Effects of Brimonidine on Retinal Pigment Epithelial Cells and Müller Cells Exposed to Amyloid-Beta 1–42 Peptide In Vitro

Abstract

To evaluate whether brimonidine can prevent cytotoxicity in human retinal pigment epithelial (RPE) and Müller (MIO) cells after exposure to amyloid-beta 1-42 (Aβ42). An in vitro model of geographic atrophy (GA), which is an end-stage complication of age-related macular degeneration (AMD), simulated with the application of Aβ42 in cell culture. RPE and MIO cells were pretreated with brimonidine for 6 hours, then exposed to 10μM Aβ42 for 24 hours. Several concentrations (one time [1×], two times [2×], and five times [5×]) of brimonidine were used to assess for a dose-related effect. Assays were immediately run following the treatment period. 2',7'-Dichlorofluorescein diacetate was used to assess reactive oxygen species production, the MTT assay was used to assess cell viability, and the JC-1 dye assay was used to assess mitochondrial membrane potential. The main outcome measures were reactive oxygen species (ROS) production, cell viability, and mitochondrial membrane potential (ΔΨm) of RPE and MIO cells following the treatment phase. High-dose (5×) brimonidine was capable of reducing ROS production in RPE and MIO cells with exposure to Aβ42. The application of Aβ42 alone did not trigger a rise in ROS production. Brimonidine was unable to rescue cell viability and ΔΨm after exposure to Aβ42 in both cell cultures. Instead, high-dose (5×) brimonidine appeared to increase the toxicity to cell viability and ΔΨm in cultures exposed to Aβ42. However, this was not due to medication toxicity alone, because high-dose (5×) brimonidine without exposure to Aβ42 did not affect the cell viability in both cell types. Brimonidine may have a role in preventing oxidative cellular injury in AMD. However, this role does not appear to translate into protection against some of the cytotoxic effects observed from this in vitro model of GA. In this cellular model of GA, brimonidine is able to reduce oxidative stress but is unable to rescue cell viability or prevent mitochondrial dysfunction. [Ophthalmic Surg Lasers Imaging Retina. 2018;49:S23-S28.].