Figure 4. Possible role of electrophilic p-quinone in DJ-1 oxidation induced by 6-OHDA.

(A) The determination of p-quinone from 6-OHDA. The formation of p-quinone was monitored at 490 nm in the serum medium (n = 3). (B) Cells were treated with 1 mM H₂O₂ or 600 µM 6-OHDA in the presence or absence of 50 U/ml catalase (CAT) for 20 h and subjected to the MTT assay. *, ** Significantly different from the value of control (n = 3, * p<0.05, ** p<0.01, Tukey, ANOVA). (C) Cell samples obtained from the SH-SY5Y cells treated under indicated conditions for 3 h were separated by 2D-PAGE and subsequently subjected to western blot analysis using the anti-DJ-1 antibody. The ratio of oxidized DJ-1 is shown under each condition (n = 2).