LASSO regression shows histidine and sphingosine 1 phosphate are linked to both sepsis mortality and endothelial damage.

Sepsis is a major cause of death worldwide, with a mortality rate that has remained stubbornly high. The current gold standard of risk stratifying sepsis patients provides limited mechanistic insight for therapeutic targeting. An improved ability to predict sepsis mortality and to understand the risk factors would allow better treatment targeting. Sepsis causes metabolic dysregulation in patients; therefore, metabolomics offers a promising tool to study sepsis. It is also known that that in sepsis endothelial cells affecting their function regarding blood clotting and vascular permeability. We integrated metabolomics data from patients admitted to an intensive care unit for sepsis, with commonly collected clinical features of their cases and two measures of endothelial function relevant to blood vessel function, platelet endothelial cell adhesion molecule and soluble thrombomodulin concentrations in plasma. We used least absolute shrinkage and selection operator penalized regression, and pathway enrichment analysis to identify features most able to predict 30-day survival. The features important to sepsis survival include carnitines, and amino acids. Endothelial proteins in plasma also predict 30-day mortality and the levels of these proteins also correlate with a somewhat overlapping set of metabolites. Overall metabolic dysregulation, particularly in endothelial cells, may be a contributory factor to sepsis response. By exploring sepsis metabolomics data in conjunction with clinical features and endothelial proteins we have gained a better understanding of sepsis risk factors.

SKI-349, a Sphingosine Kinases 1/2 Inhibitor, Suppresses Cell Viability, Invasion, and AKT/mTOR Signaling Pathway, and Shows Synergistic Cytotoxic Effects with Sorafenib in Hepatocellular Carcinoma.

SKI-349 is a novel sphingosine kinases (SPHK) inhibitor with anti-tumor effects. This study aimed to assess the effect of SKI-349 on cell biological behaviors, downstream pathways, and its synergistic effect with sorafenib in hepatocellular carcinoma (HCC). HCC cell lines (Huh7 and Hep3B) were treated with SKI-349 at concentrations of 1, 2, 4, or 8 µM. Then, SPHK1/2 activity, cell viability, proliferation, apoptosis, invasion, and protein expressions of phosphorylated-protein kinase B (p-AKT), AKT, phosphorylated-mammalian target of rapamycin (p-mTOR) and mTOR were detected. Combination index values of SKI-349 (0, 1, 2, 4, or 8 µM) and sorafenib (0, 2.5, 5, 10, or 20 µM) were calculated. SKI-349 decreased the relative SPHK1 and SPHK2 activity compared with blank control in a dose-dependent manner in the Huh7 and Hep3B cell lines. Meanwhile, SKI-349 reduced cell viability, 5-ethynyl-2'-deoxyuridine (EdU) positive cells, and invasive cells, while it increased apoptotic cells compared to blank control in a dose-dependent manner in Huh7 and Hep3B cell lines. Based on the western blot assay, SKI-349 decreased the ratio of p-AKT to AKT and that of p-mTOR to mTOR compared with blank control in a dose-dependent manner in the Huh7 and Hep3B cell lines. Additionally, SKI-349 combined with sorafenib declined cell viability with concentration gradient effects compared to SKI-349 sole treatment, and they had synergistic cytotoxic effects in Huh7 and Hep3B cell lines. SKI-349 suppresses SPHK1 and SPHK2 activity, cell viability, invasion, and AKT/mTOR signaling pathway, as well as exhibits a synergistic cytotoxic effect with sorafenib in HCC.

Blocking sphingosine 1-phosphate receptor 1 with modulators reduces immune cells infiltration and alleviates endometriosis in mice.

RESEARCH QUESTION: Do sphingosine 1-phosphate (S1P) modulators have therapeutic effects on endometriosis in mice and, if they do, which receptor is responsible for these effects? DESIGN: A surgically induced endometriosis mouse model was established. In the pilot experiment, lesions were harvested to assess fibrosis and inflammation and determine the optimal concentration of a broad-spectrum S1P modulator, FTY720. Subsequently, FTY720 was compared with a selective S1P receptor 1 modulator, SEW2871 to evaluate their effects on endometriotic lesion growth, fibrosis, inflammation and immune cell infiltration. RESULTS: The results demonstrated that both FTY720 and SEW2871, two S1P receptor modulators, effectively inhibited the growth and fibrosis of endometriotic lesions. SEW2871 inhibited inflammation-related cytokine expression, including PTGS-2, IL-1ß, TNF-α and TGF-ß1, more effectively compared with FTY720. Lymphopaenia was mainly caused by FTY720, whereas SEW2871 had a lesser effect. Both FTY720 and SEW2871 significantly reduced CD45+ cells (P = 0.002 and P = 0.032, respectively) and F4/80+ cells (P < 0.001 and P = 0.004, respectively) infiltration into the lesions, with FTY720 exerting a strong regulatory effect on CD4+ T cells. CONCLUSIONS: This study suggests that S1P receptor 1 could be investigated as a potential novel therapeutic target for endometriosis in the future.

