Endoplasmic Reticulum Stress and Disrupted Neurogenesis in the Brain Are Associated with Cognitive Impairment and Depressive-Like Behavior after Spinal Cord Injury

Multidimensional review of cognitive impairment after spinal cord injury

Cognitive impairment is highly prevalent in the population with spinal cord injury (SCI) and exerts a significant impact on functional independence and quality of life in this population. A number of neuroscientists have conducted preliminary investigations of cognitive deficits after SCI, but achieved marginally contradictory results due to some limitations such as the heterogeneity in the sample population, sample size, types of tests utilized, study design, and time since SCI. Therefore, this review mainly focuses on the characteristics, assessments, potential causality and treatment of cognitive impairment for better understanding such deficits in the SCI population.

The voltage-gated proton channel Hv1 plays a detrimental role in contusion spinal cord injury via extracellular acidosis-mediated neuroinflammation

Tissue acidosis is an important secondary injury process in the pathophysiology of traumatic spinal cord injury (SCI). To date, no studies have examined the role of proton extrusion as mechanism of pathological acidosis in SCI. In the present study, we hypothesized that the phagocyte-specific proton channel Hv1 mediates hydrogen proton extrusion after SCI, contributing to increased extracellular acidosis and poor long-term outcomes. Using a contusion model of SCI in adult female mice, we demonstrated that tissue pH levels are markedly lower during the first week after SCI. Acidosis was most evident at the injury site, but also extended into proximal regions of the cervical and lumbar cord. Tissue reactive oxygen species (ROS) levels and expression of Hv1 were significantly increased during the week of injury. Hv1 was exclusively expressed in microglia within the CNS, suggesting that microglia contribute to ROS production and proton extrusion during respiratory burst. Depletion of Hv1 significantly attenuated tissue acidosis, NADPH oxidase 2 (NOX2) expression, and ROS production at 3 d post-injury. Nanostring analysis revealed decreased gene expression of neuroinflammatory and cytokine signaling markers in Hv1 knockout (KO) mice. Furthermore, Hv1 deficiency reduced microglia proliferation, leukocyte infiltration, and phagocytic oxidative burst detected by flow cytometry. Importantly, Hv1 KO mice exhibited significantly improved locomotor function and reduced histopathology. Overall, these data suggest an important role for Hv1 in regulating tissue acidosis, NOX2-mediated ROS production, and functional outcome following SCI. Thus, the Hv1 proton channel represents a potential target that may lead to novel therapeutic strategies for SCI.

VX-765 reduces neuroinflammation after spinal cord injury in mice

Inflammation is a major cause of neuronal injury after spinal cord injury. We hypothesized that inhibiting caspase-1 activation may reduce neuroinflammation after spinal cord injury, thus producing a protective effect in the injured spinal cord. A mouse model of T9 contusive spinal cord injury was established using an Infinite Horizon Impactor, and VX-765, a selective inhibitor of caspase-1, was administered for 7 successive days after spinal cord injury. The results showed that: (1) VX-765 inhibited spinal cord injury-induced caspase-1 activation and interleukin-1β and interleukin-18 secretion. (2) After spinal cord injury, an increase in M1 cells mainly came from local microglia rather than infiltrating macrophages. (3) Pro-inflammatory Th1Th17 cells were predominant in the Th subsets. VX-765 suppressed total macrophage infiltration, M1 macrophages/microglia, Th1 and Th1Th17 subset differentiation, and cytotoxic T cells activation; increased M2 microglia; and promoted Th2 and Treg differentiation. (4) VX-765 reduced the fibrotic area, promoted white matter myelination, alleviated motor neuron injury, and improved functional recovery. These findings suggest that VX-765 can reduce neuroinflammation and improve nerve function recovery after spinal cord injury by inhibiting caspase-1/interleukin-1β/interleukin-18. This may be a potential strategy for treating spinal cord injury. This study was approved by the Animal Care Ethics Committee of Bengbu Medical College (approval No. 2017-037) on February 23, 2017.

Forelimb Motor Skills Deficits Following Thoracic Spinal Cord Injury: Underlying Dopaminergic and Neural Oscillatory Changes in Rat Primary Motor Cortex

The loss of spinal sensorimotor pathways following spinal cord injury (SCI) can induce retrograde neurodegeneration in the primary motor cortex (M1). However, the effect of thoracic SCI on forelimb motor skills has not been studied clearly. So, herein we aimed to examine the effects of the thoracic SCI model on forelimb motor skills learning, parallel with dopaminergic and oscillatory changes in hindlimb and forelimb areas (HLA and FLA) of M1 in rats. Male Wistar rats were randomly subjected to laminectomy (Control) or contusion SCI at the thoracic (T10) level. Oscillatory activity and motor skills performance were evaluated for six consecutive days using local field potential (LFP) recording and skilled forelimb reaching task, respectively. Dopamine (DA) levels and expression of dopamine receptors (D1R and D2R) were determined in HLA and FLA by ELISA and western blotting. LFP recording results showed a sustained increase of LFP power in SCI rats compared with uninjured rats through skilled reaching training. Also, the SCI group had a lower reaching performance and learning rate in contrast to the Control group. Biochemical analysis of HLA and FLA showed a reduction in DA levels and expression of D1R and D2R after SCI. According to these findings, thoracic SCI causes aberrant changes in the oscillatory activity and dopaminergic system of M1, which are not restricted to HLA but also found in FLA accompanied by a deficit in forelimb motor skills performance.Summary statement: The reorganization of the primary motor cortex, following spinal cord injury, is not restricted to the hind limb area, and interestingly extends to the forelimb limb area, which appears as a dysfunctional change in oscillations and dopaminergic system, associated with a deficit in motor skills learning of forelimb.

Serum CCL21 as a Potential Biomarker for Cognitive Impairment in Spinal Cord Injury

Objective

Cognitive impairment is considered to be an important complication of spinal cord injury (SCI), but its underlying mechanism remains unclear. The purpose of this study is to explore whether serum CCL21 can be used as a potential biomarker of cognitive impairment in SCI.

Methods

In Neck-Shoulder and Lumbocrural Pain Hospital, Shandong First Medical University & Shandong Academy of Medical Sciences, hospitalized or treated acute SCI patients were included in the study as the SCI group (SCI). At the same time, a normal control group (NC) matching the age and sex of the SCI group was recruited in the outpatient clinic. Once the two groups were enrolled, their demographics and clinical characteristics were collected immediately. Enzyme-linked immunosorbent assay (ELISA) was used to detect serum CCL21 levels within 24 hours of admission. Three months later, the Montreal Cognitive Assessment (MoCA) was used to test the cognitive function of the population.

Results

A total of 84 SCI patients and 49 NC populations were eligible for inclusion in the study. There was no significant statistical difference in the demographics and clinical characteristics (age, gender, BMI, TG, LDL-C, FBG, SBP, and DBP) between the two groups (p > 0.05). Compared with the NC group, the SCI group had a higher serum CCL21 level (p < 0.001) and a lower MoCA score (p < 0.001). Serum CCL21 level in SCI was negatively correlated with MoCA score (p = 0.023). Multivariable analyses showed that serum CCL21 level is an independent prognostic factor of cognitive impairment in SCI.

Conclusions

MoCA score has a linear relationship with serum CCL21 quartile, and SCI cognitive function has a negative correlation with serum CCL21. Serum CCL21 is an independent risk factor for cognitive impairment after SCI.

