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Author: Gulpreet Kaur Publisher: ISBN: Category : Languages : en Pages : 87
Book Description
The retinal pigment epithelium (RPE) performs many functions that are indispensable for vision, such as recycling vitamin A for the visual cycle, and participating in the daily renewal of photoreceptors. Over time, vitamin A metabolites, called lipofuscin, accumulate within RPE lysosomes and are thought to compromise RPE and photoreceptor health and promote inflammation. The RPE is also an initial site of insult in blinding diseases such as age-related macular degeneration. Accumulation of lipofuscin is a feature of inherited macular degenerations and could also contribute to age-related macular degeneration (AMD); however, the mechanisms behind this are still under study. We have previously established that RPE with vitamin A metabolites have increased ceramide and defects in autophagic and endo-lysosomal pathways. In this study, we have investigated two consequences of ceramide accumulation: 1) increased biogenesis of early endosomes, due to ceramide-induced negative curvature and inward budding; and 2) altered organelle traffic due to ceramide-induced accumulation of acetylated microtubules. First, we have identified the mechanism by which ceramide accumulation in RPE with vitamin A metabolites leads to enlarged early endosomes. These swollen endosomes internalize and cleave the complement protein, C3, into its active component, C3a. The acid sphingomyelinase inhibitor, desipramine reduces ceramide levels in RPE with vitamin A metabolites, corrects early endosome defects, and prevents complement activation. Second, we have previously noted that RPE with vitamin A metabolites have defective autophagosome trafficking and autophagic flux. In this study, we investigated the role of histone deacetylase 6 (HDAC6), a tubulin deacetylator, in autophagy. We established that HDAC6 inhibition results in accumulation of acetylated microtubules and reduced autophagic flux and trafficking. It remains to be determined if acetylated microtubule accumulation in RPE with vitamin A metabolites is dependent on HDAC6 activity. Our approach is to study healthy and stressed RPE at a cellular and molecular level, using techniques such as high-speed live imaging of polarized primary RPE cultures and mouse models of inherited macular degeneration, such as the Abca4-/- model of Stargardt disease. Our studies have investigated the role of organelle morphology and dynamics in maintenance of RPE health.
Author: Gulpreet Kaur Publisher: ISBN: Category : Languages : en Pages : 87
Book Description
The retinal pigment epithelium (RPE) performs many functions that are indispensable for vision, such as recycling vitamin A for the visual cycle, and participating in the daily renewal of photoreceptors. Over time, vitamin A metabolites, called lipofuscin, accumulate within RPE lysosomes and are thought to compromise RPE and photoreceptor health and promote inflammation. The RPE is also an initial site of insult in blinding diseases such as age-related macular degeneration. Accumulation of lipofuscin is a feature of inherited macular degenerations and could also contribute to age-related macular degeneration (AMD); however, the mechanisms behind this are still under study. We have previously established that RPE with vitamin A metabolites have increased ceramide and defects in autophagic and endo-lysosomal pathways. In this study, we have investigated two consequences of ceramide accumulation: 1) increased biogenesis of early endosomes, due to ceramide-induced negative curvature and inward budding; and 2) altered organelle traffic due to ceramide-induced accumulation of acetylated microtubules. First, we have identified the mechanism by which ceramide accumulation in RPE with vitamin A metabolites leads to enlarged early endosomes. These swollen endosomes internalize and cleave the complement protein, C3, into its active component, C3a. The acid sphingomyelinase inhibitor, desipramine reduces ceramide levels in RPE with vitamin A metabolites, corrects early endosome defects, and prevents complement activation. Second, we have previously noted that RPE with vitamin A metabolites have defective autophagosome trafficking and autophagic flux. In this study, we investigated the role of histone deacetylase 6 (HDAC6), a tubulin deacetylator, in autophagy. We established that HDAC6 inhibition results in accumulation of acetylated microtubules and reduced autophagic flux and trafficking. It remains to be determined if acetylated microtubule accumulation in RPE with vitamin A metabolites is dependent on HDAC6 activity. Our approach is to study healthy and stressed RPE at a cellular and molecular level, using techniques such as high-speed live imaging of polarized primary RPE cultures and mouse models of inherited macular degeneration, such as the Abca4-/- model of Stargardt disease. Our studies have investigated the role of organelle morphology and dynamics in maintenance of RPE health.
