Schizophrenia in the spectrum of gene-stress interactions: the FKBP5 example

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

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

Effects of Antipsychotics on the Hypothalamus-Pituitary-Adrenal Axis in a Phencyclidine Animal Model of Schizophrenia

Schizophrenia (SCH) is a mental disorder that requires long-term antipsychotic treatment. SCH patients are thought to have an increased sensitivity to stress. The dysregulation of the hypothalamic-pituitary-adrenal (HPA) axis, observed in SCH, could include altered levels of glucocorticoids, glucocorticoid receptors (GRs), and associated proteins. The perinatal administration of phencyclidine (PCP) to rodents represents an animal model of SCH. This study investigated the effects of perinatal PCP exposure and subsequent haloperidol/clozapine treatment on corticosterone levels measured by ELISA and the expression of GR-related proteins (GR, pGR, HSP70, HSP90, FKBP51, and 11β-Hydroxysteroid dehydrogenase-11β-HSD) determined by Western blot, in different brain regions of adult rats. Six groups of male rats were treated on the 2nd, 6th, 9th, and 12th postnatal days (PN), with either PCP or saline. Subsequently, one saline and one PCP group received haloperidol/clozapine from PN day 35 to PN day 100. The results showed altered GR sensitivity in the rat brain after PCP exposure, which decreased after haloperidol/clozapine treatment. These findings highlight disturbances in the HPA axis in a PCP-induced model of SCH and the potential protective effects of antipsychotics. To the best of our knowledge, this is the first study to investigate the effects of antipsychotic drugs on the HPA axis in a PCP animal model of SCH.

Stress, Environment and Early Psychosis

Existing literature provides extended evidence of the close relationship between stress dysregulation, environmental insults, and psychosis onset. Early stress can sensitize genetically vulnerable individuals to future stress, modifying their risk for developing psychotic phenomena. Neurobiological substrate of the aberrant stress response to hypothalamic-pituitary-adrenal axis dysregulation, disrupted inflammation processes, oxidative stress increase, gut dysbiosis, and altered brain signaling, provides mechanistic links between environmental risk factors and the development of psychotic symptoms. Early-life and later-life exposures may act directly, accumulatively, and repeatedly during critical neurodevelopmental time windows. Environmental hazards, such as pre- and perinatal complications, traumatic experiences, psychosocial stressors, and cannabis use might negatively intervene with brain developmental trajectories and disturb the balance of important stress systems, which act together with recent life events to push the individual over the threshold for the manifestation of psychosis. The current review presents the dynamic and complex relationship between stress, environment, and psychosis onset, attempting to provide an insight into potentially modifiable factors, enhancing resilience and possibly influencing individual psychosis liability.

Analysis of the Selective Antagonist SAFit2 as a Chemical Probe for the FK506-Binding Protein 51

The FK506-binding protein 51 (FKBP51) has emerged as an important regulator of the mammalian stress response and is involved in persistent pain states and metabolic pathways. The FK506 analog SAFit2 (short for selective antagonist of FKBP51 by induced fit) was the first potent and selective FKBP51 ligand with an acceptable pharmacokinetic profile. At present, SAFit2 represents the gold standard for FKBP51 pharmacology and has been extensively used in numerous biological studies. Here we review the current knowledge on SAFit2 as well as guidelines for its use.

Association of job stress, FK506 binding protein 51 (FKBP5) gene polymorphisms and their interaction with sleep disturbance

Background

Sleep disturbance is an outcome of multiple factors including environmental and genetic influences. Job stress, a complex environmental factor, likely affects sleep quality, significantly reducing the quality of life of workers. Additionally, FK506 binding protein 51 (FKBP5) may be a pathogenic factor for sleep disturbance as it regulates hypothalamic-pituitary-adrenal (HPA) axis activity, where HPA axis has been found to be involved in the regulation mechanism of sleep and stress response.

Objectives

The main aim of this study was to investigate the association between job stress and FKBP5 gene polymorphism as well as their interaction with sleep disturbance in Chinese workers; to date, these relationships have not been explored.

Methods

This is a cross-sectional study. A total of 675 railway workers (53.8% male) completed a short Effort-Reward Imbalance questionnaire and the Pittsburgh Sleep Quality Index. The SNaPshot single nucleotide polymorphism (SNP) assay was carried out by screening for FKBP5 SNPs in every participant. Generalized multifactor dimensionality reduction (GMDR) was used to identify the strongest G×E interaction combination.

