Enzimas que hidrolisam nucleotídeos de adenina em plaquetas, agregação plaquetária e polimorfismo do gene α2 da integrina α2β1 em pacientes com a doença de von Willebrand

Abstract

Von Willebrand disease (vWD) is one of the most common inherited bleeding diseases, caused by a qualitative or quantitative deficiency of the von Willebrand factor (vWF). vWF is a multimeric glycoprotein synthesized by megakaryocytes and endothelial cells and it is present in the subendothelial matrix, blood plasma, platelets and endothelium. This glycoprotein represents an important role in thrombus formation by initiating platelet adhesion to sites of injury as well as platelet aggregation. The objective of this study was determine the activities of NTPDase (CD39), 5 -nucleotidase (EC 3.1.3.5, CD73) and Ectonucleotide Pyrophosphatase/Phosphodiesterase (E-NPP) enzymes in platelets patients from von Willebrand disease and healthy patients, as well as ristocetin-induced platelet aggregation (RIPA) and polymorphisms of the α2 gene of the α2β1 integrin. The following groups were studied: 14 patients diagnosed with vWD and 14 healthy patients for control group. For ristocetin-induced platelet aggregation was used a Platelet Rich Plasma (PRP) and Platelet Poor Plasma (PPP), using a final concentration of ristocetin in 1.25mg/mL. The polymorphisms of the α2 gene was analyzed through the Polymerase chain reaction (PCR), used for digestion of the PCR product of the Bgl II restriction site. NTPDase and E-NPP were decreased in platelets of patients with vWD compared to the group control. Moreover, the activity of the enzyme 5'- nucleotidase was not statistically significant. The results of the RIPA were significantly reduced in patients with vWD compared with the control. The allelic frequencies among vWD patients were found to be 78.57% for 807C and 21.43% for 807T. Our results indicate an decreased NTPDase and E-NPP activities in platelets, may be related to the low adhesiveness of platelets in patients with vWD. The allelic frequency 807C predominant suggests, in agreement with other studies, this polymorphism and factor characteristic of hemorrhagic manifestations in patients with DvW.