Relevance of interactions between dopamine and glutamate neurotransmission in schizophrenia

Dissecting the shared molecular mechanisms underlying polycystic ovary syndrome and schizophrenia etiology: a translational integrative approach

Recent evidence suggests that individuals with polycystic ovary syndrome (PCOS) have an increased risk of developing mental health disorders and comorbidities linked to nervous system dysfunction. Interestingly, patients with schizophrenia (SCZ) often exhibit PCOS symptoms, indicating a possible connection between the two conditions. However, the underlying molecular links between these diseases remain poorly understood. We employed a comprehensive in-silico approach, utilizing publicly available datasets to investigate shared biomarkers candidates and key regulators involved in the development of PCOS and SCZ. We retrieved the datasets from the NCBI GEO database and differentially expressed genes (DEGs) were identified for each dataset. Common DEGs (cDEGs) were determined, and transcription factors (TFs) and miRNA targeting cDEGs were examined using the mirDIP portal and TRRUST database, respectively. We also assessed the TF-miRNA interactions by TransmiR database and constructed a regulatory network including TFs-microRNAs-cDEGs. Our analysis identified a total of 15 cDEGs that are regulated by 15 TFs and 8 mRNAs. Among our findings, we prioritized RELA as a potential TF regulator for both diseases, demonstrating synergistic interaction with four cDEGs (EGR1, CXCL8, IL1RN, IL1B) and seven microRNAs (hsa-miR-580, hsa-miR-5695, hsa-miR-936, hsa-miR-3675, hsa-miR-634, hsa-miR-603, hsa-miR-222) that target these genes. Our data highlights potential common biomarkers for PCOS and SCZ, presenting a novel regulatory network that elucidates the molecular mechanisms underlying both conditions. This emphasizes the importance of further research to explore new translational approaches, which may ultimately lead to improved diagnostic and therapeutic strategies for affected individuals.

The dopaminergic system and Alzheimer's disease

Alzheimer's disease is a common neurodegenerative disorder in older adults. Despite its prevalence, its pathogenesis remains unclear. In addition to the most widely accepted causes, which include excessive amyloid-beta aggregation, tau hyperphosphorylation, and deficiency of the neurotransmitter acetylcholine, numerous studies have shown that the dopaminergic system is also closely associated with the occurrence and development of this condition. Dopamine is a crucial catecholaminergic neurotransmitter in the human body. Dopamine-associated treatments, such as drugs that target dopamine receptor D and dopamine analogs, can improve cognitive function and alleviate psychiatric symptoms as well as ameliorate other clinical manifestations. However, therapeutics targeting the dopaminergic system are associated with various adverse reactions, such as addiction and exacerbation of cognitive impairment. This review summarizes the role of the dopaminergic system in the pathology of Alzheimer's disease, focusing on currently available dopamine-based therapies for this disorder and the common side effects associated with dopamine-related drugs. The aim of this review is to provide insights into the potential connections between the dopaminergic system and Alzheimer's disease, thus helping to clarify the mechanisms underlying the condition and exploring more effective therapeutic options.

Developing a risk assessment model for treatment-resistant schizophrenia: The role of niacin receptor GPR109A and prostaglandin receptors DP1, EP2, and EP4 in the niacin-induced flushing pathway

Schizophrenia patients show attenuated niacin flush responses compared to healthy controls (HC) attributed to abnormalities in the niacin-induced flushing pathway. Underlying immunological abnormalities may reduce the niacin receptor GPR109A's response and implicated in treatment-resistant schizophrenia (TRS). This pathway involves GPR109A and the downstream vasodilatory prostaglandins (PGs), PGD2 and PGE2, along with their receptors DP1, EP2, and EP4, contributing to vasodilation and neuroprotection. We hypothesized that the niacin receptor GPR109A, PGs, and their receptors play a significant role in the pathogenesis of TRS. We aimed to investigate GPR109A, DP1, PGD2, PGE2, EP2, and EP4 as potential biomarkers for identifying TRS and construct a risk assessment model for TRS. We recruited 58 TRS, 67 NTRS patients, and 115 HC. We observed significant differences in niacin flush responses and expression levels of GPR109A, PGE2, DP1, EP2, and EP4 between the schizophrenia and HC groups. TRS group exhibited lower expression levels of GPR109A, DP1, EP2, and EP4 than NTRS group. Receiver operating characteristic curve analysis combining the six markers for schizophrenia versus HC yielded an area under the curve (AUC) of 0.98, whereas an analysis combining the four markers for TRS versus NTRS yielded an AUC of 0.91. Niacin-induced flushing signaling cascade enrichment is linked to the intensity of the inflammatory response, with associated mediators and their receptor affinities potentially regulating pharmacological effects. These findings suggest that the niacin receptor GPR109A and PG receptors DP1, EP2, and EP4, which are involved in the niacin-induced flushing pathway, may serve as biomarkers for predicting TRS.

Developing algorithmic psychiatry via multi-level spanning computational models

Modern psychiatry faces challenges in translating neurobiological insights into treatments for severe illnesses. The mid-20th century witnessed the rise of molecular mechanisms as pathophysiological and treatment models, with recent holistic proposals keeping this focus unaltered. In this perspective, we explore how psychiatry can utilize systems neuroscience to develop a vertically integrated understanding of brain function to inform treatment. Using schizophrenia as a case study, we discuss scale-related challenges faced by researchers studying molecules, circuits, networks, and cognition and clinicians operating within existing frameworks. We emphasize computation as a bridging language, with algorithmic models like hierarchical predictive processing offering explanatory potential for targeted interventions. Developing such models will not only facilitate new interventions but also optimize combining existing treatments by predicting their multi-level effects. We conclude with the prognosis that the future is bright, but that continued investment in research closely driven by clinical realities will be critical.

Mechanisms of Flame Retardant Toxicity and Their Impacts on Anxiety and Cognition in the Brain

Flame retardants have been used extensively to reduce flammability in household and industrial materials raising significant concerns due to their toxicological effects, particularly on neurodevelopment and cognition. These chemicals, including legacy compounds such as polybrominated diphenyl ethers and newer organophosphate flame retardant, exhibit endocrine-disrupting properties that interfere with hormonal pathways, neurotransmission, and synaptic plasticity. Epidemiological studies have linked flame retardant exposure to adverse developmental outcomes, including anxiety and cognitive deficits. Mechanistic research reveals that flame retardants disrupt neurogenesis, synaptogenesis, and neurotransmitter pathways, often mediated through oxidative stress, mitochondrial dysfunction, and nuclear receptor modulation. Animal studies corroborate these findings, showing impaired spatial memory, altered anxiety-like behaviors, and disrupted neurochemical homeostasis following perinatal and postnatal exposure to flame retardants. Emerging organophosphate flame retardants, such as bis(2-ethylhexyl) phenyl phosphate, demonstrate comparable or increased toxicity, further emphasizing the need for regulatory scrutiny and safer alternatives. This review synthesizes current knowledge on the neurotoxic mechanisms of flame retardants, highlighting their impact on anxiety and cognition across developmental stages. Understanding these pathways is essential to mitigating the long-term environmental and human health effects of flame retardant exposure.

Challenges and Frontiers in Computational Metabolic Psychiatry

One of the primary challenges in metabolic psychiatry is that the disrupted brain functions that underlie psychiatric conditions arise from a complex set of downstream and feedback processes that span multiple spatiotemporal scales. Importantly, the same circuit can have multiple points of failure, each of which results in a different type of dysregulation, and thus elicits distinct cascades downstream that produce divergent signs and symptoms. Here, we illustrate this challenge by examining how subtle differences in circuit perturbations can lead to divergent clinical outcomes. We also discuss how computational models can perform the spatially heterogeneous integration and bridge in vitro and in vivo paradigms. By leveraging recent methodological advances and tools, computational models can integrate relevant processes across scales (e.g., tricarboxylic acid cycle, ion channel, neural microassembly, whole-brain macrocircuit) and across physiological systems (e.g., neural, endocrine, immune, vascular), providing a framework that can unite these mechanistic processes in a manner that goes beyond the conceptual and descriptive to the quantitative and generative. These hold the potential to sharpen our intuitions toward circuit-based models for personalized diagnostics and treatment.