Results

The findings showed that job stress was significantly associated with sleep disturbance; specifically, scores on the PSQI subscales (sleep disturbance, sleep medication, and daytime dysfunction) exhibited significant differences between the two job stress groups (X² = 18.10, p = 0.01). Additionally, the FKBP5 SNP rs1360780-TT (adjusted odds ratio [AOR] = 4.98, 95% confidence interval [CI] = 2.80-8.84) and rs3800373-CC genotype (AOR = 2.06, CI = 1.10-3.86) were associated with an increased risk of sleep disturbance. Job stress and rs1360780 and rs3800373 variants showed a high-dimensional interaction with sleep disturbance as determined by the GMDR model.

Conclusion

The FKBP5 gene may increase susceptibility to job stress and result in sleep disturbance, especially in the presence of negative work-related events. These findings contribute to the field of sleep disturbance prevention and treatment.

Diurnal Alterations in Gene Expression Across Striatal Subregions in Psychosis

BACKGROUND

Psychosis is a defining feature of schizophrenia and highly prevalent in bipolar disorder. Notably, individuals with these illnesses also have major disruptions in sleep and circadian rhythms, and disturbances of sleep and circadian rhythms can precipitate or exacerbate psychotic symptoms. Psychosis is associated with the striatum, though to our knowledge, no study to date has directly measured molecular rhythms and determined how they are altered in the striatum of subjects with psychosis.

METHODS

We performed RNA sequencing and both differential expression and rhythmicity analyses to investigate diurnal alterations in gene expression in human postmortem striatal subregions (nucleus accumbens, caudate, and putamen) in subjects with psychosis (n = 36) relative to unaffected comparison subjects (n = 36).

RESULTS

Across regions, we found differential expression of immune-related transcripts and a substantial loss of rhythmicity in core circadian clock genes in subjects with psychosis. In the nucleus accumbens, mitochondrial-related transcripts had decreased expression in subjects with psychosis, but only in those who died at night. Additionally, we found a loss of rhythmicity in small nucleolar RNAs and a gain of rhythmicity in glutamatergic signaling in the nucleus accumbens of subjects with psychosis. Between-region comparisons indicated that rhythmicity in the caudate and putamen was far more similar in subjects with psychosis than in matched comparison subjects.

CONCLUSIONS

Together, these findings reveal differential and rhythmic gene expression differences across the striatum that may contribute to striatal dysfunction and psychosis in psychotic disorders.

Modulating FKBP5/FKBP51 and autophagy lowers HTT (huntingtin) levels

Current disease-modifying therapies for Huntington disease (HD) focus on lowering mutant HTT (huntingtin; mHTT) levels, and the immunosuppressant drug rapamycin is an intriguing therapeutic for aging and neurological disorders. Rapamycin interacts with FKBP1A/FKBP12 and FKBP5/FKBP51, inhibiting the MTORC1 complex and increasing cellular clearance mechanisms. Whether the levels of FKBP (FK506 binding protein) family members are altered in HD models and if these proteins are potential therapeutic targets for HD have not been investigated. Here, we found levels of FKBP5 are significantly reduced in HD R6/2 and zQ175 mouse models and human HD isogenic neural stem cells and medium spiny neurons derived from induced pluripotent stem cells. Moreover, FKBP5 interacts and colocalizes with HTT in the striatum and cortex of zQ175 mice and controls. Importantly, when we decreased FKBP5 levels or activity by genetic or pharmacological approaches, we observed reduced levels of mHTT in our isogenic human HD stem cell model. Decreasing FKBP5 levels by siRNA or pharmacological inhibition increased LC3-II levels and macroautophagic/autophagic flux, suggesting autophagic cellular clearance mechanisms are responsible for mHTT lowering. Unlike rapamycin, the effect of pharmacological inhibition with SAFit2, an inhibitor of FKBP5, is MTOR independent. Further, in vivo treatment for 2 weeks with SAFit2, results in reduced HTT levels in both HD R6/2 and zQ175 mouse models. Our studies establish FKBP5 as a protein involved in the pathogenesis of HD and identify FKBP5 as a potential therapeutic target for HD.Abbreviations : ACTB/β-actin: actin beta; AD: Alzheimer disease; BafA1: bafilomycin A1; BCA: bicinchoninic acid; BBB: blood brain barrier; BSA: bovine serum albumin; CoIP: co-immunoprecipitation; DMSO: dimethyl sulfoxide; DTT: dithiothreitol; FKBPs: FK506 binding proteins; HD: Huntington disease; HTT: huntingtin; iPSC: induced pluripotent stem cells; MAP1LC3/LC3:microtubule associated protein 1 light chain 3; MAPT/tau: microtubule associated protein tau; MES: 2-ethanesulfonic acid; MOPS: 3-(N-morphorlino)propanesulfonic acid); MSN: medium spiny neurons; mHTT: mutant huntingtin; MTOR: mechanistic target of rapamycin kinase; NSC: neural stem cells; ON: overnight; PD: Parkinson disease; PPIase: peptidyl-prolyl cis/trans-isomerases; polyQ: polyglutamine; PPP1R1B/DARPP-32: protein phosphatase 1 regulatory inhibitor subunit 1B; PTSD: post-traumatic stress disorder; RT: room temperature; SQSTM1/p62: sequestosome 1; SDS-PAGE: sodium dodecyl sulfate-polyacrylamide gel electrophoresis; TBST:Tris-buffered saline, 0.1% Tween 20; TUBA: tubulin; ULK1: unc-51 like autophagy activating kinase 1; VCL: vinculin; WT: littermate controls.

