The Lipid Status in Patients with Ulcerative Colitis: Sphingolipids are Disease-Dependent Regulated

The factors that contribute to the development of ulcerative colitis (UC), are still not fully identified. Disruption of the colon barrier is one of the first events leading to invasion of bacteria and activation of the immune system. The colon barrier is strongly influenced by sphingolipids. Sphingolipids impact cell-cell contacts and function as second messengers. We collected blood and colon tissue samples from UC patients and healthy controls and investigated the sphingolipids and other lipids by LC-MS/MS or LC-QTOFMS. The expression of enzymes of the sphingolipid pathway were determined by RT-PCR and immunohistochemistry. In inflamed colon tissue, the de novo-synthesis of sphingolipids is reduced, whereas lactosylceramides are increased. Reduction of dihydroceramides was due to posttranslational inhibition rather than altered serine palmitoyl transferase or ceramide synthase expression in inflamed colon tissue. Furthermore, in human plasma from UC-patients, several sphinglipids change significantly in comparison to healthy controls. Beside sphingolipids free fatty acids, lysophosphatidylcholines and triglycerides changed significantly in the blood of colitis patients dependent on the disease severity. Our data indicate that detraction of the sphingolipid de novo synthesis in colon tissue might be an important trigger for UC. Several lipids changed significantly in the blood, which might be used as biomarkers for disease control; however, diet-related variabilities need to be considered.

S1P induces pulmonary artery smooth muscle cell proliferation by activating calcineurin/NFAT/OPN signaling pathway

The upregulation of osteopontin(OPN) has been found to contribute to the proliferation of pulmonary artery smooth muscle cells(PASMCs), and activation of PPARγ has been shown to suppress OPN expression in THP-1 cells. However, the molecular mechanisms underlying the upregulation of OPN expression and PPARγ agonist modulation of OPN expression in PASMCs remain largely unclear. Here we found that S1P stimulated PASMCs proliferation and up-regulated OPN expression in rat PASMCs, which was accompanied with the activation of phospholipase C(PLC), calcineurin and translocation of NFATc3 to nucleus. Further study showed that inhibition of PLC by U73122, suppression of calcineurin activity by cyclosporine A(CsA) or knockdown of NFATc3 using small interfering RNA suppressed S1P-induced OPN up-regulation. Activation of PPARγ by pioglitazone suppressed S1P-induced activation of calcineurin/NFATc3 signaling pathway and followed OPN up-regulation. Taken together, our study indicates that S1P stimulates OPN expression by activation of PLC/calcineurin/NFATc3 signaling pathway, and activation of PPARγ suppresses calcineurin/NFATc3-mediated OPN expression in PASMCs.

Pro-Inflammatory Role of S1P3 in Macrophages

Sphingosine kinase 1 and its product, sphingosine 1-phosphate (S1P), as well as their receptors, have been implicated in inflammatory responses. The functions of receptors S1P₁ and S1P₂ on cell motility have been investigated. However, the function of S1P₃ has been poorly investigated. In this study, the roles of S1P₃ on inflammatory response were investigated in primary perito-neal macrophages. S1P₃ receptor was induced along with sphingosine kinase 1 by stimulation of lipopolysaccharide (LPS). LPS treatment induced inflammatory genes, such iNOS, COX-2, IL-1β, IL-6 and TNF-α. TY52156, an antagonist of S1P₃ suppressed the induction of inflammatory genes in a concentration dependent manner. Suppression of iNOS and COX-2 induction was further confirmed by western blotting and NO measurement. Suppression of IL-1β induction was also confirmed by western blotting and ELISA. Caspase 1, which is responsible for IL-1β production, was similarly induced by LPS and suppressed by TY52156. Therefore, we have shown S1P₃ induction in the inflammatory conditions and its pro-inflammatory roles. Targeting S1P₃ might be a strategy for regulating inflammatory diseases.

A therapy with miglustat, 2-hydroxypropyl-ß-cyclodextrin and allopregnanolone restores splenic cholesterol homeostasis in Niemann-pick disease type C1

BACKGROUND

Niemann-Pick disease type C1 (NPC1) is an autosomal-recessive lipid-storage disorder with an estimated minimal incidence of 1/120,000 live births. Besides other neuronal and visceral symptoms, NPC1 patients develop spleen dysfunction, isolated spleno- or hepatosplenomegaly and infections. The mechanisms of splenomegaly and alterations of lipid metabolism-related genes in NPC1 disease are still poorly understood.

METHODS

Here, we used an NPC1 mouse model to study a splenoprotective effect of a treatment with miglustat, 2-hydroxypropyl-ß-cyclodextrin and allopregnanolone and showed that this treatment has a positive effect on spleen morphology and lipid metabolism.

RESULTS

Disease progress can be halted and blocked at the molecular level. Mutant Npc1 (Npc1^-/-) mice showed increased spleen weight and increased lipid accumulation that could be avoided by our treatment. Also, FACS analyses showed that the increased number of splenic myeloid cells in Npc1^-/- mice was normalized by the treatment. Treated Npc1^-/- mice showed decreased numbers of cytotoxic T cells and increased numbers of T helper cells.

CONCLUSIONS

In summary, the treatment promotes normal spleen morphology, stabilization of lipid homeostasis and blocking of inflammation, but alters the composition of T cell subtypes.

