vpc32183 and sphingosine-1-phosphate

Lysophosphatidic acid (LPA) is a membrane-derived lysophospholipid that can induce pleomorphic effects in neural progenitor cells (NPCs) from the cerebral cortex, including alterations in ionic conductance. LPA-induced, calcium-mediated conductance changes have been reported; however, the underlying molecular mechanisms have not been determined. We show here that activation of specific cognate receptors accounts for nearly all intracellular calcium responses evoked by LPA in acutely cultured nestin-positive NPCs from the developing mouse cerebral cortex. Fast-onset changes in intracellular calcium levels required release from thapsigargin-sensitive stores by a pertussis toxin-insensitive mechanism. The influx of extracellular calcium through Cd(2+)/Ni(2+)-insensitive influx pathways, approximately one-half of which were Gd(3+) sensitive, contributed to the temporal diversity of responses. Quantitative reverse transcription-PCR revealed the presence of all five known LPA receptors in primary NPCs, with prominent expression of LPA(1), LPA(2), and LPA(4). Combined genetic and pharmacological studies indicated that NPC responses were mediated by LPA(1) (approximately 30% of the cells), LPA(2) (approximately 30%), a combination of receptors on single cells (approximately 30%), and non-LPA(1,2,3) pathways (approximately 10%). LPA responsivity was significantly reduced in more differentiated TuJ1(+) cells within cultures. Calcium transients in a large proportion of LPA-responsive NPCs were also initiated by the closely related signaling lipid S1P (sphingosine-1-phosphate). These data demonstrate for the first time the involvement of LPA receptors in mediating surprisingly diverse NPC calcium responses involving multiple receptor subtypes that function within a single cell. Compared with other known factors, lysophospholipids represent the major activator of calcium signaling identified within NPCs at this early stage in corticogenesis.

Topics: Animals; Cadmium Chloride; Calcium; Calcium Signaling; Cells, Cultured; Cerebral Cortex; Dose-Response Relationship, Drug; Embryo, Mammalian; Extracellular Fluid; Female; Gene Expression Regulation, Developmental; Glutamic Acid; Intracellular Signaling Peptides and Proteins; Isoxazoles; Lysophospholipids; Membrane Proteins; Mice; Mice, Inbred C57BL; Mice, Knockout; Nerve Tissue Proteins; Neurogenesis; Neurons; Nickel; Organophosphates; Pertussis Toxin; Pituitary Adenylate Cyclase-Activating Polypeptide; Pregnancy; Propionates; Pyridines; RNA, Messenger; Sphingosine; Thapsigargin

Lysophosphatidic acid (LPA) is a simple lipid with many important biological functions such as the regulation of cellular proliferation, cellular migration, differentiation, and suppression of apoptosis. Although a direct angiogenic effect of LPA has not been reported to date, there are indications that LPA promotes angiogenesis. In addition, LPA is a chemoattractant for cultured endothelial cells and promotes barrier function in such cultures. To test the hypothesis that LPA is angiogenic, we used the chicken chorio-allantoic membrane (CAM) assay. Sequence analysis of the cloned, full-length chicken LPA receptor cDNAs revealed three receptor types that are orthologous to the mammalian LPA(1), LPA(2), and LPA(3) receptors. We document herein that LPA is angiogenic in the CAM system and further that synthetic LPA receptor agonists and antagonists mimic or block this response, respectively. Our results predict that LPA receptor antagonists are a possible therapeutic route to interdicting angiogenesis.

Topics: Amino Acid Sequence; Angiogenesis Inhibitors; Animals; Chick Embryo; Drug Evaluation, Preclinical; Lysophospholipids; Molecular Sequence Data; Neovascularization, Physiologic; Organophosphates; Pyridines; Receptors, Lysophosphatidic Acid; Sequence Homology, Amino Acid; Sphingosine; Substrate Specificity; Vascular Endothelial Growth Factor A