Sphingosine-1-phosphate hinders the osteogenic differentiation of dental pulp stem cells in association with AKT signaling pathways / 国际口腔科学杂志·英文版

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.

Research advances of the roles of sphingosine-1-phosphate in acute lung injury / 中华烧伤杂志

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.

Research progress on the biological regulatory function of lysophosphatidic acid in bone tissue cells / 华西口腔医学杂志

Lysophosphatidic acid (LPA) is a small phospholipid that is present in all eukaryotic tissues and blood plasma. As an extracellular signaling molecule, LPA mediates many cellular functions by binding to six known G protein-coupled receptors and activating their downstream signaling pathways. These functions indicate that LPA may play important roles in many biological processes that include organismal development, wound healing, and carcinogenesis. Recently, many studies have found that LPA has various biological effects in different kinds of bone cells. These findings suggest that LPA is a potent regulator of bone development and remodeling and holds promising application potential in bone tissue engineering. Here, we review the recent progress on the biological regulatory function of LPA in bone tissue cells.

Effect of STAT3 on Lysophosphatidic Acid-Induced Oral Cancer Cell Invasion / 치위생과학회지

BACKGROUND: Oral cancer has a high incidence worldwide and has been closely associated with smoking, alcohol, and infection by the human papillomavirus. Metastasis is highly important for oral cancer survival. Lysophosphatidic acid (LPA) is a bioactive lipid mediator that promotes various cellular processes, including cell survival, proliferation, metastasis, and invasion. Signal transducer and activator of transcription (STATs) are transcription factors that mediate gene expression. Among the seven types of STATs in mammals, STAT3 is involved in invasion and metastasis of numerous tumors. However, little is known about the role of STAT3 in oral tumor invasion. In the present study, we hypothesized that STAT3 mediates LPA-induced oral cancer invasion. METHODS: Immunoblotting was performed to analyze LPA-induced STAT3 activation. 3-(4,5-Dimethyl-2-thiazolyl)-2,5-diphenyl-2H-tetrazolium bromide (MTT) assay was performed to assess the survival rates of YD-10B cells. STAT3 levels in LPA-treated oral tumor cells were evaluated by performing in vitro invasion assay. RESULTS: To the best of our knowledge, this is the first study to demonstrate that LPA enhances STAT3 phosphorylation in oral cancer. In addition, treatment with WP1066, a selective inhibitor of STAT3, at a concentration that does not cause severe reduction in cell viability, significantly attenuated LPA-induced YD-10B cancer cell invasion. CONCLUSION: The results suggested that LPA induces oral tumor cells with greater invasive potential via STAT3 activation. Our findings provided important insights into the mechanisms underlying mouth neoplasms.

Effect of Resveratrol on Oral Cancer Cell Invasion Induced by Lysophosphatidic Acid / 치위생과학회지

The aim of the current study was to demonstrate the potential therapeutic efficacy of resveratrol in oral cancer patients. Lysophosphatidic acid (LPA) intensifies cancer cell invasion and metastasis, whereas resveratrol, a natural polyphenolic compound, possesses antitumor activity, suppressing cell proliferation and progression in various cancer cell lines (ovarian, gastric, oral, pancreatic, colon, and prostate cancer cells). In addition, resveratrol has been identified as an inhibitor of LPA-induced proteolytic enzyme expression and ovarian cancer invasion. Furthermore, resveratrol was shown to inhibit oral cancer cell invasion by downregulating hypoxia-inducible factor 1α and vascular endothelial growth factor expression. Recently, we demonstrated that LPA is important for the expression of transcription factors TWIST and SLUG during epithelial-mesenchymal transition (EMT) in oral squamous carcinoma cells. In this study, we treated serum-starved cultures of oral squamous carcinoma cell line YD-10B with resveratrol for 24 hours prior to stimulation with LPA. To identify an optimal resveratrol concentration that does not induce apoptosis in oral squamous carcinoma cells, we determined the toxicity of resveratrol in YD-10B cells by assessing their viability using the MTT assay. Another assay was performed using Matrigel-coated cell culture inserts to detect oral cancer cell invasion activity. Immunoblotting was applied for analyzing protein expression of SLUG, TWIST1, E-cadherin, and GAPDH. We demonstrated that resveratrol efficiently inhibited LPA-induced oral cancer cell EMT and invasion by downregulating SLUG and TWIST1 expression. Therefore, resveratrol may potentially reduce oral squamous carcinoma cell invasion and metastasis in oral cancer patients, improving their survival outcomes. In summary, we identified new targets for the development of therapies against oral cancer progression and characterized the therapeutic potential of resveratrol for the treatment of oral cancer patients.

