The therapeutic effect of glatiramer acetate in a murine model of inflammatory bowel disease is mediated by anti-inflammatory T-cells

Repurposing of glatiramer acetate to treat cardiac ischemia in rodent models

Myocardial injury may ultimately lead to adverse ventricular remodeling and development of heart failure (HF), which is a major cause of morbidity and mortality worldwide. Given the slow pace and substantial costs of developing new therapeutics, drug repurposing is an attractive alternative. Studies of many organs, including the heart, highlight the importance of the immune system in modulating injury and repair outcomes. Glatiramer acetate (GA) is an immunomodulatory drug prescribed for patients with multiple sclerosis. Here, we report that short-term GA treatment improves cardiac function and reduces scar area in a mouse model of acute myocardial infarction and a rat model of ischemic HF. We provide mechanistic evidence indicating that, in addition to its immunomodulatory functions, GA exerts beneficial pleiotropic effects, including cardiomyocyte protection and enhanced angiogenesis. Overall, these findings highlight the potential repurposing of GA as a future therapy for a myriad of heart diseases.

Impact of Disease-Modifying Therapies on Gut-Brain Axis in Multiple Sclerosis

Multiple sclerosis is a chronic, autoimmune-mediated, demyelinating disease whose pathogenesis remains to be defined. In past years, in consideration of a constantly growing number of patients diagnosed with multiple sclerosis, the impacts of different environmental factors in the pathogenesis of the disease have been largely studied. Alterations in gut microbiome composition and intestinal barrier permeability have been suggested to play an essential role in the regulation of autoimmunity. Thus, increased efforts are being conducted to demonstrate the complex interplay between gut homeostasis and disease pathogenesis. Numerous results confirm that disease-modifying therapies (DMTs) used for the treatment of MS, in addition to their immunomodulatory effect, could exert an impact on the intestinal microbiota, contributing to the modulation of the immune response itself. However, to date, the direct influence of these treatments on the microbiota is still unclear. This review intends to underline the impact of DMTs on the complex system of the microbiota-gut-brain axis in patients with multiple sclerosis.

Treatment approaches to patients with multiple sclerosis and coexisting autoimmune disorders

The past decades have yielded major therapeutic advances in many autoimmune conditions - such as multiple sclerosis (MS) - and thus ushered in a new era of more targeted and increasingly potent immunotherapies. Yet this growing arsenal of therapeutic immune interventions has also rendered therapy much more challenging for the attending physician, especially when treating patients with more than one autoimmune condition. Importantly, some therapeutic strategies are either approved for several autoimmune disorders or may be repurposed for other conditions, therefore opening new curative possibilities in related fields. In this article, we especially focus on frequent and therapeutically relevant concomitant autoimmune conditions faced by neurologists when treating patients with MS, namely psoriasis, rheumatoid arthritis and inflammatory bowel diseases. We provide an overview of the available disease-modifying therapies, highlight possible contraindications, show pathophysiological overlaps and finally present which therapeutics can be utilized as a combinatory treatment, in order to 'kill two birds with one stone'.

Can FDA-Approved Immunomodulatory Drugs be Repurposed/Repositioned to Alleviate Chronic Pain?

Pain is among the most widespread chronic health condition confronting society today and our inability to manage chronic pain contributes to the opioid abuse epidemic in America. The immune system is known to contribute to acute and chronic pain, but only limited therapeutic treatments such as non-steroid anti-inflammatory drugs have resulted from this knowledge. The last decade has shed light on neuro-immune interactions mediating the development, maintenance, and resolution of chronic pain. Here, we do not aim to perform a comprehensive review of all immune mechanisms involved in chronic pain, but to briefly review the contribution of the main cytokines and immune cells (macrophages, microglia, mast cells and T cells) to chronic pain. Given the urgent need to address the Pain crisis, we provocatively propose to repurpose/reposition FDA-approved immunomodulatory drugs for their potential to alleviate chronic pain. Repositioning or repurposing offers an attractive way to accelerate the arrival of new analgesics.

