The Antioxidant Mechanisms Underlying the Aged Garlic Extract- and S-Allylcysteine-Induced Protection

Figure 4

Effect of aged garlic extract (AGE) or S-allylcysteine (SAC) on Nrf2/Keap1 complex. Left panel: Upon unstressed conditions, this complex is dissociated and Nrf2 can either suffer proteosomal degradation or respond to stimuli typical of basal cell metabolism. In the later, Nrf2 is phosphorylated and translocated to the nucleus forming heterodimers with Maf and acting on antioxidant response element (ARE). Right panel: Under stress oxidative conditions, or in the presence of inducers, several cysteine residues suffer changes inducing its Nrf2 dissociation and further translocation of this factor to nucleus, where it will induce phase 2 genes transcription. SAC could modify cysteine residues on Keap1 domain, hence releasing Nrf2 and allowing its transactivation. Nrf2: transcription factor nuclear factor-E2-related factor 2, Keap1: kelch-related erythroid cell-derived protein with CNC homology (ECH) protein 1, UBQ: ubiquitin, ROS: reactive oxygen species, NQO1: NAD(P)H:quinone oxidoreductase 1, GST: glutathione-S-transferase, HO-1: heme oxygenase-1, GCL: glutamate cysteine ligase.