Inflammation and the two-hit hypothesis of schizophrenia

Trajectories of working memory and decision making abilities along juvenile development in mice

Rodents commonly serve as model organisms for the investigation of human mental disorders by capitalizing on behavioral commonalities. However, our understanding of the developmental dynamics of complex cognitive abilities in rodents remains incomplete. In this study, we examined spatial working memory as well as odor-and texture-based decision making in mice using a delayed non-match to sample task and a two-choice set-shifting task, respectively. Mice were investigated during different stages of development: pre-juvenile, juvenile, and young adult age. We show that, while working memory abilities in mice improve with age, decision making performance peaks during juvenile age by showing a sex-independent trajectory. Moreover, cFos expression, as a first proxy for neuronal activity, shows distinct age-and brain area-specific changes that relate to task-specific behavioral performance. The distinct developmental trajectories of working memory and decision making in rodents resemble those previously reported for humans.

Lights and shadows of clozapine on the immune system in schizophrenia: a narrative literature review

Schizophrenia is a chronic mental disorder and one of the main causes of disability in the world. Approximately 1% of the general population suffers from this disorder, and almost 30% of cases are unresponsive to antipsychotic therapies. Clozapine is a Food and Drug Administration (FDA)-approved antipsychotic drug for treatment-resistant schizophrenia (TRS). Clozapine is also approved for the prevention of suicide associated with schizophrenia. However, clozapine is not the preferred first-line medication because of its potential AEs, including agranulocytosis, metabolic syndromes, and myocarditis. Clozapine prescription requires weekly absolute neutrophil count (ANC) monitoring for the first six months, followed by biweekly monitoring until the patient has finished one year of treatment. Several psychiatric disorders have been reported to be associated with inflammatory biomarkers. Dysregulation of the immune system and the elevation of pro-inflammatory cytokines were also reported to be associated with schizophrenia, highlighting the necessity of further research into the etiology of the disease and the relationship between the immune system and clozapine-responsiveness to support better management of symptoms and potential AEs. In this framework, we searched PubMed using the medical subject headings (MeSH) terms "clozapine", "antipsychotics", "schizophrenia", "treatment-resistant schizophrenia", "immune system", "inflammation", "neuroinflammation", "biomarker", "cytokine", and "chemokine" with the aim of overview the impact of clozapine on the immune system in individuals with treatment-responsive and treatment-resistant schizophrenia.

The Balance in the Head: How Developmental Factors Explain Relationships Between Brain Asymmetries and Mental Diseases

Cerebral lateralisation is a core organising principle of the brain that is characterised by a complex pattern of hemispheric specialisations and interhemispheric interactions. In various mental disorders, functional and/or structural hemispheric asymmetries are changed compared to healthy controls, and these alterations may contribute to the primary symptoms and cognitive impairments of a specific disorder. Since multiple genetic and epigenetic factors influence both the pathogenesis of mental illness and the development of brain asymmetries, it is likely that the neural developmental pathways overlap or are even causally intertwined, although the timing, magnitude, and direction of interactions may vary depending on the specific disorder. However, the underlying developmental steps and neuronal mechanisms are still unclear. In this review article, we briefly summarise what we know about structural, functional, and developmental relationships and outline hypothetical connections, which could be investigated in appropriate animal models. Altered cerebral asymmetries may causally contribute to the development of the structural and/or functional features of a disorder, as neural mechanisms that trigger neuropathogenesis are embedded in the asymmetrical organisation of the developing brain. Therefore, the occurrence and severity of impairments in neural processing and cognition probably cannot be understood independently of the development of the lateralised organisation of intra- and interhemispheric neuronal networks. Conversely, impaired cellular processes can also hinder favourable asymmetry development and lead to cognitive deficits in particular.

Peering into the mind: unraveling schizophrenia's secrets using models

Schizophrenia (SCZ) is a complex mental disorder characterized by a range of symptoms, including positive and negative symptoms, as well as cognitive impairments. Despite the extensive research, the underlying neurobiology of SCZ remain elusive. To overcome this challenge, the use of diverse laboratory modeling techniques, encompassing cellular and animal models, and innovative approaches like induced pluripotent stem cell (iPSC)-derived neuronal cultures or brain organoids and genetically engineered animal models, has been crucial. Immortalized cellular models provide controlled environments for investigating the molecular and neurochemical pathways involved in neuronal function, while iPSCs and brain organoids, derived from patient-specific sources, offer significant advantage in translational research by facilitating direct comparisons of cellular phenotypes between patient-derived neurons and healthy-control neurons. Animal models can recapitulate the different psychopathological aspects that should be modeled, offering valuable insights into the neurobiology of SCZ. In addition, invertebrates' models are genetically tractable and offer a powerful approach to dissect the core genetic underpinnings of SCZ, while vertebrate models, especially mammals, with their more complex nervous systems and behavioral repertoire, provide a closer approximation of the human condition to study SCZ-related traits. This narrative review provides a comprehensive overview of the diverse modeling approaches, critically evaluating their strengths and limitations. By synthesizing knowledge from these models, this review offers a valuable source for researchers, clinicians, and stakeholders alike. Integrating findings across these different models may allow us to build a more holistic picture of SCZ pathophysiology, facilitating the exploration of new research avenues and informed decision-making for interventions.

Blood-Brain Barrier Disruption in Schizophrenia: Insights, Mechanisms, and Future Directions

The blood-brain barrier (BBB) plays a crucial role in maintaining the homeostasis of the central nervous system by regulating solute transport and preventing neurotoxic substances from infiltrating brain tissue. In schizophrenia, emerging evidence identifies BBB dysfunction as a key pathophysiological factor associated with neuroinflammation, tight junction abnormalities, and endothelial dysfunction. Recent advancements in neuroimaging techniques, such as arterial spin labeling (ASL), have provided valuable tools for investigating BBB permeability and its role in disease progression. This review synthesizes findings from postmortem studies, serum and cerebrospinal fluid biomarker analyses, and advanced neuroimaging research to elucidate BBB alterations in schizophrenia. It highlights the mechanistic roles of tight junction protein dysregulation, neurovascular unit dysfunction, and immune responses in disrupting BBB integrity. Furthermore, the review examines the bidirectional effects of antipsychotic medications on BBB, addressing both therapeutic opportunities and potential challenges. By emphasizing the pivotal role of BBB dysfunction in schizophrenia pathogenesis, this review underscores its translational potential. Through the integration of multidisciplinary evidence, it lays the foundation for innovative diagnostic approaches and therapeutic strategies, enhancing our understanding of schizophrenia's complex pathophysiology.

Schizophrenia and Bone Marrow Disorders: An Emerging Clinical Association

Schizophrenia is a chronic psychiatric disorder with a complex etiology involving genetic, neurobiological, and environmental factors. Many individuals with schizophrenia experience treatment resistance despite advances in pharmacologic and non-pharmacologic interventions. Immune dysregulation, characterized by altered cytokine levels, immune-related gene expression, and neuroinflammation, plays a critical role in schizophrenia's pathogenesis. Furthermore, associations between schizophrenia and bone marrow malignancies, with documentation of remission of treatment-resistant schizophrenia following bone marrow transplantation for malignancies, are emerging. This review synthesizes findings on the immunological underpinnings of schizophrenia, explores potential connections with bone marrow dysfunction, and evaluates the therapeutic potential of immune-modulating approaches, including bone marrow transplantation. By highlighting these connections, the study aims to advance understanding and stimulate prospective research into innovative treatments for this debilitating condition.

Maternal Immune Activation and the Endocannabinoid System: Focus on Two-Hit Models of Schizophrenia

The devastating effects of the COVID-19 pandemic have underscored the significant threat that infectious diseases pose to our society. Pregnancy represents a period of heightened vulnerability to infections, which can compromise maternal health and increase the risk of neurodevelopmental disorders in offspring. Preclinical and clinical investigations suggest a potential association between maternal immune activation (MIA), which is triggered by viral or bacterial infections, and increased risk for neurodevelopmental disorders such as autism and schizophrenia. Genetic and environmental factors may contribute to the overall risk. Therefore, the two-hit hypothesis of schizophrenia suggests that MIA could act as a first trigger, with subsequent factors, such as stress or drug abuse, exacerbating latent abnormalities. A growing body of research is focused on the interaction between MIA and cannabis use during adolescence, considering the role of the endocannabinoid (eCB) system in neurodevelopment and in neurodevelopmental disorders. The eCB system, crucial for fetal brain development, may be disrupted by MIA, leading to adverse outcomes in adulthood. Recent research indicates the eCB system's significant role in the pathophysiology of neurodevelopmental disorders in preclinical models. However, findings on adolescent cannabinoid exposure in MIA-exposed animals have revealed unexpected complexities, with several studies failing to support the exacerbation of MIA-related abnormalities. In this review, we delve into the functional implications of the eCB system in MIA models, emphasizing the role of 2-AG (2-arachidonoylglycerol) signaling in synaptic plasticity and neuroinflammation and its relevance to the two-hit model of schizophrenia.

