A time-course analysis of changes in cerebral metal levels following a controlled cortical impact

© 2016 The Royal Society of Chemistry. Traumatic brain injury (TBI) is complicated by a sudden and dramatic change in brain metal levels, including iron (Fe), copper (Cu) and zinc (Zn). Specific 'metallo-pathological' features of TBI include increased non-heme bound Fe and the liberation of free Zn ions, both of which may contribute to the pathogenesis of TBI. To further characterise the metal dyshomeostasis that occurs following brain trauma, we performed a quantitative time-course survey of spatial Fe, Cu and Zn distribution in mice receiving a controlled cortical impact TBI. Images of brain metal levels produced using laser ablation-inductively coupled plasma-mass spectrometry (LA-ICP-MS) in the upper quadrant of the ipsilateral hemisphere were compared to the corresponding contralateral hemisphere, together with regional areas radiating toward the center of the brain from the site of lesion. Significant regional and time point specific elevations in Fe, Zn and Cu were detected immediately and up to 28 days after TBI. The magnitude and timeframe of many of these changes suggest that TBI results in a pronounced and sustained alteration in normal metal levels within the brain. Such alterations are likely to play a role in both the short- and long-term consequences of head trauma and suggest that pharmacological modulation to normalize these metal levels may be efficacious in improving functional outcome

Age modulates the injury-induced metallomic profile in the brain

© 2017 The Royal Society of Chemistry. The biological transition metals iron (Fe), copper (Cu) and zinc (Zn) are thought to contribute to the neuronal pathologies that occur following traumatic brain injury (TBI), and indeed our previously published work in young (3 month-old) mice clearly demonstrates a significant spatiotemporal modulation of metals following TBI. Of note, however, is the literature observation that there is both an apparent detrimental effect of aging on TBI outcomes and an alteration in metals and their various transporters with normal advancing age. Therefore, to determine whether there was an interaction between aging, metals and TBI, we have utilised laser ablation-inductively coupled plasma-mass spectrometry to examine the spatial and temporal distribution of Fe, Zn and Cu following an acute controlled cortical impact brain injury in aged (24 months) rodents. The relative abundance of metals in corresponding regions within the ipsilateral and contralateral hemispheres as well as the hippocampus was assessed. Substantial region and time point specific alterations in Fe, Zn and Cu were identified immediately and up to 28 days post-TBI. The data from this follow-up study has also been compared to our previous data from young animals, and aged mice exhibit an appreciably enhanced and persistent elevation of all metals in every region surveyed, with individual metal disparities at various time points observed post-injury. This may potentially contribute to the acceleration in the onset of cognitive decline and neurological disease that has been observed in the aged population following head trauma

Trehalose improves traumatic brain injury-induced cognitive impairment

© 2017 Portbury et al. This is an open access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited. Traumatic brain Injury (TBI) is a significant cause of death and long-term disability for which there are currently no effective pharmacological treatment options. In this study then, we utilized a mouse model of TBI to assess the therapeutic potential of the stable disaccharide trehalose, which is known to protect against oxidative stress, increase levels of chaperone molecules and enhance autophagy. Furthermore, trehalose has demonstrated neuroprotective properties in numerous animal models and has been proposed as a potential treatment for neurodegeneration. As TBI (and associated neurodegenerative disorders) is complicated by a sudden and dramatic change in brain metal concentrations, including iron (Fe) and zinc (Zn), the collective accumulation and translocation of which has been hypothesized to contribute to the pathogenesis of TBI, then we also sought to determine whether trehalose modulated the metal dyshomeostasis associated with TBI. In this study three-month-old C57Bl/6 wildtype mice received a controlled cortical impact TBI, and were subsequently treated for one month with trehalose. During this time animals were assessed on multiple behavioral tasks prior to tissue collection. Results showed an overall significant improvement in the Morris water maze, Y-maze and open field behavioral tests in trehalose-treated mice when compared to controls. These functional benefits occurred in the absence of any change in lesion volume or any significant modulation of biometals, as assessed by laser ablation inductively coupled plasma mass spectrometry. Western blot analysis, however, revealed an upregulation of synaptophysin, doublecortin and brain derived neurotrophic factor protein in trehalose treated mice in the contralateral cortex. These results indicate that trehalose may be efficacious in improving functional outcomes following TBI by a previously undescribed mechanism of action that has relevance to multiple disorders of the central nervous system

Zinc Signal in Brain Diseases

The divalent cation zinc is an integral requirement for optimal cellular processes, whereby it contributes to the function of over 300 enzymes, regulates intracellular signal transduction, and contributes to efficient synaptic transmission in the central nervous system. Given the critical role of zinc in a breadth of cellular processes, its cellular distribution and local tissue level concentrations remain tightly regulated via a series of proteins, primarily including zinc transporter and zinc import proteins. A loss of function of these regulatory pathways, or dietary alterations that result in a change in zinc homeostasis in the brain, can all lead to a myriad of pathological conditions with both acute and chronic effects on function. This review aims to highlight the role of zinc signaling in the central nervous system, where it may precipitate or potentiate diverse issues such as age-related cognitive decline, depression, Alzheimer's disease or negative outcomes following brain injury

Trehalose Improves Cognition in the Transgenic Tg2576 Mouse Model of Alzheimer's Disease.

