Therapeutic effects of FTY720, a new immunosuppressive agent, in a murine model of acute viral myocarditis

The Role of Non-coding RNAs in Viral Myocarditis

Viral myocarditis (VMC) is a disease characterized as myocardial parenchyma or interstitium inflammation caused by virus infection, especially Coxsackievirus B3 (CVB3) infection, which has no accurate non-invasive examination for diagnosis and specific drugs for treatment. The mechanism of CVB3-induced VMC may be related to direct myocardial damage of virus infection and extensive damage of abnormal immune response after infection. Non-coding RNA (ncRNA) refers to RNA that is not translated into protein and plays a vital role in many biological processes. There is expanding evidence to reveal that ncRNAs regulate the occurrence and development of VMC, which may provide new treatment or diagnosis targets. In this review, we mainly demonstrate an overview of the potential role of ncRNAs in the pathogenesis, diagnosis and treatment of CVB3-induced VMC.

FTY720 (Gilenya) treatment prevents spontaneous autoimmune myocarditis and dilated cardiomyopathy in transgenic HLA-DQ8-BALB/c mice

Although dilated cardiomyopathy (DCM) is often caused by viral infections, it frequently involves autoimmune mechanisms associated with particular HLA-DR and DQ alleles. Our homozygous HLA-DQ8Ab(0) transgenic mice in the BALB/c background (HLA-DQ8(BALB/c)-Tg) developed early and progressive fatal heart failure from 4 to 5 weeks of age. Clinical signs of the disease included cyanotic eyes, tachycardia with dyspnea (from pale to cyanotic limbs), and terminal whole body edema. Sick mice had extremely dilated hearts, enlarged liver and spleen, and pleural/peritoneal effusion. Histology of the heart showed extensive heart muscle destruction with signs of fibrosis. The autoimmune nature of the disease was shown by high titers of antimyosin antibodies in the sera and IgG deposits in sick heart muscles, as well as focal neutrophil, T cell, and macrophage infiltration of the heart muscle. The sera of the sick mice showed a granular staining pattern on sections of healthy heart muscle. Quantitative analyses of DCM-specific gene expression studies revealed that sets of genes are involved in inflammation, hypoxia, and fibrosis. Treatment with FTY720 (Fingolimod/Gilenya) protected animals from the development of cardiomyopathy. HLA-DQ8(BALB/c)-Tg mice represent a spontaneous autoimmune myocarditis model that may provide a useful tool for studying the autoimmune mechanism of DCM and testing immunosuppressive drugs.

KRP-203, Sphingosine 1-Phosphate Receptor Type 1 Agonist, Ameliorates Atherosclerosis in LDL-R −/− Mice

Objective—

Sphingosine 1-phosphate (S1P) partly accounts for antiatherogenic properties of high-density lipoproteins. We previously demonstrated that FTY720, a synthetic S1P analog targeting all S1P receptors but S1P receptor type 2, inhibits murine atherosclerosis. Here, we addressed the identity of S1P receptor mediating atheroprotective effects of S1P.

Approach and Results—

Low-density lipoprotein receptor–deficient mice on cholesterol-rich diet were given selective S1P receptor type 1 agonist KRP-203 (3.0 mg/kg per day; 6 and 16 weeks). KRP-203 substantially reduced atherosclerotic lesion formation without affecting plasma lipid concentrations. However, KRP-203 induced lymphopenia, reduced total (CD4 + , CD8 + ) and activated (CD69 + /CD8 + , CD69 + /CD4 + ) T cells in peripheral lymphoid organs, and interfered with lymphocyte function, as evidenced by decreased T-cell proliferation and interleukin-2 and interferon-γ production in activated splenocytes. Cyto- and chemokine (tumor necrosis factor-α, regulated and normal T cell expressed and secreted) levels in plasma and aortas were reduced by KRP-203 administration. Moreover, macrophages from KRP-203–treated mice showed reduced expression of activation marker MCH-II and poly(I:C)-elicited production of tumor necrosis factor-α, monocyte chemoattractant protein-1, and interleukin-6. In vitro studies demonstrated that KRP-203 reduced tumor necrosis factor-α, interleukin-6, and interferon-γ–induced protein-10 production; IκB and signal transducer and activator of transcription-1 phosphorylation; and nuclear factor κB and signal transducer and activator of transcription-1 activation in poly(I:C)-, lipopolysaccharide-, or interferon-γ–stimulated bone marrow macrophages, respectively.