Loop Interrupted: Dysfunctional Chromatin Relations in Neurological Diseases

The majority of genetic variants for psychiatric disorders have been found within non-coding genomic regions. Physical interactions of gene promoters with distant regulatory elements carrying risk alleles may explain how the latter affect gene expression. Recently, whole genome maps of long-range chromosomal contacts from human postmortem brains have been integrated with gene sequence and chromatin accessibility data to decipher disease-specific alterations in chromatin architecture. Cell culture and rodent models provide a causal link between chromatin conformation, long-range chromosomal contacts, gene expression, and disease phenotype. Here, we give an overview of the techniques used to study chromatin contacts and their limitations in brain research. We present evidence for three-dimensional genome changes in physiological brain function and assess how its disturbance contributes to psychiatric disorders. Lastly, we discuss remaining questions and future research directions with a focus on clinical applications.

Environmental Risk Factors for Schizophrenia and Bipolar Disorder and Their Relationship to Genetic Risk: Current Knowledge and Future Directions

Schizophrenia (SZ) and bipolar disorder (BD) are severe psychiatric disorders which result from complex interplay between genetic and environmental factors. It is well-established that they are highly heritable disorders, and considerable progress has been made identifying their shared and distinct genetic risk factors. However, the 15-40% of risk that is derived from environmental sources is less definitively known. Environmental factors that have been repeatedly investigated and often associated with SZ include: obstetric complications, infections, winter or spring birth, migration, urban living, childhood adversity, and cannabis use. There is evidence that childhood adversity and some types of infections are also associated with BD. Evidence for other risk factors in BD is weaker due to fewer studies and often smaller sample sizes. Relatively few environmental exposures have ever been examined for SZ or BD, and additional ones likely remain to be discovered. A complete picture of how genetic and environmental risk factors confer risk for these disorders requires an understanding of how they interact. Early gene-by-environment interaction studies for both SZ and BD often involved candidate genes and were underpowered. Larger samples with genome-wide data and polygenic risk scores now offer enhanced prospects to reveal genetic interactions with environmental exposures that contribute to risk for these disorders. Overall, although some environmental risk factors have been identified for SZ, few have been for BD, and the extent to which these account for the total risk from environmental sources remains unknown. For both disorders, interactions between genetic and environmental risk factors are also not well understood and merit further investigation. Questions remain regarding the mechanisms by which risk factors exert their effects, and the ways in which environmental factors differ by sex. Concurrent investigations of environmental and genetic risk factors in SZ and BD are needed as we work toward a more comprehensive understanding of the ways in which these disorders arise.

The FKBP5 genotype and childhood trauma effects on FKBP5 DNA methylation in patients with psychosis, their unaffected siblings, and healthy controls

Hypothalamic-pituitary-adrenal (HPA) axis activity mediates the relationship between childhood trauma (CT) and psychosis. The FKBP5 gene, one of the key regulators of HPA axis activity after stress exposure, has been found associated with psychosis. Allele-specific and CT related FKBP5 demethylation in intron 7 was revealed in different psychiatric disorders. However, no studies have investigated FKBP5 methylation in subjects with different genetic liability for psychosis. A total of 144 participants were included in the study: 48 patients with psychotic disorders, 50 unaffected siblings, and 46 healthy controls. CT was assessed by Childhood Trauma Questionnaire. The FKBP5 rs1360780 was genotyped and FKBP5 methylation analyses were performed using bisulfite conversion followed by Sanger sequencing at three CpG sites in intron 7. Mixed linear model was used to assess group differences depending on rs1360780 T allele and CT. Results showed a significant T allele-dependent decrease of FKBP5 methylation in patients compared to unaffected siblings and controls. Effect of interaction between T allele and CT exposure on FKBP5 demethylation was found in controls. No effect of both risk factors (T allele and CT) on FKBP5 methylation level was found in unaffected siblings. We confirmed previous evidence of the association between the FKBP5 rs1360780 T allele, CT, and decreased FKBP5 methylation in intron 7. Allele-specific FKBP5 demethylation found in patients could shed a light on altered HPA axis activity in a subgroup of patients related to stress-induced psychosis. FKBP5 methylation and potential protective mechanisms in unaffected siblings after trauma exposure require further investigation.

