Jeff R Liddell
Publications
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4.93Impact points
Astrocytes retain their antioxidant capacity into advanced old age.
Glia. 09/2010; 58(12):1500-9.
Oxidative stress has been implicated in the progression of ageing and in many age-related neurodegenerative conditions. Astrocytes play a major role in the antioxidant protection of the brain, yet little is known about how the antioxidant defenses of astrocytes change across the lifespan. This study... [more] Oxidative stress has been implicated in the progression of ageing and in many age-related neurodegenerative conditions. Astrocytes play a major role in the antioxidant protection of the brain, yet little is known about how the antioxidant defenses of astrocytes change across the lifespan. This study assessed the antioxidant capacity and glutathione metabolism of astrocytes cultured from the brains of neonatal (<24 h old), mature (12-month-old), old (25-month-old), and senescent (31-month-old) C57BL/6J mice. When exposed to 100 microM hydrogen peroxide, mature, old, and senescent astrocytes cleared the peroxide approximately 30% more slowly than neonatal astrocytes. This difference persisted when catalase was inhibited by 3-aminotriazole, but was abolished when glutathione was depleted by application of buthionine sulfoximine, suggesting a deficit in the glutathione system. Correspondingly, the specific glutathione reductase activity of mature, old, and senescent astrocytes was approximately 30% lower than that of neonatal cultures, whereas no age-related change was observed in the specific activities of glutathione peroxidase, catalase, or in total antioxidant capacity. In addition, the specific rate of glutathione export was almost identical in mature, old, and senescent astrocytes, but was more than double that of neonatal astrocytes. These results indicate that the antioxidant capacity and glutathione metabolism of astrocytes are preserved from mature adulthood into senescence. It is concluded that the oxidative stress seen in ageing brains is likely due to factors extrinsic to astrocytes, rather than to an impairment of the antioxidative functions of astrocytes.
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2.99Impact points
Sustained hydrogen peroxide stress decreases lactate production by cultured astrocytes.
Journal of neuroscience research. 05/2009;
Oxidative stress and disrupted energy metabolism are common to many pathological conditions of the brain. Because astrocytes play an important role in the glucose metabolism of the brain, we have investigated whether sustained oxidative stress affects astroglial glucose metabolism with cultured prim... [more] Oxidative stress and disrupted energy metabolism are common to many pathological conditions of the brain. Because astrocytes play an important role in the glucose metabolism of the brain, we have investigated whether sustained oxidative stress affects astroglial glucose metabolism with cultured primary rat astrocytes as a model system. Cultured astrocytes were exposed to a sustained concentration of approximately 50 muM H(2)O(2) in the presence of [U-(13)C]glucose, and cellular and extracellular contents of lactate and glucose were analysed by enzymatic assays and NMR spectroscopy. Exposure of the cells to sustained H(2)O(2) stress for up to 120 min significantly lowered the rate of lactate accumulation in the media to 61% +/- 14% of that in cultures incubated without peroxide. In addition, the ratio of lactate release to glucose consumption was lowered in peroxide-treated astrocytes to 77% +/- 13% of that in control cells, and the specific activity of glyceraldehyde-3-phosphate dehydrogenase had declined to about 10% of control cells within 90 min. In addition, the (13)C enrichment of intracellular and extracellular [(13)C]lactate was about 30% and 95%, respectively, and was not affected by the presence of peroxide, demonstrating that two metabolic pools of lactate are present in cultured astrocytes. The decreased rate of lactate production by astrocytes that have been exposed to peroxide stress is a new example of an alteration by oxidative stress of an important metabolic pathway in astrocytes. Such alterations could contribute to the pathological conditions that have been connected with oxidative stress and disrupted energy metabolism in the brain. (c) 2009 Wiley-Liss, Inc.
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4.93Impact points
Glutathione peroxidase 1 and a high cellular glutathione concentration are essential for effective organic hydroperoxide detoxification in astrocytes.
Glia. 01/2007; 54(8):873-9.
