Selective inhibition of the platelet phosphoinositide 3-kinase p110β as promising new strategy for platelet protection during extracorporeal circulation

Summary

Extracorporeal circulation (ECC) is used in cardiac surgery for cardiopulmonary bypass as well as in ventricular assist devices and for extracorporeal membrane oxygenation. Blood contact with the artificial surface and shear stress of ECC activates platelets and leukocytes resulting in a coagulopathy and proinflammatory events. Blockers of the platelet glycoprotein (GP) IIb/IIIa (CD41/CD61) can protect platelet function during ECC, a phenomenon called “platelet anaesthesia”, but may be involved in post-ECC bleeding. We hypothesized that the new selective phosphoinositide 3-kinase p110β inhibitor TGX-221 that inhibits shear-induced platelet activation without prolonging the bleeding time in vivo may also protect platelet function during ECC. Heparinized blood of healthy volunteers (n=6) was treated in vitro with either the GP IIb/IIIa blocker tirofiban, TGX-221 or as control and circulated in an ECC moand after 30 minutes circulation CD41 expression on the ECCtubing as measure for platelet-ECC binding and generation of the platelet activation marker β-thromboglobulin were determined using ELISA. Platelet aggregation and platelet-granulocyte binding were analysed in flow cytometry. After log-transforming the data statistical evaluation was performed using multifactor ANOVA in combination with Tukey’s HSD test (global alpha = 5%).Tirofiban and TGX-221 inhibited platelet-ECC interaction, platelet aggregation and platelet-granulocyte binding. Tirofiban also inhibited ECC-induced β-thromboglobulin release.The observed inhibition of platelet-ECC interaction and platelet activation by tirofiban contributes to explain the mechanism of“platelet anaesthesia”.TGX-221 represents a promising alternative to GP IIb/IIIa blockade and should be further investigated for use during ECC in vivo.

