Figure 2.

Ethanolic extract of propolis (EEP) exacerbated copper-induced neuronal death in P19 neurons. P19 neurons were obtained from the mouse embryonal carcinoma cells in the presence of all-trans retinoic acid (ATRA). Measurements are performed at 24 h from the beginning of treatment with copper and EEP. (a) P19 neurons were incubated with increasing concentrations of EEP (1–100 µg/mL) for 24 h and their viability was assessed by an MTT assay. Both non-toxic and toxic concentrations of EEP augmented neuronal death induced by exposure to 0.5 mM CuSO₄ (b) and 0.75 mM CuSO₄ (c). This effect of EEP on the reduction of the neuronal viability was not evident when oxidative stress was induced by exposure to 1 mM H₂O₂ (d). Data are expressed as means ± SEM from four to six independent experiments performed in quadruplets. ^a P < 0.05; ^b P < 0.01; ^c P < 0.001 and ^d P < 0.0001 one-way ANOVA followed by Dunnett’s multiple comparison test.