Metabolic dysregulation in glaucoma

Glaucoma is a multifactorial neurodegenerative disorder characterised by the progressive loss of retinal ganglion cells, ultimately leading to irreversible blindness worldwide. Recent research highlights metabolic dysregulation as a crucial factor in the pathophysiology of glaucoma. This review examines the intricate relationship between metabolic processes and glaucoma, with a focus on key mechanisms such as mitochondrial dysfunction, lipid metabolism, glucose metabolism, and the roles of specific metabolites. Mitochondrial dysfunction is commonly observed in glaucoma, leading to impaired energy production that compromises cellular viability. Alterations in lipid metabolism, including changes in fatty acid profiles and lipid peroxidation, contribute to cellular injury and apoptosis of retinal ganglion cells. Moreover, disturbances in glucose metabolism, such as reduced glycolytic activity, affect energy availability and neurotrophic support that are vital for retinal ganglion cells survival. The review also explores the roles of specific metabolites, including lactate and glutamate, in the context of retinal ganglion cells health, and how their dysregulation may exacerbate glaucomatous damage. Additionally, the interplay between metabolic dysregulation and elevated intraocular pressure is analysed, particularly with regard to its impact on ocular blood flow and retinal health. Understanding these metabolic mechanisms is essential for identifying potential therapeutic strategies. By deepening our understanding of the metabolic foundations of glaucoma, new avenues for effective treatments may arise, addressing the multifactorial nature of this complex disease and improving patient outcomes.

Effect of Paliperidone Combined with Sertraline in the Treatment of Schizophrenia and its Influence on Serum Neurofunctional Related Factors

Objective

This study aimed to evaluate the efficacy of paliperidone combined with sertraline in treating schizophrenia (SCZ) and its effect on serum neurofunctional factors.

Methods

A retrospective analysis was conducted on SCZ patients admitted between June 2020 and June 2021. Initially, 80 patients were treated with paliperidone, while 36 received a combination of paliperidone and sertraline. Propensity score matching based on 3 covariates resulted in 2 groups: the control group (paliperidone alone, n = 36) and the observation group (paliperidone + sertraline, n = 36). The clinical efficacy, adverse reactions, quality of life scores, serum biomarkers levels related to nerve and liver function, and anxiety and depression levels were compared between the 2 groups.

Results

The observation group demonstrated higher total effectiveness than the control group (p = 0.011). Post-treatment, the scores of all dimensions of quality of life in both groups were improved, and the observation group was higher than the control group (p < 0.001). Post-treatment, the observation group exhibited lower neuron-specific enolase (NSE) and higher neuregulin 1 (NRG1) levels than the control group (p < 0.001). The levels of aminotransferase (AST), total bilirubin (TBiL) and alanine aminotransferase (ALT) increased in both groups post-treatment (p < 0.001). The levels of tumor necrosis factor-α (TNF-α), interleukin-6 (IL-6), and interleukin-2 (IL-2) decreased in both groups post-treatment, and the observation group had lower levels of these cytokines compared to the control group after treatment (p < 0.001). Post-treatment, Hamilton Anxiety Scale (HAMA) score and Hamilton Depression Scale (HAMD) score decreased in both groups, with the observation group showing lower scores than the control group (p < 0.001). The changes in the scores of various dimensions of quality of life, HAMA and HAMD scores, neurofunctional factors and inflammatory markers levels in the observation group were greater than those in the control group (p < 0.001). There were no serious side effects during and after treatment in both groups.

Conclusions

Paliperidone combined with sertraline effectively improves serum neuregulin levels in SCZ patients, alleviates negative emotional effects without causing liver or kidney damage, and demonstrates excellent clinical efficacy and safety.

Role of Glial Cells and Receptors in Schizophrenia Pathogenesis

The specific pathogeneses of schizophrenia (SCZ) remain an enigma despite extensive research that has implicated both genetic and environmental factors. Recent revelations that dysregulated immune system caused by glial cell overactivation result in neuroinflammation, a key player in neurodegenerative as well as neuropsychiatric disorders including SCZ are providing novel clues on potential therapeutic interventions. Here, we review the roles of glial cells (Dr. Arne Schousboe's passion) and two of their most implicated receptors, toll-like receptors (TLRs), and nicotinic cholinergic receptors, in SCZ pathology with suggestions as potential targets in this devastating neuropsychiatric condition.

Advancement in utilization of magnetic resonance imaging and biomarkers in the understanding of schizophrenia

Historically, psychiatric diagnoses have been made based on patient’s reported symptoms applying the criteria from diagnostic and statistical manual of mental disorders. The utilization of neuroimaging or biomarkers to make the diagnosis and manage psychiatric disorders remains a distant goal. There have been several studies that examine brain imaging in psychiatric disorders, but more work is needed to elucidate the complexities of the human brain. In this editorial, we examine two articles by Xu et al and Stoyanov et al, that show developments in the direction of using neuroimaging to examine the brains of people with schizophrenia and depression. Xu et al used magnetic resonance imaging to examine the brain structure of patients with schizophrenia, in addition to examining neurotransmitter levels as biomarkers. Stoyanov et al used functional magnetic resonance imaging to look at modulation of different neural circuits by diagnostic-specific scales in patients with schizophrenia and depression. These two studies provide crucial evidence in advancing our understanding of the brain in prevalent psychiatric disorders.

Neuron-Derived Extracellular Vesicles miRNA Profiles Identify Children Who Experience Adverse Events after Ketamine Administration for Procedural Sedation

Ketamine provides the highest safety profile among sedatives for procedural sedation and analgesia in the pediatric emergency setting. However, it can cause vomiting and recovery agitation. No studies have examined epigenetic factors, such as microRNAs, for predicting the occurrence of these adverse events. Neuronal-derived extracellular vesicle microRNA profiles were studied to predict the occurrence of ketamine-induced vomiting and recovery agitation in children. For this aim, a single-center prospective pharmacoepigenetic study was performed and 50 children who underwent procedural sedation with intravenous ketamine as the only sedative drug were enrolled between October 2019 and November 2022. MiRNA profiling in plasma neural-derived extracellular vesicles was analyzed through next-generation sequencing and measured before treatment with ketamine. Twenty-two patients experienced vomiting or recovery agitation. Among the 16 differentially expressed microRNAs, the upregulated miR-15a-5p and miR-484 targeted genes related to N-methyl-D-aspartate (NMDA) receptor activity, including glutamate ionotropic receptor NMDA type subunit 2A (GRIN2A). Preliminary data confirmed lower GRIN2A levels in patients who developed these events. Downregulated miR-126-3p and miR-24-3p targeted AMPA receptor-associated genes. Functional analyses of gene targets revealed the enrichment of glutamatergic and neurotrophins signaling. Recovery agitation was associated with this network. Vomiting was related to dopaminergic and cholinergic systems. Three miRNAs (miR-18a-3p, miR-484, and miR-548az-5p) were identified as predictive biomarkers (AUC 0.814; 95% CI: 0.632-0.956) for ketamine-induced vomiting and recovery agitation. MicroRNA profiles can predict the development of ketamine-induced vomiting or recovery agitation in children. This study contributes to the understanding of the mechanisms underlying ketamine-induced adverse events.