Early central vs. peripheral immunological and neurobiological effects of fingolimod-a longitudinal study

Fingolimod (FTY) is known to have multiple effects on the immune system and the central nervous system (CNS) in patients with multiple sclerosis (MS). In this study, we evaluated the immunological and neurobiological effects of FTY in MS. Blood and cerebrospinal fluid (CSF) samples were collected from 15 MS patients before first FTY administration and after 4 months of FTY therapy. Immunophenotyping and evaluation of sphingosine-1-phosphate (S1P), neurofilament light chain (NFL), S-100 and neuron-specific enolase (NSE) levels were conducted. After 4 months of FTY therapy, absolute cell count in CSF was decreased from 6.33 to 2.43 MPt/l, accompanied by decreases of CD3+ (2.22 to 0.65 MPt/l) and of CD4+ counts (1.60 to 0.39 MPt/l). In blood, CD3+ (1.05 to 0.09 GPt/l), CD4+ (0.80 to 0.02 GPt/l), CD8+ (0.23 to 0.04 GPt/l) and CD19+ (0.21 to 0.01GPt/l) cell counts were as well reduced. CD14+ cell count remained stable over the same period (0.24 to 0.26GPt/l). NFL and S1P levels in CSF and blood were reduced over time (NFL: CSF 1759 to 1359 pg/l, blood 8.42 to 7.36 pg/l; S1P: CSF 2.12 to 0.71 nmol/l, blood 392.1 to 312.9 nmol/l). Strong correlations between CSF and blood NFL levels were observed. Neuronal damage markers such as S-100 (1.86 to 1.69 μg/l) and NSE (9.53 to 8.67 μg/l) were reduced to a lesser degree than other markers. FTY exerted significant effects on immunological and neurobiological markers in the central and peripheral compartment. Decreases in levels of neuroinflammatory and neurodegenerative markers were already evident after 4 months of treatment. Four-month serum NFL level appears to be a useful marker for FTY efficacy that correlates well with changes in the CNS compartment. KEY MESSAGES: FTY has important immunological effects in both central and peripheral compartments. Cellular effects of FTY effects are more pronounced in the blood than in the CSF. FTY reduces S1P and NFL levels in CSF and serum. Serum NFL appears to be a useful marker for FTY therapy.

The Intra-nuclear SphK2-S1P Axis Facilitates M1-to-M2 Shift of Microglia via Suppressing HDAC1-Mediated KLF4 Deacetylation

Sphingosine 1-phosphate (S1P) is involved in a variety of cellular responses including microglial activation and polarization. However, the impacts of S1P on ischemia-induced microglial activation and polarization remain unclear. In the present study, Sprague-Dawley rats were selected for middle cerebral artery occlusion (MCAO) establishment and treated with S1P analog FTY720 (0.5, 1, 2 mg/kg) for 24 h. The impacts of FTY720 on oxygen-glucose deprivation (OGD)-induced microglial polarization were examined in the primary cultured microglia. FTY720 treatment could prevent ischemia-induced brain injury and neurological dysfunction, also decrease the levels of IL-1β and TNF-α and promote M2 microglial polarization in rats. Further, we found that FTY720 inhibited the expressions of M1 markers, but increased the expressions of M2 markers in the OGD-insulted microglia. And FTY720 could enhance the phagocytic function of microglia. The sphingosine kinase 1/2 (SphK1/2) or the Sphk2 inhibitor could prevent the M1 to M2 phenotype shift improved by FTY720, but the Sphk1 inhibitor failed to affect the roles of FTY720. Furthermore, the Sphk1/2 or Sphk2 inhibitor promoted the activities of histone deacetylase (HDAC1) and inhibited the histone acetylation of the Krüppel-like factor 4 (KLF4) promoter regions, indicating that intra-nuclear pFTY720 inhibited HDAC1 activations and prevented KLF4 to interact with HDAC1, and thereby suppresses KLF4 deacetylation. Therefore, our data reveals that intra-nuclear SphK2-S1P axis might facilitate the transformation of microglial polarization from M1 to M2 phenotype, which might be intra-nuclear regulatory mechanisms of FTY720-prevented neuroinflammation.

Decreased S1P and SPHK2 are involved in pancreatic acinar cell injury

Aim: The roles of S1P in acute pancreatitis (AP) or non-AP patients with pancreatic acinar cell injury (PACI) are not well understood. Materials & methods: Serum S1P, in 40 healthy individuals and 99 patients with PACI, was retrospectively analyzed. Additionally, we detected and analyzed S1P in AP mice and the AR42J acinar cell line. Results: Serum S1P was significantly decreased in PACI patients, compared with that of healthy controls. Patients with gall stones, normal serum calcium or normal blood lipids showed relative higher levels of serum S1P. Interestingly, in patients with gall or liver disease, serum S1P was positively associated with γ-GT and ALT. Additionally, S1P and SPHK2 were decreased in AP mice and AR42J cells, relative to the levels of corresponding controls. Conclusion: Serum S1P is decreased in PACI, which may be partly due to downregulation of pancreatic SPHK2.

