As a multifunctional regulatory center, the mitochondria of the cell are being increasingly recognized as a central feature in both health and disease. Not only are they responsible for supplying a steady stream of ATP to fuel cellular processes, but they play a substantial role in immune response, signal transduction, and a cell’s developmental path.
Mitochondria are unique in that they contain their own DNA (mtDNA). MtDNA is what controls and dictates mitochondrial respiratory capacity and ATP production. Any compromise to the integrity of mtDNA results in an inefficient electron transport chain that spews out harmful reactive oxygen species. These species damage the cell, set off a stress response, and may initiate cell death, at which point mtDNA can leak out into the cytoplasm or extracellular space. Mislocalized mtDNA is recognized as foreign, acting as a damage-associated molecular pattern (DAMP) that triggers an innate immune response.
MtDNA exhibits a high mutation rate in part owed to its high replication rate, exposure to oxidative stress, lack of protection from histone proteins, and poor DNA repair mechanisms. Its high copy number serves to mitigate these impacts to some extent, but eventually the proportion of mutated DNA far exceeds that of wild-type DNA. This is known as the heteroplasmy level, the threshold at which mitochondrial function declines.
The accumulation of damage and mutations is correlated with diseases of aging, including cardiovascular and neurodegenerative diseases. MtDNA mutations incite proliferation of reactive oxygen species, creating a self-reinforcing feedback loop of oxidative stress, mitochondrial dysfunction, and even more mtDNA damage, replication errors, and mutations. Mitochondrial respiration suffers, ATP synthesis falls, reactive oxygen species rise, the mitochondrial membrane falters, and mtDNA leaks out. The innate immune system becomes hyper-activated and chronic inflammation ensues.
Alterations to mitochondrial membrane structure and potential additionally impair the fusion/fission process and persistent inflammation contributes to senescence. Mutated mtDNA may hinder proper clearance of damaged mitochondria, so-called mitophagy. Senescent cells continually secrete inflammatory factors such as IL-6 and IL-8 that attract larger quantities of immune cells. Senescent mitochondria are specific in their release of IL-10, TNF-a, and HMGB1. Mutated mtDNA can also undermine metabolic processes involved in histone acetylation and DNA methylation, ultimately leading to activation of other inflammatory genes.
Therapeutic strategies are under investigation with the aim of restoring fusion/fission balance, clearing reactive oxygen species, supporting mitophagy, protecting against DNA damage and mutations, and halting the inflammatory cascade. MitoQ is a mitochondrial-targeted coenzyme Q antioxidant supplement that acts to scavenge reactive oxygen species and protect the mitochondrial membrane, thereby suppressing NLRP3 inflammasome activation. N-acetylcysteine also has the potential to attenuate reactive oxygen species accumulation as well as enhance mitophagy and the provision of ATP. Similarly, flavonoids, sulfur-containing molecules, and triterpenoid saponins are other natural compounds that exhibit antioxidant activity and may serve to lessen reactive oxygen species-induced mtDNA damage and upregulate mitophagy.
In terms of attenuating mtDNA damage and mutations, rapamycin improves mitophagy, thereby assisting with compromised mtDNA removal. IL-37 prevents mtDNA damage and release. The cGAS-STING pathway has been elucidated as a core stimulus prompting mtDNA release-associated inflammation. H-151 is a selective and irreversible STING inhibitor and both melatonin and senolytics (fisetin, dasatinib, quercetin) can repress the cGAS-STING pathway, subsequently blocking inflammatory signaling and allowing for removal of senescent cells. Acetylcholine has similarly been used owing to its action as an NLRP3 inhibitor, while doxycycline and metformin block mtDNA synthesis to inhibit NLRP3.
In the end, the goal is to promote adequate clearance and renewal of damaged mitochondria in order to avert chronic low-grade inflammation and accretion of senescent cells. The two latter features are hallmarks of aging that potentiate mitochondrial impairment, DNA damage and mutations, production of reactive oxygen species, and immune system dysfunction. Optimizing mitochondrial function through cutting-edge approaches and small molecule therapeutics is a hopeful strategy for enhancing health span.
Wang S, Wu F, Zhou H. Mitochondrial DNA: Bridging cellular senescence and chronic inflammation in aging and beyond. Mutat Res Rev Mutat Res. 2026;797:108587. doi:10.1016/j.mrrev.2026.108587
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