Proton extrusion during oxidative burst in microglia exacerbates pathological acidosis following traumatic brain injury

Acidosis is among the least studied secondary injury mechanisms associated with neurotrauma. Acute decreases in brain pH correlate with poor long‐term outcome in patients with traumatic brain injury (TBI), however, the temporal dynamics and underlying mechanisms are unclear. As key drivers of neuroinflammation, we hypothesized that microglia directly regulate acidosis after TBI, and thereby, worsen neurological outcomes. Using a controlled cortical impact model in adult male mice we demonstrate that intracellular pH in microglia and extracellular pH surrounding the lesion site are significantly reduced for weeks after injury. Microglia proliferation and production of reactive oxygen species (ROS) were also increased during the first week, mirroring the increase in extracellular ROS levels seen around the lesion site. Microglia depletion by a colony stimulating factor 1 receptor (CSF1R) inhibitor, PLX5622, markedly decreased extracellular acidosis, ROS production, and inflammation in the brain after injury. Mechanistically, we identified that the voltage‐gated proton channel Hv1 promotes oxidative burst activity and acid extrusion in microglia. Compared to wildtype controls, microglia lacking Hv1 showed reduced ability to generate ROS and extrude protons. Importantly, Hv1‐deficient mice exhibited reduced pathological acidosis and inflammation after TBI, leading to long‐term neuroprotection and functional recovery. Our data therefore establish the microglial Hv1 proton channel as an important link that integrates inflammation and acidosis within the injury microenvironment during head injury.

Reductive stress promotes protein aggregation and impairs neurogenesis

Redox homeostasis regulates key cellular signaling in both physiology and pathology. While perturbations result in shifting the redox homeostasis towards oxidative stress are well documented, the influence of reductive stress (RS) in neurodegenerative diseases and its mechanisms are unknown. Here, we postulate that a redox shift towards the reductive arm (through the activation of Nrf2 signaling) will damage neurons and impair neurogenesis. In proliferating and differentiating neuroblastoma (Neuro 2a/N2a) cells, sulforaphane-mediated Nrf2 activation resulted in increased transcription/translation of antioxidants and glutathione (GSH) production along with significantly declined ROS in a dose-dependent manner leading to a reductive-redox state (i.e. RS). Interestingly, this resulted in endoplasmic reticulum (ER) stress leading to subsequent protein aggregation/proteotoxicity in neuroblastoma cells. Under RS, we also observed elevated Tau/α-synuclein and their co-localization with other protein aggregates in these cells. Surprisingly, we noticed that acute RS impaired neurogenesis as evidenced from reduced neurite outgrowth/length. Furthermore, maintaining the cells in a sustained RS condition (for five consecutive generations) dramatically reduced their differentiation and prevented the formation of axons (p < 0.05). This impairment in RS mediated neurogenesis occurs through the alteration of Tau dynamics i.e. RS activates the pathogenic GSK3β/Tau cascade thereby promoting the phosphorylation of Tau leading to proteotoxicity. Of note, intermittent withdrawal of sulforaphane from these cells suppressed the proteotoxic insult and re-activated the differentiation process. Overall, this results suggest that either acute or chronic RS could hamper neurogenesis through GSK3β/TAU signaling and proteotoxicity. Therefore, investigations identifying novel redox mechanisms impacting proteostasis are crucial to preserve neuronal health.

Animal Models of Cerebral Changes Secondary to Spinal Cord Injury

Spinal cord injuries (SCIs) are difficult to treat. The first animal SCI model (featuring the dropping of a weight) was established by Allen in 1911, and other animal models have been developed since then. Most animal studies have focused only on the molecular features of SCIs, which remain disputed. Recently, it has become clear that SCI may trigger mental and cognitive disorders, however, and brain changes secondary to SCI are under investigation. No consensus on an optimal animal model for cerebral research has emerged. We discuss the appropriate SCI models for studying secondary brain changes.

Delayed microglial depletion after spinal cord injury reduces chronic inflammation and neurodegeneration in the brain and improves neurological recovery in male mice

Neuropsychological deficits, including impairments in learning and memory, occur after spinal cord injury (SCI). In experimental SCI models, we and others have reported that such changes reflect sustained microglia activation in the brain that is associated with progressive neurodegeneration. In the present study, we examined the effect of pharmacological depletion of microglia on posttraumatic cognition, depressive-like behavior, and brain pathology after SCI in mice.

Methods: Young adult male C57BL/6 mice were subjected to moderate/severe thoracic spinal cord contusion. Microglial depletion was induced with the colony-stimulating factor 1 receptor (CSF1R) antagonist PLX5622 administered starting either 3 weeks before injury or one day post-injury and continuing through 6 weeks after SCI. Neuroinflammation in the injured spinal cord and brain was assessed using flow cytometry and NanoString technology. Neurological function was evaluated using a battery of neurobehavioral tests including motor function, cognition, and depression. Lesion volume and neuronal counts were quantified by unbiased stereology.

Results: Flow cytometry analysis demonstrated that PLX5622 pre-treatment significantly reduced the number of microglia, as well as infiltrating monocytes and neutrophils, and decreased reactive oxygen species production in these cells from injured spinal cord at 2-days post-injury. Post-injury PLX5622 treatment reduced both CD45^int microglia and CD45^hi myeloid counts at 7-days. Following six weeks of PLX5622 treatment, there were substantial changes in the spinal cord and brain transcriptomes, including those involved in neuroinflammation. These alterations were associated with improved neuronal survival in the brain and neurological recovery.

Conclusion: These findings indicate that pharmacological microglia-deletion reduces neuroinflammation in the injured spinal cord and brain, improving recovery of cognition, depressive-like behavior, and motor function.

CRID3, a blocker of apoptosis associated speck like protein containing a card, ameliorates murine spinal cord injury by improving local immune microenvironment

Background

After spinal cord injury (SCI), destructive immune cell subsets are dominant in the local microenvironment, which are the important mechanism of injury. Studies have shown that inflammasomes play an important role in the inflammation following SCI, and apoptosis-associated speck-like protein containing a card (ASC) is the adaptor protein shared by inflammasomes. Therefore, we speculated that inhibiting ASC may improve the local microenvironment of injured spinal cord. Here, CRID3, a blocker of ASC oligomerization, was used to study its effect on the local microenvironment and the possible role in neuroprotection following SCI.

Methods

Murine SCI model was created using an Infinite Horizon impactor at T9 vertebral level with a force of 50 kdynes and CRID3 (50 mg/kg) was intraperitoneally injected following injury. ASC and its downstream molecules in inflammasome signaling pathway were measured by western blot. The immune cell subsets were detected by immunohistofluorescence (IHF) and flow cytometry (FCM). The spinal cord fibrosis area, neuron survival, myelin preservation, and functional recovery were assessed.

Results

Following SCI, CRID3 administration inhibited inflammasome-related ASC and caspase-1, IL-1β, and IL-18 activation, which consequently suppressed M1 microglia, Th1 and Th1Th17 differentiation, and increased M2 microglia and Th2 differentiation. Accordingly, the improved histology and behavior have also been found.

Conclusions

CRID3 may ameliorate murine SCI by inhibiting inflammasome activation, reducing proinflammatory factor production, restoring immune cell subset balance, and improving local immune microenvironment, and early administration may be a promising therapeutic strategy for SCI.

Reducing Neuron Apoptosis in the Pontine Micturition Center by Nerve Root Transfer for Restoration of Micturition Function after Spinal Cord Injury

Objective

The rate of neuronal apoptosis increases after spinal cord injury (SCI). Anastomosing the normal nerve roots above the SCI level to the injured sacral nerve roots can enhance the functional recovery of neurons. Therefore, we evaluated the effect of sacral nerve root transfer after SCI on pontine neuronal survival.

Methods

Sprague–Dawley rats were randomly divided into three groups: Group A, reconstruction of afferent and efferent nerve pathways of the bladder after SCI; Group B, SCI only; and Group C, control group. We examined pontine neuronal morphology using hematoxylin and eosin (H&E) staining after SCI and nerve transfer. Bcl-2 and Bax protein expression changes in the pontine micturition center were quantified by immunohistochemistry. The number of apoptotic neurons was determined by TUNEL staining. We examined pontine neuronal apoptosis by transmission electron microscopy (TEM) at different time points.