Regulation of S1PR2 by the EBV oncogene LMP1 in aggressive ABC-subtype diffuse large B-cell lymphoma

The Epstein-Barr virus (EBV) is found almost exclusively in the activated B-cell (ABC) subtype of diffuse large B-cell lymphoma (DLBCL), yet its contribution to this tumour remains poorly understood. We have focused on the EBV-encoded latent membrane protein-1 (LMP1), a constitutively activated CD40 homologue expressed in almost all EBV-positive DLBCLs and which can disrupt germinal centre (GC) formation and drive lymphomagenesis in mice. Comparison of the transcriptional changes that follow LMP1 expression with those that follow transient CD40 signalling in human GC B cells enabled us to define pathogenic targets of LMP1 aberrantly expressed in ABC-DLBCL. These included the down-regulation of S1PR2, a sphingosine-1-phosphate (S1P) receptor that is transcriptionally down-regulated in ABC-DLBCL, and when genetically ablated leads to DLBCL in mice. Consistent with this, we found that LMP1-expressing primary ABC-DLBCLs were significantly more likely to lack S1PR2 expression than were LMP1-negative tumours. Furthermore, we showed that the down-regulation of S1PR2 by LMP1 drives a signalling loop leading to constitutive activation of the phosphatidylinositol-3-kinase (PI3-K) pathway. Finally, core LMP1-PI3-K targets were enriched for lymphoma-related transcription factors and genes associated with shorter overall survival in patients with ABC-DLBCL. Our data identify a novel function for LMP1 in aggressive DLBCL. Copyright © 2019 Pathological Society of Great Britain and Ireland. Published by John Wiley & Sons, Ltd.

Examination of the role of sphingosine kinase 2 in a murine model of systemic lupus erythematosus

Systemic lupus erythematosus is an autoimmune disease characterized by overproduction of type 1 IFN that causes multiple organ dysfunctions. Plasmacytoid dendritic cells (pDCs) that secrete large amounts of IFN have recently been implicated in the initiation of the disease in preclinical mouse models. Sphingosine-1-phosphate, a bioactive sphingolipid metabolite, is produced by 2 highly conserved isoenzymes, sphingosine kinase (SphK) 1 and SphK2, and regulates diverse processes important for immune responses and autoimmunity. However, not much is known about the role of SphK2 in autoimmune disorders. In this work, we examined the role of SphK2 in pDC development and activation and in the pristane-induced lupus model in mice that mimics the hallmarks of the human disease. Increases in pDC-specific markers were observed in peripheral blood of SphK2 knockout mice. In agreement, the absence of SphK2 increased the differentiation of FMS-like tyrosine kinase 3 ligand dendritic cells as well as expression of endosomal TLRs, TLR7 and TLR9, that modulate production of IFN. Surprisingly, however, SphK2 deficiency did not affect the initiation or progression of pristane-induced lupus. Moreover, although absence of SphK2 increased pDC frequency in pristane-induced lupus, there were no major changes in their activation status. Additionally, SphK2 expression was unaltered in lupus patients. Taken together, our results suggest that SphK2 may play a role in dendritic cell development. Yet, because its deletion had no effect on the clinical lupus parameters in this preclinical model, inhibitors of SphK2 might not be useful for treatment of this devastating disease.-Mohammed, S., Vineetha, N. S., James, S., Aparna, J. S., Lankadasari, M. B., Allegood, J. C., Li, Q.-Z., Spiegel, S., Harikumar, K. B. Examination of the role of sphingosine kinase 2 in a murine model of systemic lupus erythematosus.

Sphingosine 1 Phosphate (S1P) Increased IL-6 Expression and Cell Growth in Endometriotic Cells

OBJECTS

There is growing evidence that sphingosine 1-phosphate (S1P) is involved in inflammatory diseases. As endometriosis is known as an inflammatory disease, we investigated the role of S1P system in the development of endometriosis.

METHODS

The expression of sphingosine kinase (SphK) 1 in endometriosis lesions was examined by immunohistochemistry. The cystic fluid of ovarian cysts/tumors were obtained to measure S1P concentrations. Endometriotic stromal cells (ESC) derived from endometrioma were used for in vitro experiments.

RESULTS

Sphingosine kinase 1 was detected in epithelium and stromal cells of endometriotic lesions. The mean S1P concentration in the cystic fluid of endometriomas was higher than that in nonendometriomas significantly (98.2 nM vs less than 1.5 nM, P < .01). Interleukin-1β (IL-1β) or transforming growth factor-β exhibited 2.7-fold and 11.5-fold increase in SphK1 messenger RNA (mRNA) expression in ESC, respectively (P < .01). Higher dose of S1P (125nM) increased the cell number of ESC by 20%, and low dose of S1P (1.25 nM and 12.5 nM) induced IL-6 mRNA production and IL-6 secretion by ESC dose-dependently. JTE013, an antagonist for S1PR2, partially suppressed IL-6 induction by S1P (P < .05). JTE013 and VPC23019, an antagonist for S1PR1 and S1PR3, suppressed the ESC proliferation induced by S1P.

CONCLUSION

The present study for the first time proved that the SphK-S1P-S1PR axis play a role of accelerating inflammation and growth of endometriotic cells.

Differential expression of S1P receptor subtypes in human bladder transitional cell carcinoma

PURPOSE

Sphingosine 1 phosphate (S1P), S1P receptors (S1PRs) and their signaling pathways play an important role in the fate of cancer cells. The expression pattern of S1PR subtypes (S1PR1-S1PR5) may alter in cancer development stages, depending on the origin and the pathologic features of tumors. The present study aimed to examine the relationship between plasma S1P levels and the expression of S1PR subtypes in bladder tumors.