Conclusions—

Present results demonstrate that activation of S1P signaling pathways inhibit atherosclerosis by modulating lymphocyte and macrophage function and suggest that S1P receptor type 1 at least partially mediates antiatherogenic effects of S1P.

Hematopoietic sphingosine 1-phosphate lyase deficiency decreases atherosclerotic lesion development in LDL-receptor deficient mice

AIMS

Altered sphingosine 1-phosphate (S1P) homeostasis and signaling is implicated in various inflammatory diseases including atherosclerosis. As S1P levels are tightly controlled by S1P lyase, we investigated the impact of hematopoietic S1P lyase (Sgpl1(-/-)) deficiency on leukocyte subsets relevant to atherosclerosis.

METHODS AND RESULTS

LDL receptor deficient mice that were transplanted with Sgpl1(-/-) bone marrow showed disrupted S1P gradients translating into lymphopenia and abrogated lymphocyte mitogenic and cytokine response as compared to controls. Remarkably however, Sgpl1(-/-) chimeras displayed mild monocytosis, due to impeded stromal retention and myelopoiesis, and plasma cytokine and macrophage expression patterns, that were largely compatible with classical macrophage activation. Collectively these two phenotypic features of Sgpl1 deficiency culminated in diminished atherogenic response.

CONCLUSIONS

Here we not only firmly establish the critical role of hematopoietic S1P lyase in controlling S1P levels and T cell trafficking in blood and lymphoid tissue, but also identify leukocyte Sgpl1 as critical factor in monocyte macrophage differentiation and function. Its, partly counterbalancing, pro- and anti-inflammatory activity spectrum imply that intervention in S1P lyase function in inflammatory disorders such as atherosclerosis should be considered with caution.

Sphingosine kinase inhibition exerts both pro- and anti-atherogenic effects in low-density lipoprotein receptor-deficient (LDL-R(-/-)) mice

Sphingosine 1-phosphate (S1P), a lysosphingolipid associated with high-density lipoprotein (HDL), contributes to the anti-atherogenic potential attributed to this lipoprotein. This study examined whether a reduction of S1P plasma levels affects atherosclerosis in a murine model of disease. LDL-R(-/-)mice on Western diet were given ABC294640, an inhibitor of sphingosine kinase (SphK) for 16 weeks. ABC294640 decreased plasma S1P by approximately 30%. However, ABC294640 failed to affect atherosclerotic lesion formation. Plasma triglycerides were reduced whereas total and HDL-cholesterol remained unchanged in course of ABC294640 treatment. ABC294640 increased plasma interleukin (IL)-12p70 and RANTES concentration as well as IL-12p70, RANTES and interferon (IFN)-γ production by peritoneal cells and this was paralleled by enhanced activity of peritoneal and spleen dendritic cells as evidenced by up-regulation of CD86 and MHC-II on CD11c(+) cells. As a consequence, increased T-cell activation was noted in ABC294640-treated mice as indicated by enhanced CD4(+) splenocyte proliferation, IFN-γ and IL-2 production, and CD69 expression. Concomitantly, however, ABC294640 treatment redistributed CD4(+) and CD8(+) cells from blood to lymphatic organs and reduced T-cell number within atherosclerotic lesions. In addition, plasma sVCAM-1, sICAM-1, and MCP-1 levels as well as in vivo leukocyte adhesion and CCL19-induced T-cell penetration into peritoneum were lower in ABC294640-treated animals. In vitro experiments demonstrated reduced VCAM-1 and ICAM-1 expression and lymphocyte adhesion to endothelial cells exposed to ABC294640. In conclusion, treatment with SphK inhibitor leads to both pro- and anti-atherogenic effects in LDL-R(-/-) mice. As a consequence, SphK inhibition fails to affect atherosclerosis despite significant S1P reduction in plasma.

