Interleukin-1 receptor antagonist suppresses experimental autoimmune encephalomyelitis (EAE) in rats by influencing the activation and proliferation of encephalitogenic cells

Endoplasmic reticulum stress response in immune cells contributes to experimental autoimmune encephalomyelitis pathogenesis in rats

We examined the role of endoplasmic reticulum (ER) stress and the ensuing unfolded protein response (UPR) in the development of the central nervous system (CNS)-directed immune response in the rat model of experimental autoimmune encephalomyelitis (EAE). The induction of EAE with syngeneic spinal cord homogenate in complete Freund's adjuvant (CFA) caused a time-dependent increase in the expression of ER stress/UPR markers glucose-regulated protein 78 (GRP78), X-box-binding protein 1 (XBP1), C/EBP homologous protein (CHOP), and phosphorylated eukaryotic initiation factor 2α (eIF2α) in the draining lymph nodes of both EAE-susceptible Dark Agouti (DA) and EAE-resistant Albino Oxford (AO) rats. However, the increase in ER stress markers was more pronounced in AO rats. CFA alone also induced ER stress, but the effect was weaker and less sustained compared to full immunization. The ultrastructural analysis of DA lymph node tissue by electron microscopy revealed ER dilatation in lymphocytes, macrophages, and plasma cells, while immunoblot analysis of CD3-sorted lymph node cells demonstrated the increase in ER stress/UPR markers in both CD3+ (T cell) and CD3- (non-T) cell compartments. A positive correlation was observed between the levels of ER stress/UPR markers in the CNS-infiltrated mononuclear cells and the clinical activity of the disease. Finally, the reduction of EAE clinical signs by ER stress inhibitor ursodeoxycholic acid was associated with the decrease in the expression of mRNA encoding pro-inflammatory cytokines TNF and IL-1β, and encephalitogenic T cell cytokines IFN-γ and IL-17. Collectively, our data indicate that ER stress response in immune cells might be an important pathogenetic factor and a valid therapeutic target in the inflammatory damage of the CNS.

Complete Freund's adjuvant as a confounding factor in multiple sclerosis research

Complete Freund's adjuvant (CFA) is used as a standard adjuvant for the induction of experimental autoimmune encephalomyelitis (EAE), the most commonly used animal model in multiple sclerosis studies. Still, CFA induces glial activation and neuroinflammation on its own and provokes pain. In addition, as CFA contains Mycobacteria, an immune response against bacterial antigens is induced in parallel to the response against central nervous system antigens. Thus, CFA can be considered as a confounding factor in multiple sclerosis-related studies performed on EAE. Here, we discuss the effects of CFA in EAE in detail and present EAE variants induced in experimental animals without the use of CFA. We put forward CFA-free EAE variants as valuable tools for studying multiple sclerosis pathogenesis and therapeutic approaches.

Cytokines, Vascular Endothelial Growth Factors, and PlGF in Autoimmunity: Insights From Rheumatoid Arthritis to Multiple Sclerosis

In this review, we will explore the intricate roles of cytokines and vascular endothelial growth factors in autoimmune diseases (ADs), with a particular focus on rheumatoid arthritis (RA) and multiple sclerosis (MS). AD is characterized by self-destructive immune responses due to auto-reactive T lymphocytes and Abs. Among various types of ADs, RA and MS possess inflammation as a central role but in different sites of the patients. Other common aspects among these two ADs are their chronicity and relapsing-remitting symptoms requiring continuous management. First factor inducing these ADs are cytokines, such as IL-6, TNF-α, and IL-17, which play significant roles in the pathogenesis by contributing to inflammation, immune cell activation, and tissue damage. Secondly, vascular endothelial growth factors, including VEGF and angiopoietins, are crucial in promoting angiogenesis and inflammation in these two ADs. Finally, placental growth factor (PlGF), an emerging factor with bi-directional roles in angiogenesis and T cell differentiation, as we introduce as an "angio-lymphokine" is another key factor in ADs. Thus, while angiogenesis recruits more inflammatory cells into the peripheral sites, cytokines secreted by effector cells play critical roles in the pathogenesis of ADs. Various therapeutic interventions targeting these soluble molecules have shown promise in managing autoimmune pathogenic conditions. However, delicate interplay between cytokines, angiogenic factors, and PlGF has more to be studied when considering their complementary role in actual pathogenic conditions. Understanding the complex interactions among these factors provides valuable insights for the development of innovative therapies for RA and MS, offering hope for improved patient outcomes.

Unleashing nature's potential and limitations: Exploring molecular targeted pathways and safe alternatives for the treatment of multiple sclerosis (Review)

Driven by the limitations and obstacles of the available approaches and medications for multiple sclerosis (MS) that still cannot treat the disease, but only aid in accelerating the recovery from its attacks, the use of naturally occurring molecules as a potentially safe and effective treatment for MS is being explored in model organisms. MS is a devastating disease involving the brain and spinal cord, and its symptoms vary widely. Multiple molecular pathways are involved in the pathogenesis of the disease. The present review showcases the recent advancements in harnessing nature's resources to combat MS. By deciphering the molecular pathways involved in the pathogenesis of the disease, a wealth of potential therapeutic agents is uncovered that may revolutionize the treatment of MS. Thus, a new hope can be envisioned in the future, aiming at paving the way toward identifying novel safe alternatives to improve the lives of patients with MS.

Osteopontin Is Associated with Multiple Sclerosis Relapses

BACKGROUND

Osteopontin, an extracellular matrix protein involved in bone remodeling, tissue repair and inflammation, has previously been associated with increased inflammation and neurodegeneration in multiple sclerosis (MS), promoting a worse disease course. Osteopontin is also likely involved in acute MS relapses.

METHODS

In 47 patients with relapsing-remitting MS, we explored the correlation between the time elapsed between the last clinical relapse and lumbar puncture, and the cerebrospinal fluid (CSF) levels of osteopontin and a group of inflammatory cytokines and adipokines such as resistin, plasminogen activator inhibitor-1, osteoprotegerin, interleukin (IL)-1β, IL-2, IL-6 and IL-1 receptor antagonist (IL-1ra). We also analyzed the correlations between CSF levels of osteopontin and the other CSF molecules considered.

RESULTS

Osteopontin CSF concentrations were higher in patients with a shorter time interval between the last clinical relapse and CSF withdrawal. In addition, CSF levels of osteopontin were positively correlated with the proinflammatory cytokines IL-2 and IL-6 and negatively correlated with the anti-inflammatory molecule IL-1ra.

CONCLUSIONS

Our results further suggest the role of osteopontin in acute MS relapses showing that, in proximity to relapses, osteopontin expression in CSF may be increased along with other proinflammatory mediators and correlated with decreased concentrations of anti-inflammatory molecules.

The Therapeutic Prospects of Targeting IL-1R1 for the Modulation of Neuroinflammation in Central Nervous System Disorders

The interleukin-1 receptor type 1 (IL-1R1) holds pivotal roles in the immune system, as it is positioned at the “epicenter” of the inflammatory signaling networks. Increased levels of the cytokine IL-1 are a recognized feature of the immune response in the central nervous system (CNS) during injury and disease, i.e., neuroinflammation. Despite IL-1/IL-1R1 signaling within the CNS having been the subject of several studies, the roles of IL-1R1 in the CNS cellular milieu still cause controversy. Without much doubt, however, the persistent activation of the IL-1/IL-1R1 signaling pathway is intimately linked with the pathogenesis of a plethora of CNS disease states, ranging from Alzheimer’s disease (AD), Parkinson’s disease (PD), amyotrophic lateral sclerosis (ALS) and multiple sclerosis (MS), all the way to schizophrenia and prion diseases. Importantly, a growing body of evidence is showing that blocking IL-1R1 signaling via pharmacological or genetic means in different experimental models of said CNS diseases leads to reduced neuroinflammation and delayed disease progression. The aim of this paper is to review the recent progress in the study of the biological roles of IL-1R1, as well as to highlight key aspects that render IL-1R1 a promising target for the development of novel disease-modifying treatments for multiple CNS indications.

