Regional vulnerability after traumatic brain injury: gender differences in mice that overexpress human copper, zinc superoxide dismutase

The dual role of VEGF-A in a complex in vitro model of oxaliplatin-induced neurotoxicity: Pain-related and neuroprotective effects

Vascular endothelial growth factor (VEGF)-A is a main player in the development of neuropathic pain induced by chemotherapy and the pharmacological blockade of VEGF receptor (VEGFR) subtype 1 is a pain killer strategy. Interestingly, VEGF-A has been demonstrated to have also neuroprotective properties. The aim of the study was to investigate the neuroprotective role of VEGF-A against oxaliplatin neurotoxicity, attempting to discriminate pain-related and restorative signaling pathways. We used rat organotypic spinal cord slices treated with oxaliplatin, as an in vitro model to study chemotherapy-induced toxicity. In this model, 10 ​μM oxaliplatin caused a time-dependent release of VEGF-A, which was reduced by the astrocyte inhibitor fluorocitrate. Moreover, glia inhibition exacerbated oxaliplatin-induced cytotoxicity in a VEGF-A sensitive manner. Treatment with VEGF165b, the main isoform of VEGF-A, prevented the oxaliplatin-induced neuronal damage (indicated by NeuN staining) and astrocyte activation (indicated by GFAP staining). In addition, the blockade of VEGFR-2 by the selective antibody DC101 blunted the protective action of VEGF165b. In the same model, VEGF165b increased the release of molecules relevant in pain signaling, like substance P and CGRP, as well as the mRNA expression of glutamate transporters (EAAT1 and EAAT2), similarly to oxaliplatin and these effects were prevented by the selective VEGFR-1 blocker antibody D16F7. In conclusion, VEGF-A plays a dichotomic role in an in vitro model of chemotherapy-induced toxicity, either promoting neuroprotection or triggering pain mediators release, depending on which of its two receptors is activated. The selective management of VEGF-A signaling is suggested as a therapeutic approach.

Chronic glial activation and behavioral alterations induced by acute/subacute pioglitazone treatment in a mouse model of traumatic brain injury

Traumatic brain injury (TBI) is a disabling neurotraumatic condition and the leading cause of injury-related deaths and disability in the United States. Attenuation of neuroinflammation early after TBI is considered an important treatment target; however, while these inflammatory responses can induce secondary brain injury, they are also involved in the repair of the nervous system. Pioglitazone, which activates peroxisome proliferator-activated receptor gamma, has been shown to decrease inflammation acutely after TBI, but the long-term consequences of its use remain unknown. For this reason, the impacts of treatment with pioglitazone during the acute/subacute phase (30 min after injury and each subsequent 24 h for 5 days) after TBI were interrogated during the chronic phase (30- and 274-days post-injury (DPI)) in mice using the controlled cortical impact model of experimental TBI. Acute/subacute pioglitazone treatment after TBI results in long-term deleterious consequences, including disruption of tau homeostasis, chronic glial cell activation, neuronal pathology, and worsened injury severity particularly at 274 DPI, with male mice being more susceptible than female mice. Further, male pioglitazone-treated TBI mice exhibited increased dominant and offensive-like behavior while having a decreased non-social exploring behavior at 274 DPI. After TBI, both sexes exhibited glial activation at 30 DPI when treated with pioglitazone; however, while injury severity was increased in females it was not impacted in male mice. This work reveals that although pioglitazone has been shown to lead to attenuated TBI outcomes acutely, sex-based differences, timing and long-term consequences of treatment with glitazones must be considered and further studied prior to their clinical use for TBI therapy.

Morphological and Immunohistochemical Changes in Progressive Postmortem Autolysis of the Murine Brain

In this time series study, the temporal sequences of postmortem changes in brains kept at different temperatures were investigated in different areas of mouse brains. Fixation of tissues kept at different storage temperatures (4 °C, 22 °C, 37 °C) was delayed for four time points (24, 120, 168, 336 h). Histological and immunohistochemical investigations were carried out to determine how postmortem autolysis may affect the cellular morphology and the expression of neural cell epitopes. Results showed that the autolytic changes started earlier in brains at 22 °C and 37 °C and in the grey matter compared to the white matter, with the cerebellum and hippocampus showing the earliest postmortem changes. The cellular antigens were differently affected by the autolytic process overtime: NeuN and Olig2 immunoreactivity was gradually lost at the nuclear site and diffused into the cytoplasm; increased background staining was observed with SMI-32; GFAP showed an increase in immunolabeling, whereas 2F11 immunoreactivity decreased. This study suggests that the morphological analysis and immunohistochemical investigation of the brain tissue could be satisfactorily applied to forensic cases, providing useful data for the estimation of the postmortem interval.

Physical exercise as a cognitive rehabilitation treatment after traumatic brain injury: Intensity- and sex-dependent effects

We investigated the effects of forced physical exercise (PE) intensity on cognitive dysfunction and histological changes associated with traumatic brain injury (TBI), in both male and female rats. Controlled cortical impact (CCI) produced similar short- and long-term memory deficits in both sexes, and these deficits were associated with reduced volume and neuronal loss in the hippocampus, but not with changes in neurogenesis. We found sex differences in the effects of intensity of forced PE on cognitive recovery: all PE intensities tested improved short-term memory in both sexes, but to a greater extent in females, while long-term memory benefits were intensity- and sex-dependent. Males benefited most from low-intensity PE, while females showed optimal results at moderate intensity. These optimal PE intensities increased the neurogenesis in both sexes. A neuroprotective effect of low-intensity PE was evident in males, but no effect was observed in females. These findings suggest an intensity- and sex-specific effect of PE post-TBI, emphasizing the need for tailored PE protocols based on sex to enhance therapeutic outcomes.

Analysis of miRNAs involved in mouse brain injury upon Coxsackievirus A6 infection

Introduction

Coxsackievirus A6 (CV-A6) has emerged as the predominant epidemic strain responsible for hand, foot and mouth disease (HFMD). CV-A6 infection can result in severe clinical manifestations, including encephalitis, meningitis, and potentially life-threatening central nervous system disorders. Our previous research findings demonstrated that neonatal mice infected with CV-A6 exhibited limb weakness, paralysis, and ultimately succumbed to death. However, the underlying mechanism of CV-A6-induced nervous system injury remains elusive. Numerous reports have highlighted the pivotal role of miRNAs in various viral infections.

Methods

Separately established infection and control groups of mice were used to create miRNA profiles of the brain tissues before and after CV-A6 transfection, followed by experimental verification, prediction, and analysis of the results.

Results

At 2 days post-infection (dpi), 4 dpi, and 2dpi vs 4dpi, we identified 175, 198 and 78 significantly differentially expressed miRNAs respectively using qRT-PCR for validation purposes. Subsequently, we predicted target genes of these differentially expressed miRNAs and determined their potential targets through GO (Gene Ontology) enrichment analysis and KEGG (Kyoto Encyclopedia of Genes and Genomes) enrichment analysis. Finally, we verified the miRNA-mRNA pairing via double luciferase experiments while confirming functional enrichment of target genes through Western Blotting analyses.

Discussion

The results from this study suggest that transcriptional regulation, neuronal necrosis, pro-inflammatory cytokine release, and antiviral immunity are all implicated in the pathogenesis of central nervous system injury in mice infected with CV-A6. Brain injury resulting from CV-A6 infection may involve multiple pathways, including glial cell activation, neuronal necrosis, synaptic destruction, degenerative diseases of the nervous system. It can even encompass destruction of the blood-brain barrier, leading to central nervous system injury. The dysregulated miRNAs and signaling pathways discovered in this study provide valuable insights for further investigations into the pathogenesis of CV-A6.