METHODS/PATIENTS

These changes were evaluated in terms of the pathologic grades and stages of human bladder cancer samples. For this, tumor biopsies from 41 new bladder cancer patients as well as 26 normal-looking bladder tissues were collected and processed for immunohistochemistry (IHC) and quantitative real-time RT-PCR of S1PR subtypes. Plasma S1P level was measured using liquid chromatography-tandem mass spectrometry (LC-MS/MS).

RESULTS

The results show that tissue S1PR1, S1PR2 and S1PR3 are over-expressed in all tumors regardless of their pathological grade (~ 3, ~ 6 and ~ 104 folds, respectively). These results were corroborated by IHC data showing accumulation of S1PR subtypes 1 and 2 in the tissues. Plasma S1P in the plasma samples from patients was in the range of control samples (Controls; 256 ± 47; patients, 270 ± 41).

CONCLUSIONS

Overexpression of S1PR1, S1PR2 and S1PR3 in bladder tumor biopsies which were corroborated with the pathological grades and stages may suggest that S1PR profile in tumor biopsies is a promising marker in the diagnosis of bladder carcinoma.

Protective role of epigallocatechin-3-gallate in NADPH oxidase-MMP2-Spm-Cer-S1P signalling axis mediated ET-1 induced pulmonary artery smooth muscle cell proliferation

The signalling pathway involving MMP-2 and sphingosine-1-phosphate (S1P) in endothelin-1 (ET-1) induced pulmonary artery smooth muscle cell (PASMC) proliferation is not clearly known. We, therefore, investigated the role of NADPH oxidase derived O₂^.--mediated modulation of MMP2-sphingomyeline-ceramide-S1P signalling axis in ET-1 induced increase in proliferation of PASMCs. Additionally, protective role of the tea cathechin, epigallocatechin-3-gallate (EGCG), if any, in this scenario has also been explored. ET-1 markedly increased NADPH oxidase and MMP-2 activities and proliferation of bovine pulmonary artery smooth muscle cells (BPASMCs). ET-1 also caused significant increase in sphingomyelinase (SMase) activity, ERK1/2 and sphingosine kinase (SPHK) phosphorylations, and S1P level in the cells. EGCG inhibited ET-1 induced increase in SMase activity, ERK1/2 and SPHK phosphorylations, S1P level and the SMC proliferation. EGCG also attenuated ET-1 induced activation of MMP-2 by inhibiting NADPH oxidase activity upon inhibiting the association of the NADPH oxidase components, p47phox and p67phox in the cell membrane. Molecular docking study revealed a marked binding affinity of p47phox with the galloyl group of EGCG. Overall, our study suggest that ET-1 induced proliferation of the PASMCs occurs via NADPH oxidase-MMP2- Spm- Cer-S1P signalling axis, and EGCG attenuates ET-1 induced increase in proliferation of the cells by inhibiting NADPH oxidase activity.

Sphingosine-1-phosphate attenuates hypoxia/reoxygenation-induced cardiomyocyte injury via a mitochondrial pathway

Our previous study showed that Sphingosine-1-phosphate (S1P) could protect cardiomyocytes against hypoxia/reoxygenation (H/R) injury via the JAK-STAT pathway and maintain normal myocardial mitochondria integrity in vivo. However, it is not known yet whether S1P can relieve mitochondrial dysfunction via the mitochondrial apoptotic pathway and its detailed mechanism remains to be investigated. The aim of this study was to demonstrate the mitochondrial protective effects of S1P in a cardiomyocyte H/R injury model. In the present study, we established a H/R model in H9c2 cells. Cell viability was determined by the MTT assay, and apoptosis was evaluated by annexin V-FITC/PI staining. Mitochondrial calcium ion concentration, mitochondrial membrane potential (ΔΨm), opening of the mitochondrial permeability transition pore (mPTP), and release of cytochrome C were detected by laser confocal microscopy. The results showed that S1P inhibited the decrease in cell viability induced by H/R injury and reduced apoptosis. Confocal microscopy showed that S1P prevented loss of ΔΨm, relieved mitochondrial calcium overload, and inhibited opening of the mPTP and release of cytochrome C. The STAT3 inhibitor STATTIC can reverse the antiapoptotic effects of S1P and block the effect of S1P on mitochondria. Taken together, our results indicate that S1P protects cardiomyocytes against H/R injury by relieving mitochondrial dysfunction via the STAT3 pathway.

S1P/S1PR3 axis promotes aerobic glycolysis by YAP/c-MYC/PGAM1 axis in osteosarcoma

Background

Osteosarcoma (OS) is a malignant tumor mainly occurring in young people. Due to the limited effective therapeutic strategies, OS patients cannot achieve further survival improvement. G-protein-coupled receptors (GPCRs) constitute the largest family of cell membrane receptors and consequently hold the significant promise for tumor imaging and targeted therapy. We aimed to explore the biological functions of Sphingosine 1-phosphate receptor 3 (S1PR3), one of the members of GPCRs family, in OS and the possibility of S1PR3 as an effective target for the treatment of osteosarcoma.