Interleukin-1 receptor antagonist: An exploratory plasma biomarker that correlates with disability and provides pathophysiological insights in relapsing-remitting multiple sclerosis

BACKGROUND

Multiple sclerosis (MS) is a chronic inflammatory demyelinating and neurodegenerative disorder. Interleukin-1 receptor antagonist (IL-1RA) is an endogenous soluble antagonist of the IL-1 receptor and blocks the pro-inflammatory effects of IL-1β known to contribute to MS pathology. The objectives of this study were to determine whether IL-1RA is associated with disability in MS and how this correlates with neurofilament light (NfL) levels in cerebrospinal fluid (CSF).

METHODS

Peripheral blood and CSF were collected from consenting MS patients. Patient demographic and clinical variables, including past relapse activity, were also collected. Circulating levels of IL-1RA, IL-18, and IL-1β were measured in plasma; IL-1RA and NfL were measured in the CSF via Bio-plex multiplex immunoassay kits and ELISA, respectively. IL-1RA expression was investigated in vitro using primary human macrophages and microglia, and in situ using post-mortem MS tissue.

RESULTS

Following a multiple regression analysis, IL-1RA levels in plasma correlated with expanded disability status scale score independent of all other variables. In a separate cohort, CSF IL-1RA significantly correlated with NfL. In vitro, induction of the NLRP3 inflammasome, a pathological hallmark within MS lesions, led to increased release of IL-1RA from primary human microglia and macrophages. In the CNS, IL-1RA⁺ macrophages/microglia were present at the rim of mixed active/inactive MS lesions.

CONCLUSIONS

Results presented in this study demonstrate that IL-1RA is a novel exploratory biomarker in relapsing-remitting MS, which correlates with disability and provides mechanistic insights into the regulatory inflammatory responses within the demyelinated CNS.

Immune Soluble Factors in the Cerebrospinal Fluid of Progressive Multiple Sclerosis Patients Segregate Into Two Groups

Primary-progressive (PP) and secondary-progressive (SP) multiple sclerosis (MS) are characterized by neurological deficits caused by a permanent neuronal damage, clinically quantified by the expanded disability status scale (EDSS). Neuronal tissue damage is also mediated by immune infiltrates producing soluble factors, such as cytokines and chemokines, which are released in the cerebrospinal fluid (CSF). The mechanisms regulating the production of a soluble factor are not completely defined. Using multiplex bead-based assays, we simultaneously measured 27 immune soluble factors in the CSF collected from 38 patients, 26 with PP-MS and 12 with SP-MS. Then, we performed a correlation matrix of all soluble factors expressed in the CSF. The CSF from patients with PP-MS and SP-MS had similar levels of cytokines and chemokines; however, the stratification of patients according to active or inactive magnetic resonance imaging (MRI) unveils some differences. Correlative studies between soluble factors in the CSF of patients with PP-MS and SP-MS revealed two clusters of immune mediators with pro-inflammatory functions, namely IFN-γ, MCP-1, MIP-1α, MIP-1β, IL-8, IP-10, and TNF-α (group 1), and anti-inflammatory functions, namely IL-9, IL-15, VEGF, and IL-1ra (group 2). However, most of the significant correlations between cytokines of group 1 and of group 2 were lost in patients with more severe disability (EDSS ≥ 4) compared to patients with mild to moderate disability (EDSS < 4). These results suggest a common regulation of cytokines and chemokines belonging to the same group and indicate that, in patients with more severe disability, the production of those factors is less coordinated, possibly due to advanced neurodegenerative mechanisms that interfere with the immune response.

Association between familial Mediterranean fever and multiple sclerosis: A case series from the JIR cohort and systematic literature review

INTRODUCTION

Familial Mediterranean fever (FMF) is the most frequent monogenic autoinflammatory disorder; and leads to the uncontrolled production of interleukin (IL)-1β. Multiple sclerosis (MS) is an inflammatory disease of the central nervous system; and its development seems to be partly correlated with IL-1β levels. It is hypothesized that FMF could be associated with MS. We aim to describe the features of patients displaying both diseases and to investigate the MEFV mutation rate in MS patients.

METHODS

Patients with definite MS were retrieved from the cohort of FMF patients in the Reference Center for Rare Auto-inflammatory Diseases and Amyloidosis (CEREMAIA). We also performed a systematic literature review of articles from PubMed that were published from 1990 to 2020.

RESULTS

Twenty-four patients were included in the case series: five patients (1.3%) from our cohort of 364 and 19 patients from the literature. The sex ratio was 2:1. The mean age at diagnosis of FMF was 19 years old; and that for MS was 29 years old. Seven studies investigating the MEFV mutation rate in MS patients were included. Three studies found a higher mutation rate in MS patients than in the control group.

CONCLUSION

FMF and MS features were comparable to those of patients with unrelated diseases; and MEFV mutation carriage was not positively correlated with MS. However; MS prevalence in FMF patients was higher than was expected in a healthy population. To a lesser extent; FMF prevalence in MS patients was higher than expected in a healthy population and the difference might not be significant. These data suggest that FMF could be associated with MS; and further studies are needed to investigate a potential causal association.

Mobilized Multipotent Hematopoietic Progenitors Stabilize and Expand Regulatory T Cells to Protect Against Autoimmune Encephalomyelitis

Achieving immunoregulation via in vivo expansion of Foxp3⁺ regulatory CD4⁺ T cells (Treg) remains challenging. We have shown that mobilization confers to multipotent hematopoietic progenitors (MPPs) the capacity to enhance Treg proliferation. Transcriptomic analysis of Tregs co-cultured with MPPs revealed enhanced expression of genes stabilizing the suppressive function of Tregs as well as the activation of IL-1β-driven pathways. Adoptive transfer of only 25,000 MPPs effectively reduced the development of experimental autoimmune encephalomyelitis (EAE), a pre-clinical model for multiple sclerosis (MS). Production of the pathogenic cytokines IL-17 and GM-CSF by spinal cord-derived CD4⁺ T-cells in MPP-protected recipients was reduced while Treg expansion was enhanced. Treg depletion once protection by MPPs was established, triggered disease relapse to the same level as in EAE mice without MPP injection. The key role of IL-1β was further confirmed in vivo by the lack of protection against EAE in recipients of IL-1β-deficient MPPs. Mobilized MPPs may thus be worth considering for cell therapy of MS either per se or for enrichment of HSC grafts in autologous bone marrow transplantation already implemented in patients with severe refractory multiple sclerosis.

Potential for Targeting Myeloid Cells in Controlling CNS Inflammation

Multiple Sclerosis (MS) is characterized by immune cell infiltration to the central nervous system (CNS) as well as loss of myelin. Characterization of the cells in lesions of MS patients revealed an important accumulation of myeloid cells such as macrophages and dendritic cells (DCs). Data from the experimental autoimmune encephalomyelitis (EAE) model of MS supports the importance of peripheral myeloid cells in the disease pathology. However, the majority of MS therapies focus on lymphocytes. As we will discuss in this review, multiple strategies are now in place to target myeloid cells in clinical trials. These strategies have emerged from data in both human and mouse studies. We discuss strategies targeting myeloid cell migration, growth factors and cytokines, biological functions (with a focus on miRNAs), and immunological activities (with a focus on nanoparticles).

