The glucocorticoid receptor-FKBP51 complex contributes to fear conditioning and posttraumatic stress disorder

The Role of FKBPs in Complex Disorders: Neuropsychiatric Diseases, Cancer, and Type 2 Diabetes Mellitus

Stress is a common denominator of complex disorders and the FK-506 binding protein (FKBP)51 plays a central role in stress. Hence, it is not surprising that multiple studies imply the involvement of the FKBP51 protein and/or its coding gene, FKBP5, in complex disorders. This review summarizes such reports concentrating on three disorder clusters-neuropsychiatric, cancer, and type 2 diabetes mellitus (T2DM). We also attempt to point to potential mechanisms suggested to mediate the effect of FKBP5/FKBP51 on these disorders. Neuropsychiatric diseases considered in this paper include (i) Huntington's disease for which increased autophagic cellular clearance mechanisms related to decreased FKBP51 protein levels or activity is discussed, Alzheimer's disease for which increased FKBP51 activity has been shown to induce Tau phosphorylation and aggregation, and Parkinson's disease in the context of which FKBP12 is mentioned; and (ii) mental disorders, for which significant association with the single nucleotide polymorphism (SNP) rs1360780 of FKBP5 intron 7 along with decreased DNA methylation were revealed. Since cancer is a large group of diseases that can start in almost any organ or tissue of the body, FKBP51's role depends on the tissue type and differences among pathways expressed in those tumors. The FKBP51-heat-shock protein-(Hsp)90-p23 super-chaperone complex might function as an oncogene or as a tumor suppressor by downregulating the serine/threonine protein kinase (AKt) pathway. In T2DM, two potential pathways for the involvement of FKBP51 are highlighted as affecting the pathogenesis of the disease-the peroxisome proliferator-activated receptor-γ (PPARγ) and AKt.

EF1α-associated protein complexes affect dendritic spine plasticity by regulating microglial phagocytosis in Fmr1 knock-out mice

Fragile X syndrome (FXS) is the most common inherited cause of intellectual disability. There is no specific treatment for FXS due to the lack of therapeutic targets. We report here that Elongation Factor 1α (EF1α) forms a complex with two other proteins: Tripartite motif-containing protein 3 (TRIM3) and Murine double minute (Mdm2). Both EF1α-Mdm2 and EF1α-TRIM3 protein complexes are increased in the brain of Fmr1 knockout mice as a result of FMRP deficiency, which releases the normal translational suppression of EF1α mRNA and increases EF1α protein levels. Increased EF1α-Mdm2 complex decreases PSD-95 ubiquitination (Ub-PSD-95) and Ub-PSD-95-C1q interaction. The elevated level of TRIM3-EF1α complex is associated with decreased TRIM3-Complement Component 3 (C3) complex that inhibits the activation of C3. Both protein complexes thereby contribute to a reduction in microglia-mediated phagocytosis and dendritic spine pruning. Finally, we created a peptide that disrupts both protein complexes and restores dendritic spine plasticity and behavioural deficits in Fmr1 knockout mice. The EF1α-Mdm2 and EF1α-TRIM3 complexes could thus be new therapeutic targets for FXS.

Chronic adolescent stress alters GR-FKBP5 interactions in the hippocampus of adult female rats

Chronic stress exposure during development can have lasting behavioral consequences that differ in males and females. More specifically, increased depressive behaviors in females, but not males, are observed in both humans and rodent models of chronic stress. Despite these known stress-induced outcomes, the molecular consequences of chronic adolescent stress in the adult brain are less clear. The stress hormone corticosterone activates the glucocorticoid receptor, and activity of the receptor is regulated through interactions with co-chaperones-such as the immunophilin FK506 binding proteins 5 (FKBP5). Previously, it has been reported that the adult stress response is modified by a history of chronic stress; therefore, the current study assessed the impact of chronic adolescent stress on the interactions of the glucocorticoid receptor (GR) with its regulatory co-chaperone FKBP5 in response to acute stress in adulthood. Although protein presence for FKBP5 did not differ by group, assessment of GR-FKBP5 interactions demonstrated that adult females with a history of chronic adolescent stress had elevated GR-FKBP5 interactions in the hippocampus following an acute stress challenge which could potentially contribute to a reduced translocation pattern given previous literature describing the impact of FKBP5 on GR activity. Interestingly, the altered co-chaperone interactions of the GR in the stressed female hippocampus were not coupled to an observable difference in transcription of GR-regulated genes. Together, these studies show that chronic adolescent stress causes lasting changes to co-chaperone interactions with the glucocorticoid receptor following stress exposure in adulthood and highlight the potential role that FKBP5 plays in these modifications. Understanding the long-term implications of adolescent stress exposure will provide a mechanistic framework to guide the development of interventions for adult disorders related to early life stress exposures.

A novel dopamine D2 receptor-NR2B protein complex might contribute to morphine use disorders

Dopamine receptors can form heteromeric interactions with other receptors, including glutamate receptors, and present a novel pharmacological target because it contribute to dopamine-dysregulated brain disorders such as addiction and other motor-related diseases. In addition, dopamine receptors D2 (D2Rs) and glutamate NMDA receptors subtype-NR2B have been implicated in morphine use disorders; however, the molecular mechanism underlying the heteromeric complex of these two receptors in morphine use disorders is unclear. Herein, we focus on interactions between D2R and NR2B in morphine-induced conditioned place preference (CPP) and hyperlocomotion mice models. We found that the D2R-NR2B complex significantly increases in morphine-induced mice models, accompanied by ERK signaling impairment, implying the complex could contribute to the morphine addiction pathophysiological process. Further, we design a brain-penetrant interfering peptide (TAT-D2-KT), which could disrupt interactions of D2R-NR2B and decrease addictive-like behaviors concurrent to ERK signaling improvement. In summary, our data provided the first evidence for a D2R-NMDAR complex formation in morphine use disorders and its underlying mechanism of ERK signaling, which could present a novel therapeutic target with direct implications for morphine acquisition and relapse treatment.

