Prevention of experimentally induced autoimmune type I diabetes in rats by the new immunosuppressive reagent FTY720

Diabetes tolerogenic vaccines targeting antigen-specific inflammation

Tolerance controls the magnitude of inflammation, and balance between beneficial and harmful effects of inflammation is crucial for organ function and survival. Inadequate tolerance leads to various inflammatory diseases. Antigen specific tolerance is ideal for inflammation control as alternative anti-inflammatory interventions are non-specific and consequently increase the risk of infection and tumorigenesis. With inherent antigen specificity, tolerogenic vaccines are potentially ideal for control of inflammation. Although the concept of tolerogenic vaccines is still in its infancy, tolerogenic mucosal vaccines and specific immuno-therapies have long been proven effective in pioneering examples. Now a body of evidence supporting the concept of tolerogenic vaccines has also accumulated. Here we comment on recent successes of the tolerogenic vaccine concept, present new evidence with a type 1 diabetes vaccine as an example and draw conclusions on the advantages and potential for inflammatory disease control at the bedside.

Effect of FTY720 on some physiological indexes of Non-Obese Diabetic (NOD) Mice

The studies were performed to investigate the physiological characteristics of non-obese diabetic (NOD) mice treated with FTY720. At the age of 12 weeks, each mouse was fed with FTY720 or physiological saline once a day for 10 weeks running, and their blood glucose, weight, anti-GAD antibody and organ indexes were determined. No mouse in group FTY720 (NOD mice treated with FTY720) showed diabetic symptoms. The average content of serum anti-GAD antibody in group FTY720 decreased 48.75% (P < 0.01). It was concluded that the spleen, kidney and liver of NOD mice treated with FTY720 shriveled significantly in the progression of diabetes (P < 0.01 or P < 0.05). The body weight of group FTY720 mice was slightly lower than that of the model control (MC) group and these two groups both had less body weight than the normal control (NC) group (P < 0.01). The result of tests of anti-GAD antibody suggested that FTY720 treatment could suppress the anti-GAD response.

Insights into the pharmacological relevance of lysophospholipid receptors

The discovery of lysophospholipid (LP) 7-transmembrane, G protein-coupled receptors (GPCRs) that began in the 1990s, together with research into the functional roles of the major LPs known as lysophosphatidic acid (LPA) and sphingosine 1-phosphate (S1P), have opened new research avenues into their biological processes and mechanisms. Major examples of LP signalling effects include embryogenesis, nervous system development, vascular development, uterine implantation, immune cell trafficking, and inflammatory reactions. LP signalling also influences the pathophysiology of many diseases including cancer, autoimmune and inflammatory diseases, which indicate that LP receptors may be attractive targets for pharmacological therapies. A key example of such a therapeutic agent is the S1P receptor modulator FTY720, which upon phosphorylation and continued drug exposure, acts as an S1P receptor functional antagonist. This compound (also known as fingolimod or Gilenya) has recently been approved by the FDA for the treatment of relapsing forms of multiple sclerosis. Continued basic and translational research on LP signalling should provide novel insights into both basic biological mechanisms, as well as novel therapeutic approaches to combat a range of human diseases.

Lysophospholipid activation of G protein-coupled receptors

One of the major lipid biology discoveries in last decade was the broad range of physiological activities of lysophospholipids that have been attributed to the actions of lysophospholipid receptors. The most well characterized lysophospholipids are lysophosphatidic acid (LPA) and sphingosine 1-phosphate (S1P). Documented cellular effects of these lipid mediators include growth-factor-like effects on cells, such as proliferation, survival, migration, adhesion, and differentiation. The mechanisms for these actions are attributed to a growing family of 7-transmembrane, G protein-coupled receptors (GPCRs). Their pathophysiological actions include immune modulation, neuropathic pain modulation, platelet aggregation, wound healing, vasopressor activity, and angiogenesis. Here we provide a brief introduction to receptor-mediated lysophospholipid signaling and physiology, and then discuss potential therapeutic roles in human diseases.

The sphingosine 1-phosphate receptor agonist FTY720 differentially affects the sequestration of CD4+/CD25+ T-regulatory cells and enhances their functional activity

The sphingosine 1-phosphate (S1P) receptor agonist FTY720 is well known for its immunomodulatory activity, sequestering lymphocytes from blood and spleen into secondary lymphoid organs and thereby preventing their migration to sites of inflammation. Because inflammation is critically dependent on a balance between Ag-specific Th/effector cells and T-regulatory cells, we investigated the effect of FTY720 on T-regulatory cell trafficking and functional activity. An increased number of CD4+/CD25+ T cells was found in blood and spleens of FTY720-treated mice, and transfer of these cells resulted in a significantly more pronounced accumulation in spleens but not lymph nodes after treatment, suggesting that this compound differentially affects the homing properties of T-regulatory cells compared with other T cell subsets. Indeed, CD4+/CD25+ T cells express lower levels of S1P1 and S1P4 receptors and demonstrate a reduced chemotactic response to S1P. Moreover, analysis of the functional response of FTY720-treated CD4+/CD25+ T cells revealed an increased suppressive activity in an in vitro Ag-specific proliferation assay. This correlated with enhanced function in vivo, with T-regulatory cells obtained from FTY720-treated mice being able to suppress OVA-induced airway inflammation. Thus, FTY720 differentially affects the sequestration of T-regulatory cells and importantly, increases the functional activity of T-regulatory cells, suggesting that it may have disease-modifying potential in inflammatory disorders.

