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- Brunk, Ulf, et al.
(författare)
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Lysosomal involvement in apoptosis
- 2001
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Ingår i: Redox report. - : Informa UK Limited. - 1351-0002 .- 1743-2928. ; 6:2, s. 91-97
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Forskningsöversikt (refereegranskat)
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| 6. |
- Persson, Lennart, 1961-, et al.
(författare)
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Novel cellular defenses against iron and oxidation : ferritin and autophagocytosis preserve lysosomal stability in airway epithelium
- 2001
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Ingår i: Redox report. - : Informa UK Limited. - 1351-0002 .- 1743-2928. ; 6:1, s. 57-63
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Tidskriftsartikel (refereegranskat)abstract
- Adsorbed to a variety of particles, iron may be carried to the lungs by inhalation thereby contributing to a number of inflammatory lung disorders. Redox-active iron is a potent catalyst of oxidative processes, but intracellularly it is bound primarily to ferritin in a non-reactive form and probably is catalytically active largely within the lysosomal compartment. Damage to the membranes of these organelles causes the release to the cytosol of a host of powerful hydrolytic enzymes, inducing apoptotic or necrotic cell death. The results of this study, using cultured BEAS-2B cells, which are adenovirus transformed human bronchial epithelial cells, and A549 cells, which have characteristics similar to type II alveolar epithelial cells, suggest that the varying abilities of different types of lung cells to resist oxidative stress may be due to differences in intralysosomal iron chelation. Cellular ferritin and iron were assayed by ELISA and atomic absorption, while plasma and lysosomal membrane stability were evaluated by the acridine orange uptake and trypan blue dye exclusion tests, respectively. Normally, and also after exposure to an iron complex, A549 cells contained significantly more ferritin (2.26 ± 0.60 versus 0.63 ± 0.33 ng/μg protein, P <0.001) and less iron (0.96 ± 0.14 versus 1.48 ± 0.21 ng/μg protein, P <0.05) than did BEAS-2B cells. Probably as a consequence, iron-exposed A549 cells displayed more stable lysosomes (P <0.05) and better survival (P <0.05) following oxidative stress. Following starvation-induced autophagocytosis, which also enhances resistance to oxidant stress, the A549 cells showed a significant reduction in ferritin, and the BEAS-2B cells did not. These results suggest that intralysosomal ferritin enhances lysosomal stability by iron-chelation, preventing Fenton-type chemistry. This notion was further supported by the finding that endocytosis of apoferritin, added to the medium, stabilized lysosomes (P <0.001 versus P <0.01) and increased survival (P <0.01 versus P <0.05) of iron-loaded A549 and BEAS-2B cells. Assuming that primary cell lines of the alveolar and bronchial epithelium behave in a similar manner as these respiratory cell lines, intrabronchial instillation of apoferritin-containing liposomes may in the future be a treatment for iron-dependent airway inflammatory processes.
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| 7. |
- Persson, Lennart, et al.
(författare)
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α-lipoic acid and α-lipoamide prevent oxidant-induced lysosomal rupture and apoptosis
- 2001
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Ingår i: Redox report. - : Informa UK Limited. - 1351-0002 .- 1743-2928. ; 6:5, s. 327-334
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Tidskriftsartikel (refereegranskat)abstract
- α-Lipoic acid (LA) and its corresponding derivative, α-lipoamide (LM), have been described as antioxidants, but the mechanisms of their putative antioxidant effects remain largely uncharacterised. The vicinal thiols present in the reduced forms of these compounds suggest that they might possess metal chelating properties. We have shown previously that cell death caused by oxidants may be initiated by lysosomal rupture and that this latter event may involve intralysosomal iron which catalyzes Fenton-type chemistry and resultant peroxidative damage to lysosomal membranes. Here, using cultured J774 cells as a model, we show that both LA and LM stabilize lysosomes against oxidative stress, probably by chelating intralysosomal iron and, consequently, preventing intralysosomal Fenton reactions. In preventing oxidant-mediated apoptosis, LM is significantly more effective than LA, as would be expected from their differing capacities to enter cells and concentrate within the acidic lysosomal compartment. As previously reported, the powerful iron-chelator, desferrioxamine (Des) (which also locates within the lysosomal compartment), also provides protection against oxidant-mediated cell death. Interestingly, although Des enhances the partial protection afforded by LA, it confers no additional protection when added with LM. Therefore, the antioxidant actions of LA and LM may arise from intralysosomal iron chelation, with LM being more effective in this regard.
