The Role of Calcium in Light-Induced Photoreceptor Apoptosis

dc.contributor.advisorCollier, Robert
dc.contributor.committeeMemberAgarwal, Neeraj
dc.contributor.committeeMemberWordinger, Robert J.
dc.creatorKrueger, Darrel Scott
dc.description.abstractKrueger, Darrel Scott, The Role of Calcium in Light-Induced Photoreceptor Cell Apoptosis. Doctor of Philosophy (Biomedical Sciences), May, 2002; 305 pp., 15 tables, 31 illustrations, bibliography, 421 titles. Retinal degenerative diseases such as retinitis pigmentosa (RP) and age-related macular degeneration (AMD) result in loss of photoreceptors by apoptosis. Photo-oxidative stress accelerates the rate of photoreceptor apoptosis in models of retinal dystrophies. Thus, a better understanding of light-induced apoptosis is important for developing preventative and treatment options for persons with these blinding diseases. The goals of this dissertation were to investigate the effect of photo-oxidative stress on [Ca2+]I in rat photoreceptor cells and determine whether cell death could be prevented by altering cells’ abilities to manage [Ca2+]i. Thirty minutes of light exposure resulted in significant elevation of [Ca2+]i, determined using Fura-2 ratiometric imaging, which increased with additional light exposure. At 120 minutes, the F340/380 ratio was 3-times the beginning baseline ratio. Using multiple techniques indicative of early and late phases of apoptosis, changes consistent with apoptosis were observed, including early labeling (30 Min) with Annexin-V, activation of caspase-3 (2IIr), TUNEL labeling and Propidium Iodidc staining. TUNEL and Propidium labeling were more intense at 3Hrs light exposure, reflecting late phase changes. Apoptosis was confirmed using electron microscopy (TEM). TEM showed mitochondrial swelling, indicative of permeabilization, prior to chromatin condensation. Pharmacological agents were utilized to mediate participation of cellular calcium sources or storage sites in the maintenance of intracellular calcium homeostasis during photo-oxidative stress. Agents were separately added to the media prior to light exposure and their effects on cell viability were assessed using the Formazan assay. Mitochondria were confirmed to be the site of action affected by elevated [Ca2+]I, since prevention of calcium uptake by ruthenium red (1-100-μM) provided significant protection of cell viability in a dose-related manner. The 100- μM concentration resulted in complete maintenance of viability. BAPTA-AM also demonstrated some protection (50%) indicating that reduction of [Ca2+]I independent of source is beneficial is maintaining cell viability. Identification of mitochondrial uptake and cytosolic buffering of calcium as key viability determinants in light-induced apoptosis is a significant discovery for targeting future research for preventing or inhibiting photoreceptor cell apoptosis associated with retinal dystrophies such as RP and AMD.
dc.subjectCell and Developmental Biology
dc.subjectCell Biology
dc.subjectComparative and Laboratory Animal Medicine
dc.subjectEye Diseases
dc.subjectLife Sciences
dc.subjectMedical Cell Biology
dc.subjectMedical Immunology
dc.subjectMedical Sciences
dc.subjectMedicine and Health Sciences
dc.subjectOther Cell and Developmental Biology
dc.subjectSense Organs
dc.subjectVision Science
dc.subjectlight-induced photoreceptor cell apoptosis
dc.subjectretinal degenerative disease
dc.subjectphoto-oxidative stress
dc.subjectretinal dystrophy
dc.subjectelectron microscopy
dc.subjectcell death
dc.titleThe Role of Calcium in Light-Induced Photoreceptor Apoptosis
dc.type.materialtext School of Biomedical Sciences Sciences of North Texas Health Science Center at Fort Worth of Philosophy


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