Results

H&E staining demonstrated that the number of neurons had increased in Group A, but more cells in Group B displayed nuclear pyknosis, with the disappearance of the nucleus. Compared with Group B, Group A had significantly higher Bcl-2 expression, significantly lower Bax expression, and a significantly higher Bcl-2/Bax ratio. The number of apoptotic neurons and neuron bodies in Group A was significantly lower than that in Group B, as indicated by TUNEL staining and TEM.

Conclusions

These findings demonstrate that lumbosacral nerve transfer can reduce neuronal apoptosis in the pontine micturition center and enhance functional recovery of neurons. This result further suggests that lumbosacral nerve transfer can be used as a new approach for reconstructing bladder function after spinal cord injury.

Spinal Cord Injury Leads to Hippocampal Glial Alterations and Neural Stem Cell Inactivation

The hippocampus encodes spatial and contextual information involved in memory and learning. The incorporation of new neurons into hippocampal networks increases neuroplasticity and enhances hippocampal-dependent learning performances. Only few studies have described hippocampal abnormalities after spinal cord injury (SCI) although cognitive deficits related to hippocampal function have been reported in rodents and even humans. The aim of this study was to characterize in further detail hippocampal changes in the acute and chronic SCI. Our data suggested that neurogenesis reduction in the acute phase after SCI could be due to enhanced death of amplifying neural progenitors (ANPs). In addition, astrocytes became reactive and microglial cells increased their number in almost all hippocampal regions studied. Glial changes resulted in a non-inflammatory response as the mRNAs of the major pro-inflammatory cytokines (IL-1β, TNFα, IL-18) remained unaltered, but CD200R mRNA levels were downregulated. Long-term after SCI, astrocytes remained reactive but on the other hand, microglial cell density decreased. Also, glial cells induced a neuroinflammatory environment with the upregulation of IL-1β, TNFα and IL-18 mRNA expression and the decrease of CD200R mRNA. Neurogenesis reduction may be ascribed at later time points to inactivation of neural stem cells (NSCs) and inhibition of ANP proliferation. The number of granular cells and CA1 pyramidal neurons decreased only in the chronic phase. The release of pro-inflammatory cytokines at the chronic phase might involve neurogenesis reduction and neurodegeneration of hippocampal neurons. Therefore, SCI led to hippocampal changes that could be implicated in cognitive deficits observed in rodents and humans.

Dementia, Depression, and Associated Brain Inflammatory Mechanisms after Spinal Cord Injury

Evaluation of the chronic effects of spinal cord injury (SCI) has long focused on sensorimotor deficits, neuropathic pain, bladder/bowel dysfunction, loss of sexual function, and emotional distress. Although not well appreciated clinically, SCI can cause cognitive impairment including deficits in learning and memory, executive function, attention, and processing speed; it also commonly leads to depression. Recent large-scale longitudinal population-based studies indicate that patients with isolated SCI (without concurrent brain injury) are at a high risk of dementia associated with substantial cognitive impairments. Yet, little basic research has addressed potential mechanisms for cognitive impairment and depression after injury. In addition to contributing to disability in their own right, these changes can adversely affect rehabilitation and recovery and reduce quality of life. Here, we review clinical and experimental work on the complex and varied responses in the brain following SCI. We also discuss potential mechanisms responsible for these less well-examined, important SCI consequences. In addition, we outline the existing and developing therapeutic options aimed at reducing SCI-induced brain neuroinflammation and post-injury cognitive and emotional impairments.

Effect of VX‑765 on the transcriptome profile of mice spinal cords with acute injury

Previous studies have shown that caspase-1 plays an important role in the acute inflammatory response of spinal cord injury (SCI). VX‑765, a novel and irreversible caspase‑1 inhibitor, has been reported to effectively intervene in inflammation. However, the effect of VX‑765 on genome‑wide transcription in acutely injured spinal cords remains unknown. Therefore, in the present study, RNA‑sequencing (RNA‑Seq) was used to analyze the effect of VX‑765 on the local expression of gene transcription 8 h following injury. The differentially expressed genes (DEGs) underwent enrichment analysis of functions and pathways by Gene Ontology and Kyoto Encyclopedia of Genes and Genomes analyses, respectively. Parallel analysis of western blot confirmed that VX‑765 can effectively inhibit the expression and activation of caspase‑1. RNA‑Seq showed that VX‑765 treatment resulted in 1,137 upregulated and 1,762 downregulated DEGs. These downregulated DEGs and their associated signaling pathways, such as focal adhesion, cytokine‑cytokine receptor interaction, leukocyte transendothelial migration, extracellular matrix‑receptor interaction, phosphatidylinositol 3‑kinase‑protein kinase B, Rap1 and hypoxia inducible factor‑1 signaling pathway, are mainly associated with inflammatory response, local hypoxia, macrophage differentiation, adhesion migration and apoptosis of local cells. This suggests that the application of VX‑765 in the acute phase can improve the local microenvironment of SCI by inhibiting caspase‑1. However, whether VX‑765 can be used as a therapeutic drug for SCI requires further exploration. The sequence data have been deposited into the Sequence Read Archive (https://www.ncbi.nlm.nih.gov/sra/PRJNA548970).

Sustained neuronal and microglial alterations are associated with diverse neurobehavioral dysfunction long after experimental brain injury

Traumatic brain injury (TBI) can cause progressive neurodegeneration, sustained neuroinflammation and chronic neurological dysfunction. Few experimental studies have explored the long-term neurobehavioral and functional cellular changes beyond several months. The present study examined the effects of a single moderate-level TBI on functional outcome 8 months after injury. Male C57BL/6 mice were subjected to controlled cortical impact injury and followed for changes in motor performance, learning and memory, as well as depressive-like and social behavior. We also used a novel flow cytometry approach to assess cellular functions in freshly isolated neurons and microglia from the injured tissue. There were marked and diverse, sustained neurobehavioral changes in injured mice. Compared to sham controls, chronic TBI mice showed long-term deficits in gait dynamics, nest building, spatial working memory and recognition memory. The tail suspension, forced swim, and sucrose consumption tests showed a marked depressive-like phenotype that was associated with impaired sociability. At the cellular level, there were lower numbers of Thy1⁺Tuj1⁺ neurons and higher numbers of activated CD45^loCD11b⁺ microglia. Functionally, both neurons and microglia exhibited significantly higher levels of oxidative stress after injury. Microglia exhibited chronic deficits in phagocytosis of E. coli bacteria, and increased uptake of myelin and dying neurons. Living neurons showed decreased expression of synaptophysin and postsynaptic density (PSD)-95, along with greater numbers of microtubule-associated protein light chain 3 (LC3)-positive autophagosomes and increased mitochondrial mass that suggest dysregulation of autophagy. In summary, the late neurobehavioral changes found after murine TBI are similar to those found chronically after moderate-severe human head injury. Importantly, such changes are associated with microglial dysfunction and changes in neuronal activity.

Inhibition of microRNA-711 limits angiopoietin-1 and Akt changes, tissue damage, and motor dysfunction after contusive spinal cord injury in mice

Spinal cord injury (SCI) causes neuronal cell death and vascular damage, which contribute to neurological dysfunction. Given that many biochemical changes contribute to such secondary injury, treatment approaches have increasingly focused on combined therapies or use of multi-functional drugs. MicroRNAs (miRs) are small (20-23 nucleotide), non-protein-coding RNAs and can negatively regulate target gene expression at the post-transcriptional level. As individual miRs can potentially modulate expression of multiple relevant proteins after injury, they are attractive candidates as upstream regulators of the secondary SCI progression. In the present study we examined the role of miR-711 modulation after SCI. Levels of miR-711 were increased in injured spinal cord early after SCI, accompanied by rapid downregulation of its target angiopoietin-1 (Ang-1), an endothelial growth factor. Changes of miR-711 were also associated with downregulation of the pro-survival protein Akt (protein kinase B), another target of miR-711, with sequential activation of glycogen synthase kinase 3 and the pro-apoptotic BH3-only molecule PUMA. Central administration of a miR-711 hairpin inhibitor after SCI limited decreases of Ang-1/Akt expression and attenuated apoptotic pathways. Such treatment also reduced neuronal/axonal damage, protected microvasculature and improved motor dysfunction following SCI. In vitro, miR-711 levels were rapidly elevated by neuronal insults, but not by activated microglia and astrocytes. Together, our data suggest that post-traumatic miR-711 elevation contributes to neuronal cell death after SCI, in part by inhibiting Ang-1 and Akt pathways, and may serve as a novel therapeutic target.

