Abstract
Endothelial dysfunction is a major atherogenic proinflammatory event. LDL causes the activation and phenotypic changes of cultured vascular endothelial cells (ECs). We previously reported that LDL activates c-Jun and AP-1 in ECs. In this study, we demonstrated that p38-ATF-2 is activated by LDL in human ECs and that this activation is mediated by Ras. When ECs are incubated with LDL in pathophysiological concentrations, the p38-mediated ATF-2 phosphorylation and ATF-2 transactivation are increased in a time- and dose-dependent manner. To elucidate the upstream mechanism in LDL-activated p38 in ECs, we demonstrate that LDL increases Ras translocation from the cytoplasm to the cellular membrane, with concurrent increases in Ras binding activity to GST-Raf-1. Overexpression of RasN17, a dominant negative mutant of Ras, attenuates the LDL-induced increases in (1) phosphorylation of ATF-2, (2) phosphorylation of c-Jun, (3) AP-1 binding, and (4) AP-1-driven luciferase activity. To study the effect of p38 in the regulation of an LDL targeting gene, we show that a specific p38 inhibitor attenuates LDL-induced E-selectin at the mRNA level. Thus, LDL activates both p38 and JNK signaling pathways through Ras activation, and furthermore, these events may play an important role in LDL-induced endothelial activation.
Publication types
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Research Support, Non-U.S. Gov't
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Research Support, U.S. Gov't, P.H.S.
MeSH terms
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Activating Transcription Factor 2
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Cells, Cultured
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Cyclic AMP Response Element-Binding Protein / metabolism
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E-Selectin / biosynthesis
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E-Selectin / genetics
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Endothelium, Vascular / drug effects
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Endothelium, Vascular / enzymology*
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Enzyme Activation
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Enzyme Inhibitors / pharmacology
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Humans
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Imidazoles / pharmacology
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JNK Mitogen-Activated Protein Kinases
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Lipoproteins, LDL / pharmacology*
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Mitogen-Activated Protein Kinases / antagonists & inhibitors
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Mitogen-Activated Protein Kinases / metabolism*
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Mutation
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Protein Transport
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Proto-Oncogene Proteins c-jun / metabolism
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Proto-Oncogene Proteins p21(ras) / genetics
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Proto-Oncogene Proteins p21(ras) / physiology*
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Pyridines / pharmacology
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RNA, Messenger / biosynthesis
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Trans-Activators / metabolism
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Transcription Factor AP-1 / metabolism
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Transcription Factors / metabolism
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p38 Mitogen-Activated Protein Kinases
Substances
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ATF2 protein, human
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Activating Transcription Factor 2
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Cyclic AMP Response Element-Binding Protein
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E-Selectin
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Enzyme Inhibitors
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Imidazoles
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Lipoproteins, LDL
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Proto-Oncogene Proteins c-jun
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Pyridines
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RNA, Messenger
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Trans-Activators
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Transcription Factor AP-1
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Transcription Factors
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JNK Mitogen-Activated Protein Kinases
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Mitogen-Activated Protein Kinases
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p38 Mitogen-Activated Protein Kinases
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HRAS protein, human
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Proto-Oncogene Proteins p21(ras)
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SB 203580