Lysophosphatidic Acid-Induced TWIST1 and Slug Expression in Oral Cancer Cell Invasion / 치위생과학회지

Relative to its incidence, oral cancer has serious negative social effects. The exact causes of oral cancer have not been clarified, but many studies have implicated smoking and drinking. However, the fundamental mechanism of oral cancer causation has yet to be elucidated. Lysophosphatidic acid (LPA) augments epithelial mesenchymal transition (EMT) and development of various cancer cells. However, a detailed mechanistic explanation for LPA-induced EMT and the effects of EMT-promoting conditions on oral squamous cell carcinoma development remain elusive. In the present study, a quantitative reverse transcription polymerase chain reaction was used to analyze TWIST1, Slug, E-cadherin, and glyceraldehyde-3-phosphate dehydrogenase (GAPDH) transcript expression. Immunoblotting was used to analyze TWIST1, Slug, E-cadherin, and GAPDH protein expression. siRNAs were used to silence TWIST1 and Slug transcript expression. A matrigel-coated in vitro invasion insert was used to analyze oral cancer cell invasion. The results of the present study show that the expression levels of TWIST1 and Slug, which are EMT factors, were increased by LPA treatment in YD-10B oral squamous cell carcinoma. Conversely, E-cadherin expression was significantly reduced. In addition, transfection of the cells with TWIST1 and Slug siRNA strongly inhibited LPA-induced oral cancer cell invasion. The present study shows that TWIST1 and Slug mediate LPA-induced oral cancer cell EMT and invasiveness. The present study confirmed the mechanism by which LPA promotes oral cancer cell development, with TWIST1 and Slug providing novel biomarkers and promising therapeutic targets for oral cancer cell development.

The Phospholipid Linoleoylglycerophosphocholine as a Biomarker of Directly Measured Insulin Resistance

BACKGROUND: Plasma concentrations of some lysophospholipids correlate with metabolic alterations in humans, but their potential as biomarkers of insulin resistance (IR) is insufficiently known. We aimed to explore the association between plasma linoleoylglycerophosphocholine (LGPC) and objective measures of IR in adults with different metabolic profiles. METHODS: We studied 62 men and women, ages 30 to 69 years, (29% normal weight, 59% overweight, 12% obese). Participants underwent a 5-point oral glucose tolerance test (5p-OGTT) from which we calculated multiple indices of IR and insulin secretion. Fifteen participants additionally underwent a hyperinsulinemic-euglycemic clamp for estimation of insulin-stimulated glucose disposal. Plasma LGPC was determined using high performance liquid chromatography/time-of-flight mass spectrometry. Plasma LGPC was compared across quartiles defined by the IR indices. RESULTS: Mean LGPC was 15.4±7.6 ng/mL in women and 14.1±7.3 ng/mL in men. LGPC did not correlate with body mass in-dex, percent body fat, waist circumference, blood pressure, glycosylated hemoglobin, log-triglycerides, or high density lipoprotein cholesterol. Plasma LGPC concentrations was not systematically associated with any of the studied 5p-OGTT-derived IR indices. However, LGPC exhibited a significant negative correlation with glucose disposal in the clamp (Spearman r=−0.56, P=0.029). Despite not being diabetic, participants with higher plasma LGPC exhibited significantly higher post-challenge plasma glucose excursions in the 5p-OGTT (P trend=0.021 for the increase in glucose area under the curve across quartiles of plasma LGPC). CONCLUSION: In our sample of Latino adults without known diabetes, LGPC showed potential as a biomarker of IR and impaired glucose metabolism.

