Fungal metabolites. Part 11. A potent immunosuppressive activity found in Isaria sinclairii metabolite

KRP-203, a novel synthetic immunosuppressant, prolongs graft survival and attenuates chronic rejection in rat skin and heart allografts

BACKGROUND

A novel immunomodulator, KRP-203, the molecular structure of which has some similarity to FTY720, has been developed for use in organ transplantation. The present study was designed to investigate the potency and safety of KRP-203 on allograft survival against both acute and chronic rejection in rat skin and heart transplantation.

METHODS AND RESULTS

KRP-203 significantly prolonged skin or heart allograft survival of a minor histocompatibility complex (mHC)-disparate (LEW to F344) rat combination. Histopathological and immunohistochemical analysis at 100 days after mHC-disparate rat heart transplantation revealed that KRP-203 treatment significantly inhibited infiltration of inflammatory cells, including macrophages and T cells; expression of endothelin-1 and transforming growth factor-beta1; and IgG deposition and eventually attenuated neointimal formation and myocardial fibrosis. KRP-203 also prolonged heart allograft survival in a major histocompatibility complex (MHC)-incompatible (DA to LEW) rat combination, but the efficacy was not as significant. However, KRP-203 combined with a subtherapeutic dose of cyclosporin A synergistically prolonged the heart allograft survival. Flow cytometric analysis demonstrated that KRP-203 reduced the number of peripheral blood mononuclear cells (lymphocytes and monocytes) but not granulocytes and enhanced lymphocyte homing into peripheral lymph nodes. The influence of KRP-203 on heart rate changes in Hartley guinea pigs was examined. KRP-203 had less of a tendency to cause bradycardia than FTY720.

CONCLUSIONS

These findings demonstrated that KRP-203 prolonged skin and heart allograft survival and significantly attenuated chronic rejection and bradycardia as an adverse effect. Therefore, KRP-203 offers considerable potential as a novel therapeutic immunosuppressant in patients with organ transplantation.

FTY720, a fungus metabolite, inhibitsin vivo growth of androgen-independent prostate cancer

FTY720, a derivative of fungus, has demonstrated dramatic anticancer effect in several malignancies recently. Our study evaluates the therapeutic potential of FTY720 in the treatment of androgen-independent prostate cancer using a human prostate cancer xenograft in nude mice. CWR22R, an androgen-independent human prostate tumor xenograft was inoculated into castrated nude mice and the animals were administrated with either normal saline or FTY720 (10 mg/kg) through intraperitoneal (i.p.) injection for 20 days. Body weight and tumor volume were recorded every 2 days, and serum prostate specific antigen (PSA) levels were also measured before and after the treatment. The effect of FTY720 on tumor cell proliferation was examined using antibodies against PCNA and Ki-67 by immunohistochemical staining, MTT assay and colony forming assay, whereas apoptotic effect of FTY720 was evaluated by TUNEL assay and immunostaining using antibodies against cleaved caspase 3 and Bcl-2. In addition, the potential inhibitory effect of FTY720 on prostate cancer angiogenesis and metastasis was investigated by immunostaining of CD31, VEGF, E-cadherin and beta-catenin. Our results showed that FTY720 treatment led to suppression of CWR22R tumor growth without causing any detectable side effects in nude mice. The FTY720-induced tumor suppression was correlated with decreased serum PSA level as well as reduced proliferation rate, suppression of angiogenic factors, and restoration of E-cadherin and beta-catenin expression. In addition, the FTY720-treated tumors showed increased apoptosis rate demonstrated by increased TUNEL- and cleaved caspase 3-positive cells, and decreased Bcl-2 expression. Our results suggest a potential novel agent in the suppression of androgen-independent prostate cancer.

A Novel Immunomodulator, FTY720, Prevents Development of Experimental Autoimmune Myasthenia Gravis in C57BL/6 Mice

Prophylactic oral administration of a novel immunomodulator (immunosuppressant), FTY720 (1 mg/kg, three times a week), completely prevented the development of experimental autoimmune myasthenia gravis (EAMG) in C57BL/6 mice. EAMG has been used as an animal model for human myasthenia gravis, and was established by immunizing the mice with acetylcholine receptor (AChR) from Torpedo californica. FTY720 also suppressed the production of both anti-Torpedo californica AChR antibody and anti-mouse AChR autoantibody by the mice, which were observed in mice in which EAMG had become established. These results strongly suggest that FTY720 is a promising candidate for treatment of human myasthenia gravis.

Total Synthesis and Biological Activities of (+)-Sulfamisterin (AB5366) and its Analogues

The first total synthesis of (+)-sulfamisterin (AB5366), a naturally occurring alpha-substituted alpha-amino acid derivative possessing a sulfonated hydroxy function, is described. Overman rearrangement of an allylic trichloroacetimidate derived from D-tartrate effectively generated the tetrasubstituted carbon containing a nitrogen substituent. Construction of the amino acid moiety and sulfonation of the hydroxy group, followed by deprotection completed the total synthesis, which fully confirmed the proposed absolute structure of the natural product. The possible stereoisomers of (+)-sulfamisterin and their desulfonated derivatives were also synthesized. Biological assessment of all synthetic compounds revealed that natural (+)-sulfamisterin and its 3-epimer as well as their desulfonated derivatives possessing 2S-configuration strongly inhibit the serine palmitoyl transferase both in vitro and in vivo, whereas compounds with 2R-configuration were found to show much weaker inhibitory activity.

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.

