Molecular determinants of dysregulated GABAergic gene expression in the prefrontal cortex of subjects with schizophrenia

Expression of activity-regulated transcripts in pyramidal neurons across the cortical visuospatial working memory network in unaffected comparison individuals and individuals with schizophrenia

Visuospatial working memory (vsWM), which is impaired in schizophrenia (SZ), is mediated by multiple cortical regions including the primary (V1) and association (V2) visual, posterior parietal (PPC) and dorsolateral prefrontal (DLPFC) cortices. In these regions, parvalbumin (PV) or somatostatin (SST) GABA neurons are altered in SZ as reflected in lower levels of activity-regulated transcripts. As PV and SST neurons receive excitatory inputs from neighboring pyramidal neurons, we hypothesized that levels of activity-regulated transcripts are also lower in pyramidal neurons in these regions. Thus, we quantified levels of four activity-regulated, pyramidal neuron-selective transcripts, namely adenylate cyclase-activating polypeptide-1 (ADCYAP1), brain-derived neurotrophic factor (BDNF), neuronal pentraxin-2 (NPTX2) and neuritin-1 (NRN1) mRNAs, in V1, V2, PPC and DLPFC from unaffected comparison and SZ individuals. In SZ, BDNF and NPTX2 mRNA levels were lower across all four regions, whereas ADCYAP1 and NRN1 mRNA levels were lower in V1 and V2. The regional pattern of deficits in BDNF and NPTX2 mRNAs was similar to that in transcripts in PV and SST neurons in SZ. These findings suggest that lower activity of pyramidal neurons expressing BDNF and/or NPTX2 mRNAs might contribute to alterations in PV and SST neurons across the vsWM network in SZ.

Long-term adaptation of prefrontal circuits in a mouse model of NMDAR hypofunction

Pharmacological approaches to induce N-methyl-d-aspartate receptor (NMDAR) hypofunction have been intensively used to understand the aetiology and pathophysiology of schizophrenia. Yet, the precise cellular and molecular mechanisms that relate to brain network dysfunction remain largely unknown. Here, we used a set of complementary approaches to assess the functional network abnormalities present in male mice that underwent a 7-day subchronic phencyclidine (PCP 10 mg/kg, subcutaneously, once daily) treatment. Our data revealed that pharmacological intervention with PCP affected cognitive performance and auditory evoked gamma oscillations in the prefrontal cortex (PFC) mimicking endophenotypes of some schizophrenia patients. We further assessed PFC cellular function and identified altered neuronal intrinsic membrane properties, reduced parvalbumin (PV) immunostaining and diminished inhibition onto L5 PFC pyramidal cells. A decrease in the strength of optogenetically-evoked glutamatergic current at the ventral hippocampus to PFC synapse was also demonstrated, along with a weaker shunt of excitatory transmission by local PFC interneurons. On a macrocircuit level, functional ultrasound measurements indicated compromised functional connectivity within several brain regions particularly involving PFC and frontostriatal circuits. Herein, we reproduced a panel of schizophrenia endophenotypes induced by subchronic PCP application in mice. We further recapitulated electrophysiological signatures associated with schizophrenia and provided an anatomical reference to critical elements in the brain circuitry. Together, our findings contribute to a better understanding of the physiological underpinnings of deficits induced by subchronic NMDAR antagonist regimes and provide a test system for characterization of pharmacological compounds.

Comparison of microRNA expression levels in patients with schizophrenia before and after electroconvulsive therapy

OBJECTIVE

Exploring the role of microRNAs in the antipsychotic efficacy of electroconvulsive therapy (ECT) will contribute to understanding the underlying mechanism through which ECT exerts its therapeutic effects. The primary objective of this study was to identify microRNA alterations before and after ECT in patients with schizophrenia.

METHODS

We compared microarray-based microRNA profiles in peripheral blood from eight patients with schizophrenia before and after ECT and eight healthy controls. Then, we aimed to validate selected differentially expressed microRNAs in 30 patients with schizophrenia following a course of ECT, alongside 30 healthy controls by using quantitative reverse-transcription PCR.

RESULTS

Microarray-based expression profiling revealed alterations in 681 microRNAs when comparing pre- and post-ECT samples. Subsequent quantitative reverse-transcription PCR analysis of the selected microRNAs (miR-20a-5p and miR-598) did not reveal any statistical differences between pre- and post-ECT samples nor between pre-ECT samples and those of healthy controls.

CONCLUSION

As neuroepigenetic studies on ECT are still in their infancy, the results reported in this study are best interpreted as exploratory outcomes. Additional studies are required to explore the potential epigenetic mechanisms underlying the therapeutic efficacy of ECT.

Developmental dynamics of the prefrontal cortical SST and PV interneuron networks: Insights from the monkey highlight human-specific features

The primate prefrontal cortex (PFC) is a quintessential hub of cognitive functions. Amidst its intricate neural architecture, the interplay of distinct neuronal subtypes, notably parvalbumin (PV) and somatostatin (SST) interneurons (INs), emerge as a cornerstone in sculpting cortical circuitry and governing cognitive processes. While considerable strides have been made in elucidating the developmental trajectory of these neurons in rodent models, our understanding of their postmigration developmental dynamics in primates still needs to be studied. Disruptions to this developmental trajectory can compromise IN function, impairing signal gating and circuit modulation within cortical networks. This study examined the expression patterns of PV and SST, ion transporter KCC2, and ion channel subtypes Kv3.1b, and Nav1.1 - associated with morphophysiological stages of development in the postnatal marmoset monkey in different frontal cortical regions (granular areas 8aD, 8aV, 9, 46; agranular areas 11, 47L). Our results demonstrate that the maturation of PV+ INs extends into adolescence, characterized by discrete epochs associated with specific expression dynamics of ion channel subtypes. Interestingly, we observed a postnatal decrease in SST interneurons, contrasting with studies in rodents. This endeavor broadens our comprehension of primate cortical development and furnishes invaluable insights into the etiology and pathophysiology of neurodevelopmental disorders characterized by perturbations in PV and SST IN function.

LPS-induced inflammation reduces GABAergic interneuron markers and brain-derived neurotrophic factor in mouse prefrontal cortex and hippocampus

Inflammation, reduced gamma-aminobutyric acidergic (GABAergic) function and altered neuroplasticity are co-occurring pathophysiologies in major depressive disorder (MDD). However, the link between these biological changes remains unclear. We hypothesized that inflammation induces deficits in GABAergic interneuron markers and that this effect is mediated by brain-derived neurotrophic factor (BDNF). We report here that systemic inflammation induced by intraperitoneal injection of lipopolysaccharide (LPS) (0.125, 0.25, 0.5, 1, 2 mg/kg) in the first cohort of C57BL/6 mice (n = 72; 10-11 weeks; 50% female) resulted in increased interleukin 1-beta and interleukin-6 in prefrontal cortex (PFC) and hippocampus (HPC), as measured using enzyme-linked immunosorbent assay (ELISA). Quantitative real-time polymerase reaction (qPCR) was used to explore the effect of LPS on the expression of GABAergic interneuron markers. In the PFC of the second cohort (n = 39; 10-11 weeks; 50% female), 2 mg/kg of LPS decreased the expression of somatostatin (Sst) (p = 0.0014), parvalbumin (Pv) (p = 0.0257), cortistatin (Cort) (p = 0.0003), neuropeptide Y (Npy) (p = 0.0033) and cholecystokinin (Cck) (p = 0.0041), and did not affect corticotropin-releasing hormone (Crh) and vasoactive intestinal peptide (Vip) expression. In the HPC, 2 mg/kg of LPS decreased the expression of Sst (p = 0.0543), Cort (p = 0.0011), Npy (p = 0.0001), and Cck (p < 0.0001), and did not affect Crh, Pv, and Vip expression. LPS decreased the expression of Bdnf in the PFC (p < 0.0001) and HPC (p = 0.0003), which significantly correlated with affected markers (Sst, Pv, Cort, Cck, and Npy). Collectively, these results suggest that inflammation may causally contribute to cortical cell microcircuit GABAergic deficits observed in MDD.

BDNF Modulation by microRNAs: An Update on the Experimental Evidence

MicroRNAs can interfere with protein function by suppressing their messenger RNA translation or the synthesis of its related factors. The function of brain-derived neurotrophic factor (BDNF) is essential to the proper formation and function of the nervous system and is seen to be regulated by many microRNAs. However, understanding how microRNAs influence BDNF actions within cells requires a wider comprehension of their integrative regulatory mechanisms. Aim: In this literature review, we have synthesized the evidence of microRNA regulation on BDNF in cells and tissues, and provided an analytical discussion about direct and indirect mechanisms that appeared to be involved in BDNF regulation by microRNAs. Methods: Searches were conducted on PubMed.gov using the terms "BDNF" AND "MicroRNA" and "brain-derived neurotrophic factor" AND "MicroRNA", updated on 1 September 2023. Papers without open access were requested from the authors. One hundred and seventy-one papers were included for review and discussion. Results and Discussion: The local regulation of BDNF by microRNAs involves a complex interaction between a series of microRNAs with target proteins that can either inhibit or enhance BDNF expression, at the core of cell metabolism. Therefore, understanding this homeostatic balance provides resources for the future development of vector-delivery-based therapies for the neuroprotective effects of BDNF.

Identifying the differentially expressed peripheral blood microRNAs in psychiatric disorders: a systematic review and meta-analysis

Background

Evidence has suggested that microRNAs (miRNAs) may play an important role in the pathogenesis of psychiatric disorders (PDs), but the results remain inconclusive. We aimed to identify specific differentially expressed miRNAs and their overlapping miRNA expression profiles in schizophrenia (SZ), major depression disorder (MDD), and bipolar disorder (BD), the three major PDs.

Methods

The literatures up to September 30, 2023 related to peripheral blood miRNAs and PDs were searched and screened from multiple databases. The differences in miRNA levels between groups were illustrated by the standardized mean difference (SMD) and 95% confidence interval (95% CI).

