Fig. 2. NAC alleviates DNA damage (including telomere deprotection) and partially rescues RPE senescence upon A2E photosensitization by decreasing oxidative stress.

a An MTT assay was performed in RPE cells treated with 25 μM A2E under photosensitization with or without 1 mM NAC. Data are presented as means ± SD; * indicates p value < 0.05, ** indicates p value < 0.01, **** indicates p value < 0.0001. The experiment was performed independently at least three times. b Statistical analysis of the mean fluorescence intensity of DHE by flow cytometry; * indicates p < 0.05, *** indicates p < 0.001 compared to RPE cells treated with 25 μM A2E under photosensitization. The experiment was performed independently at least three times. c Representative images of confocal sections of immunofluorescence assays in RPE cells treated with 1 mM NAC or 25 μM A2E under photosensitization. γ-H2AX foci are labeled red and TRF1 foci are labeled green. d Quantification of the number of γ-H2AX foci per nucleus in RPE cells treated with 1 mM NAC or 25 μM A2E under photosensitization. Data are presented as means ± SD; *** indicates p value < 0.001, **** indicates p < 0.0001. e Quantification of TIFs per nucleus in RPE cells with 1 mM NAC or 25 μM A2E under photosensitization. The data are presented as means ± SD; * indicates p value < 0.05, ** indicates p value < 0.01, **** indicates p < 0.0001. f Representative microscopic images of β-galactosidase staining in RPE cells treated with 25 μM A2E under photosensitization with or without 1 mM NAC. PDL = 15. g Quantification of the percentage of cells with positive SA-β-gal staining shown in e; *** indicates p < 0.001, **** indicates p < 0.0001 compared to control. The experiment was performed independently at least three times