Stimulatory and inhibitory actions of lysophosphatidylcholine, depending on its fatty acid residue, on the phospholipase C/Ca2+ system in HL-60 leukaemia cells

Abstract

We examined the mechanism of action of lysophosphatidylcholine (LPC), which is suggested to be involved in the pathogenesis of atherosclerosis and inflammatory disorders, in HL-60 leukaemia cells. Extracellular 1-palmitoyl LPC increased the intracellular Ca2+ concentration in association with production of inositol phosphate. These actions of LPC were markedly inhibited by treatment of the cells with pertussis toxin and U73122, a phospholipase C inhibitor. The lipid-induced stimulation of the phospholipase C/Ca2+ system was also attenuated in the dibutyryl cAMP-induced differentiated (neutrophil-like) cells, in which phospholipase C activation induced by NaF or formyl-Met-Leu-Phe was enhanced. In contrast with the stimulatory action of 1-palmitoyl LPC, 1-stearoyl LPC was inhibitory for the phospholipase C/Ca2+ system stimulated by NaF as well as by 1-palmitoyl LPC or other Ca2+-mobilizing agonists. In a cell-free system, only an inhibitory effect on phospholipase C activity was observed even by 1-palmitoyl LPC; 1-stearoyl LPC was more inhibitive than 1-palmitoyl LPC. Taken together, these results suggest that atherogenic and inflammatory LPC exerts both stimulatory and inhibitory actions on the phospholipase C/Ca2+ system depending on the species of fatty acid residue of the lipid; the stimulatory effect is possibly mediated through G-protein-coupled receptors; the inhibitory effect might be caused by dysfunction of the components involved in the enzyme system owing to the amphiphilic nature of the lipid. 1-Palmitoyl LPC prefers the former receptor stimulation at least in intact cells, but 1-stearoyl LPC preferentially exerts the latter inhibitory action.

βγ Subunits of Pertussis Toxin-sensitive G Proteins Mediate A1 Adenosine Receptor Agonist-induced Activation of Phospholipase C in Collaboration with Thyrotropin

“…Immunoblot Analysis-Crude plasma membranes and their cholate extracts were prepared as described previously (33,34). The cholate extract (25 g of protein) was resolved on SDS-12.5% polyacrylamide slab gel electrophoresis and then electrophoretically transferred to a Millipore Immobilon sheet (35).…”

Lysophosphatidylcholine Potentiates the Mitogenic Effect of Various Vasoactive Compounds on Rabbit Aortic Smooth Muscle Cells.

“…[8][9][10][11] Lyso-PC stimulates phospholipase C, leading to the generation of inositol trisphosphate, which is involved in intracellular Ca 2+ mobilization. 30) Lyso-PC also induces p44/42 MAPK (extracellular signal-regulated kinase [ERK1/2]) activation, c-fos and c-jun mRNA expression, and subsequent enhancement of activator protein-1 binding activity in VSMCs.…”

Immunomodulatory Actions of Lysophosphatidylcholine

“…Further, fMLP-induced ROS and other fMLP-induced signaling in neutrophils, as well as lung injury induced by fMLP-stimulated neutrophils were inhibited by LPC (0.1, 1 µM) treatment through elevation of cAMP (Lin et al, 2005). In HL60 leukemic cells, an inhibitory effect of LPC (C18:0) on stimulated PLC- [Ca 2+ ] i signal was reported (Okajima et al, 1998). Because cAMP-PKA system negatively regulates inflammatory processes in immune cells, LPC-induced increase in cAMP (most probably via GPCR-Gs protein signaling) may underlie, at lest in part, some of the negative regulatory actions cited above.…”

“…Synergistically enhances PMA-induced superoxide anion generation (Englberger et al, 1987) Generation from stored blood (Silliman et al, 1994;Silliman et al, 1996) Superoxide anion generation is inhibited with PI3K inhibitors (Nishioka et al, 1998) H 2 O 2 generation/bactericidal activity in a G2A-dependent manner (Yan et al, 2004) Priming of NADPH oxidase is dependent on [Ca 2+ ] i increase Apoptosis↓ (Biffl et al, 2003) [Ca 2+ ] i ↑ via G2A/mobilization of G2A along with secretory vesicles (Frasch et al, 2007) [Ca 2+ ] i ↑ via PLC in HL60 cells (Okajima et al, 1998) macrophages, chemotaxis of these cells to LPC is mediated by G2A (Peter et al, 2008).…”

“…In HL60 leukemic cells, LPC (C16:0, 30 µM) increases [Ca 2+ ] i by stimulation of PLC in a PTX-sensitive manner, whereas LPC (C18:0, 30 µM), which per se very slightly increases [Ca 2+ ] i , inhibits the effect of LPC (C16:0, 30 µM) (Okajima et al, 1998). In the same cell line, a slight discrepancy was reported in that LPC (C18:0, 10 µM) and LPC (C16:0, 10 µM) show equipotent activity regarding [Ca 2+ ] i increase, although the onset of [Ca 2+ ] i increase induced by LPC (C18:0, 10 µM) is slower than LPC (C16:0, 10 µM)-induced one .…”