Lipids as targets for novel anti-inflammatory therapies

Lipids serve important functions as membrane constituents and also as energy storing molecules. Besides these functions certain lipid species have now been recognized as signalling molecules that regulate a multitude of cellular responses including cell growth and death, and also inflammatory reactions. Bioactive lipids are generated by hydrolysis from membrane lipids mainly by phospholipases giving rise to fatty acids and lysophospholipids that either directly exert their function or are further converted to active mediators. This review will summarize the present knowledge about bioactive lipids that either promote or attenuate inflammatory reactions. These lipids include polyunsaturated fatty acids (PUFA), eicosanoids including the epoxyeicosatrienoic acids (EET), peroxisome proliferation activating receptor (PPAR) activators, cannabinoids and the sphingolipids ceramide, sphingosine 1-phosphate and sphingosylphosphorylcholine.

Ascomycete derivative to MS therapeutic: S1P receptor modulator FTY720

Fingolimod (FTY720) represents the first in a new class of immune-modulators whose target is sphingosine-1-phosphate (S1P) receptors. It was first identified by researchers at Kyoto University and Yoshitomi Pharmaceutical as a chemical derivative of the ascomycete metabolite ISP-1 (myriocin). Unlike its natural product parent, FTY720 does not interfere with sphingolipid biosynthesis. Instead, its best characterized mechanism of action upon in vivo phosphorylation, leading to the active principle FTY720-P, is the rapid and reversible inhibition of lymphocyte egress from peripheral lymph nodes. As a consequence of S1P1 receptor internalization, tissue-damaging T-cells can not recirculate and infiltrate sites of inflammation such as the central nervous system (CNS). Furthermore, FTY720-P modulation of S1P receptor signaling also enhances endothelial barrier function. Due to its mode of action, FTY720 effectively prevents transplant rejection and is active in various autoimmune disease models. The most striking efficacy is in the multiple sclerosis (MS) model of experimental autoimmune encephalomyelitis, which has now been confirmed in the clinic. FTY720 demonstrated promising results in Phase II trials and recently entered Phase III in patients with relapsing MS. Emerging evidence suggests that its efficacy in the CNS extends beyond immunomodulation to encompass other aspects of MS pathophysiology, including an influence on the blood-brain-barrier and glial repair mechanisms that could ultimately contribute to restoration of nerve function. FTY720 may represent a potent new therapeutic modality in MS, combined with the benefit of oral administration.

Novel therapeutic targets in viral myocarditis

Viral myocarditis is an elusive infection of the heart that is currently without an effective or definitive treatment. Viral myocarditis has a complex disease progression that can be divided into early, middle and late phases. Direct cytopathic injury, apoptosis, activation of the innate and adaptive immune system and cardiac remodeling have all been implicated in the pathogenesis of viral myocarditis. Novel treatment approaches are evolving at a rapid pace. The purpose of this review is to provide an update on current research focused on identifying potential treatment options for viral myocarditis.

[FTY720 (Fingolimod) as a new therapeutic option for multiple sclerosis]

All currently available therapeutic options for multiple sclerosis have to be administered parenterally. Several oral substances are currently in the late clinical development stage. One of them, FTY720 (also known as fingolimod) is highlighted in this review. The biological effects of FTY720 are presented as well as animal data and first clinical data from a phase II trial in multiple sclerosis patients. The effects of FTY720 are based on an innovative approach and apparently target several key elements in the pathogenesis of multiple sclerosis. The first clinical data with FTY720 show very promising results, with a relapse reduction of over 50% compared to placebo and an acceptable safety profile. These results currently await confirmation in two international phase III studies which are recruiting patients worldwide.

