Structure−Activity Analysis of the Effects of Lysophosphatidic Acid on Platelet Aggregation

Abstract

Lysophosphatidic acid (1-acyl-sn-glycero-3-phosphate or LPA) is a phospholipid mediator displaying numerous and widespread biological activities and thought to act via G-protein-coupled receptors. Here we have studied the effects on human platelets of a number of LPA analogues, including two enantiomers of both N-palmitoyl-(L)-serine-3-phosphate ((L) and (D)NAPS for N-acyl-phosphoserine) and 2-(R)-N-palmitoyl-norleucinol-1-phosphate ((R) and (S)PNPA), cyclic analogues of 1-acyl-sn-glycero-3-phosphate (cPA) and of 1-O-hexadecyl-sn-glycero-3-phosphate (cAGP), sphingosine-1-phosphate (SPP), as well as two palmitoyl derivatives of dioxazaphosphocanes bearing either a P-H or a P-OH bond (DOXP-H and DOXP-OH, respectively). Nine of these compounds induced platelet aggregation with the following order of potency: SPP < cAGP < DOXP-OH < (L)NAPS = (D)NAPS < (R)PNPA = (S)PNPA < LPA < AGP, EC50 varying between 9.8 nM and 8.3 microM. Two of these compounds (SPP and cAGP) appeared as weak agonists inducing platelet aggregation to only 33% and 41%, respectively, of the maximal response attained with LPA and other analogues. In cross-desensitization experiments, all of these compounds specifically inhibited LPA-induced aggregation, suggesting that they were all acting on the same receptor(s). In contrast, cPA and DOXP-H did not trigger platelet aggregation but instead specifically inhibited the effects of LPA in a concentration-dependent manner. The inhibitory action of cPA did not vary with the acyl chain length or the presence of a double bond and did not involve an increase in cAMP. These data thus confirm the lack of stereospecificity of platelet LPA receptor(s). In addition, since the order of potency of some analogues is different from that described in other cells, our results suggest that platelets contain (a) pharmacologically distinct receptor(s) whose molecular identity still remains to be established. Finally, this unique series of compounds might be used for further characterization of other endogenous or recombinant LPA receptors.

Assembly of a fibronectin matrix by adherent platelets stimulated by lysophosphatidic acid and other agonists

“…17,35,65 LPA and S1P have been reported to cause shape change and aggregation of platelets in suspension. 40,43,44,66,67 The magnitude of the platelet response in suspension is greater with LPA than with S1P. 43,66 Our results support these previous observations on suspended platelets because we observed greater response with LPA than with S1P in the assembly of FN by adherent platelets.…”

Lysophosphatidic Acid-induced Mitogenesis Is Regulated by Lipid Phosphate Phosphatases and Is Edg-receptor Independent

“…The platelet response lacks stereoselectivity (36), requires micromolar concentrations of LPA (36,(51)(52)(53), and displays distinct ligand selectivity with respect to 1-O-alkyl LPA (ether linkage) (34). Gueguen and colleagues (36) have proposed, based on these observations, that there is an LPA re-error bars reflect standard error.…”

“…Platelet Aggregation Has a Ligand Selectivity Similar to the Mitogenic Response-Like the mitogenic response to LPA, platelet aggregation requires micromolar concentrations (even though the assay lasts only 1-2 min) and lacks stereoselectivity in response to NASPA/carboxy ethanolamide phosphoric acid and related chiral LPA analogs when tested at a single high concentration (36). We determined platelet aggregation dose-3 D.-S. Im and K. R. Lynch, unpublished data.…”

Lysophosphatidic Acid Inhibits Bacterial Endotoxin-Induced Pro-Inflammatory Response: Potential Anti-Inflammatory Signaling Pathways

“…It evokes various immunodulatory responses including prevention of apoptosis, chemotaxis, cytokine and chemokine secretion, platelet aggregation, and enhanced wound healing (19)(20)(21). LPA binds to at least four specific G-proteincoupled receptors (GPCRs): LPA 1 /EDG2, LPA 2 /EDG4, LPA 3 /EDG7, and LPA 4 / GPR23/p2y9 (22).…”