Graphene quantum dots inhibit T cell-mediated neuroinflammation in rats

We investigated the therapeutic capacity of nano-sized graphene sheets, called graphene quantum dots (GQD), in experimental autoimmune encephalomyelitis (EAE), an animal model of immune-mediated central nervous system (CNS) damage. Intraperitoneally administered GQD (10 mg/kg/day) accumulated in the lymph node and CNS cells of Dark Agouti rats in which EAE was induced by immunization with spinal cord homogenate in complete Freund's adjuvant. GQD significantly reduced clinical signs of EAE when applied throughout the course of the disease (day 0-32), while the protection was less pronounced if the treatment was limited to the induction (day 0-7 post-immunization) or effector (from day 8 onwards) phase of the disease. GQD treatment diminished immune infiltration, demyelination, axonal damage, and apoptotic death in the CNS of EAE animals. GQD also reduced the numbers of interferon-γ-expressing T helper (Th)1 cells, as well as the expression of Th1 transcription factor T-bet and proinflammatory cytokines tumor necrosis factor, interleukin-1, and granulocyte-macrophage colony-stimulating factor in the lymph nodes and CNS immune infitrates. The protective effect of GQD in EAE was associated with the activation of p38 and p42/44 mitogen-activated protein kinases (MAPK) and Akt in the lymph nodes and/or CNS. Finally, GQD protected oligodendrocytes and neurons from T cell-mediated damage in the in vitro conditions. Collectively, these data demonstrate the ability of GQD to gain access to both immune and CNS cells during neuroinflammation, and to alleviate immune-mediated CNS damage by modulating MAPK/Akt signaling and encephalitogenic Th1 immune response.

CCR5 knockout suppresses experimental autoimmune encephalomyelitis in C57BL/6 mice

Multiple sclerosis (MS) is an inflammatory disease in which myelin in the spinal cord is damaged. C-C chemokine receptor type 5 (CCR5) is implicated in immune cell migration and cytokine release in central nervous system (CNS). We investigated whether CCR5 plays a role in MS progression using a murine model, experimental autoimmune encephalomyelitis (EAE), in CCR5 deficient (CCR5-/-) mice. CCR5-/- and CCR5+/+ (wild-type) mice were immunized with myelin oligodendrocyte glycoprotein 35-55 (MOG35-55) followed by pertussis toxin, after which EAE paralysis was scored for 28 days. We found that clinical scoring and EAE neuropathology were lower in CCR5-/- mice than CCR5+/+ mice. Immune cells (CD3+, CD4+, CD8+, B cell, NK cell and macrophages) infiltration and astrocytes/microglial activation were attenuated in CCR5-/- mice. Moreover, levels of IL-1β, TNF-α, IFN-γ and MCP-1 cytokine levels were decreased in CCR5-/- mice spinal cord. Myelin basic protein (MBP) and CNPase were increased while NG2 and O4 were decreased in CCR5-/- mice, indicating that demyelination was suppressed by CCR5 gene deletion. These findings suggest that CCR5 is likely participating in demyelination in the spinal cord the MS development, and that it could serve as an effective therapeutic target for the treatment of MS.

Amyloid-β Homeostasis Bridges Inflammation, Synaptic Plasticity Deficits and Cognitive Dysfunction in Multiple Sclerosis

Cognitive deficits are frequently observed in multiple sclerosis (MS), mainly involving processing speed and episodic memory. Both demyelination and gray matter atrophy can contribute to cognitive deficits in MS. In recent years, neuroinflammation is emerging as a new factor influencing clinical course in MS. Inflammatory cytokines induce synaptic dysfunction in MS. Synaptic plasticity occurring within hippocampal structures is considered as one of the basic physiological mechanisms of learning and memory. In experimental models of MS, hippocampal plasticity is profoundly altered by proinflammatory cytokines. Although mechanisms of inflammation-induced hippocampal pathology in MS are not completely understood, alteration of Amyloid-β (Aβ) metabolism is emerging as a key factor linking together inflammation, synaptic plasticity and neurodegeneration in different neurological diseases. We explored the correlation between concentrations of Aβ_1–42 and the levels of some proinflammatory and anti-inflammatory cytokines (interleukin-1β (IL-1β), IL1-ra, IL-8, IL-10, IL-12, tumor necrosis factor α (TNFα), interferon γ (IFNγ)) in the cerebrospinal fluid (CSF) of 103 remitting MS patients. CSF levels of Aβ_1–42 were negatively correlated with the proinflammatory cytokine IL-8 and positively correlated with the anti-inflammatory molecules IL-10 and interleukin-1 receptor antagonist (IL-1ra). Other correlations, although noticeable, were either borderline or not significant. Our data show that an imbalance between proinflammatory and anti-inflammatory cytokines may lead to altered Aβ homeostasis, representing a key factor linking together inflammation, synaptic plasticity and cognitive dysfunction in MS. This could be relevant to identify novel therapeutic approaches to hinder the progression of cognitive dysfunction in MS.

New Insights into the Role of IL-1β in Experimental Autoimmune Encephalomyelitis and Multiple Sclerosis

Multiple sclerosis (MS), and its animal model experimental autoimmune encephalomyelitis, are neuroinflammatory diseases driven by autoreactive pathogenic T_H cells that elicit demyelination and axonal damage. How T_H cells acquire pathogenicity and communicate with myeloid cells and cells of the CNS remain unclear. IL-1β is recognized to play an important role in experimental autoimmune encephalomyelitis (EAE) and perhaps MS. Clinical EAE is significantly attenuated in IL-1R-deficient and IL-1β-deficient mice, and IL-1β is found in the blood, cerebrospinal fluid, and CNS lesions of MS patients. In this article, we focus on new reports that elucidate the cellular sources of IL-1β and its actions during EAE, in both lymphoid tissues and within the CNS. Several immune cell types serve as critical producers of IL-1β during EAE, with this cytokine inducing response in both hematopoietic and nonhematopoietic cells. These findings from the EAE model should inspire efforts toward investigating the therapeutic potential of IL-1 blockade in MS.

Astrocytic tight junctions control inflammatory CNS lesion pathogenesis

Lesions and neurologic disability in inflammatory CNS diseases such as multiple sclerosis (MS) result from the translocation of leukocytes and humoral factors from the vasculature, first across the endothelial blood-brain barrier (BBB) and then across the astrocytic glia limitans (GL). Factors secreted by reactive astrocytes open the BBB by disrupting endothelial tight junctions (TJs), but the mechanisms that control access across the GL are unknown. Here, we report that in inflammatory lesions, a second barrier composed of reactive astrocyte TJs of claudin 1 (CLDN1), CLDN4, and junctional adhesion molecule A (JAM-A) subunits is induced at the GL. In a human coculture model, CLDN4-deficient astrocytes were unable to control lymphocyte segregation. In models of CNS inflammation and MS, mice with astrocyte-specific Cldn4 deletion displayed exacerbated leukocyte and humoral infiltration, neuropathology, motor disability, and mortality. These findings identify a second inducible barrier to CNS entry at the GL. This barrier may be therapeutically targetable in inflammatory CNS disease.

Activated IL-1RI Signaling Pathway Induces Th17 Cell Differentiation via Interferon Regulatory Factor 4 Signaling in Patients with Relapsing-Remitting Multiple Sclerosis

IL-1β plays a crucial role in the differentiation of human Th17 cells. We report here that IL-1RI expression is significantly increased in both naive and memory CD4⁺ T cells derived from relapsing-remitting multiple sclerosis (RR MS) patients in comparison to healthy controls. Interleukin 1 receptor (IL-1R)I expression is upregulated in the in vitro-differentiated Th17 cells from RR MS patients in comparison to the Th1 and Th2 cell subsets, indicating the role of IL-1R signaling in the Th17 cell differentiation in RR MS. When IL-1RI gene expression was silenced using siRNA, human naive CD4⁺ T cells cultured in the presence of Th17-polarizing cytokines had a significantly decreased expression of interleukin regulatory factor 4 (IRF4), RORc, IL-17A, IL-17F, IL-21, IL-22, and IL-23R genes, confirming that IL-1RI signaling induces Th17 cell differentiation. Since IL-1R gene expression silencing inhibited IRF4 expression and Th17 differentiation, and IRF4 gene expression silencing inhibited Th17 cell differentiation, our results indicate that IL-1RI induces human Th17 cell differentiation in an IRF4-dependant manner. Our study has identified that IL-1RI-mediated signaling pathway is constitutively activated, leading to an increased Th17 cell differentiation in IRF4-dependent manner in patients with RR MS.

