Purchase this article with an account.
Gurugirijha Rathnasamy, Li Xuan Tan, Aparna Lakkaraju; Live-cell imaging of mitochondrial dynamics in the retinal pigment epithelium. Invest. Ophthalmol. Vis. Sci. 2018;59(9):4028.
Download citation file:
© ARVO (1962-2015); The Authors (2016-present)
The retinal pigment epithelium (RPE) performs numerous functions to support and nourish photoreceptors, and ensure healthy vision. These functions place high demands on the mitochondria of post-mitotic RPE. Recent work from our lab has shown that the mitochondrial network in the RPE is very robust and can withstand stressors such as lipofuscin accumulation and complement attack. However, mitochondrial defects and mitochondrial DNA mutations are seen in patients with blinding diseases like age-related macular degeneration (AMD) suggesting that over time, RPE mitochondria become vulnerable to environmental insults. How this occurs is yet unclear. Here, we investigated mitochondrial dynamics in live RPE monolayers and examined the role of the antioxidant transcription factor nuclear factor erythroid 2–related factor 2 (Nrf2) in maintaining the integrity of the RPE mitochondrial network.
Primary RPE monolayers were transduced with BacMAM mito-RFP; RPE flatmounts from wild-type and Abca4-/- mice were labeled with MitoTracker. Spinning disk microscopy was used for live imaging of mitochondrial dynamics. Nrf2 was depleted from RPE using shRNA and efficiency of knockdown was monitored by immunoblotting.
Live-cell imaging revealed highly interconnected mitochondrial networks in healthy RPE. In Abca4-/- mice and in RPE with vitamin A metabolites did not alter mitochondrial integrity, but, affected mitochondrial motility. Oxidative stress in the presence of A2E or loss of antioxidant transcription factor nuclear factor erythroid 2–related factor 2 (Nrf2), a key regulator of mitochondrial health in the RPE, resulted in mitochondrial fragmentation.
These data suggest that vitamin A metabolites modulate RPE mitochondrial dynamics and thereby the health of mitochondria. Additional studies are underway to see how mitochondrial distribution in the RPE and mitophagy, a process by which cells remove damaged mitochondria, are affected by vitamin A metabolites and by Nrf2 depletion. Our studies support the hypothesis that impaired mitochondrial dynamics in the context of age-related accumulation of visual cycle metabolites could cause chronic stress on RPE mitochondria and thus contribute to AMD.
This is an abstract that was submitted for the 2018 ARVO Annual Meeting, held in Honolulu, Hawaii, April 29 - May 3, 2018.
This PDF is available to Subscribers Only