Asako Chiba

Mucosal-associated invariant T cells regulate Th1 response in multiple sclerosis

Mucosal-associated invariant T (MAIT) cells are innate T cells expressing an invariant Vα7.2-Jα33 T-cell antigen receptor α chain and are enriched in mucosal-associated lymphoid tissues. Although the regulatory role of MAIT cells in experimental autoimmune encephalomyelitis has been determined, their role in multiple sclerosis (MS) has not been elucidated. In the present study, the character of MAIT cells in the peripheral blood of MS patients was analyzed. Compared with healthy controls, the frequency of MAIT cells in peripheral blood was significantly reduced in MS patients in remission and even more profoundly reduced in those with relapse. The frequency of MAIT cells reflected the disease activity, as they were reduced significantly in patients with active disease compared with stable patients, and when blood samples from patients undergoing attack were analyzed 2-3 months later, the frequency significantly increased in parallel with clinical recovery. The frequency of MAIT cells positively correlated with the frequency of CD4(+) invariant NKT cells and of CD56(bright) NK cells in healthy controls but not in MS patients. This suggests the existence of an immune-regulatory link between MAIT cells and these other cell populations with disruption of this cross talk in MS. Moreover, MAIT cells showed a suppressive activity against IFN-γ production by T cells in vitro. This suppression required cell contact but was independent of IL-10, inducible co-stimulator or the presence of B cells. Taken together, these results suggest an immune-regulatory role of MAIT cells in MS through suppression of pathogenic T(h)1 cells.

Suppression of Experimental Autoimmune Encephalomyelitis by Ghrelin

Ghrelin is a recently identified gastric hormone that displays strong growth hormone-releasing activity mediated by the growth hormone secretagogue receptor. While this unique endogenous peptide participates in the regulation of energy homeostasis, increases food intake, and decreases energy expenditure, its ability to inhibit the production of proinflammatory cytokines in vitro indicates its role in the regulation of inflammatory process in vivo. Here we examine the effect of exogenous ghrelin on the development of experimental autoimmune encephalomyelitis (EAE), a representative model of multiple sclerosis. In the C57BL/6 mouse model of EAE induced by sensitization to myelin oligodendrocyte glycoprotein 35–55 peptide, we found that alternate-day s.c. injections of ghrelin (5 μg/kg/day) from day 1 to 35 significantly reduced the clinical severity of EAE. The suppression of EAE was accompanied by reduced mRNA levels of proinflammatory cytokines such as TNF-α, IL-1β, and IL-6 in the spinal cord cellular infiltrates and microglia from ghrelin-treated mice at the peak of disease, suggesting the role of ghrelin as an antiinflammatory hormone. Consistently, ghrelin significantly suppressed the production of proinflammatory cytokines in LPS-stimulated microglia in vitro. These results shed light on the new role of ghrelin in the regulation of inflammation with possible implications for management of human diseases.

Mucosal‐associated invariant T cells promote inflammation and exacerbate disease in murine models of arthritis

OBJECTIVE The function of mucosal-associated invariant T (MAIT) cells remains largely unknown. We previously reported an immunoregulatory role of MAIT cells in an animal model of multiple sclerosis. The aim of this study was to use animal models to determine whether MAIT cells are involved in the pathogenesis of arthritis. METHODS MR1-/- and MR1+/+ DBA/1J mice were immunized with bovine type II collagen (CII) in complete Freunds adjuvant to trigger collagen-induced arthritis (CIA). To assess CII-specific T cell recall responses, lymph node cells from mice with CIA were challenged with CII ex vivo, and cytokine production and proliferation were evaluated. Serum levels of CII-specific antibodies were measured by enzyme-linked immunosorbent assay. Collagen antibody-induced arthritis (CAIA) was induced in MR1-/- and MR1+/+ C57BL/6 mice by injection of anti-CII antibodies followed by injection of lipopolysaccharide. To demonstrate the involvement of MAIT cells in arthritis, we induced CAIA in MR1-/- C57BL/6 mice that had been reconstituted with adoptively transferred MAIT cells. MAIT cell activation in response to cytokine stimulation was investigated. RESULTS The severity of CIA was reduced in MR1-/- DBA/1J mice. However, T and B cell responses to CII were comparable in MR1-/- and MR1+/+ DBA/1J mice. MR1-/- C57BL/6 mice were less susceptible to CAIA, and reconstitution with MAIT cells induced severe arthritis in MR1-/- C57BL/6 mice, demonstrating an effector role of MAIT cells in arthritis. MAIT cells became activated upon stimulation with interleukin-23 (IL-23) or IL-1β in the absence of T cell receptor stimuli. CONCLUSION These results indicate that MAIT cells exacerbate arthritis by enhancing the inflammation.

