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V
3 antagonists inhibit sickle red cell adhesion to vascular endothelium and vasoocclusionDepartment of Chemical Engineering, Northeastern University, Boston, Massachusetts; Division of Hematology, Albert Einstein College of Medicine, Bronx, New York; and Merck, Darmstadt, Germany
Submitted 26 September 2006 ; accepted in final form 30 April 2007
Abnormal adhesion of sickle red blood cells (SS RBCs) to vascular endothelium may play an important role in vasoocclusion in sickle cell disease. Accruing evidence shows that endothelial
V
3-integrin has an important role in SS RBC adhesion because of its ability to bind several adhesive proteins implicated in this interaction. In the present studies, we tested therapeutic efficacy of small-molecule cyclic pentapeptides for their ability to block
V
3-mediated SS RBC adhesion by using two well-established assay systems, i.e., cultured human umbilical vein endothelial cells (HUVEC) and artificially perfused mesocecum vasculature of the rat under flow conditions. We tested the efficacy of two RGD-containing cyclic pentapeptides, i.e., cRGDFV (EMD 66203) and cRGDF-ACHA (
-amino cyclohexyl carboxylic acid) (EMD 270179), based on their known ability to bind
V
3. An inactive peptide, EMD 135981 (cR
-ADFV) was used as control. Cyclization and the introduction of D-Phe (F) results in a marked increase in the ability of cyclic peptides to selectively bind
V
3 receptors. In the mesocecum vasculature, both EMD 66203 and EMD 270179 ameliorated platelet-activating factor-induced enhanced SS RBC adhesion, postcapillary blockage, and significantly improved hemodynamic behavior. Infusion of a fluorescent derivative of EMD 66203 resulted in colocalization of the antagonist with vascular endothelium. Also, pretreatment of HUVEC with either
V
3 antagonist resulted in a significant decrease in SS RBC adhesion. Because of their metabolic stability, the use of these cyclic
V
3 antagonists may constitute a novel therapeutic strategy to block SS RBC adhesion and associated vasoocclusion under flow conditions.
sickle cell disease;
V
3-integrin; peripheral resistance unit; sickle erythrocytes
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