FTY720: a novel approach to the treatment of hepatic ischemia-reperfusion injury

Sphingosine-1-Phosphate Signaling in Ischemic Stroke: From Bench to Bedside and Beyond

Sphingosine-1-phosphate (S1P) signaling is being increasingly recognized as a strong modulator of immune cell migration and endothelial function. Fingolimod and other S1P modulators in ischemic stroke treatment have shown promise in emerging experimental models and small-scale clinical trials. In this article, we will review the current knowledge of the role of S1P signaling in brain ischemia from the aspects of inflammation and immune interventions, sustaining endothelial functions, regulation of blood-brain barrier integrity, and functional recovery. We will then discuss the current and future therapeutic perspectives of targeting S1P for the treatment of ischemic stroke. Mechanism studies would help to bridge the gap between preclinical studies and clinical practice. Future success of bench-to-bedside translation shall be based on in depth understanding of S1P signaling during stroke and on the ability to have a fine temporal and spatial regulation of the signal pathway.

FTY720 Regulates Mitochondria Biogenesis in Dendritic Cells to Prevent Kidney Ischemic Reperfusion Injury

Dendritic cells (DCs) are central in regulating immune responses of kidney ischemia-reperfusion injury (IRI), and strategies to alter DC function may provide new therapeutic opportunities. Sphingosine 1-phosphate (S1P) modulates immunity through binding to its receptors (S1P1-5), and protection from kidney IRI occurs in mice treated with S1PR agonist, FTY720 (FTY). We tested if ex vivo propagation of DCs with FTY could be used as cellular therapy to limit the off-target effects associated with systemic FTY administration in kidney IRI. DCs have the ability of regulate innate and adaptive responses and we posited that treatment of DC with FTY may underlie improvements in kidney IRI. Herein, it was observed that treatment of bone marrow derived dendritic cells (BMDCs) with FTY induced mitochondrial biogenesis, FTY-treated BMDCs (FTY-DCs) showed significantly higher oxygen consumption rate and ATP production compared to vehicle treated BMDCs (Veh-DCs). Adoptive transfer of FTY-DCs to mice 24 h before or 4 h after IRI significantly protected the kidneys from injury compared to mice treated with Veh-DCs. Additionally, allogeneic adoptive transfer of C57BL/6J FTY-DCs into BALB/c mice equally protected the kidneys from IRI. FTY-DCs propagated from S1pr1-deficient DCs derived from CD11cCreS1pr1^fl/fl mice as well as blunting mitochondrial oxidation in wildtype (WT) FTY-DCs prior to transfer abrogated the protection observed by FTY-DCs. We queried if DC mitochondrial content alters kidney responses after IRI, a novel but little studied phenomenon shown to be integral to regulation of the immune response. Transfer of mitochondria rich FTY-DCs protects kidneys from IRI as transferred FTY-DCs donated their mitochondria to recipient splenocytes (i.e., macrophages) and prior splenectomy abrogated this protection. Adoptive transfer of FTY-DCs either prior to or after ischemic injury protects kidneys from IRI demonstrating a potent role for donor DC-mitochondria in FTY's efficacy. This is the first evidence, to our knowledge, that DCs have the potential to protect against kidney injury by donating mitochondria to splenic macrophages to alter their bioenergetics thus making them anti-inflammatory. In conclusion, the results support that ex vivo FTY720-induction of the regulatory DC phenotype could have therapeutic relevance that can be preventively infused to reduce acute kidney injury.

Effects of FTY720 on Lung Injury Induced by Hindlimb Ischemia Reperfusion in Rats

Background

Sphingosine-1-phosphate (S1P) is a biologically active lysophospholipid mediator involved in modulating inflammatory process. We investigated the effects of FTY720, a structural analogue of S1P after phosphorylation, on lung injury induced by hindlimb ischemia reperfusion (IR) in rats.

Methods

Fifty Sprague-Dawley rats were divided into groups SM, IR, F3, F5, and F10. Group SM received sham operation, and bilateral hindlimb IR was established in group IR. The rats in groups F3, F5, and F10 were pretreated with 3, 5, and 10 mg/kg/d FTY720 for 7 days before IR. S1P lyase (S1PL), sphingosine kinase (SphK) 1, and SphK2 mRNA expressions, wet/dry weight (W/D), and polymorphonuclear/alveolus (P/A) in lung tissues were detected, and the lung injury score was evaluated.

