Inflammation-related transcripts define "high" and "low" subgroups of individuals with schizophrenia and bipolar disorder in the midbrain

The relationship between neuropsychiatric disorders and aging: A review on telomere length, oxidative stress, and inflammation

Aging is the group of time-independent changes that occur in an organism and that ultimately end in death. The relationship between aging and neuropsychiatric disorders is complex. Not only does the incidence of several neuropsychiatric disorders rise with age, but also these disorders are linked with premature mortality and are even thought to be syndromes of accelerated biological aging. Oxidative stress, inflammation and telomere length are factors commonly used to assess biological aging. The purpose of this review is to sum up the existing information about the state of those factors in schizophrenia, depression, bipolar disorder and anxiety disorders, and to summarize the effects of treatment on telomere length in patients with those neuropsychiatric disorders. The main focus, however, is on telomere length seeing the highly controversial study results on this biomarker in neuropsychiatric disorders. There is no scientific consensus on the state of those factors in the mentioned neuropsychiatric disorders or on the effects of treatment on telomere length, thus further research is needed where confounding variables are controlled. Regarding telomere length, it is highly important to explore whether short telomeres lead to the development of neuropsychiatric disorders or vice versa, as it carries huge clinical potential.

Transcriptional evidence of reduced BDNF trophic capacity in the post-mortem human midbrain of schizophrenia cases with high inflammation

Elevated inflammation in the midbrain of ~45% of people with schizophrenia may relate to altered trophic support for neurons. Dopamine neurons require trophic support from Brain-Derived Neurotrophic Factor (BDNF), that signals via the full-length Tropomyosin kinase B receptor (TrkBTK+). The truncated BDNF receptor (TrkBTK-) and the apoptosis-related p75 receptor may counteract the effects of BDNF. We hypothesised that transcriptional changes in either BDNF, and/or a transcription factor critical for the maintenance of dopamine neurons (Nuclear Receptor Related-1 protein; NURR1), and/or BDNF receptors - TrkB (TK+ or TK-) and p75, would be found in the post-mortem schizophrenia midbrain, particularly in schizophrenia cases defined as "high inflammation". The neuroinflammatory status was delineated based on elevated expression levels of a combination of pro-inflammatory transcripts (SERPINA3, IL6, IL1β and TNFα) and defined as a subgroup (46%) by 2-step recursive clustering. Using RT-qPCR, mRNA levels of NURR1, BDNF, TrkB and p75 was quantified in schizophrenia (n = 65) and control (n = 64) ventral mesencephalon. We found significant decreases in BDNF, TrkBTK+ and NURR1 (14-18%) and increases in TrkBTK- and p75 (18-35%) mRNA levels in schizophrenia compared to controls (all p < 0.05), with exacerbation of changes identified in high inflammation schizophrenia. To determine whether these changes would be consistent with resulting from chronic antipsychotic treatment, we treated healthy adult rats with antipsychotics (haloperidol and risperidone) for 7 months and found all transcripts to be unaltered compared to control rats. SnRNAseq of human midbrain showed that p75 receptor mRNA is primarily localised in oligodendrocytes and pan-TrkB mRNA is in both neurons and astrocytes. We confirmed that p75 was localised to oligodendrocyte-like cells by immunohistochemistry. Altogether, we find transcriptional evidence of reduced trophic support in schizophrenia midbrain and suggest that this may directly impact dopamine neuron health, particularly when neuroinflammation is also present.

Toxoplasma gondii, endothelial cells and schizophrenia: is it just a barrier matter?

Toxoplasma gondii is an obligatory intracellular parasite responsible for causing toxoplasmosis. It is estimated that approximately one-third of the world's population has positive serology for toxoplasmosis. Acute T. gondii infection often results in subtle symptoms because of its nonspecific nature. Owing to immune pressure, parasites tend to encyst and persist in different tissues and organs, such as the brain, chronicling the infection. While most chronically infected individuals do not develop significant symptoms, the parasite can affect the central nervous system (CNS), leading to symptoms that range from dizziness to behavioral changes. To reach the CNS, parasites must overcome the blood-brain barrier, which is composed primarily of endothelial cells. While these cells are typically efficient at separating blood elements from the CNS, in T. gondii infection, they not only permit parasitic colonization of the CNS but also contribute to an inflammatory profile that may exacerbate previously established conditions at both the local CNS and systemic levels. An increasing body of research has demonstrated a potential link between the CNS, infection by T. gondii and the cellular or humoral response to infection, with the worsening of psychiatric conditions, such as schizophrenia. Therefore, continually advancing research aimed at understanding and mitigating the relationship between parasitic infection and schizophrenia is imperative.

Schizophrenia-associated changes in neuronal subpopulations in the human midbrain

