Figure 7. Schematic representation illustrating the relationship between Nrf2 and IDD as well as the protective effects of Kin on IDD. Briefly, the decreased Nrf2 expression compromises the antioxidant ability of NPCs, which further contributes to the excessive apoptosis and senescence of NPCs under oxidative stress, and eventually the disc degeneration. However, Kin is able to activate the AKT-ERK1/2-Nrf2 signaling pathway in NPCs, alleviating mitochondrial dysfunction, apoptosis and senescence in vitro and ameliorating IDD in vivo.