Biomechanically induced gene iex-1 inhibits vascular smooth muscle cell proliferation and neointima formation.
Mechanotransduction plays a prominent role in vascular pathophysiology but is incompletely understood. In this study, we report the biomechanical induction of the immediate early response gene iex-1 in vascular smooth muscle cells (SMCs). Mechanical induction of iex-1 was confirmed by Northern (30-fold induction after 2 hours) and Western (6-fold induction after 24 hours) analyses. Expression of iex-1 was regulated by mechanical activation of nuclear factor (NF)-kappaB and abolished by overexpression of IkappaB in SMCs. The function of iex-1 in SMCs was explored by gene transfer using adenoviral vectors overexpressing iex-1. After 48 hours of 4% cyclic mechanical strain, adenoviral vectors overexpressing iex-1-infected cells had lower 3[H]-thymidine incorporation compared with AdGFP-infected controls (71.3+/-8.5% versus 180.2+/-19.4% in controls; P<0.001). Overexpression of iex-1 suppressed mitogenesis induced by platelet-derived growth factor (208.1+/-108.3% versus 290.0+/-120.5% in controls; P<0.05). This was accompanied by reduced degradation of p27kip1, inhibition of Rb hyperphosphorylation, and reduced cell cycle progression. To investigate functional effects of iex-1 in vivo, we performed carotid artery mechanical injury and endothelial denudation in low-density lipoprotein receptor-deficient mice followed by intraluminal injection of adenoviral vectors (3x10(9) pfu in 50 microL) for overexpression of iex-1 or gfp (control). Vascular overexpression of iex-1 reduced neointima formation 2 weeks after injury (intima/media ratio, 0.23+/-0.04 versus 0.5+/-0.24 in controls; P<0.05). Our findings demonstrate that biomechanical strain induces iex-1 with subsequent antiproliferative effects in SMCs and that selective gene transfer of iex-1 inhibits the local vascular response after injury. These findings suggest that the induction of iex-1 represents a novel negative biomechanical feedback mechanism limiting the vascular response to injury.
Cardiovascular Division, Department of Medicine, Brigham and Women's Hospital, Harvard Medical School, Boston, Mass 02139, USA.
P Christian
PC
Schulze
Gilles W
GW
de Keulenaer
Kimberly A
KA
Kassik
Tomosaburo
T
Takahashi
Zhiping
Z
Chen
Daniel I
DI
Simon
Richard T
RT
Lee
D000818:Animals; D001057:Apolipoproteins E / Q000235:genetics; D051017:Apoptosis Regulatory Proteins; D001161:Arteriosclerosis / Q000235:genetics / Q000503:physiopathology; D020212:Carotid Artery Injuries / Q000235:genetics / Q000503:physiopathology; D002453:Cell Cycle / Q000502:physiology; D002455:Cell Division / Q000502:physiology; D002478:Cells, Cultured; D005786:Gene Expression Regulation; D049452:Green Fluorescent Proteins; D006801:Humans; D017874:Immediate-Early Proteins / Q000235:genetics* / Q000378:metabolism; D008164:Luminescent Proteins / Q000235:genetics / Q000378:metabolism; D040542:Mechanotransduction, Cellular / Q000502:physiology; D008565:Membrane Proteins; D051379:Mice; D018345:Mice, Knockout; D009131:Muscle, Smooth, Vascular / Q000166:cytology / Q000378:metabolism*; D016328:NF-kappa B / Q000378:metabolism; D009363:Neoplasm Proteins / Q000235:genetics* / Q000378:metabolism; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism; D011973:Receptors, LDL / Q000235:genetics; D011993:Recombinant Fusion Proteins / Q000235:genetics / Q000378:metabolism; D013314:Stress, Mechanical; D017539:Tunica Intima / Q000503:physiopathology*
D001057:Apolipoproteins E; D051017:Apoptosis Regulatory Proteins; C099815:IER3 protein, human; D017874:Immediate-Early Proteins; D008164:Luminescent Proteins; D008565:Membrane Proteins; D016328:NF-kappa B; D009363:Neoplasm Proteins; D012333:RNA, Messenger; D011973:Receptors, LDL; D011993:Recombinant Fusion Proteins; D049452:Green Fluorescent Proteins