Microbiome in Multiple Sclerosis; Where Are We, What We Know and Do Not Know

An increase of multiple sclerosis (MS) incidence has been reported during the last decade, and this may be connected to environmental factors. This review article aims to encapsulate the current advances targeting the study of the gut-brain axis, which mediates the communication between the central nervous system and the gut microbiome. Clinical data arising from many research studies, which have assessed the effects of administered disease-modifying treatments in MS patients to the gut microbiome, are also recapitulated.

The intestinal barrier in multiple sclerosis: implications for pathophysiology and therapeutics

Biological barriers are essential for the maintenance of homeostasis in health and disease. Breakdown of the intestinal barrier is an essential aspect of the pathophysiology of gastrointestinal inflammatory diseases, such as inflammatory bowel disease. A wealth of recent studies has shown that the intestinal microbiome, part of the brain-gut axis, could play a role in the pathophysiology of multiple sclerosis. However, an essential component of this axis, the intestinal barrier, has received much less attention. In this review, we describe the intestinal barrier as the physical and functional zone of interaction between the luminal microbiome and the host. Besides its essential role in the regulation of homeostatic processes, the intestinal barrier contains the gut mucosal immune system, a guardian of the integrity of the intestinal tract and the whole organism. Gastrointestinal disorders with intestinal barrier breakdown show evidence of CNS demyelination, and content of the intestinal microbiome entering into the circulation can impact the functions of CNS microglia. We highlight currently available studies suggesting that there is intestinal barrier dysfunction in multiple sclerosis. Finally, we address the mechanisms by which commonly used disease-modifying drugs in multiple sclerosis could alter the intestinal barrier and the microbiome, and we discuss the potential of barrier-stabilizing strategies, including probiotics and stabilization of tight junctions, as novel therapeutic avenues in multiple sclerosis.

The Evolving Mechanisms of Action of Glatiramer Acetate

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

CD69 enhances immunosuppressive function of regulatory T-cells and attenuates colitis by prompting IL-10 production

Foxp3⁺ regulatory T cells (Tregs) can inhibit immune responses and maintain immune tolerance by secreting immunosuppressive TGF-β1 and IL-10. However, the efficiency of Tregs become the major obstacle to their use for immunotherapy. In this study, we investigated the relevance of the C-type lectin receptor CD69 to the suppressive function. Compared to CD4⁺Foxp3⁺CD69⁻ Tregs (CD69⁻ Tregs), CD4⁺Foxp3⁺CD69⁺ Tregs (CD69⁺ Tregs) displayed stronger ability to maintain immune tolerance. CD69⁺ Tregs expressed higher levels of suppression-associated markers such as CTLA-4, ICOS, CD38 and GITR, and secreted higher levels of IL-10 but not TGF-β1. CD69⁺ Tregs from Il10^+/+ rather than Il10^−/− mice significantly inhibit the proliferation of CD4⁺ T cells. CD69 over-expression stimulated higher levels of IL-10 and c-Maf expression, which was compromised by silencing of STAT3 or STAT5. In addition, the direct interaction of STAT3 with the c-Maf promoter was detected in cells with CD69 over-expression. Moreover, adoptive transfer of CD69⁺ Tregs but not CD69⁻Tregs or CD69⁺ Tregs deficient in IL-10 dramatically prevented the development of inflammatory bowel disease (IBD) in mice. Taken together, CD69 is important to the suppressive function of Tregs by promoting IL-10 production. CD69⁺ Tregs have the potential to develop new therapeutic approach for autoimmune diseases like IBD.

