Fig. 3.

DA enhances ROS production and cytotoxicity induced by PQ⁺. EM4 cells with empty vector, Oct3, or DAT expression were treated with 200 μM PQ²⁺ plus 0.5 mM SDT for 20 min. Then the cells were washed and incubated in culture medium with or without 50 μM DA, 50 μM tyramine, or 1 μM GBR12909 (a DAT inhibitor). H₂O₂ (30 μM for 1 h) was used as a positive control for ROS production. After 48 h, cells were assessed for ROS levels using flow cytometry (A). In a parallel set of experiments, cells with empty vector (B) and DAT (C) treated with varying concentrations of PQ²⁺ as described in A were assessed for cell viability using a MTT assay. n = 4 independent experiments in quadruplicate, analyzed by one-way ANOVA followed by the Newman–Keuls post hoc test. ^aP < 0.05 compared with respective EV; ^bP < 0.05 compared with the respective Oct3 groups; *P < 0.05.