Cytotoxic CD4+ tissue-resident memory T cells are associated with asthma severity

BACKGROUND

Patients with severe uncontrolled asthma represent a distinct endotype with persistent airway inflammation and remodeling that is refractory to corticosteroid treatment. CD4+ TH2 cells play a central role in orchestrating asthma pathogenesis, and biologic therapies targeting their cytokine pathways have had promising outcomes. However, not all patients respond well to such treatment, and their effects are not always durable nor reverse airway remodeling. This observation raises the possibility that other CD4+ T cell subsets and their effector molecules may drive airway inflammation and remodeling.

METHODS

We performed single-cell transcriptome analysis of >50,000 airway CD4+ T cells isolated from bronchoalveolar lavage samples from 30 patients with mild and severe asthma.

FINDINGS

We observed striking heterogeneity in the nature of CD4+ T cells present in asthmatics' airways, with tissue-resident memory T (TRM) cells making a dominant contribution. Notably, in severe asthmatics, a subset of CD4+ TRM cells (CD103-expressing) was significantly increased, comprising nearly 65% of all CD4+ T cells in the airways of male patients with severe asthma when compared to mild asthma (13%). This subset was enriched for transcripts linked to T cell receptor activation (HLA-DRB1, HLA-DPA1) and cytotoxicity (GZMB, GZMA) and, following stimulation, expressed high levels of transcripts encoding for pro-inflammatory non-TH2 cytokines (CCL3, CCL4, CCL5, TNF, LIGHT) that could fuel persistent airway inflammation and remodeling.

CONCLUSIONS

Our findings indicate the need to look beyond the traditional T2 model of severe asthma to better understand the heterogeneity of this disease.

FUNDING

This research was funded by the NIH.

SIRT1 in the BNST modulates chronic stress-induced anxiety of male mice via FKBP5 and corticotropin-releasing factor signaling

Although clinical reports have highlighted association of the deacetylase sirtuin 1 (SIRT1) gene with anxiety, its exact role in the pathogenesis of anxiety disorders remains unclear. The present study was designed to explore whether and how SIRT1 in the mouse bed nucleus of the stria terminalis (BNST), a key limbic hub region, regulates anxiety. In a chronic stress model to induce anxiety in male mice, we used site- and cell-type-specific in vivo and in vitro manipulations, protein analysis, electrophysiological and behavioral analysis, in vivo MiniScope calcium imaging and mass spectroscopy, to characterize possible mechanism underlying a novel anxiolytic role for SIRT1 in the BNST. Specifically, decreased SIRT1 in parallel with increased corticotropin-releasing factor (CRF) expression was found in the BNST of anxiety model mice, whereas pharmacological activation or local overexpression of SIRT1 in the BNST reversed chronic stress-induced anxiety-like behaviors, downregulated CRF upregulation, and normalized CRF neuronal hyperactivity. Mechanistically, SIRT1 enhanced glucocorticoid receptor (GR)-mediated CRF transcriptional repression through directly interacting with and deacetylating the GR co-chaperone FKBP5 to induce its dissociation from the GR, ultimately downregulating CRF. Together, this study unravels an important cellular and molecular mechanism highlighting an anxiolytic role for SIRT1 in the mouse BNST, which may open up new therapeutic avenues for treating stress-related anxiety disorders.

Time-course analysis of frontal gene expression profiles in the rat model of posttraumatic stress disorder and a comparison with the conditioned fear model

Posttraumatic stress disorder (PTSD) is a complex disorder that involves physiological, emotional, and cognitive dysregulation that may occur after exposure to a life-threatening event. In contrast with the condition of learned fear with resilience to extinction, abnormal fear with impaired fear extinction and exaggeration are considered crucial factors for the pathological development of PTSD. The prefrontal cortex (mPFC) is considered a critical region of top-down control in fear regulation, which involves the modulation of fear expression and extinction. The pathological course of PTSD is usually chronic and persistent; a number of studies have indicated temporal progression in gene expression and phenotypes may be involved in PTSD pathology. In the current study, we use a well-established modified single-prolonged stress (SPS&FS) rat model to feature PTSD-like phenotypes and compared it with a footshock fear conditioning model (FS model); we collected the frontal tissue after extreme stress exposure or fear conditioning and extracted RNA for transcriptome-level gene sequencing. We compared the genetic profiling of the mPFC at early (<2 h after solely FS or SPS&FS exposure) and late (7 days after solely FS or SPS&FS exposure) stages in these two models. First, we identified temporal differences in the expressional patterns between these two models and found pathways such as protein synthesis factor eukaryotic initiation factor 2 (EIF2), transcription factor NF-E2-related factor 2 (NRF2)-mediated oxidative stress response, and acute phase responding signaling enriched in the early stage in both models with significant p-values. Furthermore, in the late stage, the sirtuin signaling pathway was enriched in both models; other pathways such as STAT3, cAMP, lipid metabolism, Gα signaling, and increased fear were especially enriched in the late stage of the SPS&FS model. However, pathways such as VDR/RXR, GP6, and PPAR signaling were activated significantly in the FS model's late stage. Last, the network analysis revealed the temporal dynamics of psychological disorder, the endocrine system, and also genes related to increased fear in the two models. This study could help elucidate the genetic temporal alteration and stage-specific pathways in these two models, as well as a better understanding of the transcriptome-level differences between them.

