Selective inhibition of Panx1 channels decreases hemostasis and thrombosis in vivo.

Background: Hemostasis is a tightly regulated physiological process to rapidly induce hemostatic plugs at sites of vascular injury. Inappropriate activation of this process may lead to thrombosis, i.e. pathological blood clot formation in uninjured vessels or on atherosclerotic lesions. ATP release through Pannexin1 (Panx1) membrane channels contributes to collagen-induced platelet aggregation in vitro.

Objective: To investigate the effects of genetic and pharmacological inhibition of Panx1 on hemostasis and thrombosis in vivo.

Results: Bleeding time after tail clipping was increased by 2.5-fold in Panx1 mice compared to wild-type controls, suggesting that Panx1 deficiency impairs primary hemostasis. Wire myography on mesenteric arteries revealed diminished vasoconstriction in response to phenylephrine or U446619 in Panx1 mice. Mice with platelet-specific deletion of Panx1 (Panx1) displayed 2-fold longer tail bleeding times than Panx1 controls. Moreover, venous thromboembolism (VTE) after injection of collagen/epinephrine in the jugular vein was reduced in Panx1 and Panx1 mice. Panx1 mice also showed reduced FeCl-induced thrombosis in mesenteric arteries. BrilliantBlue-FCF, a Panx1 channel inhibitor, decreased collagen-induced platelet aggregation in vitro, increased tail bleeding time and reduced VTE in wild-type mice. Furthermore, we developed a specific Panx1 blocking antibody targeting a Panx1 extracellular loop, which reduced ATP release from platelets in vitro. Treating wild-type mice with this antibody increased tail bleeding time and decreased VTE compared to control antibody.

Conclusions: Panx1 channel deletion or inhibition diminishes clot formation during hemostasis and thrombosis in vivo. Blocking Panx1 channels may be an attractive strategy for modulating platelet aggregation in thrombotic disease.