Sphingosine 1-phosphate receptors in health and disease: mechanistic insights from gene deletion studies and reverse pharmacology

Sphingosine 1-phosphate (S1P) is a bioactive sphingolipid that is critically involved in the embryonic development of the cardiovascular and central nervous systems. In the adult, S1P can produce cytoskeletal re-arrangements in many cell types to regulate immune cell trafficking, vascular homeostasis and cell communication in the central nervous system. S1P is contained in body fluids and tissues at different concentrations, and excessive production of the pleiotropic mediator at inflammatory sites may participate in various pathological conditions. Gene deletion studies and reverse pharmacology (techniques aiming to identify both ligands and function of receptors) provided evidence that many effects of S1P are mediated via five G-protein-coupled S1P receptor subtypes, and novel therapeutic strategies based on interaction with these receptors are being initiated. The prototype S1P receptor modulator, FTY720 (fingolimod), targets four of the five S1P receptor subtypes and may act at several levels to modulate lymphocyte trafficking via lymphocytic and endothelial S1P1 and, perhaps, other inflammatory processes through additional S1P receptor subtypes. A recently completed Phase II clinical trial suggested that the drug may provide an effective treatment of relapsing-remitting multiple sclerosis. FTY720 is currently being evaluated in larger-scale, longer-term, Phase III studies. This review provides an overview on S1P activities and S1P receptor function in health and disease, and summarizes the clinical experience with FTY720 in transplantation and multiple sclerosis.

FTY720, a Synthetic Sphingosine 1 Phosphate Analogue, Inhibits Development of Atherosclerosis in Low-Density Lipoprotein Receptor–Deficient Mice

BACKGROUND

Numerous in vitro studies suggest that sphingosine 1-phosphate (S1P), a bioactive lysosphingolipid associated with high-density lipoproteins, accounts at least partly for the potent antiinflammatory properties of high-density lipoprotein and, thereby, contributes to the antiatherogenic potential attributed to high-density lipoproteins. The present study was undertaken to investigate whether modulation of S1P signaling would affect atherosclerosis in a murine model of disease.

METHODS AND RESULTS

Low-density lipoprotein receptor-deficient mice on a cholesterol-rich diet were given FTY720, a synthetic S1P analogue, at low (0.04 mg/kg per day) or high (0.4 mg/kg per day) doses for 16 weeks. FTY720 dose-dependently reduced atherosclerotic lesion formation, both in the aortic root and brachiocephalic artery, and almost completely blunted necrotic core formation. Plasma lipids remained unchanged during the course of FTY720 treatment. However, FTY720 lowered blood lymphocyte count (at a high dose) and significantly interfered with lymphocyte function, as evidenced by reduced splenocyte proliferation and interferon-gamma levels in plasma. Plasma concentrations of proinflammatory cytokines such as tumor necrosis factor-alpha, interleukin (IL)-6, IL-12, and regulated on activation normal T cell expressed and secreted were reduced by FTY720 administration. Moreover, lipopolysaccharide-elicited generation of nitrite/nitrate and IL-6--two markers of classical (M1) macrophage activation--was inhibited, whereas IL-4-induced production of IL-1-receptor antagonist, a marker of alternative (M2) macrophage activation, was augmented in peritoneal macrophages from FTY720-treated low-density lipoprotein receptor-deficient mice.

CONCLUSIONS

The present results demonstrate that an S1P analogue inhibits atherosclerosis by modulating lymphocyte and macrophage function, and these results are consistent with the notion that S1P contributes to the antiatherogenic potential of high-density lipoprotein.