Sex-Specific and Traumatic Brain Injury Effects on Dopamine Receptor Expression in the Hippocampus

Traumatic brain injury (TBI) is a major health concern. Each year, over 50 million individuals worldwide suffer from TBI, and this leads to a number of acute and chronic health issues. These include affective and cognitive impairment, as well as an increased risk of alcohol and drug use. The dopaminergic system, a key component of reward circuitry, has been linked to alcohol and other substance use disorders, and previous research indicates that TBI can induce plasticity within this system. Understanding how TBI modifies the dopaminergic system may offer insights into the heightened substance use and reward-seeking behavior following TBI. The hippocampus, a critical component of the reward circuit, is responsible for encoding and integrating the spatial and salient aspects of rewarding stimuli. This study explored TBI-related changes in neuronal D2 receptor expression within the hippocampus, examining the hypothesis that sex differences exist in both baseline hippocampal D2 receptor expression and its response to TBI. Utilizing D2-expressing tdTomato transgenic male and female mice, we implemented either a sham injury or the lateral fluid percussion injury (FPI) model of TBI and subsequently performed a region-specific quantification of D2 expression in the hippocampus. The results show that male mice exhibit higher baseline hippocampal D2 expression compared to female mice. Additionally, there was a significant interaction effect between sex and injury on the expression of D2 in the hippocampus, particularly in regions of the dentate gyrus. Furthermore, TBI led to significant reductions in hippocampal D2 expression in male mice, while female mice remained mostly unaffected. These results suggest that hippocampal D2 expression varies between male and female mice, with the female dopaminergic system demonstrating less susceptibility to TBI-induced plasticity.

Characterizing Sex Differences in Mitochondrial Dysfunction After Severe Traumatic Brain Injury in Mice

Traumatic brain injury (TBI) is caused by an impact or penetrating injury to the head resulting in abnormal brain function. Mitochondrial dysfunction is an important hallmark of TBI and has been thoroughly studied in male rodent models of brain injury, but relatively little is known about these outcomes in females. These studies were designed to examine sex as a biological variable for mitochondria-related outcomes after the severe controlled cortical impact (CCI) mouse model of TBI. Synaptic and non-synaptic mitochondria were isolated from the sham- or CCI-injured cortex as well as the hippocampus ipsilateral to the craniotomy 3, 12, 24, or 48 h post-surgery, and then bioenergetics were measured. Subtle variations were observed in the timeline of mitochondrial dysfunction between sexes. Non-synaptic cortical mitochondria from injured females showed early impairment at 12 h post-CCI compared to mitochondria from injured males at 24 h post-CCI. Contrastingly, in the synaptic fraction, mitochondria from injured males showed early impairment at 12 h post-CCI, whereas mitochondria from injured females showed impairment at 24 h post-CCI. Based on bioenergetic impairments at 24 h post-CCI, synaptic and non-synaptic mitochondrial calcium loading was also measured at this time point. Consistent with bioenergetic data at 24 h, non-synaptic mitochondria from injured males had increased calcium loading compared to uninjured control, but this effect was not observed in females. Finally, histological assessment of cortical tissue sparing in each sex was measured at 7 days post-injury. There was a lack of sex-based differences in cortical tissue sparing after severe CCI. Overall, there were some subtle sex differences in mitochondrial outcomes after CCI, but these findings were not statistically significant. This study highlights the importance of utilizing both sexes when measuring mitochondrial function after severe CCI.

Fructooligosaccharide (FOS) and Galactooligosaccharide (GOS) Improve Neuroinflammation and Cognition By Up-regulating IRS/PI3K/AKT Signaling Pathway in Diet-induced Obese Mice

Increasing evidence has indicated that prebiotics as an alternative treatment for neuropsychiatric diseases. This study evaluated the prebiotics Fructooligosaccharides (FOS) and Galactooligosaccharides (GOS) on the modulation of neuroinflammation and cognition in an experimental model of mice high-fat diet fed. Initially, mice were distributed in the following groups: (A) control standard diet (n = 15) and (B) HFD for 18 weeks (n = 30). In the 13th week, the mice were later divided into the following experimental groups: (A) Control (n = 15); (B) HFD (n = 14); and (C) HFD + Prebiotics (n = 14). From the 13th week, the HFD + Prebiotics group received a high-fat diet and a combination of FOS and GOS. In the 18th week, all animals performed the T-maze and Barnes Maze, and were later euthanized. Biochemical and molecular analyzes were performed to assess neuroinflammation, neurogenesis, synaptic plasticity, and intestinal inflammation. Mice fed HFD had higher blood glucose, triglyceridemia, cholesterolemia, and higher serum IL-1β associated with impaired learning and memory. These obese mice also showed activation of microglia and astrocytes and significant immunoreactivity of neuroinflammatory and apoptosis markers, such as TNF-α, COX-2, and Caspase-3, in addition to lower expression of neurogenesis and synaptic plasticity markers, such as NeuN, KI-67, CREB-p, and BDNF. FOS and GOS treatment significantly improved the biochemistry profile and decreased serum IL-1β levels. Treatment with FOS and GOS also reduced TNF-α, COX-2, Caspase-3, Iba-1, and GFAP-positive cells in the dentate gyrus, decreasing neuroinflammation and neuronal death caused by chronic HFD consumption. In addition, FOS and GOS promoted synaptic plasticity by increasing NeuN, p-CREB, BDNF, and KI-67, restoring spatial learning ability and memory. Moreover, FOS and GOS on HFD modulated the insulin pathway, which was proved by up-regulating IRS/PI3K/AKT signaling pathway, followed by a decreasing Aβ plate and Tau phosphorylation. Furthermore, the prebiotic intervention reshaped the HFD-induced imbalanced gut microbiota by modulating the composition of the bacterial community, markedly increasing Bacteroidetes. In addition, prebiotics decreased intestinal inflammation and leaky gut. In conclusion, FOS and GOS significantly modulated the gut microbiota and IRS/PI3K/AKT signaling pathway, decreased neuroinflammation, and promoted neuroplasticity improving spatial learning and memory. Schematic summarizing of the pathways by FOS and GOS improves memory and learning through the gut-brain axis. FOS and GOS improve the microbial profile, reducing intestinal inflammation and leaky gut in the distal colon. Specifically, the administration of FOS and GOS decreases the expression of TLR4, TNF-α, IL-1β, and MMP9 and increases the expression of occludin and IL-10. Prebiotics inhibit neuroinflammation, neuronal apoptosis, and reactive gliosis in the hippocampus but restore synaptic plasticity, neuronal proliferation, and neurogenesis.

Neuronal somatic plasmalemmal permeability and dendritic beading caused by head rotational traumatic brain injury in pigs-An exploratory study

Closed-head traumatic brain injury (TBI) is induced by rapid motion of the head, resulting in diffuse strain fields throughout the brain. The injury mechanism(s), loading thresholds, and neuroanatomical distribution of affected cells remain poorly understood, especially in the gyrencephalic brain. We utilized a porcine model to explore the relationships between rapid head rotational acceleration-deceleration loading and immediate alterations in plasmalemmal permeability within cerebral cortex, sub-cortical white matter, and hippocampus. To assess plasmalemmal compromise, Lucifer yellow (LY), a small cell-impermeant dye, was delivered intraventricularly and diffused throughout the parenchyma prior to injury in animals euthanized at 15-min post-injury; other animals (not receiving LY) were survived to 8-h or 7-days. Plasmalemmal permeability preferentially occurred in neuronal somata and dendrites, but rarely in white matter axons. The burden of LY+ neurons increased based on head rotational kinematics, specifically maximum angular velocity, and was exacerbated by repeated TBI. In the cortex, LY+ cells were prominent in both the medial and lateral gyri. Neuronal membrane permeability was observed within the hippocampus and entorhinal cortex, including morphological changes such as beading in dendrites. These changes correlated with reduced fiber volleys and synaptic current alterations at later timepoints in the hippocampus. Further histological observations found decreased NeuN immunoreactivity, increased mitochondrial fission, and caspase pathway activation in both LY+ and LY- cells, suggesting the presence of multiple injury phenotypes. This exploratory study suggests relationships between plasmalemmal disruptions in neuronal somata and dendrites within cortical and hippocampal gray matter as a primary response in closed-head rotational TBI and sets the stage for future, traditional hypothesis-testing experiments.

