Granulocyte macrophage colony-stimulating factor-induced macrophages of individuals with autism spectrum disorder adversely affect neuronal dendrites through the secretion of pro-inflammatory cytokines.

BACKGROUND: A growing body of evidence suggests that immune dysfunction and inflammation in the peripheral tissues as well as the central nervous system are associated with the neurodevelopmental deficits observed in autism spectrum disorder (ASD). Elevated expression of pro-inflammatory cytokines in the plasma, serum, and peripheral blood mononuclear cells of ASD has been reported. These cytokine expression levels are associated with the severity of behavioral impairments and symptoms in ASD. In a prior study, our group reported that tumor necrosis factor-α (TNF-α) expression in granulocyte-macrophage colony-stimulating factor-induced macrophages (GM-CSF MΦ) and the TNF-α expression ratio in GM-CSF MΦ/M-CSF MΦ (macrophage colony-stimulating factor-induced macrophages) was markedly higher in individuals with ASD than in typically developed (TD) individuals. However, the mechanisms of how the macrophages and the highly expressed cytokines affect neurons remain to be addressed. METHODS: To elucidate the effect of macrophages on human neurons, we used a co-culture system of control human-induced pluripotent stem cell-derived neurons and differentiated macrophages obtained from the peripheral blood mononuclear cells of five TD individuals and five individuals with ASD. All participants were male and ethnically Japanese. RESULTS: Our results of co-culture experiments showed that GM-CSF MΦ affect the dendritic outgrowth of neurons through the secretion of pro-inflammatory cytokines, interleukin-1α and TNF-α. Macrophages derived from individuals with ASD exerted more severe effects than those derived from TD individuals. LIMITATIONS: The main limitations of our study were the small sample size with a gender bias toward males, the use of artificially polarized macrophages, and the inability to directly observe the interaction between neurons and macrophages from the same individuals. CONCLUSIONS: Our co-culture system revealed the non-cell autonomous adverse effects of GM-CSF MΦ in individuals with ASD on neurons, mediated by interleukin-1α and TNF-α. These results may support the immune dysfunction hypothesis of ASD, providing new insights into its pathology.

Brain-derived neurotrophic factor from microglia regulates neuronal development in the medial prefrontal cortex and its associated social behavior.

Microglia and brain-derived neurotrophic factor (BDNF) are essential for the neuroplasticity that characterizes critical developmental periods. The experience-dependent development of social behaviors-associated with the medial prefrontal cortex (mPFC)-has a critical period during the juvenile period in mice. However, whether microglia and BDNF affect social development remains unclear. Herein, we aimed to elucidate the effects of microglia-derived BDNF on social behaviors and mPFC development. Mice that underwent social isolation during p21-p35 had increased Bdnf in the microglia accompanied by reduced adulthood sociability. Additionally, transgenic mice overexpressing microglial Bdnf-regulated using doxycycline at different time points-underwent behavioral, electrophysiological, and gene expression analyses. In these mice, long-term overexpression of microglial BDNF impaired sociability and excessive mPFC inhibitory neuronal circuit activity. However, administering doxycycline to normalize BDNF from p21 normalized sociability and electrophysiological function in the mPFC, whereas normalizing BDNF from later ages (p45-p50) did not normalize electrophysiological abnormalities in the mPFC, despite the improved sociability. To evaluate the possible role of BDNF in human sociability, we analyzed the relationship between adverse childhood experiences and BDNF expression in human macrophages, a possible proxy for microglia. Results show that adverse childhood experiences positively correlated with BDNF expression in M2 but not M1 macrophages. In summary, our study demonstrated the influence of microglial BDNF on the development of experience-dependent social behaviors in mice, emphasizing its specific impact on the maturation of mPFC function, particularly during the juvenile period. Furthermore, our results propose a translational implication by suggesting a potential link between BDNF secretion from macrophages and childhood experiences in humans.

Diagnosing psychiatric disorders from history of present illness using a large-scale linguistic model.