Influence of S1PR5 Defect on the Lymphocyte Distribution in Mice / 中国实验血液学杂志

<p><b>BACKGROUND</b>The sphingosine 1-phosphate (S1P) receptors (S1PRs) are a group of G protein-coupled receptors expressed on the surface of lymphocytes. The interaction between S1P and S1PRs plays a significant role in the migration and distribution of lymphocytes.</p><p><b>OBJECTIVE</b>To investigate the influence of S1PR5 defect on the lymphocytes distribution in mice.</p><p><b>METHODS</b>The distribution of different subsets of lymphocyte in the mice with S1PR5 defect was examined by flow cytometry.</p><p><b>RESULTS</b>Compared with wild type mice, the number of NK cells in the peripheral blood (PB) and spleen (SP) from the mice with S1PR5 defect decreased very significantly 〔PB: 6.4±0.45% vs 2.2±0.47(P<0.01,n=3)；SP: 3.0±0.91% vs 0.68±0.14%(P<0.05,n=3)〕. However, the NK cell number in the bone marrow (BM) and lymphonodes (LN) of the mice with S1PR5 defect increased very significantly 〔BM: 0.97±0.20 % vs 2.6±0.35% (P<0.01, n=3); LN: 0.35±0.16% vs 1.7±0.15% (P<0.01, n=3)〕. The percentages of CD3(+) lymphocyte in peripheral blood, spleen and lymph node were not statistically significantly different between these 2 types of mice 〔PB: 17.3±7.9% vs 17.0±4.6% (P>0.05, n=3); SP: 33.0±6.0% vs 27.4±1.8% (P>0.05, n=3); LN: 42.3±10.7% vs 51.2±2.7% (P>0.05, n=3)〕.</p><p><b>CONCLUSION</b>S1PR5 defect can significantly influence the NK cell distribution.</p>

Expression of Sphingosine-1-phosphate (S1P) on the cerebral vasospasm after subarachnoid hemorrhage in rabbits

PURPOSE:To demonstrate the relationship between of sphingosine-1-phosphate (S1P) expression and subarachnoid hemorrhage (SAH).METHODS:The basilar arteries from a "double-hemorrhage" rabbit model of SAH were used to investigate the relation between S1P expression and SAH. Various symptoms, including blood clots, basilar artery cross-sectional area, and S1P phosphatase expression were measured at day 3, 5, 7, 9.RESULTS: The expression of S1P was enhanced in the cerebral vasospasm after subarachnoid hemorrhage in the rabbits. And S1P expression was consistent with the basilar artery cross-sectional area changes at day 3, 5, 7, 9.CONCLUSION: Sphingosine-1-phosphate expression in the cerebral arterial may be a new indicator in the development of cerebral vasospasm after subarachnoid hemorrhage and provide a new therapeutic method for SAH.

Lysophosphatidic acid (LPA) stimulates invasion and metastatic colonization of ovarian cancer cells through Rac activation / 中华肿瘤杂志

<p><b>OBJECTIVE</b>To investigate the mechanisms of lysophosphatidic acid (LPA) in stimulating invasion and metastatic colonization of ovarian cancer cells.</p><p><b>METHODS</b>The 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.</p><p><b>RESULTS</b>The 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.</p><p><b>CONCLUSION</b>Lysophosphatidic acid stimulates invasion and metastasis of ovarian cancer cells through Rac activation.</p>

Recent advances in study of sphingolipids on liver diseases / 药学学报

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.

Papel das vias de sinalização Rho-ROCK e STAT3 no controle da proliferação celular induzida pelo LPA em células de carcinoma de cólon, HCT-116 / [Role of the Rho-ROCK and STAT3 signaling pathways in the control of LPA-induced cell proliferation in colon carcinoma cells, HCT-116]

