Fig. 1

Dopamine, tyramine or DAquinone leads to cell death. A, B Bar graphs show cell death after 24 h, as quantified by trypan blue or propidium iodide (PI) positive cells. SH-SY5Y cells are treated with different concentrations of dopamine (DA). N-acetyl cysteine (NAC)/mitoTEMPO/pargyline are administered 30 min before DA treatment. *P ≤ 0.05, **P ≤ 0.01, ***P ≤ 0.001, ****P ≤ 0.0001 when compared to control group. #P ≤ 0.05, ###P ≤ 0.001, ####P ≤ 0.0001 when compared to the 300 µM DA treated group. C Cell death is measured in SH-SY5Y cells, as mentioned in A, after 24 h of tyramine (Tyr) treatment. **P ≤ 0.01 when compared to control group. D Monoamine oxidase A is overexpressed in SH-SY5Y cells and tyramine (Tyr) in mentioned concentration is treated for 24 h. Bar graphs represent cell as in A. ***P ≤ 0.001, ****P ≤ 0.0001 as compared to control. E SH-SY5Y cells are treated with tyramine (Tyr) for 48 h. NAC or mitoTEMPO is treated 30 min before Tyr treatment. Cell death is measured as mentioned above. **P ≤ 0.01, ***P ≤ 0.001 when compared to control group. #P ≤ 0.05 when compared to the 1000 µM Tyr treated group. F Cells are treated with DA (300 µM) and Tyrosinase (co: co treated) for 24 h. Alternately DA and Tyrosinase is incubated beforehand (pre: pre-incubation) and then administered to the cells. In the relevant groups mitoTEMPO is administered 30 min before the treatment. Cell death is measured as mentioned in A. ****P ≤ 0.0001 when compared to control group., ^##P ≤ 0.01, ^###P ≤ 0.0001 when compared to the respective 300 µM DA + Tyrosinase treated group. Bar graphs represent mean ± SEM. N = at least 3 for each group. P values are calculated by one way ANOVA followed by Tukey’s/Dunnett’s multiple comparison test, when compared between mean of each group or mean of control group, respectively