Preliminary analysis of hippocampus synaptic apoptosis and microglial phagocytosis induced by severe restraint stress.

AIM: Several studies reported stress-induced microglial phagocytosis, but the biochemical mechanisms by which stress alters microglial synaptic phagocytosis are not fully uncovered. Local or limited apoptosis without cell death was observed at neuronal synapses in previous studies, and proposed as an upstream mechanism for microglial synapse elimination. In this micro-report, we aimed to preliminary examine local synaptic apoptosis in the mouse hippocampus following severe restraint stress, and its effect on microglial phagocytosis. METHODS: Mice were exposed to 10-day water immersion restraint stress (WIRS). Brain sections including stratum lucidum in the hippocampal CA3 subfield were stained with antibodies against cleaved caspase 3, ionized calcium-binding adapter molecule1 (Iba1), lysosomal-associated membrane protein1 (LAMP1), vesicular glutamate transporter1 (VGLUT1). Co-localization among these proteins were calculated. RESULTS: Our image analysis revealed that synaptic apoptosis was increased while there were no significant changes in microglial phagocytic activity and synaptic phagocytosis following 10-day WIRS. CONCLUSION: Severe restraint stress enhanced pre-synaptic apoptosis in mouse CA3 stratum lucidum region, but did not promote microglial phagocytosis. The phenomenon microglia fail to phagocytose weakened and unnecessary synapses may be related to pathology of stress.

Tbx1, a gene encoded in 22q11.2 copy number variant, is a link between alterations in fimbria myelination and cognitive speed in mice.

Copy number variants (CNVs) have provided a reliable entry point to identify the structural correlates of atypical cognitive development. Hemizygous deletion of human chromosome 22q11.2 is associated with impaired cognitive function; however, the mechanisms by which the CNVs contribute to cognitive deficits via diverse structural alterations in the brain remain unclear. This study aimed to determine the cellular basis of the link between alterations in brain structure and cognitive functions in mice with a heterozygous deletion of Tbx1, one of the 22q11.2-encoded genes. Ex vivo whole-brain diffusion-tensor imaging (DTI)-magnetic resonance imaging (MRI) in Tbx1 heterozygous mice indicated that the fimbria was the only region with significant myelin alteration. Electron microscopic and histological analyses showed that Tbx1 heterozygous mice exhibited an apparent absence of large myelinated axons and thicker myelin in medium axons in the fimbria, resulting in an overall decrease in myelin. The fimbria of Tbx1 heterozygous mice showed reduced mRNA levels of Ng2, a gene required to produce oligodendrocyte precursor cells. Moreover, postnatal progenitor cells derived from the subventricular zone, a source of oligodendrocytes in the fimbria, produced fewer oligodendrocytes in vitro. Behavioral analyses of these mice showed selectively slower acquisition of spatial memory and cognitive flexibility with no effects on their accuracy or sensory or motor capacities. Our findings provide a genetic and cellular basis for the compromised cognitive speed in patients with 22q11.2 hemizygous deletion.

[Stress Mediated Microglial Hyper-Activation and Psychiatric Diseases].

Stress is a trigger for depression and PTSD, with current studies suggesting the involvement of microglial hyperactivation and dysfunction in the pathophysiology of these diseases. In this review, we introduced microglial functional changes in animal models, which exhibit fear memory dysregulation that is characteristic of PTSD, and human microglia-focused clinical studies on depression and PTSD. Stress has been found to affect cytokine and neurotrophic factor releases from the microglia, promoting microglia-mediated synaptic phagocytosis. In particular, animal models of PTSD have indicated that abnormal microglial cytokine production engage in decontextualized fear memory, fear extinction deficit, and fear generalization, and impaired microglial phagocytosis may also participate in fear generalization and fear forgetting. It is not possible to evaluate higher mental dysfunction in stress-related psychiatric disorders using model animals alone. PET studies with TSPO ligands, for one, suggest that inflammatory microglial changes are enhanced in depressed patients, whereas these changes are suppressed in PTSD patients. Thus, we conducted a reverse-translational research to explore the involvement of microglia in depression using human peripheral blood. We believe that interactive research in humans and animals is needed to elucidate the pathophysiology of stress-related psychiatric disorders for the development of treatment options for such patients.

Computational identification of variables in neonatal vocalizations predictive for postpubertal social behaviors in a mouse model of 16p11.2 deletion.

Autism spectrum disorder (ASD) is often signaled by atypical cries during infancy. Copy number variants (CNVs) provide genetically identifiable cases of ASD, but how early atypical cries predict a later onset of ASD among CNV carriers is not understood in humans. Genetic mouse models of CNVs have provided a reliable tool to experimentally isolate the impact of CNVs and identify early predictors for later abnormalities in behaviors relevant to ASD. However, many technical issues have confounded the phenotypic characterization of such mouse models, including systematically biased genetic backgrounds and weak or absent behavioral phenotypes. To address these issues, we developed a coisogenic mouse model of human proximal 16p11.2 hemizygous deletion and applied computational approaches to identify hidden variables within neonatal vocalizations that have predictive power for postpubertal dimensions relevant to ASD. After variables of neonatal vocalizations were selected by least absolute shrinkage and selection operator (Lasso), random forest, and Markov model, regression models were constructed to predict postpubertal dimensions relevant to ASD. While the average scores of many standard behavioral assays designed to model dimensions did not differentiate a model of 16p11.2 hemizygous deletion and wild-type littermates, specific call types and call sequences of neonatal vocalizations predicted individual variability of postpubertal reciprocal social interaction and olfactory responses to a social cue in a genotype-specific manner. Deep-phenotyping and computational analyses identified hidden variables within neonatal social communication that are predictive of postpubertal behaviors.