Role of endoplasmic reticulum stress in depression (Review)

Depression is a devastating mood disorder that causes profound disability worldwide. Despite the increasing number of antidepressant medications available, the treatment options for depression are limited. Therefore, understanding the etiology and pathophysiology of depression, and exploiting potential novel agents to treat and prevent this disorder are imperative. Endoplasmic reticulum (ER) stress activates the unfolded protein response and mediates the pathogenesis of psychiatric diseases, including depression. Emerging evidence in human and animal models suggests an intriguing link between ER stress and depression. The ER serves as an important subcellular organelle for the synthesis, folding, modification, and transport of proteins, a process that is highly developed in neuronal cells. Perturbations of ER homeostasis lead to ER stress, and ER stress helps to restore the normal ER function by restoring the protein-folding capacity of the ER. This biological defense mechanism is imperative to prevent the disease. However, excessive or persistent ER stress eventually causes cell death. If the damage occurs in the hippocampus, the amygdala and striatum and other areas of the neurons will be involved in the development of depression. In this review article, we explore how ER stress might have an important role in the pathophysiology of depression and how different drugs affect depression through ER stress.

Adult neurogenesis in the mammalian dentate gyrus

Earlier observations in neuroscience suggested that no new neurons form in the mature central nervous system. Evidence now indicates that new neurons do form in the adult mammalian brain. Two regions of the mature mammalian brain generate new neurons: (a) the border of the lateral ventricles of the brain (subventricular zone) and (b) the subgranular zone (SGZ) of the dentate gyrus of the hippocampus. This review focuses only on new neuron formation in the dentate gyrus of the hippocampus. During normal prenatal and early postnatal development, neural stem cells (NSCs) give rise to differentiated neurons. NSCs persist in the dentate gyrus SGZ, undergoing cell division, with some daughter cells differentiating into functional neurons that participate in learning and memory and general cognition through integration into pre-existing neural networks. Axons, which emanate from neurons in the entorhinal cortex, synapse with dendrites of the granule cells (small neurons) of the dentate gyrus. Axons from granule cells synapse with pyramidal cells in the hippocampal CA3 region, which send axons to synapse with CA1 hippocampal pyramidal cells that send their axons out of the hippocampus proper. Adult neurogenesis includes proliferation, differentiation, migration, the death of some newly formed cells and final integration of surviving cells into neural networks. We summarise these processes in adult mammalian hippocampal neurogenesis and discuss the roles of major signalling molecules that influence neurogenesis, including neurotransmitters and some hormones. The recent controversy raised concerning whether or not adult neurogenesis occurs in humans also is discussed.

TMEM16F inhibition limits pain-associated behavior and improves motor function by promoting microglia M2 polarization in mice

Spinal cord injury (SCI) leads to sensorimotor deficits and autonomic changes. Macrophages and microglia could be polarized into the classically activated pro-inflammatory M1 phenotype or the alternatively activated anti-inflammatory M2 phenotype. Transmembrane protein with unknown function 16F (TMEM16F) exhibits functional diversity and may contribute to microglial function. However, the effects of TMEM16F on the modulation of macrophage/microglial polarization are still not fully understood. In the study, TMEM16F up-regulation was detected after SCI in mice, and TMEM16F protein was found in macrophages/microglia in injured spinal cord sections. Depletion of TMEM16F improved motor function in male mice with SCI. M1-type macrophages/microglia accumulated in lower numbers in the injured spinal cord of TMEM16F-knockout (KO) mice. M2 polarization inhibited by SCI was improved in mice with TMEM16F deficiency. TMEM16F deletion also attenuated microglial/macrophage pro-inflammatory response. Furthermore, significant down-regulation of A disintegrin and metalloprotease 17 (ADAM17) was observed in TMEM16F-KO mice. Importantly, TMEM16F-promoted M1 polarization and -inhibited M1 polarization were largely associated with the suppression of ADAM17. Overall, our findings provided new insights into the regulatory mechanisms of macrophage/microglial polarization, thereby possibly facilitating the development of new therapeutic strategies for SCI through the regulation of TMEM16F/ADAM17 signaling.

Inhibition of NOX2 signaling limits pain-related behavior and improves motor function in male mice after spinal cord injury: Participation of IL-10/miR-155 pathways

NADPH oxidase (NOX2) is an enzyme that induces reactive oxygen species (ROS) and serves as a switch between the pro-inflammatory and neurorestorative microglial/macrophage phenotypes; such changes play an important role in neuropathic pain and motor dysfunction. Increased NOX2 expression after spinal cord injury (SCI) has been reported, and inhibition of NOX2 improves motor function. However, the underlying mechanisms of NOX2 in post-traumatic pain and motor deficit remain unexplored. In the present study, we report that depletion of NOX2 (NOX2^-/-) or inhibition of NOX2 using NOX2ds-tat significantly reduced mechanical/thermal cutaneous hypersensitivity and motor dysfunction after moderate contusion SCI at T10 in male mice. Western blot (WB, 3 mm lesion area) and immunohistochemistry (IHC) showed that SCI elevates NOX2 expression predominantly in microglia/macrophages up to 8 weeks post-injury. Deletion of NOX2 significantly reduced CD11b⁺/CD45^hiF4/80⁺ macrophage infiltration at 24 h post-injury detected by flow cytometry and 8-OHG⁺ ROS production at 8 weeks post-injury by IHC in both lesion area and lumbar enlargement. NOX2 deficiency also altered microglial/macrophage pro-inflammatory and anti-inflammatory balance towards the neurorestorative response. WB analysis showed robust increase of Arginase-1 and YM1 proteins in NOX2^-/- mice. Furthermore, qPCR analysis showed significant up-regulation of anti-inflammatory cytokine IL-10 levels in NOX2^-/- mice, associated with reduced microRNA-155 expression. These findings were confirmed in CD11b⁺ microglia/macrophages isolated from spinal cord at 3 days post-injury. Taken together, our data suggest an important role for IL-10/miR-155 pathway in regulating NOX2-mediated SCI-dysfunction. Thus, specific targeting of NOX2 may provide an effective strategy for treating neurological dysfunction in SCI patients.

cPLA2 activation contributes to lysosomal defects leading to impairment of autophagy after spinal cord injury

The autophagy–lysosomal pathway plays an essential role in cellular homeostasis as well as a protective function against a variety of diseases including neurodegeneration. Conversely, inhibition of autophagy, for example due to lysosomal dysfunction, can lead to pathological accumulation of dysfunctional autophagosomes and consequent neuronal cell death. We previously reported that autophagy is inhibited and contributes to neuronal cell death following spinal cord injury (SCI). In this study, we examined lysosomal function and explored the mechanism of lysosomal defects following SCI. Our data demonstrated that expression levels and processing of the lysosomal enzyme cathepsin D (CTSD) are decreased by 2 h after SCI. Enzymatic activity levels of CTSD and another lysosomal enzyme, N-acetyl-alpha-glucosaminidase, are both decreased 24 h post injury, indicating general lysosomal dysfunction. Subcellular fractionation and immunohistochemistry analysis demonstrated that this dysfunction is due to lysosomal membrane permeabilization and leakage of lysosomal contents into the cytosol. To directly assess extent and mechanisms of damage to lysosomal membranes, we performed mass spectrometry-based lipidomic analysis of lysosomes purified from SCI and control spinal cord. At 2 h post injury our data demonstrated increase in several classes of lysosophospholipids, the products of phospholipases (PLAs), as well as accumulation of PLA activators, ceramides. Phospholipase cPLA2, the main PLA species expressed in the CNS, has been previously implicated in mediation of secondary injury after SCI, but the mechanisms of its involvement remain unclear. Our data demonstrate that cPLA2 is activated within 2 h after SCI preferentially in the lysosomal fraction, where it colocalizes with lysosomal-associated membrane protein 2 in neurons. Inhibition of cPLA2 in vivo decreased lysosomal damage, restored autophagy flux, and reduced neuronal cell damage. Taken together our data implicate lysosomal defects in pathophysiology of SCI and for the first time indicate that cPLA2 activation leads to lysosomal damage causing neuronal autophagosome accumulation associated with neuronal cell death.