Results

In total, 30 peripheral blood miRNAs were included in the meta-analysis, including 16 for SZ, 12 for MDD, and 2 for BD, each was reported in more than 3 independent studies. Compared with the control group, miR-181b-5p, miR-34a-5p, miR-195-5p, miR-30e-5p, miR-7-5p, miR-132-3p, miR-212-3p, miR-206, miR-92a-3p and miR-137-3p were upregulated in SZ, while miR-134-5p, miR-107 and miR-99b-5p were downregulated. In MDD, miR-124-3p, miR-132-3p, miR-139-5p, miR-182-5p, miR-221-3p, miR-34a-5p and miR-93-5p were upregulated, while miR-144-5p and miR-135a-5p were downregulated. However, we failed to identify statistically differentially expressed miRNAs in BD. Interestingly, miR-132-3p and miR-34a-5p were upregulated in both SZ and MDD.

Conclusions

Our study identified 13 differentially expressed miRNAs in SZ and 9 in MDD, among which miR-132-3p and miR-34a-5p were upregulated in both SZ and MDD by systematically analyzing qualified studies. These miRNAs may be used as potential biomarkers for the diagnosis of SZ and MDD in the future.

Systematic Review Registration

http://www.crd.york.ac.uk/PROSPERO, identifier CRD42023486982.

GABAergic and inflammatory changes in the frontal cortex following neonatal PCP plus isolation rearing, as a dual-hit neurodevelopmental model for schizophrenia

The pathogenesis of schizophrenia begins in early neurodevelopment and leads to excitatory-inhibitory imbalance. It is therefore essential that preclinical models used to understand disease, select drug targets and evaluate novel therapeutics encompass similar neurochemical deficits. One approach to improved preclinical modelling incorporates dual-hit neurodevelopmental insults, like neonatal administration of phencyclidine (PCP, to disrupt development of glutamatergic circuitry) then post-weaning isolation (Iso, to mimic adolescent social stress). We recently showed that male Lister-hooded rats exposed to PCP-Iso exhibit reduced hippocampal expression of the GABA interneuron marker calbindin. The current study expanded on this by investigating changes to additional populations of GABAergic interneurons in frontal cortical and hippocampal tissue from the same animals (by immunohistochemistry) as well as levels of GABA itself (via ELISA). Because inflammatory changes are also implicated in schizophrenia, we performed additional immunohistochemical evaluations of Iba-1 positive microglia as well as ELISA analysis of IL-6 in the same brain regions. Single-hit isolation-reared and dual-hit PCP-Iso rats both showed reduced parvalbumin immunoreactivity in the prelimbic/infralimbic region of the frontal cortex. However, this was more widespread in PCP-Iso, extending to the medial/ventral and lateral/dorsolateral orbitofrontal cortices. Loss of GABAergic markers was accompanied by increased microglial activation in the medial/ventral orbitofrontal cortices of PCP-Iso, together with frontal cortical IL-6 elevations not seen following single-hit isolation rearing. These findings enhance the face validity of PCP-Iso, and we advocate the use of this preclinical model for future evaluation of novel therapeutics-especially those designed to normalise excitatory-inhibitory imbalance or reduce neuroinflammation.

The potential role of miRNAs in the pathogenesis of schizophrenia - A focus on signaling pathways interplay

microRNAs (miRNAs) play a crucial role in brain growth and function. Hence, research on miRNA has the potential to reveal much about the etiology of neuropsychiatric diseases. Among these, schizophrenia (SZ) is a highly intricate and destructive neuropsychiatric ailment that has been thoroughly researched in the field of miRNA. Despite being a relatively recent area of study about miRNAs and SZ, this discipline has advanced enough to justify numerous reviews that summarize the findings from the past to the present. However, most reviews cannot cover all research, thus it is necessary to synthesize the large range of publications on this topic systematically and understandably. Consequently, this review aimed to provide evidence that miRNAs play a role in the pathophysiology and progression of SZ. They have also been investigated for their potential use as biomarkers and therapeutic targets.

Diagnostic value and role of serum miR-15a-5p in patients with schizophrenia

BACKGROUND

More and more studies have confirmed that the heredity plays an important role in mental disorders, especially microRNA. The objective of this research was to explore the level of miR-15a-5p in patients with schizophrenia (SZ), and to evaluate the feasibility of this miRNA as a diagnostic marker of SZ.

METHODS

The serum level of miR-15a-5p in patients with SZ and healthy people was detected by RT-qPCR. ROC curve was established to evaluate the clinical diagnostic significance of miR-15a-5p in SZ. Pearson correlation coefficient was used to evaluate the correlation between miR-15a-5p level and PANSS score. Logistic regression was used to assess the risk factors of SZ. A rat model of SZ was established, and the effects of miR-15a-5p on the behavior of SZ rats were observed through water maze test and open field test.

RESULTS

The serum level of miR-15a-5p in patients with SZ was significantly increased, and ROC analysis revealed that miR-15a-5p had clinical diagnostic value in SZ. High level of miR-15a-5p was positively correlated with the positive symptom, negative symptom and general psychopathology subscore of patients. Logistic regression results showed that miR-15a-5p was a risk factor affecting the occurrence of SZ. Animal studies showed that the serum level of miR-15a-5p was elevated in the SZ rats, and inhibiting the expression of miR-15a-5p has a positive effect on improving the cognitive function and anxiety behavior of SZ rats.

CONCLUSIONS

Serum miR-15a-5p is a risk factor for SZ, which is of great significance for the diagnosis of SZ.

Diagnostic Specificity and Association With Cognition of Molecular Alterations in Prefrontal Somatostatin Neurons in Schizophrenia

Importance

Individuals with schizophrenia (SZ) exhibit pronounced deficits in somatostatin (SST) messenger RNA (mRNA) levels in the dorsolateral prefrontal cortex (DLPFC). Molecularly distinct subtypes of SST neurons, located in the superficial and deep zones of the DLPFC, are thought to contribute to different functional processes of this region; understanding the specificity of SST alterations in SZ across these zones could inform the functional consequences of those alterations, including cognitive impairments characteristic of SZ.

Objective

To quantify mRNA levels of SST and related neuropeptides in the DLPFC in individuals with SZ, bipolar disorder (BPD), or major depressive disorder (MDD) and unaffected comparison individuals.

Design, Setting, and Participants

This case-control study, conducted from January 20, 2020, to March 30, 2022, used postmortem brain tissue specimens previously obtained from individuals with SZ, MDD, or BPD and unaffected individuals from a community population through 2 medical examiners' offices. Demographic, clinical, and educational information was ascertained through psychological autopsies.

Exposures

Diagnosis of SZ, BPD, or MDD.

Main Outcome and Measures

The main outcome was levels of SST and related neuropeptide mRNA in 2 DLPFC zones, examined using laser microdissection and quantitative polymerase chain reaction or fluorescent in situ hybridization (FISH). Findings were compared using educational attainment as a proxy measure of premorbid cognition.

Results

A total of 200 postmortem brain specimens were studied, including 65 from unaffected comparison individuals (42 [65%] male; mean [SD] age, 49.2 [14.1] years); 54 from individuals with SZ (37 [69%] male; mean [SD] age, 47.5 [13.3] years); 42 from individuals with MDD (24 [57%] male; mean [SD] age, 45.6 [12.1] years); and 39 from individuals with BPD (23 [59%] male; mean (SD) age, 46.2 [12.5] years). Compared with unaffected individuals, levels of SST mRNA were lower in both superficial (Cohen d, 0.68; 95% CI, 0.23-1.13; P = .004) and deep (Cohen d, 0.60; 95% CI, 0.16-1.04; P = .02) DLPFC zones in individuals with SZ; findings were confirmed using FISH. Levels of SST were lower only in the superficial zone in the group with MDD (Cohen d, 0.58; 95% CI, 0.14-1.02; P = .12), but the difference was not significant; SST levels were not lower in either zone in the BPD group. Levels of neuropeptide Y and tachykinin 1 showed similar patterns. Neuropeptide alterations in the superficial, but not deep, zone were associated with lower educational attainment only in the group with SZ (superficial: adjusted odds ratio, 1.71 [95% CI, 1.11-2.69]; P = .02; deep: adjusted odds ratio, 1.08 [95% CI, 0.64-1.84]; P = .77).

Conclusions and Relevance

The findings revealed diagnosis-specific patterns of molecular alterations in SST neurons in the DLPFC, suggesting that distinct disease processes are reflected in the differential vulnerability of SST neurons in individuals with SZ, MDD, and BPD. In SZ, alterations specifically in the superficial zone may be associated with cognitive dysfunction.

Blood-Based MicroRNAs in Psychotic Disorders-A Systematic Review

Psychotic disorders are a heterogenous class of mental illness, with an intricate pathophysiology, involving genetics and environmental factors, and their interaction. The identification of accessible biomarkers in bodily systems such as blood may lead to more accurate diagnosis, and more effective treatments targeting dysfunctional pathways, and could assist in monitoring the disease evolution. This systematic review aims to highlight the dysregulated microRNAs (miRNAs) in the peripheral blood of patients with psychotic disorders. Using the PRISMA protocol, PubMed and Science Direct databases were investigated and 22 articles were included. Fifty-five different miRNAs were found differentially expressed in the blood of psychotic patients compared to controls. Seventeen miRNAs (miR-34a, miR-181b, miR-432, miR-30e, miR-21, miR-137, miR-134, miR-7, miR-92a, miR-1273d, miR-1303, miR-3064-5p, miR-3131, miR-3687, miR-4428, miR-4725-3p, and miR-5096) were dysregulated with the same trend (up- or down-regulation) in at least two studies. Of note, miR-34a and miR-181b were up-regulated in the blood of psychotic patients in seven and six studies, respectively. Moreover, the level of miR-181b in plasma was found to be positively correlated with the amelioration of negative symptoms. The panel of miRNAs identified in this review could be validated in future studies in large and well-characterized cohorts of psychotic patients.