AIM: Recent advances in natural language processing models are expected to provide diagnostic assistance in psychiatry from the history of present illness (HPI). However, existing studies have been limited, with the target diseases including only major diseases, small sample sizes, or no comparison with diagnoses made by psychiatrists to ensure accuracy. Therefore, we formulated an accurate diagnostic model that covers all psychiatric disorders. METHODS: HPIs and diagnoses were extracted from discharge summaries of 2,642 cases at the Nara Medical University Hospital, Japan, from 21 May 2007, to 31 May 31 2021. The diagnoses were classified into 11 classes according to the code from ICD-10 Chapter V. Using UTH-BERT pre-trained on the electronic medical records of the University of Tokyo Hospital, Japan, we predicted the main diagnoses at discharge based on HPIs and compared the concordance rate with the results of psychiatrists. The psychiatrists were divided into two groups: semi-Designated with 3-4 years of experience and Residents with only 2 months of experience. RESULTS: The model's match rate was 74.3%, compared to 71.5% for the semi-Designated psychiatrists and 69.4% for the Residents. If the cases were limited to those correctly answered by the semi-Designated group, the model and the Residents performed at 84.9% and 83.3%, respectively. CONCLUSION: We demonstrated that the model matched the diagnosis predicted from the HPI with a high probability to the principal diagnosis at discharge. Hence, the model can provide diagnostic suggestions in actual clinical practice.

Structural alterations in the amygdala and impaired social incentive learning in a mouse model of a genetic variant associated with neurodevelopmental disorders.

Copy number variants (CNVs) are robustly associated with psychiatric disorders and their dimensions and changes in brain structures and behavior. However, as CNVs contain many genes, the precise gene-phenotype relationship remains unclear. Although various volumetric alterations in the brains of 22q11.2 CNV carriers have been identified in humans and mouse models, it is unknown how the genes in the 22q11.2 region individually contribute to structural alterations and associated mental illnesses and their dimensions. Our previous studies have identified Tbx1, a T-box family transcription factor encoded in 22q11.2 CNV, as a driver gene for social interaction and communication, spatial and working memory, and cognitive flexibility. However, it remains unclear how TBX1 impacts the volumes of various brain regions and their functionally linked behavioral dimensions. In this study, we used volumetric magnetic resonance imaging analysis to comprehensively evaluate brain region volumes in congenic Tbx1 heterozygous mice. Our data show that the volumes of anterior and posterior portions of the amygdaloid complex and its surrounding cortical regions were reduced in Tbx1 heterozygous mice. Moreover, we examined the behavioral consequences of an altered volume of the amygdala. Tbx1 heterozygous mice were impaired for their ability to detect the incentive value of a social partner in a task that depends on the amygdala. Our findings identify the structural basis for a specific social dimension associated with loss-of-function variants of TBX1 and 22q11.2 CNV.

Brain-derived neurotrophic factor from microglia regulates neuronal development in the medial prefrontal cortex and its associated social behavior.

Microglia and brain-derived neurotrophic factor (BDNF) are essential for the neuroplasticity that characterizes critical developmental periods. The experience-dependent development of social behaviors-associated with the medial prefrontal cortex (mPFC)-has a critical period during the juvenile period in mice. However, whether microglia and BDNF affect social development remains unclear. Herein, we aimed to elucidate the effects of microglia-derived BDNF on social behaviors and mPFC development. Mice that underwent social isolation during p21-p35 had increased Bdnf in the microglia accompanied by reduced adulthood sociability. Additionally, transgenic mice overexpressing microglia Bdnf-regulated using doxycycline at different time points-underwent behavioral, electrophysiological, and gene expression analyses. In these mice, long-term overexpression of microglia BDNF impaired sociability and excessive mPFC inhibitory neuronal circuit activity. However, administration of doxycycline to normalize BDNF from p21 normalized sociability and electrophysiological functions; this was not observed when BDNF was normalized from a later age (p45-p50). To evaluate the possible role of BDNF in human sociability, we analyzed the relationship between adverse childhood experiences and BDNF expression in human macrophages, a possible substitute for microglia. Results show that adverse childhood experiences positively correlated with BDNF expression in M2 but not M1 macrophages. Thus, microglia BDNF might regulate sociability and mPFC maturation in mice during the juvenile period. Furthermore, childhood experiences in humans may be related to BDNF secretion from macrophages.

Structural alterations in the amygdala and impaired social incentive learning in a mouse model of a genetic variant associated with neurodevelopmental disorders.