Role of FKBP5 and its genetic mutations in stress-induced psychiatric disorders: an opportunity for drug discovery

Stress-induced mental health disorders are affecting many people around the world. However, effective drug therapy for curing psychiatric diseases does not occur sufficiently. Many neurotransmitters, hormones, and mechanisms are essential in regulating the body's stress response. One of the most critical components of the stress response system is the hypothalamus-pituitary-adrenal (HPA) axis. The FKBP prolyl isomerase 51 (FKBP51) protein is one of the main negative regulators of the HPA axis. FKBP51 negatively regulates the cortisol effects (the end product of the HPA axis) by inhibiting the interaction between glucocorticoid receptors (GRs) and cortisol, causing reduced transcription of downstream cortisol molecules. By regulating cortisol effects, the FKBP51 protein can indirectly regulate the sensitivity of the HPA axis to stressors. Previous studies have indicated the influence of FKBP5 gene mutations and epigenetic changes in different psychiatric diseases and drug responses and recommended the FKBP51 protein as a drug target and a biomarker for psychological disorders. In this review, we attempted to discuss the effects of the FKBP5 gene, its mutations on different psychiatric diseases, and drugs affecting the FKBP5 gene.

Melatonin-mediated FKBP4 downregulation protects against stress-induced neuronal mitochondria dysfunctions by blocking nuclear translocation of GR

The physiological crosstalk between glucocorticoid and melatonin maintains neuronal homeostasis in regulating circadian rhythms. However, the stress-inducing level of glucocorticoid triggers mitochondrial dysfunction including defective mitophagy by increasing the activity of glucocorticoid receptors (GRs), leading to neuronal cell death. Melatonin then suppresses glucocorticoid-induced stress-responsive neurodegeneration; however, the regulatory mechanism of melatonin, i.e., associated proteins involved in GR activity, has not been elucidated. Therefore, we investigated how melatonin regulates chaperone proteins related to GR trafficking into the nucleus to suppress glucocorticoid action. In this study, the effects of glucocorticoid on suppressing NIX-mediated mitophagy, followed by mitochondrial dysfunction, neuronal cell apoptosis, and cognitive deficits were reversed by melatonin treatment by inhibiting the nuclear translocation of GRs in both SH-SY5Y cells and mouse hippocampal tissue. Moreover, melatonin selectively suppressed the expression of FKBP prolyl isomerase 4 (FKBP4), which is a co-chaperone protein that works with dynein, to reduce the nuclear translocation of GRs among the chaperone proteins and nuclear trafficking proteins. In both cells and hippocampal tissue, melatonin upregulated melatonin receptor 1 (MT1) bound to Gαq, which triggered the phosphorylation of ERK1. The activated ERK then enhanced DNA methyltransferase 1 (DNMT1)-mediated hypermethylation of FKBP52 promoter, reducing GR-mediated mitochondrial dysfunction and cell apoptosis, the effects of which were reversed by knocking down DNMT1. Taken together, melatonin has a protective effect against glucocorticoid-induced defective mitophagy and neurodegeneration by enhancing DNMT1-mediated FKBP4 downregulation that reduced the nuclear translocation of GRs.

Epigenetic modifications and fetal programming: Molecular mechanisms to control hypertension inheritance

Cardiovascular diseases (CVD) are the number 1 cause of death in the United States and hypertension is a highly prevalent risk factor for CVD. It is estimated that up to 50 % of the hypertensive trait is genetically inherited while the other 50 % is determined by modifiable factors involving lifestyle, behaviors, and the environment. Interestingly, the hypertensive trait is induced or inhibited by epigenetic modifications modulated by modifiable factors. This review focused on the underlying mechanisms of stress, sleep deprivation, obesity and sedentarism as key players for epigenetic modifications contributing to the development of the hypertensive trait and, on the other hand, how epigenetic modifications induced by physical exercise and healthier habits may contribute to overturn and prevent the inheritance of hypertension trait. Furthermore, adversities during gestation and perinatal life also increase the risk for hypertension and CVD later in life, which can perpetuate the inheritance of the hypertensive trait whereas healthier habits during gestation and lactation may counteract fetal programming to improve the cardiovascular health of the progeny. Therefore, it is promising that a healthier lifestyle causes long-lasting epigenetic modifications and is transmitted to the next generation, strengthening the fight against the inheritance of hypertension.

Serum amyloid P component (SAP) modulates antidepressant effects through promoting membrane insertion of the serotonin transporter

Serum amyloid P component (SAP) is a universal constituent of human amyloid deposits including those in Alzheimer's disease. SAP has been observed to be elevated in patients with depression, and higher SAP levels are associated with better response to the antidepressant escitalopram. The mechanisms underlying these clinical observations remain unclear. We examined the effect of SAP on serotonin transporter (SERT) expression and localization using Western blot, confocal microscopy, and positron emission tomography with the radioligand [11C]DASB. We also investigated the effect of SAP on treatment response to escitalopram in mice with the forced swim test (FST), a classical behaviour paradigm to assess antidepressant effects. SAP reduced [11C]DASB binding as an index of SERT levels, consistent with Western blots showing decreased total SAP protein because of increased protein degradation. In conjunction with the global decrease in SERT levels, SAP also promotes VAMP-2 mediated SERT membrane insertion. SAP levels are correlated with behavioural despair and SSRI treatment response in mice with FST. In MDD patients, the SAP and membrane SERT levels are correlated with response to SSRI treatment. SAP has complex effects on SERT levels and localization, thereby modulating the effect of SSRIs, which could partially explain clinical variability in antidepressant treatment response. These results add to our understanding of the mechanism for antidepressant drug action, and with further work could be of clinical utility.