Glatiramer Acetate Enhances Myeloid-Derived Suppressor Cell Function via Recognition of Paired Ig-like Receptor B

Glatiramer acetate (GA; Copaxone) is a copolymer therapeutic that is approved by the Food and Drug Administration for the relapsing-remitting form of multiple sclerosis. Despite an unclear mechanism of action, studies have shown that GA promotes protective Th2 immunity and stimulates release of cytokines that suppress autoimmunity. In this study, we demonstrate that GA interacts with murine paired Ig-like receptor B (PIR-B) on myeloid-derived suppressor cells and suppresses the STAT1/NF-κB pathways while promoting IL-10/TGF-β cytokine release. In inflammatory bowel disease models, GA enhanced myeloid-derived suppressor cell-dependent CD4⁺ regulatory T cell generation while reducing proinflammatory cytokine secretion. Human monocyte-derived macrophages responded to GA by reducing TNF-α production and promoting CD163 expression typical of alternative maturation despite the presence of GM-CSF. Furthermore, GA competitively interacts with leukocyte Ig-like receptors B (LILRBs), the human orthologs of PIR-B. Because GA limited proinflammatory activation of myeloid cells, therapeutics that target LILRBs represent novel treatment modalities for autoimmune indications.

Therapeutic effects of glatiramer acetate and grafted CD115⁺ monocytes in a mouse model of Alzheimer's disease

Weekly glatiramer acetate immunization of transgenic mice modelling Alzheimer's disease resulted in retained cognition (Morris water maze test), decreased amyloid-β plaque burden, and regulation of local inflammation through a mechanism involving enhanced recruitment of monocytes. Ablation of bone marrow-derived myeloid cells exacerbated plaque pathology, whereas weekly administration of glatiramer acetate enhanced cerebral recruitment of innate immune cells, which dampened the pathology. Here, we assessed the therapeutic potential of grafted CD115(+) monocytes, injected once monthly into the peripheral blood of transgenic APPSWE/PS1ΔE9 Alzheimer's disease mouse models, with and without weekly immunization of glatiramer acetate, as compared to glatiramer acetate alone. All immune-modulation treatment groups were compared with age-matched phosphate-buffered saline-injected control transgenic and untreated non-transgenic mouse groups. Two independent cohorts of mice were assessed for behavioural performance (6-8 mice/group); treatments started in 10-month-old symptomatic mice and spanned a total of 2 months. For all three treatments, our data suggest a substantial decrease in cognitive deficit as assessed by the Barnes maze test (P < 0.0001-0.001). Improved cognitive function was associated with synaptic preservation and reduction in cerebral amyloid-β protein levels and astrogliosis (P < 0.001 and P < 0.0001), with no apparent additive effects for the combined treatment. The peripherally grafted, green fluorescent protein-labelled and endogenous monocytes, homed to cerebral amyloid plaques and directly engulfed amyloid-β; their recruitment was further enhanced by glatiramer acetate. In glatiramer acetate-immunized mice and, moreover, in the combined treatment group, monocyte recruitment to the brain was coupled with greater elevation of the regulatory cytokine IL10 surrounding amyloid-β plaques. All treated transgenic mice had increased cerebral levels of MMP9 protein (P < 0.05), an enzyme capable of degrading amyloid-β, which was highly expressed by the infiltrating monocytes. In vitro studies using primary cultures of bone marrow monocyte-derived macrophages, demonstrated that glatiramer acetate enhanced the ability of macrophages to phagocytose preformed fibrillar amyloid-β1-42 (P < 0.0001). These glatiramer acetate-treated macrophages exhibited increased expression of the scavenger receptors CD36 and SCARA1 (encoded by MSR1), which can facilitate amyloid-β phagocytosis, and the amyloid-β-degrading enzyme MMP9 (P < 0.0001-0.001). Overall, our studies indicate that increased cerebral infiltration of monocytes, either by enrichment of their levels in the circulation or by weekly immunization with glatiramer acetate, resulted in substantial attenuation of disease progression in murine Alzheimer's models by mechanisms that involved enhanced cellular uptake and enzymatic degradation of toxic amyloid-β as well as regulation of brain inflammation.