Effect of myriocin on plasma sphingolipid metabolism and atherosclerosis in apoE-deficient mice

Sphingolipids play a very important role in cell membrane formation, signal transduction, and plasma lipoprotein metabolism, all of which may well have an impact on the development of atherosclerosis. To investigate the relationship between sphingolipid metabolism and atherosclerosis, we utilized myriocin to inhibit mouse serine palmitoyl-CoA transferase (SPT), the key enzyme for sphingolipid biosynthesis. We injected 8-week-old apoE-deficient mice with myriocin (0.3 mg/kg/every other day, intraperitoneal) for 60 days. On a chow diet, myriocin treatment caused a significant decrease (50%) in liver SPT activity (p < 0.001), significant decreases in plasma sphingomyelin, ceramide, and sphingosine-1-phosphate levels (54, 32, and 73%, respectively) (p < 0.0001), and a significant increase in plasma phosphatidylcholine levels (91%) (p < 0.0001). Plasma total cholesterol and triglyceride levels demonstrated no significant changes, but there was a significant decrease in atherosclerotic lesion area (42% in root and 36% in en face assays) (p < 0.01). On a high fat diet, myriocin treatment caused marked decreases in plasma sphingomyelin, ceramide, and sphingosine-1-phosphate levels (59, 66, and 81%, respectively) (p < 0.0001), and a marked increase in plasma phosphatidylcholine levels (100%) (p < 0.0001). Total cholesterol and triglyceride demonstrated no significant changes, but there was a significant decrease in atherosclerotic lesion area (39% in root and 37% in en face assays) (p < 0.01). These results indicate that, apart from cholesterol levels, sphingolipids have an effect on atherosclerotic development and that SPT has proatherogenic properties. Thus, inhibition of SPT activity could be an alternative treatment for atherosclerosis.

Inhibition of sphingomyelin synthesis reduces atherogenesis in apolipoprotein E-knockout mice

BACKGROUND

In clinical studies, sphingomyelin (SM) plasma levels correlated with the occurrence of coronary heart disease independently of plasma cholesterol levels. We hypothesized that inhibition of SM synthesis would have antiatherogenic effects. To test this hypothesis, apolipoprotein E (apoE)-knockout (KO) mice were treated with myriocin, a potent inhibitor of serine palmitoyltransferase, the rate-limiting enzyme in SM biosynthesis.

METHODS AND RESULTS

Diet-admix treatment of apoE-KO mice with myriocin in Western diet for 12 weeks lowered SM and sphinganine plasma levels. Decreases in sphinganine and SM concentrations were also observed in the liver and aorta of myriocin-treated animals compared with controls. Inhibition of de novo sphingolipid biosynthesis reduced total cholesterol and triglyceride plasma levels. Cholesterol distribution in lipoproteins demonstrated a decrease in beta-VLDL and LDL cholesterol and an increase in HDL cholesterol. Oil red O staining of total aortas demonstrated reduction of atherosclerotic lesion coverage in the myriocin-treated group. Atherosclerotic plaque area was also reduced in the aortic root and brachiocephalic artery.

CONCLUSIONS

Inhibition of de novo SM biosynthesis in apoE-KO mice lowers plasma cholesterol and triglyceride levels, raises HDL cholesterol, and prevents development of atherosclerotic lesions.

SLI1 (YGR212W) is a major gene conferring resistance to the sphingolipid biosynthesis inhibitor ISP-1, and encodes an ISP-1 N-acetyltransferase in yeast

ISP-1 (myriocin) is a potent inhibitor of serine palmitoyltransferase, the primary enzyme of sphingolipid biosynthesis, and is a useful tool for studying the biological functions of sphingolipids in both mammals and yeast (Saccharomyces cerevisiae). In a previous study, we cloned yeast multicopy suppressor genes for ISP-1, and one of these, YPK1/SLI2, was shown to encode a serine/threonine kinase which is a yeast homologue of mammalian SGK1 (serum/glucocorticoid-regulated kinase 1). In the present study, another gene, termed SLI1 (YGR212W; GenBank accession number CAA97239.1), was characterized. Sli1p has weak similarity to Atf1p and Atf2p, which are alcohol acetyltransferases. Although a sli1-null strain grew normally, the IC50 of ISP-1 for the growth of this strain was markedly decreased compared with that for the parental strain, indicating that Sli1p is a major contributor to ISP-1 resistance in yeast. On a sli1-null background, the increase in resistance to ISP-1 induced by YPK1 gene transfection was almost abolished. These data indicate that Sli1p co-operates with Ypk1p in mediating resistance to ISP-1 in yeast. Sli1p was found to convert ISP-1 into N-acetyl-ISP-1 in vitro. Furthermore, N-acetyl-ISP-1 did not share the ability of ISP-1 to inhibit the growth of yeast cells, and the serine palmitoyltransferase inhibitory activity of N-acetyl-ISP-1 was much lower than that of ISP-1. These data suggest that Sli1p inactivates ISP-1 due to its N-acetyltransferase activity towards ISP-1.

Rejection following donor or recipient preoperative treatment with FTY720 in rat small bowel transplantation

BACKGROUND

Severe rejection of small bowel transplantation (SBTx) has been ascribed to abundant lymphoid tissues in the small intestine without well-established evidence. However, the role of donor lymphocytes in rejection is still unclear. The novel immunosuppressant, FTY720, is reported to transfer peripheral blood lymphocytes (PBLs) to lymphoid tissues such as mesenteric lymph nodes (MLNs) and Peyer patches (PP). In the present study, the number of donor lymphocytes in the graft was increased by FTY720, and the influence on rejection was studied in a rat model. Furthermore, the number of the PBL of recipient was decreased by FTY720 before SBTx and the effect on rejection was examined.

MATERIALS AND METHODS

Orthotopic total SBTx was performed in Brown-Norway and Lewis rats. In the donor pretreatment study, FTY720 was administrated to donor rats 24 h prior to harvesting to increase the number of graft lymphocytes (FTY donor-pretreated group). In contrast, MLNs were surgically removed from the grafts to decrease the number of graft lymphocytes (MLN-resected group). In the recipient pretreatment study, FTY720 was administrated to recipient rats 24 h before SBTx to decrease recipient PBL (FTY group). In contrast, a subclinical dose of cyclosporine A (CsA) was administrated after SBTx (CsA group). Rats were administrated preoperative FTY720 combined with post-SBTx CsA (FTY+CsA group). Graft survival, pathology, lymphocyte count, and subtype were examined.

RESULTS

In the donor pretreatment study, pretreatment with FTY720 did not enhance graft rejection. MLN resection did not prolong graft survival. In the recipient pretreatment study, FTY720 caused a significant reduction in the number of infiltrating lymphocytes in the graft, as well as the percentage of recipient CD4+ and CD25+ cells within the graft. FTY720 and CsA synergistically prolonged graft survival.

CONCLUSION

SBTx rejection correlated with the number of recipient PBL, and not with the number of donor lymphocytes transplanted together with the graft. The pretreatment of the recipient with FTY720 was effective in the case of combined use of the low-dose postoperative CsA.