Facial expression analysis using convolutional neural network for drug-naive and chronic schizophrenia

OBJECTIVE

Facial images have been shown to convey mental conditions as clinical symptoms. This study aimed to use facial images to detect patients with drug-naive schizophrenia (DN-SCZ) or chronic schizophrenia (C-SCZ) from healthy controls (HCs), and to investigate differences in facial expressions among these 3 groups, as well as relationships between facial expressions and psychiatric symptoms.

METHODS

We recruited 45 DN-SCZ patients, 106 C-SCZ patients and 101 HCs for the study, and videotaped their facial expressions through a fixed experimental paradigm. The video data was converted to facial images and divided into two sets: one for training a group classification-convolutional neural network (CNN) with the classification of DN-SCZ patient, C-SCZ patient and HC as output, and the other for evaluating classification results of the group classification-CNN. Subsequently, we extracted and evaluated 300 labeled facial images for each basic facial expression. These labeled images were employed to train separate facial expression-CNNs for each group (DN-SCZ, C-SCZ, and HCs). All facial images from the videos were then processed by their facial expression-CNNs to output the most probable facial expressions. The psychiatric symptoms were assessed using the Positive and Negative Syndrome Scale. Statistical analyses were conducted on the predicted facial expressions to identify differences among the groups, and to examine relationships between the predicted facial expressions and the clinical data of DN/C-SCZ patients.

RESULTS

The group classification-CNN achieved an accuracy of 90.99% in correctly classifying participants based on facial images. The 3 facial expression-CNNs achieved accuracies of 95.95%, 87.23%, and 92.11% in predicting 8 basic facial expressions within the 3 groups. Facial images of HCs were rated higher in valence, arousal and attractiveness, but lower in deviation from normal face than those of DN/C-SCZ patients. Happy images of DN-SCZ patients were rated lower in valence and arousal than those of C-SCZ patients, while their angry images were rated higher in arousal, attractiveness and deviation from normal images than those of C-SCZ patients. Within the fixed experimental paradigm, DN-SCZ patients exhibited sadder, more surprised expressions, while displaying fewer happy, angry and disgusted expressions, statistical metrics of their fearful and angry expressions were correlated with their total positive symptom score and total general psychopathology score, respectively. C-SCZ patients exhibited happier, more content, angry and neutral expressions, while showing fewer surprised expressions, no significant relationships were observed between their facial expressions and clinical data.

CONCLUSIONS

Facial expressions can potentially serve as indicative signs for detecting DN-SCZ and C-SCZ patients. There are objective differences in certain facial expressions among the 3 groups, and certain facial expressions in DN-SCZ patients are associated with some of their psychiatric symptoms.

Nrf2 and Ferroptosis: Exploring Translational Avenues for Therapeutic Approaches to Neurological Diseases

Nrf2, a crucial protein involved in defense mechanisms, particularly oxidative stress, plays a significant role in neurological diseases (NDs) by reducing oxidative stress and inflammation. NDs, including Alzheimer's, Parkinson's, Huntington's, amyotrophic lateral sclerosis, stroke, epilepsy, schizophrenia, depression, and autism, exhibit ferroptosis, iron-dependent regulated cell death resulting from lipid and iron-dependent reactive oxygen species (ROS) accumulation. Nrf2 has been shown to play a critical role in regulating ferroptosis in NDs. Age-related decline in Nrf2 expression and its target genes (HO-1, Nqo-1, and Trx) coincides with increased iron-mediated cell death, leading to ND onset. The modulation of iron-dependent cell death and ferroptosis by Nrf2 through various cellular and molecular mechanisms offers a potential therapeutic pathway for understanding the pathological processes underlying these NDs. This review emphasizes the mechanistic role of Nrf2 and ferroptosis in multiple NDs, providing valuable insights for future research and therapeutic approaches.

IUPHAR themed review: The gut microbiome in schizophrenia

Gut microbial dysbiosis or altered gut microbial consortium, in schizophrenia suggests a pathogenic role through the gut-brain axis, influencing neuroinflammatory and neurotransmitter pathways critical to psychotic, affective, and cognitive symptoms. Paradoxically, conventional psychotropic interventions may exacerbate this dysbiosis, with antipsychotics, particularly olanzapine, demonstrating profound effects on microbial architecture through disruption of bacterial phyla ratios, diminished taxonomic diversity, and attenuated short-chain fatty acid synthesis. To address these challenges, novel therapeutic strategies targeting the gut microbiome, encompassing probiotic supplementation, prebiotic compounds, faecal microbiota transplantation, and rationalised co-pharmacotherapy, show promise in attenuating antipsychotic-induced metabolic disruptions while enhancing therapeutic efficacy. Harnessing such insights, precision medicine approaches promise to transform antipsychotic prescribing practices by identifying patients at risk of metabolic side effects based on their microbial profiles. This IUPHAR review collates the current literature landscape of the gut-brain axis and its intricate relationship with schizophrenia while advocating for integrating microbiome assessments and therapeutic management. Such a fundamental shift in proposing microbiome-informed psychotropic prescriptions to optimise therapeutic efficacy and reduce adverse metabolic impacts would align antipsychotic treatments with microbiome safety, prioritising 'gut-neutral' or gut-favourable drugs to safeguard long-term patient outcomes in schizophrenia therapy.

Volatile oil from Acori graminei Rhizoma affected the synaptic plasticity of rats with tic disorders by modulating dopaminergic and glutamatergic systems

ETHNOPHARMACOLOGICAL RELEVANCE

Acori graminei Rhizoma is a commonly used traditional Chinese medicine for treating TD, with its main component being calamus volatile oil. Volatile Oil from Acori graminei Rhizoma (VOA)can protect nerve cells and alleviate learning and memory disorders. However, the mechanism of anti-tic of VOA is still unclear.

AIM OF THE STUDY

We aimed to explore the effects of Volatile Oil from Acori Tatarinowii Rhizoma (VOA) on striatal dopaminergic and glutamatergic systems and synaptic plasticity of rats with Tic Disorder (TD), as well as its pharmaceutical mechanism against TD.

MATERIALS AND METHODS

This study involved 48 (three-week-old) Sprague Dawley (SD) rats, which were randomly divided into two primary groups: Control (8) and TD (40). Rats in the TD group were injected intraperitoneally with 3,3-iminodipropionitrile (IDPN) to construct the TD rat model. They were divided into five subgroups: Model, Tiapride, VOA-high, VOA-medium, and VOA-low (N = 8). After modeling, VOA was administrated to rats in the VOA groups through gavage (once/day for four consecutive weeks), while rats in the blank control and model groups received normal saline of the same volume. The animals' behavioral changes were reflected using the stereotypic and motor behavior scores. After interferences, patterns of striatal neurons and the density of dendritic spines were investigated using H&E and Golgi staining, and the ultrastructure of striatal synapses was examined using Transmission Electron Microscopy (TEM). Furthermore, Ca2+ content was determined using the Ca2+ detector, and Dopamine (DA) and Glutamate (GLU) contents in serum and striatum were detected through ELISA. Finally, DRD1, DRD2, AMPAR1, NMPAR1, DAT, VMAT2, CAMKⅡ, and CREB expression in the striatum was detected using Quantitative real-time PCR (qRT-PCR), Western Blotting (WB) and Immunohistochemical (IHC) methods.

RESULTS

Compared to rats in the blank control and model groups, rats in the VOA groups showed lower stereotypic behavior scores. Furthermore, rats in the VOA groups exhibited relieved, neuron damage and increased quantities of neuronal dendrites and dendritic spines Additionally, based on TEM images show that, the VOA groups showed a clear synaptic structure and increased amounts of postsynaptic dense substances and synaptic vesicles. The VOA groups also exhibited reduced Ca2+ contents, and upregulation of DRD1, DRD2, DAT, AMPAR1, and NMPAR1 and downregulation of VMAT-2, CAMKⅡ, and CREB in the striatum.

