FTY720 attenuates hepatic ischemia-reperfusion injury in normal and cirrhotic livers

The role of PI3k/AKT signaling pathway in attenuating liver fibrosis: a comprehensive review

Excessive accumulation of extracellular matrix (ECM) components within the liver leads to a pathological condition known as liver fibrosis. Alcohol abuse, non-alcoholic fatty liver disease (NAFLD), autoimmune issues, and viral hepatitis cause chronic liver injury. Exploring potential therapeutic targets and understanding the molecular mechanisms involved in liver fibrosis are essential for the development of effective interventions. The goal of this comprehensive review is to explain how the PI3K/AKT signaling pathway contributes to the reduction of liver fibrosis. The potential of this pathway as a therapeutic target is investigated through a summary of results from in vivo and in vitro studies. Studies focusing on PI3K/AKT activation have shown a significant decrease in fibrosis markers and a significant improvement in liver function. The review emphasizes how this pathway may prevent ECM synthesis and hepatic stellate cell (HSC) activation, ultimately reducing the fibrotic response. The specific mechanisms and downstream effectors of the PI3K/AKT pathway in liver fibrosis constitute a rapidly developing field of study. In conclusion, the PI3K/AKT signaling pathway plays a significant role in attenuating liver fibrosis. Its complex role in regulating HSC activation and ECM production, demonstrated both in vitro and in vivo, underscores its potential as a effective therapeutic approach for managing liver fibrosis and slowing disease progression. A comprehensive review of this field provides valuable insights into its future developments and implications for clinical applications.

Effects of iNOS in Hepatic Warm Ischaemia and Reperfusion Models in Mice and Rats: A Systematic Review and Meta-Analysis

Warm ischaemia is usually induced by the Pringle manoeuver (PM) during hepatectomy. Currently, there is no widely accepted standard protocol to minimise ischaemia-related injury, so reducing ischaemia-reperfusion damage is an active area of research. This systematic review and meta-analysis focused on inducible nitric oxide synthase (iNOS) as an early inflammatory response to hepatic ischaemia reperfusion injury (HIRI) in mouse- and rat-liver models. A systematic search of studies was performed within three databases. Studies meeting the inclusion criteria were subjected to qualitative and quantitative synthesis of results. We performed a meta-analysis of studies grouped by different HIRI models and ischaemia times. Additionally, we investigated a possible correlation of endothelial nitric oxide synthase (eNOS) and nitric oxide (NO) regulation with iNOS expression. Of 124 included studies, 49 were eligible for the meta-analysis, revealing that iNOS was upregulated in almost all HIRIs. We were able to show an increase of iNOS regardless of ischemia or reperfusion time. Additionally, we found no direct associations of eNOS or NO with iNOS. A sex gap of primarily male experimental animals used was observed, leading to a higher risk of outcomes not being translatable to humans of all sexes.

Fingolimod does not prevent syndecan-4 shedding from the endothelial glycocalyx in a cultured human umbilical vein endothelial cell model of vascular injury

Background

Shedding of the endothelial glycocalyx (EG) is associated with poor outcomes in a range of conditions including sepsis. Fresh frozen plasma (FFP) restores the damaged EG to baseline thickness, however the mechanism for this effect is unknown, and some components of FFP have adverse effects unrelated to the EG. There is some limited evidence that sphingosine-1-phosphate (S1P) within FFP restores the EG by activating the endothelial cell S1P receptor 1 (S1PR₁). However, there are disadvantages to using S1P clinically as an EG restorative therapy. A potential alternative is the S1PR agonist fingolimod (FTY720). The aim of this study was to assess whether FTY720 prevents EG shedding in injured cultured human umbilical vein endothelial cells.

Methods

Shedding of the EG was induced in cultured human umbilical vein endothelial cells (HUVECs) by exposure to adrenaline, TNF-α and H₂O₂. The cells were then assigned to one of six conditions for 4 h: uninjured and untreated, injured and untreated, injured and treated with FTY720 with and without the S1PR₁ inhibitor W146, and injured and treated with 25% FFP with and without W146. Syndecan-4, a component of the EG, was measured in cell supernatants, and syndecan-4 and thrombomodulin mRNA expression was quantitated in cell lysates.

Results

The injury resulted in a 2.1-fold increase in syndecan-4 (p < 0.001), consistent with EG shedding. Syndecan-4 and thrombomodulin mRNA expression was increased (p < 0.001) and decreased (p < 0.05), respectively, by the injury. Syndecan-4 shedding was not affected by treatment with FTY720, whereas FFP attenuated syndecan-4 shedding back to baseline levels in the injured cells and this was unaffected by W146. Neither treatment affected syndecan-4 or thrombomodulin mRNA expression.

Conclusions

FTY720 did not prevent syndecan-4 shedding from the EG in the HUVEC model of endothelial injury, suggesting that activation of S1PR does not prevent EG damage. FFP prevented syndecan-4 shedding from the EG via a mechanism that was independent of S1PR₁ and upregulation of SDC-4 production. Further studies to examine whether FTY720 or another S1PR agonist might have EG-protective effects under different conditions are warranted, as are investigations seeking the mechanism of EG protection conferred by FFP in this experimental model.

One Shoot, Two Birds: Alleviating Inflammation Caused by Ischemia/Reperfusion Injury to Reduce the Recurrence of Hepatocellular Carcinoma

Inflammation is crucial to tumorigenesis and the development of metastasis. Hepatic ischemia/reperfusion injury (IRI) is an unresolved problem in liver resection and transplantation which often establishes and remodels the inflammatory microenvironment in liver. More and more experimental and clinical evidence unmasks the role of hepatic IRI and associated inflammation in promoting the recurrence of hepatocellular carcinoma (HCC). Meanwhile, approaches aimed at alleviating hepatic IRI, such as machine perfusion, regulating the gut-liver axis, and targeting key inflammatory components, have been proved to prevent HCC recurrence. This review article highlights the underlying mechanisms and promising therapeutic strategies to reduce tumor recurrence through alleviating inflammation induced by hepatic IRI.

Nanotheranostics for the Management of Hepatic Ischemia-Reperfusion Injury

Hepatic ischemia-reperfusion injury (IRI), in which an insufficient oxygen supply followed by reperfusion leads to an inflammatory network and oxidative stress in disease tissue to cause cell death, always occurs after liver transplantations and sections. Although pharmacological treatments favorably prevent or protect the liver against experimental IRI, there have been few successes in clinical applications for patient benefits because of the incomprehension of complicated IRI-induced signaling events as well as short blood circulation time, poor solubility, and severe side reactions of most antioxidants and anti-inflammatory drugs. Nanomaterials can achieve targeted delivery and controllable release of contrast agents and therapeutic drugs in desired hepatic IRI regions for enhanced imaging sensitivity and improved therapeutic effects, emerging as novel alternative approaches for hepatic IRI diagnosis and therapy. In this review, the application of nanotechnology is summarized in the management of hepatic IRI, including nanomaterial-assisted hepatic IRI diagnosis, nanoparticulate systems-mediated remission of reactive oxygen species-induced tissue injury, and nanoparticle-based targeted drug delivery systems for the alleviation of IRI-related inflammation. The current challenges and future perspectives of these nanoenabled strategies for hepatic IRI treatment are also discussed.