NF-κB Pathways in the Pathogenesis of Multiple Sclerosis and the Therapeutic Implications

Nuclear factor kappa-light-chain-enhancer of activated B cells (NF-κB) signaling pathways are involved in cell immune responses, apoptosis and infections. In multiple sclerosis (MS), NF-κB pathways are changed, leading to increased levels of NF-κB activation in cells. This may indicate a key role for NF-κB in MS pathogenesis. NF-κB signaling is complex, with many elements involved in its activation and regulation. Interestingly, current MS treatments are found to be directly or indirectly linked to NF-κB pathways and act to adjust the innate and adaptive immune system in patients. In this review, we will first focus on the intricacies of NF-κB signaling, including the activating pathways and regulatory elements. Next, we will theorize about the role of NF-κB in MS pathogenesis, based on current research findings, and discuss some of the associated therapeutic implications. Lastly, we will review four new MS treatments which interrupt NF-κB pathways—fingolimod, teriflunomide, dimethyl fumarate (DMF) and laquinimod (LAQ)—and explain their mechanisms, and the possible strategy for MS treatments in the future.

Dendritic cells as therapeutic targets in neuroinflammation

Multiple sclerosis (MS) is the most common chronic inflammatory demyelinating disorder of the central nervous system characterized by infiltration of immune cells and progressive damage to myelin sheaths and neurons. There is still no cure for the disease, but drug regimens can reduce the frequency of relapses and slightly delay progression. Myeloid cells or antigen-presenting cells (APCs) such as dendritic cells (DC), macrophages, and resident microglia, are key players in both mediating immune responses and inducing immune tolerance. Mounting evidence indicates a contribution of these myeloid cells to the pathogenesis of multiple sclerosis and to the effects of treatment, the understanding of which might provide strategies for more potent novel therapeutic interventions. Here, we review recent insights into the role of APCs, with specific focus on DCs in the modulation of neuroinflammation in MS.

Myeloid cell transmigration across the CNS vasculature triggers IL-1β-driven neuroinflammation during autoimmune encephalomyelitis in mice

Growing evidence supports a role for IL-1 in multiple sclerosis and experimental autoimmune encephalomyelitis (EAE), but how it impacts neuroinflammation is poorly understood. We show that susceptibility to EAE requires activation of IL-1R1 on radiation-resistant cells via IL-1β secreted by bone marrow-derived cells. Neutrophils and monocyte-derived macrophages (MDMs) are the main source of IL-1β and produce this cytokine as a result of their transmigration across the inflamed blood-spinal cord barrier. IL-1R1 expression in the spinal cord is found in endothelial cells (ECs) of the pial venous plexus. Accordingly, leukocyte infiltration at EAE onset is restricted to IL-1R1(+) subpial and subarachnoid vessels. In response to IL-1β, primary cultures of central nervous system ECs produce GM-CSF, G-CSF, IL-6, Cxcl1, and Cxcl2. Initiation of EAE or subdural injection of IL-1β induces a similar cytokine/chemokine signature in spinal cord vessels. Furthermore, the transfer of Gr1(+) cells on the spinal cord is sufficient to induce illness in EAE-resistant IL-1β knockout (KO) mice. Notably, transfer of Gr1(+) cells isolated from C57BL/6 mice induce massive recruitment of recipient myeloid cells compared with cells from IL-1β KO donors, and this recruitment translates into more severe paralysis. These findings suggest that an IL-1β-dependent paracrine loop between infiltrated neutrophils/MDMs and ECs drives neuroinflammation.

Neuroprotective arylpiperazine dopaminergic/serotonergic ligands suppress experimental autoimmune encephalomyelitis in rats

Arylpiperazine-based dopaminergic/serotonergic ligands exert neuroprotective activity. We examined the effect of arylpiperazine D2 /5-HT1A ligands, N-{4-[2-(4-phenyl-piperazin-1-yl)-ethyl}-phenyl]-picolinamide (6a) and N-{3-[2-(4-phenyl-piperazin-1-yl)-ethyl]-phenyl}-picolinamide (6b), in experimental autoimmune encephalomyelitis (EAE), a model of neuroinflammation. Both compounds (10 mg/kg i.p.) reduced EAE clinical signs in spinal cord homogenate-immunized Dark Agouti rats. Compound 6b was more efficient in delaying the disease onset and reducing the maximal clinical score, which correlated with its higher affinity for D2 and 5-HT1A receptors. The protection was retained if treatment was limited to the effector (from day 8 onwards), but not the induction phase (day 0-7) of EAE. Compound 6b reduced CNS immune infiltration and expression of mRNA encoding the proinflammatory cytokines tumor necrosis factor, IL-6, IL-1, and GM-CSF, TH 1 cytokine IFN-γ, TH 17 cytokine IL-17, as well as the signature transcription factors of TH 1 (T-bet) and TH 17 (RORγt) cells. Arylpiperazine treatment reduced apoptosis and increased the activation of anti-apoptotic mediators Akt and p70S6 kinase in the CNS of EAE animals. The in vitro treatment with 6b protected oligodendrocyte cell line OLN-93 and neuronal cell line PC12 from mitogen-activated normal T cells or myelin basic protein-activated encephalitogenic T cells. In conclusion, arylpiperazine dopaminergic/serotonergic ligands suppress EAE through a direct neuroprotective action and decrease in CNS inflammation. Arylpiperazine dopaminergic/serotonergic ligands reduce neurological symptoms of acute autoimmune encephalomyelitis in rats without affecting the activation of autoreactive immune response, through mechanisms involving a decrease in CNS immune infiltration, as well as direct protection of CNS from immune-mediated damage. These data indicate potential usefulness of arylpiperazine-based compounds in the treatment of neuroinflammatory disorders such as multiple sclerosis.

Functional Magnetic Resonance Imaging of Rats with Experimental Autoimmune Encephalomyelitis Reveals Brain Cortex Remodeling

Cortical reorganization occurring in multiple sclerosis (MS) patients is thought to play a key role in limiting the effect of structural tissue damage. Conversely, its exhaustion may contribute to the irreversible disability that accumulates with disease progression. Several aspects of MS-related cortical reorganization, including the overall functional effect and likely modulation by therapies, still remain to be elucidated. The aim of this work was to assess the extent of functional cortical reorganization and its brain structural/pathological correlates in Dark Agouti rats with experimental autoimmune encephalomyelitis (EAE), a widely accepted preclinical model of chronic MS. Morphological and functional MRI (fMRI) were performed before disease induction and during the relapsing and chronic phases of EAE. During somatosensory stimulation of the right forepaw, fMRI demonstrated that cortical reorganization occurs in both relapsing and chronic phases of EAE with increased activated volume and decreased laterality index versus baseline values. Voxel-based morphometry demonstrated gray matter (GM) atrophy in the cerebral cortex, and both GM and white matter atrophy were assessed by ex vivo pathology of the sensorimotor cortex and corpus callosum. Neuroinflammation persisted in the relapsing and chronic phases, with dendritic spine density in the layer IV sensory neurons inversely correlating with the number of cluster of differentiation 45-positive inflammatory lesions. Our work provides an innovative experimental platform that may be pivotal for the comprehension of key mechanisms responsible for the accumulation of irreversible brain damage and for the development of innovative therapies to reduce disability in EAE/MS.

SIGNIFICANCE STATEMENT

Since the early 2000s, functional MRI (fMRI) has demonstrated profound modifications in the recruitment of cortical areas during motor, cognitive, and sensory tasks in multiple sclerosis (MS) patients. Experimental autoimmune encephalomyelitis (EAE) represents a reliable model of the chronic-progressive variant of MS. fMRI studies in EAE have not been performed extensively up to now. This paper reports fMRI studies in a rat model of MS with somatosensory stimulation of the forepaw. We demonstrated modifications in the recruitment of cortical areas consistent with data from MS patients. To the best of our knowledge, this is the first report of cortical remodeling in a preclinical in vivo model of MS.