A Preliminary Study of Pharmacokinetics and Pharmacodynamics of Oral Fingolimod in Dogs.

BACKGROUND/AIM: Fingolimod is a sphingosine-1-phosphate receptor modulator that prevents lymphocytes egress from lymphoid organs. It has been used as a disease-modifying drug for human multiple sclerosis and has shown better therapeutic effects than other conventional therapies. Therefore, this study was performed to obtain preclinical data of fingolimod in dogs. MATERIALS AND METHODS: Nine laboratory Beagle dogs were used and randomized into three groups for pharmacokinetics (PK) and pharmacodynamics (PD). The dogs were administered once with a low-dose (0.01 mg/kg, n=3), medium-dose (0.05 mg/kg, n=3), and high-dose (0.1 mg/kg, n=3) of fingolimod, orally. Samples were collected serially at predetermined time points, and whole blood fingolimod concentrations were measured using high-performance liquid chromatography-mass spectrometry. Differential counts of leukocytes over time were determined to identify immune cells' response to fingolimod. RESULTS: Regarding PK, the concentration of fingolimod in the blood increased in a dose-dependent manner, but it was not proportional. Regarding PD, the number of lymphocytes significantly decreased compared to baseline in all dose groups (low-dose, p=0.0002; medium-dose, p<0.0001; high-dose, p=0.0012). Eosinophils were significantly reduced in low- (p=0.0006) and medium- (p=0.0006) doses, and neutrophils were also significantly reduced in medium-(p=0.0345) and high- (p=0.0016) doses. CONCLUSION: This study provides the basis for future clinical applications of fingolimod in dogs with immune-mediated diseases, such as meningoencephalitis of unknown etiology.

Sphingosine-1-Phosphate Receptor 4 Attenuates Neutrophilic Airway Inflammation in Experimental Asthma via Repressing Proinflammatory Macrophage Activation.

Patients with eosinophilic asthma react well to conventional treatment of asthma while individualized therapy for non-eosinophilic endotypes have yet to be developed. Dysregulated sphingosine metabolites are associated with the pathophysiology of different asthma endotypes with their receptors involved. However, whether the sphingosine-1-phosphate receptor 4 (S1PR4) contributes to disease progression of asthma remains underappreciated. In this study, we demonstrated that sphingosine metabolism was disturbed in asthma while it could not be used to distinguish between different endotypes of asthma. S1PR4, a vital receptor of bioactive sphingosine metabolites and mainly expressed in macrophages, exhibited lower expression both in patients and experimental mice with neutrophilic airway inflammation. Additionally, S1pr4 deficiency aggravated the OVA/LPS-induced pulmonary inflammation in mice along with a significant up-regulation in M1 macrophage activation. Mechanistic studies showed that S1PR4 was strongly connected to bioactive oxylipins concurrent with bounding to formyl peptide receptor 2 to influence the phosphorylation of JNK and contributed to the macrophage M1 program, which in turn secreted amounts of inflammatory cytokines associated to the inflammatory response of neutrophilic asthma. Furthermore, treating mice with S1PR4 agonist CYM50308 was characterized by less pulmonary inflammatory infiltration. Our research indicates S1PR4 a promising therapeutic target for non-eosinophilic phenotypes of asthma.

Unveiling the biological role of sphingosine-1-phosphate receptor modulators in inflammatory bowel diseases.

