Mitochondria, Nrf2 and mTOR

Gino Cortopassi. Free Radical Biology and Medicine, Volume 128, Supplement 1, 2018, Page S7, doi:10.1016/j.freeradbiomed.2018.10.382.

Abstract: Friedreich's ataxia (FA) is the most common recessive ataxia, and it's phenotype is clinically indistinguishable from AVED, a deficiency of Vitamin E transport. We were the first to show that Friedreich's patient cells are very sensitive to oxidative stress. Ultimately this defect appears to reside in a deficiency of the antioxidant pathway Nrf2, which is less active in Friedreich's patient cells, and in FA animal models. Perhaps as a result of this Nrf2 defect, there is increased inflammation in Friedreich's patient cells and mice. But as Nrf2 is not only important in antioxidant homeostasis, but also mitochondrial homeostasis, this was investigated in Friedreich's models and patients. We found that Friedreich's cells, mice, and even people have an approximately 40% mitochondrial biogenesis defect. A high-throughput screening campaign for drugs that rescued Friedreich's cells from death identified three Nrf2 inducers, which could be of benefit in human Friedreich's therapy. One of these drugs, dimethyl fumarate, was shown to dose-dependently increase mitochondrial biogenesis and function when dosed in cells, and to increase mitochondrial biogenesis in mouse and human tissues, with a mechanism that appears to require Nrf2. Thus there is an interplay between Nrf2, mitochondrial biogenesis, and antioxidant status. We observed in a particular cancer there are alterations of mitochondrial biogenesis, which appear to result from differential Nrf2 activity. These differences in mitochondrial number allow the selective killing of such cells by mitochondrial inhibitors and a novel category of mTOR inhibitors.