Figure 2. Mechanisms by which DNA damage could promote aging.

DNA damage, including damage at telomeres (center), once detected, if not repaired, can interfere with replication or transcription, resulting in the activation of signaling events that alter cell physiology. One outcome of these signaling events is apoptosis, which while depleting important cells like stem cells or neurons may not be the most potent driver of aging. DNA damage can also result in mitochondrial dysfunction, impaired autophagy, metabolic changes, and the triggering of cellular senescence (small circles). These live but physiologically altered cells are predicted to be a more potent driver of aging and disease. Endpoints used to measure these consequences of DNA damage are indicated with arrows in the larger circles. These outcomes are all interconnected in that mitochondrial dysfunction can cause metabolic changes, impaired autophagy and proteostasis, more DNA damage, and senescence. This creates a cycle of increasing damage and dysfunction, which can spread to other cells via SASP, that is likely the proximal cause of aging and the diseases associated with it (outer circle).