Retinal protective effect of curcumin metabolite hexahydrocurcumin against blue light-induced RPE damage.

BACKGROUND: Age-related macular degeneration (AMD) is a disease of retinal pigment epithelium (RPE) cells. We have previously demonstrated that blue light can damage RPE cells and their underlying mechanisms. We found that hexahydrocurcumin (HHC), a metabolite of curcumin, had better retinal protection than curcumin. However, the involved mechanisms remain unclear. METHODS: By exposing ARPE-19 human RPE cells and mouse primary RPE cells to blue light, the intracellular mechanisms of HHC in cells were investigated, including the proliferation of RPE cells and the effects of HHC on activating intracellular protective mechanisms and related factors. Next-generation sequencing (NGS) RNA sequencing revealed the underlying mechanisms involved in the induction and regulation of HHC treatment following blue light exposure. RESULTS: HHC promoted autophagy by enhancing autophagic flux, reduced oxidative stress and endoplasmic reticulum (ER) stress, and effectively reversed blue light-induced cell death. RNA sequencing-based bioinformatics approaches comprehensively analyze HHC-mediated cellular processes. CONCLUSION: Our findings elucidate the mechanisms of HHC against blue light damage in RPE cells and are beneficial for the development of natural metabolite-based preventive drugs or functional foods.

The Role of Oxidative Stress and Autophagy in Blue-Light-Induced Damage to the Retinal Pigment Epithelium in Zebrafish In Vitro and In Vivo.

Age-related macular degeneration (AMD) is the progressive degeneration of the retinal pigment epithelium (RPE), retina, and choriocapillaris among elderly individuals and is the leading cause of blindness worldwide. Thus, a better understanding of the underlying mechanisms in retinal tissue activated by blue light exposure is important for developing novel treatment and intervention strategies. In this study, blue-light-emitting diodes with a wavelength of 440 nm were applied to RPE cells at a dose of 3.7 ± 0.75 mW/cm2 for 24 h. ARPE-19 cells were used to investigate the underlying mechanism induced by blue light exposure. A trypan blue exclusion assay was used for the cell viability determination. Flow cytometry was used for apoptosis rate detection and autophagy analysis. An immunofluorescence microscopy analysis was used to investigate cellular oxidative stress and DNA damage using DCFDA fluorescence staining and an anti-γH2AX antibody. Blue light exposure of zebrafish larvae was established to investigate the effect on retinal tissue development in vivo. To further demonstrate the comprehensive effect of blue light on ARPE-19 cells, next-generation sequencing (NGS) was performed for an ingenuity pathway analysis (IPA) to reveal additional related mechanisms. The results showed that blue light exposure caused a decrease in cell proliferation and an increase in apoptosis in ARPE-19 cells in a time-dependent manner. Oxidative stress increased during the early stage of 2 h of exposure and activated DNA damage in ARPE-19 cells after 8 h. Furthermore, autophagy was activated in response to blue light exposure at 24-48 h. The zebrafish larvae model showed the unfavorable effect of blue light in prohibiting retinal tissue development. The RNA-Seq results confirmed that blue light induced cell death and participated in tissue growth inhibition and maturation. The current study reveals the mechanisms by which blue light induces cell death in a time-dependent manner. Moreover, both the in vivo and NGS data uncovered blue light's effect on retinal tissue development, suggesting that exposing children to blue light could be relatively dangerous. These results could benefit the development of preventive strategies utilizing herbal medicine-based treatments for eye diseases or degeneration in the future.