FIGURE 3.

Oxidative stress impairs proteasome activity in RPE. ARPE-19 cells were cultured in serum-, pyruvate-, and phenol red-free DMEM in the presence of different concentrations of H₂O₂ for 1 h (panel A) or in the presence of different concentrations of paraquat for 1 h (panel B). Alternatively, ARPE-19 cells were treated with blue light, A2E, or A2E plus blue light as indicated under “Experimental Procedures” (panel C). Proteasome activity was determined using a fluorogenic peptide as a substrate as described under “Experimental Procedures.” The results are the mean ± S.D. of three independent experiments. p < 0.01 as compared with the control group.