Nrf2-regulated phase II enzymes are induced by chronic ambient nanoparticle exposure in young mice with age-related impairments

► Inhaled nanoparticles (nPM) induce phase II enzymes systemically in young mice. ► Middle-aged mice had elevated phase II enzymes, but induction by nPM was impaired. ► Nrf2 increased with age and was induced by nPM in young but not middle-aged mice. ► Nrf2 inhibitors, c-Myc and Bach1, increased with age along with depressed induction. ► Depressed enzyme induction by nPM in aging may increase air pollution vulnerability.