Background Dual antiplatelet therapy is recommended after coronary stenting to prevent thrombotic complications, yet the benefits and risks of treatment beyond 1 year are uncertain. Methods Subjects were enrolled after a drug-eluting coronary stent procedure. After 12 months of thienopyridine (clopidogrel bisulfate [Plavix] or prasugrel [Effient/Efient]) with aspirin, subjects were randomized to continued thienopyridine or placebo for another 18 months; all continued aspirin. The co-primary effectiveness end points were stent thrombosis and major adverse cardiovascular and cerebrovascular events (a composite of death, myocardial infarction, or stroke) at 12 to 30 months. The primary safety end point was moderate or severe bleeding. Results Subjects (N=9,961) were randomized to continued thienopyridine or placebo. Continued thienopyridine reduced stent thrombosis (0.4% vs. 1.4%, hazard ratio 0.29, 95% confidence interval [CI] 0.17-0.48, P<0.001) and major adverse cardiovascular and cerebrovascular events (4.3% vs. 5.9%, hazard ratio 0.71, 95% CI 0.59-0.85, P<0.001). Myocardial infarction was reduced (2.1% vs. 4.1%, hazard ratio 0.47, P<0.001). Rates of all-cause mortality in the continued thienopyridine and placebo groups were 2.0 and 1.5%, respectively (hazard ratio 1.36, 95% CI 1.00-1.85, P=0.052). Moderate or severe bleeding was increased with continued thienopyridine (2.5% vs. 1.6%, P=0.001). An elevated hazard for stent thrombosis and myocardial infarction was observed in both groups during the 3 months following thienopyridine discontinuation. Conclusion Dual antiplatelet therapy beyond one year after drug-eluting stent placement significantly reduced the risks of stent thrombosis and major adverse cardiovascular and cerebrovascular events compared with aspirin alone, but was associated with increased bleeding.

Endothelium-derived relaing factor (EDRF) activity has been attributed to the highly labile nitric oxide radical (NO). In view of the fact that the plasma and cellular mifleux contain reactive species that can rapidly inactivate NO, it has been postulated that NO is stabilized by a carrier molecule that preserves its biological activity. Reduced thiol species are candidates for this role, reacting readily in the presence of NO to yield biologically active S-nitrosothiols that are more stable than NO itself. Because sulfhydryl groups in proteins represent an abundant source of reduced thiol in biologic systems, we examined the reaction of several sulfhy--I dryl-containing proteins of diverse nature and function upon exposure to authentic NO and EDRF. We demonstrate that S-nitroso proteins form readily under physiologic conditions and possess EDRF-like effects of vasodilation and platelet inhibition. These observations suggest that S-nitrosothiol groups in proteins may serve as intermediates in the cellular metabolism ofNO and raise the possibility ofan additional type of cellular regulatory mechanism.The richest source of reduced thiol in plasma (and a particularly prevalent source in cellular cytosol) is protein sulflydryl groups (19). The reaction ofNO with protein thiols has not been previously studied, and the potential biological significance ofthis reaction has been neglected because ofthe exclusion of proteins from (bio)assays of the functional activity and half-life of EDRF and from analyses of its chemical characteristics. We therefore investigated the reaction of protein thiols exposed to NO, and we present data showing that a variety of proteins of biological significance and relative abundance can be S-nitrosylated. S-Nitrosylation of proteins endows these molecules with potent and long-lasting EDRF-like effects of vasodilation and platelet inhibition that are mediated by guanylate cyclase activation. These observations raise the possibility that S-nitrosothiol groups in proteins may serve as intermediates in the cellular metabolism or bioactivity ofNO and that their formation may represent an important cellular regulatory mechanism.The endothelium-dependent relaxation of vascular smooth muscle first observed by Furchgott and Zawadski (1) has been largely attributed to nitric oxide (NO) derived from L-arginine through the action of NO synthase (2)(3)(4). This free radical ultimately stimulates guanylate cyclase by the formation of a nitrosyl-heme complex at the activator site of the enzyme (5, 6); however, the molecular mechanism(s) by which NO is transferred from synthase to cyclase remains poorly understood. The rapidity of the reaction of NO with molecular oxygen (7), superoxide anion (8), and heme (2) as well as nonheme iron (9) and the ready availability of these inactivating reactants in the plasma and cellular milieux militate against simple diffusion-limited transport of free NO in this medium. That endothelium-derived relaxing factor (EDRE) has the relatively long half-life of the ord...