Inflammatory bowel disease (IBD) is chronic inflammation of the gastrointestinal tract that has a high epidemiological prevalence worldwide. The increasing disease burden worldwide, lack of response to current biologic therapeutics, and treatment-related immunogenicity have led to major concerns regarding the clinical management of IBD patients and treatment efficacy. Understanding disease pathogenesis and disease-related molecular mechanisms is the most important goal in developing new and effective therapeutics. Sphingosine-1-phosphate (S1P) receptor (S1PR) modulators form a class of oral small molecule drugs currently in clinical development for IBD have shown promising effects on disease improvement. S1P is a sphingosine-derived phospholipid that acts by binding to its receptor S1PR and is involved in the regulation of several biological processes including cell survival, differentiation, migration, proliferation, immune response, and lymphocyte trafficking. T lymphocytes play an important role in regulating inflammatory responses. In inflamed IBD tissue, an imbalance between T helper (Th) and regulatory T lymphocytes and Th cytokine levels was found. The S1P/S1PR signaling axis and metabolism have been linked to inflammatory responses in IBD. S1P modulators targeting S1PRs and S1P metabolism have been developed and shown to regulate inflammatory responses by affecting lymphocyte trafficking, lymphocyte number, lymphocyte activity, cytokine production, and contributing to gut barrier function.

The role of serum sphingolipids as potential biomarkers of non-response to direct acting antiviral therapy in chronic hepatitis C virus infection.

Elimination strategies of chronic hepatitis C virus (HCV) infection aim to optimize the high antiviral potency of direct-acting antivirals (DAAs). Sphingolipids (SLs) constitute bioactive lipid compounds with a remarkable second messenger potential. SL levels associate with responsiveness to interferon treatment in HCV-patients, thus prompting the question whether failure to DAAs can be predicted by the serologic sphingolipidomic profile. Liquid chromatography coupled to tandem mass spectrometry (LC-MS/MS) was used to retrospectively quantify various sphingolipid metabolites in baseline serum samples of 97 chronic HCV patients with DAA failure compared with an age-matched cohort of 95 HCV-patients with sustained virological response (SVR). Sphingosine, sphinganine, sphingosine-1-phosphate (S1P) and sphinganine-1-phosphate (SA1P) serum concentrations were significantly upregulated at baseline in patients with DAA failure compared to patients with SVR. Similarly, GluC24:1Cer baseline levels were significantly upregulated in patients with DAA failure compared to the patients with SVR. However, GluC18Cer serum levels showed decreased baseline levels for patients with DAA failure compared to patients with SVR. In multivariate analysis sphinganine (OR 0.08494, CI 0.07393-0.9759, p = .021223), SA1P (OR 0.9818, CI 0.9653-0.9987, p = .034801), GluCerC18 (OR 1.0683, CI 1.0297-1.1104, p = .000786) and GluCer24:1 (OR 0.9961, CI 0.994-0.998, p = .000294) constituted independent predictors of treatment response. In conclusion, serum sphingolipid concentrations, in particular sphingosine, sphinganine and their derivatives S1P and SA1P as well as glucosylceramides may identify at baseline the minority of HCV patients with DAA failure. Serum sphingolipids could constitute additional biomarkers for national treatment strategies aiming to eliminate HCV infection.

Ponesimod: An Oral Second-Generation Selective Sphingosine 1-Phosphate Receptor Modulator for the Treatment of Multiple Sclerosis.

OBJECTIVE: To describe the safety, efficacy, and potential role in therapy of ponesimod, which was recently approved by the Food and Drug Administration (FDA) as a therapeutic option for the treatment of multiple sclerosis (MS). DATA SOURCES: A PubMed literature search using the following terms: ponesimod and MS (January 1, 2012-October 31, 2022). FDA product labeling was also reviewed for pertinent data sources. STUDY SELECTION AND DATA EXTRACTION: All relevant English-language articles examining efficacy and/or safety of ponesimod were considered for inclusion. DATA SYNTHESIS: Ponesimod is an orally administered second-generation sphingosine 1-phospate (S1-P) receptor modulator classified as a disease modifying treatment (DMT) for MS. Clinical studies have shown that ponesimod prevents relapse in patients with relapsing-remitting MS (RRMS) and has superior efficacy compared with teriflunomide. Nasopharyngitis, upper respiratory tract infections, headache, high blood pressure, and liver dysfunction were some of the common adverse effects associated with ponesimod. Dyspnea, bradyarrhythmias, atrioventricular conduction delays, and macular edema were some of the rare but serious adverse effects associated with ponesimod. RELEVANCE TO PATIENT CARE AND CLINICAL PRACTICE IN COMPARISON WITH EXISTING AGENTS: Some advantages of ponesimod over other S1-P receptor modulators approved for RRMS include selectivity for the S1-P1 receptor and short half-life, which allows for quick reversal of immunosuppressive effects. However, data from long-term efficacy and safety studies and more direct comparison studies with other DMTs are required. CONCLUSION: Currently available data suggest that ponesimod is a useful addition to other high-efficacy DMTs available to treat patients with MS.

