1. Agonist potency at P2X7 receptors is modulated by structurally diverse lipids
- Author
-
Michel, A D and Fonfria, E
- Subjects
Purinergic P2 Receptor Agonists ,Dose-Response Relationship, Drug ,Octoxynol ,Receptors, Purinergic P2 ,Phosphorylcholine ,Interleukin-1beta ,Palmitoylcarnitine ,Lysophosphatidylcholines ,Research Papers ,Lipids ,Cell Line ,Rats ,Mice ,Radioligand Assay ,Surface-Active Agents ,Adenosine Triphosphate ,Sphingosine ,Ethidium ,Animals ,Humans ,Calcium ,Fluorometry ,Receptors, Purinergic P2X7 ,Receptors, Purinergic P2X2 - Abstract
The P2X(7) receptor exhibits a high degree of plasticity with agonist potency increasing after prolonged receptor activation. In this study we investigated the ability of lipids to modulate agonist potency at P2X(7) receptors.A variety of lipids, including lysophosphatidylcholine, sphingosylphosphorylcholine and hexadecylphosphorylcholine were studied for their effect on P2X(7) receptor-stimulated ethidium bromide accumulation in cells expressing human recombinant P2X(7) receptors and on P2X(7) receptor-stimulated interleukin-1 beta (IL1 beta) release from THP-1 cells. The effects of the lipids were also assessed in radioligand binding studies on human P2X(7) receptors.At concentrations (3-30 microM) below the threshold to cause cell lysis, the lipids increased agonist potency and/or maximal effects at P2X(7) receptors in both ethidium accumulation and IL1 beta release studies. There was little structure activity relationship (SAR) for this effect and sub-lytic concentrations of Triton X-100 partially mimicked the effects of the lipids. The lipids caused cell lysis and increased intracellular calcium at higher concentrations (30-100 microM) which complicated interpretation of their effects in functional studies. However, the lipids (3-100 microM) also increased agonist potency 30-100 fold in radioligand binding studies.This study demonstrates that a diverse range of lipids increase agonist potency at the P2X(7) receptor in functional and binding studies. The broad SAR, including the effect of Triton X-100, suggests this may reflect changes in membrane properties rather than a direct effect on the P2X(7) receptor. Since many of the lipids studied accumulate in disease states they may enhance P2X(7) receptor function under pathophysiological conditions.
- Published
- 2007