Asymmetric allylic alkylation, an enabling methodology

The diversity of mechanisms for enantiodiscrimination and of bond types that can be formed make Pd-catalyzed asymmetric allylic alkylation a powerful key step for simplification of synthetic strategy to complex molecular targets. Using a wide range of different classes of compounds including alkaloids, polyhydrofurans, nucleosides and carbanucleosides, cyclohexitols and cyclopentitols, chromanes, cyclopentanoids, amino acids, barbiturates, etc., novel synthetic strategies emerge that provide short efficient asymmetric syntheses.

Iron-catalyzed cross-coupling reactions. A scalable synthesis of the immunosuppressive agent FTY720

A chemo- and regioselective cross-coupling reaction of the functionalized aryl triflate 5 with octylmagnesium bromide catalyzed by cheap, nontoxic, and environmentally benign Fe(acac)(3) sets the basis for a practical and scaleable synthesis of the octylbenzene derivative 6, which serves as a key building block for the preparation of FTY720 (1). This 2-amino-1,3-propanediol derivative shows highly promising immunosuppressive properties and is currently in human clinical phase III trials.

Disruption of sphingolipid homeostasis by myriocin, a mycotoxin, reduces thymic and splenic T-lymphocyte populations

Myriocin is a naturally occurring fungal metabolite possessing potent immunosuppressive properties. The biochemical mechanism of action of this compound is inhibition of serine palmitoyltransferase (SPT), the key rate limiting enzyme in sphingolipid biosynthesis, intermediates of which are important mediators of immune signaling. Previous studies have shown that myriocin strongly suppressed immune function with T-lymphocyte functions being most sensitive. To further our understanding of the mechanisms of this effect, we investigated the impact of subacute treatment with myriocin on lymphocyte populations in the thymus and spleen of male BALB/c mice following intraperitoneal injection of myriocin at 0, 0.1, 0.3, and 1.0 mg/kg daily for 5 consecutive days. Cellular analysis of the thymus demonstrated that total cellularity was dose-dependently reduced and the reduction was significant in mice treated with 1.0 mg/kg myriocin. Phenotyping showed that CD4+ and CD4+/CD8+ double positive lymphocyte populations were sensitive to myriocin. No change in total cellularity of the spleen was noted but there was a significant reduction in the CD4+ lymphocyte population in mice treated with 1.0 mg/kg myriocin. There was a strong positive correlation between total CD4+ lymphocytes in the thymus and those in the spleen. Analysis of sphingolipid levels showed a dose-dependent reduction of sphinganine in the thymus, which were positively correlated with all reductions in lymphocyte populations. These results suggest that the immunosuppressive properties of myriocin may be due to diminished T-lymphocyte populations likely related to inhibition of SPT and disruption of sphingolipid homeostasis.

FTY720 prolongs clear corneal allograft survival with a differential effect on different lymphocyte populations

BACKGROUND

FTY720 is a potent immunomodulator with unique effects on lymphocyte homing and has recently proved to be safe and effective in renal transplantation in man. The authors investigated the potency of FTY720 in inhibiting allograft rejection in the rat model of orthotopic allogeneic penetrating keratoplasty.

METHODS

Penetrating keratoplasties were performed using Fisher rats as donors and Lewis rats as recipients or donors: group 1 (n = 10), allogeneic control; group 2 (n = 10), Lewis/Lewis syngeneic control; group 3 (n = 9), mycophenolate mofetile (MMF) 40 mg/kg; group 4 (n = 10), FTY720 1.2 mg/kg; group 5 (n = 8), FTY720 0.3 mg/kg. Four animals from each group were sacrificed for immunohistological evaluation on day 14. Medication in the therapy groups was given for 18 days.

RESULTS

The mean (SD) rejection free graft survival time was 11.3 (0.8) days for the allogeneic control (group 1), 24.6 (2.5) days for group 3 (MMF), 44.5 (5.7) days for group 4 (FTY720 1.2 mg/kg), and 35.3 (5.7) days for group 5 (FTY720 0.3 mg/kg) (p<0.05). The allogeneic control showed a dense infiltration with CD4+, CD8+, CD161+ (NK-cells), CD25+ (IL2 receptor), and macrophages. In the therapy groups the density of infiltrating CD4+, CD8+, CD161+ (NK-cells), and CD25+ (IL2 receptor) cells was notably reduced compared with the allogeneic control (p<0.05). In group 5 however, the reduction of infiltration by CD4+ cells was higher than the reduction of infiltration by CD8+ (p<0.05) and CD161+ (NK) cells.

DISCUSSION

Oral immunosuppression with FTY720 significantly prolongs corneal allograft survival in this transplant model. The results suggest that FTY720 has a different effect on certain lymphocyte populations. CD4+ cells seem to be more affected than CD8+ cells and NK-cells.

The sphingosine 1-phosphate receptor agonist FTY720 supports CXCR4-dependent migration and bone marrow homing of human CD34+ progenitor cells

The novel immunosuppressant FTY720 activates sphingosine 1-phosphate receptors (S1PRs) that affect responsiveness of lymphocytes to chemokines such as stromal cell-derived factor 1 (SDF-1), resulting in increased lymphocyte homing to secondary lymphoid organs. Since SDF-1 and its receptor CXCR4 are also involved in bone marrow (BM) homing of hematopoietic stem and progenitor cells (HPCs), we analyzed expression of S1PRs and the influence of FTY720 on SDF-1/CXCR4-mediated effects in human HPCs. By reverse transcriptase-polymerase chain reaction (RT-PCR), S1PRs were expressed in mobilized CD34+ HPCs, particularly in primitive CD34+/CD38- cells. Incubation of HPCs with FTY720 resulted in prolonged SDF-1-induced calcium mobilization and actin polymerization, and substantially increased SDF-1-dependent in vitro transendothelial migration, without affecting VLA-4, VLA-5, and CXCR4 expression. In nonobese diabetic-severe combined immunodeficient (NOD/SCID) mice, the number of CD34+/CD38- cells that homed to the BM after 18 hours was significantly raised by pretreatment of animals and cells with FTY720, tending to result in improved engraftment. In addition, in vitro growth of HPCs (week-5 cobblestone area-forming cells [CAFCs]) was 2.4-fold increased. We conclude that activation of S1PRs by FTY720 increases CXCR4 function in HPCs both in vitro and in vivo, supporting homing and proliferation of HPCs. In the hematopoietic microenvironment, S1PRs are involved in migration and maintenance of HPCs by modulating the effects of SDF-1.