Brain metabolic profiling of schizophrenia: a path towards a better understanding of the neuropathogenesis of psychosis

Schizophrenia (SCZ) is a complex psychotic syndrome whose pathogenesis involves countless protagonists, none of which, to date, can fully explain how this disorder develops. In this narrative review, an overview of the biochemical impairment is offered according to several perspectives. Indeed, the metabolic framework behind SCZ dopaminergic hypotheses, glutamate - gamma-amynobutyric acid dysregulation, norepinephrine and serotonin, calcium channel dysfunction is addressed together with the energetic impairment, involving glucose and lipids in SCZ etiopathogenesis, in order to highlight the multilevel pathways affected in this neuropsychiatric disorder. Furthermore, neuroinflammation is analyzed, by virtue of its important role, widely investigated in recent years, in neurodegeneration. Tracing the neurotransmitter activity at the brain level by assessing the metabolic network behind the abovementioned molecules puts into light as unavoidable the need for future studies to adopt an integrate approach to address SCZ pathological and clinical picture. The combination of all these factors, essential in acquiring an overview on the complexity of SCZ pathophysiology represents a crucial step in the development of a more targeted management of SCZ patients.

The effect of clozapine on immune-related biomarkers in schizophrenia patients

Globally, schizophrenia is one of the main causes of disability. Approximately 1 % of the general population suffers from schizophrenia, and 30 % of cases are unresponsive to therapy. Clozapine is the gold standard for therapy-resistant schizophrenia (TRS), yet it has limited effectiveness and serious adverse events in some patients. Because of the possibility of severe neutropenia, clozapine administration requires monthly hematological monitoring in the first four months. Previous investigations have demonstrated the immune system alteration after clozapine treatment in schizophrenia patients. Besides, it has been proposed that clozapine changes the cytokines profile in schizophrenia patients. These findings highlighted the need to learn more about the disease's etiology and investigate the relationship between peripheral immune system markers and clozapine response to support strategies for better treatment outcomes. The time decision-making to start clozapine could be significantly decreased if some biomarkers were developed to assist physicians in anticipating whether a particular patient will respond to the medication. Therefore, this study aimed to comprehensively review the effect of clozapine on immune-related biomarkers in schizophrenia patients.

Development of Prefrontal Circuits and Cognitive Abilities

The prefrontal cortex is considered as the site of multifaceted higher-order cognitive abilities. These abilities emerge late in life long after full sensorimotor maturation, in line with the protracted development of prefrontal circuits that has been identified on molecular, structural, and functional levels. Only recently, as a result of the impressive methodological progress of the last several decades, the mechanisms and clinical implications of prefrontal development have begun to be elucidated, yet major knowledge gaps still persist. Here, we provide an overview on how prefrontal circuits develop to enable multifaceted cognitive processing at adulthood. First, we review recent insights into the mechanisms of prefrontal circuit assembly, with a focus on the contribution of early electrical activity. Second, we highlight the major reorganization of prefrontal circuits during adolescence. Finally, we link the prefrontal plasticity during specific developmental time windows to mental health disorders and discuss potential approaches for therapeutic interventions.

Schizophrenia and Rheumatoid Arthritis Genetic Scenery: Potential Non-HLA Genes Involved in Both Diseases Relationship

Background: The link between rheumatoid arthritis (RA) and schizophrenia (SZ) has long been a hot topic of deliberation among scientists from various fields. Especially when it comes to genetics, the connection between RA and SZ is still up for discussion, as can be observed in this study. The HLA genes are the most disputed in identifying a connection between the two diseases, but a more thorough investigation of other genes that may be ignored could yield something even more interesting. Thus, finding the genes responsible for this long-sought relationship will necessitate looking for them. Materials and Methods: Shared and overlapped associated genes involved between SZ and RA were extracted from four databases. The overlapping genes were examined using Database for Annotation, Visualization and Integrated Discovery (DAVID) and InnateDB to search the pertinent genes that concatenate between these two disorders. Results: A total of 91 overlapped genes were discovered, and that 13 genes, divided into two clusters, showed a similarity in function, suggesting that they may serve as an important meeting point. FCGR2A, IL18R, BTNL2, AGER, and CTLA4 are five non-HLA genes related to the immune system, which could lead to new discoveries about the connection between these two disorders. Conclusion: An in-depth investigation of these functionally comparable non-HLA genes that overlap could reveal new interesting information in both diseases. Understanding the molecular and immune-related aspects of RA and SZ may shed light on their etiology and inform future research on targeted treatment strategies.

Introducing neurofilament light chain measure in psychiatry: current evidence, opportunities, and pitfalls

The recent introduction of new-generation immunoassay methods allows the reliable quantification of structural brain markers in peripheral matrices. Neurofilament light chain (NfL), a neuron-specific cytoskeletal component released in extracellular matrices after neuroaxonal impairment, is considered a promising blood marker of active brain pathology. Given its sensitivity to a wide range of neuropathological alterations, NfL has been suggested for the use in clinical practice as a highly sensitive, but unspecific tool to quantify active brain pathology. While large efforts have been put in characterizing its clinical profile in many neurological conditions, NfL has received far less attention as a potential biomarker in major psychiatric disorders. Therefore, we briefly introduce NfL as a marker of neuroaxonal injury, systematically review recent findings on cerebrospinal fluid and blood NfL levels in patients with primary psychiatric conditions and highlight the opportunities and pitfalls. Current evidence suggests an elevation of blood NfL levels in patients with major depression, bipolar disorder, psychotic disorders, anorexia nervosa, and substance use disorders compared to physiological states. However, blood NfL levels strongly vary across diagnostic entities, clinical stage, and patient subgroups, and are influenced by several demographic, clinical, and analytical factors, which require accurate characterization. Potential clinical applications of NfL measure in psychiatry are seen in diagnostic and prognostic algorithms, to exclude neurodegenerative disease, in the assessment of brain toxicity for different pharmacological compounds, and in the longitudinal monitoring of treatment response. The high inter-individual variability of NfL levels and the lack of neurobiological understanding of its release are some of the main current limitations. Overall, this primer aims to introduce researchers and clinicians to NfL measure in the psychiatric field and to provide a conceptual framework for future research directions.

Development of an anti-inflammatory diet for first-episode psychosis (FEP): a feasibility study protocol

Background

Evidence suggests inflammation plays a role in the pathophysiology of psychosis even in early illness, indicating a potential avenue for anti-inflammatory interventions that simultaneously address high rates of metabolic disease in this population. The aim of this study is to design a novel anti-inflammatory diet intervention (DI) that is feasible to implement in a first-episode psychosis (FEP) population.

Methods

Eligible FEP Participants are aged 15-30. The DI is currently being refined through a multi-phase process that includes the recruitment of focus groups that provide insight into feasibility of measures and nutritional education, as well as the implementation of the DI. The phases in the study are the Development Phase, Formative Phase, and the Feasibility Phase.

Results

The Development phase has resulted in the creation of a flexible DI for FEP based on existing research on nutritional health and informed by providers. This study has just completed the Formative phase, recruiting eligible participants to join focus groups that gleaned information about dietary habits, preferences, and food environments to further refine the DI.

Conclusion

Findings from earlier phases have advised the current Feasibility Phase in which this novel DI is being administered to a small cohort of FEP participants (N = 12) to determine acceptability of the DI from a lived experience perspective. Naturalistic changes in inflammatory biomarkers, metabolic health, and symptoms will also be measured.