Results

W/D, P/A, and mRNA expressions of S1PL, SphK1, and SphK2 were higher in group IR than in group SM, while these were decreased in both groups F5 and F10 as compared to IR (p < 0.05). The lung tissue presented severe lesions in group IR, which were attenuated in groups F5 and F10 with lower lung injury scores than in group IR (p < 0.05).

Conclusions

FTY720 pretreatment could attenuate lung injury induced by hindlimb IR by modulating S1P metabolism and decreasing pulmonary neutrophil infiltration.

Pharmacological pre- and post-conditioning with the sphingosine-1-phosphate receptor modulator FTY720 after myocardial ischaemia-reperfusion

BACKGROUND AND PURPOSE

Our recent experiments demonstrated that the Sphingosine-1-phosphate (S1P) receptor agonist FTY720 (2-amino-2-[2-(4-octylphenyl)ethyl]-1,3-propanediol hydrochloride) improves recovery of function after myocardial ischaemia-reperfusion ex vivo. Therefore, we tested the hypothesis that pharmacological post-conditioning with FTY720 reduces infarct size after myocardial ischaemia-reperfusion in vivo.

EXPERIMENTAL APPROACH

Myocardial ischaemia was induced in Wistar rats by ligation of the left coronary artery for 45 min. FTY720 (0.5 mg kg(-1)) was applied i.p. either once, before reperfusion, or twice, 24 h before myocardial ischaemia and before reperfusion. After 24 h reperfusion, we determined infarct size by triphenyltetrazolium chloride staining and granulocyte infiltration by immunohistochemistry. Tumour necrosis factor-alpha (TNF)-alpha concentration was determined by elisa. S1P receptor expression was studied by Western blot. Calcium transients were evaluated in Indo-1-loaded cardiomyocytes.

KEY RESULTS

In both groups, FTY720 significantly reduced lymphocyte count in peripheral blood. FTY720 treatment attenuated granulocyte infiltration and TNF-alpha protein expression in reperfused myocardium. However, both treatment regimens were not able to reduce infarct size. FTY720 increased mortality due to induction of fatal ventricular tachyarrhythmias when administered once before reperfusion, but protected against reperfusion arrhythmias when given 24 h prior to ischaemia. Pretreatment selectively down-regulated S1P(1) receptor expression within the myocardium. S1P receptor agonists did not induce calcium deregulation in cardiomyocytes.

CONCLUSIONS AND IMPLICATIONS

FTY720 applied during reperfusion did not reduce infarct size but increased mortality during myocardial ischaemia-reperfusion due to induction of arrhythmias. Pretreatment with FTY720 before ischaemia abrogated the deleterious pro-arrhythmic effects without reducing infarct size.

Activation of sphingosine-1-phosphate 1 receptor in the proximal tubule protects against ischemia-reperfusion injury

Agonists of the sphingosine-1-phosphate receptor (S1PR) attenuate kidney ischemia-reperfusion injury (IRI). Previous studies suggested that S1P1R-induced lymphopenia mediates this protective effect, but lymphocyte-independent mechanisms could also contribute. Here, we investigated the effects of S1PR agonists on kidney IRI in mice that lack T and B lymphocytes (Rag-1 knockout mice). Administration of the nonselective S1PR agonist FTY720 or the selective S1P1R agonist SEW2871 reduced injury in both Rag-1 knockout and wild-type mice. In vitro, SEW2871 significantly attenuated LPS- or hypoxia/reoxygenation-induced apoptosis in cultured mouse proximal tubule epithelial cells, supporting a direct protective effect of S1P1R agonists via mitogen-activated protein kinase and/or Akt pathways. S1P1Rs in the proximal tubule mediated IRI in vivo as well: Mice deficient in proximal tubule S1P1Rs experienced a greater decline in renal function after IRI than control mice and their kidneys were no longer protected by SEW2871 administration. In summary, S1PRs in the proximal tubule are necessary for stress-induced cell survival, and S1P1R agonists are renoprotective via direct effects on the tubule cells. Selective agonists of S1P1Rs may hold therapeutic potential for the prevention and treatment of acute kidney injury.