Functions of the Hsp90-Binding FKBP Immunophilins

The Hsp90 chaperone is known to interact with a diverse array of client proteins. However, in every case examined, Hsp90 is also accompanied by a single or several co-chaperone proteins. One class of co-chaperone contains a tetratricopeptide repeat (TPR) domain that targets the co-chaperone to the C-terminal region of Hsp90. Within this class are Hsp90-binding peptidylprolyl isomerases, most of which belong to the FK506-binding protein (FKBP) family. Despite the common association of FKBP co-chaperones with Hsp90, it is abundantly clear that the client protein influences, and is often influenced by, the particular FKBP bound to Hsp90. Examples include Xap2 in aryl hydrocarbon receptor complexes and FKBP52 in steroid receptor complexes. In this chapter, we discuss the known functional roles played by FKBP co-chaperones and, where possible, relate distinctive functions to structural differences between FKBP members.

The GR-FKBP51 interaction modulates fear memory but not spatial or recognition memory

The glucocorticoid receptor (GR) forms a protein complex with FKBP51 that is increased in post-traumatic stress disorder (PTSD) and by fear conditioned learning. Disrupting the GR-FKBP51 complex with a synthetic peptide can block the storage or retrieval of fear conditioned memories, which could be a novel approach to the alleviate fear associated memory in PTSD. However, a potential unacceptable side effect could be the impairment of other types of memory. Thus, we investigated the effect of disrupting the GR-FKBP51 complex on recognition memory using the novel object and displaced object recognition tasks, spatial memory in the Morris water maze, and on social interaction in Crawley's three-chamber social interaction test. We did not observe adverse effects on these other types of memory and conclude that the GR-FKBP51 interaction remains a promising target for treating psychiatric disorders characterized by unwanted aversive memories such as in PTSD.

Development of a novel peptide to prevent entry of SARS-CoV-2 into lung and olfactory bulb cells of hACE2 expressing mice

Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) is a novel coronavirus that has caused a global pandemic Coronavirus Disease 2019 (COVID-19). Currently, there are no effective treatments specifically for COVID-19 infection. The initial step in SARS-CoV-2 infection is attachment to the angiotensin-converting enzyme 2 (ACE2) on the cell surface. We have developed a protein peptide that effectively disrupts the binding between the SARS-CoV-2 spike protein and ACE2. When delivered by nasal spray, our peptide prevents SARS-CoV-2 spike protein from entering lung and olfactory bulb cells of mice expressing human ACE2. Our peptide represents a potential novel treatment and prophylaxis against COVID-19.

Tricyclic antidepressants target FKBP51 SUMOylation to restore glucocorticoid receptor activity

FKBP51 is an important inhibitor of the glucocorticoid receptor (GR) signaling. High FKBP51 levels are associated to stress-related disorders, which are linked to GR resistance. SUMO conjugation to FKBP51 is necessary for FKBP51's inhibitory action on GR. The GR/FKBP51 pathway is target of antidepressant action. Thus we investigated if these drugs could inhibit FKBP51 SUMOylation and therefore restore GR activity. Screening cells using Ni²⁺ affinity and in vitro SUMOylation assays revealed that tricyclic antidepressants- particularly clomipramine- inhibited FKBP51 SUMOylation. Our data show that clomipramine binds to FKBP51 inhibiting its interaction with PIAS4 and therefore hindering its SUMOylation. The inhibition of FKBP51 SUMOylation decreased its binding to Hsp90 and GR facilitating FKBP52 recruitment, and enhancing GR activity. Reduction of PIAS4 expression in rat primary astrocytes impaired FKBP51 interaction with GR, while clomipramine could no longer exert its inhibitory action. This mechanism was verified in vivo in mice treated with clomipramine. These results describe the action of antidepressants as repressors of FKBP51 SUMOylation as a molecular switch for restoring GR sensitivity, thereby providing new potential routes of antidepressant intervention.

Diverse therapeutic developments for post-traumatic stress disorder (PTSD) indicate common mechanisms of memory modulation

Post-traumatic stress disorder (PTSD), characterized by abnormally persistent and distressing memories, is a chronic debilitating condition in need of new treatment options. Current treatment guidelines recommend psychotherapy as first line management with only two drugs, sertraline and paroxetine, approved by U.S. Food and Drug Administration (FDA) for treatment of PTSD. These drugs have limited efficacy as they only reduce symptoms related to depression and anxiety without producing permanent remission. PTSD remains a significant public health problem with high morbidity and mortality requiring major advances in therapeutics. Early evidence has emerged for the beneficial effects of psychedelics particularly in combination with psychotherapy for management of PTSD, including psilocybin, MDMA, LSD, cannabinoids, ayahuasca and ketamine. MDMA and psilocybin reduce barrier to therapy by increasing trust between therapist and patient, thus allowing for modification of trauma related memories. Furthermore, research into the memory reconsolidation mechanisms has allowed for identification of various pharmacological targets to disrupt abnormally persistent memories. A number of pre-clinical and clinical studies have investigated novel and re-purposed pharmacological agents to disrupt fear memory in PTSD. Novel therapeutic approaches like neuropeptide Y, oxytocin, cannabinoids and neuroactive steroids have also shown potential for PTSD treatment. Here, we focus on the role of fear memory in the pathophysiology of PTSD and propose that many of these new therapeutic strategies produce benefits through the effect on fear memory. Evaluation of recent research findings suggests that while a number of drugs have shown promising results in preclinical studies and pilot clinical trials, the evidence from large scale clinical trials would be needed for these drugs to be incorporated in clinical practice.

