Lysophosphatidylcholine stimulates phospholipase d in human
coronary endothelial cells: role of protein kinase c.
Cox, David A., and Marlene L. Cohen.
Cardiovascular Research, Lilly Research Laboratories, Indianapolis,
IN, 46285
APStracts 3:0307H, 1996.
Lysophosphatidylcholine (lyso PC) mediated multiple potentially
atherogenic effects on endothelial cells, although the cellular
mechanism of these effects remain unclear. Phospholipase D (PLD) has
been recognized as a novel second messenger system that may regulate
cellular function. The purpose of this study was to determine the
effect of lyso PC on PLD activity in human coronary artery
endothelial cells (HCAEC) by measuring 3H-phosphatidylethanol
production in 3H-myristic acid-labeled cells. After incubation with
lyso PC (20 mM) for 40 min, PLD activity was markedly stimulated 5 to
6 fold. Stimulation of PLD activity by lyso PC was concentration
-dependent (EC50=7.6 mM) and was not mimicked by phosphatidylcholine
(20 mM). Because PLD can be regulated by protein kinases, the effect
of several protein kinase inhibitors on lyso PC-stimulated PLD
activity was tested. The protein kinase A inhibitor H-89 (300 nM) and
the tyrosine kinase inhibitors genistein (30 mM) and tyrphostin A25
(100 mM) had no effect on the stimulation of PLD by lyso PC (20 mM).
The protein kinase C (PKC) inhibitor calphostin C (10 - 300 nM)
affected neither lyso PC (20 mM)- nor phorbol dibutyrate (PDBu, 300
nM)-stimulated PLD activity, suggesting that this agent may not
inhibit PKC in these cells. In contrast, the selective PKC inhibitors
GF109203X (0.3 - 10 mM) and chelerythrine (1 - 30 mM) concentration
-dependently inhibited lyso PC (20 mM)-stimulated PLD activity and
blocked PDBu (300 nM)-stimulated PLD activity. Together, these data
document that lyso PC stimulated PLD in human endothelial cells,
possibly by a PKC-dependent mechanism, and provides evidence that PLD
activation in human endothelium is a novel and important mechanism by
which lyso PC mediates its cellular and possibly atherogenic effects.
Received 15 April 1996; accepted in final form 28 June 1996.
APS Manuscript Number H333-6.
Article publication pending Am. J. Physiol. (Heart Circ. Physiology).
ISSN 1080-4757 Copyright 1996 The American Physiological Society.
Published in APStracts on 25 July 1996