Oxidized low density lipoproteins downregulate LPS-induced platelet-activating factor receptor expression in human monocyte-derived macrophages: implications for LPS-induced nuclear factor-kappaB binding activity.
Monocytes/macrophages play a key role in atherogenesis due to their inflammatory properties including formation of lipid mediators such as platelet-activating-factor (PAF). We investigated the effect of oxidized low-density lipoprotein (oxLDL) on lipopolysaccharide (LPS)-induced PAF receptor (PAF-R) expression in human macrophages and the implication of the nuclear factor (NF)-kappaB in this regulation. LPS-treatment (1 microg.mL(-1)) of macrophages increased PAF binding and PAF-R mRNA expression by 56% (P < 0.05) and twofold (P < 0.01), respectively. In contrast, highly oxidized low-density lipoprotein [ox24hLDL; 100 microg.mL(-1); thiobarbituric acid reacting substances: 31 +/- 3 nmol equiv. malondialdehyde (MDA).mg protein LDL-1] diminished PAF-R expression (-69%; P < 0.05) and mRNA level (- 45%; P < 0.01). LPS pretreatment induced the activated form of p65 in the nuclear compartment of macrophages (detected by Western blotting) and NF-kappaB binding activity (by electrophoretic mobility shift assay). Treatment of macrophages with ox24hLDL suppressed the LPS-induced binding of NF-kappaB to DNA. In addition, treatment of macrophages with lysophosphatidylcholine (2 and 10 microM), a major component of oxLDL, inhibited the LPS-induced NF-kappaB binding to DNA and reduced PAF binding by 30 and 70%, respectively. In conclusion, oxLDL may downregulate PAF-R expression in human macrophages by inhibiting LPS-induced NF-kappaB binding to DNA.
Hourton
D
D
INSERM U525 Génétique Epidémiologique Moléculaire des Pathologies Cardiovasculaires', IFR 14 'Muscle Coeur et Vaisseaux' and UFR Médecine Sud (Université Pierre et Marie Curie), Paris, France.
Stengel
D
D
Chapman
M J
MJ
Ninio
E
E
D001161:Arteriosclerosis / Q000209:etiology; D004247:DNA / Q000378:metabolism; D015536:Down-Regulation; D006801:Humans; D008070:Lipopolysaccharides / Q000494:pharmacology*; D008077:Lipoproteins, LDL / Q000494:pharmacology*; D008244:Lysophosphatidylcholines / Q000494:pharmacology; D008264:Macrophages / Q000737:chemistry / Q000187:drug effects*; D009000:Monocytes / Q000187:drug effects* / Q000378:metabolism; D016328:NF-kappa B / Q000378:metabolism*; D010972:Platelet Activating Factor / Q000378:metabolism; D010980:Platelet Membrane Glycoproteins / Q000187:drug effects*; D011956:Receptors, Cell Surface; D043562:Receptors, G-Protein-Coupled
D008070:Lipopolysaccharides; D008077:Lipoproteins, LDL; D008244:Lysophosphatidylcholines; D016328:NF-kappa B; D010972:Platelet Activating Factor; D010980:Platelet Membrane Glycoproteins; D011956:Receptors, Cell Surface; D043562:Receptors, G-Protein-Coupled; C099252:oxidized low density lipoprotein; C039351:platelet activating factor receptor; D004247:DNA