Heterogeneity and mitochondrial vulnerability configurate the divergent immunoreactivity of human induced microglia-like cells

Microglia play versatile roles in progression of and protection against neuroinflammatory diseases. Little is known, however, about the mechanisms underlying the diverse reactivity of microglia to inflammatory conditions. We investigated how human induced microglia-like (iMG) cells respond to innate immune ligands. Quantitative PCR showed that poly-I:C and lipopolysaccharide (LPS) activated the expression of IL1B and TNF. Immunoreactivity of iMG did not differ between controls (n = 11) and patients with neuroinflammatory diseases (n = 24). Flow cytometry revealed that CD14high cells expressed interleukin (IL) -1β after LPS treatment. Immunoblotting showed that poly-I:C and LPS differentially activated inflammatory pathways but commonly induced mitochondrial instability and the expression of pyruvate kinase isoform M2 (PKM2). Furthermore, a potent stimulator of PKM2 (DASA-58) alleviated IL-1β production after LPS treatment. These data indicate that heterogeneous cell populations and mitochondrial stability underlie the divergent immunoreactivity of human iMG in environments.

Angiogenic and inflammatory responses in human induced microglia-like (iMG) cells from patients with Moyamoya disease

Angiogenic factors associated with Moyamoya disease (MMD) are overexpressed in M2 polarized microglia in ischemic stroke, suggesting that microglia may be involved in the pathophysiology of MMD; however, existing approaches are not applicable to explore this hypothesis. Herein we applied blood induced microglial-like (iMG) cells. We recruited 25 adult patients with MMD and 24 healthy volunteers. Patients with MMD were subdivided into progressive (N = 7) or stable (N = 18) group whether novel symptoms or radiographic advancement of Suzuki stage within 1 year was observed or not. We produced 3 types of iMG cells; resting, M1-, and M2-induced cells from monocytes, then RNA sequencing followed by GO and KEGG pathway enrichment analysis and qPCR assay were performed. RNA sequencing of M2-induced iMG cells revealed that 600 genes were significantly upregulated (338) or downregulated (262) in patients with MMD. Inflammation and immune-related factors and angiogenesis-related factors were specifically associated with MMD in GO analysis. qPCR for MMP9, VEGFA, and TGFB1 expression validated these findings. This study is the first to demonstrate that M2 microglia may be involved in the angiogenic process of MMD. The iMG technique provides a promising approach to explore the bioactivity of microglia in cerebrovascular diseases.

Systemic Inflammation Leads to Changes in the Intracellular Localization of KLK6 in Oligodendrocytes in Spinal Cord White Matter

Axonal injury and demyelination occur in demyelinating diseases, such as multiple sclerosis, and the detachment of myelin from axons precedes its degradation. Paranodes are the areas at which each layer of the myelin sheath adheres tightly to axons. The destruction of nodal and paranodal structures during inflammation is an important pathophysiology of various neurological disorders. However, the underlying pathological changes in these structures remain unclear. Kallikrein 6 (KLK6), a serine protease produced by oligodendrocytes, is involved in demyelinating diseases. In the present study, we intraperitoneally injected mice with LPS for several days and examined changes in the localization of KLK6. Transient changes in the intracellular localization of KLK6 to paranodes in the spinal cord were observed during LPS-induced systemic inflammation. However, these changes were not detected in the upper part of brain white matter. LPS-induced changes were suppressed by minocycline, suggesting the involvement of microglia. Moreover, nodal lengths were elongated in LPS-treated wild-type mice, but not in LPS-treated KLK6-KO mice. These results demonstrate the potential involvement of KLK6 in the process of demyelination.

Ameliorative effects of Fingolimod (FTY720) on microglial activation and psychosis-related behavior in short term cuprizone exposed mice

Schizophrenia is a psychiatric disorder that affects around 1% of the population in widespread populations, with severe cases leading to long-term hospitalization and necessitation of lifelong treatment. Recent studies on schizophrenia have highlighted the involvement of inflammatory and immunoregulatory mechanisms with the onset of symptoms, and the usage of anti-inflammatory treatments are being tested against periods of rapid psychosis. In the central nervous system, microglia are the innate immune population which are activated in response to a wide range of physical and psychological stress factors and produce proinflammatory mediators such as cytokines. Microglial activation and neuroinflammation has been associated to numerous psychiatric disorders including schizophrenia, especially during psychotic episodes. Thus, novel treatments which dampen microglial activation may be of great relevance in the treatment of psychiatric disorders. Fingolimod (FTY720) is a drug used as an immunosuppressive treatment to multiple sclerosis. Recent clinical trials have focused on FTY720 as a treatment for the behavioral symptoms in schizophrenia. However, the mechanisms of Fingolimod in treating the symptoms of schizophrenia are not clear. In this study we use a recently developed neuroinflammatory psychosis model in mice: cuprizone short-term exposure, to investigate the effects of FTY720 administration. FTY720 administration was able to completely alleviate methamphetamine hypersensitivity caused by cuprizone exposure. Moreover, administration of FTY720 improved multiple measures of neuroinflammation (microglial activation, cytokine production, and leucocyte infiltration). In conclusion, our results highlight the future use of FTY720 as a direct anti-inflammatory treatment against microglial activation and psychosis.

