Mechanism of myocardial damage induced by doxorubicin via calumenin-regulated mitochondrial dynamics and the calcium-Cx43 pathway.

Background: The clinical application of doxorubicin (DOX) is limited by its potential to cause cardiac cardiotoxicity.

Aim: To investigate the correlation between calumenin (CALU) and mitochondrial kinetic-related proteins in rats with DOX cardiomyopathy.

Methods: A rat model of DOX-induced cardiomyopathy was used to evaluate the effects of DOX. We observed the effect of DOX on electrical conduction in cardiomyocytes using the electromapping technique. Masson staining was performed to evaluate myocardium fibrosis. Electron microscopy was used to observe the changes in pathological ultrastructure of the myocardium. Western blotting and ELISAs were performed to detect protein levels and intracellular free Ca²⁺ concentration.

Results: DOX slowed conduction and increased conduction dispersion in cardiomyocytes. The myocardial pathology in rats treated with DOX exhibited a significant deterioration, as demonstrated by an increase in mitochondrial Ca²⁺ concentration and a decrease in the expression of CALU, optic atrophy-1, and Bcl-2. Additionally, there was an increase in the expression of connexin 43 (Cx43) and the mitochondrial mitotic proteins dynamin-related protein 1, CHOP, Cytochrome C, and Bax in DOX rats. Decreased expression of CALU in cardiomyocytes triggered an increase in cytoplasmic free calcium concentration, which would normally be taken up by mitochondria, but decreased expression of mitochondrial outer membrane fusion proteins triggered a decrease in mitochondrial Ca²⁺ uptake, and the increase in cytoplasmic free calcium concentration triggered cell apoptosis.

Conclusion: Increased cytoplasmic free calcium ion concentration induces calcium overload in ventricular myocytes, leading to decreased Cx43 protein, slowed conduction in myocytes, and increased conduction dispersion, resulting in arrhythmias.