Senescent cells have been demonstrated to have lower cellular NAD+ levels and are involved in the development of various age-related diseases, including
age-related macular degeneration (AMD).
Sodium iodate (
NaIO3) has been primarily used as an
oxidant to establish a model of dry AMD. Results of previous studies have showed that
NaIO3 induced
retinal tissue senescence in vivo. However, the role of
NaIO3 and the mechanism by which it induces retinal pigment epithelium (RPE) senescence remains unknown. In this study, RPE cell senescence was confirmed to be potentially induced by
NaIO3. The results showed that the number of senescence-associated-β-
galactosidase (SA-β-gal-)-positive cells and the
protein levels of p16 and p21 increased after
NaIO3 treatment. Additionally, the senescent RPE cells underwent oxidative stress and NAD+ depletion. Furthermore, significant DNA damage and
mitochondrial dysfunction were also detected in senescent RPE cells. The
antioxidant N-acetylcysteine (NAC) could alleviate cellular senescence only by a minimal degree, whereas supplementation with
nicotinamide mononucleotide (NMN) strongly ameliorated RPE senescence through the alleviation of DNA damage and the maintenance of mitochondrial function. The protective effects of NMN were demonstrated to rely on undisturbed
Sirt1 signaling. Moreover, both the expression of senescence markers of RPE and subretinal inflammatory cell infiltration were decreased by NMN treatment in vivo. Our results indicate that RPE senescence induced by
NaIO3 acquired several key features of AMD. More importantly, NMN may potentially be used to treat RPE senescence and senescence-associated pre-AMD changes by restoring the NAD+ levels in cells and tissues.