Coxsackievirus-induced myocarditis: new trends in treatment

Myocarditis is a common inflammatory heart disease in children and young adults that may result in chronically dilated cardiomyopathy. Coxsackievirus B3 is the major etiologic agent of this disease. Current treatments for patients with viral myocarditis are almost entirely supportive. In recent years, some promising therapeutic candidates have emerged, including novel treatments and improvements of existing drugs. Among these are molecules that specially target virus entry, such as pleconaril, WIN 54954 and CAR-Fc; nucleic acid-based antiviral agents that inhibit viral translation and/or transcription, such as antisense oligodeoxynucleotide and short interfering RNA; and immunomodulatory agents that augment the host-protective immune responses to effectively clear viruses from target tissues, including interferons and immunoglobulins. In addition, certain new antiviral strategies, still in the early stages, include modulation of signal transduction pathways responsible for viral replication using enzyme inhibitors, which have revealed potential therapeutic targets for viral myocarditis. Finally, the progress in cellular cardiomyoplasty for end-stage therapy, in particular the preliminary clinical trials, is also discussed with respect to its potential future application.

FTY720 suppresses CD4+CD44highCD62L- effector memory T cell-mediated colitis

FTY720, a sphingosine-derived immunomodulator, causes immunosuppression via enhancement of lymphocyte sequestration into secondary lymphoid organs, thereby preventing their antigen-activated T cell egress to sites of inflammation. FTY720 is highly effective in inhibiting autoimmunity in various animal models. However, there is little known about how FTY720 controls the migration property of memory T cells. Here, we demonstrated that FTY720 prevents the development of colitis induced by the adoptive transfer of lamina propria (LP) colitogenic effector memory CD4+ T cells (TEM cells; CD45RB(low)CD44(high)CD62L-) into severe combined immunodeficiency (SCID) mice and suppresses interferon-gamma, interleukin-2, and tumor necrosis factor-alpha production by LP CD4+ T cells. The numbers of spleen, peripheral blood, mesenteric lymph node, and LP CD4+ T cells in FTY720-treated mice were significantly reduced compared with those in control mice. Notably, LP CD4+ TEM cells as well as splenic CD4+CD45RBhigh T cells expressed several spingosine-1-phosphate receptors that are targets for FTY720. Furthermore, FTY720 also prevented the development of colitis induced by the adoptive transfer of splenic CD4+CD45RBhigh T cells into SCID mice. Collectively, the present data indicate that FTY720 treatment may offer the potential not only to prevent the onset of disease but also to treat memory T cell-mediated autoimmune diseases including inflammatory bowel diseases.

Activated nuclear transcription factor kappaB in patients with myocarditis and dilated cardiomyopathy--relation to inflammation and cardiac function

OBJECTIVES AND BACKGROUND

Myocarditis is caused by various agents and autoimmune processes. It is unknown whether viral genome persistence represents inactive remnants of previous infections or whether it is attributed to ongoing adverse processes. The latter also applies to the course of autoimmune myocarditis. One principal candidate for an adverse remodeling is nuclear factor-kappaB (NFkappaB).

METHODS

A total of 93 patients with suspected myocarditis/cardiomyopathy was examined. Hemodynamics were assessed by echocardiography as well as right and left heart catheterization. Endomyocardial biopsies were taken from the left ventricle. Biopsies were examined by immunohistochemistry and PCR for viral genomes. Selective immunostaining of activated NFkappaB was performed.

RESULTS

NFkappaB was increased in patients with myocarditis when compared with controls (11.1+/-7.1% vs. 5.0+/-5.3%, P<0.005) whereas dilated cardiomyopathy showed no significant increase. Patients with myocarditis and preserved left ventricular function exhibited increased activated NFkappaB when compared with reduced function (r2=0.72, P<0.001). In parallel, inverse correlation of NFkappaB and left ventricular enddiasstolic volume was found (r2=0.43, P<0.02). Increased activated NFkappaB was found in adenovirus persistence when compared with controls (P=0.001). Only a trend of increased NFkappaB activation was seen in cytomegalovirus persistence. Parvovirus B19 persistence did not affect NFkappaB activation.