CONCLUSIONS

In summary, VOA could influence synaptic plasticity by tuning the dopaminergic and glutamatergic systems, thus relieving TD.

Mechanisms of glutamate receptors hypofunction dependent synaptic transmission impairment in the hippocampus of schizophrenia susceptibility gene Opcml-deficient mouse model

Schizophrenia is a severe psychiatric disorder with high heritability, characterized by positive and negative symptoms as well as cognitive abnormalities. Dysfunction in glutamate synapse is strongly implicated in the pathophysiology of schizophrenia. However, the precise role of the perturbed glutamatergic system in contributing to the cognitive abnormalities of schizophrenia at the synaptic level remains largely unknown. Although our previous work found that Opcml promotes spine maturation and Opcml-deficient mice exhibit schizophrenia-related cognitive impairments, the synaptic mechanism remains unclear. By using whole-cell patch clamp recording, we found that decreased neuronal excitability and alterations in intrinsic membrane properties of CA1 PNs in Opcml-deficient mice. Furthermore, Opcml deficiency leads to impaired glutamatergic transmission in hippocampus, which is closely related to postsynaptic AMPA/NMDA receptors dysfunction, resulting in the disturbances of E/I balance. Additionally, we found that the aripiprazole which we used to ameliorate abnormal cognitive behaviors also rescued the impaired glutamatergic transmission in Opcml-deficient mice. These findings will help to understand the synaptic mechanism in schizophrenia pathogenesis, providing insights into schizophrenia therapeutics with glutamatergic disruption.

On the genesis and unique functions of zinc neuromodulation

In addition to the essential structural and catalytic functions of zinc, evolution has adopted synaptic zinc as a neuromodulator. In the brain, synaptic zinc is released primarily from glutamatergic neurons, notably in the neocortex, hippocampus, amygdala, and auditory brainstem. In these brain areas, synaptic zinc is essential for neuronal and sensory processing fine-tuning. But what niche does zinc fill in neural signaling that other neuromodulators do not? Here, we discuss the evolutionary history of zinc as a signaling agent and its eventual adoption as an essential neuromodulator in the mammalian brain. We then attempt to describe the unique roles that zinc has carved out of the vast and diverse landscape of neuromodulators.

Inhibitory neuron links the causal relationship from air pollution to psychiatric disorders: a large multi-omics analysis

Psychiatric disorders are severe health challenges that exert a heavy public burden. Air pollution has been widely reported as related to psychiatric disorder risk, but their casual association and pathological mechanism remained unclear. Herein, we systematically investigated the large genome-wide association studies (6 cohorts with 1,357,645 samples), single-cell RNA (26 samples with 157,488 cells), and bulk-RNAseq (1595 samples) datasets to reveal the genetic causality and biological link between four air pollutants and nine psychiatric disorders. As a result, we identified ten positive genetic correlations between air pollution and psychiatric disorders. Besides, PM2.5 and NO2 presented significant causal effects on schizophrenia risk which was robust with adjustment of potential confounders. Besides, transcriptome-wide association studies identified the shared genes between PM2.5/NO2 and schizophrenia. We then discovered a schizophrenia-derived inhibitory neuron subtype with highly expressed shared genes and abnormal synaptic and metabolic pathways by scRNA analyses and confirmed their abnormal level and correlations with the shared genes in schizophrenia patients in a large RNA-seq cohort. Comprehensively, we discovered robust genetic causality between PM2.5, NO2, and schizophrenia and identified an abnormal inhibitory neuron subtype that links schizophrenia pathology and PM2.5/NO2 exposure. These discoveries highlight the schizophrenia risk under air pollutants exposure and provide novel mechanical insights into schizophrenia pathology, contributing to pollutant-related schizophrenia risk control and therapeutic strategies development.

Graphical Abstract

GPCR-mediated natural products and compounds: Potential therapeutic targets for the treatment of neurological diseases

G protein-coupled receptors (GPCRs), widely expressed in the human central nervous system (CNS), perform numerous physiological functions and play a significant role in the pathogenesis of diseases. Consequently, identifying key therapeutic GPCRs targets for CNS-related diseases is garnering immense interest in research labs and pharmaceutical companies. However, using GPCRs drugs for treating neurodegenerative diseases has limitations, including side effects and uncertain effective time frame. Recognizing the rich history of herbal treatments for neurological disorders like stroke, Alzheimer's disease (AD), and Parkinson's disease (PD), modern pharmacological research is now focusing on the understanding of the efficacy of traditional Chinese medicinal herbs and compounds in modulating GPCRs and treatment of neurodegenerative conditions. This paper will offer a comprehensive, critical review of how certain natural products and compounds target GPCRs to treat neurological diseases. Conducting an in-depth study of herbal remedies and their efficacies against CNS-related disorders through GPCRs targeting will augment our strategies for treating neurological disorders. This will not only broaden our understanding of effective therapeutic methodologies but also identify the root causes of altered GPCRs signaling in the context of pathophysiological mechanisms in neurological diseases. Moreover, it would be informative for the creation of safer and more effective GPCR-mediated drugs, thereby establishing a foundation for future treatment of various neurological diseases.

Role of mitochondria-endoplasmic reticulum contacts in neurodegenerative, neurodevelopmental and neuropsychiatric conditions

Mitochondria-endoplasmic reticulum contacts (MERCs) mediate a close and continuous communication between both organelles that is essential for the transfer of calcium and lipids to mitochondria, necessary for cellular signalling and metabolic pathways. Their structural and molecular characterisation has shown the involvement of many proteins that bridge the membranes of the two organelles and maintain the structural stability and function of these contacts. The crosstalk between the two organelles is fundamental for proper neuronal function and is now recognised as a component of many neurological disorders. In fact, an increasing proportion of MERC proteins take part in the molecular and cellular basis of pathologies affecting the nervous system. Here we review the alterations in MERCs that have been reported for these pathologies, from neurodevelopmental and neuropsychiatric disorders to neurodegenerative diseases. Although mitochondrial abnormalities in these debilitating conditions have been extensively attributed to the high energy demand of neurons, a distinct role for MERCs is emerging as a new field of research. Understanding the molecular details of such alterations may open the way to new paths of therapeutic intervention.

Xanthurenic acid: A role in brain intercellular signaling

Xanthurenic acid (XA) raises a growing multidisciplinary interest based upon its oxidizing properties, its ability to complex certain metal ions, and its detoxifier capacity of 3-hydroxykynurenine (3-HK), its brain precursor. However, little is still known about the role and mechanisms of action of XA in the central nervous system (CNS). Therefore, many research groups have recently investigated XA and its central functions extensively. The present paper critically reviews and discusses all major data related to XA properties and neuronal activities to contribute to the improvement of the current knowledge on XA's central roles and mechanisms of action. In particular, our data showed the existence of a specific G-protein-coupled receptor (GPCR) for XA localized exclusively in brain neurons exhibiting Ca2+-dependent dendritic release and specific electrophysiological responses. XA properties and central activities suggest a role for this compound in brain intercellular signaling. Indeed, XA stimulates cerebral dopamine (DA) release contrary to its structural analog, kynurenic acid (KYNA). Thus, KYNA/XA ratio could be fundamental in the regulation of brain glutamate and DA release. Cerebral XA may also represent an homeostatic signal between the periphery and several brain regions where XA accumulates easily after peripheral administration. Therefore, XA status in certain psychoses or neurodegenerative diseases seems to be reinforced by its brain-specific properties in balance with its formation and peripheral inputs.

