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Published on: March 27, 2017
Effects of Brimonidine on Retinal Pigment Epithelial Cells and Müller Cells Exposed to Amyloid-Beta 1-42 Peptide In
Background And Objective:
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).
Materials And Methods:
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.
Results:
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.
Conclusion:
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.].
Insights
Brimonidine reduced oxidative stress in retinal cells exposed to amyloid-beta 1-42, but did not prevent cell death or mitochondrial dysfunction in this geographic atrophy model. Further research is needed to explore its potential role in age-related macular degeneration.
Area of Science:
- Ophthalmology
- Cell Biology
- Neuroscience
Background:
- Geographic atrophy (GA) is an advanced stage of age-related macular degeneration (AMD).
- Amyloid-beta 1-42 (Aβ42) is implicated in the pathogenesis of AMD and GA.
- Human retinal pigment epithelial (RPE) and Müller (MIO) cells are crucial for retinal health and are affected in AMD.
Purpose of the Study:
- To investigate the potential of brimonidine in preventing Aβ42-induced cytotoxicity in RPE and MIO cells.
- To evaluate the dose-dependent effects of brimonidine on cellular responses to Aβ42.
- To assess brimonidine's impact on oxidative stress, cell viability, and mitochondrial function.
Main Methods:
- An in vitro model of GA was established using RPE and MIO cells exposed to Aβ42.
- Cells were pretreated with varying concentrations of brimonidine before Aβ42 exposure.
- Assays measured reactive oxygen species (ROS) production, cell viability (MTT assay), and mitochondrial membrane potential (JC-1 dye assay).
Main Results:
- High-dose brimonidine (5×) significantly reduced ROS production in cells exposed to Aβ42.
- Aβ42 alone did not increase ROS production in this experimental setup.
- Brimonidine failed to improve cell viability or mitochondrial membrane potential, and high doses exacerbated toxicity.
Conclusions:
- Brimonidine demonstrates an ability to mitigate oxidative stress in RPE and MIO cells challenged with Aβ42.
- However, brimonidine does not confer protection against the cytotoxic effects or mitochondrial dysfunction induced by Aβ42 in this GA model.
- The findings suggest that while brimonidine may impact oxidative pathways, it does not translate to a therapeutic benefit for Aβ42-mediated cellular damage in AMD.
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