Retinitis pigmentosa (RP) is a group of intractable blindness disorders that affects 1.5 million individuals worldwide. RP is characterized by a stereotypical pattern of photoreceptor death whereby rod apoptosis precedes a secondary loss of cones. Importantly, generation of therapies for RP is complicated by the fact that mutations in over 60 genes can yield the disease. However, current evidence suggests that a common pathway, regardless of the inciting mutation, leads to cone death and thus represents a potential therapeutic target. Though preservation of rods would be ideal, it is the detection of light by cones that produces the high acuity, color vision that drives the most important aspects of human behavior. Therefore, the long-term goal of this research is to characterize the cone death pathway in order to uncover gene therapy approaches to specifically enhance cone viability in all forms of RP. The current literature suggests that oxidative stress, inflammation and activation of microglia occur as a result of rod death and exacerbate photoreceptor cell injury in murine RP. Importantly, indirect evidence of these processes has been detected in the eyes of human RP patients. My central hypothesis portends that blockade of oxidative stress, inflammation, and microglial activation will preserve cone viability and vision in RP. This hypothesis will be tested through two specific aims: 1) Perform preclinical studies of rAAV vectors delivering either antioxidant or anti-inflammatory cDNAs in mouse models of autosomal dominant RP (adRP). 2) Characterize microglial and macrophage activation in mouse models of adRP.
In aim 1, utilizing two mouse models of RP, I will test the efficacy of two rAAV vectors that either a) enhance the signaling of an antioxidant transcription factor known as nuclear factor erythroid 2-related factor 2 (Nrf2), or b) simultaneously block the activity of two inflammatory signaling molecules, the Nlrp3 inflammasome and Nuclear Factor kappa B (NF?B). Expounding on preliminary studies, aim 2 will characterize the evolving phenotype of microglia and macrophage, either M1 (neuroinflammatory) or M2 (neuroprotective), in the retina as photoreceptors die during RP pathogenesis. Additionally, the M1 phenotype of microglia contributes to other central nervous system (CNS) disorders, such as stroke and Alzheimer?s disease. Thus, to better understand the protective effects of the vectors employed in specific aim 1, their ability to block the M1 phenotype will be explored both in vitro and in vivo. The research proposed in this application is significant because it would produce important information that will facilitate the generation of successful therapies that preserve cones in human patients affected by RP. Furthermore, the gene therapy approaches tested here are innovative because they deviate significantly from the current status quo of RP treatment, which involves nutritional supplementation, and would only require a single dose for the lifetime of the patient. Finally, since the retina is nervous tissue, results derived from the proposed research could be extended to other CNS diseases with an oxidative, inflammatory, or microglial component, such as seen in spinal cord injury and Parkinson?s disease.
/ Public Health Relevance Statement Retinitis pigmentosa (RP) is an incurable and progressive form of inherited blindness where the cells in the eye that detect light die. Many gene mutations can cause RP, therefore therapies need to be formulated that work for all genetic forms of the disease so that the estimated 1.5 million individuals affected world-wide could potentially maintain vision in to old age. Therefore, the goal of the proposed research is to test gene therapy strategies that we believe will preserve vision and to characterize the events in the eye that lead to central blindness in RP.
| Massengill, Michael T; Ahmed, Chulbul M; Lewin, Alfred S et al. (2018) Neuroinflammation in Retinitis Pigmentosa, Diabetic Retinopathy, and Age-Related Macular Degeneration: A Minireview. Adv Exp Med Biol 1074:185-191 |