Involvement of microglia in disturbed fear memory regulation: Possible microglial contribution to the pathophysiology of posttraumatic stress disorder.

Microglia, immune cells in the brain, play a crucial role in brain inflammation and synaptic plasticity by releasing inflammatory mediators and neurotrophic factors as well as, phagocytosing synaptic elements. Recent studies have shown peripheral inflammation, immune alteration in the brain are associated with post-traumatic stress disorder (PTSD) in humans. Several preclinical studies using Pavlovian fear conditioning have suggested that microglia are involved in fear memory dysregulation and altered fear neuronal networks. Microglial priming resulting from previous stressful experiences may also have an effect. This review will introduce the current knowledge of microglial contribution to disturbed fear memory regulation, a fundamental feature of PTSD.

The effects of eicosapentaenoic acid dietary supplementation on behavioral parameters and expression of hippocampal brain-derived neurotrophic factor in an animal model of post-traumatic stress disorder.

Post-traumatic stress disorder (PTSD) is a trauma- and stressor-related disorder, characterized by bi-directional symptomatic manifestations of increase in both hyperarousal/hypervigilance and numbing/avoidance. In our previous reports, we have proposed an animal model of PTSD using avoidance/escape task sessions in the shuttle box after delivering an inescapable foot-shock traumatization in the same box (Wakizono et al., 2007), and demonstrated the efficacy of 2-week administration of antidepressant on the hyperarousal/hypervigilant behavioral parameters (Sawamura et al., 2004) in the model. In this study, we observed a partial but significant efficacy of oral supplementation of eicosapentaenoic acid (EPA) for five weeks on the numbing/avoidance behavior in the experimental model. Additionally, western blot analyses using brain-derived neurotrophic factor (BDNF) monoclonal antibody revealed a decreased expression of BDNF protein, in the hippocampal region of the rats, due to foot-shock traumatization and a significantly increased expression of BDNF protein after oral EPA supplementation. The results indicate a possibility that alteration of the numbing/avoidance behavior parallels the expression of hippocampal BDNF in the rat brain. The present study suggests a possibility that EPA supplementation in the treatment of PTSD ameliorates persistent numbing/avoidance symptoms. (185 words).

Depression Promotes the Onset of Irritable Bowel Syndrome through Unique Dysbiosis in Rats.

Background/Aims: Although studies using conventional animal models have shown that specific stressors cause irritable bowel syndrome (IBS), it is unclear whether depression itself causes IBS. Our aim was to establish a rat model to determine if depression itself promotes the onset of IBS and to elucidate the role of gut microbiota in brain-gut axis pathogenesis during coincident depression and IBS. Methods: Rat models of depression were induced using our shuttle box method of learned helplessness. Visceral hypersensitivity was evaluated by colorectal distension (CRD) to diagnose IBS. Gut microbiota compositions were analyzed using high-throughput sequencing. In the subanalysis of rats without depression-like symptoms, rats with posttraumatic stress disorder (PTSD) were also examined. Results: The threshold value of CRD in depressed rats was significantly lower than that in control rats. Microbial community analysis of cecal microbiota showed that the relative abundance of Clostridiales incertae sedis, the most prevalent microbe, was significantly lower in depressed rats than in control rats. The distribution pattern of the microbiota clearly differed between depressed rats and control rats. Neither visceral hypersensitivity nor the composition of gut microbiota was altered in rats with PTSD-like phenotypes. Conclusions: Our rat model of depression is useful for clarifying the effect of depression on IBS and suggests that depression itself, rather than specific stressors, promotes the onset of IBS. Further, we provided evidence that various psychiatric diseases, viz., depression and PTSD, are associated with unique gut microbiota profiles, which could differentially affect the onset and progression of coincident IBS.

Differential effects of voluntary wheel running and toy rotation on the mRNA expression of neurotrophic factors and FKBP5 in a post-traumatic stress disorder rat model with the shuttle-box task.

