Factor VII activating protease (FSAP) inhibits the outcome of ischemic stroke in mouse models

Factor VII activating protease (FSAP) is a circulating serine protease, and individuals with the Marburg I (MI) single nucleotide polymorphism (SNP), which results in an inactive enzyme, have an increased risk of stroke. The outcome of ischemic stroke is more marked in FSAP-deficient mice compared to their wild-type (WT) counterparts. Plasma FSAP levels are raised in patients as well as mice after stroke. In vitro , FSAP promotes fibrinolysis by cleavage of fibrinogen, activates protease-activated receptors and decreases the cellular cytotoxicity of histones. Since these are desirable properties in stroke treatment, we tested the effect of recombinant serine protease domain of FSAP (FSAP-SPD) on ischemic stroke in mice. A combination of tissue plasminogen activator (tPA) and FSAP-SPD enhanced clot lysis, improved microvascular perfusion and neurological outcome and reduced infarct volumes in a mouse model of thromboembolic stroke. In the tail bleeding model FSAP-SPD treatment provoked a faster clotting time indicating that it has a pro-coagulant effect that is described before. FSAP-SPD improved stroke outcome and diminished the negative effects of co-treatment with tPA in the transient middle cerebral artery occlusion model. The inactive MI-isoform of FSAP did not have any effects in either model. In mice with FSAP deficiency there were minor differences in the outcomes of stroke but the treatment with FSAP-SPD was equally effective. Thus, FSAP represents a promising novel therapeutic strategy in the treatment of ischemic stroke that requires further evaluation.