The aim of the present study was to explore the role of orphan G protein-coupled receptor 55 (GPR55) in diabetic gastroparesis (DG). Streptozotocin (STZ) was used to mimic the DG model, and the body weight and blood glucose concentration were tested 4 weeks after STZ injection (i.p.). Electrogastrogram and phenolsulfonphthalein test were used for detecting gastric emptying. Motilin (MTL), gastrin (GAS), vasoactive intestinal peptide (VIP), and somatostatin (SS) levels in plasma were determined using radioimmunology. Real-time PCR and Western blot were applied to identify the expression of GPR55 in gastric tissue, and immunohistochemistry was used to detect the distribution. The effect of lysophosphatidylinositol (LPI), an agonist of GPR55, was observed. STZ mice showed increased blood glucose concentration, lower body weight, decreased amplitude of slow wave, and delayed gastric emptying. LPI antagonized these effects of STZ. Compared to the control group, STZ caused significant decreases of MTL and GAS levels (P < 0.01), as well as increases of SS and VIP levels (P < 0.01). The changes of these hormones induced by STZ were counteracted when using LPI. GPR55 located in mice stomach, and it was up-regulated in DG. Although LPI showed no effects on the distribution and expression of GPR55 in normal mice, it could inhibit STZ-induced GPR55 up-regulation. These results suggest GPR55 is involved in the regulation of gastric movement of DG, and may serve as a new target of DG treatment. LPI, an agonist of GPR55, can protect against STZ-induced DG, and the mechanism may involve the change of GPR55 expression and modification of gastrointestinal movement regulating hormones.
Animals ; Diabetes Mellitus, Experimental ; metabolism ; pathology ; Gastroparesis ; metabolism ; pathology ; Lysophospholipids ; pharmacology ; Mice ; Receptors, Cannabinoid ; metabolism

Sphingosine-1-phosphate (S1P) is the main metabolite produced in the process of phospholipid metabolism, which can promote proliferation, migration, and apoptosis of cells, and maintain the barrier function of vascular endothelium. The latest researches showed that S1P can alleviate acute lung injury (ALI) and the inflammation caused by ALI, while the dosage of S1P is still needed to be considered. Mesenchymal stem cells (MSCs) have been a emerging therapy with potential therapeutic effects on ALI because of their characteristics of self-replication and multi-directional differentiation, and their advantages in hematopoiesis, immune regulation, and tissue repair. S1P can promote differentiation of MSCs and participate in immune regulation, while MSCs can regulate the homeostasis of S1P in the body. The synergistic effect of S1P and MSC provides a new treatment method for ALI. This article reviews the production and biological function of S1P, receptor and signal pathway of S1P, the therapeutic effects of S1P on ALI, and the research advances of S1P combined with MSCs in the treatment of ALI, aiming to provide theoretical references for the development of S1P targeted drugs in the treatment of ALI and the search for new combined treatment schemes for ALI.
Acute Lung Injury ; Animals ; Lung/metabolism* ; Lysophospholipids/pharmacology* ; Mice ; Mice, Inbred C57BL ; Sphingosine/pharmacology*

AIMTo establish the methods for determining the activity of sphingosine kinase(SPK) and the content of sphingosine 1-phosphate (S1P) in biological samples.

METHODSThe ECV304 cells were transfected with pcDNA3 vector encoding Flag-labeled SPK gene. The expression of SPK was measured by Western blot assay and the activity of SPK was determined by enzymatic reaction, isotope incorporation and thin-layer chromatography methods. The S1P in biological samples was extracted, digested by alkaline phosphatase and then catalyzed by SPK. The S1P contents were determined according to the amounts of products.

RESULTSSPK gene transfection could enhance the expression and activity of SPK in cells markedly, and the cellular S1P was also increased obviously. HGF stimulation could increase the activity of SPK and cellular S1P in ECV304 cells.

CONCLUSIONMethods for determining the activity of SPK and the content of SPK in biological samples were established.

