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- Nilsson, Sven Erik, 1931-, et al.
(författare)
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Aging of cultured retinal pigment epithelial cells : oxidative reactions,lipofuscin formation and blue light damage
- 2003
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Ingår i: Documenta Ophthalmologica. - 0012-4486 .- 1573-2622. ; 106:1, s. 13-16
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Tidskriftsartikel (refereegranskat)abstract
- This report reviews our experimental work on cultured retinal pigment epithelial (RPE) cells, fed native or UV-irradiated photoreceptor outer segments (POS). We showed that significantly more lipofuscin (LF) was formed in cells cultured in 40% oxygen than in cells cultured in 8% oxygen, indicating an involvement of oxidative mechanisms in LF formation. The antioxidants -tocopherol, lycopene, zeaxanthin and lutein significantly reduced LF formation. RPE cells high in melanin content exhibited significantly less formation of LF than cells low in or devoid of melanin, suggesting that melanin acts as an effective antioxidant. The phagocytic capacity of LF-loaded RPE cells was significantly reduced compared to that of unloaded control cells, indicating that LF-loaded RPE cells may be unable to serve the photoreceptors sufficiently regarding phagocytosis of shed outer segment tips. Blue light irradiation destabilized lysosomal membranes in LF-loaded RPE cells and significantly reduced the viability of such cells compared to unloaded, irradiated control cells. These results may be of significance in relation to the development of age-related macular degeneration (AMD).
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| 3. |
- Baird, Sarah K, et al.
(författare)
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Metallothionein protects against oxidative stress-induced lysosomal destabilization
- 2006
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Ingår i: Biochemical Journal. - 0264-6021 .- 1470-8728. ; 394:1, s. 275-283
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Tidskriftsartikel (refereegranskat)abstract
- The introduction of apo-ferritin or the iron chelator DFO (desferrioxamine) conjugated to starch into the lysosomal compartment protects cells against oxidative stress, lysosomal rupture and ensuing apoptosis/necrosis by binding intralysosomal redox-active iron, thus preventing Fenton-type reactions and ensuing peroxidation of lysosomal membranes. Because up-regulation of MTs (metallothioneins) also generates enhanced cellular resistance to oxidative stress, including X-irradiation, and MTs were found to be capable of iron binding in an acidic and reducing lysosomal-like environment, we propose that these proteins might similarly stabilize lysosomes following autophagocytotic delivery to the lysosomal compartment. Here, we report that Zn-mediated MT up-regulation, assayed by Western blotting and immunocytochemistry, results in lysosomal stabilization and decreased apoptosis following oxidative stress, similar to the protection afforded by fluid-phase endocytosis of apo-ferritin or DFO. In contrast, the endocytotic uptake of an iron phosphate complex destabilized lysosomes against oxidative stress, but this was suppressed in cells with up-regulated MT. It is suggested that the resistance against oxidative stress, known to occur in MT-rich cells, may be a consequence of autophagic turnover of MT, resulting in reduced iron-catalysed intralysosomal peroxidative reactions. © 2006 Biochemical Society.
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| 5. |
- Brunk, Ulf, 1937-, et al.
(författare)
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Commentary: Peroxide hormesis? A commentary on "Hydrogen peroxide inhibits caspase-dependent apoptosis by inactivating procaspase-9 in an iron-dependent manner" : Refers to: Alexandra Barbouti, Christos Amorgianiotis, Evangelos Kolettas, Panagiotis Kanavaros, Dimitrios Galaris Hydrogen peroxide inhibits caspase-dependent apoptosis by inactivating procaspase-9 in an iron-dependent mannerFree Radical Biology and Medicine, Volume 43, Issue 10, 15 November 2007, Pages 1377-1387
- 2007
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Ingår i: Free Radical Biology and Medicine. - : Elsevier. - 0891-5849. ; 43:10, s. 1372-1373
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Tidskriftsartikel (övrigt vetenskapligt/konstnärligt)
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| 6. |
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| 7. |
- Brunk, Ulf, 1937-, et al.
(författare)
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Lipofuscin : Mechanisms of age-related accumulation and influence on cell function
- 2002
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Ingår i: Free Radical Biology & Medicine. - 0891-5849 .- 1873-4596. ; 33:5, s. 611-619
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Tidskriftsartikel (refereegranskat)abstract
- The accumulation of lipofuscin within postmitotic cells is a recognized hallmark of aging occuring with a rate inversely related to longevity. Lipofuscin is an intralysosomal, polymeric substance, primarily composed of cross-linked protein residues, formed due to iron-catalyzed oxidative processes. Because it is undegradable and cannot be removed via exocytosis, lipofuscin accumulation in postmitotic cells is inevitable, whereas proliferative cells efficiently dilute it during division. The rate of lipofuscin formation can be experimentally manipulated. In cell culture models, oxidative stress (e.g., exposure to 40% ambient oxygen or low molecular weight iron) promotes lipofuscin accumulation, whereas growth at 8% oxygen and treatment with antioxidants or iron-chelators diminish it. Lipofuscin is a fluorochrome and may sensitize lysosomes to visible light, a process potentially important for the pathogenesis of age-related macular degeneration. Lipofuscin-associated iron sensitizes lysosomes to oxidative stress, jeopardizing lysosomal stability and causing apoptosis due to release of lysosomal contents. Lipofuscin accumulation may also diminish autophagocytotic capacity by acting as a sink for newly produced lysosomal enzymes and, therefore, interfere with recycling of cellular components. Lipofuscin, thus, may be much more directly related to cellular degeneration at old age than was hitherto believed.
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| 10. |
- Brunk, Ulf, 1937-, et al.
(författare)
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The mitochondrial-lysosomal axis theory of aging : Accumulation of damaged mitochondria as a result of imperfect autophagocytosis
- 2002
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Ingår i: European Journal of Biochemistry. - : Wiley. - 0014-2956 .- 1432-1033. ; 269:8, s. 1996-2002
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Tidskriftsartikel (refereegranskat)abstract
- Cellular manifestations of aging are most pronounced in postmitotic cells, such as neurons and cardiac myocytes. Alterations of these cells, which are responsible for essential functions of brain and heart, are particularly important contributors to the overall aging process. Mitochondria and lysosomes of postmitotic cells suffer the most remarkable age-related alterations of all cellular organelles. Many mitochondria undergo enlargement and structural disorganization, while lysosomes, which are normally responsible for mitochondrial turnover, gradually accumulate an undegradable, polymeric, autofluorescent material called lipofuscin, or age pigment. We believe that these changes occur not only due to continuous oxidative stress (causing oxidation of mitochondrial constituents and autophagocytosed material), but also because of the inherent inability of cells to completely remove oxidatively damaged structures (biological 'garbage'). A possible factor limiting the effectiveness of mitochondial turnover is the enlargement of mitochondria which may reflect their impaired fission. Non-autophagocytosed mitochondria undergo further oxidative damage, resulting in decreasing energy production and increasing generation of reactive oxygen species. Damaged, enlarged and functionally disabled mitochondria gradually displace normal ones, which cannot replicate indefinitely because of limited cell volume. Although lipofuscin-loaded lysosomes continue to receive newly synthesized lysosomal enzymes, the pigment is undegradable. Therefore, advanced lipofuscin accumulation may greatly diminish lysosomal degradative capacity by preventing lysosomal enzymes from targeting to functional autophagosomes, further limiting mitochondrial recycling. This interrelated mitochondrial and lysosomal damage irreversibly leads to functional decay and death of postmitotic cells.
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