Myriocin, a serine palmitoyltransferase inhibitor, alters regional brain neurotransmitter levels without concurrent inhibition of the brain sphingolipid biosynthesis in mice

Myriocin is a specific serine palmitoyltransferase (SPT) inhibitor whose effect on the brain is unknown. Brain amine metabolism and sphingolipid biosynthesis were studied in mice treated intraperitoneally with 0, 0.1, 0.3 or 1 mg/kg per day of myriocin for 5 days. Regional concentrations of dopamine (DA), 3,4-dihydroxyphenylacetic acid (DOPAC), homovanillic acid (HVA), 5-hydroxytryptamine (5-HT, serotonin), 5-hydroxyindoleacetic acid (5-HIAA) and norepinephrine (NE), were determined. Sphinganine (Sa) and sphingosine (So) concentrations and SPT activity in brain and liver were used to evaluate the impact of myriocin on sphingolipid biosynthesis. Myriocin treatment increased DA in striatum and hippocampus and reduced it in cortex. NE concentration decreased in cerebellum and 5-HT levels were reduced in cortex and in medulla oblongata. Changes in ratios for DOPAC/DA and HVA/DA were observed in hippocampus, cortex and midbrain. Brain Sa, So and SPT activity remained unchanged, whereas Sa and SPT activity decreased in liver. Results showed that myriocin may alter the levels and metabolism of brain amines and this effect is not related with inhibition of sphingolipid biosynthesis in the nervous system.

Sphingosine 1-phosphate and its type 1 G protein-coupled receptor: trophic support and functional regulation of T lymphocytes

The lysophospholipid (LPL) growth factors sphingosine 1-phosphate (S1P) and lysophosphatidic acid (LPA) are generated by macrophages, dendritic cells, mast cells, and platelets, which leads to lymph and plasma concentrations of 0.1-1 microM. Distinctive profiles of G protein-coupled receptors (GPCRs) for S1P and LPA are expressed by each type of immune cell and are regulated by cellular activation. At 1-100 nM, S1P signals T cells through their principal S1P(1) GPCRs with consequent protection from apoptosis, enhancement of chemotaxis, and facilitation of optimal regulatory activity of CD4(+)25(+) T cells. At 0.3-3 microM, S1P inhibits T cell chemotaxis and to a lesser extent other functions. These S1P-S1P(1) GPCR signals suppress homing of blood and spleen T cells to secondary lymphoid tissues. S1P(1) GPCR antagonists evoke lymphopenia by permitting blood T cells to enter lymph nodes and blocking S1P(1) GPCR-dependent T cell efflux from lymph nodes. Inversely, there is a decrease in lymphoid tissue traffic of T cells in transgenic mice, which overexpress lymphocyte S1P(1) GPCRs. The immunotherapeutic activity of S1P(1) GPCR antagonists, which limits T cell access to organ grafts and autoimmune antigens, does not reduce other functional capabilities of T cells. LPLs and their GPCRs thus constitute an immunoregulatory system of sufficient prominence for pharmacological targeting in transplantation, autoimmunity, and immunodeficiency.

The immunosuppressant FTY720 down-regulates sphingosine 1-phosphate G-protein-coupled receptors

FTY720 is an immunosuppressant that reduces circulating levels of naïve lymphocytes by increasing their localization and sequestration in secondary lymphoid organs. It is considered to be an agonist for sphingosine 1-phosphate (S1P) G protein-coupled receptors (GPCRs) after phosphorylation at micromolar concentrations. We now describe its nonagonist and noncompetitive inhibitory activity at low nanomolar concentrations for types 1 and 5 S1P-GPCRs and of moderate potency for type 2 S1P-GPCRs. FTY720 blocks S1P signaling through S1P1,2,5 by inducing their internalization and intracellular partial degradation without affecting S1P3 or S1P4. S1P-R internalization is maximal several hours after only seconds of incubation with FTY720 at 37 degrees C and washing, and continues for days before recovery of surface expression and functions. The timing and extent of S1P-R internalization are highly dependent on FTY720 concentration. FTY720 is therefore an S1P-GPCR-selective and noncompetitive inhibitor with a unique mechanism of action.

The immunosuppressant FTY720 is phosphorylated by sphingosine kinase type 2

The potent immunosuppressive drug FTY720, a sphingosine analog, induces redistribution of lymphocytes from circulation to secondary lymphoid tissues. FTY720 is phosphorylated in vivo and functions as an agonist for four G-protein-coupled sphingosine-1-phosphate receptors. The identity of the kinase that phosphorylates FTY720 is still not known. Here we report that although both sphingosine kinase type 1 (SphK1) and type 2 (SphK2) can phosphorylate FTY720 with low efficiency, SphK2 is much more effective than SphK1. FTY720 inhibited phosphorylation of sphingosine catalyzed by SphK2 to a greater extent than it inhibits SphK1. Thus, SphK2 may be the relevant enzyme that is responsible for in vivo phosphorylation of FTY720.

The emerging matrix of immunosuppressive agents

In recent years, significant milestones have been reached in the field of transplantation through the development of immunosuppressive drugs that inhibit lymphocyte activation, cytokine signal transduction, and cellular proliferation. However, the widespread tissue distribution of the molecular targets exploited to date-calcineurin, mammalian target of rapamycin (mTOR), and inosine monophosphate dehydrogenase-produces an array of collateral toxicities. Avoiding these side effects requires new strategies that selectively block destructive immune responses: a fifth generation of immunosuppressants. These agents must target molecules that are critical for and specific to the adaptive immune response.