Astrocytes in schizophrenia

Schizophrenia is a severe and clinically heterogenous mental disorder affecting approximately 1% of the population worldwide. Despite tremendous achievements in the field of schizophrenia research, its precise aetiology remains elusive. Besides dysfunctional neuronal signalling, the pathophysiology of schizophrenia appears to involve molecular and functional abnormalities in glial cells, including astrocytes. This article provides a concise overview of the current evidence supporting altered astrocyte activity in schizophrenia, which ranges from findings obtained from post-mortem immunohistochemical analyses, genetic association studies and transcriptomic investigations, as well as from experimental investigations of astrocyte functions in animal models. Integrating the existing data from these research areas strongly suggests that astrocytes have the capacity to critically affect key neurodevelopmental and homeostatic processes pertaining to schizophrenia pathogenesis, including glutamatergic signalling, synaptogenesis, synaptic pruning and myelination. The further elucidation of astrocytes functions in health and disease may, therefore, offer new insights into how these glial cells contribute to abnormal brain development and functioning underlying this debilitating mental disorder.

Gene Expression Meta-Analysis of Cerebellum Samples Supports the FKBP5 Gene-Environment Interaction Model for Schizophrenia

BACKGROUND

One of the most studied molecular models of gene-environment interactions is that of FKBP5, which has been shown to interact with childhood adversity to increase the risk of psychiatric disorders, and has been implicated in schizophrenia. While the model predicts up-regulation of FKBP5, previous brain samples gene expression studies yielded inconsistent results.

METHODS

We performed a systematic gene expression meta-analysis of FKBP5 and NR3C1, a glucocorticoid receptor inhibited by FKBP5, in cerebellum samples of patients with schizophrenia. The gene expression databases GEO, SMRI and those of NIMH were searched, and out of six screened datasets, three were eligible for the meta-analysis (overall 69 with schizophrenia and 78 controls).

RESULTS

We detected up-regulation of FKBP5 and down-regulation of NR3C1 in schizophrenia, and a negative correlation between their expression patterns. Correlation analysis suggested that the detected differential expression did not result from potential confounding factors.

CONCLUSIONS

Our results give significant support to the FKBP5 gene-environment interaction model for schizophrenia, which provides a molecular mechanism by which childhood adversity is involved in the development of the disorder. To explore FKBP5's potential as a therapeutic target, a mapping of its differential expression patterns in different brain regions of schizophrenia patients is needed.

Social Defeat Stress During Early Adolescence Confers Resilience Against a Single Episode of Prolonged Stress in Adult Rats

Early-life adverse experiences (first hit) lead to coping strategies that may confer resilience or vulnerability to later experienced stressful events (second hit) and the subsequent development of stress-related psychopathologies. Here, we investigated whether exposure to two stressors at different stages in life has long-term effects on emotional and cognitive capabilities, and whether the interaction between the two stressors influences stress resilience. Male rats were subjected to social defeat stress (SDS, first hit) in adolescence and to a single episode of prolonged stress (SPS, second hit) in adulthood. Behavioral outcomes, hippocampal expression of brain-derived neurotrophic factor, and plasma corticosterone levels were tested in adulthood. Rats exposed to both stressors exhibited resilience against the development of stress-induced alterations in emotional behaviors and spatial memory, but vulnerability to cued fear memory dysfunction. Rats subjected to both stressors demonstrated resilience against the SDS-induced alterations in hippocampal brain-derived neurotrophic factor expression and plasma corticosterone levels. SPS alone altered locomotion and spatial memory retention; these effects were absent in SDS-exposed rats later exposed to SPS. Our findings reveal that exposure to social stress during early adolescence influences the ability to cope with a second challenge experienced later in life.

Sex-specific sensitivity to methamphetamine-induced schizophrenia-relevant behaviours in neuregulin 1 type III overexpressing mice

BACKGROUND

Gene-environment interactions contribute to schizophrenia aetiology. Neuregulin 1 is a well-established genetic risk factor for schizophrenia, and elevated expression of type III neuregulin 1 mRNA in the dorsolateral prefrontal cortex is observed in patients with a core risk haplotype. A mouse model of type III Nrg1 overexpression (Nrg1 III tg) possesses face and construct validity for schizophrenia; however, the sensitivity of these transgenic mice to environmental risk factors relevant to schizophrenia is unknown.

