosis as a by-product of the failure to sustain protective autoimmunity: a paradigm shift

Autoimmune diseases are traditionally viewed as an outcome of a chaotic situation in which an individual's immune system reacts against the body's own proteins. In multiple sclerosis, a disease of the white matter of the central nervous system (CNS), the immune attack is directed against myelin proteins. In this article, the authors propose a paradigm shift in the perception of autoimmune disease. They suggest that an autoimmune disease may be viewed as a by-product of the malfunctioning of a physiological autoimmune response whose purpose is protective. The proposed view is based on observations by their group suggesting that an autoimmune response is the body's own mechanism for coping with CNS damage. According to this view, all individuals are endowed with the potential ability to evoke an autoimmune response to CNS injuries. However, the inherent ability to control this response so that its beneficial effect will be expressed is limited and is correlated with the individual's inherent ability to resist autoimmune disease induction. The same autoimmune T cells are responsible for neuroprotection and for disease development. In patients with CNS trauma or neurodegenerative disorders, it might be possible to gain maximal autoimmune protection and avoid autoimmune disease induction by boosting the immune response, using myelin-associated peptides that are nonpathogenic or antigens that simulate the activities of such peptides. In patients with multiple sclerosis and other neurodegenerative diseases, where the aim is to block the autoimmune disorder while deriving the potential benefit of the autoimmune response, the effect of treatment should be immunomodulatory rather than immunosuppressive. In this article, the authors present a novel concept of protective autoimmunity and propose that autoimmune disease is a by-product of failure to sustain it. They summarize the basic findings that led them to formulate the new concept and offer an explanation for the commonly observed presence of cells and antibodies directed against self-components in healthy individuals. The therapeutic implications of the new concept and their experimental findings are discussed.

Transient anti-CD154-mediated immunotherapy of ongoing relapsing experimental autoimmune encephalomyelitis induces long-term inhibition of disease relapses

Relapsing experimental autoimmune encephalomyelitis (R-EAE) is a Th1-mediated central nervous system (CNS) autoimmune disease with pathology similar to that of relapsing-remitting multiple sclerosis. Among recent therapeutic approaches to prevent or treat relapsing disease is the strategic blockade of the CD154-CD40 ligand pair interactions. We have previously shown that CD154 blockade at the peak of acute disease can, in the short term, inhibit spontaneous disease relapse and this is at least partly associated with the inhibition of T cell effector function and blockade of inflammatory cell recruitment to and/or retention in the CNS. However, little is understood about the long-term effects of CD154 blockade in the inhibition of immune responses to encephalitogenic antigens. Here we demonstrate that transient anti-CD154 blockade of CD154-CD40 interactions at the peak of acute phase of R-EAE resulted in significant long-term inhibition (by >80%) of clinical relapses and that clinical disease in those mice that did relapse was reduced in duration and severity compared to control antibody-treated mice. Additionally, we show that this strategy permanently inhibits DTH responses of T cells specific for relapse-associated encephalitogenic epitopes. Thus, transient CD154 blockade during ongoing disease has a long-term therapeutic efficacy in preventing disease relapses.

Dual action of glatiramer acetate (Cop-1) in the treatment of CNS autoimmune and neurodegenerative disorders

Protective autoimmunity is the body's defense mechanism against destructive self-compounds such as those commonly associated with neurodegenerative disorders. Autoimmune disease and neurodegenerative disorders can thus be viewed as two extreme manifestations of the same process. Therefore, when designing therapy, it is important to avoid an approach that will cure the one by invoking the other. One way to stop, or at least slow down, the progression of neurodegeneration without risking development of an autoimmune disease is by boosting protective autoimmunity in a well-controlled way. Copolymer 1 (Cop-1), an approved drug for the treatment of multiple sclerosis, can be used as a treatment for autoimmune diseases and as a therapeutic vaccine for neurodegenerative diseases. We propose that the protective effect of Cop-1 vaccination is obtained through a well-controlled inflammatory reaction, and that the activity of Cop-1 in driving this reaction derives from its ability to serve as a 'universal antigen' by weakly activating a wide spectrum of self-reactive T cells.

