2011 — 2015 |
Malek, Goldis |
R01Activity Code Description: To support a discrete, specified, circumscribed project to be performed by the named investigator(s) in an area representing his or her specific interest and competencies. |
Lipid Activated Nuclear Receptors in Age-Related Macular Degeneration
DESCRIPTION (provided by applicant): The cellular and molecular pathways of sub-retinal pigment epithelial (sub-RPE) deposit formation, the hallmark of the early 'dry' form of age-related macular degeneration (AMD), and the leading cause of vision loss in the elderly, are not known. Epidemiology studies have identified age, n-6 polyunsaturated fatty acid (PUFA) dietary intake and oxidant injury as risks for AMD. Further, studies from several laboratories, including our own, suggest that pathways regulating lipid and cholesterol processing and secretion play a pivotal role in deposit formation. However, the link between dietary intake of PUFAs and signaling pathways that promote production of deposits formation is not known. Our goal therefore is to identify the pathogenic mechanisms by which lipids, including PUFAs, regulate deposit formation. Peroxisome proliferator activating receptors (PPARs) are nuclear receptors that act as lipid sensors. Of the three isoforms, PPAR¿/d mediates the regulatory effects of dietary fatty acids, including n-6 PUFAs, on gene expression and stimulates the proliferation of peroxisomes, organelles involved in fatty acid oxidation. PPAR transcriptional activity is coupled with upregulation of molecules associated with cholesterol and lipid efflux, altered extracellular matrix (ECM) synthesis, and mitochondrial dysfunction; these families of molecules are also associated with deposit formation. With this in mind, we asked a corollary question: does dietary lipid activation of the PPAR¿/d signaling pathway in RPE cells stimulate deposit formation? In our preliminary studies, we found that exposure of RPE cell cultures to native and oxidized derivatives of n-6 PUFAs resulted in profound cellular changes in the expression of molecules associated with and regulating deposit formation. The changes included (1) increased synthesis and secretion of ECM molecule collagen IV; (2) increased expression of cholesterol and lipid efflux regulatory genes ABCA1 and CD36; (3) accumulation of damaged mitochondria and reactive oxygen species; (4) activation of PPAR ¿/d; and (5) upregulation of PPAR¿/d specific target genes regulating ECM molecules, and lipid secretion. Based on this preliminary data, we hypothesize that dietary n-6 fatty acids stimulate production of molecules found in deposits through activation of PPAR¿/d and increased proliferation of peroxisomes. Accumulation of deposits requires lipid and cholesterol secretion by the RPE and dysregulated synthesis of ECM molecules by the RPE, leads to trapping of lipids. We further propose that additional 'stressors' on the PPAR¿/d pathway (i.e., age, oxidants) lead to upregulation of these processes and further compromise RPE cell function, mediated by mitochondrial dysfunction. To test this hypothesis we will use a combination of cell culture assays with human RPE cells and mouse models of deposits to investigate the role of PPARs in deposit formation. We will also investigate if decreasing activity of PPAR¿/d can slow the progression of AMD in murine models of deposit formation.
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0.97 |
2016 — 2020 |
Malek, Goldis |
P30Activity Code Description: To support shared resources and facilities for categorical research by a number of investigators from different disciplines who provide a multidisciplinary approach to a joint research effort or from the same discipline who focus on a common research problem. The core grant is integrated with the center's component projects or program projects, though funded independently from them. This support, by providing more accessible resources, is expected to assure a greater productivity than from the separate projects and program projects. |
Animal Models Core
Animal Models Module Abstract The objective of the Animal Models Module is to enhance the capabilities of individual investigators to conduct cutting edge research in the vision sciences, which involves generation and characterization of animal models of disease. Our Aims are: 1) to provide resources, support and training required for conducting animal studies at the level exceeding the capabilities of any individual laboratory; 2) to promote collegiality across the community of vision scientists through sharing resources, techniques and expertise; and 3) to engage colleagues into conducting vision research, including support of the next generation of basic and clinician scientists. To achieve these Aims, this Module will support sophisticated facilities equipped with state-of-the- art instrumentation, including surgical equipment and instrumentation for morphological and functional analyses of animal eyes. The Module will be supervised and operated by highly experienced personnel, with expertise in conducting a broad array of animal studies and deep understanding of associated regulatory conditions. These shared resources will open new research possibilities for both experienced and novice users, and will serve as a platform for fostering interactions among a broad swath of our research community.