Copy number variants (CNVs) are robustly associated with psychiatric disorders and their dimensions and changes in brain structures and behavior. However, as CNVs contain many genes, the precise gene-phenotype relationship remains unclear. Although various volumetric alterations in the brains of 22q11.2 CNV carriers have been identified in humans and mouse models, it is unknown how the genes in the 22q11.2 region individually contribute to structural alterations and associated mental illnesses and their dimensions. Our previous studies have identified Tbx1, a T-box family transcription factor encoded in 22q11.2 CNV, as a driver gene for social interaction and communication, spatial and working memory, and cognitive flexibility. However, it remains unclear how TBX1 impacts the volumes of various brain regions and their functionally linked behavioral dimensions. In this study, we used volumetric magnetic resonance imaging analysis to comprehensively evaluate brain region volumes in congenic Tbx1 heterozygous mice. Our data show that the volumes of anterior and posterior portions of the amygdaloid complex and its surrounding cortical regions were reduced in Tbx1 heterozygous mice. Moreover, we examined the behavioral consequences of an altered volume of the amygdala. Tbx1 heterozygous mice were impaired for their ability to detect the incentive value of a social partner in a task that depends on the amygdala. Our findings identify the structural basis for a specific social dimension associated with loss-of-function variants of TBX1 and 22q11.2 CNV.

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.

Tumor necrosis factor-α expression aberration of M1/M2 macrophages in adult high-functioning autism spectrum disorder.

The etiology of autism spectrum disorder (ASD) is complex, and its pathobiology is characterized by enhanced inflammatory activities; however, the precise pathobiology and underlying causes of ASD remain unclear. This study was performed to identify inflammatory indicators useful for diagnosing ASD. The mRNA expression of cytokines, including tumor necrosis factor-α (TNF-α), was measured in cultured M1 and M2 macrophages from patients with ASD (n = 29) and typically developed (TD) individuals (n = 30). Additionally, TNF-α expression in the monocytes of patients with ASD (n = 7), showing aberrations in TNF-α expression in M1/M2 macrophages and TD individuals (n = 6), was measured. TNF-α expression in M1 macrophages and the TNF-α expression ratio in M1/M2 macrophages were markedly higher in patients with ASD than in TD individuals; however, this increase was not observed in M2 macrophages (M1: sensitivity = 34.5%, specificity = 96.7%, area under the curve = 0.74, positive likelihood ratio = 10.34; ratio of M1/M2: sensitivity = 55.2%, specificity = 96.7%, area under the curve = 0.79, positive likelihood ratio = 16.55). Additionally, TNF-α expression in monocytes did not significantly differ between patients with ASD and TD individuals. In conclusion, further studies on TNF-α expression in cultured macrophages may improve the understanding of ASD pathobiology. LAY SUMMARY: TNF-α expression in differentiated M1 macrophages and TNF-α expression ratio in differentiated M1/M2 macrophages were markedly higher in patients with ASD than in TD individuals, while no difference in TNF-α expression was found in pre-differentiation cells such as monocytes. These measurements allow elucidation of the novel pathobiology of ASD and can contribute to biomarker implementation for the diagnosis of adult high-functioning ASD.

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.

A retrospective study of factors associated with persistent delirium.

BACKGROUND: It has been reported that delirium causes various problems. Many researchers have reported the risk factors associated with the onset of delirium; however, there are few reports focused on persistent delirium. This study aimed to identify the risk factors associated with persistent delirium. METHODS: A total of 573 patients hospitalised in Nara Prefecture General Medical Centre from October 2014 through September 2017 who were referred to the psychiatry consultation service were included in this study. Persistent delirium was defined as delirium lasting for 14 days or more. A retrospective study was carried out based on the patients' records. The relationship between various background factors and persistent delirium was statistically analysed. RESULTS: Of the 573 hospitalised patients, 295 were diagnosed as having delirium. Forty-six patients with persistent delirium and 181 patients with nonpersistent delirium were included in this study. Multivariable logistic regression analyses revealed that male gender, opioid analgesics use, non-opioid analgesics use, and low serum sodium were significantly and independently associated with persistent delirium. Ramelteon or trazodone was used significantly more in persistent delirium, although each use was not significant. CONCLUSION: This is the first study to reveal that male gender and use of analgesics were associated with persistent delirium in general hospital. However, as this is a case-control study and may contain bias, future cohort studies and intervention studies are needed. It is also necessary to investigate the relevance of the 'degree of pain' behind the use of analgesics.

Heterozygosity of murine Crkl does not recapitulate behavioral dimensions of human 22q11.2 hemizygosity.

