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1.
Lysophosphatidic acid (LPA) is a low-molecular-weight lysophospholipid enriched in platelets and mildly oxidized low-density lipoprotein (OxLDL). It is suggested that LPA is involved in atherosclerosis, and our previous studies showed that LPA regulates inflammation in multiple cell types. The main aim of this study was to investigate the effects of LPA on the uptake of OxLDL by mouse J774A.1 macrophages. We observed that LPA upregulated fluorescence-labeled DiI-OxLDL uptake in J774A.1 cells. Meanwhile, expression of the class A scavenger receptor (SR-A), a receptor for modified LDL, was also enhanced. Furthermore, pertussis toxin (PTx) or Ki16425 significantly abolished LPA's effects, indicating that G(i) and LPA(3) are involved in OxLDL uptake and SR-A expression. Of most importance, the LPA-induced OxLDL uptake could be inhibited when cells were incubated with a functional blocking antibody of SR-A. Our results suggest that LPA-enhanced OxLDL uptake is mediated via LPA(3)-G(i) activation and subsequent SR-A expression.  相似文献   

2.
3.
Lysophosphatidic acid (LPA) receptors belong to G protein-coupled transmembrane receptors and mediate a variety of cellular responses through the binding of LPA. So far, six types of LPA receptors (LPA receptor-1 (LPA1) to LPA6) have been identified. Recently, it has been demonstrated that each LPA receptor has opposite effects on malignant property of cancer cells. In this study, to evaluate an involvement of LPA receptors on angiogenic process in mammary tumor cells, we generated Lpar1- and Lpar3-expressing (FM3A-a1 and FM3A-a3A9, respectively) cells from FM3A cells, and investigated the effects on cell proliferation and migration abilities of endothelial F-2 cells by those cells. In Vegf-A and Vegf-C genes, FM3A-a1 cells indicated high expression and FM3A-a3A9 cells showed low expression, compared with control cells. When F-2 cells were cultured with a supernatant from FM3A-a1 cells, the cell growth rate and migration ability of F-2 cells was significantly higher than control cells. By contrast, a supernatant from FM3A-a3A9 cells significantly inhibited those abilities of F-2 cells. These results suggest that LPA1 and LPA3 may play opposite roles on the regulation of endothelial cells in mouse mammary tumor FM3A cells.  相似文献   

4.
LPA and LPA1 have been shown to increase osteoblastic proliferation and differentiation as well as activation of osteoclasts. Cell and animal model studies have suggested that LPA is produced by bone cells and bone tissues. We obtained data from invalidated mice which support the hypothesis that LPA1 is involved in bone development by promoting osteogenesis. LPA1-invalidated mice demonstrate growth and sternal and costal abnormalities, which highlights the specific roles of LPA1 during bone development. Microcomputed tomography and histological analysis demonstrate osteoporosis in the trabecular and cortical bone of LPA1-invalidated mice. Moreover, bone marrow mesenchymal progenitors from these mice displayed decreased osteoblastic differentiation. Infrared analysis did not indicate osteomalacia in the bone tissue of LPA1-invalidated mice. LPA1 displays opposite effects to LPA4 on the related G proteins Gi and Gs, responsible for decrease and increase of the cAMP level respectively, which itself is essential to the control of osteoblastic differentiation. The opposite effects of LPA1 and LPA4 during osteoblastic differentiation support the possibility that new pharmacological agents derived from the LPA pathways could be found and used in clinical practice to positively influence bone formation and treat osteoporosis. The paracrine effect of LPA is potentially modulated by its concentration in bone tissues, which may result from various intracellular and extracellular pathways. The relevance of LPA1 in bone remodeling, as a receptor able to influence both osteoblast and osteoclast activity, still deserves further clarification. This article is part of a Special Issue entitled Advances in Lysophospholipid Research.  相似文献   

