FIGURE 1.

Reactive oxygen species promote health and lifespan. (A) Multiple mitochondria converging stresses results in an increased production of mitochondrial reactive oxygen species (mtROS), which are able to activate a transcriptional retrograde response, between the organelle and the nucleus, linking mtROS to nuclear events. The result of this pathway is an increased cell stress resistance that can extend health and lifespan. (B) This effect relies on a mitochondrial process called mitohormesis, in which mtROS engages a non-linear response (green), instead of the linear response (red) postulated by the classical free radical theory of aging. The mitohormetic response (green) is characterized by health span-promoting effects at low mtROS doses, while cellular and systemic damage are the consequence of higher mtROS doses.