Allium cepa Extract and Quercetin Protect Neuronal Cells from Oxidative Stress via PKC-ε Inactivation/ERK1/2 Activation

Figure 1

Effects of Allium cepa extract (ACE) and quercetin (QCT) on L-buthionine sulfoximine- (BSO-) induced neuronal cell death. (a) Cortical cells were pretreated with ACE (1, 3, and 10 mg/mL) and QCT (1, 3, and 10 μM) for 30 min and then exposed to 10 mM BSO for 24 h. Lactate dehydrogenase (LDH) release was measured after a 24 h BSO treatment. (b) Apoptotic cell death was examined by counting the number of terminal deoxynucleotidyl transferase dUTP nick end labeling- (TUNEL-) positive cells. (Top) TUNEL staining photographs; arrows indicate TUNEL-positive cells, and arrowheads indicate intact cells. (Bottom) Cortical cells were pretreated with ACE (1, 3, and 10 mg/mL) and QCT (1, 3, and 10 μM) for 30 min and then exposed to 10 mM BSO for 24 h. The number of TUNEL-positive (%) cells was calculated by dividing the number of TUNEL-stained cells by the total number of cells after a 24 h BSO treatment. (c) Fluorescence photomicrographs (stained with 10 μM DCF-DA) of cells after a 4 h BSO treatment and the control. Cortical cells were pretreated with ACE (10 mg/mL) and QCT (10 μM) for 30 min and then exposed to 10 mM BSO for 4 h before measuring fluorescence. (d) Reactive oxygen species (ROS) generation during BSO treatment was quantified by pretreating the cells with ACE (10 mg/mL) and QCT (10 μM) simultaneously with 10 mM BSO. ROS levels in the cells were quantified by measuring DCF-DA fluorescence intensity and are represented as the percentage (%) of intensity at 0 min. All data are mean ± standard error (). versus control (CTL); versus vehicle (VEH).

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