This study assessed the therapeutic utility of the autophagy enhancing stable disaccharide trehalose in the Tg2576 transgenic mouse model of Alzheimer's disease (AD) via an oral gavage of a 2% trehalose solution for 31 days. Furthermore, as AD is a neurodegenerative condition in which the transition metals, iron, copper, and zinc, are understood to be intricately involved in the cellular cascades leading to the defining pathologies of the disease, we sought to determine any parallel impact of trehalose treatment on metal levels. Trehalose treatment significantly improved performance in the Morris water maze, consistent with enhanced learning and memory. The improvement was not associated with significant modulation of full length amyloid-β protein precursor or other amyloid-β fragments. Trehalose had no effect on autophagy as assessed by western blot of the LC3-1 to LC3-2 protein ratio, and no alteration in biometals that might account for the improved cognition was observed. Biochemical analysis revealed a significant increase in the hippocampus of both synaptophysin, a synaptic vesicle protein and surrogate marker of synapses, and doublecortin, a reliable marker of neurogenesis. The growth factor progranulin was also significantly increased in the hippocampus and cortex with trehalose treatment. This study suggests that trehalose might invoke a suite of neuroprotective mechanisms that can contribute to improved cognitive performance in AD that are independent of more classical trehalose-mediated pathways, such as Aβ reduction and activation of autophagy. Thus, trehalose may have utility as a potential AD therapeutic, with conceivable implications for the treatment of other neurodegenerative disorders

Trehalose Improves Cognition in the Transgenic Tg2576 Mouse Model of Alzheimer's Disease

This study assessed the therapeutic utility of the autophagy enhancing stable disaccharide trehalose in the Tg2576 transgenic mouse model of Alzheimer's disease (AD) via an oral gavage of a 2% trehalose solution for 31 days. Furthermore, as AD is a neurodegenerative condition in which the transition metals, iron, copper, and zinc, are understood to be intricately involved in the cellular cascades leading to the defining pathologies of the disease, we sought to determine any parallel impact of trehalose treatment on metal levels. Trehalose treatment significantly improved performance in the Morris water maze, consistent with enhanced learning and memory. The improvement was not associated with significant modulation of full length amyloid-β protein precursor or other amyloid-β fragments. Trehalose had no effect on autophagy as assessed by western blot of the LC3-1 to LC3-2 protein ratio, and no alteration in biometals that might account for the improved cognition was observed. Biochemical analysis revealed a significant increase in the hippocampus of both synaptophysin, a synaptic vesicle protein and surrogate marker of synapses, and doublecortin, a reliable marker of neurogenesis. The growth factor progranulin was also significantly increased in the hippocampus and cortex with trehalose treatment. This study suggests that trehalose might invoke a suite of neuroprotective mechanisms that can contribute to improved cognitive performance in AD that are independent of more classical trehalose-mediated pathways, such as Aβ reduction and activation of autophagy. Thus, trehalose may have utility as a potential AD therapeutic, with conceivable implications for the treatment of other neurodegenerative disorders

Zinc Transporter-3 Knockout Mice Demonstrate Age-Dependent Alterations in the Metalloproteome

Metals are critical cellular elements that are involved in a variety of cellular processes, with recent literature demonstrating that zinc, and the synaptic zinc transporter (ZnT3), are specifically involved in learning and memory and may also be key players in age-related neurodegenerative disorders such as Alzheimer's disease. Whilst the cellular content and location of metals is critical, recent data has demonstrated that the metalation state of proteins is a determinant of protein function and potential toxicity. As we have previously reported that ZnT3 knockout (KO) mice have deficits in total zinc levels at both 3 and 6 months of age, we were interested in whether there might be changes in the metalloproteomic profile in these animals. To do this, we utilised size exclusion chromatography-inductively coupled plasma mass spectrometry (SEC-ICP-MS) and examined hippocampal homogenates from ZnT3 KO and age-matched wild-type mice at 3, 6 and 18 months of age. Our data suggest that there are alterations in specific metal binding proteins, for zinc, copper and iron all being modulated in the ZnT3 KO mice compared to wild-type (WT). These data suggest that ZnT3 KO mice may have impairments in the levels or localisation of multiple transition metals, and that copper- and iron-dependent cellular pathways may also be impacted in these mice

Laser ablation-inductively coupled plasma-mass spectrometry imaging of white and gray matter iron distribution in Alzheimer's disease frontal cortex

Iron deposition in the brain is a feature of normal aging, though in several neurodegenerative disorders, including Alzheimer's disease, the rate of iron accumulation is more advanced than in age-matched controls. Using laser ablation-inductively coupled plasma-mass spectrometry imaging we present here a pilot study that quantitatively assessed the iron content of white and gray matter in paraffin-embedded sections from the frontal cortex of Alzheimer's and control subjects. Using the phosphorus image as a confirmed proxy for the white/gray matter boundary, we found that increased intrusion of iron into gray matter occurs in the Alzheimer's brain compared to controls, which may be indicative of either a loss of iron homeostasis in this vulnerable brain region, or provide evidence of increased inflammatory processes as a response to chronic neurodegeneration. We also observed a trend of increasing iron within the white matter of the frontal cortex, potentially indicative of disrupted iron metabolism preceding loss of myelin integrity. Considering the known potential toxicity of excessive iron in the brain, our results provide supporting evidence for the continuous development of novel magnetic resonance imaging approaches for assessing white and gray matter iron accumulation in Alzheimer's disease