Endothelial lipase (EL) and EL-generated lysophosphatidylcholines promote IL-8 expression in endothelial cells.
OBJECTIVE
Previously we identified palmitoyl-lysophosphatidylcholine (LPC 16:0), as well as linoleoyl-, arachidonoyl- and oleoyl-LPC (LPC 18:2, 20:4 and 18:1) as the most prominent LPC species generated by the action of endothelial lipase (EL) on high-density lipoprotein (HDL). In the present study, the impact of EL and EL-generated LPC on interleukin-8 (IL-8) synthesis was examined in vitro in primary human aortic endothelial cells (HAEC) and in mice.


RESULTS
Adenovirus-mediated overexpression of the catalytically active EL, but not its inactive mutant, increased endothelial synthesis of IL-8 mRNA and protein in a time- and HDL-concentration-dependent manner. While LPC 18:2 was inactive, LPC 16:0, 18:1 and 20:4 promoted IL-8 mRNA- and protein-synthesis, differing in potencies and kinetics. The effects of all tested LPC on IL-8 synthesis were completely abrogated by addition of BSA and chelation of intracellular Ca(2+). Underlying signaling pathways also included NFkB, p38-MAPK, ERK, PKC and PKA. In mice, adenovirus-mediated overexpression of EL caused an elevation in the plasma levels of MIP-2 (murine IL-8 analogue) accompanied by a markedly increased plasma LPC/PC ratio. Intravenously injected LPC also raised MIP-2 plasma concentration, however to a lesser extent than EL overexpression.


CONCLUSIONS
Our results indicate that EL and EL-generated LPC, except of LPC 18:2, promote endothelial IL-8 synthesis, with different efficacy and kinetics, related to acyl-chain length and degree of saturation. Accordingly, due to its capacity to modulate the availability of the pro-inflammatory and pro-adhesive chemokine IL-8, EL should be considered an important player in the development of atherosclerosis.
Institute of Molecular Biology and Biochemistry, Harrachgasse 21/III, Medical University Graz, 8010 Graz, Austria.
Monika
M
Riederer
Margarete
M
Lechleitner
Andelko
A
Hrzenjak
Harald
H
Koefeler
Gernot
G
Desoye
Akos
A
Heinemann
Saša
S
Frank
D000818:Animals; D002118:Calcium / Q000378:metabolism; D002478:Cells, Cultured; D054426:Chemokine CXCL2 / Q000097:blood; D017868:Cyclic AMP-Dependent Protein Kinases / Q000378:metabolism; D042783:Endothelial Cells / Q000201:enzymology* / Q000276:immunology; D048049:Extracellular Signal-Regulated MAP Kinases / Q000378:metabolism; D006801:Humans; D007275:Injections, Intravenous; D016209:Interleukin-8 / Q000096:biosynthesis* / Q000235:genetics; D007700:Kinetics; D008049:Lipase / Q000235:genetics / Q000378:metabolism*; D008075:Lipoproteins, HDL / Q000378:metabolism; D008244:Lysophosphatidylcholines / Q000008:administration & dosage / Q000378:metabolism*; D008297:Male; D051379:Mice; D008810:Mice, Inbred C57BL; D009154:Mutation; D016328:NF-kappa B / Q000378:metabolism; D011493:Protein Kinase C / Q000378:metabolism; D012333:RNA, Messenger / Q000378:metabolism; D015398:Signal Transduction; D013997:Time Factors; D014162:Transfection; D015854:Up-Regulation; D048051:p38 Mitogen-Activated Protein Kinases / Q000378:metabolism
C508606:CXCL8 protein, human; D054426:Chemokine CXCL2; C404915:Cxcl2 protein, mouse; D016209:Interleukin-8; D008075:Lipoproteins, HDL; D008244:Lysophosphatidylcholines; D016328:NF-kappa B; D012333:RNA, Messenger; D017868:Cyclic AMP-Dependent Protein Kinases; D011493:Protein Kinase C; D048049:Extracellular Signal-Regulated MAP Kinases; D048051:p38 Mitogen-Activated Protein Kinases; C410382:LIPG protein, human; D008049:Lipase; D002118:Calcium