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      Stent Implantation Activates RhoA in Human Arteries: Inhibitory Effect of Rapamycin

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          In-stent restenosis is a novel pathobiologic process resulting from vascular smooth muscle cell (VSMC) proliferation, migration and excessive matrix production. The present study was designed to assess the activity of RhoA, a major regulator of VSMC proliferation and migration, after stenting and to determine its role in the neointimal formation. Analysis of RhoA activity in an ex vivo organ culture model of human internal mammary arteries demonstrates that stenting induced a time-dependent increase in RhoA activity (4.9 ± 0.4 vs. 1.2 ± 0.2 in control at 28 days, n = 4, p < 0.0001) associated with a concomitant decrease in p27 expression. Treatment of stented arteries with the permeant RhoA inhibitor TAT-C3 (10 µg/ml) or Rho-kinase inhibitors (Y-27632, 10 µmol/l; fasudil, 10 µmol/l) inhibited both neointimal formation and decrease in p27 expression. Rapamycin (1 and 10 nmol/l) also inhibited neointimal formation, and induced a loss of RhoA expression. The inhibitory effect of rapamycin on neointimal thickening is prevented by the dominant active form of RhoA. Our study shows that stent implantation induces maintained RhoA activation and demonstrates that the inhibitory action of rapamycin on RhoA expression plays a key role in its antirestenotic effect.

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          Most cited references 22

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          Interleukin-2-mediated elimination of the p27Kip1 cyclin-dependent kinase inhibitor prevented by rapamycin.

          The cyclin-dependent kinase (Cdk) enzymes, when associated with the G1 cyclins D and E, are rate-limiting for entry into the S phase of the cell cycle. During T-cell mitogenesis, antigen-receptor signalling promotes synthesis of cyclin E and its catalytic partner, Cdk2, and interleukin-2 (IL-2) signalling activates cyclin E/Cdk2 complexes. Rapamycin is a potent immunosuppressant which specifically inhibits G1-to-S-phase progression, leading to cell-cycle arrest in yeast and mammals. Here we report that IL-2 allows Cdk activation by causing the elimination of the Cdk inhibitor protein p27Kip1, and that this is prevented by rapamycin. By contrast, the Cdk inhibitor p21 is induced by IL-2 and this induction is blocked by rapamycin. Our results show that p27Kip1 governs Cdk activity during the transition from quiescence to S phase in T lymphocytes and that p21 function may be restricted to cycling cells.
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            Cyclic GMP-dependent protein kinase signaling pathway inhibits RhoA-induced Ca2+ sensitization of contraction in vascular smooth muscle.

            The potent vasodilator action of cyclic GMP-dependent protein kinase (cGK) involves decreasing the Ca(2+) sensitivity of contraction of smooth muscle via stimulation of myosin light chain phosphatase through unknown mechanisms (Wu, X., Somlyo, A. V., and Somlyo, A. P. (1996) Biochem. Biophys. Res. Commun. 220, 658-663). Myosin light chain phosphatase activity is controlled by the small GTPase RhoA and its target Rho kinase. Here we demonstrate cGMP effects mediated by cGK that inhibit RhoA-dependent Ca(2+) sensitization of contraction of blood vessels and actin cytoskeleton organization in cultured vascular myocytes. Ca(2+) sensitization and actin organization were inhibited by both 8-bromo-cGMP and sodium nitroprusside (SNP). SNP also caused translocation of activated RhoA from the membrane to the cytosol. SNP-induced actin disassembly was lost in vascular myocytes in culture after successive passages but was restored by transfection of cells with cGK I. Furthermore, cGK phosphorylated RhoA in vitro, and addition of cGK I inhibited RhoA-induced Ca(2+) sensitization in permeabilized smooth muscle. 8-Bromo-cGMP-induced actin disassembly was inhibited in vascular myocytes expressing RhoA(Ala-188), a mutant that could not be phosphorylated. Collectively, these results indicate that cGK phosphorylates and inhibits RhoA and suggest that the consequent inhibition of RhoA-induced Ca(2+) sensitization and actin cytoskeleton organization contributes to the vasodilator action of nitric oxide.
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              Stent-based delivery of sirolimus reduces neointimal formation in a porcine coronary model.

              The purpose of this study was to determine the efficacy of stent-based delivery of sirolimus (SRL) alone or in combination with dexamethasone (DEX) to reduce in-stent neointimal hyperplasia. SRL is a potent immunosuppressive agent that inhibits SMC proliferation by blocking cell cycle progression. Stents were coated with a nonerodable polymer containing 185 microgram SRL, 350 microgram DEX, or 185 microgram SRL and 350 microgram DEX. Polymer biocompatibility studies in the porcine and canine models showed acceptable tissue response at 60 days. Forty-seven stents (metal, n=13; SRL, n=13; DEX, n=13; SRL and DEX, n=8) were implanted in the coronary arteries of 16 pigs. The tissue level of SRL was 97+/-13 ng/artery, with a stent content of 71+/-10 microgram at 3 days. At 7 days, proliferating cell nuclear antigen and retinoblastoma protein expression were reduced 60% and 50%, respectively, by the SRL stents. After 28 days, the mean neointimal area was 2.47+/-1.04 mm(2) for the SRL alone and 2.42+/-1.04 mm(2) for the combination of SRL and DEX compared with the metal (5.06+/-1.88 mm(2), P<0.0001) or DEX-coated stents (4.31+/-3.21 mm(2), P<0.001), resulting in a 50% reduction of percent in-stent stenosis. Stent-based delivery of SRL via a nonerodable polymer matrix is feasible and effectively reduces in-stent neointimal hyperplasia by inhibiting cellular proliferation.

                Author and article information

                J Vasc Res
                Journal of Vascular Research
                S. Karger AG
                February 2005
                28 January 2005
                : 42
                : 1
                : 21-28
                aINSERM U 533, Faculté des Sciences and bDepartment of Cardiac Surgery, CHU, Nantes, and cInstitut de Recherche International Servier, Suresnes, France
                82873 J Vasc Res 2005;42:21–28
                © 2005 S. Karger AG, Basel

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                Page count
                Figures: 4, References: 41, Pages: 8
                Research Paper


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