Depression-like behavior corresponds with cardiac changes in a rodent model of spinal cord injury

In previous studies we have shown that approximately 1/3 of male Sprague Dawley rats develop symptoms of depression following a spinal cord injury (SCI). Using established behavioral tests to measure depression in rodents, we found that after SCI, subjects characterized as depressed had decreased sucrose preference, open field activity, social exploration, and burrowing behavior. As some of these tests of depression could be affected by the compromised motor function inherent to the SCI condition, the current study examined whether non-subjective, physiological differences in heart rate and heart rate variability were also associated with depression, as seen in humans. Male Sprague Dawley rats were implanted with radiotelemetry devices and either received a moderate contusion injury or remained intact. The implanted telemetry devices recorded home cage activity, body temperature, heart rate, and heart rate variability for 5 min/h throughout a 30-day post-injury assessment period. Depression behavior was evaluated using a battery of tests conducted on days 9-10 and 19-20 post-injury. Locomotor recovery and pain reactivity were also examined. Hierarchical clustering, based on the behavioral scores collected on the tests of depression, revealed that 28% of the SCI subjects displayed symptoms of depression, relative to the remaining 72% of SCI subjects. The subjects characterized as depressed had significantly lower social interaction and burrowing activity than the group that was not depressed. Interestingly, the subjects behaviorally characterized as depressed also had significantly lower heart rate variability than the not-depressed intact group. There was no difference between not-depressed SCI and intact rats on this measure. Therefore, in addition to behavior, depressed and not-depressed rats differ on measures of physiological function that are associated with depression in humans. These physiological differences further validate the rodent model of depression after SCI.

Spinal cord injury by clip-compression induces anxiety and depression-like behaviours in female rats: The role of the inflammatory response

Traumatic spinal cord injury (SCI) promotes long-term disability that affects mobility and functional independence. The spinal cord inflammatory response after the initial mechanical insult substantially impacts locomotor impairment and development of neuropsychiatric disorders, including anxiety and depression. However, these psychiatric events are scarcely investigated in females. This study investigated the anxiety/depression-like behaviours and inflammatory responses related to the production/release of pro- and anti-inflammatory cytokines in female adult Wistar rats submitted to severe clip-compression SCI. Data showed that SCI impaired the locomotor performance assessment by the BBB scale, but did not alter exploratory activity in open-field test. Animals' locomotor impairment was associated with anxious and depressive-like behaviours characterised by a decreased amount of time in the open arms of the elevated plus-maze test, and the motivational reduction of social interaction and anhedonia assessed by social exploration and sucrose preference tests. By contrast, SCI decreased the immobility time in the forced swimming test. Moreover, SCI caused a significant increase in local and systemic proinflammatory cytokines (TNF-α, INF-γ, IL-1β, and IL-6) and a reduction in the anti-inflammatory cytokine IL-10. Finally, there were significant negative correlations between depression-like behaviour, but not anxiety, and increased plasma concentrations of TNF-α, IL-1β, IL-6, and INF-γ. Additionally, the laminectomy procedure provoked the inflammatory response associated with reduced sucrose intake in Sham animals, although less expressively than in the SCI group. Collectively, these results indicate that SCI by clip-compression in female rats promotes a neuropsychiatric-like profile associated with an imbalance in the production/release of pro- and anti-inflammatory cytokines.

Hyperglycemia aggravates spinal cord injury through endoplasmic reticulum stress mediated neuronal apoptosis, gliosis and activation

BACKGROUND

Hyperglycemia has been shown to influence prognostic outcome of spinal cord injury (SCI). However, the corresponding mechanism is not very clear.

AIM

This study is expected to explore the role of endoplasmic reticulum (ER) stress in hyperglycemia aggravated SCI.

METHODS

Hyperglycemia was established in rats by intraperitoneal (i.p.) injection of streptozotocin. SCI was performed at the T10 of spinal cord through weight dropping. ER stress was suppressed by oral gavage of 4-PBA. ER stress, histological change of the injured spinal cords, neuronal apoptosis, demyelination, glial proliferation, inflammatory factor production, blood-spinal cord barrier (BSCB) permeability, TJ (Occludin, Claudin5) and AJ (β-catenin, P120) protein degradation, and locomotor recovery were determined using western blotting, immunohistochemistry, HE staining, Evan's Blue assay, BBB scores and inclined plane test, respectively. In vitro, rat spinal cord neurons cells (RSCNCs) and cerebral microvascular endothelial cells (RCMECs) were stimulated with high glucose (HG) and/or thapsigargin (TG). The effects of HG and/or TG on RSCNCs apoptosis, and AJ and TJ expression by RCMECs were evaluated with flow cytometry and western blotting, respectively.

RESULTS

Hyperglycemic rats exhibited enhanced ER stress, increased neuronal apoptosis, aggravated demyelination, increased glial proliferation and inflammatory factors secretion, more serious BSCB disruption and disturbed locomotor recovery. ER stress inhibition alleviated hyperglycemia induced adverse effect on neuronal apoptosis and BSCB permeability, whereas showed little influence on glial activation and inflammation.

CONCLUSION

ER stress was aggravated in hyperglycemic rats after SCI, and subsequently promoted neuronal apoptosis and BSCB disruption in rats.

Endoplasmic reticulum stress contributes to the pathogenesis of stress urinary incontinence in postmenopausal women

Objective

To investigate the relationship between endoplasmic reticulum stress (ERS) and the pathogenesis of stress urinary incontinence (SUI) in postmenopausal women.

Methods

Anterior vaginal wall tissue was collected from postmenopausal women with SUI and control subjects. Western blotting was performed for glucose-regulated protein (GRP78), inositol-requiring enzyme 1(IRE1), protein kinase-like endoplasmic reticulum kinase (PERK), activating transcription factor 6 (ATF6), C/EBP-homologous protein (CHOP), and B-cell lymphoma 2 (Bcl-2). Additionally, mRNA expression levels of PERK, activating transcription factor 4 (ATF4), and CHOP were examined by real-time polymerase chain reaction.

Results

GRP78 protein and mRNA expression levels were significantly lower in women with SUI, compared with control subjects. PERK and p-PERK expression levels were higher in women with SUI than in control subjects. However, no differences in IRE1 or ATF6 expression levels were observed in either group. Notably, higher CHOP and lower Bcl-2 protein expression levels were detected in women with SUI, compared with control subjects. Furthermore, PERK, ATF4, and CHOP mRNA expression levels were significantly higher in women with SUI than in control subjects.

Conclusions

Alterations of ERS markers in SUI suggest that ERS may be involved in the development of SUI in postmenopausal women.