Cell Line ; Cytophotometry ; Humans ; Isotope Labeling ; Lysophospholipids ; metabolism ; Phosphotransferases (Alcohol Group Acceptor) ; metabolism ; Sphingosine ; analogs & derivatives ; metabolism

OBJECTIVETo investigate the effect and potential mechanism of lysophosphatidic acid (LPA) and antiarrhythmic peptide (AAP10) on rabbit ventricular arrhythmia.

METHODSTwenty-four rabbits were randomly divided into three groups (n = 8 each): control group, LPA group and AAP10 + LPA group. Using arterially perfused rabbit ventricular wedge preparations, transmural ECG and action potentials from both endocardium and epicardium were simultaneously recorded in the whole process of all experiments with two separate floating microeletrodes. The incidence of ventricular arrhythmia post S1S2 stimulation was recorded. Protein levels of nonphosphorylated Cx43 and total Cx43 were evaluated by Western blot. The distribution of nonphosphorylated Cx43 was observed by confocal immunofluorescence microscopy.

RESULTSCompared with the control group, the QT interval, endocardial action potential duration, transmural repolarization dispersion (TDR) and incidence of ventricular arrhythmia were significantly increased and nonphosphorylated Cx43 expression was significantly upregulated in the LPA group. Compared with the LPA group, cotreatment with AAP10 can reduce the QT interval, endocardial action potential duration, TDR and incidence of ventricular arrhythmia (25.0% vs 62.5%, P < 0.01) and downregulate nonphosphorylated Cx43.

CONCLUSIONSLPA could promote the arrhythmia possibly by upregulating nonphosphorylated Cx43 and subsequent gap junction transmission inhibition. Gap junction enhancer AAP10 could attenuate the pro-arrhythmic effect of LPA probably by downregulating myocardial nonphosphorylated Cx43 expression.

Animals ; Anti-Arrhythmia Agents ; pharmacology ; Arrhythmias, Cardiac ; chemically induced ; metabolism ; physiopathology ; Connexin 43 ; metabolism ; Lysophospholipids ; adverse effects ; Oligopeptides ; pharmacology ; Rabbits

Sphingolipids, especially ceramide and S1P, are structural components of biological membranes and bioactive molecules which participate in diverse cellular activities such as cell division, differentiation, gene expression and apoptosis. Emerging evidence demonstrates the role of sphingolipids in hepatocellular death, which contributes to the progression of several liver diseases including ischaemia-reperfusion liver injury, steatohepatitis or hepatocarcinogenesis. Furthermore, some data indicate that the accumulation of some sphingolipids contributes to the hepatic dysfunctions. Hence, understanding of sphingolipid may open up a novel therapeutic avenue to liver diseases. This review focuses on the progress in the sphingolipid metabolic pathway with a focus on hepatic diseases and drugs targeting the sphingolipid pathway.
Apoptosis ; Ceramides ; metabolism ; Fatty Liver ; metabolism ; physiopathology ; Humans ; Liver Diseases ; metabolism ; physiopathology ; Lysophospholipids ; metabolism ; Reperfusion Injury ; metabolism ; physiopathology ; Sphingolipids ; metabolism ; Sphingosine ; analogs & derivatives ; metabolism

OBJECTIVEDiabetic nephropathy (DN) is the major cause of end-stage renal disease worldwide and its prevalence continues to increase. Currently, therapies for DN provide only partial renoprotection; hence new targets for therapeutic intervention need to be identified. In this review, we summarized the new target, sphingosine kinase-1/sphingosine 1-phosphate (SphK1/S1P) pathway, explored its potential therapeutic role in the prevention and treatment of DN.

DATA SOURCESMost relevant articles were mainly identified by searching PubMed in English.

STUDY SELECTIONMainly original articles and critical review articles by major pioneer investigators in this field were selected to be reviewed.

RESULTSSphK1/S1P pathway can be activated by hyperglycemia, advanced glycation end products, and many pro-inflammatory cytokines, which leads to fibronectin, transforming growth factor-β1 up-regulation and AP-1 activation. And then it could promote glomerular mesangial cells proliferation and extracellular matrix accumulation, mediating the initiation and progression of diabetic renal fibrosis.