Impact of S1P Mimetics on Mesenteric Ischemia/Reperfusion Injury

Mesenteric ischemia/reperfusion (I/R), following the transient deprivation of blood flow to the gut, triggers an acute flogistic process involving the disruption of endothelial and epithelial barriers integrity, the activation of immune cells, and the abundant release of inflammatory mediators. Among them, the lipid mediator sphingosine-1-phosphate (S1P) is involved in maintaining epithelial and endothelial barrier integrity and in governing the migration of immune cells through the interaction with S1P_1–5 receptors. Therefore, the present work aims to investigate the involvement of S1P signaling in intestinal I/R-induced injury by studying the effects of FTY720, the non-selective S1P_1,3–5 agonist, and comparing them with the responses to ozanimod, selective S1P_1,5 agonist, in a murine model of gut I/R. Intestinal edema, gut and lung neutrophil infiltration, and oxidative stress were evaluated through biochemical and morphological assays. The collected results highlight the protective action of FTY720 against the inflammatory cascade elicited by mesenteric I/R injury, mainly through the control of vascular barrier integrity. While these beneficial effects were mimicked by ozanimod and can be therefore attributed largely to the effects exerted by FTY720 on S1P₁, the recruitment of myeloid cells to the injured areas, limited by FTY720 but not by ozanimod, rather suggests the involvement of other receptor subtypes.

Serum Sphingosine-1-Phosphate Is Decreased in Patients With Acute-on-Chronic Liver Failure and Predicts Early Mortality

Sphingosine‐1‐phosphate (S1P) regulates pathophysiological processes, including liver regeneration, vascular tone control, and immune response. In patients with liver cirrhosis, acute deterioration of liver function is associated with high mortality rates. The present study investigated whether serum S1P concentrations are associated with disease severity in patients with chronic liver disease from compensated cirrhosis (CC), acute decompensation (AD), or acute‐on‐chronic liver failure (ACLF). From August 2013 to October 2017, patients who were admitted to the University Hospital Frankfurt with CC, AD, or ACLF were enrolled in our cirrhosis cohort study. Tandem mass spectrometry was performed on serum samples of 127 patients to assess S1P concentration. Our study comprised 19 patients with CC, 55 with AD, and 51 with ACLF, aged 29 to 76 years. We observed a significant decrease of S1P according to advanced liver injury from CC and AD up to ACLF (P < 0.001). S1P levels further decreased with progression to ACLF grade 3 (P < 0.05), and S1P highly inversely correlated with the Model for End‐Stage Liver Disease score (r = −0.508; P < 0.001). In multivariate analysis, S1P remained an independent predictor of 7‐day mortality with high diagnostic accuracy (area under the curve, 0.874; P < 0.001). Conclusion: In patients with chronic liver disease, serum S1P levels dramatically decreased with advanced stages of liver disease and were predictive of early mortality. Because S1P is a potent regulator of endothelial integrity and immune response, low S1P levels may significantly influence progressive multiorgan failure. Our data justify further elucidation of the diagnostic and therapeutic role of S1P in ACLF.

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.

FTY720 Suppresses Liver Tumor Growth and Metastasis by Reducing Circulating Regulating T Cells and Enhancing the Anti-Tumor Effect of Rapamycin

Background

In this study, we aimed to study the effect of FTY720 treatment in reducing circulating Tregs level and then suppressing liver tumor metastasis after hepatectomy and I/R injury in animal models. Furthermore, we also investigated the synergistic anti-tumor effect of FTY720 combined with rapamycin on hepatocellular carcinoma.

Methods

The effect of FTY720 on suppressing Tregs mobilization and tumor metastasis after hepatectomy was investigated in an orthotopic liver tumor rat model with hepatectomy and hepatic ischemia/reperfusion (I/R) injury. The synergistic anti-tumor effect of FTY720 combined with rapamycin was further explored both in in vitro functional study and in orthotopic liver tumor mouse model.

Results

In rat model, hepatic I/R promoted tumor metastasis and increased circulating Tregs after hepatectomy. The treatment of FTY720 reduced liver tumor metastasis and the number of circulating Tregs. Furthermore, FTY720 enhanced the anti-tumor capacity of rapamycin by inhibiting tumor cell proliferation and migration in vitro and reducing tumor growth in vivo through suppressing hepatic stellate cell activation and tumor angiogenesis.

Conclusion

FTY720 suppressed liver tumor growth and metastasis by reducing the population of circulating Tregs and enhancing the anti-tumor effect of rapamycin. It was suggested that FTY720 single or combined with rapamycin might provide novel insight for suppressing tumor growth and metastasis for HCC patients.

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.

Neuroinflammation after Intracerebral Hemorrhage and Potential Therapeutic Targets

Spontaneous intracerebral hemorrhage (ICH) is a catastrophic illness causing significant morbidity and mortality. Despite advances in surgical technique addressing primary brain injury caused by ICH, little progress has been made treating the subsequent inflammatory cascade. Pre-clinical studies have made advancements identifying components of neuroinflammation, including microglia, astrocytes, and T lymphocytes. After cerebral insult, inflammation is initially driven by the M1 microglia, secreting cytokines (e.g., interleukin-1β [IL-1β] and tumor necrosis factor-α) that are involved in the breakdown of the extracellular matrix, cellular integrity, and the blood brain barrier. Additionally, inflammatory factors recruit and induce differentiation of A1 reactive astrocytes and T helper 1 (Th1) cells, which contribute to the secretion of inflammatory cytokines, augmenting M1 polarization and potentiating inflammation. Within 7 days of ICH ictus, the M1 phenotype coverts to a M2 phenotype, key for hematoma removal, tissue healing, and overall resolution of inflammation. The secretion of anti-inflammatory cytokines (e.g., IL-4, IL-10) can drive Th2 cell differentiation. M2 polarization is maintained by the secretion of additional anti-inflammatory cytokines by the Th2 cells, suppressing M1 and Th1 phenotypes. Elucidating the timing and trigger of the anti-inflammatory phenotype may be integral in improving clinical outcomes. A challenge in current translational research is the absence of an equivalent disease animal model mirroring the patient population and comorbid pathophysiologic state. We review existing data and describe potential therapeutic targets around which we are creating a bench to bedside translational research model that better reflects the pathophysiology of ICH patients.

Cardioprotective mechanism of FTY720 in ischemia reperfusion injury

Cardioprotection is a very challenging area in the field of cardiovascular sciences. Myocardial damage accounts for nearly 50% of injury due to reperfusion, yet there is no effective strategy to prevent this to reduce the burden of heart failure. During last couple of decades, by combining genetic and bimolecular studies, many new drugs have been developed to treat hypertension, heart failure, and cancer. The use of percutaneous coronary intervention has reduced the mortality and morbidity of acute coronary syndrome dramatically. However, there is no standard therapy available that can mitigate cardiac reperfusion injury, which contributes to up to half of myocardial infarcts. Literature shows that the activation of sphingosine receptors, which are G protein-coupled receptors, induces cardioprotection both in vitro and in vivo. The exact mechanism of this protection is not clear yet. In this review, we discuss the mechanism of ischemia reperfusion injury and the role of the FDA-approved sphingosine 1 phosphate drug fingolimod in cardioprotection.

Mitogen Activated Protein Kinases in Steatotic and Non-Steatotic Livers Submitted to Ischemia-Reperfusion

We analyzed the participation of mitogen-activated protein kinases (MAPKs), namely p38, JNK and ERK 1/2 in steatotic and non-steatotic livers undergoing ischemia-reperfusion (I-R), an unresolved problem in clinical practice. Hepatic steatosis is a major risk factor in liver surgery because these types of liver tolerate poorly to I-R injury. Also, a further increase in the prevalence of steatosis in liver surgery is to be expected. The possible therapies based on MAPK regulation aimed at reducing hepatic I-R injury will be discussed. Moreover, we reviewed the relevance of MAPK in ischemic preconditioning (PC) and evaluated whether MAPK regulators could mimic its benefits. Clinical studies indicated that this surgical strategy could be appropriate for liver surgery in both steatotic and non-steatotic livers undergoing I-R. The data presented herein suggest that further investigations are required to elucidate more extensively the mechanisms by which these kinases work in hepatic I-R. Also, further researchers based in the development of drugs that regulate MAPKs selectively are required before such approaches can be translated into clinical liver surgery.