Hydrogen Sulfide Ameliorates Blood-Spinal Cord Barrier Disruption and Improves Functional Recovery by Inhibiting Endoplasmic Reticulum Stress-Dependent Autophagy

Spinal cord injury (SCI) induces the disruption of blood-spinal cord barrier (BSCB), which elicits neurological deficits by triggering secondary injuries. Hydrogen sulfide (H₂S) is a gaseous mediator that has been reported to have neuroprotective effect in the central nervous system. However, the relationship between H₂S and BSCB disruption during SCI remains unknown. Therefore, it is interesting to evaluate whether the administration of NaHS, a H₂S donor, can protect BSCB integrity against SCI and investigate the potential mechanisms underlying it. In present study, we found that SCI markedly activated endoplasmic reticulum (ER) stress and autophagy in a rat model of complete crushing injury to the spinal cord at T9 level. NaHS treatment prevented the loss of tight junction (TJ) and adherens junction (AJ) proteins both in vivo and in vitro. However, the protective effect of NaHS on BSCB restoration was significantly reduced by an ER stress activator (tunicamycin, TM) and an autophagy activator (rapamycin, Rapa). Moreover, SCI-induced autophagy was remarkably blocked by the ER stress inhibitor (4-phenylbutyric acid, 4-PBA). But the autophagy inhibitor (3-Methyladenine, 3-MA) only inhibited autophagy without obvious effects on ER stress. Finally, we had revealed that NaHS significantly alleviated BSCB permeability and improved functional recovery after SCI, and these effects were markedly reversed by TM and Rapa. In conclusion, our present study has demonstrated that NaHS treatment is beneficial for SCI recovery, indicating that H₂S treatment is a potential therapeutic strategy for promoting SCI recovery.

Neuropathic Pain After Spinal Cord Injury: Challenges and Research Perspectives

Neuropathic pain is a debilitating consequence of spinal cord injury (SCI) that remains difficult to treat because underlying mechanisms are not yet fully understood. In part, this is due to limitations of evaluating neuropathic pain in animal models in general, and SCI rodents in particular. Though pain in patients is primarily spontaneous, with relatively few patients experiencing evoked pains, animal models of SCI pain have primarily relied upon evoked withdrawals. Greater use of operant tasks for evaluation of the affective dimension of pain in rodents is needed, but these tests have their own limitations such that additional studies of the relationship between evoked withdrawals and operant outcomes are recommended. In preclinical SCI models, enhanced reflex withdrawal or pain responses can arise from pathological changes that occur at any point along the sensory neuraxis. Use of quantitative sensory testing for identification of optimal treatment approach may yield improved identification of treatment options and clinical trial design. Additionally, a better understanding of the differences between mechanisms contributing to at- versus below-level neuropathic pain and neuropathic pain versus spasticity may shed insights into novel treatment options. Finally, the role of patient characteristics such as age and sex in pathogenesis of neuropathic SCI pain remains to be addressed.

Lysosomal damage after spinal cord injury causes accumulation of RIPK1 and RIPK3 proteins and potentiation of necroptosis

Necroptosis, a regulated necrosis pathway mediated by the receptor-interacting protein kinases 1 and 3 (RIPK1 and RIPK3), is induced following spinal cord injury (SCI) and thought to contribute to neuronal and glial cell death. However, mechanisms leading to activation of necroptosis after SCI remain unclear. We have previously shown that autophagy, a catabolic pathway facilitating degradation of cytoplasmic proteins and organelles in a lysosome-dependent manner, is inhibited following SCI in rats. Our current data confirm that inhibition of autophagy also occurs after thoracic contusive SCI in the mouse model, as indicated by accumulation of both the autophagosome marker, LC3-II and autophagy cargo protein, p62/SQSTM1. This was most pronounced in the ventral horn neurons and was caused by rapid inhibition of lysosomal function after SCI. Interestingly, RIPK1, RIPK3, and the necroptosis effector protein MLKL also rapidly accumulated after SCI and localized to neurons with disrupted autophagy, suggesting that these events may be related. To determine if lysosomal dysfunction could contribute to induction of necroptosis, we treated PC12 cells and primary rat cortical neurons with lysosomal inhibitors. This led to rapid accumulation of RIPK1 and RIPK3, confirming that they are normally degraded by the lysosomal pathway. In PC12 cells lysosomal inhibition also sensitized cells to necroptosis induced by tumor necrosis factor α (TNFα) and caspase inhibitor. Imaging studies confirmed that RIPK1 partially localized to lysosomes in both untreated and lysosomal inhibitor treated cells. Similarly, we detected presence of RIPK1, RIPK3 and MLKL in both cytosol and at lysosomes after SCI in vivo. Furthermore, stimulation of autophagy and lysosomal function with rapamycin treatment led to decreased accumulation of RIPK1 and attenuated cell death after SCI. These data suggest that lysosomal dysfunction after SCI may contribute to both inhibition of autophagy and sensitize cells to necroptosis by promoting RIPK1 and RIPK3 accumulation.

Tauroursodeoxycholic acid produces antidepressant-like effects in a chronic unpredictable stress model of depression via attenuation of neuroinflammation, oxido-nitrosative stress, and endoplasmic reticulum stress

Depression is a common psychiatric disorder with heavy economic and social burdens. Searching new agents with better antidepressant-like activities is of great significance for depression therapy. Tauroursodeoxycholic acid (TUDCA), a clinical drug for gallstone treatment, possesses neuroprotective effects in different brain disorders. However, whether it affects depression remains unclear. We addressed this issue by evaluating the effect of TUDCA on depression induced by chronic unpredictable stress (CUS). Results showed that TUDCA treatment at 200 but not 100 mg/kg prevented the 5 weeks of CUS-induced increases in the immobile time of C57BL6/J mice in the experiments of forced swimming test and tail suspension test as well as the CUS-induced decrease in sucrose intake and crossing numbers in the open-field test, and did not enhance the antidepressant-like effect of fluoxetine. Attenuation of neuroinflammation may be involved in the antidepressant-like effect of TUDCA, as TUDCA treatment (200 mg/kg) normalized the levels of tumor necrosis factor-α and interleukin-6 in both hippocampus and prefrontal cortex. The increases in inflammasome and microglial activation markers, including interleukin-β, nod-like receptor protein 3, and Iba-1, in CUS-treated mice were reduced by TUDCA treatment (200 mg/kg). TUDCA treatment (200 mg/kg) also normalized the changes in markers reflecting the oxidative-nitrosative and endoplasmic reticulum (ER) stress induced by CUS, such as nitric oxide, reduced glutathione, malondialdehyde, glucose-regulated protein 78, and C/EBP homologous protein. These results revealed that TUDCA improved the CUS-induced depression-like behaviors likely through attenuation of neuroinflammation, oxido-nitrosative, and ER stress.

Critical role of sigma-1 receptors in central neuropathic pain-related behaviours after mild spinal cord injury in mice

Sigma-1 receptor (σ1R) knockout (KO) CD1 mice, generated by homologous recombination, and separate pharmacological studies in wild type (WT) mice were done to investigate the role of this receptor in the development of pain-related behaviours (thermal hyperalgesia and mechanical allodynia) in mice after spinal cord contusion injury (SCI) - a model of central neuropathic pain. The modulatory effect of σ1R KO on extracellular mediators and signalling pathways in the spinal cord was also investigated. In particular, changes in the expression of inflammatory cytokines (tumour necrosis factor TNF-α, interleukin IL-1β) and both the expression and activation (phosphorylation) of the N-methyl-D-aspartate receptor subunit 2B (NR2B-NMDA) and extracellular signal-regulated kinases (ERK1/2) were analysed. Compared with WT mice, both mechanical and thermal hypersensitivity were attenuated in σ1R KO mice following SCI. Accordingly, treatment of WT mice with the σ1R antagonist MR309 (previously developed as E-52862; S1RA) after SCI exerted antinociceptive effects (i.e. reduced mechanical allodynia and thermal hyperalgesia). Attenuated nociceptive responses in σ1R KO were accompanied by reduced expression of TNF- α and IL-1β as well as decreased activation/phosphorylation of NR2B-NMDA receptors and ERK1/2. These findings suggest that σ1R may modulate central neuropathic pain and point to regulation of sensitization-related phenomena as a possible mechanism.