AIMS

To determine sensitivity of Nrg1 III tg mice to the psychostimulant methamphetamine (METH) in schizophrenia and addiction-relevant behavioural tests.

METHODS

We examined behavioural responses of adult male and female Nrg1 III tg mice METH (1-3 mg/kg) in schizophrenia-relevant paradigms (drug-induced locomotion, sensorimotor gating) and drug reward (conditioned place preference).

RESULTS

Male Nrg1 III tg mice were less sensitive to METH-induced stereotypies, yet showed a greater negative impact of METH on prepulse inhibition compared with wild type-like males. In contrast, female Nrg1 III tg mice were less sensitive to METH-induced locomotion than wild type-like females, while sensorimotor gating was similarly impaired by METH between the genotypes. There were no genotype differences for METH reward, or anxiety-like and exploratory behaviours.

CONCLUSIONS

These results indicate that overexpression of Nrg1 type III modulates schizophrenia-relevant behaviours, and may help to explain increased sensitivity to the psychoactive effects of METH in patients with schizophrenia.

Hypothalamic-pituitary-adrenal axis-related genes and cognition in major mood disorders and schizophrenia: a systematic review

Hypothalamic-pituitary-adrenal (HPA) axis dysregulation and cognitive deficits are two well-characterized endophenotypes present in different serious mental illnesses (SMIs), including major depressive disorder, bipolar disorder and schizophrenia. Our aim was to study the influence of genetic and epigenetic variations in HPA axis-related genes on cognitive performance in clinical samples, including patients with major mood disorders and schizophrenia. A systematic search was performed using PubMed (Medline), PsycINFO and Scopus databases. The systematic review identified 12 studies dealing with HPA-related genes and cognition in samples including patients with SMIs, focusing on single nucleotide polymorphism (SNP) variants, while no studies analysing epigenetic variations were found. The results suggest different and specific effects on the cognitive performance of SNP variants in the HPA axis-related genes studied, as well as interactions with traumatic experiences. There was high heterogeneity in the studied samples, genes analysed, and cognitive tasks evaluated. The relationship between HPA-related genes and cognition in SMIs is still largely unknown, and further studies including larger samples and epigenetic variations are needed.

Association of FKBP5 polymorphisms with patient susceptibility to coronary artery disease comorbid with depression

BACKGROUND

Coronary artery disease (CAD) and depression cause great burden to society and frequently co-occur. The exact mechanisms of this comorbidity are unclear. FK506-binding protein 51 (FKBP51) is correlated with cardiovascular disease and depression. The aim of this study was to determine the role of the seven single nucleotide polymorphisms (SNPs) of FKBP5 that code FKBP51, namely, rs1360780 (C>T), rs2817032 (T>C), rs2817035 (G>A), rs9296158 (G>A), rs9470079 (G>A), rs4713902 (T>C), and rs3800373 (C>T) in a patient's susceptibility to comorbid CAD and depression.

METHODS

We enrolled 271 Northern Chinese Han patients with CAD, including 123 patients with depression and 147 patients without depression. We also included 113 healthy controls that match the patients' sex and age. Genomic DNA from whole blood was extracted, and seven SNPs were assessed using MassArray method. Patient Health Questionnaire-9 was applied to access the depression.

RESULTS

The GA genotype for rs9470079 was associated with a significantly decreased risk of CAD (odds ratio = 0.506, 95% confidence interval = 0.316-0.810, P = 0.005) when the GG genotype was used as reference. A statistically significant difference was observed among females but not among males in the rs9470079 genotype and allele frequency. Patients with CAD were further divided into CAD+D and CAD-D groups according to the presence of comorbid depression and were compared with the controls. Significant differences were found regarding the genotype and allele frequency of rs2817035 and rs9470079 in CAD+H groups compared with the control subjects in all groups and the female groups (P < 0.05).

CONCLUSIONS

The current study found a remarkable association between FKBP5 gene variations and the risk of comorbid CAD and depression in a north Chinese population. rs9470079 may be a potential gene locus for the incidence of comorbid CAD and depression.

Neurocognitive Endophenotypes of Schizophrenia and Bipolar Disorder and Possible Associations with FKBP Variant rs3800373

Introduction

Schizophrenia(SCZ) and Bipolar disorder (BD) are frequently occurring and impairing disorders that affect around 1% of the population. Important endophenotypes in the genetic research of SCZ and BD are cognitive functions. Core symptoms for SCZ and BD are impairments in working memory, declarative memory and attention, all of which fulfill the criteria for an endophenotype. The FK506 Binding Protein 5 (FKBP5) gene codes for a co-chaperone of the glucocorticoid receptor and has been reported to be associated with cognition.