Author: Li Xuan Tan Publisher: ISBN: Category : Languages : en Pages : 0
Book Description
The retinal pigment epithelium (RPE) is a key site of damage in macular degeneration, which causes irreversible blindness in 30-50 million people globally. Our work aims to elucidate disease mechanisms and identify promising therapeutic targets. Using live-cell imaging, biochemical approaches and a mouse model of disease, this thesis examined the role of organelle trafficking in autophagy and complement regulation, two pathways implicated in macular degeneration. Autophagy is a major cellular clearance pathway essential for maintaining homeostasis in post-mitotic tissues such as the RPE. However, little is known regarding how autophagy is regulated in the RPE. Here, we showed that pathological accumulation of vitamin A metabolites in macular degeneration traps cholesterol in the RPE and inhibits both autophagosome biogenesis and autophagic clearance. Mechanistically, we determined that cholesterol activates acid sphingomyelinase (ASMase), causing increased generation of ceramide. This in turn promotes aberrant stabilization of microtubules and constraints autophagosome trafficking, preventing effective clearance of autophagic substrates. The work in this thesis also establishes a central role for organelle trafficking in regulating protective mechanisms against the abnormal activation of the complement system, which has been implicated in macular degeneration. These novel protective mechanisms in the RPE include accelerated recycling of the complement regulatory protein CD59 to the cell surface, and lysosome exocytosis-mediated membrane repair. Both protective mechanisms are impaired in diseased RPE due to alteration in organelle trafficking, leading to mitochondrial damage and oxidative stress upon exposure to complement. A key RPE function indispensable for vision is the phagocytosis and degradation of photoreceptor outer segments. The thesis characterized sequential interactions of outer segment phagosomes with autophagic machinery as the phagosomes traffic from the cell surface into the RPE. Moreover, outer segment phagocytosis activates transcription factor EB (TFEB), which regulates a vast arsenal of autophagy and lysosomal genes. Thus, the RPE may employ autophagy machineries for efficient clearance of phagocytosed outer segments. Altogether, these studies highlight the importance of organelle trafficking in RPE health and function. Importantly, this research revealed that removing excess cholesterol or inhibiting ASMase using FDA-approved drugs corrects organelle trafficking, thereby restoring autophagy and complement regulation in models of macular degeneration.
Author: Michelle Marie Giarmarco Publisher: ISBN: Category : Languages : en Pages : 104
Book Description
The eye is a complex organ with many tissue and cell types working together to facilitate vision. Photoreceptor cells in the retina initiate vision, converting light into a neuronal signal that is integrated and used to form an image in the brain. These polarized cells have high energy demands that fluctuate with light exposure, and they employ a unique metabolic program to balance energy production and essential anabolic pathways. Neighboring retinal pigment epithelial (RPE) cells and Müller glia cells support photoreceptors with complementary and distinct metabolic programs of their own. Breakdown of these metabolic relationships, and consequent photoreceptor death, is thought to underlie many types of inherited and age-related retinal disease. We studied metabolic and mitochondrial adaptations in RPE and photoreceptor cells. Using a combination of animal imaging studies and cultured RPE cells, we demonstrated that RPE cells are capable of transporting large amounts of glucose for uptake by the retina. Photoreceptors extract energy from the glucose by converting it to lactate, then they release lactate from the cell. Additionally, we showed that RPE cells can use lactate to fuel energy production in their mitochondria, which reduces their use of glucose destined for the retina. These findings in the context of recent literature point to distinct metabolic schemes in the RPE and retina. RPE cells have active mitochondria capable of making energy from a wide range of fuels and don’t always need to oxidize glucose. Photoreceptors rely heavily on glucose for both immediate energy production and anabolism, but little is known about how these processes are affected by light or subsequently Ca2+. We performed imaging experiments with transgenic zebrafish expressing a fluorescent Ca2+ indicator in cones to explore the effects of Ca2+ uptake into cone mitochondria. We found that cytosolic Ca2+ in cones is separated into two distinct pools on either side of a large dense cluster of mitochondria. In addition to being a potential physical barrier to diffusion of free Ca2+, we found that cone mitochondria take up Ca2+ and that this uptake is required to keep the cytosolic pools separate. Ca2+ uptake into mitochondria occurs through a uniporter, and could have far-reaching effects on metabolism and other processes necessary for photoreceptor function. Collectively this work highlights some of the mitochondrial adaptations RPE and photoreceptors might employ in a healthy retina. Additionally, a live tissue slice preparation was developed for fluorescent imaging experiments with retinas of zebrafish and mice. This adaptable tool can help answer future questions about metabolism, mitochondrial dynamics, and signaling in the retina.
Author: Martin Zinkernagel Publisher: Springer ISBN: 3030228789 Category : Medical Languages : en Pages : 121
Book Description
This book focuses on the emerging non-invasive imaging technique of Fluorescence Lifetime Imaging Ophthalmoscopy (FLIO). FLIO reveals unique information on retinal diseases, ranging from age-related macular degeneration and vascular diseases to hereditary retinal dystrophies. Fluorescence lifetimes enable the evaluation of disease progression before irreversible structural changes occur. The image acquisition is suitable for diagnostic purposes and follow-up examinations to investigate the natural course of disease, and to monitor the effects of possible therapies. This book fills the gap between available literature and gives state-of-the-art guidance on the principles of the FLIO technique, image acquisition, and data analysis. Written by a team of expert leaders within this field, this book will be relevant for scientists and clinicians with an interest in ophthalmoscopy.