Laminar-Specific Alterations in Calbindin-Positive Boutons in the Prefrontal Cortex of Subjects With Schizophrenia

BACKGROUND

Cognitive deficits in schizophrenia are associated with altered GABA (gamma-aminobutyric acid) neurotransmission in the prefrontal cortex (PFC). GABA neurotransmission requires GABA synthesis by 2 isoforms of glutamic acid decarboxylase (GAD65 and GAD67) and packaging by the vesicular GABA transporter (vGAT). Current postmortem findings suggest that GAD67 messenger RNA is lower in a subset of the calbindin-expressing (CB+) class of GABA neurons in schizophrenia. Hence, we assessed if CB+ GABA neuron boutons are affected in schizophrenia.

METHODS

For 20 matched pairs of subjects with schizophrenia and unaffected comparison subjects, PFC tissue sections were immunolabeled for vGAT, CB, GAD67, and GAD65. The density of CB+ GABA boutons and levels of the 4 proteins per bouton were quantified.

RESULTS

Some CB+ GABA boutons contained both GAD65 and GAD67 (GAD65+/GAD67+), whereas others contained only GAD65 (GAD65+) or GAD67 (GAD67+). In schizophrenia, vGAT+/CB+/GAD65+/GAD67+ bouton density was not altered, vGAT+/CB+/GAD65+ bouton density was 86% higher in layers 2/superficial 3 (L2/3s), and vGAT+/CB+/GAD67+ bouton density was 36% lower in L5-6. Bouton GAD levels were differentially altered across bouton types and layers. In schizophrenia, the sum of GAD65 and GAD67 levels in vGAT+/CB+/GAD65+/GAD67+ boutons was 36% lower in L6, GAD65 levels were 51% higher in vGAT+/CB+/GAD65+ boutons in L2, and GAD67 levels in vGAT+/CB+/GAD67+ boutons were 30% to 46% lower in L2/3s-6.

CONCLUSIONS

These findings indicate that schizophrenia-associated alterations in the strength of inhibition from CB+ GABA neurons in the PFC differ across cortical layers and bouton classes, suggesting complex contributions to PFC dysfunction and cognitive impairments in schizophrenia.

Neurotransmission-related gene expression in the frontal pole is altered in subjects with bipolar disorder and schizophrenia

The frontal pole (Brodmann area 10, BA10) is the largest cytoarchitectonic region of the human cortex, performing complex integrative functions. BA10 undergoes intensive adolescent grey matter pruning prior to the age of onset for bipolar disorder (BP) and schizophrenia (SCHIZ), and its dysfunction is likely to underly aspects of their shared symptomology. In this study, we investigated the role of BA10 neurotransmission-related gene expression in BP and SCHIZ. We performed qPCR to measure the expression of 115 neurotransmission-related targets in control, BP, and SCHIZ postmortem samples (n = 72). We chose this method for its high sensitivity to detect low-level expression. We then strengthened our findings by performing a meta-analysis of publicly released BA10 microarray data (n = 101) and identified sources of convergence with our qPCR results. To improve interpretation, we leveraged the unusually large database of clinical metadata accompanying our samples to explore the relationship between BA10 gene expression, therapeutics, substances of abuse, and symptom profiles, and validated these findings with publicly available datasets. Using these convergent sources of evidence, we identified 20 neurotransmission-related genes that were differentially expressed in BP and SCHIZ in BA10. These results included a large diagnosis-related decrease in two important therapeutic targets with low levels of expression, HTR2B and DRD4, as well as other findings related to dopaminergic, GABAergic and astrocytic function. We also observed that therapeutics may produce a differential expression that opposes diagnosis effects. In contrast, substances of abuse showed similar effects on BA10 gene expression as BP and SCHIZ, potentially amplifying diagnosis-related dysregulation.

MicroRNA schizophrenia: Etiology, biomarkers and therapeutic targets

The three sets of symptoms associated with schizophrenia-positive, negative, and cognitive-are burdensome and have serious effects on public health, which affects up to 1% of the population. It is now commonly believed that in addition to the traditional dopaminergic mesolimbic pathway, the etiology of schizophrenia also includes neuronal networks, such as glutamate, GABA, serotonin, BDNF, oxidative stress, inflammation and the immune system. Small noncoding RNA molecules called microRNAs (miRNAs) have come to light as possible participants in the pathophysiology of schizophrenia in recent years by having an impact on these systems. These small RNAs regulate the stability and translation of hundreds of target transcripts, which has an impact on the entire gene network. There may be improved approaches to treat and diagnose schizophrenia if it is understood how these changes in miRNAs alter the critical related signaling pathways that drive the development and progression of the illness.

Chronic haloperidol administration downregulates select BDNF transcript and protein levels in the dorsolateral prefrontal cortex of rhesus monkeys

Post-mortem studies in the prefrontal cortex and hippocampal formation from schizophrenia patients have revealed significant disruptions in the expression molecules associated with cytoarchitecture, synaptic structure, function, and plasticity, known to be regulated in part by brain derived neurotrophic factor (BDNF). Interestingly, several studies using postmortem brain tissue from individuals diagnosed with schizophrenia have revealed a significant reduction in BDNF mRNA and protein levels in the dorsolateral prefrontal cortex (DLPFC), hippocampus and related areas; however, differentiating the effects of illness from antipsychotic history has remained difficult. We hypothesized that chronic antipsychotic treatment may contribute to the altered BDNF mRNA and protein expression observed in post-mortem brains of individuals diagnosed with schizophrenia. To address the influence of antipsychotic administration on BDNF expression in the primate brain, rhesus monkeys orally administered haloperidol, clozapine, or vehicle twice daily for 180 days. We found BDNF splice variants 4 and 5 in the DLPFC and variant 2 in the EC were significantly down-regulated following chronic administration of haloperidol. In addition, proBDNF and mature BDNF expression in the DLPFC, but not the EC, were significantly reduced. Based on the known regulation of BDNF expression by BDNF-AS, we assessed the expression of this lncRNA and found expression was significantly upregulated in the DLPFC, but not EC. The results of the present study provide evidence of haloperidol-induced regulation of BDNF mRNA and protein expression in the DLFPC and suggest an important role for BDNF-AS in this regulation. Given the role of BDNF in synaptic plasticity, neuronal survival and maintenance, aberrant expression induced by haloperidol likely has significant ramifications for neuronal populations and circuits in primate cortex.

Prospects for Neurotrophic Factor-Based Early Intervention in Schizophrenia: Lessons Learned from the Effects of Antipsychotic Drugs on Cognition, Neurogenesis, and Neurotrophic Factors

Although reducing psychotic symptoms in schizophrenia has been a major focus of therapeutic interventions for decades, improving cognition is considered a better predictor of functional outcomes. However, the most commonly prescribed antipsychotic drugs (APDs) show only marginal beneficial effects on cognition in patients with schizophrenia. The neural mechanisms underlying cognitive disturbances in schizophrenia remain unknown that making drug development efforts very challenging. Since neurotrophic factors are the primary architects of neurogenesis, synaptic plasticity, learning, and memory, the findings from preclinical and clinical studies that assess changes in neurogenesis and neurotrophic factors and their relationship to cognitive performance in schizophrenia, and how these mechanisms might be impacted by APD treatment, may provide valuable clues in developing therapies to combat cognitive deficit in schizophrenia. Numerous evidence produced over the years suggests a deficit in a wide spectrum of neurotrophic factors in schizophrenia. Since schizophrenia is considered a neurodevelopmental disorder, early intervention with neurotrophic factors may be more effective in ameliorating the cognitive deficits and psychopathological symptoms associated with this pathology. In this context, results from initial clinical trials with neurotrophic factors and their future potential to improve cognition and psychosocial functioning in schizophrenia are discussed.

Mapping miRNA Research in Schizophrenia: A Scientometric Review

Micro RNA (miRNA) research has great implications in uncovering the aetiology of neuropsychiatric conditions due to the role of miRNA in brain development and function. Schizophrenia, a complex yet devastating neuropsychiatric disorder, is one such condition that had been extensively studied in the realm of miRNA. Although a relatively new field of research, this area of study has progressed sufficiently to warrant dozens of reviews summarising findings from past to present. However, as a majority of reviews cannot encapsulate the full body of research, there is still a need to synthesise the diversity of publications made in this area in a systematic but easy-to-understand manner. Therefore, this study adopted bibliometrics and scientometrics, specifically document co-citation analysis (DCA), to review the literature on miRNAs in the context of schizophrenia over the course of history. From a literature search on Scopus, 992 papers were found and analysed with CiteSpace. DCA analysis generated a network of 13 major clusters with different thematic focuses within the subject area. Finally, these clusters are qualitatively discussed. miRNA research has branched into schizophrenia, among other medical and psychiatric conditions, due to previous findings in other forms of non-coding RNA. With the rise of big data, bioinformatics analyses are increasingly common in this field of research. The future of research is projected to rely more heavily on interdisciplinary collaboration. Additionally, it can be expected that there will be more translational studies focusing on the application of these findings to the development of effective treatments.

Decreased Oligodendrocyte Number in Hippocampal Subfield CA4 in Schizophrenia: A Replication Study

Hippocampus-related cognitive deficits in working and verbal memory are frequent in schizophrenia, and hippocampal volume loss, particularly in the cornu ammonis (CA) subregions, was shown by magnetic resonance imaging studies. However, the underlying cellular alterations remain elusive. By using unbiased design-based stereology, we reported a reduction in oligodendrocyte number in CA4 in schizophrenia and of granular neurons in the dentate gyrus (DG). Here, we aimed to replicate these findings in an independent sample. We used a stereological approach to investigate the numbers and densities of neurons, oligodendrocytes, and astrocytes in CA4 and of granular neurons in the DG of left and right hemispheres in 11 brains from men with schizophrenia and 11 brains from age- and sex-matched healthy controls. In schizophrenia, a decreased number and density of oligodendrocytes was detected in the left and right CA4, whereas mean volumes of CA4 and the DG and the numbers and density of neurons, astrocytes, and granular neurons were not different in patients and controls, even after adjustment of variables because of positive correlations with postmortem interval and age. Our results replicate the previously described decrease in oligodendrocytes bilaterally in CA4 in schizophrenia and point to a deficit in oligodendrocyte maturation or a loss of mature oligodendrocytes. These changes result in impaired myelination and neuronal decoupling, both of which are linked to altered functional connectivity and subsequent cognitive dysfunction in schizophrenia.

