Decrease in total and free magnesium concentration following traumatic brain injury in rats

31P magnetic resonance spectroscopy was used to determine the intracellular free Mg2+ concentration prior to and following fluid percussion induced traumatic brain injury in rats. Prior to injury, cerebral intracellular free Mg2+ concentration in the rat was 0.93 +/- 0.19 mM (mean +/- SE; n = 5). Following injury, free Mg2+ in the injured cortex declined by 70% within the first hour, and did not recover over the next 3 hours. Total Mg2+ also declined by 10% over this time period; however, there were no changes in brain Na+ or tissue water content. Because of its primary role in cellular metabolism, the early decline in tissue Mg2+ following brain trauma may be a critical factor in the development of irreversible tissue injury.     

Critical role of NADPH oxidase in neuronal oxidative damage and microglia activation following traumatic brain injury

Background

Oxidative stress is known to play an important role in the pathology of traumatic brain injury. Mitochondria are thought to be the major source of the damaging reactive oxygen species (ROS) following TBI. However, recent work has revealed that the membrane, via the enzyme NADPH oxidase can also generate the superoxide radical (O₂ ⁻), and thereby potentially contribute to the oxidative stress following TBI. The current study thus addressed the potential role of NADPH oxidase in TBI.

Methodology/Principal Findings

The results revealed that NADPH oxidase activity in the cerebral cortex and hippocampal CA1 region increases rapidly following controlled cortical impact in male mice, with an early peak at 1 h, followed by a secondary peak from 24–96 h after TBI. In situ localization using oxidized hydroethidine and the neuronal marker, NeuN, revealed that the O₂ ⁻ induction occurred in neurons at 1 h after TBI. Pre- or post-treatment with the NADPH oxidase inhibitor, apocynin markedly inhibited microglial activation and oxidative stress damage. Apocynin also attenuated TBI-induction of the Alzheimer''s disease proteins β-amyloid and amyloid precursor protein. Finally, both pre- and post-treatment of apocynin was also shown to induce significant neuroprotection against TBI. In addition, a NOX2-specific inhibitor, gp91ds-tat was also shown to exert neuroprotection against TBI.

Conclusions/Significance

As a whole, the study demonstrates that NADPH oxidase activity and superoxide production exhibit a biphasic elevation in the hippocampus and cortex following TBI, which contributes significantly to the pathology of TBI via mediation of oxidative stress damage, microglial activation, and AD protein induction in the brain following TBI.     

Plasma copeptin concentration and outcome after pediatric traumatic brain injury

Higher plasma copeptin level has been associated with poor outcomes of critical illness. The present study was undertaken to investigate the plasma copeptin concentrations in children with traumatic brain injury (TBI) and to analyze the correlation of copeptin with disease outcome. Plasma copeptin concentrations of 126 healthy children and 126 children with acute severe TBI were measured by enzyme-linked immunosorbent assay. Twenty-one patients (16.7%) died and 38 patients (30.2%) had an unfavorable outcome (Glasgow Outcome Scale score of 1–3) at 6 months. Plasma copeptin level was obviously higher in patients than in healthy children (46.2 ± 20.8 pmol/L vs. 9.6 ± 3.0 pmol/L, P < 0.001). Plasma copeptin level was identified as an independent predictor for 6-month mortality [odds ratio (OR) 1.261, 95% confidence interval (CI) 1.112–1.538, P = 0.005] and unfavorable outcome (OR 1.313, 95% CI 1.146–1.659, P = 0.003). The predictive value of copeptin was similar to that of Glasgow Coma Scale (GCS) score for 6-month mortality [area under curve (AUC) 0.832, 95% CI 0.755–0.892 vs. AUC 0.873, 95% CI 0.802–0.926, P = 0.412] and unfavorable outcome (AUC 0.863, 95% CI 0.790–0.918 vs. AUC 0.885, 95% CI 0.816–0.935, P = 0.596). Copeptin improved the AUC of GCS score for 6-month unfavorable outcome (AUC 0.929, 95% CI 0.869–0.967, P = 0.013), but not for 6-month mortality (AUC 0.887, 95% CI 0.818–0.936, P = 0.600). Thus, plasma copeptin level represents a novel biomarker for predicting 6-month clinical outcome in children with TBI.     