We have recently shown that nitric oxide or authentic endothelium-derived relaxing factor generated in a biologic system reacts in the presence of specific protein thiols to form S-nitrosoprotein derivatives that have endotheliumderived relaxing factor-like properties. The single free cysteine of serum albumin, Cys-34, is particularly reactive toward nitrogen oxides (most likely nitrosonium ion) under physiologic conditions, primarily because of its anomalously low pK; given its abundance in plasma, where it accounts for -0.5 mM thiol, we hypothesized that this plasma protein serves as a reservoir for nitric oxide produced by the endothelial cell. To test this hypothesis, we developed a methodology, which involves UV photolytic cleavage of the S-NO bond before reaction with ozone for chemiluminescence detection, with which to measure free nitric oxide, S-nitrosodiols, and S-nitrosoproteins in biologic systems. We found that human plasma contains =7 pIM S-nitrosothiols, of which 96% are S-nitrosoproteins, 82% of which is accounted for by S-nitroso-erum albumin. By contrast, plasma levels of free nitric oxide are only in the 3-nM range. In rabbits, plasma S-nitrosothiols are present at -1 #M; 60 min after administration of NG-monomethyl-Larginine at 50 mg/ml, a selective and potent inhibitor of nitric oxide synthetases, S-nitrosothiols decreased by "40% (>95% of which were accounted for by S-nitrosoproteins, and ""80% of which was S-nitroso-serum albumin); this decrease was accompanied by a concomitant increase in mean arterial blood pressure of 22%. These data suggest that naturally produced nitric oxide circulates in plasma primarily complexed in S-nitrosothiol species, principal among which is S-nitroso-serum albumin. This abundant, relatively long-lived adduct likely serves as a reservoir with which plasma levels of highly reactive, short-lived free nitric oxide can be regulated for the maintenance of vascular tone.Endothelium-derived relaxing factor (EDRF), first described by Furchgott and Zawadzki (1), is a product of the normal endothelial cell having both vasodilatory (2) and antiplatelet (3,4) properties. Pharmacologic studies suggest that disease states as varied as septic shock (5), atherosclerosis (6), and hypoxia-induced pulmonary hypertension (7) may be associated with abnormal concentrations of EDRF in the vascular milieu. As a result of the seminal work of two groups (8, 9), this bioactive substance is believed to be equivalent to nitric oxide or a chemical congener or adduct thereof. Among the species thought of potential importance as adducts of nitric oxide are S-nitrosothiols-adducts with the sulfhydryl groups of amino acids, peptides, and proteins. We have recently shown that nitric oxide and authentic EDRF react with free thiol groups of proteins under physiologic conditions in vitro to form S-nitrosoproteins (10)-nitric oxide adducts with bioactivities comparable to EDRF but with half-lives of the order of hours. Although the facile formation of such species is intrinsically interest...

Integrin function is central to inflammation, immunity, and tumor progression. The urokinase-type plasminogen activator receptor (uPAR) and integrins formed stable complexes that both inhibited native integrin adhesive function and promoted adhesion to vitronectin via a ligand binding site on uPAR. Interaction of soluble uPAR with the active conformer of integrins mimicked the inhibitory effects of membrane uPAR. Both uPAR-mediated adhesion and altered integrin function were blocked by a peptide that bound to uPAR and disrupted complexes. These data provide a paradigm for regulation of integrins in which a nonintegrin membrane receptor interacts with and modifies the function of activated integrins.

