Systems biology dissection of PTSD and MDD across brain regions, cell types, and blood

Advancing an Inflammatory Subtype of Major Depression

Chronic inflammation plays a prominent role in multiple medical disorders, including psychiatric diseases such as major depression. Exposure to inflammatory stimuli leads to changes in neurotransmitter systems and neurocircuits in the brain that are associated with depressive symptoms. Blockade of inflammatory cytokines can reduce depressive symptoms in medically ill and medically healthy individuals with depression. Increased levels of biomarkers of inflammation are associated with an overrepresentation of neurovegetative symptoms, including anhedonia, fatigue, and psychomotor slowing, and can predict response to antidepressant treatments. Importantly, however, increased inflammatory biomarkers occur in only a subgroup of individuals with depression. Thus, there appears to be a subset of patients with depression with a unique symptom presentation and treatment response whose disease is primarily driven by inflammation. Further identifying and characterizing this inflammatory subtype of depression can foster the development of treatments targeting the immune system and its effects on the brain. Moreover, by using this mechanism-based approach to parsing the heterogeneity of depression, we can refine our diagnostic nosology and model a strategy for precision medicine and targeted therapeutics in psychiatry.

An Update on the Psychiatric Genomics of Posttraumatic Stress Disorder (PTSD)

Posttraumatic Stress Disorder (PTSD) is a prevalent psychiatric condition characterized by intrusive thoughts, hyperarousal, avoidance, and negative cognitive alterations following traumatic events. While a significant portion of individuals experience trauma, only 5% to 30% develop PTSD, with certain groups at higher risk. Research indicates that PTSD's pathophysiology involves altered fear processing, neuroendocrine dysfunction, and immune system changes. Genetic studies, particularly twin studies, suggest a heritability estimate of 30% to 40% for PTSD. Initially focused on gene-environment interactions, recent advancements in genome-wide association studies have identified significant genetic markers enhancing understanding of PTSD's genetic underpinnings.

The evolving neurobiology of early-life stress

Because early-life stress is common and constitutes a strong risk factor for cognitive and mental health disorders, it has been the focus of a multitude of studies in humans and experimental models. Yet, we have an incomplete understanding of what is perceived as stressful by the developing brain, what aspects of stress influence brain maturation, what developmental ages are particularly vulnerable to stress, which molecules mediate the effects of stress on brain operations, and how transient stressful experiences can lead to enduring emotional and cognitive dysfunctions. Here, we discuss these themes, highlight the challenges and progress in resolving them, and propose new concepts and avenues for future research.

Canonical and non-canonical roles of oligodendrocyte precursor cells in mental disorders

Psychiatric research has shifted from a neuroncentric view to understanding mental disorders as disturbances of heterogeneous brain networks. Oligodendrocyte precursor cells (OPCs)- actively involved in the modulation of neuronal functions - are altered in psychiatric patients, but the extent and related consequences are unclear. This review explores canonical and non-canonical OPC-related pathways in schizophrenia, bipolar disorder, post-traumatic stress disorder, and depression in humans, highlighting potential mechanisms shared across diagnostic entities.

Systematic review and mega-analysis of the peripheral blood transcriptome in depression implicates dysregulation of lymphoid cells and histones

Background

Depression has been associated with transcriptomic changes in peripheral blood. However, the contribution of specific immune cell subsets or pathways remains unclear, and findings have been variable across previous studies, which have not tended to account for sample cellular composition.

Methods

We performed a systematic review of peripheral blood transcriptome studies in depression. For the five datasets meeting criteria (total N=6,011), we performed harmonized reprocessing and cell-composition-adjusted differential gene and transcript analyses, followed by a bias- and inflation-adjusted weighted Z-score mega-analysis. We investigated the biological pathways and cell subsets implicated by the results. We also performed a sex-stratified gene network mega-analysis using consensus weighted gene co-expression network analysis (WGCNA).

Results

Few genes showed robust differential gene expression (DGE) in depression. Depression was reproducibly associated with decreases in replication-dependent histones, and with a decrease in oxidative phosphorylation pathways in females only. Cell source analyses implicated lymphoid cells (T cells and NK cells) as likely contributors to the depression differential expression signature. WGCNA mega-analysis revealed multiple consensus modules associated with depression, with a PUF60-related module upregulated in both female and male depression in sex-stratified analyses. Two genes predicted to be causally relevant to depression by transcriptome-wide association studies (GPX4 and GYPE) showed significant DGE.

