Visual Transduction and Age-Related Changes in Lipofuscin

RóŻanowski, Malgorzata; Rozanowski, Bartosz

doi:10.1007/978-1-59745-374-5_20

Cited by 15 publications

(40 citation statements)

References 175 publications

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“…[1][2][3][4]. RPE lipofuscin, monitored in vivo as fundus autofluorescence, may be associated with retinal degenerative diseases such as Best macular dystrophy, Stargardt disease, and age-related macular degeneration (AMD) (1,4,5).…”

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confidence: 99%

Retinal Pigment Epithelium Lipofuscin Proteomics

Gugiu

Renganathan

et al. 2008

Molecular & Cellular Proteomics

152

136

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Lipofuscin accumulates with age in the retinal pigment epithelium (RPE) in discrete granular organelles and may contribute to age-related macular degeneration. Because previous studies suggest that lipofuscin contains protein that may impact pathogenic mechanisms, we pursued proteomics analysis of lipofuscin. The composition of RPE lipofuscin and its mechanisms of pathogenesis are poorly understood in part because of the heterogeneity of isolated preparations. We purified RPE lipofuscin granules by treatment with proteinase K or SDS and showed by light, confocal, and transmission electron microscopy that the purified granules are free of extragranular material and associated membranes. Crude and purified lipofuscin preparations were quantitatively compared by (i) LC MS/MS proteomics analyses, (ii) immunoanalyses of oxidative protein modifications, (iii) amino acid analysis, (iv) HPLC of bisretinoids, and (v) assaying phototoxicity to RPE cells. From crude lipofuscin preparations 186 proteins were identified, many of which appeared to be modified. In contrast, very little protein (ϳ2% (w/w) by amino acid analysis) and no identifiable protein were found in the purified granules, which retained full phototoxicity to cultured RPE cells. Our analyses showed that granules in purified and crude lipofuscin preparations exhibit no statistically significant differences in diameter or circularity or in the content of the bisretinoids A2E, isoA2E, and all-trans-retinal dimer-phosphatidylethanolamine. The finding that the purified granules contain minimal protein yet retain phototoxic activity suggests that RPE lipofuscin pathogenesis is largely independent of associated protein. The purified granules also exhibited oxidative protein modifications, including nitrotyrosine generated from reactive nitrogen oxide species and carboxyethylpyrrole and iso[4]levuglandin E 2 adducts generated from reactive lipid fragments. This finding is consistent with previous studies demonstrating RPE lipofuscin to be a potent generator of reactive oxygen species and supports the hypothesis that such species, including reactive fragments from lipids and retinoids, contribute to the mechanisms of RPE lipofuscin pathogenesis.

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confidence: 99%

Retinal Pigment Epithelium Lipofuscin Proteomics

Gugiu

Renganathan

et al. 2008

Molecular & Cellular Proteomics

152

136

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“…These effects were exacerbated by exposure to visible light. In all these experiments, the cytotoxic concentrations of AtRal were equivalent to only a small fraction of AtRal which can be released from visual pigments upon photoexcitation (1–3).…”

Section: Discussionmentioning

confidence: 99%

“…All‐ trans ‐retinal (AtRal) is formed in the retina as a result of photoisomerisation of the visual pigment chromophore, 11‐ cis ‐retinylidene followed by its hydrolysis from the protein, opsin (reviewed in 1–3). During exposure to light under conditions where the rate of AtRal release exceeds the rate of its enzymatic removal, AtRal can accumulate in photoreceptor outer segments (POS).…”

Section: Introductionmentioning

confidence: 99%

“…During exposure to light under conditions where the rate of AtRal release exceeds the rate of its enzymatic removal, AtRal can accumulate in photoreceptor outer segments (POS). AtRal is a potent photosensitizer which upon photoexcitation with UVA or blue light in the presence of oxygen leads to formation of singlet oxygen ( 1 O 2 ), highly capable of oxidizing biological molecules such as nucleic acids, proteins and unsaturated lipids (1–3). POS are composed mainly from lipids and proteins, which themselves may become targets of photosensitized damage mediated by AtRal.…”

Section: Introductionmentioning

confidence: 99%

“…POS are in intimate proximity to the retinal pigment epithelium (RPE), a monolayer of cells separating the retina from the choroidal blood supply which is essential for proper function and survival of photoreceptors (4). Experiments in vitro and in vivo have revealed several pathways by which AtRal can be damaging to the RPE in dark (1–3,5–13). Dysfunction of the RPE is followed by dysfunction and ultimately loss of photoreceptors, and, as a consequence, visual loss.…”

Section: Introductionmentioning

confidence: 99%

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Cytotoxicity of All‐Trans‐Retinal Increases Upon Photodegradation^†

Rozanowska

Handzel

Boulton

et al. 2012

Photochem & Photobiology

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All-trans-retinal (AtRal) can accumulate in the retina as a result of excessive exposure to light. The purpose of this study was to compare cytotoxicity of AtRal and photodegraded AtRal (dAtRal) on cultured human retinal pigment epithelial cells in dark and upon exposure to visible light. AtRal was degraded by exposure to visible light. Cytotoxicity was monitored by imaging of cell morphology, propidium iodide staining of cells with permeable plasma membrane and measurements of reductive activity of cells. Generation of singlet oxygen photosensitized by AtRal and dAtRal was monitored by time-resolved measurements of characteristic singlet oxygen phosphorescence. Photodegradation of AtRal resulted in a decrease in absorption of visible light and accumulation of the degradation products with absorption maximum at ~330 nm. Toxicity of dAtRal was concentration-dependent and was greater during irradiation with visible light than in dark. DAtRal was more cytotoxic than AtRal both in dark and during exposure to visible light. Photochemical properties of dAtRal indicate that it may be responsible for the maximum in the action spectra of retinal photodamage recorded in animals. In conclusion, photodegradation products of AtRal may impose a significant threat to the retina and therefore their roles in retinal pathology need to be explored.

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