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.

CD206 Expression in Induced Microglia-Like Cells From Peripheral Blood as a Surrogate Biomarker for the Specific Immune Microenvironment of Neurosurgical Diseases Including Glioma

Targeting the unique glioma immune microenvironment is a promising approach in developing breakthrough immunotherapy treatments. However, recent advances in immunotherapy, including the development of immune checkpoint inhibitors, have not improved the outcomes of patients with glioma. A way of monitoring biological activity of immune cells in neural tissues affected by glioma should be developed to address this lack of sensitivity to immunotherapy. Thus, in this study, we sought to examine the feasibility of non-invasive monitoring of glioma-associated microglia/macrophages (GAM) by utilizing our previously developed induced microglia-like (iMG) cells. Primary microglia (pMG) were isolated from surgically obtained brain tissues of 22 patients with neurological diseases. iMG cells were produced from monocytes extracted from the patients’ peripheral blood. Quantitative reverse transcription-polymerase chain reaction (qRT-PCR) revealed a significant correlation of the expression levels of representative markers for M1 and M2 microglia phenotypes between pMG and the corresponding iMG cells in each patient (Spearman’s correlation coefficient = 0.5225, P <0.0001). Synchronous upregulation of CD206 expression levels was observed in most patients with glioma (6/9, 66.7%) and almost all patients with glioblastoma (4/5, 80%). Therefore, iMG cells can be used as a minimally invasive tool for monitoring the disease-related immunological state of GAM in various brain diseases, including glioma. CD206 upregulation detected in iMG cells can be used as a surrogate biomarker of glioma.

ProBDNF induces sustained elevation of intracellular Ca2+ possibly mediated by TRPM7 channels in rodent microglial cells

Microglia are intrinsic immune cells that release factors including pro- and anti-inflammatory cytokines, nitric oxide (NO) and neurotrophins following activation in the brain. Elevation of intracellular Ca²⁺ concentration ([Ca²⁺ ]i) is important for microglial functions, such as the release of cytokines or NO from activated microglia. Brain-derived neurotrophic factor (BDNF) is a neurotrophin well known for its roles in the activation of microglia. Interestingly, proBDNF, the precursor form of mature BDNF, and mature BDNF elicit opposing neuronal responses in the brain. Mature BDNF induces sustained intracellular Ca²⁺ elevation through the upregulation of the surface expression of TRPC3 channels in rodent microglial cells. In addition, TRPC3 channels are important for the BDNF-induced suppression of NO production in activated microglia. In this study, we observed that proBDNF and mature BDNF have opposite effects on the relative expression of surface p75 neurotrophin receptor (p75^NTR ) in rodent microglial cells. ProBDNF induces a sustained elevation of [Ca²⁺ ]i through binding to the p75^NTR , which is possibly mediated by Rac 1 activation and TRPM7 channels in rodent microglial cells. Flow cytometry showed that proBDNF increased the relative surface expression of TRPM7. Although proBDNF did not affect either mRNA expression of pro- and anti-inflammatory cytokines or the phagocytic activity, proBDNF potentiates the generation of NO induced by IFN-γ and TRPM7 channels could be involved in the proBDNF-induced potentiation of IFN-γ-mediated production of NO. We show direct evidence that rodent microglial cells are able to respond to proBDNF, which might be important for the regulation of inflammatory responses in the brain.

