title: Homocysteine exerts cell type-specific inhibition of AP-1 transcription factor.
abstract: Homocysteine (Hcy) exerts either promoting or suppressive effects on mitogenesis in a cell type-specific manner. Hcy elicits proliferation of vascular smooth muscle cells, but is rather inhibitory to growth of endothelial cells and NIH/3T3 cells. In NIH/3T3 cells, we found that physiologically relevant concentrations (20-100 microM) of Hcy inhibit the activity of activating protein-1 (AP-1) transcription factor, although it is capable of eliciting immediate-early signaling events. Hcy induced p44/42 mitogen-activated protein kinase (MAPK) phosphorylation in control cells, but not in dominant negative p21ras transfected cells, indicating induction of the Ras-MAPK pathway. Hcy also induced the activity of serum response factor and expression of c-fos and c-jun genes. Despite the activation of these upstream events, Hcy potently inhibited AP-1 activity. Oxidized forms of Hcy (Hcy thiolactone, homocystine) were less effective in affecting AP-1. Hcy-mediated inhibition of AP-1 activity was not observed in A7r5 vascular smooth muscle cells. These results demonstrate that Hcy exerts cell type- and redox-specific inhibition of AP-1 dependent biological events.
authors.affiliation: Antioxidants Research Laboratory, Jean Mayer United States Department of Agriculture Human Nutrition Research Center on Aging at Tufts University, Boston, MA 02111, USA. ysuzuki@hnrc.tufts.edu
authors.forename: Y J
authors.initials: YJ
authors.lastname: Suzuki
authors.forename: M V
authors.initials: MV
authors.lastname: Lorenzi
authors.forename: S S
authors.initials: SS
authors.lastname: Shi
authors.forename: R M
authors.initials: RM
authors.lastname: Day
authors.forename: J B
authors.initials: JB
authors.lastname: Blumberg
mesh_terms: D016475:3T3 Cells / Q000187:drug effects / Q000378:metabolism; D000818:Animals; D002455:Cell Division / Q000187:drug effects; D004268:DNA-Binding Proteins / Q000096:biosynthesis / Q000235:genetics; D004789:Enzyme Activation / Q000187:drug effects; D005786:Gene Expression Regulation / Q000187:drug effects*; D017781:Genes, Immediate-Early / Q000187:drug effects; D016762:Genes, fos / Q000187:drug effects; D016758:Genes, jun / Q000187:drug effects; D011905:Genes, ras; D006710:Homocysteine / Q000494:pharmacology*; D048031:JNK Mitogen-Activated Protein Kinases; D020935:MAP Kinase Signaling System / Q000187:drug effects; D051379:Mice; D019950:Mitogen-Activated Protein Kinase 1 / Q000378:metabolism; D048052:Mitogen-Activated Protein Kinase 3; D020928:Mitogen-Activated Protein Kinases / Q000378:metabolism; D009131:Muscle, Smooth, Vascular / Q000166:cytology / Q000187:drug effects; D009687:Nuclear Proteins / Q000096:biosynthesis / Q000235:genetics; D009928:Organ Specificity; D010084:Oxidation-Reduction; D020133:Reverse Transcriptase Polymerase Chain Reaction; D026362:Serum Response Factor; D018808:Transcription Factor AP-1 / Q000037:antagonists & inhibitors*; D014162:Transfection
chemical_list: D004268:DNA-Binding Proteins; D009687:Nuclear Proteins; D026362:Serum Response Factor; D018808:Transcription Factor AP-1; D006710:Homocysteine; D048031:JNK Mitogen-Activated Protein Kinases; D019950:Mitogen-Activated Protein Kinase 1; D048052:Mitogen-Activated Protein Kinase 3; D020928:Mitogen-Activated Protein Kinases