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| 8. |
- Terman, Alexei, 1957-
(författare)
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Garbage catastrophe theory of aging : Imperfect removal of oxidative damage?
- 2001
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Ingår i: Redox report. - : Informa UK Limited. - 1351-0002 .- 1743-2928. ; 6:1, s. 15-26
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Tidskriftsartikel (refereegranskat)abstract
- Increasing evidence suggests an important role of oxidant-induced damage in the progress of senescent changes, providing support for the free radical theory of aging proposed by Harman in 1956. However, considering that biological organisms continuously renew their structures, it is not clear why oxidative damage should accumulate with age. No strong evidence has been provided in favor of the concept of aging as an accumulation of synthetic errors (e.g. Orgel's 'error-catastrophe' theory and the somatic mutation theory). Rather, we believe that the process of aging may derive from imperfect clearance of oxidatively damaged, relatively indigestible material, the accumulation of which further hinders cellular catabolic and anabolic functions. From this perspective, it might be predicted that: (i) suppression of oxidative damage would enhance longevity, (ii) accumulation of incompletely digested material (e.g. lipofuscin pigment) would interfere with cellular functions and increase probability of death, (iii) rejuvenation during reproduction is mainly provided by dilution of undigested material associated with intensive growth of the developing organism, and (iv) age-related damage starts to accumulate substantially when development is complete, and mainly affects postmitotic cells and extracellular matrix, not proliferating cells. There is abundant support for all these predictions.
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| 9. |
- Yu, Zhengquan, 1965-, et al.
(författare)
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The radioprotective agent, amifostine, suppresses the reactivity of intralysosomal iron
- 2003
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Ingår i: Redox report. - : Informa UK Limited. - 1351-0002 .- 1743-2928. ; 8:6, s. 347-355
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Tidskriftsartikel (refereegranskat)abstract
- Amifostine (2-[(3-aminopropyl)amino]ethane-thiol dihydrogen phosphate ester; WR-2721) is a radioprotective agent used clinically to minimize damage from radiation therapy to adjacent normal tissues. This inorganic thiophosphate requires dephosphorylation to produce the active, cell-permeant thiol metabolite, WR-1065. The activation step is presumably catalyzed by membrane-bound alkaline phosphatase, activity of which is substantially higher in the endothelium of normal tissues. This site-specific delivery may explain the preferential protection of normal versus neoplastic tissues. Although it was developed several decades ago, the mechanisms through which this agent exerts its protective effects remain unknown. Because WR-1065 is a weak base (pKa = 9.2), we hypothesized that the drug should preferentially accumulate (via proton trapping) within the acidic environment of intracellular lysosomes. These organelles contain abundant 'loose' iron and represent a likely initial target for oxidant- and radiation-mediated damage. We further hypothesized that, within the lysosomal compartment, the thiol groups of WR-1065 would interact with this iron, thereby minimizing iron-catalyzed lysosomal damage and ensuing cell death. A similar mechanism of protection via intralysosomal iron chelation has been invoked for the hexadentate iron chelator, desferrioxamine (DFO; although DFO enters the lysosomal compartment by endocytosis, not proton trapping). Using cultured J774 cells as a model system, we found substantial accumulation of WR-1065 within intracellular granules as revealed by reaction with the thiol-binding fluorochrome, BODIPY FL L-cystine. These granules are lysosomes as indicated by co-localization of BODIPY staining with LysoTracker Red. Compared to 1 mM DFO, cells pre-treated with 0.4 ?M WR-1065 are protected from hydrogen peroxide-mediated lysosomal rupture and ensuing cell death. On a molar basis in this experimental system, WR-1065 is approximately 2500 times more effective than DFO in preventing oxidant-induced lysosomal rupture and cell death. This increased effectiveness is most likely due to the preferential concentration of this weak base within the acidic lysosomal apparatus. By electron spin resonance, we found that the generation of hydroxyl radical, which normally occurs following addition of hydrogen peroxide to J774 cells, is totally blocked by pretreatment with either WR-1065 or DFO. These findings suggest a single and plausible explanation for the radioprotective effects of amifostine and may provide a basis for the design of even more effective radio- and chemoprotective drugs.
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