Methods

The quantitative real time PCR (qRT-PCR) and western blotting were used to analyze the mRNA and protein expressions. Cell counting kit-8 (CCK8), colony formation assay and cell apoptosis assay were performed to test the cellular proliferation in vitro. Subcutaneous xenograft mouse model was generated to evaluate the functions of S1PR3 in vivo. RNA sequencing was used to compare gene expression patterns between S1PR3-knockdown and control MNNG-HOS cells. In addition, metabolic alternations in OS cells were monitored by XF96 metabolic flux analyzer. Co-immunoprecipitation (Co-IP) assay was used to explore the interaction between Yes-associated protein (YAP) and c-MYC. Chromatin immunoprecipitation was used to investigate the binding capability of PGAM1 and YAP or c-MYC. Moreover, the activities of promoter were determined by the luciferase reporter assay.

Findings

S1PR3 and its specific ligand Sphingosine 1-phosphate (S1P) were found elevated in OS, and the higher expression of S1PR3 was correlated with the poor survival rate. Moreover, our study has proved that the S1P/S1PR3 axis play roles in proliferation promotion, apoptosis inhibition, and aerobic glycolysis promotion of osteosarcoma cells. Mechanistically, the S1P/S1PR3 axis inhibited the phosphorylation of YAP and promoted the nuclear translocation of YAP, which contributed to the formation of the YAP–c-MYC complex and enhanced transcription of the important glycolysis enzyme PGAM1. Moreover, the S1PR3 antagonist TY52156 exhibited in vitro and in vivo synergistic inhibitory effects with methotrexate on OS cell growth.

Interpretation

Our study unveiled a role of S1P, a bioactive phospholipid, in glucose metabolism reprogram through interaction with its receptor S1PR3. Targeting S1P/S1PR3 axis might serve as a potential therapeutic target for patients with OS.

Fund

This research was supported by National Natural Science Foundation of China (81472445 and 81672587).

Characterizing Sphingosine Kinases and Sphingosine 1-Phosphate Receptors in the Mammalian Eye and Retina

Sphingosine 1-phosphate (S1P) signaling regulates numerous biological processes including neurogenesis, inflammation and neovascularization. However, little is known about the role of S1P signaling in the eye. In this study, we characterize two sphingosine kinases (SPHK1 and SPHK2), which phosphorylate sphingosine to S1P, and three S1P receptors (S1PR1, S1PR2 and S1PR3) in mouse and rat eyes. We evaluated sphingosine kinase and S1P receptor gene expression at the mRNA level in various rat tissues and rat retinas exposed to light-damage, whole mouse eyes, specific eye structures, and in developing retinas. Furthermore, we determined the localization of sphingosine kinases and S1P receptors in whole rat eyes by immunohistochemistry. Our results unveiled unique expression profiles for both sphingosine kinases and each receptor in ocular tissues. Furthermore, these kinases and S1P receptors are expressed in mammalian retinal cells and the expression of SPHK1, S1PR2 and S1PR3 increased immediately after light damage, which suggests a function in apoptosis and/or light stress responses in the eye. These findings have numerous implications for understanding the role of S1P signaling in the mechanisms of ocular diseases such as retinal inflammatory and degenerative diseases, neovascular eye diseases, glaucoma and corneal diseases.

Peptidoglycan Recognition Protein 4 Suppresses Early Inflammatory Responses to Bordetella pertussis and Contributes to Sphingosine-1-Phosphate Receptor Agonist-Mediated Disease Attenuation

Incidence of whooping cough (pertussis), a bacterial infection of the respiratory tract caused by the bacterium Bordetella pertussis, has reached levels not seen since the 1950s. Antibiotics fail to improve the course of disease unless administered early in infection. Therefore, there is an urgent need for the development of antipertussis therapeutics. Sphingosine-1-phosphate receptor (S1PR) agonists have been shown to reduce pulmonary inflammation during Bordetella pertussis infection in mouse models. However, the mechanisms by which S1PR agonists attenuate pertussis disease are unknown. We report the results of a transcriptome sequencing study examining pulmonary transcriptional responses in B. pertussis-infected mice treated with S1PR agonist AAL-R or vehicle control. This study identified peptidoglycan recognition protein 4 (PGLYRP4) as one of the most highly upregulated genes in the lungs of infected mice following S1PR agonism. PGLYRP4, a secreted, innate mediator of host defenses, was found to limit early inflammatory pathology in knockout mouse studies. Further, S1PR agonist AAL-R failed to attenuate pertussis disease in PGLYRP4 knockout (KO) mice. B. pertussis virulence factor tracheal cytotoxin (TCT), a secreted peptidoglycan breakdown product, induces host tissue damage. TCT-oversecreting strains were found to drive an early inflammatory response similar to that observed in PGLYRP4 KO mice. Further, TCT-oversecreting strains induced significantly greater pathology in PGLYRP4-deficient animals than their wild-type counterparts. Together, these data indicate that S1PR agonist-mediated protection against pertussis disease is PGLYRP4 dependent. Our data suggest PGLYRP4 functions, in part, by preventing TCT-induced airway damage.

SphK1/S1P Mediates PDGF-Induced Pulmonary Arterial Smooth Muscle Cell Proliferation via miR-21/BMPRII/Id1 Signaling Pathway

BACKGROUND/AIMS

The underlying molecular mechanisms involved in sphingosine kinase 1 (SphK1)/sphingosine 1-phosphate (S1P) mediation of platelet-derived growth factor (PDGF)-induced pulmonary arterial smooth muscle cell (PASMC) proliferation are still unclear, and the present study aims to address this issue.

