Inhibition of Hb Binding to GP1bα Abrogates Hb-Mediated Thrombus Formation on Immobilized VWF and Collagen under Physiological Shear Stress.
Reports including our own describe that intravascular hemolysis increases the risk of thrombosis in hemolytic disorders. Our recent study shows that plasma Hb concentrations correlate directly with platelet activation in patients with paroxysmal nocturnal hemoglobinuria (PNH). The binding of Hb to glycoprotein1bα (GP1bα) increases platelet activation. A peptide AA1-50, designed from N-terminal amino acid sequence of GP1bα significantly inhibits the Hb binding to GP1bα as well as Hb-induced platelet activation. This study further examined if the Hb-mediated platelet activation plays any significant role in thrombus formation on subendothelium matrix under physiological flow shear stresses and the inhibition of Hb-platelet interaction can abrogate the above effects of Hb.



Study performed thrombus formation assay in vitro by perfusing whole blood over immobilized VWF or collagen type I in presence of Hb under shear stresses simulating arterial or venous flow. The Hb concentrations ranging from 5 to 10 μM, commonly observed level in plasma of the hemolytic patients including PNH, dose-dependently increased thrombus formation on immobilized VWF under higher shear stress of 25 dyne/cm2, but not at 5 dyne/cm2. The above Hb concentrations also increased thrombus formation on immobilized collagen under both shear stresses of 5 and 25 dyne/cm2. The peptide AA1-50 abrogated invariably the above effects of Hb on thrombus formation.



This study therefore indicates that the Hb-induced platelet activation plays a crucial role in thrombus formation on immobilized VWF or collagen under physiological flow shear stresses. Thus suggesting a probable role of this mechanism in facilitating thrombosis under hemolytic conditions.
Disease Biology Laboratory, Regional Centre for Biotechnology, National Capital Region Biotech Science Cluster, Faridabad, India.|Biotechnology Department, Manipal University, Karnataka, India.
Gowtham K
GK
Annarapu
Disease Biology Laboratory, Regional Centre for Biotechnology, National Capital Region Biotech Science Cluster, Faridabad, India.|Biotechnology Department, Manipal University, Karnataka, India.
Rashi
R
Singhal
Cardiovascular Research Section, Department of Medicine, Baylor College of Medicine, Houston, Texas, United States of America.
Yuandong
Y
Peng
Disease Biology Laboratory, Regional Centre for Biotechnology, National Capital Region Biotech Science Cluster, Faridabad, India.
Prasenjit
P
Guchhait
D000595:Amino Acid Sequence; D024042:Collagen Type I / Q000378:metabolism*; D006454:Hemoglobins / Q000378:metabolism*; D006457:Hemoglobinuria, Paroxysmal / Q000097:blood / Q000378:metabolism; D006461:Hemolysis; D006801:Humans; D055767:Immobilized Proteins / Q000378:metabolism; D010455:Peptides / Q000378:metabolism / Q000494:pharmacology; D015539:Platelet Activation / Q000187:drug effects; D019038:Platelet Glycoprotein GPIb-IX Complex / Q000378:metabolism*; D011485:Protein Binding / Q000187:drug effects; D013314:Stress, Mechanical; D013927:Thrombosis / Q000378:metabolism* / Q000517:prevention & control; D014841:von Willebrand Factor / Q000378:metabolism*
D024042:Collagen Type I; D006454:Hemoglobins; D055767:Immobilized Proteins; D010455:Peptides; D019038:Platelet Glycoprotein GPIb-IX Complex; D014841:von Willebrand Factor