The dual role of short fatty acid chains in the pathogenesis of autoimmune disease models

Autoimmune diseases are influenced by both genetic and environmental factors. The gut environment has attracted much attention as an essential component that modulates immune responses, and therefore immune-mediated disorders, such as autoimmune diseases. Growing evidence suggests that microbiota and their metabolites are critical factors for immune modulation. Recently, we reported that the microbiome in patients with multiple sclerosis, an autoimmune disease targeting the myelin sheath of the central nervous system, is characterized by a reduction of bacteria belonging to Clostridia clusters IV and XIVa, which are potent producers of short-chain fatty acids (SCFAs) by fermentation of indigestible carbohydrates. In the present study, we investigated the role of SCFAs in the regulation of inflammation. We demonstrated that oral administration of SCFAs ameliorated the disease severity of systemic autoimmune inflammatory conditions mediated by lymphocytes such as experimental autoimmune encephalitis and collagen-induced arthritis. Amelioration of disease was associated with a reduction of Th1 cells and an increase in regulatory T cells. In contrast, SCFAs contributed to the exaggeration of K/BxN serum transfer arthritis, representing the effector phase of inflammation in rheumatoid arthritis. An increased understanding of the effect of microbiota metabolites will lead to the effective treatment and prevention of systemic inflammatory disorders.

MAIT cells are activated and accumulated in the inflamed mucosa of ulcerative colitis

Ulcerative colitis (UC) is a chronic, relapsing and remitting, inflammatory disorder of the large intestine. Mucosal associated invariant T (MAIT) cells are a member of innate‐like lymphocytes found abundantly in the mucosal tissue. The contribution of MAIT cells in the pathogenesis of UC is still unclear; therefore, this study aimed at investigating the role of these cells in patients with UC.

Involvement of Mucosal-associated Invariant T cells in Ankylosing Spondylitis

Objective. Ankylosing spondylitis (AS) is characterized by chronic inflammation of the axial and peripheral joints and ligamentous attachments. Gut immunity is thought to be involved in AS, because a prominent coexistence of gut and joint inflammation has been observed in patients with AS. Mucosal-associated invariant T (MAIT) cells are preferentially located in the gut lamina propria and produce inflammatory cytokines such as interleukin 17 (IL-17) and tumor necrosis factor-α (TNF-α), which are therapeutic targets for AS. This study aimed to investigate the involvement of MAIT cells in AS. Methods. The frequency of MAIT cells and their cytokine production were determined in patients with AS and healthy controls (HC). The expression of a MAIT cell activation marker (CD69) was analyzed in patients with AS by using flow cytometry. Results. The frequency of MAIT cells in the peripheral blood was lower in patients with AS compared with HC. The levels of IL-17 produced by MAIT cells after activation were higher in patients with AS than in the HC. CD69 expression on MAIT cells correlated with the Ankylosing Spondylitis Disease Activity Score in patients with AS. Conclusion. These results suggest the involvement of MAIT cells in the pathogenesis of AS.

A 4-trifluoromethyl analogue of celecoxib inhibits arthritis by suppressing innate immune cell activation

IntroductionCelecoxib, a highly specific cyclooxygenase-2 (COX-2) inhibitor has been reported to have COX-2-independent immunomodulatory effects. However, celecoxib itself has only mild suppressive effects on arthritis. Recently, we reported that a 4-trifluoromethyl analogue of celecoxib (TFM-C) with 205-fold lower COX-2-inhibitory activity inhibits secretion of IL-12 family cytokines through a COX-2-independent mechanism that involves Ca2+-mediated intracellular retention of the IL-12 polypeptide chains. In this study, we explored the capacity of TFM-C as a new therapeutic agent for arthritis.MethodsTo induce collagen-induced arthritis (CIA), DBA1/J mice were immunized with bovine type II collagen (CII) in Freunds adjuvant. Collagen antibody-induced arthritis (CAIA) was induced in C57BL/6 mice by injecting anti-CII antibodies. Mice received 10 μg/g of TFM-C or celecoxib every other day. The effects of TFM-C on clinical and histopathological severities were assessed. The serum levels of CII-specific antibodies were measured by ELISA. The effects of TFM-C on mast cell activation, cytokine producing capacity by macophages, and neutrophil recruitment were also evaluated.ResultsTFM-C inhibited the severity of CIA and CAIA more strongly than celecoxib. TFM-C treatments had little effect on CII-specific antibody levels in serum. TFM-C suppressed the activation of mast cells in arthritic joints. TFM-C also suppressed the production of inflammatory cytokines by macrophages and leukocyte influx in thioglycollate-induced peritonitis.ConclusionThese results indicate that TFM-C may serve as an effective new disease-modifying drug for treatment of arthritis, such as rheumatoid arthritis.

