SS-31

Doxorubicin (DOX) is a widely used anticancer drug associated with severe cardiotoxicity primarily driven by mitochondrial dysfunction and reactive oxygen species (ROS) production. Hydrogen peroxide (H2O2), a major mitochondrial ROS, significantly contributes to cardiotoxicity, yet its precise mechanistic role in DOX-induced cardiotoxicity remains incompletely understood. Here, we investigated the critical role of mitochondrial H2O2 in DOX-induced cardiotoxicity using rat cardiomyocyte H9c2 cells with stable knockdown or reconstitution of mitochondrial antioxidant enzyme peroxiredoxin Ⅲ (PrxⅢ), which specifically regulates mitochondrial H2O2 levels.

Our results demonstrated that severe mitochondrial H2O2 accumulation (>10-fold compared to control) in PrxⅢ-depleted cells exacerbated mitochondrial oxidative stress, evidenced by increased cardiolipin oxidation and mitochondrial membrane potential dissipation. Furthermore, excessive mitochondrial H2O2 impaired mitochondrial fusion by reducing fusion-related protein expression, disrupted autophagic flux via lysosomal dysfunction, and significantly attenuated mitophagy, ultimately leading to enhanced apoptosis. Conversely, moderate mitochondrial H2O2 levels (5- to 8-fold increase compared to control) observed in PrxⅢ-expressing cells promoted mitochondrial elongation, enhanced mitophagy, and preserved autophagic flux, suggesting a protective adaptation against DOX-induced oxidative stress.

In vivo experiments using PrxⅢ knockout mice confirmed that loss of PrxⅢ aggravated DOX-induced cardiac dysfunction. Bioinformatic analysis of independent public transcriptome datasets and targeted qPCR validation in PrxⅢ-deficient cardiac tissues further confirmed that the mitochondrial quality control pathways identified in vitro are robustly dysregulated in vivo. Additionally, PrxⅢ deficiency markedly increased mitochondrial structural damage without significantly affecting cardiac fibrosis or hypertrophy.

Notably, mitigating the mitochondrial H2O2 burden and protecting the mitochondrial inner membrane using the mitochondria-targeted antioxidant peptide SS-31 successfully rescued this exacerbated cardiac dysfunction. In conclusion, our findings establish mitochondrial H2O2 as a pivotal determinant in DOX-induced mitochondrial dysfunction and cardiotoxicity, highlighting PrxⅢ as a promising therapeutic target for mitigating oxidative cardiac injury.