Multiple sclerosis: deeper understanding of its pathogenesis reveals new targets for therapy

Cytosolic RIG-I-like helicases act as negative regulators of sterile inflammation in the CNS

The action of cytosolic RIG-I-like helicases (RLHs) in the CNS during autoimmunity is largely unknown. Using a mouse model of multiple sclerosis, we found that mice lacking the RLH adaptor IPS-1 developed exacerbated disease that was accompanied by markedly higher inflammation, increased axonal damage and elevated demyelination with increased encephalitogenic immune responses. Furthermore, activation of RLH ligands such as 5'-triphosphate RNA oligonucleotides decreased CNS inflammation and improved clinical signs of disease. RLH stimulation repressed the maintenance and expansion of committed T(H)1 and T(H)17 cells, whereas T-cell differentiation was not altered. Notably, T(H)1 and T(H)17 suppression required type I interferon receptor engagement on dendritic cells, but not on macrophages or microglia. These results identify RLHs as negative regulators of T(H)1 and T(H)17 responses in the CNS, demonstrate a protective role of the RLH pathway for brain inflammation, and establish oligonucleotide ligands of RLHs as potential therapeutics for the treatment of multiple sclerosis.

Telemedicine for multiple sclerosis patients: assessment using Health Value Compass

BACKGROUND

Telemedicine carries the potential of improving accessibility to health services, especially for disabled people.

OBJECTIVE

To assess the health-related outcomes of short-term implementation of telemedicine (telemed) for MS patients.

METHODS

A prospective study of 40 MS patients divided into a control group and a telemed group was conducted, in two stages: A. Six months' follow-up for measurement of baseline health-related variables; B. Implementation stage, adding home telecare to the telemed group. A Health Value Compass was applied to assess the outcomes of home telecare implementation. Clinical status, cost data, patients' self-assessment of Health Related Quality of Life (HRQoL) and satisfaction with telecare were studied.

RESULTS

Patients in the telemed group demonstrated improved clinical outcome measured by symptoms severity. There was a decrease of at least 35% in the medical costs for 67% of the telemed group patients. Satisfaction with telecare was high and most patients would recommend this service to others.

CONCLUSIONS

The present pilot study, applying Health Value Compass-based analysis, suggests that telecare is a powerful tool for monitoring MS patients at home, carries the potential to improve health care while reducing costs, and should be considered for implementation as part of the management of chronic neurological diseases.

Infiltrating monocytes trigger EAE progression, but do not contribute to the resident microglia pool

In multiple sclerosis and the experimental autoimmune encephalitis (EAE) mouse model, two pools of morphologically indistinguishable phagocytic cells, microglia and inflammatory macrophages, accrue from proliferating resident precursors and recruitment of blood-borne progenitors, respectively. Whether these cell types are functionally equivalent is hotly debated, but is challenging to address experimentally. Using a combination of parabiosis and myeloablation to replace circulating progenitors without affecting CNS-resident microglia, we found a strong correlation between monocyte infiltration and progression to the paralytic stage of EAE. Inhibition of chemokine receptor-dependent recruitment of monocytes to the CNS blocked EAE progression, suggesting that these infiltrating cells are essential for pathogenesis. Finally, we found that, although microglia can enter the cell cycle and return to quiescence following remission, recruited monocytes vanish, and therefore do not ultimately contribute to the resident microglial pool. In conclusion, we identified two distinct subsets of myelomonocytic cells with distinct roles in neuroinflammation and disease progression.

Chronic progressive multiple sclerosis - pathogenesis of neurodegeneration and therapeutic strategies

Multiple sclerosis (MS) is an inflammatory, autoimmune, demyelinating disease of the central nervous system (CNS) that usually starts as a relapsing-remitting disease. In most patients the disease evolves into a chronic progressive phase characterized by continuous accumulation of neurological deficits. While treatment of relapsing-remitting MS (RRMS) has improved dramatically over the last decade, the therapeutic options for chronic progressive MS, both primary and secondary, are still limited. In order to find new pharmacological targets for the treatment of chronic progressive MS, the mechanisms of the underlying neurodegenerative process that becomes apparent as the disease progresses need to be elucidated. New animal models with prominent and widespread progressive degenerative components of MS have to be established to study both inflammatory and non-inflammatory mechanisms of neurodegeneration. Here, we discuss disease mechanisms and treatment strategies for chronic progressive 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.

Regulation of the severity of neuroinflammation and demyelination by TLR-ASK1-p38 pathway

Apoptosis signal-regulating kinase 1 (ASK1) is an evolutionarily conserved mitogen-activated protein kinase (MAPK) kinase kinase which plays important roles in stress and immune responses. Here, we show that ASK1 deficiency attenuates neuroinflammation in experimental autoimmune encephalomyelitis (EAE), without affecting the proliferation capability of T cells. Moreover, we found that EAE upregulates expression of Toll-like receptors (TLRs) in activated astrocytes and microglia, and that TLRs can synergize with ASK1-p38 MAPK signalling in the release of key chemokines from astrocytes. Consequently, oral treatment with a specific small molecular weight inhibitor of ASK1 suppressed EAE-induced autoimmune inflammation in both spinal cords and optic nerves. These results suggest that the TLR-ASK1-p38 pathway in glial cells may serve as a valid therapeutic target for autoimmune demyelinating disorders including multiple sclerosis.

Monoclonal antibody therapy in multiple sclerosis: Paradigm shifts and emerging challenges

Therapeutic approaches to multiple sclerosis (MS) are based on altering the functions of the immune system, either by using broad immunosuppressive drugs used for transplantation rejection and rheumatology, or by modulating them more discreetly with beta interferon and synthetic amino-acid copolymers. These strategies are only partially successful, have important safety and tolerability limitations, and have shown to be mostly effective in earlier stages of the disease, in which acute relapses dominate the clinical picture. For progressive phenotypes of MS there are currently no effective therapeutic options. As very specific and potent immunosuppressive agents, monoclonal antibodies (mAbs) may offer considerable advantages over other therapies for MS. During the last decade, anti-a4 integrin natalizumab became the first approved mAb for treatment of relapsing MS, after convincingly demonstrating clinically significant effects on two large Phase 3 trials. Moreover, the concept of disease remission was introduced for the first time, to describe patients that show no signs of clinical or imaging markers of disease activity during therapy with natalizumab. Of the mAbs under development for MS, alemtuzumab and rituximab have also shown promising evidence of effectiveness, and potentially expanded the therapeutic horizon to reversal of disease progression in early relapsing patients, and progressive patients who previously had not been studied. However, the appearance of progressive multifocal leukoencephalopathy (PML) in natalizumab-treated MS patients, as well as in patients with lymphoma, lupus and rheumatoid arthritis treated with rituximab, and autoimmune-type complications in alemtuzumab-treated MS patients underlines the fact that extended efficacy comes with significant clinical risks. The challenge is then how best to utilize therapies that have evidently superior efficacy in a chronic disease of young adults, to obtain the best benefit-risk ratio, and how to monitor and prevent emergent safety concerns.