Epigenetics of alcohol-related liver diseases

Alcohol-related liver disease (ARLD) is a primary cause of chronic liver disease in the United States. Despite advances in the diagnosis and management of ARLD, it remains a major public health problem associated with significant morbidity and mortality, emphasising the need to adopt novel approaches to the study of ARLD and its complications. Epigenetic changes are increasingly being recognised as contributing to the pathogenesis of multiple disease states. Harnessing the power of innovative technologies for the study of epigenetics (e.g., next-generation sequencing, DNA methylation assays, histone modification profiling and computational techniques like machine learning) has resulted in a seismic shift in our understanding of the pathophysiology of ARLD. Knowledge of these techniques and advances is of paramount importance for the practicing hepatologist and researchers alike. Accordingly, in this review article we will summarise the current knowledge about alcohol-induced epigenetic alterations in the context of ARLD, including but not limited to, DNA hyper/hypo methylation, histone modifications, changes in non-coding RNA, 3D chromatin architecture and enhancer-promoter interactions. Additionally, we will discuss the state-of-the-art techniques used in the study of ARLD (e.g. single-cell sequencing). We will also highlight the epigenetic regulation of chemokines and their proinflammatory role in the context of ARLD. Lastly, we will examine the clinical applications of epigenetics in the diagnosis and management of ARLD.

Preterm birth, stillbirth and early neonatal mortality during the Danish COVID-19 lockdown

Using provisional or opportunistic data, three nationwide studies (The Netherlands, the USA and Denmark) have identified a reduction in preterm or extremely preterm births during periods of COVID-19 restrictions. However, none of the studies accounted for perinatal deaths. To determine whether the reduction in extremely preterm births, observed in Denmark during the COVID-19 lockdown, could be the result of an increase in perinatal deaths and to assess the impact of extended COVID-19 restrictions, we performed a nationwide Danish register-based prevalence proportion study. We examined all singleton pregnancies delivered in Denmark during the COVID-19 strict lockdown calendar periods (March 12-April 14, 2015-2020, N = 31,164 births) and the extended calendar periods of COVID-19 restrictions (February 27-September 30, 2015-2020, N = 214,862 births). The extremely preterm birth rate was reduced (OR 0.27, 95% CI 0.07 to 0.86) during the strict lockdown period in 2020, while perinatal mortality was not significantly different. During the extended period of restrictions in 2020, the extremely preterm birth rate was marginally reduced, and a significant reduction in the stillbirth rate (OR 0.69, 0.50 to 0.95) was observed. No changes in early neonatal mortality rates were found.Conclusion: Stillbirth and extremely preterm birth rates were reduced in Denmark during the period of COVID-19 restrictions and lockdown, respectively, suggesting that aspects of these containment and control measures confer an element of protection. The present observational study does not allow for causal inference; however, the results support the design of studies to ascertain whether behavioural or social changes for pregnant women may improve pregnancy outcomes. What is Known: • The aetiologies of preterm birth and stillbirth are multifaceted and linked to a wide range of socio-demographic, medical, obstetric, foetal, psychosocial and environmental factors. • The COVID-19 lockdown saw a reduction in extremely preterm births in Denmark and other high-income countries. An urgent question is whether this reduction can be explained by increased perinatal mortality. What is New: • The reduction in extremely preterm births during the Danish COVID-19 lockdown was not a consequence of increased perinatal mortality, which remained unchanged during this period. • The stillbirth rate was reduced throughout the extended period of COVID-19 restrictions.

Interaction Between Glucocorticoid Receptors and FKBP5 in Regulating Neurotransmission of the Hippocampus

FK501 binding protein 51 (FKBP5) is a stress response prolyl isomerase that inhibits the translocation of the glucocorticoid receptor (GR) heterocomplex to the nucleus. Previous studies have shown that the expression levels of FKBP5 are positively correlated with psychiatric disorders, including depression and post-traumatic stress disorder. In rodents, FKBP5 deletion in the brain leads to be resilient to stress-induced depression. The hippocampus is known to be one of the primary locations mediating stress responses in the brain by providing negative feedback signals to the hypothalamus-pituitaryadrenal gland axis. Therefore, we aimed to investigate the role of FKBP5 and its interaction with GRs in the hippocampus. We observed that FKBP5 deletion in the hippocampus resulted in a minimal change in synaptic transmission. In the hippocampus, GR activation alters the release probability in inhibitory synapses as well as the postsynaptic contribution of glutamate receptors in excitatory synapses; however, no such alterations were induced in the absence of FKBP5. FKBP5 deficiency causes insensitivity to activated GRs in the hippocampus suggesting that FKBP5 mediates synaptic changes caused by GR activation. Our study provides electrophysiological evidence of stress resilience observed in FKBP5-deficient mice.

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.

Extracellular Vesicle Proteins and MicroRNAs Are Linked to Chronic Post-Traumatic Stress Disorder Symptoms in Service Members and Veterans With Mild Traumatic Brain Injury

Symptoms of post-traumatic stress disorder (PTSD) are common in military populations, and frequently associated with a history of combat-related mild traumatic brain injury (mTBI). In this study, we examined relationships between severity of PTSD symptoms and levels of extracellular vesicle (EV) proteins and miRNAs measured in the peripheral blood in a cohort of military service members and Veterans (SMs/Vs) with chronic mTBI(s). Participants (n = 144) were divided into groups according to mTBI history and severity of PTSD symptoms on the PTSD Checklist for DSM-5 (PCL-5). We analyzed EV levels of 798 miRNAs (miRNAs) as well as EV and plasma levels of neurofilament light chain (NfL), Tau, Amyloid beta (Aβ) 42, Aβ40, interleukin (IL)-10, IL-6, tumor necrosis factor-alpha (TNFα), and vascular endothelial growth factor (VEGF). We observed that EV levels of neurofilament light chain (NfL) were elevated in participants with more severe PTSD symptoms (PCL-5 ≥ 38) and positive mTBI history, when compared to TBI negative controls (p = 0.024) and mTBI participants with less severe PTSD symptoms (p = 0.006). Levels of EV NfL, plasma NfL, and hsa-miR-139–5p were linked to PCL-5 scores in regression models. Our results suggest that levels of NfL, a marker of axonal damage, are associated with PTSD symptom severity in participants with remote mTBI. Specific miRNAs previously linked to neurodegenerative and inflammatory processes, and glucocorticoid receptor signaling pathways, among others, were also associated with the severity of PTSD symptoms. Our findings provide insights into possible signaling pathways linked to the development of persistent PTSD symptoms after TBI and biological mechanisms underlying susceptibility to PTSD.