Conclusions

These results are convergent with immunogenetic evidence implicating lymphoid cell dysregulation in depression, while also highlighting histone alterations as a key molecular signature in depression. They also indicate the importance of large-scale datasets for biomarker discovery in the context of heterogeneous disorders like depression.

Stress-induced changes in the molecular processes underlying fear memories: implications for PTSD and relevant animal models

Most of the fear literature on humans and animals tests healthy individuals. However, fear memories can differ between healthy individuals and those previously exposed to traumatic stress, such as a car accident, sexual abuse, military combat and personal assault. Traumatic stress can lead to post-traumatic stress disorder (PTSD) which presents alterations in fear memories, such as an impairment of fear extinction and extinction recall. PTSD-like animal models are exposed to a single highly stressful experience in the laboratory, such as stress immobilization or single-prolonged stress. Some days later, animals exposed to a PTSD-like model can be tested in fear procedures that help uncover molecular mechanisms of fear memories. In this review, there are discussed the molecular mechanisms in stress-induced fear memories of patients with PTSD and PTSD-like animal models. The focus is on the effects of estradiol and cortisol/corticosterone hormones and of different genes, such as FKBP prolyl isomerase 5 gene (FKBP5) - FK506 binding protein 51 (FKBP51), pituitary adenylate cyclase-activating peptide (PACAP) - pituitary adenylate cyclase-activating polypeptide type I receptor (PAC1R), endocannabinoid (eCB) system and the tropomyosin receptor kinase B (TrkB) - brain-derived neurotrophic factor (BDNF). The conclusion is that greater emphasis should be placed on investigating the molecular mechanisms of fear memories in PTSD, through direct testing of patients with PTSD or the use of relevant PTSD-like models.

Psychedelic control of neuroimmune interactions governing fear

Neuroimmune interactions-signals transmitted between immune and brain cells-regulate many aspects of tissue physiology1, including responses to psychological stress2-5, which can predispose individuals to develop neuropsychiatric diseases6-9. Still, the interactions between haematopoietic and brain-resident cells that influence complex behaviours are poorly understood. Here, we use a combination of genomic and behavioural screens to show that astrocytes in the amygdala limit stress-induced fear behaviour through epidermal growth factor receptor (EGFR). Mechanistically, EGFR expression in amygdala astrocytes inhibits a stress-induced, pro-inflammatory signal-transduction cascade that facilitates neuron-glial crosstalk and stress-induced fear behaviour through the orphan nuclear receptor NR2F2 in amygdala neurons. In turn, decreased EGFR signalling and fear behaviour are associated with the recruitment of meningeal monocytes during chronic stress. This set of neuroimmune interactions is therapeutically targetable through the administration of psychedelic compounds, which reversed the accumulation of monocytes in the brain meninges along with fear behaviour. Together with validation in clinical samples, these data suggest that psychedelics can be used to target neuroimmune interactions relevant to neuropsychiatric disorders and potentially other inflammatory diseases.

A multi-omic approach implicates novel protein dysregulation in post-traumatic stress disorder

BACKGROUND

Post-traumatic stress disorder (PTSD) is a common and disabling psychiatric disorder. PTSD involves multiple brain regions and is often comorbid with other psychiatric disorders, such as major depressive disorder (MDD). Recent genome-wide association studies (GWASs) have identified many PTSD risk loci and transcriptomics studies of postmortem brain have found differentially expressed genes associated with PTSD cases. In this study, we integrated genome-wide measures across modalities to identify convergent molecular effects in the PTSD brain.

METHODS

We performed tandem mass spectrometry (MS/MS) on a large cohort of donors (N = 66) in two prefrontal cortical areas, dorsolateral prefrontal cortex (DLPFC), and subgenual prefrontal cortex (sgPFC). We also coupled the proteomics data with transcriptomics and microRNA (miRNA) profiling from RNA-seq and small-RNA sequencing, respectively for the same cohort. Additionally, we utilized published GWAS results of multiple psychiatric disorders for integrative analysis.

