Physical exercise positively modulates DOX-induced hepatic oxidative stress, mitochondrial dysfunction and quality control signaling

Abstract

Doxorubicin (DOX), a widely used and efficient antineoplastic agent, is mainly limited by cardiotoxicity, although other tissues including liver are also affected. The effects of exercise to cope with DOX side-effects has already been studied in the heart and brain, demonstrating successful results. However, the benefits of this non-pharmacological strategy have not been so extensively checked in the liver. We here aimed to ascertain whether exercise could mitigate DOX-induced liver harmful effects using mitochondria as a model for evaluating toxicity. Twenty-four male rats were divided into four groups: SED + SAL (sedentary with saline administration), SED + DOX (sedentary with DOX administration), ET + DOX (endurance-trained with DOX administration) and VPA + DOX (voluntary physical activity with DOX administration). Isolated liver mitochondria were obtained for evaluation of their respiratory activity and transmembrane electrical potential endpoints. Molecular markers of oxidative damage (carbonyls, MDA, aconitase, MnSOD), mitochondrial dynamics (PGC-1α, TFAM, OPA1, DRP1, MFN1) and auto(mito)phagy signaling (p62, LC3, Beclin1, Bcl-2, PINK, Parkin) were measured. Transmission electron microscopy evaluation was used to analyze mitochondrial morphological alterations. When compared to SED + SAL, respiratory function of SED + DOX was compromised. Decreased SOD and aconitase activities and increased MDA content, decreases in PGC-1α, TFAM, OPA1 and MFN1 expressions, and increases in DRP1 and LC3II/LC3I ratio were also observed after DOX administration. However, these alterations were reverted or mitigated in the ET + DOX group. Semi-quantitative and qualitative analyses from microphotographs showed that liver mitochondria of SED + DOX animals were more circular and had lower density, whereas the animals with exercise showed a tendency to revert this phenotype and increase the mitochondrial density. Taken together, our results suggest that physical exercise, particularly ET, positively reversed the deleterious effects caused by DOX administration, such as oxidative damage, mitochondrial dysfunction, and altered mitochondrial dynamics toward fission, thus contributing to increase liver resistance against DOX administration.

Keywords: Doxorubicin; Exercise; Hepatotoxicity; Mitochondrial dysfunction.