Effect of memantine, an anti-Alzheimer's drug, on rodent microglial cells in vitro

The pathophysiology of Alzheimer's disease (AD) is related to neuroinflammatory responses mediated by microglia. Memantine, an antagonist of N-methyl-D-aspartate (NMDA) receptors used as an anti-Alzheimer's drug, protects from neuronal death accompanied by suppression of proliferation and activation of microglial cells in animal models of AD. However, it remains to be tested whether memantine can directly affect microglial cell function. In this study, we examined whether pretreatment with memantine affects intracellular NO and Ca2+ mobilization using DAF-2 and Fura-2 imaging, respectively, and tested the effects of memantine on phagocytic activity by human β-Amyloid (1-42) phagocytosis assay in rodent microglial cells. Pretreatment with memantine did not affect production of NO or intracellular Ca2+ elevation induced by TNF in rodent microglial cells. Pretreatment with memantine also did not affect the mRNA expression of pro-inflammatory (TNF, IL-1β, IL-6 and CD45) or anti-inflammatory (IL-10, TGF-β and arginase) phenotypes in rodent microglial cells. In addition, pretreatment with memantine did not affect the amount of human β-Amyloid (1-42) phagocytosed by rodent microglial cells. Moreover, we observed that pretreatment with memantine did not affect 11 major proteins, which mainly function in the phagocytosis and degradation of β-Amyloid (1-42), including TREM2, DAP12 and neprilysin in rodent microglial cells. To the best of our knowledge, this is the first report to suggest that memantine does not directly modulate intracellular NO and Ca2+ mobilization or phagocytic activity in rodent microglial cells. Considering the neuroinflammation hypothesis of AD, the results might be important to understand the effect of memantine in the brain.

Plasma acetylcholine and nicotinic acid are correlated with focused preference for photographed females in depressed males: an economic game study

Interpersonal difficulties are often observed in major depressive disorder (MDD), while the underlying psychological and biological mechanisms have not yet been elucidated. In the present case–control study, a PC-based trust game was conducted for 38 drug-free MDD patients and 38 healthy controls (HC). In the trust game, participants invested money in a partner (trusting behaviors), and also rated each partner’s attractiveness (preference for others). In addition, blood biomarkers including metabolites were measured. Both MDD and HC males exhibited more trusting behaviors compared to females. MDD males’ preference for ordinary-attractive partners (lay-person photographs) was lower than HC males, whereas their preference for high-attractive females (fashion-model photographs) was similar levels to HC males. This tendency in MDD males could reflect a “focused (narrowed) preference for females”. As for blood biomarker analysis, the levels of 37 metabolites including acetylcholine, AMP, GMP, nicotinic acid and tryptophan were significantly different between two groups. Interestingly, among male participants, acetylcholine and nicotinic acid were negatively correlated with the level of focused preference for photographed females. In sum, we have revealed some behavioral, psychological and biological traits of trusting behaviors and preference for others especially in MDD males. Larger studies should be conducted to validate our preliminary findings.

Personality classification enhances blood metabolome analysis and biotyping for major depressive disorders: two-species investigation

BACKGROUND

The relationship between depression and personality has long been suggested, however, biomarker investigations for depression have mostly overlooked this connection.

METHODS

We collected personality traits from 100 drug-free patients with major depressive disorders (MDD) and 100 healthy controls based on the Five-Factor Model (FFM) such as Neuroticism (N) and Extraversion (E), and also obtained 63 plasma metabolites profiles by LCMS-based metabolome analysis.

RESULTS

Partitional clustering analysis using the NEO-FFI data classified all subjects into three major clusters. Eighty-six subjects belonging to Cluster 1 (C1: less personality-biased group) constituted half of MDD patients and half of healthy controls. C2 constituted 50 subjects mainly MDD patients (N ^high + E ^low), and C3 constituted 64 subjects mainly healthy subjects (N ^low + E ^high). Using metabolome information, the machine learning model was optimized to discriminate MDD patients from healthy controls among all subjects and C1, respectively. The performance of the model for all subjects was moderate (AUC = 0. 715), while the performance was extremely improved when limited to C1 (AUC = 0. 907). Tryptophan-pathway plasma metabolites including tryptophan, serotonin and kynurenine were significantly lower in MDD patients especially among C1. We also validated metabolomic findings using a social-defeat mice model of stress-induced depression.

LIMITATIONS

A case-control study design and sample size is not large.

CONCLUSIONS

Our results suggest that personality classification enhances blood biomarker analysis for MDD patients and further translational investigations should be conducted to clarify the biological relationship between personality traits, stress and depression.