Dual-specific phosphatase-6 (Dusp6) and ERK mediate AMPA receptor-induced oligodendrocyte death

Oligodendrocytes, the myelinating cells of the CNS, are highly vulnerable to glutamate excitotoxicity, a mechanism involved in tissue damage in multiple sclerosis. Thus, understanding oligodendrocyte death at the molecular level is important to develop new therapeutic approaches to treat the disease. Here, using microarray analysis and quantitative PCR, we observed that dual-specific phosphatase-6 (Dusp6), an extracellular regulated kinase-specific phosphatase, is up-regulated in oligodendrocyte cultures as well as in optic nerves after AMPA receptor activation. In turn, Dusp6 is overexpressed in optic nerves from multiple sclerosis patients before the appearance of evident damage in this structure. We further analyzed the role of Dusp6 and ERK signaling in excitotoxic oligodendrocyte death and observed that AMPA receptor activation induces a rapid increase in ERK1/2 phosphorylation. Blocking Dusp6 expression, which enhances ERK1/2 phosphorylation, significantly diminished AMPA receptor-induced oligodendrocyte death. In contrast, MAPK/ERK pathway inhibition with UO126 significantly potentiates excitotoxic oligodendrocyte death and increases cytochrome c release, mitochondrial depolarization, and mitochondrial calcium overload produced by AMPA receptor stimulation. Upstream analysis demonstrated that MAPK/ERK signaling alters AMPA receptor properties. Indeed, Dusp6 overexpression as well as incubation with UO126 produced an increase in AMPA receptor-induced inward currents and cytosolic calcium overload. Together, these data suggest that levels of phosphorylated ERK, controlled by Dusp6 phosphatase, regulate glutamate receptor permeability and oligodendroglial excitotoxicity. Therefore, targeting Dusp6 may be a useful strategy to prevent oligodendrocyte death in multiple sclerosis and other diseases involving CNS white matter.

The cellular prion protein in multiple sclerosis: A potential target for neurotherapeutics?

Multiple sclerosis (MS) is a debilitating disease that affects millions. There is no known cure for the disease and neither is the cause of the disease known. Recent studies have indicated that it is a multi-factorial disease with several genes involved. Importantly, sunlight and vitamin D have been implicated in the progression of the disease. The pathogenesis of MS chiefly involves loss of oligodendrocytes, which in addition to being killed by inflammatory mediators in the CNS, also succumbs to loss of trophic support from astrocytes. Neurotrophins play an important role in myelination and the cellular prion protein (PrPC) is a key player in this process. Although the physiological roles of PrPC remain to be fully understood, increasing evidence suggests multiple roles for PrPC in regulation of cellular immunity and for its interaction with several neurotrophins that are necessary for homeostasis of the nervous system. This mini-review focuses on the findings establishing a crucial role for PrPC in the neuropathogenesis of MS, emphasizing its neuroprotective role. Since MS is a multi-factorial disease with unknown etiology and no cure, this review aims to highlight endogenous repair mechanisms mediated by PrPC that might contribute to functional recovery in MS patients.

Autophagy, inflammation and neurodegenerative disease

Autophagy is emerging as a central regulator of cellular health and disease and, in the central nervous system (CNS), this homeostatic process appears to influence synaptic growth and plasticity. Herein, we review the evidence that dysregulation of autophagy may contribute to several neurodegenerative diseases of the CNS. Up-regulation of autophagy may prevent, delay or ameliorate at least some of these disorders, and - based on recent findings from our laboratory - we speculate that this goal may be achieved using a safe, simple and inexpensive approach.

IL-7Rα confers susceptibility to experimental autoimmune encephalomyelitis

Multiple sclerosis (MS) is a neurological disorder that causes paralysis in young adults and affects women more frequently than men. The etiology of MS is not known, but it is generally viewed as an autoimmune disease of the central nervous system (CNS), influenced by genetic and environmental factors. Recent studies have identified interleukin-7 receptor α (IL-7Rα) as a risk factor for MS. But the role of IL-7Rα in experimental autoimmune encephalomyelitis (EAE) model of MS is not known. In this study we demonstrate that IL-7Rα-deficient (IL-7Rα(-/-)) mice remain resistant to MOGp35-55-induced EAE. When compared with C57BL/6 wild-type mice, IL-7Rα(-/-) mice showed less severe inflammation and demyelination in the CNS. The attenuation of EAE in IL-7Rα(-/-) mice was associated with a decrease in T-helper (Th) 1 and Th17 responses in the CNS and lymphoid organs. IL-7Rα(-/-) mice also showed an increase in Th2 response and CD4(+)Foxp3(+) regulatory T cells. These findings highlight that IL-7Rα confers susceptibility by influencing autoimmune Th1/Th17 responses in EAE model of MS.

New approaches in the management of multiple sclerosis

Multiple sclerosis (MS) is a central nervous system chronic inflammatory disease that is characterized by an extensive and complex immune response. Scientific advances have occurred in immunology, pathophysiology, and diagnostic and clinical assessment tools, and recent discovery of unique therapeutic targets has spurred numerous Phase II and Phase III clinical trials. Reductions in MS relapse rates and improvements in T₂ or gadolinium-enhancing lesion burdens have been reported from Phase III trials that include fingolimod, alemtuzumab, cladribine, and rituximab. Promising Phase II trial data exist for teriflunomide, daclizumab, laquinimod, and fumarate. The optimism created by these favorable findings must be tempered with evaluation of the adverse effect profile produced by these new agents. Given the discovery of progressive multifocal leukoencephalopathy with the use of natalizumab, ongoing vigilance for rare and life-threatening reactions due to new agents should be paramount. Patients with MS often experience difficulty with ambulation, spasticity, and cognition. Recent clinical trial data from two Phase III dalfampridine-SR trials indicate certain patients receive benefits in ambulation. This article provides an overview of data from clinical trials of newer agents of potential benefit in MS.