Sphinganine-1-phosphate attenuates both hepatic and renal injury induced by hepatic ischemia and reperfusion in mice

Hepatic ischemia/reperfusion (I/R) injury is a major complication after liver transplantation, major hepatic resection, or prolonged portal vein occlusion. Furthermore, acute kidney injury is frequent after hepatic I/R and greatly increases postoperative complications. Sphinganine-1-phosphate is a sphingolipid with uncharacterized physiological effects. We serendipitously determined that plasma levels of sphinganine-1-phosphate fell significantly after liver I/R in mice. In this study, we hypothesized that repletion of plasma sphinganine-1-phosphate would protect against liver and kidney injuries after liver I/R. C57BL/6 mice were subjected to 60 min of partial hepatic I/R and treated with either vehicle or with sphinganine-1-phosphate (given immediately before and 2 h after reperfusion). Vehicle-treated mice subjected to liver I/R developed acute liver and kidney injuries with elevated plasma alanine aminotransferase and creatinine 5 and 24 h after liver I/R. However, liver and kidney injuries were significantly attenuated with sphinganine-1-phosphate treatment. Sphinganine-1-phosphate markedly inhibited liver and kidney necrosis and apoptosis 24 h after liver I/R. Moreover, sphinganine-1-phosphate attenuated neutrophil infiltration, reduced plasma IL-6 and TNF-alpha upregulation, and preserved liver and kidney vascular integrity while reducing liver and kidney F-actin degradation after liver I/R. Finally, sphinganine-1-phosphate-mediated hepatic and renal protection was blocked by VPC23019, an antagonist for sphingosine-1-phosphate type 1 receptor. Therefore, sphinganine-1-phosphate improves acute liver and kidney injuries after hepatic I/R via sphingosine-1-phosphate type 1 receptor-mediated inhibition of necrosis and apoptosis and by improving vascular integrity. Harnessing the mechanisms of cytoprotection with sphinganine-1-phosphate activation may lead to new therapies for perioperative hepatic I/R injury and subsequent remote organ injury.

Immunomodulatory drug FTY720 induces regulatory CD4(+)CD25(+) T cells in vitro

As a novel immunosuppressant, FTY720 (2-amino-2-(2-[4-octylphenyl] ethyl)-1, 3-propanediol hydrochloride) has been used to prevent the allograft rejection in organ transplantation. FTY720 can prolong markedly survival of the allograft by inducing apoptosis of reactive lymphocytes and by redirecting the homing of lymphocytes. However, as the archetype of a new class of immune modulators, the potential effect of FTY720 on the immune response needs to be elucidated further. In this study, FTY720 was added into the mixed lymphocyte reaction (MLR) consisting of murine splenocytes from BALB/c and C57BL/6, to observe its direct effect on the induction of CD4(+)CD25(+) regulatory T cells. It was demonstrated that the proportion of CD4(+)CD25(+) and CD4(+)CD25(+)forkhead box P3 (FoxP3)(+) T cells in MLR were increased significantly by FTY720 treatment, and the expression of FoxP3 mRNA in lymphocytes was also enhanced markedly by the drug. A synergetic effect was observed between FTY720 and co-stimulation blockades. Moreover, analysis of the function of FTY720-treated cells manifested an increased suppressive activity in an in vitro antigen-specific proliferation assay. In conclusion, FTY720 can increase the number and enhance the functional activity of CD4(+)CD25(+) regulatory T cells in MLR, and these FTY720-treated cells possess the activity to down-regulate the alloreactivity of lymphocytes, indicating its potential use for therapeutic purposes.

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.

Protective effects of sphingosine-1-phosphate receptor agonist treatment after myocardial ischaemia-reperfusion

AIMS

Several experimental studies have demonstrated protection against cardiac ischaemia-reperfusion injury achieved by pre-treatment with exogenous sphingosine-1-phosphate (S1P). We tested the hypothesis that pharmacological S1P receptor agonists improve recovery of function when applied with reperfusion.