Imaging brain cortisol regulation in PTSD with a target for 11β-hydroxysteroid dehydrogenase type 1

BACKGROUNDInvestigations of stress dysregulation in posttraumatic stress disorder (PTSD) have focused on peripheral cortisol, but none have examined cortisol in the human brain. This study used positron emission tomography (PET) to image 11β-hydroxysteroid dehydrogenase type 1 (11β-HSD1), a cortisol-producing enzyme, as a putative brain cortisol marker in PTSD.METHODSSixteen individuals with PTSD and 17 healthy, trauma-exposed controls (TCs) underwent PET imaging with [18F]AS2471907, a radioligand for 11β-HSD1.RESULTSPrefrontal-limbic 11β-HSD1 availability, estimated as [18F]AS2471907 volume of distribution (VT), was significantly higher in the PTSD group compared with the TC group (β = 1.16, P = 0.0057). Lower prefrontal-limbic 11β-HSD1 availability was related to greater overall PTSD severity (R2 = 0.27, P = 0.038) in the PTSD group. 11β-HSD1 availability was not related to plasma cortisol levels (R2 = 0.026, P = 0.37). In a PTSD subset (n = 10), higher 11β-HSD1 availability was associated with higher availability of translocator protein (TSPO), a microglial marker (β = 4.40, P = 0.039).CONCLUSIONHigher brain cortisol-producing 11β-HSD1 in the PTSD group may represent a resilience-promoting neuroadaptation resulting in lower PTSD symptoms. Along with preliminary associations between 11β-HSD1 and TSPO, corroborating previous evidence of immune suppression in PTSD, these findings collectively challenge previous hypotheses of the deleterious effects of both excessive brain glucocorticoid and brain immune signaling in PTSD.FUNDINGBrain and Behavior Research Foundation Independent Investigator Grant, National Institute of Mental Health grants F30MH116607 and R01MH110674, the Veterans Affairs National Center for PTSD, the Gustavus and Louise Pfeiffer Foundation Fellowship, Clinical and Translational Science Awards grant UL1 TR000142 from the NIH National Center for Advancing Translational Science.

Analysis of the cerebellar molecular stress response led to first evidence of a role for FKBP51 in brain FKBP52 expression in mice and humans

As the cerebellar molecular stress response is understudied, we assessed protein expression levels of hypothalamic-pituitary-adrenal (HPA) axis regulators and neurostructural markers in the cerebellum of a male PTSD mouse model and of unstressed vs. stressed male FK506 binding protein 51 (Fkbp5) knockout (KO) vs. wildtype mice. We explored the translatability of our findings in the Fkbp5 KO model to the situation in humans by correlating mRNA levels of candidates with those of FKBP5 in two whole transcriptome datasets of post-mortem human cerebellum and in blood of unstressed and stressed humans. Fkbp5 deletion rescued the stress-induced loss in hippocampal, prefrontal cortical, and, possibly, also cerebellar FKBP52 expression and modulated post-stress cerebellar expression levels of the glucocorticoid receptor (GR) and possibly (trend) also of glial fibrillary acidic protein (GFAP). Accordingly, expression levels of genes encoding for these three genes correlated with those of FKBP5 in human post-mortem cerebellum, while other neurostructural markers were not related to Fkbp5 either in mouse or human cerebellum. Also, gene expression levels of the two immunophilins correlated inversely in the blood of unstressed and stressed humans. We found transient changes in FKBP52 and persistent changes in GR and GFAP in the cerebellum of PTSD-like mice. Altogether, upon elucidating the cerebellar stress response we found first evidence for a novel facet of HPA axis regulation, i.e., the ability of FKBP51 to modulate the expression of its antagonist FKBP52 in the mouse and, speculatively, also in the human brain and blood and, moreover, detected long-term single stress-induced changes in expression of cerebellar HPA axis regulators and neurostructural markers of which some might contribute to the role of the cerebellum in fear extinction.

Glucocorticoid-Responsive Transcription Factor Krüppel-Like Factor 9 Regulates fkbp5 and Metabolism

Krüppel-like factor 9 (Klf9) is a feedforward regulator of glucocorticoid receptor (GR) signaling. Here we show that in zebrafish klf9 is expressed with GR-dependent oscillatory dynamics in synchrony with fkbp5, a GR target that encodes a negative feedback regulator of GR signaling. We found that fkbp5 transcript levels are elevated in klf9 -/- mutants and that Klf9 associates with chromatin at the fkbp5 promoter, which becomes hyperacetylated in klf9 -/ - mutants, suggesting that the GR regulates fkbp5 via an incoherent feedforward loop with klf9. As both the GR and Fkbp5 are known to regulate metabolism, we asked how loss of Klf9 affects metabolic rate and gene expression. We found that klf9 -/- mutants have a decreased oxygen consumption rate (OCR) and upregulate glycolytic genes, the promoter regions of which are enriched for potential Klf9 binding motifs. Our results suggest that Klf9 functions downstream of the GR to regulate cellular glucocorticoid responsivity and metabolic homeostasis.

Long-term molecular differences between resilient and susceptible mice after a single traumatic exposure

BACKGROUND AND PURPOSE

PTSD is a heterogeneous disorder induced by trauma, resulting in severe long-term impairments of an individual's mental health. Interestingly, PTSD does not develop in every individual; thus, some individuals are more resilient than others. However, the underlying molecular mechanisms are poorly understood. Here, we aimed at shedding light on these processes.