Cadmium-induced neurotoxic effects on rat basal forebrain cholinergic system through thyroid hormones disruption

Cadmium (Cd) single and repeated exposure produces cognitive dysfunctions. Basal forebrain cholinergic neurons (BFCN) regulate cognitive functions. BFCN loss or cholinergic neurotransmission dysfunction leads to cognitive disabilities. Thyroid hormones (THs) maintain BFCN viability and functions, and Cd disrupts their levels. However, Cd-induced BFCN damages and THs disruption involvement was not studied. To research this we treated male Wistar rats intraperitoneally with Cd once (1 mg/kg) or repetitively for 28 days (0.1 mg/kg) with/without triiodothyronine (T3, 40 µg/kg/day). Cd increased thyroid-stimulating-hormone (TSH) and decreased T3 and tetraiodothyronine (T4). Cd altered cholinergic transmission and induced a more pronounced neurodegeneration on BFCN, mediated partially by THs reduction. Additionally, Cd antagonized muscarinic 1 receptor (M1R), overexpressed acetylcholinesterase S variant (AChE-S), downregulated AChE-R, M2R, M3R and M4R, and reduced AChE and choline acetyltransferase activities through THs disruption. These results may assist to discover cadmium mechanisms that induce cognitive disabilities, revealing a new possible therapeutic tool.

The Influence of Murine Genetic Background in Adeno-Associated Virus Transduction of the Mouse Brain

Adeno-associated virus (AAV) vectors have become an important tool for delivering therapeutic genes for a wide range of neurological diseases. AAV serotypes possess differential cellular tropism in the central nervous system. Although several AAV serotypes or mutants have been reported to transduce the brain efficiently, conflicting data occur across studies with the use of various rodent strains from different genetic backgrounds. Herein, we performed a systematic comparison of the brain transduction properties among five AAV serotypes (AAV2, 5, 7, 8, and 9) in two common rodent strains (C57BL/6J and FVB/N), following local intrastriatal injection of AAV vectors encoding enhanced green fluorescent protein (EGFP) driven by the CBh promoter. Important differences were found regarding overall cellular tropism and transduction efficiency, including contralateral transduction among the AAV serotypes and between the mouse strains. We have further found loss of NeuN-immunoreactivity and microglial activation from AAV transduction in the different mouse strains. The important strain-specific differences from our study suggest that the genetic background of the mouse may affect AAV serotype transduction properties in the brain. These data can provide valuable information about how to choose an effective AAV vector for clinical application and interpret the data obtained from preclinical studies and clinical trials.

Sevoflurane sedation attenuates early cerebral oedema formation through stabilisation of the adherens junction protein beta catenin in a model of subarachnoid haemorrhage: A randomised animal study

BACKGROUND

Severe neurological impairment is a problem after subarachnoid haemorrhage (SAH). Although volatile anaesthetics, such as sevoflurane, have demonstrated protective properties in many organs, their use in cerebral injury is controversial. Cerebral vasodilation may lead to increased intracranial pressure (ICP), but at the same time volatile anaesthetics are known to stabilise the SAH-injured endothelial barrier.

OBJECTIVE

To test the effect of sevoflurane on ICP and blood-brain barrier function.

DESIGN

Randomised study.

PARTICIPANTS

One hundred male Wistar rats included, 96 analysed.

INTERVENTIONS

SAH was induced by the endoluminal filament method under ketamine/xylazine anaesthesia. Fifteen minutes after sham surgery or induction of SAH, adult male Wistar rats were randomised to 4 h sedation with either propofol or sevoflurane.

MAIN OUTCOME MEASURES

Mean arterial pressure (MAP), ICP, extravasation of water (small), Evan's blue (intermediate) and IgG (large molecule) were measured. Zonula occludens-1 (ZO-1) and beta-catenin (β-catenin), as important representatives of tight and adherens junction proteins, were determined by western blot.

RESULTS

Propofol and sevoflurane sedation did not affect MAP or ICP in SAH animals. Extravasation of small molecules was higher in SAH-propofol compared with SAH-sevoflurane animals (79.1 ± 0.9 vs. 78.0 ± 0.7%, P = 0.04). For intermediate and large molecules, no difference was detected (P = 0.6 and P = 0.2). Both membrane and cytosolic fractions of ZO-1 as well as membrane β-catenin remained unaffected by the injury and type of sedation. Decreased cytosolic fraction of β-catenin in propofol-SAH animals (59 ± 15%) was found to reach values of sham animals (100%) in the presence of sevoflurane in SAH animals (89 ± 21%; P = 0.04).

CONCLUSION

This experiment demonstrates that low-dose short-term sevoflurane sedation after SAH in vivo did not affect ICP and MAP and at the same time may attenuate early brain oedema formation, potentially by preserving adherens junctions.

TRIAL REGISTRATION

No 115/2014 Veterinäramt Zürich.

Myricitrin blocks activation of NF-κB and MAPK signaling pathways to protect nigrostriatum neuron in LPS-stimulated mice

Myricitrin, a bioactive and natural flavonoids, is well known for its anti-inflammatory and antioxidant properties. However, the anti-neuroinflammation and possible mechanism has not been fully elucidated. Therefore, the present study was to investigate the possible mechanism of its neuroprotection and anti-neuroinflammation in the nigrostriatum of LPS-stimulated mice. The results showed that myricitrin improved neuron injury and raised the expressions of PSD-95 protein and TH protein in the nigrostriatum of LPS-stimulated mice. In addition, myricitrin decreased the production of pro-inflammatory factors including IL-1β, IL-6 and TNFα, decreased the level of chemokine MCP-1, and suppressed the expressions of COX-2 and iNOS. Meanwhile, myricitrin suppressed HMGB1, TLR4, and MyD88 expression in the nigrostriatum of LPS-stimulated mice. Furthermore, myricitrin inhibited NF-κB and MAPK signaling pathways activated by LPS. In conclusion, our studies suggest that myricitrin blocks activation of protects NF-κB and MAPK signaling pathways to nigrostiatum neuron from injury in LPS-stimulated mice and is beneficial to treatment nigrostriatum inflammation of PD.

Sex Differences in Traumatic Brain Injury: What We Know and What We Should Know

There is growing recognition of the problem of male bias in neuroscience research, including in the field of traumatic brain injury (TBI) where fewer women than men are recruited to clinical trials and male rodents have predominantly been used as an experimental injury model. Despite TBI being a leading cause of mortality and disability worldwide, sex differences in pathophysiology and recovery are poorly understood, limiting clinical care and successful drug development. Given growing interest in sex as a biological variable affecting injury outcomes and treatment efficacy, there is a clear need to summarize sex differences in TBI. This scoping review presents an overview of current knowledge of sex differences in TBI and a comparison of human and animal studies. We found that overall, human studies report worse outcomes in women than men, whereas animal studies report better outcomes in females than males. However, closer examination shows that multiple factors including injury severity, sample size, and experimental injury model may differentially interact with sex to affect TBI outcomes. Additionally, we explore how sex differences in mitochondrial structure and function might contribute to possible sex differences in TBI outcomes. We propose recommendations for future investigations of sex differences in TBI, which we hope will lead to improved patient management, prognosis, and translation of therapies from bench to bedside.

Tadalafil restores long-term memory and synaptic plasticity in mice with hepatic encephalopathy

BACKGROUND AND AIM

Tadalafil displays important neuroprotective effects in experimental models of neurodegenerative diseases, however its mechanisms of action remain poorly understood. The aim of the present study was to investigate the action of Tadalafil on learning and memory, neuroinflammation, glial cell activation and neuroprotection in the experimental model of hepatic encephalopathy (HE) induced by Thioacetamide (TAA) in mice.

METHODS

Mice received intraperitoneal injections of TAA, for 3 consecutive days, reaching the final dose of 600 mg/kg. Tadalafil 15 mg/kg body weight was administered by gavage during 15 days after TAA induction. Mice underwent a Barnes maze for learning and memory evaluation.

RESULTS

Animals with hepatic encephalopathy showed reduced learning and spatial memory in the Barnes Maze, presented astrocyte and microglia activation and increased neuroinflammatory markers such as TNF-α, IL-1β, IL-6, p-p38, p-ERK and p-NF-kB. In addition, the signaling pathway PKA/PKG/CREB/BDNF/NeuN/synaptophysin and glutamate receptors were deregulated by TAA. Tadalafil treatment regulated the inflammation signaling pathways restoring learning and spatial memory.