Endogenous progesterone and lordosis behavior in male rats given estrogen alone

Male rats castrated as adults were given successive doses of estradiol benzoate (EB) combined or not, with dexamethasone (DEXA) at the end of estrogen treatment. Two experiments were done to determine if progesterone (P) of adrenocortical origin was involved in the display of lordosis behavior under these experimental circumstances. There was a significant rise in blood P concentration in animals given 0.5 and 1.0 microgram EB when compared with oil-control injected animals, an effect which was completely suppressed by DEXA treatment. An increase in the proportion of estrogen treated animals displaying lordosis responses to male mounts was found with increasing doses of EB and paralleled the effects of EB on P adrenocortical secretion. However, the number of feminized animals given 1 microgram EB + DEXA was reduced to the level corresponding to the effects of 0.5 microgram EB on lordosis behavior. These data show that the secretion of P by the adrenals is involved in the expression of lordosis behavior in castrated male rats primed with repeated doses of estrogen.     

创伤性颅脑损伤脑脊液代谢谱改变及临床意义

目的:探讨创伤性颅脑外伤患者脑脊液中代谢谱的改变及其临床意义。方法:用高分辨率质子核磁共振代谢组学检验创伤性颅脑损伤对脑化学物质和代谢的影响。在重型创伤性颅脑损伤组(n=6),损伤后的脑脊液分析脑代谢的变化,并与轻,中型颅脑损伤组(n=6)相比较。结果:与轻型,中型颅脑损伤组相比,发现了乙酰乙酸,尿酸,3-硝基酪氨酸升高的证据。3组脑脊液中乙酰乙酸,尿酸,3-硝基酪氨酸含量有显著性差异(p<0.01)。结论:颅脑创伤后脑脊液中乙酰乙酸,尿酸,3-硝基酪氨酸值均有不同程度升高,且升高越明显则病情越严重。说明乙酰乙酸,尿酸,3-硝基酪氨酸可作为颅脑创伤病情的监测指标。     

Augmentation of progesterone receptor concentration by progesterone and estrogen treatments in the chick oviduct

Cytosol receptors for progesterone in the chick oviduct were measured by charcoal-adsorbtion assay by using ORG 2058 as a ligand after long-term administration of progesterone and diethylstilbestrol (DES). Steroid administration was carried out by using daily injections or silastic capsules. DES treatment increased the progesterone receptor concentration (from 11500 to 21500 sites per cell, day 14). Progesterone also augmented the concentration of its own receptors (from 11500 to 29000 sites per cell, day 14). In the experiments with capsule administration the same trend was seen. This indicates that both diethylstilbestrol and progesterone are able to increase the concentration of progesterone specific cytosol receptors in the non-differentiated chick oviduct.     

Principal component analysis of the cytokine and chemokine response to human traumatic brain injury

There is a growing realisation that neuro-inflammation plays a fundamental role in the pathology of Traumatic Brain Injury (TBI). This has led to the search for biomarkers that reflect these underlying inflammatory processes using techniques such as cerebral microdialysis. The interpretation of such biomarker data has been limited by the statistical methods used. When analysing data of this sort the multiple putative interactions between mediators need to be considered as well as the timing of production and high degree of statistical co-variance in levels of these mediators. Here we present a cytokine and chemokine dataset from human brain following human traumatic brain injury and use principal component analysis and partial least squares discriminant analysis to demonstrate the pattern of production following TBI, distinct phases of the humoral inflammatory response and the differing patterns of response in brain and in peripheral blood. This technique has the added advantage of making no assumptions about the Relative Recovery (RR) of microdialysis derived parameters. Taken together these techniques can be used in complex microdialysis datasets to summarise the data succinctly and generate hypotheses for future study.     

