Introduction:
Chemotherapy-induced cardiotoxicity remains prevalent and deadly, with no effective therapy to slow the progression to irreversible heart failure, which in the case of doxorubicin (Dox) can reach 50% mortality. Dox impact on cardiomyocytes (CMs) is multifocal, including oxidative stress, lysosome alkalinization, and apoptosis. PLGAs, poly(DL-lactide-co-glycolide), are FDA-approved polymers, form defined nanoparticles (NPs). We hypothesize that PLGA NPs target the lysosomal compartments, restore lysosomal acidity after Dox, and confer cardioprotective effects.
Methods:
We synthesized fluorescent PLGA NPs by click chemistry. In H9C2 myocytes exposed to 1-5 μM of Dox +/- 1 mg/ml of PLGA, we measured cell viability (MTT), lysosomal pH (OG-514), mitochondrial membrane potential (JC-1), and autophagy proteins (western blot). We further co-injected C57Bl6 mice with PLGA (10 mg/kg, i.v.) and Dox (15 mg/kg, i.p.), to image apoptosis (Annexin) and autophagy (cathepsin-activatable autophagy probe, ADN, unpublished) after 24 hrs, or 4 mg/kg Dox weekly, 5x, i.p. and echo after 3-4 weeks.
Results:
PLGA NPs formulated are of controlled size and valency, emits near-infrared fluorescence (Fig. A). In H9C2s, PLGA significantly improved survival after Dox (Fig. B), acidified lysosomes (Fig. C), did not impact cell energetics (Fig. D), and further restored autophagic flux (Fig. E). Imaging in Dox mice revealed significant apoptosis reduction and autophagy activation (Fig. F-H), and cardiac function recovery (Fig. I).
Conclusions:
PLGA NPs may represent a novel class of cardioprotective therapeutics of early chemotherapy stress, and with translational potential.