RESULTS

We found differentially expressed proteins and co-expression protein modules disrupted by PTSD. Integrative analysis with transcriptomics and miRNA data from the same cohort pointed to hsa-mir-589 as a regulatory miRNA responsible for dysregulation of neuronal protein networks for PTSD, including the gamma-aminobutyric acid (GABA) vesicular transporter, SLC32A1. In addition, we identified significant enrichment of risk genes for other psychiatric disorders, such as autism spectrum disorder (ASD) and major depressive disorder (MDD) within PTSD protein co-expression modules, suggesting shared molecular pathology.

CONCLUSIONS

We integrated genome-wide measures of mRNA and miRNA expression and proteomics profiling from PTSD, MDD, and control (CON) brains to identify convergent and divergent molecular processes across genomic modalities. We substantially expand the number of differentially expressed genes and proteins in PTSD and identify downregulation of GABAergic processes in the PTSD proteome. This provides a novel framework for future studies integrating proteomic profiling with transcriptomics and non-coding RNAs in the human brain studies.

1,2,4-Trimethoxybenzene ameliorates depression-like behaviors by inhibiting the activation of NLRP3 inflammasome

Our previous works identified that 1,2,4-Trimethoxybenzene (1,2,4-TTB) is an NOD-like receptor (NLR) family pyrin domain-containing-3 (NLRP3) inflammasome-specific inhibitor and ameliorates the severity of experimental autoimmune encephalomyelitis. This study explored whether 1,2,4-TTB has an antidepressive-like role, which depends on suppressing NLRP3 inflammasome. In the current study, the depression-like behaviors induced by lipopolysaccharide (LPS) or fear conditioning were used to determine the antidepressive-like role of 1,2,4-TTB. The results showed that NLRP3 inflammasome is activated in the hippocampus by repetitive injection of LPS. 1,2,4-TTB attenuates the depression-like behaviors and suppresses hippocampal NLRP3 inflammasome activation in LPS-induced depression model mice. In addition, we proved that 1,2,4-TTB enhances the fear memory extinction and alleviates anxiety- and depression-like behavior in mice stimulated by fear conditioning. Consistently,1,2,4-TTB inhibited the activation of hippocampal NLRP3 inflammasome in mice subjected to fear conditioning. Therefore, our study demonstrates that 1,2,4-TTB mitigates depression-like behaviors, depending on its inhibitory role in NLRP3 inflammasome activation.

Should Inflammation Be a Specifier for Major Depression in the DSM-6?

This Viewpoint discusses the opportunity to include inflammatory biomarkers as specifiers for major depression in the upcoming Sixth Edition of the Diagnostic and Statistical Manual of Mental Disorders (DSM-6).

Corticosteroid-regulated gene transcription in SH-SY5Y-derived neurons: Insights into the mineralocorticoid and glucocorticoid receptor-mediated response

Post-traumatic stress disorder (PTSD) and major depressive disorder (MDD) are debilitating stress-related psychiatric disorders that can develop following exposure to traumatic events or chronic stress in some individuals. The neurobiological processes leading to disease remain largely unknown. Among others, these disorders are characterized by a dysregulated hypothalamic-pituitary-adrenal axis, which is regulated by the glucocorticoid receptor (GR) and the mineralocorticoid receptor (MR). This leads to altered downstream corticosteroid-induced gene expression. In vitro models are promising tools to investigate specific neurobiological underpinnings of the stress response in the brain. Here, we investigated the suitability of SH-SY5Y-derived neurons as a cost-efficient system to study the role of GR and MR in the neuronal stress response. SH-SY5Y-derived neurons were characterized, exposed to corticosteroids, and analyzed on transcriptomic and proteomic levels. We show that (i) these neurons express sufficient and seemingly functional GR and MR to allow the study of corticosteroid-induced transcription, (ii) three corticosteroids cortisol, dexamethasone, and aldosterone, induced similar transcriptomic effects, (iii) the antagonist spironolactone mildly attenuated the effects of dexamethasone in FKBP5, DUSP1, and SUPV3L1. Mifepristone did not significantly alter the effect of aldosterone. (iv) Integrating transcriptomic alterations of these corticosteroid-exposed neurons with those of iPSC-derived neurons exposed to dexamethasone showed concordant corticosteroid-induced effects in the two in vitro systems. To determine translational validity, we compared the gene expression in these neurons with the transcriptome of postmortem brain samples from individuals with PTSD and MDD, yielding stronger negative correlations of corticosteroid effects in SH-SY5Y-derived neurons with PTSD signatures than with MDD signatures. Upon further refinement and validation, SH-SY5Y-derived neurons may serve as a simplistic tool to study neuronal corticosteroid-induced gene expression and the implicated molecular networks around GR and MR. Strengthening our insight into these receptors' functions improves our understanding of the hypothalamic-pituitary-adrenal axis, which is commonly altered in stress-related psychiatric disorders such as PTSD and MDD.