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0.97 |
2018 — 2021 |
Malek, Goldis |
R01Activity Code Description: To support a discrete, specified, circumscribed project to be performed by the named investigator(s) in an area representing his or her specific interest and competencies. |
Novel Signaling Pathways Regulated by the Liver X Receptor in Age-Related Macular Degeneration
SUMMARY Age-related macular degeneration (AMD) is the leading cause of vision loss in the Western World. The fundamental abnormalities occurring in retinal pigment epithelial (RPE) cells leading to their progressive dysfunction and eventually atrophy in AMD are not known. Multiple epidemiological, biochemical, and histological studies highlight the role of altered cholesterol metabolism in the pathogenesis of AMD. The liver x receptor is an important regulator of reverse cholesterol transport. Beyond this established function it has also been shown to regulate inflammation, cell metabolism and apoptosis. We have recently found that aged LXR knockout mice develop cardinal features of dry AMD including accumulation of cholesterol and neutral lipids within Bruch's membrane and development of significant sub-RPE deposits. Herein we propose to investigate the role of two modulators of LXR in RPE biology and pathogenesis of AMD.
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0.97 |
2018 — 2021 |
Malek, Goldis |
R01Activity Code Description: To support a discrete, specified, circumscribed project to be performed by the named investigator(s) in an area representing his or her specific interest and competencies. |
Regulation of Inflammation and Lipid Homeostasis by the Aryl Hydrocarbon Receptor in Age-Related Macular Degeneration
Project Summary: Dry age-related macular degeneration (AMD) is the leading cause of vision loss in the Western World with a complex etiology. The fundamental abnormalities occurring in retinal pigment epithelial (RPE) cells, resulting in their progressive dysfunction and subsequent atrophy in AMD, are still not known. However, candidate pathogenic pathways linked to development of disease have emerged from the convergence of a sundry of epidemiological, genetic, morphological, and biochemical studies. Of these mechanistic pathways, three are strongly associated with initiation and progression of AMD and include inflammation, lipid dysregulation, and impaired protein degradation and clearance. Currently there are no drugs available to treat dry AMD. The aryl hydrocarbon receptor (AhR) is a ligand-dependent transcription factor activated by a diverse array of endogenous and environmental compounds including toxins and lipids. It has been studied extensively in the context of its role as a regulator of the cellular response to environmental toxicants. However, recent reports highlight non-classical mechanisms of AhR, most notably regulation of inflammatory pathways, cholesterol homeostasis, and autophagy/lysosomal function and permeability, pathways also important in the pathogenesis of AMD. Importantly, mechanisms regulated by AhR have been shown to be ligand and cell/tissue specific (e.g. toxic or pro-inflammatory response in one cell type yet anti-inflammatory in another cell type). As such, we are interested in investigating mechanisms underlying the AhR-mediated signal transduction pathway in RPE cells and the consequence of AhR activation on RPE health to counter injury and dysfunction. Our preliminary studies show that the activity of the AhR decreases as a function of age in human RPE cells. Additionally we have observed that aged AhR knockout (AhR-/-) mice develop phenotypic features of dry AMD, including thick continuous sub- RPE deposits, RPE dysfunction and degeneration, and accumulation of sub-retinal immune cells. Our findings not only support the potential importance of this signaling pathway in the pathogenesis of AMD, but also suggest an age-related compromise in AhR-mechanisms associated with normal RPE cellular clearance. Three specific aims have been proposed to test our hypothesis that the AhR represents a therapeutic target for prevention and treatment of AMD by simultaneously regulating aberrant cholesterol homeostasis and pro-inflammatory pathways in cells vulnerable in AMD.