The effect of Fingolimod on patients with moderate to severe COVID-19.

Hyper-inflammation, cytokine storm, and recruitment of immune cells lead to uncontrollable endothelial cell damage in patients with coronavirus disease 2019 (COVID-19). Sphingosine 1-phosphate (S1P) signaling is needed for endothelial integrity and its decreased serum level is a predictor of clinical severity in COVID-19. In this clinical trial, the effect of Fingolimod, an agonist of S1P, was evaluated on patients with COVID-19. Forty patients with moderate to severe COVID-19 were enrolled and divided into two groups including (1) the control group (n = 21) receiving the national standard regimen for COVID-19 patients and (2) the intervention group (n = 19) that prescribed daily Fingolimod (0.5 mg) for 3 days besides receiving the standard national regimen for COVID-19. The hospitalization period, re-admission rate, intensive care unit (ICU) administration, need for mechanical ventilation, and mortality rate were assessed as primary outcomes in both groups. The results showed that re-admission was significantly decreased in COVID-19 patients who received Fingolimod compared to the controls (p = .04). In addition, the hemoglobin levels of the COVID-19 patients in the intervention group were increased compared to the controls (p = .018). However, no significant differences were found regarding the intubation or mortality rate between the groups (p > .05). Fingolimod could significantly reduce the re-admission rate after hospitalization with COVID-19. Fingolimod may not enhance patients' outcomes with moderate COVID-19. It is necessary to examine these findings in a larger cohort of patients with severe to critical COVID-19.

Siponimod ameliorates metabolic oligodendrocyte injury via the sphingosine-1 phosphate receptor 5.

Multiple sclerosis (MS), an autoimmune-driven, inflammatory demyelinating disease of the central nervous system (CNS), causes irreversible accumulation of neurological deficits to a variable extent. Although there are potent disease-modifying agents for its initial relapsing-remitting phase, immunosuppressive therapies show limited efficacy in secondary progressive MS (SPMS). Although modulation of sphingosine-1 phosphate receptors has proven beneficial during SPMS, the underlying mechanisms are poorly understood. In this project, we followed the hypothesis that siponimod, a sphingosine-1 phosphate receptor modulator, exerts protective effects by direct modulation of glia cell function (i.e., either astrocytes, microglia, or oligodendrocytes). To this end, we used the toxin-mediated, nonautoimmune MS animal model of cuprizone (Cup) intoxication. On the histological level, siponimod ameliorated cuprizone-induced oligodendrocyte degeneration, demyelination, and axonal injury. Protective effects were evident as well using GE180 translocator protein 18-kDa (TSPO) imaging with positron emission tomography (PET)/computed tomography (CT) imaging or next generation sequencing (NGS). Siponimod also ameliorated the cuprizone-induced pathologies in Rag1-deficient mice, demonstrating that the protection is independent of T and B cell modulation. Proinflammatory responses in primary mixed astrocytes/microglia cell cultures were not modulated by siponimod, suggesting that other cell types than microglia and astrocytes are targeted. Of note, siponimod completely lost its protective effects in S1pr5-deficient mice, suggesting direct protection of degenerating oligodendrocytes. Our study demonstrates that siponimod exerts protective effects in the brain in a S1PR5-dependent manner. This finding is not just relevant in the context of MS but in other neuropathologies as well, characterized by a degeneration of the axon-myelin unit.

Structural insights into sphingosine-1-phosphate receptor activation.

