Axonal damage is reduced following glatiramer acetate treatment in C57/bl mice with chronic-induced experimental autoimmune encephalomyelitis

Glatiramer Acetate for the Treatment of Multiple Sclerosis: From First-Generation Therapy to Elucidation of Immunomodulation and Repair

Multiple sclerosis (MS) is a chronic inflammatory demyelinating and neurodegenerative disease of the central nervous system (CNS), with a putative autoimmune origin and complex pathogenesis. Modification of the natural history of MS by reducing relapses and slowing disability accumulation was first attained in the 1990 s with the development of the first-generation disease-modifying therapies. Glatiramer acetate (GA), a copolymer of L-alanine, L-lysine, L-glutamic acid, and L-tyrosine, was discovered due to its ability to suppress the animal model of MS, experimental autoimmune encephalomyelitis. Extensive clinical trials and long-term assessments established the efficacy and the safety of GA. Furthermore, studies of the therapeutic processes induced by GA in animal models and in MS patients indicate that GA affects various levels of the innate and the adaptive immune response, generating deviation from proinflammatory to anti-inflammatory pathways. This includes competition for binding to antigen presenting cells; driving dendritic cells, monocytes, and B-cells toward anti-inflammatory responses; and stimulating T-helper 2 and T-regulatory cells. The immune cells stimulated by GA reach the CNS and secrete in situ anti-inflammatory cytokines alleviating the pathological processes. Furthermore, cumulative findings reveal that in addition to its immunomodulatory effect, GA promotes neuroprotective repair processes such as neurotrophic factors secretion, remyelination, and neurogenesis. This review aims to provide an overview of MS pathology diagnosis and treatment as well as the diverse mechanism of action of GA. SIGNIFICANCE STATEMENT: Understanding the complex MS immune pathogenesis provided multiple targets for therapeutic intervention, resulting in a plethora of agents, with various mechanisms of action, efficacy, and safety profiles. However, promoting repair beyond the body's limited spontaneous extent is still a major challenge. GA, one of the first approved disease-modifying therapies, induces diverse immunomodulatory effects. Furthermore, GA treatment results in elevated neurotrophic factors secretion, remyelination and neurogenesis, supporting the notion that immunomodulatory treatment can support in situ a growth-promoting and repair environment.

The relevance of BDNF for neuroprotection and neuroplasticity in multiple sclerosis

Background

Neuroplasticity as a mechanism to overcome central nervous system injury resulting from different neurological diseases has gained increasing attention in recent years. However, deficiency of these repair mechanisms leads to the accumulation of neuronal damage and therefore long-term disability. To date, the mechanisms by which remyelination occurs and why the extent of remyelination differs interindividually between multiple sclerosis patients regardless of the disease course are unclear. A member of the neurotrophins family, the brain-derived neurotrophic factor (BDNF) has received particular attention in this context as it is thought to play a central role in remyelination and thus neuroplasticity, neuroprotection, and memory.

Objective

To analyse the current literature regarding BDNF in different areas of multiple sclerosis and to provide an overview of the current state of knowledge in this field.

Conclusion

To date, studies assessing the role of BDNF in patients with multiple sclerosis remain inconclusive. However, there is emerging evidence for a beneficial effect of BDNF in multiple sclerosis, as studies reporting positive effects on clinical as well as MRI characteristics outweighed studies assuming detrimental effects of BDNF. Furthermore, studies regarding the Val66Met polymorphism have not conclusively determined whether this is a protective or harmful factor in multiple sclerosis, but again most studies hypothesized a protective effect through modulation of BDNF secretion and anti-inflammatory effects with different effects in healthy controls and patients with multiple sclerosis, possibly due to the pro-inflammatory milieu in patients with multiple sclerosis. Further studies with larger cohorts and longitudinal follow-ups are needed to improve our understanding of the effects of BDNF in the central nervous system, especially in the context of multiple sclerosis.

JAB1 deletion in oligodendrocytes causes senescence-induced inflammation and neurodegeneration in mice

Oligodendrocytes are the primary target of demyelinating disorders and progressive neurodegenerative changes may evolve in the CNS. DNA damage and oxidative stress are considered key pathogenic events, but the underlying molecular mechanisms remain unclear. Moreover, animal models do not fully recapitulate human diseases, complicating the path to effective treatments. Here we report that mice with cell autonomous deletion of the nuclear COP9 signalosome component CSN5 (JAB1) in oligodendrocytes develop DNA damage and defective DNA repair in myelinating glial cells. Interestingly, oligodendrocytes lacking JAB1 expression underwent a senescence-like phenotype that fostered chronic inflammation and oxidative stress. These mutants developed progressive CNS demyelination, microglia inflammation and neurodegeneration, with severe motor deficits and premature death. Notably, blocking microglia inflammation did not prevent neurodegeneration, whereas the deletion of p21CIP1 but not p16INK4a pathway ameliorated the disease. We suggest that senescence is key to sustaining neurodegeneration in demyelinating disorders and may be considered a potential therapeutic target.

Molecular Effects of FDA-Approved Multiple Sclerosis Drugs on Glial Cells and Neurons of the Central Nervous System

Multiple sclerosis (MS) is characterized by peripheral and central inflammatory features, as well as demyelination and neurodegeneration. The available Food and Drug Administration (FDA)-approved drugs for MS have been designed to suppress the peripheral immune system. In addition, however, the effects of these drugs may be partially attributed to their influence on glial cells and neurons of the central nervous system (CNS). We here describe the molecular effects of the traditional and more recent FDA-approved MS drugs Fingolimod, Dimethyl Fumarate, Glatiramer Acetate, Interferon-β, Teriflunomide, Laquinimod, Natalizumab, Alemtuzumab and Ocrelizumab on microglia, astrocytes, neurons and oligodendrocytes. Furthermore, we point to a possible common molecular effect of these drugs, namely a key role for NFκB signaling, causing a switch from pro-inflammatory microglia and astrocytes to anti-inflammatory phenotypes of these CNS cell types that recently emerged as central players in MS pathogenesis. This notion argues for the need to further explore the molecular mechanisms underlying MS drug action.

