Remodeling of axo-spinous synapses in the pathophysiology and treatment of depression

Beyond the serotonin deficit hypothesis: communicating a neuroplasticity framework of major depressive disorder

The serotonin deficit hypothesis explanation for major depressive disorder (MDD) has persisted among clinicians and the general public alike despite insufficient supporting evidence. To combat rising mental health crises and eroding public trust in science and medicine, researchers and clinicians must be able to communicate to patients and the public an updated framework of MDD: one that is (1) accessible to a general audience, (2) accurately integrates current evidence about the efficacy of conventional serotonergic antidepressants with broader and deeper understandings of pathophysiology and treatment, and (3) capable of accommodating new evidence. In this article, we summarize a framework for the pathophysiology and treatment of MDD that is informed by clinical and preclinical research in psychiatry and neuroscience. First, we discuss how MDD can be understood as inflexibility in cognitive and emotional brain circuits that involves a persistent negativity bias. Second, we discuss how effective treatments for MDD enhance mechanisms of neuroplasticity-including via serotonergic interventions-to restore synaptic, network, and behavioral function in ways that facilitate adaptive cognitive and emotional processing. These treatments include typical monoaminergic antidepressants, novel antidepressants like ketamine and psychedelics, and psychotherapy and neuromodulation techniques. At the end of the article, we discuss this framework from the perspective of effective science communication and provide useful language and metaphors for researchers, clinicians, and other professionals discussing MDD with a general or patient audience.

Early pharmacological interventions for prevention of post-traumatic stress disorder (PTSD) in individuals experiencing acute traumatic stress symptoms

BACKGROUND

Acute traumatic stress symptoms may develop in people who have been exposed to a traumatic event. Although they are usually self-limiting in time, some people develop post-traumatic stress disorder (PTSD), a severe and debilitating condition. Pharmacological interventions have been proposed for acute symptoms to act as an indicated prevention measure for PTSD development. As many individuals will spontaneously remit, these interventions should balance efficacy and tolerability.

OBJECTIVES

To assess the efficacy and acceptability of early pharmacological interventions for prevention of PTSD in adults experiencing acute traumatic stress symptoms.

SEARCH METHODS

We searched the Cochrane Common Mental Disorders Controlled Trial Register (CCMDCTR), CENTRAL, MEDLINE, Embase and two other databases. We checked the reference lists of all included studies and relevant systematic reviews. The search was last updated on 23 January 2023.

SELECTION CRITERIA

We included randomised controlled trials on adults exposed to any kind of traumatic event and presenting acute traumatic stress symptoms, without restriction on their severity. We considered comparisons of any medication with placebo, or with another medication. We excluded trials that investigated medications as an augmentation to psychotherapy.

DATA COLLECTION AND ANALYSIS

We used standard Cochrane methodological procedures. Using a random-effects model, we analysed dichotomous data as risk ratios (RR) and calculated the number needed to treat for an additional beneficial/harmful outcome (NNTB/NNTH). We analysed continuous data as mean differences (MD) or standardised mean differences (SMD). Our primary outcomes were PTSD severity and dropouts due to adverse events. Secondary outcomes included PTSD rate, functional disability and quality of life.

MAIN RESULTS

We included eight studies that considered four interventions (escitalopram, hydrocortisone, intranasal oxytocin, temazepam) and involved a total of 779 participants. The largest trial contributed 353 participants and the next largest, 120 and 118 participants respectively. The trials enrolled participants admitted to trauma centres or emergency departments. The risk of bias in the included studies was generally low except for attrition rate, which we rated as high-risk. We could meta-analyse data for two comparisons: escitalopram versus placebo (but limited to secondary outcomes) and hydrocortisone versus placebo. One study compared escitalopram to placebo at our primary time point of three months after the traumatic event. There was inconclusive evidence of any difference in terms of PTSD severity (mean difference (MD) on the Clinician-Administered PTSD Scale (CAPS, score range 0 to 136) -11.35, 95% confidence interval (CI) -24.56 to 1.86; 1 study, 23 participants; very low-certainty evidence), dropouts due to adverse events (no participant left the study early due to adverse events; 1 study, 31 participants; very low-certainty evidence) and PTSD rates (RR 0.59, 95% CI 0.03 to 13.08; NNTB 37, 95% CI NNTB 15 to NNTH 1; 1 study, 23 participants; very low-certainty evidence). The study did not assess functional disability or quality of life. Three studies compared hydrocortisone to placebo at our primary time point of three months after the traumatic event. We found inconclusive evidence on whether hydrocortisone was more effective in reducing the severity of PTSD symptoms compared to placebo (MD on CAPS -7.53, 95% CI -25.20 to 10.13; I2 = 85%; 3 studies, 136 participants; very low-certainty evidence) and whether it reduced the risk of developing PTSD (RR 0.47, 95% CI 0.09 to 2.38; NNTB 14, 95% CI NNTB 8 to NNTH 5; I2 = 36%; 3 studies, 136 participants; very low-certainty evidence). Evidence on the risk of dropping out due to adverse events is inconclusive (RR 3.19, 95% CI 0.13 to 75.43; 2 studies, 182 participants; low-certainty evidence) and it is unclear whether hydrocortisone might improve quality of life (MD on the SF-36 (score range 0 to 136, higher is better) 19.70, 95% CI -1.10 to 40.50; 1 study, 43 participants; very low-certainty evidence). No study assessed functional disability.

