Alison Ziesel

Light-Induced Retinal Degeneration Is Prevented by Zinc, a Component in the Age-related Eye Disease Study Formulation †

Mineral supplements are often included in multivitamin preparations because of their beneficial effects on metabolism. In this study, we used an animal model of light‐induced retinal degeneration to test for photoreceptor cell protection by the essential trace element zinc. Rats were treated with various doses of zinc oxide and then exposed to intense visible light for as long as 8 h. Zinc treatment effectively prevented retinal light damage as determined by rhodopsin and retinal DNA recovery, histology and electrophoretic analysis of DNA damage and oxidized retinal proteins. Zinc oxide was particularly effective when given before light exposure and at doses two‐ to four‐fold higher than recommended by the age‐related eye disease study group. Treated rats exhibited higher serum and retinal pigment epithelial zinc levels and an altered retinal gene expression profile. Using an Ingenuity database, 512 genes with known functional annotations were found to be responsive to zinc supplementation, with 45% of these falling into a network related to cellular growth, proliferation, cell cycle and death. Although these data suggest an integrated and extensive regulatory response, zinc induced changes in gene expression also appear to enhance antioxidative capacity in retina and reduce oxidative damage arising from intense light exposure.

Circadian Effects on Retinal Light Damage

Light-induced retinal damage has long served as a model of retinal dysfunction and visual cell loss arising from inherited disease or caused by oxidative stress. Its utility resides in the fact that nearly the entire complement of retinal photoreceptors is simultaneously involved in a now well-defined progression of cellular degeneration and active cell death. Numerous extrinsic factors are known to influence the extent of visual cell loss, including previous light-rearing history, light intensity and duration, and diet. However, visual cell damage is also impacted by intrinsic factors such as circadian rhythms. These endogenous rhythms are known to affect the cellular machinery involved with light reception and metabolism, receptor function and signaling, and the cascade of apoptotic cell death. Herein we describe the progression of light-induced oxidative damage and visual cell death in retina and how circadian-dependent gene expression affects the process. The time course of retinal gene expression and light damage susceptibility has been compared at various times of the day or night. In addition to genes known to exhibit a circadian profile of regulation, we also describe a number of genes previously not recognized as affecting the progression of visual cell damage and loss.

MultiPriDe: automated batch development of quantitative real-time PCR primers

Quantitative reverse transcriptase polymerase chain reaction (qRT–PCR) is a commonly employed gene expression quantification technique. This requires the development of appropriately targeted oligonucleotide primers, which necessitates the identification of ideal amplicons, development of optimized oligonucleotide sequences under most favorable pre-determined reaction conditions, and management of the resultant target-oligonucleotide pair information for each gene to be studied. The Primer3 utility exists for development of oligonucleotide primers and fills that role effectively. However, the manual process of identifying target sites and individually generating primers is inefficient and prone to user-introduced error, especially when a large number of genes are to be examined. We have developed MultiPriDe (Multiple Primer Design), a Perl utility that accepts batch lists of Gene database identifiers, collects available intron and exon position data critical to qRT–PCR primer development, and supplies these sites as identified targets for the Primer3 utility. This automated ‘gene to primer’ procedure is coupled with a set of optimized hybridization conditions used by the Primer3 utility to maximize successful primer design. MultiPriDe and assembled repeat libraries are available upon request. Please direct requests to aziesel@emory.edu.

Development of Bile Acids as Anti-Apoptotic and Neuroprotective Agents in Treatment of Ocular Disease

The hydrophilic bile acids ursodeoxycholic acid and tauroursodeoxycholic acid are approved by regulatory bodies of many countries for treatment of gallstones and cirrhosis. Delivery is by oral administration and side effects are minimal. This chapter reviews evidence demonstrating that systemic treatment with the two compounds is protective in models of neuronal and retinal degeneration and injury. Variability in the regulation of circulating bile acids suggests a need to explore local delivery as a treatment modality. Our initial experiments testing in vivo intraocular injections and in vitro transscleral permeability indicate that this is feasible and efficacious.