Platelets are critical to arterial thrombosis that underlies myocardial infarction and stroke. Activated platelets, regardless of nature of stimulus, initiate energy-intensive processes that sustain thrombus, while adapting to potential adversities of hypoxia and nutrient deprivation within the densely packed thrombus milieu. We report here that stimulated platelets switch their energy metabolism to aerobic glycolysis by modulating enzymes at key checkpoints in glucose metabolism. We found aerobic glycolysis to, in turn, accelerate flux through pentose phosphate pathway and support platelet activation. Hence, reversing metabolic adaptations of platelets could be an effective alternative to conventional anti-platelet approaches that are crippled by remarkable redundancy in platelet agonists and ensuing signaling pathways. Concurring with this proposition, small-molecule modulators of pyruvate dehydrogenase, pyruvate kinase M2 and glucose-6-phosphate dehydrogenase, all of which disfavor aerobic glycolysis and/or pentose phosphate pathway, restrained the agonist-induced platelet responses ex vivo. These drugs, which include the anti-neoplastic candidate - dichloroacetate, and FDA-approved dehydroepiandrosterone, profoundly impaired thrombosis in mice, thereby exhibiting potential as anti-thrombotic agents.

Fibrinolytic therapy for arterial or venous thrombotic disorders involves the systemic administration of thrombolytics such as streptokinase, which is associated with serious bleeding complications. With this study, we provide a proof-of-concept of photothermal thrombus ablation with gold nanorods exposed to near-infrared irradiation, both in vitro using materials generated from purified fibrinogen or plasma and in vivo in murine blood vessels. This is the first report of the application of photothermal therapy as an anti-thrombotic measure. Remarkably, the addition of streptokinase had a multimodal additive effect with regard to acceleration of photothermal lysis of thrombi even at a dose significantly below the therapeutic concentration, thus minimizing the life-threatening side effects and adverse complications. This combinatorial approach exhibits great promise for lysing pathological clots while effectively overcoming the drawbacks of existing therapies.

Oxygen-compromised environment like high altitude are associated with platelet hyperactivity. Platelets confined within the relatively impervious core of aggregate/thrombus have restricted access to oxygen, yet they continue to perform energy-intensive procoagulant activities that sustain thrombus. Therefore, studying platelet signaling under hypoxia is critical to our understanding of the mechanistic basis of thrombus stability. We report here that, hypoxia-inducible factor (HIF)-2α is translated from pre-existing mRNAs and stabilized against proteolytic degradation in enucleate platelets exposed to hypoxia. Hypoxic stress, too, stimulates platelets to synthesize plasminogen-activator inhibitor (PAI)-1 and shed extracellular vesicles, both of which potentially contribute to pro-thrombotic phenotype associated with hypoxia. Stabilization of HIF-α by administering hypoxia-mimetics into mice accelerates thrombus formation in mesenteric arterioles. In agreement, platelets from patients with chronic obstructive pulmonary disease and high altitude residents exhibiting thrombogenic attributes have abundant expression of HIF-2α and PAI-1. Thus, targeting platelet hypoxia signaling could be an effective anti-thrombotic strategy.

Oncotarget | https://doi.org/10.18632/oncotarget.27223 Jyotsna Kailashiya, Vineeta Gupta, Debabrata Dash