title: Free hemoglobin increases von Willebrand factor-mediated platelet adhesion in vitro: implications for circulatory devices.
abstract: Intravascular hemolysis occurs in patients on extracorporeal membrane oxygenation. High levels of free acellular adult hemoglobin (free HbA) are associated with clotting in this mechanical device that can result in thrombotic complications. Adsorption of fibrinogen onto the surface of biomaterial correlates with platelet adhesion, which is mediated by von Willebrand factor (VWF). Because free Hb interacts with VWF, we studied the effect of hemoglobin (Hb) on platelet adhesion to fibrin(ogen) under conditions of different hydrodynamic forces. This effect was investigated using purified human HbA and fibrinogen, extracellular matrix, collagen, or purified plasma VWF as surface-coated substrates to examine flow-dependent platelet adhesion. Antibodies and VWF-deficient plasma were also used. Free Hb (≥50 mg/dL) effectively augmented platelet adhesion, and microthrombi formation on fibrin(ogen), extracellular matrix, and collagen at high shear stress. The effect of free Hb was effectively blocked by anti-glycoprotein Ibα (GPIbα) antibodies or depletion of VWF. Unexpectedly, free Hb also promoted firm platelet adhesion and stable microthrombi on VWF. Lastly, we determined that Hb interacts directly with the A1 domain. This study is the first to demonstrate that extracellular Hb directly affects the GPIbα-VWF interaction in thrombosis, and describes another mechanism by which hemolysis is connected to thrombotic events.
authors: Section of Cardiovascular Research and Department of Medicine, Baylor College of Medicine, Houston, TX; Center for Translational Research on Inflammatory Diseases, Michael E. DeBakey VA Medical Center, Houston, TX;
authors: Qi
authors: Q
authors: Da
authors: Department of Medicine, Baylor College of Medicine, Houston, TX;
authors: Miho
authors: M
authors: Teruya
authors: Disease Biology Laboratory, Regional Centre for Biotechnology, Gurgaon, India;
authors: Prasenjit
authors: P
authors: Guchhait
authors: Section of Cardiovascular Research and Department of Medicine, Baylor College of Medicine, Houston, TX; Departments of Pathology & Immunology and Pediatrics, Baylor College of Medicine, Houston, TX; and.
authors: Jun
authors: J
authors: Teruya
authors: Department of BioSciences, Rice University, Houston, TX.
authors: John S
authors: JS
authors: Olson
authors: Section of Cardiovascular Research and Department of Medicine, Baylor College of Medicine, Houston, TX; Center for Translational Research on Inflammatory Diseases, Michael E. DeBakey VA Medical Center, Houston, TX;
authors: Miguel A
authors: MA
authors: Cruz
mesh_terms: D000906:Antibodies / Q000737:chemistry; D001792:Blood Platelets / Q000737:chemistry / Q000378:metabolism* / Q000473:pathology; D006439:Hemodynamics; D006454:Hemoglobins / Q000737:chemistry / Q000378:metabolism*; D006801:Humans; D039421:Integrin alpha2 / Q000737:chemistry / Q000378:metabolism; D010973:Platelet Adhesiveness; D017434:Protein Structure, Tertiary; D013927:Thrombosis / Q000378:metabolism* / Q000473:pathology; D014841:von Willebrand Factor / Q000737:chemistry / Q000378:metabolism*
chemical_list: D000906:Antibodies; D006454:Hemoglobins; D039421:Integrin alpha2; D014841:von Willebrand Factor