Dysfunctional GABAergic and dopaminergic neurons are thought to exist in the ventral midbrain of patients with schizophrenia, yet transcriptional changes underpinning these abnormalities have not yet been localized to specific neuronal subsets. In the ventral midbrain, control over dopaminergic activity is maintained by both excitatory (glutamate) and inhibitory (GABA) input neurons. To elucidate neuron pathology at the single-cell level, we characterized the transcriptional diversity of distinct NEUN+ populations in the human ventral midbrain and then tested for schizophrenia-associated changes in neuronal subset proportions and gene activity changes within neuronal subsets. Combining single nucleus RNA-sequencing with fluorescence-activated sorting of NEUN+ nuclei, we analysed 31 669 nuclei. Initially, we detected 18 transcriptionally distinct neuronal populations in the human ventral midbrain, including two 'mixed' populations. The presence of neuronal populations in the midbrain was orthogonally validated with immunohistochemical stainings. 'Mixed' populations contained nuclei expressing transcripts for vesicular glutamate transporter 2 (SLC17A6) and glutamate decarboxylase 2 (GAD2), but these transcripts were not typically co-expressed by the same nucleus. Upon more fine-grained subclustering of the two 'mixed' populations, 16 additional subpopulations were identified that were transcriptionally classified as excitatory or inhibitory. In the midbrains of individuals with schizophrenia, we observed potential differences in the proportions of two (sub)populations of excitatory neurons, two subpopulations of inhibitory neurons, one 'mixed' subpopulation, and one subpopulation of TH-expressing neurons. This may suggest that transcriptional changes associated with schizophrenia broadly affect excitatory, inhibitory, and dopamine neurons. We detected 99 genes differentially expressed in schizophrenia compared to controls within neuronal subpopulations identified from the two 'mixed' populations, with most (67) changes within small GABAergic neuronal subpopulations. Overall, single-nucleus transcriptomic analyses profiled a high diversity of GABAergic neurons in the human ventral midbrain, identified putative shifts in the proportion of neuronal subpopulations, and suggested dysfunction of specific GABAergic subpopulations in schizophrenia, providing directions for future research.

Interleukin 18 and the brain: neuronal functions, neuronal survival and psycho-neuro-immunology during stress

Interleukin 18 (IL-18) is a pleiotropic cytokine that regulates peripheral innate and adaptive immune response and is also expressed in the brain. Here, we summarize the current knowledge on the biology of IL-18 in the brain and the efforts to determine its significance concerning neurological and psychiatric conditions. The picture that emerges is that of a heavily regulated molecule that can contribute to neuroinflammatory-mediated neuronal survival but can also serve as a neuromodulator that affects behaviour. We also summarize evidence showing how the brain can control the synthesis of peripheral IL-18 during stress by hormonal and neuronal signalling, regulating tissue-specific promoter usage. We discuss how this may represent one of the mechanisms by which the brain affects immune functions and what its implications are when considering IL-18 as a biomarker of psychiatric conditions.

Potential benefits of ketone therapy as a novel immunometabolic treatment for schizophrenia

Therapeutic ketosis could target the potential bio-energetic pathophysiology of schizophrenia. Ideally, novel treatments also target the possible inflammatory aspects of schizophrenia. Adult mice (n = 30) were treated with ketone ester (KE) or vehicle for 3 days, next LPS- or PBS-injected. Brains were collected the next day. KE significantly attenuated the increased transcription of the pro-inflammatory cytokines Tnf-a, Il-6 and Il-1b, without affecting anti-inflammatory/immunomodulatory cytokines (Il-4, Il-10, Il-11) in whole brain. KE potently dampened neuro-inflammation in this acute inflammation mouse model. Ketone therapy could simultaneously target two possible pathophysiological pathways in schizophrenia. We encourage more research into the immunometabolic potential of therapeutic ketosis in schizophrenia.

Implications of the choroid plexus in Niemann-Pick disease Type C neuropathogenesis

BACKGROUND

Niemann-Pick Disease Type C (NPC) is an ultra-rare disorder characterized by progressive psychiatric and neurologic manifestations, with late infantile, juvenile, and adolescent/adult presentations. We examined morphological properties of the choroid plexus, a protective blood-cerebrospinal fluid barrier, in NPC, and their relationship with neurodegeneration, clinical status, and circulatory markers. This study also determined whether choroid plexus morphology differentiates between NPC and more prevalent illnesses, schizophrenia (SZ) and bipolar disorder (BD), which have overlapping psychiatric symptoms with adolescent and adult-onset NPC and are associated with misdiagnosis.

METHODS

Patients with NPC were assessed using neuroimaging, clinical instruments, and plasma protein quantification focusing on inflammatory markers. Morphological properties (i.e., choroid plexus volumes) were compared between patients with NPC (n = 17), SZ (n = 20), BD (n = 24), and healthy controls (HCs, n = 106).

RESULTS

Choroid plexus enlargement (p < 0.05) and reduced thalamic volumes (p < 0.05) were observed in NPC patients versus HCs and SZ or BD patients. A logistic regression model with choroid plexus and thalamic volumes as predictors yielded high prediction accuracy for NPC vs. HCs, NPC vs. SZ, and NPC vs. BD (area under the receiver operating characteristics curve [AUROC] of 1). Choroid plexus volumes were negatively correlated with left (p = 0.009-0.012) and right (p = 0.007-0.025) thalamic volumes, left (r = -0.69, p = 0.003) and right (r = -0.71, p = 0.002) crus I of the cerebellum, and greater severity on the NPC-Suspicion Index psychiatric subscale (ρ = 0.72, p = 0.042). Targeted protein expression quantification revealed differential expression of TGFA, HLA-DRA, TNFSF12, EGF, INFG, and IL-18 in NPC patients vs. HCs (p < 0.05), with higher choroid plexus volumes correlating with IL-18 levels (ρ = 0.71, p = 0.047).

CONCLUSION

The choroid plexus may play a critical role in NPC neuropathogenesis and serve as a novel biomarker for monitoring neurodegenerative and inflammatory processes in NPC.

