Reduced Levels of Antioxidants in Brains of Apolipoprotein E-Deficient Mice Following Closed Head Injury

doi:10.1016/S0091-3057(96)00412-1

Pharmacology Biochemistry and Behavior

Volume 56, Issue 4, April 1997, Pages 669-673

https://doi.org/10.1016/S0091-3057(96)00412-1 Get rights and content

Abstract

Recent animal model studies using apolipoprotein E (apoE)-deficient (knockout) mice revealed that these mice have memory deficits and neurochemical derangements and that they recover from closed head injury less adequately than control mice. In the present study, we examined the possibility that the diminished recovery of apoE-deficient mice from head injury is related to a reduction in their ability to counteract oxidative damage. Measurements of reducing agents by cyclic voltammetry revealed that cortical homogenates of apoE-deficient and control mice contain similar levels of these compounds, whose oxidation potentials for the two groups of mice are at 400 ± 40 mV and 900 ± 50 mV. The responses of the apoE-deficient and control groups to closed head injury were both biphasic and were composed of initial reductions followed by subsequent increases in the levels of reducing antioxidant equivalents. However, the two groups differed markedly in the magnitude of their response. This difference was most pronounced with the 400-mV reducing compounds, such that at 4 h after injury their levels in injured control mice increased over twofold relative to the noninjured control mice, whereas the corresponding anodic current of the apoE-deficient mice recovered only to its original level and did not increase further even by 24 h after injury. In vitro studies using recombinant apoE allele E3 and β very low density lipoprotein revealed that this lipoprotein can delay Cu²⁺-induced lipid peroxidation. This suggests that the inability of the apoE-deficient mice to respond to brain injury by a surge in brain reducing compounds may be related, at least in part, to direct antioxidant activity of apoE.

Section snippets

Closed Head Injury

Four-month-old apoE-deficient male mice (∼23 g) and a matched group of control mice from the same original parent litter [20]were used in this study. Closed head injury to seven mice in each group was produced under anesthesia as modified by Chen et al. [4]after Shapira et al. [23]. A weight-drop device was employed in which a calibrated weight (333 g) was allowed to fall from a height of 3 cm onto the exposed skull, over the left cervical hemisphere, 1–2 mm lateral to the midline of the

Results

The possibility that the diminished recovery of apoE-deficient mice from closed head injury is related to a diminution in their ability to counteract oxidative damage was examined by cyclic voltammetry. This was pursued by measurements using homogenates of distinct brain areas of injured and noninjured apoE-deficient and control mice. A representative volt-ammogram thus obtained from a cortical homogenate of a control mouse prior to closed head injury is presented in Fig. 1. Cortical

Discussion

This study revealed that prior to head injury, apoE-deficient and control mice have similar levels of antioxidant reducing compounds but that their levels differ markedly following closed head injury. In control mice, closed head injury results in an initial decrease and in a subsequent surge of antioxidant reducing substances, whereas in the apoE-deficient mice, the initial decrease and particularly the subsequent increase are much less pronounced. Below we discuss possible mechanisms that may

Acknowledgements

We thank Prof. D. Lictenberg for his advice and generous help. This work was supported in part by grants to D. M. M. from the Joseph K. & Inez Eichenbaum Foundation, the Simon Revah-Kabelli Fund, the U.S. Israel Binational Foundation, and the Israel Science Foundation, and to L. L. from the Robinowitch Fund.

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Chen, Y.; Lomnitski, L.; Michaelson, D. M.; Shohami, E.: Motor and memory deficits in apoE-deficient mice after closed...