5.
Lysophosphatidic acid (LPA) is a major constituent of blood and is involved in a variety of physiological and pathophysiological processes. LPA signals via the ubiquitously expressed G protein-coupled receptors (GPCRs), LPA1 and LPA2 that are specific for LPA. However, in large, the molecular mechanisms that regulate the signalling of these receptors are unknown. We show that the small GTPase RalA associates with both LPA1 and LPA2 in human embryonic kidney (HEK 293) cells and that stimulation of LPA1 receptors with LPA triggers the activation of RalA. While RalA was not found to play a role in the endocytosis of LPA receptors, we reveal that LPA1 receptor stimulation promoted Ral-dependent phospholipase C activity. Furthermore, we found that GRK2 is required for the desensitization of LPA1 and LPA2 and have identified a novel interaction between RalA and GRK2, which is promoted by LPA1 receptor activity. Taken together, these results establish RalA and GRK2 as key regulators of LPA receptor signalling and demonstrate for the first time that LPA1 activity facilitates the formation of a novel protein complex between these two proteins.  相似文献   

6.
The enhanced migration found in tumor cells is often caused by external stimuli and the sequential participation of cytoskeleton‐related signaling molecules. However, until now, the molecular connection between the lysophosphatidic acid (LPA) receptor and nonmuscle myosin II (NM II) has not been analyzed in detail for LPA‐induced migration. Here, we demonstrate that LPA induces migration by activating the LPA1 receptor which promotes phosphorylation of the 20 kDa NM II light chain through activation of Rho kinase (ROCK). We show that LPA‐induced migration is insensitive to pertussis toxin (PTX) but does require the LPA1 receptor as determined by siRNA and receptor antagonists. LPA activates ROCK and also increases GTP‐bound RhoA activity, concomitant with the enhanced membrane recruitment of RhoA. LPA‐induced migration and invasion are attenuated by specific inhibitors including C3 cell‐permeable transferase and Y‐27632. We demonstrate that NM II plays an important role in LPA‐induced migration and invasion by inhibiting its cellular function with blebbistatin and shRNA lentivirus directed against NM II‐A or II‐B. Inhibition or loss of either NM II‐A or NM II‐B in 4T1 cells results in a decrease in migration and invasion. Restoration of the expression of NM II‐A or NM II‐B also rescued LPA‐induced migration. Taken together, these results suggest defined pathways for signaling through the LPA1 receptor to promote LPA‐mediated NM II activation and subsequent cell migration in 4T1 breast cancer cells. J. Cell. Physiol. 226: 2881–2893, 2011. © 2011 Wiley‐Liss, Inc.  相似文献   

7.
Lysophosphatidic acid (LPA) receptors (LPA1 to LPA6) indicate a variety of cellular responses, such as cell proliferation, migration, differentiation, and morphogenesis. However, the role of each LPA receptor is not functionally equivalent. Ethionine, an ethyl analog of methionine, is well known to be one of the potent liver carcinogens in rats. In this study, to assess whether ethionine may regulate cell motile activity through LPA receptors, rat liver epithelial (WB-F344) cells were treated with ethionine for 48 h. In cell motility assay with a cell culture insert, the treatment of ethionine at 1.0 and 10 μM enhanced significantly high cell motile activity, compared with untreated cells. The expression levels of LPA receptor genes in cells treated with ethionine were measured by quantitative real time RT-PCR analysis. The expression of the Lpar3 gene in ethionine-treated cells was significantly higher than that in untreated cells. Furthermore, to confirm an involvement of LPA3 on cell motility increased by ethionine, the Lpar3 knockdown cells were also used. The cell motile activity by ethionine was completely suppressed in the Lpar3 knockdown cells. These results suggest that LPA signaling through LPA3 may be involved in cell motile activity stimulated by ethionine in WB-F344 cells.  相似文献   

