Attenuation of hypothermia-induced platelet activation and platelet adhesion to artificial surfaces in vitro by modification of hemoglobin to carry S-nitric oxide and polyethylene glycol

Hypothermic cardiopulmonary bypass alters platelet function and hypothermia is associated with postoperative myocardial ischemia, Thrombogenic surface s such as extracorporeal circuits, vascular graft materials, and components of atherosclerotic plaque induce activation of platelets. The effects of h uman hemoglobin (Hb) covalently modified to carry S-nitric oxide (NO) funct ional groups (SNO-Hb), polyethylene glycol (PEC-Hb), and SNO-PEG-Hb on plat elet activation were studied. Platelet activation was assessed by cytometri c analysis of GPIIb-IIIa activation and P-selectin expression;It hypothermi c condition (22 degreesC) after stimulation with Hb derivatives. Platelet a dhesion and aggregation were measured in a parallel glass plate chamber coa ted with unmodified Hb, SNO-Hb, PEC-Hb, SNO-PEG-Hb, and collagen. Platelet binding of antibodies to GPIIb-IIIa and P-selectin was significantly enhanc ed by hypothermic condition and by unmodified Hb. There was significantly l ess platelet binding of antibodies to GPIIb-IIIa and P-selectin with SNO-Hb , PEG-Hb, and SNO-PEG-Hb compared with unmodified Hb. There was significant ly less platelet attachment, adhesion, and aggregation on the SNO-Hb, PEG-H b and SNO-PEG-Hb coated surfaces compared with unmodified Hb-coated and -un coated surfaces. SNO-Hb, PEG-Hb, and SNO-PEG-Hb induced less platelet activ ation at hypothermic temperature, and induced less platelet adhesion and ag gregation on thrombogenic surfaces compared with unmodified Hb. The inhibit ory effect may be derived from antiadhesive properties of Hb, antiplatelet actions of NO, and molecular barrier action of PEG. (C) 2000 Elsevier Scien ce Ltd. All rights reserved.