Effect of pretreatment with FTY720 and cyclosporin on ischaemia-reperfusion injury of the liver in rats

Preclinical Evaluation of Fingolimod in Rodent Models of Stroke With Age or Atherosclerosis as Comorbidities

Preclinical data indicate that fingolimod improves outcome post-ischaemia. This study used a rigorous study design in normal male C57BL/6JOlaHsd mice and in mice with common stroke comorbidities to further evaluate the translational potential of fingolimod. Stroke was induced via middle cerebral artery electrocoagulation in 8–9-week old mice (young mice), 18 month old mice (aged mice), and in high-fat diet-fed 22-week old ApoE−/− mice (hyperlipidaemic mice). Recovery was evaluated using motor behavioural tests 3 and 7 days after stroke. Tissue damage was evaluated at 7 days. A lower dose of fingolimod, 0.5 mg/kg, but not 1 mg/kg, increased lesion size but decreased ipsilateral brain atrophy in younger mice, without an effect on behavioural outcomes. Fingolimod-treated aged mice showed a significant improvement over saline-treated mice in the foot fault test at 7 days. Fingolimod-treated hyperlipidaemic mice showed a decreased infarct size but no difference in behavioural performance. Increasing fingolimod treatment time to 10 days showed no benefit in young mice. Pooled data showed that fingolimod improved performance in the foot fault test. Flow cytometry studies showed that fingolimod had marked effects on T cell frequencies in various tissues. The results show that the effects of fingolimod in stroke are less robust than the existing literature might indicate and may depend on the inflammatory status of the animals.

FTY720 Protects Against Ischemia-Reperfusion Injury by Preventing the Redistribution of Tight Junction Proteins and Decreases Inflammation in the Subacute Phase in an Experimental Stroke Model

Injury due to brain ischemia followed by reperfusion (I/R) may be an important therapeutic target in the era of thrombectomy. FTY720, a widely known sphingosine-1-phosphate receptor agonist, exerts various neuroprotective effects. The aim of this study was to examine the protective effect of FTY720 with respect to I/R injury, especially focusing on blood-brain barrier (BBB) protection and anti-inflammatory effects. Male rats were subjected to transient ischemia and administered vehicle or 0.5 or 1.5 mg/kg of FTY720 immediately before reperfusion. Positron emission tomography (PET) with [¹⁸F]DPA-714 was performed 2 and 9 days after the insult to serially monitor neuroinflammation. Bovine and rat brain microvascular endothelial cells (MVECs) were also subjected to oxygen-glucose deprivation (OGD) and reperfusion, and administered FTY720, phosphorylated-FTY720 (FTY720-P), or their inhibitor. FTY720 dose-dependently reduced cell death, the infarct size, cell death including apoptosis, and inflammation. It also ameliorated BBB disruption and neurological deficits compared to in the vehicle group. PET indicated that FTY720 significantly inhibited the worsening of inflammation in later stages. FTY720-P significantly prevented the intracellular redistribution of tight junction proteins but did not increase their mRNA expression. These results suggest that FTY720 can ameliorate I/R injury by protecting the BBB and regulating neuroinflammation.

Mitochondrial Ca2+ and regulation of the permeability transition pore

The mitochondrial permeability transition pore was originally described in the 1970's as a Ca2+ activated pore and has since been attributed to the pathogenesis of many diseases. Here we evaluate how each of the current models of the pore complex fit to what is known about how Ca2+ regulates the pore, and any insight that provides into the molecular identity of the pore complex. We also discuss the central role of Ca2+ in modulating the pore's open probability by directly regulating processes, such as ATP/ADP balance through the tricarboxylic acid cycle, electron transport chain, and mitochondrial membrane potential. We review how Ca2+ influences second messengers such as reactive oxygen/nitrogen species production and polyphosphate formation. We discuss the evidence for how Ca2+ regulates post-translational modification of cyclophilin D including phosphorylation by glycogen synthase kinase 3 beta, deacetylation by sirtuins, and oxidation/ nitrosylation of key residues. Lastly we introduce a novel view into how Ca2+ activated proteolysis through calpains in the mitochondria may be a driver of sustained pore opening during pathologies such as ischemia reperfusion injury.