A Review of Molecular Interplay between Neurotrophins and miRNAs in Neuropsychological Disorders

Various neurotrophins (NTs), including nerve growth factor, brain-derived neurotrophic factor, neurotrophin-3, and neurotrophin-4, promote cellular differentiation, survival, and maintenance, as well as synaptic plasticity, in the peripheral and central nervous system. The function of microRNAs (miRNAs) and other small non-coding RNAs, as regulators of gene expression, is pivotal for the appropriate control of cell growth and differentiation. There are positive and negative loops between NTs and miRNAs, which exert modulatory effects on different signaling pathways. The interplay between NTs and miRNAs plays a crucial role in the regulation of several physiological and pathological brain procedures. Emerging evidence suggests the diagnostic and therapeutic roles of the interactions between NTs and miRNAs in several neuropsychological disorders, including epilepsy, multiple sclerosis, Alzheimer's disease, Huntington's disease, amyotrophic lateral sclerosis, schizophrenia, anxiety disorders, depression, post-traumatic stress disorder, bipolar disorder, and drug abuse. Here, we review current data regarding the regulatory interactions between NTs and miRNAs in neuropsychological disorders, for which novel diagnostic and/or therapeutic strategies are emerging. Targeting NTs-miRNAs interactions for diagnostic or therapeutic approaches needs to be validated by future clinical studies.

Potential diagnostic biomarkers for schizophrenia

Schizophrenia (SCH) is a complex and severe mental disorder with high prevalence, disability, mortality and carries a heavy disease burden, the lifetime prevalence of SCH is around 0.7%-1.0%, which has a profound impact on the individual and society. In the clinical practice of SCH, key problems such as subjective diagnosis, experiential treatment, and poor overall prognosis are still challenging. In recent years, some exciting discoveries have been made in the research on objective biomarkers of SCH, mainly focusing on genetic susceptibility genes, metabolic indicators, immune indices, brain imaging, electrophysiological characteristics. This review aims to summarize the biomarkers that may be used for the prediction and diagnosis of SCH.

Reduced d-serine levels drive enhanced non-ionotropic NMDA receptor signaling and destabilization of dendritic spines in a mouse model for studying schizophrenia

Schizophrenia is a psychiatric disorder that affects over 20 million people globally. Notably, schizophrenia is associated with decreased density of dendritic spines and decreased levels of d-serine, a co-agonist required for opening of the N-methyl-d-aspartate receptor (NMDAR). We hypothesized that lowered d-serine levels associated with schizophrenia would enhance ion flux-independent signaling by the NMDAR, driving destabilization and loss of dendritic spines. We tested our hypothesis using the serine racemase knockout (SRKO) mouse model, which lacks the enzyme for d-serine production. We show that activity-dependent spine growth is impaired in SRKO mice, but can be acutely rescued by exogenous d-serine. Moreover, we find a significant bias of synaptic plasticity toward spine shrinkage in the SRKO mice as compared to wild-type littermates. Notably, we demonstrate that enhanced ion flux-independent signaling through the NMDAR contributes to this bias toward spine destabilization, which is exacerbated by an increase in synaptic NMDARs in hippocampal synapses of SRKO mice. Our results support a model in which lowered d-serine levels associated with schizophrenia enhance ion flux-independent NMDAR signaling and bias toward spine shrinkage and destabilization.

Identification of Vulnerable Interneuron Subtypes in 15q13.3 Microdeletion Syndrome Using Single-Cell Transcriptomics

BACKGROUND

A number of rare copy number variants (CNVs) have been linked to neurodevelopmental disorders. However, because CNVs encompass many genes, it is often difficult to identify the mechanisms that lead to developmental perturbations.

METHODS

We used 15q13.3 microdeletion to propose and validate a novel strategy to predict the impact of CNV genes on brain development that could further guide functional studies. We analyzed single-cell transcriptomics datasets containing cortical interneurons to identify their developmental vulnerability to 15q13.3 microdeletion, which was validated in mouse models.

RESULTS

We found that Klf13-but not other 15q13.3 genes-is expressed by precursors and neuroblasts in the medial and caudal ganglionic eminences during development, with a peak of expression at embryonic day (E)13.5 and E18.5, respectively. In contrast, in the adult mouse brain, Klf13 expression is negligible. Using Df(h15q13.3)/+ and Klf13^+/- embryos, we observed a precursor subtype-specific impairment in proliferation in the medial ganglionic eminence and caudal ganglionic eminence at E13.5 and E17.5, respectively, corresponding to vulnerability predicted by Klf13 expression patterns. Finally, Klf13^+/- mice showed a layer-specific decrease in parvalbumin and somatostatin cortical interneurons accompanied by changes in locomotor and anxiety-related behavior.

CONCLUSIONS

We show that the impact of 15q13.3 microdeletion on precursor proliferation is grounded in a reduction in Klf13 expression. The lack of Klf13 in Df(h15q13.3)/+ cortex might be the major reason for perturbed density of cortical interneurons. Thus, the behavioral defects seen in 15q13.3 microdeletion could stem from a developmental perturbation owing to selective vulnerability of cortical interneurons during sensitive stages of their development.

Preterm Birth Alters the Maturation of the GABAergic System in the Human Prefrontal Cortex

Developmental changes in GABAergic and glutamatergic systems during frontal lobe development have been hypothesized to play a key role in neurodevelopmental disorders seen in children born very preterm or at/with low birth weight, but the associated cellular changes have not yet been identified. Here we studied the molecular development of the GABAergic system specifically in the dorsolateral prefrontal cortex, a region that has been implicated in neurodevelopmental and psychiatric disorders. The maturation state of the GABAergic system in this region was assessed in human post-mortem brain samples, from term infants ranging in age from 0 to 8 months (n = 17 male, 9 female). Gene expression was measured for 47 GABAergic genes and used to calculate a maturation index. This maturation index was significantly more dynamic in male than female infants. To evaluate the impact of premature birth on the GABAergic system development, samples from 1-month-old term (n = 9 male, 4 female) and 1-month corrected-age very preterm (n = 8 male, 6 female) infants, were compared using the same gene list and methodology. The maturation index for the GABAergic system was significantly lower (−50%, p < 0.05) in male preterm infants, with major alterations in genes linked to GABAergic function in astrocytes, suggesting astrocytic GABAergic developmental changes as a new cellular mechanism underlying preterm brain injury.

Association between neuropeptide Y gene polymorphism and antipsychotics effect

OBJECTIVE

The pathogenesis of schizophrenia is associated with neuropeptide Y (NPY) gene polymorphism to explore the relationship between rs16141, rs16145, and rs5573 polymorphisms in the NPY gene and antipsychotics response in the Chinese population.

METHODS

The unrelated 228 Chinese Han patients with schizophrenia were enrolled in the present study. Genotypisation within NPY gene was performed using the KASP genotyping assays. Before treatment and on the weekends of the 2nd, 4th, and 8th weeks after treatment, the medication status of the patients was recorded and the positive and negative syndrome scale (PANSS) was used to evaluate the clinical effect. A reduction in total PANSS scores ≥50% were classified as good responders, while others were poor responders. We evaluated the association between NPY gene and antipsychotic efficacy by comparing allele and genotype distribution, correlation analysis, linkage imbalance, and five genetic models between the two groups.

RESULTS

No significant associations were found in the rs16141, rs16145, and rs5573 of NPY and antipsychotic treatment response (all p > 0.05). There was no significant relationship between the three SNPs polymorphisms in the NPY gene and the changes of positive, negative and general psychopathology subscales scores at each stage (all p > 0.05). The distribution of genotype and allele frequencies of locus rs16141 was not statistically difference between good responders and poor responders (genotype: χ2 =4.088, p=0.043, p-correction = 0.129; allele: χ² = 4.088, p = 0.027, p-correction = 0.081). The allele distribution of rs5573 was significantly different between groups, yet the difference was disappeared after correcting (χ² = 4.136, p = 0.042, p-correction =0.126). The distribution frequencies of TA/TG and GG haplotypes constituted by rs16141 and rs5573 showed no statistical difference between the two groups (p > 0.05). In recessive inheritance mode, NPYrs5573 was found to be associated with antipsychotic drug response (G/G vs. A/A +A/G: p = 0.028, AIC = 197.2, BIC = 210.9).

CONCLUSIONS

This study didn't found association between polymorphisms in the NPY gene locus (rs16141, rs16145, and rs5573) and the response to antipsychotics after Bonferroni correction. The polymorphism of NPY gene and the efficacy of antipsychotic drugs in patients with schizophrenia need further study.

