Evaluation of DNA aptamers directed to thrombin as potential thrombus imaging agents.

Abstract

Two DNA aptamers directed against two separate exosites on human alpha-thrombin were evaluated for thrombus-imaging potential. Aptamer ODN 1 is directed to the thrombin substrate binding site (exosite 1). Our finding that ODN 1 competes with fibrin for binding to exosite 1 on thrombin suggests that ODN 1 will not be useful for thrombus imaging. Aptamer ODN 2 is directed against the thrombin heparin binding site (exosite 2). ODN 2 bound to model thrombi that were formed either by clotting purified fibrinogen with thrombin, or by recalcifying citrated plasma. As the thrombin content of thrombi was increased the rate of ODN 2 uptake into preformed thrombi increased, whereas the rate of release of ODN 2 out of preformed thrombi decreased. This in vitro data suggested that ODN 2 might be useful for thrombus imaging because it can bind to exosite 2 on fibrin-bound thrombin. However, in a rabbit jugular vein model using thrombus supplemented with human thrombin, ODN 2 uptake was equal to the ovalbumin control, and did not reflect thrombin content. While the in vitro results with ODN 2 were consistent with thrombus imaging, the rapid clearance of ODN 2 from circulation, combined with slow mass transfer in the clot, seem to work against in vivo thrombin-dependent imaging or washout analysis.

• Authors: Hayes Dougan, Jeffrey I Weitz, Alan R Stafford, Kris D Gillespie, Petr Klement, John B Hobbs, Donald M Lyster
• Journal: Nuclear medicine and biology (Nucl Med Biol) Vol. 30 Issue 1 Pg. 61-72 (Jan 2003) ISSN: 0969-8051 [Print] United States
• PMID: 12493544 (Publication Type: Comparative Study, Evaluation Study, Journal Article, Research Support, Non-U.S. Gov't)
• Copyright: Copyright 2003 Elsevier Science Inc.

Chemical References

• Anticoagulants
• Iodine Radioisotopes
• Ligands
• Oligonucleotides
• Radiopharmaceuticals
• Fibrinogen
• DNA
• Serine Endopeptidases
• atroxin
• Thrombin

Topics

• Animals
• Anticoagulants (blood, pharmacokinetics)
• Base Sequence
• Binding Sites (genetics)
• DNA (blood, pharmacokinetics)
• Endothelium, Vascular (diagnostic imaging, injuries, metabolism)
• Female
• Fibrinogen (metabolism)
• Fluoroscopy (methods)
• Humans
• Iodine Radioisotopes (blood, pharmacokinetics)
• Isotope Labeling (methods)
• Jugular Veins (diagnostic imaging, metabolism)
• Ligands
• Molecular Sequence Data
• Oligonucleotides (blood, classification, pharmacokinetics)
• Plasma (diagnostic imaging, metabolism)
• Protein Binding
• Rabbits
• Radionuclide Imaging
• Radiopharmaceuticals (blood, pharmacokinetics)
• Serine Endopeptidases (pharmacology)
• Thrombin (metabolism)
• Thrombosis (diagnostic imaging, metabolism)