Kavalactones protect neural cells against amyloid beta peptide-induced neurotoxicity via extracellular signal-regulated kinase 1/2-dependent nuclear factor erythroid 2-related factor 2 activation

One hallmark of Alzheimer's disease is the accumulation of amyloid beta-peptide (AP), which can initiate a cascade of oxidative events that may result in neuronal death. Because nuclear factor erythroid 2-related factor 2 (Nrf2) is the major regulator for a battery of genes encoding detoxifying and antioxidative Enzymes via binding to the antioxidant response element (ARE), it is of great interest to find nontoxic activators of Nrf2 rendering neuronal cells more resistant to AP toxicity. Using ARE-luciferase assay and Western blot, we provide evidence that the kavalactones methysticin, kavain, and yangonin activate Nrf2 time- and dose-dependently in neural PC-12 and astroglial C6 cells and thereby up-regulate cytoprotective genes. Viability and cytotoxicity assays demonstrate that Nrf2 activation is able to protect neural cells from amyloid beta-(1-42) induced neurotoxicity. Down-regulation of Nrf2 by small hairpin RNA as well as extracellular signal-regulated kinase 1/2 inhibition abolishes cytoprotection. We further give evidence that kavalactone-mediated Nrf2 activation is not dependent on oxidative stress production. Our results demonstrate that kavalactones attenuate amyloid beta-peptide toxicity by inducing protective gene expression mediated by Nrf2 activation in vitro. These findings indicate that the use of purified kavalactones might be considered as an adjunct therapeutic strategy to combat neural demise in Alzheimer disease and other oxidative stress-related diseases.