The proposed research program endeavors to advance our understanding of the mechanisms by which the lipofuscin that accumulates in retinal pigment epithelial cells (RPE) contributes to disease processes in atrophic macular degeneration, including age-related and juvenile (Stargardt disease and Best vitelliform macular dystrophy) forms. The lipofuscin of RPE cells originates primarily in photoreceptor cells and is generated, in large part, from reactions of all-trans-retinal, which forms when visual pigment absorbs photons of light. To achieve our objectives, we will conduct experiments using cell culture, in vitro assays and mouse models. In light of genetic discoveries linking age-related macular degeneration (AMD) to inflammatory processes, we will investigate photooxidation products of bisretinoid RPE lipofuscin pigments as activators of complement, an element of immune pathways (Aim 1). These studies address four factors posited as being associated with AMD: inflammation, oxidative damage, drusen and RPE lipofuscin. We will also compare known lipofuscin constituents in terms of their propensity for photo-generating reactive forms of oxygen and for photo-induced cleavage (Aim 2). In studies related to Best vitelliform macular dystrophy and other VMD2-associated disorders, we will explore the hypothesis that dysfunctioning of bestrophin-1, the protein product of VMD2, alters intracellular chloride conductances thereby changing pH-dependent rates of photooxidation and equilibria between protonated/conjugated and unprotonated/unconjugated forms of the all-trans-retinal dimer series of RPE lipofuscin pigments. We propose that the shift in equilibrium favors an RPE lipofuscin constituent (unconjugated all-trans-retinal dimer) that is aldehyde-bearing and more photoreactive (Aim 3).
The National Eye Institute has as a 5-year program goal, improved understanding of the molecular and biochemical basis of macular degeneration. AMD affects more than 1.75 million people in the United States. Based on a prevalence of 1/10,000, an additional 30,000 Americans are afflicted with Stargardt disease. Due to the trend toward population aging, the number of cases of AMD could increase to 3 million by 2020. Greater insight into the identities and properties of individual RPE lipofuscin pigments, their adverse behaviors and the factors that influence their formation will facilitate the emergence of novel therapeutic approaches to minimize lipofuscin accumulation and/or neutralize its impact, and thus reduce the incidence and progression of macular degeneration.
|Zhao, Jin; Kim, Hye Jin; Sparrow, Janet R (2017) Multimodal Fundus Imaging of Sodium Iodate-Treated Mice Informs RPE Susceptibility and Origins of Increased Fundus Autofluorescence. Invest Ophthalmol Vis Sci 58:2152-2159|
|Wang, Yong; Kim, Hye Jin; Sparrow, Janet R (2017) Quercetin and cyanidin-3-glucoside protect against photooxidation and photodegradation of A2E in retinal pigment epithelial cells. Exp Eye Res 160:45-55|
|Sparrow, Janet R (2016) Vitamin A-aldehyde adducts: AMD risk and targeted therapeutics. Proc Natl Acad Sci U S A 113:4564-9|
|Ueda, Keiko; Zhao, Jin; Kim, Hye Jin et al. (2016) Photodegradation of retinal bisretinoids in mouse models and implications for macular degeneration. Proc Natl Acad Sci U S A 113:6904-9|
|Zhou, Jilin; Ueda, Keiko; Zhao, Jin et al. (2015) Correlations between Photodegradation of Bisretinoid Constituents of Retina and Dicarbonyl Adduct Deposition. J Biol Chem 290:27215-27|
|Liu, Zhao; Ueda, Keiko; Kim, Hye Jin et al. (2015) Photobleaching and Fluorescence Recovery of RPE Bisretinoids. PLoS One 10:e0138081|
|Liu, Zhenzhen; Qin, Tingyu; Zhou, Jilin et al. (2014) Impairment of the ubiquitin-proteasome pathway in RPE alters the expression of inflammation related genes. Adv Exp Med Biol 801:237-50|
|Sparrow, Janet R; Zhou, Jilin; Ghosh, Shanti Kaligotla et al. (2014) Bisretinoid degradation and the ubiquitin-proteasome system. Adv Exp Med Biol 801:593-600|
|Flynn, Erin; Ueda, Keiko; Auran, Emily et al. (2014) Fundus autofluorescence and photoreceptor cell rosettes in mouse models. Invest Ophthalmol Vis Sci 55:5643-52|
|Sparrow, Janet R; Duncker, Tobias (2014) Fundus Autofluorescence and RPE Lipofuscin in Age-Related Macular Degeneration. J Clin Med 3:1302-21|
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