8.
Lysophosphatidic acid (LPA) mediates a variety of biological functions via the binding of G protein-coupled LPA receptors (LPA receptor-1 (LPA1) to LPA6). This study aimed to investigate the roles of LPA2 and LPA3 in the modulation of chemoresistance to anticancer drug in lung cancer A549 cells. In cell survival assay, cells were treated with cisplatin (CDDP) every 24 h for 2 days. The cell survival rate to CDDP of A549 cells was significantly elevated by an LPA2 agonist, GRI-977143. To evaluate the roles of LPA2-mediated signaling in cell survival during tumor progression, highly migratory (A549-R10) cells were generated from A549 cells. In the presence of GRI-977143, the cell survival rate to CDDP of A549-R10 cells were markedly higher than that of A549 cells, correlating with LPAR2 expression level. Moreover, to assess the effects of long-term anticancer drug treatment on cell survival, the long-term CDDP treated (A549-CDDP) cells were established from A549 cells. The cell survival rate to CDDP of A549-CDDP cells was elevated by GRI-977143. Since LPAR3 expression level was significantly higher in A549-CDDP cells than in A549 cells, we investigated the roles of LPA3 in the cell survival to CDDP of A549 cells, using an LPA3 agonist, 1-oleoyl-2-methyl-sn-glycero-3-phosphothionate ((2S)-OMPT). The cell survival rate to CDDP of A549 cells was significantly reduced by (2S)-OMPT treatment. In the presence of (2S)-OMPT, the cell survival rate to CDDP of A549 cells was elevated by LPA3 knockdown. These results suggest that LPA signaling via LPA2 and LPA3 is involved in the regulation of chemoresistance in A549 cells treated with CDDP.  相似文献   

9.
Lysophosphatidic acid (LPA) is a simple biophysical lipid which interacts with at least six subtypes of G protein-coupled LPA receptors (LPA1–LPA6). In cancer cells, LPA signaling via LPA receptors is involved in the regulation of malignant properties, such as cell growth, motility, and invasion. The aim of this study was to assess whether LPA receptors regulate cellular functions of fibrosarcoma cells treated with anticancer drug. HT1080 cells were maintained by the stepwise treatment of cisplatin (CDDP) at a range of 0.01 to 1.0 µM for approximately 6 months. The cell motile and invasive activities of long-term CDDP-treated (HT-CDDP) cells were significantly stimulated by LPA treatment, while HT-CDDP cells in the static state showed the low cell motile and invasive activities in comparison with HT1080 cells. Since the expression level of LPAR2 gene was markedly elevated in HT-CDDP cells, LPA2 knockdown cells were generated from HT-CDDP cells. The cell motile and invasive activities of HT-CDDP cells were reduced by LPA2 knockdown. In colony assay, large-sized colonies formed by long-term CDDP treatment were suppressed by LPA2 knockdown. In addition, LPA2 knockdown cells reduced LPA production by autotaxin (ATX), correlating with ATX expression level. These results suggest that LPA signaling via LPA2 may play an important role in the regulation of cellular functions in HT1080 cells treated with CDDP.  相似文献   

10.
Lysophosphatidic acid (LPA) is a natural bioactive lipid with growth factor-like functions due to activation of a series of six G protein-coupled receptors (LPA1–6). LPA receptor type 1 (LPA1) signaling influences the pathophysiology of many diseases including cancer, obesity, rheumatoid arthritis, as well as lung, liver and kidney fibrosis. Therefore, LPA1 is an attractive therapeutic target. However, most mammalian cells co-express multiple LPA receptors whose co-activation impairs the validation of target inhibition in patients because of missing LPA receptor-specific biomarkers. LPA1 is known to induce IL-6 and IL-8 secretion, as also do LPA2 and LPA3. In this work, we first determined the LPA induced early-gene expression profile in three unrelated human cancer cell lines expressing different patterns of LPA receptors (PC3: LPA1,2,3,6; MDA-MB-231: LPA1,2; MCF-7: LPA2,6). Among the set of genes upregulated by LPA only in LPA1-expressing cells, we validated by QPCR and ELISA that upregulation of heparin-binding EGF-like growth factor (HB-EGF) was inhibited by LPA1–3 antagonists (Ki16425, Debio0719). Upregulation and downregulation of HB-EGF mRNA was confirmed in vitro in human MDA-B02 breast cancer cells stably overexpressing LPA1 (MDA-B02/LPA1) and downregulated for LPA1 (MDA-B02/shLPA1), respectively. At a clinical level, we quantified the expression of LPA1 and HB-EGF by QPCR in primary tumors of a cohort of 234 breast cancer patients and found a significantly higher expression of HB-EGF in breast tumors expressing high levels of LPA1. We also generated human xenograph prostate tumors in mice injected with PC3 cells and found that a five-day treatment with Ki16425 significantly decreased both HB-EGF mRNA expression at the primary tumor site and circulating human HB-EGF concentrations in serum. All together our results demonstrate that HB-EGF is a new and relevant biomarker with potentially high value in quantifying LPA1 activation state in patients receiving anti-LPA1 therapies.  相似文献   