Ubiquitin pathway proteins influence the mechanism of action of the novel immunosuppressive drug FTY720 in Saccharomyces cerevisiae

FTY720 is an immunosuppressive drug in clinical development for transplant graft protection in humans. This agent is of particular interest because, unlike currently available regimes, it acts to sequester lymphocytes without causing cytotoxicity or blocking differentiation and growth potential. In an effort to elucidate the mechanism of action of FTY720, and identify its downstream effectors, we have screened genomic libraries and spontaneous mutants of the model system Saccharomyces cerevisiae for resistance to FTY720. We identified several proteins and pathways as being involved in the mechanism of action of FTY720. We show specifically that the two amino acid transporters TAT1 and TAT2, the two ubiquitin proteases UBP5 and UBP11, and the heat shock protein CAJ1 confer growth resistance to FTY720 when overexpressed. Another amino acid transporter, GNP1, and the ubiquitin structural gene UBI4 as well as the ubiquitin ligase RSP5, and its binding protein BUL1 confer growth resistance in a mutated form. Supporting the importance of amino acid transport in the growth resistance phenotype of S. cerevisiae to the immunosuppressive agent FTY720, a prototrophic strain was more resistant to FTY720 than the isogenic auxotroph. To further explore these results, the effects on amino acid uptake and protein degradation were measured in the presence of FTY720. Due to the high conservation of these proteins and pathways between yeast and humans, these results may provide valuable insights into the mechanism of action of FTY720 in lymphocyte sequestration in humans.

Pharmacodynamics of single doses of the novel immunosuppressant FTY720 in stable renal transplant patients

FTY720, a new and potent immunosuppressant, causes in animal models a rapid, reversible reduction of all subsets of peripheral blood lymphocytes, inducing their migration to secondary lymphoid organs. In this human phase I trial, the pharmacodynamics of single oral doses of FTY720 were evaluated. A randomized, double-blind, placebo-controlled, time-lagged study of six different single ascending oral doses of FTY720 ranging from 0.25 to 3.5 mg was conducted in stable renal transplant patients receiving a cyclosporine-based regimen. Absolute and subset lymphocyte counts, as well as absolute differential leukocyte counts, were determined by differential blood counts and flow cytometry at screening and multiple intervals thereafter. A pharmacodynamic model was established. Twenty-four single doses of FTY720 that were administered caused a transient, reversible pan-lymphopenia within 4 h. Lymphocyte subgroup analysis revealed that almost all subsets declined, with CD4- and CD45RA-positive cells being affected the most. Natural killer cells, granulocytes and monocytes were not influenced by FTY720. The lymphocyte count returned to baseline within 72 h in all dosing cohorts except the highest. Pharmacokinetik/pharmacodynamic modelling revealed a nonlinear dose effect and resulted in a good fit with observed values. These data show that FTY720 is highly effective in humans, with single oral doses of FTY720 ranging from 0.25 to 3.5 mg causing a reversible selective panlymphopenia.

Serine palmitoyltransferase, a key enzyme of sphingolipid metabolism

The first step in the biosynthesis of sphingolipids is the condensation of serine and palmitoyl CoA, a reaction catalyzed by serine palmitoyltransferase (SPT) to produce 3-ketodihydrosphingosine (KDS). This review focuses on recent advances in the biochemistry and molecular biology of SPT. SPT belongs to a family of pyridoxal 5'-phosphate (PLP)-dependent alpha-oxoamine synthases (POAS). Mammalian SPT is a heterodimer of 53-kDa LCB1 and 63-kDa LCB2 subunits, both of which are bound to the endoplasmic reticulum (ER) most likely with the type I topology, whereas other members of the POAS family are soluble homodimer enzymes. LCB2 appears to be unstable unless it is associated with LCB1. Potent inhibitors of SPT structurally resemble an intermediate in a probable multistep reaction mechanism for SPT. Although SPT is a housekeeping enzyme, its activity is regulated transcriptionally and post-transcriptionally, and its up-regulation is suggested to play a role in apoptosis induced by certain types of stress. Specific missense mutations in the human LCB1 gene cause hereditary sensory neuropathy type I, an autosomal dominantly inherited disease, and these mutations confer dominant-negative effects on SPT activity.

FTY720, an immunosuppressant that alters lymphocyte trafficking, abrogates chronic rejection in combination with cyclosporine A

BACKGROUND

Chronic rejection remains the leading cause of failure after transplantation (Tx). FTY720, a new immunosuppressant altering lymphocyte trafficking, is effective against acute rejection, but its activity against chronic rejection is not known.

METHODS

A valid model of chronic rejection was produced. Heart transplantation (HTx) was performed using fully mismatched RA (RT1p) and PVG (RT1c) rats. Administration of donor-specific blood transfusion 12 days before HTx prolongs graft survival, but features of chronic rejection including intimal hyperplasia and vascular obliteration (VO) develop with time only in allogeneic Tx. This is therefore a valid model of chronic rejection. VO was assessed on post-Tx day 90 in six groups differing according to the maintenance immunosuppressive regimen administered. group 1, donor-specific blood transfusion only and no other treatment; group 2, FTY720 (0.3 mg/kg/day orally) for 90 days; group 3, cyclosporine A (CsA) (1 mg/kg/day orally) for 90 days; group 4, combined administration of FTY720 and CsA for 90 days; group 5, transient administration of combined FTY720 and CsA for 7 days; and group 6, syngeneic HTx (RA to RA). Graft infiltrate, endothelial immunoglobulin (Ig) G deposition, and complement binding were also examined on post-Tx day 90.

RESULTS

In control group 1, severe VO was observed, compared with syngeneic HTx (group 6). Monotherapy with FTY720 (group 2) or with CsA (group 3) significantly but partially reduced VO. On the contrary, combined administration of FTY720 and CsA (group 4) abrogated VO. A 1-week treatment with combined FTY720 and CsA (group 5) reduced VO but only partially. In group 1, arteriosclerosis was accompanied by graft infiltrate, endothelial IgG deposition, and complement binding. In groups 2, 3, and 5, graft infiltrating scores were partially decreased compared with group 1 but remained higher than in syngeneic controls; endothelial IgG deposition and complement binding were still present. In group 4, continuous administration of combined FTY720 and CsA reduced graft infiltrate to the level of syngeneic control and abrogated both endothelial IgG deposition and complement binding.

CONCLUSIONS

Maintenance treatment with either FTY720 or CsA monotherapy partially prevents chronic rejection; short-term treatment with combined FTY720 and CsA reduces chronic rejection only partially; and continuous treatment with combined FTY720 and CsA abrogates chronic rejection, and this is accompanied by dramatic reduction of graft infiltrating cells, endothelial IgG deposition, and complement binding. Prevention of chronic rejection by maintenance treatment with FTY720 and CsA represents indirect evidence that normal lymphocyte trafficking and function are mandatory for development of chronic rejection.

