Increased oxidative stress accompanied by activation of the Nrf2 pathway in PARK2 iPSC-derived neurons. (A) GSH levels were significantly reduced in PARK2 (PA1, 9 and 22, and PB2, 18 and 20) iPSC-derived neurospheres compared with those in control A (YA9) and B (WD39) neurospheres. (B, C) DCF fluorescence intensity in PARK2 (PA1, 9 and 22, and PB2 and 20) iPSC-derived neurons was significantly higher than that in control A (B7) and B (WD39) neurons. (D, E) Immunoblot analysis of Nrf2 and NQO1 levels in iPSC-derived neurons from PA and PB. Expression of Nrf2 and NQO1 in PARK2 (PA9 and PB2) iPSC-derived neurons was significantly higher than that in control A (YA9) and B (WD39) neurons. Relative protein abundance was normalized to β-actin. ** indicates P < 0.01 (Mann–Whitney U-test). Data represent the mean and SEM of at least three experiments for each group.