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ApoE−/− mice also have increased infarct volumes and higher mortality rates than WT after stroke (Sheng et al., 1999a; Sheng et al., 1998; Laskowitz et al., 1997b). In closed head injury paradigms, apoE−/− mice have decreased levels of antioxidant compounds (Lomnitski et al., 1999a; Lomnitski et al., 1997) and impaired functional recovery and neuronal loss (Chen et al., 1997a; Han and Chung, 2000). Notably, treatment with exogenous apoE decrease the anatomical and functional deficits in the animal models of several neurological diseases, such as ischemic stroke (Horsburgh et al., 2000; Tu et al., 2017), of Alzheimer's disease (Sarantseva et al., 2009), traumatic brain injury (Wang et al., 2007; Lynch et al., 2005; Laskowitz et al., 2010; Kaufman et al., 2010; Hoane et al., 2009; Laskowitz et al., 2017; Cao et al., 2016), or EAE (Li et al., 2006).
Apolipoprotein E (apoE), a plasma lipoprotein well known for its important role in lipid and cholesterol metabolism, has also been implicated in many neurological diseases. In this study, we examined the effect of apoE on the pathophysiology of traumatic spinal cord injury (SCI). ApoE-deficient mutant (apoE^−/−) and wild-type mice received a T9 moderate contusion SCI and were evaluated using histological and behavioral analyses after injury. At 3 days after injury, the permeability of spinal cord-blood-barrier, measured by extravasation of Evans blue dye, was significantly increased in apoE^−/− mice compared to wild type. The inflammation and spared white matter was also significantly increased and decreased, respectively, in apoE^−/− mice compared to the wild type ones. The apoptosis of both neurons and oligodendrocytes was also significantly increased in apoE^−/− mice. At 42 days after injury, the inflammation was still robust in the injured spinal cord in apoE^−/− but not wild type mice. CD45 + leukocytes from peripheral blood persisted in the injured spinal cord of apoE^−/− mice. The spared white matter was significantly decreased in apoE^−/− mice compared to wild type ones. Locomotor function was significantly decreased in apoE^−/− mice compared to wild type ones from week 1 to week 8 after contusion. Treatment of exogenous apoE mimetic peptides partially restored the permeability of spinal cord-blood-barrier in apoE^−/− mice after SCI. Importantly, the exogenous apoE peptides decreased inflammation, increased spared white matter and promoted locomotor recovery in apoE^−/− mice after SCI. Our results indicate that endogenous apoE plays important roles in maintaining the spinal cord-blood-barrier and decreasing inflammation and spinal cord tissue loss after SCI, suggesting its important neuroprotective function after SCI. Our results further suggest that exogenous apoE mimetic peptides could be a novel and promising neuroprotective reagent for SCI.
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Traumatic Brain Injury (TBI) is known to result in oxidative stress, and as variation at the Apolipoprotein E (APOE) gene has been shown to influence outcome following TBI, but through as yet unclear mechanisms, we used transgenic APOE mouse models to examine the relationship between APOE genotype and oxidative stress following TBI. We administered a controlled cortical impact (CCI) injury or sham injury to transgenic mice expressing either human APOE3 or APOE4 on a murine APOE-deficient background. RNA was prepared from the ipsilateral hippocampi and cortices retrieved at 24 h and 1 month post-TBI. Microarray analysis was performed on unpooled samples from three mice per group to determine the genomic response to TBI and to specifically investigate the response of genes involved in oxidative stress mechanisms. Our data demonstrated TBI-induced expression of many more anti-oxidant related genes in the APOE3 mice, suggesting a potential anti-oxidative role for ApoE3 compared to ApoE4. However, in an additional cohort of mice we isolated the ipsilateral hippocampi, cortices, and cerebella at 1 month after TBI or sham injury for immunohistochemical analysis of markers of oxidative stress: the formation and presence of carbonyls (indication of general oxidative modification), 3-nitrotyrosine (3NT; specific to protein modification), or 4-hydroxyl-2-nonenal (HNE; specific to lipid peroxidation). Although we observed significant increases in all three markers of oxidative stress in response to injury, and genotype was a significant factor for carbonyl and 3NT, we found no significant interaction between genotype and injury. This may be due to the overwhelming effect of injury compared to genotype in our ANOVA, but nonetheless suggests that an influence on oxidative stress response is not the primary mechanism behind the APOE-genotype dependent effects on outcome following TBI.
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ArticlesReduced Levels of Antioxidants in Brains of Apolipoprotein E-Deficient Mice Following Closed Head Injury

Abstract

Section snippets

Closed Head Injury

Results

Discussion

Acknowledgements

Neurobiol. Aging

Neurosci. Lett.

Prog. Brain Res.

Neurosci. Lett.

Pharmacol. Ther.

Arch. Biochem. Biophys.

Exp. Neurol.

Brain Res.

Cell

Closed head injury induces changes in reducing capacity of rat brain. A potential endogenous neuroprotective mechanism

J. Cerebr. Blood Flow Metab.

The relation of oxidative stress and hyperexcitation to neurological disease

Proc. Soc. Exp. Biol. Med.

Articles
Reduced Levels of Antioxidants in Brains of Apolipoprotein E-Deficient Mice Following Closed Head Injury