| 1. |
- Daré, Elisabetta, et al.
(författare)
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Methylmercury and H2O2 provoke lysosomal damage in human astrocytoma D384 cells followed by apoptosis
- 2001
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Ingår i: Free Radical Biology & Medicine. - Linköping : Elsevier. - 0891-5849 .- 1873-4596. ; 30:12, s. 1347-1356
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Tidskriftsartikel (refereegranskat)abstract
- Methylmercury (MeHg) is a neurotoxic agent acting via diverse mechanisms, including oxidative stress. MeHg also induces astrocytic dysfunction, which can contribute to neuronal damage. The cellular effects of MeHg were investigated in human astrocytoma D384 cells, with special reference to the induction of oxidative-stress-related events. Lysosomal rupture was detected after short MeHg-exposure (1 μM, 1 h) in cells maintaining plasma membrane integrity. Disruption of lysosomes was also observed after hydrogen peroxide (H2O2) exposure (100 μM, 1 h), supporting the hypothesis that lysosomal membranes represent a possible target of agents causing oxidative stress. The lysosomal alterations induced by MeHg and H2O2 preceded a decrease of the mitochondrial potential. At later time points, both toxic agents caused the appearance of cells with apoptotic morphology, chromatin condensation, and regular DNA fragmentation. However, MeHg and H2O2 stimulated divergent pathways, with caspases being activated only by H2O2. The caspase inhibitor z-VAD-fmk did not prevent DNA fragmentation induced by H2O2, suggesting that the formation of high-molecular-weight DNA fragments was caspase independent with both MeHg and H2O2. The data point to the possibility that lysosomal hydrolytic enzymes act as executor factors in D384 cell death induced by oxidative stress.
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| 2. |
- Larsson, David A, et al.
(författare)
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Oxysterol mixtures, in atheroma-relevant proportions, display synergistic and proapoptotic effects
- 2006
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Ingår i: Free Radical Biology & Medicine. - : Elsevier BV. - 0891-5849 .- 1873-4596. ; 41:6, s. 902-910
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Tidskriftsartikel (refereegranskat)abstract
- Apoptotic cells in atheroma lesions may contribute to plaque development and instability. Oxysterols constitute the major toxic component in oxLDL and are present in mixed forms in human atheroma lesions. However, the cellular effects of oxysterols have been mostly studied individually. In the present study, we investigated the cytotoxic effects of 7β-hydroxycholesterol (7βOH), 7-ketocholesterol (7keto), 25-hydroxycholesterol (25OH), and 27-hydroxycholesterol (27OH) on U937 monocytic cells, both individually and in atheroma-relevant mixtures mimicking the oxysterol composition reported in human atheroma lesions. Apoptosis and necrosis were studied by examining cell morphology, phosphatidylserine exposure, caspase activation, and the terminal dUTP nick end-labeling technique. Cellular reactive oxygen species and total amount of reduced thiols were measured by using fluorescence probes and 5,5′-dithiobis-(2-nitrobenzoic acid), respectively. We found that 7βOH and 7keto induced caspase activation, ROS production, cellular thiol depletion, permeabilization of lysosomal and mitochondrial membranes, and cell death. 25OH and 27OH did not cause any of the above alterations, whereas 7βOH and 7keto exerted synergistic toxic effects. Although single 25OH or 27OH exhibited quenching effects on both 7βOH- and 7keto-induced cell death, the combination of all four oxysterols in atheroma-relevant proportions was proapoptotic. Our findings indicate that the major oxysterols accumulated in human atheroma are proapoptotic and may contribute to atherosclerotic lesion development. © 2006 Elsevier Inc. All rights reserved.
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| 3. |
- Li, Wei, 1962-, et al.