Anti-inflammatory properties of a novel peptide interleukin 1 receptor antagonist

Background

Interleukin 1 (IL-1) is implicated in neuroinflammation, an essential component of neurodegeneration. We evaluated the potential anti-inflammatory effect of a novel peptide antagonist of IL-1 signaling, Ilantide.

Methods

We investigated the binding of Ilantide to IL-1 receptor type I (IL-1RI) using surface plasmon resonance, the inhibition of Il-1β-induced activation of nuclear factor κB (NF-κB) in HEK-Blue cells that contained an IL-1β-sensitive reporter, the secretion of TNF-α in macrophages, protection against IL-1-induced apoptosis in neonatal pancreatic islets, and the penetration of Ilantide through the blood–brain barrier using competitive enzyme-linked immunosorbent assay (ELISA). We studied the effects of the peptide on social behavior and memory in rat models of lipopolysaccharide (LPS)- and amyloid-induced neuroinflammation, respectively, and its effect in a rat model of experimental autoimmune enchephalomyelitis.

Results

Ilantide bound IL-1RI, inhibited the IL-1β-induced activation of NF-κB, and inhibited the secretion of TNF-α in vitro. Ilantide protected pancreatic islets from apoptosis in vitro and reduced inflammation in an animal model of arthritis. The peptide penetrated the blood–brain barrier. It reduced the deficits in social activity and memory in LPS- and amyloid-treated animals and delayed the development of experimental autoimmune enchephalomyelitis.

Conclusions

These findings indicate that Ilantide is a novel and potent IL-1RI antagonist that is able to reduce inflammatory damage in the central nervous system and pancreatic islets.

Interleukin-1β and interleukin-1 receptor antagonist appear in grey matter additionally to white matter lesions during experimental multiple sclerosis

BACKGROUND

Multiple sclerosis (MS) has been mainly attributed to white matter (WM) pathology. However, recent evidence indicated the presence of grey matter (GM) lesions. One of the principal mediators of inflammatory processes is interleukin-1β (IL-1β), which is known to play a role in MS pathogenesis. It is unknown whether IL-1β is solely present in WM or also in GM lesions. Using an experimental MS model, we questioned whether IL-1β and the IL-1 receptor antagonist (IL-1ra) are present in GM in addition to affected WM regions.

METHODS

The expression of IL-1β and IL-1ra in chronic-relapsing EAE (cr-EAE) rats was examined using in situ hybridization, immunohistochemistry and real-time PCR. Rats were sacrificed at the peak of the first disease phase, the trough of the remission phase, and at the peak of the relapse. Histopathological characteristics of CNS lesions were studied using immunohistochemistry for PLP, CD68 and CD3 and Oil-Red O histochemistry.

RESULTS

IL-1β and IL-ra expression appears to a similar extent in affected GM and WM regions in the brain and spinal cord of cr-EAE rats, particularly in perivascular and periventricular locations. IL-1β and IL-1ra expression was dedicated to macrophages and/or activated microglial cells, at sites of starting demyelination. The time-dependent expression of IL-1β and IL-1ra revealed that within the spinal cord IL-1β and IL-1ra mRNA remained present throughout the disease, whereas in the brain their expression disappeared during the relapse.

CONCLUSIONS

The appearance of IL-1β expressing cells in GM within the CNS during cr-EAE may explain the occurrence of several clinical deficits present in EAE and MS which cannot be attributed solely to the presence of IL-1β in WM. Endogenously produced IL-1ra seems not capable to counteract IL-1β-induced effects. We put forward that IL-1β may behold promise as a target to address GM, in addition to WM, related pathology in MS.

Interleukin-1β alters glutamate transmission at purkinje cell synapses in a mouse model of multiple sclerosis

Cerebellar deficit contributes significantly to disability in multiple sclerosis (MS). Several clinical and experimental studies have investigated the pathophysiology of cerebellar dysfunction in this neuroinflammatory disorder, but the cellular and molecular mechanisms are still unclear. In experimental autoimmune encephalomyelitis (EAE), a mouse model of MS, proinflammatory cytokines, together with a degeneration of inhibitory neurons, contribute to impair GABAergic transmission at Purkinje cells (PCs). Here, we investigated glutamatergic transmission to gain insight into the pathophysiology of cerebellar dysfunction in EAE. Electrophysiological recordings from PCs showed increased duration of spontaneous excitatory postsynaptic currents (EPSCs) during the symptomatic phase of EAE, suggesting an alteration of glutamate uptake played by Bergmann glia. We indeed observed an impaired functioning of the glutamate-aspartate transporter/excitatory amino acid transporter 1 (GLAST/EAAT1) in EAE cerebellum caused by protein downregulation and in correlation with prominent astroglia activation. We have also demonstrated that the proinflammatory cytokine interleukin-1β (IL-1β), released by a subset of activated microglia/macrophages and infiltrating lymphocytes, was involved directly in such synaptic alteration. In fact, brief incubation of IL-1β in normal cerebellar slices replicated EAE modifications through a rapid GLAST/EAAT1 downregulation, whereas incubation of an IL-1 receptor antagonist (IL-1ra) in EAE slices reduced spontaneous EPSC alterations. Finally, EAE mice treated with intracerebroventricular IL-1ra showed normal glutamatergic and GABAergic transmissions, along with GLAST/EAAT1 normalization, milder inflammation, and reduced motor deficits. These results highlight the crucial role played by the proinflammatory IL-1β in triggering molecular and synaptic events involved in neurodegenerative processes that characterize neuroinflammatory diseases such as MS.

The role of interferon-β in the treatment of multiple sclerosis and experimental autoimmune encephalomyelitis - in the perspective of inflammasomes

Inflammasomes in innate immune cells mediate the induction of inflammation by sensing microbes and pathogen-associated/damage-associated molecular patterns. Inflammasomes are also known to be involved in the development of some human and animal autoimmune diseases. The Nod-like receptor family pyrin domain containing 3 (NLRP3) inflammasome is currently the most fully characterized inflammasome, although a limited number of studies have demonstrated its role in demyelinating autoimmune diseases in the central nervous system of humans and animals. Currently, the development of experimental autoimmune encephalomyelitis (EAE), an animal model of multiple sclerosis (MS), is known to be induced by the NLRP3 inflammasome through enhanced recruitment of inflammatory immune cells in the central nervous system. On the other hand, interferon-β (IFNβ), a first-line drug to treat MS, inhibits NLRP3 inflammasome activation, and ameliorates EAE. The NLRP3 inflammasome is indeed a factor capable of inducing EAE, but it is dispensable when EAE is induced by aggressive disease induction regimens. In such NLRP3 inflammasome-independent EAE, IFN-β treatment is generally not effective. This might therefore be one mechanism that leads to occasional failures of IFN-β treatment in EAE, and possibly, in MS as well. In the current review, we discuss inflammasomes and autoimmunity; in particular, the impact of the NLRP3 inflammasome on MS/EAE, and on IFN-β therapy.

NLRP3 Inflammasome and MS/EAE

Inflammasomes are cytosolic sensors that detect pathogens and danger signals in the innate immune system. The NLRP3 inflammasome is currently the most fully characterized inflammasome and is known to detect a wide array of microbes and endogenous damage-associated molecules. Possible involvement of the NLRP3 inflammasome (or inflammasomes) in the development of multiple sclerosis (MS) was suggested in a number of studies. Recent studies showed that the NLRP3 inflammasome exacerbates experimental autoimmune encephalomyelitis (EAE), an animal model of MS, although EAE can also develop without the NLRP3 inflammasome. In this paper, we discuss the NLRP3 inflammasome in MS and EAE development.

