Figure 2.

Age-associated loss of adaptive homeostasis. Young organisms, pretreated with a nondamaging amount of an oxidant or stimulant, are capable of a robust increase in multiple stress-responsive enzymes (Nrf2, mitochondrial Lon protease, the 20S proteasome, and heat shock proteins). Yet, with age, although steady-state basal concentrations of these proteins increase, their induction, following pretreatment, is no longer possible. Hence the compression of adaptive homeostasis with age.