The Role of microRNA in Schizophrenia: A Scoping Review

Schizophrenia is a serious mental disease that is regulated by multiple genes and influenced by multiple factors. Due to the complexity of its etiology, the pathogenesis is still unclear. MicroRNAs belong to a class of small non-coding RNAs that are highly conserved in endogenous evolution and play critical roles in multiple biological pathways. In recent years, aberrant miRNA expression has been implicated in schizophrenia, with certain miRNAs emerging as potential diagnostic and prognostic biomarkers for this disorder. In this review, our objective is to investigate the differential expression of miRNAs in schizophrenia, elucidate their potential mechanisms of action, and assess their feasibility as biomarkers. The PubMed electronic database and Google Scholar were searched for the years 2003 to 2024. The study focused on schizophrenia and miRNA as the research topic, encompassing articles related to biomarkers, etiology, action mechanisms, and differentially expressed genes associated with schizophrenia and miRNA. A total of 1488 articles were retrieved, out of which 49 were included in this scope review. This study reviewed 49 articles and identified abnormal expression of miRNA in different tissues of both schizophrenia patients and healthy controls, suggesting its potential role in the pathogenesis and progression of schizophrenia. Notably, several specific miRNAs, including miR-34a, miR-130b, miR-193-3p, miR-675-3p, miR-1262, and miR-218-5p, may serve as promising biological markers for diagnosing schizophrenia. Furthermore, this study summarized potential mechanisms through which miRNAs may contribute to the development of schizophrenia. The studies within the field of miRNA's role in schizophrenia encompass a broad spectrum of focus. Several selected studies have identified dysregulated miRNAs associated with schizophrenia across various tissues, thereby highlighting the potential utility of specific miRNAs as diagnostic biomarkers for this disorder. Various mechanisms underlying dysregulated miRNAs in schizophrenia have been explored; however, further investigations are needed to determine the exact mechanisms by which these dysregulated miRNAs contribute to the pathogenesis of this condition. The exploration of miRNA's involvement in the etiology and identification of biomarkers for schizophrenia holds significant promise in informing future clinical trials and advancing our understanding in this area.

Long-term disruption of tissue levels of glutamate and glutamatergic neurotransmission neuromodulators, taurine and kynurenic acid induced by amphetamine

RATIONALE

Chronic amphetamine (AMPH) use leading to addiction results in adaptive changes within the central nervous system that persist well beyond the drug's elimination from the body and can precipitate relapse. Notably, alterations in glutamatergic neurotransmission play a crucial role in drug-associated behaviours.

OBJECTIVES

This study aimed to identify changes induced by amphetamine in glutamate levels and the neuromodulators of glutamatergic neurotransmission (taurine and kynurenic acid) observable after 14 and 28 days of abstinence in key brain regions implicated in addiction: the cortex (Cx), nucleus accumbens (Acb), and dorsolateral striatum (CPu-L).

METHODS

The rats were administered 12 doses of amphetamine (AMPH) intraperitoneally (i.p.) at 1.5 mg/kg. The behavioural response was evaluated through ultrasonic vocalizations (USV). High-performance liquid chromatography (HPLC) was used to measure the levels of glutamate, taurine, and kynurenic acid in the Cx, Acb, and CPu-L after 14 and 28 days of abstinence.

RESULTS

AMPH administration led to sensitisation towards AMPH's rewarding effects, as evidenced by changes in USV. There was a noticeable decrease in kynurenic acid levels and an increase in both taurine and glutamate in the CPu-L, along with an increase in glutamate levels in the Cx, 28 days following the final AMPH injection.

CONCLUSIONS

The most significant changes in the tissue levels of glutamate, taurine, and kynurenic acid were seen in the CPu-L 28 days after the last dose of AMPH. The emergence of these changes exclusively after 28 days suggests that the processes initiated by AMPH use and subsequent abstinence take time to become apparent and may be enduring. This could contribute to the incubation of craving and the risk of relapse. Developing pharmacological strategies to counteract the reduction in kynurenic acid induced by psychostimulants may provide new avenues for therapy development.

The Underlying Neurobiological Mechanisms of Psychosis: Focus on Neurotransmission Dysregulation, Neuroinflammation, Oxidative Stress, and Mitochondrial Dysfunction

Psychosis, defined as a set of symptoms that results in a distorted sense of reality, is observed in several psychiatric disorders in addition to schizophrenia. This paper reviews the literature relevant to the underlying neurobiology of psychosis. The dopamine hypothesis has been a major influence in the study of the neurochemistry of psychosis and in development of antipsychotic drugs. However, it became clear early on that other factors must be involved in the dysfunction involved in psychosis. In the current review, it is reported how several of these factors, namely dysregulation of neurotransmitters [dopamine, serotonin, glutamate, and γ-aminobutyric acid (GABA)], neuroinflammation, glia (microglia, astrocytes, and oligodendrocytes), the hypothalamic-pituitary-adrenal axis, the gut microbiome, oxidative stress, and mitochondrial dysfunction contribute to psychosis and interact with one another. Research on psychosis has increased knowledge of the complexity of psychotic disorders. Potential new pharmacotherapies, including combinations of drugs (with pre- and probiotics in some cases) affecting several of the factors mentioned above, have been suggested. Similarly, several putative biomarkers, particularly those related to the immune system, have been proposed. Future research on both pharmacotherapy and biomarkers will require better-designed studies conducted on an all stages of psychotic disorders and must consider confounders such as sex differences and comorbidity.

Progress in The Research of Lactate Metabolism Disruption And Astrocyte-Neuron Lactate Shuttle Impairment in Schizophrenia: A Comprehensive Review

Schizophrenia (SCZ) is a complex neuropsychiatric disorder widely recognized for its impaired bioenergy utilization. The astrocyte-neuron lactate shuttle (ANLS) plays a critical role in brain energy supply. Recent studies have revealed abnormal lactate metabolism in SCZ, which is associated with mitochondrial dysfunction, tissue hypoxia, gastric acid retention, oxidative stress, neuroinflammation, abnormal brain iron metabolism, cerebral white matter hypermetabolic activity, and genetic susceptibility. Furthermore, astrocytes, neurons, and glutamate abnormalities are prevalent in SCZ with abnormal lactate metabolism, which are essential components for maintaining ANLS in the brain. Therefore, an in-depth study of the pathophysiological mechanisms of ANLS in SCZ with abnormal lactate metabolism will contribute to a better understanding of the pathogenesis of SCZ and provide new ideas and approaches for the diagnosis and treatment of SCZ.

EEG analysis in patients with schizophrenia based on microstate semantic modeling method

Introduction

Microstate analysis enables the characterization of quasi-stable scalp potential fields on a sub-second timescale, preserving the temporal dynamics of EEG and spatial information of scalp potential distributions. Owing to its capacity to provide comprehensive pathological insights, it has been widely applied in the investigation of schizophrenia (SCZ). Nevertheless, previous research has primarily concentrated on differences in individual microstate temporal characteristics, neglecting potential distinctions in microstate semantic sequences and not fully considering the issue of the universality of microstate templates between SCZ patients and healthy individuals.

Methods

This study introduced a microstate semantic modeling analysis method aimed at schizophrenia recognition. Firstly, microstate templates corresponding to both SCZ patients and healthy individuals were extracted from resting-state EEG data. The introduction of a dual-template strategy makes a difference in the quality of microstate sequences. Quality features of microstate sequences were then extracted from four dimensions: Correlation, Explanation, Residual, and Dispersion. Subsequently, the concept of microstate semantic features was proposed, decomposing the microstate sequence into continuous sub-sequences. Specific semantic sub-sequences were identified by comparing the time parameters of sub-sequences.

