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Chelation of neurotoxic zinc levels does not improve neurobehavioral outcome after traumatic brain injury.

ABSTRACT: Increases of synaptically released zinc and intracellular accumulation of zinc in hippocampal neurons after traumatic or ischemic brain injury is neurotoxic and chelation of zinc has been shown to reduce neurodegeneration. Although our previous studies showed that zinc chelation in traumatically brain-injured rats correlated with an increase in whole-brain expression of several neuroprotective genes and reduced numbers of apoptotic neurons, the effect on functional outcome has not been determined, and the question of whether this treatment may actually be clinically relevant has not been answered. In the present study, we show that treatment of TBI rats with the zinc chelator calcium EDTA reduces the numbers of injured, Fluoro-Jade-positive neurons in the rat hippocampus 24 h after injury but does not improve neurobehavioral outcome (spatial memory deficits) 2 weeks post-injury. Our data suggest that zinc chelation, despite providing short-term histological neuroprotection, fails to improve long-term functional outcome, perhaps because long-term disruptions in homeostatic levels of zinc adversely influence hippocampus-dependent spatial memory.

SUBMITTER: Hellmich HL

PROVIDER: S-EPMC2532498 | biostudies-literature | 2008 Aug

REPOSITORIES: biostudies-literature

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Chelation of neurotoxic zinc levels does not improve neurobehavioral outcome after traumatic brain injury.

Hellmich Helen L HL Eidson Kristine K Cowart Jeremy J Crookshanks Jeanna J Boone Deborah K DK Shah Syed S Uchida Tatsuo T DeWitt Douglas S DS Prough Donald S DS

Neuroscience letters 20080523 2

Increases of synaptically released zinc and intracellular accumulation of zinc in hippocampal neurons after traumatic or ischemic brain injury is neurotoxic and chelation of zinc has been shown to reduce neurodegeneration. Although our previous studies showed that zinc chelation in traumatically brain-injured rats correlated with an increase in whole-brain expression of several neuroprotective genes and reduced numbers of apoptotic neurons, the effect on functional outcome has not been determine ...[more]

PMID: 18556117

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Project description:Outcome after traumatic brain injury (TBI) varies largely and degree of immune activation is an important determinant factor. This meta-analysis evaluates the efficacy of drugs with anti-inflammatory properties in improving neurological and functional outcome. The systematic search following PRISMA guidelines resulted in 15 randomized placebo-controlled trials (3734 patients), evaluating progesterone, erythropoietin and cyclosporine. The meta-analysis (15 studies) showed that TBI patients receiving a drug with anti-inflammatory effects had a higher chance of a favorable outcome compared to those receiving placebo (RR = 1.15; 95% CI 1.01-1.32, p = 0.041). However, publication bias was indicated together with heterogeneity (I2 = 76.59%). Stratified analysis showed that positive effects were mainly observed in patients receiving this treatment within 8 h after injury. Subanalyses by drug type showed efficacy for progesterone (8 studies, RR 1.22; 95% CI 1.01-1.47, p = 0.040), again heterogeneity was high (I2 = 62.92%) and publication bias could not be ruled out. The positive effect of progesterone covaried with younger age and was mainly observed when administered intramuscularly and not intravenously. Erythropoietin (4 studies, RR 1.20; p = 0.110; I2 = 76.59%) and cyclosporine (3 studies, RR 0.75; p = 0.189, I2 = 0%) did not show favorable significant effects. While negative findings for erythropoietin may reflect insufficient power, cyclosporine did not show better outcome at all. Current results do not allow firm conclusions on the efficacy of drugs with anti-inflammatory properties in TBI patients. Included trials showed heterogeneity in methodological and sample parameters. At present, only progesterone showed positive results and early administration via intramuscular administration may be most effective, especially in young people. The anti-inflammatory component of progesterone is relatively weak and other mechanisms than mitigating overall immune response may be more important.

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Chelation of neurotoxic zinc levels does not improve neurobehavioral outcome after traumatic brain injury.

Publications

Chelation of neurotoxic zinc levels does not improve neurobehavioral outcome after traumatic brain injury.

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