STROKE THROMBOLYSIS WITH r-tPA IMPROVED BY CERIUM OXIDE NANOPARTICLES – STRIC-ON

Ischemic stroke results from the thrombotic obstruction of cervical or cerebral arteries leading to cerebral infarction with neurological dysfunction, and represents the second cause of mortality and the first cause of acquired disability in France and Europe. The primary goal of stroke treatment is therefore the on-time restoration of blood flow in the occluded artery. Currently, r-tPA (recombinant tissue plasminogen activator), a thrombolytic agent, is been used for this purpose. However, age-related contraindications or delay to instore the treatment has limited its use to less than 15% of patients. Furthermore, early arterial recanalization with good outcome and reduced mortality in these patients is obtained in only one-third of treated cases. The mechanism of this resistance to thrombolysis by r-tPA remains unknown. A special attention was recently given to the presence of DNA fibers or NETs (neutrophil extracellular traps) entangled with the mesh of fibrin in the clot. Since DNA fibers are resistant to the effect of plasmin their presence in the clot may explain the failure of r-tPA to lyse thrombi. In this project, we aim to evaluate the impact of DNase I, a specific nucleolytic enzyme, on thrombus lysis as adjuvant of r-tPA treatment. Our hypothesis is that concomitant treatment with r-tPA and DNase I specifically targeted to the thrombus will contribute to an efficient and safe thrombolytic strategy to improve stroke outcome. The simultaneous hydrolysis of both DNA and its core proteins by combined proteolytic and nucleolytic activity of serum DNase I and plasmin locally generated seems necessary to disintegrate NETs.
The main objective of our project is to use nanoparticulate carrier-based systems that convey active DNase I and preferentially accumulate on the clot by being equipped with ligands that target the clot fibrin. To tailor new all-in-one nanovectors fulfilling these characteristics, we propose the use of cerium oxide nanoparticles (CeO2 or nanoceria) coated with DNase I. Cerium oxide nanocrystals are non-stoichiometric particles with tri- and tetravalent cations Ce3+ and Ce4+ at their surface. The coexistence of two oxidation states confers to these particles remarkable catalytic properties, their activity being similar to that of catalase, superoxide dismutase or peroxidase enzymes. Catalytic processes involving sub-10 nm nanoceria were shown to lead to the decomposition of reactive oxygen species. In upstream research, nanoceria has been used as a therapeutic agent in the treatment of oxidative stress associated with diseases in animal models including cardiomyopathy, sepsis, multiple sclerosis. Oxidative stress that occurs after a stroke is a well-known and major contributor to neuronal but also vascular lesions, which in turn lead to cerebral hemorrhages particularly deleterious for the patients. Moreover, recanalization after stroke, through oxygen transported by the blood may aggravate oxidative stress. Cerium oxide nanoparticles with their antioxidant capacities may thus protect vessels during recanalization and prevents cerebral hemorrhages. Our approach complements classical r-tPA fibrinolysis by focusing on NETs and oxidative stress using bifunctional cerium oxyde nanoparticles bearing DNase I activity.