CONCLUSIONS

Increased activation of NFkappaB is related to inflammatory processes in myocarditis. Since activated NFkappaB correlates with left ventricular function, it could be assumed that NFkappaB activation occurs at early stages of inflammation. Potentially, NFkappaB could inhibit loss of cardiomyocytes by apoptosis and protect from cardiac dilation. Since NFkappaB is a crucial key transcription factor of inflammation, its prognostic and future therapeutic relevance should be addressed.

Emerging treatments for viral myocarditis

Although viral myocarditis has been mostly attributed to enterovirus and adenovirus infection, the importance of hepatitis C virus has recently been noted. Clinical trials of antiviral agents, such as interferons, are in progress, while new therapies such as viral vaccines, recombinant virus and virus receptors, are in preclinical development. Whereas immunosuppression with corticosteroids or cyclosporin is ineffective, immunosuppressors that do not promote viral replication, such as FTY720, and immunomodulation by interleukin-10, are promising new approaches. Inhibition of nuclear factor-κB, angiotensin II and endothelin effectively suppresses inflammation in experimental viral myocarditis. Embryonic stem cell therapy has been demonstrated to be beneficial; however, this requires further investigation.

Synthesis, stereochemical determination and biochemical characterization of the enantiomeric phosphate esters of the novel immunosuppressive agent FTY720

The novel immunosuppressive agent FTY720 (1) is phosphorylated in vivo in a variety of species yielding an active metabolite that is an agonist of four of the five known G-protein-coupled sphingosine-1-phosphate (S1P) receptors. A synthesis amenable to producing gram quantities of the stereoisomeric phosphate esters, a determination of their absolute stereochemistry via an enantioselective synthesis and their characterization as S1P receptor agonists and antagonists is reported.

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.

FTY720: from bench to bedside

FTY720, a synthetic myriocin analogue derived from culture filtrates of Isaria sinclairii, is a novel immunosuppressant that in experimental animals and nonhuman primates produces lymphocytopenia and prolongs allograft survival in dose-dependent fashion. FTY720 exerts synergistic interactions not only with calcineurin antagonists, but also with proliferation signal inhibitors. These interactions offer the possibility of reducing exposure to and mitigating toxicity of existing drugs. The mechanism of drug action is not entirely clear. FTY720 appears to undergo phosphorylation by sphingosine phosphokinase 2, rendering it capable of interacting with the specific G protein-linked receptors for its structural homologue-sphingosine-1-phosphate. However, it is not clear how this interaction leads to emigration of lymphocytes from the peripheral blood and sequestration in secondary lymphoid structures. Present theories suggest that the drug prevents emigration rather than directing the onset of sequestration. Thus, the drug is the archetype of a new class of agents that alter lymphocyte homing patterns: the adhesion-migration paradigm. These modalities reduce interstitial infiltration of grafts and attenuate their release from lymph nodes. Since FTY720 seems to spare nonspecific elements of host resistance, it may not only represent a useful addition to the immunosuppressive armamentarium but also address the not infrequent complications of infections associated with existing therapies.

FTY720: sphingosine 1-phosphate receptor-1 in the control of lymphocyte egress and endothelial barrier function

The novel immunomodulator FTY720 is effective in experimental models of transplantation and autoimmunity, and is currently undergoing Phase III clinical trials for prevention of kidney graft rejection. In contrast to conventional immunosuppressants, FTY720 does not impair T- and B-cell activation, proliferation and effector function, but interferes with cell traffic between lymphoid organs and blood. The molecular basis for the mode of action of the drug has only recently been established. FTY720, after phosphorylation, acts as a high-affinity agonist at the G protein-coupled sphingosine 1-phosphate receptor-1 (S1P(1)) on thymocytes and lymphocytes, thereby inducing aberrant internalization of the receptor. This renders the cells unresponsive to the serum lipid sphingosine 1-phosphate (S1P), depriving them from an obligatory signal to egress from lymphoid organs. As a consequence, lymphocytes are unable to recirculate to peripheral inflammatory tissues and graft sites but remain functional in the lymphoid compartment. In addition to the effects on lymphocyte recirculation, the drug acts on endothelial cells and preserves vascular integrity by enhancing adherens junction assembly and endothelial barrier function. The available data establish S1P(1) as a key target for FTY720, and further point to therapeutically relevant effects of the drug on lymphocytes and vascular endothelium.

