Glutathione Peroxidase-3 Deficiency Promotes Platelet-Dependent Thrombosis In Vivo

Abstract

Background Glutathione peroxidase-3 (GPx-3) is a selenocysteine-containing plasma protein that scavenges reactive oxygen species in the extracellular compartment. A deficiency of this enzyme has been associated with platelet-dependent thrombosis, and a promoter haplotype with reduced function has been associated with stroke risk in young individuals. Methods and Results We recently developed a genetic mouse model to assess platelet function in hemostasis and thrombosis in the setting of GPx-3 deficiency. GPx-3(−/−) mice showed an attenuated bleeding time compared with wild-type mice. Platelet aggregation studies revealed an enhanced aggregation response to the agonist ADP in GPx-3(−/−) compared to wild-type mice. We also found an increase in the plasma levels of soluble P-selectin and a decrease in plasma cyclic GMP in GPx-3(−/−) mice compared with wild-type mice. ADP was infused into the right ventricle of mice to induce platelet aggregation in the pulmonary vasculature, and produced a more robust platelet activation response in the GPx-3(−/−) mice than in wild-type mice; histological sections from the pulmonary vasculature of GPx-3(−/−) compared with wild-type mice show increased platelet-rich thrombi and a higher percentage of occluded vessels. Endothelial function studies using a cremaster muscle preparation revealed dysfunction in the GPx-3(−/−) compared to wild-type mice. Using a no-flow ischemia-reperfusion stroke model, GPx-3(−/−) mice had significantly larger cerebral infarctions compared with wild-type mice. To investigate the effect of platelet inhibition on stroke size in GPx-3 deficiency, we found that clopidogrel treatment reduced stroke size significantly in GPx-3(−/−) mice compared with vehicle-treated controls. To assess the neuroprotective role of antioxidants in this model, we found that MnTBAP treatment reduced stroke size in GPx-3(−/−) mice compared with vehicle-treated controls. Conclusions These findings demonstrate that GPx-3 deficiency results in a prothrombotic state and vascular dysfunction that promotes platelet-dependent arterial thrombosis. These data illustrate the importance of this plasma antioxidant enzyme in regulating platelet activity, endothelial function, platelet-dependent thrombosis, and vascular thrombotic propensity.

mTORC1 promotes aging-related venous thrombosis in mice via elevation of platelet volume and activation

“…43,44 Previous reports on the role of mTORC1 in thrombosis have focused on the consequence of rapalog use in patients receiving organ transplants or implantation of rapamycin-eluting stents on artery thrombosis, with conflicting results. For instance, hepatic artery thrombosis was observed shortly after liver transplantation in patients treated with rapamycin, and subacute coronary artery thrombosis induced after the implantation of rapamycin-eluting stents.…”

Redox Regulation of Mitochondrial Function

“…GPx-3 is a secreted glycoprotein, and its in vivo cofactor is a subject of debate. Deficiency of GPx-3 in humans or knockout mice potentiates platelet activation and thrombosis (139,193,212). Furthermore, in GPx-3 knockout mice, deficiency of this extracellular antioxidant causes endothelial dysfunction and increased sensitivity to neuronal injury in a brain model of ischemia reperfusion injury by mechanisms related to its key functions as an antioxidant enzyme and regulator of plateletdependent thrombosis (193 (166,216)].…”

Immediate Antioxidant and Antiplatelet Effect of Atorvastatin via Inhibition of Nox2

“…An experimental study in animals provided support for such interplay by showing that animals with knockout of glutathione peroxidase, an enzyme with antioxidant property, are prone to thrombosis via a mechanism involving platelet overactivation. 7 Agonist-stimulated platelets release reactive oxidant species, which are implicated in the propagation of platelet activation by inactivating nitric oxide, releasing platelet agonists such as ADP, or forming isoprostanes. 8,9 Isoprostanes are a family of eicosanoids that, unlike TxA 2 , are chemically stable and greatly contribute to propagate platelet aggregation via activation of the glycoprotein IIb/IIIa.…”