S-allyl cysteine protects retinal pigment epithelium cells from hydroquinone-induced apoptosis through mitigating cellular response to oxidative stress.

Abstract

Retinal pigment epithelium (RPE) degenerative death is an evident hallmark of advanced age-related macular degeneration (AMD). The present study aims to evaluate the protective effects of S-allyl L-cysteine (SAC), a bioactive component from aged garlic extracts, on the oxidative stress-related apoptosis of RPE cells and to investigate the potential underlying mechanisms. Cell Counting Kit-8 (CCK-8) assay, flow cytometry, and terminal deoxynucleotidyl transferase-mediated dUTP-biotin nick end labeling (TUNEL) staining were performed to evaluate the effects of SAC on the hydroquinone-treated human ARPE19 cells. The Reactive Oxygen Species (ROS) production was measured by virtue of flow cytometry or determined under an inverted fluorescence microscope. Furthermore, the expression of antioxidant factor Nrf2, as well as downstream antioxidant genes, including NQO1, SOD1, SOD2, and HO1 was assessed in hydroquinone stimulated ARPE19 cells, in the presence or absence of SAC pretreatment. Hydroquinone incitement contributed to a marked decrease in cell viability, but enhanced cell apoptosis, whereas SAC addition did not cause significant alterations. When cells were pre-treated with SAC, cell proliferation was dramatically enhanced whereas apoptosis was mitigated, and the ROS generation induced by hydroquinone was also significantly suppressed, indicating a prominent function of SAC in preventing ARPE19 cells from oxidant-related apoptosis. The elevated expression levels of Nrf2 and other antioxidant genes driven by hydroquinone were downregulated by SAC addition. These data suggest that SAC can effectively attenuate hydroquinone-induced oxidative damage in human RPE cells. Our work is the first to demonstrate that SAC modulates oxidative stress-induced RPE apoptosis, thereby potentially proving new insights into the treatment of AMD.