[Screening and analysis of coagulation factor VIII inhibitor in patients with hemophilia A].

In order to detect coagulation factor VIII (FVIII) inhibitor in patients with severe hemophilia A (HA) and preliminarily study the genetic mutation in patients with inhibitor positive. Totally 58 patients with HA (FVIII: C < 1%) were enrolled. FVIII: C activity was measured by one-stage coagulation assay. FVIII inhibitor was screened by using APTT method and FVIII inhibitor in screened positive patients with HA was quantitatively analyzed by using Bethesda method. Using genomic DNA as template, 12, 14, 16 exons of FVIII in screened positive patients were amplified, and the mutations of amplified products were detected by direct sequencing. The results indicated that the FVIII inhibitor could be detected in 4 patients (6.9%) from 58 HA patients, no gene mutations in 12, 14, 16 exons of FVIII were found. It is concluded that the positive rate of FVIII inhibitor in HA patients is lower than that reported in literature. The causes of inhibitor production needs to further investigate.

A novel anticoagulant purified from fish protein hydrolysate inhibits factor XIIa and platelet aggregation.

A novel fish protein having anticoagulant and antiplatelet properties was enzymatically extracted from the marine fish, yellowfin sole (Limanda aspera) and purified to homogeneity producing an overall purification fold of 206.6. MALDI-TOF mass spectroscopic and SDS-PAGE analysis identified the purified protein as 12.01 kDa single-chain monomeric protein. It inhibited the activated coagulation factor XII (FXIIa) by forming an inactive complex regardless of Zn2+ mediation, and was named, yellowfin sole anticoagulant protein (YAP). In addition, YAP act to antagonize platelet membrane glycoprotein integrin, to arrest platelet aggregation. However, YAP was not able to block the adhesion of platelets to collagen, which mediate via major collagen receptors, GPIa/IIa on platelet membrane. Furthermore, YAP did not possess plasminogen activator-like activity to activate fibrinolysis. In fact, our findings indicate that YAP binds with FXIIa and platelet membrane integrins to inhibit thrombosis in vitro.

Discovery and pre-clinical development of antithrombotics from hematophagous invertebrates.

Bloodfeeding (hematophagous) parasites have evolved effective means of inhibiting mammalian thrombosis, thereby facilitating the acquisition and digestion of a bloodmeal. To date, specific inhibitors of coagulation and platelet function have been identified from numerous invertebrate species, representing an impressive array of convergent functional strategies. These parasite antithrombotics, in addition to playing a critical role in the diseases caused or transmitted by bloodfeeding invertebrates, may also serve as potentially useful therapeutic agents for the treatment of a variety of conditions associated with activation of thrombosis. A number of naturally occurring anticoagulants and platelet inhibitors have been evaluated in vivo, with some currently in varying stages of preclinical and clinical development. Because of the unique specificity and potency of parasite antithrombotics, these invertebrate natural products hold great promise for improving the treatment of a variety of human illnesses, including heart disease, stroke, and cancer.

Disruption of protein-membrane binding and identification of small-molecule inhibitors of coagulation factor VIII.

Factor VIII is a critical member of the blood coagulation cascade. It binds to the membrane surfaces of activated platelets at the site of vascular injury via a highly specific interaction between factor VIII's carboxy-terminal C2 domain and their phosphatidylserine-rich lipid bilayer. We have identified small-molecule inhibitors of factor VIII's membrane binding activity that have IC50 values as low as 2.5 microM. This interaction is approximately 10(3)-fold tighter than that of free o-phospho-L-serine. These compounds also inhibit factor VIII-dependent activation of factor X, indicating that disruption of membrane lipid binding leads to inhibition of the intrinsic coagulation pathway. The tightest binding inhibitor is specific and does not prevent membrane binding by the closely related coagulation factor V. These results indicate that this and related compounds may be used as leads to develop novel antithrombotic agents.