Multiple sclerosis: altered glutamate homeostasis in lesions correlates with oligodendrocyte and axonal damage

Glutamate excitotoxicity, recently demonstrated in an animal model of multiple sclerosis (MS), is evoked by altered glutamate homeostasis. In the present study, we investigated the major regulating factors in glutamate excitotoxicity by immunohistochemistry in MS and control white matter with markers for glutamate production (glutaminase), glutamate transport (GLAST, GLT-1 and EAAT-1), glutamate metabolism (glutamate dehydrogenase [GDH] and glutamine synthetase [GS]), axonal damage (SMI 32) and CNS cell types. Active MS lesions showed high-level glutaminase expression in macrophages and microglia in close proximity to dystrophic axons. Correlation between glutaminase expression and axonal damage was confirmed experimentally in animals. White matter from other inflammatory neurologic diseases displayed glutaminase reactivity, whereas normals and noninflammatory conditions showed none. All three glutamate transporters were expressed robustly, mainly on oligodendrocytes, in normal, control and MS white matter, except for GLT-1, which showed low-level expression around active MS lesions. GS and GDH were present in oligodendrocytes in normal and non-MS white matter but were absent from both active and chronic silent MS lesions, suggesting lasting metabolic impediments. Thus, imbalanced glutamate homeostasis contributes to axonal and oligodendroglial pathology in MS. Manipulation of this imbalance may have therapeutic import.

Normal CNS myelination in transgenic mice overexpressing MHC class I H-2L(d) in oligodendrocytes

In demyelinating diseases, such as multiple sclerosis, an upregulation of MHC class I expression is thought to contribute to oligodendrocyte/myelin damage. In order to investigate potential physiological consequences of upregulated MHC class I expression in oligodendrocytes, we generated transgenic mice that overexpress H-2L(d) under the control of the proteolipid protein (PLP) promoter (PLP-L(d) mice). We focused our studies on the MHC class I molecule H-2L(d), because of its unique intracellular transport characteristics. In the CNS of PLP-L(d) mice, H-2L(d) was expressed by oligodendrocytes. Furthermore, H-2L(d) protein was transported to and expressed on the surface of oligodendrocytes. Most importantly, this upregulation of MHC class I expression in the CNS of PLP-L(d) mice did not by itself result in a de- or dysmyelinating phenotype. These transgenic mice are likely to provide a unique and novel tool for the analysis of potential roles of MHC class I-mediated mechanisms in demyelinating pathologies.

Structural dynamics of oligodendrocyte lysis by perforin in culture: relevance to multiple sclerosis

The mechanism by which oligodendrocytes are depleted from active lesions in multiple sclerosis (MS) is not clear but many reports implicate a cytolytic process. The most applied animal model for MS, chronic relapsing experimental autoimmune encephalomyelitis (EAE), has been established in inbred strains of mice, especially SJL and PL. Studies on oligodendrocytes from these strains in vitro have been hampered to date by an inability to grow these cells from mouse CNS tissue. We report here a successful method to culture SJL mouse oligodendrocytes and have analyzed lysis of these cells in vitro mediated by the pore-forming protein, perforin, a candidate effector molecule in inflammatory demyelination. Cultures were exposed to murine perforin, 36-72 hemolytic U, for up to 2.5 hr and examined using the oligodendrocyte phenotypic markers O4, galactocerebroside and myelin basic protein (MBP), in addition to a membrane dye (DiI) and a marker of necrosis, propidium iodide, (PI). Cultures were imaged chronologically by phase contrast, immunofluorescence, digital, light and electron microscopy. Findings showed that the majority of oligodendrocytes were killed within 60-90 min via pore expansion and ultimately, membrane disruption. The structural features of the cellular damage comprised swelling of the cell body, fenestration and fragmentation of membranes and processes, cytoplasmic vacuolation and breakdown of the nuclear envelope. Astrocytes in the same system were relatively resistant to cell lysis. The above patterns of oligodendrocyte damage in SJL oligodendrocytes were reminiscent of patterns in the MS lesion, leaving us to conclude that perforin may play an important role in the human disease.

Determination of soluble ICAM-1 and TNFalphaR in the cerebrospinal fluid and serum levels in a population of Brazilian patients with relapsing-remitting multiple sclerosis

Cytokines and adhesion molecules have been implicated in the pathogenesis of multiple sclerosis (MS), a chronic inflammatory disease of the central nervous system. In this study we analyzed intrathecal (CSF) and serum levels of soluble intercellular adhesion molecule (ICAM-1) and TNFalphaR (60kD) from 20 patients with clinically definite MS during acute relapse or stable disease. Comparing to control groups of healthy individuals and patients with intervertebral herniated disc, MS patients showed increased levels (p< 0.001) of sICAM-1 and TNFalphaR in both serum and CSF samples. Regardless stage of disease there was no significant difference in the levels of sICAM-1 during acute relapse (657+/-124.9 ng/ml) or remission (627+/-36.2 ng/ml). A steady increase of TNFalphaR (60kD) in both serum and CSF, indicate the existence of a continuous inflammatory process within the brain tissue of MS patients despite absence of clinical signs of disease activity.