Amelioration of experimental autoimmune encephalomyelitis in Lewis rats by FTY720 treatment

Experimental autoimmune encephalomyelitis (EAE) is a T-cell-dependent autoimmune disease that reproduces the inflammatory demyelinating pathology of multiple sclerosis (MS). We investigated the efficacy and mechanism of immunosuppression against EAE by administering 2-amino-[2-(4-octylphenyl) ethyl]-1,3-propanediol hydrochloride (FTY720) in Lewis rats immunized with myelin basic protein together with complete Freund's adjuvant. FTY720 treatment almost completely protected the rats against disease. The protection by FTY720 was associated with a dramatic reduction in the number of lymphocytes staining for T-cell receptors in the spinal cord as examined by immunohistochemistry. The mRNA expression of Th1 cytokines interleukin (IL)-2, IL-6, and interferon-gamma in the spinal cord was also reduced dramatically as assessed by reverse-transcription polymerase chain reaction. Furthermore, lymphocytes isolated from the spleen of FTY720-treated rats were transferred into naive recipient rats against EAE manifestation by reducing both disease incidence and clinical score. These results suggested that the protective anti-inflammatory effect of treatment with FTY720 was, to a large extent, due to the inhibition of encephalitogenic T-cell responses and/or their migration into the central nervous system and may be a potential candidate for use in treating patients with MS.

The immune modulator FYT720 prevents autoimmune diabetes in nonobese diabetic mice

FTY720 is a novel immune regulatory drug derived from the fungal sphingosine analog ISP-1 (myriocin). FTY720 causes a redistribution of lymphocytes from circulation to secondary lymphoid tissues. Type 1 diabetes is an autoimmune disorder caused by cellular-mediated destruction of insulin-producing pancreatic beta cells in the islets of Langerhans. Indeed, local infiltration of islets by mononuclear cells is the hallmark of Type 1 diabetes. Based on both FTY720's action and the involvement of cellular infiltration in the disease progression, we tested FTY720 for its ability to prevent autoimmune diabetes in diabetes-prone, nonobese diabetic (NOD) mice. We found that treatment with FTY720 completely prevented NOD mice from developing autoimmune diabetes. The FTY720-treated animals showed both reduced numbers of circulating lymphocytes and sharply diminished cellular infiltration of pancreatic islets. These results suggest that FTY720 may be effective in prevention of autoimmune diabetes or in slowing its progression.

Elimination of cell-cycle regulators during caspase-3-dependent apoptosis caused by an immunosuppressant, FTY720

The immunosuppressant, FTY720 causes apoptosis of lymphocytes, reduces numbers of lymphocytes in peripheral blood, and prevents infiltration of lymphocytes into allografts, which may be one of the mechanisms involved in its effects. Here we compared caspase activation and expression of cell-cycle regulators during apoptosis caused by FTY720, and Fas-stimulation in a mouse lymphoma transfected with human Fas antigen. FTY720 activated caspases-3, -8, and -9 as rapidly as did Fas-mediated apoptosis. The activation was blocked by a peptide inhibitor for caspase-3, DEVD-CHO. Fas-induced activation of caspases-8 and -9 was unaffected by the inhibitor. FTY720 eliminated proliferating cell nuclear antigen, retinoblastoma family members, differentiation regulated transcription factor polypetide-1, and cyclin H. These cell-cycle regulators were not eliminated when the peptide inhibitor was used. Dysfunction of cell-cycle regulators may play a critical role in the signal transduction pathway for activation of FTY720-mediated apoptosis.

A novel role for sphingolipid intermediates in activation-induced cell death in T cells

Activation-induced cell death (AICD), a process mediated by CD95 and CD95 ligand (CD95L), plays a critical role in regulating homeostasis of the immune system. Although the role of sphingolipids such as ceramides has been suggested to participate in CD95-mediated apoptosis, the exact role of these molecules in this process remains controversial. We employed myriocin, a specific inhibitor of serine palmitoyl-CoA transferase that mediates the first commitment step in sphingolipid synthesis. We found that myriocin could effectively block AICD in T-cell hybridomas and T-cell blasts. However, fumonisin B1, an inhibitor of the final step of ceramide synthesis, or inhibitors of sphingomyelinases did not prevent AICD. Furthermore, ceramide analogues, such as C2 and C6, could not reverse the inhibitory effect of myriocin. Interestingly, sphinganine, an intermediate of ceramide synthesis, completely reversed the inhibitory effect of myriocin, indicating a critical role of sphinganine. Myriocin did not modulate the expression of CD95 or CD95L, instead, it interfered with the early steps of CD95-mediated caspase activation. Therefore, we have uncovered a novel mechanism by which sphingolipid intermediates regulate CD95-mediated apoptosis.

Linking Chinese medicine and G-protein-coupled receptors

Following the purification of the immunosuppressant ISP-1 from a Chinese medicine, Japanese scientists have developed a more potent immune modulator, FTY720, that induces T-cell homing. FTY720, a promising immunosuppressant for use in patients with tissue transplants and autoimmune diseases, is currently in clinical trials. Two recent studies have elucidated that the mechanism of action of FTY720 is via a subset of G-protein-coupled receptors for the lysophospholipid mediator sphingosine-1-phosphate.

T cell selective apoptosis by a novel immunosuppressant, FTY720, is closely regulated with Bcl-2

1. A novel immunosuppressant FTY720 caused a significant decrease in peripheral T lymphocytes, but not in B lymphocytes upon oral administration. This decrease was mainly a result of FTY720-induced apoptosis. In this study, we confirmed FTY720-induced T cell selective apoptosis using lymphoma cell lines in vitro. 2. Viability loss, DNA fragmentation, Annexin V binding, and caspases activation (caspase-3, -8, and -9) were observed in Jurkat cells (T lymphoma cells), but not significantly in BALL-1 cells (B lymphoma cells). These results indicated that FTY720 selectively induced apoptosis in T cell lymphoma to a greater extent than in B cell lymphoma, a finding that is similar to the result observed when FTY720 was treated with T lymphocytes and B lymphocytes in vitro. 3. FTY720 released cytochrome c from mitochondria in Jurkat intact cells as well as from isolated Jurkat mitochondria directly, but not from mitochondria in BALL-1 cells nor from isolated BALL-1 mitochondria. 4. BALL-1 cells and B cells had more abundant mitochondria-localized anti-apoptotic protein Bcl-2 than did Jurkat cells and T cells. 5. FTY720-induced apoptosis is inhibited by the overexpression of Bcl-2, suggesting that the cellular Bcl-2 level regulates the sensitivity to FTY720.