Advances in the study of phencyclidine-induced schizophrenia-like animal models and the underlying neural mechanisms

Schizophrenia (SZ) is a chronic, severe mental disorder with heterogeneous clinical manifestations and unknown etiology. Research on SZ has long been limited by the low reliability of and ambiguous pathogenesis in schizophrenia animal models. Phencyclidine (PCP), a noncompetitive N-methyl-D-aspartate receptor (NMDAR) antagonist, rapidly induces both positive and negative symptoms of SZ as well as stable SZ-related cognitive impairment in rodents. However, the neural mechanism underlying PCP-induced SZ-like symptoms is not fully understood. Nondopaminergic pathophysiology, particularly excessive glutamate release induced by NMDAR hypofunction in the prefrontal cortex (PFC), may play a key role in the development of PCP-induced SZ-like symptoms. In this review, we summarize studies on the behavioral and metabolic effects of PCP and the cellular and circuitary targets of PCP in the PFC and hippocampus (HIP). PCP is thought to target the ventral HIP-PFC pathway more strongly than the PFC-VTA pathway and thalamocortical pathway. Systemic PCP administration might preferentially inhibit gamma-aminobutyric acid (GABA) neurons in the vHIP and in turn lead to hippocampal pyramidal cell disinhibition. Excitatory inputs from the HIP may trigger sustained, excessive and pathological PFC pyramidal neuron activation to mediate various SZ-like symptoms. In addition, astrocyte and microglial activation and oxidative stress in the cerebral cortex or hippocampus have been observed in PCP-induced models of SZ. These findings perfect the hypoglutamatergic hypothesis of schizophrenia. However, whether these effects direct the consequences of PCP administration and how about the relationships between these changes induced by PCP remain further elucidation through rigorous, causal and direct experimental evidence.

Mutual effects of gestational diabetes and schizophrenia: how can one promote the other?: A review

Although the physical complications of gestational diabetes mellitus (GDM) are well known, emerging evidence suggests a significant link with psychiatric conditions such as schizophrenia (SCZ). This review aimed to explore the extent, nature, and implications of the association between GDM and SCZ, exploring how the 2 conditions may reciprocally influence each other. We conducted a comprehensive literature review and, analyzed clinical and mechanistic evidence supporting the mutual effects of GDM and SCZ. This review examined factors such as neurodevelopment and the impact of antipsychotics. The study found that Maternal GDM increases the risk of SCZ in offspring. Conversely, women with SCZ were more prone to hyperglycemic pregnancies. The research highlights significant regional variations in GDM prevalence, with the highest rate in the Middle East, North Africa, and South-East Asia regions. These regional variations may have an impact on the epidemiology of SCZ. Furthermore, this review identifies the potential biological and environmental mechanisms underlying these associations. There is a bidirectional relationship between GDM and SCZ, with each disorder potentially exacerbating the others. This relationship has significant implications for maternal and offspring health, particularly in regions with high GDM prevalence. These findings underline the need for integrated care approaches for women with SCZ during pregnancy and the importance of monitoring and managing GDM to mitigate the risk of SCZ in the offspring. Notably, this study recognizes the need for further research to fully understand these complex interactions and their implications for healthcare.

Prenatal Immune Challenge Differentiates the Effect of Aripiprazole and Risperidone on CD200-CD200R and CX3CL1-CX3CR1 Dyads and Microglial Polarization: A Study in Organotypic Cortical Cultures

Microglia are the primary innate immune cells of the central nervous system and extensively contribute to brain homeostasis. Dysfunctional or excessive activity of microglia may be associated with several neuropsychiatric disorders, including schizophrenia. Therefore, we examined whether aripiprazole and risperidone could influence the expression of the Cd200-Cd200r and Cx3cl1-Cx3cr1 axes, which are crucial for the regulation of microglial activity and interactions of these cells with neurons. Additionally, we evaluated the impact of these drugs on microglial pro- and anti-inflammatory markers (Cd40, Il-1β, Il-6, Cebpb, Cd206, Arg1, Il-10 and Tgf-β) and cytokine release (IL-6, IL-10). The research was executed in organotypic cortical cultures (OCCs) prepared from the offspring of control rats (control OCCs) or those exposed to maternal immune activation (MIA OCCs), which allows for the exploration of schizophrenia-like disturbances in animals. All experiments were performed under basal conditions and after additional stimulation with lipopolysaccharide (LPS), following the "two-hit" hypothesis of schizophrenia. We found that MIA diminished the mRNA level of Cd200r and affected the OCCs' response to additional LPS exposure in terms of this parameter. LPS downregulated the Cx3cr1 expression and profoundly changed the mRNA levels of pro- and anti-inflammatory microglial markers in both types of OCCs. Risperidone increased Cd200 expression in MIA OCCs, while aripiprazole treatment elevated the gene levels of the Cx3cl1-Cx3cr1 dyad in control OCCs. The antipsychotics limited the LPS-generated increase in the expression of proinflammatory factors (Il-1β and Il-6) and enhanced the mRNA levels of anti-inflammatory components (Cd206 and Tgf-β) of microglial polarization, mostly in the absence of the MIA procedure. Finally, we observed a more pronounced modulating impact of aripiprazole on the expression of pro- and anti-inflammatory cytokines when compared to risperidone in MIA OCCs. In conclusion, our data suggest that MIA might influence microglial activation and crosstalk of microglial cells with neurons, whereas aripiprazole and risperidone could beneficially affect these changes in OCCs.

Establishment of a two-hit mouse model of environmental factor induced autism spectrum disorder

Autism spectrum disorder (ASD) is a group of developmental diseases characterized by social dysfunction and repetitive stereotype behaviors. Besides genetic mutations, environmental factors play important roles in the development of ASD. Valproic acid (VPA) is widely used for modeling environmental factor induced ASD in rodents. However, traditional VPA modeling is low-in-efficiency and the phenotypes often vary among different batches of experiments. To optimize this ASD-modeling method, we tested "two-hit" hypothesis by single or double exposure of VPA and poly:IC at the critical time points of embryonic and postnatal stage. The autistic-like behaviors of mice treated with two-hit schemes (embryonic VPA plus postnatal poly:IC, embryonic poly:IC plus postnatal VPA, embryonic VPA plus poly: IC, or postnatal VPA plus poly:IC) were compared with mice treated with traditional VPA protocol. The results showed that all single-hit and two-hit schemes produced core ASD phenotypes as VPA single treatment did. Only one group, namely, mice double-hit by VPA and poly:IC simultaneously at E12.5 showed severe impairment of social preference, social interaction and ultrasonic communication, as well as significant increase of grooming activity and anxiety-like behaviors, in comparation with mice treated with the traditional VPA protocol. These data demonstrated that embryonic two-hit of VPA and poly:IC is more efficient in producing ASD phenotypes in mice than the single-hit of VPA, indicating this two-hit scheme could be utilized for modeling environmental factors induced ASD.

TNF receptor 2 knockout mouse had reduced lung cancer growth and schizophrenia-like behavior through a decrease in TrkB-dependent BDNF level

The relationship between schizophrenia (SCZ) and cancer development remains controversial. Based on the disease-gene association platform, it has been revealed that tumor necrosis factor receptor (TNFR) could be an important mediatory factor in both cancer and SCZ development. TNF-α also increases the expression of brain-derived neurotrophic factor (BDNF) and tropomyosin receptor kinase B (TrkB) in the development of SCZ and tumor, but the role of TNFR in mediating the association between the two diseases remains unclear. We studied the vital roles of TNFR2 in the progression of tumor and SCZ-like behavior using A549 lung cancer cell xenografted TNFR2 knockout mice. TNFR2 knockout mice showed significantly decreased tumor size and weight as well as schizophrenia-like behaviors compared to wild-type mice. Consistent with the reduced tumor growth and SCZ-like behaviors, the levels of TrkB and BDNF expression were significantly decreased in the lung tumor tissues and pre-frontal cortex of TNFR2 knockout mice. However, intravenous injection of BDNF (160 μg/kg) to TNFR2 knockout mice for 4 weeks increased tumor growth and SCZ-like behaviors as well as TrkB expression. In in vitro study, significantly decreased cell growth and expression of TrkB and BDNF by siTNFR2 transfection were found in A549 lung cancer cells. However, the addition of BDNF (100 ng/ml) into TNFR2 siRNA transfected A549 lung cancer cells recovered cell growth and the expression of TrkB. These results suggest that TNFR2 could be an important factor in mediating the comorbidity between lung tumor growth and SCZ development through increased TrkB-dependent BDNF levels.

Investigating the structural network underlying brain-immune interactions using combined histopathology and neuroimaging: a critical review for its relevance in acute and long COVID-19

Current views on immunity support the idea that immunity extends beyond defense functions and is tightly intertwined with several other fields of biology such as virology, microbiology, physiology and ecology. It is also critical for our understanding of autoimmunity and cancer, two topics of great biological relevance and for critical public health considerations such as disease prevention and treatment. Central to this review, the immune system is known to interact intimately with the nervous system and has been recently hypothesized to be involved not only in autonomic and limbic bio-behaviors but also in cognitive function. Herein we review the structural architecture of the brain network involved in immune response. Furthermore, we elaborate upon the implications of inflammatory processes affecting brain-immune interactions as reported recently in pathological conditions due to SARS-Cov-2 virus infection, namely in acute and post-acute COVID-19. Moreover, we discuss how current neuroimaging techniques combined with ad hoc clinical autopsies and histopathological analyses could critically affect the validity of clinical translation in studies of human brain-immune interactions using neuroimaging. Advances in our understanding of brain-immune interactions are expected to translate into novel therapeutic avenues in a vast array of domains including cancer, autoimmune diseases or viral infections such as in acute and post-acute or Long COVID-19.

