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Biomedical subjects

B Halliwell

Publications and source records attributed to B Halliwell.

At least 19 recordsLinked to original sources
PubMed2001

Effect of overexpression of wild-type and mutant Cu/Zn-superoxide dismutases on oxidative damage and antioxidant defences: relevance to Down's syndrome and familial amyotrophic lateral sclerosis.

Patients with Down's syndrome (DS) show elevated levels of copper, zinc-containing superoxide dismutase (SOD1) and appear to have increased lipid peroxidation and oxidative damage to DNA as well as elevated glutathione peroxidase activity. Increasing SOD1 levels by gene transfection in NT-2 and SK-N-MC cell lines also led to a rise in glutathione peroxidase activity, but this was nevertheless accompanied by decreased proliferation rates, increased lipid peroxidation and protein carbonyls, and a trend to a rise in 8-hydroxyguanine and protein-bound 3-nitrotyrosine. Transfection of these cell lines with DNA encoding two mutant SOD1 enzymes (G37R and G85R) associated with familial amyotrophic lateral sclerosis (FALS), produced similar, but more severe changes, i.e. even lower growth rates, higher lipid peroxidation, 3-nitrotyrosine and protein carbonyl levels, decreased GSH levels, raised GSSG levels and higher glutathione peroxidase activities. Since G85R has little SOD activity, these changes cannot be related to increased O(2)(-) scavenging. In no case was SOD2 (mitochondrial Mn-SOD) level altered. Our cellular systems reproduce many of the biochemical changes observed in patients with DS or ALS, and in transgenic mice overexpressing mutant SOD1. They also show the potentially deleterious effects of SOD1 overexpression on cellular proliferation, which may be relevant to abnormal development in DS.

Aldehydes↗
PubMed2001

Effect of the overexpression of wild-type or mutant alpha-synuclein on cell susceptibility to insult.

Mutations in alpha-synuclein (A30P and A53T) are involved in some cases of familial Parkinson's disease (FPD), but it is not known how they result in nigral cell death. We examined the effect of alpha-synuclein overexpression on the response of cells to various insults. Wild-type alpha-synuclein and alpha-synuclein mutations associated with FPD were overexpressed in NT-2/D1 and SK-N-MC cells. Overexpression of wild-type alpha-synuclein delayed cell death induced by serum withdrawal or H(2)O(2), but did not delay cell death induced by 1-methyl-4-phenylpyridinium ion (MPP(+)). By contrast, wild-type alpha-synuclein transfectants were sensitive to viability loss induced by staurosporine, lactacystin or 4-hydroxy-2-trans-nonenal (HNE). Decreases in glutathione (GSH) levels were attenuated by wild-type alpha-synuclein after serum deprivation, but were aggravated following lactacystin or staurosporine treatment. Mutant alpha-synucleins increased levels of 8-hydroxyguanine, protein carbonyls, lipid peroxidation and 3-nitrotyrosine, and markedly accelerated cell death in response to all the insults examined. The decrease in GSH levels was enhanced in mutant alpha-synuclein transfectants. The loss of viability induced by toxic insults was by apoptosic mechanism. The presence of abnormal alpha-synucleins in substantia nigra in PD may increase neuronal vulnerability to a range of toxic agents.

1-Methyl-4-phenylpyridinium↗
PubMed2000

A reevaluation of the peroxynitrite scavenging activity of some dietary phenolics.

Peroxynitrite is implicated in many diseases. Hence, there is considerable interest in potential therapeutic peroxynitrite scavengers. Diet-derived phenolics have been claimed to be powerful peroxynitrite scavengers. However, the reactivity of peroxynitrite can be significantly modified by bicarbonate and this has not been considered in evaluations of the scavenging activity of phenols. Bicarbonate (25 mM) significantly decreased the ability of several phenolic compounds (caffeic acid, o- and p-coumaric acid, gallic acid, ferulic acid) but not others (catechin and epicatechin) to inhibit peroxynitrite-mediated tyrosine nitration. Bicarbonate (25 mM) also decreased the ability of catechin, epicatechin, quercetin and ferulic acid but not chlorogenic acid, gallic acid, caffeic acid and o-coumaric acid to inhibit peroxynitrite-mediated alpha(1)-antiproteinase inactivation. These results show that physiological concentrations of bicarbonate substantially modify the ability of dietary phenolics to prevent peroxynitrite-mediated reactions. When assessing compounds for peroxynitrite scavenging, experiments should be conducted in the presence of bicarbonate to avoid misleading results.