As a critical sphingolipid metabolite, sphingosine-1-phosphate (S1P) plays an essential role in immune and vascular systems. There are five S1P receptors, designated as S1PR1 to S1PR5, encoded in the human genome, and their activities are governed by endogenous S1P, lipid-like S1P mimics, or nonlipid-like therapeutic molecules. Among S1PRs, S1PR1 stands out due to its nonredundant functions, such as the egress of T and B cells from the thymus and secondary lymphoid tissues, making it a potential therapeutic target. However, the structural basis of S1PR1 activation and regulation by various agonists remains unclear. Here, we report four atomic resolution cryo-electron microscopy (cryo-EM) structures of Gi-coupled human S1PR1 complexes: bound to endogenous agonist d18:1 S1P, benchmark lipid-like S1P mimic phosphorylated Fingolimod [(S)-FTY720-P], or nonlipid-like therapeutic molecule CBP-307 in two binding modes. Our results revealed the similarities and differences of activation of S1PR1 through distinct ligands binding to the amphiphilic orthosteric pocket. We also proposed a two-step "shallow to deep" transition process of CBP-307 for S1PR1 activation. Both binding modes of CBP-307 could activate S1PR1, but from shallow to deep transition may trigger the rotation of the N-terminal helix of Gαi and further stabilize the complex by increasing the Gαi interaction with the cell membrane. We combine with extensive biochemical analysis and molecular dynamic simulations to suggest key steps of S1P binding and receptor activation. The above results decipher the common feature of the S1PR1 agonist recognition and activation mechanism and will firmly promote the development of therapeutics targeting S1PRs.

Tumor Derived Extracellular Vesicles Drive T Cell Exhaustion in Tumor Microenvironment through Sphingosine Mediated Signaling and Impacting Immunotherapy Outcomes in Ovarian Cancer.

SPHK1 (sphingosine kinase-1) catalyzes the phosphorylation of sphingosine to sphingosine-1-phosphate (S1P), is found to be highly expressed in solid tumors. Here, extracellular vesicles (EVs) are identified as the key transporters of SPHK1 to the tumor microenvironment. Consequently, SPHK1-packaged EVs elevate S1P levels in the tumor microenvironment, where S1P appears as an immunosuppressive agent. However, the exact mechanism of how S1P mediates its immunosuppressive effects in cancer is not understood. It is investigated that S1P can induce T cell exhaustion. S1P can also upregulate programmed death ligand-1 (PDL-1) expression through E2F1-mediated transcription. Notably, an SPHK1 inhibitor PF543 improves T cell-mediated cytotoxicity. Furthermore, combining PF543 with an anti-PD-1 antibody reduces tumor burden and metastasis more effectively than PF543 alone in vivo. These data demonstrate a previously unrecognized mechanism of how SPHK1-packaged EVs contribute to the progression of ovarian cancer and thus present the potential clinical application of inhibiting SPHK1/S1P signaling to improve immune checkpoint blockage (anti-PD-1 antibody) therapy in ovarian cancer.

Sphingosine 1-phosphate modulation and immune cell trafficking in inflammatory bowel disease.

Immune cell trafficking is a critical element of the intestinal immune response, both in homeostasis and in pathological conditions associated with inflammatory bowel disease (IBD). This process involves adhesion molecules, chemoattractants and receptors expressed on immune cell surfaces, blood vessels and stromal intestinal tissue as well as signalling pathways, including those modulated by sphingosine 1-phosphate (S1P). The complex biological processes of leukocyte recruitment, activation, adhesion and migration have been targeted by various monoclonal antibodies (vedolizumab, etrolizumab, ontamalimab). Promising preclinical and clinical data with several oral S1P modulators suggest that inhibition of lymphocyte egress from the lymph nodes to the bloodstream might be a safe and efficacious alternative mechanism for reducing inflammation in immune-mediated disorders, including Crohn's disease and ulcerative colitis. Although various questions remain, including the potential positioning of S1P modulators in treatment algorithms and their long-term safety, this novel class of compounds holds great promise. This Review summarizes the critical mediators and mechanisms involved in immune cell trafficking in IBD and the available evidence for efficacy, safety and pharmacokinetics of S1P receptor modulators in IBD and other immune-mediated disorders. Further, it discusses potential future approaches to incorporate S1P modulators into the treatment of IBD.

Review article: the sphingosine 1 phosphate/sphingosine 1 phosphate receptor axis - a unique therapeutic target in inflammatory bowel disease.

BACKGROUND: Ozanimod, a high selective sphingosine 1 phosphate (S1P) receptor (S1PR) 1/5 modulator was approved by the Food and Drug Administration for the treatment of adult patients with moderately to severely active ulcerative colitis. Additional S1PR modulators are being tested in clinical development programmes for both ulcerative colitis and Crohn's disease. AIM: To provide an overview of advances in understanding S1PRs biology and summarise preclinical and clinical investigations of S1P receptor modulators in chronic inflammatory disease with special emphasis on inflammatory bowel diseases (IBD). METHODS: We performed a narrative review using PubMed and ClinicalTrials.gov. RESULTS: Through S1PRs, S1P regulates multiple cellular processes, including proliferation, migration, survival, and vascular barrier integrity. The S1PRs function of regulating lymphocyte trafficking is well known, but new functions of S1PRs expand our knowledge of S1PRs biology. Several S1PR modulators are in clinical development for both ulcerative colitis and Crohn's disease and have shown promise in phase II and III studies with ozanimod now being approved for ulcerative colitis. CONCLUSIONS: S1P receptor modulators constitute a novel, promising, safe, and convenient strategy for the treatment of IBD.

