MicroRNA223 promotes pathogenic T‐cell development and autoimmune inflammation in central nervous system in mice

Multiple sclerosis (MS) is an incurable central nervous system autoimmune disease. Understanding MS pathogenesis is essential for the development of new MS therapies. In the present study, we identified a novel microRNA (miR) that regulates experimental autoimmune encephalomyelitis (EAE), an animal model of MS. Expression of miR223 was up‐regulated specifically in spinal cords and lymphoid organs but not in other examined tissues. A global miR223 knockout (miR223^?/?) in mice led to a significant delay in EAE onset, reduction in spinal cord lesion, and lessening of neurological symptoms. These protective effects could be reproduced in bone marrow chimeras reconstituted with miR223^?/? haematopoietic stem cells. We also found that miR223 deficiency reduced T helper type 1 (Th1) and Th17 infiltration into spinal cords. To address underlying mechanisms, we investigated the role of miR223 in regulating the function, development and interaction of the major immune cells. Expression of the genes associated with dendritic cell (DC) activation (CD86 and MHC II) and Th1 and Th17 differentiation [interleukin‐12 (IL‐12) and IL‐23, respectively] was significantly decreased in the spleens of miR223^?/? mice bearing EAE. The miR223^?/? DCs expressed significantly lower levels of basal and lipopolysaccharide‐induced IL‐12 and IL‐23 compared with the wild‐type DCs. These data are consistent with the observed lower efficiency of miR223^?/? DCs to support Th1 and Th17 differentiation from naive T cells over‐expressing an EAE antigen‐specific T‐cell receptor. Our data suggest that miR223 promotes EAE, probably through enhancing DC activation and subsequently the differentiation of naive T cells toward Th1 and Th17 effector cells.     

The p38 mitogen‐activated protein kinase cascade modulates T helper type 17 differentiation and functionality in multiple sclerosis

The p38 mitogen‐activated protein kinase cascade is required for the induction of a T helper type 17 (Th17) ‐mediated autoimmune response, which underlies the development and progression of several autoimmune diseases, such as experimental autoimmune encephalomyelitis, the animal model of multiple sclerosis (MS). However, the contribution of p38 phosphorylation to human Th cell differentiation has not been clarified. Here we demonstrate that the p38 signalling pathway is implicated in the generation of Th17 lymphocytes from human CD4⁺ CD27⁺ CD45RA⁺ naive T cells, both in healthy donors and in patients affected by the relapsing–remitting form of MS. Our data also indicate that p38 activation is essential for interleukin‐17 release from central memory lymphocytes and committed Th17 cell clones. Furthermore, CD4⁺ T cells isolated from individuals with relapsing–remitting MS display an altered responsiveness of the p38 cascade, resulting in increased p38 phosphorylation upon stimulation. These findings suggest that the p38 signalling pathway, by modulating the Th17 differentiation and response, is involved in the pathogenesis of MS, and open new perspectives for the use of p38 inhibitors in the treatment of Th17‐mediated autoimmune diseases.     

Oestrogen treatment of experimental autoimmune encephalomyelitis requires 17β‐oestradiol‐receptor‐positive B cells that up‐regulate PD‐1 on CD4+ Foxp3+ regulatory T cells

It is now well accepted that sex hormones have immunoregulatory activity and may prevent exacerbations in multiple sclerosis during pregnancy. Our previous studies demonstrated that oestrogen (17β-oestradiol; E₂) protection against experimental autoimmune encephalomyelitis (EAE) is mediated mainly through oestrogen receptor-α (ERα) and the membrane receptor G-protein-coupled receptor 30 (GPR30) and is abrogated in the absence of B cells and the co-inhibitory receptor, Programmed Death-1 (PD-1). To critically evaluate the cell source of the E₂ and PD-1 co-inhibitory pathways in EAE regulation, we assessed the requirement for ERs on transferred B cells and downstream effects on expression of PD-1/PD-ligand on CD4⁺ Foxp3⁺ regulatory T (Treg) cells in B-cell-replenished, E₂-treated B-cell-deficient (μMT^−/−) mice with EAE. The results clearly demonstrated involvement of ERα and GPR30 on transferred B cells that mediated the protective E₂ treatment effect on EAE and further showed an E₂-mediated B-cell-dependent up-regulation of PD-1 on CD4⁺ Foxp3⁺ Treg cells. These findings identify regulatory B-cell populations as key players in potentiating Treg-cell activity during E₂-mediated protection against EAE.     

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.     

Efficacy and immunomodulatory actions of ONO‐4641, a novel selective agonist for sphingosine 1‐phosphate receptors 1 and 5, in preclinical models of multiple sclerosis

ONO‐4641 is a next‐generation sphingosine 1‐phosphate (S1P) receptor agonist selective for S1P receptors 1 and 5. The objective of the study was to characterize the immunomodulatory effects of ONO‐4641 using preclinical data. ONO‐4641 was tested in both in‐vitro pharmacological studies as well as in‐vivo models of transient or relapsing–remitting experimental autoimmune encephalomyelitis (EAE). In vitro, ONO‐4641 showed highly potent agonistic activities versus S1P receptors 1 and 5 [half maximal effective concentration (EC₅₀) values of 0·0273 and 0·334 nM, respectively], and had profound S1P receptor 1 down‐regulating effects on the cell membrane. ONO‐4641 decreased peripheral blood lymphocyte counts in rats by inhibiting lymphocyte egress from secondary lymphoid tissues. In a rat experimental autoimmune encephalomyelitis (EAE) model, ONO‐4641 suppressed the onset of disease and inhibited lymphocyte infiltration into the spinal cord in a dose‐dependent manner at doses of 0·03 and 0·1 mg/kg. Furthermore, ONO‐4641 prevented relapse of disease in a non‐obese diabetic mouse model of relapsing‐remitting EAE. These observations suggest that ONO‐4641 may provide therapeutic benefits in the treatment of multiple sclerosis.