Results

The SCZ recognition test was performed on the public dataset for both the quality features and semantic features of microstate sequences, yielding an impressive accuracy of 97.2%. Furthermore, cross-subject experimental validation was conducted, demonstrating that the method proposed in this paper achieves a recognition rate of 96.4% between different subjects.

Discussion

This research offers valuable insights for the clinical diagnosis of schizophrenia. In the future, further studies will seek to augment the sample size to enhance the effectiveness and reliability of this method.

New Therapeutic Targets and Drugs for Schizophrenia Beyond Dopamine D2 Receptor Antagonists

Schizophrenia is a disease with a complex pathological mechanism that is influenced by multiple genes. The study of its pathogenesis is dominated by the dopamine hypothesis, as well as other hypotheses such as the 5-hydroxytryptamine hypothesis, glutamate hypothesis, immune-inflammatory hypothesis, gene expression abnormality hypothesis, and neurodevelopmental abnormality hypothesis. The first generation of antipsychotics was developed based on dopaminergic receptor antagonism, which blocks dopamine D2 receptors in the brain to exert antipsychotic effects. The second generation of antipsychotics acts by dual blockade of 5-hydroxytryptamine and dopamine receptors. From the third generation of antipsychotics onwards, the therapeutic targets for antipsychotic schizophrenia expanded beyond D2 receptor blockade to explore D2 receptor partial agonism and the antipsychotic effects of new targets such as D3, 5-HT1A, 5-HT7, and mGlu2/3 receptors. The main advantages of the second and third generation antipsychotics over first-generation antipsychotics are the reduction of side effects and the improvement of negative symptoms, and even though third-generation antipsychotics do not directly block D2 receptors, the modulation of the dopamine transmitter system is still an important part of their antipsychotic process. According to recent research, several receptors, including 5-hydroxytryptamine, glutamate, γ-aminobutyric acid, acetylcholine receptors and norepinephrine, play a role in the development of schizophrenia. Therefore, the focus of developing new antipsychotic drugs has shifted towards agonism or inhibition of these receptors. Specifically, the development of NMDARs stimulants, GABA receptor agonists, mGlu receptor modulators, cholinergic receptor modulators, 5-HT2C receptor agonists and alpha-2 receptor modulators has become the main direction. Animal experiments have confirmed the antipsychotic effects of these drugs, but their pharmacokinetics and clinical applicability still require further exploration. Research on alternative targets for antipsychotic drugs, beyond the dopamine D2 receptor, has expanded the potential treatment options for schizophrenia and gives an important way to address the challenge of refractory schizophrenia. This article aims to provide a comprehensive overview of the research on therapeutic targets and medications for schizophrenia, offering valuable insights for both treatment and further research in this field.

Metabolomic profiling of ocular tissues in rabbit myopia: Uncovering differential metabolites and pathways

To investigate the metabolic difference among tissue layers of the rabbits' eye during the development of myopia using metabolomic techniques and explore any metabolic links or cascades within the ocular wall. Ultra Performance Liquid Chromatography - Mass Spectrometry (UPLC-MS) was utilized for untargeted metabolite screening (UMS) to identify the significant differential metabolites produced between myopia (MY) and control (CT) (horizontal). Subsequently, we compared those key metabolites among tissues (Sclera, Choroid, Retina) of MY for distribution and variation (longitudinal). A total of 6285 metabolites were detected in the three tissues. The differential metabolites were screened and the metabolic pathways of these metabolites in each myopic tissue were labeled, including tryptophan and its metabolites, pyruvate, taurine, caffeine metabolites, as well as neurotransmitters like glutamate and dopamine. Our study suggests that multiple metabolic pathways or different metabolites under the same pathway, might act on different parts of the eyeball and contribute to the occurrence and development of myopia by affecting the energy supply to the ocular tissues, preventing antioxidant stress, affecting scleral collagen synthesis, and regulating various neurotransmitters mutually.

Association between elevated serum matrix metalloproteinase-2 and tumor necrosis factor-α, and clinical symptoms in male patients with treatment-resistant and chronic medicated schizophrenia

BACKGROUND

Inflammation has an important role in the pathogenesis of schizophrenia. The aim of this study was to investigate the levels of tumor necrosis factor (TNF) and matrix metalloproteinase-2 (MMP-2) in male patients with treatment-resistant schizophrenia (TRS) and chronic medicated schizophrenia (CMS), and the relationship with psychopathology.

METHODS

The study enrolled 31 TRS and 49 cm male patients, and 53 healthy controls. Serum MMP-2 and TNF-α levels were measured by the Luminex liquid suspension chip detection method. Positive and Negative Syndrome Scale (PANSS) scores were used to evaluate symptom severity and Repeatable Battery for the Assessment of Neuropsychological Status was used to assess cognitive function.

RESULTS

Serum TNF-α and MMP-2 levels differed significantly between TRS, CMS and healthy control patients (F = 4.289, P = 0.016; F = 4.682, P = 0.011, respectively). Bonferroni correction demonstrated that serum TNF-α levels were significantly elevated in CMS patients (P = 0.022) and MMP-2 levels were significantly higher in TRS patients (P = 0.014) compared to healthy controls. In TRS patients, TNF-α was negatively correlated with age (r=-0.435, P = 0.015) and age of onset (r=-0.409, P = 0.022). In CMS patients, MMP-2 and TNF-α were negatively correlated with PANSS negative and total scores, and TNF-α was negatively correlated with PANSS general psychopathology scores (all P < 0.05). MMP-2 levels were positively correlated with TNF-α levels (P < 0.05), but not with cognitive function (P > 0.05).

CONCLUSION

The results indicate the involvement of inflammation in the etiology of TRS and CMS. Further studies are warranted.

Schizophrenia in the genetic era: a review from development history, clinical features and genomic research approaches to insights of susceptibility genes

Schizophrenia is a devastating neuropsychiatric disorder affecting 1% of the world population and ranks as one of the disorders providing the most severe burden for society. Schizophrenia etiology remains obscure involving multi-risk factors, such as genetic, environmental, nutritional, and developmental factors. Complex interactions of genetic and environmental factors have been implicated in the etiology of schizophrenia. This review provides an overview of the historical origins, pathophysiological mechanisms, diagnosis, clinical symptoms and corresponding treatment of schizophrenia. In addition, as schizophrenia is a polygenic, genetic disorder caused by the combined action of multiple micro-effective genes, we further detail several approaches, such as candidate gene association study (CGAS) and genome-wide association study (GWAS), which are commonly used in schizophrenia genomics studies. A number of GWASs about schizophrenia have been performed with the hope to identify novel, consistent and influential risk genetic factors. Finally, some schizophrenia susceptibility genes have been identified and reported in recent years and their biological functions are also listed. This review may serve as a summary of past research on schizophrenia genomics and susceptibility genes (NRG1, DISC1, RELN, BDNF, MSI2), which may point the way to future schizophrenia genetics research. In addition, depending on the above discovery of susceptibility genes and their exact function, the development and application of antipsychotic drugs will be promoted in the future.

Preliminary data from a 4-year mirror-image and multicentre study of patients initiating paliperidone palmitate 6-monthly long-acting injectable antipsychotic: the Paliperidone 2 per Year study

Background

Paliperidone palmitate 6-monthly (PP6M) is the first long-acting antipsychotic injectable (LAI) to allow for only two medication administrations per year, though there is presently limited insight into its effectiveness and potential added value in real clinical practice conditions.

Objectives

To present our ongoing study and draw its preliminary data on patient characteristics initiating PP6M and adherence during the first year of treatment.

Methods

The paliperidone 2 per year (P2Y) study is a 4-year, multicentre, prospective mirror-image pragmatic study taking place at over 20 different sites in Europe. The mirror period covers 2 years either side of the PP6M LAI initiation. Retrospective data for the previous 2 years are collected for each patient from the electronic health records. Prospective data are recorded at baseline, 6, 12, 18 and 24 months of drug administration and also cover information on concomitant psychiatric medication, relapses, hospital admissions, side effects, discontinuation and its reasons. Meanwhile, here we present preliminary data from the P2Y study at basal and 6-month period (first and second PP6M administration).