The effects of adrenomedullin in traumatic brain injury

Traumatic brain injury (TBI) is a common cause of death and disability throughout the world. A multifunctional peptide adrenomedullin (AM) has protective effects in the central nervous system. We evaluated AM in an animal model as a therapeutic agent that reduces brain damage after traumatic brain injury. A total of 36 rats was divided into 3 groups as sham, head trauma plus intraperitoneal (ip) saline, and head trauma plus adrenomedullin ip. The diffuse brain injury model of Marmarou et al. was used. Blood samples were taken from all groups at the 1st, 6th and 24th hours for analysis of TNF-α (tumor necrosis factor-α), IL-1β (interleukin-1β) and IL-6 (interleukin-6) levels. At the end of the study (at the 24th hour) a neurological examination was performed and half of the rats were decapitated to obtain blood and tissue samples, the other half were perfused transcardiacally for studying the histopathology of the brain tissue. There were no statistically significant changes in plasma levels of IL-1β, IL-6 and TNF-α relative to the sham group. Also, changes in tissue levels of malonedialdehyde, myeloperoxidase and glutathione were not statistically significant. However, neurological scores and histopathological examinations revealed healing. AM individually exerts neuroprotective effects in animal models of acute brain injury. But the mechanisms of action remain to be assessed.     

Differential modulation of carbachol and trans-ACPD-stimulated phosphoinositide turnover following traumatic brain injury

In the fluid percussion model of traumatic brain injury (TBI), we examined muscarinic and metabotropic glutamate receptor-stimulated polyphosphoinositide (PPI) turnover in rat hippocampus. Moderate injury was obtained by displacement and deformation of the brain within the closed cranial cavity using a fluid percussion device. Carbachol and (±)-1-Aminocyclopentane-trans-1,3.-dicarboxylic acid (trans-ACPD)-stimulated PPI hydrolysis was assayed in hippocampus from injured and sham-injured controls at both 1 hour and 15 days following injury. At 1 hour after TBI, the response to carbachol was enhanced in injured rats by up to 200% but the response to trans-ACPD was diminished by as much as 28%. By contrast, at 15 days after TBI, the response to carbachol was enhanced by 25% and the response to trans-ACPD was enhanced by 73%. The ionotropic glutamate agonists N-methyl-D-aspartate (NMDA), and -amino-3 hydroxy-5-methyl-4-isoxazolepropionate (AMPA), did not increase PPI hydrolysis in either sham or injured rats and injury did not alter basal hydrolysis. Thus, hippocampal muscarinic and metabotropic receptors linked to phospholipase C are differentially altered by TBI.Abbreviations used TBI traumatic brain injury - EAA excitatory amino acids - PPI polyphosphoinositides - IP inositol phosphates - NMDA N-methyl-D-aspartate - AMPA -amino-3-hydroxy-5-methylisoxazole-4-propionate - trans-ACPD (±)-1-Aminocyclopentanetrans-1,3-dicarboxylic acid - LTP long term potentiation     

Differential regulation of metallothionein-I and metallothionein-II mRNA expression in the rat brain following traumatic brain injury

In this study, we investigated the expression of metallothionein (MT)-I and MT-II in the rat brain following traumatic brain injury (TBI). In the early stage, significant induction of MT-I and MT-II were observed in various regions including ventricle walls, pia mater, and dentate gyrus. At 12-24 h after TBI, strong induction of MT-I mRNA was observed in cerebral cortical layer II/III, amygdala, and piriform cortex where neurons reside. On the other hand, MT-II appeared to be expressed mainly in glial cells localized in the cerebral cortex and hippocampal formation. Three days after TBI, MTs were observed in the vimentin-positive astrocytes in the penumbra as revealed by double immunohistochemistry. The differences in expression of MT-I and MT-II in different brain regions and cell types (neuron vs. glial cells) suggests that multiple regulatory mechanisms are involved in the control of MT expression following brain injury.     

