Antioxidant Activity of Flavonoid Glabranin by Upregulating Antioxidant Gene Expression via MEK/ERK and PI3K/Akt Pathways in Human Neuroblastoma SH-SY5Y Cells.

Oxidative stress is associated with neuronal cell death in neurodegenerative diseases, including Alzheimer’s disease and Parkinson’s disease. Glabranin, a flavonoid found in the stems and leaves of Glycyrrhiza glabra (licorice), exhibits antioxidant and anti-inflammatory properties. However, the effect of glabranin on the antioxidant response and the underlying mechanism including the specific signaling pathways, remain unclear. In the current study, we investigated the protective effect of glabranin on hydrogen peroxide (H2O2)-induced neurotoxicity in human neuroblastoma SH-SY5Y cells and its underlying mechanisms. H2O2-induced death of SH-SY5Y cells was restored by glabranin in a concentration-dependent manner. The number of H2O2-increased apoptotic cells was reduced by co-treatment with glabranin. Moreover, glabranin attenuated H2O2-induced cleaved caspase-3/7 levels. In addition, glabranin decreased H2O2-induced intracellular ROS levels via promoting the nuclear translocation of nuclear factor erythroid 2-related factor 2 and upregulating the antioxidant gene expression. Furthermore, glabranin enhanced the phosphorylation of extracellular signal-regulated kinase (ERK) and protein kinase B (Akt) following H2O2 treatment. Inhibition of mitogen-activated protein kinase kinase (MEK)/ERK and phosphoinositide 3-kinase (PI3K)/Akt pathways abrogated glabranin-mediated elevation of antioxidant gene expression and neuroprotective effects. These findings suggest that glabranin mitigated H2O2-induced apoptosis by increasing the expression of antioxidant genes through activation of the MEK/ERK and PI3K/Akt pathways in SH-SY5Y cells. Therefore, glabranin has the potential to prevent and treat neurodegenerative diseases as an antioxidant agent.