Divergent changes in complement pathway gene expression in schizophrenia and bipolar disorder: Links to inflammation and neurogenesis in the subependymal zone

Deficits in neurogenesis markers in the subependymal zone (SEZ) are associated with elevated inflammation in schizophrenia and bipolar disorder. However, the extent to which complement factors are also changed in the SEZ of these major psychiatric disorders and their impact on neurogenesis remains poorly understood. We extracted RNA from the SEZ of 93 brains, including controls (n = 32), schizophrenia (n = 32), and bipolar disorder (n = 29) cases. Quantitative RT-PCR measured 13 complement transcripts encoding initiators, convertases, effectors or inhibitors. Differences in abundance were analysed by diagnosis and inflammatory subgroups (high- or low-inflammation), which were previously defined by SEZ cytokine and inflammation marker expression. Complement mRNAs C1QA (p = 0.011), C1QB (p < 0.001), C1R (p = 0.027), and Factor B (p = 0.025) were increased in high-inflammation schizophrenia versus low-inflammation controls. Conversely, high-inflammation bipolar cases had decreased C1QC (p = 0.011) and C3 (p = 0.003). Complement mRNAs C1R (SCZ, p = 0.010; BD, p = 0.047), C1S (SCZ, p = 0.026; BD, p = 0.017), and Factor B (BD, p = 0.025) were decreased in low-inflammation schizophrenia and bipolar subgroups versus low-inflammation controls. Complement inhibitors varied by subgroup: Factor H was increased in high-inflammation schizophrenia (p < 0.001), and CD59 in high-inflammation bipolar disorder (p = 0.020). Complement activator and inhibitor mRNAs were positively correlated with quiescent neural stem cell marker GFAPD (q < 0.05) but negatively with immature neuron markers DLX6-AS1 (q < 0.05) and DCX (q < 0.05). These findings suggest altered complement cascade expression in the SEZ in high- and low-inflammation schizophrenia and bipolar disorder, with opposite directional changes suggesting distinct molecular pathology. Complement activation may promote stem cell quiescence and reduce differentiation or survival of newborn neurons.

Endophenotype 2.0: updated definitions and criteria for endophenotypes of psychiatric disorders, incorporating new technologies and findings

Recent genetic studies have linked numerous loci to psychiatric disorders. However, the biological pathways that connect these genetic associations to psychiatric disorders' specific pathophysiological processes are largely unclear. Endophenotypes, first defined over five decades ago, are heritable traits, independent of disease state that are associated with a disease, encompassing a broad range of neurophysiological, biochemical, endocrinological, neuroanatomical, cognitive, and neuropsychological characteristics. Considering the advancements in genetics and genomics over recent decades, we propose a revised definition of endophenotypes as 'genetically influenced phenotypes linked to disease or treatment characteristics and their related events.' We also updated endophenotype criteria to include (1) reliable measurement, (2) association with the disease or its related events, and (3) genetic mediation. 'Genetic mediation' is introduced to differentiate between causality and pleiotropic effects and allows non-linear relationships. Furthermore, this updated Endophenotype 2.0 framework expands to encompass genetically regulated responses to disease-related factors, including environmental risks, illness progression, treatment responses, and resilience phenotypes, which may be state-dependent. This broadened definition paves the way for developing new endophenotypes crucial for genetic analyses in psychiatric disorders. Integrating genetics, genomics, and diverse endophenotypes into multi-dimensional mechanistic models is vital for advancing our understanding of psychiatric disorders. Crucially, elucidating the biological underpinnings of endophenotypes will enhance our grasp of psychiatric genetics, thereby improving disease risk prediction and treatment approaches.

Molecular Evidence for Altered Angiogenesis in Neuroinflammation-Associated Schizophrenia and Bipolar Disorder Implicate an Abnormal Midbrain Blood-Brain Barrier

BACKGROUND AND HYPOTHESIS

Angiogenesis triggered by inflammation increases BBB permeability and facilitates macrophage transmigration. In the midbrain, we have discovered molecular alterations related to the blood-brain barrier (BBB), including endothelial cell changes associated with macrophage diapedesis, in neuroinflammatory schizophrenia and bipolar disorder, but changes in angiogenesis are yet to be reported. Hypothesis: We expected to discover molecular evidence of altered angiogenesis in the midbrain in individuals with schizophrenia and bipolar disorder compared to controls, with these changes more evident in "high" inflammation schizophrenia as compared to "low" inflammation.

STUDY DESIGN

In a case-control post-mortem cohort including schizophrenia (n = 35), bipolar disorder (n = 35), and controls (n = 33), we measured mRNA (RT-PCR) and protein (multiplex immunoassays) and performed immunohistochemistry to determine levels and anatomical distribution of angiogenesis-related molecules in the ventral midbrain.

STUDY RESULTS

We found large changes in angiogenesis factors in bipolar disorder high inflammatory subgroup (increased angiopoietin-2 and SERPINE1 mRNAs, but decreased angiopoietin-1, angiopoietin-2, and TEK receptor proteins). In schizophrenia high inflammatory subgroup, we found a robust increase in SERPINE1 mRNA and protein levels. However, we found no significant changes in angiopoietins in schizophrenia. We found that VEGFA mRNA level was increased in high inflammation schizophrenia, but only reached statistical significance compared to one low inflammatory subgroup.

CONCLUSIONS

Thus, angiogenesis signaling pathways appeared to be involved in the BBB alterations when inflammation is also present in the midbrain of schizophrenia and bipolar disorder, with increased levels of SERPINE1 in schizophrenia high inflammatory subgroup and with a putative suppression of angiopoietin signaling in bipolar disorder high inflammatory subgroup.