Extracellular vesicles from human-induced pluripotent stem cell-derived mesenchymal stromal cells (hiPSC-MSCs) protect against renal ischemia/reperfusion injury via delivering specificity protein (SP1) and transcriptional activating of sphingosine kinase 1 and inhibiting necroptosis

Renal ischemia-reperfusion is a main cause of acute kidney injury (AKI), which is associated with high mortality. Here we show that extracellular vesicles (EVs) secreted from hiPSC-MSCs play a critical role in protection against renal I/R injury. hiPSC-MSCs-EVs can fuse with renal cells and deliver SP1 into target cells, subsequently active SK1 expression and increase S1P formation. Chromatin immunoprecipitation (ChIP) analyses and luciferase assay were used to confirm SP1 binds directly to the SK1 promoter region and promote promoter activity. Moreover, SP1 inhibition (MIT) or SK1 inhibition (SKI-II) completely abolished the renal protective effect of hiPSC-MSCs-EVs in rat I/R injury mode. However, pre-treatment of necroptosis inhibitor Nec-1 showed no difference with the administration of hiPSC-MSCs-EVs only. We then generated an SP1 knockout hiPSC-MSC cell line by CRISPR/Cas9 system and found that SP1 knockout failed to show the protective effect of hiPSC-MSCs-EVs unless restoring the level of SP1 by Ad-SP1 in vitro and in vivo. In conclusion, this study describes an anti-necroptosis effect of hiPSC-MSCs-EVs against renal I/R injury via delivering SP1 into target renal cells and intracellular activating the expression of SK1 and the generation of S1P. These findings suggest a novel mechanism for renal protection against I/R injury, and indicate a potential therapeutic approach for a variety of renal diseases and renal transplantation.

Characterization and Expression of Sphingosine 1-Phosphate Receptors in Human and Rat Heart

Aim: Sphingosine 1-phosphate (S1P), sphingolipid derivatives are known anti-inflammatory, anti-apoptotic, and anti-oxidant agent. S1P have been demonstrated to have a role in the cardiovascular system. The purpose of this study was to understand the precise expression and distribution of S1P receptors (S1PRs) in human and rat cardiovascular tissues to know the significance and possible implementation of our experimental studies in rat models. Methods and Results: In this study, we investigated the localization of S1PRs in human heart samples from cardiac surgery department, University of Verona Hospital and rat samples. Immunohistochemical investigation of paraffin-embedded sections illustrated diffused staining of the myocardial samples from human and rat. The signals of the human heart were similar to those of the rat heart in all chambers of the heart. The immunohistochemical expression levels correlated well with the results of RT-PCR-based analysis and western blotting. We confirmed by all techniques that S1PR1 expressed strongly as compared to S1PR3, and are uniformly distributed in all chambers of the heart with no significant difference in human and rat myocardial tissue. S1PR2 expression was significantly weak while S1PR4 and S1PR5 were not detectable in RT-PCR results in both human and rat heart. Conclusion: These results indicate that experimental studies using S1PR agonists on rat models are more likely to have a potential for translation into clinical studies, and second important information revealed by this study is, S1P receptor agonist can be used for cardioprotection in global ischemia-reperfusion injury.

Sphingosine-1-Phosphate Receptor Agonist Fingolimod Increases Myocardial Salvage and Decreases Adverse Postinfarction Left Ventricular Remodeling in a Porcine Model of Ischemia/Reperfusion

BACKGROUND

Fingolimod, a sphingosine-1-phosphate receptor agonist, is used for the treatment of multiple sclerosis and exerts antiapoptotic properties. We hypothesized that sphingosine-1-phosphate receptor activation with fingolimod during acute myocardial infarction (MI) inhibits apoptosis, leading to increased myocardial salvage, reduced infarct size, and mitigated left ventricular (LV) remodeling in a porcine model of ischemia/reperfusion.

METHODS AND RESULTS

Ischemia/reperfusion was induced in pigs by balloon occlusion of the left anterior descending artery, followed by reperfusion. Animals randomly received fingolimod or saline (control). In short-term experiments, fingolimod treatment activated the cardioprotective reperfusion injury salvage kinase and survivor activating factor enhancement pathways in the infarct border zone 24 hours after MI, leading to decreased cardiomyocyte apoptosis and reduced myocardial oxidative stress. These effects were abolished by specific inhibitors of both pathways, demonstrating that fingolimod-induced cardioprotection was mediated by reperfusion injury salvage kinase and survivor activating factor enhancement pathways. In long-term experiments, fingolimod significantly improved myocardial salvage, reduced infarct size, and improved systolic LV function measured by cardiac magnetic resonance 1 week and 1 month after MI. Importantly, fingolimod mitigated the development of adverse post-MI LV remodeling 1 month after MI. Specifically, fingolimod treatment led to a significant reduction in LV mass, LV dilatation, and neurohormonal activation, and it preserved LV geometry. Furthermore, fingolimod decreased interstitial fibrosis, cardiomyocyte hypertrophy, and chronic activation of Akt and extracellular receptor kinase 1/2 in the remote noninfarcted myocardium.

CONCLUSIONS

Sphingosine-1-phosphate receptor activation with fingolimod during acute MI reduced infarct size via the reperfusion injury salvage kinase and survivor activating factor enhancement pathways, improved systolic LV function, and mitigated post-MI LV remodeling. Our data strongly support a cardioprotective role for sphingosine-1-phosphate receptor activation during MI.

A sphingosine-1 phosphate agonist (FTY720) limits trauma/hemorrhagic shock-induced multiple organ dysfunction syndrome

BACKGROUND

Trauma/hemorrhagic shock (T/HS) is one of the major consequences of battlefield injury as well as civilian trauma. FTY720 (sphingosine-1-phosphate agonist) has the capability to decrease the activity of the innate and adaptive immune systems and, at the same time, maintain endothelial cell barrier function and vascular homeostasis during stress. For this reason, we hypothesize that FTY720, as part of resuscitation therapy, would limit T/HS-induced multiple organ dysfunction syndrome in a rodent T/HS model.

METHODS

Rats subjected to trauma/sham shock (T/SS) or T/HS (30 mm Hg × 90 min) were administered FTY720 (1 mg/kg) post-T/HS during volume resuscitation. Lung injury (permeability to Evans blue dye), polymorphonuclear leukocyte (PMN) priming (respiratory burst activity), and red blood cell (RBC) rigidity were measured. In addition, lymph duct-cannulated rats were used to quantify the effect of FTY720 on gut injury (permeability and morphology) and the biologic activity of T/HS versus T/SS lymph on PMN-RBC and RBC deformability.

RESULTS

Trauma/hemorrhagic shock-induced increased lung permeability, PMN priming, and RBC rigidity were all abrogated by FTY720. The systemic protective effect of FTY720 was only partially at the gut level, because FTY720 did not prevent T/HS-induced gut injury (morphology or permeability); however, it did abrogate T/HS lymph-induced increased respiratory burst and RBC rigidity.

CONCLUSIONS

FTY720 limited T/HS-induced multiple organ dysfunction syndrome (lung injury, red cell injury, and neutrophil priming) as well as T/HS lymph bioactivity, although it did not limit gut injury.

