PPARalpha inhibits TGF-beta-induced beta5 integrin transcription in vascular smooth muscle cells by interacting with Smad4.
Integrins play an important role in vascular smooth muscle cell (VSMC) migration, a crucial event in the development of restenosis and atherosclerosis. Transforming growth factor-beta (TGF-beta) is highly expressed in restenotic and atherosclerotic lesions, and known to induce integrin expression. Peroxisome proliferator-activated receptor alpha (PPARalpha), a member of the nuclear receptor superfamily, regulates gene expression in a variety of vascular cells. We investigated the effects of PPARalpha ligands on TGF-beta-induced beta3 and beta5 integrin expression and potential interaction between PPARalpha and TGF-beta signaling. PPARalpha ligands WY-14643 (100 micromol/L) and 5,8,11,14-eicosatetranoic acid (ETYA, 50 micromol/L) inhibited TGF-beta-induced beta5 integrin protein expression by 72+/-6.8% and 73+/-7.1%, respectively (both P<0.05). TGF-beta-stimulated beta3 integrin expression was not affected by PPARalpha ligands. Both PPARalpha ligands also suppressed TGF-beta-induced beta5 integrin mRNA levels. PPARalpha ligands inhibited TGF-beta-inducible transcription of beta5 integrin by an interaction with a TGF-beta response element between nucleotides -63 and -44, which contains a Sp1/Sp3 transcription factor binding site. Nuclear complexes binding to the TGF-beta response region contained Sp1/Sp3 and TGF-beta-regulated Smad 2, 3, and 4 transcription factors. TGF-beta-stimulated Sp1/Smad4 nuclear complex formation was inhibited by WY-14643 and ETYA with a parallel induction of PPARalpha/Smad4 interactions. However, in vitro pull-down experiments failed to demonstrate direct binding between PPARalpha/Smad4. Both PPARalpha ligands blocked PDGF-directed migration of TGF-beta-pretreated VSMCs, a process mediated, in part, by beta5 integrins. The present study demonstrates that PPARalpha activators inhibit TGF-beta-induced beta5 integrin transcription in VSMCs through a novel indirect interaction between ligand-activated PPARalpha and the TGF-beta-regulated Smad4 transcription factors. The full text of this article is available at http://www.circresaha.org.
Kintscher
Ulrich
U
Department of Medicine, Division of Endocrinology, Diabetes and Hypertension, University of California, Los Angeles, School of Medicine, Los Angeles, Calif 90095, USA.
Lyon
Christopher
C
Wakino
Shu
S
Bruemmer
Dennis
D
Feng
Xu
X
Goetze
Stephan
S
Graf
Kristof
K
Moustakas
Aristidis
A
Staels
Bart
B
Fleck
Eckart
E
Hsueh
Willa A
WA
Law
Ronald E
RE
D015117:5,8,11,14-Eicosatetraynoic Acid / Q000494:pharmacology; D000818:Animals; D002465:Cell Movement / Q000187:drug effects; D002478:Cells, Cultured; D004268:DNA-Binding Proteins / Q000378:metabolism*; D015870:Gene Expression / Q000187:drug effects; D017930:Genes, Reporter; D039641:Integrin beta Chains / Q000096:biosynthesis* / Q000235:genetics; D039661:Integrin beta3 / Q000096:biosynthesis / Q000235:genetics; D008024:Ligands; D046911:Macromolecular Substances; D009131:Muscle, Smooth, Vascular / Q000166:cytology / Q000187:drug effects / Q000378:metabolism*; D009687:Nuclear Proteins / Q000378:metabolism; D010982:Platelet-Derived Growth Factor / Q000494:pharmacology; D011401:Promoter Regions, Genetic / Q000235:genetics; D011485:Protein Binding / Q000187:drug effects / Q000502:physiology; D011743:Pyrimidines / Q000494:pharmacology; D012333:RNA, Messenger / Q000378:metabolism; D051381:Rats; D017207:Rats, Sprague-Dawley; D018160:Receptors, Cytoplasmic and Nuclear; D015398:Signal Transduction / Q000187:drug effects / Q000502:physiology; D051901:Smad4 Protein; D015534:Trans-Activators / Q000378:metabolism*; D014157:Transcription Factors / Q000494:pharmacology*; D014158:Transcription, Genetic / Q000187:drug effects*; D016212:Transforming Growth Factor beta / Q000494:pharmacology*
D004268:DNA-Binding Proteins; D039641:Integrin beta Chains; D039661:Integrin beta3; D008024:Ligands; D046911:Macromolecular Substances; D009687:Nuclear Proteins; D010982:Platelet-Derived Growth Factor; D011743:Pyrimidines; D012333:RNA, Messenger; D018160:Receptors, Cytoplasmic and Nuclear; D051901:Smad4 Protein; C490811:Smad4 protein, rat; D015534:Trans-Activators; D014157:Transcription Factors; D016212:Transforming Growth Factor beta; C084344:integrin beta5; D015117:5,8,11,14-Eicosatetraynoic Acid; C006253:pirinixic acid