Bioinformatics analysis of long non-coding RNA-associated competing endogenous RNA network in schizophrenia

Schizophrenia (SCZ) is a serious psychiatric condition with a 1% lifetime risk. SCZ is one of the top ten global causes of disabilities. Despite numerous attempts to understand the function of genetic factors in SCZ development, genetic components in SCZ pathophysiology remain unknown. The competing endogenous RNA (ceRNA) network has been demonstrated to be involved in the development of many kinds of diseases. The ceRNA hypothesis states that cross-talks between coding and non-coding RNAs, including long non-coding RNAs (lncRNAs), via miRNA complementary sequences known as miRNA response elements, creates a large regulatory network across the transcriptome. In the present study, we developed a lncRNA-related ceRNA network to elucidate molecular regulatory mechanisms involved in SCZ. Microarray datasets associated with brain regions (GSE53987) and lymphoblasts (LBs) derived from peripheral blood (sample set B from GSE73129) of SCZ patients and control subjects containing information about both mRNAs and lncRNAs were downloaded from the Gene Expression Omnibus database. The GSE53987 comprised 48 brain samples taken from SCZ patients (15 HPC: hippocampus, 15 BA46: Brodmann area 46, 18 STR: striatum) and 55 brain samples taken from control subjects (18 HPC, 19 BA46, 18 STR). The sample set B of GSE73129 comprised 30 LB samples (15 patients with SCZ and 15 controls). Differentially expressed mRNAs (DEmRNAs) and lncRNAs (DElncRNAs) were identified using the limma package of the R software. Using DIANA-LncBase, Human MicroRNA Disease Database (HMDD), and miRTarBase, the lncRNA- associated ceRNA network was generated. Pathway enrichment of DEmRNAs was performed using the Enrichr tool. We developed a protein-protein interaction network of DEmRNAs and identified the top five hub genes by the use of STRING and Cytoscape, respectively. Eventually, the hub genes, DElncRNAs, and predictive miRNAs were chosen to reconstruct the subceRNA networks. Our bioinformatics analysis showed that twelve key DEmRNAs, including BDNF, VEGFA, FGF2, FOS, CD44, SOX2, NRAS, SPARC, ZFP36, FGG, ELAVL1, and STARD13, participate in the ceRNA network in SCZ. We also identified DLX6-AS1, NEAT1, MINCR, LINC01094, DLGAP1-AS1, BABAM2-AS1, PAX8-AS1, ZFHX4-AS1, XIST, and MALAT1 as key DElncRNAs regulating the genes mentioned above. Furthermore, expression of 15 DEmRNAs (e.g., ADM and HLA-DRB1) and one DElncRNA (XIST) were changed in both the brain and LB, suggesting that they could be regarded as candidates for future biomarker studies. The study indicated that ceRNAs could be research candidates for investigating SCZ molecular pathways.

Non-coding RNAs and their bioengineering applications for neurological diseases

Engineering of cellular biomolecules is an emerging landscape presenting creative therapeutic opportunities. Recently, several strategies such as biomimetic materials, drug-releasing scaffolds, stem cells, and dynamic culture systems have been developed to improve specific biological functions, however, have been confounded with fundamental and technical roadblocks. Rapidly emerging investigations on the bioengineering prospects of mammalian ribonucleic acid (RNA) is expected to result in significant biomedical advances. More specifically, the current trend focuses on devising non-coding (nc) RNAs as therapeutic candidates for complex neurological diseases. Given the pleiotropic and regulatory role, ncRNAs such as microRNAs and long non-coding RNAs are deemed as attractive therapeutic candidates. Currently, the list of non-coding RNAs in mammals is evolving, which presents the plethora of hidden possibilities including their scope in biomedicine. Herein, we critically review on the emerging repertoire of ncRNAs in neurological diseases such as Alzheimer’s disease, Parkinson’s disease, neuroinflammation and drug abuse disorders. Importantly, we present the advances in engineering of ncRNAs to improve their biocompatibility and therapeutic feasibility as well as provide key insights into the applications of bioengineered non-coding RNAs that are investigated for neurological diseases.

Epigenetics of Schizophrenia

Schizophrenia (SCZ) is a chronic psychotic disorder that contributes significantly to disability, affecting behavior, thought, and cognition. It has long been known that there is a heritable component to schizophrenia; studies in both the pre-genomic and post-genomic era, however, have failed to elucidate fully the genetic basis for this complex disease. Epigenetic processes - broadly, those which contribute to changes in gene expression without altering the genetic code itself - may help to understand better the mechanisms leading to development of SCZ. The objective of this review is to synthesize current knowledge of the epigenetic mechanisms involved in schizophrenia. Specifically, DNA methylation studies in both peripheral and post-mortem brain samples in SCZ are reviewed, as are epigenetic mechanisms including histone modification. The promising role of non-coding RNA including micro-RNA (miRNA) and its role as a potential diagnostic and therapeutic biomarker is outlined, as are epigenetic age acceleration and telomere shortening. Finally, we discuss limitations in current knowledge and propose future research directions.

A Role for Somatostatin-Positive Interneurons in Neuro-Oscillatory and Information Processing Deficits in Schizophrenia

Alterations in neocortical GABAergic interneurons (INs) have been affiliated with neuropsychiatric diseases, including schizophrenia (SZ). Significant progress has been made linking the function of a specific subtype of GABAergic cells, parvalbumin (PV) positive INs, to altered gamma-band oscillations, which, in turn, underlie perceptual and feedforward information processing in cortical circuits. Here, we review a smaller but growing volume of literature focusing on a separate subtype of neocortical GABAergic INs, somatostatin (SST) positive INs. Despite sharing similar neurodevelopmental origins, SSTs exhibit distinct morphology and physiology from PVs. Like PVs, SSTs are altered in postmortem brain samples from multiple neocortical regions in SZ, although basic and translational research into consequences of SST dysfunction has been relatively sparse. We highlight a growing body of work in rodents, which now indicates that SSTs may also underlie specific aspects of cortical circuit function, namely low-frequency oscillations, disinhibition, and mediation of cortico-cortical feedback. SSTs may thereby support the coordination of local cortical information processing with more global spatial, temporal, and behavioral context, including predictive coding and working memory. These functions are notably deficient in some cases of SZ, as well as other neuropsychiatric disorders, emphasizing the importance of focusing on SSTs in future translational studies. Finally, we highlight the challenges that remain, including subtypes within the SST class.

Reductions in midbrain GABAergic and dopamine neuron markers are linked in schizophrenia

Reductions in the GABAergic neurotransmitter system exist across multiple brain regions in schizophrenia and encompass both pre- and postsynaptic components. While reduced midbrain GABAergic inhibitory neurotransmission may contribute to the hyperdopaminergia thought to underpin psychosis in schizophrenia, molecular changes consistent with this have not been reported. We hypothesised that reduced GABA-related molecular markers would be found in the midbrain of people with schizophrenia and that these would correlate with dopaminergic molecular changes. We hypothesised that downregulation of inhibitory neuron markers would be exacerbated in schizophrenia cases with high levels of neuroinflammation. Eight GABAergic-related transcripts were measured with quantitative PCR, and glutamate decarboxylase (GAD) 65/67 and GABA_A alpha 3 (α3) (GABRA3) protein were measured with immunoblotting, in post-mortem midbrain (28/28 and 28/26 control/schizophrenia cases for mRNA and protein, respectively), and analysed by both diagnosis and inflammatory subgroups (as previously defined by higher levels of four pro-inflammatory cytokine transcripts). We found reductions (21 – 44%) in mRNA encoding both presynaptic and postsynaptic proteins, vesicular GABA transporter (VGAT), GAD1, and parvalbumin (PV) mRNAs and four alpha subunits (α1, α2, α3, α5) of the GABA_A receptor in people with schizophrenia compared to controls (p < 0.05). Gene expression of somatostatin (SST) was unchanged (p = 0.485). We confirmed the reduction in GAD at the protein level (34%, p < 0.05). When stratifying by inflammation, only GABRA3 mRNA exhibited more pronounced changes in high compared to low inflammatory subgroups in schizophrenia. GABRA3 protein was expressed by 98% of tyrosine hydroxylase-positive neurons and was 23% lower in schizophrenia, though this did not reach statistical significance (p > 0.05). Expression of transcripts for GABA_A receptor alpha subunits 2 and 3 (GABRA2, GABRA3) were positively correlated with tyrosine hydroxylase (TH) and dopamine transporter (DAT) transcripts in schizophrenia cases (GABRA2; r > 0.630, GABRA3; r > 0.762, all p < 0.001) but not controls (GABRA2; r < − 0.200, GABRA3; r < 0.310, all p > 0.05). Taken together, our results support a profound disruption to inhibitory neurotransmission in the substantia nigra regardless of inflammatory status, which provides a potential mechanism for disinhibition of nigrostriatal dopamine neurotransmission.

Neuronal and glial 3D chromatin architecture informs the cellular etiology of brain disorders

Cellular heterogeneity in the human brain obscures the identification of robust cellular regulatory networks, which is necessary to understand the function of non-coding elements and the impact of non-coding genetic variation. Here we integrate genome-wide chromosome conformation data from purified neurons and glia with transcriptomic and enhancer profiles, to characterize the gene regulatory landscape of two major cell classes in the human brain. We then leverage cell-type-specific regulatory landscapes to gain insight into the cellular etiology of several brain disorders. We find that Alzheimer's disease (AD)-associated epigenetic dysregulation is linked to neurons and oligodendrocytes, whereas genetic risk factors for AD highlighted microglia, suggesting that different cell types may contribute to disease risk, via different mechanisms. Moreover, integration of glutamatergic and GABAergic regulatory maps with genetic risk factors for schizophrenia (SCZ) and bipolar disorder (BD) identifies shared (parvalbumin-expressing interneurons) and distinct cellular etiologies (upper layer neurons for BD, and deeper layer projection neurons for SCZ). Collectively, these findings shed new light on cell-type-specific gene regulatory networks in brain disorders.