Bicarbonates↗
PubMed2000

Hydrogen peroxide in the human body.

Hydrogen peroxide (H(2)O(2)) is widely regarded as a cytotoxic agent whose levels must be minimized by the action of antioxidant defence enzymes. In fact, H(2)O(2) is poorly reactive in the absence of transition metal ions. Exposure of certain human tissues to H(2)O(2) may be greater than is commonly supposed: substantial amounts of H(2)O(2) can be present in beverages commonly drunk (especially instant coffee), in freshly voided human urine, and in exhaled air. Levels of H(2)O(2) in the human body may be controlled not only by catabolism but also by excretion, and H(2)O(2) could play a role in the regulation of renal function and as an antibacterial agent in the urine. Urinary H(2)O(2) levels are influenced by diet, but under certain conditions might be a valuable biomarker of 'oxidative stress'.

Anti-Infective Agents, Local↗
PubMed2000

Potential problems of ascorbate and iron supplementation: pro-oxidant effect in vivo?

The comparison was undertaken between the effects of ascorbate versus ascorbate plus iron supplementation on DNA damage. Twenty healthy subjects with initial levels of plasma ascorbate of 67.2 +/- 23.3 micromol/l were randomly assigned to and cycled through one of three supplementation regimes: placebo, 260 mg/d ascorbate, 260 mg/d ascorbate plus 14 mg/d iron for 6 weeks separated by 8-week washout periods. Supplementation did not cause a rise in total oxidative DNA damage measured by GC-MS. However, a significant decrease occurred in levels of 8-oxo-7,8-dihydroguanine by ascorbate supplementation and 5-hydroxymethyl uracil by both ascorbate and ascorbate plus iron supplementation, relative to the pre-supplemental levels but not to the placebo group. In addition, levels of 5-hydroxymethyl hydantoin and 5-hydroxy cytosine increased significantly, only relative to pre-supplementation, by ascorbate plus iron treatment. No compelling evidence for a pro-oxidant effect of ascorbate supplementation, in the presence or absence of iron, on DNA base damage was observed.

Adult↗
PubMed2000

Artifacts in cell culture: rapid generation of hydrogen peroxide on addition of (-)-epigallocatechin, (-)-epigallocatechin gallate, (+)-catechin, and quercetin to commonly used cell culture media.

There is considerable current interest in the possible beneficial health effects of quercetin, catechins, epigallocatechins, epigallocatechin gallates, and related phenolic compounds found in teas, wines, and other plant products. As a result, many laboratories are studying the effects of these compounds on cells in culture. The present paper shows that addition of these compounds to commonly used cell culture media leads to generation of substantial amounts of hydrogen peroxide (H(2)O(2)). Dulbecco's modified Eagle medium gives the highest H(2)O(2) level for all the compounds tested, with levels reaching >400 microM within 2 h for addition of 1 mM concentrations of gallic acid, epigallocatechin gallate, and epigallocatechin. Catechin and quercetin produced lower, but still significant, levels of H(2)O(2). McCoy's 5A and RPMI 1640 media also promoted H(2)O(2) production from the above phenolic compounds. This rapid generation of H(2)O(2) could account for some or all of the reported effects of phenolic compounds on cells in culture.

Artifacts↗
PubMed2000

Caloric restriction prevents oxidative damage induced by the carcinogen clofibrate in mouse liver.

Long-term caloric restriction in rodents is known to decrease levels of oxidative damage, which may contribute to an 'anti-ageing' effect. We show here that a shorter period (10 months) of caloric restriction had only small effects on levels of oxidative DNA and protein damage in the livers of mice, but completely attenuated increased oxidative damage caused by the carcinogen clofibrate. Since clofibrate is thought to exert its actions by increasing oxidative damage, our data suggest that 10 months of caloric restriction can increase the resistance of tissues to agents inducing oxidative stress. This may be an important factor in explaining how caloric restriction decreases cancer incidence.