CONCLUSION

Tadalafil significantly reduced neuroinflammation, promoted neuroprotection and plasticity, regulated the expression of hippocampal glutamate receptor and restored spatial learning ability and memory.

Sex Differences in Animal Models of Traumatic Brain Injury

Traumatic brain injury (TBI) is highly prevalent and there is currently no adequate treatment. Understanding the underlying mechanisms governing TBI and recovery remains an elusive goal. The heterogeneous nature of injury and individual's response to injury have made understanding risk and susceptibility to TBI of great importance. Epidemiologic studies have provided evidence of sex-dependent differences following TBI. However, preclinical models of injury have largely focused on adult male animals. Here, we review 50 studies that have investigated TBI in both sexes using animal models. Results from these studies are highly variable and model dependent, but largely show females to have a protective advantage in behavioral outcomes and pathology following TBI. Further research of both sexes using newer models that better recapitulate mild and repetitive TBI is needed to characterize the nature of sex-dependent injury and recovery, and ultimately identifies targets for enhanced recovery.

Sex-related responses after traumatic brain injury: Considerations for preclinical modeling

Traumatic brain injury (TBI) has historically been viewed as a primarily male problem, since men are more likely to experience a TBI because of more frequent participation in activities that increase risk of head injuries. This male bias is also reflected in preclinical research where mostly male animals have been used in basic and translational science. However, with an aging population in which TBI incidence is increasingly sex-independent due to falls, and increasing female participation in high-risk activities, the attention to potential sex differences in TBI responses and outcomes will become more important. These considerations are especially relevant in designing preclinical animal models of TBI that are more predictive of human responses and outcomes. This review characterizes sex differences following TBI with a special emphasis on the contribution of the female sex hormones, progesterone and estrogen, to these differences. This information is potentially important in developing and customizing TBI treatments.

Sexual dimorphism in the inflammatory response to traumatic brain injury

The activation of resident microglial cells, alongside the infiltration of peripheral macrophages, are key neuroinflammatory responses to traumatic brain injury (TBI) that are directly associated with neuronal death. Sexual disparities in response to TBI have been previously reported; however it is unclear whether a sex difference exists in neuroinflammatory progression after TBI. We exposed male and female mice to moderate-to-severe controlled cortical impact injury and studied glial cell activation in the acute and chronic stages of TBI using immunofluorescence and in situ hybridization analysis. We found that the sex response was completely divergent up to 7 days postinjury. TBI caused a rapid and pronounced cortical microglia/macrophage activation in male mice with a prominent activated phenotype that produced both pro- (IL-1β and TNFα) and anti-inflammatory (Arg1 and TGFβ) cytokines with a single-phase, sustained peak from 1 to 7 days. In contrast, TBI caused a less robust microglia/macrophage phenotype in females with biphasic pro-inflammatory response peaks at 4 h and 7 days, and a delayed anti-inflammatory mRNA peak at 30 days. We further report that female mice were protected against acute cell loss after TBI, with male mice demonstrating enhanced astrogliosis, neuronal death, and increased lesion volume through 7 days post-TBI. Collectively, these findings indicate that TBI leads to a more aggressive neuroinflammatory profile in male compared with female mice during the acute and subacute phases postinjury. Understanding how sex affects the course of neuroinflammation following brain injury is a vital step toward developing personalized and effective treatments for TBI.

Long-Term Tissue Culture of Adult Brain and Spleen Slices on Nanostructured Scaffolds

Long-term tissue culture of adult mammalian organs is a highly promising approach to bridge the gap between single cell cultures and animal experiments, and bears the potential to reduce in vivo studies. Novel biomimetic materials open up new possibilities to maintain the complex tissue structure in vitro; however, survival times of adult tissues ex vivo are still limited to a few days with established state-of-the-art techniques. Here, it is demonstrated that TiO₂ nanotube scaffolds with specific tissue-tailored characteristics can serve as superior substrates for long-term adult brain and spleen tissue culture. High viability of the explants for at least two weeks is achieved and compared to tissues cultured on standard polytetrafluoroethylene (PTFE) membranes. Histological and immunohistochemical staining and live imaging are used to investigate tissue condition after 5 and 14 d in vitro, while environmental scanning electron microscopy qualifies the interaction with the underlying scaffold. In contrast to tissues cultured on PTFE membranes, enhanced tissue morphology is detected in spleen slices, as well as minor cell death in neuronal tissue, both cultured on nanotube scaffolds. This novel biomimetic tissue model will prove to be useful to address fundamental biological and medical questions from tissue regeneration up to tumor progression and therapeutic approaches.

Metabolomics and neuroanatomical evaluation of post-mortem changes in the hippocampus

Understanding the human brain is the ultimate goal in neuroscience, but this is extremely challenging in part due to the fact that brain tissue obtained from autopsy is practically the only source of normal brain tissue and also since changes at different levels of biological organization (genetic, molecular, biochemical, anatomical) occur after death due to multiple mechanisms. Here we used metabolomic and anatomical techniques to study the possible relationship between post-mortem time (PT)-induced changes that may occur at both the metabolomics and anatomical levels in the same brains. Our experiments have mainly focused on the hippocampus of the mouse. We found significant metabolomic changes at 2 h PT, whereas the integrity of neurons and glia, at the anatomical/ neurochemical level, was not significantly altered during the first 5 h PT for the majority of histological markers.

Verification of the Cross Immunoreactivity of A60, a Mouse Monoclonal Antibody against Neuronal Nuclear Protein

A60, the mouse monoclonal antibody against the neuronal nuclear protein (NeuN), is the most widely used neuronal marker in neuroscience research and neuropathological assays. Previous studies identified fragments of A60-immunoprecipitated protein as Synapsin I (Syn I), suggesting the antibody will demonstrate cross immunoreactivity. However, the likelihood of cross reactivity has never been verified by immunohistochemical techniques. Using our established tissue processing and immunofluorescent staining protocols, we found that A60 consistently labeled mossy fiber terminals in hippocampal area CA3. These A60-positive mossy fiber terminals could also be labeled by Syn I antibody. After treating brain slices with saponin in order to better preserve various membrane and/or vesicular proteins for immunostaining, we observed that A60 could also label additional synapses in various brain areas. Therefore, we used A60 together with a rabbit monoclonal NeuN antibody to confirm the existence of this cross reactivity. We showed that the putative band positive for A60 and Syn I could not be detected by the rabbit anti-NeuN in Western blotting. As efficient as Millipore A60 to recognize neuronal nuclei, the rabbit NeuN antibody demonstrated no labeling of synaptic structures in immunofluorescent staining. The present study successfully verified the cross reactivity present in immunohistochemistry, cautioning that A60 may not be the ideal biomarker to verify neuronal identity due to its cross immunoreactivity. In contrast, the rabbit monoclonal NeuN antibody used in this study may be a better candidate to substitute for A60.

Neuronal Injury, Gliosis, and Glial Proliferation in Two Models of Temporal Lobe Epilepsy

It is estimated that 30%-40% of epilepsy patients are refractory to therapy and animal models are useful for the identification of more efficacious therapeutic agents. Various well-characterized syndrome-specific models are needed to assess their relevance to human seizure disorders and their validity for testing potential therapies. The corneal kindled mouse model of temporal lobe epilepsy (TLE) allows for the rapid screening of investigational compounds, but there is a lack of information as to the specific inflammatory pathology in this model. Similarly, the Theiler murine encephalomyelitis virus (TMEV) model of TLE may prove to be useful for screening, but quantitative assessment of hippocampal pathology is also lacking. We used immunohistochemistry to characterize and quantitate acute neuronal injury and inflammatory features in dorsal CA1 and dentate gyrus regions and in the directly overlying posterior parietal cortex at 2 time points in each of these TLE models. Corneal kindled mice were observed to have astrogliosis, but not microgliosis or neuron cell death. In contrast, TMEV-injected mice had astrogliosis, microgliosis, neuron death, and astrocyte and microglial proliferation. Our results suggest that these 2 animal models might be appropriate for evaluation of distinct therapies for TLE.