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

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

The pharmacokinetics of glatiramer acetate for multiple sclerosis treatment

INTRODUCTION

Multiple sclerosis (MS) is a T-cell-mediated disease affecting the central nervous system (CNS), characterized by demyelination and axonal degeneration. INF-β1b was the first drug approved for MS patients in 1993. In 1996, glatiramer acetate (GA), a synthetic copolymer, was approved in the USA for the treatment of relapsing-remitting MS (RRMS) and clinically isolated syndrome (CIS). Although the immunological action of GA has been fully investigated, the exact mechanisms of action of GA are still not completely elucidated. Several in vitro studies on mice and human antigen-presenting cells (APCs) have shown that GA is able to bind to the major histocompatibility complex (MHC), on the surface of APCs, recognizing myelin basic protein (MBP).

AREAS COVERED

This review explores the pharmacological characteristics of GA, its mechanism of action and its pharmacokinetics properties. The article also provides information on the efficacy, tolerability and an overview of the most important clinical data on GA.

EXPERT OPINION

Despite the development of novel compounds, it is not surprising that GA is, to date, one of the most prescribed drugs for RRMS patients and CIS patients. The proven efficacy and the mild adverse events, makes GA a good therapeutic option in the early stage of the disease. This is particularly useful for patients who suffer flu-like symptoms from other RRMS therapies as an alternative.

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

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

The yin yang of bacterial polysaccharides: lessons learned from B. fragilis PSA

Over the past several years, there have been remarkable advances in our understanding of how commensal organisms shape host immunity. Although the full cast of immunogenic bacteria and their immunomodulatory molecules remains to be elucidated, lessons learned from the interactions between bacterial zwitterionic polysaccharides (ZPSs) and the host immune system represent an integral step toward better understanding how the intestinal microbiota effect immunologic changes. Somewhat paradoxically, ZPSs, which are found in numerous commensal organisms, are able to elicit both proinflammatory and immunoregulatory responses; both these outcomes involve fine-tuning the balance between T-helper 17 cells and interleukin-10-producing regulatory T cells. In this review, we discuss the immunomodulatory effects of the archetypal ZPS, Bacteroides fragilis PSA. In addition, we highlight some of the opportunities and challenges in applying these lessons in clinical settings.

T cell PPARγ is required for the anti-inflammatory efficacy of abscisic acid against experimental IBD

The phytohormone abscisic acid (ABA) has been shown to be effective in ameliorating chronic and acute inflammation. The objective of this study was to investigate whether ABA's anti-inflammatory efficacy in the gut is dependent on peroxisome proliferator-activated receptor γ (PPARγ) in T cells. PPARγ-expressing and T cell-specific PPARγ null mice were fed diets with or without ABA (100 mg/kg) for 35 days prior to challenge with 2.5% dextran sodium sulfate. The severity of clinical disease was assessed daily, and mice were euthanized on Day 7 of the dextran sodium sulfate challenge. Colonic inflammation was assessed through macroscopic and histopathological examination of inflammatory lesions and real-time quantitative RT-PCR-based quantification of inflammatory genes. Flow cytometry was used to phenotypically characterize leukocyte populations in the blood and mesenteric lymph nodes. Colonic sections were stained immunohistochemically to determine the effect of ABA on colonic regulatory T (T(reg)) cells. ABA's beneficial effects on disease activity were completely abrogated in T cell-specific PPARγ null mice. Additionally, ABA improved colon histopathology, reduced blood F4/80(+)CD11b(+) monocytes, increased the percentage of CD4(+) T cells expressing the inhibitory molecule cytotoxic T lymphocyte antigen 4 in blood and enhanced the number of T(reg) cells in the mesenteric lymph nodes and colons of PPARγ-expressing but not T cell-specific PPARγ null mice. We conclude that dietary ABA ameliorates experimental inflammatory bowel disease by enhancing T(reg) cell accumulation in the colonic lamina propria through a PPARγ-dependent mechanism.

