Figure 1: Inhibition of melanin synthesis reduces intracellular ROS in melanocytes. (a) Human melanocytes (MC) were either untreated (−) or treated (+) with 200 μM PTU (Sigma) for 14 days (left panel). Fibroblasts (FB) were isolated from the same donors. Endogenous ROS were detected by the addition of 20 μM DCFDA (Invitrogen) and measured as previously described . Error bars represent S.E.M. of triplicate determinations, and results are representative of two experiments performed. (two-sided test). ns, not significant. (b) PTU treatment of melanocytes transfected with either a control scrambled (Scr) siRNA sequence, or siRNA specific for p16, decreases melanin content (upper panel). Error bars represent S.E.M. of ROS determinations made from three separate donors (middle panel). , (paired two-sided test). ns, not significant. Representative Western blot showing p16 levels in siRNAi-transfected cells (lower panel).