The Anti-Infectious Role of Sphingosine in Microbial Diseases.

Sphingolipids are important structural membrane components and, together with cholesterol, are often organized in lipid rafts, where they act as signaling molecules in many cellular functions. They play crucial roles in regulating pathobiological processes, such as cancer, inflammation, and infectious diseases. The bioactive metabolites ceramide, sphingosine-1-phosphate, and sphingosine have been shown to be involved in the pathogenesis of several microbes. In contrast to ceramide, which often promotes bacterial and viral infections (for instance, by mediating adhesion and internalization), sphingosine, which is released from ceramide by the activity of ceramidases, kills many bacterial, viral, and fungal pathogens. In particular, sphingosine is an important natural component of the defense against bacterial pathogens in the respiratory tract. Pathologically reduced sphingosine levels in cystic fibrosis airway epithelial cells are normalized by inhalation of sphingosine, and coating plastic implants with sphingosine prevents bacterial infections. Pretreatment of cells with exogenous sphingosine also prevents the viral spike protein of severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2) from interacting with host cell receptors and inhibits the propagation of herpes simplex virus type 1 (HSV-1) in macrophages. Recent examinations reveal that the bactericidal effect of sphingosine might be due to bacterial membrane permeabilization and the subsequent death of the bacteria.

A Rationale for Hypoxic and Chemical Conditioning in Huntington's Disease.

Neurodegenerative diseases are characterized by adverse cellular environments and pathological alterations causing neurodegeneration in distinct brain regions. This development is triggered or facilitated by conditions such as hypoxia, ischemia or inflammation and is associated with disruptions of fundamental cellular functions, including metabolic and ion homeostasis. Targeting intracellular downstream consequences to specifically reverse these pathological changes proved difficult to translate to clinical settings. Here, we discuss the potential of more holistic approaches with the purpose to re-establish a healthy cellular environment and to promote cellular resilience. We review the involvement of important molecular pathways (e.g., the sphingosine, δ-opioid receptor or N-Methyl-D-aspartate (NMDA) receptor pathways) in neuroprotective hypoxic conditioning effects and how these pathways can be targeted for chemical conditioning. Despite the present scarcity of knowledge on the efficacy of such approaches in neurodegeneration, the specific characteristics of Huntington's disease may make it particularly amenable for such conditioning techniques. Not only do classical features of neurodegenerative diseases like mitochondrial dysfunction, oxidative stress and inflammation support this assumption, but also specific Huntington's disease characteristics: a relatively young age of neurodegeneration, molecular overlap of related pathologies with hypoxic adaptations and sensitivity to brain hypoxia. The aim of this review is to discuss several molecular pathways in relation to hypoxic adaptations that have potential as drug targets in neurodegenerative diseases. We will extract the relevance for Huntington's disease from this knowledge base.

Sphingosylphosphorylcholine blocks ovariectomy-induced bone loss by suppressing Ca2+ /calmodulin-mediated osteoclast differentiation.

Osteoporosis is a disease in which bone mineral density decreases due to abnormal activity of osteoclasts, and is commonly found in post-menopausal women who have decreased levels of female hormones. Sphingosylphosphorylcholine (SPC) is an important biological lipid that can be converted to sphingosine-1-phosphate (S1P) by autotaxin. S1P is known to be involved in osteoclast activation by stimulating osteoblasts, but bone regulation by SPC is not well understood. In this study, we found that SPC strongly inhibits RANKL-induced osteoclast differentiation. SPC-induced inhibitory effects on osteoclast differentiation were not affected by several antagonists of S1P receptors or pertussis toxin, suggesting cell surface receptor independency. However, SPC inhibited RANKL-induced calcineurin activation and subsequent NFATc1 activity, leading to decrease of the expression of Trap and Ctsk. Moreover, we found that bone loss in an experimental osteoporosis mouse model was recovered by SPC injection. SPC also blocked ovariectomy-induced body weight increase and Nfatc1 gene expression in mice. We also found that SPC inhibits RANKL-induced osteoclast differentiation in human macrophages. Since currently available treatments for osteoporosis, such as administration of female hormones or hormone receptor modulators, show serious side effects, SPC has potential as a new agent for osteoporosis treatment.