IM-03 CD206 expression in peripheral blood-derived induced-microglia-like cells as a surrogate biomarker for the specific immune microenvironment of glioma

INTRODUCTION: As recent advancement of multimodal treatments including immune-check point inhibitors have not led to massive outcome improvement of glioma. Targeting the peculiar immune microenvironment of glioma is a promising approach to innovate a breakthrough treatment, however, there remains to be technical and ethical burdens for monitoring the bioactivities of immune cells in neural tissues. Herein, we examined the feasibility of non-invasive monitoring of glioma-associated microglia/macrophages (GAM) properties through utilization of our originally developed induced-microglia-like (iMG) cells technique. METHODS: We isolated primary microglia (pMG) from surgically-obtained brain tissues of 15 patients with neurosurgical diseases. We induced iMG cells from monocyte extracted from their corresponding peripheral blood by MACS treatment. Expression profiles of representative markers for an M1 and M2 microglia phenotype were analyzed in both pMG and iMG cells by qPCR. RESULTS: q-PCR revealed that a significant correlation of expression level of microglial markers between pMG and the corresponding iMG in each patient. Synchronous upregulations of CD206 were exclusively detected in patients with glioma. CONCLUSION: The present study suggested that iMG cells can be a less-invasive monitor tool for disease-related bioactivity of microglia, thereby seem to be utilized as an intermedium for investigation of relationship between microglia and neuronal diseases including glioma. CD206 upregulation detected by iMG technique can surrogate the specific microenvironment of glioma surrounding tissues and might be utilized as a future biomarker of glioma.

GNAO1 organizes the cytoskeletal remodeling and firing of developing neurons

Developmental and epileptic encephalopathy (DEE) represents a group of neurodevelopmental disorders characterized by infantile-onset intractable seizures and unfavorable prognosis of psychomotor development. To date, hundreds of genes have been linked to the onset of DEE. GNAO1 is a DEE-associated gene encoding the alpha-O1 subunit of guanine nucleotide-binding protein (Gα_O ). Despite the increasing number of reported children with GNAO1 encephalopathy, the molecular mechanisms underlying their neurodevelopmental phenotypes remain elusive. We herein present that co-immunoprecipitation and mass spectrometry analyses identified another DEE-associated protein, SPTAN1, as an interacting partner of Gα_O . Silencing of endogenous Gnao1 attenuated the neurite outgrowth and calcium-dependent signaling. Inactivation of GNAO1 in human-induced pluripotent stem cells gave rise to anomalous brain organoids that only weakly expressed SPTAN1 and Ankyrin-G. Furthermore, GNAO1-deficient organoids failed to conduct synchronized firing to adjacent neurons. These data indicate that Gα_O and other DEE-associated proteins organize the cytoskeletal remodeling and functional polarity of neurons in the developing brain.

Forskolin rapidly enhances neuron-like morphological change of directly induced-neuronal cells from neurofibromatosis type 1 patients

Aim

Neurofibromatosis type 1 (NF1) is a multifaceted disease, and frequently comorbid with neurodevelopmental disorders such as autism spectrum disorder (ASD) and learning disorder. Dysfunction of adenylyl cyclase (AC) is one of the candidate pathways in abnormal development of neuronal cells in the brain of NF1 patients, while its dynamic abnormalities have not been observed. Direct conversion technology can generate induced‐neuronal (iN) cells directly from human fibroblasts within 2 weeks. Just recently, we have revealed that forskolin, an AC activator, rescues the gene expression pattern of iN cells derived from NF1 patients (NF1‐iN cells). In this microreport, we show the dynamic effect of forskolin on NF1‐iN cells.

Methods

iN cells derived from healthy control (HC‐iN cells) and NF1‐iN cells were treated with forskolin (final concentration 10 μM), respectively. Morphological changes of iN cells were captured by inverted microscope with CCD camera every 2 minutes for 90 minutes.

Results

Prior to forskolin treatment, neuron‐like spherical‐form cells were observed in HC‐iN cells, but most NF1‐iN cells were not spherical‐form but flatform. Only 20 minutes after forskolin treatment, the morphology of the iN cells were dramatically changed from flatform to spherical form, especially in NF1‐iN cells.

Conclusion

The present pilot data indicate that forskolin or AC activators may have therapeutic effects on the growth of neuronal cells in NF1 patients. Further translational research should be conducted to validate our pilot findings for future drug development of ASD.

Neurofibromatosis type 1 (NF1) is highly comorbid with neurodevelopmental disorders such as autism spectrum disorder (ASD) and learning disorder, and underlying mechanisms have not been well clarified. We herein showed that forskolin, an AC activator, rapidly enhances neuron‐like morphological change of directly induced‐neuronal (iN) cells from NF1 patients. The present pilot data using the direct conversion technology indicate that forskolin or AC activators may have therapeutic effects on the growth of neuronal cells in NF1 patients.