Paeoniflorin, a Monoterpene Glycoside, Protects the Brain from Cerebral Ischemic Injury via Inhibition of Apoptosis

Paeoniflorin (PF) is a principal bioactive component, which exhibits many pharmacological effects, including protection against ischemic injury. This paper aimed to investigate the protective effect of PF both in vivo and in vitro. Middle cerebral artery occlusion (MCAO) was performed on male Sprague-Dawley (SD) rat for 2 h, and different doses of PF or vehicle were administered 2 h after reperfusion. Rats were sacrificed after 7 days treatment of PF/vehicle. PF treatment for 7 days ameliorated MCAO-induced neurological deficit and decreased the infarct area. Further study demonstrated that PF inhibited the over-activation of astrocytes and apoptosis of neurons, and PF promoted up-regulation of neuronal specific marker neuron-specific nuclear (NeuN) and microtubule-associated protein 2 (MAP-2) in brain. Moreover, NMDA-induced neuron apoptosis was employed. The in vitro study revealed that PF treatment protected against NMDA-induced cell apoptosis and neuronal loss via up-regulation of neuronal specific marker NeuN, MAP-2 and Bcl-2 and the down-regulation Bax. Taken together, the present study demonstrates that PF produces its protective effect by inhibiting the over-activation of astrocytes, apoptosis of neurons and up-regulation of neuronal specific marker NeuN, MAP-2, and B-cell lymphoma-2 (Bcl-2), and down-regulation Bax. Our study reveals that PF may be a potential neuroprotective agent for stroke and can provide basic data for clinical use.

Widespread microglial activation in patients deceased from traumatic brain injury

PRIMARY OBJECTIVE

The role of microglial activation in traumatic brain injury (TBI) has been extensively described in established animal models. In contrast, very few studies have analysed this process in human patients, the majority being focused on the local reaction in the contused parenchyma. In this work, the main objective was the analysis of microglial activation in brain regions distant from the primary lesion.

RESEARCH DESIGN

Morphological changes of microglia were evaluated in the cerebral cortex of patients deceased from TBI in comparison with control subjects.

METHODS AND PROCEDURES

Cortical samples from five cases with TBI and 10 controls were evaluated using Ricinus communis lectin histochemistry and conventional Hematoxylin-eosin staining.

MAIN OUTCOMES AND RESULTS

It was observed that microglial cells from patients with TBI presented shorter and thicker cellular projections compared with controls. Moreover, the percentage of histological area reactive to lectin was statistically higher in samples from subjects with TBI. These signs of microglial activation were observed in all of the analysed cortical areas, thus indicating a generalized effect on the whole cerebral cortex. The results are consistent with previous imaging PET studies performed in living patients with the 11C-PK11195 radiotracer.

CONCLUSIONS

The findings indicate that TBI induces a widespread activation of brain microglia which affects all cortical areas, including those distant from the contusion site.

Identification of the Avulsion-Injured Spinal Motoneurons

In laboratory studies, counting the spinal motoneurons that survived axonal injury is a major method to estimate the severity and regenerative capacity of the injured motoneurons after the axonal injury and rehabilitation surgery. However, the typical motoneuron marker, the choline acetyltransferase (ChAT), could not be detected in the injured motoneurons within the first 3–4 weeks postinjury. It is necessary to explore the useful and reliable specific phenotypic markers to assess the fate of injured motoneurons in axonal injury. Here, we used the fluorogold to retrograde trace the injured motoneurons in the spinal cord and studied the expression patterns of the alpha-motoneuron marker, the neuronal nuclei DNA-binding protein (NeuN) and the peripheral nerve injury marker, the activating transcriptional factor (ATF-3), and the oxidative stress marker, the neuronal nitric oxide synthase (nNOS) within the first 4 weeks of the root avulsion of the right brachial plexus (BPRA) in the adult male Sprague-Dawley rats. Our results showed that ATF-3 was rapidly induced and sustained to express only in the nuclei of the fluorogold-labeled injured motoneurons but none in the unaffected motoneurons from the 24 h of the injury; meanwhile, the NeuN almost disappeared in the avulsion-affected motoneurons within the first 4 weeks. The nNOS was not detected in the motoneurons until the second week of the injury. On the basis of the present data, we suggest that ATF-3 labels avulsion-injured motoneurons while NeuN and nNOS are poor markers within the first 4 weeks of BPRA.

Neuroprotective effects of Gualou Guizhi decoction in vivo and in vitro

ETHNOPHARMACOLOGICAL RELEVANCE

Gualou Guizhi decoction (GLGZD) prescribed in traditional Chinese medicine has been reported to have protective effects on ischemic stroke. The present study is to investigate the therapeutic effect of GLGZD on ischemic stroke and explore its mode of action.

MATERIALS AND METHODS

GLGZD was studied on transient middle cerebral artery occlusion (MCAO) followed by reperfusion in vivo, as well as on hippocampal primary neuron cultures in vitro.

RESULTS

In vivo, it was shown that GLGZD treatment for 7 days could ameliorate transient middle cerebral artery occlusion (MCAO)-induced neurological deficit, histopathology changes and decrease infarct area. Further study demonstrated that GLGZD inhibited over-activation of astrocytes and apoptosis of neurons and GLGZD promoted up-regulation of neuronal specific marker neuron-specific nuclear (NeuN) and microtubule-associated protein 2 (MAP-2) in brain. Moreover, the in vitro study revealed that GLGZD treatment protected against NMDA-induced cell apoptosis and neuronal loss, and promoted up-regulation of neuronal specific marker NeuN.

CONCLUSIONS

Taken together, the present study demonstrates that GLGZD produces a protection in the MCAO model rats via inhibiting over-activation of astrocytes, apoptosis of neurons and up-regulation of neuronal specific marker NeuN and MAP-2. Our study reveals that GLGZD might be a potential neuroprotective agent for stroke and can provide basic data for clinical use.

Gender issues in antiepileptogenic treatments

Disease modification of epilepsy refers to the alleviation of epileptogenesis or comorbidities after genetic or acquired epileptogenic brain insults. There are currently 30 proof-of-concept experimental pharmacologic studies that have demonstrated some beneficial disease-modifying effects. None of these studies, however, has yet passed from the laboratory to the clinic. The International League Against Epilepsy and American Epilepsy Society working groups on antiepileptogenic (AEG) therapies recently released recommendations for conducting preclinical AEG studies, taking into account many of the critiques raised by previous study designs. One of the issues relates to the lack of analysis of AEG efficacy in both sexes. A review of the literature reveals that most of the preclinical studies have been performed using male rodents, whereas clinical study cohorts include both males and females. Therefore, it is important to determine whether sex differences should be taken into account to a greater extent than they have been historically at different phases of experimental studies. Here we address the following questions based on analysis of available experimental AEG studies: (a) whether sex differences should be considered when searching for novel AEG targets, (b) how sex differences can affect the preclinical AEG study designs and analysis of outcome measures, and (c) what factors should be considered when examining the effect of sex on outcome of clinical AEG trials or the clinical use of AEGs.

Neuronal nuclear antigen (NeuN): a useful marker of neuronal immaturity in sudden unexplained perinatal death

INTRODUCTION

In the developing brain neuronal differentiation is associated with permanent exit from the mitotic cycle. Neuronal nuclear antigen (NeuN) is a nuclear protein widely expressed in the mature postmitotic neurons.

METHODS

We applied NeuN immunocytochemistry in 65 cases of perinatal death (16 victims of sudden intrauterine unexplained death syndrome/SIUDS, 19 of sudden infant death syndrome/SIDS and 30 controls) to test the physiological status of the brain neurons. In addition we applied both TUNEL and Caspase 3 immunohistochemical methods in order to highlight a possible relation between decreased NeuN expression and apoptotic outcome. We also attempted to see whether or not NeuN pathological changes can be related to cigarette smoke absorption in pregnancy.

