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Showing 1701–1720 of 2058 publications.
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Vallely, Michael P.; Bannon, Paul Gerard; Hughes, Cliff Frederick; Kritharides, LeonardEndothelial cell activation and the cell surface expression of adhesion molecules are considered to be crucial steps in the systemic inflammatory response to cardiopulmonary bypass. Endothelial cell adhesion molecules mediate the process of leukocyte adhesion to the endothelium and their subsequent transmigration and degranulation in the subendothelial tissues. The levels of soluble endothelial adhesion molecules in plasma have been used to draw conclusions regarding the cell surface expression of these molecules; the limitations of such studies are discussed. Inhibition of cell adhesion molecules may prevent the inflammatory condition caused by cardiopulmonary bypass and reperfusion injury. Further studies are needed to define the role of endothelial cell adhesion molecules in this inflammatory response.
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Witting, Paul Kenneth; Mauk, Grant; Douglas, Donald J.; Stocker, RolandMixtures of human myoglobin (Mb) (or the Y103F variant of human Mb), authentic peroxynitrite (ONOO-, ONOO-:protein 2 mol/mol), and 5,5-dimethyl-1-pyrroline-N-oxide (DMPO) gave radicals adducts at cysteine-110 (DMPO-C110) that are detected directly by electron paramagnetic magnetic spectroscopy (EPR). DMPO-C110 was detected exclusively over a range of DMPO concentrations (DMPO:protein ratios 25-100 mol/mol). Treatment of human Mb (or Y103F Mb) with the ONOO- generator 5-amino-3-(4-morpholinyl)-1,2,3-oxadiazolium (SIN-1) chloride (ONOO-: protein 5 mol/mol) yielded a cross-linked Mb dimer as judged by SDS-PAGE analyses. Addition of DMPO or carbonate effectively eliminated the cross-linked product. Mass analyses of samples containing human Mb (or Y103F Mb), carbonate, and ONOO- indicated that nitration occurs exclusively at Y103. Thus, reaction of human Mb and ONOO- yields specific products that depend on the presence or absence of physiological concentrations of carbonate. These products may serve as biomarkers for the participation of Mb-derived radicals in the oxidative damage associated with myocardial reperfusion injury. 2001 Academic Press.
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Sanni, Latifu A.; Rae, Caroline D.; Maitland, Annie; Stocker, Roland; Hunt, Nicholas H.Sequestration of parasitized erythrocytes in the central nervous system microcirculation and increased cerebrospinal fluid lactate are prominent features of cerebral malaria (CM), suggesting that sequestration causes mechanical obstruction and ischemia. To examine the potential role of ischemia in the pathogenesis of CM, Plasmodium berghei ANKA (PbA) infection in CBA mice was compared to infection with P. berghei K173 (PbK) which does not cause CM (the non-CM model, NCM). Cerebral metabolite pools were measured by 1H nuclear magnetic resonance spectroscopy during PbA and PbK infections. Lactate and alanine concentrations increased significantly at the terminal stage of CM, but not in NCM mice at any stage. These changes did not correlate with parasitemia. Brain NAD/NADH ratio was unchanged in CM and NCM mice at any time studied, but the total NAD pool size decreased significantly in the CM mice on day 7 after inoculation. Brain levels of glutamine and several essential amino acids were increased significantly in CM mice. There was a significant linear correlation between the time elapsed after infection and small, progressive decreases in the cell density/cell viability markers glycerophosphocholine and Nacetylaspartate in CM, indicative of gradual loss of cell viability. The metabolite changes followed a different pattern, with a sudden significant alteration in the levels of lactate, alanine, and glutamine at the time of terminal CM. In NCM, there were significant decreases with time of glutamate, the osmolyte myo-inositol, and glycerophosphocholine. These results are consistent with an ischemic change in the metabolic pattern of the brain in CM mice, whereas in NCM mice the changes were more consistent with hypoxia without vascular obstruction. Mild obstructive ischemia is a likely cause of the metabolic changes during CM, but a role for immune cell effector molecules cannot be ruled out.
