Thesis Title: Pharmacological senolysis as a new therapeutic approach for the prevention of doxorubicin-induced cardiotoxicity

Author: Araceli Lérida Viso

PhD. Supervisors: Ramón Martínez Máñez, Dra. Alba García Fernández

Summary:

The present PhD thesis focuses on exploring the elimination of senescent cells (senolysis) in vitro and in vivo by administration of the senolytic drug, navitoclax, as a therapeutic option to prevent cardiotoxicity associated with antitumor treatment doxorubicin. Doxorubicin exposure severely affects the cardiac cell population in both mouse and human hearts by inducing premature senescence and navitoclax is one of the most potent and widely known senolytics in the field of cellular senescence, but its administration is associated with the occurrence of adverse effects, mainly thrombocytopenia.

In the first experimental section, we addressed the induction of senescence in an in vitro cardiomyocyte model and evaluated senolytic therapy as a therapeutic strategy. We also developed and characterized the nanoparticles targeting senescent cells and the navitoclax-based prodrug. The senolytic nanodevice is based on MSNs loaded with navitoclax and functionalized with a hexa-galacto-oligosaccharide (galactan). The prodrug is obtained after conjugation of navitoclax to an acetylated galactose molecule. In both cases, the mechanism of targeted therapy lies in the presence of the lysosomal enzyme ß-galactosidase, which is highly expressed in senescent cells. Upon entering the lysosome of senescent cells, the glycosidic bonds are hydrolyzed by the action of the enzyme, releasing the drug. The results show an increase in the therapeutic effect of the free drug.

Next, we developed a murine model of cardiotoxicity in which we demonstrated that systemic administration of doxorubicin induces the expression of markers of cardiotoxicity and senescence in the heart of treated mice and contributes to the deterioration of the cardiac function of the animals followed by echocardiography. In this preclinical model, the combined treatment of doxorubicin with the senolytic navitoclax, in the different formulations described above, leads to significant decrease in senescence and cardiotoxicity markers along with restoration of cardiac function. Similar results were observed with the three strategies mentioned: free drug, encapsulated drug, and prodrug formulation.

The scientific results presented in this thesis highlight the role of senescence in the progression of cardiotoxicity by doxorubicin administration and it is concluded that the senolytic systems evaluated here could be an important tool for the development of new therapeutic strategies in the field of prevention of therapy-associated side effects and represent an alternative to the limitations of current treatments.