A randomized controlled double-masked trial of albuterol add-on therapy in patients with multiple sclerosis

BACKGROUND

Interleukin 12 (IL-12), a cytokine that promotes generation of helper T cells subtype 1, is increased in multiple sclerosis. Albuterol sulfate, a β2-adrenergic agonist, reduces IL-12 expression, so we tested the effect of albuterol as an add-on treatment to glatiramer acetate therapy.

OBJECTIVES

To investigate the clinical and immunologic effects of albuterol treatment as an add-on therapy in patients starting glatiramer acetate treatment.

DESIGN

Single-center double-masked clinical trial.

SETTING

Academic research. Patients Subjects with relapsing-remitting multiple sclerosis.

MAIN OUTCOME MEASURES

In this single-center double-masked clinical trial, subjects with relapsing-remitting multiple sclerosis were randomized to receive a subcutaneous injection of glatiramer acetate (20 mg) plus an oral dose of placebo daily for 2 years or a subcutaneous injection of glatiramer acetate (20 mg) plus an oral dose of albuterol daily for 2 years. The primary clinical efficacy measurement was the change in Multiple Sclerosis Functional Composite at 2 years, and the primary immunologic end point was the change in expression of IL-13 and interferon γ at each study time point. The classification level of evidence from this trial is C for each question, as this is the first class II clinical trial addressing the efficacy of glatiramer acetate plus albuterol.

RESULTS

Forty-four subjects were randomized to receive glatiramer acetate plus albuterol or glatiramer acetate plus placebo, and 39 subjects contributed to the analysis. Improvement in the Multiple Sclerosis Functional Composite was observed in the glatiramer acetate plus albuterol group at the 6-month (P = .005) and 12-month (P = .04) time points but not at the 24-month time point. A delay in the time to first relapse was also observed in the glatiramer acetate plus albuterol group (P = .03). Immunologically, IL-13 and interferon-γ production decreased in both treatment groups, and a treatment effect on IL-13 production was observed at the 12-month time point (P < .05). Adverse events were generally mild, and only 3 moderate or severe events were considered related to the treatment.

CONCLUSION

Treatment with glatiramer acetate plus albuterol is well tolerated and improves clinical outcomes in patients with multiple sclerosis.

TRIAL REGISTRATION

clinicaltrials.gov Identifier: NCT00039988.

MHC class II-restricted antigen presentation by plasmacytoid dendritic cells inhibits T cell-mediated autoimmunity

Although plasmacytoid dendritic cells (pDCs) express major histocompatibility complex class II (MHCII) molecules, and can capture, process, and present antigens (Ags), direct demonstrations that they function as professional Ag-presenting cells (APCs) in vivo during ongoing immune responses remain lacking. We demonstrate that mice exhibiting a selective abrogation of MHCII expression by pDCs develop exacerbated experimental autoimmune encephalomyelitis (EAE) as a consequence of enhanced priming of encephalitogenic CD4⁺ T cell responses in secondary lymphoid tissues. After EAE induction, pDCs are recruited to lymph nodes and establish MHCII-dependent myelin-Ag–specific contacts with CD4⁺ T cells. These interactions promote the selective expansion of myelin-Ag–specific natural regulatory T cells that dampen the autoimmune T cell response. pDCs thus function as APCs during the course of EAE and confer a natural protection against autoimmune disease development that is mediated directly by their ability to present of Ags to CD4⁺ T cells in vivo.

Protective effect of recombinant human IL-1Ra on CCl4-induced acute liver injury in mice

AIM: To evaluate the effects of positive regulation of recombinant human interleukin 1 receptor antagonist (rhIL-1Ra) on hepatic tissue recovery in acute liver injury in mice induced by carbon tetrachloride (CCl₄).

METHODS: Acute liver damage was induced by injecting 8-wk-old mice with CCl₄ 1 mL/kg (1:3 dilution in corn oil) intraperitoneally (ip). Survival after liver failure was assessed by injecting 8-wk-old mice with a lethal dose of CCl₄ 2.6 mL/kg (1:1 dilution in corn oil) ip. Mice were subcutaneously injected with 1 mg/kg recombinant human IL-1Ra twice a day after CCl₄ treatment for 5 d. Serum alanine amino transferase (ALT) and aspartate aminotransferase (AST) levels were determined with a commercial assay kit. Serum IL-1β, IL-1Ra levels were measured by enzyme-linked immunosorbent assay kit. Quantitative real-time polymerase chain reaction was used to determine liver IL-1β, IL-1Ra and IL-6 expression during CCl₄-induced acute liver injury. Liver sections were stained with hematoxylin-eosin. A histology-injury grading system was used to evaluate the degree of necrosis after acute liver injury. Proliferating cell nuclear antigen (PCNA) staining was used to evaluate the role of rhIL-1Ra in promoting hepatocyte proliferation.

RESULTS: Quantitative analysis showed a higher level of IL-6 mRNA expression and reduced serum AST and ALT levels in the livers of the rhIL-1Ra-treated group at the early phase of CCl₄-induced acute liver injury. Histological examination indicated a decrease in centrilobular necrotic areas in mice treated with rhIL-1Ra, and a novel role of rhIL-1Ra in promoting hepatocyte proliferation was also supported by an increase of PCNA staining. All these results, accompanied by a strong survival benefit in rhIL-1Ra-treated vs PBS-treated groups, demonstrated that rhIL-1Ra administration ameliorated the histological damage and accelerated the regeneration and recovery process of the liver.

CONCLUSION: rhIL-1Ra could be further developed as a novel therapeutic agent for the treatment of acute liver injury because of its ability to reduce hepatocellular damage and facilitate liver regeneration.

Time-dependent fate of transplanted neural precursor cells in experimental autoimmune encephalomyelitis mice

Transplanted Neural Precursor Cells (NPCs) are capable of long-distance migration inside the inflamed CNS, but exhibit limited myelinating capacities in animal models of Multiple Sclerosis (MS). Inflammation seems to be both beneficial for the recruitment and migration of NPCs and restrictive for their terminal differentiation. In the present study, a set of transplantation experiments was applied in order to investigate the migratory potential, the differentiation pattern and long-term survival of NPCs in Experimental Autoimmune Encephalomyelitis (EAE) mice, the animal model of MS. The in vitro differentiation potential of NPCs in the presence of either pro- (TNFa, INFγ) or anti- (TGFb) inflammatory cytokines was also analyzed. According to the in vivo results obtained, at the acute phase of EAE only a small fraction of transplanted NPCs succeed to differentiate, whereas at chronic phase most of them followed a differentiation process to glial cell lineage along white matter tracts. However, this differentiation was not fully completed, since 8 months after their transplantation a number of NPCs remained as pre-oligodendrocytes. Glial differentiation of NPCs was also found to be inhibited or promoted following their treatment with TNFa or TGFb respectively, in vitro. Our findings suggest that inflammation triggers migration whereas the anti-inflammatory component is a prerequisite for NPCs to follow glial differentiation thereby providing myelinating oligodendrocytes. It is speculated that the fine balance between the pro- and anti-inflammatory determinants in the CNS may be a key factor for transplanted NPCs to exhibit a better therapeutic effect in EAE and MS. This article is part of a Special Issue entitled "Interaction between repair, disease, & inflammation."

