Nrf2 Controls Mitochondrial Bioenergetics

Abstract

The transcription factor nuclear factor E2-related factor 2 (Nrf2) and its repressor Kelch-like ECH-associated protein 1 (Keap1) are known to regulate the antioxidant response element (ARE) pathway responsible for controlling the expression of a network of cytoprotective genes, including antioxidant and anti-inflammatory genes as well as genes involved in mitochondrial biogenesis. Using biochemical techniques in addition to live cell imaging and respirometry we now show that the Keap1-Nrf2 pathway is further involved in the control of mitochondrial metabolism. Experiments in mouse embryonic fibroblasts from wild-type, Nrf2 and Keap1 knockout (KO) animals show that, compared to wild-type, cells lacking Nrf2 have decreased mitochondrial membrane potential while Keap1 KO cells on the other hand show an increase. Interestingly, Nrf2 KO cells show significant inhibition of the rate of oxygen consumption, suggesting that the decrease in mitochondrial membrane potential is not due to mitochondrial uncoupling. We further demonstrate in primary neuroglia cultures (isolated from wild-type, Nrf2 KO and Keap1 knockdown mice) that this pathway has a significant effect on the FAD and NADH redox states of the cells and the defect could not be reversed by application of mitochondrial substrates. Finally, Nrf2 KO cells show increased dependence on glycolysis, as seen by both live cell imaging and western blot. In conclusion, the Keap1-Nrf2 pathway is not only important in the anti-oxidant defence of the cells but also plays a major role in energy metabolism.