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.

FTY720: A new kid on the block for transplant immunosuppression

FTY720, a synthetic analogue of myriocin (ISP-1), is derived from culture filtrates of the fungus Isaria sinclairii. As a sphingosine analogue, FTY720 appears to undergo phosphorylation and thereby interact with specific G-protein-linked receptors. In vivo, FTY720 causes emigration of lymphocytes from peripheral blood to secondary lymphoid structures. Thus, the drug is the archetype of a new class of agents that alter cellular homing patterns: the adhesion-migration paradigm. Since FTY720 seems to spare nonspecific elements of host resistance, it may address the not infrequent complications of infections associated with existing therapies. In experimental rodent, canine and non-human primate models, FTY720 produces lymphopenia and immunosuppression, prolonging the survival of allografts. Because of synergistic interactions, it promotes the immunosuppressive effects not only of calcineurin antagonists, but also of proliferation signal inhibitors. These interactions proffer the possibility of large reductions in exposure to and mitigated toxicity of existing drugs. In humans, FTY720 causes dose-dependent peripheral blood lymphopenia, a reduced incidence of acute rejection episodes and only one apparent adverse reaction - a negative chronotropic effect - particularly after the loading dose. While the clinical utility of FTY720 is difficult to predict before completion of Phase III studies that elucidate its benefits versus unanticipated side effects, the initial data suggest several potential advantages: it does not produce hyperlipidaemia, diabetes mellitus, nephrotoxicity, neurotoxicity or myelosuppression, which are characteristic of other immunosuppressants. Furthermore, it displays high oral bioavailability and a low interindividual coefficient of variation. Clearly, structural analogues, as well as other agents that alter the balance of chemokines or affect cellular adhesion to activated endothelium, will represent important components of future regimens.

Antiinflammatory therapy in myocarditis

Acute viral myocarditis progresses through several stages, including acute viral infection, autoimmunity, and dilated cardiomyopathy. Recent studies have identified an important role for the myocardial inflammatory response during the initial phases of acute viral myocarditis. In this review, we discuss new insights into the innate host response to viral myocarditis and the various therapeutic strategies that have been attempted in managing the deleterious consequences of the myocardial inflammatory response in acute viral myocarditis.

FTY720: targeting G-protein-coupled receptors for sphingosine 1-phosphate in transplantation and autoimmunity

The novel immunomodulator FTY720 is remarkably effective in models of transplantation and autoimmunity. Recent data show that phosphorylated FTY720 is an agonist at four sphingosine 1-phosphate receptors. Stimulation of sphingosine 1-phosphate receptors leads to sequestration of lymphocytes in secondary lymphatic tissues and thus away from inflammatory lesions and graft sites.

The immune modulator FTY720 targets sphingosine 1-phosphate receptors

Immunosuppressant drugs such as cyclosporin have allowed widespread organ transplantation, but their utility remains limited by toxicities, and they are ineffective in chronic management of autoimmune diseases such as multiple sclerosis. In contrast, the immune modulating drug FTY720 is efficacious in a variety of transplant and autoimmune models without inducing a generalized immunosuppressed state and is effective in human kidney transplantation. FTY720 elicits a lymphopenia resulting from a reversible redistribution of lymphocytes from circulation to secondary lymphoid tissues by unknown mechanisms. Using FTY720 and several analogs, we show now that FTY720 is phosphorylated by sphingosine kinase; the phosphorylated compound is a potent agonist at four sphingosine 1-phosphate receptors and represents the therapeutic principle in a rodent model of multiple sclerosis. Our results suggest that FTY720, after phosphorylation, acts through sphingosine 1-phosphate signaling pathways to modulate chemotactic responses and lymphocyte trafficking.