Genetic associations in type I interferon related pathways with autoimmunity

Type I interferons play an outstanding role in innate and adaptive immunity by enhancing functions of dendritic cells, inducing differentiation of monocytes, promoting immunoglobulin class switching in B cells and stimulating effector functions of T cells. The increased production of IFNα/β by plasmacytoid dendritic cells could be responsible for not only efficient antiviral defence, but it also may be a pathological factor in the development of various autoimmune disorders. The first evidence of a genetic link between type I interferons and autoimmune diseases was the observation that elevated IFNα activity is frequently detected in the sera of patients with systemic lupus erythematosus, and that this trait shows high heritability and familial aggregation in their first-degree healthy relatives. To date, a number of genes involved in interferon signalling have been associated with various autoimmune diseases. Patients with systemic lupus erythematosus, Sjögren's syndrome, dermatomyositis, psoriasis, and a fraction of patients with rheumatoid arthritis display a specific expression pattern of interferon-dependent genes in their leukocytes, termed the interferon signature. Here, in an attempt to understand the role of type I interferons in the pathogenesis of autoimmunity, we review the recent advances in the genetics of autoimmune diseases focusing on the association of genes involved in type I interferon pathways.

Characterization of relapsing-remitting and chronic forms of experimental autoimmune encephalomyelitis in C57BL/6 mice

Multiple sclerosis (MS) is an autoimmune, demyelinating disease of the central nervous system (CNS). Like MS, the animal model experimental autoimmune encephalomyelitis (EAE) is characterized by CNS inflammation and demyelination and can follow a relapsing-remitting (RR) or chronic (CH) disease course. The molecular and pathological differences that underlie these different forms of EAE are not fully understood. We have compared the differences in RR- and CH-EAE generated in the same mouse strain (C57BL/6) using the same antigen. At the peak of disease when mice in both groups have similar clinical scores, CH-EAE is associated with increased lesion burden, myelin loss, axonal damage, and chemokine/cytokine expression when compared with RR-EAE. We further showed that inflammation and myelin loss continue to worsen in later stages of CH-EAE, whereas these features are largely resolved at the equivalent stage in RR-EAE. Additionally, axonal loss at these later stages is more severe in CH-EAE than in RR-EAE. We also demonstrated that CH-EAE is associated with a greater predominance of CD8(+) T cells in the CNS that exhibit MOG(35-55) antigen specificity. These studies therefore showed that, as early as the peak stage of disease, RR- and CH-EAE differ remarkably in their immune cell profile, chemokine/cytokine responses, and histopathological features. These data also indicated that this model of CH-EAE exhibits pathological features of a chronic-progressive disease profile and suggested that the sustained chronic phenotype is due to a combination of axonal loss, myelin loss, and continuing inflammation.

Analysis of the cellular mechanism underlying inhibition of EAE after treatment with anti-NKG2A F(ab')2

Autoimmune encephalomyelitis may be ameliorated experimentally by enhancing NK cell-mediated elimination of activated autoreactive T cells through a mutation that interrupts the interaction between Qa-1(b) and CD94/NKG2A. Here we evaluate the ability of an anti-NKG2A F(ab')(2) Ab to enhance elimination of autoreactive T cells and reduce experimental autoimmune encephalomyelitis (EAE). Anti-NKG2A F(ab')(2) treatment diminishes progression of both myelin oligodendrocyte glycoprotein (MOG)-induced EAE in intact C57BL/6 mice and after adoptive transfer of disease-causing T cells. Analyses of the underlying mechanism revealed that administration of anti-NKG2A F(ab')(2) Ab reduces CD4(+) T recall responses to MOG and skews the proportion of IL-17- and IFNgamma-producing CD4(+) T cells toward the protective IL-4- and IL-10-secreting CD4(+) T cell subpopulations. CD94/NKG2A-dependent inhibition of inflammatory damage to spinal cord is associated with decreased infiltration of T cells and reduced microglia activation in the central nervous system. Because anti-NKG2A F(ab')(2) treatment had no detectable effect on the numbers or activity of T and B lymphocytes and NK cells in peripheral lymphoid tissues, this anti-NKG2A-based approach may represent a safe and effective therapy for this CNS disorder.

SLAT/Def6 plays a critical role in the development of Th17 cell-mediated experimental autoimmune encephalomyelitis

SWAP-70-like adapter of T cells (SLAT; also known as Def6) is a novel guanine nucleotide exchange factor for Rho GTPases that has been previously shown to play a role in CD4+ T cell activation and Th1/Th2 differentiation. However, the role of SLAT/Def6 in autoimmunity and its associated Th1- and Th17-specific responses has not yet been clearly elucidated. We used a prototypical and pathologically relevant Th1/Th17-mediated autoimmune model, that is, experimental autoimmune encephalomyelitis, to assess the role of SLAT/Def6 in autoantigen-specific T cell response. We found that T cell-expressed SLAT/Def6 was critical for experimental autoimmune encephalomyelitis development and pathogenesis, as evidenced by the resistance of Def6-deficient (Def6(-/-)) mice to clinical signs of the disease associated with a lack of CNS inflammation and demyelination in myelin oligodendrocyte glycoprotein-immunized Def6(-/-) mice. Moreover, Def6 deficiency resulted in a severely diminished myelin oligodendrocyte glycoprotein-specific CD4+ T cell proliferation as well as a defect in IFN-gamma and IL-17 production in secondary lymphoid organs and the CNS. Lastly, Def6(-/-) CD4+ T cells were grossly deficient in their ability to differentiate into Th17 cells both in vitro and in vivo in a T cell-intrinsic manner. Therefore, our study establishes T cell-expressed SLAT/Def6 as a pivotal positive regulator of Th17 inflammatory responses and, thus, essential in controlling autoimmune and inflammatory diseases.

