title: A novel nucleotide-based thrombin inhibitor inhibits clot-bound thrombin and reduces arterial platelet thrombus formation.
abstract: A novel thrombin inhibitor based on single-stranded (ss) deoxynucleotides with the sequence GGTTGGTGTGGTTGG (thrombin aptamer) has been recently discovered. In this study, we tested its efficacy in inhibiting clot-bound thrombin activity and platelet thrombus formation in an ex vivo whole artery angioplasty model. The thrombin aptamer showed a specific dose-dependent inhibition of thrombin-induced platelet aggregation (0.5 U/mL) in human platelet-rich plasma, with an IC50 of approximately 70 to 80 nmol/L. In an in vitro clot-bound thrombin assay system, heparin, used at clinically relevant concentrations of 0.2 U/mL and 0.4 U/mL, was ineffective in inhibiting clot-bound thrombin (6.5% and 34.9% inhibition at 0.2 U/mL and 0.4 U/mL, respectively). In contrast, the thrombin aptamer at an equivalent anticoagulant concentration inhibited clot-bound thrombin (79.7% inhibition). In an ex vivo whole artery angioplasty model, the thrombin aptamer markedly suppressed the generation of fibrinopeptide A (FPA), whereas heparin at 2 U/mL was ineffective. Compared with a scrambled ssDNA control, the thrombin aptamer reduced platelet deposition by 34.5% +/- 5% (mean +/- SEM, n = 4, P = .09) at low shear rates (approximately 200 s-1) and 61.3% +/- 11% (mean +/- SEM, n = 4, P = .05) at high shear rates (approximately 850 s-1). Thrombin aptamers based on ssDNA molecules represent a new class of thrombin inhibitors with potent anticoagulant and antithrombotic properties.
authors.affiliation: Division of Hematology, Stanford University School of Medicine, CA.
authors.forename: W X
authors.initials: WX
authors.lastname: Li
authors.forename: A V
authors.initials: AV
authors.lastname: Kaplan
authors.forename: G W
authors.initials: GW
authors.lastname: Grant
authors.forename: J J
authors.initials: JJ
authors.lastname: Toole
authors.forename: L L
authors.initials: LL
authors.lastname: Leung
mesh_terms: D017130:Angioplasty; D000925:Anticoagulants / Q000494:pharmacology*; D052157:Aptamers, Nucleotide; D001483:Base Sequence; D004305:Dose-Response Relationship, Drug; D005344:Fibrinopeptide A / Q000096:biosynthesis; D006801:Humans; D008969:Molecular Sequence Data; D009841:Oligonucleotides; D010974:Platelet Aggregation / Q000187:drug effects; D010975:Platelet Aggregation Inhibitors / Q000494:pharmacology; D011119:Polynucleotides / Q000494:pharmacology*; D013917:Thrombin / Q000037:antagonists & inhibitors*; D013927:Thrombosis / Q000517:prevention & control*
chemical_list: D000925:Anticoagulants; D052157:Aptamers, Nucleotide; D009841:Oligonucleotides; D010975:Platelet Aggregation Inhibitors; D011119:Polynucleotides; C081676:thrombin aptamer; D005344:Fibrinopeptide A; D013917:Thrombin