AI as an accelerator for defining new problems that transcends boundaries

Interdisciplinary, transdisciplinary, convergence, and No-Boundary Thinking (NBT) research are methodology and technology-agnostic approaches to problem solving. The focus is on defining problems informed by access to multiple knowledge sources and expert perspectives across different domains, with the goal of accessing all available knowledge sources and perspectives. While access to all available knowledge sources and perspectives could be seen as a difficult to attain objective, with the recent rise of AI we might be closer to approaching this goal. We review several examples of methodologies and technologies that have been used to put these strategies into action, but the primary focus of this paper is on how recent advances in AI now enable a quantum leap forward in defining new problems. By leveraging the capacity of AI to synthesize knowledge from multiple domains, these tools can be used to propose multiple candidate problem definitions. AI is uniquely able to draw upon many more knowledge sources than any individual-or even a very large team-could. Coupled with human intelligence, better problems can be defined to address complex scholarly or societal challenges.

Stress Molecular Signaling in Interaction With Cognition

Exposure to stressful life events is associated with a high risk of developing psychiatric disorders with a wide variety of symptoms. Cognitive symptoms in stress-related psychiatric disorders can be particularly challenging to understand, both for those experiencing them and for health care providers. To gain insights, it is important to capture stress-induced structural, epigenomic, transcriptomic, and proteomic changes in relevant brain regions such as the amygdala, hippocampus, locus coeruleus, and prefrontal cortex that result in long-lasting alterations in brain function. In this review, we will emphasize a subset of stress molecular mechanisms that alter neuroplasticity, neurogenesis, and balance between excitatory and inhibitory neurons. Then, we discuss how to identify genetic risk factors that may accelerate stress-driven or stress-induced cognitive impairment. Despite the development of new technologies such as single-cell resolution sequencing, our understanding of the molecular effects of stress in the brain remains to be deepened. A better understanding of the diversity of stress effects in different brain regions and cell types is a prerequisite to open new avenues for mechanism-informed prevention and treatment of stress-related cognitive symptoms.

Single-Nucleus RNA Sequencing Reveals That Gabra6+ Neurons in Prefrontal Cortex Promote the Progression of PTSD After Shockwave-Induced TBI

Shockwave-induced traumatic brain injury (TBI) results in the onset of post-traumatic stress disorder (PTSD), triggered either by the TBI itself or other stressors. However, the interplay and underlying mechanisms of how these factors synergistically induce PTSD remain inadequately elucidated. Here, mice in the TBI (induced by biological shock tube blast injury) and PTSD (induced by single prolonged stress method) groups both displayed symptoms of PTSD behaviors, with the TBI+PTSD (composite model) group exhibiting more severe manifestations. The result of snRNA-seq demonstrated a noticeable increase in the population of Gabra6+ neurons in the prefrontal cortex region of mice in the TBI+PTSD group. Knocking down cortical Gabra6 mitigated PTSD-related behavioral outcomes. Mechanistically, the Smad3/4 complex activation led to the upregulation of Gabra6 expression in cortical neurons. Interaction of Gabra6 with Homer1 activated downstream cAMP signaling pathways. Homer1KO-Nestin mice show reduced susceptibility to PTSD. Subsequently, the efficacy of monoclonal antibody intervention at the 218 site of Gabra6 in ameliorating PTSD development is verified. This study suggests that TBI and stressors act as independent components in PTSD development, with Gabra6+ neurons pivotal in synergistically facilitating PTSD formation. Strategies geared toward minimizing exposure to singular or combined stressors may effectively diminish the risk of developing PTSD.