Suicide and Microglia: Recent Findings and Future Perspectives Based on Human Studies

Suicide is one of the most disastrous outcomes for psychiatric disorders. Recent advances in biological psychiatry have suggested a positive relationship between some specific brain abnormalities and specific symptoms in psychiatric disorders whose organic bases were previously completely unknown. Microglia, immune cells in the brain, are regarded to play crucial roles in brain inflammation by releasing inflammatory mediators and are suggested to contribute to various psychiatric disorders such as depression and schizophrenia. Recently, activated microglia have been suggested to be one of the possible contributing cells to suicide and suicidal behaviors via various mechanisms especially including the tryptophan-kynurenine pathway. Animal model research focusing on psychiatric disorders has a long history, however, there are only limited animal models that can properly express psychiatric symptoms. In particular, to our knowledge, animal models of human suicidal behaviors have not been established. Suicide is believed to be limited to humans, therefore human subjects should be the targets of research despite various ethical and technical limitations. From this perspective, we introduce human biological studies focusing on suicide and microglia. We first present neuropathological studies using the human postmortem brain of suicide victims. Second, we show recent findings based on positron emission tomography (PET) imaging and peripheral blood biomarker analysis on living subjects with suicidal ideation and/or suicide-related behaviors especially focusing on the tryptophan-kynurenine pathway. Finally, we propose future perspectives and tasks to clarify the role of microglia in suicide using multi-dimensional analytical methods focusing on human subjects with suicidal ideation, suicide-related behaviors and suicide victims.

Neuron-related blood inflammatory markers as an objective evaluation tool for major depressive disorder: An exploratory pilot case-control study

BACKGROUND

Neuroinflammation is suggested to be a crucial factor in the pathophysiology of major depressive disorder (MDD). Analysis of neuron-derived exosomes (NDE) in peripheral blood has recently been highlighted to reveal the pathophysiology of brain diseases without using brain biopsy. Currently, human NDE studies require a considerable amount of peripheral blood to measure multiple substances inside exosomes. Previously, NDE-based clinical studies focusing on MDD have not been reported.

METHODS

As an exploratory pilot case-control study between healthy controls (HC) and drug-free MDD patients (each; N = 34), we searched for NDE-related blood biomarkers with a small amount of peripheral blood using a novel sandwich immunoassay between anti-neuron antibody and antibodies against CD81 (an exosome marker) and against other proteins related to neuroinflammation and synaptic functions.

RESULTS

Most neuron-related blood biomarkers had moderately to strongly positive correlation with CD81 (NDE), thus we normalized the above biomarkers by CD81 (quantity of each biomarker/CD81) to predict NDE-related blood substances. Interleukin 34 (IL34)/CD81 levels were significantly higher in MDD group compared to HC group. Synaptophysin (SYP), SYP/CD81, and tumor necrosis factor receptor 1 (TNFR1)/CD81 were positively correlated with severities of depression and/or various sub-symptoms.

LIMITATIONS

We did not actually extract NDE from peripheral blood.

CONCLUSIONS

Using a small amount of peripheral blood, we have successfully detected possible NDE-related blood biomarkers. This is the first study to suggest that not only SYP and TNFR1 but also IL34 are important blood biomarkers for patients with MDD. Further studies are warranted to evaluate the present study.

Tryptophan-kynurenine and lipid related metabolites as blood biomarkers for first-episode drug-naïve patients with major depressive disorder: An exploratory pilot case-control study

BACKGROUND

Early intervention in depression has been critical to prevent its negative impact including suicide. Recent blood biomarker studies for major depressive disorder (MDD) have suggested that tryptophan-kynurenine and lipid related metabolites are involved in the pathophysiology of MDD. However, there have been limited studies investigating these blood biomarkers in first-episode drug-naïve MDD, which are particularly important for early intervention in depression.

METHODS

As an exploratory pilot case-control study, we examined the above blood biomarkers, and analyzed how these biomarkers are associated with clinical variables in first-episode drug-naïve MDD patients, based on metabolome/lipidome analysis.

RESULTS

Plasma tryptophan and kynurenine levels were significantly lower in MDD group (N = 15) compared to healthy controls (HC) group (N = 19), and plasma tryptophan was the significant biomarker to identify MDD group (area under the curve = 0.740). Lower serum high density lipoprotein-cholesterol (HDL-C) was the predictive biomarker for severity of depression in MDD group (R² = 0.444). Interestingly, depressive symptoms were variously correlated with plasma tryptophan-kynurenine and lipid related metabolites. Moreover, plasma tryptophan-kynurenine metabolites and cholesteryl esters (CEs) were significantly correlated in MDD group, but not in HC group.

