Experimental Neurology最新文献

Introduction

After mild traumatic brain injury (mTBI), the brain is labile for weeks and months and vulnerable to repeated concussions. During this time, patients are exposed to everyday circumstances that, in themselves, affect brain metabolism and blood flow and neural processing. How commonplace activities interact with the injured brain is unknown. The present study in an animal model investigated the extent to which three commonly experienced exposures—daily caffeine usage, chronic sleep loss, and chronic sleep aid medication—affect the injured brain in the chronic phase.

Methods

Subclinical trauma by repeated mTBIs was produced by our head rotational acceleration injury model, which causes brain injury consistent with the mechanism of concussion in humans. Forty-eight hours after a third mTBI, chronic administrations of caffeine, sleep restriction, or zolpidem (sedative hypnotic) began and were continued for 70 days. On Days 30 and 60 post injury, resting state functional magnetic resonance imaging (fMRI) and diffusion tensor imaging (DTI) were performed.

Results

Chronic caffeine, sleep restriction, and zolpidem each changed the subclinical brain characteristics of mTBI at both 30 and 60 days post injury, detected by different MRI modalities. Each treatment caused microstructural alterations in DTI metrics in the insular cortex and retrosplenial cortex compared with mTBI, but also uniquely affected other gray and white matter regions. Zolpidem administration affected the largest number of individual structures in mTBI at both 30 and 60 days, and not necessarily toward normalization (sham treatment). Chronic sleep restriction changed local functional connectivity at 30 days in diametrical opposition to chronic caffeine ingestion, and both treatment outcomes were different from sham, mTBI-only and zolpidem comparisons. The results indicate that commonly encountered exposures modify subclinical brain activity and structure long after healing is expected to be complete.

Conclusions

Changes in activity and structure detected by fMRI are widely understood to reflect changes in the functions of the affected region which conceivably underlie mTBI neuropathology and symptomatology in the chronic phase after injury.

Prader–Willi syndrome (PWS) is a multisystemic disorder. Notably, many characteristic symptoms of PWS are correlated with locus coeruleus norepinephrine system (LC-NE) dysfunction, including impairment in arousal, learning, pain modulation, and stress-induced negative affective states. Although electrophysiological experiments in necdin-deficient mice, an established PWS animal model, have revealed decreased spontaneous neuronal firing activity in the LC and impaired excitability, the behavioral phenotypes related to LC-NE dysfunction remain unexplored. In this study, heterozygous necdin-deficient mice (B6.Cg-Ndn^tm1ky) were bred from wild-type (WT) females to generate WT (+m/+p) and heterozygous (+m/−p) animals. Compared to WT mice, Ndn + m/−p mice demonstrated impaired visual-spatial memory in the Y-maze test, reduced social interaction, impaired sexual recognition, and shorter falling latency on the Rotarod. Using the open field test (OFT) and elevated plus maze (EPM), we observed similar locomotion activity of Ndn + m/−p and WT mice, but Ndn + m/−p mice were less anxious. After acute restraint, Ndn + m/−p mice exhibited significant impairment in stress-induced anxiety. Additionally, the plasma norepinephrine surge following exposure to acute restraint stress was also impaired. Pretreatment with atomoxetine, a norepinephrine reuptake inhibitor aimed to enhance LC function, restored Ndn + m/−p mice to exhibit a normal response to acute restraint stress. Furthermore, by employing chemogenetic approaches to facilitate LC neuronal firing, post-stress anxious responses were also partially rescued in Ndn + m/−p mice. These data strongly suggest that LC dysfunction is implicated in the pathogenesis of stress-related neuropsychiatric symptoms in PWS. Manipulation of LC activity may hold therapeutic potential for patients with PWS.