Association of interleukin-1 gene polymorphisms with multiple sclerosis: a meta-analysis

BACKGROUND

Dysregulated levels of interleukin-1 (IL-1) were observed in patients with multiple sclerosis (MS). Previous studies have provided conflicting evidence implicating the IL-1 gene polymorphisms in MS risk.

METHODS

A meta-analysis of 16 case-control studies involving 3,482 cases and 3,528 controls was conducted to evaluate this association.

RESULTS

No association was found between the IL-1α -889 (rs1800587), IL-1α +4,845 (rs17561), IL-1β -511 (rs16944), IL-1β +3,953 (rs1143634), IL-1ra variable number tandem repeat (VNTR) polymorphisms and MS risk. However, in subgroup analyses for the IL-1ra VNTR polymorphism, we found that individuals carrying the 2 allele had a 32 % increased risk for bout-onset MS (relapsing remitting and secondary progressive MS) when compared to the LL homozygotes (OR = 1.32, 95 % CI = 1.06-1.66, P (z) = 0.014).

CONCLUSION

Common variants in the IL-1 region are not associated with MS risk but our data suggest that the IL-1ra VNTR polymorphism might be associated with bout-onset MS subtype.

Mutations of complement factor I and potential mechanisms of neuroinflammation in acute hemorrhagic leukoencephalitis

PURPOSE

Acute Hemorrhagic Leukoencephalitis (AHLE) is a rare demyelinating disorder of acute onset, rapid deterioration and significant morbidity and mortality. Most often described as a post-infectious complication of an upper respiratory illness, its precise pathophysiology remains unclear. We describe two pediatric patients with AHLE with partial complement factor I (FI) deficiency whose successful treatment included the interleukin-1 (IL-1) receptor antagonist, anakinra, implicating a role for FI and IL-1 in this disorder.

METHODS

Extensive clinical workup of two patients presenting with AHLE revealed complement abnormalities, specifically related to the alternative pathway and its regulator, FI. Aggressive management with steroids, immunoglobulin, and anakinra ultimately led to improvement of clinical status and near return to neurologic baseline in both patients. Genetic sequencing of the FI coding regions of the patients and their families was performed. In vitro protein expression studies and immunohistochemistry of fixed brain tissue was used to investigate pathogenic mechanisms.

RESULTS

Two novel mutations in FI were identified in our patients, which result in failure to secrete FI. Immunohistochemical evaluation of brain tissue demonstrated positive staining for C3, membrane attack complex (MAC) and IL-1.

CONCLUSIONS

We propose AHLE is an unreported, rare phenotype for partial FI deficiency. The upregulation of C3, MAC and IL-1 with subsequent demyelination support a pathologic role for complement activation in AHLE, and suggest anakinra as an important adjunctive therapy in this disease.

Endothelial IL-1R1 is a critical mediator of EAE pathogenesis

Interleukin-1 (IL-1) has been implicated in the disease progression of multiple sclerosis (MS). In the animal model of MS, experimental autoimmune encephalomyelitis (EAE), the induction of disease is significantly attenuated in mice lacking the type I IL-1 receptor (IL-1R1). In this study, we created a transgenic mouse (eIL-1R1 kd) in which IL-1R1 expression is knocked down specifically in endothelial cells. Induction of EAE in eIL-1R1 kd mice results in a decrease in incidence, severity and delayed onset of EAE. In addition, eIL-1R1 kd mice show significant decrease in VCAM-1 expression and diminished CD45(+) and CD3(+) infiltrating leukocytes in the spinal cord in animals challenged with EAE. Further, IL-1 and IL-23 stimulate IL-17 production by splenocytes from both wild type and the eIL-1R1 kd animals. Similarly, IL-1 and IL-23 synergistically stimulate splenocytes proliferation in these two strains of animals. After immunization with MOG(79-96), although eIL-1R1 kd mice displayed greatly reduced clinical scores, their splenocytes produced IL-17 and proliferated in response to a second MOG challenge, similar to wild type animals. These findings indicate a critical role for endothelial IL-1R1 in mediating the pathogenesis of EAE, and describe a new model that can be used to study endothelial IL-1R1.

A role of IL-1R1 signaling in the differentiation of Th17 cells and the development of autoimmune diseases

IL-1 cytokine family plays a key role in the innate immune response against pathogen- and danger-associated molecular patterns. More recently, IL-1 receptor type 1 (IL-R1) signaling has been identified as a critical step in the differentiation and commitment of Th17 cells, which mediate the development of autoimmune diseases. Given its significance in the induction of the adoptive immune response, this complex signaling pathway is tightly regulated. Upon binding of IL-1 to IL-1R1, IL-1R accessory protein (AcP) is recruited to form a high affinity IL-1R1-IL-1RAcP heterodimeric receptor, which initiates the downstream signaling cascade. Multiple negative regulators of this pathway, including inhibitory membrane-bound IL-RII, secreted soluble (s)IL-1RI, sIL-RII and sIL-1RAcP, the regulatory IL-1R1 antagonist (IL-1R1a) and the IL-1R1-signlaing-induced single Ig-IL-1R-related (SIGIRR), provide a negative feedback control of this pathway, and suppress excessive IL-1 signaling and Th17 cell differentiation. IL-1R1 signaling induces human Th17 cell differentiation, leading to the expression of IL-1R-associated protein kinase (IRAK)4 and retinoic acid-related orphan nuclear hormone receptor (ROR), Th17 cell lineage transcription factors, which together with signal transducer and activator of the transcription (STAT)3, activate this cell lineage's specific cytokine expression profile, including IL-17A, IL-17F, IL-21 and IL-22. Given the role of IL-1 signaling and Th17 cells in the development of the autoinflammatory and autoimmune diseases, therapeutic strategies inhibiting IL-1R1 signaling are discussed as a novel approach for the treatment of autoimmune diseases and particularly multiple sclerosis (MS).

The inflammasome sensor, NLRP3, regulates CNS inflammation and demyelination via caspase-1 and interleukin-18

Inflammation is increasingly recognized as an important contributor to a host of CNS disorders; however, its regulation in the brain is not well delineated. Nucleotide-binding domain, leucine-rich repeat, pyrin domain containing 3 (NLRP3) is a key component of the inflammasome complex, which also includes ASC (apoptotic speck-containing protein with a card) and procaspase-1. Inflammasome formation can be triggered by membrane P2X(7)R engagement leading to cleavage-induced maturation of caspase-1 and interleukin-1β (IL-1β)/IL-18. This work shows that expression of the Nlrp3 gene was increased >100-fold in a cuprizone-induced demyelination and neuroinflammation model. Mice lacking the Nlrp3 gene (Nlrp3(-/-)) exhibited delayed neuroinflammation, demyelination, and oligodendrocyte loss in this model. These mice also showed reduced demyelination in the experimental autoimmune encephalomyelitis model of neuroinflammation. This outcome is also observed for casp1(-/-) and IL-18(-/-) mice, whereas IL-1β(-/-) mice were indistinguishable from wild-type controls, indicating that Nlrp3-mediated function is through caspase-1 and IL-18. Additional analyses revealed that, unlike the IL-1β(-/-) mice, which have been previously shown to show delayed remyelination, Nlrp3(-/-) mice did not exhibit delayed remyelination. Interestingly, IL-18(-/-) mice showed enhanced remyelination, thus providing a possible compensatory mechanism for the lack of a remyelination defect in Nlrp3(-/-) mice. These results suggest that NLRP3 plays an important role in a model of multiple sclerosis by exacerbating CNS inflammation, and this is partly mediated by caspase-1 and IL-18. Additionally, the therapeutic inhibition of IL-18 might decrease demyelination but enhance remyelination, which has broad implications for demyelinating diseases.