LIMITATIONS

This study had small sample size, and we did not use the multiple test correction.

CONCLUSIONS

This is the first study to suggest that not only tryptophan-kynurenine metabolites but also HDL-C and CEs are important blood biomarkers for first-episode drug-naïve MDD patients. The present study sheds new light on early intervention in clinical practice in depression, and further clinical studies especially large-scale prospective studies are warranted.

p66Shc Signaling Mediates Diabetes-Related Cognitive Decline

Accumlating evidence have suggested that diabetes mellitus links dementia, notably of Alzheimer's disease (AD). However, the underlying mechanism remains unclear. Several studies have shown oxidative stress (OS) to be one of the major factors in the pathogenesis of diabetic complications. Here we show OS involvement in brain damage in a diabetic animal model that is at least partially mediated through an AD-pathology-independent mechanism apart from amyloid-β accumulation. We investigated the contribution of the p66Shc signaling pathway to diabetes-related cognitive decline using p66Shc knockout (-/-) mice. p66Shc (-/-) mice have less OS in the brain and are resistant to diabetes-induced brain damage. Moreover, p66Shc (-/-) diabetic mice show significantly less cognitive dysfunction and decreased levels of OS and the numbers of microglia. This study postulates a p66Shc-mediated inflammatory cascade leading to OS as a causative pathogenic mechanism in diabetes-associated cognitive impairment that is at least partially mediated through an AD-pathology-independent mechanism.

Blood biomarkers of Hikikomori, a severe social withdrawal syndrome

Hikikomori, a severe form of social withdrawal syndrome, is a growing social issue in Japan and internationally. The pathophysiology of hikikomori has not yet been elucidated and an effective treatment remains to be established. Recently, we revealed that avoidant personality disorder is the most common comorbidity of hikikomori. Thus, we have postulated that avoidant personality is the personality underpinning hikikomori. First, we herein show relationships between avoidant personality traits, blood biomarkers, hikikomori-related psychological features, and behavioural characteristics assessed by a trust game in non-hikikomori volunteers. Avoidant personality traits were negatively associated with high-density lipoprotein cholesterol (HDL-C) and uric acid (UA) in men, and positively associated with fibrin degeneration products (FDP) and high sensitivity C-reactive protein (hsCRP) in women. Next, we recruited actual individuals with hikikomori, and compared avoidant personality traits, blood biomarkers, and psychological features between individuals with hikikomori and age-matched healthy controls. Individuals with hikikomori had higher avoidant personality scores in both sexes, and showed lower serum UA levels in men and lower HDL-C levels in women compared with healthy controls. This is the first report showing possible blood biomarkers for hikikomori, and opens the door to clarify the underlying biological pathophysiology of hikikomori.

Donepezil suppresses intracellular Ca2+ mobilization through the PI3K pathway in rodent microglia

Background

Microglia are resident innate immune cells which release many factors including proinflammatory cytokines or nitric oxide (NO) when they are activated in response to immunological stimuli. Pathophysiology of Alzheimer’s disease (AD) is related to the inflammatory responses mediated by microglia. Intracellular Ca²⁺ signaling is important for microglial functions such as release of NO and cytokines. In addition, alteration of intracellular Ca²⁺ signaling underlies the pathophysiology of AD, while it remains unclear how donepezil, an acetylcholinesterase inhibitor, affects intracellular Ca²⁺ mobilization in microglial cells.

Methods

We examined whether pretreatment with donepezil affects the intracellular Ca²⁺ mobilization using fura-2 imaging and tested the effects of donepezil on phagocytic activity by phagocytosis assay in rodent microglial cells.

Results

In this study, we observed that pretreatment with donepezil suppressed the TNFα-induced sustained intracellular Ca²⁺ elevation in both rat HAPI and mouse primary microglial cells. On the other hand, pretreatment with donepezil did not suppress the mRNA expression of both TNFR1 and TNFR2 in rodent microglia we used. Pretreatment with acetylcholine but not donepezil suppressed the TNFα-induced intracellular Ca²⁺ elevation through the nicotinic α7 receptors. In addition, sigma 1 receptors were not involved in the donepezil-induced suppression of the TNFα-mediated intracellular Ca²⁺ elevation. Pretreatment with donepezil suppressed the TNFα-induced intracellular Ca²⁺ elevation through the PI3K pathway in rodent microglial cells. Using DAF-2 imaging, we also found that pretreatment with donepezil suppressed the production of NO induced by TNFα treatment and the PI3K pathway could be important for the donepezil-induced suppression of NO production in rodent microglial cells. Finally, phagocytosis assay showed that pretreatment with donepezil promoted phagocytic activity of rodent microglial cells through the PI3K but not MAPK/ERK pathway.