Activation status of mucosal-associated invariant T cells reflects disease activity and pathology of systemic lupus erythematosus

BackgroundMucosal-associated invariant T (MAIT) cells are innate-like lymphocytes constituting a large proportion of peripheral blood T cells expressing αβ T-cell receptor in humans. In this study, we aimed to investigate their involvement in systemic lupus erythematosus (SLE).MethodsPeripheral blood MAIT cells from patients with SLE were assessed for their frequency, activation markers, and cell death by flow cytometry. The correlation between plasma cytokine levels and CD69 expression on MAIT cells was analyzed. The major histocompatibility complex class I-related protein MR1-restricted antigen-presenting capacity of antigen-presenting cells was investigated. Cytokine-mediated activation of MAIT cells in the absence of exogenous antigens was also examined.ResultsThe frequency of MAIT cells was markedly reduced in SLE. The reduced number of MAIT cells was not attributable to the downregulation of surface markers, but it was partially due to the enhanced cell death of MAIT cells, possibly by activation-induced cell death. The CD69 expression levels on MAIT cells in SLE correlated with disease activity. Moreover, monocytes from patients with SLE exhibited increased ability to induce MAIT cell activation. The plasma concentration of interleukin (IL)-6, IL-18, and interferon (IFN)-α positively correlated with the expression levels of CD69 on MAIT cells in SLE. MAIT cells were activated by cytokines, including IFN-α, IL-15, and IL-12 plus IL-18, in the absence of exogenous antigens.ConclusionsThese results suggest that MAIT cells reflect the pathological condition of SLE and that their activated status correlates with presence of disease.

IL-38: A new factor in rheumatoid arthritis

The newly characterized cytokine IL-38 (IL-1F10) belongs to the IL-1 family of cytokines. Previous work has demonstrated that IL-38 inhibited Candida albicans-induced IL-17 production from peripheral blood mononuclear cells. However, it is still unclear whether IL-38 is an inflammatory or an anti-inflammatory cytokine. We generated anti-human IL-38 monoclonal antibodies in order to perform immunohistochemical staining and an enzyme-linked immunosorbent assay. While human recombinant IL-38 protein was not cleaved by recombinant caspase-1, chymase, or PR3 in vitro, overexpression of IL-38 cDNA produced a soluble form of IL-38 protein. Furthermore, immunohistochemical analysis showed that synovial tissues obtained from RA patients strongly expressed IL-38 protein. To investigate the biological role of IL-38, C57BL/6 IL-38 gene-deficient (−/−) mice were used in an autoantibody-induced rheumatoid arthritis (RA) mouse model. As compared with control mice, IL-38 (−/−) mice showed greater disease severity, accompanied by higher IL-1β and IL-6 gene expression in the joints. Therefore, IL-38 acts as an inhibitor of the pathogenesis of autoantibody-induced arthritis in mice and may have a role in the development or progression of RA in humans.

A Trifluoromethyl Analogue of Celecoxib Exerts Beneficial Effects in Neuroinflammation

Celecoxib is a selective cyclooxygenase-2 (COX2) inhibitor. We have previously shown that celecoxib inhibits experimental autoimmune encephalomyelitis (EAE) in COX-2-deficient mice, suggestive for a mode of action involving COX2-independent pathways. In the present study, we tested the effect of a trifluoromethyl analogue of celecoxib (TFM-C) with 205-fold lower COX-2 inhibitory activity in two models of neuroinflammation, i.e. cerebellar organotypic cultures challenged with LPS and the EAE mouse model for multiple sclerosis. TFM-C inhibited secretion of IL-1β, IL-12 and IL-17, enhanced that of TNF-α and RANTES, reduced neuronal axonal damage and protected from oxidative stress in the organotypic model. TFM-C blocked TNF-α release in microglial cells through a process involving intracellular retention, but induced TNF-α secretion in primary astrocyte cultures. Finally, we demonstrate that TFM-C and celecoxib ameliorated EAE with equal potency. This coincided with reduced secretion of IL-17 and IFN-γ by MOG-reactive T-cells and of IL-23 and inflammatory cytokines by bone marrow-derived dendritic cells. Our study reveals that non-coxib analogues of celecoxib may have translational value in the treatment of neuro-inflammatory conditions.