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Linton, Stuart Maxwell; Davies, Michael J.; Dean, Roger T.Organisms produce reactive oxygen species (ROS) throughout their lives. The activities of a number of key antioxidant enzymes, such as catalase, superoxide dismutase and glutathione peroxidase, which protect against the damaging effects of ROS, have been reported to decrease with increasing age, though this is not unequivocal. In contrast, sacrificial antioxidants such as ascorbate, thiols and tocopherol do not appear to decrease with increasing age. It is also possible that ROS production increases with age as a result of poorer coupling of electron transport components, and an increased level of redox-active metal ions that could catalyse oxidant formation. As a result of this decrease in antioxidant defences, and increased rate of ROS formation, it is possible that the impact of ROS increases with age. ROS are known to oxidise biological macromolecules, with proteins an important target. If the argument that the impact of ROS increases with age is true, then proteins would be expected to accumulate oxidised materials with age, and the rate of such accumulation should increase with time, reflecting impaired inefficiency of homeostasis. Here we review the evidence for the accumulation of oxidised, or modified, extra- and intra-cellular proteins in vivo. 2001 Elsevier Science Inc.
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Lyons, Malcolm A.; Brown, Andrew J.7-Ketocholesterol (7K) is a quantitatively important oxysterol in both atherosclerotic lesions and macrophage foam cells. We reported recently that radiolabeled 7K delivered to rodents in a modified lipoprotein or chylomicron remnant-like emulsion, both cleared predominantly by the liver, was rapidly excreted into the intestine as water-soluble products, presumably bile acids. Herein, we aimed to elucidate the early or initial reactions in 7K metabolism. The hypothesis was tested that sterol 27-hydroxylase, a mitochondrial cytochrome P450 and the first enzyme of the acidic bile acid pathway, is responsible for the initial metabolism of 7K by HepG2 cells, a human hepatoblastoma cell-line. The 27-hydroxylated product of 7K (27OH-TK) was shown to be the initial, lipid-soluble product of 7K metabolism. It was produced in mitochondrial incubations and whole cells and was readily released into the media from cells. Intact cells generated metabolites of 7K that had undergone conversion from lipid-soluble precursors to water-soluble products rapidly and extensively. Their production was ablated with cyclosporin A, a sterol 27-hydroxylase inhibitor. Furthermore, we demonstrated the effectiveness of two novel selective inhibitors of this enzyme, GW273297X and GI268267X. These inhibitors also ablated the production of water-soluble products by cells; and the inhibitor of choice, GW273297X, decreased the production of 27OH-7K in mitochondrial preparations. This is the first study to demonstrate that sterol 27-hydroxylase plays an important role in the metabolism of oxysterols such as 7K in liver cells.
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Heydeck, Dagmar; Upston, Joanne M.; Viita, Helena; YlHerttuala, Seppo Pasi Antero; Stocker, Roland15-Lipoxygenase (15-LO)-induced oxidation of lipids in human LDL may be pro-atherogenic. However, the extent to which 15-LO promotes enzymatic oxidation of esterified (i.e., major) lipids in LDL may depend on various factors. Here, we show that overall, LDL lipid oxidation was favored with high activity of human 15-LO, that phospholipids were the preferred esterified substrate, and that low temperature maintained a higher proportion of enzymatic product. However, under all conditions, 15-LO induced ?-tocopherol consumption and the accumulation of nonenzymatic products that predominated with increasing time of incubation and inactivation of the enzyme. Lysates prepared from cells overexpressing human 15-LO oxidized linoleic acid readily and in an almost exclusive enzymatic manner. In sharp contrast, such lysates failed to oxidize LDL lipids unless linoleic acid was added, in which case nonenzymatic oxidation of LDL lipids occurred. We conclude that although purified 15-LO can oxidize isolated LDL lipids in vitro, such oxygenation always includes nonenzymatic reactions that likely play a major role in the more extensive oxidation of LDL by cell-derived 15-LO.