RESULTS

NeuN staining was considerably reduced or lost in SIUDS/SIDS compared to controls. However neurons with decreased NeuN-labeling showed no sign of apoptosis. A significant association was found between NeuN depletion and maternal smoking.

CONCLUSION

Altered NeuN expression can be a marker of immature and/or suffering neurons. The exclusive presence of this pattern of expression in SIUDS/SIDS victims, leads us to recommend the NeuN immunohistochemistry as a routine method in neuropathological protocols to convalidate a diagnosis of sudden perinatal death.

Multiple interacting cell death mechanisms in the mediation of excitotoxicity and ischemic brain damage: a challenge for neuroprotection

There is currently no approved neuroprotective pharmacotherapy for acute conditions such as stroke and cerebral asphyxia. One of the reasons for this may be the multiplicity of cell death mechanisms, because inhibition of a particular mechanism leaves the brain vulnerable to alternative ones. It is therefore essential to understand the different cell death mechanisms and their interactions. We here review the multiple signaling pathways underlying each of the three main morphological types of cell death--apoptosis, autophagic cell death and necrosis--emphasizing their importance in the neuronal death that occurs during cerebral ischemia and hypoxia-ischemia, and we analyze the interactions between the different mechanisms. Finally, we discuss the implications of the multiplicity of cell death mechanisms for the design of neuroprotective strategies.

Mitochondrial functions in astrocytes: neuroprotective implications from oxidative damage by rotenone

Mitochondria are critical for cell survival and normal development, as they provide energy to the cell, buffer intracellular calcium, and regulate apoptosis. They are also major targets of oxidative stress, which causes bioenergetics failure in astrocytes through the activation of different mechanisms and production of oxidative molecules. This review provides an insightful overview of the recent discoveries and strategies for mitochondrial protection in astrocytes. We also discuss the importance of rotenone as an experimental approach for assessing oxidative stress in the brain and delineate some molecular strategies that enhance mitochondrial function in astrocytes as a promising strategy against brain damage.

Caffeic Acid phenethyl ester protects blood-brain barrier integrity and reduces contusion volume in rodent models of traumatic brain injury

A number of studies have established a deleterious role for inflammatory molecules and reactive oxygen species (ROS) in the pathology of traumatic brain injury (TBI). Caffeic acid phenethyl ester (CAPE) has been shown to exert both antioxidant and anti-inflammatory effects. The primary objective of the present study was to examine if CAPE could be used to reduce some of the pathological consequences of TBI using rodent models. Male Sprague-Dawley rats and C57BL/6 mice were subjected to controlled cortical impact (CCI) injury. Blood-brain barrier (BBB) integrity was assessed by examining claudin-5 expression and the extravasation of Evans blue dye. The effect of post-injury CAPE administration on neurobehavioral function was assessed using vestibulomotor, motor, and two hippocampus-dependent learning and memory tasks. We report that post-TBI administration of CAPE reduces Evans blue extravasation both in rats and mice. This improvement was associated with preservation of the levels of the tight junction protein claudin-5. CAPE treatment did not improve performance in either vestibulomotor/motor function (tested using beam balance and foot-fault tests), or in learning and memory function (tested using the Morris water maze and associative fear memory tasks). However, animals treated with CAPE were found to have significantly less cortical tissue loss than vehicle-treated controls. These findings suggest that CAPE may provide benefit in the treatment of vascular compromise following central nervous system injury.

Neuronal deletion of caspase 8 protects against brain injury in mouse models of controlled cortical impact and kainic acid-induced excitotoxicity

Background

Acute brain injury is an important health problem. Given the critical position of caspase 8 at the crossroads of cell death pathways, we generated a new viable mouse line (Ncasp8^−/−), in which the gene encoding caspase 8 was selectively deleted in neurons by cre-lox system.

Methodology/Principal Findings

Caspase 8 deletion reduced rates of neuronal cell death in primary neuronal cultures and in whole brain organotypic coronal slice cultures prepared from 4 and 8 month old mice and cultivated up to 14 days in vitro. Treatments of cultures with recombinant murine TNFα (100 ng/ml) or TRAIL (250 ng/mL) plus cyclohexamide significantly protected neurons against cell death induced by these apoptosis-inducing ligands. A protective role of caspase 8 deletion in vivo was also demonstrated using a controlled cortical impact (CCI) model of traumatic brain injury (TBI) and seizure-induced brain injury caused by kainic acid (KA). Morphometric analyses were performed using digital imaging in conjunction with image analysis algorithms. By employing virtual images of hundreds of brain sections, we were able to perform quantitative morphometry of histological and immunohistochemical staining data in an unbiased manner. In the TBI model, homozygous deletion of caspase 8 resulted in reduced lesion volumes, improved post-injury motor performance, superior learning and memory retention, decreased apoptosis, diminished proteolytic processing of caspases and caspase substrates, and less neuronal degeneration, compared to wild type, homozygous cre, and caspase 8-floxed control mice. In the KA model, Ncasp8^−/− mice demonstrated superior survival, reduced seizure severity, less apoptosis, and reduced caspase 3 processing. Uninjured aged knockout mice showed improved learning and memory, implicating a possible role for caspase 8 in cognitive decline with aging.

Conclusions

Neuron-specific deletion of caspase 8 reduces brain damage and improves post-traumatic functional outcomes, suggesting an important role for this caspase in pathophysiology of acute brain trauma.

Astrocytic-neuronal crosstalk: implications for neuroprotection from brain injury

The older neurocentric view of the central nervous system (CNS) has changed radically with the growing understanding of the many essential functions of astrocytes. Advances in our understanding of astrocytes include new observations about their structure, organization, function and supportive actions to other cells. Although the contribution of astrocytes to the process of brain injury has not been clearly defined, it is thought that their ability to provide support to neurons after cerebral damage is critical. Astrocytes play a fundamental role in the pathogenesis of brain injury-associated neuronal death, and this secondary injury is primarily a consequence of the failure of astrocytes to support the essential metabolic needs of neurons. These needs include K+ buffering, glutamate clearance, brain antioxidant defense, close metabolic coupling with neurons, and the modulation of neuronal excitability. In this review, we will focus on astrocytic activities that can both protect and endanger neurons, and discuss how manipulating these functions provides a novel and important strategy to enhance neuronal survival and improve the outcome following brain injury.

A selective role for ARMS/Kidins220 scaffold protein in spatial memory and trophic support of entorhinal and frontal cortical neurons

Progressive cortical pathology is common to several neurodegenerative and psychiatric disorders. The entorhinal cortex (EC) and frontal cortex (FC) are particularly vulnerable, and neurotrophins have been implicated because they appear to be protective. A downstream signal transducer of neurotrophins, the ankyrin repeat-rich membrane spanning scaffold protein/Kidins 220 (ARMS) is expressed in the cortex, where it could play an important role in trophic support. To test this hypothesis, we evaluated mice with a heterozygous deletion of ARMS (ARMS(+/-) mice). Remarkably, the EC and FC were the regions that demonstrated the greatest defects. Many EC and FC neurons became pyknotic in ARMS(+/-) mice, so that large areas of the EC and FC were affected by 12 months of age. Areas with pyknosis in the EC and FC of ARMS(+/-) mice were also characterized by a loss of immunoreactivity to a neuronal antigen, NeuN, which has been reported after insult or injury to cortical neurons. Electron microscopy showed that there were defects in mitochondria, myelination, and multilamellar bodies in the EC and FC of ARMS(+/-) mice. Although primarily restricted to the EC and FC, pathology appeared to be sufficient to cause functional impairments, because ARMS(+/-) mice performed worse than wild-type on the Morris water maze. Comparisons of males and females showed that female mice were the affected sex in all comparisons. Taken together, the results suggest that the expression of a prominent neurotrophin receptor substrate normally protects the EC and FC, and that ARMS may be particularly important in females.