Reboxetine Treatment Reduces Neuroinflammation and Neurodegeneration in the 5xFAD Mouse Model of Alzheimer's Disease: Role of CCL2

The reduction of brain noradrenaline levels is associated to the initiation of Alzheimer's disease and contributes to its progression. This seems to be due mainly to the anti-neuroinflammatory actions of noradrenaline. The analysis of noradrenaline effects on brain cells demonstrates that it also regulates the production of the chemokine CCL2. In the present study, we analyzed the effect of the selective noradrenaline reuptake inhibitor, reboxetine, on the inflammatory and neurodegenerative alterations present in 5xFAD mice, and how the genetic removal of CCL2 affects reboxetine actions. We observed that the removal of CCL2 reduced the memory impairments in 5xFAD mice as well as the neuroinflammatory response, the accumulation of amyloid beta plaques, and the degeneration of neurons in the brain cortex. The administration of reboxetine with osmotic pumps for 28 days also resulted in anti-inflammatory and neuroprotective changes in 5xFAD mice, even in the absence of CCL2. Yet, 6-month-old CCL2KO mice presented a significant degree of neuroinflammation and neuronal damage. These findings indicate that reboxetine treatment prevents the brain alterations caused by prolonged overproduction of amyloid beta, being these effects independent of CCL2, which is a mediator of the damage caused by amyloid beta in the brain cortex, but necessary for the prevention of the development of neurodegeneration in normal healthy conditions.

The Evolving Mechanisms of Action of Glatiramer Acetate

Glatiramer acetate (GA) is a synthetic amino acid copolymer that is approved for treatment of relapsing remitting multiple sclerosis (RRMS) and clinically isolated syndrome (CIS). GA reduces multiple sclerosis (MS) disease activity and has shown comparable efficacy with high-dose interferon-β. The mechanism of action (MOA) of GA has long been an enigma. Originally, it was recognized that GA treatment promoted expansion of GA-reactive T-helper 2 and regulatory T cells, and induced the release of neurotrophic factors. However, GA treatment influences both innate and adaptive immune compartments, and it is now recognized that antigen-presenting cells (APCs) are the initial cellular targets for GA. The anti-inflammatory (M2) APCs induced following treatment with GA are responsible for the induction of anti-inflammatory T cells that contribute to its therapeutic benefit. Here, we review studies that have shaped our current understanding of the MOA of GA.

On the horizon: possible neuroprotective role for glatiramer acetate

Inflammation and neurodegeneration characterize the pathogenesis of multiple sclerosis (MS). Slow axonal degeneration, rather than acute inflammation, is considered the cause of chronic disability in MS. The signs of acute axonal damage and loss have been shown to occur early in the lesion development of patients with chronic MS and often correlate with demyelination and inflammation. While immune activity in the central nervous system has traditionally been considered to be a detrimental event in MS, recent studies have found that autoimmune T cells may play an important role in protecting neurons from the ongoing spreading damage. Neuroprotectio n in MS is a new and evolving concept, and many questions remain with regard to potential targets for therapeutic intervention. Preliminary studies, both in animals and in humans, have suggested that glatiramer acetate (GA) may confer neuroprotective activity in addition to bystander suppression. Additional research is needed to determine if these promising neuroprotective effects correlate with the long-term effect of G A in MS.

Acute axonal damage in three different murine models of multiple sclerosis: A comparative approach

Axonal damage has been identified as a significant contributor to permanent clinical disability in multiple sclerosis. In the context of demyelinating disorders, this destructive event can be the result of inflammation, demyelination and/or the activation of innate defense cells such as microglia or monocytes. The relative contribution of each of these variables to acute axonal injury is, however, unknown. In the present study, we compared the extent of acute axonal damage in three different murine demyelination models using anti-amyloid precursor protein (APP) immunohistochemistry. T cell dependent (MOG_35-55-induced experimental autoimmune encephalomyelitis (EAE)) as well as T cell independent demyelination models (cuprizone- and lysolecithin-induced demyelination) were used. APP⁺ spheroids were present in all three experimental demyelination models. The number of APP⁺ spheroids was highest within LPC-induced lesions. Equal amounts were found in the spinal cord of MOG_35-55-EAE animals and the corpus callosum of cuprizone-intoxicated animals. Moreover, we detected increased immunoreactivity of the pre-synaptic protein vesicular glutamate transporter 1 (VGluT1) in demyelinated foci. VGluT1-staining revealed long stretched, ovoid-like axonal structures which co-localized with APP. In summary, we showed that acute axonal damage is evident under various experimental demyelination paradigms. Furthermore, disturbed axonal transport mechanisms, which are responsible for intra-axonal APP accumulation, do not only disturb APP, but also the transport of other synaptic proteins. These results indicate that, despite differences in their characteristics, all three models may serve as valid and suitable systems for investigating responsible mechanisms of axonal damage and potential protective strategies.

A monoclonal natural human IgM protects axons in the absence of remyelination

BACKGROUND

Whereas demyelination underlies early neurological symptoms in multiple sclerosis (MS), axonal damage is considered critical for permanent chronic deficits. Intracerebral infection of susceptible mouse strains with Theiler's murine encephalomyelitis virus (TMEV) results in chronic induced demyelinating disease (TMEV-IDD) with progressive axonal loss and neurologic dysfunction similar to progressive forms of MS. We previously reported that treatment of chronic TMEV-IDD mice with a neurite outgrowth-promoting natural human antibody, HIgM12, improved brainstem NAA concentrations and preserved functional motor activity. In order to translate this antibody toward clinical trial, we generated a fully human recombinant form of HIgM12, rHIgM12, determined the optimal in vivo dose for functional improvement in TMEV-IDD, and evaluated the functional preservation of descending spinal cord axons by retrograde labeling.

FINDINGS

SJL/J mice at 45 to 90 days post infection (dpi) were studied. A single intraperitoneal dose of 0.25 mg/kg of rHIgM12 per mouse is sufficient to preserve motor function in TMEV-IDD. The optimal dose was 10 mg/kg. rHIgM12 treatment protected the functional transport in spinal cord axons and led to 40 % more Fluoro-Gold-labeled brainstem neurons in retrograde transport studies. This suggests that axons are not only present but also functionally competent. rHIgM12-treated mice also contained more mid-thoracic (T6) spinal cord axons than controls.