A mouse model of schizophrenia induced by autoantibodies against SFT2D2

Schizophrenia (SCZ) is a highly heterogeneous, severe neuropsychiatric disorder of unknown etiopathology. Increasing data indicate an overlap between schizophrenia and pathological processes related to immunological dysregulation as well as inflammation, such as high levels of pro-inflammatory substances in patients' blood and cerebrospinal fluid and autoantibodies against synaptic and nerve cell membrane proteins. Autoantibodies against SFT2D2 have been reported in patients with SCZ. However, their roles in inflammation have not yet been established. We performed a continuous intracerebroventricular infusion of polyclonal rabbit anti-SFT2D2-IgG in male C57BL/6 mice. Behavioral tests were conducted after 2 weeks of treatment. Our results showed an increased density of microglia and activated astrocytes in the primary somatosensory cortex of the anti-SFT2D2-IgG-infused mice. Quantitative reverse transcription-polymerase chain reactions showed that the expression of pro-inflammatory genes was upregulated in the primary somatosensory cortex and hippocampus of the anti-SFT2D2-IgG-infused mice. Additionally, the mice exhibited defective sensorimotor gating, memory deficits, motor impairment, and anxiety-related behaviors without signs of depression. These findings indicate that anti-SFT2D2 autoantibodies can induce encephalitis, cause a series of behavioral changes associated with schizophrenia, and offer a model for testing novel therapies to improve treatment strategies for a subgroup of patients with SCZ.

Increased Parenchymal Macrophages are associated with decreased Tyrosine Hydroxylase mRNA levels in the Substantia Nigra of people with Schizophrenia and Bipolar Disorder

Increased activation of inflammatory macrophages and altered expression of dopamine markers are found in the midbrains of people with schizophrenia (SZ). The relationship of midbrain macrophages to dopamine neurons has not been explored, nor is it known if changes in midbrain macrophages are also present in bipolar disorder (BD) or major depressive disorder (MDD). Herein, we determined whether there were differences in CD163+ cell density in the Substantia Nigra (SN), and cerebral peduncles (CP) of SZ, BD, and MDD compared to controls (CTRL). We also analyzed whether CD163 protein and dopamine-synthesizing enzyme tyrosine hydroxylase (TH) mRNA levels differed among diagnostic groups and if they correlated with the density of macrophages. Overall, perivascular CD163+ cell density was higher in the gray matter (SN) than in the white matter (CP). Compared to CTRL, we found increased density of parenchymal CD163+ cells in the SN of the three psychiatric groups and increased CD163 protein levels in SZ. CD163 protein was positively correlated with density of perivascular CD163+ cells. TH mRNA was reduced in SZ and BD and negatively correlated with parenchymal CD163+ cell density. We provide the first quantitative and molecular evidence of an increase in the density of parenchymal macrophages in the midbrain of major mental illnesses and show that the presence of these macrophages may negatively impact dopaminergic neurons.

Molecular evidence of altered stress responsivity related to neuroinflammation in the schizophrenia midbrain

Stress and inflammation are risk factors for schizophrenia. Chronic psychosocial stress is associated with subcortical hyperdopaminergia, a core feature of schizophrenia. Hyperdopaminergia arises from midbrain neurons, leading us to hypothesise that changes in stress response pathways may occur in this region. To identify whether transcriptional changes in glucocorticoid and mineralocorticoid receptors (NR3C1/GR, NR3C2/MR) or other stress signalling molecules (FKBP4, FKBP5) exist in schizophrenia midbrain, we measured gene expression in the human brain (N = 56) using qRT-PCR. We assessed whether alterations in these mRNAs were related to previously identified high/low inflammatory status. We investigated relationships between stress-related transcripts themselves, and between FKBP5 mRNA, dopaminergic, and glial cell transcripts in diagnostic and inflammatory subgroups. Though unchanged by diagnosis, GR mRNA levels were reduced in high inflammatory compared to low inflammatory schizophrenia cases (p = 0.026). We found no effect of diagnosis or inflammation on MR mRNA. FKBP4 mRNA was decreased and FKBP5 mRNA was increased in schizophrenia (p < 0.05). FKBP5 changes occurred in high inflammatory (p < 0.001), whereas FKBP4 changes occurred in low inflammatory schizophrenia cases (p < 0.05). The decrease in mRNA encoding the main stress receptor (GR), as well as increased transcript levels of the stress-responsive negative regulator (FKBP5), may combine to blunt the midbrain response to stress in schizophrenia when neuroinflammation is present. Negative correlations between FKBP5 mRNA and dopaminergic transcripts in the low inflammatory subgroup suggest higher levels of FKBP5 mRNA may also attenuate dopaminergic neurotransmission in schizophrenia even when inflammation is absent. We report alterations in GR-mediated stress signalling in the midbrain in schizophrenia.

The potential role of the p75 receptor in schizophrenia: neuroimmunomodulation and making life or death decisions

The nerve growth factor receptor, also referred to as tumour necrosis factor II and the p75 neurotrophin receptor (p75), serves pleiotropic functions in both the peripheral and central nervous system, involving modulation of immune responses, cell survival and cell death signalling in response to multiple ligands including cytokines such as TNFα, as well as proneurotrophins and mature neurotrophins. Whilst in vitro and in vivo studies have characterised various responses of the p75 receptor in isolated conditions, it remains unclear whether the p75 receptor serves to provide neuroprotection or contributes to neurotoxicity in neuroinflammatory and neurotrophin-deficit conditions, such as those presenting in schizophrenia. The purpose of this mini-review is to characterise the potential signalling mechanisms of the p75 receptor respective to neuropathological changes prevailing in schizophrenia to ultimately propose how specific functions of the receptor may underlie altered levels of p75 in specific cell types. On the basis of this evaluation, this mini-review aims to promote avenues for future research in utilising the therapeutic potential of ligands for the p75 receptor in psychiatric disorders, whereby heightened inflammation and reductions in trophic signalling mechanisms coalesce in the brain, potentially resulting in tissue damage.

