DNA damage theory of ageing

Processes and types of damage

Cells encounter a variety of DNA insults: single- and double-strand breaks, base modifications, crosslinks, and replication errors. Sources include endogenous reactive oxygen species, replication stress, and environmental agents. Damage can occur in both the nuclear genome and the mitochondrial genome; this article emphasizes nuclear DNA while noting important mitochondrial contributions and the role of the cell nucleus in coordinating responses.

Repair pathways and limitations

Multiple repair systems counter DNA damage: base excision repair, nucleotide excision repair, mismatch repair, and double-strand break repair (non-homologous end joining and homologous recombination). These pathways maintain genomic stability, but efficiency varies by tissue, cell type and age. Some lesions are repaired imperfectly, or persist in non-dividing cells, producing mutations, chromosomal rearrangements, or persistent signaling that alters cell function.

Evidence and experimental findings

Animal and cellular studies support a causal role for DNA damage in ageing: organisms with defects in repair genes often show accelerated ageing features, while enhanced maintenance can extend healthy function in model systems. However, ageing is multifactorial; DNA damage interacts with metabolic, proteostatic and inflammatory processes rather than acting alone.

Consequences, interventions and significance

• Consequences: accumulated DNA damage can drive cellular senescence, apoptosis, stem cell exhaustion and altered gene expression.
• Interventions under study: boosting repair capacity, reducing damage (e.g., antioxidants or lifestyle changes), and clearing damaged cells are active research areas.
• Implications: understanding DNA damage helps explain cancer risk, degenerative disease and the trade-offs between maintenance and reproduction.

Distinguishing this theory from others is important: it complements ideas like telomere shortening, proteostasis loss and metabolic theories by offering a molecular mechanism for accumulation of functional defects. For further reading and entry points into the literature, see linked overview pages above and specialized reviews at ageing and DNA resources.