CONCLUSIONS

This study confirms that a fully human recombinant neurite outgrowth-promoting monoclonal IgM is therapeutic in a model of progressive MS using multiple reparative readouts. The minimum effective dose is similar to that of a remyelination-promoting monoclonal human IgM discovered by our group that is presently in clinical trials for MS.

[A place of first-line drugs in treatment of multiple sclerosis]

A rapidly changing set of drugs for treatment of multiple sclerosis (MS) leads to the necessity of searching for predictors of their efficacy. Understanding of pathogenetic processes in MS and mechanisms of action of different drugs play an important role in the search for markers of potential responders. The author analyses the presently accumulated information on the original drug copaxone (glatiramer acetate) including current concepts on the mechanism of action, long-term safety and efficacy. Data on the frequency and significance of adverse effects during treatment with glatiramer acetate as well as on the influence of the drug on pregnancy, postpartum course of MS and development of the infant who received glatiramer acetate prenatally compared to other disease-modifying drugs are presented.

Prior regular exercise improves clinical outcome and reduces demyelination and axonal injury in experimental autoimmune encephalomyelitis

Although previous studies have shown that forced exercise modulates inflammation and is therapeutic acutely for experimental autoimmune encephalomyelitis (EAE), the long-term benefits have not been evaluated. In this study, we investigated the effects of preconditioning exercise on the clinical and pathological progression of EAE. Female C57BL/6 mice were randomly assigned to either an exercised (Ex) or unexercised (UEx) group and all of them were induced for EAE. Mice in the Ex group had an attenuated clinical score relative to UEx mice throughout the study. At 42 dpi, flow cytometry analysis showed a significant reduction in B cells, CD4(+) T cells, and CD8(+) T cells infiltrating into the spinal cord in the Ex group compared to UEx. Ex mice also had a significant reduction in myelin damage with a corresponding increase in proteolipid protein expression. Finally, Ex mice had a significant reduction in axonal damage. Collectively, our study demonstrates for the first time that a prolonged and forced preconditioning protocol of exercise improves clinical outcome and attenuates pathological hallmarks of EAE at chronic disease. In this study, we show that a program of 6 weeks of preconditioning exercise promoted a significant reduction of cells infiltrating into the spinal cord, a significant reduction in myelin damage and a significant reduction in axonal damage in experimental autoimmune encephalomyelitis (EAE) mice at 42 dpi. Collectively, our study demonstrates for the first time that a preconditioning protocol of exercise improves clinical outcome and attenuates pathological hallmarks of EAE at chronic disease.

Therapeutic strategies in multiple sclerosis: a focus on neuroprotection and repair and relevance to schizophrenia

Multiple sclerosis is the leading nontraumatic cause of neurologic disability in young adults. The need to prevent neurodegeneration and promote repair in multiple sclerosis (MS) has gained increasing interest in the last decade leading to the search and development of pharmacological agents and non-pharmacologic strategies able to target not only the inflammatory but also the neurodegenerative component of the disease. This paper will provide an overview of the therapeutics currently employed in MS, with a focus on their potential neuroprotective effects and on the MRI methods employed to detect and monitor in-vivo neuroprotection and repair and the relevance of this information to schizophrenia investigation and treatment.

Restoration of axon conduction and motor deficits by therapeutic treatment with glatiramer acetate

Glatiramer acetate (GA; Copaxone) is an approved drug for the treatment of multiple sclerosis (MS). The underlying multifactorial anti-inflammatory, neuroprotective effect of GA is in the induction of reactive T cells that release immunomodulatory cytokines and neurotrophic factors at the injury site. These GA-induced cytokines and growth factors may have a direct effect on axon function. Building on previous findings that suggest a neuroprotective effect of GA, we assessed the therapeutic effects of GA on brain and spinal cord pathology and functional correlates using the chronic experimental autoimmune encephalomyelitis (EAE) mouse model of MS. Therapeutic regimens were utilized based on promising prophylactic efficacy. More specifically, C57BL/6 mice were treated with 2 mg/mouse/day GA for 8 days beginning at various time points after EAE post-induction day 15, yielding a thorough, clinically relevant assessment of GA efficacy within the context of severe progressive disease. Therapeutic treatment with GA significantly decreased clinical scores and improved rotorod motor performance in EAE mice. These functional improvements were supported by an increase in myelinated axons and fewer amyloid precursor protein-positive axons in the spinal cords of GA-treated EAE mice. Furthermore, therapeutic GA decreased microglia/macrophage and T cell infiltrates and increased oligodendrocyte numbers in both the spinal cord and corpus callosum of EAE mice. Finally, GA improved callosal axon conduction and nodal protein organization in EAE. Our results demonstrate that therapeutic GA treatment has significant beneficial effects in a chronic mouse model of MS, in which its positive effects on both myelinated and non-myelinated axons results in improved axon function.

Immunomodulation neuroprotection and remyelination - the fundamental therapeutic effects of glatiramer acetate: a critical review

Multiple sclerosis (MS) is a multifaceted heterogeneous disease with various patterns of tissue damage. In addition to inflammation and demyelination, widespread axonal and neuronal pathologies are central components of this disease. MS therapies aim to restrain the pathological processes, enhance protective mechanisms, and prevent disease progression. The amino acid copolymer, glatiramer acetate (GA, Copaxone), an approved treatment for MS, has a unique mode of action. Evidence from the animal model experimental autoimmune encephalomyelitis (EAE) and from MS patients indicates that GA affects various levels of the innate and the adaptive immune response, inducing deviation from the pro-inflammatory to the anti-inflammatory pathways. This includes competition for the binding of antigen presenting cells, driving dendritic cells, monocytes, and B-cells towards anti-inflammatory responses, induction of Th2/3 and T-regulatory cells, and downregulating of both Th1 and Th-17 cells. The immune cells induced by GA reach the inflamed disease organ and secrete in situ anti-inflammatory cytokines alleviating the pathological processes. Furthermore, cumulative findings have revealed that in addition to its immunomodulatory activities GA promotes neuroprotective repair processes such as neurotrophic factors secretion and remyelination. This review aims to provide a comprehensive overview on the diverse mechanism of action of GA in EAE/MS, in particular on the in situ effect of GA and its ability to generate neuroprotection and repair in the CNS. In view of its immunomodulatory activity, the beneficial effects of GA in various models of additional autoimmune related pathologies, such as immune rejection and inflammatory bowel disease (IBD), are also presented.

