title: Decreased levels of von Willebrand factor-cleaving protease in coronary heart disease and thrombotic thrombocytopenic purpura: study of a simplified method for assaying the enzyme activity based on ristocetin-induced platelet aggregation.
abstract: The haemostatic activity of von Willebrand Factor (VWF) is dependent on VWF multimer stability. Fragments, arising from the proteolytic cleavage of the multimers by VWF-cleaving protease, are ineffective in initiating platelet aggregation. We designed a simple method to determine the protease activity, which was expressed as the reduction in the level of ristocetin-induced platelet aggregation between the inactive enzyme and the enzyme when activated by the addition of calcium. Samples from senior women (n = 14) with chronic coronary heart disease (CHD), age-matched control subjects (n = 15) and young healthy individuals (n = 13), as well as patients with either thrombotic thrombocytopenic purpura (TTP) (n = 2) or von Willebrand disease type 2A (VWD-2A) (n = 2), were examined. The lower protease activity observed in the CHD group, compared with the control subjects, indicated that the increased levels of VWF found in CHD relate to impaired enzyme function. The assessment of TTP patients reconfirmed the reduced protease activity previously observed in this disorder. In VWD-2A, normal enzyme function was observed, suggesting that there is an increased sensitivity of the mutated VWF protein to the protease, rather than an increase in the activity or quantity of the enzyme involved in pathogenesis. In summary, the present simplified method efficiently determines VWF protease activity and is suitable for use in laboratories where platelet aggregation analyses can be performed.
authors.affiliation: Coagulation Research, Department of Surgical Sciences, Karolinska Institutet, S-17176 Stockholm, Sweden.
authors.forename: Gina
authors.initials: G
authors.lastname: Yoo
authors.forename: Margareta
authors.initials: M
authors.lastname: Blombäck
authors.forename: Karin
authors.initials: K
authors.lastname: Schenck-Gustafsson
authors.forename: Shu
authors.initials: S
authors.lastname: He
mesh_terms: D051722:ADAM Proteins; D000071120:ADAMTS13 Protein; D000293:Adolescent; D000328:Adult; D000368:Aged; D000900:Anti-Bacterial Agents / Q000494:pharmacology; D016022:Case-Control Studies; D003327:Coronary Disease / Q000097:blood*; D004789:Enzyme Activation; D005260:Female; D006801:Humans; D008666:Metalloendopeptidases / Q000097:blood*; D008875:Middle Aged; D010974:Platelet Aggregation; D011697:Purpura, Thrombotic Thrombocytopenic / Q000097:blood*; D012310:Ristocetin / Q000494:pharmacology; D018709:Statistics, Nonparametric; D014841:von Willebrand Factor / Q000032:analysis / Q000378:metabolism
chemical_list: D000900:Anti-Bacterial Agents; D014841:von Willebrand Factor; D012310:Ristocetin; D051722:ADAM Proteins; D008666:Metalloendopeptidases; D000071120:ADAMTS13 Protein; C099604:ADAMTS13 protein, human