EAE mediated by a non-IFN-γ/non-IL-17 pathway

Previous studies have shown that EAE can be elicited by the adoptive transfer of either IFN-γ-producing (Th1) or IL-17-producing (Th17) myelin-specific CD4(+) T-cell lines. Paradoxically, mice deficient in either IFN-γ or IL-17 remain susceptible to EAE following immunization with myelin antigens in CFA. These observations raise questions about the redundancy of IFN-γ and IL-17 in autoimmune demyelinating disease mediated by a diverse, polyclonal population of autoreactive T cells. In this study, we show that an atypical form of EAE, induced in C57BL/6 mice by the adoptive transfer of IFN-γ-deficient effector T cells, required IL-17 signaling for the development of brainstem infiltrates. In contrast, classical EAE, characterized by predominant spinal cord inflammation, occurred in the combined absence of IFN-γ and IL-17 signaling, but was dependent on GM-CSF and CXCR2. Our findings contribute to a growing body of data, indicating that individual cytokines vary in their importance across different models of CNS autoimmunity.

Minocycline protects against neurologic complications of rapid correction of hyponatremia

Osmotic demyelination syndrome is a devastating neurologic condition that occurs after rapid correction of serum sodium in patients with hyponatremia. Pathologic features of this injury include a well-demarcated region of myelin loss, a breakdown of the blood-brain barrier, and infiltration of microglia. The semisynthetic tetracycline minocycline is protective in some animal models of central nervous system injury, including demyelination, suggesting that it may also protect against demyelination resulting from rapid correction of chronic hyponatremia. Using a rat model of osmotic demyelination syndrome, we found that treatment with minocycline significantly decreases brain demyelination, alleviates neurologic manifestations, and reduces mortality associated with rapid correction of hyponatremia. Mechanistically, minocycline decreased the permeability of the blood-brain barrier, inhibited microglial activation, decreased both the expression of IL1α and protein nitrosylation, and reduced the loss of GFAP immunoreactivity. In conclusion, minocycline modifies the course of osmotic demyelination in rats, suggesting its possible therapeutic use in the setting of inadvertent rapid correction of chronic hyponatremia in humans.

Identification of a serum-induced transcriptional signature associated with type 1 diabetes in the BioBreeding rat

OBJECTIVE

Inflammatory mediators associated with type 1 diabetes are dilute and difficult to measure in the periphery, necessitating development of more sensitive and informative biomarkers for studying diabetogenic mechanisms, assessing preonset risk, and monitoring therapeutic interventions.

RESEARCH DESIGN AND METHODS

We previously utilized a novel bioassay in which human type 1 diabetes sera were used to induce a disease-specific transcriptional signature in unrelated, healthy peripheral blood mononuclear cells (PBMCs). Here, we apply this strategy to investigate the inflammatory state associated with type 1 diabetes in biobreeding (BB) rats.

RESULTS

Consistent with their common susceptibility, sera of both spontaneously diabetic BB DRlyp/lyp and diabetes inducible BB DR+/+ rats induced transcription of cytokines, immune receptors, and signaling molecules in PBMCs of healthy donor rats compared with control sera. Like the human type 1 diabetes signature, the DRlyp/lyp signature, which is associated with progression to diabetes, was differentiated from that of the DR+/+ by induction of many interleukin (IL)-1-regulated genes. Supplementing cultures with an IL-1 receptor antagonist (IL-1Ra) modulated the DRlyp/lyp signature (P < 10(-6)), while administration of IL-1Ra to DRlyp/lyp rats delayed onset (P = 0.007), and sera of treated animals did not induce the characteristic signature. Consistent with the presence of immunoregulatory cells in DR+/+ rats was induction of a signature possessing negative regulators of transcription and inflammation.

CONCLUSIONS

Paralleling our human studies, serum signatures in BB rats reflect processes associated with progression to type 1 diabetes. Furthermore, these studies support the potential utility of this approach to detect changes in the inflammatory state during therapeutic intervention.

Glatiramer acetate triggers PI3Kδ/Akt and MEK/ERK pathways to induce IL-1 receptor antagonist in human monocytes

Glatiramer acetate (GA), an immunomodulator used in multiple sclerosis (MS) therapy, induces the production of secreted IL-1 receptor antagonist (sIL-1Ra), a natural inhibitor of IL-1β, in human monocytes, and in turn enhances sIL-1Ra circulating levels in MS patients. GA is a mixture of peptides with random Glu, Lys, Ala, and Tyr sequences of high polarity and hydrophilic nature that is unlikely to cross the blood-brain barrier. In contrast, sIL-1Ra crosses the blood-brain barrier and, in turn, may mediate GA anti-inflammatory activities within the CNS by counteracting IL-1β activities. Here we identify intracellular signaling pathways induced by GA that control sIL-1Ra expression in human monocytes. By using kinase knockdown and specific inhibitors, we demonstrate that GA induces sIL-1Ra production via the activation of PI3Kδ, Akt, MEK1/2, and ERK1/2, demonstrating that both PI3Kδ/Akt and MEK/ERK pathways rule sIL-1Ra expression in human monocytes. The pathways act in parallel upstream glycogen synthase kinase-3α/β (GSK3α/β), the knockdown of which enhances sIL-1Ra production. Together, our findings demonstrate the existence of signal transduction triggered by GA, further highlighting the mechanisms of action of this drug in MS.

Disruption of central nervous system barriers in multiple sclerosis

The delicate microenvironment of the central nervous system (CNS) is protected by the blood-brain barrier (BBB) and the blood-cerebrospinal fluid barrier (BCB). These barriers function in distinct CNS compartments and their anatomical basis lay on the junctional proteins present in endothelial cells for the BBB and in the choroidal epithelium for the BCB. During neuroinflammatory conditions like multiple sclerosis (MS) and its murine model experimental autoimmune encephalomyelitis (EAE), activation or damage of the various cellular components of these barriers facilitate leukocyte infiltration leading to oligodendrocyte death, axonal damage, demyelination and lesion development. This manuscript will review in detail the features of these barriers under physiological and pathological conditions, particularly when focal immune activation promotes the loss of the BBB and BCB phenotype, the upregulation of cell adhesion molecules (CAMs) and the recruitment of immune cells.

Anti-inflammatory effect by lentiviral-mediated overexpression of IL-10 or IL-1 receptor antagonist in rat glial cells and macrophages

Neuroinflammation, as defined by activation of local glial cells and production of various inflammatory mediators, is an important feature of many neurological disorders. Expression of pro-inflammatory mediators produced by glial cells in the central nervous system (CNS) is considered to contribute to the neuropathology observed in those diseases. To diminish the production or action of pro-inflammatory mediators, we have used lentiviral (LV) vector-mediated encoding rat interleukin-10 (rIL-10) or rat interleukin-1 receptor antagonist (rIL-1ra) to direct the local, long-term expression of these anti-inflammatory cytokines in the CNS. We have shown that cultured macrophages or astroglia transduced with LV-rIL-10 or LV-rIL-1ra produced far less tumor necrosis factor (TNF)alpha or IL-6, respectively in response to pro-inflammatory stimuli. Moreover, intracerebroventricular (i.c.v.) administration of LV-rIL-10 or LV-rIL-1ra resulted in transduction of glial cells and macrophages and, subsequently reduced TNFalpha, IL-6 and inducible nitric oxide synthase (iNOS) expression in various brain regions induced by inflammatory stimuli, whereas peripheral expression of these mediators remained unaffected. In addition, expression levels of the anti-inflammatory cytokines IL-4 and transforming growth factor-beta were not altered in either brain or pituitary gland. Furthermore, i.c.v. administration of LV-rIL-10 or LV-rIL-1ra given during the remission phase of chronic-relapsing experimental autoimmune encephalomyelitis, an animal model of multiple sclerosis, improved the clinical outcome of the relapse phase. Thus, local application of LV vectors expressing anti-inflammatory cytokines could be of therapeutic interest to counteract pro-inflammatory processes in the brain without interfering with the peripheral production of inflammatory mediators.