Altered expression of oligodendrocyte and neuronal marker genes predicts the clinical onset of autoimmune encephalomyelitis and indicates the effectiveness of multiple sclerosis-directed therapeutics

Experimental autoimmune encephalomyelitis (EAE) is a valuable model for studying immunopathology in multiple sclerosis (MS) and for exploring the interface between autoimmune responses and CNS tissue that ultimately leads to lesion development. In this study, we measured gene expression in mouse spinal cord during myelin oligodendrocyte gp35-55 peptide-induced EAE, using quantitative RT-PCR, to identify gene markers that monitor individual hallmark pathological processes. We defined a small panel of genes whose longitudinal expression patterns provided insight into the timing, interrelationships, and mechanisms of individual disease processes and the efficacy of therapeutics for the treatment of MS. Earliest transcriptional changes were upregulation of Il17a and sharp downregulation of neuronal and oligodendrocyte marker genes preceding clinical disease onset, whereas neuroinflammatory markers progressively increased as symptoms and tissue lesions developed. EAE-induced gene-expression changes were not altered in mice deficient in IKKβ in cells of the myeloid lineage compared with controls, but the administration of a selective inhibitor of soluble TNF to mice from the day of immunization delayed changes in the expression of innate inflammation, myelin, and neuron markers from the presymptomatic phase. Proof of principle that the gene panel shows drug screening potential was obtained using a well-established MS therapeutic, glatiramer acetate. Prophylactic treatment of mice with glatiramer acetate normalized gene marker expression, and this correlated with the level of therapeutic success. These results show that neurons and oligodendrocytes are highly sensitive to CNS-directed autoimmunity before the development of clinical symptoms and immunopathology and reveal a role for soluble TNF in mediating the earliest changes in gene expression.

The mechanism of action of glatiramer acetate in multiple sclerosis and beyond

In multiple sclerosis (MS) and its animal model experimental autoimmune encephalomyelitis (EAE), the immune system reacts again self myelin constitutes in the central nervous system (CNS), initiating a detrimental inflammatory cascade that leads to demyelination as well as axonal and neuronal pathology. The amino acid copolymer glatiramer acetate (GA, Copaxone) is an approved first-line treatment for MS that has a unique mode of action. Accumulated evidence from EAE-induced animals and from MS patients indicates that GA affects various levels of the innate and the adaptive immune response, generating deviation from the pro-inflammatory to the anti-inflammatory pathway. This review aims to provide a comprehensive perspective on the diverse mechanism of action of GA in EAE/MS, in particular on the in situ immunomodulatory effect of GA and its ability to generate neuroprotective repair consequences in the CNS. In view of its immunomodulatory activity, the beneficial effect of GA in various models of other autoimmune related pathologies, such as immune rejection and inflammatory bowel disease (IBD) is noteworthy.

Opioid growth factor arrests the progression of clinical disease and spinal cord pathology in established experimental autoimmune encephalomyelitis

An endogenous neuropeptide, opioid growth factor (OGF), chemically termed [Met(5)]-enkephalin, arrested the progression of established disease in a mouse model of multiple sclerosis (MS) called experimental autoimmune encephalomyelitis (EAE). This study treated mice who demonstrated 2 consecutive days of behavioral decline following injections of myelin oligodendrocyte glycoprotein (MOG) with daily injections of OGF (10mg/kg) or saline (0.1ml) for 40 days. Within 6 days of OGF treatment, mice initially demonstrating clinical signs of EAE had significant reductions (45% reduction) in their behavioral scores relative to EAE mice receiving saline. Behavior was attenuated for the entire 40-day period with mice receiving OGF showing only limp tails and wobbly gait in comparison to saline-treated EAE mice who displayed paralysis of one or more limbs. Neuropathological studies revealed that OGF treatment initiated after the appearance of disease reduced the number of activated astrocytes and damaged neurons, decreased demyelination, and inhibited T cell proliferation. These results demonstrate that OGF can halt the progression of established EAE, return aberrant pain sensitivity to normal levels, inhibit proliferation of T cells and astrocytes, and prevent further spinal cord pathology. The data extend our observations that OGF given at the time of disease induction prevented disease onset, reduced the severity of clinical signs of disease, and reversed neurological deficits in a non-toxic manner. Our data substantiate the role of the OGF-OGFr axis in EAE and support the use of OGF as a biotherapy for MS.

Experimental autoimmune encephalomyelitis (EAE) as a model for multiple sclerosis (MS)

Experimental autoimmune encephalomyelitis (EAE) is the most commonly used experimental model for the human inflammatory demyelinating disease, multiple sclerosis (MS). EAE is a complex condition in which the interaction between a variety of immunopathological and neuropathological mechanisms leads to an approximation of the key pathological features of MS: inflammation, demyelination, axonal loss and gliosis. The counter-regulatory mechanisms of resolution of inflammation and remyelination also occur in EAE, which, therefore can also serve as a model for these processes. Moreover, EAE is often used as a model of cell-mediated organ-specific autoimmune conditions in general. EAE has a complex neuropharmacology, and many of the drugs that are in current or imminent use in MS have been developed, tested or validated on the basis of EAE studies. There is great heterogeneity in the susceptibility to the induction, the method of induction and the response to various immunological or neuropharmacological interventions, many of which are reviewed here. This makes EAE a very versatile system to use in translational neuro- and immunopharmacology, but the model needs to be tailored to the scientific question being asked. While creating difficulties and underscoring the inherent weaknesses of this model of MS in straightforward translation from EAE to the human disease, this variability also creates an opportunity to explore multiple facets of the immune and neural mechanisms of immune-mediated neuroinflammation and demyelination as well as intrinsic protective mechanisms. This allows the eventual development and preclinical testing of a wide range of potential therapeutic interventions.