Clustering Schizophrenia Genes by Their Temporal Expression Patterns Aids Functional Interpretation

BACKGROUND

Schizophrenia is a highly heritable brain disorder with a typical symptom onset in early adulthood. The 2-hit hypothesis posits that schizophrenia results from differential early neurodevelopment, predisposing an individual, followed by a disruption of later brain maturational processes that trigger the onset of symptoms.

STUDY DESIGN

We applied hierarchical clustering to transcription levels of 345 genes previously linked to schizophrenia, derived from cortical tissue samples from 56 donors across the lifespan. We subsequently calculated clustered-specific polygenic risk scores for 743 individuals with schizophrenia and 743 sex- and age-matched healthy controls.

STUDY RESULTS

Clustering revealed a set of 183 genes that was significantly upregulated prenatally and downregulated postnatally and 162 genes that showed the opposite pattern. The prenatally upregulated set of genes was functionally annotated to fundamental cell cycle processes, while the postnatally upregulated set was associated with the immune system and neuronal communication. We found an interaction between the 2 scores; higher prenatal polygenic risk showed a stronger association with schizophrenia diagnosis at higher levels of postnatal polygenic risk. Importantly, this finding was replicated in an independent clinical cohort of 3233 individuals.

CONCLUSIONS

We provide genetics-based evidence that schizophrenia is shaped by disruptions of separable biological processes acting at distinct phases of neurodevelopment. The modeling of genetic risk factors that moderate each other's effect, informed by the timing of their expression, will aid in a better understanding of the development of schizophrenia.

Microglial activation in the lateral amygdala promotes anxiety-like behaviors in mice with chronic moderate noise exposure

BACKGROUND

Long-term non-traumatic noise exposure, such as heavy traffic noise, can elicit emotional disorders in humans. However, the underlying neural substrate is still poorly understood.

METHODS

We exposed mice to moderate white noise for 28 days to induce anxiety-like behaviors, measured by open-field, elevated plus maze, and light-dark box tests. In vivo multi-electrode recordings in awake mice were used to examine neuronal activity. Chemogenetics were used to silence specific brain regions. Viral tracing, immunofluorescence, and confocal imaging were applied to define the neural circuit and characterize the morphology of microglia.

RESULTS

Exposure to moderate noise for 28 days at an 85-dB sound pressure level resulted in anxiety-like behaviors in open-field, elevated plus maze, and light-dark box tests. Viral tracing revealed that fibers projecting from the auditory cortex and auditory thalamus terminate in the lateral amygdala (LA). A noise-induced increase in spontaneous firing rates of the LA and blockade of noise-evoked anxiety-like behaviors by chemogenetic inhibition of LA glutamatergic neurons together confirmed that the LA plays a critical role in noise-induced anxiety. Noise-exposed animals were more vulnerable to anxiety induced by acute noise stressors than control mice. In addition to these behavioral abnormalities, ionized calcium-binding adaptor molecule 1 (Iba-1)-positive microglia in the LA underwent corresponding morphological modifications, including reduced process length and branching and increased soma size following noise exposure. Treatment with minocycline to suppress microglia inhibited noise-associated changes in microglial morphology, neuronal electrophysiological activity, and behavioral changes. Furthermore, microglia-mediated synaptic phagocytosis favored inhibitory synapses, which can cause an imbalance between excitation and inhibition, leading to anxiety-like behaviors.

CONCLUSIONS

Our study identifies LA microglial activation as a critical mediator of noise-induced anxiety-like behaviors, leading to neuronal and behavioral changes through selective synapse phagocytosis. Our results highlight the pivotal but previously unrecognized roles of LA microglia in chronic moderate noise-induced behavioral changes.

Parkinson's disease and schizophrenia interactomes contain temporally distinct gene clusters underlying comorbid mechanisms and unique disease processes

Genome-wide association studies suggest significant overlaps in Parkinson's disease (PD) and schizophrenia (SZ) risks, but the underlying mechanisms remain elusive. The protein-protein interaction network ('interactome') plays a crucial role in PD and SZ and can incorporate their spatiotemporal specificities. Therefore, to study the linked biology of PD and SZ, we compiled PD- and SZ-associated genes from the DisGeNET database, and constructed their interactomes using BioGRID and HPRD. We examined the interactomes using clustering and enrichment analyses, in conjunction with the transcriptomic data of 26 brain regions spanning foetal stages to adulthood available in the BrainSpan Atlas. PD and SZ interactomes formed four gene clusters with distinct temporal identities (Disease Gene Networks or 'DGNs'1-4). DGN1 had unique SZ interactome genes highly expressed across developmental stages, corresponding to a neurodevelopmental SZ subtype. DGN2, containing unique SZ interactome genes expressed from early infancy to adulthood, correlated with an inflammation-driven SZ subtype and adult SZ risk. DGN3 contained unique PD interactome genes expressed in late infancy, early and late childhood, and adulthood, and involved in mitochondrial pathways. DGN4, containing prenatally-expressed genes common to both the interactomes, involved in stem cell pluripotency and overlapping with the interactome of 22q11 deletion syndrome (comorbid psychosis and Parkinsonism), potentially regulates neurodevelopmental mechanisms in PD-SZ comorbidity. Our findings suggest that disrupted neurodevelopment (regulated by DGN4) could expose risk windows in PD and SZ, later elevating disease risk through inflammation (DGN2). Alternatively, variant clustering in DGNs may produce disease subtypes, e.g., PD-SZ comorbidity with DGN4, and early/late-onset SZ with DGN1/DGN2.

Temporal changes of gene expression in health, schizophrenia, bipolar disorder, and major depressive disorder

The molecular events underlying the development, manifestation, and course of schizophrenia, bipolar disorder, and major depressive disorder span from embryonic life to advanced age. However, little is known about the early dynamics of gene expression in these disorders due to their relatively late manifestation. To address this, we conducted a secondary analysis of post-mortem prefrontal cortex datasets using bioinformatics and machine learning techniques to identify differentially expressed gene modules associated with aging and the diseases, determine their time-perturbation points, and assess enrichment with expression quantitative trait loci (eQTL) genes. Our findings revealed early, mid, and late deregulation of expression of functional gene modules involved in neurodevelopment, plasticity, homeostasis, and immune response. This supports the hypothesis that multiple hits throughout life contribute to disease manifestation rather than a single early-life event. Moreover, the time-perturbed functional gene modules were associated with genetic loci affecting gene expression, highlighting the role of genetic factors in gene expression dynamics and the development of disease phenotypes. Our findings emphasize the importance of investigating time-dependent perturbations in gene expression before the age of onset in elucidating the molecular mechanisms of psychiatric disorders.

Genetic evidence for causal effects of immune dysfunction in psychiatric disorders: where are we?

The question of whether immune dysfunction contributes to risk of psychiatric disorders has long been a subject of interest. To assert this hypothesis a plethora of correlative evidence has been accumulated from the past decades; however, a variety of technical and practical obstacles impeded on a cause-effect interpretation of these data. With the advent of large-scale omics technology and advanced statistical models, particularly Mendelian randomization, new studies testing this old hypothesis are accruing. Here we synthesize these new findings from genomics and genetic causal inference studies on the role of immune dysfunction in major psychiatric disorders and reconcile these new data with pre-omics findings. By reconciling these evidences, we aim to identify key gaps and propose directions for future studies in the field.

Metalloproteinases as Biomarkers and Sociomarkers in Human Health and Disease

Metalloproteinases (MPs) are zinc-dependent enzymes with proteolytic activity and a variety of functions in the pathophysiology of human diseases. The main objectives of this review are to analyze a specific family of MPs, the matrix metalloproteinases (MMPs), in the most common chronic and complex diseases that affect patients' social lives and to better understand the nature of the associations between MMPs and the psychosocial environment. In accordance with the PRISMA extension for a scoping review, an examination was carried out. A collection of 24 studies was analyzed, focusing on the molecular mechanisms of MMP and their connection to the manifestation of social aspects in human disease. The complexity of the relationship between MMP and social problems is presented via an interdisciplinary approach based on complexity paradigm as a new approach for conceptualizing knowledge in health research. Finally, two implications emerge from the study: first, the psychosocial states of individuals have a profound impact on their overall health and disease conditions, which implies the importance of adopting a holistic perspective on human well-being, encompassing both physical and psychosocial aspects. Second, the use of MPs as biomarkers may provide physicians with valuable tools for a better understanding of disease when used in conjunction with "sociomarkers" to develop mathematical predictive models.

