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

Endocrinology. 2001 Jul;142(7):3125-34. doi: 10.1210/endo.142.7.8272.

Abstract

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.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • 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
  • RNA Stability
  • RNA, Messenger / antagonists & inhibitors
  • RNA, Messenger / chemistry
  • Rats
  • Rats, Sprague-Dawley
  • Receptor, Angiotensin, Type 1
  • Receptor, Angiotensin, Type 2
  • Receptors, Angiotensin / genetics*
  • Receptors, Angiotensin / metabolism
  • Receptors, Cytoplasmic and Nuclear / physiology*
  • Sp1 Transcription Factor / antagonists & inhibitors
  • Sp1 Transcription Factor / metabolism
  • Thymidine / metabolism
  • Transcription Factors / physiology*
  • Transcription, Genetic / physiology*

Substances

  • Angiotensin Receptor Antagonists
  • Ligands
  • RNA, Messenger
  • Receptor, Angiotensin, Type 1
  • Receptor, Angiotensin, Type 2
  • Receptors, Angiotensin
  • Receptors, Cytoplasmic and Nuclear
  • Sp1 Transcription Factor
  • Transcription Factors
  • Angiotensin II
  • Thymidine