Glatiramer acetate in the treatment of multiple sclerosis: emerging concepts regarding its mechanism of action

Glatiramer acetate is a synthetic, random copolymer widely used as a first-line agent for the treatment of relapsing-remitting multiple sclerosis (MS). While earlier studies primarily attributed its clinical effect to a shift in the cytokine secretion of CD4+ T helper (T(h)) cells, growing evidence in MS and its animal model, experimental autoimmune encephalomyelitis (EAE), suggests that glatiramer acetate treatment is associated with a broader immunomodulatory effect on cells of both the innate and adaptive immune system. To date, glatiramer acetate-mediated modulation of antigen-presenting cells (APC) such as monocytes and dendritic cells, CD4+ T(h) cells, CD8+ T cells, Foxp3+ regulatory T cells and antibody production by plasma cells have been reported; in addition, most recent investigations indicate that glatiramer acetate treatment may also promote regulatory B-cell properties. Experimental evidence suggests that, among these diverse effects, a fostering interplay between anti-inflammatory T-cell populations and regulatory type II APC may be the central axis in glatiramer acetate-mediated immune modulation of CNS autoimmune disease. Besides altering inflammatory processes, glatiramer acetate could exert direct neuroprotective and/or neuroregenerative properties, which could be of relevance for the treatment of MS, but even more so for primarily neurodegenerative disorders, such as Alzheimer's or Parkinson's disease. In this review, we provide a comprehensive and critical overview of established and recent findings aiming to elucidate the complex mechanism of action of glatiramer acetate.

Improving the translational hit of experimental treatments in multiple sclerosis

BACKGROUND

In other neurological diseases, the failure to translate pre-clinical findings to effective clinical treatments has been partially attributed to bias introduced by shortcomings in the design of animal experiments.

OBJECTIVES

Here we evaluate published studies of interventions in animal models of multiple sclerosis for methodological design and quality and to identify candidate interventions with the best evidence of efficacy.

METHODS

A systematic review of the literature describing experiments testing the effectiveness of interventions in animal models of multiple sclerosis was carried out. Data were extracted for reported study quality and design and for neurobehavioural outcome. Weighted mean difference meta-analysis was used to provide summary estimates of the efficacy for drugs where this was reported in five or more publications.

RESULTS

The use of a drug in a pre-clinical multiple sclerosis model was reported in 1152 publications, of which 1117 were experimental autoimmune encephalomyelitis (EAE). For 36 interventions analysed in greater detail, neurobehavioural score was improved by 39.6% (95% CI 34.9-44.2%, p < 0.001). However, few studies reported measures to reduce bias, and those reporting randomization or blinding found significantly smaller effect sizes.

CONCLUSIONS

EAE has proven to be a valuable model in elucidating pathogenesis as well as identifying candidate therapies for multiple sclerosis. However, there is an inconsistent application of measures to limit bias that could be addressed by adopting methodological best practice in study design. Our analysis provides an estimate of sample size required for different levels of power in future studies and suggests a number of interventions for which there are substantial animal data supporting efficacy.

The immunomodulator glatiramer acetate influences spinal motoneuron plasticity during the course of multiple sclerosis in an animal model

The immunomodulador glatiramer acetate (GA) has been shown to significantly reduce the severity of symptoms during the course of multiple sclerosis and in its animal model--experimental autoimmune encephalomyelitis (EAE). Since GA may influence the response of non-neuronal cells in the spinal cord, it is possible that, to some extent, this drug affects the synaptic changes induced during the exacerbation of EAE. In the present study, we investigated whether GA has a positive influence on the loss of inputs to the motoneurons during the course of EAE in rats. Lewis rats were subjected to EAE associated with GA or placebo treatment. The animals were sacrificed after 15 days of treatment and the spinal cords processed for immunohistochemical analysis and transmission electron microscopy. A correlation between the synaptic changes and glial activation was obtained by performing labeling of synaptophysin and glial fibrillary acidic protein using immunohistochemical analysis. Ultrastructural analysis of the terminals apposed to alpha motoneurons was also performed by electron transmission microscopy. Interestingly, although the GA treatment preserved synaptophysin labeling, it did not significantly reduce the glial reaction, indicating that inflammatory activity was still present. Also, ultrastructural analysis showed that GA treatment significantly prevented retraction of both F and S type terminals compared to placebo. The present results indicate that the immunomodulator GA has an influence on the stability of nerve terminals in the spinal cord, which in turn may contribute to its neuroprotective effects during the course of multiple sclerosis.

Glatiramer acetate reduces the risk for experimental cerebral malaria: a pilot study

Background

Cerebral malaria (CM) is associated with high mortality and morbidity caused by a high rate of transient or persistent neurological sequelae. Studies on immunomodulatory and neuroprotective drugs as ancillary treatment in murine CM indicate promising potential. The current study was conducted to evaluate the efficacy of glatiramer acetate (GA), an immunomodulatory drug approved for the treatment of relapsing remitting multiple sclerosis, in preventing the death of C57Bl/6J mice infected with Plasmodium berghei ANKA.

Methods and Results

GA treatment led to a statistically significant lower risk for developing CM (57.7% versus 84.6%) in treated animals. The drug had no effect on the course of parasitaemia. The mechanism of action seems to be an immunomodulatory effect since lower IFN-gamma levels were observed in treated animals in the early course of the disease (day 4 post-infection) which also led to a lower number of brain sequestered leukocytes in treated animals. No direct neuro-protective effect such as an inhibition of apoptosis or reduction of micro-bleedings in the brain was found.

Conclusion

These findings support the important role of the host immune response in the pathophysiology of murine CM and might lead to the development of new adjunctive treatment strategies.

