Platycodin D stimulates AMPK activity to inhibit the neurodegeneration caused by reactive oxygen species-induced inflammation and apoptosis.

Abstract

Alzheimer's disease (AD) was considered to be a neurodegenerative disease that caused cognitive impairment. Reactive Oxidative stress (ROS) was considered to be one of a major cause of the onset and progression of AD. Platycodin D (PD), a representative saponin from Platycodon grandiflorum, has conspicuous antioxidant activity. However, whether PD could protect nerve cell against oxidative injury remains unknown. This study investigated the regulatory effects of PD on neurodegeneration caused by ROS. To determine whether PD could play its own antioxidant role in neuronal protection. First, PD(2.5, 5mg/kg) ameliorated the memory impairment induced by AlCl3 (100mg/kg) combined with D-galactose (D-Gal) (200mg/kg) in mice, using the radial arm maze (RAM) test, and neuronal apoptosis in the hippocampus was evaluated by hematoxylin and eosin staining (HE). Next, the effects of PD (0.5, 1, and 2μM) on okadaic-acid (OA) (40nM) -induced apoptosis and inflammation of HT22cells were investigated. Mitochondrial ROS production was measured by fluorescence staining. The potential signaling pathways were identified through Gene Ontology enrichment analysis. The role of PD in regulating AMP-activated protein kinase (AMPK) was assessed using siRNA silencing of genes and an ROS inhibitor. In vivo, PD improved memory in mice, and recovered the morphological changes of brain tissue and nissl bodies. In vitro experiment, PD increased cell viability (p<0.01; p<0.05;p<0.001), decreased apoptosis (p<0.01), reduced excessive ROS and MDA, rised SOD and CAT content(p<0.01; p<0.05). Morover, it can block the inflammatory response caused by ROS. Be important, PD strengthen antioxidant ability by elevating AMPK activation both in vivo and in vitro. Furthermore, molecular docking suggested a good likelihood of PD-AMPK binding. AMPK activity is vital for the neuroprotective effect of PD, suggesting that PD may be a potential pharmaceutical agent to treat ROS-induced neurodegeneration.