Impact of human myelin on the maturation and function of human monocyte-derived dendritic cells

Macrophages and dendritic cells (DC) play an important role in the immunopathology of multiple sclerosis. We analyzed the impact of human myelin on monocyte-derived DC and describe their immunostimulatory capacity. Cells were grown on myelin and stimulated with LPS or a defined maturation cocktail. DC activation was analyzed by the expression of cell surface markers and the secretion of cytokines and chemokines. The immunostimulatory capacity of DC was assessed by allogeneic mixed-leukocyte reactions via proliferation. Additionally, their ability to bias T cells towards Th1, Th17 or Treg differentiation was investigated. We found that phagocytosis of myelin impaired the activation of DC, displayed by an impaired ability to stimulate allogeneic T cells, an increased production of TGF-beta1 and a diminished upregulation of CCR7 but did not affect the differentiation into T helper cell subsets. We hypothesize that myelin influences DC activation and plays a pivotal role in balancing immunity and tolerance.

Plasmacytoid DC promote priming of autoimmune Th17 cells and EAE

EAE, an animal model for MS, is a Th17 and Th1-cell-mediated autoimmune disease, but the mechanisms leading to priming of encephalitogenic T cells in autoimmune neuroinflammation are poorly understood. To investigate the role of plasmacytoid DC (pDC) in the initiation of autoimmune Th17- and Th1-cell responses and EAE, we depleted pDC with anti-pDC Ag-1 (anti-PDCA1) mAb prior to immunization of C57BL/6 mice with myelin oligodendrocyte glycoprotein (MOG). pDC-depleted mice developed less severe clinical and histopathological signs of EAE than control mice, which demonstrates a promoting role for pDC in the initiation of EAE. The levels of type I IFN were much lower in the sera from anti-PDCA1-treated mice. However, neutralization of type I IFN ameliorated the early phase of EAE but did not alter the severity of disease. Thus, only a minor part of the EAE-promoting effect of pDC appears to be mediated by IFN-alpha/beta secretion. The numbers of MOG-specific Th17 cells, but not Th1 cells, were lower in spleen from anti-PDCA1-treated mice compared with controls. In contrast, pDC depletion a week after MOG immunization resulted in more severe clinical signs of EAE. In conclusion, we demonstrate that pDC promote initiation of MOG-induced Th17-cell responses and EAE.

The clinical utility of inhibiting CD28-mediated costimulation

SUMMARY

This volume covers many topics in the field of T-cell costimulation. The need for such a volume is testament to the growth of the field. From its beginning as a concept in the 1980s, we have now progressed to the point where many molecules now have functionally defined roles in T-cell costimulation. In addition, the field has progressed 'from bench to bedside'. Abatacept [cytotoxic T-lymphocyte antigen-4 (CTLA-4)-immunoglobulin (Ig) (CTLA-4-Ig)], an inhibitor of CD28-mediated T-cell costimulation, was approved for the treatment of moderate-to-severe rheumatoid arthritis in 2006 by the Food and Drug Administration and in 2007 by the European Medicines Agency. This chapter first presents a personal historical perspective on the early basic studies on the elucidation of the CD28/B7 T-cell costimulatory pathway and the discovery of CTLA-4-Ig. We next present an overview of studies of CTLA-4-Ig in preclinical animal studies. The material discussed in these first two sections is selective rather than exhaustive; their purpose is to provide context for the final section, a summary of human clinical studies performed with abatacept.

Novel reliable real-time PCR for differential detection of MSRVenv and syncytin-1 in RNA and DNA from patients with multiple sclerosis

Two components of the HERV-W family of human endogenous retroviruses are activated during multiple sclerosis (MS) and proposed immunopathogenic co-factors: MSRV (MS-associated retrovirus), and ERVWE1 (whose env protein, syncytin-1, reaches the plasma membrane). MSRVenv and syncytin-1 are closely related, and difficult to distinguish each other. The sequences of extracellular MSRVenv and of syncytin-1 available in GenBank were compared with those found in MS patients and controls of the cohort under study. With respect to syncytin-1, MSRVenv sequences have a 12-nucleotide insertion in the trans-membrane moiety. Based on this insertion, discriminatory real-time PCR assays were developed, that can amplify selectively either MSRVenv or syncytin-1. The data of MS patients and controls indicated that MSRV and ERVWE1 are both expressed in the brain of MS patients, while only MSRV is present in the blood; MSRV was released in culture by PBMCs of MSRV-producer individuals. These cells expressed the complete MSRVenv gene in the absence of syncytin-1 expression, up to the final, fully glycosylated envelope protein product, since western blot staining with anti-HERV-Wenv antibody detected two bands of the same molecular weight (73 and 61kDa) of the fully glycosylated and partially glycosylated HERV-Wenv uncleaved proteins. Beyond MSRVenv DNA copy numbers were more abundant in MS patients than in healthy humans, while syncytin-1 were unchanged. These findings reinforce the link between MSRV and MS.

A molecular trio in relapse and remission in multiple sclerosis

Two thirds of patients with multiple sclerosis have the relapsing-remitting form, which often progresses to more debilitating disease. Striking clinical recovery, termed remission, often follows these periodic neurological defects, termed relapses. Recent work has revealed the role of three key molecules in relapse and remission: alpha4beta1 integrin (also known as VLA4) is an adhesion molecule that mediates T cell migration from the blood into the brain; osteopontin binds to alpha4beta1 integrin, stimulating the production of pro-inflammatory cytokines and inhibiting apoptosis; and alphaB crystallin inhibits inflammation in the brain. This Review discusses how this molecular trio interacts to initiate relapses (in the case of osteopontin and alpha4beta1 integrin) and then to terminate them as remissions in multiple sclerosis (in the case of alphaB crystallin).

Autoantigen immunization at different sites reveals a role for anti-inflammatory effects of IFN-gamma in regulating susceptibility to experimental autoimmune encephalomyelitis

Experimental autoimmune encephalomyelitis is induced in B10.PL (H-2(u)) mice by immunization with the immunodominant N-terminal epitope of myelin basic protein, Ac1-9. In the present study, we show that the site of immunization impacts disease incidence and severity. This effect is more marked in female mice than in males. Although immunization in the flanks is effective in eliciting disease, delivery of Ag in the footpad and tailbase results in poor induction. Analyses of the immune responses in female mice following different immunization regimens indicates that resistance to disease is accompanied by higher levels of IFN-gamma and CD11b(+)Gr-1(int) myeloid cells. Such myeloid cells are known to have a suppressive function, and consistent with this knowledge, blockade of IFN-gamma results in increased disease activity and decreased levels of splenic CD11b(+)Gr-1(int) cells. Conversely, injection of adjuvants (CFA or Pam(3)CSK(4)) in the footpad decreases experimental autoimmune encephalomyelitis incidence and severity. Our study indicates that the site of immunization can impact the magnitude of the ensuing inflammatory response, and that at a certain threshold a protective, regulatory circuit can be elicited.