CONCLUSIONSSphK1/S1P pathway is closely correlated with the pathogenesis of DN. The results suggest that SphK1/S1P pathway as a new target for clinically improving DN in future is of great prospect.

Diabetic Nephropathies ; enzymology ; metabolism ; Extracellular Matrix ; metabolism ; Humans ; Lysophospholipids ; metabolism ; Phosphotransferases (Alcohol Group Acceptor) ; metabolism ; Signal Transduction ; Sphingosine ; analogs & derivatives ; metabolism

Autotaxin (ATX), a member of nucleotide pyrophosphatase/phosphodiesterase (NPP) family, is also named as phosphodiesterase Iα (PD-Iα) or NPP2. ATX is the unique member among the NPPs that can function as a lysophospholipase D (lysoPLD), converting lysophosphatidylcholine into lysophosphatidic acid (LPA). LPA acts on specific G-protein-coupled receptors to elicit a wide range of cellular response, including cell proliferation, cell migration and cell contraction, etc. As the major LPA-producing phospholipase, many ATX's features and functions are dependent on the production of LPA. ATX and LPA together form the ATX-LPA functional axis. The present review summarizes the current progress in function and biological activities of ATX-LPA axis.
Animals ; Cell Movement ; physiology ; Cell Proliferation ; Humans ; Lysophosphatidylcholines ; metabolism ; Lysophospholipids ; metabolism ; physiology ; Phospholipases ; metabolism ; Phosphoric Diester Hydrolases ; metabolism ; physiology ; Receptors, G-Protein-Coupled ; physiology

Sphingosine 1-phosphate (S1P) is an important biologically active lysophospholipid that transmits signals through a family of G-protein-coupled receptors (GPCRs) to regulate the vital functions of several types of immune cells. The S1P GPCRs suppress both generation of specialized functional cytokines, such as IFN-gamma and IL-4, and proliferation of T-cells. Although S1P is chemotactic to T cells, B cells, dendritic cells, and natural killer cells, the major effect of S1P on the immune system is the regulation of lymphocyte recirculation and tissue distribution by S1P and S1P1. Chemotactic response of CD4+CD25+ regulatory T cells to S1P is reduced, but its optimal suppressive activities require S1P. FTY720, a new class of immunomodulator, is rapidly phosphorylated by sphingosine kinase 2 in vivo to form the biologically active phosphorylated-FTY720 (FTY720-P), which closely resembles S1P. The FTY720-P is a true agonist for S1P1, S1P3, S1P4, and S1P5, it affects the tissue distribution and functional activity of T cells, B cells, dendritic cells and regulatory T cells. FTY720 were demonstrated to be a hypotoxic, great effective and reversible immunosuppressive efficacy to prevent allograft rejection and treat some autoimmune diseases. In this article, the synthesis and metabolism of S1P, the expression of S1P GPCRs in immune cells, the effect of S1P on immune cells, the drugs targeted to S1P GPCRs and their clinical implications are reviewed.
Fingolimod Hydrochloride ; Humans ; Immunomodulation ; physiology ; Lysophospholipids ; immunology ; physiology ; Propylene Glycols ; metabolism ; Receptors, G-Protein-Coupled ; immunology ; physiology ; Sphingosine ; analogs & derivatives ; immunology ; metabolism ; physiology

OBJECTIVETo investigate the mechanisms of lysophosphatidic acid (LPA) in stimulating invasion and metastatic colonization of ovarian cancer cells.

METHODSThe metastatic ability in vivo of ovarian cancer SK-OV3, HEY, OVCAR3, and IGROV1 cells was determined in tumor-bearing nude mouse models. Matrigel assay was used to detect the changes of response in vitro of ovarian cancer cells to LPA after Rac(-) or Rac(+) adenovirus treatment. LPA-induced Rho GTPase activation was detected by GST-fusion protein binding assay.

