Figure 1.

Relationship between reactive oxygen species (ROS) production and aging. The balance between oxidant sources and oxidant scavengers gives rise to pathologically high or physiologically low levels of ROS. High levels of ROS induce oxidative stress, leading to advanced glycation end-products (AGE) accumulation [20], insoluble protein aggregation [21], lipid peroxidation [22] and nucleic acid damage [23]. Low levels of ROS activate cellular signaling, such as apoptosis [24], cell proliferation and differentiation [25], metabolic regulation [26] and pathogen defense [27]. High or low levels of ROS cause age-related diseases or successful aging, respectively.