Mitochondrial superoxide-mediated mitohormesis protects against doxorubicin-induced cardiotoxicity [6Week_RNAseq]

In a mouse embryonic fibroblast model of mitohormesis, we found transient SOD2-knockdown resulted in similar mitohormetic outcomes to those in heart, including increased mitochondrial biogenesis and antioxidant responses, histone acetylation, and resistance to doxorubicin-induced cell death. In this model, mitochondrial matrix superoxide inhibited the tricarboxylic acid cycle enzyme aconitase (ACO2), thereby redirecting its substrate citrate into the cytosol where it is converted by ACLY to acetyl-CoA for histone acetylation.

Thus, we conclude that citrate is a redox-sensitive second messenger of mitochondrial superoxide stress that initiates this form of mitohormesis. Supporting this conclusion, genetic loss of the mitochondrial citrate transporter, SLC25A1, prevented the mitohormetic response, while knockdown of ACO2 or addition of exogenous citrate recapitulated the superoxide- mediated adaptations. We speculate this redox-sensitive mitohormetic signaling pathway might illuminate new therapeutic approaches for DIC and possibly other pathology involving mitochondrial defects and oxidative stress.