Protective autoimmunity in the nervous system

The immune system can play both detrimental and beneficial roles in the nervous system. Multiple arms of the immune system, including T cells, B cells, NK cells, mast cells, macrophages, dendritic cells, microglia, antibodies, complement and cytokines participate in limiting damage to the nervous system during toxic, ischemic, hemorrhagic, infective, degenerative, metabolic and immune-mediated insults and also assist in the process of repair after injury has occurred. Immune cells have been shown to produce neurotrophic growth factors and interact with neurons and glial cells to preserve them from injury and stimulate growth and repair. The immune system also appears to participate in proliferation of neural progenitor stem cells and their migration to sites of injury. Neural stem cells can also modify the immune response in the central and peripheral nervous system to enhance neuroprotective effects. Evidence for protective and reparative functions of the immune system has been found in diverse neurologic diseases including traumatic injury, ischemic and hemorrhagic stroke, multiple sclerosis, infection, and neurodegenerative diseases (Alzheimer's disease, Parkinson's disease and amyotrophic lateral sclerosis). Existing therapies including glatiramer acetate, interferon-beta and immunoglobulin have been shown to augment the protective and regenerative aspects of the immune system in humans, and other experimental interventions such as vaccination, minocycline, antibodies and neural stem cells, have shown promise in animal models of disease. The beneficent aspects of the immune response in the nervous system are beginning to be appreciated and their potential as pharmacologic targets in neurologic disease is being explored.

Prevention of axonal injury using calpain inhibitor in chronic progressive experimental autoimmune encephalomyelitis

Axonal injury is the major correlate of permanent disability in neurodegenerative diseases such as multiple sclerosis (MS), especially in secondary-progressive MS which follows relapsing-remitting disease course. Proteolytic enzyme, calpain, is a potential candidate for causing axonal injury. Most current treatment options only target the inflammatory component of MS. Previous work using calpain inhibitor CYLA in our laboratory showed significant reduction in clinical sign, demyelination and tissue calpain content in acute experimental autoimmune encephalomyelitis (EAE). Here we evaluated markers of axonal injury (amyloid precursor protein, Na(v)1.6 channels), neuronal calpain content and the effect of CYLA on axonal protection using histological methods in chronic EAE [myelin oligodendrocyte glycoprotein (MOG)-induced disease model of MS]. Intraperitoneal application of CYLA (2 mg/mouse/day) significantly reduced the clinical signs, tissue calpain content, demyelination and inflammatory infiltration of EAE. Similarly, markers for axonal injury were barely detectable in the treated mice. Thus, this novel drug, which markedly suppresses the disease course, axonal injury and its progression, is a candidate for the treatment of a neurodegenerative disease such as multiple sclerosis.

An experimental model of secondary progressive multiple sclerosis that shows regional variation in gliosis, remyelination, axonal and neuronal loss

Multiple sclerosis (MS) represents a considerable challenge to experimentally model due to its twin pathologies of inflammatory demyelination and neurodegeneration along with its multifocal and multiphasic nature. Experimental autoimmune encephalomyelitis (EAE) in Biozzi ABH mice has previously been shown to reproduce many clinical features also found in secondary progressive MS. In this study we sought to characterise the pathology of chronic EAE in ABH mice. In addition to marked gliosis, we report substantial demyelination, remyelination and axonal and neuronal loss. Together with the clinical pattern, our findings identify chronic EAE as an excellent model of secondary progressive multiple sclerosis.

Demyelination arrest and remyelination induced by glatiramer acetate treatment of experimental autoimmune encephalomyelitis

The interplay between demyelination and remyelination is critical in the progress of multiple sclerosis (MS) and its animal model, experimental autoimmune encephalomyelitis (EAE). In the present study, we explored the capacity of glatiramer acetate (GA, Copaxone) to affect the demyelination process and/or lead to remyelination in mice inflicted by chronic EAE, using both scanning electron microscopy and immunohistological methods. Spinal cords of untreated EAE mice revealed substantial demyelination accompanied by tissue destruction and axonal loss. In contrast, in spinal cords of GA-treated mice, in which treatment started concomitantly with disease induction (prevention), no pathology was observed. Moreover, when treatment was initiated after the appearance of clinical symptoms (suppression) or even in the chronic disease phase (delayed suppression) when substantial demyelination was already manifested, it resulted in a significant decrease in the pathological damage. Detection of oligodendrocyte progenitor cells (OPCs) expressing the NG2 or O4 markers via colocalization with the proliferation marker BrdU indicated their elevated levels in spinal cords of GA-treated mice. The mode of action of GA in this system is attributed to increased proliferation, differentiation, and survival of OPCs along the oligodendroglial maturation cascade and their recruitment into injury sites, thus enhancing repair processes in situ.

Glatiramer acetate: evidence for a dual mechanism of action

Glatiramer acetate is a disease-modifying drug approved for the treatment of relapsing-remitting multiple sclerosis. Since its discovery almost four decades ago, and in particular since the observation of its beneficial clinical effects in the late 1980s and early 1990s, numerous data have been generated and contribute pieces of a puzzle to help explain the mechanism of action of glatiramer acetate. Two major themes have emerged, namely (i) the induction of glatiramer acetate-reactive TH2 immunoregulatory cells, and (ii) the stimulation of neurotrophin secretion in the central nervous system that may promote neuronal repair.

Remyelination protects axons from demyelination-associated axon degeneration

In multiple sclerosis, demyelination of the CNS axons is associated with axonal injury and degeneration, which is now accepted as the major cause of neurological disability in the disease. Although the kinetics and the extent of axonal damage have been described in detail, the mechanisms by which it occurs are as yet unclear; one suggestion is failure of remyelination. The goal of this study was to test the hypothesis that failure of prompt remyelination contributes to axonal degeneration following demyelination. Remyelination was inhibited by exposing the brain to 40 Gy of X-irradiation prior to cuprizone intoxication and this resulted in a significant increase in the extent of axonal degeneration and loss compared to non-irradiated cuprizone-fed mice. To exclude the possibility that this increase was a consequence of the X-irradiation and to highlight the significance of remyelination, we restored remyelinating capacity to the X-irradiated mouse brain by transplanting of GFP-expressing embryo-derived neural progenitors. Restoring the remyelinating capacity in these mice resulted in a significant increase in axon survival compared to non-transplanted, X-irradiated cuprizone-intoxicated mice. Our results support the concept that prompt remyelination protects axons from demyelination-associated axonal loss and that remyelination failure contributes to the axon loss that occurs in multiple sclerosis.