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Thomas, Shane R.; Leichtweis, Steve B.; Pettersson, Knut S.; Croft, Kevin D.; Mori, Trevor A.; Brown, Andrew J.; Stocker, RolandIntimal oxidation of LDL is considered an important early event in atherogenesis, and certain antioxidants are antiatherogenic. Dietary coenrichment with vitamin E (VitE) plus ubiquinone-10 (CoQ<inf>10</inf>, which is reduced during intestinal uptake to the antioxidant ubiquinol-10, CoQ<inf>10</inf>H<inf>2</inf>) protects, whereas enrichment with VitE alone can increase oxidizability of LDL lipid against ex vivo oxidation. In the present study, we tested whether VitE plus CoQ<inf>10</inf> cosupplementation is more antiatherogenic than either antioxidant alone, by use of apolipoprotein E-deficient (apoE-/-) mice fed a high-fat diet without (control) or with 0.2% (wt/wt) VitE, 0.5% CoQ<inf>10</inf>, or 0.2% VitE plus 0.5% CoQ<inf>10</inf> (VitE+CoQ<inf>10</inf>) for 24 weeks. None of the supplements affected plasma cholesterol concentrations, whereas in the VitE and CoQ<inf>10</inf> groups, plasma level of the respective supplement increased. Compared with control, plasma from CoQ<inf>10</inf> or VitE+CoQ<inf>10</inf> but not VitE-supplemented animals was more resistant to ex vivo lipid peroxidation induced by peroxyl radicals. VitE supplementation increased VitE levels in aorta, heart, brain, and skeletal muscle, whereas CoQ<inf>10</inf> supplementation increased CoQ<inf>10</inf> only in plasma and aorta and lowered tissue VitE. All treatments significantly lowered aortic cholesterol compared with control, but only VitE+CoQ<inf>10</inf> supplementation significantly decreased tissue lipid hydroperoxides when expressed per parent lipid. In contrast, none of the treatments affected aortic ratios of 7-ketocholesterol to cholesterol. Compared with controls, VitE+CoQ<inf>10</inf> supplementation decreased atherosclerosis at the aortic root and arch and descending thoracic aorta to an extent that increased with increasing distance from the aortic root. CoQ<inf>10</inf> significantly inhibited atherosclerosis at aortic root and arch, whereas VitE decreased disease at aortic root only. Thus, in apoE-/- mice, VitE+CoQ<inf>10</inf> supplements are more antiatherogenic than CoQ<inf>10</inf> or VitE supplements alone and disease inhibition is associated with a decrease in aortic lipid hydroperoxides but not 7-ketocholesterol.
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Green, Dena A.; Wong, Stuart J.; Chitambar, Christopher R.; Antholine, William E.; Richardson, Des RaymondThe key roles of iron and iron proteins in cell proliferation make them potential targets for cancer therapy. However, clinical trials directed toward perturbation of tumor iron homeostasis by iron chelation have been limited to the use of deferoxamine (DFO). There is thus a need to develop agents with greater efficacy. In the present study, we investigated the mechanism of cytotoxicity of 311 (2-hydroxy-1,-naphthylaldehyde benzoyl hydrazone), a novel iron chelator of the pyridoxal isonicotinoyl class. We found that 311 inhibited the growth of CCRF-CEM cells in a time- and concentration-dependent fashion with an IC<inf>50</inf> that was ?20-fold lower than that of DFO. 311 also inhibited the growth of breast, bladder, and head and neck cancer cell lines. Using electron spin resonance (ESR) spectroscopy analysis, we found that a 12-h exposure of CCRF-CEM cells to 311 inhibited the tyrosyl radical ESR signal of the R2 subunit of ribonucleotide reductase. However, overproduction of the R2 subunit in hydroxyurea-resistant CCRF-CEM cells was associated with a decrease in sensitivity of cells to 311 but not to DFO. Our studies show that 311 is a more potent cytotoxic agent than DFO, with activity against both hematopoietic and nonhematopoietic cell lines regardless of their p53 status. Furthermore, the ESR studies suggest that inhibition of the R2 subunit of ribonucleotide reductase is at least one mechanism by which 311 blocks cell proliferation.
