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  • Title: Functional role of Egr-1 mediating VEGF-induced tissue factor expression in the retinal capillary endothelium.
    Author: Sassa Y, Hata Y, Murata T, Yamanaka I, Honda M, Hisatomi T, Fujisawa K, Sakamoto T, Kubota T, Nakagawa K, Sueishi K, Ishibashi T.
    Journal: Graefes Arch Clin Exp Ophthalmol; 2002 Dec; 240(12):1003-10. PubMed ID: 12483323.
    Abstract:
    PURPOSE: To investigate the causal relationship between VEGF and tissue factor (TF) expression, and its intracellular signaling in the retinal capillary endothelium both in vitro and in vivo. METHODS: TF mRNA and protein expression in cultured bovine retinal capillary endothelial cells (BRECs) were detected by RT-PCR and western blotting. The expression and subcellular localization of Egr-1 were analyzed by immunocytochemistry and western blotting. Involvement of p44/p42 MAPK pathway in this signaling was assessed using PD98059. Electrophoretic mobility shift assay (EMSA) was performed using human TF Egr-1/Sp-1 overlapping promoter region (-85 to -70). Decoy oligonucleotide was transfected into BRECs to clarify the critical transcription factor mediating VEGF-induced TF gene expression. To evaluate the importance of GC rich region in VEGF-induced TF protein expression in rat retinas, Mithramycin was intraperitoneally administered. RESULTS: VEGF stimulated TF mRNA and protein expression in cultured BRECs, reaching maximal effect after 4 h and 10 h, respectively. VEGF activated transcription factor Egr-1 within 60 min. Inactivation of Egr-1 by PD98059 resulted in the prohibition of VEGF-induced TF gene expression. EMSA revealed the increment of Egr-1 binding with TF promoter region by displacing Sp1 after treatment with VEGF. Transfection of the Egr-1/Sp-1 overlapping decoy into BRECs inhibited VEGF-dependent TF gene expression. Mithramycin almost completely suppressed VEGF-induced TF protein expression in retinal capillary system in vivo (80%, p<0.01). CONCLUSION: Transcription factor Egr-1, which lies downstream of p44/p42 MAPK, critically mediates VEGF-dependent TF expression in the retinal capillary endothelium.
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