Environmental enrichment or selective activation of parvalbumin-expressing interneurons ameliorates synaptic and behavioral deficits in animal models with schizophrenia-like behaviors during adolescence

Synaptic deficit-induced excitation and inhibition (E/I) imbalance have been implicated in the pathogenesis of schizophrenia. Using in vivo two-photon microscopy, we examined the dynamic plasticity of dendritic spines of pyramidal neurons (PNs) and "en passant" axonal bouton of parvalbumin-expressing interneurons (PVINs) in the frontal association (FrA) cortex in two adolescent mouse models with schizophrenia-like behaviors. Simultaneous imaging of PN dendritic spines and PV axonal boutons showed that repeated exposure to N-methyl-D-aspartate receptor (NMDAR) antagonist MK801 during adolescence disrupted the normal developmental balance of excitatory and inhibitory synaptic structures. This MK801-induced structural E/I imbalance significantly correlated with animal recognition memory deficits and could be ameliorated by environmental enrichment (EE). In addition, selective chemogenetic activation of PVINs in the FrA mimicked the effects of EE on both synaptic plasticity and animal behavior, while selective inhibition of PVIN abolished EE's beneficial effects. Electrophysiological recordings showed that chronic MK801 treatment significantly suppressed the frequency of mEPSC/mIPSC ratio of layer (L) 2/3 PNs and significantly reduced the resting membrane potential of PVINs, the latter was rescued by selective activation of PVINs. Such manipulations of PVINs also showed similar effects in PV-Cre; ErbB4^fl/fl animal model with schizophrenia-like behaviors. EE or selective activation of PVINs in the FrA restored behavioral deficits and structural E/I imbalance in adolescent PV-Cre; ErbB4^fl/fl mice, while selective inhibition of PVINs abolished EE's beneficial effects. Our findings suggest that the PVIN activity in the FrA plays a crucial role in regulating excitatory and inhibitory synaptic structural dynamics and animal behaviors, which may provide a potential therapeutic target for schizophrenia treatment.

Increased excitation-inhibition balance and loss of GABAergic synapses in the serine racemase knockout model of NMDA receptor hypofunction

There is substantial evidence that both N-methyl-D-aspartate receptor (NMDAR) hypofunction and dysfunction of GABAergic neurotransmission contribute to schizophrenia, though the relationship between these pathophysiological processes remains largely unknown. Although models using cell-type-specific genetic deletion of NMDARs have been informative, they display overly pronounced phenotypes extending beyond those of schizophrenia. Here, we used the serine racemase knockout (SRKO) mice, a model of reduced NMDAR activity rather than complete receptor elimination, to examine the link between NMDAR hypofunction and decreased GABAergic inhibition. The SRKO mice, in which there is a >90% reduction in the NMDAR coagonist d-serine, exhibit many of the neurochemical and behavioral abnormalities observed in schizophrenia. We found a significant reduction in inhibitory synapses onto CA1 pyramidal neurons in the SRKO mice. This reduction increases the excitation/inhibition balance resulting in enhanced synaptically driven neuronal excitability without changes in intrinsic excitability. Consistently, significant reductions in inhibitory synapse density in CA1 were observed by immunohistochemistry. We further show, using a single-neuron genetic deletion approach, that the loss of GABAergic synapses onto pyramidal neurons observed in the SRKO mice is driven in a cell-autonomous manner following the deletion of SR in individual CA1 pyramidal cells. These results support a model whereby NMDAR hypofunction in pyramidal cells disrupts GABAergic synapses leading to disrupted feedback inhibition and impaired neuronal synchrony.NEW & NOTEWORTHY Recently, disruption of excitation/inhibition (E/I) balance has become an area of considerable interest for psychiatric research. Here, we report a reduction in inhibition in the serine racemase knockout mouse model of schizophrenia that increases E/I balance and enhances synaptically driven neuronal excitability. This reduced inhibition was driven cell-autonomously in pyramidal cells lacking serine racemase, suggesting a novel mechanism for how chronic NMDA receptor hypofunction can disrupt information processing in schizophrenia.

Behavioral changes and brain epigenetic alterations induced by maternal deficiencies of B vitamins in a mouse model

RATIONALE

B vitamins play essential roles in brain development and functionality; however, the effects of their deficiency during early life on mental health are not thoroughly understood.

OBJECTIVES

The objective of this study is to investigate the effects of a maternal deficiency of vitamin B6, B9 (folate), and B12 on behavioral changes in adult offspring.

METHODS

Female C57BL/6 J mice were put on a diet lacking vitamin B6, B9, B12, or the above three vitamins from pregnancy to weaning. The growth and developmental characteristics of both the pregnant mothers and offspring were collected. In the adult offspring, the serum levels of neuroactive substances were measured using an enzyme-linked immunosorbent assay. The level of BDNF and dimethylated lysine 9 on histone H3 (H3K9me2) was detected by immunohistochemical staining. In addition, their depressive-like behaviors, anxiety-like behaviors, and sociability were recorded using sucrose preference, a forced swim, social interaction, tail suspension, and open field tests.

RESULTS

The maternal deficiency of the three B vitamins delayed offspring development. Compared to the controls, all of the groups showed decreased serum levels of 5-HT and neuropeptide Y. In the groups with deficiency of B9 or the three B vitamins, there were significant changes in sociability and social novelty preference. In groups with deficiencies in B9, B12, or all three B vitamins, the expression levels of BDNF and H3K9me2 in the hippocampus were significantly decreased.

CONCLUSIONS

Maternal deficiencies of the major B vitamins caused changes in social behaviors in adult mice accompanied with epigenetic alterations in the brain and changes in the serum levels of neuroactive substances.

Differential correlation of serum BDNF and microRNA content in rats with rapid or late onset of heavy alcohol use

Heavy alcohol use reduces the levels of the brain-derived neurotrophic factor (BDNF) in the prefrontal cortex of rodents through the upregulation of microRNAs (miRs) targeting BDNF mRNA. In humans, an inverse correlation exists between circulating blood levels of BDNF and the severity of psychiatric disorders including alcohol abuse. Here, we set out to determine whether a history of heavy alcohol use produces comparable alterations in the blood of rats. We used an intermittent access to 20% alcohol using the two-bottle choice paradigm (IA20%2BC) and measured circulating levels of BDNF protein and miRs targeting BDNF in the serum of Long-Evans rats before and after 8 weeks of excessive alcohol intake. We observed that the drinking profile of heavy alcohol users is not unified, whereas 70% of the rats gradually escalate their alcohol intake (late onset), and 30% of alcohol users exhibit a very rapid onset of drinking (rapid onset). We found that serum BDNF levels are negatively correlated with alcohol intake in both rapid onset and late onset rats. In contrast, increased expression of the miRs targeting BDNF, miR30a-5p, miR-195-5p, miR191-5p and miR206-3p, was detected only in the rapid onset rats. Finally, we report that the alcohol-dependent molecular changes are not due to alterations in platelet number. Together, these data suggest that rats exhibit both late and rapid onset of alcohol intake. We further show that heavy alcohol use produces comparable changes in BDNF protein levels in both groups. However, circulating microRNAs are responsive to alcohol only in the rapid onset rats.

The microRNA-195 - BDNF pathway and cognitive deficits in schizophrenia patients with minimal antipsychotic medication exposure

Cognitive impairment is a core characteristic of schizophrenia, but its underlying neural mechanisms remain poorly understood. Reduced brain-derived neurotrophic factor (BDNF), a protein critical for neural plasticity and synaptic signaling, is one of the few molecules consistently associated with cognitive deficits in schizophrenia although the etiological pathway leading to BDNF reduction in schizophrenia is unclear. We examined microRNA-195 (miR-195), a known modulator of BDNF protein expression, as a potential mechanistic component. One-hundred and eighteen first-episode patients with schizophrenia either antipsychotic medication-naïve or within two weeks of antipsychotic medication exposure and forty-seven age- and sex-matched healthy controls were enrolled. MiR-195 and BDNF mRNA and BDNF protein levels in peripheral blood were tested. Cognitive function was assessed using the MATRICS Consensus Cognitive Battery (MCCB). MiR-195 was significantly higher (p = 0.01) whereas BDNF mRNA (p < 0.001) and protein (p = 0.016) levels were significantly lower in patients compared with controls. Higher miR-195 expression was significantly correlated to lower BDNF protein levels in patients (partial r = -0.28, p = 0.003) and lower BDNF protein levels were significantly associated with poorer overall cognitive performance by MCCB and also in speed of processing, working memory, and attention/vigilance domains composite score (p = 0.002-0.004). The subgroup of patients with high miR-195 and low BDNF protein showed the lowest level of cognitive functions, and miR-195 showed significant mediation effects on cognitive functions through BDNF protein. Elevated miR-195 may play a role in regulating BDNF protein expression thereby influencing cognitive impairments in schizophrenia, suggesting that development of cognition enhancing treatment for schizophrenia may consider a micro-RNA based strategy.

Neuronal Development-Related miRNAs as Biomarkers for Alzheimer's Disease, Depression, Schizophrenia and Ionizing Radiation Exposure

Radiation exposure may induce Alzheimer's disease (AD), depression or schizophrenia. A number of experimental and clinical studies suggest the involvement of miRNA in the development of these diseases, and also in the neuropathological changes after brain radiation exposure. The current literature review indicated the involvement of 65 miRNAs in neuronal development in the brain. In the brain tissue, blood, or cerebral spinal fluid (CSF), 11, 55, or 28 miRNAs are involved in the development of AD respectively, 89, 50, 19 miRNAs in depression, and 102, 35, 8 miRNAs in schizophrenia. We compared miRNAs regulating neuronal development to those involved in the genesis of AD, depression and schizophrenia and also those driving radiation-induced brain neuropathological changes by reviewing the available data. We found that 3, 11, or 8 neuronal developmentrelated miRNAs from the brain tissue, 13, 16 or 14 miRNAs from the blood of patient with AD, depression and schizophrenia respectively were also involved in radiation-induced brain pathological changes, suggesting a possibly specific involvement of these miRNAs in radiation-induced development of AD, depression and schizophrenia respectively. On the other hand, we noted that radiationinduced changes of two miRNAs, i.e., miR-132, miR-29 in the brain tissue, three miRNAs, i.e., miR- 29c-5p, miR-106b-5p, miR-34a-5p in the blood were also involved in the development of AD, depression and schizophrenia, thereby suggesting that these miRNAs may be involved in the common brain neuropathological changes, such as impairment of neurogenesis and reduced learning memory ability observed in these three diseases and also after radiation exposure.

MicroRNA-195 predicts olanzapine response in drug-free patients with schizophrenia: A prospective cohort study

BACKGROUND

Disturbances of microRNA-195 have been implicated in the pathogenesis of schizophrenia. However, microRNA-195 levels in schizophrenia are controversial.