(författare)
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Alpha-tocopherol and astaxanthin decrease macrophage infiltration, apoptosis and vulnerability in atheroma of hyperlipidaemic rabbits
- 2004
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Ingår i: Journal of Molecular and Cellular Cardiology. - : Elsevier BV. - 0022-2828 .- 1095-8584. ; 37:5, s. 969-978
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Tidskriftsartikel (refereegranskat)abstract
- The composition of atherosclerotic plaques, not just macroscopical lesion size, has been implicated in their susceptibility to rupture and the risk of thrombus formation. By focusing on the quality of lipids, macrophages, apoptosis, collagen, metalloproteinase expression and plaque integrity, we evaluated the possible anti-atherosclerotic effect of the antioxidants α-tocopherol and astaxanthin in Watanabe heritable hyperlipidemic (WHHL) rabbits. Thirty-one WHHL rabbits were divided into three groups and were fed a standard diet, as controls (N =10), or a standard diet with the addition of 500 mg α-tocopherol per kg feed (N =11) or 100 mg astaxanthin per kg feed (N =10) for 24 weeks. We found that both antioxidants, particularly astaxanthin, significantly decreased macrophage infiltration in the plaques although they did not affect lipid accumulation. All lesions in the astaxanthin-treated rabbits were classified as early plaques according to the distribution of collagen and smooth muscle cells. Both antioxidants also improved plaque stability and significantly diminished apoptosis, which mainly occurred in macrophages, matrix metalloproteinase three expressions and plaque ruptures. Although neither antioxidant altered the positive correlations between the lesion size and lipid accumulation, the lesion size and apoptosis were only positively correlated in the control group. Astaxanthin and α-tocopherol may improve plaque stability by decreasing macrophage infiltration and apoptosis in this atherosclerotic setting. Apoptosis reduction by α-tocopherol and astaxanthin may be a new anti-atherogenic property of these antioxidants. © 2004 Elsevier Ltd. All rights reserved.
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| 4. |
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| 5. |
- Li, Wei, 1962-, et al.
(författare)
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Apoptotic Death of Inflammatory Cells in Human Atheroma
- 2001
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Ingår i: Arteriosclerosis, Thrombosis and Vascular Biology. - : Ovid Technologies (Wolters Kluwer Health). - 1079-5642 .- 1524-4636. ; 21:7, s. 1124-1130
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Tidskriftsartikel (refereegranskat)abstract
- Although the accumulation of cholesterol and other lipidic material is unquestionably important in atherogenesis, the reasons why this material progressively accumulates, rather than being effectively cleared by phagocytic cells such as macrophages, are not completely understood. We hypothesize that atheromatous lesions may represent "death zones" that contain toxic materials such as oxysterols and in which monocytes/macrophages become dysfunctional and apoptotic. Indeed, cathepsins B and L, normally confined to the lysosomal compartment, are present in the cytoplasm and nuclei of apoptotic (caspase-3-positive) macrophages within human atheroma. The possible involvement of oxysterols is suggested by experiments in which cultured U937 and THP-1 cells exposed to 7-oxysterols similarly undergo marked lysosomal destabilization, caspase-3 activation, and apoptosis. Like macrophages within atheroma, intralysosomal cathepsins B and L are normally present in the cytoplasm and nuclei of these oxysterol-exposed cells. Lysosomal destabilization, cathepsin release, and apoptosis may be causally related, because inhibitors of cathepsins B and L suppress oxysterol-induced apoptosis. Thus, toxic materials such as 7-oxysterols in atheroma may impair the clearance of cholesterol and other lipidic material by fostering the apoptotic death of phagocytic cells, thereby contributing to further development of atherosclerotic lesions.
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| 6. |
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| 7. |
- Li, Wei, 1962-, et al.
(författare)
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Foam cell death induced by 7β-hydroxycholesterol is mediated by labile iron-driven oxidative injury : Mechanisms underlying induction of ferritin in human atheroma
- 2005
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Ingår i: Free Radical Biology & Medicine. - : Elsevier BV. - 0891-5849 .- 1873-4596. ; 39:7, s. 864-875
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Tidskriftsartikel (refereegranskat)abstract
- Human atherosclerotic lesions typically contain large amounts of ferritin associated with apoptotic macrophages and foam cells, although the reasons are unknown. In the present investigation, we studied the relationship between ferritin induction and occurrence of apoptosis in 7β-hydroxycholesterol (7β-OH)-treated monocytic cells and macrophages. We found that 7β-OH enlarges the intracellular labile iron pool, increases formation of reactive oxygen species (ROS), and induces ferritin and cytosolic accumulation of lipid droplets, lysosomal destabilization, and apoptototic macrophage death. Since ferritin is a phase II-type protective protein, our findings suggest that ferritin upregulation here worked as an inefficient defense mechanism. Addition to the culture medium of both a membrane-permeable iron chelator 10-phenanthroline and the non-membrane-permeable iron chelators apoferritin and desferrioxamine afforded significant protection against the 7β-OH-induced effects. Consequently, endocytosed iron compounds dramatically augmented 7β-OH-induced cytotoxicity. We conclude that oxidized lipid 7β-OH causes not only foam cell formation but also oxidative damage with abnormal metabolism of cellular iron. The findings suggest that modulation of iron metabolism in human atheroma may be a potential therapeutic strategy against atherosclerosis. © 2005 Elsevier Inc. All rights reserved.