Differential regulation of innate immune system in frontal cortex and hippocampus in a "double-hit" neurodevelopmental model in rats

Neurodevelopmental disorders (NDs) are neuropsychiatric conditions affecting central nervous system development, characterized by cognitive and behavioural alterations. Inflammation has been recently linked to NDs. Animal models are essential for understanding their pathophysiology and identifying therapeutic targets. Double-hit models can reproduce neurodevelopmental and neuroinflammatory impairments. Sixty-seven newborn rats were assigned to four groups: Control, Maternal deprivation (MD, 24-h-deprivation), Isolation (Iso, 5 weeks), and Maternal deprivation ​+ ​Isolation (MD ​+ ​Iso, also known as double-hit). Cognitive dysfunction was assessed using behavioural tests. Inflammasome, MAPKs, and TLRs inflammatory elements expression in the frontal cortex (FC) and hippocampus (HP) was analysed through western blot and qRT-PCR. Oxidative/nitrosative (O/N) evaluation and corticosterone levels were measured in plasma samples. Double-hit group was affected in executive and working memory. Most inflammasomes and TLRs inflammatory responses were increased in FC compared to the control group, whilst MAPKs were downregulated. Conversely, hippocampal inflammasome and inflammatory components were reduced after the double-hit exposure, while MAPKs were elevated. Our findings reveal differential regulation of innate immune system components in FC and HP in the double-hit group. Further investigations on MAPKs are necessary to understand their role in regulating HP neuroinflammatory status, potentially linking our MAPKs results to cognitive impairments through their proliferative and anti-inflammatory activity.

Aripiprazole Attenuates Cognitive Impairments Induced by Lipopolysaccharide in Rats through the Regulation of Neuronal Inflammation, Oxidative Stress, and Apoptosis

Background and Objectives: Aripiprazole (APZ), an atypical antipsychotic, is mainly prescribed for conditions such as schizophrenia and bipolar disorder, while ongoing research indicates promising neuroprotective qualities. APZ's mechanism of action, involving the regulation of neurotransmitter levels, appears to contribute to its potential to shield neural tissues from specific forms of harm and degeneration. Materials and Methods: To investigate its neuroprotective mechanisms, groups of rats were orally administered APZ at 1 or 2 mg/kg once daily for a 30-day period. In addition, neuronal toxicity was induced through intraperitoneal injection of four doses of lipopolysaccharide (LPS) at a concentration of 1 mg/kg. To evaluate cognitive function, particularly, short-term recognition memory, the procedure implemented the novel object recognition (NOR) task. Subsequently, brain tissues were gathered to examine markers linked with neuroinflammation, oxidative stress, and apoptosis. Results: The administration of LPS led to a decline in memory performance during the NOR tasks. Simultaneously, this LPS treatment raised inflammatory markers like cyclooxygenase (COX)-2, tumor necrosis factor (TNF)-α, and nuclear factor kappa B (NF-κB), increased oxidative markers such as malondialdehyde (MDA), and triggered apoptosis markers like Caspase-3 and Bcl2 associated X protein (Bax) within the brain. Furthermore, it decreased levels of antioxidants like reduced glutathione (GSH) and catalase, as well as the anti-apoptotic marker B-cell lymphoma (Bcl)-2 in brain tissue. The use of APZ resulted in enhanced recognition memory performance, as indicated by improved exploration and discrimination abilities of the objects in the NOR task. Moreover, APZ lowered the markers associated with neuronal vulnerability, such as COX-2, NF-κB, MDA, Caspase-3, and Bax. Additionally, it increased the levels of protective markers, including GSH, catalase, and Bcl-2 in LPS-challenged brains. Conclusions: In summary, the findings suggest that APZ exhibits protective properties against neuronal inflammation, oxidative stress, and apoptosis markers in the context of inflammatory-related neurodegeneration. Additional in-depth investigations are needed to further explore potential applications.

Toll-Like Receptor (TLR) 1, 2, and 6 Gene Polymorphisms Support Evidence of Innate Immune Factors in Schizophrenia

Introduction

Schizophrenia is a complex psychiatric disorder with an important genetic contribution. Immunological abnormalities have been reported in schizophrenia. Toll-like receptor (TLR) genes play an important role in the activation of the innate immune response, which may help to explain the presence of inflammation in people with this disorder. The aim of this study was to analyze the association of TLR1, TLR2, and TLR6 gene polymorphisms in the etiology of schizophrenia.

Methods

We included 582 patients with schizophrenia and 525 healthy controls. Genetic analysis was performed using allelic discrimination with TaqMan probes.

Results

We observed significant differences between patients and controls in the genotype and allele frequencies of TLR1/rs4833093 (χ2 = 17.3, p = 0.0002; χ2 = 15.9, p = 0.0001, respectively) and TLR2/rs5743709 (χ2 = 29.5, p = 0.00001; χ2 = 7.785, p = 0.0053, respectively), and in the allele frequencies of TLR6/rs3775073 (χ2 = 31.1, p = 0.00001). Finally, we found an interaction between the TLR1/rs4833093 and TLR2/rs5743709 genes, which increased the risk of developing schizophrenia (OR = 2.29, 95% CI [1.75, 3.01]).

Discussion

Our findings add to the evidence suggesting that the activation of innate immune response might play an important role in the development of schizophrenia.

Examination of the role of adrenergic receptor stimulation in the sensitization of neuroinflammatory-based depressive-like behavior in isolated Guinea pig pups

Early-life attachment disruption appears to sensitize neuroinflammatory signaling to increase later vulnerability for stress-related mental disorders, including depression. How stress initiates this process is unknown, but studies with adult rats and mice suggest sympathetic nervous system activation and/or cortisol elevations during the early stress are key. Guinea pig pups isolated from their mothers exhibit an initial active behavioral phase characterized by anxiety-like vocalizing. This is followed by inflammatory-dependent depressive-like behavior and fever that sensitize on repeated isolation. Using strategies that have been successful in adult studies, we assessed whether sympathetic nervous system activity and cortisol contributed to the sensitization process in guinea pig pups. In Experiment 1, the adrenergic agonist ephedrine (3 or 10 mg/kg), either alone or with cortisol (2.5 mg/kg), did not increase depressive-like behavior or fever during initial isolation the following day as might have been expected to if this stimulation was sufficient to account for the sensitization process. In Experiment 2, both depressive-like behavior and fever sensitized with repeated isolation, but beta-adrenergic receptor blockade with propranolol (10 or 20 mg/kg) did not affect either of these responses or their sensitization. The high dose of propranolol did, however, reduce vocalizing. These results suggest sympathetic nervous system activation is neither necessary nor sufficient to induce the presumptive neuroinflammatory signaling underlying sensitization of depressive-like behavioral or febrile responses in developing guinea pigs. Thus, processes mediating sensitization of neuroinflammatory-based depressive-like behavior following early-life attachment disruption in this model appear to differ from those previously found to underlie neuroinflammatory priming in adults.

The neural, stress hormone and inflammatory correlates of childhood deprivation and threat in psychosis: A systematic review

Childhood adversity increases the risk of developing psychosis, but the biological mechanisms involved are unknown. Disaggregating early adverse experiences into core dimensions of deprivation and threat may help to elucidate these mechanisms. We therefore systematically searched the literature investigating associations between deprivation and threat, and neural, immune and stress hormone systems in individuals on the psychosis spectrum. Our search yielded 74 articles, from which we extracted and synthesized relevant findings. While study designs were heterogeneous and findings inconsistent, some trends emerged. In psychosis, deprivation tended to correlate with lower global cortical volume, and some evidence supported threat-related variation in prefrontal cortex morphology. Greater threat exposure was also associated with higher C-reactive protein, and higher and lower cortisol measures. When examined, associations in controls were less evident. Overall, findings indicate that deprivation and threat may associate with partially distinct biological mechanisms in the psychosis spectrum, and that associations may be stronger than in controls. Dimensional approaches may help disentangle the biological correlates of childhood adversity in psychosis, but more studies are needed.