Aim

The aims of our research were to determine the degree of cognitive impairment in patients suffering from SCZ and BD and to explore the association of the FKBP5 variant rs3800373 genotype with the cognitive endophenotypes.

Material and Methods

Patients and healthy controls were recruited over a period of two years from the Psychiatric Clinic, Clinical Center University of Sarajevo. Genotyping and neuropsychological assessments were performed for 263 subjects (129 SCZ, 53 BD, and 81 healthy controls [HC]). Neuropsychological assessments were performed for all patients with the Trail Making Test-A&B (TMT-A&B) and Digit-span forward&backwards tasks. The single nucleotide polymorphism (SNP) rs3800373 in the FKBP5 gene was genotyped using Infinium PsychArray Bead Chips.

Results and Conclusion

SCZ and BD patients performed lower than HC in the TMT-A&B and in the Digit-span backwards task, while no differences were observed between SCZ and BD patients. While SCZ patients performed lower than HC in the Digit-span forwards task, there were no differences between BD and HC or between BD and SCZ. Rs 3800373 was not associated with performance in the TMT-A&B or Digit-span forwards&backwards tasks. SCZ and BD share largely overlapping neurocognitive characteristics. Rs3800373 was not associated with performance in the neuropsychological tests. However, given the limited sample size, the results do not exclude an association with the rs3800373 variant in a larger sample. Furthermore, as the analysis was limited to one SNP, the results cannot be generalized to other genetic variants in FKBP5.

The neurobiology of depression, ketamine and rapid-acting antidepressants: Is it glutamate inhibition or activation?

The discovery of the antidepressant effects of ketamine has opened a breakthrough opportunity to develop a truly novel class of safe, effective, and rapid-acting antidepressants (RAADs). In addition, the rapid and robust biological and behavioral effects of ketamine offered a unique opportunity to utilize the drug as a tool to thoroughly investigate the neurobiology of stress and depression in animals, and to develop sensitive and reproducible biomarkers in humans. The ketamine literature over the past two decades has considerably enriched our understanding of the mechanisms underlying chronic stress, depression, and RAADs. However, considering the complexity of the pharmacokinetics and in vivo pharmacodynamics of ketamine, several questions remain unanswered and, at times, even answered questions continue to be considered controversial or at least not fully understood. The current perspective paper summarizes our understanding of the neurobiology of depression, and the mechanisms of action of ketamine and other RAADs. The review focuses on the role of glutamate neurotransmission - reviewing the history of the "glutamate inhibition" and "glutamate activation" hypotheses, proposing a synaptic connectivity model of chronic stress pathology, and describing the mechanism of action of ketamine. It will also summarize the clinical efficacy findings of putative RAADs, present relevant human biomarker findings, and discuss current challenges and future directions.

Pharmacogenetics and Pharmacotherapy of Military Personnel Suffering from Post-traumatic Stress Disorder

Background:

Posttraumatic stress disorder (PTSD) is a severe problem among soldiers with combating experience difficult to treat. The pathogenesis is still not fully understood at the psychological level. Therefore, genetic research became a focus of interest. The identification of single nucleotide polymorphisms (SNPs) may help to predict, which persons are at high risk to develop PTSD as a starting point to develop novel targeted drugs for treatment.

Methods:

We conducted a systematic review on SNPs in genes related to PTSD pathology and development of targeted pharmacological treatment options based on PubMed database searches. We focused on clinical trials with military personnel.

Results:

SNPs in 22 human genes have been linked to PTSD. These genes encode proteins acting as neurotransmitters and receptors, downstream signal transducers and metabolizing enzymes. Pharmacological inhibitors may serve as drug candidates for PTSD treatment, e.g. β2 adrenoreceptor antagonists, dopamine antagonists, partial dopamine D2 receptor agonists, dopamine β hydroxylase inhibitors, fatty acid amid hydrolase antagonists, glucocorticoid receptor agonists, tropomyosin receptor kinase B agonists, selective serotonin reuptake inhibitors, catechol-O-methyltransferase inhibitors, gamma-amino butyric acid receptor agonists, glutamate receptor inhibitors, monoaminoxidase B inhibitors, N-methyl-d-aspartate receptor antagonists.

Conclusion:

The combination of genetic and pharmacological research may lead to novel target-based drug developments with improved specificity and efficacy to treat PTSD. Specific SNPs may be identified as reliable biomarkers to assess individual disease risk. Focusing on soldiers suffering from PTSD will not only help to improve treatment options for this specific group, but for all PTSD patients and the general population.