Life-threatening experiences can result in the development of post-traumatic stress disorder. We have developed an animal model for post-traumatic stress disorder (PTSD) using a shuttle box in rats. In this paradigm, the rats were exposed to inescapable foot-shock stress (IS) in a shuttle box, and then an avoidance/escape task was performed in the same box 2 weeks after IS. A previous study using this paradigm revealed that environmental enrichment (EE) ameliorated avoidance/numbing-like behaviors, but not hyperarousal-like behaviors, and EE also elevated hippocampal brain-derived neurotrophic factor (BDNF) expression. However, the differential effects of EE components, i.e., running wheel (RW) or toy rotation, on PTSD-like behaviors has remained unclear. In this experiment, we demonstrated that RW, toy rotation, and EE (containing RW and toy rotation) ameliorated avoidance/numbing-like behaviors, induced learning of avoidance responses, and improved depressive-like behaviors in traumatized rats. The RW increased the hippocampal mRNA expression of neurotrophic factors, especially BDNF and glial-cell derived neurotrophic factor. Toy rotation influenced FK506 binding protein 5 mRNA expression, which is believed to be a regulator of the hypothalamic-pituitary-adrenal (HPA)-axis system, in the hippocampus and amygdala. This is the first report to elucidate the differential mechanistic effects of RW and toy rotation. The former appears to exert its effects via neurotrophic factors, while the latter exerts its effects via the HPA axis. Further studies will lead to a better understanding of the influence of environmental factors on PTSD.

Activated brain-derived neurotrophic factor/TrkB signaling in rat dorsal and ventral hippocampi following 10-day electroconvulsive seizure treatment.

Electroconvulsive therapy (ECT) is still the most effective strategy to treat severe and drug-resistant depressive disorders. Electroconvulsive seizure (ECS), which induces neuroplastic structural alterations and resilient behavioral changes in experimental animals, is the model of the ECT for human depression. ECT is typically administered three times per week for up to 4 weeks, while ECS treatments are administered daily for 10days. The increased expression of hippocampal brain-derived neurotrophic factor (BDNF) induced by antidepressive ECS treatment in experimental animals has been well documented. BDNF executes various neuroplastic functions by phosphorylating its high-affinity receptor, full-length TrkB, which has an intrinsic tyrosine kinase domain. However, the exact activation of BDNF/TrkB signaling following multiple ECS treatments has not been well elucidated. In epileptogenesis, conflicting effects of BDNF have been reported; while acute BDNF administration enhanced neuronal hyperexcitability and induced epileptiform activities, continuous BDNF infusion inhibited epileptogenesis. These conflicting results have been attributed to agonist-induced adaptive response of expressional down-regulation of the BDNF receptor. In the present study, using western blotting, we demonstrated increased phosphorylation as well as decreased expression of the full-length TrkB receptor (145kD) in both dorsal and ventral hippocampal regions of rats after a 10-day ECS treatment. The expression of mature BDNF (14kD) was up-regulated while that of proBDNF (32kD) remained unaltered in both hippocampal regions after the ECS treatment. Our results indicate that the hippocampal BDNF/TrkB signaling pathway is activated by multiple ECS treatments despite the ligand-induced down-regulation of the full-length TrkB receptor.

Increased expression of endocytosis-Related proteins in rat hippocampus following 10-day electroconvulsive seizure treatment.

Although electroconvulsive therapy (ECT) is clinically used for severe depression and drug-resistant Parkinson's disease, its exact biological background and mechanism have not yet been fully elucidated. Two potential explanations have been presented so far to explain the increased neuroplastic and resilient profiles of multiple ECT administrations. One is the alteration of central neurotransmitter receptor densities and the other is the expressional upregulation of brain derived neurotrophic factor in various brain regions with enhanced hippocampal neurogenesis and mossy fiber sprouting. In the present report, western blot analyses revealed significantly upregulated expression of various endocytosis-related proteins following 10-day electroconvulsive seizure (ECS) treatment in rat hippocampal homogenates and hippocampal lipid raft fractions extracted using an ultracentrifugation procedure. Upregulated proteins included endocytosis-related scaffolding proteins (caveolin-1, flotillin-1, and heavy and light chains of clathrin) and small GTPases (Rab5, Rab7, Rab11, and Rab4) specifically expressed on various types of endosomes. Two scaffolding proteins, caveolin-1 and flotillin-1, were also increased in the lipid raft fraction. Together with our previous finding of increased autophagy-related proteins in the hippocampal region, the present results suggest membrane trafficking machinery is enhanced following 10-day ECS treatment. We consider that the membrane trafficking machinery that transports functional proteins in the neuronal cells and from or into the synaptic membranes is one of the new candidates supporting the cellular and behavioral neuroplastic profiles of ECS treatments in animal experiments and ECT administrations in clinical settings.

Electroconvulsive therapy-induced Wolff-Parkinson-White syndrome: a case report.

OBJECTIVE: Wolff-Parkinson-White (WPW) syndrome is characterized by premature ventricular excitation due to the presence of an abnormal accessory pathway. Electrocardiography (ECG) of patients with WPW syndrome portrays a short PR interval and a wide QRS interval with a delta wave. METHODS: Herein, we report the case of a patient with schizophrenia who developed a wide QRS interval with a delta wave immediately following electroconvulsive therapy (ECT). RESULTS: Initially, the delta wave disappeared within 2 days after ECT. However, the duration of the delta wave increased exponentially to 4 months when ECT was repeated. CONCLUSION: Although the patient's cardiocirculatory dynamics remained normal, we continued to monitor her ECG until the delta wave disappeared because WPW syndrome can lead to serious arrhythmia.