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.

Pharmacokinetics and cell trafficking dynamics of 2-amino-2-[2-(4-octylphenyl)ethyl]propane-1,3-diol hydrochloride (FTY720) in cynomolgus monkeys after single oral and intravenous doses

The pharmacokinetics and cell trafficking dynamics of 2-amino-2-[2-(4-octylphenyl)ethyl]propane-1,3-diol hydrochloride (FTY720), a novel immunosuppressive agent, were examined in cynomolgus monkeys (three males and three females). After single doses of 0.1 mg/kg p.o. or i.v. bolus and 1 mg/kg p.o. were administered to the animals, the concentrations of FTY720, and the numbers of lymphocytes, CD20+CD2-B cells, and CD2+CD20-T cells in blood were measured over 23 days. A linear three-compartment model characterized the time course of FTY720 concentrations with a terminal half-life of about 31 h, clearance of about 0.53 l/h/kg, and bioavailability of about 38%. The dynamic responses were not area under the curve (or dose) proportional for either males or females. An indirect response model with a distribution pool captured the cell trafficking data for all doses for each cell type, where initial blood counts (R(0)) were about 7650, 2100, and 5250 cells/microl; maximum fractional inhibition (I(max)) about 0.88, 0.85, and 0.91; influx (k(in)) about 6014, 1312, and 5662 cells/microl/h; efflux (k(out)) about 0.798, 0.555, and 1.08 h(-1); intercompartmental k(cp) about 0.134, 0.192, and 0.082 h(-1); and intercompartmental k(pc) rate constants about 3.9 x 10(-4), and 0.016 and 8.9 x 10(-6) h(-1) for lymphocytes, B cells, and T cells, respectively. The inhibition concentration IC(50) was about 0.48 microg/l for all cells, which was remarkably low. The apparent distribution volumes of peripheral pool (V(p)) were markedly larger than blood volume (V(b)) for all cells. The I(max) for cell trafficking was achieved at doses smaller than that producing graft protection, indicating stronger central than peripheral effects of this drug. The profound cell trafficking effects of FTY720 can be readily captured and interpreted with an extended indirect response model.

First human trial of FTY720, a novel immunomodulator, in stable renal transplant patients

FTY720 is a novel immunomodulator to be developed for use in organ transplantation. The primary objective of this study was to measure safety, single-dose pharmacokinetics, and pharmacodynamics in stable renal transplant patients-the first human use of FTY720. This study used a randomized, double-blind, placebo-controlled design that explored single oral doses of FTY720 from 0.25 to 3.5 mg in 20 stable renal transplant patients on a cyclosporine-based regimen. Safety assessments and blood samples were taken predose and at multiple time points during a 96-h period postdose. Standard pharmacokinetic parameters were derived from the FTY720 whole blood concentrations, measured by HPLC/MS/MS. FTY720 was well tolerated, with no serious adverse events. Transient, asymptomatic bradycardia occurred after administration in 10 of 24 doses of FTY720. Pharmacokinetics are characterized by a prolonged absorption phase; the terminal elimination phase started 36 h after the administration, with elimination half-life (t(1/2)) ranging from 89 to 157 h independent of dose. Maximum plasma concentration and AUC were proportional to dose with low intersubject variability, the apparent volume of distribution (V(d)/F) ranged from 1116 to 1737 L. FTY pharmacodynamics were characterized by a reversible transient lymphopenia within 6 h, the nadir being 42% of baseline. The lymphocyte count returned to baseline within 72 h in all dosing cohorts except the highest. Single oral doses of FTY720 ranging from 0.25 to 3.5 mg were well tolerated and caused a reversible selective lymphopenia. Transient, but asymptomatic bradycardia was the most common adverse event. The long t(1/2) suggests less frequent dosing intervals. The size of V(d)/F is in excess of blood volume, consistent with widespread tissue distribution

Current practices: immunosuppression induction, maintenance, and rejection regimens in contemporary post-heart transplant patient treatment

Cardiac transplantation is the definitive treatment for eligible patients with end-stage cardiomyopathy. Survival rates have improved dramatically during the last 10 years, especially since the advent of cyclosporine-A. Cardiac allograft rejection, previously considered a major cause of early mortality after transplantation, is no longer the limiting factor for early survival, with the use of newer and more specific immunosuppression regimens. Very few randomized, prospective trials, including comparisons between immunosuppression regimens, have been conducted in this area. Therefore, practices vary with physician and institutional experience. Most centers use a multipronged approach to immunosuppression, targeting multiple sites in the immune cascade that lead to allograft rejection. Multiple new agents in development are reviewed. Drugs such as sirolimus and its derivative, everolimus, act on specific intracellular receptors within lymphocytes, whereas other medications such as Daclizumab (Roche Laboratories, Nutley, NJ) block the interleukin-2 receptor on the surface of activated T cells. The immune response to foreign antigens is complex, with multiple redundant levels. Immunosuppression regimens continue to seek a fine balance between overimmunosuppression and insufficient protection, which may lead to allograft rejection or loss.

Update on pharmacokinetic/pharmacodynamic studies with FTY720 and sirolimus

Expanding the cytokine paradigm beyond the use of calcineurin inhibitors as baseline therapy provides new strategies in immunosuppression. Drugs such as FTY720 alter the sensitivity of lymphocytes to homing chemokines, and agents such as sirolimus (SRL) disrupt downstream cytokine signal transduction. Confirming studies in rodents and nonhuman primates, administration of either FTY720 or both of these drugs afford synergistic interactions with cyclosporine to renal transplant patients to rapidly and dramatically deplete peripheral blood lymphocytes (PBL) but neither granulocytes nor monocytes. Present information suggests that FTY720 facilitates lymphocyte homing mechanisms, leading to T and B cell sequestration in secondary lymphoid structures. Interestingly, FTY720 displays pharmacokinetic characteristics suggesting that therapeutic drug monitoring (TDM) will not be essential for clinical applications. In contrast, SRL is a critical-dose drug that requires TDM. SRL disrupts costimulatory and cytokine-stimulated T cell activation by inhibiting a multifunctional kinase, mammalian target of sirolimus (mTOR). Two pivotal trials including more than 1,300 patients demonstrated that addition of SRL to a CsA-based regimen reduces the incidence, time to onset, and severity of acute rejection episodes. When used alone, SRL seems therapeutically equivalent to CsA. In the coming decade, SRL is likely to be used in a variety of drug combination regimens both simultaneously and sequentially, not only to avert acute rejection episodes, but also to forestall chronic nephropathic processes. These two new agents are likely to usher in a new era of transplant therapy.

