Melatonin antagonizes oxidative stress-induced mitochondrial dysfunction in retinal pigmented epithelium cells via melatonin receptor 1 (MT1)

Abstract

High energy-consumption in retinal pigmented epithelium (RPE) cells poses oxidative stress (OS) and contributes to mitochondrial dysfunction (MD) for retinal degeneration-associated diseases. In the present study, we evaluated the protective role of Melatonin, a natural antioxidant, against the hydrogen peroxide (H₂O₂)-induced damage to RPE cells. The cellular viability, apoptosis, the expression of apoptosis-associated proteins and mitochondrial function were examined in the retinal ARPE-19 cells, post the treatment with H₂O₂ or (and) with Melatonin. The regulation by Melatonin receptor 1 (MT1) on the Melatonin-mediated protection was also examined via MT1 knockdown with siRNA. Results demonstrated that Melatonin significantly ameliorated cell viability reduction, reduced apoptosis and downregulated the apoptosis-associated proteins in H₂O₂-treated ARPE-19 cells. The H₂O₂-induced mitochondrial dysfunction was also significantly blocked by the Melatonin treatment, presenting as a reduced accumulation of reactive oxygen species (ROS) and mitochondrial superoxide and an ameliorated reduction of mitochondrial membrane potential (MMP). In addition, the knockdown of MT1 with MT1-specific siRNA inhibited the Melatonin-mediated protection against OS damage in ARPE-19 cells. In summary, we confirmed the protective role of Melatonin against H₂O₂-induced mitochondrial dysfunction in RPE cells. MT1 knockdown blocked such protective role of Melatonin. It is implied that Melatonin exerts a protective role against oxidative stress via Melatonin-MT1 signaling in RPE cells.