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Murray, Michael; Sefton, Rachel M.; Croft, Kevin D.; Butler, Alison M.1. The hepatic CYP4A-dependent ?-hydroxylation of arachidonic acid and CYP2Cll-dependent 2?-/16?-hydroxylations of testosterone were decreased to 74 and 60% of respective control in microsomal fractions from vitamin A-deficient rats. Decreases in the rates of arachidonic acid ?-1-hydroxylation and testosterone 6?-, 7?- and 17?-hydroxylations were less pronounced. 2. Corresponding decreases in microsomal CYP4A and CYP2Cll immunoreactive protein expression to 64 and 68% of respective control were observed in vitamin A-deficient rat liver. Expression of CYP3A proteins was unchanged from vitamin A-adequate control. 3. Northern analysis revealed a selective decrease in CYP4A2 mRNA expression in vitamin A-deficient rat liver to ?5% of control; expression of the related CYP4A1/4A3 mRNAs was not decreased. CYP2C11 mRNA expression was also decreased in vitamin A-deficient male rat liver to 39% of control levels. 4. Intake of the deficient diet containing all-trans-retinoic acid (ATRA) during the final week of the experiment restored CYP4A2 mRNA and CYP4A protein. Administration of exogenous androgen or episodic growth hormone was ineffective. In contrast, CYP2Cll expression was restored by ATRA and androgen, but not by growth hormone. 5. From these studies it emerges that CYP4A2, a fatty acid ?-hydroxylase in rat liver, is highly dependent on vitamin A for optimal expression, whereas CYP2Cll is indirectly down regulated by androgen deficiency resulting from vitamin A-deficiency. Altered CYP expression in vitamin A-deficiency provides insights into the relationship between dietary constituents and the intracellular formation of vasoactive eicosanoids as well as the clearance of androgenic steroids.
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Vallely, Michael P.; Bannon, Paul Gerard; Kritharides, Leonard[No abstract available]
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Richardson, Des RaymondThe role of the orally active iron (Fe) chelator deferiprone in the treatment of ?-thalassemia remains a controversial subject. Despite initial studies showing high Fe chelation efficacy in vitro and also in animals and human subjects, several latter studies have not been so successful. In fact, it has been reported in several clinical trials that deferiprone after long-term treatment had either little effect or actually increased hepatic Fe loading. In addition, an increase in liver fibrosis was noted in one study. However, more recently, results by other investigators have suggested that the drug may be used under some circumstances without marked toxicity. In particular, it has been demonstrated that the combination of deferoxamine (DFO) and deferiprone results in more Fe excretion than when either chelator is used alone. Moreover, a combination of both drugs led to a decrease in deferiprone-mediated toxicity. Other studies performed in patients for up to 10 years showed no progressive fibrosis after deferiprone therapy, while a possible trend toward increasing fibrosis was noted in another investigation. Additional studies using larger numbers of deferiprone-treated patients are essential to determine the efficacy and safety of this drug, particularly in relation to the development of fibrosis. The present review discusses the possible role of deferiprone in the treatment of Fe overload.
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Baoutina, Anna; Dean, Roger T.; Jessup, Wendy K.[No abstract available]
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Pattison, David I.; Levina, Aviva; Davies, Michael J.; Lay, Peter AndrewThe well-known monoanionic Cr tris(3,5-di-tert-butylcatecholato) complex, [Cr(DTBC)<inf>3</inf>]-, has been studied by X-ray absorption spectroscopy. The multiple-scattering fit to the XAFS gave good correlation (R = 19.8%) and good values for all of the bond lengths, angles, and Debye-Waller factors. The principal bond lengths and angles around the metal center (Cr-O, 1.96 O-C, 1.28 O-Cr-O, 81.8; Cr-O-C, 113.3) were most consistent with the XRD structure for [Cr(X<inf>4</inf>C<inf>6</inf>O<inf>2</inf>)<inf>3</inf>]- (X = Cl, Br), compared to those in other oxidation states, [Cr-(DTBC)<inf>3</inf>], [Cr(Cl<inf>4</inf>C<inf>6</inf>O<inf>2</inf>)<inf>3</inf>], and [Cr(O<inf>2</inf>C<inf>6</inf>H<inf>4</inf>)<inf>3</inf>]3-. The XANES spectrum shows the main K edge at 6003.3 eV and a preedge peak at 5992.9 eV, which is ?8% of the intensity of the main K edge. The XANES data were compared to those for Cr-ehba complexes (ehbaH<inf>2</inf> = 2-ethyl-2-hydroxybutanoic acid) of known oxidation states (III, IV, and V) and show, in conjunction with EPR spectroscopy and a reevaluation of XRD structures and theoretical calulations, that the complex is best described as a Cr(V) center with delocalization from the catechol ligands. The [Cr(catecholato)<inf>3</inf>]n+ (n = 1, 0) complexes have similar EPR spectroscopic and structural properties, respectively, to the 1 - complex and are also best described as Cr(V) complexes. Such intermediates are important in the redox reactions of catechol(amine)s, and oxidized amino acids (e.g., DOPA), with carcinogenic Cr(VI) and may have relevance in Cr-induced cancers.