Deletions in 22q11.2 human chromosome are known to be associated with psychiatric disorders, such as intellectual disability, schizophrenia, autism spectrum disorder, and anxiety disorders. This copy number variation includes a 3.0 Mb deletion and a nested proximal 1.5 Mb hemizygous deletion in the same region. Evidence indicates that the distal 22q11.2 region outside the nested 1.5 Mb deletion also might be contributory in humans. However, the precise genetic architecture within the distal region responsible for psychiatric disorders remains unclear, and this issue cannot be experimentally evaluated beyond the correlation in humans. As CRKL (CRK-like Proto-Oncogene, Adaptor Protein) is one of the genes encoded in the distal 22q11.2 segment and its homozygous deletion causes physical phenotypes of 22q11.2 hemizygous deletion, we tested the hypothesis that its murine homolog Crkl contributes to behavioral phenotypes relevant to psychiatric disorders in mice. Congenic Crkl heterozygosity reduced thigmotaxis, an anxiety-related behavior, in an inescapable open field, but had no apparent effect on social interaction, spontaneous alternation in a T-maze, anxiety-like behavior in an elevated plus maze, or motor activity in an open field. Our data indicate that the heterozygosity of murine Crkl does not recapitulate social deficits, working memory deficits, repetitive behavior traits or hyperactivity of human 22q11.2 hemizygous deletion. Moreover, while 22q11.2 hemizygous deletion is associated with high levels of phobia and anxiety in humans, our data suggest that Crkl heterozygosity rather acts as a protective factor for phobia-like behavior in an open field.

Prefrontal cortex infusion of beta-hydroxybutyrate, an endogenous NLRP3 inflammasome inhibitor, produces antidepressant-like effects in a rodent model of depression.

AIMS: Neuroinflammation is deeply related to the pathophysiology of depression. Beta-hydroxybutyrate (BHB), which is an endogenous ketone body, exerts anti-inflammatory effects, and peripheral administration of BHB induces antidepressant effects in an animal model of depression; however, it is unclear whether BHB specifically mediates these actions in the brain. Thus, we administered BHB directly into the brain in a rodent model of depression using a chronic unpredictable stress (CUS) paradigm. METHODS: BHB was continuously microinjected into the prefrontal cortex (PFC) using osmotic pumps for 21 days. Behavioral testing included the forced swim test (FST) and the open field test (OFT); the levels of pro-inflammatory cytokines, such as interleukin 1ß (IL-1ß) and tumor necrosis factor α (TNF-α), were quantified in the PFC, and the concentration of corticosterone in blood serum was measured. RESULTS: BHB administration into the PFC significantly decreased immobility time in the FST, without significantly altering locomotor activity assessed in the OFT. Also, CUS significantly increased the levels of TNF-α in the PFC and decreased serum corticosterone levels; these changes were attenuated by BHB administration. These findings suggest that a small amount of BHB administered into the PFC directly produces antidepressant effects, possibly through anti-inflammatory mechanisms, and can improve hypothalamus-pituitary-adrenal axis responses. CONCLUSION: BHB may be a novel therapeutic candidate for the treatment of depression based on the neuro-inflammatory hypothesis, and the PFC is a region implicated in the antidepressant action of BHB.

Modeling and Predicting Developmental Trajectories of Neuropsychiatric Dimensions Associated With Copy Number Variations.

Copy number variants, such as duplications and hemizygous deletions at chromosomal loci of up to a few million base pairs, are highly associated with psychiatric disorders. Hemizygous deletions at human chromosome 22q11.2 were found to be associated with elevated instances of schizophrenia and autism spectrum disorder in 1992 and 2002, respectively. Following these discoveries, many mouse models have been developed and tested to analyze the effects of gene dose alterations in small chromosomal segments and single genes of 22q11.2. Despite several limitations to modeling mental illness in mice, mouse models have identified several genes on 22q11.2-Tbx1, Dgcr8, Comt, Sept5, and Prodh-that contribute to dimensions of autism spectrum disorder and schizophrenia, including working memory, social communication and interaction, and sensorimotor gating. Mouse studies have identified that heterozygous deletion of Tbx1 results in defective social communication during the neonatal period and social interaction deficits during adolescence/adulthood. Overexpression of Tbx1 or Comt in adult neural progenitor cells in the hippocampus delays the developmental maturation of working memory capacity. Collectively, mouse models of variants of these 4 genes have revealed several potential neuronal mechanisms underlying various aspects of psychiatric disorders, including adult neurogenesis, microRNA processing, catecholamine metabolism, and synaptic transmission. The validity of the mouse data would be ultimately tested when therapies or drugs based on such potential mechanisms are applied to humans.

Anti-inflammatory Effect of Ghrelin in Lymphoblastoid Cell Lines From Children With Autism Spectrum Disorder.