What role for FTY720, a novel immunosuppressive agent, in canine nonmyeloablative hematopoietic stem cell transplantation?

BACKGROUND

Stable mixed donor/host hematopoietic chimerism was almost uniformly achieved in dogs given 200 cGy total body irradiation (TBI) before, and a short course of immunosuppression after, transplantation of marrow from dog leukocyte antigen-identical littermates, but was transient when the TBI dose was decreased to 100 cGy. Here, we examined whether stable engraftment could be achieved in five dogs given FTY720 (days -5 and -4), followed by 100 cGy TBI, dog leukocyte antigen-identical marrow grafts, and mycophenolate mofetil/cyclosporine.

RESULTS AND CONCLUSIONS

Although all five dogs showed initial engraftment, four dogs rejected their grafts within 11 weeks, whereas one dog was euthanized on day 17 due to enteritis. This was not different from the control dogs not given FTY720 (P=0.32). Thus, FTY720 failed to enhance allogeneic engraftment in this model, perhaps due to in vivo T-cell depletion of the graft resulting from sequestration of donor lymphocytes in host central lymphoid tissues.

gem-Diacetates as carbonyl surrogates for asymmetric synthesis. Total syntheses of sphingofungins E and F

The equivalent of an asymmetric addition to a carbonyl group with a stabilized anion is accomplished by discriminating between the enantiotopic C-O single bonds of a gem-diacetate. In this way, enantioselective total syntheses of two antifugal agents, sphingofungins E and F, have been accomplished. The synthetic strategy is based on a series of catalytic processes whereby all of the chiral centers are created with high stereoselectivities. The first two stereocenters are introduced by an asymmetric allylic alkylation reaction of gem-diacetate 9 with azlactone 10. The complex of Pd(0) and ligand 14 efficiently catalyzes this key reaction, which differentiates both the enantiotopic leaving groups of a gem-diacetate and enantiotopic faces of the enolate of an azlactone in high enantiomeric excess and diastereomeric excess. From these two stereocenters, the configurations of the remaining two centers are set by a diastereoselective Os(VIII)-catalyzed dihydroxylation reaction with excellent stereocontrol. The trans-alkene is established by Cr(II)-mediated olefination, and a subsequent B-alkyl Suzuki coupling reaction conjoins the polar head unit and the nonpolar, 13-carbon lipid tail. The efficiency of our strategy is illustrated by the completion of syntheses of sphingofungins F and E in 15 and 17 steps, and in 17% and 5% overall yields, respectively.

Coordinate involvement of cell cycle arrest and apoptosis strengthen the effect of FTY720

A novel reagent, FTY720 (2-amino-2-[2-(4-octylphenyl)ethyl]-1,3-propanediol hydrochloride), has been shown to induce a significant decrease of lymphocytes and lymphoma cells and is expected to be a potent immunosuppressant and anti-tumor drug. The decrease in lymphocytes and lymphoma cells is mainly the result of FTY720-induced apoptosis. FTY720 directly affects mitochondria and induces cell death. Moreover, FTY720 activates protein phosphatase (PP) 2A and affects anti-apoptotic intracellular signal transduction proteins to attenuate the anti-apoptotic effect. In this study, we examined the relationship between FTY720-induced apoptosis and cell cycle regulation. FTY720 induced apoptosis significantly at the G0 / G1 phase and caused G0 / G1 cell cycle arrest of the human lymphoma cell lines HL-60RG and Jurkat. Simultaneously, retinoblastoma protein (pRB) was dephosphorylated, suggesting that dephosphorylation of pRB was related to FTY720-induced G0 / G1 cell cycle arrest. Because this dephosphorylation was completely blocked by a specific PP1 / 2A inhibitor, okadaic acid, it appears that FTY720-activated PP2A is essential for FTY720-induced cell cycle arrest. FTY720-induced apoptosis was inhibited by Bcl-2 overexpression in Jurkat cells, but this did not prevent FTY720-induced cell cycle arrest, suggesting that the mechanism of FTY720-induced cell cycle arrest is independent of the mechanism of FTY720-induced apoptosis. These two independent pathways strengthen the effect of FTY720.

Development of applied microbiology to modern biotechnology in Japan

Development of modern biotechnology in Japan is characterized by unique contributions from applied microbiology and bioindustry. This review tries to summarize these original contributions with special emphasis on industrial production of useful substances by microorganisms. In the first part, development of applied microbiology and bioindustry in the last half of the twentieth century is summarized with a brief overview of the traditional background. In the second part, recent progress is reviewed with citation of typical achievements in biotechnology, applied enzymology, secondary metabolites, genetic engineering, and screening of microbial diversity, respectively.

FTY720, a novel immunosuppressive agent, induces apoptosis in human glioma cells

FTY720, a metabolite from Isaria sinclairii, has been developed to be a potent immunosuppressive drug with induction of apoptosis in T cells and several cell lines. We investigated whether FTY720 induces apoptosis in human glioma cell lines, since they are relatively resistant to multiple apoptotic stimuli. In human glioma cells including T98G, FTY720 induced apoptosiswith ED50 between 1 to 10 microg/ml, while etoposidedid not induce apoptosis at the same doses. Among the caspase family proteases, mainly caspase-6 was activated during the apoptosis by FTY720 but not etoposide. In addition, FTY720 caused tyrosine dephosphorylation of FAK and did not activate a FAK-PI3-kinase survival pathway. This was confirmed also by the observation that orthovanadate prevented FTY720-induced dephosphorylation of FAK and inhibited FTY720-induced cell death. We assumed that FTY720 induced FAK dephosphorylation and cut off the FAK-PI3-kinase pathway resulting in the induction of apoptosis via caspase-6 activation in these glioma cells.