| 1. |
- Nilsson, Sven Erik, 1931-, et al.
(author)
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Aging of cultured retinal pigment epithelial cells : oxidative reactions,lipofuscin formation and blue light damage
- 2003
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In: Documenta Ophthalmologica. - 0012-4486 .- 1573-2622. ; 106:1, s. 13-16
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Journal article (peer-reviewed)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.
(author)
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Lipofuscin accumulation in cultured retinal pigment epithelial cells reduces their phagocytic capacity
- 1998
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In: Current Eye Research. - : Informa UK Limited. - 0271-3683 .- 1460-2202. ; 17:8, s. 851-857
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Journal article (peer-reviewed)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.
(author)
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Divergent pathways for TNF and C₂-ceramide toxicity in HTC hematoma cells
- 2009
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In: Biochimica et Biophysica Acta. - : Elsevier. - 0006-3002 .- 1878-2434. ; 1793, s. 1182-1190
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Journal article (peer-reviewed)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.
(author)
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Metallothionein protects against oxidative stress-induced lysosomal destabilization
- 2006
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In: Biochemical Journal. - 0264-6021 .- 1470-8728. ; 394:1, s. 275-283
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Journal article (peer-reviewed)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.
(author)
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Ascorbate and endocytosed Motexafin gadolinium induce lysosomal rupture.
- 2011
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In: Cancer Letters. - : Elsevier BV. - 0304-3835 .- 1872-7980. ; 307:2, s. 119-23
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Journal article (peer-reviewed)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.
(author)
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Chelation of lysosomal iron protects against ionizing radiation.
- 2010
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In: Biochemical Journal. - 0264-6021 .- 1470-8728. ; 432:2, s. 295-301
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Journal article (peer-reviewed)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.
(author)
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Protective Induction of Hsp70 in Heat-Stressed Primary Myoblasts: Involvement of MAPKs
- 2013
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In: Journal of Cellular Biochemistry. - : Wiley-Blackwell. - 0730-2312 .- 1097-4644. ; 114:9, s. 2024-2031
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Journal article (peer-reviewed)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.
(author)
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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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In: Free Radical Biology and Medicine. - : Elsevier. - 0891-5849. ; 43:10, s. 1372-1373
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Journal article (other academic/artistic)
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| 11. |
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| 12. |
- Brunk, Ulf, 1937-, et al.
(author)
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Lipofuscin : Mechanisms of age-related accumulation and influence on cell function
- 2002
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In: Free Radical Biology & Medicine. - 0891-5849 .- 1873-4596. ; 33:5, s. 611-619
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Journal article (peer-reviewed)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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| 13. |
- Brunk, Ulf
(author)
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Lysosomal involvement in apoptosis
- 2002
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In: Free Radical Biology & Medicine. - 0891-5849 .- 1873-4596. ; 33, s. 195-
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Conference paper (other academic/artistic)
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| 14. |
- Brunk, Ulf, et al.
(author)
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Lysosomal involvement in apoptosis
- 2001
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In: Redox report. - : Informa UK Limited. - 1351-0002 .- 1743-2928. ; 6:2, s. 91-97
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Research review (peer-reviewed)
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| 15. |
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| 16. |
- Brunk, Ulf, et al.
(author)
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Lysosomes, iron and oxidative stress
- 2003
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In: Free radical research. - 1071-5762 .- 1029-2470. ; 37, s. 34-34
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Conference paper (other academic/artistic)
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| 17. |
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| 18. |
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| 19. |
- Brunk, Ulf, et al.