AUTHORS' CONCLUSIONS

This review provides uncertain evidence regarding the use of escitalopram, hydrocortisone, intranasal oxytocin and temazepam for people with acute stress symptoms. It is therefore unclear whether these pharmacological interventions exert a positive or negative effect in this population. It is important to note that acute traumatic stress symptoms are often limited in time, and that the lack of data prevents the careful assessment of expected benefits against side effects that is therefore required. To yield stronger conclusions regarding both positive and negative outcomes, larger sample sizes are required. A common operational framework of criteria for inclusion and baseline assessment might help in better understanding who, if anyone, benefits from an intervention. As symptom severity alone does not provide the full picture of the impact of exposure to trauma, assessment of quality of life and functional impairment would provide a more comprehensive picture of the effects of the interventions. The assessment and reporting of side effects may facilitate a more comprehensive understanding of tolerability.

Methylone is a rapid-acting neuroplastogen with less off-target activity than MDMA

Background

Post-traumatic stress disorder (PTSD) is a highly prevalent psychiatric disorder that can become chronic and debilitating when left untreated. Available pharmacotherapies are limited, take weeks to show modest benefit and remain ineffective for up to 40% of patients. Methylone is currently in clinical development for the treatment of PTSD. Preclinical studies show rapid, robust and long-lasting antidepressant-like and anxiolytic effects. The mechanism of action underlying these effects is not yet fully understood. This study investigated the downstream gene expression changes and signaling pathways affected by methylone in key brain areas linked to PTSD and MDD. It also sought to determine whether neuroplasticity-related genes were involved. We compared effects of methylone with MDMA to explore similarities and differences in their brain effects because MDMA-assisted psychotherapy has recently shown benefit in clinical trials for PTSD and methylone is a structural analog of MDMA.

Methods

Monoamine binding, uptake and release studies were performed and a high-throughput-screen evaluated agonist/antagonist activities at 168 GPCRs in vitro. We used RNA sequencing (RNA-seq) to probe drug-induced gene expression changes in the amygdala and frontal cortex, two brain areas responsible for emotional learning that are affected by PTSD and MDD. Rats were treated with methylone or MDMA (both 10 mg/kg, IP), and their responses were compared with controls. We performed functional enrichment analysis to identify which pathways were regulated by methylone and/or MDMA. We confirmed changes in gene expression using immunohistochemistry.

Results

Methylone, a monoamine uptake inhibitor and releaser, demonstrated no off-target effects at 168 GPCRs, unlike MDMA, which showed activity at 5HT2A and 5HT2C receptors. RNA-seq results revealed significant regulation of myelin-related genes in the amygdala, confirmed by immunohistochemistry. In the frontal cortex, methylone significantly upregulated genes implicated in neuroplasticity.

Conclusion

Results suggest that (1) methylone is a rapid-acting neuroplastogen that affects key brain substrates for PTSD and MDD and that (2) methylone appears to exhibit higher specificity and fewer off-target effects than MDMA. Together, these results are consistent with the reported clinical experiences of methylone and MDMA and bolster the potential use of methylone in the treatment of PTSD and, potentially, other neuropsychiatric disorders.

Impaired monoamine neural system in the mPFC of SHRSP/Ezo as an animal model of attention-deficit/hyperactivity disorder

Attention-deficit/hyperactivity disorder (ADHD) is the most common childhood-onset psychiatric disorder. We investigated the effects of systemic administration of monoamine reuptake inhibitors on long-term potentiation (LTP) formation and monoamine release in the medial prefrontal cortex (mPFC) of the stroke-prone spontaneously hypertensive rat (SHRSP)/Ezo, an animal model of ADHD, and its genetic control, Wistar Kyoto (WKY)/Ezo, to elucidate the functional changes in the mPFC monoamine neural system. Methylphenidate (dopamine (DA) and noradrenaline (NA) reuptake inhibitor) and desipramine (NA reuptake inhibitor) improved LTP formation defects in the mPFC of SHRSP/Ezo, suggesting that NA or both DA and NA are required for improvement of impaired LTP. Methylphenidate increased mPFC DA in both WKY/Ezo and SHRSP/Ezo, but the increase was greater in the former. GBR-12909 (DA reuptake inhibitor) increased mPFC DA in WKY/Ezo but had no effect in SHRSP/Ezo. This may be because DA transporter in SHRSP/Ezo is functionally impaired and contributes less to DA reuptake, so its inhibition did not increase DA level. Meanwhile, basal DA levels in the mPFC of SHRSP/Ezo were paradoxically decreased. These results suggest that functional changes in the DA and NA neural system in the frontal lobe are involved in the pathology of ADHD.

