Systemic inﬂammation can lead to coagulopathy and disseminated intravascular coagulation (DIC). In prior studies, the recombinant A2 domain of human von Willebrand factor (VWF; A2 protein) attenuated DIC and decreased mortality in lipopolysaccharide (LPS)-treated mice. Here, we performed studies to dissect the mechanism by which the A2 protein moderates DIC. We used confocal microscopy to analyze the ﬁbrin clot structure in plasma from healthy humans and endotoxemic mice, turbidity assays to examine ﬁbrin polymerization, and a murine model for LPS-induced DIC and introduced a loss-of-function mutation into the A2 protein for ﬁbrin. The mutation of the residue E1567 located in the a2 helix of the folded A2 domain of VWF inhibited binding activity for ﬁbrin, possibly mapping a novel region containing a putative binding site for ﬁbrin. The A2 protein increased the initial rate of change of ﬁbrin polymerization, intercalated into the ﬁbrin network, and modiﬁed the resultant clot structure in vitro. Furthermore, ex vivo experiments using plasma from mice with endotoxemia treated with the A2 protein revealed an increased rate of ﬁbrin formation and an altered clot structure as compared with plasma from nontreated sick animals. Moreover, and in contrast to the A2 mutant, the A2 protein improved survival and reduced ﬁbrin deposition and microvascular thrombosis in mice with endotoxemia-induced DIC. Importantly, in vivo and in vitro studies indicated that the A2 protein did not affect experimental thrombosis. Thus, we provide evidence for a novel treatment to attenuate systemic inﬂammation-induced coagulopathy/DIC via targeting ﬁbrin formation, without an increased risk for bleeding.
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