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FTY720 in Corneal Concordant Xenotransplantation

BACKGROUND

: Currently, there are no effective treatments for the control of corneal xenograft rejection. We evaluated the efficacy and mode of action of a novel immunosuppressant, FTY720, in a model of corneal xenograft transplantation.

METHODS

: Rat-to-mouse corneal xenografts were performed and the effects of treatment with daily intraperitoneal injections of FTY720 (0.5 or 3.0 mg/kg/day) or saline from 2 days pretransplantation were assessed clinically. Immunohistochemical studies of the grafts and flow cytometry of the draining lymph node subpopulations were performed at the time of clinical rejection.

RESULTS

: Treatment with FTY720 delayed the onset of corneal rejection, from 8 days postgraft in saline-treated mice to 12.0 +/- 0.89 days for low-dose FTY720 treatment and 15.6 +/- 3.1 days for high-dose FTY720 treatment (both P<0.001). Histologically, FTY-treated animals had a markedly reduced inflammatory response in the anterior chamber and cornea after replacement of the xenograft epithelium with normal healthy host epithelium. In contrast, saline-treated xenografts had persisting corneal epithelial defects and ulceration. In the draining lymph nodes, FTY720 not only inhibited the increase in the cell number observed in saline-treated recipients of xenografts, but also reduced the expression of activation markers on B cells (MHC class II and CD86).

CONCLUSIONS

: FTY720 treatment significantly delayed rejection and decreased its severity in a dose-dependent manner in a rat-to-mouse model of corneal xenotransplantation. Since corneal xenograft rejection is mediated not by natural antibodies or CD8+ T cells directly, but by CD4+ T cells, the data from these experiments imply that FTY720 mediated its effect via CD4+ T cells.

Sphingosine 1-phosphate receptor agonists attenuate relapsing–remitting experimental autoimmune encephalitis in SJL mice

FTY720 is a prodrug for FTY-phosphate, an agonist at four of the five known receptors for sphingosine-1-phosphate (S1P). We show that administration of either FTY720 or FTY-P to SJL mice with established relapsing-remitting experimental autoimmune encephalitis (EAE) results in a rapid and sustained improvement in their clinical status, and a reversal of changes in expression of mRNAs encoding some myelin proteins and inflammatory mediators. EAE produced by adoptively transferring lymph node cells from immunized mice to naïve hosts is similarly ameliorated by FTY-P. Treatment with FTY-P is accompanied by a dose-responsive peripheral lymphopoenia.

The effect of immunomodulators on prevention of autoimmune diabetes is stage dependent: FTY720 prevents diabetes at three different stages in the diabetes-resistant biobreeding rat

BACKGROUND

Autoimmune diabetes of the diabetes-resistant biobreeding (DRBB) rat shares similarities with diabetes in humans and has stages of diabetes that can be controlled and compared. FTY720 is an immunomodulator that has been efficacious in transplant and autoimmune models without inducing an immunosuppressed state. We determined the stages of diabetes that are affected by FTY720 in the DRBB rat.

METHODS

Autoimmune diabetes was induced with RT6.1 T-cell-depleting antibody and polyIC starting at 4 weeks of age. FTY720 (1 mg/kg/d) was started at day 0, 5, 7, and 14 following the start of depletion. The rats that did not develop diabetes were maintained for 60 d following the last dose of FTY720 before undergoing a second course of depletion.

RESULTS

FTY720 starting at day 0, 5, 7, and 14 of depletion prevented diabetes in 100, 100, 50, and 20% of the DRBB rats compared to 0% of the control rats. The surviving rats in the 5-, 7-, and 14-d groups developed diabetes after FTY720 treatment was stopped. Histological examination indicated insulitis in the control rats between day 7 and 11 of depletion and end-stage insulitis by day 18 of depletion compared to negligible insulitis in rats without diabetes. Redepletion in the surviving day 0 rats resulted in development of diabetes in 25% of these rats compared to none of the age-matched controls.

SUMMARY

FTY720 can prevent autoimmune diabetes, if administered before and/or during stimulation and expansion of the autoreactive T cells or in the early stages of insulitis. The effectiveness diminishes with each successive stage of diabetes.