Author: Nikolai V. Gorbunov Publisher: Elsevier ISBN: 0128227567 Category : Science Languages : en Pages : 208
Book Description
Tissue Barriers in Disease, Injury and Regeneration focuses on the molecular and cellular fundamentals of homeostatic and defense responses of tissue barriers, covering the damaging impacts and exposure to pathogens and engineered nanomaterials. Sections emphasize the role of mesenchymal stoma, vascular, epithelial, telocyte, myofibroblast, lymphoid and reticuloendothelial cells, along with reactions that bridge the effects of ambient factors, medical treatments, drag delivery systems with alterations in barrier integrity, tissue/organ functions, and metabolic status. Other sections cover the role of progenitor cells of different origins in the remodeling and regeneration of tissue stroma, vasculature of blood-tissue barriers, and more. - Includes special emphasis on the role of mesenchymal stoma, vascular, epithelial, telocyte, myofibroblast, lymphoid and reticuloendothelial cells in the development of reactions that bridge the effects of ambient factors, medical treatments, drag delivery systems with alterations in barrier integrity, tissue/organ functions, and in metabolic status - Examines the role of progenitor cells of different origins in the remodeling and regeneration of tissue stroma, the vasculature of blood-tissue barriers, and mucosa and external epithelium
Author: Joel Rothman Publisher: Academic Press ISBN: 0123946204 Category : Medical Languages : en Pages : 475
Book Description
The second part of an updated edition of the classic Methods in Cell Biology, Volume 48, this book emphasizes diverse methods and technologies needed to investigate C. elegans, both as an integrated organism and as a model system for research inquiries in cell, developmental, and molecular biology, as well as in genetics and pharmacology. By directing its audience to tried-and-true and cutting-edge recipes for research, this comprehensive collection is intended to guide investigators of C. elegans for years to come. Diverse, up-to-date techniques covered will be useful to the broadening community of C. elegans researchers for years to come Chapters written by leaders in the field Tried and true methods deliver busy researchers a one-stop compendium of essential protocols
Author: Michael F. Marmor Publisher: Oxford University Press, USA ISBN: 9780195109566 Category : Medical Languages : en Pages : 0
Book Description
The retinal pigment epithelium is a critical tissue within the eye. It lies directly behind the retina, where it provides metabolic support to the photoreceptors and controls their local environment. As a result, the RPE is vital to retinal function, but also a site of aging and disease that cause dysfunction and visual loss. This book brings together comprehensive reviews of basic and clinical science concerning the RPE. It is organized to juxtapose chapters on RPE disease with chapters on the underlying pathophysiology. These include up-to-date accounts of growth factors, laser effects, proliferative vitreoretinopathy, Bruch's membrane pathology, as well as new diagnostic tools such as ocular coherence tomography, in vivo imaging of lipofuscin and non-photic electrical responses. Other chapters cover pharmacology and toxicology, mechanisms of retinal adhesion and detachment, RPE pigments and transport, congenital and dystrophic diseases, animal models of RPE disease, and different aspects of age-related macular degeneration. The history and evolutionary aspects of the RPE are also presented. The contributing authors are experienced clinicians and eminent basic scientists who work on this critical part of the eye. The book will be a valuable resource for anyone interested in the eye, and a necessity for specialists in the fields of retinal physiology and retinal disease.
Author: Alexa Karina Klettner Publisher: Springer Nature ISBN: 3030283844 Category : Medical Languages : en Pages : 351
Book Description
This book provides a contemporary resource on one of the major players in retinal diseases – the Retinal Pigment Epithelium (RPE). Throughout the book, the physiological and the pathological function of the RPE are covered on equal terms, to help readers to understand the RPE as a whole. Moreover, the development of RPE in diagnostics and therapy are covered, as well as some practical knowledge about RPE experimental models. Retinal Pigment Epithelium in Health and Disease highlights new findings of RPE research and includes the state-of-the-art knowledge of each RPE topic presented. This important feature sets this book apart from other publications, with the chapters following a design which leads from the general to the specific, to give a precise collection of the facts known. The chapters are written by well-known experts that are currently active in the field as consultants, basic scientists, and group leaders, providing expert guidance on the current aspects and future outlooks of this topic.
Author: Giuseppe Prota Publisher: Academic Press ISBN: 0323139396 Category : Science Languages : en Pages : 305
Book Description
This volume covers all aspects of melanin pigmentation, providing a concise, comprehensive picture of new knowledge gained at the frontiers of research. It draws heavily on the author's 30-year activity in the field and his continuing work with specialists of widely diverse disciplines. The core of the volume deals with the structure, physicochemical properties, and biosynthesis of the major classes of melanin pigments, including neuromelanins. Further discussions include the biology of the various types of pigment-producing cells, the structure and mode of action of tyrosinase, and the chemistry of urinary melanogens and their biomedical applications as metabolic markers of melanocyte activity, especially for the follow-up of malignant melanoma. Finally, the volume considers progress in the photobiology and photochemistry of melanins, with special emphasis on the controversial role of these pigments in skin photoprotection. Melanins and Melanogenesis is ideally suited as a basic guide for newcomers, and a handy source of specific information for practitioners in academic, medical, and industrial settings.
Author: Gulpreet Kaur
Author: Gulpreet Kaur
Author: Li Xuan Tan
Author: Michelle Marie Giarmarco
Author: Martin Zinkernagel
Author: Nikolai V. Gorbunov
Author: Joel Rothman
Author: Keith M. Zinn
Author: Michael F. Marmor
Author: Alexa Karina Klettner
Author: Giuseppe Prota