(author)
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Septic shock and the lysosomal-mitochondrial axis theory of apoptosis
- 2009
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In: Molecular Mechanism of Severe Shock. - Kerala, India : Research Signpost. - 9788130803388 ; , s. 91-106
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Book chapter (other academic/artistic)abstract
- Over 250 years ago, Le Dran, a distinguished French Surgeon, first used the word “shock” in his treatise. Since then, much progress has been made in shock research. However, many questions have still confused the medical doctors until now. For example, why the reduced blood pressure can’t return to normal after anti-shock treatment in severe shock, why the high mortality of septic shock can’t be reduced though many new therapies are reported, what is the reason for the development of systemic inflammatory response syndrome and multiple organ dysfunction syndrome following a prolonged severe shock, and what event triggers the connection among shock, systemic inflammation, and multi-organ dysfunction, etc. In order to resolve these questions, research on the pathogenesis of shock has been made at molecular level in recent years. Current advances of shock molecular mechanism are presented in this book, which is divided into 10 chapters, including new theory about auto-digestion in shock and organ failure, septic shock and the lysosomal-mitochondrial axis theory in apoptosis, molecular mechanism of endotoxin action, HMGB-1 and sepsis after burns, role of MAPK in inflammation and septic shock, ion channels and low vasoreactivity in severe shock, vascular permeability in shock, lymphatic microcirculation and shock, calcium signaling in cardiac dysfunction of burns, the effect and mechanism of a new anti-shock medicine Polydatin. We hope that these chapters will help the readers to develop strategies and tactics that will promote shock research. We want to thank all the authors for their excellent cooperation and manuscript preparation. We also give special thanks to Dr. Pandalai for inviting us to edit and publish this review book in Research Signpost
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| 20. |
- Brunk, Ulf T., et al.
(author)
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Cytochemical evidence for the leakage of acid phosphatase through ultrastructurally intact lysosomal membranes
- 1972
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In: The Histochemical Journal. - 0018-2214 .- 1573-6865. ; 4:6, s. 479-491
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Journal article (peer-reviewed)abstract
- Fixation under 'improper' conditions ofin vitro cultivated cells results in an extensive diffusion of the lysosomal enzyme acid phosphatase because of the influence of a low effective osmotic pressure. In the present investigation, advantage was taken of this predictable diffusion in order to establish whether or not leakage of acid phosphatase could take place through ultrastructurally 'intact' lysosomal membranes.In order to reveal small holes in the lysosomal membranes, secondary lysosomes were labelled with thorium dioxide particles, which were presumed to appear free in the cell sap if ruptures in the membranes larger than about Ioo Å were created.The experiments revealed that following the fixation ofin vitro cultivated human glia cells under 'improper' conditions, mitochondria and ground cytoplasm show considerable swelling artifacts, while secondary lysosomes appear to be essentially unaffected. The lysosomes, nevertheless, apparently lost most of their content of acid phosphatase, as judged from enzyme cytochemical studies. These findings indicate that leakage of acid phosphatase from ultrastructurally 'intact' lysosomes is possible.
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| 21. |
- Brunk, Ulf, 1937-, et al.
(author)
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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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In: European Journal of Biochemistry. - : Wiley. - 0014-2956 .- 1432-1033. ; 269:8, s. 1996-2002
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Journal article (peer-reviewed)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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| 22. |
- Cuervo, Ana Maria, et al.
(author)
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Autophagy and aging - The importance of maintaining "clean" cells
- 2005
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In: autophagy. - : Informa UK Limited. - 1554-8627 .- 1554-8635. ; 1:3, s. 131-140
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Research review (peer-reviewed)abstract
- A decrease in the turnover of cellular components and the intracellular accumulation of altered macromolecules and organelles are features common to all aged cells. Diminished autophagic activity plays a major role in these age-related manifestations. In this work we review the molecular defects responsible for the malfunctioning of two forms of autophagy, macroautophagy and chaperone-mediated outophagy, in old mammals, and highlight general and cell-type specific consequences of dysfunction of the autophagic system with age. Dietary caloric restriction and antilipolytic agents have been proven to efficiently stimulate autophagy in old rodents. These and other possible experimental restorative efforts are discussed.
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| 23. |
- Dong, Lan-Feng, et al.
