isoquercitrin and isopentenyl-pyrophosphate

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 [(14)C]acetate into [(14)C]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.

Topics: Cell Line, Tumor; Cell Membrane; Cholesterol; Gene Expression Profiling; Gene Expression Regulation, Neoplastic; Hemiterpenes; Humans; Hydrogen Peroxide; Hydroxymethylglutaryl CoA Reductases; Hydroxymethylglutaryl-CoA Reductase Inhibitors; Intramolecular Transferases; Lipid Metabolism; Lipid Peroxidation; Neoplasm Proteins; Neuroblastoma; Oligonucleotide Array Sequence Analysis; Organophosphorus Compounds; Oxidative Stress; Quercetin; RNA, Small Interfering; Signal Transduction; Sterol Regulatory Element Binding Protein 2