The role and molecular mechanisms of the early growth response 3 gene in schizophrenia

Schizophrenia is a chronic, debilitating mental illness caused by both genetic and environmental factors. Genetic factors play a major role in schizophrenia development. Early growth response 3 (EGR3) is a member of the EGR family, which is associated with schizophrenia. Accumulating studies have investigated the relationship between EGR3 and schizophrenia. However, the role of EGR3 in schizophrenia pathogenesis remains unclear. In the present review, we focus on the progress of research related to the role of EGR3 in schizophrenia, including association studies between EGR3 and schizophrenia, abnormal gene expressional analysis of EGR3 in schizophrenia, biological function studies of EGR3 in schizophrenia, the molecular regulatory mechanism of EGR3 and schizophrenia susceptibility candidate genes, and possible role of EGR3 in the immune system function in schizophrenia. In summary, EGR3 is a schizophrenia risk candidate factor and has comprehensive regulatory roles in schizophrenia pathogenesis. Further studies investigating the molecular mechanisms of EGR3 in schizophrenia are warranted for understanding the pathophysiology of this disorder as well as the development of new therapeutic strategies for the treatment and control of this disorder.

Transcriptome profiling as a biological marker for bipolar disorder sub-phenotypes

PURPOSE

Bipolar affective disorder (BP) causes major functional impairment and reduced quality of life not only for patients, but also for many close relatives. We aimed to investigate mRNA levels in BP patients to find differentially expressed genes linked to specific clinical course variants; assuming that several gene expression alterations might indicate vulnerability pathways for specific course and severity of the disease.

MATERIALS

We searched for up- and down-regulated genes comparing patients with diagnosis of BP type I (BPI) vs type II (BPII), history of suicide attempts, psychotic symptoms, predominance of manic/hypomanic episodes, and history of numerous episodes and comorbidity of substance use disorders or anxiety disorders. RNA was extracted from peripheral blood mononuclear cells and analyzed with use of microarray slides.

RESULTS

Differentially expressed genes (DEGs) were found in all disease characteristics compared. The lowest number of DEGs were revealed when comparing BPI and BPII patients (18 genes), and the highest number when comparing patients with and without psychotic symptoms (3223 genes). Down-regulated genes identified here with the use of the DAVID database were among others linked to cell migration, defense response, and inflammatory response.

CONCLUSIONS

The most specific transcriptome profile was revealed in BP with psychotic symptoms. Differentially expressed genes in this variant include, among others, genes involved in inflammatory and immune processes. It might suggest the overlap of biological background between BP with a history of psychotic features and schizophrenia.

Anti-SFT2D2 autoantibodies alter dendrite spine and cause psychotic behavior in mice

BACKGROUND

Autoimmunity plays an important role in schizophrenia (SCZ). Autoantibodies against SFT2D2 have been reported in patients with SCZ; however, the specific mechanism remains unclear. This study aimed to describe an autoimmune model, namely, mice immunized against SFT2D2-peptides.

METHODS

ApoE-/- and WT mice (C57BL/6) were immunized four times (day 0, day 14, day 21, day 35) with SFT2D2 peptide or KLH via subcutaneous injection. Behavioral tests were conducted after the third immunization, and immunochemistry of brain tissue were performed after the sacrifice of the mice.

RESULTS

Active immunization with KLH-coupled SFT2D2-derived peptides in both WT and ApoE-/- (compromised blood-brain barrier) mice led to high circulating levels of anti-SFT2D2 IgG. While there was no detectable deficit in WT mice, impaired pre-pulse inhibition, motor impairments, and reduced cognition in ApoE-/- mice, without signs of anxiety and depression were observed. In addition, immunohistochemical assays demonstrated that activated microglia and astrocytes were increased but neuronal dendritic spine densities were decreased, accompanied by increased expression of complement molecule C4 across brain regions in ApoE-/- mice.

CONCLUSIONS

In model mice with compromised blood-brain barrier, endogenous anti-SFT2D2 IgG can activate glial cells and modulate synaptic plasticity, and induce a series of psychosis-like changes. These antibodies may reveal valuable therapeutic targets, which may improve the treatment strategies for a subgroup of SCZ patients.

Neuromelanin-sensitive MRI of the substantia nigra distinguishes bipolar from unipolar depression

Depression in bipolar disorder (BD-II) is frequently misdiagnosed as unipolar depression (UD) leading to inappropriate treatment and downstream complications for many bipolar sufferers. In this study, we evaluated whether neuromelanin-MR signal and volume changes in the substantia nigra (SN) can be used as potential biomarkers to differentiate BD-II from UD. The signal intensities and volumes of the SN regions were measured, and contrast-to-noise ratio (CNR) to the decussation of the superior cerebellar peduncles were calculated and compared between healthy controls (HC), BD-II and UD subjects. Results showed that compare to HC, both BD-II and UD subjects had significantly decreased CNR and increased volume on the right and left sides. Moreover, the volume in BD-II group was significantly increased compared to UD group. The area under the receiver operating characteristic curve (AUC) for discriminating BD from HC was the largest for the Volume-L (AUC, 0.85; 95% confidence interval [CI]: 0.77, 0.93). The AUC for discriminating UD from HC was the largest for the Volume-L (AUC, 0.76; 95% CI: 0.65, 0.86). Furthermore, the AUC for discriminating BD from UD was the largest for the Volume-R (AUC, 0.73; 95% CI: 0.62, 0.84). Our findings suggest that neuromelanin-sensitive magnetic resonance imaging techniques can be used to differentiate BD-II from UD.