Myriocin prevents muscle ceramide accumulation but not muscle fiber atrophy during short-term mechanical unloading

Bedridden patients in intensive care unit or after surgery intervention commonly develop skeletal muscle weakness. The latter is promoted by a variety of prolonged hospitalization-associated conditions. Muscle disuse is the most ubiquitous and contributes to rapid skeletal muscle atrophy and progressive functional strength reduction. Disuse causes a reduction in fatty acid oxidation, leading to its accumulation in skeletal muscle. We hypothesized that muscle fatty acid accumulation could stimulate ceramide synthesis and promote skeletal muscle weakness. Therefore, the present study was designed to determine the effects of sphingolipid metabolism on skeletal muscle atrophy induced by 7 days of disuse. For this purpose, male Wistar rats were treated with myriocin, an inhibitor of de novo synthesis of ceramides, and subjected to hindlimb unloading (HU) for 7 days. Soleus muscles were assayed for fiber diameter, ceramide levels, protein degradation, and apoptosis signaling. Serum and liver were removed to evaluate the potential hepatoxicity of myriocin treatment. We found that HU increases content of saturated C16:0 and C18:0 ceramides and decreases soleus muscle weight and fiber diameter. HU increased the level of polyubiquitinated proteins and induced apoptosis in skeletal muscle. Despite a prevention of C16:0 and C18:0 muscle accumulation, myriocin treatment did not prevent skeletal muscle atrophy and concomitant induction of apoptosis and proteolysis. Moreover, myriocin treatment increased serum transaminases and induced hepatocyte necrosis. These data highlight that inhibition of de novo synthesis of ceramides during immobilization is not an efficient strategy to prevent skeletal muscle atrophy and exerts adverse effects like hepatotoxicity.

Fingolimod provides long-term protection in rodent models of cerebral ischemia

OBJECTIVE

The sphingosine-1-phosphate (S1P) receptor agonist fingolimod (FTY720), that has shown efficacy in advanced multiple sclerosis clinical trials, decreases reperfusion injury in heart, liver, and kidney. We therefore tested the therapeutic effects of fingolimod in several rodent models of focal cerebral ischemia. To assess the translational significance of these findings, we asked whether fingolimod improved long-term behavioral outcomes, whether delayed treatment was still effective, and whether neuroprotection can be obtained in a second species.

METHODS

We used rodent models of middle cerebral artery occlusion and cell-culture models of neurotoxicity and inflammation to examine the therapeutic potential and mechanisms of neuroprotection by fingolimod.

RESULTS

In a transient mouse model, fingolimod reduced infarct size, neurological deficit, edema, and the number of dying cells in the core and periinfarct area. Neuroprotection was accompanied by decreased inflammation, as fingolimod-treated mice had fewer activated neutrophils, microglia/macrophages, and intercellular adhesion molecule-1 (ICAM-1)-positive blood vessels. Fingolimod-treated mice showed a smaller infarct and performed better in behavioral tests up to 15 days after ischemia. Reduced infarct was observed in a permanent model even when mice were treated 4 hours after ischemic onset. Fingolimod also decreased infarct size in a rat model of focal ischemia. Fingolimod did not protect primary neurons against glutamate excitotoxicity or hydrogen peroxide, but decreased ICAM-1 expression in brain endothelial cells stimulated by tumor necrosis factor alpha.

INTERPRETATION

These findings suggest that anti-inflammatory mechanisms, and possibly vasculoprotection, rather than direct effects on neurons, underlie the beneficial effects of fingolimod after stroke. S1P receptors are a highly promising target in stroke treatment.

Effect of ONO-4057 and tacrolimus on ischemia-reperfusion injury of the liver

AIM: To investigate the effects of a novel Leukotriene B₄ receptor antagonist and/or tacrolimus on ischemia-reperfusion in a rat liver model.

METHODS: Male Lewis rats were pretreated with ONO-4057 (100 mg/kg) and/or tacrolimus (1 mg/kg) orally, and divided into four experimental groups; group 1 (control), group 2 (ONO-4057), group 3 (tacrolimus), group 4 (ONO-4057 + tacrolimus).

RESULTS: There was a tendency for long survival in the groups treated with tacrolimus alone and ONO-4057 plus tacrolimus. Post-reperfusion serum aspartate aminotransferase levels decreased more significantly in ONO-4057 plus tacrolimus group (P < 0.01), than in the tacrolimus alone group (P < 0.05), compared to controls.

CONCLUSION: This study demonstrated that pretreatment with ONO-4057 in combination with tacrolimus produced additive effects in a rat model of liver ischemia-reperfusion injury.

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.