FTY720, a sphingosine-1 phosphate receptor modulator, improves liver fibrosis in a mouse model by impairing the motility of bone marrow-derived mesenchymal stem cells

FTY720 is a novel immunosuppressant that modulates sphingosine 1-phosphate (S1P) receptors for the treatment of several diseases. Several hallmarks of liver fibrosis are influenced by S1P, and the interference of S1P signaling by treatment with FTY720 results in beneficial effects in various animal models of fibrosis. However, whether these treatment strategies suppress liver fibrosis progression is incompletely understood. Here, we investigated the effects and mechanisms by which FTY720 improves liver fibrosis in the carbon tetrachloride (CCl4)-induced mouse model. FTY720 treatment significantly attenuated the expression of fibrotic markers in the injured liver of both wild-type and SCID-beige mice. The migration of bone marrow-derived mesenchymal stem cells (BMSCs) to circulation, and subsequently the injured liver, was suppressed by FTY720. Furthermore, in vitro, phosphorylated-FTY720 blocked the migration of BMSCs mediated by S1P. Thus, FTY720 is an effective therapy for liver fibrosis via the suppression of BMSC migration in the CCl4-induced mouse model.

Revisiting Cerebral Postischemic Reperfusion Injury: New Insights in Understanding Reperfusion Failure, Hemorrhage, and Edema

Cerebral postischemic reperfusion injury is defined as deterioration of ischemic brain tissue that parallels and antagonizes the benefits of restoring cerebral circulation after therapeutic thrombolysis for acute ischemic stroke. To understand the paradox of injury caused by treatment, we first emphasize the phenomenon in which recanalization of an occluded artery does not lead to tissue reperfusion. Additionally, no-reflow after recanalization may be due to injury of the neurovascular unit, distal microthrombosis, or both, and certainly worsens outcome. We examine the mechanism of molecular and sub-cellular damage in the neurovascular unit, notably oxidative stress, mitochondrial dysfunction, and apoptosis. At the level of the neurovascular unit, which mediates crosstalk between the damaged brain and systemic responses in blood, we summarize emerging evidence demonstrating that individual cell components play unique and cumulative roles that lead to damage of the blood–brain barrier and neurons. Furthermore, we review the latest developments in establishing a link between the immune system and microvascular dysfunction during ischemic reperfusion. Progress in assessing reperfusion injury has also been made, and we review imaging studies using various magnetic resonance imaging modalities. Lastly, we explore potential treatment approaches, including ischemic preconditioning, postconditioning, pharmacologic agents, and hypothermia.

The immunosuppressant FTY720 prolongs survival in a mouse model of diet-induced coronary atherosclerosis and myocardial infarction

FTY720, an analogue of sphingosine-1-phosphate, is cardioprotective during acute injury. Whether long-term FTY720 affords cardioprotection is unknown. Here, we report the effects of oral FTY720 on ischemia/reperfusion injury and in hypomorphic apoE mice deficient in SR-BI receptor expression (ApoeR61(h/h)/SRB1(-/- mice), a model of diet-induced coronary atherosclerosis and heart failure. We added FTY720 (0.3 mg·kg(-1)·d(-1)) to the drinking water of C57BL/6J mice. After ex vivo cardiac ischemia/reperfusion injury, these mice had significantly improved left ventricular (LV) developed pressure and reduced infarct size compared with controls. Subsequently, ApoeR61(h/h)/SRB1(-/-) mice fed a high-fat diet for 4 weeks were treated or not with oral FTY720 (0.05 mg·kg(-1)·d(-1)). This sharply reduced mortality (P < 0.02) and resulted in better LV function and less LV remodeling compared with controls without reducing hypercholesterolemia and atherosclerosis. Oral FTY720 reduced the number of blood lymphocytes and increased the percentage of CD4+Foxp3+ regulatory T cells (Tregs) in the circulation, spleen, and lymph nodes. FTY720-treated mice exhibited increased TGF-β and reduced IFN-γ expression in the heart. Also, CD4 expression was increased and strongly correlated with molecules involved in natural Treg activity, such as TGF-β and GITR. Our data suggest that long-term FTY720 treatment enhances LV function and increases longevity in mice with heart failure. These benefits resulted not from atheroprotection but from systemic immunosuppression and a moderate reduction of inflammation in the heart.

Ischemia-reperfusion injury in stroke

Despite ongoing advances in stroke imaging and treatment, ischemic and hemorrhagic stroke continue to debilitate patients with devastating outcomes at both the personal and societal levels. While the ultimate goal of therapy in ischemic stroke is geared towards restoration of blood flow, even when mitigation of initial tissue hypoxia is successful, exacerbation of tissue injury may occur in the form of cell death, or alternatively, hemorrhagic transformation of reperfused tissue. Animal models have extensively demonstrated the concept of reperfusion injury at the molecular and cellular levels, yet no study has quantified this effect in stroke patients. These preclinical models have also demonstrated the success of a wide array of neuroprotective strategies at lessening the deleterious effects of reperfusion injury. Serial multimodal imaging may provide a framework for developing therapies for reperfusion injury.

FTY720 attenuates hypoxia-reoxygenation-induced apoptosis in cardiomyocytes

FTY720, sphingosine 1 phosphate (S1P) receptor agonist, is a potent immunosuppressive agent. Numerous studies have documented a relationship between S1P and cardioprotection. We therefore hypothesized that a S1P analogue FTY720 would attenuate hypoxia/reoxygenation (H/R) induced cadiomyocyte apoptosis. H9C2 cardiomyocytes were employed to establish an in vitro model of H/R. Cells were treated or not with different doses of FTY720. Cell viability was measured by flow cytometry and TUNEL staining. Western blot was used to analyze downstream signaling pathway. We observed that FTY720 inhibits the expression of cleaved caspase-3 and activates both AKT and ERK1/2 pathways. AKT pathway can be blocked by MEK kinase inhibitor PD98059. ERK1/2 pathway can be blocked by the phosphoinositide-3 kinase inhibitor wortmannin. AKT and ERK1/2 activation can also be inhibited by S1P1/3 receptor antagonist VPC23019, Gi antagonist PTX. The protein levels of TNF-α and IL1ß were upregulated during hypoxia/reoxygenation and were attenuated by FTY720. We conclude that FTY720, via its cargo of S1P, can protect cardiomyocytes against hypoxia/reoxygenation injury. This effect is achieved by inhibiting caspase-3 expression, inflammatory cytokine levels and activating AKT and ERK1/2 signaling pathways. The prosurvival signal activation is dependent on S1P1, 3 subtype receptors and Gi protein.

Isoflurane provides neuroprotection in neonatal hypoxic ischemic brain injury

Isoflurane is a volatile anesthetic that is widely used clinically as an inhalational anesthetic. In recent years, several studies have indicated that isoflurane has neuroprotective properties. This has led to the beneficial effects of isoflurane being analyzed in both cell culture and animal models, including various models of brain injury. Neonatal hypoxia ischemia may be characterized as injury that occurs in the immature brain, resulting in delayed cell death via excitotoxicity and oxidative stress. These adverse events in the developing brain often lead to detrimental neurological defects in the future. Currently, there are no well-established effective therapies for neonatal hypoxia ischemia. In line with this, isoflurane, which displays neuroprotective properties in several paradigms and has been shown to improve neurological deficits caused by brain injuries, has the capability to be an extremely relevant clinical therapy for the resolution of deficits concomitant with neonatal hypoxic ischemic brain injuries. This review therefore seeks to explore and analyze the current information on isoflurane, looking at general isoflurane anesthetic properties, and the protection it confers in different animal models, focusing particularly on neuroprotection as shown in studies with neonatal hypoxic ischemic brain injury.