8-Hydroxy-2'-Deoxyguanosine↗
PubMed2000

Distribution of hydroxynonenal-modified proteins in the kainate-lesioned rat hippocampus: evidence that hydroxynonenal formation precedes neuronal cell death.

Decomposition of lipid peroxides gives rise to a wide range of aldehydes. 4-Hydroxyalkenals and in particular 4-hydroxynonenal (HNE) are often the most toxic products. Frequently, it is unclear at which stage in the tissue injury process HNE is formed, i.e., is it a late stage or an early stage in which HNE contributes to subsequent cell death? The present study was carried out using an antibody to HNE-modified proteins to elucidate the time course and distribution of HNE in the lesioned hippocampus after kainate injections. HNE was absent from normal neurons, but dense staining to HNE was observed in degenerating neurons after kainate injection. The increase in HNE staining occurred as early as 1 d postinjection, at a time when there was no histological evidence of cell death. HNE immunoreactivity was observed in the degenerating CA1 and CA3 fields at 3 d and 1 week postinjection, but was confined to a cluster of neurons at the edge of the degenerating CA fields, at 2 and 3 weeks postinjection. These observations suggest that HNE formation is an early event after this tissue injury, and may contribute to later cell death.

Aldehydes↗
PubMed2000

Nitrite-induced deamination and hypochlorite-induced oxidation of DNA in intact human respiratory tract epithelial cells.

No modification of purine or pyrimidine bases was observed when isolated DNA was incubated with 1 mM nitrite at pH 7.4. However, exposure of human bronchial epithelial cells in culture medium at pH 7.4 to nitrite at concentrations of 100 microM or greater led to deamination of purine bases in cellular DNA. Deamination was more extensive in cells exposed to lower extracellular pH values and higher nitrite concentrations. Significant increases in the levels of xanthine and hypoxanthine, putative deamination products of guanine and adenine, respectively, were observed in DNA from nitrite-treated cells but no rise in any base oxidation products such as 8-hydroxyguanine. This pattern of damage suggests that exposure of cells to nitrite (even at pH 7.4) leads to intracellular generation of "reactive nitrogen species" capable of deaminating purines in DNA. In addition, significant DNA strand breakage occurred in nitrite-treated cells. The time course of base damage suggested that the repair of deaminated purine lesions in these cells is slow. By contrast, DNA isolated from cells exposed to hypochlorous acid (HOCl) has significant oxidation of pyrimidine bases and chlorination of cytosine but little oxidation of purines. Exposure of cells to both species (NO(2)(-) plus HOCl) potentiated the oxidative DNA base damage observed but decreased the extent of deamination. We hypothesize that this is due to the formation of nitryl chloride (NO(2)Cl) from reaction of HOCl with *NO(2)(-). The relevance of our observations to events in the stomach and respiratory tract, at sites of inflammation, and in ischemic tissues is discussed.

Bronchi↗
PubMed2000

Evaluation of the postprandial effects of a fast-food meal on human plasma F(2)-isoprostane levels.

Measurement of the F(2)-isoprostane, 8-epi-PGF(2alpha) is increasingly used as a sensitive and reliable marker of lipid peroxidation in vivo. Because the majority of 8-epi-PGF(2alpha) in plasma is associated with lipoproteins, it is possible that 8-epi-PGF(2alpha) derived from polyunsaturated fatty acid-rich food may become incorporated within these lipoproteins during synthesis and could contribute to the levels detected in plasma. In this study, we evaluated the postprandial effect of a single fast-food meal (McDonald's Big Mac meal, McDonald's Corp., London, England) on plasma total 8-epi-PGF(2alpha) in nine healthy subjects. Blood was collected before and 2 h postprandially. 8-Epi-PGF(2alpha) was measured by immunoaffinity extraction and gas chromatography-mass spectrometry. Fasting plasma 8-epi-PGF(2alpha) (875 +/- 25 pM) increased postprandially (956 +/- 23 pM, p <.05), although no significant change was observed in the normalized concentrations (2. 78 +/- 0.1 vs. 2.95 +/- 0.3 nmol/mmol arachidonic acid). Plasma lipid hydroperoxides, fatty acids, vitamin E, total antioxidant status, cholesterol, and triglycerides were not altered. Plasma glucose increased postmeal (4.4 +/- 0.1 vs. 4.9 +/- 0.1 mM, p <.05). These results indicate that the overall contribution of this lipid-rich meal to plasma 8-epi-PGF(2alpha) and other lipid peroxidation markers was small.