O câncer colorretal (CCR) é o segundo tipo de neoplasia mais incidente na população brasileira feminina e o terceiro na masculina. Durante a progressão do CCR, células adquirem capacidades proliferativas, migratórias e invasivas. Diversos estímulos são capazes de modular tais eventos, por exemplo, o ácido lisofosfatídico (LPA). Esse fosfolipídeo se liga em re Palavras-chave: 1. Câncer colorretal 2. Ácido Lisofosfatídico 3.GTPase RhoA 4. Proliferação celular ceptores específicos desencadeando diversas vias de sinalização envolvidas com a progressão tumoral. No entanto, pouco se sabe sobre o papel do LPA na progressão do CCR. O objetivo desse estudo foi investigar o papel do LPA em eventos celulares e moleculares relacionados com a progressão do CCR, assim como identificar as vias de sinalização ativadas por este agente. Inicialmente, células derivadas de câncer de cólon com diferentes potenciais invasivos e metastáticos (Caco-2, HT-29 e HCT-116) tiveram seu perfil de expressão proteica dos três principais receptores de LPA (LPA 1-3) analisados por immunoblotting. Em seguida, avaliamos a capacidade do LPA em mediar migração, invasão e crescimento independente de ancoragem e verificamos que este agente não induziu alteração destes eventos. Verificamos então, se o LPA era capaz de causar mudanças no potencial proliferativo nessas linhagens usando a técnica de cristal violeta e analisando a progressão do ciclo celular por citometria de fluxo. Observamos que o LPA causou um aumento de proliferação apenas nas células HCT-116 e de forma dependente da GTPase Rho e de sua efetora ROCK. Sabendo que as vias de ß-catenina e de STAT 3 podem ser reguladas pela via Rho-ROCK, verificamos a capacidade do LPA modular a atividade transcricional de ß-catenina e os níveis de fosforilação de STAT 3 (pSTAT). Embora os resultados não tenham indicado a ativação de ß-catenina pelo ensaio de luciferase de TCF/Lef, observamos um aumento nos níveis de pSTAT por immunoblotting e de sua localização nuclear por microscopia confocal, indicando ativação desta via. Além disso, essa ativação foi independente da via Rho-ROCK, visto que o inibidor de ROCK, Y27632, não reverteu esse efeito. De forma interessante, observamos que a inibição farmacológica de ambos, STAT 3, com STA21, e ROCK, com Y27632, prevenia o aumento de proliferação induzido pelo LPA em HCT-116 e que a inibição conjunta dessas vias apresentava um efeito ainda maior na prevenção da progressão do ciclo celular causada pelo LPA. Finalmente, a análise de expressão gênica global das células HCT-116 tratadas com LPA por ChipArrray, mostrou um aumento na expressão gênica das ciclinas E1, A2 e B1, efeito este confirmado por immunoblotting. Ainda, nossos resultados mostraram que a inibição concomitante das vias Rho-ROCK e STAT 3 preveniu o aumento da expressão dessas proteínas. Em conclusão, no presente estudo mostramos que o LPA aumenta o potencial proliferativo das células HCT-116, uma linhagem celular com potencial mais invasivo, através de um mecanismo envolvendo uma cooperação das vias Rho-ROCK e STAT3 no controle do ciclo celular.

Lysophosphatidic acid increases SLC26A3 expression in inflamed intestine and reduces diarrheal severity in C57BL/6 mice with dextran-sodium-sulfate-induced colitis / 中华医学杂志(英文版)

<p><b>BACKGROUND</b>Diarrhea is a common clinical feature of ulcerative colitis resulting from unbalanced intestinal fluid and salt absorption and secretion. The Cl(-)/HCO3(-) exchanger SLC26A3 is strongly expressed in the mid-distal colon and plays an essential role in colonic Cl(-) absorption and HCO3(-) secretion. Slc26a3 expression is up-regulated by lysophosphatidic acid (LPA) in vitro. Our study was designed to investigate the effects of LPA on SLC26A3 expression and the diarrheal phenotype in a mouse colitis model.</p><p><b>METHODS</b>Colitis was induced in C57BL/6 mice by adding 4% of dextran sodium sulfate (DSS) to the drinking water. The mice were assigned to LPA treatment DSS group, phosphate-buffered saline (PBS) treatment DSS group, DSS only group and untreated mice with a completely randomized design. Diarrhea severity was evaluated by measuring mice weight, disease activity index (DAI), stool water content and macroscopic evaluation of colonic damage. The effect of LPA treatment on Slc26a3 mRNA level and protein expression in the different groups of mice was investigated by quantitative PCR and Western blotting.</p><p><b>RESULTS</b>All mice treated with DSS lost weight, but the onset and severity of weight loss was attenuated in the LPA treatment DSS group. The increases in stool water content and the macroscopic inflammation score in LPA treatment DSS group were significantly lower compared to DSS control group or PBS treatment DSS group ((18.89±8.67)% vs. (28.97±6.95)% or (29.48±6.71)%, P = 0.049, P = 0.041, respectively and 2.67±0.81 vs. 4.5±0.83 or 4.5±0.54, P = 0.020, P = 0.006, respectively), as well as the increase in DAI (P = 0.004, P = 0.008, respectively). LPA enema resulted in higher Slc26a3 mRNA and protein expression levels compared to PBS-treated and untreated DSS colitis mice.</p><p><b>CONCLUSION</b>LPA increases Slc26a3 expression in the inflamed intestine and reduces diarrhea severity in DSS-induced colitis, suggesting LPA might be a therapeutic strategy in the treatment of colitis associated diarrhea.</p>

