Analysis of lysophophatidylcholine-induced endothelial dysfunction.
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 Gi-2 protein. Experiments were performed to analyze the mechanisms underlying this effect. Bradykinin (BK: Gi-2 protein-independent), serotonin (5-HT: Gi-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 Gi alpha-2 between control and lysoPC-treated cells. Activation of the Gi-2 protein by serotonergic or alpha 2-adrenoceptor stimulation decreased the pertussis toxin-catalyzed ADP-ribosylation of Gi alpha-2 protein in membranes from control but not lysoPC-treated cells. However, direct activation of the Gi-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 Gi-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:Gi-2-protein uncoupling.
Freeman
J E
JE
Department of Medicine, Johns Hopkins University School of Medicine, Baltimore, Maryland 21205, USA.
Kuo
W Y
WY
Drenger
B
B
Barnett
T N
TN
Levine
M A
MA
Flavahan
N A
NA
D000818:Animals; D001161:Arteriosclerosis / Q000139:chemically induced / Q000503:physiopathology; D015153:Blotting, Western; D001920:Bradykinin / Q000494:pharmacology; D015237:Dinoprost / Q000494:pharmacology; D004730:Endothelium, Vascular / Q000187:drug effects* / Q000378:metabolism; D019206:GTP-Binding Protein alpha Subunits, Gi-Go / Q000378:metabolism*; D008244:Lysophosphatidylcholines / Q000633:toxicity*; D009131:Muscle, Smooth, Vascular / Q000378:metabolism; D009569:Nitric Oxide / Q000032:analysis; D037342:Pertussis Toxin; D013481:Superoxides / Q000378:metabolism; D013552:Swine; D014664:Vasodilation / Q000187:drug effects*; D010566:Virulence Factors, Bordetella / Q000494:pharmacology
D008244:Lysophosphatidylcholines; D010566:Virulence Factors, Bordetella; D013481:Superoxides; D009569:Nitric Oxide; D015237:Dinoprost; D037342:Pertussis Toxin; D019206:GTP-Binding Protein alpha Subunits, Gi-Go; D001920:Bradykinin