Effects of traumatic brain injury of different severities on emotional, cognitive, and oxidative stress-related parameters in mice.
ABSTRACT Cognitive deficits and psychiatric disorders are significant sequelae of traumatic brain injury (TBI). Animal models have been widely employed in TBI research, but few studies have addressed the effects of experimental TBI of different severities on emotional and cognitive parameters. In this study, mice were subjected to weight-drop TBI to induce mild, intermediate, or severe TBI. After neurological assessment, the mice recovered for 10 days, and were then subjected to a battery of behavioral tests, which included open-field, elevated plus-maze, forced swimming, tail suspension, and step-down inhibitory avoidance tests. Oxidative stress-related parameters (nonprotein thiols [NPSH], glutathione peroxidase [GPx], glutathione reductase [GR], and thiobarbituric acid reactive species [TBARS]) were quantified in the cortex and hippocampus at 2 and 24 h and 14 days after TBI, and histopathological analysis was performed 15 days after TBI. Mice subjected to mild TBI showed increased anxiety and depressive-like behaviors, while intermediate and severe TBI induced robust memory deficits. The severe TBI group also displayed increased locomotor activity. Intermediate and severe TBI caused extensive macroscopic and microscopic brain damage, while mild TBI typically had no histological abnormalities. Moreover, a significant increase in TBARS in the ipsilateral cortex and GPx in the ipsilateral hippocampus was observed at 24 h and 14 days, respectively, following intermediate TBI. The current experimental TBI model induced emotional and cognitive changes comparable to sequelae seen in human TBI, and it might therefore represent a useful approach to the study of mechanisms of and new treatments for TBI and related disorders.
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ABSTRACT: Traumatic brain injury (TBI) is frequently associated with abnormal blood-brain barrier function, resulting in the release of factors that can be used as molecular biomarkers of TBI, among them GFAP, UCH-L1, S100B, and NSE. Although many experimental studies have been conducted, clinical consolidation of these biomarkers is still needed to increase the predictive power and reduce the poor outcome of TBI. Interestingly, several of these TBI biomarkers are oxidatively modified to carbonyl groups, indicating that markers of oxidative stress could be of predictive value for the selection of therapeutic strategies. Some drugs such as corticosteroids and progesterone have already been investigated in TBI neuroprotection but failed to demonstrate clinical applicability in advanced phases of the studies. Dietary antioxidants, such as curcumin, resveratrol, and sulforaphane, have been shown to attenuate TBI-induced damage in preclinical studies. These dietary antioxidants can increase antioxidant defenses via transcriptional activation of NRF2 and are also known as carbonyl scavengers, two potential mechanisms for neuroprotection. This paper reviews the relevance of redox biology in TBI, highlighting perspectives for future studies.BioMed research international. 01/2014; 2014:723060.
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ABSTRACT: Emotional disorders are a common outcome from mild traumatic brain injury (TBI) in humans, but their pathophysiological basis is poorly understood. We have developed a mouse model of closed-head blast injury using an air pressure wave delivered to a small area on one side of the cranium, to create mild TBI. We found that 20-psi blasts in 3-month-old C57BL/6 male mice yielded no obvious behavioral or histological evidence of brain injury, while 25-40 psi blasts produced transient anxiety in an open field arena but little histological evidence of brain damage. By contrast, 50-60 psi blasts resulted in anxiety-like behavior in an open field arena that became more evident with time after blast. In additional behavioral tests conducted 2-8 weeks after blast, 50-60 psi mice also demonstrated increased acoustic startle, perseverance of learned fear, and enhanced contextual fear, as well as depression-like behavior and diminished prepulse inhibition. We found no evident cerebral pathology, but did observe scattered axonal degeneration in brain sections from 50 to 60 psi mice 3-8 weeks after blast. Thus, the TBI caused by single 50-60 psi blasts in mice exhibits the minimal neuronal loss coupled to "diffuse" axonal injury characteristic of human mild TBI. A reduction in the abundance of a subpopulation of excitatory projection neurons in basolateral amygdala enriched in Thy1 was, however, observed. The reported link of this neuronal population to fear suppression suggests their damage by mild TBI may contribute to the heightened anxiety and fearfulness observed after blast in our mice. Our overpressure air blast model of concussion in mice will enable further studies of the mechanisms underlying the diverse emotional deficits seen after mild TBI.Frontiers in Neurology 01/2014; 5:2.
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ABSTRACT: Concussion remains a symptom-based diagnosis clinically, yet preclinical studies investigating traumatic brain injury, of which concussion is believed to represent a 'mild' form, emphasize histological endpoints with functional assessments often minimized or ignored all together. Recently, clinical studies have identified the importance of cognitive and neuropsychiatric symptoms, in addition to somatic complaints, following concussion. How these findings may translate to preclinical studies is unclear at present. To address the contrasting endpoints utilized clinically compared to those in preclinical studies and the potential role of functional assessments in a commonly used model of diffuse axonal injury (DAI). Animals were subjected to DAI using the impact-acceleration model. Functional and behavioral assessments were conducted over 1 week following DAI prior to completion of histological assessment at 1-week post-DAI. We show, despite the suggestion that this model represents concussive injury, no functional impairments as determined using common measures of motor, sensorimotor, cognitive, and neuropsychiatric function following injury over the course of 1 week. The lack of functional deficits is in sharp contrast to neuropathologic findings indicating neural degeneration, astrocyte reactivity, and microglial activation. Future studies are needed to identify functional assessments, neurophysiologic techniques, and imaging assessments more apt to distinguish differences following so-called 'mild' traumatic brain injury (TBI) in preclinical models and determine whether these models are truly studying concussive or subconcussive injury. These studies are needed to not only understand mechanism of injury and production of subsequent deficits, but also for rigorous evaluation of potential therapeutic agents.Neurosurgery 01/2014; · 2.53 Impact Factor