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0.97 |
2021 |
Malek, Goldis |
P30Activity Code Description: To support shared resources and facilities for categorical research by a number of investigators from different disciplines who provide a multidisciplinary approach to a joint research effort or from the same discipline who focus on a common research problem. The core grant is integrated with the center's component projects or program projects, though funded independently from them. This support, by providing more accessible resources, is expected to assure a greater productivity than from the separate projects and program projects. |
Animal Models Module
Animal Models Module Abstract The objective of the Animal Models Module is to enhance the capabilities of individual investigators to conduct cutting edge research in the vision sciences, which involves studying normal function of the visual system and generation and characterization of animal models of disease. Our Aims are: 1) to provide resources, support and training required for conducting animal studies at the level exceeding the capabilities of any individual laboratory; 2) to promote collegiality across the community of vision scientists through sharing resources, techniques and expertise; and 3) to engage colleagues into conducting vision research, including support of the next generation of basic and clinician scientists. To achieve these Aims, this Module will support sophisticated facilities equipped with state-of-the-art instrumentation, including surgical equipment and instrumentation for morphological, functional and behavioral analyses of animal eyes and visual performance. The Module is supervised and operated by highly experienced personnel, with expertise in conducting a broad array of animal studies and deep understanding of associated regulatory conditions. These shared resources will open new research possibilities for both experienced and novice users, and will serve as a platform for fostering interactions among a broad swath of our research community.
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0.97 |
2021 |
Malek, Goldis |
R01Activity Code Description: To support a discrete, specified, circumscribed project to be performed by the named investigator(s) in an area representing his or her specific interest and competencies. |
Nuclear Receptor Driven Mechanisms in Aging and Amd
Summary Dry age-related macular degeneration (AMD) is the leading cause of vision loss in the Western World with a complex etiology. The fundamental abnormalities occurring in retinal pigment epithelial (RPE) cells, resulting in their progressive dysfunction and subsequent atrophy in AMD, are still not known. However, candidate pathogenic pathways linked to development of disease have emerged from the convergence of a sundry of epidemiological, genetic, morphological, and biochemical studies, including inflammation, lipid dysregulation, apoptosis, and RPE barrier dysfunction among others. Currently there are no drugs available to treat dry AMD. However, targeting a potential master regulator of these pathways is one avenue to pursue. Our overarching goal is to discover molecular mechanisms by which nuclear receptors modulate pathologies characteristic of AMD. In this proposal we concentrate on investigating the biology and function of NURR1 (NR4A1, Nuclear Receptor Related-1 protein), an orphan nuclear receptor, in cells vulnerable in AMD. Studies of the central nervous system as well as some systemic diseases have revealed NURR1 as a regulator of a variety of biological processes including cellular proliferation, differentiation, apoptosis, inflammation, lipid homeostasis and metabolism, highlighting its importance in overall cell health. However, as a nuclear receptor, its role has also been shown to vary and be ligand and cell/tissue specific. Given the overlap between process regulated by NURR1 and those important in the development and progression of AMD, we propose to systematically investigate NURR1?s role and potential for therapeutic targeting in ocular cells including RPE, as this has yet to be discovered. Herein we build on preliminary observations including (1) NURR1 expression in human RPE cells decreases with age; (2) NURR1 accumulates extracellularly in drusen and basal deposits of human AMD donor tissue; (3) NURR1 activation attenuates TNFa-induced RPE epithelial-to-mesenchymal (EMT) transition in vitro; and (4) oral administration of a NURR1 activating ligand ameliorates visual function deficits in a mouse model featuring several dry AMD phenotypes. Our findings collectively support an age-related compromise in NURR1- mechanisms in RPE cellular homeostasis. Based on our preliminary data we propose three specific aims to test the hypothesis that NURR1 represents a therapeutic target for AMD by simultaneously regulating aberrant RPE barrier function, cellular lipid metabolism, and inflammation, in cells vulnerable in AMD.
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0.97 |