Excitotoxic mechanisms and the role of astrocytic glutamate transporters in traumatic brain injury

Glutamate excitotoxicity plays an important role in the development of secondary injuries that occur following traumatic brain injury (TBI), and contributes significantly to expansion of the total volume of injury. Acute increases in extracellular glutamate levels have been detected in both experimental brain trauma models and in human patients, and can lead to over-stimulation of glutamate receptors, resulting in a cascade of excitotoxic-related mechanisms culminating in neuronal damage. These elevated levels of glutamate can be effectively controlled by the astrocytic glutamate transporters GLAST (EAAT1) and GLT-1 (EAAT2). However, evidence indicate these transporters and splice variant are downregulated shortly following the insult, which then precipitates glutamate-mediated excitotoxic conditions. Lack of success with glutamate receptor antagonists as a potential source of clinical intervention treatment following TBI has resulted in the necessity for a better understanding of the mechanisms that underlie the process of excitotoxicity, including the function and regulation of glutamate transporters. Such new insight should improve the likelihood of development of novel avenues for therapeutic intervention following TBI.     

Tissue compartment-specific role of estrogen receptor subtypes in immune cell cytokine production following trauma-hemorrhage.

Although 17beta-estradiol administration following trauma-hemorrhage attenuates plasma cytokines and alteration in immune cell cytokine production, it is not known whether the salutary effects are mediated via estrogen receptor (ER)-alpha or ER-beta. Accordingly, we examined which ER subtype predominantly mediates the salutary effects of 17beta-estradiol on systemic inflammatory response/immune cell cytokine production in various tissues following trauma-hemorrhage. Male rats underwent trauma-hemorrhage (mean blood pressure: 40 mmHg for 90 min) and fluid resuscitation. The ER-alpha agonist propyl pyrazole triol (PPT; 5 microg/kg), the ER-beta agonist diarylpropionitrile (DPN; 5 microg/kg), 17beta-estradiol (50 microg/kg), or vehicle (10% DMSO) was injected subcutaneously during resuscitation, and various measurements were made 24 h thereafter. 17beta-Estradiol or PPT administration following trauma-hemorrhage prevented the increase in plasma IL-6 and IL-10 levels that were observed in vehicle-treated animals. IL-6 and TNF-alpha production by Kupffer cells increased; however, splenic macrophages (SMPhi), alveolar macrophages (AMPhi), and peripheral blood mononuclear cells (PBMC) had decreased release of these cytokines after trauma-hemorrhage. IL-10 production, however, increased in all macrophage populations. Administration of 17beta-estradiol following trauma-hemorrhage prevented all of these alterations. PPT had the same effects as 17beta-estradiol on IL-6 and TNF-alpha production by Kupffer cells and SMPhi, and DPN had the same effects on AMPhi and PBMC. The same effects as 17beta-estradiol on IL-10 production were observed by PPT on Kupffer cells and DPN on PBMC. Both agonists were equally effective on SMPhi and AMPhi. Thus ER subtypes have tissue compartment-specific roles in mediating the effects of 17beta-estradiol on immune cell functions following trauma-hemorrhage.     

A physiological role for estrogen and progesterone in breast cancer

Breast cancer is often hormone responsive, since growth or regression of tumors can often be modulated by appropriate endocrine manipulations. Estrogen and progesterone are major hormones involved in regulation of breast cancer tumor growth. Considerable insight into the mechanism of action of these hormones on tumor growth stimulation has been provided by demonstration of specific receptors for each. The inference that each hormone acts independently through its receptor to control tumor growth is belied by current studies which show that certain hormones are capable of regulating the receptor sites, metabolism, or nuclear translocation of others. This may begin to explain the complex hormonal interactions and requirements of normal and neoplastic breast tissues. Considerable progress has thus been made in understanding the basis for success of various ablative therapies.The pharmacologie actions of estrogens and progestins in causing breast tumor regression is much less well understood. The role of hormone receptor sites has not been established in the mechanism of tumor regression caused by these pharmacological therapies. Nevertheless, when estrogen receptors are absent in a tumor, we can with accuracy pre.dict that endocrine therapies will fail, whereas when ER is present the likelihood of a successful response to pharmacological or ablative therapy is high.Receptor sites seem to be a common denominator and useful marker for hormone dependence or hormone responsiveness, irrespective of their actual role in the tumor regression process. Further investigations into the receptor functions should lead to new approaches in the endocrine management of patients with breast cancer.     

