Noriyasu Seki

Fingolimod (FTY720), sphingosine 1-phosphate receptor modulator, shows superior efficacy as compared with interferon-β in mouse experimental autoimmune encephalomyelitis

Fingolimod (FTY720), a sphingosine 1-phosphate (S1P) receptor modulator, inhibits S1P-dependent lymphocyte egress from secondary lymphoid organs and is highly effective in experimental autoimmune encephalomyelitis (EAE) in mice. In this study, we directly compared the therapeutic effects of FTY720 and recombinant mouse interferon (rm-IFN)-β on relapse and progression of EAE in mice. When FTY720 at oral dose of 0.03 to 1 mg/kg was administered daily after establishment of EAE induced by myelin proteolipid protein (PLP) in SJL/J mice, relapse of EAE was significantly inhibited during administration period. Subcutaneous injection of rm-IFN-β (10,000 IU/mouse) also inhibited the relapse of EAE at early period; however EAE was relapsed in all the mice within administration period. Therapeutic administration of FTY720 (0.03 to 1 mg/kg) significantly improved the symptoms of chronic EAE induced by myelin oligodendrocyte glycoprotein in C57BL/6 mice whereas rm-IFN-β (10,000 IU/mouse) showed no clear effect. These results indicate that FTY720 is more efficacious in mouse EAE as compared with rm-IFN-β. FTY720 markedly reduced the frequency of PLP-specific Th17 and Th1 cells in the spinal cord of EAE mice. On the contrary, FTY720 increased the frequency of PLP-specific Th17 and Th1 cells in the inguinal lymph nodes, suggesting inhibition of egress of myelin antigen-specific Th cells from draining lymph nodes. From these results, the ameliorating effects of FTY720 on EAE are likely due to reduction of infiltration of myelin antigen-specific Th17 and Th1 cells into the central nervous system.

Sphingosine 1-phosphate receptor type 1 regulates egress of mature T cells from mouse bone marrow

Sphingosine 1-phosphate (S1P) and its receptor, S1P receptor type 1 (S1P(1)), are essential for lymphocyte egress from secondary lymphoid organs (SLO). Fingolimod (FTY720), the S1P receptor modulator, inhibits lymphocyte egress from SLO and decreases circulating lymphocytes; however, it also induces a significant decrease in the number of peripheral blood lymphocytes in alymphoplasia (aly/aly) mice lacking SLO. In this study, we demonstrated that the administration of FTY720 induced sequestration of mature lymphocytes, particularly T cells, into the bone marrow (BM) in aly/aly mice, implying that the reduction of circulating lymphocytes in these mice by FTY720 was due to inhibition of lymphocyte egress from the BM. Since sequestration of mature T cells into the BM was also induced in normal mice by selective S1P(1) agonist or S1P lyase inhibitor, it is suggested that S1P(1) expression and the S1P gradient play an important role in egress of mature T cells from the BM. Prophylactic administration of FTY720 to ovalbumin (OVA)-immunized mice significantly inhibited footpad swelling induced by OVA challenging with a marked reduction of OVA-specific T(h) cells in the BM, indicating that immunomodulation by FTY720 is likely due to reduced circulation of antigen-specific T(h) cells. On the other hand, OVA-specific T(h) cells, like naive T cells, were also sequestered into the BM and SLO of OVA-immunized mice by a short exposure of FTY720 after OVA challenging. These results suggest that the S1P-S1P(1) axis plays a regulatory role in egress of mature T cells including antigen-specific T(h) cells from the BM.

IL-17–Producing Vγ4+ γδ T Cells Require Sphingosine 1-Phosphate Receptor 1 for Their Egress from the Lymph Nodes under Homeostatic and Inflammatory Conditions

Conventional αβ T cells require sphingosine 1-phosphate (S1P) receptor 1 (S1P1) for circulation through the lymph nodes (LN); however, it is unclear whether γδ T cells use similar mechanisms. In this study, we found that treatment with fingolimod (FTY720, 1 mg/kg, orally) markedly reduced not only conventional CD4 T cells but also circulating γδ T cells (Vγ4+ and Vγ4− subsets) in the blood of mice. In contrast, IL-17+Vγ4+, IL-17+Vγ4−, and IL-17−Vγ4− subsets were significantly accumulated in the LN after 6 h of FTY720 treatment. By skin application of a synthetic TLR7/8 agonist, Vγ4+ γδ T cells (IL-17+ and IL-17− subsets) were accumulated and expanded in the draining LN (DLN), whereas the IL-17+ subset predominantly migrated to the inflamed skin. FTY720 induced a marked sequestration of IL-17–producing Vγ4+ γδ T cells in the DLN and inhibited their infiltration into the inflamed skin. Similarly, FTY720 inhibited infiltration of Vγ4+ γδ T cells into the CNS by their sequestration into the DLN in experimental autoimmune encephalomyelitis. Vγ4+ γδ T cells expressed a significant level of S1P1 and showed a migratory response toward S1P. FTY720 treatment induced almost complete downregulation of S1P1 expression and S1P responsiveness in Vγ4+ γδ T cells. Our findings strongly suggest that IL-17–producing Vγ4+ γδ T cells require S1P1 for their egress from the LN under homeostatic and inflammatory conditions. Consequently, inhibition of S1P1-dependent egress of pathogenic IL-17–producing Vγ4+ γδ T cells from the DLN may partly contribute the clinical therapeutic effects of FTY720 in relapsing multiple sclerosis.

A New Phenylpyrazoleanilide, Y-320, Inhibits Interleukin 17 Production and Ameliorates Collagen-Induced Arthritis in Mice and Cynomolgus Monkeys

Interleukin (IL)-15 and IL-17 are thought to play an important role in the pathogenesis of rheumatoid arthritis (RA) because both pro-inflammatory cytokines are found in synovial fluid of RA patients. In this study, we examined the pharmacological profiles of Y-320, a new phenylpyrazoleanilide immunomodulator. Y-320 inhibited IL-17 production by CD4 T cells stimulated with IL-15 with IC50 values of 20 to 60 nM. Oral administration of Y-320 (0.3 to 3 mg/kg) significantly inhibited the development and progression of arthritis and joint destruction with reduction of IL-17 mRNA expression in arthritic joints of type II collagen-induced arthritis (CIA) in DBA/1J mice. Y-320 in combination with anti-murine tumor necrosis factor-α monoclonal antibody showed a synergistic effect on mouse CIA. Moreover, therapeutic treatment with Y-320 (0.3 and 1 mg/kg orally) ameliorated CIA in cynomolgus monkeys. Our results suggest that Y-320, an orally active inhibitor for IL-17 production, provides a useful therapy for RA.

Therapeutic Effects of the Sphingosine 1-Phosphate Receptor Modulator, Fingolimod (FTY720), on Experimental Autoimmune Encephalomyelitis

2-Amino-2-[2-(4-octylphenyl)ethyl]propane-1,3-diol hydrochloride (FTY720, fingolimod hydrochloride) is an orally active sphingosine 1-phosphate (S1P) receptor modulator with a structure closely related to sphingosine (Adachi et al., 1995; Chiba et al., 1996, 1997) (Fig. 1). FTY720 sequesters circulating mature lymphocytes into the secondary lymphoid organs (SLO) and thymus by long-term down-regulation of S1P receptor type 1 (S1P1) on lymphocytes, and shows potent immunomodulating effects (Brinkmann et al., 2000, 2002a, 2002b, 2004; Chiba et al., 1998, 1999, Chiba, 2005; Matloubian et al., 2004).