Regulation of Stress-Induced Immunosuppression in the Context of Neuroendocrine, Cytokine, and Cellular Processes

Understanding the regulatory mechanisms of stress-induced immunosuppression and developing reliable diagnostic methods are important tasks in clinical medicine. This will allow for the development of effective strategies for the prevention and treatment of conditions associated with immune system dysfunction induced by chronic stress. The purpose of this review is to conduct a comprehensive analysis and synthesis of existing data on the regulatory mechanisms of stress-induced immunosuppression. The review is aimed at identifying key neuroendocrine, cytokine, and cellular processes underlying the suppression of the immune response under stress. This study involved a search of scientific literature covering the neuroendocrine, cellular, and molecular mechanisms of stress-induced immunosuppression regulation, as well as modern methods for its diagnosis. Major international bibliographic databases covering publications in biomedicine, psychophysiology, and immunology were selected for the search. The results of the analysis identified key mechanisms regulating stress-induced immunosuppression. The reviewed publications provided detailed descriptions of the neuroendocrine and cytokine processes underlying immune response suppression under stress. A significant portion of the data confirms that the activation of the hypothalamic-pituitary-adrenal (HPA) axis and subsequent elevation of cortisol levels exert substantial immunosuppressive effects on immune cells, particularly macrophages and lymphocytes, leading to the suppression of innate and adaptive immune responses. The data also highlight the crucial role of cortisol and catecholamines (adrenaline and noradrenaline) in initiating immunosuppressive mechanisms under chronic stress.

SKA2 enhances stress-related glucocorticoid receptor signaling through FKBP4-FKBP5 interactions in neurons

Genes involved in regulating the hypothalamic-pituitary-adrenal (HPA) axis, including the glucocorticoid receptor (GR), are linked to various stress-related psychopathologies including bipolar disorder as well as other mood and trauma-related disorders. The protein product of the cell cycle gene, SKA2, is a GR interaction partner in peripheral cells. However, the precise roles of SKA2 in stress and GR signaling in the brain, specifically in nonreplicating postmitotic neurons, and its involvement in HPA axis regulation remain unclear. Here, we demonstrate, using diverse in vitro cell assays, a mechanism by which SKA2 promotes GR signaling through enhancing GR-FKBP4 interaction leading to dissociation of FK506-bindingprotein 51 (FKBP5) from the complex. FKBP4 and FKBP5 are cochaperones known to regulate GR function in opposite directions. Notably in mice, SKA2 in Crh+ neurons of the paraventricular nucleus of the hypothalamus is crucial for HPA axis responsiveness and for maintaining the negative feedback loop underlying allostasis. Moreover, we show that SKA2 expression is increased in postmortem human hippocampus and amygdala from individuals with BD. Our study highlights a critical role of SKA2 in HPA axis function, adds to the understanding of the molecular basis of stress-related psychiatric disorders, and points to potential targets for intervention.

H2S improves hippocampal synaptic plasticity in SPS rats via PI3K/AKT signaling pathway

Post-traumatic stress disorder (PTSD) is a severe mental illness that could impose heavy burdens on individuals and society, but effective and precise treatment modalities are unknown. The level of hydrogen sulfide (H2S) in the brain plays an important role in psychiatric diseases. However, it is still unclear whether PTSD exposure could affect the level of H2S and whether there is a correlation between H2S levels and the pathogenesis of PTSD. In this study, we selected single prolonged stress (SPS) as a PTSD model and found that SPS exposure decreased the endogenous H2S content accompanied by abnormal behavioral changes and dysregulation of the hippocampal synaptic plasticity in SPS rats. We further found that the exogenous administration of H2S could alleviate PTSD-like behaviors and improve hippocampal synaptic plasticity in SPS rats. In addition, we further used the phosphatidylinositol-3 kinase (PI3K) inhibitor LY294002 to interfere with the PI3K/AKT/BDNF signaling pathway. It was found that LY294002 significantly blocked the anti-anxiety effect and the improvement in synaptic plasticity derived from the exogenous administration of H2S in SPS rats. These results suggested that the endogenous H2S content was decreased in SPS rats, and that the exogenous administration of H2S could ameliorate abnormal disorders and improve hippocampal synaptic plasticity by mediating the PI3K/AKT pathway.