Delayed Influence of Spinal Cord Injury on the Amino Acids of NO• Metabolism in Rat Cerebral Cortex Is Attenuated by Thiamine

Severe spinal cord injuries (SCIs) result in chronic neuroinflammation in the brain, associated with the development of cognitive and behavioral impairments. Nitric oxide (NO•) is a gaseous messenger involved in neuronal signaling and inflammation, contributing to nitrosative stress under dysregulated production of reactive nitrogen species. In this work, biochemical changes induced in the cerebral cortex of rats 8 weeks after SCI are assessed by quantification of the levels of amino acids participating in the NO• and glutathione metabolism. The contribution of the injury-induced neurodegeneration is revealed by comparison of the SCI- and laminectomy (LE)-subjected animals. Effects of the operative interventions are assessed by comparison of the operated (LE/SCI) and non-operated animals. Lower ratios of citrulline (Cit) to arginine (Arg) or Cit to ornithine and a more profound decrease in the ratio of lysine to glycine distinguish SCI animals from those after LE. The data suggest decreased NO• production from both Arg and homoarginine in the cortex 8 weeks after SCI. Both LE and SCI groups show a strong decrease in the level of cortex glutathione. The neurotropic, anti-inflammatory, and antioxidant actions of thiamine (vitamin B1) prompted us to study the thiamine effects on the SCI-induced changes in the NO• and glutathione metabolism. A thiamine injection (400 mg/kg intraperitoneally) within 24 h after SCI abrogates the changes in the cerebral cortex amino acids related to NO•. Thiamine-induced normalization of the brain glutathione levels after LE and SCI may involve increased supply of glutamate for glutathione biosynthesis. Thus, thiamine protects from sequelae of SCI on NO•-related amino acids and glutathione in cerebral cortex.

Methamphetamine-mediated endoplasmic reticulum (ER) stress induces type-1 programmed cell death in astrocytes via ATF6, IRE1α and PERK pathways

Methamphetamine (MA), a psychostimulant drug has been associated with a variety of neurotoxic effects which are thought to be mediated by induction of pro-inflammatory cytokines/chemokines, oxidative stress and damage to blood-brain-barrier. Conversely, the ER stress-mediated apoptosis has been implicated in several neurodegenerative diseases. However, its involvement in MA-mediated neurodegenerative effects remains largely unexplored. The present study was undertaken to assess the effect of MA on ER stress and its possible involvement in apoptosis. For this purpose, SVGA astrocytes were treated with MA, which induced the expressions of BiP and CHOP at both, mRNA and protein levels. This phenomenon was also confirmed in HFA and various regions of mouse brain. Assessment of IRE1α, ATF6 and PERK pathways further elucidated the mechanistic details underlying MA-mediated ER stress. Knockdown of various intermediate molecules in ER stress pathways using siRNA demonstrated reduction in MA-mediated CHOP. Finally, MA-mediated apoptosis was demonstrated via MTT assay and TUNEL staining. The involvement of ER stress in the apoptosis was demonstrated with the help of MTT and TUNEL assays in the presence of siRNA against various ER stress proteins. The apoptosis also involved activation of caspase-3 and caspase-9, which was reversed by knockdown with various siRNAs. Altogether, this is the first report demonstrating mechanistic details responsible for MA-mediated ER stress and its role in apoptosis. This study provides a novel group of targets that can be explored in future for management of MA-mediated cell death and MA-associated neurodegenerative disorders.

BICAO-induced ischaemia caused depressive-like behaviours and caspase-8/-9-dependent brain regional neural cell apoptosis in mice

Introduction

Cerebral ischaemia-induced depression is among the most frequent neuropsychiatric consequences and adversely impact the prognosis and recovery of patients. Although several brain regions have been implied in the development of ischaemia-induced depression, the brain region-specific neural cell apoptosis pathways have not been clarified yet.

Methods

In this study, bilateral internal carotid artery occlusion (BICAO) mouse model was established to induce cerebral ischaemia. Sucrose preference, tail suspension and forced swim tests were conducted on mice at 7, 21 and 30 days after BICAO treatment. In addition, brain regional ischaemic neuron loss was investigated by using immunofluorescent staining of neuronal nuclei (NeuN) and caspase-8/-9-dependent cell apoptosis was also examined by western blot analysis.

Results

BICAO-induced cerebral ischaemia resulted in decreased sucrose preference and increased immobility times, which were representative depressive-like behaviours of mice until 30 days after BICAO treatment compared with Sham-operated mice. This outcome was associated with significant neuron loss by using immunofluorescent staining and increased cleavage levels of pro-caspase-3/-8/-9, but not pro-caspase-12, by western blot analysis in hypothalamus, midbrain, prefrontal cortex and hippocampus of mice.

Conclusions

This study showed that BICAO-induced ischaemia caused depressive-like behaviours and caspase-8/-9-dependent neural cell apoptosis in several brain regions, including hypothalamus and midbrain of mice.

Associations between suicidal behavior and childhood abuse and neglect: A meta-analysis

BACKGROUND

Relationships of some types of childhood maltreatment and suicidal behavior remain controversial and inconclusive.

METHODS

Medline, Embase, PsycINFO and Cochrane library were searched for eligible studies, and the results were synthesized in meta-analyses.

RESULTS

childhood maltreatment was associated positively with suicidal behavior in the total population and maltreatment subgroups. Emotional abuse had the strongest effect (OR =2.33, SMD =0.660, P<0.001). Subgroup analyses showed that the effects of childhood abuse (OR =1.55, SMD =0.523) and neglect (OR =1.25, SMD =0.31) were significant. According to the analysis of dichotomous outcomes, childhood maltreatment was associated positively with suicidal behavior in men and women (women: OR =4.84, P<0.001; men: OR =1.03, P<0.001). Among populations, childhood maltreatment had the strongest effect on suicidal behavior in the general population (OR =3.78, P<0.001). However, the analysis of continuous outcomes showed that the effect was strongest in patients with chronic schizophrenia (SMD =0.89, P<0.001). In addition, childhood maltreatment was associated positively with suicide attempt (OR =1.11, SMD =0.48, P<0.001), but not with suicidal ideation.

LIMITATIONS

Some subgroup samples were not sufficiently large.

CONCLUSIONS

Childhood maltreatment increases the risk of suicidal behavior. Emotional abuse had the strongest effect among the five types of maltreatment. The risk of suicidal behavior is higher in the general population, women, and individuals with chronic schizophrenia who have histories of childhood maltreatment.

The course and prognostic factors of cognitive status after central nervous system trauma: a systematic review protocol

INTRODUCTION

Traumatic brain injury (TBI) is among the most disabling injuries, resulting in a range of cognitive impairments. Traumatic spinal cord injury (SCI) often occurs in conjunction with TBI; the two are best considered together in the context of trauma to the central nervous system (CNS). Despite strong indications of cognitive dysfunction in CNS trauma, little is known about its natural history or relationship with other factors. The current protocol outlines a strategy for a systematic review of the current evidence examining CNS trauma as a prognostic factor of cognitive decline in the adult population.

METHODS AND ANALYSIS

The review will be conducted and reported in accordance with the Preferred Reporting Items for Systematic Reviews and Meta-Analyses guidelines. All peer-reviewed English language publications with a longitudinal design that focus on cognition in adults (ages 18 and older) with either TBI or SCI, or both from inception to December 2016 found through Medline, Central, Embase, Scopus, PsycINFO, supplemental PubMed and bibliographies of identified articles will be considered eligible. Quality will be evaluated using published guidelines. Results will be grouped by: (1) prognostic factors of cognitive deficits; and (2) development of, or time until development of, cognitive deficit in patients with CNS trauma. Close attention will be paid to the evaluative properties of the measurements used to assess cognition.

