lysophosphatidylserine and Glioma

Lysophosphatidylserine (LPS) was found to stimulate intracellular calcium increase in U87 human glioma cells. LPS also stimulated chemotactic migration of U87 human glioma cells, which was completely inhibited by pertussis toxin (PTX). Moreover, LPS was also found to stimulate ERK, p38 MAPK, JNK, and Akt activities in U87 cells. We observed that LPS-induced U87 chemotaxis was mediated by PI3K, p38 MAPK, and JNK. LPS-induced chemotactic migration in U87 cells was inhibited by Ki16425, an LPA(1/3) receptor-selective antagonist, which suggested that the Ki16425-sensitive G-protein coupled receptor (GPCR) played a role in this process. Moreover, U87 cells were found to uniquely express LPA(1) but not LPA(2-5). In addition, LPS failed to stimulate the NF-kappaB-driven luciferase activity in exogenously LPA(1)-transfected HepG2 cells. Taken together, we propose that LPS stimulates GPCR, which is in contrast to the well-known LPA receptors, thus resulting in the chemotactic migration in U87 human glioma cells.

Topics: Brain Neoplasms; Cell Line, Tumor; Chemotaxis; Glioma; Humans; Isoxazoles; JNK Mitogen-Activated Protein Kinases; Lysophospholipids; p38 Mitogen-Activated Protein Kinases; Phosphatidylinositol 3-Kinases; Propionates; Proto-Oncogene Proteins c-akt; Receptors, G-Protein-Coupled; Receptors, Lysophosphatidic Acid

Lysophosphatidylserine (LPS) can be generated following phosphatidylserine-specific phospholipase A2 activation. The effects of LPS on cellular activities and the identities of its target molecules, however, have not been fully elucidated. In this study, we observed that LPS stimulated intracellular calcium increased in mouse bone marrow-derived mast cells (BMMC), and rat C6 glioma and human HCT116 colon cancer cells and compared the LPS-induced Ca2+ increases with the response by lysophosphatidic acid (LPA), a structurally related bioactive lysolipid. In order to test involvement of signaling molecules in the LPS-induced Ca2+ signaling, we used pertussis toxin (PTX), U73122, and 2-APB, which are specific inhibitors for G proteins, phospholipase C (PLC), and IP3 receptors, respectively. The increases due to LPS and LPA were inhibited by PTX, U-73122 and 2-APB, suggesting that both lipids stimulate calcium signaling via G proteins (Gi/o types), PLC activation, and subsequent IP3 production, although the sensitivity to pharmacological inhibitors varied from complete inhibition to partial inhibition depending on cell type and lysolipid. Furthermore, we observed that Ki16425 completely inhibited an LPS-induced Ca2+ response in three cell types, but that the effect of VPC32183 varied from complete inhibition in BMMC and C6 glioma cells to partial inhibition in HCT116 cells. Therefore, we conclude that LPS increases [Ca2+]i through Ki16425/VPC32183-sensitive G protein-coupled receptors (GPCR), G protein, PLC, and IP3 in mouse BMMC, rat C6, and human HCT116 cells.

Topics: Animals; Bone Marrow Cells; Calcium Signaling; Colonic Neoplasms; Dose-Response Relationship, Drug; Enzyme Inhibitors; Estrenes; Glioma; HCT116 Cells; Humans; Inositol 1,4,5-Trisphosphate Receptors; Isoxazoles; Lysophospholipids; Male; Mast Cells; Mice; Mice, Inbred BALB C; Organophosphates; Pertussis Toxin; Propionates; Pyridines; Pyrrolidinones; Rats; Receptors, Lysophosphatidic Acid; Time Factors; Type C Phospholipases

Previously, we reported on the distinct effects of bioactive lysophospholipids, including lysophosphatidic acid (LPA), lysophosphatidylcholine (LPC), and sphingosylphosphorylcholine (SPC), on membrane potentials in rat C6 glioma cells. In the present report we have tested lysophosphatidylserine (LPS), another bioactive lysophospholipid, on membrane potentials in the same cell line. Membrane potentials were estimated by measuring the fluorescence changes of DiBAC-loaded glioma cells. LPS largely increased membrane potentials in a concentration-dependent manner. The LPS-induced membrane potential increases were not affected by treatment with pertussis toxin, implying no involvement of Gi/o proteins. In contrast to other lysophospholipids, the LPS-induced membrane potential increase was not diminished by a Na(+)-free media but was enhanced by suramin. Furthermore, this change was blunted by EIPA, an inhibitor of Na(+)/H(+) exchanger, but not by SITS, a specific inhibitor of bicarbonate transporter. Our observations suggest that LPS acts on membrane potentials in a unique manner in the C6 glioma cells, although the precise action mechanism requires additional investigation.

Topics: 4-Acetamido-4'-isothiocyanatostilbene-2,2'-disulfonic Acid; Amiloride; Animals; Cell Line, Tumor; Glioma; GTP-Binding Proteins; Lysophospholipids; Membrane Potentials; Rats; Receptors, G-Protein-Coupled