Oxidized low-density lipoprotein elicits an intracellular calcium rise and increases the binding activity of the transcription factor NFAT.
Oxidized low-density lipoprotein (OxLDL) plays a key role in the generation and progression of atherosclerosis, which might be considered as an inflammatory disease. The transcription factor NFAT(Nuclear Factor of Activated T cells) plays an important role in the control of cytokine genes involved in the inflammatory response. The effect of copper-oxidized LDL (CuLDL) and monocyte-oxidized LDL (M-LDL) on the DNA-binding activity of NFAT was investigated in the T lymphocyte cell line Jurkat. Both OxLDL increased NFAT-binding activity in a dose-dependent manner within the range of 25-75 microg LDL protein/ml. This effect reached a maximum 1 h after the introduction of OxLDL in the medium. CuLDL and M-LDL both induce an intracellular calcium rise in a dose-dependent manner, with a maximum increase 15 min after the addition of OxLDL. The CuLDL-induced NFAT-binding activity was abolished in the presence of the calcium chelator EGTA or of the intracellular calcium trapping drug BAPTA, further indicating the involvement of calcium ions in the effect of OxLDL. In addition, cyclosporin A and FK 506, two inhibitors of calcineurin, a calcium-dependent phosphatase upstream of NFAT, also prevented the CuLDL-induced NFAT-binding activity, thus demonstrating the role of calcineurin. CuLDL and M-LDL also induced an increase in the intracellular level of reactive oxygen species (ROS), which reached a maximum 30 min after the addition of OxLDL. Finally, a pretreatment of cells with the antioxidant vitamin E blocked the CuLDL-induced increase in reactive oxygen species, in intracellular calcium rise and the CuLDL-induced NFAT-binding activity. The lipid extract of CuLDL, which includes the lipid peroxidation products, reproduced the effect of the CuLDL itself. These results suggest that the effect of OxLDL on NFAT is initiated by an oxidative stress, which then in turn activates the calcium-calcineurin signaling pathway of the transcription factor NFAT. This effect of OxLDL might be involved in the inflammatory process observed in atherosclerotic lesions.
Mazière
Cécile
C
Laboratoire de Biochimie, EA 2087 and EA 2086, CHU Amiens, Hôpital Nord, Place Victor Pauchet, 80054 Amiens Cedex 1, France. maziere.cecile@chu-amiens.fr
Morlière
Patrice
P
Massy
Ziad
Z
Kamel
Said
S
Louandre
Christophe
C
Conte
Marie-Alix
MA
Mazière
Jean-Claude
JC
D000975:Antioxidants / Q000494:pharmacology; D065095:Calcineurin Inhibitors; D002118:Calcium / Q000378:metabolism*; D020013:Calcium Signaling / Q000187:drug effects*; D002460:Cell Line; D002614:Chelating Agents / Q000494:pharmacology; D016572:Cyclosporine / Q000494:pharmacology; D004247:DNA / Q000378:metabolism*; D004533:Egtazic Acid / Q000494:pharmacology; D042783:Endothelial Cells / Q000187:drug effects / Q000378:metabolism; D005347:Fibroblasts; D006801:Humans; D008077:Lipoproteins, LDL / Q000494:pharmacology*; D008264:Macrophages / Q000187:drug effects / Q000378:metabolism; D050778:NFATC Transcription Factors / Q000378:metabolism*; D011485:Protein Binding / Q000187:drug effects; D017382:Reactive Oxygen Species / Q000378:metabolism; D016559:Tacrolimus / Q000494:pharmacology; D014810:Vitamin E / Q000494:pharmacology
D000975:Antioxidants; D065095:Calcineurin Inhibitors; D002614:Chelating Agents; D008077:Lipoproteins, LDL; D050778:NFATC Transcription Factors; D017382:Reactive Oxygen Species; C099252:oxidized low density lipoprotein; D014810:Vitamin E; D004533:Egtazic Acid; D016572:Cyclosporine; D004247:DNA; D002118:Calcium; D016559:Tacrolimus