The development of inflammatory joint disease is attenuated in mice expressing the anticoagulant prothrombin mutant W215A/E217A

Abstract

Thrombin is a positive mediator of thrombus formation through the proteolytic activation of protease-activated receptors (PARs), fibrinogen, factor XI (fXI), and other substrates, and a negative regulator through activation of protein C, a natural anticoagulant with anti-inflammatory/ cytoprotective properties. Proteaseengineering studies have established that 2 active-site substitutions, W215A and E217A (fIIWE), result in dramatically reduced catalytic efficiency with procoagulant substrates while largely preserving thrombomodulin (TM)-dependent protein C activation. To explore the hypothesis that a prothrombin variant favoring antithrombotic pathways would be compatible with development but limit inflammatory processes in vivo, we generated mice carrying the fIIWE mutations within the endogenous prothrombin gene. Unlike fIInull embryos, fIIWE/WE mice uniformly developed to term. Nevertheless, these mice ultimately succumbed to spontaneous bleeding events shortly after birth. Heterozygous fII WT/WE mice were viable and fertile despite a shift toward an antithrombotic phenotype exemplified by prolonged tail-bleeding times and times-toocclusion after FeCl3 vessel injury. More interestingly, prothrombinWE expression significantly ameliorated the development of inflammatory joint disease in mice challenged with collagen-induced arthritis (CIA). The administration of active recombinant thrombinWE also suppressed the development of CIA in wildtype mice. These studies provide a proofof-principle that pro/thrombin variants engineered with altered substrate specificity may offer therapeutic opportunities for limiting inflammatory disease processes. © 2011 by The American Society of Hematology.