Melatonin and 17β-estradiol during cobalt chloride hypoxic stress-induced in human pigment epithelial cells and Muller glial cells in vitro

Purpose: Melatonin can protect against oxidative damage and ischemia-induced cell death. 17β-Estradiol (E2) has neuroprotective effects, and its receptors are expressed in the retina. The protective effects of melatonin and E2 against hypoxic stress induced by cobalt chloride (CoCl 2 ) were investigated using human retinal cell lines. Materials and Methods: Human retinal pigment epithelial cells (ARPE-19) and Müller glial cells (MIO-M1) were pretreated for 6 h with either melatonin (200, 400, and 800 µM) or E2 (20, 40, and 80 µM) and then stressed for 48 h with CoCl 2 . Cultures were analyzed for cell metabolism (MTT assay), reactive oxygen species (ROS/H2DCFDA assay), and mitochondrial membrane potential (MMP/JC-1 assay). Results: Melatonin pretreatment significantly increased (i) the cell metabolism in ARPE-19 cells (400 µM, P = 0.0352; 800 µM, P = 0.0016) and MIO-M1 cells (200 µM, P = 0.0341; 400 µM, P = 0.0009) and (ii) mitochondrial membrane potential in ARPE-19 (400 µM, P = 0.0131; 800 µM, P = 0.0096) and also the MIO-M1 cells (800 µM, P = 0.0082) after CoCl 2 hypoxic stress. Pretreatment with E2 improved cell metabolism in ARPE-19 cells (20 µM, P = 0.0076). MIO-M1 cells showed improved metabolism at all E2 concentrations studied and higher mitochondrial membrane potential with E2 40 µM pretreatment ( P = 0.0152). ROS levels were not improved with melatonin or E2 pretreatments. Conclusions: In response to CoCl 2 -induced hypoxic stress, pretreatment with melatonin and E2 can significantly improve the cellular metabolism and mitochondrial membrane potential in human RPE and Müller glial cell lines. Translational Relevance: Our study investigates the protective effects of melatonin and 17β-estradiol against ischemic stress in vitro with the overall goal to improve cellular homeostasis and decrease retinal degeneration.