Effects of hemin, SnPPIX and DPI on MPP+-induced NOX2, NRF2 and HO-1 levels in PC12 cells. The groups are C: Control; M: MPP+ (500 μM); M+H: MPP+ (500 μM) plus hemin (20 μM); MHS: MPP+ (500 μM) plus hemin (20 μM) and SnPPIX (10 μM); MD: MPP+ (500 μM) plus DPI (1 μM). (A). The protein expression of NOX2, NRF2 and HO-1 was determined by western blot analysis; (B). NOX2 and HO-1 mRNA levels were determined by quantitative real-time PCR; (C).