Interaction between FKBP5 variability and recent life events in the anxiety spectrum: Evidence for the differential susceptibility model

Background

Gene-environment interaction (GxE) research has highlighted the importance of investigating the FK506 binding protein 51 (FKBP5) gene as a sensitivity gene. However, previous GxE studies with FKBP5 have not measured the full environmental spectrum or applied statistical tests to discern whether the GxE interaction fits better with the differential-susceptibility or diathesis-stress hypotheses. This study examined whether single nucleotide polymorphisms (SNPs) on FKBP5 gene moderate the association of positive and negative recent life events (LEs) with depressive symptoms, state-anxiety, neuroticism, and social anxiety traits.

Methods

A total of 86 nonclinical young adults were administered psychological measures and were genotyped for five FKBP5 SNPs (rs3800373, rs9296158, rs1360780, rs9470080 and rs4713916).

Results

Regression analyses indicated significant GxE interactions for social anxiety and neuroticism. The interactions predicting neuroticism fit different models for different SNPs, although the overall effect indicated by the haplotype was consistent with the differential-susceptibility hypothesis: the risk-haplotype group presented higher neuroticism in the presence of more negative LEs and lower neuroticism in the presence of more positive LEs. The GxE interactions for social anxiety were consistent with the diathesis-stress model. The lack of significance in the for-better side for social anxiety might be related to the fact that it mapped onto low extraversion, which is associated with a lower permeability to positive experiences.

Discussion

Findings underscore the importance of testing the differential-susceptibility model in relation to FKBP5 to adequately characterize its role in healthy and pathological developmental processes.

Modelling gene-environment interaction in first episodes of psychosis

INTRODUCTION

Recent research demonstrates the heterogeneous etiology of psychotic disorders, where gen-environment (GxE) interaction plays a key role. Large genetic studies have linked many genetic variants with schizophrenia, but each variant is only associated with a small effect and the GxE interaction contribution has not been evaluated.

METHODS

The PEPs Project was designed to carefully collect a large amount of genetic and environmental exposure data of 335 FEP patients and 253 matched healthy controls.780single-nucleotide polymorphisms (from 159 candidate genes)and 16 environmental variables previously reported as the main psychosis non-genetic risk factors were analyzed together using entropy-based measures of information gain.

RESULTS

Our analyses identified an interaction between nine SNPs and the exposition to the environmental risk factors of psychosis, showing a clear enrichment of genes linked to serotonin neurotransmission and neurodevelopmental processes.

CONCLUSIONS

This study has allowed the identification of several GxE-environment interactions involved in the risk of presenting a FEP. Our results highlight the importance of serotonin neurotransmission interacting with certain environmental stimuli. The serotoninergic system may be playing a key role in the regulatory network of stress and other systems implicated in the emergence and development of psychotic disorders.

The emerging role of the FKBP5 gene polymorphisms in vulnerability-stress model of schizophrenia: further evidence from a Serbian population

Increased reactivity to stress is observed in patients with schizophrenia spectrum disorders and their healthy siblings in comparison with the general population. Additionally, higher levels of neuroticism, as a proposed psychological measure of stress sensitivity, increase the risk of schizophrenia. HPA axis dysregulation is one of the possible mechanisms related to the vulnerability-stress model of schizophrenia, and recent studies revealed a possible role of the functional genetic variants of FK506-binding protein 51 (FKBP5) gene which modulate activity of HPA axis. The purpose of the present study was to investigate impact of FKBP5 on schizophrenia in Serbian patients and to explore relationship between genetic variants and neuroticism by using the case-sibling-control design. In 158 subjects, we measured psychotic experiences, childhood trauma and neuroticism. Nine single-nucleotide polymorphisms (rs9295158, rs3800373, rs9740080, rs737054, rs6926133, rs9380529, rs9394314, rs2766533 and rs12200498) were genotyped. The genetic influence was modeled using logistic regression, and the relationship between genetic variants and neuroticism was assessed by linear mixed model. Our results revealed genetic main effect of FKBP5 risk alleles (A allele of rs9296158 and T allele of rs3800373) and AGTC "risk" haplotype combination (rs9296158, rs3800373, rs9470080 and rs737054, respectively) on schizophrenia, particularly when childhood trauma was set as a confounding factor. We confirmed strong relationship between neuroticism and psychotic experiences in patients and siblings and further showed relationship between higher levels of neuroticism and FKBP5 risk variants suggesting potential link between biological and psychosocial risk factors. Our data support previous findings that trauma exposure shapes FKBP5 impact on schizophrenia.