The gut hormone ghrelin has been implicated in a variety of functional roles in the central nervous system through the brain-gut axis, one of which is an anti-inflammatory effect. An aberrant brain-gut axis producing immune dysfunction has been implicated in the pathobiology of autism spectrum disorder (ASD), and elevated expression of inflammatory markers has been shown in blood and brain tissue from subjects with ASD. We hypothesized that ghrelin may mitigate this effect. Lymphoblastoid cell lines from typically developed children (TD-C) (N = 20) and children with ASD (ASD-C) (N = 20) were cultured with PBS or human ghrelin (0.01 µM) for 24 h, and mRNA expression levels of the inflammation-related molecules interleukin-1ß (IL-1ß), interleukin-6 (IL-6), tumor necrosis factor-α (TNF-α), and nuclear factor kappa B (NF-κB) were measured to examine the effects of ghrelin as an anti-inflammatory agent. Expression levels of TNF-α and NF-κB mRNA, but not IL-1ß or IL-6, were significantly elevated in ASD-C compared to TD-C. Ghrelin showed a tendency to reduce the expression of TNF-α and NF-κB, but this was not statistically significant. Considering the heterogenous pathobiology of ASD, we examined the effects of ghrelin on TD-C and ASD-C with expression levels of TNF-α and NF-κB in the highest and lowest quartiles. We found that ghrelin markedly reduced mRNA expression of TNF-α and NF-κB s in ASD-C with highest-quartile expression, but there were no effects in ASD-C with lowest-quartile expression, TD-C with highest quartile expression, or TD-C with lowest quartile expression. Together, these findings suggest that ghrelin has potential as a novel therapeutic agent for ASD with inflammation and/or immune dysfunction.

Altered gene expression in lymphoblastoid cell lines after subculture.

Lymphoblastoid cell lines (LCLs) are nearly immortalized B lymphocytes that are used as long-lasting supply of human cells for studies on gene expression analyses. However, studies on the stability of the cellular features of LCLs are scarce. To address this issue, we measured gene expression in LCLs with different passage numbers and observed that gene expression substantially changed within 10 passages. In particular, the expression of glyceraldehyde-3-phosphate dehydrogenase (GAPDH), a well-known housekeeping gene, varied considerably during subculture; thus, the use GAPDH as an internal control may be unsuitable. In conclusion, this study highlights the need for exercising caution during determination of gene expression in LCLs.

Effects of cross-rearing with social peers on myelination in the medial prefrontal cortex of a mouse model with autism spectrum disorder.

Autism spectrum disorder (ASD) is a neurodevelopmental disorder characterized by impaired social interaction, poor communication skills, and repetitive/restrictive behaviors. Recent studies have indicated that early rehabilitative intervention can alleviate the symptoms of individuals with ASD. However, it remains unknown whether rehabilitative intervention can restore brain structures such as myelin, which generally shows abnormalities in individuals with ASD. Therefore, in the present study, we used a mouse model of ASD (BTBR mice) that demonstrated asocial behaviors and hypomyelination in the medial prefrontal cortex (mPFC) to investigate whether interaction with social peers (C57BL/6J mice) has an effect on myelination. We found that housing with C57BL/6J mice after weaning through adulthood increased the myelin thickness in mPFC, but not in the motor cortex, of BTBR mice. There was no effect of cross-rearing with C57BL/6J mice on axon diameter in mPFC of BTBR mice. This finding suggests that early rehabilitative intervention may alleviate myelin abnormalities in mPFC as well as clinical symptoms in individuals with ASD.

Beta-hydroxybutyrate, an endogenic NLRP3 inflammasome inhibitor, attenuates stress-induced behavioral and inflammatory responses.

Neuro-inflammation has been shown to play a critical role in the development of depression. Beta-hydroxybutyrate (BHB) is a ketone body and has recently been reported to exert anti-inflammatory effects via inhibition of NLRP3 inflammasome. Here, we investigated the potential antidepressant and anti-inflammatory effects of BHB on rats exposed to acute and chronic stress. We examined the influence of repeated BHB administration on depressive and anxiety behaviors in a rodent model of chronic unpredictable stress (CUS). Additionally, the influence of acute immobilization (IMM) stress and single BHB administration on hippocampal interleukin-1ß (IL-1ß) and tumor necrosis factor-α (TNF-α) were assessed. Repeated administration of BHB attenuated CUS-induced depressive- and anxiety-related behaviors. IMM stress increased levels of IL-1ß in the hippocampus, while a single pre-administration of BHB attenuated this increase. Although no effect was observed on hippocampal TNF-α levels after 1 h of IMM stress, a single BHB pre-administration reduced hippocampal TNF-α. Our previous report showed that the release of IL-1ß and TNF-α caused by stress is tightly regulated by NLRP3 inflammasome. These findings demonstrate that BHB exerts antidepressant-like effects, possibly by inhibiting NLRP3-induced neuro-inflammation in the hippocampus, and that BHB may be a novel therapeutic candidate for the treatment of stress-related mood disorders.