IL-1 acts directly on CD4 T cells to enhance their antigen-driven expansion and differentiation

IL-1 causes a marked increase in the degree of expansion of naïve and memory CD4 T cells in response to challenge with their cognate antigen. The response occurs when only specific CD4 T cells can respond to IL-1beta, is not induced by a series of other cytokines and does not depend on IL-6 or CD-28. When WT cells are primed in IL-1R1(-/-) recipients, IL-1 increases the proportion of cytokine-producing transgenic CD4 T cells, especially IL-17- and IL-4-producing cells, strikingly increases serum IgE levels and serum IgG1 levels. IL-1beta enhances antigen-mediated expansion of in vitro primed Th1, Th2, and Th17 cells transferred to IL-1R1(-/-) recipients. The IL-1 receptor antagonist diminished responses to antigen plus lipopolysaccharide (LPS) by approximately 55%. These results indicate that IL-1beta signaling in T cells markedly induces robust and durable primary and secondary CD4 responses.

Glatiramer acetate increases IL-1 receptor antagonist but decreases T cell-induced IL-1beta in human monocytes and multiple sclerosis

Mechanisms of action as well as cellular targets of glatiramer acetate (GA) in multiple sclerosis (MS) are still not entirely understood. IL-1beta is present in CNS-infiltrating macrophages and microglial cells and is an important mediator of inflammation in experimental autoimmune encephalitis (EAE), the MS animal model. A natural inhibitor of IL-1beta, the secreted form of IL-1 receptor antagonist (sIL-1Ra) improves EAE disease course. In this study we examined the effects of GA on the IL-1 system. In vivo, GA treatment enhanced sIL-1Ra blood levels in both EAE mice and patients with MS, whereas IL-1beta levels remained undetectable. In vitro, GA per se induced the transcription and production of sIL-1Ra in isolated human monocytes. Furthermore, in T cell contact-activated monocytes, a mechanism relevant to chronic inflammation, GA strongly diminished the expression of IL-1beta and enhanced that of sIL-1Ra. This contrasts with the effect of GA in monocytes activated upon acute inflammatory conditions. Indeed, in LPS-activated monocytes, IL-1beta and sIL-1Ra production were increased in the presence of GA. These results demonstrate that, in chronic inflammatory conditions, GA enhances circulating sIL-1Ra levels and directly affects monocytes by triggering a bias toward a less inflammatory profile, increasing sIL-1Ra while diminishing IL-1beta production. This study sheds light on a mechanism that is likely to participate in the therapeutic effects of GA in MS.

A fusion protein consisting of IL-16 and the encephalitogenic peptide of myelin basic protein constitutes an antigen-specific tolerogenic vaccine that inhibits experimental autoimmune encephalomyelitis

To test a novel concept for the generation of tolerogenic vaccines, fusion proteins were constructed encompassing a tolerogenic or biasing cytokine and the major encephalitogenic peptide of guinea pig myelin basic protein (GPMBP; i.e., neuroantigen or NAg). The cytokine domain was predicted to condition APC while simultaneously targeting the covalently linked encephalitogenic peptide to the MHC class II Ag processing pathway of those conditioned APC. Rats were given three s.c. injections of cytokine-NAg in saline 1-2 wk apart and then at least 1 wk later were challenged with NAg in CFA. The rank order of tolerogenic activity in the Lewis rat model of EAE was NAgIL16 > IL2NAg > IL1RA-NAg, IL13NAg >or= IL10NAg, GPMBP, GP69-88, and saline. NAgIL16 was also an effective inhibitor of experimental autoimmune encephalomyelitis when administered after an encephalitogenic challenge during the onset of clinical signs. Covalent linkage of the NAg and IL-16 was required for inhibition of experimental autoimmune encephalomyelitis. These data identify IL-16 as an optimal cytokine partner for the generation of tolerogenic vaccines and indicate that such vaccines may serve as Ag-specific tolerogens for the treatment of autoimmune disease.

Cytokine-neuroantigen fusion proteins: new tools for modulation of myelin basic protein (MBP)-specific T cell responses in experimental autoimmune encephalomyelitis

Fusion proteins incorporating anti-inflammatory cytokines and immunodominant self antigen as separate domains of a single protein may hold promise for development of antigen-specific tolerogenic vaccines. Proteins incorporating rat sequences of IL-1RA, IL-2, IL-4, IL-10, or IL-13 were expressed as fusion proteins containing the major encephalitogenic region of myelin basic protein (MBP). These fusion proteins were expressed via baculovirus (bv) expression systems and were shown to have cytokine-dependent and antigen-specific biological activity. In the case of the IL-2 and IL-4 fusion proteins, covalent linkage of the cytokine and neuroantigen domains resulted in synergistic antigen presentation. These data indicate that the cytokine domain may be able to modulate APC activity and simultaneously target the covalently tethered NAg for enhanced presentation by certain APC subsets. Cytokine/antigen fusion proteins may represent a novel tool for antigen-specific immune modulation in autoimmune disease.

HSV-1-mediated IL-1 receptor antagonist gene therapy ameliorates MOG35–55-induced experimental autoimmune encephalomyelitis in C57BL/6 mice

Primary proinflammatory cytokines, such as IL-1beta, play a crucial pathogenic role in multiple sclerosis and its animal model experimental autoimmune encephalomyelitis (EAE), and may represent, therefore, a suitable therapeutic target. We have previously established the delivery of anti-inflammatory cytokine genes within the central nervous system (CNS), based on intracisternal (i.c.) injection of non-replicative HSV-1-derived vectors. Here we show the therapeutic efficacy of i.c. administration of an HSV-1-derived vector carrying the interleukin-1receptor antagonist (IL-1ra) gene, the physiological antagonist of the proinflammatory cytokine IL-1, in C57BL/6 mice affected by myelin oligodendrocyte glycoprotein-induced EAE. IL-1ra gene therapy is effective preventively, delaying EAE onset by almost 1 week (22.4+/-1.4 days post-immunization vs 15.9+/-2.1 days in control mice; P=0.0229 log-rank test), and decreasing disease severity. Amelioration of EAE course was associated with a reduced number of macrophages infiltrating the CNS and in a decreased level of proinflammatory cytokine mRNA in the CNS, suggesting an inhibitory activity of IL-1ra on effector cell recruitment, as antigen-specific peripheral T-cell activation and T-cell recruitment to the CNS is unaffected. Thus, local IL-1ra gene therapy may represent a therapeutic alternative for the inhibition of immune-mediated demyelination of the CNS.

Essential role of the MyD88 pathway, but nonessential roles of TLRs 2, 4, and 9, in the adjuvant effect promoting Th1-mediated autoimmunity

Induction of tissue-specific experimental autoimmune diseases involves an obligatory adjuvant effect to trigger an innate response of a type that will drive a Th1-biased adaptive response. This is achieved by use of CFA containing mycobacteria (Mycobacterium tuberculosis), whose recognition by cells of the innate immune system depends on TLRs that signal through the adaptor molecule MyD88. We examined the role of selected components of the MyD88 pathway in promoting experimental autoimmune uveitis (EAU). Mice deficient in MyD88, TLR2, TLR4, or TLR9 were immunized with the retinal Ag interphotoreceptor retinoid-binding protein in CFA, and their EAU scores and associated immunological responses were examined. MyD88-/- mice were completely resistant to EAU and had a profound defect in Th1, but not Th2, responses to autoantigen challenge. Surprisingly, TLR2-/-, TLR4-/-, and TLR9-/- mice were fully susceptible to EAU and had unaltered adaptive responses to interphotoreceptor retinoid-binding protein. Examination of IL-1R family members, which share the common adaptor MyD88 with the TLR family, revealed that IL-1R-deficient mice, but not IL-18-deficient mice, are resistant to EAU and have profoundly reduced Th1 and Th2 responses. These data are compatible with the interpretation that TLR9, TLR4, and TLR2 signaling is either not needed, or, more likely, redundant in the adjuvant effect needed to induce EAU. In contrast, signaling through the IL-1R plays a necessary and nonredundant role in EAU and can by itself account for the lack of EAU development in MyD88 mice.