Correlation Between Family Dysfunction and Nonsuicidal Self-Injury in a Sample of Chinese Adolescents: The Mediating Effect of Alexithymia and circRNA_103636

Background

Adolescent group may be prone to a variety of behavioral disorders, one of which is nonsuicidal self-injury (NSSI), NSSI intervention is limited for its unknown mechanism, so this study aimed to explore the factors associated with and pathological mechanism underlying NSSI from the perspective of family dysfunction, alexithymia, circRNA_103636 in a sample of Chinese adolescents.

Methods

A total of 200 MDD adolescents with NSSI and 200 healthy controls were enrolled via a convenient sampling method in clinical settings. The Family APGAR Index (APGAR), Toronto Alexithymia Scale (TAS-20), and Adolescent Nonsuicidal Self-injury Assessment Questionnaire (ANSSIAQ) were used for mental assessment of the study group and control group participants. Real-time quantitative reverse transcription PCR (qRT-PCR) was utilized to detect circRNA_103636 expression in peripheral blood mononuclear cells (PBMCs).

Results

There were significant between-group differences of 134 patients (67%) in the study group and 42 patients in the control group (21%) with moderate or severe family dysfunction (P<0.01). The APGAR score was lower, and the difficulty identifying feeling (DIF), difficulty describing feeling (DDF) and externally oriented thinking (EOT) scores of the TAS-20 and ΔCt value of circRNA_103636 were greater in the study group than in the control group. NSSI behavior and NSSI function were negatively correlated with the APGAR score and positively correlated with DIF, DDF, and the EOT of TAS-20 and the ΔCt value of circRNA_103636. Multiple regression analysis confirmed that EOT, circRNA_103636 expression, and APGAR were predictors of ANSSIAQ, which could explain 40.5% of the variance. Similarly, the alexithymia and circRNA_103636 expression mediated the correlation between family dysfunction and NSSI in the study group, and these mediating effects accounted for 27.25% and 23.33%, respectively, of the total effect. Taken together, family dysfunction, alexithymia, and circRNA_103636 expression have predictive effects on NSSI and alexithymia, circRNA_103636 expressions are mediators between family dysfunction and NSSI in Chinese adolescent.

Conclusion

Here, we established a new model for NSSI in which exposure to family dysfunction could induce pathological process by modulating personality traits and epigenetic regulators.

Decoding the transcriptomic signatures of psychological trauma in human cortex and amygdala

Psychological trauma has profound effects on brain function and precipitates psychiatric disorders in vulnerable individuals, however, the molecular mechanisms linking trauma with psychiatric risk remain incompletely understood. Using RNA-seq data postmortem brain tissue of a cohort of 304 donors (N=136 with trauma exposure), we investigated transcriptional signatures of trauma exposures in two cortical regions (dorsolateral prefrontal cortex, and dorsal anterior cingulate cortex) and two amygdala regions (medial amygdala and basolateral amygdala) associated with stress processing and regulation. We focused on dissecting heterogeneity of traumatic experiences in these transcriptional signatures by investigating exposure to several trauma types (childhood, adulthood, complex, single acute, combat, and interpersonal traumas) and interactions with sex. Overall, amygdala regions were more vulnerable to childhood traumas, whereas cortical regions were more vulnerable to adulthood trauma (regardless of childhood experience). Using cell-type-specific expression imputation, we identified a strong transcriptional response of medial amygdala excitatory neurons to childhood trauma, which coincided with dysregulation observed in a human induced pluripotent stem cell (hiPSC)-derived glutamatergic neurons exposed to hydrocortisone. We resolved multiscale coexpression networks for each brain region and identified modules enriched in trauma signatures and whose connectivity was altered with trauma. Trauma-associated coexpression modules provide insight into coordinated functional dysregulation with different traumas and point to potential gene targets for further dissection. Together, these data provide a characterization of the long-lasting human encoding of traumatic experiences in corticolimbic regions of human brain.