Effects of the mode of re-socialization after juvenile social isolation on medial prefrontal cortex myelination and function.

Social isolation is an important factor in the development of psychiatric disorders. It is necessary to develop an effective psychological treatment, such as cognitive rehabilitation, for children who have already suffered from social isolation, such as neglect and social rejection. We used socially isolated mice to validate whether elaborate re-socialization after juvenile social isolation can restore hypomyelination in the medial prefrontal cortex (mPFC) and the attendant functions manifested in socially isolated mice. While mice who underwent re-socialization with socially isolated mice after juvenile social isolation (Re-IS mice) demonstrated less mPFC activity during exposure to a strange mouse, as well as thinner myelin in the mPFC than controls, mice who underwent re-socialization with socially housed mice after juvenile social isolation (Re-SH mice) caught up with the controls in terms of most mPFC functions, as well as myelination. Moreover, social interaction of Re-IS mice was reduced as compared to controls, but Re-SH mice showed an amount of social interaction comparable to that of controls. These results suggest that the mode of re-socialization after juvenile social isolation has significant effects on myelination in the mPFC and the attendant functions in mice, indicating the importance of appropriate psychosocial intervention after social isolation.

Microglia-derived neuregulin expression in psychiatric disorders.

Several studies have revealed that neuregulins (NRGs) are involved in brain function and psychiatric disorders. While NRGs have been regarded as neuron- or astrocyte-derived molecules, our research has revealed that microglia also express NRGs, levels of which are markedly increased in activated microglia. Previous studies have indicated that microglia are activated in the brains of individuals with autism spectrum disorder (ASD). Therefore, we investigated microglial NRG mRNA expression in multiple lines of mice considered models of ASD. Intriguingly, microglial NRG expression significantly increased in BTBR and socially-isolated mice, while maternal immune activation (MIA) mice exhibited identical NRG expression to controls. Furthermore, we observed a positive correlation between NRG expression in microglia and peripheral blood mononuclear cells (PBMCs) in mice, suggesting that NRG expression in human PBMCs may mirror microglia-derived NRG expression in the human brain. To translate these findings for application in clinical psychiatry, we measured levels of NRG1 splice-variant expression in clinically available PBMCs of patients with ASD. Levels of NRG1 type III expression in PBMCs were positively correlated with impairments in social interaction in children with ASD (as assessed using the Autistic Diagnostic Interview-Revised test: ADI-R). These findings suggest that immune cell-derived NRGs may be implicated in the pathobiology of psychiatric disorders such as ASD.

Tumor necrosis factor-alpha expression in peripheral blood mononuclear cells correlates with early childhood social interaction in autism spectrum disorder.

Autism spectrum disorder is a neurodevelopmental disorder characterized by impaired social interaction, poor communication skills, and repetitive/restrictive behaviors. Elevated blood levels of pro-inflammatory cytokines have been reported in subjects with autism spectrum disorder. On the other hand, early childhood adverse experience also increases blood levels of these cytokines. Since social experience of children with autism spectrum disorder is generally unlike to typically developing children, we hypothesized that social interaction during childhood contribute to pro-inflammatory cytokine expression in subjects with autism spectrum disorder. We compared revised Autism Diagnostic Interview scores and expression levels of pro-inflammatory cytokines in peripheral blood mononuclear cells of subjects with autism spectrum disorder (n = 30). The score of domain A on the revised Autism Diagnostic Interview, indicating social interaction impairment in early childhood, was negatively correlated with tumor necrosis factor-α mRNA expression level in peripheral blood mononuclear cells but not interleukin-1ß or -6. Consistently, tumor necrosis factor-α mRNA expression was markedly low in subjects with autism spectrum disorder compared to typically developing children who presumably experienced the regular levels of social interaction. These findings suggest that the low blood levels of tumor necrosis factor-α mRNA in subjects with autism spectrum disorder might be due to impaired social interaction in early childhood.