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Brown, Andrew J.[No abstract available]
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Headlam, Henrietta A.; Mortimer, Adam; Easton, Christopher J.; Davies, Michael J.Exposure of proteins to radicals in the presence of O<inf>2</inf> brings about multiple changes in the target molecules. These alterations include oxidation of side chains, fragmentation, cross-linking, changes in hydrophobicity and conformation, altered susceptibility to proteolytic enzymes, and formation of new reactive groups, including hydroperoxides. These processes can result in the loss of structural or enzymatic activity. Backbone fragmentation is known to occur via a number of mechanisms, most of which involve hydrogen abstraction from the ?-carbon site on the backbone. In this study, we demonstrate that initial attack at a side chain site, the ?-position (C-3), can give rise to formation of ?-carbon radicals, and hence backbone cleavage, via the formation and subsequent ?-scission of C-3 alkoxyl radicals. This ?-scission reaction is rapid (k estimated to be > 107 s-1) even with primary alkoxyl radicals derived from Ala residues, and occurs when the alkoxyl radicals are generated from a variety of precursors, including hydroperoxides and nitrate esters. These reactions release the former side chain as a reactive aldehyde or ketone; thus, Ala peptides release high yields of methanal (formaldehyde). This product has been quantified with a number of oxidized peptides and proteins, and can account for up to 64% of the initial attacking radicals with some Ala peptides. When quantified together with the hydroperoxide precursors, these species account for up to 80% of the initial radicals, confirming that this is a major process. Methanal causes cell toxicity and DNA damage and is an animal carcinogen and a genotoxic agent in human cells. Thus, the formation and subsequent reaction of alkoxyl radicals formed at the C-3 position on aliphatic amino acid side chains on peptides and proteins can give rise to both backbone fragmentation and the release of further reactive species which can cause cell toxicity and mutagenicity.
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Watts, Ralph Neal; Richardson, Des Raymond[No abstract available]
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Gao, Jin; Richardson, Des Raymond[No abstract available]
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Kwok, Juliana C.; Richardson, Des RaymondThe cardiotoxic effect of anthracyclines limits their use in the treatment of a variety of cancers. The reason for the high susceptibility of cardiac muscle to anthracyclines remains unclear, but it appears to be due, at least in part, to the interaction of these drugs with intracellular iron (Fe). The suggestion that Fe plays an important role in anthracycline cardiotoxicity has been strengthened by observation that the chelator, dexrazoxane (ICRF-187), has a potent cardioprotective effect. In the present review, the role of Fe in the cardiotoxicity of anthracyclines is discussed together with the possible role of Fe chelation therapy as a cardioprotective strategy that may also result in enhanced antitumour activity.
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Thomas, Shane R.; Stocker, RolandThis article summarises studies supporting the proposal that induction of L-tryptophan (Trp) degradation along the kynurenine pathway in human monocytes and macrophages by interferon-? (IFN?) represents a novel extracellular antioxidant defence that acts to prevent inadvertent oxidative damage to host tissue during inflammation. The studies show that formation and release of the aminophenolic antioxidant 3-hydroxyanthranilic acid (3-HAA) is responsible for the ability of IFN?-primed human macrophages to inhibit the oxidation of low density lipoprotein (LDL); an event implicated as an important event in atherogenesis. 3-HAA efficiently inhibits LDL oxidation by acting as an aqueous oxidant scavenger and a synergist for LDL-associated vitamin E. Indoleamine 2.3-dioxygenase activity (IDO) is the initial and rate limiting enzyme of Trp degradation along the kynurenine pathway. Nitric oxide inhibits IDO activity in IFN?-primed human macrophages and this may represent a physiological regulatory mechanism of the dioxygenase during inflammation.
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Cresp, Rebecca M.; Grove, Carolyn; Lalor, Emma; Valinsky, Liora; Langton, Paul E.[No abstract available]
