Figure 10. Schematic representation for the association between oxidative stress, PARP-mediated and decline in NAD⁺ content, and NAD⁺ dependent functions with aging.

Oxidative stress to DNA activates PARP leading to poly(ADP-ribosylation) of proteins in a reaction which consumes NAD⁺. Depletion of cellular NAD⁺ stores attenuates the activity of Sirt1 deacetylase leading to hyperacetylation of p53, and consequently tilting the balance to cell death via an apoptotic mechanism.