Sphingosine-1-phosphate acts as a key molecule in the direct mediation of renal fibrosis

The major sphingolipid metabolite, sphingosine‐1‐phosphate (S1P), has important biological functions. S1P serves as a ligand for a family of five G‐protein‐coupled receptors with distinct signaling pathways regulating important biological pathways. S1P induces renal fibrosis through an inflammatory pathway. However, its direct fibrosis‐inducing effect on the kidney has not been shown. The role of S1P as a direct mediator of renal fibrosis was investigated in normal rat kidney interstitial fibroblast (NRK‐49F) cells (in vitro) and kidneys of a unilateral ureteral obstruction (UUO) mouse model (in vivo). To clarify the role of S1P in renal fibrosis, we adopted nude UUO mice with immune response deficits. NRK‐49F cells were stimulated with various concentrations of exogenous S1P and FTY720 (a S1P receptor agonist) or N,N‐dimethylsphingosine (DMS; a sphingosine kinase inhibitor). C57BL6 and nude UUO mice were pretreated with FTY720, DMS, or saline. Expression levels of alpha‐smooth muscle actin (a‐SMA), E‐cadherin, collagen type 1 (COL1), collagen type 4 (COL4), tissue inhibitor of matrix metalloproteinase‐1 (TIMP1), and plasminogen activator inhibitor‐1 (PAI1) were examined. S1P stimulated fibrosis in NRK‐49F cells and UUO mice. Increased a‐SMA, COL1, COL4, TIMP1, and PAI1 and decreased E‐cadherin expression levels were observed in both the S1P‐stimulated cells and UUO mice. Nude UUO mouse kidneys expressed fibrotic markers. Fibrotic changes were successfully induced in both UUO and nude UUO mice, evident through prominent fibronectin and COL1 staining. These S1P‐induced fibrotic changes were suppressed by FTY720 and DMS both in vitro and in vivo. Thus, S1P essentially and directly mediates renal fibrosis.

Sphingosine‐1‐phosphate (S1P) stimulated fibrosis both in vitro and in vivo. Fibrotic changes were successfully induced in both unilateral ureteral obstruction (UUO) and nude mice with UUO. These results suggest that S1P is a pivotal fibrotic mediator in renal fibrosis that acts, in part, through direct fibrotic effects.

Current strategies to minimize hepatic ischemia-reperfusion injury by targeting reactive oxygen species

Ischemia-reperfusion is a major component of injury in vascular occlusion both during liver surgery and during liver transplantation. The pathophysiology of hepatic ischemia-reperfusion includes a number of mechanisms including oxidant stress that contribute to various degrees to the overall organ damage. A large volume of recent research has focused on the use of antioxidants to ameliorate this injury, although results in experimental models have not translated well to the clinic. This review focuses on critical sources and mediators of oxidative stress during hepatic ischemia-reperfusion, the status of current antioxidant interventions, and emerging mechanisms of protection by preconditioning. While recent advances in regulation of antioxidant systems by Nrf2 provide interesting new potential therapeutic targets, an increased focus must be placed on more in-depth mechanistic investigations in hepatic ischemia-reperfusion injury and translational research in order to refine current strategies in disease management.

Oral FTY720 administration induces immune tolerance and inhibits early development of atherosclerosis in apolipoprotein E-deficient mice

Orally administered immunomodulatory drugs have recently demonstrated the ability to induce an oral tolerance via inhibition of effector T cells and induction of certain subsets of regulatory T cells (Tregs) which have the potential to prevent several autoimmune diseases. In the present study, we hypothesized that short-term, low-dose, oral FTY720 administration may induce latency-associated peptide (LAP) Tregs and CD4(+) Foxp3(+) Tregs in atherogenesis, potentially resulting in remission of early development of atherosclerosis in apolipoprotein E-deficient (APOE(-/-)) mice. FTY720 was orally administered to APOE(-/-) mice 4 weeks of age on a high-cholesterol diet and atherosclerosis was assessed at 8 weeks of age. Oral administration of FTY720 significantly reduced atherosclerotic lesion formation compared with control mice. We observed a significant increase in LAP(+) and Foxp3(+) cells in the CD4+T-cell population of FTY720-treated mice in association with increased production of the anti-inflammatory cytokine transforming growth factor-β (TGF-β) as well as suppressed T-helper type 1 immune responses. Our findings reveal that short-term, low-dose oral FTY720 treatment had great benefits in inhibiting early development of atherosclerosis in mice via induction of a regulatory T-cell response and inhibition of effector T responses. These findings suggest that oral immune modulation may represent an attractive therapeutic approach to atherosclerosis.

FTY720 suppresses liver tumor metastasis by reducing the population of circulating endothelial progenitor cells

BACKGROUND

Surgical procedures such as liver resection and liver transplantation are the first-line treatments for hepatocellular carcinoma (HCC) patients. However, the high incidence of tumor recurrence and metastasis after liver surgery remains a major problem. Recent studies have shown that hepatic ischemia-reperfusion (I/R) injury and endothelial progenitor cells (EPCs) contribute to tumor growth and metastasis. We aim to investigate the mechanism of FTY720, which was originally applied as an immunomodulator, on suppression of liver tumor metastasis after liver resection and partial hepatic I/R injury.

METHODOLOGY/PRINCIPAL FINDINGS

An orthotopic liver tumor model in Buffalo rat was established using the hepatocellular carcinoma cell line McA-RH7777. Two weeks after orthotopic liver tumor implantation, the rats underwent liver resection for tumor-bearing lobe and partial hepatic I/R injury. FTY720 (2 mg/kg) was administered through the inferior caval vein before and after I/R injury. Blood samples were taken at days 0, 1, 3, 7, 14, 21 and 28 for detection of circulating EPCs (CD133+CD34+). Our results showed that intrahepatic and lung metastases were significantly inhibited together with less tumor angiogenesis by FTY720 treatment. The number of circulating EPCs was also significantly decreased by FTY720 treatment from day 7 to day 28. Hepatic gene expressions of CXCL10, VEGF, CXCR3, CXCR4 induced by hepatic I/R injury were down-regulated in the treatment group.

CONCLUSIONS/SIGNIFICANCE

FTY720 suppressed liver tumor metastasis after liver resection marred by hepatic I/R injury in a rat liver tumor model by attenuating hepatic I/R injury and reducing circulating EPCs.

The role of proline rich tyrosine kinase 2 (Pyk2) on cisplatin resistance in hepatocellular carcinoma

Aims

We previously demonstrated Proline rich tyrosine kinase 2 (Pyk2) plays important roles in regulating tumor progression, migration and invasion in hepatocellular carcinoma (HCC). In this study, we aimed to examine the role of proline rich tyrosine kinase 2 (Pyk2) on cisplatin resistance in HCC and to explore its underlying molecular mechanism.

Methodology/Principal Findings

Stable transfectants either overexpressing or suppressing Pyk2 were established in different HCC cell lines. MTT, colony formation and Annexin-V assays were employed to examine their in vitro responses to cisplatin. Xenograft ectopic and orthotopic nude mice models were generated to investigate the in vivo responses of them to cisplatin treatment. cDNA microarray was performed to identify Pyk2-induced genes which were further validated by quantitative real-time RT-PCR using clinical HCC samples. In vitro functional study demonstrated that Pyk2-overexpressing HCC transfectants exhibited relatively lower cytotoxicity, higher colony-forming ability and lower apoptosis to cisplatin compared with the control transfectants. Moreover, Pyk2 overexpressing HCC transfectants had a higher survival rate under cisplatin treatment by up-regulation of AKT phosphorylation. In vivo xenograft nude mice model demonstrated that Pyk2-overexpressing transfectants developed higher tolerance to cisplatin treatment together with less tumor necrosis and apoptosis. cDNA microarray analysis revealed that there were more than 4,000 genes differentially expressed upon overexpression of Pyk2. Several upregulated genes were found to be involved in drug resistance and invasion in cancers. Among them, the expression profiles of MDR1, GAGE1, STAT1 and MAP7 were significantly associated with the expression of Pyk2 in clinical HCC samples.

Conclusions

Our results may suggest a new evidence of Pyk2 on promoting cisplatin resistance of HCC cells through preventing cell apoptosis, activation of AKT pathway and upregulation of drug resistant genes.