METHODS

Small interfering RNA (siRNA) and microRNA inhibitor transfection was performed to block the expression of SphK1, bone morphogenetic protein receptor II (BMPRII) and microRNA-21 (miR-21). Gene expression levels of SphK1, BMPRII and inhibitor of DNA binding 1 (Id1) were detected by immunoblotting, miR-21 expression level was examined with qRT-PCR, and S1P production was measured by ELISA. Additionally, PASMC proliferation was determined by BrdU incorporation assay.

RESULTS

Our results indicated that PDGF increased the expression of SphK1 protein and S1P production, up-regulated miR-21 expression, reduced BMPRII and Id1 expression, and promoted PASMCs proliferation. Pre-silencing of SphK1 with siRNA reversed PDGF-induced S1P production, miR-21 up-regulation, BMPRII and Id1 down-regulation, as well as PASMC proliferation. Pre-inhibition of miR-21 also blocked BMPRII and Id1 down-regulation as well as PASMC proliferation caused by PDGF. Knockdown of BMPRII down-regulated Id1 expression in PASMCs. We further found that inhibition of PI3K/Akt and ERK signaling pathways, particularly ERK cascade, suppressed PDGF-induced above changes.

CONCLUSION

Our study indicates that SphK1/S1P pathway plays an important role in PDGF-induced PASMC proliferation via miR-21/BMPRII/Id1 axis and targeting against SphK1/S1P axis might be a novel strategy in the prevention and treatment of pulmonary arterial hypertension (PAH).

[The Expression of Sphingosine-1-phosphate and Sphingosine-1-phosphate Receptor 1 in Mouse Model of Pulmonary Ischemia-Reperfusion Injury]

OBJECTIVE

To investigate the expressions of sphingosine 1-phosphate (S1P) and S1P G-protein-coupled receptor 1 (S1PR1) in pulmonary ischemia reperfusion injury (PIRI) tissues and explore their relationship.

METHODS

The model of PIRI was established in vivo male C57BL/6 mice (n=8). The left pulmonary hilum was occluded for 30 min with a microvascular clamp through a left thoracotomy. Reperfusion began with removal of the clamp. Normal group (n=8) and sham group (n=8) were set as control. The hematoxylin and eosin (HE) staining of ultrastructural changes and wet-to-dry mass ratio in lung tissues were measured for judging the succeed model. The mRNA expressions of sphingosine kinase 1 (SphK1) and S1PR1 were determined by real-time PCR, and ELISA was used to detect the concentrations of S1P and S1PR1 in the lung tissues.

RESULTS

The mRNA expressions of SphK1, S1PR1 and the concentrations of S1P and S1PR1 and wet-to-dry mass ratio of the lung tissues in ischemia-reperfusion mice were higher than those normal mice and sham operation mice (P<0.05).

CONCLUSIONS

The increased expressions of S1P and S1PR1 in lung tissues after PIRI suggest that the S1P/S1PR1 signal pathway is involved in the pathophysiological process of PIRI, and may be a potential therapeutic target for it.

A Functionally Defined In Vivo Astrocyte Population Identified by c-Fos Activation in a Mouse Model of Multiple Sclerosis Modulated by S1P Signaling: Immediate-Early Astrocytes (ieAstrocytes)

Astrocytes have prominent roles in central nervous system (CNS) function and disease, with subpopulations defined primarily by morphologies and molecular markers often determined in cell culture. Here, we identify an in vivo astrocyte subpopulation termed immediate-early astrocytes (ieAstrocytes) that is defined by functional c-Fos activation during CNS disease development. An unbiased screen for CNS cells showing c-Fos activation during experimental autoimmune encephalomyelitis (EAE), a mouse model for multiple sclerosis (MS), was developed by using inducible, TetTag c-Fos reporter mice that label activated cells with a temporally stable, nuclear green fluorescent protein (GFP). Four-dimensional (3D over time) c-Fos activation maps in the spinal cord were produced by combining tissue clearing (iDISCO) and confocal microscopy that identified onset and expansion of GFP⁺ cell populations during EAE. More than 95% of the GFP⁺ cells showed glial fibrillary acidic protein (GFAP) immunoreactivity—in contrast to absent or rare labeling of neurons, microglia, and infiltrating immune cells—which constituted ieAstrocytes that linearly increased in number with progression of EAE. ieAstrocyte formation was reduced by either astrocyte-specific genetic removal of sphingosine 1-phosphate receptor 1 (S1P₁) or pharmacological inhibition by fingolimod (FTY720), an FDA-approved MS medicine that can functionally antagonize S1P₁. ieAstrocytes thus represent a functionally defined subset of disease-linked astrocytes that are the first and predominant CNS cell population activated during EAE, and that track with disease severity in vivo. Their reduction by a disease-modifying agent supports their therapeutic relevance to MS and potentially other neuroinflammatory and neurodegenerative diseases.