Sphingosine-1-Phosphate Attenuates Lipopolysaccharide-Induced Pericyte Loss via Activation of Rho-A and MRTF-A.

The high mortality seen in sepsis is caused by a systemic hypotension in part owing to a drastic increase in vascular permeability accompanied by a loss of pericytes. As has been shown previously, pericyte retention in the perivascular niche during sepsis can enhance the integrity of the vasculature and promote survival via recruitment of adhesion proteins such as VE-cadherin and N-cadherin. Sphingosine-1-phosphate (S1P) represents a lipid mediator regulating the deposition of the crucial adhesion molecule VE-cadherin at sites of interendothelial adherens junctions and of N-cadherin at endothelial-pericyte adherens junctions. Furthermore, in septic patients, S1P plasma levels are decreased and correlate with mortality in an indirectly proportional way. In the present study, we investigated the potential of S1P to ameliorate a lipopolysaccharide-induced septic hypercirculation in mice. Here we establish S1P as an antagonist of pericyte loss, vascular hyperpermeability, and systemic hypotension, resulting in an increased survival in mice. During sepsis S1P preserved VE-cadherin and N-cadherin deposition, mediated by a reduction of Src and cadherin phosphorylation. At least in part, this effect is mediated by a reduction of globular actin and a subsequent increase in nuclear translocation of MRTF-A (myocardin-related transcription factor A). These findings indicate that S1P may counteract pericyte loss and microvessel disassembly during sepsis and additionally emphasize the importance of pericyte-endothelial interactions to stabilize the vasculature.

Fingolimod (FTY720) prevents chronic rejection of rodent cardiac allografts through inhibition of the RhoA pathway.

The Fingolimod (FTY720, Gilenya) is clinically approved for the treatment of multiple sclerosis (MS). Its therapeutic effect on MS is based on the ability to bind sphingosine 1-phosphate (S1P) receptors and block the exit of immune cells from the lymphoid organs, thus preventing immune cell-dependent injury to the central nervous system (CNS). We showed recently that, besides the S1P-related activity, the FTY720 also down-regulates RhoA, which is a master regulator of the actin cytoskeleton. Our previous studies showed that FTY720 also down-regulates Rictor, which is a signature molecule of mTORC2 complex, which regulates RhoA and dictates actin cytoskeleton specificity. Because, our previous studies showed that chronic rejection correlates with the upregulation of RhoA and mTORC2 components and that the inhibition of RhoA pathway prevents chronic rejection, here we studied the effect of FTY720 on the chronic rejection of rat and mouse cardiac allografts. We show that FTY720 in conjunction with the inhibitors of early T cell response, (CTA4-Ig in mice and Everolimus in rats) blocks macrophage infiltration into the grafts and prevents chronic rejection of rat and mouse cardiac transplants. This indicates that FTY720 may be repurposed from the MS application to the clinical transplantation as an anti-chronic rejection drug.

Sphingosylphosphorylcholine alleviates hypoxia-caused apoptosis in cardiac myofibroblasts via CaM/p38/STAT3 pathway.

Blockade of hypoxia-caused nonmyocytes apoptosis helps improve survival and mitigate ventricular remodeling and dysfunction during the chronic stage of myocardial infarction. But tools affecting nonmyocyte apoptosis are very rare. Sphingosylphosphorylcholine (SPC), a naturally occurring bioactive sphingolipid in plasma, was proved to protect cardiomyocyte against apoptosis in an ischemic model in our previous study. Here, we showed that SPC also inhibited hypoxia-induced apoptosis in myofibroblasts, an important type of nonmyocytes in the heart. Calmodulin (CaM) is an identified receptor of SPC. We clarified that SPC inhibited myofibroblast apoptosis through CaM as evidenced by decreased cleaved caspase 3, PARP1 and condensed nucleus. Furthermore, the employment of inhibitor and agonist of p38 and STAT3 suggests that SPC inhibits myofibroblast apoptosis by regulating the phosphorylation of p38 and STAT3, and they act as downstream of CaM. The present work may provide new evidence on the regulation of myofibroblasts apoptosis by SPC and a novel target for heart remodeling after hypoxia.