The effects of thymoquinone and quercetin on the toxicity of acrylamide in rat glioma cells.

Acrylamide is a neurotoxic agent forming in foods. Thymoquinone and quercetin are plant-derived antioxidants in various foods with known benefits. C6 cells are glioblastoma cells. In this study, we aimed at preventing acrylamide toxicity by thymoquinone and quercetin in the C6 cell line. In our study, first, toxic doses of acrylamide, nontoxic doses of thymoquinone and quercetin in C6 cells for 24 h were determined by MTT (3-[4,5-dimethylthiazol-2-yl]-2,5 diphenyl tetrazolium bromide) colorimetric test. After that, caspase 3/7 and annexin V tests were performed by flow cytometry to evaluate whether the apoptosis pathway was inducted. Furthermore, autophagy and oxidative stress were assessed by flow cytometry. The amount of Nrf2 (nuclear factor erythroid 2-related factor 2) was determined by immunocytochemistry. The morphological examination was performed by microscopic analyses. As a result, 4 mM of acrylamide was determined to be used to induce toxicity in C6 cells. The nontoxic doses of thymoquinone and quercetin were respectively determined as 3.9 and 2.0 µM. Thymoquinone and quercetin not only reduced acrylamide-induced apoptosis in annexin V and caspase 3/7 assays but also morphological deformations in microscopic examinations. In autophagy, it was revealed that acrylamide-induced autophagy was decreased by quercetin and thymoquinone pretreatments. As for Nrf2 expression, it was observed that acrylamide increased Nrf2 expression, and thymoquinone and quercetin pretreatments increased it even further. In conclusion, in the study, acrylamide demonstrated a damaging effect on C6 glioblastoma cells, and thymoquinone and quercetin pretreatments exerted a protective effect against acrylamide-induced damage in C6 cells.