Glatiramer acetate (GA), the immunomodulatory drug, inhibits inflammatory mediators and collagen degradation in osteoarthritis (OA) cartilage

OBJECTIVE

Glatiramer acetate (GA), the generic name for Copaxone, an immunomodulatory agent, has been shown to induce interleukin-1 receptor antagonist (IL-1Ra) production in macrophages. We therefore tested the effects of GA on the catabolic activities of osteoarthritis (OA) chondrocytes.

DESIGN

Primary human chondrocytes and OA cartilage explants were utilized in this study. IL-1Ra, pro-matrix metalloproteinase-13 (proMMP-13) and prostaglandin E(2) (PGE(2)) were estimated in the cell culture supernatants and in vitro MMP-13 activity was measured using fluorogenic substrate. TaqMan Real-Time quantitative polymerase chain reaction (RT-qPCR) was performed to estimate relative expression levels of genes.

RESULTS

GA treatment significantly increased transcription and production of sIL-1Ra (P=0.001) in both culture models. Furthermore, addition of GA (100 μg) inhibited: (1) spontaneous collagen degradation as assayed by CTX II enzyme-linked immunosorbent assay (ELISA) [mean CTX II (ng/g cartilage)] in control was 7.79 [95% confidence interval (CI) 2.57-13.02]-3.415 (95% CI 0.81-6.02) (P=0.0286); (2) spontaneous proMMP-13 secretion [mean MMP-13 (ng/g cartilage)] in control was 16.98 (95% CI 7.739-26.23)-6.973 (95% CI 1.632-12.31) (P=0.0286); (3) production of IL-1β-induced inflammatory mediators such as nitric oxide (NO) [mean NO (μM)] in IL-1 cultures was 11.47 (95% CI 7.10-15.83)-0.87 (95% CI 0.18-1.56) (P=0.0022); and (4) recombinant MMP-13 in vitro activity (15-25%; P=0.004).

CONCLUSIONS

These data suggest that GA effects may be due to upregulation of IL-1Ra as well as direct inhibition of MMP-13 activity. Based on these studies, we propose that GA has potential for disease modifying properties in OA and should be evaluated in vivo in animal studies.

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

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

Recent insights into the mechanism of action of glatiramer acetate

Glatiramer acetate (GA, Copaxone®, co-polymer 1) is an immunomodulatory therapy approved in 1996 by the United States Food and Drug Administration for treatment of relapsing-remitting multiple sclerosis. GA has a good safety profile, moderate efficacy, and a unique mode of action. Recent evidence in an animal model of MS, experimental autoimmune encephalomyelitis (EAE), suggests that GA effects on NK cells and B cells may contribute to therapeutic efficacy. We review the mechanism of action of GA, with particular focus on recent data suggesting a role for regulatory B cells.

Beneficial effect of glatiramer acetate treatment on syndecan-1 expression in dextran sodium sulfate colitis

Syndecan-1, the most abundant heparan sulfate proteoglycan in the gastrointestinal tract, is reduced in the regenerative epithelium in inflammatory bowel disease (IBD). This study explored the effects of the immunomodulator glatiramer acetate (GA; Copaxone) treatment on syndecan-1 expression in dextran sodium sulfate (DSS)-induced colitis. Acute and chronic colitis was induced in C57BL/6 mice by 2 and 1.5% DSS in tap water, respectively. GA was applied subcutaneously, 2 mg per mouse per day, starting on the day of DSS induction until the mice were sacrificed. Syndecan-1 expression was assessed by immunohistochemistry. The effect of adoptive transfer of GA-specific T cells as an organ-specific therapy also was evaluated. Syndecan-1 expression was significantly lower in both colitis groups compared with that in naive mice (p < 0.0001). GA attenuated clinical scores and pathological manifestations of colitis and led to the reinstatement of normal levels of syndecan-1. After adoptive transfer, GA-specific cells homed to the surface epithelium of the distal colon, accompanied by the augmentation of syndecan-1 staining in their vicinity. We concluded that syndecan-1 expression is reduced in DSS-induced colitis and could be a potential prognostic factor in IBD. Treatment with GA exerts not only an anti-inflammatory effect but also a possible beneficial effect in stabilizing the intestinal epithelium barrier and tissue repair in DSS colitis. GA may be applied as a novel drug for IBD, shifting treatment from immunosuppression toward immunomodulation.