Role of early growth response 1 in liver injury

Liver injury is a sophisticated pathophysiological process caused by many factors. Currently, the role of early growth response 1 (EGR1) in liver injury is still controversial. Some studies show that EGR1 can amplify the systemic inflammatory response and promote apoptosis in galactosamine/lipopolysaccharide-induced acute liver injury and alpha-naphthylisothiocyanate (ANIT)-induced intrahepatic cholestasis as well as other non-liver injuries, while some other studies indicate that EGR1 protects the liver from CCl₄ exposure by regulating the expression of inducible nitric oxide synthase, cyclooxygenase-2, and tumor necrosis factor-α-regulated genes that have hepatoprotective function.

Enhancement of neoangiogenesis and follicle survival by sphingosine-1-phosphate in human ovarian tissue xenotransplants

Ovarian transplantation is one of the key approaches to restoring fertility in women who became menopausal as a result of cancer treatments. A major limitation of human ovarian transplants is massive follicular loss during revascularization. Here we investigated whether sphingosine-1-phosphate or its receptor agonists could enhance neoangiogenesis and follicle survival in ovarian transplants in a xenograft model. Human ovarian tissue xenografts in severe-combined-immunodeficient mice were treated with sphingosine-1-phosphate, its analogs, or vehicle for 1–10 days. We found that sphingosine-1-phosphate treatment increased vascular density in ovarian transplants significantly whereas FTY720 and SEW2871 had the opposite effect. In addition, sphingosine-1-phosphate accelerated the angiogenic process compared to vehicle-treated controls. Furthermore, sphingosine-1-phosphate treatment was associated with a significant proliferation of ovarian stromal cell as well as reduced necrosis and tissue hypoxia compared to the vehicle-treated controls. This resulted in a significantly lower percentage of apoptotic follicles in sphingosine-1-phosphate-treated transplants. We conclude that while sphingosine-1-phosphate promotes neoangiogenesis in ovarian transplants and reduces ischemic reperfusion injury, sphingosine-1-phosphate receptor agonists appear to functionally antagonize this process. Sphingosine-1-phosphate holds great promise to clinically enhance the survival and longevity of human autologous ovarian transplants.

In vivo lipid profiling using proton magnetic resonance spectroscopy in an experimental liver fibrosis model

RATIONALE AND OBJECTIVES

The aim of this study was to characterize early hepatic lipid changes in an experimental model of liver fibrosis using proton ((1)H) magnetic resonance spectroscopy (MRS) at high magnetic field in vivo.

MATERIALS AND METHODS

Liver fibrosis was induced in 12 Sprague-Dawley rats by twice-weekly carbon tetrachloride (CCl(4)) administration up to 4 weeks. Eight normal rats were used as controls. Single-voxel (1)H MRS experiments were performed at 7 Tesla to measure signal integrals of various lipid peaks including -CH(3), (-CH(2)-)(n), -CH(2)-C=C-CH(2)-, =C-CH(2)-C= and -CH=CH- at 0.9, 1.3, 2.0, 2.8, and 5.3 ppm, respectively, and peak from choline-containing compounds (CCC) at 3.2 ppm. Total lipid, total saturated fatty acid, total unsaturated fatty acid, total unsaturated bond, polyunsaturated bond, and CCC indices were quantified.

RESULTS

Significant increases (P < .01) in total lipid and total saturated fatty acid indices were found in animals with CCl(4)-induced fibrosis as compared with normal animals. In addition, total unsaturated bond and polyunsaturated bond indices of animals at 4 weeks after CCl(4) insult were significantly higher than (P < .01 and P < .05, respectively) those of normal animals and animals at 2 weeks following insult; whereas there was only significant increase (P < .01) in total unsaturated fatty acid index in animals with 4-week CCl(4) insult as compared with normal animals.

CONCLUSION

The hepatic lipid changes in CCl(4)-induced experimental fibrosis model were documented in vivo and longitudinally using (1)H MRS at 7 Tesla. The experimental findings suggested that total saturated fatty acid increase contributed mainly to the total lipid increase in animals with CCl(4) insult. This study also demonstrated the potential value of high field MRS to resolve lipid composition and alterations in liver fibrosis.

Diffusion tensor imaging of liver fibrosis in an experimental model

PURPOSE

To characterize changes in diffusion properties of liver using diffusion tensor imaging (DTI) in an experimental model of liver fibrosis.

MATERIALS AND METHODS

Liver fibrosis was induced in Sprague-Dawley rats (n = 12) by repetitive dosing of carbon tetrachloride (CCl(4)). The animals were examined with a respiratory-gated single-shot spin-echo echo-planar DTI protocol at 7 T before, 2 weeks after, and 4 weeks after CCl(4) insult. Apparent diffusion coefficient (ADC), directional diffusivities (ADC(//) and ADC(⊥)), and fractional anisotropy (FA) were measured. Liver histology was performed with hematoxylin-eosin staining and Masson's trichrome staining.

RESULTS

Significant decrease (P < 0.01) in ADC was found at 2 weeks (0.86 ± 0.09 × 10(-3) mm(2)/s) and 4 weeks (0.74 ± 0.09 × 10(-3) mm(2)/s) following CCl(4) insult, as compared with that before insult (0.97 ± 0.08 × 10(-3) mm(2)/s). Meanwhile, FA at 2 weeks (0.18 ± 0.03) after CCl(4) insult was significantly lower (P < 0.01) than that before insult (0.26 ± 0.05), and subsequently normalized at 4 weeks (0.26 ± 0.07) after the insult. Histology showed collagen deposition, presence of intracellular fat vacuoles, and cell necrosis/apoptosis in livers with CCl(4) insult.

CONCLUSION

DTI detected the progressive changes in water diffusivities and diffusion anisotropy of liver tissue in this liver fibrosis model. ADC and FA are potentially valuable in detecting liver fibrosis at early stages and monitoring its progression. Future human studies are warranted to further verify the applicability of DTI in characterizing liver fibrosis and to determine its role in clinical settings.

Identification of liver proteins and their roles associated with carbon tetrachloride-induced hepatotoxicity

Carbon tetrachloride (CCl(4)) is a common hepatotoxin used in experimental models to elicit liver injury. To identify the proteins involved in CCl(4)-induced hepatotoxicity, two-dimensional gel electrophoresis was employed followed by mass spectrometry - mass spectrometry (MS/MS) to study the differentially expressed proteins during CCl(4) exposure in the Fischer 344 rat liver proteome for 5 weeks. Ten spots with notable changes between the Control and CCl(4) groups were successfully identified. Among them, four proteins with significant up-regulation, namely calcium-binding protein 1, protein disulfide isomerase, mitochondrial aldehyde dehydrogenase precursor, and, glutathione-S-transferase mu1 and six proteins with significant down-regulation, namely catechol-O-methyltransferase, hemoglobin-alpha-2-chain, hemopexin precursor, methionine sulfoxide reductase A, catalase and carbonic anhydrase 3, were identified. The data indicates that CCl(4) causes hepatotoxicity by depleting oxygen radical scavengers in the hepatocytes. In this rat model, we profiled hepatic proteome alterations in response to CCl(4) intoxication. The findings should facilitate understanding of the mechanism of CCl(4)-induced liver injury.

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.