Sphingosine-1-phosphate selectively activates vagal afferent C-fiber subtype in guinea pig esophagus

BACKGROUND

Activation and sensitization of visceral afferent nerves by inflammatory mediators play important roles in visceral nociception. Sphingosine-1-phosphate (S1P) is a lipid with intracellular and extracellular functions. Extracellularly, it can act as an autacoid via interactions with S1P receptors. The present study aims to determine the effect of S1P on esophageal vagal afferent nerve functions.

METHODS

Extracellular single-unit recordings were performed in ex vivo guinea pig esophageal-vagal preparations. The action potentials (APs) evoked by mechanical distension and chemical perfusions applied to the vagal afferent nerve endings in the esophagus were recorded at their intact neuronal cell bodies in either nodose or jugular ganglia. The effects of S1P and its receptor subtype agonists on vagal afferents were recorded and compared. The expression of S1P receptors (S1PR1-3) in esophageal-labeled vagal nodose and jugular neurons was studied by single-cell RT-PCR.

KEY RESULTS

Sphingosine-1-phosphate evoked AP discharges in almost all esophageal jugular but not nodose C-fibers without changing their responses to esophageal distension. Esophageal-labeled vagal nodose and jugular neurons highly expressed transcripts of S1PR1 and S1PR3. Agonists of S1PR1 and S1PR3 each partially mimicked S1P-induced effect in jugular C-fibers, suggesting that these receptors may contribute partially to S1P-induced activation effect on esophageal jugular C-fiber subtype.

CONCLUSIONS & INFERENCES

These data, for the first time, demonstrated a selective activation effect of S1P on vagal afferent nerve subtype in the gastrointestinal tract. This may help to better understand its role in visceral inflammatory nociception.

Ginsenoside Rb1 Enhances Keratinocyte Migration by a Sphingosine-1-Phosphate-Dependent Mechanism

The cutaneous wound healing process is tightly regulated by a range of cellular responses, including migration. Sphingosine-1-phosphate (S1P) is a signaling lipid produced in keratinocytes (KC) and it is known to stimulate skin wound repair through increased KC migration. Of the multifunctional triterpene ginsenosides, Rb1 enhances cutaneous wound healing process by increasing KC migration, but cellular mechanisms responsible for the Rb1-mediated increase in KC migration are largely unknown. Therefore, we hypothesized that, and assessed whether, Rb1 could stimulate KC migration through S1P-dependent mechanisms. Rb1 significantly increases S1P production by regulating the activity of metabolic conversion enzymes associated with S1P generation and degradation, sphingosine kinase 1 (SPHK1) and S1P lyase, respectively, in parallel with enhanced KC migration. However, blockade of ceramide to S1P metabolic conversion using a specific inhibitor of SPHK1 attenuated the expected Rb1-mediated increase in KC migration. Furthermore, a pan-S1P receptor inhibitor pertussis toxin significantly attenuated Rb1-induced stimulation of KC migration. Moreover, the Rb1-induced increases in KC migration required S1P receptor(s)-mediated activation of ERK1/2 and NF-κB, leading to production of key cutaneous migrating proteins, matrix metalloproteinase (MMP)-2 and MMP-9. Taken together, the results show that Rb1 stimulates KC migration through an S1P→S1P receptor(s)→ERK1/2→NF-κB→MMP-2/-9 pathway. This research revealed a previously unidentified cellular mechanism for Rb1 in enhancing KC migration and pointing to a new therapeutic approach to stimulate the cutaneous wound healing process.

Potent anti-inflammatory properties of HDL in vascular smooth muscle cells mediated by HDL-S1P and their impairment in coronary artery disease due to lower HDL-S1P: a new aspect of HDL dysfunction and its therapy

Dysfunctional HDL is associated with coronary artery disease (CAD), but its effect on inflammation in vascular smooth muscle cells (VSMCs) in atherosclerosis is unknown. We investigated the effect of healthy human HDL and CAD-HDL on TNF-α-driven inflammation in VSMCs and examined whether HDL-associated sphingosine-1-phosphate (HDL-S1P) could modulate inflammation with the aim of designing novel HDL-based anti-inflammatory strategies. Healthy human HDL, human CAD-HDL, and mouse HDL were isolated by ultracentrifugation, S1P was measured by liquid chromatography-tandem mass spectrometry, and TNF-α-induced inflammation was characterized by gene expression and analysis of NF-κB-dependent signaling. Mechanisms of S1P interference with TNF-α were assessed by S1P receptor antagonists, mouse knockouts, and short interfering RNA. We observed that healthy HDL potently inhibited the induction of TNF-α-stimulated inflammatory genes, such as iNOS (inducible NO synthase) and MMP9 (matrix metalloproteinase 9), a process that was entirely dependent on HDL-S1P, as evidenced by loss-of-function using S1P-less HDL and mimicked by genuine S1P. Inhibition was based on suppression of TNF-α-activated Akt signaling resulting in reduced IkBαSer32 and p65Ser534 NF-κB phosphorylation based on a persistent phosphatase and tensin homolog activation by S1P through the S1P receptor 2. Intriguingly, S1P suppressed inflammation even hours after initial TNF-α stimulation. The anti-inflammatory effect of healthy HDL correlated with HDL-S1P content and was superior to that of CAD-HDL featuring lower HDL-S1P. Nevertheless, therapeutic loading of HDL with S1P completely restored the anti-inflammatory capacity of CAD-HDL and greatly boosted that of both healthy and CAD-HDL. Suppression of inflammation by HDL-S1P defines a novel pathophysiologic characteristic that distinguishes functional from dysfunctional HDL. The anti-inflammatory HDL function can be boosted by S1P-loading and exploited by S1P receptor-targeting to prevent and even turn off ongoing inflammation.-Keul, P., Polzin, A., Kaiser, K., Gräler, M., Dannenberg, L., Daum, G., Heusch, G., Levkau, B. Potent anti-inflammatory properties of HDL in vascular smooth muscle cells mediated by HDL-S1P and their impairment in coronary artery disease due to lower HDL-S1P: a new aspect of HDL dysfunction and its therapy.

