Low-density lipoprotein in hypercholesterolemic human plasma induces vascular endothelial cell apoptosis by inhibiting fibroblast growth factor 2 transcription.
BACKGROUND
Apoptosis of vascular endothelial cells (ECs) can be induced in vitro by experimentally modified LDL. Description of proapoptotic circulating lipoproteins may significantly enhance understanding of atherothrombosis pathophysiology.


RESULTS
Fast protein liquid chromatography of LDL samples from 7 asymptomatic, hypercholesterolemic patients yielded subfractions L1-L5 in increasing electronegativity. L4 and L5 were not detectable or collectible in normolipidemic samples. In bovine aortic EC cultures, L5 induced marked apoptosis and L4 had a mild effect, whereas hypercholesterolemic or normolipidemic L1-L3 had negligible effects. Compared with copper-oxidized LDL, L5 was only mildly oxidized, although its propensity to form conjugated dienes in response to copper exceeded that of other subfractions. L5-induced apoptosis was associated with suppressed fibroblast growth factor 2 (FGF-2) transcription, as assessed by nuclear run-on analysis. Degrading platelet-activating factor (PAF)-like lipids in L5 by a recombinant PAF acetylhydrolase prevented both FGF-2 downregulation and apoptosis. Furthermore, the ability of L5 lipid extract to induce calcium influx into neutrophils was lost after pretreatment of the extract with PAF acetylhydrolase. FGF-2 supplementation, PAF receptor (PAFR) blockade with WEB-2086, and inactivation of PAFR-coupled Gi protein with pertussis toxin all effectively attenuated L5-induced apoptosis.


CONCLUSIONS
Our findings indicate that a highly electronegative, mildly oxidized LDL subfraction present in human hypercholesterolemic but not normolipidemic plasma can induce apoptosis in cultured ECs. The evidence that a freshly isolated LDL species modulates transcription of FGF-2 may provide a physiological insight into the mechanism of vascular EC apoptosis in hypercholesterolemia.
Chen
Chu-Huang
CH
MS A-601, Department of Medicine, Baylor College of Medicine, 6565 Fannin St, Houston, Texas 77030, USA. cchen@bcm.tmc.edu
Jiang
Tao
T
Yang
Jun-Hai
JH
Jiang
Wei
W
Lu
Jonathan
J
Marathe
Gopal K
GK
Pownall
Henry J
HJ
Ballantyne
Christie M
CM
McIntyre
Thomas M
TM
Henry
Philip D
PD
Yang
Chao-Yuh
CY
D000328:Adult; D000818:Animals; D017209:Apoptosis; D002118:Calcium / Q000378:metabolism; D002417:Cattle; D002478:Cells, Cultured; D005591:Chemical Fractionation; D004730:Endothelium, Vascular / Q000166:cytology / Q000187:drug effects / Q000378:metabolism*; D005260:Female; D016222:Fibroblast Growth Factor 2 / Q000096:biosynthesis* / Q000235:genetics; D005786:Gene Expression Regulation; D006801:Humans; D006937:Hypercholesterolemia / Q000097:blood*; D017136:Ion Transport / Q000187:drug effects; D008077:Lipoproteins, LDL / Q000097:blood / Q000302:isolation & purification / Q000494:pharmacology*; D008297:Male; D008875:Middle Aged; D009504:Neutrophils / Q000187:drug effects / Q000378:metabolism; D015398:Signal Transduction; D014158:Transcription, Genetic / Q000187:drug effects
D008077:Lipoproteins, LDL; D016222:Fibroblast Growth Factor 2; D002118:Calcium