Inhibition of Th1- and Th2-mediated airway inflammation by the sphingosine 1-phosphate receptor agonist FTY720

The sphingosine 1-phosphate receptor agonist FTY720 is a novel immunomodulator that sequesters lymphocytes in secondary lymphoid organs and thereby prevents their migration to sites of inflammation. However, there is currently no information available on whether this drug affects Th1 or Th2 cell-mediated lung-inflammatory responses. The effect of FTY720 was therefore investigated in a murine airway inflammation model using OVA-specific, in vitro differentiated, and adoptively transferred Th1 and Th2 cells. Both Th1 and Th2 cells express a similar pattern of FTY720-targeted sphingosine 1-phosphate receptors. The OVA-induced Th1-mediated airway inflammation characterized by increased numbers of lymphocytes and neutrophils in bronchoalveolar lavage fluid was significantly inhibited by oral FTY720 treatment. Similarly, FTY720 suppressed the Th2 cell-induced bronchoalveolar lavage fluid eosinophilia and the infiltration of T lymphocytes and eosinophils into the bronchial tissue. Moreover, the Ag-induced bronchial hyperresponsiveness to inhaled metacholine was almost completely blocked. The inhibitory effect of FTY720 on airway inflammation, induction of bronchial hyperresponsiveness, and goblet cell hyperplasia could be confirmed in an actively Ag-sensitized murine asthma model, clearly indicating that Th2 cell-driven allergic diseases such as asthma could benefit from such treatment.

Effects of immunosuppressant FTY720 on renal and hepatic hemodynamics in the rat

BACKGROUND

FTY720 is a novel immunomodulator that may provide an opportunity for a reduction in calcineurin inhibitor dosage in transplant recipients with renal/hepatic side effects. However, the effects of FTY720 on renal or hepatic hemodynamics are unknown. The aim of this study was to establish the hemodynamic and renal actions of FTY720 at therapeutically relevant dosages.

METHODS

The effects of acute and repeat oral administration of FTY720 on systemic, renal, and hepatic hemodynamics were investigated in the anesthetized male Lewis rat. Renal function and renal tubular parameters were examined in animals that received repeat high dosage of FTY720.

RESULTS

Seven-day oral administration of FTY720 did not cause any significant changes in markers of hepatocyte injury, nor did it cause any reduction in renal function (elevated urea and creatinine). Histological examination of liver and kidney from animals treated with repeat FTY720 for 1 or 3 weeks did not reveal any sclerosis, tubular changes, infiltrates, or fibrosis. Hepatocyte, vascular, and biliary structures were normal. Compared with the vehicle (saline), oral administration of FTY720 at dosages up to 5 mg/kg/day for 1 week did not have any significant effects on systemic, hepatic, or renal hemodynamics. Five min after intravenous FTY720 administration (1 mg/kg), mean arterial pressure (MAP) rose to 114+/-3.3% of baseline (P <0.01) before returning to the normal range within 30-45 min. Lower doses of FTY720 (0.3 and 0.5 mg/kg, i.v.) did not affect MAP. Renal cortical perfusion, renal artery blood flow, and renal vascular resistance were not altered by FTY720 at i.v. doses up to 1 mg/kg. Animals that received FTY720 (5 mg/kg/day) for 3 weeks showed a significant reduction in body weight (-4.8+/-1% of baseline at 3 weeks, P <0.001); however, weight-adjusted creatinine clearance, 24 h urine production, and urine osmolality were not different from those in control animals (0.71+/-0.1 vs. 0.74+/-0.1 ml/min/100 g, 2.63+/-0.2 vs. 3.12+/-0.2 ml/100 g, and 2003+/-33 vs. 1966+/-56 mOsm/kg, respectively). FTY720 at the same repeat oral dosage was, nevertheless, associated with a significantly lower 24 h sodium excretion and a significantly lower fractional excretion of sodium compared with those in control animals (223.4+/-35 vs. 304.5+/-50 micromol/100 g and 1.75+/-0.3 vs. 2.23+/-0.3%, respectively; P <0.05).

CONCLUSIONS

Our data indicate that, at least in the short term, oral FTY720 does not cause any significant adverse effects on renal or hepatic hemodynamics, nor does it cause any reduction in glomerular perfusion and thus may provide reasonable rescue/add-on therapy in calcineurin-inhibitor treated transplant recipients. At high repeat oral dosages, however, FTY720 may alter renal handling of sodium.

FTY720 prevents development of experimental autoimmune myocarditis through reduction of circulating lymphocytes

FTY720 is a new immunosuppressant agent and selectively decreases the number of circulating lymphocytes. In this study, we compared the effects of FTY720 with those of tacrolimus on experimental autoimmune myocarditis (EAM) in rats. A significant decrease in circulating lymphocyte counts was noted after a single administration of FTY720 in normal rats. At day 0, 7-week-old male Lewis rats were immunized with purified porcine cardiac myosin emulsified in complete Freund's adjuvant. FTY720 or tacrolimus was administered intraperitoneally daily. The number of myocarditis-affected areas in the FTY720 treatment groups with doses of 0.1 mg/kg/ day was significantly lower than those in control groups at days 14 and 28. In addition, at day 28, the myocarditis-affected areas in the FTY720 treatment group were significantly smaller than those in the tacrolimus treatment group receiving the same dose. Effects of early administration (days 0-10) and delayed administration (days 11-20) of FTY720 also were examined. At day 28, the myocarditis-affected areas in the early therapy group were significantly lower than those in the control group. In conclusion, we demonstrated that the development of EAM could be prevented by FTY720. These data also indicated that lymphocyte-mediated immunity is critically involved in the development of EAM.