A two-hour window for hypothermic modulation of early events that impact delayed opening of the rat blood-brain barrier after ischemia

Opening of the blood-brain barrier (BBB) and consequent edema are known to intensify 24-72 h after ischemic stroke, and research on potential ameliorative therapies in animal models may lead to improved clinical treatments to prevent brain swelling and the secondary damage it causes. In this study, post-ischemic hypothermia treatment, which is an established neuroprotective strategy, was examined for its ability to prevent delayed BBB opening in a rat model of global ischemia. Anesthetized, normothermic SD rats (340-380 g) underwent 20 min of two-vessel (carotid) occlusion plus hypotension (2VO ischemia, between 0900-1100 h). Marked cortical BBB leakiness, which developed overnight, was indicated at sacrifice 24 h post-2VO by an average six- to eightfold increase above baseline in transfer constant values (K(i) ) for rate of blood to brain diffusion of intravenously delivered [(3)H]sucrose. A post-2VO treatment involving whole body cooling to 31.5 degrees-32.5 degrees C, maintenance for 6 h and rewarming to normothermia, significantly reduced BBB leakiness at 24 h, whether cooling was initiated immediately after reperfusion, or after a 1-h delay, but not after 2-h delay. Immediate hypothermia treatment reduced overall tissue injury at 24 h as evidenced by an assay of mitochondrial succinate dehydrogenase activity, and also reduced brain edema. By contrast, treatment of rats with the anti-inflammatory drugs cyclosporine A or minocycline offered no protection of BBB or mitochondria. It is concluded that hypothermic alteration of critical events during the first 2 h after prolonged ischemia powerfully mitigates the BBB damage and associated events that normally develop 24 h later.

Partial protective effect of Y-27632, a Rho kinase inhibitor, against hepatic ischemia–reperfusion injury in rats

(+)-(R)-trans-4-(1-aminoethyl)-N-(4-pyridyl)-cyclohexanecarboxamide dihydrochloride (Y-27632), a Rho kinase inhibitor, has a suppressive effect on the functions of polymorphonuclear leukocytes. In this study, the influence of Y-27632 on ischemia-reperfusion injury of the liver was examined in rats. Y-27632 (3 mg/kg) or vehicle alone was intravenously injected into rats 60 min before occlusion. Blood samples were obtained for 48 h after reperfusion. At the end of the experiment, the hepatic content of myeloperoxidase, which reflects the number of polymorphonuclear leukocytes in liver tissues, was determined. The increases in serum hepatic aminotransferases and inflammatory cytokines [tumor necrosis factor-alpha (TNF-alpha), interleukin (IL)-6] after reperfusion were partially, but significantly, inhibited by Y-27632. The increased hepatic myeloperoxidase content was significantly lowered by Y-27632. These results suggest that Y-27632 has a partial protective effect against hepatic ischemia-reperfusion injury through the suppression of polymorphonuclear leukocytes and inflammatory cytokines.

Alterações metabólicas induzidas por isquemia hepática normotérmica experimental e o efeito hepatoprotetor da ciclosporina

RACIONAL: Transplante de fígado é inevitavelmente associado com períodos de isquemia completa. No entanto, o tempo de oclusão do pedículo hepático é limitado pelas conseqüências da injúria pós-isquêmica do fígado. OBJETIVO: Determinar as principais alterações metabólicas ocasionadas pela isquemia hepática e a provável ação hepatoprotetora da ciclosporina. MÉTODOS: Isquemia hepática normotérmica por 60 minutos foi induzida em ratos. Em seguida, as alterações com o tempo (0, 1, 6, 24 horas) das concentrações sangüíneas e hepáticas de lactato, piruvato, glicose, corpos cetônicos e razão acetoacetato/3-hidroxibutirato, bem como o estado redox citoplasmático e mitocondrial do tecido hepático foram determinados. Outro grupo de animais foi pré-tratado com ciclosporina (10 mg/kg), sendo estudadas as alterações metabólicas no tempo 1 hora após revascularização hepática. RESULTADOS: A isquemia hepática causou elevação da concentração de lactato no fígado, sugerindo que pronunciado grau de metabolismo anaeróbico ocorreu durante o período de isquemia. Isquemia hepática acarretou ainda queda da concentração e da razão dos corpos cetônicos (acetoacetato/3-hidroxibutirato) no sangue arterial no tempo de 1 hora após revascularização. Tal fato reflete que a injuria isquêmica do fígado interfere na cetogênese. CONCLUSÃO: O tratamento com ciclosporina causa elevação das concentrações dos corpos cetônicos e da razão acetoacetato/3-hidroxibutirato no sangue arterial após 1 hora de reperfusão hepática, sugerindo que esta droga acelera a cetogênese e, conseqüentemente, a recuperação da lesão isquêmica do fígado.