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| 8. |
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| 9. |
- Yuan, Xi Ming, 1959-, et al.
(författare)
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Lysosomal destabilization during macrophage damage induced by cholesterol oxidation products
- 2000
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Ingår i: Free Radical Biology & Medicine. - 0891-5849 .- 1873-4596. ; 28:2, s. 208-218
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Tidskriftsartikel (refereegranskat)abstract
- We have previously shown that oxidized low-density lipoprotein (LDL) induces damage to the macrophage lysosomal membranes, with ensuing leakage of lysosomal contents and macrophage cell death. Cholesterol oxidation products (ChOx) have been reported to be the major cytotoxic components of oxidized LDL/LDL− and also to stimulate cholesterol accumulation in vascular cells. In the present study, we characterized the initial events during macrophage damage induced by cholesterol oxidation products (ChOx). Within 24 h of exposure, ChOx caused lysosomal destabilization, release to the cytosol of the lysosomal marker-enzyme cathepsin D, apoptosis, and postapoptotic necrosis. Enhanced autophagocytosis and chromatin margination was found 12 h after the exposure to ChOx, whereas apoptosis and postapoptotic necrosis was pronounced 24 and 48 h after the exposure. Some lysosomal vacuoles were then filled with degraded cellular organelles, indicating phagocytosis of apoptotic bodies by surviving cells. Because caspase-3 activation was detected in the ChOx-exposed cells, lysosomal destabilization may associate with the leakage of lysosomal enzymes, and activation of the caspase cascade. MnSOD mRNA levels were markedly increased after 24 h of exposure to ChOx, suggesting associated induction of mitochondrial protection repair or turnover. We conclude that ChOx-induced damage to lysosomes and mitochondria are sequelae to the cascade of oxysterol cytotoxic events. The early disruption of lysosomes induced by ChOx, with resultant autophagocytosis may be a critical event in apoptosis and/or necrosis of macrophages/foam cells during the development of atherosclerotic lesions.
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| 10. |
- Yuan, Xi Ming, 1959-, et al.
(författare)
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Secretion of ferritin by iron-laden macrophages and influence of lipoproteins
- 2004
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Ingår i: Free radical research. - : Informa UK Limited. - 1071-5762 .- 1029-2470. ; 38:10, s. 1133-1142
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Tidskriftsartikel (refereegranskat)abstract
- Increasing evidence supports a role of cellular iron in the initiation and development of atherosclerosis. We and others reported earlier that iron-laden macrophages are associated with LDL oxidation, angiogenesis, nitric oxide production and apoptosis in atherosclerotic processes. Here we have further studied perturbed iron metabolism in macrophages, their interaction with lipoproteins and the origin of iron accumulation in human atheroma. In both early and advanced human atheroma lesions, hemoglobin and ferritin accumulation correlated with the macrophage-rich areas. Iron uptake into macrophages, via transferrin receptors or scavenger receptor-mediated erythrophagocytosis, increased cellular iron and accelerated ferritin synthesis at both mRNA and protein levels. The binding activity of iron regulatory proteins was enhanced by desferrioxamine (DFO) and decreased by hemin and iron compounds. Iron-laden macrophages exocytosed both iron and ferritin into the culture medium. Exposure to oxidized low-density lipoprotein (oxLDL, ≥50 μg/ml,) resulted in <20% apoptosis of iron-laden human macrophages, but cells remained impermeable after a 24 h period and an increased excretion of ferritin could be observed by immunostaining techniques. Exposure to high-density lipoprotein (HDL) significantly decreased ferritin excretion from these cells. We conclude: (i) erythrophagocytosis and hemoglobin catabolism by macrophages contribute to ferritin accumulation in human atherosclerotic lesions and, (ii) iron uptake into macrophages leads to increased synthesis and secretion of ferritin, (iii) oxidized LDL and HDL have different effects on these processes.
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