PM2.5 exposure induces the oxidative stress response and affects the activation of the Nrf2 pathway in human melanocytes. PIG1 or PIG3V cells were exposed to (0-200 µg/ml) PM2.5 for 24 h, and MDA contents, SOD and GSH-Px levels were measured using specific respective MDA, SOD and GSH-Px assay kits. The Nrf2 pathway related-protein expressions were determined by western blotting. PM2.5 exposure suppressed the activities of SOD and GSH-Px, while enhancing MDA contents in both (A) PIG1 and (B) PIG3V cells. PM2.5 exposure activated the Nrf2 pathway in (C) PIG1 cells, while only a high concentration (200 µg/ml) of PM2.5 exposure could significantly promote the expression of Nrf2(N) and HO-1 in (D) PIG3V cells. Data are presented as the mean ± SD. n=6. *P<0.05, **P<0.01 vs. respective 0 µg/ml PM2.5. PM2.5, particulate matter 2.5; MDA, malondialdehyde; GSH-Px, glutathione peroxidase; SOD, superoxide dismutase; Nrf2, nuclear factor erythroid 2-related factor 2; HO-1, heme oxygenase-1; N, nuclear; T, total.