Abstract Body (Do not enter title and authors here): Introduction Chemotherapy-induced cardiotoxicity is a growing clinical challenge lacking effective FDA-approved interventions to delay the onset of heart failure. Lysosomal dysfunction is a hallmark of a myriad of cardiovascular diseases, including doxorubicin (Dox)-induced cardiotoxicity. We hypothesize that maintaining cardiomyocyte (CM) lysosomal pH can mitigate Dox-induced cardiac dysfunction and presents a viable cardioprotective strategy for translation.

Methods FDA-approved PLGA polymer composed of lactic and glycolic acids was chosen to modulate lysosomal pH due to biosafety and ease of chemical modifications. PLGA was covalently labeled with near-infrared fluorescent peptides to enhance cellular uptake and facilitate tracking in vivo. PLGA was formulated into nanoparticles of 100 nm and characterized by electron microscopy, NMR and absorbance spectroscopy. In H9C2 rat CMs co-treated with 5 μM of Dox +/- 1 mg/ml of PLGA, we measured PLGA uptake by FACS, cell viability by MTT, lysosomal pH by OG-514, and autophagy by western blot. PLGA’s impact on breast cancer cell viability was measured by MTT. In C57Bl/6 wildtype mice challenged with Dox (15 mg/kg, i.p.) +/- co-injection of PLGA (10 mg/kg, i.v.), myocardial PLGA uptake at 4 hours and apoptosis (by Annexin V) at 24 hours were assessed by direct imaging. Echocardiography to assess cardiac function was performed in a separate cohort of mice injected with weekly Dox (4 mg/kg, i.p.) +/- PLGA (10 mg/kg, i.v.). Moreover, PLGA biocompatibility was evaluated in 3 healthy beagle dogs by echocardiography and blood chemistry.

Results In Dox-treated murine CMs, PLGA significantly improved survival by restoring lysosomal acidity and autophagy, a key homeostatic process. No protective effect was observed with non-acidifying control polymer. PLGA also did not alter viability in human breast cancer cells (MCF7, MDA-MB-231) treated with Dox. When injected in mice, PLGA fully permeated the myocardium within 4 hours, significantly reduced Dox-induced apoptosis by 24 hours, and significantly improved cardiac function 4 weeks after Dox injection. In healthy canines, PLGA can be safely administered, supporting further clinical trials.

Conclusions PLGA represents a novel class of translatable cardioprotective therapeutic that acidifies lysosomes, restores autophagy, mitigates CM apoptosis, and enhances cardiac function. PLGA holds translational potential to mitigate lysosomal dysfunction and treat cardiovascular disease.