Cognitive decline in Parkinson's Disease (PD) is a prevalent and undertreated aspect of disease. Currently, no therapeutics adequately improve this aspect of disease. It has been previously shown that MAS receptor agonism via the glycosylated Angiotensin (1–7) peptide, PNA5, effectively reduces cognitive decline in models of vascular contributions to cognitive impairment and dementia (VCID). PNA5 has a brain/plasma ratio of 0.255 indicating good brain penetration. The goal of the present study was to determine if (1) systemic administration of PNA5 rescued cognitive decline in a mouse model of PD, and (2) if improvements in cognitive status could be correlated with changes to histopathological or blood plasma-based changes. Mice over-expressing human, wild-type α-synuclein (αSyn) under the Thy1 promoter (Thy1-αSyn mice, “line 61”) were used as a model of PD with cognitive decline. Thy1-αSyn mice were treated with a systemic dose of PNA5, or saline (1 mg/kg/day) beginning at 4 months of age and underwent behavioral testing at 6 months, compared to WT. Subsequently, mice brains were analyzed for changes to brain pathology, and blood plasma was examined with a Multiplex Immunoassay for peripheral cytokine changes. Treatment with PNA5 reversed cognitive dysfunction measured by Novel Object Recognition and spontaneous alteration in a Y-maze in Thy1-αSyn mice. PNA5 treatment was specific to cognitive deficits, as fine-motor disturbances were unchanged. Enhanced cognition was associated with decreases in hippocampal inflammation and reductions in circulating levels of Macrophage Induced Protein (MIP-1β). Additionally, neuronal loss was blunted within the CA3 hippocampal region of PNA5-treated αsyn mice. These data reveal that PNA5 treatment reduces cognitive dysfunction in a mouse model of PD. These changes are associated with decreased MIP-1β levels in plasma identifying a candidate biomarker for target engagement. Thus, PNA5 treatment could potentially fill the therapeutic gap for cognitive decline in PD.

Objectives: Absence seizures impair psychosocial function, yet their detailed neuronal basis remains unknown. Recent work in a rat model suggests that cortical arousal state changes prior to seizures and that single neurons show diverse firing patterns during seizures. Our aim was to extend these investigations to a mouse model with studies of neuronal activity and arousal state to facilitate future fundamental investigations of absence epilepsy.

Methods: We performed in vivo extracellular single unit recordings on awake head-fixed C3H/HeJ mice. Mice were implanted with tripolar electrodes for cortical electroencephalography (EEG). Extracellular single unit recordings were obtained with glass micropipettes in the somatosensory barrel cortex, while animals ambulated freely on a running wheel. Signals were digitized and analyzed during seizures and at baseline.

Results: Neuronal activity was recorded from 36 cortical neurons in 19 mice while EEG showed characteristic 7–8 Hz spike-wave discharges. Different single neurons showed distinct firing patterns during seizures, but the overall mean population neuronal firing rate during seizures was no different from pre-seizure baseline. However, the rhythmicity of neuronal firing during seizures was significantly increased (p < 0.001). In addition, beginning 10s prior to seizure initiation, we observed a progressive decrease in cortical high frequency (>40 Hz) EEG and an increase in lower frequency (1–39 Hz) activity suggesting decreased arousal state.

Significance: We found that the awake head-fixed C3H/HeJ mouse model demonstrated rhythmic neuronal firing during seizures, and a decreased cortical arousal state prior to seizure onset. Unlike the rat model we did not observe an overall decrease in neuronal firing during seizures. Similarities and differences across species strengthen the ability to investigate fundamental key mechanisms. Future work in the mouse model will identify the molecular basis of neurons with different firing patterns, their role in seizure initiation and behavioral deficits, with ultimate translation to human absence epilepsy.

Neuropathic pain is a significant and persistent issue for individuals with spinal cord injuries (SCI), severely impacting their quality of life. While changes at the peripheral and spinal levels are known to contribute to SCI-related pain, whether and how supraspinal centers contribute to post SCI chronic neuropathic pain is poorly understood. Here, we first validated delayed development of chronic neuropathic pain in mice with moderate contusion SCI. To identify supraspinal regions involved in the pathology of neuropathic pain after SCI, we next performed an activity dependent genetic screening and identified multiple cortical and subcortical regions that were activated by innocuous tactile stimuli at a late stage following contusion SCI. Notably, chemogenetic inactivation of pain trapped neurons in the lateral thalamus alleviated neuropathic pain and reduced tactile stimuli evoked cortical overactivation. Retrograde tracing showed that contusion SCI led to enhanced corticothalamic axonal sprouting and over-activation of corticospinal neurons. Mechanistically, ablation or silencing of corticospinal neurons prevented the establishment or maintenance of chronic neuropathic pain following contusion SCI. These results highlighted a corticospinal-lateral thalamic feed-forward loop whose activation is required for the development and maintenance of chronic neuropathic pain after SCI. Our data thus shed lights into the central mechanisms underlying chronic neuropathic pain associated with SCI and the development of novel therapeutic avenues to treat refractory pain caused by traumatic brain or spinal cord injuries.