METHODS AND RESULTS

Isolated rat cardiomyocytes were stimulated with exogenous S1P, the selective S1P1 receptor agonist SEW2871, or the S1P1/3 receptor agonist FTY720. Western blot analysis was performed to analyse downstream signalling pathways. Ischaemia-reperfusion studies were conducted in rat cardiomyocytes, isolated Langendorff-perfused rat hearts, and in human myocardial muscle strip preparations to evaluate the effect of S1P receptor agonists on cell death and recovery of mechanical function. All S1P receptor agonists were able to activate Akt. This was associated with transactivation of the epidermal growth factor receptor. In isolated cardiomyocytes, selective stimulation of the S1P1 receptor by SEW2871 induced protection against cell death when administered either before or after ischaemia-reperfusion. In isolated rat hearts, treatment with FTY720 during reperfusion attenuated the rise in left ventricular end-diastolic pressure (LVEDP) and improved the recovery of left ventricular developed pressure without limiting infarct size. However, selective S1P1 receptor stimulation did not improve functional recovery but rather increased LVEDP. Additional experiments employing a human myocardial ischaemia-reperfusion model also demonstrated improved functional recovery induced by FTY720 treatment during reperfusion.

CONCLUSION

Pharmacological S1P receptor agonists have distinct effects on ischaemia-reperfusion injury. Their efficacy when applied during reperfusion makes them potential candidates for pharmaceutical postconditioning therapy after cardiac ischaemia.

Current perspectives on FTY720

The search for effective immunosuppressants with fewer side effects continues not only for transplantation, but also for autoimmune diseases. With a novel mechanism of action (sphingosine-1 receptor modulation), oral FTY720 (fingolimod) has the potential to address this need. FTY720 has been preclinically tested with promising results in transplantation and autoimmune disease models. Phase I studies explored the pharmacokinetics and pharmacodynamics of this novel therapeutic concept. Recently, the surprising results of two sister Phase III studies in de novo renal transplant patients, as well as a Phase II study in patients with relapsing multiple sclerosis, were published. This review discusses these findings as well as their implications for the future of sphingosine-1 receptor modulation.

Effect of 2-amino-2-[2-(4-octylphenyl) ethyl] propane-1,3-diol hydrochloride (FTY 720) on immune liver injury in mice

AIM: To investigate the protective effect against two immune liver injury models in mice by 2-amino-2-[2-(4-octylphenyl) ethyl] propane-1,3-diol hydrochloride and its possible mechanisms in Con A-induced liver damage.

METHODS: Liver tissue or hepatocyte injury was monitored biochemically by measuring alanine aminotransferase (sALT) and aspartate aminotransferase (sAST) activity. Hematoxylin & eosin (HE) staining was used for histopathological examination. To evaluate the role of IFN-γ and IL-4 in the liver injury, serum levels of IFN-γ and IL-4 were determined using commercially available ELISA kit at 12 h after Con A challenge. We also determined FTY 720-induced spleen cell apoptosis by flow cytometry analysis or spleen cell proliferation test.

RESULTS: Different doses of FTY 720 treatment dramatically reduced circulating markers of hepatocyte injury in two kinds of immunological liver injury models. FTY 720 dramatically reduced the elevated serum IFN-γ and IL-4 levels after Con A injection. Effect of spleen cell supernatants treated with Con A or FTY 720 on hepatocytes showed that ALT activities in cultured hepatocyte supernatants in Con A treatment group increased markedly and FTY 720 could reduce this elevated ALT activities in FTY 720 treatment group. FTY 720 dose-dependently increased the percentage of apoptotic cells in T cells and inhibited splenocyte proliferation induced by Con A.

CONCLUSION: Pretreatment with FTY 720 was shown to produce protective effect on the immune liver injury in mice. The possible mechanism of FTY 720 on Con A-induced liver damage is that it could inhibit lymphocyte proliferation and induce lymphocyte apoptosis, resulting in the reduction of IL-4 or IFN-γ release, and subsequently protecting liver from being damaged by Con A.