Sphingosine-1-Phosphate (S1P) Is a Feasible Biomarker in Predicting the Efficacy of Polymyxin B-Immobilized Fiber Direct Hemoperfusion (PMX-DHP) in Patients with Septic Shock

PURPOSE

The aim of this study was to identify a useful biomarker to predict the efficacy of polymyxin B-immobilized fiber direct hemoperfusion (PMX-DHP) in patients with septic shock.

METHODS

The 44 patients included in this study were divided into two groups. Group A had an increase in systolic blood pressure (SBP) over 30 mmHg after PMX-DHP treatment. Group B had an increase in SBP less than 30 mmHg after PMX-DHP treatment. We evaluated the clinical characteristics and demographics of both groups. We also assessed whether the cause of sepsis affected the efficacy of PMX-DHP and compared the prognosis of both groups. Finally, we investigated whether there were any significant differences in the levels of sepsis-related biomarkers, including sphingosine-1-phosphate (S1P), between both groups before PMX-DHP in an effort to identify a biomarker that could predict the efficacy of PMX-DHP.

RESULTS

PMX-DHP significantly increased SBP regardless of the cause of sepsis. Although there was some tendency, PMX-DHP did not significantly improve the prognosis of effective cases in comparison with non-effective cases, probably because of the limited number of patients included. Among the sepsis-related biomarkers, only S1P values were significantly different between the two groups before PMX-DHP, and S1P levels were significantly increased after treatment in the effective cases.

CONCLUSION

S1P levels prior to PMX-DHP can be used to predict its efficacy. In addition, continuous monitoring of S1P levels can indicate the effectiveness of PMX-DHP in patients with septic shock.

Alkaline ceramidase 3 promotes growth of hepatocellular carcinoma cells via regulating S1P/S1PR2/PI3K/AKT signaling

OBJECTIVE

Hepatocellular carcinoma (HCC) is one of the cancer types with poor prognosis. To effectively treat HCC, new molecular targets and therapeutic approaches must be identified. Alkaline ceramidase 3 (Acer3) hydrolyzed long-chain unsaturated ceramide to produce free fatty acids and sphingosine. However, whether and how Acer3 modulates progression of HCC remains largely unknown.

METHODS

Acer3 mRNA levels in different types of human HCC samples or normal tissues were determined from Gene Expression across Normal and Tumor tissue (GENT) database. The expression level of Acer3 in human HCC cell lines were examined by western blot. Overall survival and disease-free survival of HCC patients were determined by Kaplan-Meier analysis. Effects of Acer3 knockdown by lentivirus infection were evaluated on cell growth and apoptosis. The mechanisms involved in HCC cells growth and apoptosis were analyzed by western blot.

RESULTS

In silico analysis of TCGA databases of HCC patients showed that the expression of Acer3 significantly inversely correlates with the overall and disease-free survival of HCC patients. Knockdown expression of Acer3 resulted in decreased cell growth and increased apoptosis. Notably, inhibition of Acer3 resulted in intracellular exhaustion of Sphingosine-1-phosphate (S1P) and inhibited activation of S1PR2/PI3K/AKT signaling. Finally, knockdown of Acer3 induced up-regulation of Bax and down-regulation of Bcl-2.

CONCLUSIONS

Our study suggests that Acer3 contributes to HCC propagation, and suggests that inhibition of Acer3 may be novel strategy for treating human HCC.

Sphingosine-1-phosphate induces airway smooth muscle cell proliferation, migration, and contraction by modulating Hippo signaling effector YAP

Sphingosine-1-phosphate (S1P), a bioactive lipid, has been shown to be elevated in the airways of individuals with asthma and modulates the airway smooth muscle cell (ASMC) functions, yet its underlying molecular mechanisms are not completely understood. The aim of the present study is to address this issue. S1P induced yes-associated protein (YAP) dephosphorylation and nuclear localization via the S1PR_2/3/Rho-associated protein kinase (ROCK) pathway, and this in turn increased forkhead box M1 (FOXM1) and cyclin D1 expression leading to ASMC proliferation, migration, and contraction. Pretreatment of cells with S1PR₂ antagonist JTE013, S1PR₃ antagonist CAY10444, or ROCK inhibitor Y27632 blocked S1P-induced alterations of YAP, FOXM1, cyclin D1, and ASMC proliferation, migration, and contraction. In addition, prior silencing of YAP or FOXM1 with siRNA reversed the effect of S1P on ASMC functions. Taken together, our study indicates that S1P stimulates ASMC proliferation, migration, and contraction by binding to S1PR_2/3 and modulating ROCK/YAP/FOXM1 axis and suggests that targeting this pathway might have potential value in the management of asthma.