The synergistic effects of resveratrol and nicotinamide on cell proliferation, apoptosis, and SIRT1 gene expression in human retinal pigment epithelial cells.

The aim of our study is to evaluate the effects of Resveratrol and Nicotinamide on cell proliferation, viability, apoptosis and SIRT1 gene expression in human retinal pigment epithelial cells (RPE), with relevance to age-related macular degeneration (AMD). Healthy RPE cells were exposed to moderate oxidative stress, then treated with resveratrol (50-100-150 μmol/L) and nicotinamide (1-5-10 mM/L), both separately and in combination, for 24, 48, and 72 h. Morphological changes and cell density were examined using inverted microscopy to complement functional data. The most significant results were achieved with 72 h of combined treatment with 100 μmol/L resveratrol and 1 mM/L nicotinamide, showing increased cell viability and proliferation (p < 0.001), decreased apoptosis+necrosis values (p < 0.001), and elevated SIRT1 expression (p < 0.001). This combination was non-cytotoxic to healthy RPE cells (p > 0.05) and more effective than separate treatments. The combined application caused SIRT1 gene expression levels similar to healthy controls (p > 0.05). To confirm functional dependency on SIRT1, targeted gene silencing was performed using SIRT1 siRNA. Compared to the negative control group, SIRT1 silencing resulted in a 25.58-fold downregulation of SIRT1 mRNA, accompanied by a 5.28-fold upregulation of pro-apoptotic Bax and a 3.91-fold downregulation of anti-apoptotic Bcl-2 (p < 0.001), effectively reversing the cytoprotective effects of the co-treatment. These findings demonstrate that RV+NAM co-treatment exerts robust synergistic protection against oxidative stress-induced apoptosis in RPE cells through SIRT1-dependent mechanism, offering a promising therapeutic strategy for dry AMD. This is the first study to investigate the effects of this specific dose combination in a dry AMD model.