Immunological aspects of axon injury in multiple sclerosis

The role of immune-mediated axonal injury in the induction of nonremitting functional deficits associated with multiple sclerosis is an area of active research that promises to substantially alter our understanding of the pathogenesis of this disease and modify or change our therapeutic focus. This review summarizes the current state of research regarding changes in axonal function during demyelination, provides evidence of axonal dysmorphia and degeneration associated with demyelination, and identifies the cellular and molecular effectors of immune-mediated axonal injury. Finally, a unifying hypothesis that links neuronal stress associated with demyelination-induced axonal dysfunction to immune recognition and immunopathology is provided in an effort to shape future experimentation.

Glatiramer acetate in multiple sclerosis: a review

Multiple sclerosis (MS) is considered to be primarily an inflammatory autoimmune disease. Over the last 5 years, our view of the pathogenesis of MS has evolved considerably. The axonal damage was recognized as an early event in the disease process and as an important determinant of long-term disability. Therefore, the antiinflammatory and neuroprotective strategies are thought to represent promising approach to the therapy of MS. The therapeutic potential of glatiramer acetate (GA), a synthetic amino acid polymer composed of a mixture of L-glutamic acid, L-lysine, L-alanine, and L-tyrosine in defined proportions, in MS has been apparent for many years. GA has been shown to be effective in preventing and suppressing experimental allergic encephalomyelitis (EAE), the animal model of MS. GA has been, therefore, evaluated in several clinical studies and found to alter the natural history of relapsing-remitting (RR)MS by reducing the relapse rate and affecting disability. These findings were confirmed in open-label follow-up trials covering more than 10 years of treatment. The trials demonstrated sustained efficacy for GA in slowing the progression of disability. The clinical therapeutic effect of GA is consistent with the results of magnetic resonance imaging (MRI) findings from various clinical centers. At a daily standard dose of 20 mg, s.c., GA was generally well tolerated. The induction of GA-reactive T-helper 2-like regulatory suppressor cells is thought to be the main mechanism of the therapeutic action of this drug. In addition, it was recently shown that GA-reactive T cells produce neurotrophic factors (e.g., brain-derived neurotrophic factor [BDNF]) that protect neurons and axons in the area of injury.

Pharmacokinetics and pharmacodynamics of the interferon-betas, glatiramer acetate, and mitoxantrone in multiple sclerosis

Five disease-modifying agents are currently approved for long-term treatment of multiple sclerosis (MS), namely three interferon-beta preparations, glatiramer acetate, and mitoxantrone(1). Pharmacokinetics describes the fate of drugs in the human body by studying their absorption, distribution, metabolism and excretion. Pharmacodynamics is dedicated to the mechanisms of action of drugs. The understanding of the pharmacokinetics and pharmacodynamics of the approved disease-modifying agents against MS is of importance as it might contribute to the development of future derivatives with a potentially higher efficacy and a more favourable safety profile. This article reviews data thus far present both on the pharmacokinetics as well as on the putative mechanisms of action of the interferon-betas, glatiramer acetate, and mitoxantrone in the immunopathogenesis of MS.

Time course and distribution of inflammatory and neurodegenerative events suggest structural bases for the pathogenesis of experimental autoimmune encephalomyelitis

Murine models of experimental autoimmune encephalomyelitis (EAE) are important vehicles for studying the effects of genetic manipulation on disease processes related to multiple sclerosis (MS). Currently, a comprehensive assessment of EAE pathogenesis with respect to inflammatory and degenerating neuronal elements is lacking. By using Fluoro-jade histochemistry to mark neurodegeneration and dual immunostaining to follow T-cell, microglial, and vascular responses, the time course and distribution of pathological events in EAE was surveyed. C57BL/6J mice were killed at 7, 10, 14, 21 or 35 days after vaccination with the myelin oligodendrocyte glycoprotein peptide MOG(35-55). Disease onset occurred at day 14 and peaked at day 21. Early T-cell infiltration and microglial activation in periventricular and superficial white matter structures adjacent to meninges suggested initial recruitment of effector T cells via the cerebrospinal fluid and choroid plexus. This was associated with microglial activation at distal sites along the same white matter tracts, with subsequent vascular recruitment of T cells associated with further injury. Systematic examination of the entire CNS supported this two-step model of EAE pathogenesis, with inflammation and neurodegeneration commencing at similar times and affecting multiple levels of predominantly sensory central pathways, including their terminal fields. This included aspects of the visual, auditory/vestibular, somatosensory (lemniscal), and proprioceptive (spinocerebellar) systems. The early targeting of visual and periventricular structures followed by more widespread CNS involvement is consistent with common presenting signs in human MS patients and suggestive of a similar basis in neuropathology.

Glatiramer acetate: mechanisms of action in multiple sclerosis

Glatiramer acetate (GA) is a mixture of synthetic polypeptides composed of four amino acids resembling myelin basic protein (MBP). GA has been shown to be effective in preventing and suppressing experimental autoimmune encephalomyelitis (EAE), the animal model of multiple sclerosis. It was tested in several clinical studies and approved for the immunomodulatory treatment of relapsing-type MS in 1996. Glatiramer acetate demonstrates a strong promiscuous binding to major histocompatibility complex molecules and inhibits the T cell response to several myelin antigens. In addition, it was shown to act as a T cell receptor antagonist for the 82-100 MBP epitope. Glatiramer acetate treatment causes in vivo changes of the frequency, cytokine secretion pattern and effector function of GA-specific T cells. It was shown to induce GA-specific regulatory CD4(+) and CD8(+) T cells and a TH1-TH2 shift with consecutively increased secretion of antiinflammatory cytokines. GA-specific TH2 cells are able to migrate across the blood-brain barrier and cause in situ bystander suppression of autoaggressive TH1 T cells. In addition glatiramer acetate was demonstrated to influence antigen presenting cells (APC) such as monocytes and dendritic cells. Furthermore secretion of neurotrophic factors with potential neuroprotective effects was shown.