Keywords

GP IIb/IIIa - platelet pharmacology - surgery

• References

• 1 Kouchoukos NT, Karp RB, Blackstone EH. et al. Kirklin/Barratt-Boyes Cardiac surgery. 3rd edition. USA: Elsevier Science; 2003
• 2 Paparella D, Brister SJ, Buchanan MR. Coagulation disorders of cardiopulmonary bypass: a review. Intensive Care Med 2004; 30: 1873-1881.
• 3 Weerasinghe A, Taylor KM. The platelet in cardiopulmonary bypass. Ann Thorac Surg 1998; 66: 2145-2152.
• 4 Chang AC, McKenzie ED. Mechanical cardiopulmonary support in children and young adults: extracorporeal membrane oxygenation, ventricular assist devices, and long-term support devices. Pediatr Cardiol 2005; 26: 2-28.
• 5 King BO, Whittow ES, Serna DL. et al. Tirofiban administration attenuates platelet and platelet-neutrophil conjugation but not neutrophil degranulation during in vitro VAD circulation. Asaio J 2001; 47: 282-287.
• 6 Straub A, Wendel HP, Azevedo R. et al. The GP IIb/ IIIa inhibitor abciximab (ReoPro) decreases activation and interaction of platelets and leukocytes during in vitro cardiopulmonary bypass simulation. Eur J Cardiothorac Surg 2005; 27: 617-621.
• 7 Straub A, Azevedo R, Beierlein W. et al. Tirofiban (Aggrastat) protects platelets and decreases plateletgranulocyte binding in an extracorporeal circulation model. Thorac Cardiovasc Surg 2006; 54: 162-167.
• 8 Hiramatsu Y, Gikakis N, Anderson HL. 3rd et al. Tirofiban provides “platelet anesthesia” during cardiopulmonary bypass in baboons. J Thorac Cardiovasc Surg 1997; 113: 182-193.
• 9 Harder S, Klinkhardt U, Alvarez JM. Avoidance of bleeding during surgery in patients receiving anticoagulant and/or antiplatelet therapy: pharmacokinetic and pharmacodynamic considerations. Clin Pharmacokinet 2004; 43: 963-981.
• 10 Jackson SP, Schoenwaelder SM, Goncalves I. et al. PI 3-kinase p110beta: a new target for antithrombotic therapy. Nat Med 2005; 11: 507-514.
• 11 Schoenwaelder SM, Ono A, Sturgeon S. et al. Identification of a unique co-operative phosphoinositide 3-kinase signaling mechanism regulating integrin alpha IIb beta 3 adhesive function in platelets. J Biol Chem 2007; 282: 28648-28658.
• 12 Schneider DJ, Herrmann HC, Lakkis N. et al. Increased concentrations of tirofiban in blood and their correlation with inhibition of platelet aggregation after greater bolus doses of tirofiban. Am J Cardiol 2003; 91: 334-336.
• 13 Weber N, Wendel HP, Ziemer G. Hemocompatibility of heparin-coated surfaces and the role of selective plasma protein adsorption. Biomaterials 2002; 23: 429-439.
• 14 Straub A, Azevedo R, Beierlein W. et al. Glycoprotein IIb/IIIa inhibition reduces prothrombotic events under conditions of deep hypothermic circulatory arrest. Thromb Haemost 2005; 94: 115-122.
• 15 Doenicke A, Roizen MF, Hoernecke R. et al. Haemolysis after etomidate: comparison of propylene glycol and lipid formulations. Br J Anaesth 1997; 79: 386-388.
• 16 Addonizio VP, Colman RW. Platelets and extracorporeal circulation. Biomaterials 1982; 3: 9-15.
• 17 Goto S, Salomon DR, Ikeda Y. et al. Characterization of the unique mechanism mediating the shear-dependent binding of soluble von Willebrand factor to platelets. J Biol Chem 1995; 270: 23352-23361.
• 18 Naimushin YA, Mazurov AV. Von Willebrand factor can support platelet aggregation via interaction with activated GPIIb-IIIa and GPIb. Platelets 2004; 15: 419-425.
• 19 Pontiggia L, Steiner B, Ulrichts H. et al. Platelet microparticle formation and thrombin generation under high shear are effectively suppressed by a monoclonal antibody against GPIba. Thromb Haemost 2006; 96: 774-780.
• 20 Bizzarri F, Scolletta S, Tucci E. et al. Perioperative use of tirofiban hydrochloride (Aggrastat) does not increase surgical bleeding after emergency or urgent coronary artery bypass grafting. J Thorac Cardiovasc Surg 2001; 122: 1181-1185.
• 21 Dyke CM, Bhatia D, Lorenz TJ. et al. Immediate coronary artery bypass surgery after platelet inhibition with eptifibatide: results from PURSUIT. Platelet Glycoprotein IIb/IIIa in Unstable Angina: Receptor Suppression Using Integrelin Therapy. Ann Thorac Surg 2000; 70: 866-872.
• 22 Genoni M, Zeller D, Bertel O. et al. Tirofiban therapy does not increase the risk of hemorrhage after emergency coronary surgery. J Thorac Cardiovasc Surg 2001; 122: 630-632.
• 23 Yeo EL, Sheppard JA, Feuerstein IA. Role of P-selectin and leukocyte activation in polymorphonuclear cell adhesion to surface adherent activated platelets under physiologic shear conditions (an injury vessel wall model). Blood 1994; 83: 2498-2507.
• 24 Gawaz M, Langer H, May AE. Platelets in inflammation and atherogenesis. J Clin Invest 2005; 115: 3378-3384.
• 25 Rinder CS, Bonan JL, Rinder HM. et al. Cardiopulmonary bypass induces leukocyte-platelet adhesion. Blood 1992; 79: 1201-1205.
• 26 Wilhelm CR, Ristich J, Kormos RL. et al. Monocyte tissue factor expression and ongoing complement generation in ventricular assist device patients. Ann Thorac Surg 1998; 65: 1071-1076.
• 27 Redlich H, Vickers J, Lösche W. et al. Formation of platelet-leukocyte conjugates in whole blood. Platelets 1997; 8: 419-426.