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.

The role of T cell PPAR gamma in mice with experimental inflammatory bowel disease

Background

Peroxisome proliferator-activated receptor γ (PPAR γ) is a nuclear receptor whose activation has been shown to modulate macrophage and T cell-mediated inflammation. The objective of this study was to investigate the mechanisms by which the deletion of PPAR γ in T cells modulates immune cell distribution and colonic gene expression and the severity of experimental IBD.

Methods

PPAR γ flfl; CD4 Cre⁺ (CD4cre) or Cre- (WT) mice were challenged with 2.5% dextran sodium sulfate in their drinking water for 0, 2, or 7 days. Mice were scored on disease severity both clinically and histopathologically. Flow cytometry was used to assess lymphocyte and macrophage populations in the blood, spleen, and mesenteric lymph nodes (MLN). Global gene expression in colonic mucosa was profiled using Affymetrix microarrays.

Results

The deficiency of PPAR γ in T cells accelerated the onset of disease and body weight loss. Examination of colon histopathology revealed significantly greater epithelial erosion, leukocyte infiltration, and mucosal thickening in the CD4cre mice on day 7. CD4cre mice had more CD8⁺ T cells than WT mice and fewer CD4⁺FoxP3⁺ regulatory T cells (Treg) and IL10⁺CD4⁺ T cells in blood and MLN, respectively. Transcriptomic profiling revealed around 3000 genes being transcriptionally altered as a result of DSS challenge in CD4cre mice. These included up-regulated mRNA expression of adhesion molecules, proinflammatory cytokines interleukin-6 (IL-6) and IL-1β, and suppressor of cytokine signaling 3 (SOCS-3) on day 7. Gene set enrichment analysis (GSEA) showed that the ribosome and Krebs cycle pathways were downregulated while the apoptosis pathway was upregulated in colons of mice lacking PPAR γ in T cells.

Conclusions

The expression of PPAR γ in T cells is involved in preventing gut inflammation by regulating colonic expression of adhesion molecules and inflammatory mediators at later stages of disease while favoring the recruitment of Treg to the mucosal inductive sites.

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.

CD4+CD25+FoxP3+PD1- regulatory T cells in acute and stable relapsing-remitting multiple sclerosis and their modulation by therapy

The intracellular expression of the programmed death receptor 1 (PD1) identifies a subset of naive T(reg) cells with enhanced suppressive ability; antigen stimulation results in the surface expression of PD1. Because the role of T(reg) impairments in multiple sclerosis (MS) is still contradictory, we analyzed naive PD1- and PD1+ T(reg) cells in peripheral blood and cerebrospinal fluid (CSF) of relapsing-remitting multiple sclerosis (RR-MS) patients and of healthy control subjects. Results showed that 1) CSF PD1- T(reg) cells were significantly augmented in MS patients; 2) PD1- T(reg) cells were significantly increased in the peripheral blood of patients with stable disease (SMS) compared to those with acute (AMS) disease, and in patients responding to glatiramer acetate (COPA) compared to AMS- and COPA-unresponsive patients; and 3) PD1+ T(reg) cells were similar in CSF and peripheral blood of all groups analyzed. PD1- T(reg) cells were not increased in the peripheral blood of interferon-beta (IFNbeta) -responsive patients, but the suppressive ability of T(reg) cells was significantly higher in SMS and in COPA- or IFNbeta-responsive compared to AMS- and COPA-unresponsive individuals. The data herein suggest that PD1- T(reg) cells play a pivotal role in MS and offer a biological explanation for disease relapse and for the mechanism associated with response to COPA and IFNbeta.