Sphinganine-1-phosphate protects kidney and liver after hepatic ischemia and reperfusion in mice through S1P1 receptor activation

Liver failure due to ischemia and reperfusion (IR) and subsequent acute kidney injury are significant clinical problems. We showed previously that liver IR selectively reduced plasma sphinganine-1-phosphate levels without affecting sphingosine-1-phosphate (S1P) levels. Furthermore, exogenous sphinganine-1-phosphate protected against both liver and kidney injury induced by liver IR. In this study, we elucidated the signaling mechanisms of sphinganine-1-phosphate-mediated renal and hepatic protection. A selective S1P(1) receptor antagonist blocked the hepatic and renal protective effects of sphinganine-1-phosphate, whereas a selective S1P(2) or S1P(3) receptor antagonist was without effect. Moreover, a selective S1P(1) receptor agonist, SEW-2871, provided similar degree of liver and kidney protection compared with sphinganine-1-phosphate. Furthermore, in vivo gene knockdown of S1P(1) receptors with small interfering RNA abolished the hepatic and renal protective effects of sphinganine-1-phosphate. In contrast to sphinganine-1-phosphate, S1P's hepatic protection was enhanced with an S1P(3) receptor antagonist. Inhibition of extracellular signal-regulated kinase, Akt or pertussis toxin-sensitive G-proteins blocked sphinganine-1-phosphate-mediated liver and kidney protection in vivo. Taken together, our results show that sphinganine-1-phosphate provided renal and hepatic protection after liver IR injury in mice through selective activation of S1P(1) receptors and pertussis toxin-sensitive G-proteins with subsequent activation of ERK and Akt.

Sirolimus attenuates reduced-size liver ischemia-reperfusion injury but impairs liver regeneration in rats

BACKGROUND

Evidence has suggested that immunosuppressive drugs impact ischemia-reperfusion injury.

AIMS

The purpose of the present study was to evaluate the effect of sirolimus on hepatic injury and regeneration in a rat reduced-size liver ischemia-reperfusion model.

METHODS

Using a newly developed rat reduced-size liver ischemia-reperfusion injury model, the effects of sirolimus were evaluated by assessing liver cell apoptosis and aspartate aminotransferase, myeloperoxidase, and malondialdehyde levels. In addition, liver regeneration after sirolimus treatment was evaluated by measuring liver weight resumption and by the histological examination of bromodeoxyuridine and proliferating cell nuclear antigen expression.

RESULTS

Sirolimus significantly decreased liver cell apoptosis as well as tissue myeloperoxidase and malondialdehyde levels, but impaired postischemic liver regeneration. Ischemia-reperfusion-induced elevation of aspartate aminotransferase serum levels was significantly decreased by sirolimus.

CONCLUSIONS

Despite an impairment of postischemic liver proliferation, sirolimus demonstrated beneficial amelioration of ischemia-reperfusion-induced liver injury in a reduced-size liver model in rats.

Distinct mechanism of small-for-size fatty liver graft injury--Wnt4 signaling activates hepatic stellate cells

In this study, we aimed to investigate the significance of hepatic stellate cells (HSCs) activation in small-for-size fatty liver graft injury and to explore the underlying molecular mechanism in a rat liver transplantation model. A rat orthotopic liver transplantation model using fatty grafts (40% of fatty changes) and cirrhotic recipients was applied. Intragraft gene expression profiles, ultrastructure features and HSCs activation were compared among the rats received different types of grafts (whole vs. small-for-size, normal vs. fatty). The distinct molecular signature of small-for-size fatty graft injury was identified by cDNA microarray screening and confirmed by RT-PCR detection. In vitro functional studies were further conducted to investigate the direct effect of specific molecular signature on HSCs activation. HSCs activation was predominantly present in small-for-size fatty grafts during the first 2 weeks after transplantation, and was strongly correlated with progressive hepatic sinusoidal damage and significant upregulation of intragraft Wnt4 signaling pathway. In vitro suppression of Wnt4 expression could inhibit HSC activation directly. In conclusion, upregulation of Wnt4 signaling led to direct HSC activation and subsequently induced small-for-size fatty liver grafts injury. Discovery of this distinct mechanism may lay the foundation for prophylactic treatment for marginal graft injury in living donor liver transplantation.

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.

Protective effects of early CD4(+) T cell reduction in hepatic ischemia/reperfusion injury

AIM

CD4(+) T cells contribute to disturbances of liver microcirculation after warm ischemia/reperfusion (I/R). The aim of this study was to investigate a possible protective role of FTY720 (Sphingosine-1 phosphate receptor agonist) in this setting.

MATERIAL AND METHODS

In an in vivo model (42 Wistar rats), ischemia of the left liver lobe was induced for 90 min under anesthesia with xylazine/ketanest. Sham-operated untreated ischemic and treatment group with FTY720 (1 mg/kg body weight intravenous) were investigated. The effect of FTY on I/R injury was assessed by in vivo microscopy 30-90 min after reperfusion (perfusion rate, vessel diameter, leukocyte-endothelial cell interactions, T cell infiltration), by measurement of serum aspartate aminotransferase (AST), alanine aminotransferase (ALT), reverse transcription-polymerase chain reaction (RT-PCR) of interleukin (IL)-2, IL-6, IL-10, TNF-alpha, toll-like receptor 4 (TLR-4), and by histological investigation.

RESULTS

After 30 min of reperfusion, the number of T cells in sinusoids was increased four-fold. In the FTY group, the number of T cells was reduced to an half of the number of the ischemia group. Likewise, the number of adherent leukocytes in sinusoids (150.8 +/- 10.9% of s.o.) was reduced in the treatment group (117.3 +/- 12.2%; p < 0.05 vs ischemia), leading to an improvement in perfusion rate in this group (85.0 +/- 4.6% of sham group) compared to nontreated animals (57.5 +/- 10.8%; p < 0.05). According to improved microcirculation, AST/ALT values and histological tissue damage were reduced in the therapy group. RT-PCR revealed an increased expression of IL-2, IL-6, and TLR-4 in the nontreated ischemic group. This expression was clearly reduced in the treatment group.

CONCLUSION

In conclusion, FTY720 ameliorates the microcirculatory, biochemical, and histological manifestations of hepatic I/R injury by preventing T cell infiltration. These results indicate that T cells are pivotal mediators in hepatic I/R and may have important implications early after liver transplantation and in warm ischemia.

The immunomodulatory sphingosine 1-phosphate analog FTY720 reduces lesion size and improves neurological outcome in a mouse model of cerebral ischemia

Cerebral ischemia is accompanied by fulminant cellular and humoral inflammatory changes in the brain which contribute to lesion development after stroke. A tight interplay between the brain and the peripheral immune system leads to a biphasic immune response to stroke consisting of an early activation of peripheral immune cells with massive production of proinflammatory cytokines followed by a systemic immunosuppression within days of cerebral ischemia that is characterized by massive immune cell loss in spleen and thymus. Recent work has documented the importance of T lymphocytes in the early exacerbation of ischemic injury. The lipid signaling mediator sphingosine 1-phosphate-derived stable analog FTY720 (fingolimod) acts as an immunosuppressant and induces lymphopenia by preventing the egress of lymphocytes, especially T cells, from lymph nodes. We found that treatment with FTY720 (1mg/kg) reduced lesion size and improved neurological function after experimental stroke in mice, decreased the numbers of infiltrating neutrophils, activated microglia/macrophages in the ischemic lesion and reduced immunohistochemical features of apoptotic cell death in the lesion.

Heme oxygenase-1 contributes to an alternative macrophage activation profile induced by apoptotic cell supernatants

Apoptotic cells (AC) are rapidly engulfed by professional phagocytes such as macrophages to avoid secondary necrosis and thus inflammation. Recognition of AC polarizes macrophages toward an anti-inflammatory phenotype, which shows homology to an alternatively activated M2 macrophage. However, mechanistic details provoking these phenotype alterations are incompletely understood. Here, we demonstrate a biphasic up-regulation of heme oxygenase-1 (HO-1), a protein that bears an antiapoptotic as well as an anti-inflammatory potential, in primary human macrophages, which were exposed to the supernatant of AC. Although the first phase of HO-1 induction at 6 h was accomplished by AC-derived sphingosine-1-phosphate (S1P) acting via S1P receptor 1, the second wave of HO-1 induction at 24 h was attributed to autocrine signaling of vascular endothelial growth factor A (VEGFA), whose expression and release were facilitated by S1P. Whereas VEGFA release from macrophages was signal transducer and activator of transcription (STAT) 1-dependent, vascular endothelial growth factor itself triggered STAT1/STAT3 heterodimer formation, which bound to and activated the HO-1 promoter. Knockdown of HO-1 proved its relevance in facilitating enhanced expression of the antiapoptotic proteins Bcl-2 and Bcl-X(L), as well as the anti-inflammatory adenosine receptor A(2A). These findings suggest that HO-1, which is induced by AC-derived S1P, is critically involved in macrophage polarization toward an M2 phenotype.