Organic hydroperoxides are produced in the eicosanoid metabolism and by lipid peroxidation. To examine the contribution of glutathione peroxidase-1 (GPx1) and glutathione (GSH) in the disposal of organic hydroperoxides in brain astrocytes, primary astrocyte cultures from wild type or GPx1-deficient ... [more] Organic hydroperoxides are produced in the eicosanoid metabolism and by lipid peroxidation. To examine the contribution of glutathione peroxidase-1 (GPx1) and glutathione (GSH) in the disposal of organic hydroperoxides in brain astrocytes, primary astrocyte cultures from wild type or GPx1-deficient (GPx1(-/-)) mice were exposed to cumene hydroperoxide (CHP). After application of 100 microM CHP, the peroxide disappeared quickly from the incubation medium of wild type cells with a half-life of 9 min, whereas CHP clearance was strongly retarded in GPx1(-/-) astrocytes. Depletion of GSH by pre-incubation with buthionine sulfoximine (BSO) significantly slowed CHP clearance by wild type astrocytes, while almost completely preventing peroxide disposal by GPx1(-/-) cells. In contrast, the catalase inhibitor 3-aminotriazole (3AT) had no effect on CHP clearance. Application of CHP to wild type astrocytes was followed by a rapid and transient accumulation of GSSG, whereas in GPx1(-/-) cells no increase in the GSSG content was detected. Astrocytes from both mouse lines remained viable for up to 24 h following CHP exposure, however depletion of cellular GSH by pre-treatment with BSO compromised the viability of astrocytes, an effect that was stronger in GPx1(-/-) than in wild type cells. This cell death was almost completely prevented by iron chelators, whereas pre-incubation with iron increased CHP toxicity. These novel data demonstrate that the toxicity of organic hydroperoxides in astrocytes is iron-mediated, and that an intact GSH system is required for the effective removal of organic hydroperoxides and for protection from these peroxides.
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2.99Impact points
Glutathione peroxidase 1 and glutathione are required to protect mouse astrocytes from iron-mediated hydrogen peroxide toxicity.
Journal of neuroscience research. 09/2006; 84(3):578-86.
The enzyme glutathione peroxidase 1 (GPx1) is involved in the cellular detoxification of peroxides. To test for the consequences of GPx deficiency in astrocytes, astrocyte-rich primary cultures from wild-type and GPx1-deficient [GPx1(-/-)] mice were exposed to H(2)O(2). In GPx1(-/-) astrocytes, the ... [more] The enzyme glutathione peroxidase 1 (GPx1) is involved in the cellular detoxification of peroxides. To test for the consequences of GPx deficiency in astrocytes, astrocyte-rich primary cultures from wild-type and GPx1-deficient [GPx1(-/-)] mice were exposed to H(2)O(2). In GPx1(-/-) astrocytes, the clearance rate of H(2)O(2) was slower than in wild-type cells. In contrast to GPx1-deficient astrocytes, wild-type cells exhibited, within 2 min of H(2)O(2) application, a rapid and transient accumulation of cellular glutathione disulfide that amounted to 60% of total glutathione. The peroxide treatment did not affect the viability of wild-type astrocytes, whereas 45% of the GPx1(-/-) cells died within 8 hr. However, the viability of both types of astrocytes was strongly compromised by lowering cellular glutathione content before peroxide application. In contrast, inactivation of catalase caused substantial cell death only in GPx1(-/-) cells but not in wild-type astrocytes. The cell death observed was prevented by the iron chelators deferoxamine, 1,10-phenathroline, or 2,2'-dipyridyl, whereas preincubation with ferric ammonium citrate increased the toxicity of peroxide treatments. These results demonstrate that GPx1 contributes to the rapid clearance of H(2)O(2) by mouse astrocytes and that both GPx1 and a high concentration of glutathione are required to protect these cells from iron-dependent peroxide damage.
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1.93Impact points
Endogenous glutathione and catalase protect cultured rat astrocytes from the iron-mediated toxicity of hydrogen peroxide.
Neuroscience letters. 08/2004; 364(3):164-7.
Primary astrocyte cultures from rat brain were exposed to hydrogen peroxide (H2O2) to investigate peroxide toxicity and clearance by astrocytes. After bolus application of H2O2 (100 microM), the peroxide was eliminated from the incubation medium following first-order kinetics with a half-time of app... [more] Primary astrocyte cultures from rat brain were exposed to hydrogen peroxide (H2O2) to investigate peroxide toxicity and clearance by astrocytes. After bolus application of H2O2 (100 microM), the peroxide was eliminated from the incubation medium following first-order kinetics with a half-time of approximately 4 min. The rate of peroxide detoxification was significantly slowed by pre-incubating the cells with the glutathione synthesis inhibitor buthionine sulfoximine (BSO), or the catalase inhibitor 3-amino-1,2,4-triazole (3AT), and was retarded further when both treatments were combined. H2O2 application killed a small proportion of cells, as indicated by the levels of the cytosolic enzyme lactate dehydrogenase in the media 1 and 24h later. In contrast, cell viability was strongly compromised when the cells were pre-incubated with 3AT and/or BSO before peroxide application. The iron chelator deferoxamine completely prevented this cell loss. These results demonstrate that chelatable iron is involved in the toxicity of H2O2 and that both the glutathione system and catalase protect astrocytes from this toxicity.
Following (2)
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Claudia Zwingmann
Hospital Saint-Luc -
Peter J Crack
University of Melbourne -
Glenda M Bishop
Monash University
