Abstract
Reactive oxygen species (ROS) are byproducts of aerobic respiration and signaling molecules
that control various cellular functions. Nrf2 governs the gene expression of endogenous antioxidant
synthesis and ROS-eliminating enzymes in response to various electrophilic compounds that inactivate
the negative regulator Keap1. Accumulating evidence has shown that mitochondrial ROS (mtROS)
activate Nrf2, often mediated by certain protein kinases, and induce the expression of antioxidant
genes and genes involved in mitochondrial quality/quantity control. Mild physiological stress, such
as caloric restriction and exercise, elicits beneficial effects through a process known as “mitohormesis”.
Exercise induces NOX4 expression in the heart, which activates Nrf2 and increases endurance
capacity. Mice transiently depleted of SOD2 or overexpressing skeletal muscle-specific UCP1 exhibit
Nrf2-mediated antioxidant gene expression and PGC1α-mediated mitochondrial biogenesis. ATF4
activation may induce a transcriptional program that enhances NADPH synthesis in the mitochondria
and might cooperate with the Nrf2 antioxidant system. In response to severe oxidative stress, Nrf2
induces Klf9 expression, which represses mtROS-eliminating enzymes to enhance cell death. Nrf2
is inactivated in certain pathological conditions, such as diabetes, but Keap1 down-regulation or
mtROS elimination rescues Nrf2 expression and improves the pathology. These reports aid us in
understanding the roles of Nrf2 in pathophysiological alterations involving mtROS.
Download: Regulation of Nrf2