Molecular mechanisms of T-cell receptor and costimulatory molecule ligation/blockade in autoimmune disease therapy

SUMMARY

Pro-inflammatory CD4(+) T-cell-mediated autoimmune diseases, such as multiple sclerosis and type 1 diabetes, are hypothesized to be initiated and maintained by activated antigen-presenting cells presenting self antigen to self-reactive interferon-gamma and interleukin-17-producing CD4(+) T-helper (Th) type 1/Th17 cells. To date, the majority of Food and Drug Administration-approved therapies for autoimmune disease primarily focus on the global inhibition of immune inflammatory activity. The goal of ongoing research in this field is to develop both therapies that inhibit/eliminate activated autoreactive cells as well as antigen-specific treatments, which allow for the directed blockade of the deleterious effects of self-reactive immune cell function. According to the two-signal hypothesis, activation of a naive antigen-specific CD4(+) T cell requires both stimulation of the T-cell receptor (TCR) (signal 1) and stimulation of costimulatory molecules (signal 2). There also exists a balance between pro-inflammatory and anti-inflammatory immune cell activity, which is regulated by the type and strength of the activating signal as well as the local cytokine milieu in which the naive CD4(+) T cell is activated. To this end, the majority of ongoing research is focused on the delivery of suboptimal TCR stimulation in the absence of costimulatory molecule stimulation, or potential blockade of stimulatory accessory molecules. Therefore, the signaling pathways involved in the induction of CD4(+) T-cell anergy, as apposed to activation, are topics of intense interest.

Differing roles for members of the phospholipase A2 superfamily in experimental autoimmune encephalomyelitis

The phospholipase A(2) (PLA(2)) superfamily hydrolyzes phospholipids to release free fatty acids and lysophospholipids, some of which can mediate inflammation and demyelination, hallmarks of the CNS autoimmune disease multiple sclerosis. The expression of two of the intracellular PLA(2)s (cPLA(2) GIVA and iPLA(2) GVIA) and two of the secreted PLA(2)s (sPLA(2) GIIA and sPLA(2) GV) are increased in different stages of experimental autoimmune encephalomyelitis (EAE), an animal model of multiple sclerosis. We show using small molecule inhibitors, that cPLA(2) GIVA plays a role in the onset, and iPLA(2) GVIA in the onset and progression of EAE. We also show a potential role for sPLA(2) in the later remission phase. These studies demonstrate that selective inhibition of iPLA(2) can ameliorate disease progression when treatment is started before or after the onset of symptoms. The effects of these inhibitors on lesion burden, chemokine and cytokine expression as well as on the lipid profile provide insights into their potential modes of action. iPLA(2) is also expressed by macrophages and other immune cells in multiple sclerosis lesions. Our results therefore suggest that iPLA(2) might be an excellent target to block for the treatment of CNS autoimmune diseases, such as multiple sclerosis.

Simvastatin induces cell death in a mouse cerebellar slice culture (CSC) model of developmental myelination

Statins (inhibitors of HMG-CoA reductase) have shown promise in treating multiple sclerosis (MS). However, their effect on oligodendrocyte remyelination of demyelinated axons has not been clarified. Since developmental myelination shares many features with the remyelination process, we investigated the effect of lipophilic simvastatin on developmental myelination in organotypic cerebellar slice cultures (CSC). In this study, we first characterized developmental myelination in CSC from postnatal day (P)5 and P10 mice that express enhanced green fluorescence protein (eGFP) in oligodendrocyte-lineage cells. We then examined the effect of simvastatin on three developmental myelination stages: early myelination (P5 CSC, 2DIV), late myelination (P10 CSC, 2DIV) and full myelination (P10 CSC, 10DIV). We found that treatment with simvastatin (0.1 microM) for 6 days decreased the survival of Purkinje cells and oligodendrocytes drastically during the early myelination stage, while moderately during the late and full myelination stages. Oligodendrocytes are more resistant than Purkinje cells. The toxic effect of simvastatin could be rescued by the product of HMG-CoA reductase mevalonate but not low-density lipoprotein (LDL). Additionally, this toxic effect is independent of isoprenylation since farnesyl pyrophosphate (Fpp) but not geranylgeranyl pyrophosphate (GGpp) provided partial rescue. Our findings therefore suggest that inhibition of cholesterol synthesis is detrimental to neuronal tissue.

Impaired autoimmune T helper 17 cell responses following DNA vaccination against rat experimental autoimmune encephalomyelitis

Background

We have previously shown that vaccination with DNA encoding the encephalitogenic peptide myelin oligodendrocyte glycoprotein (MOG)_91–108 (pMOG) suppresses MOG_91–108-induced rat Experimental Autoimmune Encephalomyelitis (EAE), a model for human Multiple Sclerosis (MS). The suppressive effect of pMOG is dependent on inclusion of CpG DNA in the plasmid backbone and is associated with early induction of Interferon (IFN)-β.

Principal Findings

In this study we examined the mechanisms underlying pMOG-induced protection. We found that in the DNA vaccinated cohort proinflammatory Interleukin (IL)-17 and IL-21 responses were dramatically reduced compared to in the control group, but that the expression of Foxp3 and Tumor Growth Factor (TGF)-β1, which are associated with regulatory T cells, was not enhanced. Moreover, genes associated with Type I IFNs were upregulated. To delineate the role of IFN-β in the protective mechanism we employed short interfering RNA (siRNA) to IFN-β in the DNA vaccine. SiRNA to IFN-β completely abrogated the protective effects of the vaccine, demonstrating that a local early elaboration of IFN-β is important for EAE protection. IL-17 responses comparable to those in control rats developed in rats injected with the IFN-β-silencing DNA vaccine.

Conclusions

We herein demonstrate that DNA vaccination protects from proinflammatory Th17 cell responses during induction of EAE. The mechanism involves IFN-β as IL-17 responses are rescued by silencing of IFN-β during DNA vaccination.