Parkinson's disease (PD) involves the degeneration of dopaminergic neurons in the substantia nigra (SNpc) and manifests with both classic and non-classic motor symptoms, including respiratory failure. Our study aims to investigate the involvement of the commissural and intermediate nucleus of the solitary tract (cNTS and iNTS) in the attenuated respiratory response to hypoxia in PD. Using a PD rat model induced by bilateral injection of 6-hydroxydopamine (6-OHDA) into the striatum of male Wistar rats, we explored potential alterations in the population of Phox2b neurons or hypoxia-activated neurons in the NTS projecting to the retrotrapezoid nucleus (RTN). Additionally, we explored neuronal connectivity between SNpc and cNTS. Projections pathways were assessed using unilateral injection of the retrograde tracer Fluorogold (FG) in the cNTS and RTN. Neuronal activation was evaluated by analyzing fos expression in rats exposed to hypoxia. In the PD model, the ventilatory response, measured through whole-body plethysmography, was impaired at both baseline and in response to hypoxia. A reduction in Phox2b-expressing neurons or hypoxia-activated neurons projecting to the RTN was observed. Additionally, we identified an indirect pathway linking the SNpc and cNTS, which passes through the periaqueductal gray (PAG). In conclusion, our findings suggest impairment in the SNpc-PAG-cNTS pathway in the PD model, explaining the loss of Phox2b-expressing neurons or hypoxia-activated neurons in the cNTS and subsequent respiratory impairment during hypoxic stimulation. We propose that the reduced population of Phox2b-expressing neurons in the NTS may include the same neurons activated by hypoxia and projecting to the RTN.

Alzheimer's disease (AD) is characterized by disorders in brain energy. The lack of sufficient energy for nerve function leads to cognitive dysfunction and massive neuronal loss in AD. Ketone bodies are an alternative to glucose as a source of energy in the brain, and alternate-day fasting (ADF) promotes the production of the ketone body β-hydroxybutyric acid (βOHB). In this study, 7-month-old male WT mice and 3xTg mice underwent dietary control for 20 weeks. We found that ADF increased circulating βOHB concentrations in 3xTg mice, improved cognitive function, reduced anxiety-like behaviors, improved hippocampal synaptic plasticity, and reduced neuronal loss, Aβ oligomers and tau hyperphosphorylation. In addition, ADF improved mitochondrial bioenergetic function by promoting brain ketone metabolism and rescued brain energy deficits in 3xTg mice. A safety evaluation showed that ADF improved exercise endurance and liver and kidney function in 3xTg mice without negatively affecting muscle motor and heart functions. This study provides a theoretical basis and strong support for the application of ADF as a non-drug strategy for preventing and treating brain energy defects in the early stage of AD.

Oxidative stress can impair the endothelial barrier and thereby enable autoantibody migration in Neuromyelitis optica spectrum disorder (NMOSD). Tissue-specific vulnerability to autoantibody-mediated damage could be explained by a differential, tissue-dependent endothelial susceptibility to oxidative stress. In this study, we aim to investigate the barrier integrity and complement profiles of brain and retinal endothelial cells under oxygen-induced oxidative stress to address the question of whether the pathomechanism of NMOSD preferentially affects the brain or the retina.

Primary human brain microvascular endothelial cells (HBMEC) and primary human retinal endothelial cells (HREC) were cultivated at different cell densities (2.5*10⁴ to 2*10⁵ cells/cm²) for real-time cell analysis. Both cell types were exposed to 100, 500 and 2500 μM H₂O₂. Immunostaining (CD31, VE-cadherin, ZO-1) and Western blot, as well as complement protein secretion using multiplex ELISA were performed.

HBMEC and HREC cell growth phases were cell type-specific. While HBMEC cell growth could be categorized into an initial peak, proliferation phase, plateau phase, and barrier breakdown phase, HREC showed no proliferation phase, but entered the plateau phase immediately after an initial peak. The plateau phase was 7 h shorter in HREC. Both cell types displayed a short-term, dose-dependent adaptive response to H₂O₂. Remarkably, at 100 μM H₂O₂, the transcellular resistance of HBMEC exceeded that of untreated cells. 500 μM H₂O₂ exerted a more disruptive effect on the HBMEC transcellular resistance than on HREC. Both cell types secreted complement factors H (FH) and I (FI), with FH secretion remaining stable after 2 h, but FI secretion decreasing at higher H₂O₂ concentrations.