(author)
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Suppression of Tumor Growth In vivo by the Mitocan alpha-tocopheryl Succinate Requires Respiratory Complex II
- 2009
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In: CLINICAL CANCER RESEARCH. - 1078-0432. ; 15:5, s. 1593-1600
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Journal article (peer-reviewed)abstract
- Purpose: Vitamin E analogues are potent novel anticancer drugs. The purpose of this study was to elucidate the cellular target by which these agents, represented by alpha-tocopoheryl succinate (alpha-TOS), suppress tumors in vivo, with the focus on the mitochondrial complex II (CII). Experimental Design: Chinese hamster lung fibroblasts with functional, dysfunctional, and reconstituted CII were transformed using H-Ras. The cells were then used to form xenografts in immunocompromized mice, and response of the cells and the tumors to alpha-TOS was studied. Results: The CII-functional and CII-reconstituted cells, unlike their CII-dysfunctional counterparts, responded to alpha-TOS by reactive oxygen species generation and apoptosis execution. Tumors derived from these cell lines reciprocated their responses to alpha-TOS. Thus, growth of CII-functional and CII-reconstituted tumors was strongly suppressed by the agent, and this was accompanied by high level of apoptosis induction in the tumor cells. On the other hand, alpha-TOS did not inhibit the CII-dysfuntional tumors. Conclusions: We document in this report a novel paradigm, according to which the mitochondrial CII, which rarely mutates in human neoplasias, is a plausible target for anticancer drugs from the group of vitamin E analogues, providing support for their testing in clinical trials.
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| 24. |
- Double, K L, et al.
(author)
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The comparative biology of neuromelanin and lipofuscin in the human brain
- 2008
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In: Cellular and Molecular Life Sciences (CMLS). - : Springer Science and Business Media LLC. - 1420-682X .- 1420-9071. ; 65:11, s. 1669-1682
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Journal article (peer-reviewed)abstract
- Neuromelanin and lipofuscin are two pigments produced within the human brain that, until recently, were considered inert cellular waste products of little interest to neuroscience. Recent research has increased our understanding of the nature and interactions of these pigments with their cellular environment and suggests that these pigments may, indeed, influence cellular function. The physical appearance and distribution of the pigments within the human brain differ, but both accumulate in the aging brain and the pigments share some structural features. Lipofuscin accumulation has been implicated in postmitotic cell aging, while neuromelanin is suggested to function as an iron-regulatory molecule with possible protective functions within the cells which produce this pigment. This review presents comparative aspects of the biology of neuromelanin and lipofuscin, as well as a discussion of their hypothesized functions in brain and their possible roles in aging and neurodegenerative disease. © 2008 Birkhaueser.
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| 25. |
- Doulias, Paschalis-Thomas, et al.
(author)
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Endosomal and lysosomal effects of desferrioxamine : Protection of HeLa cells from hydrogen peroxide-induced DNA damage and induction of cell-cycle arrest
- 2003
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In: Free Radical Biology & Medicine. - 0891-5849 .- 1873-4596. ; 35:7, s. 719-728
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Journal article (peer-reviewed)abstract
- The role of endosomal/lysosomal redox-active iron in H2O 2-induced nuclear DNA damage as well as in cell proliferation was examined using the iron chelator desferrioxamine (DFO). Transient transfections of HeLa cells with vectors encoding dominant proteins involved in the regulation of various routes of endocytosis (dynamin and Rab5) were used to show that DFO (a potent and rather specific iron chelator) enters cells by fluid-phase endocytosis and exerts its effects by chelating redox-active iron present in the endosomal/lysosomal compartment. Endocytosed DFO effectively protected cells against H2O2-induced DNA damage, indicating the importance of endosomal/lysosomal redox-active iron in these processes. Moreover, exposure of cells to DFO in a range of concentrations (0.1 to 100 ╡M) inhibited cell proliferation in a fluid-phase endocytosis- dependent manner. Flow cytometric analysis of cells exposed to 100 ╡M DFO for 24 h showed that the cell cycle was transiently interrupted at the G 2/M phase, while treatment for 48 h led to permanent cell arrest. Collectively, the above results clearly indicate that DFO has to be endocytosed by the fluid-phase pathway to protect cells against H2O 2-induced DNA damage. Moreover, chelation of iron in the endosomal/lysosomal cell compartment leads to cell cycle interruption, indicating that all cellular labile iron is propagated through this compartment before its anabolic use is possible.
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