EXPERIMENTAL APPROACH

We used a single-trauma PTSD model in mice to induce long-term maladaptive behaviours and profiled the mice four weeks post-trauma into resilient or susceptible individuals. The phenotype's classification was based on their individual responses in different behavioural experiments. We analysed microbiome, circulating endocannabinoids, and long-term changes in brain phospholipid and transcript levels.

KEY RESULTS

We found a plethora of molecular differences between resilient and susceptible individuals across multiple molecular domains, including lipidome, transcriptome, and gut microbiome. Some of these differences were stable even several weeks after the trauma, indicating the long-term impact of traumatic stimuli on the organism's physiology. Furthermore, the integration of these multi-layered molecular data revealed that resilient and susceptible individuals have very distinct molecular signatures across various physiological systems.

CONCLUSIONS AND IMPLICATIONS

We showed that trauma induces individual-specific behavioural responses that, in combination with a longitudinal characterization of mice, can be used to identify distinct sub-phenotypes within the trauma-exposed group. These groups differ significantly not only in their behaviour but also in specific molecular aspects across a variety of tissues and brain regions. This approach may reveal new targets and predictive biomarkers for the pharmacological treatment and prognosis of stress-related disorders.

Stress-Responsive Gene FK506-Binding Protein 51 Mediates Alcohol-Induced Liver Injury Through the Hippo Pathway and Chemokine (C-X-C Motif) Ligand 1 Signaling

BACKGROUND AND AIMS

Chronic alcohol drinking is a major risk factor for alcohol-associated liver disease (ALD). FK506-binding protein 51 (FKBP5), a cochaperone protein, is involved in many key regulatory pathways. It is known to be involved in stress-related disorders, but there are no reports regarding its role in ALD. This present study aimed to examine the molecular mechanism of FKBP5 in ALD.

APPROACH AND RESULTS

We found a significant increase in hepatic FKBP5 transcripts and protein expression in patients with ALD and mice fed with chronic-plus-single binge ethanol. Loss of Fkbp5 in mice protected against alcohol-induced hepatic steatosis and inflammation. Transcriptomic analysis revealed a significant reduction of Transcriptional enhancer factor TEF-1 (TEA) domain transcription factor 1 (Tead1) and chemokine (C-X-C motif) ligand 1 (Cxcl1) mRNA in ethanol-fed Fkbp5-/- mice. Ethanol-induced Fkbp5 expression was secondary to down-regulation of methylation level at its 5' untranslated promoter region. The increase in Fkbp5 expression led to induction in transcription factor TEAD1 through Hippo signaling pathway. Fkbp5 can interact with yes-associated protein (YAP) upstream kinase, mammalian Ste20-like kinase 1 (MST1), affecting its ability to phosphorylate YAP and the inhibitory effect of hepatic YAP phosphorylation by ethanol leading to YAP nuclear translocation and TEAD1 activation. Activation of TEAD1 led to increased expression of its target, CXCL1, a chemokine-mediated neutrophil recruitment, causing hepatic inflammation and neutrophil infiltration in our mouse model.

CONCLUSIONS

We identified an FKBP5-YAP-TEAD1-CXCL1 axis in the pathogenesis of ALD. Loss of FKBP5 ameliorates alcohol-induced liver injury through the Hippo pathway and CXCL1 signaling, suggesting its potential role as a target for the treatment of ALD.

Disrupting the α7nAChR-NR2A protein complex exerts antidepressant-like effects

Major depressive disorder (MDD) is associated with significant morbidity and mortality. Most antidepressant medications target the serotonin and norepinephrine transporters, but a significant minority of patients do not respond to treatment and novel therapeutic targets are needed. We previously identified a protein complex composed of the α7 nicotinic acetylcholine receptor (nAChR) and NMDA glutamate receptors (NMDARs), through which α7nAChR upregulates NMDAR function. Disruption of the α7nAChR-NMDAR complex with an interfering peptide blocked α7nAChR-mediated upregulation of NMDAR function and cue-induced reinstatement of nicotine seeking in rat models of relapse. Here we report that disrupting the α7nAChR-NMDAR complex with the interfering peptide also has antidepressant-like effects in the forced swim test (FST), a common rat behaviour screening test for antidepressant effects. Furthermore, the interfering peptide significantly increases extracellular signal-regulated kinase (ERK) activity in the animals subjected to the FST. Our results provide a novel potential therapeutic target for the development of new antidepressant medications.

Advances in the pharmacotherapeutic management of post-traumatic stress disorder

Introduction: Post-traumatic stress disorder (PTSD), a mental disorder, is associated with anxiety, depression, and social awkwardness resulting from past traumatic episodes like natural disasters, accidents, terrorist attacks, war, rape, and sexual violence. It affects primarily the amygdala, cortex, and hippocampus where neurochemical changes result in altered behavior. PTSD patients display impaired fear extinction, and past events keep haunting them. The topic presents relevant sections like PTSD pharmacotherapy, associated challenges, and the novel targets and drugs for future research and therapy.Areas covered: The authors discuss the current pharmacotherapy like SSRIs, NDRIs, SNRIs, anticonvulsants, antidepressants, and benzodiazepines, used to attenuate the associated symptoms. However, the primary focus being the novel and potential targets which can be explored better to understand possible future research and advanced therapy in PTSD. For the same, an account of both preclinical and clinical studies has been covered.Expert opinion: Excessive adverse effects, limited efficacy, and lower patient compliance are some of the major challenges with conventional drugs. Moreover, they correct only fewer symptoms without halting the disease progression. Several agents are investigated in different preclinical and clinical phases, which can potentially overcome the pitfalls and limitations associated with conventional therapies.