Acute imidazenil treatment after the onset of DFP-induced seizure is more effective and longer lasting than midazolam at preventing seizure activity and brain neuropathology

Diazepam (DZ), the preferred anticonvulsant benzodiazepine (BZ) for the treatment of organophosphate (OP) nerve agent-induced seizures and neuronal damage, has been associated with unwanted effects such as sedation, amnesia, cardiorespiratory depression, anticonvulsant tolerance, and dependence liability. In a search for safer and more effective anticonvulsant BZs against OP-induced seizure and neuronal damage, we have previously shown that imidazenil (IMD), a low-intrinsic efficacy positive allosteric modulator of gamma-aminobutyric acid (GABA) action at α1-containing GABA(A) receptors, which has high intrinsic efficacy at α2-, α3-, and α5-containing GABA(A) receptors, is more potent and longer lasting than DZ pretreatment at protecting rats from diisopropyl fluorophosphate (DFP)-induced electrocorticographic (ECoG) seizures and neuronal damage. The effects of IMD were observed at doses that are devoid of sedative, amnestic, and anticonvulsant tolerance actions. In the present study, we compared the anticonvulsant and neuroprotective effects of a combination of atropine (2 mg/kg, ip) and pyridine-2-aldoxime methochloride (2-PAM, 20 mg/kg, ip) with IMD (0.5 mg/kg, ip) or midazolam (MDZ, 0.5-2 mg/kg, ip) administered after the onset of DFP (1.5 mg/kg, sc)-induced seizure activity. The severity of DFP-induced ECoG seizures was assessed by continuous radio telemetry recordings in unrestrained and freely moving rats. Furthermore, the extent of neuronal damage was evaluated using a neuron-specific nuclear protein immunolabeling and fluoro-jade B staining procedure. We report here that IMD is more efficacious and longer lasting than sedating doses of MDZ in protecting rats from DFP-induced ECoG seizures and neuronal damage.

Age is a determinant of leukocyte infiltration and loss of cortical volume after traumatic brain injury

There is increasing evidence that the inflammatory response differs in the injured developing brain as compared to the adult brain. Here we compared cerebral blood flow and profiled the inflammatory response in mice that had been subjected to traumatic brain injury (TBI) at postnatal day (P)21 or at adulthood. Relative blood flow, determined by laser Doppler, revealed a 30% decrease in flow immediately after injury followed by prominent hyperemia between 7 and 35 days after injury in both age groups. The animals were euthanized at 1-35 days after injury and the brains prepared for the immunolocalization and quantification of CD45-, GR-1-, CD4- and CD8-positive (+) cells. On average, the number of CD45+ leukocytes in the cortex was significantly higher in the P21 as compared to the adult group. A similar trend was seen for GR-1+ granulocytes, whereas no age-related differences were noted for CD4+ and CD8+ cells. While CD45+ and GR-1+ cells in the P21 group remained elevated, relative to shams, over the first 2 weeks after injury, the adult group showed a time course limited to the first 3 days after injury. The loss of ipsilateral cortical volumes at 2 weeks after injury was significantly greater in the adult relative to the P21 group. While the adult group showed no further change in cortical volumes, there was a significant loss of cortical volumes between 2 and 5 weeks after injury in the P21 group, reaching values similar to that of the adult group by 5 weeks after injury. Together, these findings demonstrate age-dependent temporal patterns of leukocyte infiltration and loss of cortical volume after TBI.

Disruption of the axon initial segment cytoskeleton is a new mechanism for neuronal injury

Many factors contribute to nervous system dysfunction and failure to regenerate after injury or disease. Here, we describe a previously unrecognized mechanism for nervous system injury. We show that neuronal injury causes rapid, irreversible, and preferential proteolysis of the axon initial segment (AIS) cytoskeleton independently of cell death or axon degeneration, leading to loss of both ion channel clusters and neuronal polarity. Furthermore, we show this is caused by proteolysis of the AIS cytoskeletal proteins ankyrinG and betaIV spectrin by the calcium-dependent cysteine protease calpain. Importantly, calpain inhibition is sufficient to preserve the molecular organization of the AIS both in vitro and in vivo. We conclude that loss of AIS ion channel clusters and neuronal polarity are important contributors to neuronal dysfunction after injury, and that strategies to facilitate recovery must preserve or repair the AIS cytoskeleton.

Glutathione peroxidase overexpression does not rescue impaired neurogenesis in the injured immature brain

Traumatic brain injury (TBI) is a leading cause of disability among young children and is associated with long-term cognitive deficits. These clinical findings have prompted an investigation of the hippocampus in an experimental model of trauma to the developing brain at postnatal day (p21). Previous studies using this model have revealed a progressive loss of neurons in the hippocampus as brain-injured animals mature to young adulthood. Here we determined whether this hippocampal vulnerability is likewise reflected in altered neurogenesis and whether the antioxidant glutathione peroxidase (GPx) modulates neurogenesis during maturation of the injured immature brain. Male transgenic mice that overexpress GPx and wild-type littermates were subjected to controlled cortical impact or sham surgery on p21. At 2 weeks postinjury, the numbers of proliferating cells and immature neurons within the subgranular zone were measured by using Ki-67 and doublecortin, respectively. Bromodeoxyuridine (BrdU) was used to label dividing cells beginning 2 weeks postinjury. Survival (BrdU(+)) and neuronal differentiation (BrdU(+)/NeuN(+)) were then measured 4 weeks later via confocal microscopy. Two-way ANOVA revealed no significant interaction between genotype and injury. Subsequent analysis of the individual effects of injury and genotype, however, showed a significant reduction in subgranular zone proliferation (Ki-67) at 2 weeks postinjury (P = 0.0003) and precursor cell survival (BrdU(+)) at 6 weeks postinjury (P = 0.016) and a trend toward reduced neuronal differentiation (BrdU(+)/NeuN(+)) at 6 weeks postinjury (P = 0.087). Overall, these data demonstrate that traumatic injury to the injured immature brain impairs neurogenesis during maturation and suggest that GPx cannot rescue this reduced neurogenesis.

TTC, fluoro-Jade B and NeuN staining confirm evolving phases of infarction induced by middle cerebral artery occlusion

Considerable debate exists in the literature on how best to measure infarct damage and at what point after middle cerebral artery occlusion (MCAO) infarct is histologically complete. As many researchers are focusing on more chronic endpoints in neuroprotection studies it is important to evaluate histological damage at later time points to ensure that standard methods of tissue injury measurement are accurate. To compare tissue viability at both acute and sub-acute time points, we used 2,3,5-triphenyltetrazolium chloride (TTC), Fluoro-Jade B, and NeuN staining to examine the evolving phases of infarction induced by a 90-min MCAO in mice. Stroke outcomes were examined at 1.5h, 6h, 12h, 24h, 3d, and 7d after MCAO. There was a time-dependent increase in infarct volume from 1.5h to 24h in the cortex, followed by a plateau from 24h to 7d after stroke. Striatal infarcts were complete by 12h. Fluoro-Jade B staining peaked at 24h and was minimal by 7d. Our results indicated that histological damage as measured by TTC and Fluoro-Jade B reaches its peak by 24h after stroke in a reperfusion model of MCAO in mice. TTC staining can be accurately performed as late as 7d after stroke. Neurological deficits do not correlate with the structural lesion but rather transient impairment of function. As the infarct is complete by 24h and even earlier in the striatum, even the most efficacious neuroprotective therapies are unlikely to show any efficacy if given after this point.