11.
Lysophophatidic acid (LPA), a low-molecular-weight lysophospholipid enriched in platelets and mildly oxidized low-density lipoproteins, is known to regulate inflammation and atherosclerosis by binding to its cognate receptors. In this study, we reported that LPA upregulated interleukin-1β (IL-1β) expression in mouse J774A.1 macrophages. By using pharmacological inhibitors, it was suggested that Gi/Rho activation and subsequent reactive oxygen species (ROS) production were involved in IL-1β induction. In addition, IL-1β induction by LPA was also observed in human primary macrophages. In summary, LPA is involved in the processes of inflammation by affecting macrophage behavior.  相似文献   

12.
Lysophosphatidic acid (LPA) is a ligand of multiple G protein–coupled receptors. The LPA1–3 receptors are members of the endothelial cell differentiation gene (Edg) family. LPA4/p2y9/GPR23, a member of the purinergic receptor family, and recently identified LPA5/GPR92 and p2y5 are structurally distant from the canonical Edg LPA receptors. Here we report targeted disruption of lpa4 in mice. Although LPA4-deficient mice displayed no apparent abnormalities, LPA4-deficient mouse embryonic fibroblasts (MEFs) were hypersensitive to LPA-induced cell migration. Consistent with negative modulation of the phosphatidylinositol 3 kinase pathway by LPA4, LPA4 deficiency potentiated Akt and Rac but decreased Rho activation induced by LPA. Reconstitution of LPA4 converted LPA4-negative cells into a less motile phenotype. In support of the biological relevance of these observations, ectopic expression of LPA4 strongly inhibited migration and invasion of human cancer cells. When coexpressed with LPA1 in B103 neuroblastoma cells devoid of endogenous LPA receptors, LPA4 attenuated LPA1-driven migration and invasion, indicating functional antagonism between the two subtypes of LPA receptors. These results provide genetic and biochemical evidence that LPA4 is a suppressor of LPA-dependent cell migration and invasion in contrast to the motility-stimulating Edg LPA receptors.  相似文献   

13.
Microglia, the immunocompetent cells of the CNS, are rapidly activated in response to injury and microglia migration towards and homing at damaged tissue plays a key role in CNS regeneration. Lysophosphatidic acid (LPA) is involved in signaling events evoking microglia responses through cognate G protein‐coupled receptors. Here we show that human immortalized C13NJ microglia express LPA receptor subtypes LPA1, LPA2, and LPA3 on mRNA and protein level. LPA activation of C13NJ cells induced Rho and extracellular signal‐regulated kinase activation and enhanced cellular ATP production. In addition, LPA induced process retraction, cell spreading, led to pronounced changes of the actin cytoskeleton and reduced cell motility, which could be reversed by inhibition of Rho activity. To get an indication about LPA‐induced global alterations in protein expression patterns a 2‐D DIGE/LC‐ESI‐MS proteomic approach was applied. On the proteome level the most prominent changes in response to LPA were observed for glycolytic enzymes and proteins regulating cell motility and/or cytoskeletal dynamics. The present findings suggest that naturally occurring LPA is a potent regulator of microglia biology. This might be of particular relevance in the pathophysiological context of neurodegenerative disorders where LPA concentrations can be significantly elevated in the CNS.  相似文献   