AIMS

To the best of our knowledge, this is the first study to examine microRNA-195 levels in untreated schizophrenia patients and their relationship to olanzapine response.

METHODS

We recruited 81 untreated schizophrenia patients and 96 healthy controls. The patients received 2 months olanzapine treatment. MicroRNA-195 levels in peripheral blood mononuclear cells were measured using quantitative real-time polymerase chain reaction testing. Psychiatric symptoms were assessed using the Positive and Negative Syndrome Scale.

RESULTS

No significant differences in microRNA-195 levels were found between patients and healthy controls (p > 0.05). Olanzapine significantly reduced microRNA-195 levels after 2 months treatment (p = 0.003). Interestingly, microRNA-195 levels decreased significantly in responders (p = 0.010), but not in non-responders (p > 0.05). Both baseline microRNA-195 levels (p = 0.027, p = 0.030) and the reduction rate of microRNA-195 levels (p = 0.034, p = 0.044) were positively associated with the reduction rate of Positive and Negative Syndrome Scale total score and general psychopathological subscale score. Multiple stepwise regression analysis revealed that baseline microRNA-195 level was an independent contributor to the reduction in Positive and Negative Syndrome Scale total score and the general psychopathological subscale score (p = 0.018, p = 0.030). Finally, logistic regression analysis suggested that baseline microRNA-195 level can serve as a biomarker for response to olanzapine (p = 0.037).

CONCLUSIONS

Our data indicate that microRNA-195 level may predict symptomatic improvement and olanzapine response in schizophrenia patients, suggesting that microRNA-195 should be considered as a potential therapeutic target for antipsychotics.

The Relation of the Brain-Derived Neurotrophic Factor with MicroRNAs in Neurodegenerative Diseases and Ischemic Stroke

Brain-derived neurotrophic factor (BDNF) is a member of the neurotrophin family of growth factors that plays a crucial role in the development of the nervous system while supporting the survival of existing neurons and instigating neurogenesis. Altered levels of BDNF, both in the circulation and in the central nervous system (CNS), have been reported to be involved in the pathogenesis of neurodegenerative diseases, including Alzheimer's disease (AD), Parkinson's disease (PD), amyotrophic lateral sclerosis (ALS), Huntington's disease (HD), multiple sclerosis (MS), and ischemic stroke. MicroRNAs (miRNAs) are a class of non-coding RNAs found in body fluids such as peripheral blood and cerebrospinal fluid. Several different miRNAs, and their target genes, are recognized to be involved in the pathophysiology of neurodegenerative and neurovascular diseases. Thus, they present as promising biomarkers and a novel treatment approach for CNS disorders. Currently, limited studies provide viable evidence of miRNA-mediated post-transcriptional regulation of BDNF. The aim of this review is to provide a comprehensive assessment of the current knowledge regarding the potential diagnostic and prognostic values of miRNAs affecting BDNF expression and its role as a CNS disorders and neurovascular disease biomarker. Moreover, a novel therapeutic approach in neurodegenerative diseases and ischemic stroke targeting miRNAs associated with BDNF will be discussed.

The prefrontal cortex as a target for atypical antipsychotics in schizophrenia, lessons of neurodevelopmental animal models

Prefrontal cortex (PFC) inflammatory imbalance, oxidative/nitrosative stress (O/NS) and impaired neuroplasticity in schizophrenia are thought to have neurodevelopmental origins. Animal models are not only useful to test this hypothesis, they are also effective to establish a relationship among brain disturbances and behavior with the atypical antipsychotics (AAPs) effects. Here we review data of PFC post-mortem and in vivo neuroimaging, human induced pluripotent stem cells (hiPSC), and peripheral blood studies of inflammatory, O/NS, and neuroplasticity alterations in the disease as well as about their modulation by AAPs. Moreover, we reviewed the PFC alterations and the AAP mechanisms beyond their canonical antipsychotic action in four neurodevelopmental animal models relevant to the study of schizophrenia with a distinct approach in the generation of schizophrenia-like phenotypes, but all converge in O/NS and altered neuroplasticity in the PFC. These animal models not only reinforce the neurodevelopmental risk factor model of schizophrenia but also arouse some novel potential therapeutic targets for the disease including the reestablishment of the antioxidant response by the perineuronal nets (PNNs) and the nuclear factor erythroid 2-related factor (Nrf2) pathway, as well as the dendritic spine dynamics in the PFC pyramidal cells.

Evidence for Decreased Density of Calretinin-Immunopositive Neurons in the Caudate Nucleus in Patients With Schizophrenia

Schizophrenia (SCH) and autism spectrum disorder (ASD) share several common aetiological and symptomatic features suggesting they may be included in a common spectrum. For example, recent results suggest that excitatory/inhibitory imbalance is relevant in the etiology of SCH and ASD. Numerous studies have investigated this imbalance in regions like the ventromedial and dorsolateral prefrontal cortex (DLPFC). However, relatively little is known about neuroanatomical changes that could reduce inhibition in subcortical structures, such as the caudate nucleus (CN), in neuropsychiatric disorders. We recently showed a significant decrease in calretinin-immunopositive (CR-ip) interneuronal density in the CN of patients with ASD without significant change in the density of neuropeptide Y-immunopositive (NPY-ip) neurons. These subtypes together constitute more than 50% of caudate interneurons and are likely necessary for maintaining excitatory/inhibitory balance. Consequently, and since SCH and ASD share characteristic features, here we tested the hypothesis, that the density of CR-ip neurons in the CN is decreased in patients with SCH. We used immunohistochemistry and qPCR for CR and NPY in six patients with schizophrenia and six control subjects. As expected, small, medium and large CR-ip interneurons were detected in the CN. We found a 38% decrease in the density of all CR-ip interneurons (P < 0.01) that was driven by the loss of the small CR-ip interneurons (P < 0.01) in patients with SCH. The densities of the large CR-ip and of the NPY-ip interneurons were not significantly altered. The lower density detected could have been due to inflammation-induced degeneration. However, the state of microglial activation assessed by quantification of ionized calcium-binding adapter molecule 1 (Iba1)- and transmembrane protein 119 (TMEM119)-immunopositive cells showed no significant difference between patients with SCH and controls. Our results warrant further studies focussing on the role of CR-ip neurons and on the striatum being a possible hub for information selection and regulation of associative cortical fields whose function have been altered in SCH.

Exploring the mRNA expression level of RELN in peripheral blood of schizophrenia patients before and after antipsychotic treatment

Background

The Reelin (RELN) gene encodes the protein reelin, which is a large extracellular matrix glycoprotein that plays a key role in brain development. Additionally, this protein may be involved in memory formation, neurotransmission, and synaptic plasticity, which have been shown to be disrupted in schizophrenia (SCZ). A decreasing trend in the expression of RELN mRNA in the brain and peripheral blood of SCZ patients has been observed. There is a need to determine whether changes in RELN mRNA expression in SCZ patients are the result of long-term antipsychotic treatment rather than the etiological characteristics of schizophrenia. The expression levels of RELN mRNA in the peripheral blood of 48 healthy controls and 30 SCZ patients before and after 12-weeks of treatment were measured using quantitative real-time PCR.

Results

The expression levels of RELN mRNA in the SCZ group were significantly lower than that of healthy controls; however, after 12-weeks of antipsychotic treatment, RELN mRNA levels were significantly increased in the SCZ group.

Conclusion

The up-regulation of RELN mRNA expression was current in SCZ patients after antipsychotic treatment, suggesting that the changes in RELN mRNA expression were related to the effect of the antipsychotic treatment.

A psychiatric disease-related circular RNA controls synaptic gene expression and cognition

Although circular RNAs (circRNAs) are enriched in the mammalian brain, very little is known about their potential involvement in brain function and psychiatric disease. Here, we show that circHomer1a, a neuronal-enriched circRNA abundantly expressed in the frontal cortex, derived from Homer protein homolog 1 (HOMER1), is significantly reduced in both the prefrontal cortex (PFC) and induced pluripotent stem cell-derived neuronal cultures from patients with schizophrenia (SCZ) and bipolar disorder (BD). Moreover, alterations in circHomer1a were positively associated with the age of onset of SCZ in both the dorsolateral prefrontal cortex (DLPFC) and orbitofrontal cortex (OFC). No correlations between the age of onset of SCZ and linear HOMER1 mRNA were observed, whose expression was mostly unaltered in BD and SCZ postmortem brain. Using in vivo circRNA-specific knockdown of circHomer1a in mouse PFC, we show that it modulates the expression of numerous alternative mRNA transcripts from genes involved in synaptic plasticity and psychiatric disease. Intriguingly, in vivo circHomer1a knockdown in mouse OFC resulted in specific deficits in OFC-mediated cognitive flexibility. Lastly, we demonstrate that the neuronal RNA-binding protein HuD binds to circHomer1a and can influence its synaptic expression in the frontal cortex. Collectively, our data uncover a novel psychiatric disease-associated circRNA that regulates synaptic gene expression and cognitive flexibility.

Turning the 'Tides on Neuropsychiatric Diseases: The Role of Peptides in the Prefrontal Cortex

Recent advancements in technology have enabled researchers to probe the brain with the greater region, cell, and receptor specificity. These developments have allowed for a more thorough understanding of how regulation of the neurophysiology within a region is essential for maintaining healthy brain function. Stress has been shown to alter the prefrontal cortex (PFC) functioning, and evidence links functional impairments in PFC brain activity with neuropsychiatric disorders. Moreover, a growing body of literature highlights the importance of neuropeptides in the PFC to modulate neural signaling and to influence behavior. The converging evidence outlined in this review indicates that neuropeptides in the PFC are specifically impacted by stress, and are found to be dysregulated in numerous stress-related neuropsychiatric disorders including substance use disorder, major depressive disorder (MDD), posttraumatic stress disorder, and schizophrenia. This review explores how neuropeptides in the PFC function to regulate the neural activity, and how genetic and environmental factors, such as stress, lead to dysregulation in neuropeptide systems, which may ultimately contribute to the pathology of neuropsychiatric diseases.