The vascular endothelium is a critical regulator of vascular function. Diverse stimuli such as proinflammatory cytokines and hemodynamic forces modulate endothelial phenotype and thereby impact on the development of vascular disease states. Therefore, identification of the regulatory factors that mediate the effects of these stimuli on endothelial function is of considerable interest. Transcriptional profiling studies identified the Kruppel-like factor (KLF)2 as being inhibited by the inflammatory cytokine interleukin-1 ␤ and induced by laminar shear stress in cultured human umbilical vein endothelial cells. Overexpression of KLF2 in umbilical vein endothelial cells robustly induced endothelial nitric oxide synthase expression and total enzymatic activity. In addition, KLF2 overexpression potently inhibited the induction of vascular cell adhesion molecule-1 and endothelial adhesion molecule E-selectin in response to various proinflammatory cytokines. Consistent with these observations, in vitro flow assays demonstrate that T cell attachment and rolling are markedly attenuated in endothelial monolayers transduced with KLF2. Finally, our studies implicate recruitment by KLF2 of the transcriptional coactivator cyclic AMP response element-binding protein (CBP/p300) as a unifying mechanism for these various effects. These data implicate KLF2 as a novel regulator of endothelial activation in response to proinflammatory stimuli.

Formation of the atherosclerotic intima must involve altered metabolism of the elastin-rich arterial extracellular matrix. Proteases potentially involved in these processes remain unclear. This study examined the expression of the potent elastases cathepsins S and K in human atheroma. Normal arteries contained little or no cathepsin K or S. In contrast, macrophages in atheroma contained abundant immunoreactive cathepsins K and S. Intimal smooth muscle cells (SMC), especially cells appearing to traverse the internal elastic laminae, also contained these enzymes. Extracts of atheromatous tissues had approximately twofold greater elastase-specific activity than extracts of uninvolved arteries, mostly due to cysteine proteases.

Cardiovascular optical coherence tomography (OCT) is a catheter-based invasive imaging system. Using light rather than ultrasound, OCT produces high-resolution in vivo images of coronary arteries and deployed stents. This comprehensive review will assist practicing interventional cardiologists in understanding the technical aspects of OCT based upon the physics of light and will also highlight the emerging research and clinical applications of OCT. Semi-automated imaging analyses of OCT systems permit accurate measurements of luminal architecture and provide insights regarding stent apposition, overlap, neointimal thickening, and, in the case of bioabsorbable stents, information regarding the time course of stent dissolution. The advantages and limitations of this new imaging modality will be discussed with emphasis on key physical and technical aspects of intracoronary image acquisition, current applications, definitions, pitfalls, and future directions.

The firm adhesion and transplatelet migration of leukocytes on vascular thrombus are both dependent on the interaction of the leukocyte integrin, Mac-1, and a heretofore unknown platelet counterreceptor. Here, we identify the platelet counterreceptor as glycoprotein (GP) Ibα, a component of the GP Ib-IX-V complex, the platelet von Willebrand factor (vWf) receptor. THP-1 monocytic cells and transfected cells that express Mac-1 adhered to GP Ibα–coated wells. Inhibition studies with monoclonal antibodies or receptor ligands showed that the interaction involves the Mac-1 I domain (homologous to the vWf A1 domain), and the GP Ibα leucine-rich repeat and COOH-terminal flanking regions. The specificity of the interaction was confirmed by the finding that neutrophils from wild-type mice, but not from Mac-1–deficient mice, bound to purified GP Ibα and to adherent platelets, the latter adhesion being inhibited by pretreatment of the platelets with mocarhagin, a protease that specifically cleaves GP Ibα. Finally, immobilized GP Ibα supported the rolling and firm adhesion of THP-1 cells under conditions of flow. These observations provide a molecular target for disrupting leukocyte–platelet complexes that promote vascular inflammation in thrombosis, atherosclerosis, and angioplasty-related restenosis.