Nrf2 signaling and oxidative stress in age-related macular degeneration

Johns Hopkins University, Baltimore MD

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Abstract

DESCRIPTION (provided by applicant): Age-related macular degeneration (AMD) is the leading cause of blindness among the elderly, yet patients with early disease are without therapy. To address this shortcoming, this proposal focuses on early disease. Two key events in early AMD are retinal pigment epithelial cell (RPE) dysfunction and drusen biogenesis. Inadequately neutralized reactive oxygen species (ROS) and dysregulated innate immunity interact together to play a pivotal role. Central to oxidative homeostasis, especially in mitochondria, is the Nrf2 transcription factor, which controls the most comprehensive antioxidant response system. Nrf2 signaling can become impaired with aging and/or smoking. The objective of this proposal to define how Nrf2 protects against RPE mitochondrial dysfunction and unregulated innate immunity. The hypothesis to be tested is that that impaired Nrf2 signaling induces mitochondrial and RPE dysfunction that results in an oxidative, inflammatory, and pathologic microenvironment. The proposed specific aims are: 1. Determine the extent that impaired Nrf2 signaling leads to un-neutralized mitochondrial ROS and RPE dysfunction with cigarette smoke exposure. Our hypothesis is that impaired Nrf2 signaling in the RPE from aging and chronic smoking reduces mitochondrial antioxidant defense resulting in inadequately neutralized ROS and RPE dysfunction. 2. Determine the extent that impaired Nrf2 signaling decreases mitophagy, and results in RPE dysfunction with cigarette smoke exposure. Our hypothesis is that impaired Nrf2 signaling in the RPE from aging and chronic smoking decreases mitophagy, cumulatively increasing the number of dysfunctional mitochondria and inadequately neutralized ROS, resulting in RPE dysfunction. 3. Determine the extent that impaired Nrf2 signaling disrupts regulation of innate immunity. Based on our work showing C3a and IL-1b generation by CS and Nrf2 deficiency, our hypothesis is that impaired Nrf2 signaling magnifies oxidative stress, which activates the inflammasome to promote a pro-inflammatory microenvironment with accumulation of macrophages with impaired function. These contributions are significant because they will establish Nrf2 as a treatment target for early AMD. The research is innovative since it will investigate understudied (decreased Nrf2 signaling on mitochondrial antioxidants and mitophagy), unresolved (inflammasome and macrophage function) and unique (the synergy of ROS and innate immunity) factors on RPE and macrophage function using unique, state-of-the- art genetic mice with fresh, but decisive factors that have not been previously tested. Macrophages will be studied from a new perspective that defines both phenotype and function since both are influenced by their surroundings. Our discovery of reduced Nrf2 with aging and CS, which generates C3a and IL-1b, a key substrate of the inflammasome, and the proposed studies, which will link complement with the inflammasome, macrophage function, and an AMD phenotype, is highly innovative. Targeted therapy that reinvigorates Nrf2 to maintain oxidative homeostasis and protective innate immunity is expected to result from this work.