Adjunctive canakinumab reduces peripheral inflammation markers and improves positive symptoms in people with schizophrenia and inflammation: A randomized control trial

BACKGROUND

Clinical trials of anti-inflammatories in schizophrenia do not show clear and replicable benefits, possibly because patients were not recruited based on elevated inflammation status. Interleukin 1-beta (IL-1β) mRNA and protein levels are increased in serum, plasma, cerebrospinal fluid, and brain of some chronically ill patients with schizophrenia, first episode psychosis, and clinical high-risk individuals. Canakinumab, an approved anti-IL-1β monoclonal antibody, interferes with the bioactivity of IL-1β and interrupts downstream signaling. However, the extent to which canakinumab reduces peripheral inflammation markers, such as, high sensitivity C-reactive protein (hsCRP) and symptom severity in schizophrenia patients with inflammation is unknown.

TRIAL DESIGN

We conducted a randomized, placebo-controlled, double-blind, parallel groups, 8-week trial of canakinumab in chronically ill patients with schizophrenia who had elevated peripheral inflammation.

METHODS

Twenty-seven patients with schizophrenia or schizoaffective disorder and elevated peripheral inflammation markers (IL-1β, IL-6, hsCRP and/or neutrophil to lymphocyte ratio: NLR) were randomized to a one-time, subcutaneous injection of canakinumab (150 mg) or placebo (normal saline) as an adjunctive antipsychotic treatment. Peripheral blood hsCRP, NLR, IL-1β, IL-6, IL-8 levels were measured at baseline (pre injection) and at 1-, 4- and 8-weeks post injection. Symptom severity was assessed at baseline and 4- and 8-weeks post injection.

RESULTS

Canakinumab significantly reduced peripheral hsCRP over time, F(3, 75) = 5.16, p = 0.003. Significant hsCRP reductions relative to baseline were detected only in the canakinumab group at weeks 1, 4 and 8 (p's = 0.0003, 0.000002, and 0.004, respectively). There were no significant hsCRP changes in the placebo group. Positive symptom severity scores were significantly reduced at week 8 (p = 0.02) in the canakinumab group and week 4 (p = 0.02) in the placebo group. The change in CRP between week 8 and baseline (b = 1.9, p = 0.0002) and between week 4 and baseline (b = 6.0, p = 0.001) were highly significant predictors of week 8 change in PANSS Positive Symptom severity scores. There were no significant changes in negative symptoms, general psychopathology or cognition in either group. Canakinumab was well tolerated and only 7 % discontinued.

CONCLUSIONS

Canakinumab quickly reduces peripheral hsCRP serum levels in patients with schizophrenia and inflammation; after 8 weeks of canakinumab treatment, the reductions in hsCRP are related to reduced positive symptom severity. Future studies should consider increased doses or longer-term treatment to confirm the potential benefits of adjunctive canakinumab in schizophrenia. Australian and New Zealand Clinical Trials Registry number: ACTRN12615000635561.

Cytomegalovirus antibodies are associated with mood disorders, suicide, markers of neuroinflammation, and microglia activation in postmortem brain samples

Cytomegalovirus (CMV) is a common, neurotrophic herpesvirus that can be reactivated by inflammation and cause central nervous system disease. We hypothesize that CMV may contribute to the neuroinflammation that underlies some psychiatric disorders by (1) exacerbating inflammation through the induction of anti-viral immune responses, and (2) translating peripheral inflammation into neuroinflammation. We investigated whether the presence of anti-CMV antibodies in blood were associated with mental illness, suicide, neuroinflammation, and microglial density in the dorsolateral prefrontal cortex (DLPFC) in postmortem samples. Data (n = 114 with schizophrenia; n = 78 with bipolar disorder; n = 87 with depression; n = 85 controls) were obtained from the Stanley Medical Research Institute. DLPFC gene expression data from a subset of 82 samples were categorized into "high" (n = 30), and "low" (n = 52) inflammation groups based on a recursive two-step cluster analysis using expression data for four inflammation-related genes. Measurements of the ratio of non-ramified to ramified microglia, a proxy of microglial activation, were available for a subset of 49 samples. All analyses controlled for age, sex, and ethnicity, as well as postmortem interval, and pH for gene expression and microglial outcomes. CMV seropositivity significantly increased the odds of a mood disorder diagnosis (bipolar disorder: OR = 2.45; major depression: OR = 3.70) and among the psychiatric samples, of suicide (OR = 2.09). Samples in the upper tercile of anti-CMV antibody titers were more likely to be members of the "high" inflammation group (OR = 4.41, an effect driven by schizophrenia and bipolar disorder samples). CMV positive samples also showed an increased ratio of non-ramified to ramified microglia in layer I of the DLPFC (Cohen's d = 0.81) as well as a non-significant increase in this ratio for the DLPFC as a whole (d = 0.56). The results raise the possibility that the reactivation of CMV contributes to the neuroinflammation that underlies some cases of psychiatric disorders.

miR-9-5p deficiency contributes to schizophrenia

MicroRNA-9-5p (miR-9-5p) is highly expressed in the brain and has been implicated in the risk of schizophrenia. We compared the expression levels of miR-9-5p in schizophrenia cases and healthy controls and evaluated whether regulatory targets of miR-9-5p are enriched in schizophrenia genome-wide risk genes. Literature-based analysis was conducted to construct molecular pathways connecting miR-9-5p and schizophrenia. We found that the expression levels of miR-9-5p were down-regulated in the peripheral blood of schizophrenia patients compared with those in healthy controls. miR-9-5p can regulate 24 out of the 1136 genome-wide risk genes of schizophrenia, which was higher than by chance (hypergeometric test P = 4.09E-06). The literature-based analysis showed that quantitative genetic changes driven by miR-9 exert more inhibitory (the IL1B, ABCB1, FGFR1 genes) than promoting (the INS gene) effects on schizophrenia, suggesting that miR-9 may protect against schizophrenia. Our results suggest that miR-9-5p deficiency may contribute to the development of schizophrenia.

