Analysis of lysophophatidylcholine-induced endothelial dysfunction
Freeman, J.E.; Kuo, W.Y.; Drenger, B.; Barnett, T.N.; Levine, M.A.; Flavahan, N.A.
Journal of Cardiovascular Pharmacology 28(3): 345-352
1996
ISSN/ISBN: 0160-2446 PMID: 8877579 Document Number: 463521
Endothelial dysfunction caused by the early atherosclerotic process or by endothelial exposure to atherogenic lipids, including lysophosphatidylcholine (lysoPC), is characterized by a selective impairment of responses mediated by the pertussis toxin-sensitive G-i-2 protein. Experiments were performed to analyze the mechanisms underlying this effect. Bradykinin (BK: G-i-2 protein-independent), serotonin (5-HT: G-i-2 protein-dependent), or direct activation of the G-i-2-protein by mastoparan increased the release of endothelium-derived nitric oxide (EDNO) from porcine arterial endothelial cells (EC). LysoPC decreased the release of EDNO caused by 5-HT, but did not affect the response to BK or mastoparan. LysoPC did not increase production of superoxide radicals detected by lucigenin-enhanced chemiluminescence. Western blot analysis showed no difference in the level of immunoreactive G-ialpha-2 between control and lysoPC-treated cells. Activation of the G-i-2 protein by serotonergic or alpha-2-adrenoceptor stimulation decreased the pertussis toxin-catalyzed ADP-ribosylation of G-ialpha-2 protein in membranes from control but not lysoPC-treated cells. However, direct activation of the G-i-2 protein by mastoparan inhibited the ADP-ribosylation in membranes from control and lysoPC-treated cells. The toxin-catalyzed reaction was reduced in lysoPC-treated cells or lysoPC-treated membranes. LysoPC reduced the ability of endothelin to increase GTP-gamma-S binding to the G-i-2 protein but did not affect the activity of mastoparan. These results suggest that lysoPC inhibits a pertussis toxin-sensitive signaling pathway in EC by an effect consistent with receptor:G-i-2-protein uncoupling.