Adult↗
PubMed2000

Analysis of free and protein-bound nitrotyrosine in human plasma by a gas chromatography/mass spectrometry method that avoids nitration artifacts.

Measurement of nitrotyrosine in biological fluids and tissues is increasingly being used to monitor the production of reactive nitrogen species in vivo. The detection of nitrotyrosine in vivo has been reported with the use of a variety of methods including immunoassay, HPLC and GLC/MS. The validity of HPLC and immunoassays have been questioned with regard to their selectivity and sensitivity limits. In principle, the measurement of nitrotyrosine by GLC/MS permits a highly specific, highly sensitive and fully quantitative assay. The nitration of tyrosine under acidic conditions in the presence of nitrite is well documented. Derivatization for the full quantification of nitrotyrosine by using GLC/MS can lead to the artifactual nitration of tyrosine if performed under acidic conditions in the presence of nitrite. We describe a novel alkaline method for the hydrolysis and derivatization of nitrotyrosine and tyrosine, and demonstrate its applicability to the measurement of plasma concentrations of both free and protein-bound nitrotyrosine and tyrosine. A detection limit of 1 pg for nitrotyrosine and 100 pg for tyrosine has been achieved. Our method allows, for the first time, the analysis of free and protein-bound nitrotyrosine and tyrosine in biological samples. The plasma concentrations (means+/-S.E.M.) of free tyrosine and nitrotyrosine in eight normal subjects were 12+/-0.6 microg/ml and 14+/-0.7 ng/ml respectively. Plasma proteins contained tyrosine and nitrotyrosine at 60.7+/-1.7 microg/mg and 2.7+/-0.4 ng/mg respectively.

Adult↗
PubMed2000

Changes in glutathione in the hippocampus of rats injected with kainate: depletion in neurons and upregulation in glia.

The aim of the present study was to elucidate the distribution of glutathione immunoreactivity in the normal hippocampus and after kainate-induced neuronal injury. A specific antibody was used that recognizes both the reduced (GSH) and oxidized (GSSG) forms of glutathione. Immunoreactivity to glutathione was observed in neurons, but few immunolabeled glial cells were observed in the normal hippocampus. After kainate injection, a decrease in glutathione immunoreactivity was observed in pyramidal neurons from as early as 1 day after injection. In contrast, dense staining to glutathione was observed in large numbers of reactive astrocytes at 3 days to 6 weeks after kainate injection. This suggests upregulation of glutathione synthesis in these cells. One possibility is that the high content of glutathione is protective to reactive astrocytes. Another possibility is that the high glutathione concentration in reactive astrocytes may be protective to neurons around the glial scar.

Animals↗
PubMed2000

No evidence for increased oxidative damage to lipids, proteins, or DNA in Huntington's disease.

It has been proposed that mitochondrial dysfunction and excitotoxic mechanisms lead to oxidative damage in the brain of Huntington;s disease patients. We sought evidence that increased oxidative damage occurs by examining postmortem brain material from patients who had died with clinically and pathologically diagnosed Huntington's disease. Oxidative damage was measured using methods that have already demonstrated the presence of increased oxidative damage in Parkinson's disease, Alzheimer's disease, and senile dementia of the Lewy body type. No alterations in the levels of lipid peroxidation (as measured by lipid peroxides and thiobarbituric acid-malondialdehyde adducts) were found in the caudate nucleus, putamen, or frontal cortex of patients with Huntington's disease compared with normal controls. Similarly, there were no elevations in the levels of 8-hydroxyguanine or of a wide range of other markers of oxidative DNA damage. Levels of protein carbonyls in these tissues were also unaltered. Our data suggest that oxidative stress is not a major component of the degenerative processes occurring in Huntington's disease, or at least not to the extent that occurs in other neurodegenerative disorders.

Adult↗