Imidazenil, a non-sedating anticonvulsant benzodiazepine, is more potent than diazepam in protecting against DFP-induced seizures and neuronal damage

Organophosphate (OP)-nerve agent poisoning may lead to prolonged epileptiform seizure activity, which can result in irreversible neuronal brain damage. A timely and effective control of seizures with pharmacological agents can minimize the secondary and long-term neuropathology that may result from this damage. Diazepam, the current anticonvulsant of choice in the management of OP poisoning, is associated with unwanted effects such as sedation, amnesia, cardio-respiratory depression, anticonvulsant tolerance, and dependence liabilities. In search for an efficacious and safer anticonvulsant benzodiazepine, we studied imidazenil, a potent anticonvulsant that is devoid of sedative action and has a low intrinsic efficacy at alpha1- but is a high efficacy positive allosteric modulator at alpha5-containing GABA(A) receptors. We compared the potency of a combination of 2 mg/kg, i.p. atropine with: (a) imidazenil 0.05-0.5 mg/kg i.p. or (b) equipotent anti-bicuculline doses of diazepam (0.5-5 mg/kg, i.p.), against diisopropyl fluorophosphate (DFP; 1.5 mg/kg, s.c.)-induced status epilepticus and its associated neuronal damage. The severity and frequency of seizure activities were determined by continuous radio telemetry recordings while the extent of neuronal damage and neuronal degeneration were assessed using the TUNEL-based cleaved DNA end-labeling technique or neuron-specific nuclear protein (NeuN)-immunolabeling and Fluoro-Jade B (FJB) staining, respectively. We report here that the combination of atropine and imidazenil is at least 10-fold more potent and longer lasting than the combination with diazepam at protecting rats from DFP-induced seizures and the associated neuronal damage or ongoing degeneration in the anterior cingulate cortex, CA1 hippocampus, and dentate gyrus. While 0.5 mg/kg imidazenil effectively attenuated DFP-induced neuronal damage and the ongoing neuronal degeneration in the anterior cingulate cortex, dentate gyrus, and CA1 hippocampus, 5 mg/kg or a higher dose of diazepam is required to produce similar protective effects. These finding suggests that imidazenil, a non-sedating anticonvulsant BZ ligand, is a more potent, effective, and safer drug than diazepam in protecting rats from DFP-induced seizures and the associated neuronal damage and/or ongoing neuronal degeneration.

Mannose binding lectin gene deficiency increases susceptibility to traumatic brain injury in mice

Mannose binding lectin (MBL) initiates complement activation and exacerbates tissue damage after systemic ischemia/reperfusion. We tested the hypothesis that MBL activates complement and worsens outcome using two levels of controlled cortical impact (CCI) in mice. After moderate CCI (0.6 mm depth), MBL immunostaining was detected on injured endothelial cells of wild-type (WT) mice and C3d was detected in MBL KO (deficient in MBL A/C) and WT mice, suggesting that MBL is dispensable for terminal complement activation after CCI. Brain neutrophils, edema, blood-brain barrier permeability, gross histopathology, and motor dysfunction were similar in injured MBL KO and WT mice. In mice subjected to mild CCI (0.2 mm), MBL KO mice had almost two-fold increased acute CA3 cell degeneration at 6 h (P<0.01 versus WT). Naive MBL KO mice had decreased brain volume but performed similar to WT mice in two distinct Morris water maze (MWM) paradigms. However, injured MBL KO mice had impaired performance in cued platform trials (P<0.05 versus WT), suggesting a transient nonspatial learning deficit in injured MBL KO mice. The data suggest that MBL deficiency increases susceptibility to CCI through C3-independent mechanisms and that MBL-deficient patients may be at increased risk of poor outcome after traumatic brain injury.

Gender-related differences in apoptotic pathways after neonatal cerebral ischemia

Many central nervous system (CNS) diseases display sexual dimorphism, specifically a predilection for one gender or a gender-dependent response to treatment. Exposure to circulating sex steroids is felt to be a chief contributor to this phenomenon. However, CNS diseases of childhood and of the elderly also demonstrate gender predominance and/or sexual dimorphism response to therapies. In this short update, we provide information concerning one of the most interesting new emerging concepts related to the influence of the sex in the pathogenesis of developmental brain injuries leading to different levels of neuroprotection between genders after cerebral hypoxia-ischemia or ischemia.

The high affinity peripheral benzodiazepine receptor ligand DAA1106 binds specifically to microglia in a rat model of traumatic brain injury: implications for PET imaging

Traumatic brain injury (TBI) is a significant cause of mortality, morbidity, and disability. Microglial activation is commonly observed in response to neuronal injury which, when prolonged, is thought to be detrimental to neuronal survival. Activated microglia can be labeled using PK11195, a ligand that binds the peripheral benzodiazepine receptor (PBR), receptors which are increased in activated microglia and sparse in the resting brain. We compared the binding properties of two PBR ligands PK11195 and DAA1106 in rats using the controlled cortical impact (CCI) model of experimental TBI. While both ligands showed relative increases with specific binding in the cortex ipsilateral to injury compared to the contralateral side, [(3)H]DAA1106 showed higher binding affinity compared with [(3)H](R)-PK11195. Combined immunohistochemistry and autoradiography in brain tissues near the injury site showed that [(3)H]DAA1106 binding co-registered with activated microglia more than astrocytes. Further, increased [(3)H]DAA1106-specific binding positively correlated with the degree of microglial activation, and to a lesser degree with reactive astrocytosis. Finally, in vivo administration of each ligand in rats with TBI showed greater retention of [(11)C]DAA1106 compared to [(11)C](R)-PK11195 at the site of the contusion as assessed by ex vivo autoradiography. These results in a rat model of TBI indicate that [(11)C]DAA1106 binds with higher affinity to microglia when compared with PK11195, suggesting that [(11)C]DAA1106 may represent a better ligand than [(11)C](R)-PK11195 for in vivo PET imaging of activated microglia in TBI.

Effects of estradiol on cognition and hippocampal pathology after lateral fluid percussion brain injury in female rats

Studies involving animal models of acute central nervous system (CNS) stroke and trauma strongly indicate that sex and/or hormonal status are important determinants of outcome after brain injury. The present study was undertaken to examine the ability of estradiol to protect hippocampal neurons from lateral fluid percussion brain injury. Sprague-Dawley female rats (211-285 g; n = 119) were ovariectomized, and a subset (n = 66) were implanted with 17beta-estradiol pellets to provide near physiological levels of estradiol. Animals were subjected to lateral fluid percussion brain injury or sham injury 1 week later. Activation of caspase-3 (n = 26) and TUNEL staining (n = 21) were assessed at 3 and 12 h after injury, respectively, in surviving control and estradiol-treated animals. Memory retention was examined using a Morris water maze test in a separate subset of animals (n = 43) at 8 days after injury. Activated caspase-3 and TUNEL staining were observed in the dentate hilus, granule cell layer, and CA3 regions in all injured rats, indicative of selective hippocampal cell apoptosis in the acute posttraumatic period. Estradiol did not significantly alter the number of hippocampal neurons exhibiting caspase-3 activity or TUNEL staining. Brain injury impaired cognitive ability, assessed at 1 week post-injury (p < 0.001). However, estradiol at physiological levels did not significantly alter injury-induced loss of memory. These data indicate that estradiol at physiological levels does not ameliorate trauma-induced hippocampal injury or cognitive deficits in ovariectomized female rats.

Gender and Estrogen Manipulation Do Not Affect Traumatic Brain Injury in Mice

As epidemiological data have suggested that female patients may have improved clinical prognoses following traumatic brain injury (TBI) compared to males, we designed experiments to determine the role of gender and estrogen in TBI-induced brain injury and inflammation in rodents. To this end, male and female C57Bl/6 mice were separated into the following four groups: intact males, intact females with vehicle supplementation, ovariectomized females with vehicle supplementation, and ovariectomized females with estrogen supplementation. All mice were subjected to a controlled cortical impact model of TBI, and cortical injury, hippocampal degeneration, microglial activation, and brain cytokine expression were analyzed after injury. Additionally, the spleens were harvested and cytokine release from cultured splenic cells was measured in response to specific stimuli. Data indicate that TBI-induced cortical and hippocampal injury, as well as injury-related microglial activation were not significantly affected by gender or estrogen manipulation. Conversely, brain levels of MCP-1 and IL-6 were significantly increased in males and intact females following TBI, but not in female mice that had been ovariectomized and supplemented with either estrogen or vehicle. Evaluation of splenic responses showed that the spleen was only moderately affected by TBI, and furthermore that spleens isolated from mice that had been given estrogen supplementation showed significantly higher release of the anti-inflammatory cytokine IL-4, regardless of the presence of absence of TBI. Overall, these data indicate that while estrogen can modulate immune responses, and indeed can predispose splenic responses towards and anti-inflammatory phenotype, these effects do not translate to decreased brain injury or inflammation following TBI in mice.