Cav1.2 channels mediate persistent chronic stress-induced behavioral deficits that are associated with prefrontal cortex activation of the p25/Cdk5-glucocorticoid receptor pathway

Chronic stress is known to precipitate and exacerbate neuropsychiatric symptoms, and exposure to stress is particularly pathological in individuals with certain genetic predispositions. Recent genome wide association studies have identified single nucleotide polymorphisms (SNPs) in the gene CACNA1C, which codes for the Ca_v1.2 subunit of the L-type calcium channel (LTCC), as a common risk variant for multiple neuropsychiatric conditions. Ca_v1.2 channels mediate experience-dependent changes in gene expression and long-term synaptic plasticity through activation of downstream calcium signaling pathways. Previous studies have found an association between stress and altered Ca_v1.2 expression in the brain, however the contribution of Ca_v1.2 channels to chronic stress-induced behaviors, and the precise Ca_v1.2 signaling mechanisms activated are currently unknown. Here we report that chronic stress leads to a delayed increase in Ca_v1.2 expression selectively within the prefrontal cortex (PFC), but not in other stress-sensitive brain regions such as the hippocampus or amygdala. Further, we demonstrate that while Ca_v1.2 heterozygous (Ca_v1.2^+/−) mice show chronic stress-induced depressive-like behavior, anxiety-like behavior, and deficits in working memory 1–2 days following stress, they are resilient to the effects of chronic stress when tested 5–7 days later. Lastly, molecular studies find a delayed upregulation of the p25/Cdk5-glucocorticoid receptor (GR) pathway in the PFC when examined 8 days post-stress that is absent in Ca_v1.2^+/− mice. Our findings reveal a novel Ca_v1.2-mediated molecular mechanism associated with the persistent behavioral effects of chronic stress and provide new insight into potential Ca_v1.2 channel mechanisms that may contribute to CACNA1C-linked neuropsychiatric phenotypes.

The Interaction between Childhood Bullying and the FKBP5 Gene on Psychotic-Like Experiences and Stress Reactivity in Real Life

AIM

The present study employed Experience Sampling Methodology to examine whether the interaction between childhood bullying and FKBP5 variability (i) is associated with the expression of psychotic-like experiences, paranoia, and negative affect, and (ii) moderates psychotic-like, paranoid, and affective reactivity to different forms of momentary stress (situational and social) in daily life.

METHODS

A total of 206 nonclinical young adults were interviewed for bullying with the Childhood Experience of Care and Abuse and were prompted randomly eight times daily for one week to complete assessments of their current experiences, affect, and stress appraisals. Participants were genotyped for three FKBP5 single nucleotide polymorphisms (SNPs) (rs3800373, rs9296158, and rs1360780) that have been linked to hypothalamus-pituitary-adrenal axis reactivity. Multilevel analyses were conducted to examine the effect of the interaction between childhood bullying and the FKBP5 haplotype derived from these three SNPs.

RESULTS

The interaction between bullying and the FKBP5 haplotype was associated with positive, but not negative, psychotic-like experiences, paranoia, and negative affect. The bullying x FKBP5 interaction also moderated the association of a social stress appraisal (specifically, being alone because people do not want to be with you) with psychotic-like experiences and negative affect in daily life. Simple slopes analyses indicated that, in all cases, the associations were significantly increased by exposure to bullying in participants with the risk haplotype, but not for those with the non-risk haplotype.

DISCUSSION

The present study provides the first evidence of the interplay between childhood bullying and FKBP5 variability in the real-world expression of psychosis proneness and social stress reactivity. The findings underscore the importance of investigating how gene-environment interactions are involved in mechanistic pathways to the extended psychosis phenotype and lend further support to the increasing relevance given to socially defeating appraisals in the experience of reality distortion.

Early Life Stress Effects on Glucocorticoid-BDNF Interplay in the Hippocampus

Early life stress (ELS) is implicated in the etiology of multiple psychiatric disorders. Important biological effects of ELS are manifested in stress-susceptible regions of the hippocampus and are partially mediated by long-term effects on glucocorticoid (GC) and/or neurotrophin signaling pathways. GC-signaling mediates the regulation of stress response to maintain homeostasis, while neurotrophin signaling plays a key role in neuronal outgrowth and is crucial for axonal guidance and synaptic integrity. The neurotrophin and GC-signaling pathways co-exist throughout the central nervous system (CNS), particularly in the hippocampus, which has high expression levels of glucocorticoid-receptors (GR) and mineralocorticoid-receptors (MR) as well as brain-derived neurotrophic factor (BDNF) and its receptor, tropomyosin-related kinase receptor B (TrkB). This review addresses the effects of ELS paradigms on GC- and BDNF-dependent mechanisms and their crosstalk in the hippocampus, including potential implications for the pathogenesis of common stress-related disorders.