Sex difference in cognitive impairment in drug-free schizophrenia: Association with miR-195 levels

OBJECTIVE

There is evidence that microRNA-195 (miR-195) is associated with schizophrenia (SZ) and cognition, but the relationship between miR-195 and cognitive impairment in SZ is still unknown. Sex differences in both microRNA (miRNA) expression and cognition were found in SZ. We aim to investigate whether sex moderates the relationship between miR-195 levels and cognition in SZ.

METHODS

We recruited 121 drug-free SZ patients and 129 healthy controls. miR-195 expression levels in peripheral blood mononuclear cells (PBMCs) were measured using qRT-PCR. The Repeatable Battery for the Assessment of Neuropsychological Status (RBANS) was performed to assess cognitive function. MANCOVA, ANCOVA, correlation analysis and hierarchical linear regression analysis were used to test the effect of sex on the aforementioned variables.

RESULTS

All RBANS scores significantly decreased in patients compared to healthy controls (all p < 0.001); ANCOVA analysis demonstrated female SZ patients had lower delayed memory score (F = 15.36, p < 0.001) and total score (F = 5.26, p = 0.024) than male patients. There was no diagnosis, sex or sex by diagnosis interaction effect on miR-195 levels (all p > 0.05). Interestingly, correlation analysis showed significant negative association between miR-195 and attention score (r = -0.389, p = 0.019), delayed memory score (r= -0.351, p = 0.036), and total score (r = -0.386, p = 0.020) only in female patients. Hierarchical regression analysis showed sex by miR-195 interaction was a significant predictor of the RBANS total score (ΔR2 = 0.042, F(1, 67) = 4.71, p = 0.033).

CONCLUSION

Our data indicate that miR-195 is associated with cognitive impairment in female SZ patients, and it may be involved in the underlying mechanism of sex differences in cognitive impairment in SZ.

Impaired hormonal regulation of appetite in schizophrenia: A narrative review dissecting intrinsic mechanisms and the effects of antipsychotics

Cardiometabolic diseases are the main contributor of reduced life expectancy in patients with schizophrenia. It is now widely accepted that antipsychotic treatment plays an important role in the development of obesity and its consequences. However, some intrinsic mechanisms need to be taken into consideration. One of these mechanisms might be related to impaired hormonal regulation of appetite in this group of patients. In this narrative review, we aimed to dissect impairments of appetite-regulating hormones attributable to intrinsic mechanisms and those related to medication effects. Early hormonal alterations that might be associated with intrinsic mechanisms include low levels of leptin and glucagon-like peptide-1 (GLP-1) together with elevated insulin levels in first-episode psychosis (FEP) patients. However, evidence regarding low GLP-1 levels in FEP patients is based on one large study. In turn, multiple-episode schizophrenia patients show elevated levels of insulin, leptin and orexin A together with decreased levels of adiponectin. In addition, patients receiving olanzapine may present with low ghrelin levels. Post mortem studies have also demonstrated reduced number of neuropeptide Y neurons in the prefrontal cortex of patients with schizophrenia. Treatment with certain second-generation antipsychotics may also point to these alterations. Although our understanding of hormonal regulation of appetite in schizophrenia has largely been improved, several limitations and directions for future studies need to be addressed. This is of particular importance since several novel pharmacological interventions for obesity and diabetes have already been developed and translation of these developments to the treatment of cardiometabolic comorbidities in schizophrenia patients is needed.

Epigenetic mechanisms in schizophrenia and other psychotic disorders: a systematic review of empirical human findings

Schizophrenia and other psychotic disorders are highly debilitating psychiatric conditions that lack a clear etiology and exhibit polygenic inheritance underlain by pleiotropic genes. The prevailing explanation points to the interplay between predisposing genes and environmental exposure. Accumulated evidence suggests that epigenetic regulation of the genome may mediate dynamic gene-environment interactions at the molecular level by modulating the expression of psychiatric phenotypes through transcription factors. This systematic review summarizes the current knowledge linking schizophrenia and other psychotic disorders to epigenetics, based on PubMed and Web of Science database searches conducted according to the PRISMA guidelines. Three groups of mechanisms in case-control studies  of human tissue (i.e., postmortem brain and bio-fluids) were considered: DNA methylation, histone modifications, and non-coding miRNAs. From the initial pool of 3,204 records, 152 studies met our inclusion criteria (11,815/11,528, 233/219, and 2,091/1,827 cases/controls for each group, respectively). Many of the findings revealed associations with epigenetic modulations of genes regulating neurotransmission, neurodevelopment, and immune function, as well as differential miRNA expression (e.g., upregulated miR-34a, miR-7, and miR-181b). Overall, actual evidence moderately supports an association between epigenetics and schizophrenia and other psychotic disorders. However, heterogeneous results and cross-tissue extrapolations call for future work. Integrating epigenetics into systems biology may critically enhance research on psychosis and thus our understanding of the disorder. This may have implications for psychiatry in risk stratification, early recognition, diagnostics, precision medicine, and other interventional approaches targeting epigenetic fingerprints.

Expression of Transcripts Selective for GABA Neuron Subpopulations across the Cortical Visuospatial Working Memory Network in the Healthy State and Schizophrenia

Visuospatial working memory (WM), which is impaired in schizophrenia, depends on a distributed network including visual, posterior parietal, and dorsolateral prefrontal cortical regions. Within each region, information processing is differentially regulated by subsets of γ-aminobutyric acid (GABA) neurons that express parvalbumin (PV), somatostatin (SST), or vasoactive intestinal peptide (VIP). In schizophrenia, WM impairments have been associated with alterations of PV and SST neurons in the dorsolateral prefrontal cortex. Here, we quantified transcripts selectively expressed in GABA neuron subsets across four cortical regions in the WM network from comparison and schizophrenia subjects. In comparison subjects, PV mRNA levels declined and SST mRNA levels increased from posterior to anterior regions, whereas VIP mRNA levels were comparable across regions except for the primary visual cortex (V1). In schizophrenia subjects, each transcript in PV and SST neurons exhibited similar alterations across all regions, whereas transcripts in VIP neurons were unaltered in any region except for V1. These findings suggest that the contribution of each GABA neuron subset to inhibitory regulation of local circuitry normally differs across cortical regions of the visuospatial WM network and that in schizophrenia alterations of PV and SST neurons are a shared feature across these regions, whereas VIP neurons are affected only in V1.

Exosomal secretion of a psychosis-altered miRNA that regulates glutamate receptor expression is affected by antipsychotics

The ability of small secretory microvesicles known as exosomes to influence neuronal and glial function via their microRNA (miRNA) cargo has positioned them as a novel and effective method of cell-to-cell communication. However, little is known about the role of exosome-secreted miRNAs in the regulation of glutamate receptor gene expression and their relevance for schizophrenia (SCZ) and bipolar disorder (BD). Using mature miRNA profiling and quantitative real-time PCR (qRT-PCR) in the orbitofrontal cortex (OFC) of SCZ (N = 29; 20 male and 9 female), BD (N = 26; 12 male and 14 female), and unaffected control (N = 25; 21 male and 4 female) subjects, we uncovered that miR-223, an exosome-secreted miRNA that targets glutamate receptors, was increased at the mature miRNA level in the OFC of SCZ and BD patients with positive history of psychosis at the time of death and was inversely associated with deficits in the expression of its targets glutamate ionotropic receptor NMDA-type subunit 2B (GRIN2B) and glutamate ionotropic receptor AMPA-type subunit 2 (GRIA2). Furthermore, changes in miR-223 levels in the OFC were positively and negatively correlated with inflammatory and GABAergic gene expression, respectively. Moreover, miR-223 was found to be enriched in astrocytes and secreted via exosomes, and antipsychotics were shown to control its cellular and exosomal localization in a cell-specific manner. Furthermore, addition of astrocytic exosomes in neuronal cultures resulted in a significant increase in miR-223 expression and a notable reduction in Grin2b and Gria2 mRNA levels, which was strongly inversely associated with miR-223 expression. Lastly, inhibition of astrocytic miR-223 abrogated the exosomal-mediated reduction in neuronal Grin2b expression. Taken together, our results demonstrate that the exosomal secretion of a psychosis-altered and glial-enriched miRNA that controls neuronal gene expression is regulated by antipsychotics.

Markers of glutamate and GABA neurotransmission in the prefrontal cortex of schizophrenia subjects: Disease effects differ across anatomical levels of resolution

Cognitive dysfunction in individuals with schizophrenia is thought to reflect, at least in part, altered levels of excitatory and inhibitory neurotransmission in the dorsolateral prefrontal cortex (DLPFC). Studies of the postmortem human brain allow for interrogation of the disease-related alterations in markers of excitatory and inhibitory neurotransmission at different levels of anatomical resolution. Here, we re-analyzed six published datasets from postmortem studies of schizophrenia to assess molecular markers of glutamate and GABA neurotransmission in the DLPFC at three levels of anatomical resolution: 1) total cortical gray matter, 2) gray matter restricted to layer 3, and 3) a layer 3 local circuit composed of excitatory pyramidal cells and inhibitory, parvalbumin-containing, GABA neurons. We formulated composite measures of glutamate and GABA neurotransmission from z-scores of key transcripts that regulate these functions. Relative to unaffected comparison subjects, the composite glutamate measure was higher in schizophrenia subjects in total gray matter homogenates but lower in samples restricted to layer 3 or the layer 3 local circuit. The composite index of GABA neurotransmission did not differ between subject groups in total gray matter homogenates but was lower in schizophrenia subjects in layer 3 and lower still in the local layer 3 circuit. These findings suggest that the balance of excitation and inhibition in the DLPFC of schizophrenia subjects differs depending on the level of anatomical resolution studied, highlighting the importance of layer- and cell type-specific studies to understand disease-related alterations in cortical circuitry.