The association between inflammation and kynurenine pathway metabolites in electroconvulsive therapy for schizophrenia: Implications for clinical efficacy

The kynurenine pathway (KP) of tryptophan has been implicated in the pathogenesis of schizophrenia and its interaction with the immune system has been suggested to play a role. In this study, 28 schizophrenia patients and 25 healthy controls were recruited and divided into different inflammatory subgroups using a two-step recursive clustering analysis. Cytokine gene expression and plasma KP metabolites were measured before, during and after treatment. Our findings indicated that schizophrenia patients had lower levels of Tryptophan (TRP), N-formylkynurenine (NFK), xanthinic acid (XA), quinolinic acid (QA), kynurenic acid (KYNA), KYNA/KYN and QA/KYNA, but higher levels of IL-18 mRNA, KYN/TRP compared to healthy controls (all p < 0.05). After electroconvulsive therapy (ECT), patients with low inflammation achieved better clinical improvement (PANSS scores) compared to those with high inflammation (F = 5.672, P = 0.025), especially in negative symptoms (F = 6.382, P = 0.018, η2 = 0.197). While IL-18 mRNA (F = 32.910, P < 0.0001) was significantly decreased following ECT, the KYN/TRP (F = 3.455, p = 0.047) and KYNA/TRP (F = 4.264, P = 0.026) only significantly decreased in patients with low inflammation. Correlation analyses revealed that baseline IL-18 gene expression significantly correlated with pre- (r = 0.537, p = 0.008) and post-KYNA/TRP (r = 0.443, p = 0.034), post-KYN/TRP (r = 0.510, p = 0.013), and post-negative symptoms (r = 0.525, p = 0.010). Moreover, baseline TRP (r = -0.438, p = 0.037) and XA (r = -0.516, p = 0.012) were negatively correlated with baseline PANSS, while post-KYN (r = -0.475, p = 0.022), 2-AA (r = -0.447, p = 0.032) and KYN/TRP (r = -0.566, p = 0.005) were negatively correlated with Montreal Cognitive Assessment (MoCA) following ECT. Overall, these findings suggested that the association between inflammation and kynurenine pathway plays an essential role in mechanism of ECT for schizophrenia and that the regulation of ECT on KP is influenced by inflammatory characteristics, which may relate to clinical efficacy in schizophrenia.

Increased prefrontal cortical cells positive for macrophage/microglial marker CD163 along blood vessels characterizes a neuropathology of neuroinflammatory schizophrenia

Transcript levels of cytokines and SERPINA3 have been used to define a substantial subset (40%) of individuals with schizophrenia with elevated inflammation and worse neuropathology in the dorsolateral prefrontal cortex (DLPFC). In this study, we tested if inflammatory proteins are likewise related to high and low inflammatory states in the human DLFPC in people with schizophrenia and controls. Levels of inflammatory cytokines (IL6, IL1β, IL18, IL8) and a macrophage marker (CD163 protein) were measured in brains obtained from the National Institute of Mental Health (NIMH) (N = 92). First, we tested for diagnostic differences in protein levels overall, then we determined the percentage of individuals that could be defined as "high" inflammation using protein levels. IL-18 was the only cytokine to show increased expression in schizophrenia compared to controls overall. Interestingly, two-step recursive clustering analysis showed that IL6, IL18, and CD163 protein levels could be used as predictors of "high and low" inflammatory subgroups. By this model, a significantly greater proportion of schizophrenia cases (18/32; 56.25%; SCZ) were identified as belonging to the high inflammatory (HI) subgroup compared to control cases (18/60; 30%; CTRL) [χ2(1) = 6.038, p = 0.014]. When comparing across inflammatory subgroups, IL6, IL1β, IL18, IL8, and CD163 protein levels were elevated in both SCZ-HI and CTRL-HI compared to both low inflammatory subgroups (all p < 0.05). Surprisingly, TNFα levels were significantly decreased (-32.2%) in schizophrenia compared to controls (p < 0.001), and were most diminished in the SCZ-HI subgroup compared to both CTRL-LI and CTRL-HI subgroups (p < 0.05). Next, we asked if the anatomical distribution and density of CD163+ macrophages differed in those with schizophrenia and high inflammation status. Macrophages were localized to perivascular sites and found surrounding small, medium and large blood vessels in both gray matter and white matter, with macrophage density highest at the pial surface in all schizophrenia cases examined. A higher density of CD163+ macrophages, that were also larger and more darkly stained, was found in the SCZ-HI subgroup (+154% p < 0.05). We also confirmed the rare existence of parenchymal CD163+ macrophages in both high inflammation subgroups (schizophrenia and controls). Brain CD163+ cell density around blood vessels positively correlated with CD163 protein levels. In conclusion, we find a link between elevated interleukin cytokine protein levels, decreased TNFα protein levels, and elevated CD163+ macrophage densities especially along small blood vessels in those with neuroinflammatory schizophrenia.