ETHICS AND DISSEMINATION

The authors will publish findings from this review in a peer-reviewed scientific journal(s) and present the results at national and international conferences. This work will advance scientific certainty regarding natural history and prognostic factors of cognitive status in males and females with CNS trauma, informing clinicians, policymakers and future researchers on the topic.

PROSPERO REGISTRATION NUMBER

CRD42017055309.

The clock is ticking. Ageing of the circadian system: From physiology to cell cycle

The circadian system is the responsible to organise the internal temporal order in relation to the environment of every process of the organisms producing the circadian rhythms. These rhythms have a fixed phase relationship among them and with the environment in order to optimise the available energy and resources. From a cellular level, circadian rhythms are controlled by genetic positive and negative auto-regulated transcriptional and translational feedback loops, which generate 24h rhythms in mRNA and protein levels of the clock components. It has been described about 10% of the genome is controlled by clock genes, with special relevance, due to its implications, to the cell cycle. Ageing is a deleterious process which affects all the organisms' structures including circadian system. The circadian system's ageing may produce a disorganisation among the circadian rhythms, arrhythmicity and, even, disconnection from the environment, resulting in a detrimental situation to the organism. In addition, some environmental conditions can produce circadian disruption, also called chronodisruption, which may produce many pathologies including accelerated ageing. Finally, some strategies to prevent, palliate or counteract chronodisruption effects have been proposed to enhance the circadian system, also called chronoenhancement. This review tries to gather recent advances in the chronobiology of the ageing process, including cell cycle, neurogenesis process and physiology.

Endoplasmic Reticulum Stress PERK-ATF4-CHOP Pathway Is Associated with Hypothalamic Neuronal Injury in Different Durations of Stress in Rats

The hypothalamus, which is the initial part of the hypothalamic-pituitary-adrenal (HPA) axis, plays a critical role in regulating stress in the central nervous system. The present study aimed to determine whether endoplasmic reticulum stress in hypothalamic neurons is differentially stimulated by varying durations of stress exposure, which ultimately leads to pathological changes in neurons by affecting HPA axis function. There is a need for better morphological evidence of the mechanisms involved in stress-induced neuron injury. A stress model was established in rats by restraining for 8 h and forced ice-water swimming for 5 min each day. The stress-inducing process lasted for 1, 3, 7, 14, and 21 days. Enzyme-linked immunosorbent assay (ELISA) was used to assay serum glucocorticoid levels. Thionine staining was used to observe morphological changes in hypothalamic neurons. Immunohistochemistry and microscopy-based multicolor tissue cytometry (MMTC) was used to detect changes in expression of endoplasmic reticulum stress protein GRP78, ATF4, and CHOP. Serum glucocorticoid levels significantly increased after 3 days of stress exposure and the levels peaked by 7 days. By 21 days, however, the levels were significantly decreased. Thionine staining revealed that prolonged stress exposure resulted in hypothalamic neurons with edema, a lack of Nissl bodies, and pyknotic neurons. Immunohistochemistry and MMTC showed that increasing stress periods significantly decreased GRP78 expression, although ATF4 and CHOP protein expression significantly increased. Stress resulted in pathological changes and significant dynamic changes because of endoplasmic reticulum stress in rat hypothalamic neurons. These results suggested that the endoplasmic reticulum stress PERK-ATF4-CHOP pathway may be associated with hypothalamic neuronal injury.

Truncated TrkB.T1-Mediated Astrocyte Dysfunction Contributes to Impaired Motor Function and Neuropathic Pain after Spinal Cord Injury

Following spinal cord injury (SCI), astrocytes demonstrate long-lasting reactive changes, which are associated with the persistence of neuropathic pain and motor dysfunction. We previously demonstrated that upregulation of trkB.T1, a truncated isoform of the brain-derived neurotrophic factor receptor (BDNF), contributes to gliosis after SCI, but little is known about the effects of trkB.T1 on the function of astrocytes. As trkB.T1 is the sole isoform of trkB receptors expressed on astrocytes, we examined the function of trkB.T1-driven astrocytes in vitro and in vivo Immunohistochemistry showed that trkB.T1⁺ cells were significantly upregulated 7 d after injury, with sustained elevation in white matter through 8 weeks. The latter increase was predominantly found in astrocytes. TrkB.T1 was also highly expressed by neurons and microglia/macrophages at 7 d after injury and declined by 8 weeks. RNA sequencing of cultured astrocytes derived from trkB.T1^+/+ (WT) and trkB.T1^-/- (KO) mice revealed downregulation of migration and proliferation pathways in KO astrocytes. KO astrocytes also exhibited slower migration/proliferation in vitro in response to FBS or BDNF compared with WT astrocytes. Reduced proliferation of astrocytes was also confirmed after SCI in astrocyte-specific trkB.T1 KO mice; using mechanical allodynia and pain-related measurements on the CatWalk, these animals also showed reduced hyperpathic responses, along with improved motor coordination. Together, our data indicate that trkB.T1 in astrocytes contributes to neuropathic pain and neurological dysfunction following SCI, suggesting that trkB.T1 may provide a novel therapeutic target for SCI.SIGNIFICANCE STATEMENT Neuropathic pain after spinal cord injury (SCI) may in part be caused by upregulation of the brain-derived neurotrophic factor (BDNF) receptor trkB.T1, a truncated isoform of BDNF. TrkB.T1 is the only isoform of tropomyosin-related receptor kinase type B (trkB) receptors expressed on astrocytes. Here, we showed that trkB.T1 is significantly increased in the injured mouse spinal cord, where it is predominantly found in astrocytes. RNA sequencing of cultured astrocytes demonstrated downregulation of migration and proliferation pathways in trkB.T1 KO astrocytes. This was validated in vivo, where deletion of trkB.T1 in astrocytes reduced cell proliferation and migration. After SCI, astrocyte-specific trkB.T1 KO mice showed reduced hyperpathic responses and improved motor coordination. Therefore, the trkB.T1 receptor plays a significant pathophysiological role after SCI, and may provide a novel therapeutic target for SCI.

Spinal cord injury drives chronic brain changes

Only a few studies have considered changes in brain structures other than sensory and motor cortex after spinal cord injury, although cognitive impairments have been reported in these patients. Spinal cord injury results in chronic brain neuroinflammation with consequent neurodegeneration and cognitive decline in rodents. Regarding the hippocampus, neurogenesis is reduced and reactive gliosis increased. These long-term abnormalities could explain behavioral impairments exhibited in humans patients suffering from spinal cord trauma.

Cognitive Impairment and Mood States after Spinal Cord Injury

Spinal cord injury (SCI) is believed to be associated with high rates of cognitive impairment, which can result in complications in recovery. This study concerned two groups of adults with SCI. The first sample involved 150 participants with SCI who were assessed once for cognitive capacity with comparisons made with 45 able-bodied adults. Sample 2 were drawn from Sample 1, and included 88 participants with SCI who were prospectively assessed for mood states (anxiety, depressive mood, and fatigue) and pain intensity at three time periods: at admission to SCI rehabilitation, at discharge, and 6 months after transition into the community. Results showed that the SCI sample had significantly lower cognitive performance than the able-bodied control group. Further, almost 29% of the adults with SCI had lowered cognitive performance believed to be indicative of cognitive impairment. The risk of an adult with SCI having cognitive impairment was almost 13 times that of someone without an SCI. Results from Sample 2 revealed that the development of negative mood states was a significant problem in those with cognitive impairment after they transitioned into the community, a time when personal resources are severely challenged. Findings suggest all adults with SCI admitted to rehabilitation should receive a cognitive screen, and that rehabilitation strategies should then be guided by the cognitive performance of the person. Special attention should also be given to improving skills of those with cognitive impairment before they transition into the community, so as to reduce risk of comorbid mental health problems.