Mouse Genetic Evidence That Tranilast Reduces Smooth Muscle Cell Hyperplasia via a p21 ^WAF1 -Dependent Pathway

Abstract

Objective-N-(3Ј4Ј-dimethoxycinnamoyl)-anthranilic acid (tranilast) is a drug that has been shown to reduce the incidence of restenosis after angioplasty in middle-scale clinical trials. Despite clinical interest in this drug, the pharmacological actions of tranilast remain relatively unexplored at a molecular level. Methods and Results-We evaluated the effects of tranilast on vascular smooth muscle cell (VSMC) proliferation in wild-type mice and in mice lacking a cyclin-dependent kinase inhibitor, p21 WAF1 (p21). Tranilast potently inhibited the proliferation of VSMC cultures derived from wild-type mice, but VSMCs derived from p21-deficient (p21Ϫ/Ϫ) mice were unaffected by this treatment. In a mouse femoral artery model of vascular injury, tranilast administration to wild-type mice led to an upregulation of p21 expression and a decrease in the number of proliferating VSMCs, as determined by immunostaining for proliferating cell nuclear antigen. In contrast, tranilast had no effect on the number of proliferating cell nuclear antigen-positive cells in the injured arteries of p21Ϫ/Ϫ mice. Administration of tranilast significantly reduced the neointimal VSMC hyperplasia in wild-type mice at 4 weeks but had no effect on lesion formation in p21Ϫ/Ϫ mice. Conclusions-Our findings provide genetic evidence that tranilast inhibits intimal hyperplasia via a p21-dependent pathway, an activity that may contribute to its efficacy in the prophylactic treatment of postangioplasty restenosis. Key Words: pharmacology Ⅲ genetically altered mice Ⅲ smooth muscle cells Ⅲ restenosis Ⅲ proliferation P ercutaneous transluminal angioplasty has been widely adopted as a treatment of atherosclerosis. However, in a significant number of cases, the procedure fails because of postangioplasty restenosis. 1 Although the increasing use of new devices to dilate stenosed arteries has lowered the incidence of acute complications, restenosis still limits the long-term outcome of percutaneous interventions. 2 Although much effort has been devoted to the development of strategies to prevent postangioplasty restenosis, 3 as yet, no pharmacological treatment has been approved to reduce postangioplasty restenosis.N-(3Ј4Ј-Dimethoxycinnamoyl)-anthranilic acid (tranilast) is a drug that may be effective in preventing angiographic restenosis after percutaneous transluminal coronary revascularization, inasmuch as the results of middle-scale, randomized, double-blind, placebo-controlled trials have shown that oral administration of tranilast significantly lowers the incidence of restenosis after conventional balloon angioplasty, 4 directional coronary atherectomy, 5 and coronary stenting. 6 A multicenter, phase-3, double-blind, placebo-controlled trial is currently under way to evaluate the effects of tranilast on clinical, angiographic, and intravascular ultrasound findings of restenosis. 7 Despite the clinical interest in this drug, the pharmacological actions of tranilast remain relatively unexplored, particularly regarding its action in the vasculature. It h...

p21Cip1 modulates arterial wound repair through the stromal cell–derived factor-1/CXCR4 axis in mice

“…To date, supporting evidence has included the observation that overexpression of recombinant p21 Cip1 decreases VSMC proliferation and attenuates the progression of vascular proliferative diseases (21,23,24,26) and that, conversely, reduced p21 Cip1 expression leads to increased neointimal formation following arterial injury (28). This has led to the evaluation of novel treatment strategies for these diseases that are at least partially mediated through p21 Cip1 upregulation (25,56,57). Our results further extend this work and serve to reinforce the important role of p21 Cip1 in modulating vascular wound repair.…”

“…p21 Cip1 transcription is activated by p53, and p21 Cip1 is part of a negative feedback mechanism that controls p53 activity during apoptosis (20). p21 Cip1 has been shown to be an important mediator of inflammation, VSMC proliferation (21,22), and vascular proliferative disease (23)(24)(25)(26)(27). Of particular relevance, p21 knockout mice have been shown to exhibit enhanced neointimal formation following arterial injury (28).…”

Trichostatin A, an Inhibitor of Histone Deacetylase, Inhibits Smooth Muscle Cell Proliferation via Induction of p21WAF1

“…The expression of p21 WAF1 in VSMCs has been shown to be crucial in the termination of vascular lesion formation 33) . Moreover, Sata et al demonstrated that tranilast failed to inhibit VSMC proliferation when endogenous p21 was genetically ablated 17) . In the same way, we showed that TSA failed to inhibit proliferation in VSMCs from p21 WAF1 knock-out mice, although there may be different mechanism(s) in the inhibitory effect between tranilast and TSA.…”

“…The second group is comprised of p21 WAF1 /p27 KIP1 family members that block cell-cycle progression by inhibiting cyclin D-, E-, and A-associated Cdk complexes 15) . Previously we and colleagues have demonstrated that tranilast, N -(3',4'-dimethoxycinnamoyl) anthranilic acid, inhibits SMC proliferation by the inhibition of Rb phosphorylation and CDK2/CDK4 activities by the increased expression of p21 WAF1 in vitro and in vivo after vascular injury 16,17) . In eukaryotic cells, chromatin must be remodeled in order to render DNA accessible to the actions of transcription factors 18) .…”

Platelet P2Y 12 Receptor Influences the Vessel Wall Response to Arterial Injury and Thrombosis

“…Male mice were anesthetized by inhalational isoflurane (maintenance rate of 1.5%), and endoluminal injury to the common femoral artery was performed with a method similar to that of Sata et al 18 A 0.12-mm wire was inserted distal to the muscular branch artery and passed 6 times back and forth along the common femoral artery. The arteriotomy site was subsequently ligated.…”