RESULTSThe peritoneal metastatic colonization assay showed overt metastatic colonization in mice receiving SK-OV3 and HEY cell inoculation, indicating that they are invasive cells. Metastatic colonization was not detected in animals receiving OVCAR3 and IGROV1 cells, indicating that these cells are non-invasive cells. In the matrigel invasion assay, exposure to LPA led to a notably greater migratory response in metastatic SK-OV3 and HEY cells (Optical density: SK-OV3 cells: 0.594±0.023 vs. 1.697±0.049, P<0.01; HEY cells: 0.804±0.070 vs. 1.851±0.095, P<0.01). But LPA did little in the non-metastatic OVCAR3 and IGROV1 cells (Optical density A: OVCAR3 cells: 0.336±0.017 vs. 0.374±0.007, P>0.05; IGROV1 cells: 0.491±0.036 vs. 0.479±0.061, P>0.05). LPA migratory responses of ovarian cancer cells were closely related to their metastatic colonization capabilities (r = 0.983, P<0.05). Rac(-) blocked the LPA response of invasive SK-OV3 and HEY cells (LPA-induced fold increase of cell migration: SK-OV3 cells: 2.988±0.095 vs. 0.997±0.100,P=0.01; HEY cells: 2.404±0.059 vs. 0.901±0.072, P=0.01). But Rac(+) confered the non-invasive cells with LPA response and invasion capability (LPA-induced fold increase of cell migration: OVCAR3 cells: 1.072±0.080 vs. 1.898±0.078, P<0.01; IGROV1 cells: 1.002±0.044 vs. 2.141±0.057, P<0.05). Among Rho GTPases, only Rac activation was different between ovarian cancer cell lines with different metastatic capability after LPA stimulation: Cdc42 could not be activated in both the invasive and non-invasive cell lines. RhoA could be activated in both the invasive and non-invasive cell lines. Rac could be activated by LPA in the invasive ovarian cancer cell lines. However, Rac could not be activated in the non-invasive cell lines.

CONCLUSIONLysophosphatidic acid stimulates invasion and metastasis of ovarian cancer cells through Rac activation.

Animals ; Cell Movement ; Female ; Humans ; Lysophospholipids ; metabolism ; Mice ; Ovarian Neoplasms ; metabolism ; Tumor Cells, Cultured ; rho GTP-Binding Proteins ; rhoA GTP-Binding Protein

Sphingosine-1-phosphate (S1P) is an important lipid mediator that regulates a diverse range of intracellular cell signaling pathways that are relevant to tissue engineering and regenerative medicine. However, the precise function of S1P in dental pulp stem cells (DPSCs) and its osteogenic differentiation remains unclear. We here investigated the function of S1P/S1P receptor (S1PR)-mediated cellular signaling in the osteogenic differentiation of DPSCs and clarified the fundamental signaling pathway. Our results showed that S1P-treated DPSCs exhibited a low rate of differentiation toward the osteogenic phenotype in association with a marked reduction in osteogenesis-related gene expression and AKT activation. Of note, both S1PR1/S1PR3 and S1PR2 agonists significantly downregulated the expression of osteogenic genes and suppressed AKT activation, resulting in an attenuated osteogenic capacity of DPSCs. Most importantly, an AKT activator completely abrogated the S1P-mediated downregulation of osteoblastic markers and partially prevented S1P-mediated attenuation effects during osteogenesis. Intriguingly, the pro-inflammatory TNF-α cytokine promoted the infiltration of macrophages toward DPSCs and induced S1P production in both DPSCs and macrophages. Our findings indicate that the elevation of S1P under inflammatory conditions suppresses the osteogenic capacity of the DPSCs responsible for regenerative endodontics.
Cell Differentiation ; Cell Proliferation ; Cells, Cultured ; Dental Pulp/metabolism* ; Lysophospholipids ; Osteogenesis ; Proto-Oncogene Proteins c-akt/metabolism* ; Signal Transduction ; Sphingosine/analogs & derivatives* ; Stem Cells