Comprehensive Profiling of Modulation of Nitric Oxide Levels and Mitochondrial Activity in the Injured Brain: An Experimental Study Based on the Fluid Percussion Injury Model in Rats

Nitric oxide (NO) has frequently been associated with secondary damage after brain injury. However, average NO levels in different brain regions before and after traumatic brain injury (TBI) and its role in post-TBI mitochondrial dysfunction remain unclear. In this comprehensive profiling study, we demonstrate for the first time that basal NO levels vary significantly in the healthy cortex (0.44 +/- 0.04 mu M), hippocampus (0.26 +/- 0.03 mu M), and cerebellum (1.24 +/- 0.08 mu M). Within 4 h of severe lateral fluid percussion injury, NO levels almost doubled in these regions, thereby preserving regional differences in NO levels. TBI-induced NO generation was associated with inducible NO synthase (iNOS) increase in ipsilateral but not in contralateral regions. The transient NO increase resulted in a persistent tyrosine nitration adjacent to the injury site. Nitrosative stress-associated cell loss via apoptosis and receptor-interacting serine/threonine-protein kinase 3 (RIPK3)-mediated necrosis were also observed in the ipsilateral cortex, despite high levels of NO in the contralateral cortex. NO-mediated impairment of mitochondrial state 3 respiration dependent on complex I substrates was transient and confined to the ipsilateral cortex. Our results demonstrate that NO dynamics and associated effects differ in various regions of the injured brain. A potential association between the observed mitochondrial electron flow through complex I, but not complex II, and the modulation of TBI induced NO levels in different brain regions has to be prospectively analyzed in more detail

Central amygdala circuitry modulates nociceptive processing through differential hierarchical interaction with affective network dynamics

In order to examine how central amygdala (CE) local circuitry interacts with brain-wide affective states, Wank et al performed gene expression analysis and optogenetic fMRI in mice, using basic nociception as a proxy. They found evidence for diverging roles of two major CE neuronal populations in modulating global brain states, which impacts on aversive processing and nocifensive behaviour

Rapid nucleus-scale reorganization of chromatin in neurons enables transcriptional adaptation for memory consolidation.

The interphase nucleus is functionally organized in active and repressed territories defining the transcriptional status of the cell. However, it remains poorly understood how the nuclear architecture of neurons adapts in response to behaviorally relevant stimuli that trigger fast alterations in gene expression patterns. Imaging of fluorescently tagged nucleosomes revealed that pharmacological manipulation of neuronal activity in vitro and auditory cued fear conditioning in vivo induce nucleus-scale restructuring of chromatin within minutes. Furthermore, the acquisition of auditory fear memory is impaired after infusion of a drug into auditory cortex which blocks chromatin reorganization in vitro. We propose that active chromatin movements at the nucleus scale act together with local gene-specific modifications to enable transcriptional adaptations at fast time scales. Introducing a transgenic mouse line for photolabeling of histones, we extend the realm of systems available for imaging of chromatin dynamics to living animals

MicroRNA-451a overexpression induces accelerated neuronal differentiation of Ntera2/D1 cells and ablation affects neurogenesis in microRNA-451a-/- mice.

MiR-451a is best known for its role in erythropoiesis and for its tumour suppressor features. Here we show a role for miR-451a in neuronal differentiation through analysis of endogenous and ectopically expressed or silenced miR-451a in Ntera2/D1 cells during neuronal differentiation. Furthermore, we compared neuronal differentiation in the dentate gyrus of hippocampus of miR-451a-/- and wild type mice. MiR-451a overexpression in lentiviral transduced Ntera2/D1 cells was associated with a significant shifting of mRNA expression of the developmental markers Nestin, βIII Tubulin, NF200, DCX and MAP2 to earlier developmental time points, compared to control vector transduced cells. In line with this, accelerated neuronal network formation in AB.G.miR-451a transduced cells, as well as an increase in neurite outgrowth both in number and length was observed. MiR-451a targets genes MIF, AKT1, CAB39, YWHAZ, RAB14, TSC1, OSR1, POU3F2, TNS4, PSMB8, CXCL16, CDKN2D and IL6R were, moreover, either constantly downregulated or exhibited shifted expression profiles in AB.G.miR-451a transduced cells. Lentiviral knockdown of endogenous miR-451a expression in Ntera2/D1 cells resulted in decelerated differentiation. Endogenous miR-451a expression was upregulated during development in the hippocampus of wildtype mice. In situ hybridization revealed intensively stained single cells in the subgranular zone and the hilus of the dentate gyrus of wild type mice, while genetic ablation of miR-451a was observed to promote an imbalance between proliferation and neuronal differentiation in neurogenic brain regions, suggested by Ki67 and DCX staining. Taken together, these results provide strong support for a role of miR-451a in neuronal maturation processes in vitro and in vivo