Glatiramer Acetate: Mechanisms of Action in Multiple Sclerosis

Glatiramer acetate (GA), formerly known as copolymer 1, is a mixture of synthetic polypeptides composed of four amino acids resembling the myelin basic protein (MSP). GA has been shown to be highly effective in preventing and suppressing experimental autoimmune encephalomyelitis (EAE), the animal model of multiple sclerosis (MS). Therefore, it was tested in several clinical studies and so approved for the immunomodulatory treatment of relapsing-type MS. In contrast to other immunomodulatory MS therapies, GA has a distinct mechanism of action: GA demonstrates an initial strong promiscuous binding to major histocompatibility complex molecules and consequent competition with various (myelin) antigens for their presentation to T cells. In addition, antigen-based therapy generating a GA-specific immune response seems to be the prerequisite for GA therapy. GA treatment induces an in vivo change of the frequency, cytokine secretion pattern and the effector function of GA-specific CD4+ and CD8+ T cells, probably by affecting the properties of antigen-presenting cells such as monocytes and dendritic cells. As demonstrated extensively in animal experiments, GA-specific, mostly, T helper 2 cells migrate to the brain and lead to in situ bystander suppression of the inflammatory process in the brain. Furthermore, GA-specific cells in the brain express neurotrophic factors like the brain-derived neurotrophic factor (BDNF) in addition to anti-inflammatory T helper 2-like cytokines. This might help tip the balance in favor of more beneficial influences because there is a complex interplay between detrimental and beneficial factors and mediators in the inflammatory milieu of MS lesions.

The heat-shock protein 90 inhibitor 17-allylamino-17-demethoxygeldanamycin suppresses glial inflammatory responses and ameliorates experimental autoimmune encephalomyelitis

The heat-shock response (HSR), a highly conserved cellular response, is characterized by rapid expression of heat-shock proteins (HSPs), and inhibition of other synthetic activities. The HSR can attenuate inflammatory responses, via suppression of transcription factor activation. A HSR can be induced pharmacologically by HSP90 inhibitors, through activation of the transcription factor Heat Shock Factor 1 (HSF1). In the present study we characterized the effects of 17-allylamino-17-demethoxygeldanamycin (17-AAG), a less toxic derivative of the naturally occurring HSP90 inhibitor geldanamycin, on glial inflammatory responses and the development of experimental autoimmune encephalomyelitis. In primary enriched glial cultures, 17-AAG dose dependently reduced lipopolysaccharide-dependent expression and activity of inducible nitric oxide synthase, attenuated interleukin (IL)-1beta expression and release, increased inhibitor of kappaB protein levels, and induced HSP70 expression. 17-AAG administration to mice immunized with myelin oligodendrocyte glycoprotein peptide prevented disease onset when given at an early time, and reduced clinical symptoms when given during ongoing disease. T cells from treated mice showed a reduced response to immunogen re-stimulation, and 17-AAG reduced CD3- and CD28-dependent IL-2 production. Together, these data suggest that HSP90 inhibitors could represent a new approach for therapeutic intervention in autoimmune diseases such as multiple sclerosis.

Effects of glatiramer acetate and interferon-beta on neurodegeneration in a model of multiple sclerosis: a comparative study

Axonal destruction and neuronal loss occur early during multiple sclerosis (MS), an autoimmune inflammatory central nervous system disease that frequently manifests with acute optic neuritis. Glatiramer acetate (GA) and interferon-beta-1b (IFN-beta-1b) are two immunomodulatory agents that have been shown to decrease the frequency of MS relapses. However, the question of whether these substances can slow neurodegeneration in MS patients is the subject of controversy. In a rat model of experimental autoimmune encephalomyelitis, we investigated the effects of GA and IFN-beta-1b on the survival of retinal ganglion cells (RGCs), the neurons that form the axons of the optic nerve. For each substance, therapy was started 14 days before immunization, on the day of immunization, or on the day of clinical disease onset. After myelin oligodendrocyte glycoprotein-induced experimental autoimmune encephalomyelitis became clinically manifest, optic neuritis was monitored by recording visual evoked potentials. The function of RGCs was measured by electroretinograms. Although early GA or IFN-beta-1b treatment showed benefit on disease activity, only treatment with GA exerted protective effects on RGCs, as revealed by measuring neurodegeneration and neuronal function. Furthermore, we demonstrate that this GA-induced neuroprotection does not exclusively depend on the reduction of inflammatory infiltrates within the optic nerve.

Glatiramer acetate therapy for multiple sclerosis: a review

The past decade has witnessed a revolution in the treatment of multiple sclerosis (MS), the most common demyelinating disorder of the human CNS. After being considered as an untreatable disease for more than a century, six disease-modifying treatments have been approved between 1993 and 2006. Glatiramer acetate (GA) is a worldwide drug approved for the treatment of relapsing-remitting MS in 1996. The drug is a synthetic copolymer of four amino acids based on the composition of myelin basic protein, one of several putative autoantigens implicated in the pathogenesis of MS. Three separate double-blind, placebo-controlled trials have established its efficacy in relapsing-remitting MS. Observations from an ongoing study, the longest prospective study in MS therapeutics so far, suggest that the effect of GA in reducing the relapse rate and neurological disability is maintained over a 10-year period. Independent investigators have identified several putative immunological mechanisms of action of GA, with the unique observation of the generation of GA-reactive T-helper 2 (anti-inflammatory) polarised lymphocytes within days to weeks of initiating therapy and sustaining an anti-inflammatory milieu for years in the peripheral immune system and, presumably, in the CNS. Emerging data from immunological and imaging studies quantifying axonal injury in the brain point towards neuroprotective abilities of GA. Combined with its remarkable safety and tolerability, long-term efficacy and neuroprotective effect, GA presents it self as a first-line choice in relapsing-remitting MS, and holds immense promise in developing its potential as a combination therapy in MS, as well as extending its indications to other neurodegenerative diseases.