The anti-viral immune response of the adult host robustly modulates neural stem cell activity in spatial, temporal, and sex-specific manners

Viruses induce a wide range of neurological sequelae through the dysfunction and death of infected cells and persistent inflammation in the brain. Neural stem cells (NSCs) are often disturbed during viral infections. Although some viruses directly infect and kill NSCs, the antiviral immune response may also indirectly affect NSCs. To better understand how NSCs are influenced by a productive immune response, where the virus is successfully resolved and the host survives, we used the CD46+ mouse model of neuron-restricted measles virus (MeV) infection. As NSCs are spared from direct infection in this model, they serve as bystanders to the antiviral immune response initiated by selective infection of mature neurons. MeV-infected mice showed distinct regional and temporal changes in NSCs in the primary neurogenic niches of the brain, the hippocampus and subventricular zone (SVZ). Hippocampal NSCs increased throughout the infection (7 and 60 days post-infection; dpi), while mature neurons transiently declined at 7 dpi and then rebounded to basal levels by 60 dpi. In the SVZ, NSC numbers were unchanged, but mature neurons declined even after the infection was controlled at 60 dpi. Further analyses demonstrated sex, temporal, and region-specific changes in NSC proliferation and neurogenesis throughout the infection. A relatively long-term increase in NSC proliferation and neurogenesis was observed in the hippocampus; however, neurogenesis was reduced in the SVZ. This decline in SVZ neurogenesis was associated with increased immature neurons in the olfactory bulb in female, but not male mice, suggesting potential migration of newly-made neurons out of the female SVZ. These sex differences in SVZ neurogenesis were accompanied by higher infiltration of B cells and greater expression of interferon-gamma and interleukin-6 in female mice. Learning, memory, and olfaction tests revealed no overt behavioral changes after the acute infection subsided. These results indicate that antiviral immunity modulates NSC activity in adult mice without inducing gross behavioral deficits among those tested, suggestive of mechanisms to restore neurons and maintain adaptive behavior, but also revealing the potential for robust NSC disruption in subclinical infections.

Modeling psychotic disorders: Environment x environment interaction

Schizophrenia is a major psychotic disorder with multifactorial etiology that includes interactions between genetic vulnerability and environmental risk factors. In addition, interplay of multiple environmental adversities affects neurodevelopment and may increase the individual risk of developing schizophrenia. Consistent with the two-hit hypothesis of schizophrenia, we review rodent models that combine maternal immune activation as the first hit with other adverse environmental exposures as the second hit. We discuss the strengths and pitfalls of the current animal models of environment x environment interplay and propose some future directions to advance the field.

Early-life stress contributes to depression-like behaviors in a two-hit mouse model

BACKGROUND

Depression is a common psychological disorder with pathogenesis involving genetic and environmental interactions. Early life stress can adversely affect physical and emotional development and dramatically increase the risk for the development of depression and anxiety disorders.

METHODS

To examine potential early life stress driving risk for anxiety and depression, we used a two-hit developmental stress model，injecting poly(I: C) into neonatal mice on P2-P6 followed by peripubertal unpredictable stress in adolescence.

RESULTS

Our study shows that early-life and adolescent stress leads to anxiety and depression-related behavioral phenotypes in male mice. Early-life stress exacerbated depression-like behavior in mice following peripubertal unpredictable stress. We confirmed that early life stress might be involved in the decreased neuronal activity in the medial prefrontal cortex (mPFC) and might be involved in shaping behavioral phenotypes of animals. We found that increased microglia and neuroinflammation in the mPFC of two-hit mice and early life stress further boost microglia activation and inflammatory factors in the mPFC region of mice following adolescent stress.

LIMITATIONS

The specific neural circuits and mechanisms by which microglia regulate depression-like behaviors require further investigation.

CONCLUSIONS

Our findings provide a novel insight into developmental risk factors and biological mechanisms in depression and anxiety disorders.

Building Predictive Models for Schizophrenia Diagnosis with Peripheral Inflammatory Biomarkers

Machine learning and artificial intelligence technologies are known to be a convenient tool for analyzing multi-domain data in precision psychiatry. In the case of schizophrenia, the most commonly used data sources for such purposes are neuroimaging, voice and language patterns, and mobile phone data. Data on peripheral markers can also be useful for building predictive models. Here, we have developed five predictive models for the binary classification of schizophrenia patients and healthy individuals. Data on serum concentrations of cytokines, chemokines, growth factors, and age were among 38 parameters used to build these models. The sample consisted of 217 schizophrenia patients and 90 healthy individuals. The models architecture was involved logistic regression, deep neural networks, decision trees, support vector machine, and k-nearest neighbors algorithms. It was shown that the algorithm based on a deep neural network (consisting of five layers) showed a slightly higher sensitivity (0.87 ± 0.04) and specificity (0.52 ± 0.06) than other algorithms. Combining all variables into a single classifier showed a cumulative effect that exceeded the effectiveness of individual variables, indicating the need to use multiple biomarkers to diagnose schizophrenia. Thus, the data obtained showed the promise of using data on peripheral biomarkers and machine learning methods for diagnosing schizophrenia.

Systemic inflammation and cortical neurochemistry in never-medicated first episode-psychosis individuals

Studies of cellular and cytokine profiles have contributed to the inflammation hypothesis of schizophrenia; however, precise markers of inflammatory dysfunction remain elusive. A number of proton magnetic resonance spectroscopy (1H-MRS) studies in patients with first-episode psychosis (FEP) have shown higher brain levels of metabolites such as glutamate, myo-inositol (mI) and choline-containing compounds (tCho), suggesting neuroinflammation. Here, we present peripheral inflammatory profiles in antipsychotic-naive FEP patients and age-and-sex matched healthy controls, as well as cortical glutamate, mI and tCho levels using 1H-MRS. Inflammatory profiles were analyzed using cytokine production by peripheral blood mononuclear cells, that were either spontaneous or stimulated, in 48 FEP patients and 23 controls. 1H-MRS of the medial prefrontal cortex was obtained in 29 FEP patients and 18 controls. Finally, 16 FEP patients were rescanned after 4 weeks of treatment (open-label) with Risperidone. FEP patients showed a higher proportion of proinflammatory Th1/Th17 subset, and an increased spontaneous production of Interleukin (IL)-6, IL-2 and IL-4 compared with the control group. Results obtained from 1H-MRS showed no significant difference in either glutamate, mI or tCho between FEP and control groups. At baseline, CD8% showed a negative correlation with glutamate in FEP patients; after 4 weeks of risperidone treatment, the FEP group exhibited a decrease in glutamate levels which positively correlated with CD4 + T cells. Nevertheless, these correlations did not survive correction for multiple comparisons. FEP patients show evidence of immune dysregulation, affecting both the innate and adaptive immune response, with a predominantly Th2 signature. These findings, along with the changes produced by antipsychotic treatment, could be associated with both systemic and central inflammatory processes in schizophrenia.

Maternal immune activation and role of placenta in the prenatal programming of neurodevelopmental disorders

Maternal infection during pregnancy, leading to maternal immune activation (mIA) and cytokine release, increases the offspring risk of developing a variety of neurodevelopmental disorders (NDDs), including schizophrenia. Animal models have provided evidence to support these mechanistic links, with placental inflammatory responses and dysregulation of placental function implicated. This leads to changes in fetal brain cytokine balance and altered epigenetic regulation of key neurodevelopmental pathways. The prenatal timing of such mIA-evoked changes, and the accompanying fetal developmental responses to an altered in utero environment, will determine the scope of the impacts on neurodevelopmental processes. Such dysregulation can impart enduring neuropathological changes, which manifest subsequently in the postnatal period as altered neurodevelopmental behaviours in the offspring. Hence, elucidation of the functional changes that occur at the molecular level in the placenta is vital in improving our understanding of the mechanisms that underlie the pathogenesis of NDDs. This has notable relevance to the recent COVID-19 pandemic, where inflammatory responses in the placenta to SARS-CoV-2 infection during pregnancy and NDDs in early childhood have been reported. This review presents an integrated overview of these collective topics and describes the possible contribution of prenatal programming through placental effects as an underlying mechanism that links to NDD risk, underpinned by altered epigenetic regulation of neurodevelopmental pathways.

Mitochondrial Dysfunction, Altered Mitochondrial Oxygen, and Energy Metabolism Associated with the Pathogenesis of Schizophrenia

The significant complexity of the brain can lead to the development of serious neuropsychiatric disorders, including schizophrenia. A number of mechanisms are involved in the etiopathogenesis of schizophrenia, pointing to its complexity and opening a new perspective on studying this disorder. In this review of currently published studies, we focused on the contribution of mitochondria to the process, with an emphasis on oxidative damage, ROS, and energy metabolism. In addition, we point out the influence of redox imbalance, which can lead to the occurrence of oxidative stress with increased lipid peroxidation, linked to the formation of toxic aldehydes such as 4-hydroxynonenal (4-HNE) and HNE protein adducts. We also analysed the role of lactate in the process of energy metabolism and cognitive functions in schizophrenia.