Sphingosine-1-phosphate receptor agonism impairs the efficiency of the local immune response by altering trafficking of naive and antigen-activated CD4+ T cells

FTY720 (2-amino-[2-(4-octylphenyl) ethyl]-1,3-propanediol hydrochloride) is an immunosuppressive agent that inhibits allograft rejection. We recently demonstrated that FTY-phosphate, the active metabolite of FTY720, acts as a full agonist for sphingosine-1-phosphate (S1P) receptors. Furthermore, activation of S1P receptors with their natural ligand, S1P, as well as pharmacological ligands leads to lymphopenia, probably due to sequestration of lymphocytes in secondary lymphoid organs. In the present study we used a local Ag-challenged mouse model to examine the effects of FTY720 on T cell activation in the draining lymph node (DLN) and on the release of activated T cells to the peripheral blood compartment. We showed that the number of Ag-activated CD4(+) T cells in the DLN after injection of Ag and CFA into a footpad was dramatically reduced after FTY720 treatment. However, T cell proliferation, both in vitro and in vivo, was not impaired by FTY720. Our results suggest that the reduced efficiency of T cell responses in the DLN in response to a local Ag is probably due to a defective recirculation of naive T cells caused by FTY720 treatment. Furthermore, we found that the numbers of naive and Ag-activated CD4(+) T cells in the peripheral blood of Ag-challenged mice were equally reduced with FTY720 treatment, suggesting that both T cell subsets are sequestered in the DLNs. Thus, FTY720 induces immunosuppression through inhibition of both the recirculation of naive T cells and the release of Ag-activated T cells from the DLN to lymph and to the blood compartment.

FTY720 pretreatment reduces warm hepatic ischemia reperfusion injury through inhibition of T-lymphocyte infiltration

Ischemia and reperfusion (IR) injury remains a significant problem in clinical liver transplantation. We investigated the effects of lymphocyte depletion with FTY720 in models of warm hepatic IR. Using 60-min partial warm hepatic IR, three groups of rats were studied: Sham--laparotomy alone; Control--water p.o. x 3 d before ischemia; Treatment--FTY720 p.o. x 3 d before ischemia. Animals were sacrificed for analysis at 6 h and 24 h post reperfusion. The effect of FTY720 pretreatment on survival was also studied using 150 min total hepatic IR with portojugular shunt. FTY720 treatment significantly reduced serum glutamic pyruvic transaminase and peripheral blood lymphocytes compared to controls at 6h and 24h (p < 0.0005). Histological grade was significantly improved in treated livers vs. controls (p < 0.05). CD3 immunocytochemical analysis revealed a significant reduction in T-cell infiltration in FTY720-treated livers (p < 0.0002). No difference in tissue myeloperoxidase levels was observed. Seven-day survival was significantly improved in treated rats vs. controls following total hepatic ischemia (p < 0.05). In conclusion, FTY720 ameliorates the biochemical and histological manifestations of hepatic IR by preventing T-lymphocyte infiltration and prolongs survival following a more severe ischemic insult. Myeloperoxidase data suggest this mechanism is independent of neutrophil activation. These results indicate that T lymphocytes are pivotal mediators in hepatic IR and may have important implications in liver transplantation.

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

BACKGROUND

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

METHODS

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

RESULTS

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

CONCLUSIONS

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

The T cell as a bridge between innate and adaptive immune systems: implications for the kidney

The T cell as a bridge between innate and adaptive immune systems: Implications for the kidney. The immune system is classically divided into innate and adaptive components with distinct roles and functions. T cells are major components of the adaptive immune system. T cells are firmly established to mediate various immune-mediated kidney diseases and are current targets for therapy. Ischemic acute renal failure, a major cause of native kidney and allograft dysfunction, is mediated in part by inflammatory components of the innate immune system. However, recent data from experimental models in kidney as well as liver, intestine, brain and heart implicate T cells as important mediators of ischemia reperfusion injury. These data reveal new insights into the pathogenesis of ischemic acute renal failure, as well as identify novel and feasible therapeutic approaches. Furthermore, the identification of T cells as a mediator of early alloantigen-independent tissue injury demonstrates that the functional capacity of T cells spreads beyond adaptive immunity into the realm of the innate immune response.