Results

At the point of PP6M initiation, the most frequent diagnosis was schizophrenia (69%), the clinical global impression scale mean score was 3.5 (moderately markedly ill) and the rate of previous hospital admissions per patient and year was 0.21. PP6M was initiated after a median of 3-4 years on previous treatment: 146 (73%) from paliperidone palmitate 3-monthly, 37 (19%) from paliperidone palmitate 1-monthly and 17 (9%) from other antipsychotics. The mean dose of the first PP6M was 1098.9 mg. The retention rate at 6 months and 1 year of treatment on PP6M in our cohort was 94%.

Conclusion

Patient and clinician preference for LAIs with longer dosing intervals was the main reason for PP6M initiation/switching resulting in high treatment persistence. Future data are needed to evaluate the full impact of PP6M in clinical practice.

Trigeminal nerve stimulation: a current state-of-the-art review

Nearly 5 decades ago, the effect of trigeminal nerve stimulation (TNS) on cerebral blood flow was observed for the first time. This implication directly led to further investigations and TNS' success as a therapeutic intervention. Possessing unique connections with key brain and brainstem regions, TNS has been observed to modulate cerebral vasodilation, brain metabolism, cerebral autoregulation, cerebral and systemic inflammation, and the autonomic nervous system. The unique range of effects make it a prime therapeutic modality and have led to its clinical usage in chronic conditions such as migraine, prolonged disorders of consciousness, and depression. This review aims to present a comprehensive overview of TNS research and its broader therapeutic potentialities. For the purpose of this review, PubMed and Google Scholar were searched from inception to August 28, 2023 to identify a total of 89 relevant studies, both clinical and pre-clinical. TNS harnesses the release of vasoactive neuropeptides, modulation of neurotransmission, and direct action upon the autonomic nervous system to generate a suite of powerful multitarget therapeutic effects. While TNS has been applied clinically to chronic pathological conditions, these powerful effects have recently shown great potential in a number of acute/traumatic pathologies. However, there are still key mechanistic and methodologic knowledge gaps to be solved to make TNS a viable therapeutic option in wider clinical settings. These include bimodal or paradoxical effects and mechanisms, questions regarding its safety in acute/traumatic conditions, the development of more selective stimulation methods to avoid potential maladaptive effects, and its connection to the diving reflex, a trigeminally-mediated protective endogenous reflex. The address of these questions could overcome the current limitations and allow TNS to be applied therapeutically to an innumerable number of pathologies, such that it now stands at the precipice of becoming a ground-breaking therapeutic modality.

Nicotine Exposure in a Phencyclidine-Induced Mice Model of Schizophrenia: Sex-Selective Medial Prefrontal Cortex Protein Markers of the Combined Insults in Adolescent Mice

Tobacco misuse as a comorbidity of schizophrenia is frequently established during adolescence. However, comorbidity markers are still missing. Here, the method of label-free proteomics was used to identify deregulated proteins in the medial prefrontal cortex (prelimbic and infralimbic) of male and female mice modelled to schizophrenia with a history of nicotine exposure during adolescence. Phencyclidine (PCP), used to model schizophrenia (SCHZ), was combined with an established model of nicotine minipump infusions (NIC). The combined insults led to worse outcomes than each insult separately when considering the absolute number of deregulated proteins and that of exclusively deregulated ones. Partially shared Reactome pathways between sexes and between PCP, NIC and PCPNIC groups indicate functional overlaps. Distinctively, proteins differentially expressed exclusively in PCPNIC mice reveal unique effects associated with the comorbidity model. Interactome maps of these proteins identified sex-selective subnetworks, within which some proteins stood out: for females, peptidyl-prolyl cis-trans isomerase (Fkbp1a) and heat shock 70 kDa protein 1B (Hspa1b), both components of the oxidative stress subnetwork, and gamma-enolase (Eno2), a component of the energy metabolism subnetwork; and for males, amphiphysin (Amph), a component of the synaptic transmission subnetwork. These are proposed to be further investigated and validated as markers of the combined insult during adolescence.

Pathogenese der Schizophrenie(n)

Schizophrenia is a mental disorder characterized by marked heterogeneity at both the phenomenological and neurobiological levels. Its diagnostic disentanglement would lead to more precise treatment and improved prognosis in people with schizophrenia. For this, a deeper understanding of the pathophysiological mechanisms of schizophrenia is needed.

The genetic basis of onset age in schizophrenia: evidence and models

Schizophrenia is a heritable neurocognitive disorder affecting about 1% of the population, and usually has an onset age at around 21-25 in males and 25-30 in females. Recent advances in genetics have helped to identify many common and rare variants for the liability to schizophrenia. Earlier evidence appeared to suggest that younger onset age is associated with higher genetic liability to schizophrenia. Clinical longitudinal research also found that early and very-early onset schizophrenia are associated with poor clinical, neurocognitive, and functional profiles. A recent study reported a heritability of 0.33 for schizophrenia onset age, but the genetic basis of this trait in schizophrenia remains elusive. In the pre-Genome-Wide Association Study (GWAS) era, genetic loci found to be associated with onset age were seldom replicated. In the post-Genome-Wide Association Study era, new conceptual frameworks are needed to clarify the role of onset age in genetic research in schizophrenia, and to identify its genetic basis. In this review, we first discussed the potential of onset age as a characterizing/subtyping feature for psychosis, and as an important phenotypic dimension of schizophrenia. Second, we reviewed the methods, samples, findings and limitations of previous genetic research on onset age in schizophrenia. Third, we discussed a potential conceptual framework for studying the genetic basis of onset age, as well as the concepts of susceptibility, modifier, and "mixed" genes. Fourth, we discussed the limitations of this review. Lastly, we discussed the potential clinical implications for genetic research of onset age of schizophrenia, and how future research can unveil the potential mechanisms for this trait.

Enhanced L-β-Aminoisobutyric Acid Is Involved in the Pathophysiology of Effectiveness for Treatment-Resistant Schizophrenia and Adverse Reactions of Clozapine

Clozapine is an effective antipsychotic for the treatment of antipsychotic-resistant schizophrenia; however, specific types of A/B adverse effects and clozapine-discontinuation syndromes are also well known. To date, both the critical mechanisms of clinical actions (effective for antipsychotic-resistant schizophrenia) and the adverse effects of clozapine remain to be elucidated. Recently, we demonstrated that clozapine increased the synthesis of L-β-aminoisobutyric acid (L-BAIBA) in the hypothalamus. L-BAIBA is an activator of the adenosine monophosphate-activated protein kinase (AMPK), glycine receptor, GABA_A receptor, and GABA_B receptor (GABA_B-R). These targets of L-BAIBA overlap as potential targets other than the monoamine receptors of clozapine. However, the direct binding of clozapine to these aminoacidic transmitter/modulator receptors remains to be clarified. Therefore, to explore the contribution of increased L-BAIBA on the clinical action of clozapine, this study determined the effects of clozapine and L-BAIBA on tripartite synaptic transmission, including GABA_B-R and the group-III metabotropic glutamate receptor (III-mGluR) using cultured astrocytes, as well as on the thalamocortical hyper-glutamatergic transmission induced by impaired glutamate/NMDA receptors using microdialysis. Clozapine increased astroglial L-BAIBA synthesis in time/concentration-dependent manners. Increased L-BAIBA synthesis was observed until 3 days after clozapine discontinuation. Clozapine did not directly bind III-mGluR or GABA_B-R, whereas L-BAIBA activated these receptors in the astrocytes. Local administration of MK801 into the reticular thalamic nucleus (RTN) increased L-glutamate release in the medial frontal cortex (mPFC) (MK801-evoked L-glutamate release). Local administration of L-BAIBA into the mPFC suppressed MK801-evoked L-glutamate release. These actions of L-BAIBA were inhibited by antagonists of III-mGluR and GABA_B-R, similar to clozapine. These in vitro and in vivo analyses suggest that increased frontal L-BAIBA signaling likely plays an important role in the pharmacological actions of clozapine, such as improving the effectiveness of treating treatment-resistant schizophrenia and several clozapine discontinuation syndromes via the activation of III-mGluR and GABA_B-R in the mPFC.

