Methods: A cell premature senescence model was established in both primary RPE cells and ARPE-19 cells by exposure of the cells to pulsed H₂O₂ stress for 5 days, and confirmed with senescence-associated β-galactosidase (SA-β-gal) staining. The final concentration of fullerenol (Fol) in the cell culture system was 5 μg/mL. Cellular redox status was determined by the examination of cellular reactive oxygen species (ROS) staining, catalase activity, and the ratio of reduced to oxidized glutathione, respectively. Deoxyribonucleic acid double-strand breaks were determined by quantitative analysis of γH₂AX. Cell cycle analysis was performed with flow cytometry. SIRT1 activity was examined with SIRT1 Assay Kit. SIRT1 overexpression and knockdown in ARPE-19 cells were performed with lentiviral-mediated infection.
Results: Pulsed H₂O₂ exposure triggered the acetylation of p53 at lysine 382 (K382) and subsequent increase in its target p21(Waf1/Cip1). It also increased the number of accumulated phospho-γH2AX foci and the level of phosphor-ATM in RPE cells. Fullerenol protected the RPE cells, as it reduced the number of positive SA-β-gal-staining cells, alleviated the depletion of cellular antioxidants, and reduced genomic DNA damage. Its mechanism might involve the activation of deacetylase SIRT1, resulting in decreased levels of acetyl-p53 and p21(Waf1/Cip1). The roles of SIRT1 in protecting cells in response to Fol were further confirmed by applications of SIRT1 activator (resveratrol) and inhibitors (nicotinamide and sirtinol), and through SIRT1 overexpression and knockdown.
Conclusions: Fullerenol could rescue RPE cells from oxidative stress-induced senescence through its antioxidation activity and the activation of SIRT1. The protective effect of Fol is useful for the development of new strategies to treat oxidative stress-related retinal diseases like AMD.