14.
Abstract

Lysophosphatidic acid (LPA) signaling via G protein-coupled transmembrane LPA receptors (LPA1 to LPA6) mediates a variety of cellular functions, including cell proliferation, migration, morphogenesis, and differentiation. Recently, we demonstrated that the different induction of LPA receptors by estrogens regulates cell motile activity of rat liver epithelial WB-F344 cells. In the present study, to assess whether endocrine disruptors (EDs) are involved in cellular functions through LPA signaling, we measured cell motile activity and LPA receptor expressions in WB-F344 cells treated with bisphenol A (BPA) and 4-nonylphenol (4-NP). Using quantitative real time RT-PCR analysis, the Lpar1 expression was elevated in BPA-treated cells, whereas the Lpar3 expression was decreased. In contrast, 4-NP increased the Lpar3 expression, but not the Lpar1 and Lpar2. For cell motility assay with a Cell Culture Insert, cell motile activity of BPA-treated cells was significantly lower than that of untreated cells. In contrast, 4-NP markedly enhanced cell motile activity. The effects of BPA and 4-NP on cell motility were inhibited by the Lpar1 or Lpar3 knockdown. These results suggest that BPA and 4-NP may regulate cell motile activity through the different induction of LPA receptors in WB-F344 cells.  相似文献   

15.
16.
Embryonic stem cells (ESC) are pluripotent and could be maintained in vitro in a self-renewing state indefinitely, at the same time preserving their potential to differentiate towards more specific lineages. Despite the progress in the field, the complex network of signalling cascades involved in the maintenance of the self-renewing and pluripotent state remains not fully understood. In the present study, we have investigated the role of lysophosphatidic acid (LPA), a potent mitogen present in serum, in Ca2+ signalling and early gene activation in mouse ESC (mESC). In these cells, we detected the expression of the G-protein coupled LPA receptor subtypes LPA1, LPA2 and LPA3. Using fluorescence Ca2+ imaging techniques, we showed that LPA induced an increase in intracellular Ca2+ concentration. This increase was also observed in the absence of extracellular Ca2+, suggesting the involvement of internal stores. Pre-treatment with BAPTA-AM, thapsigargin or U-73122 efficiently blocked this Ca2+ release, indicating that LPA was evoking Ca2+ mobilization from the endoplasmic reticulum via the phospholipase C (PLC) pathway. Interestingly, this signalling cascade initiated by LPA was involved in inducing the expression of the Ca2+-dependent early response gene c-myc, a key gene implicated in ESC self-renewal and pluripotency. Additionally, LPA increased the proliferation rate of mESC. Our findings therefore outline the physiological role of LPA in mESC.  相似文献   

17.
Lysophosphatidic acid (LPA) is a simple physiological lipid and exhibits a variety of cellular responses via the activation of G protein-coupled transmembrane LPA receptors (LPA receptor-1 (LPA1) to LPA6). The aim of our study was to investigate effects of LPA receptors on soft agar colony formation in colon cancer cells treated with anticancer drugs. DLD1 cells were treated with fluorouracil (5-FU) or cisplatin (CDDP) for at least six months (DLD-5FU and DLD-CDDP cells, respectively). LPAR1 gene expression was markedly elevated in DLD-5FU cells. In contrast, DLD-CDDP cells showed the high expression of LPAR6 gene. In colony formation assay, DLD-5FU cells formed markedly large-sized colonies, while no colony formation was observed in DLD1 and DLD-CDDP cells. The large-sized colonies formed in DLD-5FU cells were suppressed by LPA1 knockdown. In contrast, LPA6 knockdown increased the size of colonies. In addition, DLD-5FU cells were further treated with CDDP for three months (DLD-C-F cells). DLD-CDDP cells were also treated with 5-FU (DLD-F-C cells). DLD-C-F cells formed large-sized colonies, but not DLD-F-C cells, correlating with LPAR1 and LPAR6 gene expression levels. These results suggest that LPA1 and LPA6 may regulate the colony formation activity in DLD1 cells treated with anticancer drugs.  相似文献   

18.

