Post-transcriptional regulation of VEGF expression by oxidised LDL in human macrophages.
BACKGROUND
Accumulation of oxidised low density lipoproteins (oxLDL) in macrophages and their subsequent transformation into lipid-filled foam cells is generally considered an early event in atherosclerosis. Vascular Endothelial Growth Factor (VEGF) may contribute to atherogenesis through increased vascular permeability, chemoattraction towards monocytes and intraplaque vessel formation. In this study we investigate the effect and regulation of VEGF expression in human macrophages stimulated with oxLDL.


METHODS
Vascular Endothelial Growth Factor mRNA and protein expression was assayed using RT-PCR and ELISA, respectively. The activity of mitogen-activated protein kinases (MAPKs) was investigated using Western blots.


RESULTS
In human monocyte-derived macrophages, oxLDL significantly increased VEGF mRNA expression and subsequent protein secretion in a concentration-dependent manner after 6 h and 18 h, respectively. Using an in vitro mRNA decay assay, we show that this oxLDL-induced VEGF expression partly is regulated through increased stability of the VEGF mRNA. Involvement of MAPKs has previously been implicated in the stabilisation of VEGF mRNA. Activity of the p38 MAPK, but not the c-jun-N-terminal kinase (JNK), increased in macrophages stimulated with oxLDL (50 micro g mL-1) for 5-15 min. Preincubation with SB202190 (20 micro M), a specific inhibitor of p38 MAPK, significantly decreased the oxLDL-induced VEGF mRNA expression by 40%. The prolonged half-life of VEGF mRNA, induced by oxLDL, was not inhibited by SB202190.


CONCLUSIONS
OxLDL increases VEGF expression and p38 MAPK activity in human macrophages. The increased VEGF mRNA expression by oxLDL is mediated through at least two intracellular pathways, one involving p38 MAPK and another that independently of p38 MAPK activity increases VEGF mRNA stability.
Salomonsson
L
L
Wallenberg Laboratory, Sahlgrenska Academy, Göteborg, Sweden. linda.salomonsson@wlab.gu.se
Pettersson
S
S
Englund
M C O
MC
Wiklund
O
O
Ohlsson
B G
BG
D015153:Blotting, Western / Q000379:methods; D002478:Cells, Cultured; D016228:Endothelial Growth Factors / Q000032:analysis / Q000235:genetics*; D004797:Enzyme-Linked Immunosorbent Assay / Q000379:methods; D005786:Gene Expression Regulation / Q000187:drug effects*; D006801:Humans; D036341:Intercellular Signaling Peptides and Proteins / Q000032:analysis / Q000235:genetics*; D048031:JNK Mitogen-Activated Protein Kinases; D008077:Lipoproteins, LDL / Q000494:pharmacology*; D008222:Lymphokines / Q000032:analysis / Q000235:genetics*; D020935:MAP Kinase Signaling System; D008264:Macrophages / Q000187:drug effects / Q000378:metabolism*; D020928:Mitogen-Activated Protein Kinases / Q000032:analysis / Q000378:metabolism; D012333:RNA, Messenger / Q000032:analysis*; D020133:Reverse Transcriptase Polymerase Chain Reaction; D014158:Transcription, Genetic; D042461:Vascular Endothelial Growth Factor A; D042442:Vascular Endothelial Growth Factors; D048051:p38 Mitogen-Activated Protein Kinases
D016228:Endothelial Growth Factors; D036341:Intercellular Signaling Peptides and Proteins; D008077:Lipoproteins, LDL; D008222:Lymphokines; D012333:RNA, Messenger; D042461:Vascular Endothelial Growth Factor A; D042442:Vascular Endothelial Growth Factors; C099252:oxidized low density lipoprotein; D048031:JNK Mitogen-Activated Protein Kinases; D020928:Mitogen-Activated Protein Kinases; D048051:p38 Mitogen-Activated Protein Kinases