Protective Effects of Quercetin in Combination with Donepezil against H2O2-Induced Oxidative Stress in Glioblastoma Cells

Polyphenols are natural antioxidants found in the human diet, which are known to have protective effects against neurodegenerative diseases by scavenging free radicals. Recently, combination therapies including cholinesterase (ChE) inhibitors and neuroprotective agents have been shown to be more efficacious in the prevention and treatment of Alzheimer's disease. Therefore, the purpose of this work was to assess the neuroprotective impact of the combination of quercetin, a major polyphenolic compound, and donepezil, a cholinesterase inhibitor, against hydrogen peroxide-induced oxidative damage of glioblastoma (U-118 MG) cells. Following pretreatment with quercetin and donepezil, the glioblastoma cell line was subjected to H2O2-induced oxidative stress damage via application of 250 mu MH2O2 and incubation for a period of 24 h. In this study, four test groups were selected for the investigation of quercetin and donepezil as protective agents against H2O2 oxidative stress. First, quercetin and donepezil were examined in terms of their effects on glioblastoma cell viability. Next, pre- and post-application of quercetin and donepezil were used to determine their concentrations effective against the H2O2-induced oxidative damage in the U-118 MG cell line. Finally, the effect of the combined application of quercetin and donepezil on the cell viability was investigated. Viability testing of the cell lines was carried out via the advanced XTT assay using sulfonated tetrazolium. As a result of testing, no protective or therapeutic effects of donepezil alone were observed on the cell damage caused by oxidative stress. On the other hand, quercetin and combination applications exhibited protective or therapeutic effects on the cell damage. Thus, the neuroprotective effect of quercetin and its combination with donepezil provide a new approach to the search for drugs in the clinical treatment of neurodegenerative diseases.