A preliminary choroid plexus volumetric study in individuals with psychosis

The choroid plexus (ChP) is part of the blood-cerebrospinal fluid barrier, regulating brain homeostasis and the brain's response to peripheral events. Its upregulation and enlargement are considered essential in psychosis. However, the timing of the ChP enlargement has not been established. This study introduces a novel magnetic resonance imaging-based segmentation method to examine ChP volumes in two cohorts of individuals with psychosis. The first sample consists of 41 individuals with early course psychosis (mean duration of illness = 1.78 years) and 30 healthy individuals. The second sample consists of 30 individuals with chronic psychosis (mean duration of illness = 7.96 years) and 34 healthy individuals. We utilized manual segmentation to measure ChP volumes. We applied ANCOVAs to compare normalized ChP volumes between groups and partial correlations to investigate the relationship between ChP, LV volumes, and clinical characteristics. Our segmentation demonstrated good reliability (.87). We further showed a significant ChP volume increase in early psychosis (left: p < .00010, right: p < .00010) and a significant positive correlation between higher ChP and higher LV volumes in chronic psychosis (left: r = .54, p = .0030, right: r = .68; p < .0010). Our study suggests that ChP enlargement may be a marker of acute response around disease onset. It might also play a modulatory role in the chronic enlargement of lateral ventricles, often reported in psychosis. Future longitudinal studies should investigate the dynamics of ChP enlargement as a promising marker for novel therapeutic strategies.

Oxidative Stress Biomarkers among Schizophrenia Inpatients

Background. Finding the associations between schizophrenia symptoms and the biomarkers of inflammation, oxidative stress and the kynurenine pathway may lead to the individualization of treatment and increase its effectiveness. Methods. The study group included 82 schizophrenia inpatients. The Positive and Negative Symptoms Scale (PANSS), the Brief Assessment of Cognition in Schizophrenia (BACS) and the Calgary Depression in Schizophrenia Scale were used for symptom evaluation. Biochemical analyses included oxidative stress parameters and brain-derived neurotrophic factor (BDNF). Results. Linear models revealed the following: (1) malondiadehyde (MDA), N-formylkynurenine (N-formKYN), advanced oxidation protein products (AOPP), advanced glycation end-products of proteins (AGE) and total oxidative status (TOS) levels are related to the PANSS-total score; (2) MDA, reduced glutathione (GSH) and BDNF levels are related to the PANSS-negative score; (3) TOS and kynurenine (KYN) levels are related to the PANSS-positive score; (4) levels of total antioxidant status (TAS) and AOPP along with the CDSS score are related to the BACS-total score; (5) TAS and N-formKYN levels are related to the BACS-working memory score. Conclusions. Oxidative stress biomarkers may be associated with the severity of schizophrenia symptoms in positive, negative and cognitive dimensions. The identification of biochemical markers associated with the specific symptom clusters may increase the understanding of biochemical profiles in schizophrenia patients.

The Effects of Peripubertal THC Exposure in Neurodevelopmental Rat Models of Psychopathology

Adolescent exposure to cannabinoids as a postnatal environmental insult may increase the risk of psychosis in subjects exposed to perinatal insult, as suggested by the two-hit hypothesis of schizophrenia. Here, we hypothesized that peripubertal Δ⁹-tetrahydrocannabinol (aTHC) may affect the impact of prenatal methylazoxymethanol acetate (MAM) or perinatal THC (pTHC) exposure in adult rats. We found that MAM and pTHC-exposed rats, when compared to the control group (CNT), were characterized by adult phenotype relevant to schizophrenia, including social withdrawal and cognitive impairment, as revealed by social interaction test and novel object recognition test, respectively. At the molecular level, we observed an increase in cannabinoid CB1 receptor (Cnr1) and/or dopamine D2/D3 receptor (Drd2, Drd3) gene expression in the prefrontal cortex of adult MAM or pTHC-exposed rats, which we attributed to changes in DNA methylation at key regulatory gene regions. Interestingly, aTHC treatment significantly impaired social behavior, but not cognitive performance in CNT groups. In pTHC rats, aTHC did not exacerbate the altered phenotype nor dopaminergic signaling, while it reversed cognitive deficit in MAM rats by modulating Drd2 and Drd3 gene expression. In conclusion, our results suggest that the effects of peripubertal THC exposure may depend on individual differences related to dopaminergic neurotransmission.

Ethyl Acetate Fraction of Harpagophytum procumbens Prevents Oxidative Stress In Vitro and Amphetamine-Induced Alterations in Mice Behavior

Microglial activation has been associated to the physiopathology of neurodegenerative diseases, such as schizophrenia, and can occur during inflammation and oxidative stress. Pharmacological treatment is associated with severe side effects, and studies for use of plant extracts may offer alternatives with lower toxicity. Harpagophytum procumbens (HP) is a plant known for its anti-inflammatory properties. In the present study, we characterized the ethyl acetate fraction of HP (EAF HP) by ESI-ToF-MS and investigated the effects EAF HP in a lipopolysaccharide (LPS) induced inflammation model on microglial cells (BV-2 lineage). MTT (3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide), DCFH-DA (2',7'-dichlorofluorescein diacetate) and cell cycle flow cytometer analysis were performed. In vivo was investigated the amphetamine-induced psychosis model through behavioral (locomotor and exploratory activities, stereotypies and working memory) and biochemical (DCFH-DA oxidation and protein thiols) parameters in cortex and striatum of mice. EAF HP reduced activation and proliferation of microglial cells in 48 h (300 µg/mL) and in 72 h after treatments (50-500 µg/mL). Reactive oxygen species levels were lower at the concentration of 100 µg/mL EAF HP. We detected a modulatory effect on the cell cycle, with reduction of cells in S and G2/M phases. In mice, the pre-treatment with EAF HP, for 7 days, protected against positive and cognitive symptoms, as well as stereotypies induced by amphetamine. No oxidative stress was observed in this amphetamine-induced model of psychosis. Such findings suggest that EAF HP can modulate the dopaminergic neurotransmission and be a promising adjuvant in the treatment of locomotor alterations, cognitive deficits, and neuropsychiatric disorders.

The Strategy of Targeting Peroxisome Proliferator-Activated Receptor (PPAR) in the Treatment of Neuropsychiatric Disorders

Peroxisome proliferator-activated receptors (PPARs) are nonsteroid nuclear receptors and transcription factors that regulate several neuroinflammatory and metabolic processes, recently involved in several neuropsychiatric conditions, including Alzheimer's disease, Parkinson's disease, major depressive disorder, post-traumatic stress disorder (PTSD), schizophrenia spectrum disorders, and autism spectrum disorders. PPARs are ligand-activated receptors that, following stimulation, induce neuroprotective effects by decreasing neuroinflammatory processes through inhibition of the nuclear factor kappa-light-chain-enhancer of activated B cell (NF-κB) expression and consequent suppression of pro-inflammatory cytokine production. PPARs heterodimerize with the retinoid X-receptor (RXR) and bind to PPAR-responsive regulatory elements (PPRE) in the promoter region of target genes involved in lipid metabolism, synthesis of cholesterol, catabolism of amino acids, and inflammation. Interestingly, PPARs are considered functionally part of the extended endocannabinoid (eCB) system that includes the classic eCB, anandamide, which act at cannabinoid receptor types 1 (CB1) and 2 (CB2) and are implicated in the pathophysiology of stress-related neuropsychiatric disorders. In preclinical studies, PPAR stimulation improves anxiety and depression-like behaviors by enhancing neurosteroid biosynthesis. The peculiar functional role of PPARs by exerting anti-inflammatory and neuroprotective effects and their expression localization in neurons and glial cells of corticolimbic circuits make them particularly interesting as novel therapeutic targets for several neuropsychiatric disorders characterized by underlying neuroinflammatory/neurodegenerative mechanisms. Herein, we discuss the pathological hallmarks of neuropsychiatric conditions associated with neuroinflammation, as well as the pivotal role of PPARs with a special emphasis on the subtype alpha (PPAR-α) as a suitable molecular target for therapeutic interventions.

