| 1. |
- 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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| 2. |
- Sundelin, Staffan, et al.
(författare)
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Lipofuscin accumulation in cultured retinal pigment epithelial cells reduces their phagocytic capacity
- 1998
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Ingår i: Current Eye Research. - : Informa UK Limited. - 0271-3683 .- 1460-2202. ; 17:8, s. 851-857
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Tidskriftsartikel (refereegranskat)abstract
- Purpose. Retinal pigment epithelial (RPE) cells slowly accumulate lipofuscin pigment within their acidic vacuolar apparatus as a result of extra- and/or intralysosomal oxidative alterations of phagocytosed photoreceptor outer segments (POS) with consequent imperfect degradation of these structures. In old age, lipofuscin accumulation may become quite substantial. It has been suggested that pronounced accumulation of lipofuscin is related to decreased RPE function and, possibly, to age-related macular degeneration. The aim of the present investigation was to study whether heavy loading with lipofuscin of RPE acidic lysosomes would affect the further phagocytic ability of the cells.Methods. In the first section of the investigation, cultures of rabbit RPE cells were exposed daily to bovine UV-irradiated POS (artificial lipofuscin) for 4 weeks, resulting in a pronounced lipofuscin accumulation of the cells. Fluorescent latex beads (labelled with a red fluorophore) were added to unloaded control cultures at 0 and 4 weeks after their establishment, and to lipofuscin loaded cells after 4 weeks of feeding with artificial lipofuscin. Cellular amounts of lipofuscin, and their phagocytotic activity, were quantified by static fluorometry measuring lipofuscin-specific and red bead-specific fluorescence, respectively. The intracellular location of the beads was verified by confocal laser scanning microscopy.Results. Unloaded, and thus almost lipofuscin-free, control cells exposed to latex beads showed numerous cytoplasmic particles emitting reddish fluorescence, while few particles were taken up by cells initially loaded with artificial, POS-derived, lipofuscin. Measurement of the latex bead-specific fluorescence showed significantly (p < 0.001) higher levels in unloaded control cells than in lipofuscin-loaded ones.In the second part of the investigation, unloaded control cultures and lipofuscin-loaded cultures were exposed to native bovine Texas Red-X-labelled POS 4 weeks after the establishment of the cultures. Unloaded control cells showed a large number of cytopiasmic POS emitting reddish fluorescence, while fewer POS were phagocytosed by cells loaded with artificial lipofuscin. Measurement of the Texas Red-X-specific fluorescence, thus quantifying the phagocytic ability of the cells, showed significantly (p < 0.001) higher levels in control cells than in lipofuscin-loaded ones.Conclusions. Severe lipofuscin accumulation of RPE cells appears to result in a greatly decreased phagocytic capacity. The resulting reduction in ability to cope with the needs of the overlying photoreceptor cells, in order to eliminate the obsolete tips of their POS, may well be of significance in the development of age-related macular degeneration.
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| 3. |
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| 4. |
- Autelli, Riccardo, et al.
(författare)
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Divergent pathways for TNF and C₂-ceramide toxicity in HTC hematoma cells
- 2009
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Ingår i: Biochimica et Biophysica Acta. - : Elsevier. - 0006-3002 .- 1878-2434. ; 1793, s. 1182-1190
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Tidskriftsartikel (refereegranskat)abstract
- We previously showed that, in the rat hepatoma cell line HTC, TNF brings about a non-caspase-dependent, apoptosis-like process requiring NADPH oxidase activity, an iron-mediated pro-oxidant status, and a functional acidic vacuolar compartment. This process may thus involve mechanisms such as autophagy or relocation of lysosomal enzymes, perhaps secondary to the formation of ceramide by acidic sphingomyelinase. Here we investigated whether ceramide formation contributes to the apoptogenic process. HTC cells were found to be sensitive to exogenous ceramide and significantly protected against TNF by desipramine, an inhibitor of lysosomal acid sphingomyelinase. However, Bcl-2 transfection and Bcl-x(L) upregulation by dexamethasone significantly diminished the apoptogenic effect of ceramide but not that of TNF, suggesting that ceramide is not directly involved in TNF toxicity. Moreover, Bcl-x(L) silencing precluded dexamethasone-induced protection against ceramide and, by itself, induced massive death, demonstrating the strict dependence of HTC cells on Bcl-x(L) for survival also under standard culture conditions.
