title: Transcription suppression of thromboxane receptor gene by peroxisome proliferator-activated receptor-gamma via an interaction with Sp1 in vascular smooth muscle cells.
abstract: Thromboxane (TX) A(2) exerts contraction and proliferation of vascular smooth muscle cells (VSMCs) via its specific membrane TX receptor (TXR), possibly leading to the progression of atherosclerosis. A nuclear hormone receptor, peroxisome proliferator-activated receptor (PPAR)-gamma, has recently been reported to be expressed in VSMCs. Here we examined a role of PPAR-gamma in TXR gene expression in VSMCs. PPAR-gamma ligands 15-deoxy-Delta(12,14)-prostaglandin J(2) and troglitazone reduced TXR mRNA expression levels as well as cell growth as assessed by [(3)H]thymidine incorporation. Transcriptional activity of the TXR gene promoter was suppressed with PPAR-gamma ligands, and the suppression was augmented further by PPAR-gamma overexpression. By deletion and mutation analyses, the transcription suppression was shown to be the result of a -22/-7 GC box-related sequence (upstream of transcription start site). Electrophoretic mobility shift assays also showed that the sequence was bound by Sp1 but not by PPAR-gamma, and the formation of a Sp1 small middle dotDNA complex was inhibited either by coincubation with PPAR-gamma or PPAR-gamma ligand treatment of VSMCs. Moreover, glutathione S-transferase pull-down assays demonstrated a direct interaction between PPAR-gamma and Sp1. In conclusion, PPAR-gamma suppresses TXR gene transcription via an interaction with Sp1. PPAR-gamma may possibly have an antiatherosclerotic action by inhibiting TXR gene expression in VSMCs.
authors.affiliation: Division of Nephrology, Department of Medicine, Tohoku University Graduate School of Medicine, 1-1 Seiryo-cho, Aoba-ku, Sendai 980-8574, Japan. akiras2i@mail.cc.tohoku.ac.jp
authors.forename: Akira
authors.initials: A
authors.lastname: Sugawara
authors.forename: Akira
authors.initials: A
authors.lastname: Uruno
authors.forename: Masataka
authors.initials: M
authors.lastname: Kudo
authors.forename: Yukio
authors.initials: Y
authors.lastname: Ikeda
authors.forename: Kazunori
authors.initials: K
authors.lastname: Sato
authors.forename: Yoshihiro
authors.initials: Y
authors.lastname: Taniyama
authors.forename: Sadayoshi
authors.initials: S
authors.lastname: Ito
authors.forename: Kazuhisa
authors.initials: K
authors.lastname: Takeuchi
mesh_terms: D000818:Animals; D015152:Blotting, Northern; D002455:Cell Division; D002478:Cells, Cultured; D018076:DNA, Complementary / Q000378:metabolism; D005982:Glutathione Transferase / Q000378:metabolism; D008024:Ligands; D008156:Luciferases / Q000378:metabolism; D009131:Muscle, Smooth, Vascular / Q000166:cytology*; D010957:Plasmids / Q000378:metabolism; D011401:Promoter Regions, Genetic; D014176:Protein Biosynthesis; D012333:RNA, Messenger / Q000378:metabolism; D051381:Rats; D018160:Receptors, Cytoplasmic and Nuclear / Q000378:metabolism*; D017482:Receptors, Thromboxane / Q000096:biosynthesis* / Q000235:genetics; D016329:Sp1 Transcription Factor / Q000378:metabolism*; D014157:Transcription Factors / Q000378:metabolism*; D014158:Transcription, Genetic; D014162:Transfection; D015854:Up-Regulation
chemical_list: D018076:DNA, Complementary; D008024:Ligands; D012333:RNA, Messenger; D018160:Receptors, Cytoplasmic and Nuclear; D017482:Receptors, Thromboxane; D016329:Sp1 Transcription Factor; D014157:Transcription Factors; D008156:Luciferases; D005982:Glutathione Transferase