Quercetin 3-Glucoside Protects Neuroblastoma (SH-SY5Y) Cells in Vitro against Oxidative Damage by Inducing Sterol Regulatory Element-binding Protein-2-mediated Cholesterol Biosynthesis

The flavonoid quercetin 3-glucoside (Q3G) protected SH-SY5Y, HEK293, and MCF-7 cells against hydrogen peroxide-induced oxidative stress. cDNA microarray studies suggested that Q3G-pretreated cells subjected to oxidative stress up-regulate the expression of genes associated with lipid and cholesterol biosynthesis. Q3G pretreatment elevated both the expression and activation of sterol regulatory element-binding protein-2 (SREBP-2) only in SH-SY5Y cells subjected to oxidative stress. Inhibition of SREBP-2 expression by small interfering RNA or small molecule inhibitors of 2,3-oxidosqualene:lanosterol cyclase or HMG-CoA reductase blocked Q3G-mediated cytoprotection in SH-SY5Y cells. By contrast, Q3G did not protect either HEK293 or MCF-7 cells via this signaling pathway. Moreover, the addition of isopentenyl pyrophosphate rescued SH-SY5Y cells from the inhibitory effect of HMG-CoA reductase inhibition. Last, Q3G pretreatment enhanced the incorporation of [14C]acetate into [14C]cholesterol in SH-SY5Y cells under oxidative stress. Taken together, these studies suggest a novel mechanism for flavonoid-induced cytoprotection in SH-SY5Y cells involving SREBP-2-mediated sterol synthesis that decreases lipid peroxidation by maintaining membrane integrity in the presence of oxidative stress.