title: Activation transcription factor-4 induced by fibroblast growth factor-2 regulates vascular endothelial growth factor-A transcription in vascular smooth muscle cells and mediates intimal thickening in rat arteries following balloon injury.
abstract: Activation transcription factor (ATF)-4 is a member of the ATF/CREB family of basic leucine zipper transcription factors that regulates cellular responses to a variety of stresses. The role of ATF-4 in smooth muscle cells of the vessel wall is completely unknown. Here, we show that ATF-4 expression is induced in smooth muscle cells in response to injury, both in vitro using a model of mechanical injury and in the media of balloon-injured rat carotid arteries. We demonstrate that ATF-4 is activated by fibroblast growth factor (FGF)-2, an injury-induced mitogen, through the phosphatidylinositol 3-kinase pathway. Injury also activates vascular endothelial growth factor (VEGF)-A, whose expression is stimulated by ATF-4 overexpression and exposure to FGF-2. FGF-2 induces ATF-4 binding to a recognition element located in the VEGF-A gene at +1767 bp and luciferase reporter gene expression dependent on this site. Moreover, ATF-4 knockdown with small interfering RNA or ATF-4 deficiency ameliorates FGF-2-inducible VEGF-A expression. Intraluminal delivery of ATF-4 small interfering RNA in rat carotid arteries blocks balloon injury-inducible ATF-4 and VEGF-A expression after 4 hours and intimal thickening after 14 days. These findings reveal, for the first time, the induction of ATF-4 by both vascular injury and FGF-2. ATF-4 serves as a conduit for the inducible expression of 1 growth factor by another during the process of intimal thickening.
authors.affiliation: Centre for Vascular Research, University of New South Wales, Sydney, 2052, Australia.
authors.forename: Kristine P
authors.initials: KP
authors.lastname: Malabanan
authors.forename: Peter
authors.initials: P
authors.lastname: Kanellakis
authors.forename: Alexander
authors.initials: A
authors.lastname: Bobik
authors.forename: Levon M
authors.initials: LM
authors.lastname: Khachigian
mesh_terms: D051701:Activating Transcription Factor 4 / Q000235:genetics / Q000378:metabolism*; D000818:Animals; D001011:Aorta / Q000293:injuries / Q000378:metabolism; D020212:Carotid Artery Injuries / Q000378:metabolism; D002404:Catheterization / Q000009:adverse effects*; D049109:Cell Proliferation; D002478:Cells, Cultured; D004195:Disease Models, Animal; D004730:Endothelium, Vascular / Q000166:cytology / Q000293:injuries / Q000378:metabolism*; D016222:Fibroblast Growth Factor 2 / Q000378:metabolism* / Q000494:pharmacology; D006801:Humans; D051379:Mice; D009131:Muscle, Smooth, Vascular / Q000166:cytology / Q000293:injuries / Q000378:metabolism*; D034741:RNA, Small Interfering / Q000494:pharmacology; D051381:Rats; D017207:Rats, Sprague-Dawley; D015398:Signal Transduction / Q000502:physiology; D017539:Tunica Intima / Q000166:cytology / Q000293:injuries / Q000378:metabolism*; D014652:Vascular Diseases / Q000209:etiology / Q000378:metabolism; D042461:Vascular Endothelial Growth Factor A / Q000378:metabolism*
chemical_list: C497110:Atf4 protein, rat; D034741:RNA, Small Interfering; D042461:Vascular Endothelial Growth Factor A; D016222:Fibroblast Growth Factor 2; D051701:Activating Transcription Factor 4