The role of estrogen as a parahormone in brain and pituitary

Where aromatase and estrogen receptors are co-localized in brain and pituitary, estrogen functions as a parahormone, and estrogen levels which determine the occurrence or magnitude of a response are those in close proximity to targets. Teleost fish, a vertebrate group characterized by exceptionally high aromatase in neuroendocrine tissues, are technically advantageous animal models for studying the cellular location of aromatase, natural changes correlated with seasonal reproductive cycles, substrate-dependence of the reaction, steroid induction of enzyme activity, and possible non-genomic actions of estrogen on cultured neurons. In addition, characterization of steroid receptors reveals that the androgen receptor, like aromatase, is present in unusually high concentrations (10- to 100-fold higher than in mammalian brain). Since androgen receptors and aromatase both utilize testosterone as a ligand, their high abundance in teleost brain may be the consequence of a functional interdependence during evolution, although the primary causal factor is unknown. These studies illustrate the usefulness of unconventional species and a comparative approach for obtaining new insights into brain-steroid interactions.     

The role of metals in modulating metalloprotease activity in the AD brain

Biometals such as copper and zinc have an important role in Alzheimer’s disease (AD). Accumulating evidence indicates that copper homeostasis is altered in AD brain with elevated extracellular and low intracellular copper levels. Studies in animals and cell cultures have suggested that increasing intracellular copper can ameliorate AD-like pathology including amyloid deposition and tau phosphorylation. Modulating copper homeostasis can also improve cognitive function in animal models of AD. Treatments are now being developed that may result in redistribution of copper within the brain. Metal ligands such as clioquinol (CQ), DP-109 or pyrrolidine dithiocarbamate (PDTC) have shown promising results in animal models of AD, however, the actual mode of action in vivo has not been fully determined. We previously reported that CQ-metal complexes were able to increase intracellular copper levels in vitro. This resulted in stimulation of phosphoinositol-3-kinase activity and mitogen activated protein kinases (MAPK). Increased kinase activity resulted in up-regulated matrix metalloprotease (MMP2 and MMP3) activity resulting in enhanced degradation of secreted Aβ. These findings are consistent with previous studies reporting metal-mediated activation of MAPKs and MMPs. How this activation occurs is unknown but evidence suggests that copper may be able to activate membrane receptors such as the epidermal growth factor receptor (EGFR) and result in downstream activation of MAPK pathways. This has been supported by studies showing metal-mediated activation of EGFR through ligand-independent processes in a number of cell-types. Our initial studies reveal that copper complexes can in fact activate EGFR. However, further studies are necessary to determine if metal complexes such as CQ-copper induce up-regulation of Aβ-degrading MMP activity through this mechanism. Elucidation of this pathway may have important implications for the development of metal ligand based therapeutics for treatment of AD and other neurodegenerative disorders. Australian Society for Biophysics Special Issue: Metals and Membranes in Neuroscience, held in Melbourne on 11 July 2007.     

Modulation of autophagy in traumatic brain injury

Traumatic brain injury (TBI) is defined as a traumatically induced structural injury or physiological disruption of brain function as a result of external forces, leading to adult disability and death. A growing body of evidence reveals that alterations in autophagy-related proteins exist extensively in both experimentally and clinically after TBI. Of note, the autophagy pathway plays an essential role in pathophysiological processes, such as oxidative stress, inflammatory response, and apoptosis, thus contributing to neurological properties of TBI. With this in mind, this review summarizes a comprehensive overview on the beneficial and detrimental effects of autophagy in pathophysiological conditions and how these activities are linked to the pathogenesis of TBI. Moreover, the relationship between oxidative stress, inflammation, apoptosis, and autophagy occur TBI. Ultimately, multiple compounds and various drugs targeting the autophagy pathway are well described in TBI. Therefore, autophagy flux represents a potential clinical therapeutic value for the treatment of TBI and its complications.