Essential function, sophisticated regulation and pathological impact of the selective RNA-binding protein QKI in CNS myelin development

The selective RNA-binding protein QKI play a key role in advancing oligodendrocyte-dependent myelination, which is essential for the function and development of the CNS. The emerging evidence that QKI abnormalities are associated with schizophrenia and may underlie myelin impairment in this devastating disease has greatly increased interest in understanding the function of QKI. Despite the discovery of the biochemical basis for QKI-RNA interaction, a comprehensive model is currently missing regarding how QKI regulates its mRNA ligands to promote normal myelinogenesis and how deficiency of the QKI pathway is involved in the pathogenesis of human diseases that affect CNS myelin. In this review, we will focus on the role of QKI in regulating distinct mRNA targets at critical developmental steps to promote oligodendrocyte differentiation and myelin formation. In addition, we will discuss molecular mechanisms that control QKI expression and activity during normal myelinogenesis as well as the pathological impact of QKI deficiency in dysmyelination mutant animals and in human myelin disorders.

Osteopontin: role in immune regulation and stress responses

Recent research has led to a better but as yet incomplete understanding of the complex roles osteopontin plays in mammalian physiology. A soluble protein found in all body fluids, it stimulates signal transduction pathways (via integrins and CD44 variants) similar to those stimulated by components of the extracellular matrix. This appears to promote the survival of cells exposed to potentially lethal insults such as ischemia/reperfusion or physical/chemical trauma. OPN is chemotactic for many cell types including macrophages, dendritic cells, and T cells; it enhances B lymphocyte immunoglobulin production and proliferation. In inflammatory situations it stimulates both pro- and anti-inflammatory processes, which on balance can be either beneficial or harmful depending on what other inputs the cell is receiving. OPN influences cell-mediated immunity and has been shown to have Th1-cytokine functions. OPN deficiency is linked to a reduced Th1 immune response in infectious diseases, autoimmunity and delayed type hypersensitivity. OPN's role in the central nervous system and in stress responses has also emerged as an important aspect related to its cytoprotective and immune functions. Evidence suggests that either OPN or anti-OPN monoclonal antibodies (depending on the circumstances) might be clinically useful in modulating OPN function. Manipulation of plasma OPN levels may be useful in the treatment of autoimmune disease, cancer metastasis, osteoporosis and some forms of stress.

Acute disseminated encephalomyelitis: clinical and pathogenesis features

Acute disseminated encephalomyelitis (ADEM) is an immune-mediated disorder of the central nervous system (CNS). Disease typically starts with an abrupt onset of neurologic symptoms and signs within days to weeks after a viral infection or immunization. Neuropathological examination of the CNS in ADEM reveals involvement of white matter, with infiltration of monocytoid cells and perivenous demyelination.

Stat4 isoforms differentially regulate inflammation and demyelination in experimental allergic encephalomyelitis

Experimental allergic encephalomyelitis (EAE) is a T cell-mediated autoimmune disease model of multiple sclerosis. Signal transducer and activator of transcription 4 (Stat4) is a transcription factor activated by IL-12 and IL-23, two cytokines known to play important roles in the pathogenesis of EAE by inducing T cells to secrete IFN-gamma and IL-17, respectively. We and others have previously shown that therapeutic intervention or targeted disruption of Stat4 was effective in ameliorating EAE. Recently, a splice variant of Stat4 termed Stat4beta has been characterized that lacks 44 amino acids at the C terminus of the full-length Stat4alpha. In this study we examined whether T cells expressing either isoform could affect the pathogenesis of EAE. We found that transgenic mice expressing Stat4beta on a Stat4-deficient background develop an exacerbated EAE compared with wild-type mice following immunization with myelin oligodendrocyte glycoprotein peptide 35-55, while Stat4alpha transgenic mice have greatly attenuated disease. The differential development of EAE in transgenic mice correlates with increased IFN-gamma and IL-17 in Stat4beta-expressing cells in situ, contrasting increased IL-10 production by Stat4alpha-expressing cells. This study demonstrates that Stat4 isoforms differentially regulate inflammatory cytokines in association with distinct effects on the onset and severity of EAE.

Mast cell activation by myelin through scavenger receptor

A role for mast cells (MC) in the pathogenesis of multiple sclerosis (MS) has been suggested, based on the analysis of human lesions and on an animal model of the disease (EAE). What role MC play in the development of MS is not well understood. We hypothesized that the link connecting MC with demyelinating diseases may be represented by their interaction with myelin. Here we show that myelin can activate mast cells. This process could be a key event in the mast cell function required for inducing EAE in mice and possibly in MS in man.

Distinct and nonredundant in vivo functions of IFNAR on myeloid cells limit autoimmunity in the central nervous system

The action of type I interferons in the central nervous system (CNS) during autoimmunity is largely unknown. Here, we demonstrate elevated interferon beta concentrations in the CNS, but not blood, of mice with experimental autoimmune encephalomyelitis (EAE), a model for CNS autoimmunity. Furthermore, mice devoid of the broadly expressed type I IFN receptor (IFNAR) developed exacerbated clinical disease accompanied by a markedly higher inflammation, demyelination, and lethality without shifting the T helper 17 (Th17) or Th1 cell immune response. Whereas adoptive transfer of encephalitogenic T cells led to enhanced disease in Ifnar1(-/-) mice, newly created conditional mice with B or T lymphocyte-specific IFNAR ablation showed normal EAE. The engagement of IFNAR on neuroectodermal CNS cells had no protective effect. In contrast, absence of IFNAR on myeloid cells led to severe disease with an enhanced effector phase and increased lethality, indicating a distinct protective function of type I IFNs during autoimmune inflammation of the CNS.

Interferon-gamma directly induces neurotoxicity through a neuron specific, calcium-permeable complex of IFN-gamma receptor and AMPA GluR1 receptor

Interferon-gamma (IFN-gamma) is a proinflammatory cytokine that plays a pivotal role in pathology of diseases in the central nervous system (CNS), such as multiple sclerosis. However, the direct effect of IFN-gamma on neuronal cells has yet to be elucidated. We show here that IFN-gamma directly induces neuronal dysfunction, which appears as dendritic bead formation in mouse cortical neurons and enhances glutamate neurotoxicity mediated via alpha-amino-3-hydroxy-5-methyl-4-isoxazolepropionic (AMPA) receptors but not N-methyl-D-aspartate receptors. In the CNS, IFN-gamma receptor forms a unique, neuron-specific, calcium-permeable receptor complex with AMPA receptor subunit GluR1. Through this receptor complex, IFN-gamma phosphorylates GluR1 at serine 845 position by JAK1.2/STAT1 pathway, increases Ca(2+) influx and following nitric oxide production, and subsequently decreases ATP production, leading to the dendritic bead formation. These findings provide novel mechanisms of neuronal excitotoxicity, which may occur in both inflammatory and neurodegenerative diseases in the CNS.

