Constitutive knock-in of MnSODK68R causes dilated cardiomyopathy and senescence in mice

Abstract

The mitochondrial superoxide dismutase (SOD2 or MnSOD) is an essential enzyme for managing oxidative stress, particularly by removing the highly reactive superoxide generated during the normal functioning of the electron transport chain. The activity of MnSOD is regulated post-translationally by acetylation, specifically at lysine 68. The deacetylated form of MnSOD is catalytically active, and it has been shown that the deacetylation mimic, MnSOD K68R in which lysine 68 has been replaced with arginine, has upregulated dismutase activity in MCF7 and T47D human breast cancer cells. Overexpression of MnSOD has been shown to increase lifespan and protect against oxidative stress in the aging heart. We investigated a MnSOD K68R knock-in mouse with ubiquitous expression of the mutant enzyme and expected similar effects as the MnSOD overexpressing mice. However, we have found that MnSOD K68R homozygous knock-in mice develop dilated cardiomyopathy and have significantly decreased ejection fraction as evidenced by echocardiography at a young age. These mice also exhibit lower blood pressure compared to wild-type mice. Strikingly, these mice exhibit higher body weight, with increased lean mass and food consumption. Mitochondria isolated from MnSOD K68R knock-in mouse hearts showed higher respiratory capacity than WT counterparts. Biochemical analysis revealed increased lipid peroxidation, oxidized peroxiredoxin and senescence markers, possibly indicative of a premature aging phenotype. We conclude that MnSOD constitutive function upregulation may produce a sustained increase in hydrogen peroxide levels that could cause senescence and lead to dilated cardiomyopathy. This research was funded by NCI grant R01CA152601 and, R01CA214025, and the Cancer Prevention and Research Institute of Texas grant number RR20012. JS is supported by T32 AG 021890. This is the full abstract presented at the American Physiology Summit 2023 meeting and is only available in HTML format. There are no additional versions or additional content available for this abstract. Physiology was not involved in the peer review process.