Sphingosine Kinase-1/sphingosine 1-phosphate pathway in diabetic nephropathy / 中华医学杂志(英文版)

<p><b>OBJECTIVE</b>Diabetic 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.</p><p><b>DATA SOURCES</b>Most relevant articles were mainly identified by searching PubMed in English.</p><p><b>STUDY SELECTION</b>Mainly original articles and critical review articles by major pioneer investigators in this field were selected to be reviewed.</p><p><b>RESULTS</b>SphK1/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.</p><p><b>CONCLUSIONS</b>SphK1/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.</p>

Sphingosine-1-phosphate receptors respond differently to early myocardial ischemia and ischemia-reperfusion in vivo / 生理学报

Sphingosine-1-phosphate (S1P) has been demonstrated to be a mediator and marker of heart diseases. We hypothesized that the expression of S1P receptors is involved in the S1P-mediated cardioprotection in vivo and may serve as a biomarker of ischemic heart disease. In vivo models of myocardial ischemia (MI) and ischemia-reperfusion (IR) were established by ligation of the left anterior descending artery (LAD) of rat heart, the mRNA expressions of S1PR1-3 were detected using real time PCR at different time intervals after ischemia (LAD for 15 min, 30 min, and 1 h) and IR. The results showed that mRNA expression of S1PR3, but not S1PR1 and S1PR2, increased greatly after IR. No statistical difference was found in any of the three S1P receptors after MI within 1 h. Regarding the studies of lipid concentration changes in myocardiopathy, we conclude that S1P receptors are not early response biomarkers for MI. There are different mechanisms when S1P plays a protection role in heart during MI and IR. The cooperation of lipid content and S1P receptor expression appears to form a regulation network during MI and IR.

Role of orphan G protein-coupled receptor 55 in diabetic gastroparesis in mice / 生理学报

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.

Role of LPA and the Hippo pathway on apoptosis in salivary gland epithelial cells

Lysophosphatidic acid (LPA) is a bioactive lysophospholipid involved in numerous physiological responses. However, the expression of LPA receptors and the role of the Hippo signaling pathway in epithelial cells have remained elusive. In this experiment, we studied the functional expression of LPA receptors and the associated signaling pathway using reverse transcriptase-PCR, microspectrofluorimetry, western blotting and immunocytochemistry in salivary gland epithelial cells. We found that LPA receptors are functionally expressed and involved in activating the Hippo pathway mediated by YAP/TAZ through Lats/Mob1 and RhoA/ROCK. Upregulation of YAP/TAZ-dependent target genes, including CTGF, ANKRD1 and CYR61, has also been observed in LPA-treated cells. In addition, based on data suggesting that tumor necrosis factor (TNF)-alpha induces cell apoptosis, LPA upregulates TNF-induced caspase-3 and cleaved Poly(ADP-ribose)polymerase (PARP). However, small interfering RNA treatment to Yes-associated protein (YAP) or transcriptional co-activator with a PDZ-binding motif (TAZ) significantly decreased TNF-alpha- and LPA-induced apoptosis, suggesting that YAP and TAZ modulate the apoptotic pathway in salivary epithelial cells.

Kruppel-like factor 4 mediates lysophosphatidic acid-stimulated migration and proliferation of PC3M prostate cancer cells

Prostate cancer is the most frequently diagnosed malignancy and the second leading cause of cancer mortality among men in the United States. Accumulating evidence suggests that lysophosphatidic acid (LPA) serves as an autocrine/paracrine mediator to affect initiation, progression and metastasis of prostate cancer. In the current study, we demonstrate that LPA stimulates migration and proliferation of highly metastatic human prostate cancer, PC-3M-luc-C6 cells. LPA-induced migration of PC-3M-luc-C6 cells was abrogated by pretreatment of PC-3M-luc-C6 cells with the LPA receptor 1/3 inhibitor Ki16425 or small interfering RNA (siRNA)-mediated silencing of endogenous LPA receptor 1, implicating a key role of the LPA-LPA receptor 1 signaling axis in migration of PC-3M-luc-C6 cells. In addition, LPA treatment resulted in augmented expression levels of Kruppel-like factor 4 (KLF4), and siRNA or short-hairpin RNA (shRNA)-mediated silencing of KLF4 expression resulted in the abolishment of LPA-stimulated migration and proliferation of PC-3M-luc-C6 cells. shRNA-mediated silencing of KLF4 expression resulted in the inhibition of in vivo growth of PC-3M-luc-C6 cells in a xenograft transplantation animal model. Taken together, these results suggest a key role of LPA-induced KLF4 expression in cell migration and proliferation of prostate cancer cells in vitro and in vivo.