Variations of the perforin gene in patients with multiple sclerosis

Perforin is involved in cell-mediated cytotoxicity and mutations of its gene (PRF1) cause familial hemophagocytic lymphohistiocytosis (FLH2). PRF1 sequencing in 190 patients with multiple sclerosis and 268 controls detected two FLH2-associated variations (A91V, N252S) in both groups and six novel mutations (C999T, G1065A, G1428A, A1620G, G719A, C1069T) in patients. All together, carriers of these variations were more frequent in patients than in controls (phenotype frequency: 17 vs 9%, P=0.0166; odds ratio (OR)=2.06, 95% confidence interval (CI): 1.13-3.77). Although A91V was the most frequent variation and displayed a trend of association with multiple sclerosis (MS) in the first population of patients and controls (frequency of the 91V allele: 0.076 vs 0.043, P=0.044), we used it as a marker to confirm PRF1 involvement in MS and assessed its frequency in a second population of 966 patients and 1520 controls. Frequency of the 91V allele was significantly higher in patients than in controls also in the second population (0.075 vs 0.058%, P=0.019). In the combined cohorts of 1156 patients and 1788 controls, presence of the 91V allele in single or double dose conferred an OR=1.38 (95% CI=1.10-1.74). These data suggest that A91V and possibly other perforin variations indicate susceptibility to MS.

15-deoxy-Delta(12,14)-prostaglandin J(2) and curcumin modulate the expression of toll-like receptors 4 and 9 in autoimmune T lymphocyte

INTRODUCTION

Experimental allergic encephalomyelitis (EAE) is a T cell-mediated autoimmune disease model for multiple sclerosis (MS). We have shown earlier that 15-deoxy-Delta(12,14)-prostaglandin J(2) (15d-PGJ(2)) and curcumin ameliorate EAE by modulating inflammatory signaling pathways in T lymphocytes. Toll-like receptors (TLRs), expressed primarily in innate immune cells, play critical roles in the pathogenesis of EAE. T lymphocytes also express TLRs and function as costimulatory receptors to upregulate proliferation and cytokine production in response to specific agonists.

DISCUSSION

In this study, we show that naïve CD4(+) and CD8(+) T cells express detectable levels of TLR4 and TLR9 and that increase after the induction of EAE in SJL/J and C57BL/6 mice by immunization with PLPp139-151 and MOGp35-55 antigen, respectively. It is interesting to note that in vivo treatment with 15d-PGJ2 or curcumin results in a significant decrease in TLR4 and TLR9 expression in CD4(+) and CD8(+) T cells in association with the amelioration of EAE.

CONCLUSION

Although the exact mechanisms are not known, the modulation of TLR expression in T lymphocytes by 15d-PGJ(2) and curcumin suggests new therapeutic targets in the treatment of T cell-mediated autoimmune diseases.

RAR/RXR and PPAR/RXR signaling in neurological and psychiatric diseases

Retinoids are important signals in brain development. They regulate gene transcription by binding to retinoic acid receptors (RAR) and, as was discovered recently, a peroxisome proliferator-activated receptor (PPAR). Traditional ligands of PPAR are best known for their functions in lipid metabolism and inflammation. RAR and PPAR are ligand-activated transcription factors, which share members of the retinoid X receptor (RXR) family as heterodimeric partners. Both signal transduction pathways have recently been implicated in the progression of neurodegenerative and psychiatric diseases. Since inflammatory processes contribute to various neurodegenerative diseases, the anti-inflammatory activity of retinoids and PPARgamma agonists recommends them as potential therapeutic targets. In addition, genetic linkage studies, transgenic mouse models and experiments with vitamin A deprivation provide evidence that retinoic acid signaling is directly involved in physiology and pathology of motoneurons, of the basal ganglia and of cognitive functions. The activation of PPAR/RXR and RAR/RXR transcription factors has therefore been proposed as a therapeutic strategy in disorders of the central nervous system.

Unexpected regulatory roles of TLR4 and TLR9 in experimental autoimmune encephalomyelitis

Innate immune mechanisms essential for priming encephalitogenic T cells in autoimmune neuroinflammation are poorly understood. Experimental autoimmune encephalomyelitis (EAE) is a IL-17-producing Th (Th17) cell-mediated autoimmune disease and an animal model of multiple sclerosis. To investigate how upstream TLR signals influence autoimmune T cell responses, we studied the role of individual TLR and MyD88, the common TLR adaptor molecule, in the initiation of innate and adaptive immune responses in EAE. Wild type (WT) C57BL/6, TLR-deficient and MyD88-deficient mice were immunized with myelin oligodendrocyte glycoprotein (MOG) in CFA. MyD88(-/-) mice were completely EAE resistant. Purified splenic myeloid DC (mDC) from MyD88(-/-) mice expressed much less IL-6 and IL-23, and serum and T cell IL-17 were absent. TLR4(-/-) and TLR9(-/-) mice surprisingly exhibited more severe EAE symptoms than WT mice. IL-6 and IL-23 expression by mDC and Th17 responses were higher in TLR4(-/-) mice, suggesting a regulatory role of TLR4 in priming Th17 cells. IL-6 expression by splenocytes was higher in TLR9(-/-) mice. Our data suggest that MyD88 mediates the induction of mDC IL-6 and IL-23 responses after MOG immunization, which in turn drives IL-17-producing encephalitogenic Th17 cell activation. Importantly, we demonstrate that TLR4 and TLR9 regulate disease severity in MOG-induced EAE.

Therapeutic Potential of PPARγ Activation in Stroke

Stroke (focal cerebral ischemia) is a leading cause of death and disability among adult population. Many pathological events including inflammation and oxidative stress during the acute period contributes to the secondary neuronal death leading the neurological dysfunction after stroke. Transcriptional regulation of genes that promote these pathophysiological mechanisms can be an effective strategy to minimize the poststroke neuronal death. Peroxisome proliferator-activated receptors (PPARs) are ligand-activated transcription factors known to be upstream to many inflammatory and antioxidant genes. The goal of this review is to discuss the therapeutic potential and putative mechanisms of neuroprotection following PPAR activation after stroke.