Oxidized phospholipids stimulate tissue factor expression in human endothelial cells via activation of ERK/EGR-1 and Ca(++)/NFAT.
Activation of endothelial cells by lipid oxidation products is a key event in the initiation and progression of the atherosclerotic lesion. Minimally modified low-density lipoprotein (MM-LDL) induces the expression of certain inflammatory molecules such as tissue factor (TF) in endothelial cells. This study examined intracellular signaling pathways leading to TF up-regulation by oxidized 1-palmitoyl-2-arachidonoyl-sn-glycero-3-phosphorylcholine (OxPAPC), a biologically active component of MM-LDL. OxPAPC induced TF activity and protein expression in human umbilical vein endothelial cells (HUVECs). However, OxPAPC neither induced phosphorylation or degradation of I kappa B alpha nor DNA binding of nuclear factor-kappa B (NF-kappa B). Furthermore, OxPAPC-induced TF expression was not inhibited by overexpression of I kappa B alpha. These results strongly indicate that OxPAPC-induced TF expression is independent of the classical NF-kappa B pathway. However, OxPAPC stimulated phosphorylation of extracellular signal-regulated kinase (ERK) 1/2 and expression of early growth response factor 1 (EGR-1). Inhibitors of mitogen-activated kinase/ERK (MEK) or protein kinase C (PKC) blocked elevation of both EGR-1 and TF. Furthermore, overexpression of NAB2, a corepressor of EGR-1, inhibited effects of OxPAPC. In addition, OxPAPC induced rapid and reversible elevation of free cytosolic Ca(++) levels and nuclear factor of activated T cells (NFAT)/DNA binding. Induction of TF expression by OxPAPC was partially inhibited by cyclosporin A, known to block calcineurin, a Ca(++)-dependent phosphatase upstream of NFAT. Treatment of OxPAPC with phospholipase A(2) destroyed its biologic activity and 1-palmitoyl-2-glutaroyl-sn-glycero-3-phosphorylcholine was identified as one biologically active component of OxPAPC that induces TF expression. Together, the results demonstrate that OxPAPC induces TF expression in HUVECs through activation of PKC/ERK/EGR-1 and Ca(++)/calcineurin/NFAT pathways rather than by NF-kappa B-mediated transcription. Thus, oxidized phospholipids may contribute to inflammation by activating pathways alternative to the classical NF-kappa B pathway.
Bochkov
Valery N
VN
Department of Vascular Biology and Thrombosis Research, University of Vienna, Austria.
Mechtcheriakova
Diana
D
Lucerna
Marcus
M
Huber
Joakim
J
Malli
Roland
R
Graier
Wolfgang F
WF
Hofer
Erhard
E
Binder
Bernd R
BR
Leitinger
Norbert
N
D065095:Calcineurin Inhibitors; D002118:Calcium / Q000378:metabolism; D002478:Cells, Cultured; D016572:Cyclosporine / Q000494:pharmacology; D004247:DNA / Q000378:metabolism; D004268:DNA-Binding Proteins / Q000378:metabolism*; D051766:Early Growth Response Protein 1; D004730:Endothelium, Vascular / Q000187:drug effects / Q000378:metabolism*; D004789:Enzyme Activation / Q000187:drug effects; D006801:Humans; D020672:I-kappa B Proteins; D017874:Immediate-Early Proteins; D019950:Mitogen-Activated Protein Kinase 1 / Q000378:metabolism; D048052:Mitogen-Activated Protein Kinase 3; D020928:Mitogen-Activated Protein Kinases / Q000378:metabolism*; D000072000:NF-KappaB Inhibitor alpha; D016328:NF-kappa B / Q000378:metabolism; D050778:NFATC Transcription Factors; D009687:Nuclear Proteins; D010084:Oxidation-Reduction; D010741:Phospholipases A / Q000494:pharmacology; D010742:Phospholipid Ethers / Q000494:pharmacology*; D010766:Phosphorylation; D013925:Thromboplastin / Q000378:metabolism*; D014157:Transcription Factors / Q000378:metabolism*; D014471:Umbilical Veins
D065095:Calcineurin Inhibitors; D004268:DNA-Binding Proteins; C497325:EGR1 protein, human; D051766:Early Growth Response Protein 1; D020672:I-kappa B Proteins; D017874:Immediate-Early Proteins; D016328:NF-kappa B; D050778:NFATC Transcription Factors; C000606204:NFKBIA protein, human; D009687:Nuclear Proteins; D010742:Phospholipid Ethers; D014157:Transcription Factors; D000072000:NF-KappaB Inhibitor alpha; C043051:1-O-hexadecyl-2-arachidonyl-sn-glycero-3-phosphocholine; D016572:Cyclosporine; D004247:DNA; D013925:Thromboplastin; D019950:Mitogen-Activated Protein Kinase 1; D048052:Mitogen-Activated Protein Kinase 3; D020928:Mitogen-Activated Protein Kinases; D010741:Phospholipases A; D002118:Calcium