Divergent roles of sphingosine kinases in kidney ischemia-reperfusion injury

Sphingosine-1-phosphate (S1P), produced by sphingosine kinase 1 (SphK1) or kinase 2 (SphK2), mediates biological effects through intracellular and/or extracellular mechanisms. Here we determined a role for these kinases in kidney injury of wild-type mice following ischemia-reperfusion. SphK1 but not SphK2 mRNA expression and activity increased in the kidney following injury relative to sham-operated animals. Although SphK1(-/-) mice had no alteration in renal function following injury, mice with a disrupted SphK2 gene (SphK2(tr/tr)) had histological damage and impaired function. The immune-modulating pro-drug, FTY720, an S1P agonist failed to provide protection in SphK2(tr/tr) mice. Injured kidneys of these mice showed increased neutrophil infiltration and neutrophil chemokine expression along with a 3- to 5-fold increase in expression of the G-protein-coupled receptor S1P(3) compared to heterozygous SphK2(+/tr) mice. Kidney function and reduced vascular permeability were preserved in S1P(3)(-/-) compared to S1P(3)(+/-) mice after ischemia-reperfusion injury, suggesting increased S1P(3) mRNA may play a role in the injury of SphK2(tr/tr) mice. Our study suggests that constitutive expression of SphK2 may contribute to reduced ischemia-reperfusion injury of the kidney, and its absence may enhance injury due to increased neutrophil infiltration and S1P(3) activation. We also confirm that SphK2 is necessary to mediate the protective effects of FTY720.

Proline-rich tyrosine kinase 2 (Pyk2) promotes proliferation and invasiveness of hepatocellular carcinoma cells through c-Src/ERK activation

The aim of the current study is to elucidate the mechanism of proline-rich tyrosine kinase 2 (Pyk2)-mediated cell proliferation and invasiveness in hepatocellular carcinoma (HCC) cells. Human HCC cell lines PLC and MHCC97L were stably transfected with either full-length Pyk2 or C-terminal non-kinase region of Pyk2 (PRNK). Functional studies on cell proliferation and invasion were conducted in vitro by colony formation assay, adhesion assay, migration assay and wound-healing assay. For the in vivo study, an orthotopic nude mice liver tumor model was applied to investigate the effects of Pyk2 overexpression on tumor growth and metastasis. Overexpression of Pyk2 in PLC cells resulted in an upregulation of colony formation (P = 0.021) and adhesion toward laminin (P = 0.018). Pyk2 promoted wound recovery by stimulation of actin stress fiber polymerization. In the in vivo study, transfection of PRNK in MHCC97L cells significantly decreased tumor volume (P = 0.001) and the incidence of lung metastasis (P = 0.014). Overexpression of Pyk2 promoted the activation of c-Src, formation of Pyk2/c-Src complex and activated the extracellular signal-regulated kinase (ERK)/mitogen-activated protein kinase (MAPK)-signaling pathway. Pyk2 upregulated the activation of ERK1/2 that is insensitive to MAPK/ERK kinase (MEK)1/2 inhibition. On the contrary, PRNK overexpression downregulated the activation of c-Src and ERK/MAPK-signaling pathways. Immunofluorescence staining showed that the focal adhesion localization of Pyk2 is a major determinant for c-Src and ERK/MAPK activation. In conclusion, our results showed that Pyk2 promoted cell proliferation and invasiveness by upregulation of the c-Src and ERK/MAPK-signaling pathways.

Sphingosine-1-phosphate reduces CD4+ T-cell activation in type 1 diabetes through regulation of hypoxia-inducible factor short isoform I.1 and CD69

OBJECTIVES

Non-obese diabetic (NOD) mice develop spontaneous type 1 diabetes. We have shown that sphingosine-1-phosphate (S1P) reduces activation of NOD diabetic endothelium via the S1P1 receptor. In the current study, we tested the hypothesis that S1P could inhibit CD4(+) T-cell activation, further reducing inflammatory events associated with diabetes.

RESEARCH DESIGN AND METHODS

CD4(+) T-cells were isolated from diabetic and nondiabetic NOD mouse splenocytes and treated in the absence or presence of S1P or the S1P1 receptor-specific agonist, SEW2871. Lymphocyte activation was examined using flow cytometry, cytokine bead assays, and a lymphocyte:endothelial adhesion assay.

RESULTS

Diabetic T-cells secreted twofold more gamma-interferon (IFN-gamma) and interleukin-17 than nondiabetic lymphocytes. Pretreatment with either S1P or SEW2871 significantly reduced cytokine secretion by approximately 50%. Flow cytometry analysis showed increased expression of CD69, a marker of lymphocyte activation, on diabetic T-cells. Both S1P and SEW2871 prevented upregulation of CD69 on CD4(+) cells. Quantitative RT-PCR showed that lymphocytes from diabetic NOD mice had 2.5-fold lower hypoxia-inducible factor (HIF)-1alpha short isoform I.1 (HIF1alphaI.1) mRNA levels than control. HIF1alphaI.1 is a negative regulator of lymphocyte activation. S1P significantly increased HIF1alpha I.1 mRNA levels in both control and diabetic groups. IFN-gamma production and surface CD69 expression was significantly increased in lymphocytes of HIF1alphaI.1-deficient mice. S1P did not reduce either CD69 or IFN-gamma expression in lymphocytes from HIF1alphaI.1-deficient mice.

CONCLUSIONS

S1P acts through the S1P1 receptor and HIF1alpha I.1 to negatively regulate T-cell activation, providing a potential therapeutic target for prevention of diabetes and its vascular complications.

Ischemia-reperfusion of small liver remnant promotes liver tumor growth and metastases--activation of cell invasion and migration pathways

Elucidating the mechanism of liver tumor growth and metastasis after hepatic ischemia-reperfusion (I/R) injury of a small liver remnant will lay the foundation for the development of therapeutic strategies to target small liver remnant injury, and will reduce the likelihood of tumor recurrence after major hepatectomy or liver transplantation for liver cancer patients. In the current study, we aimed to investigate the effect of hepatic I/R injury of a small liver remnant on liver tumor development and metastases, and to explore the precise molecular mechanisms. A rat liver tumor model that underwent partial hepatic I/R injury with or without major hepatectomy was investigated. Liver tumor growth and metastases were compared among the groups with different surgical stress. An orthotopic liver tumor nude mice model was used to further confirm the invasiveness of the tumor cells from the above rat liver tumor model. Significant tumor growth and intrahepatic metastasis (5 of 6 vs. 0 of 6, P=0.015), and lung metastasis (5 of 6 vs. 0 of 6, P=0.015) were found in rats undergoing I/R and major hepatectomy compared with the control group, and was accompanied by upregulation of mRNA levels for Cdc42, ROCK (Rho kinase), and vascular endothelial growth factor, as well as activation of hepatic stellate cells. Most of the nude mice implanted with liver tumor from rats under I/R injury and major hepatectomy developed intrahepatic and lung metastases. In conclusion, hepatic I/R injury of a small liver remnant exacerbated liver tumor growth and metastasis by marked activation of cell adhesion, invasion, and angiogenesis pathways.