The observed differences in resistance to oxidative stress between primary brain and retinal endothelial cells may have implications for further studies of NMOSD and other autoimmune diseases affecting the eye and brain. These findings may open novel perspectives for the understanding and treatment of such diseases.

Spinal cord injury (SCI) is a rare condition with a heterogeneous presentation, making the prediction of recovery challenging. However, serological markers have been shown to be associated with severity and long-term recovery following SCI. Therefore, our investigation aimed to assess the feasibility of translating this association into a prediction of the lower extremity motor scores (LEMS) at chronic stage (52 weeks after initial injury) in patients with SCI using routine serological markers.

Serological markers, assessed within the initial seven days post-injury in the observational cohort study from the Trauma Hospital Murnau underwent diverse feature engineering approaches. These involved arithmetic measurements such as mean, median, minimum, maximum, and range, as well as considerations of the frequency of marker testing and whether values fell within the normal range. To predict LEMS scores at the chronic stage, eight different regression models (including linear, tree-based, and ensemble models) were used to quantify the predictive value of serological markers relative to a baseline model that relied on the very acute LEMS score and patient age alone.

The inclusion of serological markers did not improve the performance of the prediction model. The best-performing approach including serological markers achieved a mean absolute error (MAE) of 6.59 (2.14), which was equivalent to the performance of the baseline model. As an alternative approach, we trained separate models based on the LEMS observed at the very acute stage after injury. Specifically, we considered individuals with an LEMS of 0 or an LEMS exceeding zero separately. This strategy led to a mean improvement in MAE across all cohorts and models, of 1.20 (2.13).

We conclude that, in our study, routine serological markers hold limited power for prediction of LEMS. However, the implementation of model stratification by the very acute LEMS markedly enhanced prediction performance. This observation supports the inclusion of clinical knowledge in the modeling of prediction tasks for SCI recovery. Additionally, it lays the path for future research to consider stratified analyses when investigating the predictive power of potential biomarkers.

Objective

Multiple factors contribute to the development of perioperative neurocognitive disorders (PND). This study was designed to investigate whether Histone Deacetylase 6 (HDAC6) was involved in the formation of postoperative cognitive dysfunction in elderly mice by regulating the degree of acetylation of heat shock protein (HSP90) and related protein functions and quantities.

Methods

C57BL/6 J male mice were randomly divided into six groups: control naive (group Control), anesthesia (group Anesthesia), splenectomy surgery (group Surgery), splenectomy surgery plus dissolvent (group Vehicles), splenectomy surgery plus the inhibitor ACY-1215 (group Ricolinostat), and splenectomy surgery plus the inhibitor RU-486(group Mifepristone). After the mice were trained for Morris Water Maze (MWM) test for five days, anesthesia and operational surgery were carried out the following day. Cognitive function was assessed on the 1st, 3rd and 7th days post-surgery. The hippocampi were harvested on days 1, 3, and 7 post-surgeries for Western blots and ELISA assays.

Results

Mice with the splenectomy surgery displayed the activation of the hypothalamic–pituitary–adrenal axis (HPA-axis), marked an increase in adrenocorticotropic hormone (ACTH), glucocorticoid, mineralocorticoid at the molecular level and impaired spatial memory in the MWM test. The hippocampus of surgical groups showed a decrease in acetylated HSP90, a rise in glucocorticoid receptor (GR)-HSP90 association, and an increase in GR phosphorylation and translocation. HDAC6 was increased after the surgical treated. Using two specific inhibitors, HDAC6 inhibitor Ricolinostat (ACY-1215) and GR inhibitor Mifepristone (RU-486), can partially mitigate the effects caused by surgical operation.

Conclusions

Abdominal surgery may impair hippocampal spatial memory, possibly through the HDAC6-triggered increase in the function of HSP90, consequently strengthening the negative role of steroids in cognitive function. Targeting HDAC6- HSP90/GR signaling may provide a potential avenue for the treatment of the impairment of cognitive function after surgery.