Abstract: When exposed to excessive reactive oxygen species (ROS),living organism can enhance the expression of many protective proteins through activation of a series of complex cellular signal transductions.Nuclear factor erythroid 2-related factor 2 (Nrf2) is a master transcription factor in cellular defense against oxidative stress,which is the key to ROS-induced overexpression of antioxidant proteins.Nevertheless,the mechanisms,by which ROS activate Nrf2,are not completely understood.Some researches show that ROS can activate Nrf2 through mitogen-activated protein kinases (MAPKs) and phosphatidylinositol-3-kinase/protein kinase B (PI3K/AKT) pathways,protecting cells from oxidative stress.It indicates that MAPKs and PI3K/AKT pathways play an important role in ROS-meditated activation of Nrf2.