Targeting the orexin/hypocretin system for the treatment of neuropsychiatric and neurodegenerative diseases: from animal to clinical studies

Orexins (also known as hypocretins) are neuropeptides located exclusively in hypothalamic neurons that have extensive projections throughout the central nervous system and bind two different G protein-coupled receptors (OX1R and OX2R). Since its discovery in 1998, the orexin system has gained the interest of the scientific community as a potential therapeutic target for the treatment of different pathological conditions. Considering previous basic science research, a dual orexin receptor antagonist, suvorexant, was the first orexin agent to be approved by the US Food and Drug Administration to treat insomnia. In this review, we discuss and update the main preclinical and human studies involving the orexin system with several psychiatric and neurodegenerative diseases. This system constitutes a nice example of how basic scientific research driven by curiosity can be the best route to the generation of new and powerful pharmacological treatments.

Dysregulation of AMPA Receptor Trafficking and Intracellular Vesicular Sorting in the Prefrontal Cortex of Dopamine Transporter Knock-Out Rats

Dopamine (DA) and glutamate interact, influencing neural excitability and promoting synaptic plasticity. However, little is known regarding the molecular mechanisms underlying this crosstalk. Since perturbation of DA-AMPA receptor interaction might sustain pathological conditions, the major aim of our work was to evaluate the effect of the hyperactive DA system on the AMPA subunit composition, trafficking, and membrane localization in the prefrontal cortex (PFC). Taking advantage of dopamine transporter knock-out (DAT−/−) rats, we found that DA overactivity reduced the translation of cortical AMPA receptors and their localization at both synaptic and extra-synaptic sites through, at least in part, altered intracellular vesicular sorting. Moreover, the reduced expression of AMPA receptor-specific anchoring proteins and structural markers, such as Neuroligin-1 and nCadherin, likely indicate a pattern of synaptic instability. Overall, these data reveal that a condition of hyperdopaminergia markedly alters the homeostatic plasticity of AMPA receptors, suggesting a general destabilization and depotentiation of the AMPA-mediated glutamatergic neurotransmission in the PFC. This effect might be functionally relevant for disorders characterized by elevated dopaminergic activity.

Integration of reconfigurable microchannels into aligned three-dimensional neural networks for spatially controllable neuromodulation

Anisotropically organized neural networks are indispensable routes for functional connectivity in the brain, which remains largely unknown. While prevailing animal models require additional preparation and stimulation-applying devices and have exhibited limited capabilities regarding localized stimulation, no in vitro platform exists that permits spatiotemporal control of chemo-stimulation in anisotropic three-dimensional (3D) neural networks. We present the integration of microchannels seamlessly into a fibril-aligned 3D scaffold by adapting a single fabrication principle. We investigated the underlying physics of elastic microchannels' ridges and interfacial sol-gel transition of collagen under compression to determine a critical window of geometry and strain. We demonstrated the spatiotemporally resolved neuromodulation in an aligned 3D neural network by local deliveries of KCl and Ca2+ signal inhibitors, such as tetrodotoxin, nifedipine, and mibefradil, and also visualized Ca2+ signal propagation with a speed of ~3.7 μm/s. We anticipate that our technology will pave the way to elucidate functional connectivity and neurological diseases associated with transsynaptic propagation.

The Association of the Oral Microbiota with the Effects of Acid Stress Induced by an Increase of Brain Lactate in Schizophrenia Patients

The altered cerebral energy metabolism central to schizophrenia can be linked to lactate accumulation. Lactic acid is produced by gastrointestinal bacteria, among others, and readily crosses the blood-brain barrier, leading to the brain acidity. This study aimed to examine the association of the oral microbiota with the effects of acid stress induced by an increase of brain lactate in schizophrenia patients. The study included patients with a diagnosis of acute polyphasic psychotic disorder meeting criteria for schizophrenia at 3-month follow-up. Results: Individuals with a significantly higher total score on the Positive and Negative Syndrome Scale had statistically significantly lower lactate concentrations compared to those with a lower total score and higher brain lactate. We observed a positive correlation between Actinomyces and lactate levels in the anterior cingulate cap and a negative correlation between bacteria associated with lactate metabolism and some clinical assessment scales. Conclusions: Shifts in the oral microbiota in favour of lactate-utilising bacterial genera may represent a compensatory mechanism in response to increased lactate production in the brain. Assessment of neuronal function mediated by ALA-LAC-dependent NMDA regulatory mechanisms may, thus, support new therapies for schizophrenia, for which acidosis has become a differentiating feature of individuals with schizophrenia endophenotypes.

Activation of basolateral amygdala to anterior cingulate cortex circuit alleviates MK-801 induced social and cognitive deficits of schizophrenia

Introduction

Schizophrenia is a severe psychiatric disorder with a high prevalence worldwide, however, its pathogenesis remains poorly understood.

Methods and results

In this study, we used the non-competitive NMDA receptor antagonist MK-801 to induce schizophrenia-like behaviors and confirmed that mice exhibited stereotypic rotational behavior and hyperlocomotion, social interaction defects and cognitive dysfunction, similar to the clinical symptoms in patients. Here, the anterior cingulate cortex (ACC) and basolateral amygdala (BLA) were involved in the schizophrenia-like behaviors induced by MK-801. Furthermore, we confirmed BLA sent glutamatergic projection to the ACC. Chemogenetic and optogenetic regulation of BLA-ACC projecting neurons affected social and cognitive deficits but not stereotypic rotational behavior in MK-801-treated mice.

Discussion

Overall, our study revealed that the BLA-ACC circuit plays a major role and may be a potential target for treating schizophrenia-related symptoms.

Rational and Translational Implications of D-Amino Acids for Treatment-Resistant Schizophrenia: From Neurobiology to the Clinics

Schizophrenia has been conceptualized as a neurodevelopmental disorder with synaptic alterations and aberrant cortical–subcortical connections. Antipsychotics are the mainstay of schizophrenia treatment and nearly all share the common feature of dopamine D2 receptor occupancy, whereas glutamatergic abnormalities are not targeted by the presently available therapies. D-amino acids, acting as N-methyl-D-aspartate receptor (NMDAR) modulators, have emerged in the last few years as a potential augmentation strategy in those cases of schizophrenia that do not respond well to antipsychotics, a condition defined as treatment-resistant schizophrenia (TRS), affecting almost 30–40% of patients, and characterized by serious cognitive deficits and functional impairment. In the present systematic review, we address with a direct and reverse translational perspective the efficacy of D-amino acids, including D-serine, D-aspartate, and D-alanine, in poor responders. The impact of these molecules on the synaptic architecture is also considered in the light of dendritic spine changes reported in schizophrenia and antipsychotics’ effect on postsynaptic density proteins. Moreover, we describe compounds targeting D-amino acid oxidase and D-aspartate oxidase enzymes. Finally, other drugs acting at NMDAR and proxy of D-amino acids function, such as D-cycloserine, sarcosine, and glycine, are considered in the light of the clinical burden of TRS, together with other emerging molecules.