Esfingosina-1-fosfato y cánceres urológicos: identificando potenciales blancos terapéuticos en su etabolismo y señalización / Sphingosine-1-phosphate and urological cancers: identifying potential therapeutic targets in its metabolism and signalling

Los lípidos no sólo son moléculas estructurales de las membranas. Hay numerosos ejemplos de lípidos que median acciones fisiológicas dentro de las células. Específicamente, esfingolípidos como ceramida, esfingosina y esfingosina-1-fosfato (S1P) han sido involucrados en el control del crecimiento celular, la proliferación y la migración, todo lo cual se ha relacionado con el cáncer.Los efectos pro-apoptóticos de la ceramida y la esfingosina son revertidos por S1P. Por lo tanto, el destino de la célula puede ser modulada mediante el cambio de la proporción de estos esfingolípidos (el modelo reóstato). S1P promueve la proliferación celular, el crecimiento, la supervivencia, la migración, invasión y resistencia fármacos y radiación, en parte a través de receptores de membrana (S1PR1-5). La sobreexpresión de enzimas productoras de S1P y el aumento de los niveles de S1P se ha descrito en muchos tipos de cáncer, incluyendo cánceres urológicos. Por lo tanto, se pueden identificar posibles objetivos terapéuticos en el metabolismo y las vías de señalización de los esfingolípidos, cuya relevancia clínica debe ser determinada en futuros estudios.

Lipids are not only structural molecules of the membranes. There are numerous examples of lipids mediating physiologic actions within the cells. Specifically, sphingolipids like ceramide, sphingosine and sphingosine-1-phosphate (S1P) have been described to be involved in the control of cell growth, proliferation and migration, all of which has been linked to cancer. The pro-apoptotic effects of ceramide and sphingosine are opposed by S1P. Therefore, the fate of the cell can be modulated by changing the ratio of these sphingolipids (the rheostat model). S1P promotes cell proliferation, growth, survival, migration, invasion and resistance to drugs and radiation, in part mediated by S1P membrane receptors (S1PR1-5). Overexpression of S1P producing enzymes and increased S1P levels has been described in many cancers, including urological cancers. Therefore, potential therapeutic targets can be recognized in the metabolism and signaling pathways of sphingolipids and their clinical relevance have to be determined in future studies.

Activation of Lysophosphatidic Acid Receptor Is Coupled to Enhancement of Ca(2+)-Activated Potassium Channel Currents

The calcium-activated K+ (BKCa) channel is one of the potassium-selective ion channels that are present in the nervous and vascular systems. Ca2+ is the main regulator of BKCa channel activation. The BKCa channel contains two high affinity Ca2+ binding sites, namely, regulators of K+ conductance, RCK1 and the Ca2+ bowl. Lysophosphatidic acid (LPA, 1-radyl-2-hydroxy-sn-glycero-3-phosphate) is one of the neurolipids. LPA affects diverse cellular functions on many cell types through G protein-coupled LPA receptor subtypes. The activation of LPA receptors induces transient elevation of intracellular Ca2+ levels through diverse G proteins such as Galphaq/11, Galphai, Galpha12/13, and Galphas and the related signal transduction pathway. In the present study, we examined LPA effects on BKCa channel activity expressed in Xenopus oocytes, which are known to endogenously express the LPA receptor. Treatment with LPA induced a large outward current in a reversible and concentration-dependent manner. However, repeated treatment with LPA induced a rapid desensitization, and the LPA receptor antagonist Ki16425 blocked LPA action. LPA-mediated BKCa channel activation was also attenuated by the PLC inhibitor U-73122, IP3 inhibitor 2-APB, Ca2+ chelator BAPTA, or PKC inhibitor calphostin. In addition, mutations in RCK1 and RCK2 also attenuated LPA-mediated BKCa channel activation. The present study indicates that LPA-mediated activation of the BKCa channel is achieved through the PLC, IP3, Ca2+, and PKC pathway and that LPA-mediated activation of the BKCa channel could be one of the biological effects of LPA in the nervous and vascular systems.