Multi-omics analysis of a drug-induced model of bipolar disorder in zebrafish

Emerging studies demonstrate that inflammation plays a crucial role in the pathogenesis of bipolar disorder (BD), but the underlying mechanism remains largely unclear. Given the complexity of BD pathogenesis, we performed high-throughput multi-omic profiling (metabolomics, lipidomics, and transcriptomics) of the BD zebrafish brain to comprehensively unravel the molecular mechanism. Our research proved that in BD zebrafish, JNK-mediated neuroinflammation altered metabolic pathways involved in neurotransmission. On one hand, disturbed metabolism of tryptophan and tyrosine limited the participation of the monoamine neurotransmitters serotonin and dopamine in synaptic vesicle recycling. On the other hand, dysregulated metabolism of the membrane lipids sphingomyelin and glycerophospholipids altered the synaptic membrane structure and neurotransmitter receptors (chrnα7, htr1b, drd5b, and gabra1) activity. Our findings revealed that disturbance of serotonergic and dopaminergic synaptic transmission mediated by the JNK inflammatory cascade was the key pathogenic mechanism in a zebrafish model of BD, provides critical biological insights into the pathogenesis of BD.

Suicide in bipolar disorder patients is associated with hippocampal microglia activation and reduction of lymphocytes-activation gene 3 (LAG3) microglial checkpoint expression

BACKGROUND

Bipolar disorder (BD) is associated with marked functional impairments along with increased rate of suicide. Although there is ample evidence for the involvement of inflammatory processes and microglia activation in the pathophysiology of BD, the mechanisms that regulate these cells in BD patients, and particularly the role of microglia checkpoints, is still unclear.

METHODS

Immunohistochemical analyses of hippocampal sections from post-mortem brains of 15 BD patients and 12 control subjects were used to assess microglia density, by staining the microglia-specific receptor P2RY12, and microglia activation, by staining the activation marker MHC II. Given recent findings on the involvement of LAG3, which interacts with MHC II and serves as a negative microglia checkpoint, in depression and electroconvulsive therapy, we assessed the levels of LAG3 expression and their correlations with microglia density and activation.

RESULTS

There were no overall differences between BD patients and controls, but BD patients who committed suicide (N = 9) displayed a significant elevation in the overall microglia density and the density of MHC II-labeled microglia (but not other MHC II-labeled cells), compared with no suicide BD patients (N = 6) and controls. Furthermore, the percent of microglia expressing LAG3 was significantly reduced only in suicidal BD patients, with significant negative correlations between microglial LAG3 expression levels and the density of microglia, in general, and activated microglia, in particular.

CONCLUSION

Suicidal BD patients exhibit microglia activation, which is possibly mediated by reduced LAG3 checkpoint expression, suggesting that anti-microglial therapeutics, including LAG3 modulators, may be beneficial for this subgroup of patients.

Chemokine Dysregulation and Neuroinflammation in Schizophrenia: A Systematic Review

Chemokines are known to be immunoregulatory proteins involved not only in lymphocyte chemotaxis to the site of inflammation, but also in neuromodulation, neurogenesis, and neurotransmission. Multiple lines of evidence suggest a peripheral proinflammatory state and neuroinflammation in at least a third of patients with schizophrenia. Therefore, chemokines can be active players in these processes. In this systematic review, we analyzed the available data on chemokine dysregulation in schizophrenia and the association of chemokines with neuroinflammation. It has been shown that there is a genetic association of chemokine and chemokine receptor gene polymorphisms in schizophrenia. Besides, the most reliable data confirmed by the results of meta-analyses showed an increase in CXCL8/IL-8, CCL2/MCP-1, CCL4/MIP-1β, CCL11/eotaxin-1 in the blood of patients with schizophrenia. An increase in CXCL8 has been found in cerebrospinal fluid, but other chemokines have been less well studied. Increased/decreased expression of genes of chemokine and their receptors have been found in different areas of the brain and peripheral immune cells. The peripheral proinflammatory state may influence the expression of chemokines since their expression is regulated by pro- and anti-inflammatory cytokines. Mouse models have shown an association of schizophrenia with dysregulation of the CX3CL1-CX3CR1 and CXCL12-CXCR4 axes. Altogether, dysregulation in chemokine expression may contribute to neuroinflammation in schizophrenia. In conclusion, this evidence indicates the involvement of chemokines in the neurobiological processes associated with schizophrenia.

Single-nucleus RNA sequencing of midbrain blood-brain barrier cells in schizophrenia reveals subtle transcriptional changes with overall preservation of cellular proportions and phenotypes

The midbrain is an extensively studied brain region in schizophrenia, in view of its reported dopamine pathophysiology and neuroimmune changes associated with this disease. Besides the dopaminergic system, the midbrain contains other cell types that may be involved in schizophrenia pathophysiology. The neurovascular hypothesis of schizophrenia postulates that both the neurovasculature structure and the functioning of the blood-brain barrier (BBB) are compromised in schizophrenia. In the present study, potential alteration in the BBB of patients with schizophrenia was investigated by single-nucleus RNA sequencing of post-mortem midbrain tissue (15 schizophrenia cases and 14 matched controls). We did not identify changes in the relative abundance of the major BBB cell types, nor in the sub-populations, associated with schizophrenia. However, we identified 14 differentially expressed genes in the cells of the BBB in schizophrenia as compared to controls, including genes that have previously been related to schizophrenia, such as FOXP2 and PDE4D. These transcriptional changes were limited to the ependymal cells and pericytes, suggesting that the cells of the BBB are not broadly affected in schizophrenia.