Magnolol alleviates Alzheimer's disease-like pathology in transgenic C. elegans by promoting microglia phagocytosis and the degradation of beta-amyloid through activation of PPAR-gamma

This study aims to investigate whether magnolol (MG), a natural neolignane compound, can prevent AD induced by beta-amyloid (A beta) and the possible mechanisms involved. MG dose-dependently reduces A beta deposition, toxicity and memory impairment caused by A beta in transgenic C. elegans. More importantly, these effects are reversed by GW9662, a selective peroxisome proliferator-activated receptor-gamma (PPAR-gamma) antagonist. MG is more effective in enhancing PPAR-gamma luciferase levels than honokiol (HK). Meanwhile, MG has the potential to bind with the ligand binding domain of PPAR-gamma (PPAR-gamma-LBD). As expected, MG inhibited the luciferase activity of NF-kappa B and its target genes of inflammatory cytokines, and this effect was blocked by GW9662. The luciferase activity of Nrf2-ARE expression can be activated by MG and decreased A beta-induced reactive oxygen species (ROS). The target gene LXR of PPAR-gamma is activated by MG, which upregulates ApoE and promotes microglia phagocytosis and the degradation of A beta, and these effects were also reversed by GW9662. In summary, MG can attenuate A beta-induced AD and the underlying mechanism is the reduction of inflammation and promotion of phagocytosis and degradation of A beta, which is dependent on PPAR-gamma.