Conclusions

These suggest that donepezil could directly modulate the microglial function through the PI3K pathway in the rodent brain, which might be important to understand the effect of donepezil in the brain.

Electronic supplementary material

The online version of this article (10.1186/s12974-017-1033-0) contains supplementary material, which is available to authorized users.

[Translational Research on Neuropsychiatric Disorders: Focusing on Microglia Hypothesis]

Microglia-immune cells in the brain-have recently been highlighted to understand the pathophysiology of psychiatric disorders such as schizophrenia, depression, and autism. In this review paper, we introduce the microglia hypothesis for psychiatric disorders. In addition, we introduce our novel translational research approach to psychiatric disorders using microglia-like (iMG) cells directly induced from human blood, these iMG cells can be produced from peripheral monocytes within two weeks using two cytokines: granulocyte-macrophage colony-stimulating factor (GM-CSF) and interleukin-34 (IL-34).

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.

Microglial CD206 Gene Has Potential as a State Marker of Bipolar Disorder

The pathophysiology of bipolar disorder, especially the underlying mechanisms of the bipolarity between manic and depressive states, has yet to be clarified. Microglia, immune cells in the brain, play important roles in the process of brain inflammation, and recent positron emission tomography studies have indicated microglial overactivation in the brain of patients with bipolar disorder. We have recently developed a technique to induced microglia-like (iMG) cells from peripheral blood (monocytes). We introduce a novel translational approach focusing on bipolar disorder using this iMG technique. We hypothesize that immunological conditional changes in microglia may contribute to the shift between manic and depressive states, and thus we herein analyzed gene profiling patterns of iMG cells from three patients with rapid cycling bipolar disorder during both manic and depressive states, respectively. We revealed that the gene profiling patterns are different between manic and depressive states. The profiling pattern of case 1 showed that M1 microglia is dominant in the manic state compared to the depressive state. However, the patterns of cases 2 and 3 were not consistent with the pattern of case 1. CD206, a mannose receptor known as a typical M2 marker, was significantly downregulated in the manic state among all three patients. This is the first report to indicate the importance of shifting microglial M1/M2 characteristics, especially the CD206 gene expression pattern between depressive and manic states. Further translational studies are needed to dig up the microglial roles in the underlying biological mechanisms of bipolar disorder.

TNF-α from hippocampal microglia induces working memory deficits by acute stress in mice

The role of microglia in stress responses has recently been highlighted, yet the underlying mechanisms of action remain unresolved. The present study examined disruption in working memory due to acute stress using the water-immersion resistant stress (WIRS) test in mice. Mice were subjected to acute WIRS, and biochemical, immunohistochemical, and behavioral assessments were conducted. Spontaneous alternations (working memory) significantly decreased after exposure to acute WIRS for 2h. We employed a 3D morphological analysis and site- and microglia-specific gene analysis techniques to detect microglial activity. Morphological changes in hippocampal microglia were not observed after acute stress, even when assessing ramification ratios and cell somata volumes. Interestingly, hippocampal tumor necrosis factor (TNF)-α levels were significantly elevated after acute stress, and acute stress-induced TNF-α was produced by hippocampal-ramified microglia. Conversely, plasma concentrations of TNF-α were not elevated after acute stress. Etanercept (TNF-α inhibitor) recovered working memory deficits in accordance with hippocampal TNF-α reductions. Overall, results suggest that TNF-α from hippocampal microglia is a key contributor to early-stage stress-to-mental responses.

Introducing directly induced microglia-like (iMG) cells from fresh human monocytes: a novel translational research tool for psychiatric disorders

Microglia, glial cells with immunological functions, have been implicated in various neurological diseases and psychiatric disorders in rodent studies, and human postmortem and PET studies. However, the deeper molecular implications of living human microglia have not been clarified. Here, we introduce a novel translational research approach focusing on human microglia. We have recently developed a new technique for creating induced microglia-like (iMG) cells from human peripheral blood. Two cytokines, GM-CSF and IL-34, converted human monocytes into the iMG cells within 14 days, which show various microglial characterizations; expressing markers, forming a ramified morphology, and phagocytic activity with various cytokine releases. We have already confirmed the applicability of this technique by analyzing iMG cells from a patient of Nasu-Hakola disease (NHD; Ohgidani et al., 2014). We herein show possible applications of the iMG cells in translational research. We believe that this iMG technique will open the door to explore various unknown dynamic aspects of human microglia in psychiatric disorders. This also opens new routes for psychopharmacological approach such as drug efficacy screening and personalized medicine.