Impaired hypothalamic feedback dysregulates brain glucocorticoid signaling in genetically-selected Marchigian Sardinian alcohol-preferring rats

Genetically-selected Marchigian Sardinian alcohol-preferring (msP) rats display comorbid symptoms of increased alcohol preference and elevated anxiety-like behavior. Heightened stress sensitivity in msPs is influenced by genetic polymorphisms of the corticotropin-releasing factor receptor in the central nucleus of the amygdala (CeA), as well as reduced influence of anti-stress mechanisms that normally constrain the stress response. Given this propensity for stress dysregulation, in this study, we expand on the possibility that msPs may display differences in neuroendocrine processes that normally terminate the stress response. We utilized behavioral, biochemical, and molecular assays to compare basal and restraint stress-induced changes in the hypothalamic-pituitary-adrenal (HPA) axis of male and female msPs relative to their nonselected Wistar counterparts. The results showed that msPs display deficits in marble-burying behavior influenced by environmental factors and procedures that modulate arousal states in a sex-dependent manner. Whereas male msPs display evidence of dysregulated neuroendocrine function (higher adrenocorticotropic hormone levels and subthreshold reductions in corticosterone), females display restraint-induced elevations in corticosterone levels that were persistently higher in msPs. A dexamethasone challenge reduced the circulation of these stress hormones, although the reduction in corticosterone was generally attenuated in msP versus Wistar rats. Finally, we found evidence of diminished stress-induced glucocorticoid receptor (GR) phosphorylation in the hypothalamic paraventricular nucleus of msPs, as well as innate increases in phosphorylated GR levels in the CeA of male msPs. Collectively, these findings suggest that negative feedback processes regulating HPA responsiveness are diminished in msP rats, possibly underlying differences in the expression of anxiety-like behaviors.

FKBP5: A Key Mediator of How Vertebrates Flexibly Cope with Adversity

Flexibility in the regulation of the hypothalamic–pituitary–adrenal (HPA) axis is an important mediator of stress resilience as it helps organisms adjust to, avoid, or compensate for acute and chronic challenges across changing environmental contexts. Glucocorticoids remain the favorite metric from medicine to conservation biology to attempt to quantify stress resilience despite the skepticism around their consistency in relation to individual health, welfare, and fitness. We suggest that a cochaperone molecule related to heat shock proteins and involved in glucocorticoid receptor activity, FKBP5, may mediate HPA flexibility and therefore stress resilience because it affects how individuals can regulate glucocorticoids and therefore capacitates their abilities to adjust phenotypes appropriately to prevailing, adverse conditions. Although the molecule is well studied in the biomedical literature, FKBP5 research in wild vertebrates is limited. In the present article, we highlight the potential major role of FKBP5 as mediator of HPA axis flexibility in response to adversity in humans and lab rodents.

Exposure to the predator odor TMT induces early and late differential gene expression related to stress and excitatory synaptic function throughout the brain in male rats

Persistent changes in brain stress and glutamatergic function are associated with post-traumatic stress disorder (PTSD). Rodent exposure to the predator odor trimethylthiazoline (TMT) is an innate stressor that produces lasting behavioral consequences relevant to PTSD. As such, the goal of the present study was to assess early (6 hours and 2 days-Experiment 1) and late (4 weeks-Experiment 2) changes to gene expression (RT-PCR) related to stress and excitatory function following TMT exposure in male, Long-Evans rats. During TMT exposure, rats engaged in stress reactive behaviors, including digging and immobility. Further, the TMT group displayed enhanced exploration and mobility in the TMT-paired context 1 week after exposure, suggesting a lasting contextual reactivity. Gene expression analyses revealed upregulated FKBP5 6 hours post-TMT in the hypothalamus and dorsal hippocampus. Two days after TMT, GRM3 was downregulated in the prelimbic cortex and dorsal hippocampus, but upregulated in the nucleus accumbens. This may reflect an early stress response (FKBP5) that resulted in later glutamatergic adaptation (GRM3). Finally, another experiment 4 weeks after TMT exposure showed several differentially expressed genes known to mediate excitatory tripartite synaptic function in the prelimbic cortex (GRM5, DLG4 and SLC1A3 upregulated), infralimbic cortex (GRM2 downregulated, Homer1 upregulated), nucleus accumbens (GRM7 and SLC1A3 downregulated), dorsal hippocampus (FKBP5 and NR3C2 upregulated, SHANK3 downregulated) and ventral hippocampus (CNR1, GRM7, GRM5, SHANK3 and Homer1 downregulated). These data show that TMT exposure induces stress and excitatory molecular adaptations, which could help us understand the persistent glutamatergic dysfunction observed in PTSD.

The DISC1 R264Q variant increases affinity for the dopamine D2 receptor and increases GSK3 activity

The Disrupted in schizophrenia 1 (DISC1) gene encodes a scaffolding protein that is involved in many neural functions such as neurogenesis, neural differentiation, embryonic neuron migration and neurotransmitter signalling. DISC1 was originally implicated in schizophrenia in a single family with a drastic mutation, a chromosomal translocation severing the mid-point of the gene (aa 598). Some common DISC1 variants have also been associated with schizophrenia in the general population, but those located far from the chromosomal translocation breakpoint likely have a different functional impact. We previously reported that DISC1 forms a protein complex with dopamine D2 receptor (D2R), the main target for antipsychotic medications. The D2R-DISC1 complex is elevated in brain tissue from schizophrenia patients and facilitates glycogen synthase kinase (GSK)-3 signaling. The DISC1 R264Q variant is located within the region that binds the D2R, and we found that this polymorphism increases the affinity of DISC1 for the D2R and promotes GSK3 activity. Our results suggest a possible mechanism by which this common polymorphism could affect aspects of brain function that are relevant to psychosis and schizophrenia. This provides additional insight into molecular mechanisms underlying schizophrenia that could be exploited in the development of novel pharmacological treatments.