Apixaban decreases brain thrombin activity in a male mouse model of acute ischemic stroke

Abstract

Factor Xa (FXa) plays a critical role in the coagulation cascade by generation of thrombin. During focal ischemia thrombin levels increase in the brain tissue and cause neural damage. This study examined the hypothesis that administration of the FXa inhibitor, apixaban, following focal ischemic stroke may have therapeutic potential by decreasing brain thrombin activity and infarct volume. Male mice were divided into a treated groups that received different doses of apixaban (2, 20, 100 mg/kg administered I.P.) or saline (controls) immediately after blocking the middle cerebral artery (MCA). Thrombin activity was measured by a fluorescence assay on fresh coronal slices taken from the mice brains 24 hr following the MCA occlusion. Infarct volume was assessed using triphenyltetrazolium chloride staining. A high dose of apixaban (100 mg/kg) significantly decreased thrombin activity levels in the ipsilateral hemisphere compared to the control group (Slice#5, p = .016; Slice#6, p = .016; Slice#7, p = .016; Slice#8, p = .036; by the nonparametric Mann-Whitney test). In addition, treatment with apixaban doses of both 100 mg/kg (32 ± 8% vs. 76 ± 7% in the treatment vs. control groups respectively; p = .005 by the nonparametric Mann-Whitney test) and 20 mg/kg (43 ± 7% vs. 76 ± 7% in the treatment vs. control groups respectively; p = .019 by the nonparametric Mann-Whitney test) decreased infarct volumes in areas surrounding the ischemic core (Slices #3 and #8). No brain hemorrhages were observed either in the treated or control groups. In summary, I.P. administration of high dose of apixaban immediately after MCA occlusion decreases brain thrombin activity and reduces infarct size.

Increased brain plasmin levels following experimental ischemic stroke in male mice

“…Our study implies that after the first hours following ischemia, when we aim to increase plasmin concentration by thrombolysis to dissolve the blood clot, this should perhaps be followed by inhibition of brain plasmin as a therapeutic target. It is interesting to note that in a previous study, we have found that inhibiting factor Xa by apixaban lowers thrombin levels and infarct volume in the ischemic mouse brain (Bushi et al., 2018). A similar therapeutic strategy may be appropriate to differentially lowering plasmin levels in the ischemic brain.…”

“…Intraluminal PMCAo model with a monofilament suture was performed as previously reported by our group (Bushi et al, 2013(Bushi et al, , 2015(Bushi et al, , 2018. Anesthesia was performed with 2.5% isoflurane mixed in oxygen and delivered through a facemask.…”

Antiviral anticoagulation

“…Like all anticoagulants, apixaban must be considered as a risk to bleeding. In the current mouse antiviral experiments, apixaban was used at a dose that is similar to those previously reported (1.0 mg/kg) that facilitated anticoagulation in mice 163,164 and, like these studies, had no evidence of bleeding. While this is nearly twice the therapeutic dose in humans, it facilitated complete inhibition of virus infection, implying a much lower antiviral dose will also be efficacious but this remains untested.…”

Ischemic stroke in PAR1 KO mice: Decreased brain plasmin and thrombin activity along with decreased infarct volume

“…PMCAo model with a monofilament suture was performed as previously described [9,26,27]. Anesthesia was performed with 2.5% isoflurane mixed in oxygen and delivered through a facemask.…”