Transcriptional suppression of type 1 angiotensin II receptor gene expression by peroxisome proliferator-activated receptor-gamma in vascular smooth muscle cells

• Published in: Endocrinology (Philadelphia) 2001-07, Vol.142 (7), p.3125-3134
• Main Authors: Sugawara, A, Takeuchi, K, Uruno, A, Ikeda, Y, Arima, S, Kudo, M, Sato, K, Taniyama, Y, Ito, S
• Format: Article
• Language: English
• Subjects: Angiotensin II - pharmacology; Angiotensin Receptor Antagonists; Animals; Base Sequence - genetics; Cells, Cultured; Gene Expression - physiology; Ligands; Male; Muscle, Smooth, Vascular - cytology; Muscle, Smooth, Vascular - physiology; Promoter Regions, Genetic - genetics; Promoter Regions, Genetic - physiology; Rats; Rats, Sprague-Dawley; Receptor, Angiotensin, Type 1; Receptor, Angiotensin, Type 2; Receptors, Angiotensin - genetics; Receptors, Angiotensin - metabolism; Receptors, Cytoplasmic and Nuclear - physiology; RNA Stability; RNA, Messenger - antagonists & inhibitors; RNA, Messenger - chemistry; Sp1 Transcription Factor - antagonists & inhibitors; Sp1 Transcription Factor - metabolism; Thymidine - metabolism; Transcription Factors - physiology; Transcription, Genetic - physiology
• ISSN: 0013-7227
• DOI: 10.1210/en.142.7.3125

Angiotensin (A) II plays a critical role in vascular remodeling, and its action is mediated by type 1 AII receptor (AT1R). Recently, 15-deoxy-(Delta)(12,14)-prostaglandin J(2) and thiazolidinediones have been shown to be ligands for peroxisome proliferator-activated receptor (PPAR)-gamma and activate PPAR-gamma. In the present work, we have studied the effect of PPAR-gamma on AT1R expression in rat vascular smooth muscle cells (VSMCs). We observed that: 1) endogenous AT1R expression was significantly decreased by PPAR-gamma ligands both at messenger RNA and protein levels, whereas AT1R messenger RNA stability was not affected; 2) AII-induced increase of (3)H-thymidine incorporation into VSMCs was inhibited by PPAR-gamma ligands; 3) rat AT1R gene promoter activity was significantly suppressed by PPAR-gamma ligands, and PPAR-gamma overexpression further suppressed the promoter activity; 4) transcriptional analyses using AT1R gene promoter mutants revealed that a GC-box-related sequence within the -58/-34 region of the AT1R gene promoter was responsible for the suppression; 5) Sp1 overexpression stimulated AT1R gene transcription via the GC-box-related sequence, which was inhibited by additional PPAR-gamma overexpression; 6) electrophoretic mobility shift assay suggested that Sp1 could bind to the GC-box-related sequence whereas PPAR-gamma could not; 7) antibody supershift experiments using VSMC nuclear extracts revealed that protein-DNA complexes formed on the GC-box-related sequence, which were decreased by PPAR-gamma coincubation, were mostly composed of Sp1; and 8) glutathione S-transferase pull-down assay revealed a direct interaction between PPAR-gamma and Sp1. Taken together, it is suggested that activated PPAR-gamma suppresses AT1R gene at a transcriptional level by inhibiting Sp1 via a protein-protein interaction. PPAR-gamma ligands, thus, may inhibit AII-induced cell growth and hypertrophy in VSMCs by AT1R expression suppression and possibly be beneficial for treatment of diabetic patients with hypertension and atherosclerosis.