Lysophosphatidic acid (LPA) signaling via LPA receptors (LPA1 to LPA6) exhibits a variety of malignant properties in cancer cells. Intracellular ATP depletion leads to the development of necrosis and apoptosis. The present study aimed to evaluate the effects of LPA receptor-mediated signaling on the regulation of cancer cell functions associated with ATP reduction. Long-term ethidium bromide (EtBr) treated (MG63-EtBr) cells were established from osteosarcoma MG-63 cells. The intracellular ATP levels of MG63-EtBr cells were significantly lower than that of MG-63 cells. LPAR2, LPAR3, LPAR4 and LPAR6 gene expressions were elevated in MG63-EtBr cells. The cell motile and invasive activities of MG63-EtBr cells were markedly higher than those of MG-63 cells. The cell motile activity of MG-63 cells was increased by LPA4 and LPA6 knockdowns. In cell survival assay, cells were treated with cisplatin (CDDP) every 24 h for 3 days. The cell survival to CDDP of MG63-EtBr cells was lower than that of MG-63 cells. LPA2 knockdown decreased the cell survival to CDDP of MG-63 cells. The cell survival to CDDP of MG-63 cells was inhibited by (2 S)-OMPT (LPA3 agonist). Moreover, the cell survival to CDDP of MG-63 cells was enhanced by LPA4 and LPA6 knockdowns. These results indicate that LPA signaling via LPA receptors is involved in the regulation of cellular functions associated with ATP reduction in MG-63 cells treated with EtBr.

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19.
Lignans are major constituents of plant extracts and have important pharmacological effects on mammalian cells. Here we showed that pinoresinol-4,4′-di-O-β-d-glucoside (PDG) from Valeriana officinalis induced calcium mobilization and cell migration through the activation of lysophosphatidic acid (LPA) receptor subtypes. Stimulation of mouse embryo fibroblast (MEF) cells with 10 μM PDG resulted in strong stimulation of MEF cell migration and the EC50 was about 2 μM. Pretreatment with pertussis toxin (PTX), an inhibitor of Gi protein, completely blocked PDG-induced cell migration demonstrating that PDG evokes MEF cell migration through the activation of the Gi-coupled receptor. Furthermore, pretreatment of MEF cells with Ki16425 (10 μM), which is a selective antagonist for LPA1 and LPA3 receptors, completely blocked PDG-induced cell migration. Likewise, PDG strongly induced calcium mobilization, which was also blocked by Ki16425 in a dose-dependent manner. Prior occupation of the LPA receptor with LPA itself completely blocked PDG-induced calcium mobilization. Finally, PDG-induced MEF cell migration was attenuated by pretreatment with a phosphatidylinositol 3-kinase (PI3K) inhibitor such as LY294002. Cells lacking downstream mediator of PI3K such as Akt1 and Akt2 (DKO cells) showed loss of PDG-induced migration. Re-expression of Akt1 (but not Akt2) completely restored PDG-induced DKO cell migration. Given these results, we conclude that PDG is a strong inducer of cell migration. We suggest that the pharmacological action of PDG may occur through the activation of an LPA receptor whereby activation of PI3K/Akt signaling pathway mediates PDG-induced MEF cell migration.  相似文献   

20.
Abstract

Lysophosphatidic acid (LPA) is a simple biological lipid and mediates several biological functions with LPA receptors (LPA1 to LPA6). In the present study, to assess whether LPA receptors promote cell-invasive activity of pancreatic cancer cells, highly invasion PANC-R9 cells were established from PANC-1 cells, using Matrigel-coated Cell Culture Insert. The cell-invasive activity of PANC-R9 cells was shown to be approximately 15 times higher than that of PANC-1 cells. LPAR1 expression level was markedly elevated in PANC-R9 cells in comparison with PANC-1 cells, while LPAR3 expression level was reduced. The cell-invasive activity of PANC-R9 cells was enhanced by LPA, but LPA had no impact on PANC-1 cell invasion. Before initiation of the cell invasion assay, PANC-R9 cells were pretreated with dioctanoylglycerol pyrophosphate (DGPP), an antagonist of LPA1/LPA3. The invasive activity of PANC-R9 cells was markedly suppressed by DGPP. Autotaxin (ATX) is a key enzyme that catalyzes the conversion of lysophosphatidylcholine (LPC) to LPA. ATX expression level was elevated in PANC-R9 cells compared with PANC-1 cells. In the presence of LPC, the cell motile activity of PANC-R9 cells was markedly stimulated. In contrast, LPC did not affect the cell motile activity of PANC-1 cells. PANC-R9 cell motility was inhibited by an ATX inhibitor, PF-8380. These results suggest that LPA signaling via LPA1 is a potent molecular target for the regulation of tumor progression in PANC-1 cells.  相似文献   

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