Direct induction of ramified microglia-like cells from human monocytes: dynamic microglial dysfunction in Nasu-Hakola disease

Microglia have been implicated in various neurological and psychiatric disorders in rodent and human postmortem studies. However, the dynamic actions of microglia in the living human brain have not been clarified due to a lack of studies dealing with in situ microglia. Herein, we present a novel technique for developing induced microglia-like (iMG) cells from human peripheral blood cells. An optimized cocktail of cytokines, GM-CSF and IL-34, converted human monocytes into iMG cells within 14 days. The iMG cells have microglial characterizations; expressing markers, forming a ramified morphology, and phagocytic activity with various cytokine releases. To confirm clinical utilities, we developed iMG cells from a patient of Nasu-Hakola disease (NHD), which is suggested to be directly caused by microglial dysfunction, and observed that these cells from NHD express delayed but stronger inflammatory responses compared with those from the healthy control. Altogether, the iMG-technique promises to elucidate unresolved aspects of human microglia in various brain disorders.

Brain-derived neurotrophic factor (BDNF) induces sustained intracellular Ca2+ elevation through the up-regulation of surface transient receptor potential 3 (TRPC3) channels in rodent microglia

Microglia are immune cells that release factors, including proinflammatory cytokines, nitric oxide (NO), and neurotrophins, following activation after disturbance in the brain. Elevation of intracellular Ca(2+) concentration ([Ca(2+)]i) is important for microglial functions such as the release of cytokines and NO from activated microglia. There is increasing evidence suggesting that pathophysiology of neuropsychiatric disorders is related to the inflammatory responses mediated by microglia. Brain-derived neurotrophic factor (BDNF) is a neurotrophin well known for its roles in the activation of microglia as well as in pathophysiology and/or treatment of neuropsychiatric disorders. In this study, we sought to examine the underlying mechanism of BDNF-induced sustained increase in [Ca(2+)]i in rodent microglial cells. We observed that canonical transient receptor potential 3 (TRPC3) channels contribute to the maintenance of BDNF-induced sustained intracellular Ca(2+) elevation. Immunocytochemical technique and flow cytometry also revealed that BDNF rapidly up-regulated the surface expression of TRPC3 channels in rodent microglial cells. In addition, pretreatment with BDNF suppressed the production of NO induced by tumor necrosis factor α (TNFα), which was prevented by co-adiministration of a selective TRPC3 inhibitor. These suggest that BDNF induces sustained intracellular Ca(2+) elevation through the up-regulation of surface TRPC3 channels and TRPC3 channels could be important for the BDNF-induced suppression of the NO production in activated microglia. We show that TRPC3 channels could also play important roles in microglial functions, which might be important for the regulation of inflammatory responses and may also be involved in the pathophysiology and/or the treatment of neuropsychiatric disorders.

Residual powders from Shochu distillation remnants induce apoptosis in human hepatoma cells via the caspase-independent pathway

Shochu distillation remnants (SDR) are by-products in the manufacturing process of the Japanese liquor Shochu and include various useful organic compounds derived from the fermentation of grains. We have obtained valuable powder (PSDR) from freeze-dried SDR by the treatment with ethanol. In this study, we examined the anticancer effects of barley-, rice-, and sweet potato-PSDR against HepG2 and HuH-7 cells of human hepatocellular carcinoma (HCC) in vitro. All PSDR inhibited the growth of both these HCC cells through the induction of apoptosis. Especially, barley-PSDR was the most effective for the growth inhibition and apoptosis induction of HCC cells of all PSDR. We next examined the apoptotic mechanisms induced by barley-PSDR. Decrease in mitochondrial membrane potential and release of cytochrome c from mitochondria were observed in HCC cells after the treatment with barley-PSDR. Furthermore, barley-PSDR induced the nuclear translocation of apoptosis-inducing factor (AIF) from mitochondria, while it did not significantly affect the activities of caspase-3, -8, and -9. The results suggested that barley-PSDR induced apoptosis against HCC cells via the caspase-independent mitochondrial pathway. The findings in this study suggest that PSDR has the possibility of therapeutic and/or preventive agents of HCC.