Schizophrenia, Human Leukocyte Antigen (HLA), and Herpes Viruses: Immunogenetic Associations at the Population Level

Several factors have been implicated in schizophrenia (SZ), including human herpes viruses (HHV) and the adaptive immunity Human Leukocyte Antigen (HLA) genes. Here we investigated these issues in 2 complementary ways. In one analysis, we evaluated SZ-HLA and HHV-HLA associations at the level of a single allele by computing (a) a SZ-HLA protection/susceptibility (P/S) score based on the covariance between SZ and 127 HLA allele prevalences in 14 European countries, (b) estimating in silico HHV-HLA best binding affinities for the 9 HHV strains, and (c) evaluating the dependence of P/S score on HHV-HLA binding affinities. These analyses yielded (a) a set of 127 SZ-HLA P/S scores, varying by >200× (maximum/minimum), which could not be accounted for by chance, (b) a set of 127 alleles × 9 HHV best-estimated affinities, varying by >600×, and (c) a set of correlations between SZ-HLA P/S scores and HHV-HLA binding which indicated a prominent role of HHV1. In a subsequent analysis, we extended these findings to the individual person by taking into account the fact that every individual carries 12 HLA alleles and computed (a) the average SZ-HLA P/S scores of 12 randomly chosen alleles (2 per gene), an indicator of HLA-based SZ P/S for an individual, and (b) the average of the corresponding HHV estimated affinities for those alleles, an indicator of overall effectiveness of HHV-HLA binding. We found (a) that HLA protection for SZ was significantly more prominent than susceptibility, and (b) that protective SZ-HLA scores were associated with higher HHV-HLA binding affinities, indicating that HLA binding and subsequent elimination of several HHV strains may confer protection against schizophrenia.

The impact of maternal immune activation on embryonic brain development

The adult brain is a complex structure with distinct functional sub-regions, which are generated from an initial pool of neural epithelial cells within the embryo. This transition requires a number of highly coordinated processes, including neurogenesis, i.e., the generation of neurons, and neuronal migration. These take place during a critical period of development, during which the brain is particularly susceptible to environmental insults. Neurogenesis defects have been associated with the pathogenesis of neurodevelopmental disorders (NDDs), such as autism spectrum disorder and schizophrenia. However, these disorders have highly complex multifactorial etiologies, and hence the underlying mechanisms leading to aberrant neurogenesis continue to be the focus of a significant research effort and have yet to be established. Evidence from epidemiological studies suggests that exposure to maternal infection in utero is a critical risk factor for NDDs. To establish the biological mechanisms linking maternal immune activation (MIA) and altered neurodevelopment, animal models have been developed that allow experimental manipulation and investigation of different developmental stages of brain development following exposure to MIA. Here, we review the changes to embryonic brain development focusing on neurogenesis, neuronal migration and cortical lamination, following MIA. Across published studies, we found evidence for an acute proliferation defect in the embryonic MIA brain, which, in most cases, is linked to an acceleration in neurogenesis, demonstrated by an increased proportion of neurogenic to proliferative divisions. This is accompanied by disrupted cortical lamination, particularly in the density of deep layer neurons, which may be a consequence of the premature neurogenic shift. Although many aspects of the underlying pathways remain unclear, an altered epigenome and mitochondrial dysfunction are likely mechanisms underpinning disrupted neurogenesis in the MIA model. Further research is necessary to delineate the causative pathways responsible for the variation in neurogenesis phenotype following MIA, which are likely due to differences in timing of MIA induction as well as sex-dependent variation. This will help to better understand the underlying pathogenesis of NDDs, and establish therapeutic targets.

Functional Nutrition as Integrated Intervention for In- and Outpatient with Schizophrenia

Schizophrenia is a chronic and progressive disorder characterized by cognitive, emotional, and behavioral abnormalities associated with neuronal development and synaptic plasticity alterations. Genetic and epigenetic abnormalities in cortical parvalbumin-positive GABAergic interneurons and consequent alterations in glutamate-mediated excitatory neurotransmission during early neurodevelopment underlie schizophrenia manifestation and progression. Also, epigenetic alterations during pregnancy or early phases of postnatal life are associated with schizophrenia vulnerability and inflammatory processes, which are at the basis of brain pathology and a higher risk of comorbidities, including cardiovascular diseases and metabolic syndrome. In addition, schizophrenia patients adopt an unhealthy lifestyle and poor nutrition, leading to premature death. Here, I explored the role of functional nutrition as an integrated intervention for the long-term management of patients with schizophrenia. Several natural bioactive compounds in plant-based whole foods, including flavonoids, phytonutrients, vitamins, fatty acids, and minerals, modulate brain functioning by targeting neuroinflammation and improving cognitive decline. Although further clinical studies are needed, a functional diet rich in natural bioactive compounds might be effective in synergism with standard treatments to improve schizophrenia symptoms and reduce the risk of comorbidities.

Proline Metabolism in Neurological and Psychiatric Disorders

Proline plays a multifaceted role in protein synthesis, redox balance, cell fate regulation, brain development, and other cellular and physiological processes. Here, we focus our review on proline metabolism in neurons, highlighting the role of dysregulated proline metabolism in neuronal dysfunction and consequently neurological and psychiatric disorders. We will discuss the association between genetic and protein function of enzymes in the proline pathway and the development of neurological and psychiatric disorders. We will conclude with a potential mechanism of proline metabolism in neuronal function and mental health.

Cytokines as Potential Biomarkers of Clinical Characteristics of Schizophrenia

Immune activation plays a major role in the pathogenesis of schizophrenia, as confirmed by many studies, systematic reviews, and meta-analyses. The important role of neuroinflammation in the formation of the relation between impaired neurobiological processes and schizophrenia psychopathology is being actively discussed. We quantified serum concentrations of 22 cytokines in 236 patients with schizophrenia and 103 mentally and somatically healthy individuals by a multiplex assay. We found higher TGF-α (p = 0.014), IFN-γ (p = 0.036), IL-5 (p < 0.001), IL-6 (p = 0.047), IL-8 (p = 0.005), IL-10 (p <0.001), IL-15 (p = 0.007), IL-1RA (p = 0.007), and TNF-α (p < 0.001) levels in patients with schizophrenia than in healthy individuals. Subgroup analysis revealed a much greater number of statistically significant differences in cytokine levels among females than among males. Patients with a continuous course of schizophrenia showed statistically significantly higher levels of IL-12p70 (p = 0.019), IL-1α (p = 0.046), and IL-1β (p = 0.035) compared with patients with an episodic course. Most cytokines were positively correlated with positive, general, and total PANSS scores. In patients with a duration of schizophrenia of 10 years or more, the level of IL-10 was higher than that in patients with a disease duration of 5 years or less (p = 0.042). Thus, an imbalance in cytokines was revealed in patients with schizophrenia, depending on sex and clinical characteristics of the disease.

Attenuated transcriptional response to pro-inflammatory cytokines in schizophrenia hiPSC-derived neural progenitor cells

Maternal immune activation (MIA) during prenatal development is an environmental risk factor for psychiatric disorders including schizophrenia (SZ). Converging lines of evidence from human and animal model studies suggest that elevated cytokine levels in the maternal and fetal compartments are an important indication of the mechanisms driving this association. However, there is variability in susceptibility to the psychiatric risk conferred by MIA, likely influenced by genetic factors. How MIA interacts with a genetic profile susceptible to SZ is challenging to test in animal models. To address this gap, we examined whether differential gene expression responses occur in forebrain-lineage neural progenitor cells (NPCs) derived from human induced pluripotent stem cells (hiPSC) generated from three individuals with a diagnosis of schizophrenia and three healthy controls. Following acute (24 h) treatment with either interferon-gamma (IFNγ; 25 ng/μl) or interleukin (IL)-1β (10 ng/μl), we identified, by RNA sequencing, 3380 differentially expressed genes (DEGs) in the IFNγ-treated control lines (compared to untreated controls), and 1980 DEGs in IFNγ-treated SZ lines (compared to untreated SZ lines). Out of 4137 genes that responded significantly to IFNγ across all lines, 1223 were common to both SZ and control lines. The 2914 genes that appeared to respond differentially to IFNγ treatment in SZ lines were subjected to a further test of significance (multiple testing correction applied to the interaction effect between IFNγ treatment and SZ diagnosis), yielding 359 genes that passed the significance threshold. There were no differentially expressed genes in the IL-1β-treatment conditions after Benjamini-Hochberg correction. Gene set enrichment analysis however showed that IL-1β impacts immune function and neuronal differentiation. Overall, our data suggest that a) SZ NPCs show an attenuated transcriptional response to IFNγ treatment compared to controls; b) Due to low IL-1β receptor expression in NPCs, NPC cultures appear to be less responsive to IL-1β than IFNγ; and c) the genes differentially regulated in SZ lines - in the face of a cytokine challenge - are primarily associated with mitochondrial, "loss-of-function", pre- and post-synaptic gene sets. Our findings particularly highlight the role of early synaptic development in the association between maternal immune activation and schizophrenia risk.