FIG. 2.

miRNAs in the reactive oxygen species (ROS) signaling pathway. ROS are constantly produced as superoxides, originating as by-products of cellular metabolism, or by oxygenases from specific signaling pathways. On oxidative stress, the nulcear factor-erythroid 2-related factor 2 (Nrf2)-mediated antioxidant response is activated to maintain intracellular redox homeostasis and limit oxidative damage. miR-200a and miR-141 form the Nrf2 positive feedback loop by targeting Kelch-like ECH-associated protein 1 (Keap1), a negative regulator of Nrf2. Other miRNAs target the central regulators Nrf2, transforming growth factor (TNF)-α, and the ROS scavengers superoxide dismutatese (SOD), catalase, glutathione peroxidase (GSHPX), and thioredoxin reductase (TXNRD).