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| 5. |
- 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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| 6. |
- Berndt, Carsten, et al.
(författare)
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Ascorbate and endocytosed Motexafin gadolinium induce lysosomal rupture.
- 2011
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Ingår i: Cancer Letters. - : Elsevier BV. - 0304-3835 .- 1872-7980. ; 307:2, s. 119-23
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Tidskriftsartikel (refereegranskat)abstract
- Motexafin gadolinium (MGd) sensitizes malignant cells to ionizing radiation, although the underlying mechanisms for uptake and sensitization are both unclear. Here we show that MGd is endocytosed by the clathrin-dependent pathway with ensuing lysosomal membrane permeabilization, most likely via formation of reactive oxygen species involving redox-active metabolites, such as ascorbate. We propose that subsequent apoptosis is a synergistic effect of irradiation and high MGd concentrations in malignant cells due to their pronounced endocytic activity. The results provide novel insights into the mode of action of this promising anti-cancer drug, which is currently under clinical trials.
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| 7. |
- Berndt, Carsten, et al.
(författare)
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Chelation of lysosomal iron protects against ionizing radiation.
- 2010
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Ingår i: Biochemical Journal. - 0264-6021 .- 1470-8728. ; 432:2, s. 295-301
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Tidskriftsartikel (refereegranskat)abstract
- Ionizing radiation causes DNA damage and consequent apoptosis, mainly due to the production of hydroxyl radicals (HO•) that follows radiolytic splitting of water. However, superoxide (O2•-) and H2O2 also form and induce oxidative stress with resulting LMP (lysosomal membrane permeabilization) arising from iron-catalysed oxidative events. The latter will contribute significantly to radiation-induced cell death and its degree largely depends on the quantities of lysosomal redox-active iron present as a consequence of autophagy and endocytosis of iron-rich compounds. Therefore radiation sensitivity might be depressed by lysosome-targeted iron chelators. In the present study, we have shown that cells in culture are significantly protected from ionizing radiation damage if initially exposed to the lipophilic iron chelator SIH (salicylaldehyde isonicotinoyl hydrazone), and that this effect is based on SIH-dependent lysosomal stabilization against oxidative stress. According to its dose-response-modifying effect, SIH is a most powerful radioprotector and a promising candidate for clinical application, mainly to reduce the radiation sensitivity of normal tissue. We propose, as an example, that inhalation of SIH before each irradiation session by patients undergoing treatment for lung malignancies would protect normally aerated lung tissue against life-threatening pulmonary fibrosis, whereas the sensitivity of malignant lung tumours, which usually are non-aerated, will not be affected by inhaled SIH.
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| 8. |
- Bironaite, Daiva, et al.
(författare)
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Protective Induction of Hsp70 in Heat-Stressed Primary Myoblasts: Involvement of MAPKs
- 2013
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Ingår i: Journal of Cellular Biochemistry. - : Wiley-Blackwell. - 0730-2312 .- 1097-4644. ; 114:9, s. 2024-2031
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Tidskriftsartikel (refereegranskat)abstract
- The involvement of extracellular signal-regulated kinases 1 and 2 (ERK1,2), stress kinase p38 and c-Jun NH2-terminal kinases 1 and 2 (JNK1,2) on Hsp70-upregulation following mild heat shock, and resulting cell protection, was studied on rabbit primary myoblasts. Cells subjected to heat stress (42 degrees C; 60min) showed a significantly enhanced amount of heat-shock-induced protein 70 (Hsp70), correlating with sustained phosphorylation of MAP kinases ERK1,2, inhibition of p38 and JNK1,2 activation. Induced Hsp70 did not autocrinally suppress activation of transcription factor c-Jun, suggesting involvement of the latter in the protection of myoblasts following heat shock. The inhibition of stress kinases p38, JNK1,2, and MEK1,2 by SP600125, SB203580, and UO126, respectively, established the involvement of JNK1,2 and p38 as upstream, and ERK1,2 as downstream targets of Hsp70 induction. Moreover, the effect of the MEK1,2 inhibitor UO126 revealed a new pathway of c-Jun activation by ERK1,2 in myogenic heat-stressed stem cells. The presented data show that transient activation of JNK1, JNK2, and p38 is necessary for Hsp70 induction and ensuing cell protection. In conclusion, affecting myogenic stem cell protective mechanisms might be a useful strategy in improving stem cell survival and their expanded application in therapy.
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| 9. |
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| 10. |
- 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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