Repetitive Long-Term Hyperbaric Oxygen Treatment (HBOT) Administered after Experimental Traumatic Brain Injury in Rats Induces Significant Remyelination and a Recovery of Sensorimotor Function

<div><p>Cells in the central nervous system rely almost exclusively on aerobic metabolism. Oxygen deprivation, such as injury-associated ischemia, results in detrimental apoptotic and necrotic cell loss. There is evidence that repetitive hyperbaric oxygen therapy (HBOT) improves outcomes in traumatic brain-injured patients. However, there are no experimental studies investigating the mechanism of repetitive long-term HBOT treatment-associated protective effects. We have therefore analysed the effect of long-term repetitive HBOT treatment on brain trauma-associated cerebral modulations using the lateral fluid percussion model for rats. Trauma-associated neurological impairment regressed significantly in the group of HBO-treated animals within three weeks post trauma. Evaluation of somatosensory-evoked potentials indicated a possible remyelination of neurons in the injured hemisphere following HBOT. This presumption was confirmed by a pronounced increase in myelin basic protein isoforms, PLP expression as well as an increase in myelin following three weeks of repetitive HBO treatment. Our results indicate that protective long-term HBOT effects following brain injury is mediated by a pronounced remyelination in the ipsilateral injured cortex as substantiated by the associated recovery of sensorimotor function.</p></div

Grouping of animals and number of animals per group and testing parameter.

<p>*Uneven number of animals is due to trauma- or anaesthesia-related loss of rats. ^#Different groups were implemented since this allowed for simultaneous analysis of these parameters. Biases in the results of the distinct testing parameters due to previous handling of the animals were thereby avoided, i.e. anaesthetics and interventions during MRI or SSEP did not affect behavioural potentials of the rats and vice versa. mTBI: moderate traumatic brain injury; sTBI: severe traumatic brain injury.</p

Time-dependent changes in the central conduction times following traumatic brain injury and HBO treatment established by somatosensory-evoked potentials.

<p>A. Schematic representation of the somatosensory-evoked potential recording sites adapted from the human 10–20 system. B. The central conduction time (CCT) is calculated by subtracting the peak latency of the major response from the neck from the latency of the primary cortical response C. Time-dependent modulation in the central conduction time recorded at the ipsi- and contralateral hemisphere in treated and untreated brain injured rats. Open square: HBO-treated brain injured rats; open circle: untreated brain injured rats; ---- baseline recordings; The HBOT effect was not observed at all time points (repeated measures mixed model ANOVA; <i>F(1,20) = 0.38, n.s.</i>); however, there was a significant effect at 3 weeks. *<i>p<</i>0.05 (repeated measures ANOVA, Bonferonni corrected); ^#<i>p</i>≤0.003 (t-test), HBO-treated versus untreated injured animals. ^##<i>p<0.001</i> (ANOVA), HBO-treated animals versus sham controls; n = 5 for untreated, n = 12 for HBO-treated (uneven group sizes arise from missing data points in some animals, which were excluded in repeated measures mixed model ANOVA). Error bars represent ± standard error means.</p

Modulation of myelin in the ipsilateral cortex at day 22 following induction of traumatic brain injury and HBO treatment.

<p>A. Quantitative analysis of myelin stained by Luxol Fast Blue. The ipsilateral hemisphere was analysed as a whole in order to avoid bias. Representation of the % tissue translucence of the ipsilateral hemisphere as compared to sham controls; a minimum of 4 successive brain slices per animal were analysed, *<i>p<0.05</i>, HBO-treated versus untreated animals; B. Exemplification of proteolipid protein (PLP) staining at day 22 following induction of traumatic brain injury and HBO treatment; number of animals see <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0097750#pone-0097750-t001" target="_blank">Table 1</a>. Error bars represent ± standard error means.</p

Schematic representation of the schedule of HBO treatments and associated analytical assays following induction of traumatic brain injury by fluid percussion.

<p>Schematic representation of the schedule of HBO treatments and associated analytical assays following induction of traumatic brain injury by fluid percussion.</p

Western blot analysis of time-dependent changes in myelin basic protein isoform expression in the ipsilateral cortex following traumatic brain injury and HBO treatment.

<p>A-D Myelin basic protein isoform expression at days 4, 11, 16 and 22 as percentage of expression in sham controls and representative western blot gels. Light grey bars: expression of isoform 21.5-kDa, grey bar: expression of isoform 18.5-kDa; dark grey bar: expression of isoform 17.2-kDa isoform; insert:, 1: sham, 2: brain injured animals, 3: injured and HBO-treated animals; western blot analysis was repeated at least twice per animal sample; n≥4 for each group. *<i>p<0.05</i>, HBO treated vs untreated injured animals; ^#<i>p<0.05</i> as compared to sham controls. Error bars represent ± standard error means.</p