Fig. 1

Lidocaine induces SH-SY5Y cell death in a dose- and time-dependent manner. Neuronal SH-SY5Y cells were exposed to the indicated concentrations (0.1, 1, 4, or 10 mM) of lidocaine for varying lengths of time (0, 12, 24, and 48 h). a Graphic depiction of the levels of cell viability of treated and untreated cells at each time point, as evaluated by MTS [3-(4,5-dimethylthiazol-2-yl)-5-(3-carboxymethoxyphenyl)-2-(4-sulfophenyl)-2H-tetrazolium] assay analysis (n = 4). b and c Graphic depictions of caspase-3/7 (n = 3) and caspase-9 (n = 5) activity in each treatment group at different time points, as determined using an Apo-ONE™ Homogeneous Caspase-3/7 Assay Kit and a Caspase-Glo™ 9 Assays Kit, respectively. d Immunoblot analysis of the levels of poly (ADP-ribose) polymerase (PARP), cleaved caspase-9 and β-actin in the lysates of treated and untreated cells after 24 h. The blots are derived from two independent experiments. e Treated and untreated cells were harvested, and the levels of cell death were analyzed by flow cytometry. The ratio of propidium iodide (PI)-positive and/or annexin V-positive cells [(Q1 + Q2 + Q4)/(Q1 + Q2 + Q3 + Q4)] was used to calculate the percentage of dead cells (Additional file 1: Figure S1) (n = 3). f Graphic depiction of the average mitochondrial membrane potential (ΔΨm) of treated and untreated cells (n = 3) at each time point, as measured using a MitoPT™ JC-1 Assay Kit. Values indicate the ratio [Q2/(Q2 + Q4)] of green JC-1 monomers (527 nm emission) to red aggregates (590 nm emission). g Graphic depiction of the levels of cell death among treated and untreated cell populations. Cell death was evaluated by measuring the levels of lactate dehydrogenase (LDH) within culture supernatants (n = 4). Control was treated by the lysis buffer. Data presented in a–c and e–g are expressed as means ± standard deviations (SD). Differences between results were evaluated by two-way ANOVA (a, b, e and f), followed by Dunnett’s test for multiple comparisons in each group and one-way ANOVA (c and g) followed by Dunnett’s test for multiple comparisons. *p < 0.05 compared with the control cell population at incubation time 0 h (no treatment). #p < 0.05 compared with the control cell population at the same time period (group)