Fig. 3

Effect of synthetic antioxidants on lidocaine-induced cell death. a Graphic depiction of reactive oxygen species (ROS) production in SH-SY5Y cells exposed to the indicated concentrations of lidocaine (0, 0.1, 4, or 10 mM) for 6 h (n = 3) in the presence or absence of 10 mM N-acetyl cysteine (NAC). Data depict the ratio of ROS production in treated cells compared to that in the untreated control group. b–e SH-SY5Y cells were exposed to the indicated concentrations of lidocaine (0, 4, or 10 mM) for 24 h in the presence or absence of NAC (4 or 10 mM). b Cell viability and (c) caspase-3/7 activity were evaluated by MTS [3-(4,5-dimethylthiazol-2-yl)-5-(3-carboxymethoxyphenyl)-2-(4-sulfophenyl)-2H-tetrazolium] assay (n = 3) and Apo-ONE™ Homogeneous Caspase-3/7 Assay (n = 3) analysis, respectively. d Cells were harvested and lysates were subjected to immunoblot assay analysis using antibodies specific to poly (ADP-ribose) polymerase (PARP) and cleaved caspase-9. e Graphic depiction of the levels of cell death among treated and untreated cell populations, as evaluated by flow cytometry (n = 4). The ratio with PI or annexin V positive cells [(Q1 + Q2 + Q4)/(Q1 + Q2 + Q3 + Q4)] were indicated as dead cells (Additional file 1: Figure S1). f SH-SY5Y cells were exposed to the indicated concentrations of lidocaine (0.1, 1, 4, or 10 mM) in the presence or absence of 250 μM Trolox for 24 h, and subjected to caspase-3/7 activity assay analysis (n = 4) (left panel). Graphic depiction of the levels of cell death among treated and untreated cell populations, as evaluated by flow cytometry (n = 3) (right panel). The ratio with PI or annexin V positive cells [(Q1 + Q2 + Q4)/(Q1 + Q2 + Q3 + Q4)] were indicated as dead cells. Differences between results were evaluated by one-way analysis of variance (ANOVA) (a) followed by Dunnett’s test for multiple comparisons or two-way ANOVA (b, c, e and f) followed by Dunnett’s test for multiple comparisons in each group. *p < 0.05 compared with the control cell population at 0 h (no treatment). #p < 0.05 compared with the control treatment population in the same group