Perinatal Depression and the Role of Synaptic Plasticity in Its Pathogenesis and Treatment

Emerging evidence indicates that synaptic plasticity is significantly involved in the pathophysiology and treatment of perinatal depression. Animal models have demonstrated the effects of overstimulated or weakened synapses in various circuits of the brain in causing affective disturbances. GABAergic theory of depression, stress, and the neuroplasticity model of depression indicate the role of synaptic plasticity in the pathogenesis of depression. Multiple factors related to perinatal depression like hormonal shifts, newer antidepressants, mood stabilizers, monoamine systems, biomarkers, neurotrophins, cytokines, psychotherapy and electroconvulsive therapy have demonstrated direct and indirect effects on synaptic plasticity. In this review, we discuss and summarize the various patho-physiology-related effects of synaptic plasticity in depression. We also discuss the association of treatment-related aspects related to psychotropics, electroconvulsive therapy, neuromodulation, psychotherapy, physical exercise and yoga with synaptic plasticity in perinatal depression. Future insights into newer methods of treatment directed towards the modulation of neuroplasticity for perinatal depression will be discussed.

Repeated reserpine treatment induces depressive-like behaviors accompanied with hippocampal impairment and synapse deficit in mice

Depression remains a significant public health concern, and current animal models of depression are limited in their ability to accurately mimic human depression. However, studying the new development of antidepressants requires the use of progressive animal models. In this study, the mice were exposed to a low dose of reserpine (0.5 mg/kg) once daily for 14 days, followed by a 14-day period to allow for the development of spontaneous depression. We have successfully established a repeated reserpine-induced depressive animal model, which was characterized by emotional symptoms (anhedonia), cognitive symptoms, and psychomotor agitation or retardation. Our study demonstrated that repeated treatment with low-dose reserpine increased immobility time in the TST and FST. It also decreased the sucrose consumption ratio and induced anxiety-like behaviors. These anxiety-like behaviors were evidenced by decreased time spent in the center zone, longer first latency to center zone, and fewer entries into the center zone in the open field test. These findings support the utility of the low-dose reserpine repeated injection animal model for studying the pathogenesis of depression and the development of novel antidepressant treatments. Additionally, this study provides valuable insights into the potential of low-dose reserpine as a tool for modeling chronic depression in animals. Furthermore, our findings suggest that prolonged low-dose reserpine treatment could result in chronic depression. These findings have significant implications for the use of reserpine as a therapeutic agent for various conditions and emphasize the importance of closely monitoring patients' mental health.

Mechanisms of SSRI Therapy and Discontinuation

SSRIs are one of the most widely used drug therapies in primary care and psychiatry, and central to the management of the most common mental health problems in today's society. Despite this, SSRIs suffer from a slow onset of therapeutic effect and relatively poor efficacy as well as adverse effects, with recent concerns being focused on a disabling SSRI discontinuation syndrome. The mechanism underpinning their therapeutic effect has long shifted away from thinking that SSRIs act simply by increasing 5-HT in the synapse. Rather, a current popular view is that increased 5-HT is just the beginning of a series of complex downstream signalling events, which trigger changes in neural plasticity at the functional and structural level. These changes in plasticity are then thought to interact with neuropsychological processes to enhance re-learning of emotional experiences that ultimately brings about changes in mood. This compelling view of SSRI action is underpinning attempts to understand fast-acting antidepressants, such as ketamine and psychedelic drugs, and aid the development of future therapies. An important gap in the theory is evidence that changes in plasticity are causally linked to relevant behavioural effects. Also, predictions that the SSRI-induced neural plasticity might have applicability in other areas of medicine have not yet been borne out. In contrast to the sophisticated view of the antidepressant action of SSRIs, the mechanism underpinning SSRI discontinuation is little explored. Nevertheless, evidence of rebound increases in 5-HT neuron excitability immediately on cessation of SSRI treatment provide a starting point for future investigation. Indeed, this evidence allows formulation of a mechanistic explanation of SSRI discontinuation which draws on parallels with the withdrawal states of other psychotropic drugs.

Role of PGC-1α mediated synaptic plasticity, mitochondrial function, and neuroinflammation in the antidepressant effect of Zi-Shui-Qing-Gan-Yin

Depression is the most prevalent psychiatric disorder, which needs deeper mechanism research studies and effective therapy. Zi-Shui-Qing-Gan-Yin (ZSQGY) is a traditional Chinese medicine decoction that has been widely used in China in the treatment of depressive symptoms. The aim of the study was to examine the anti-depressive effects of ZSQGY and the possible mechanism of action in the monosodium glutamate (MSG)-induced depressive model and the corticosterone (CORT)-induced PC12 cell model. Liquid chromatography-mass spectrometry (LC-MS) was performed to determine the major compounds in the water extract of ZSQGY. The depressive behaviors were evaluated by the field swimming test (FST), the sucrose preference test (SPT), and the open field test (OFT). Golgi staining and transmission electron microscopy (TEM) were performed to display the alterations of synaptic ultrastructure. The mitochondrion function and inflammatory factors were also quantified. The changes in peroxisome proliferator-activated receptor-γ co-activator 1α (PGC-1α) expression were evaluated. The results of this study demonstrated that ZSQGY significantly improved depressive behaviors. ZSQGY also reversed the changes in synaptic plasticity, improved mitochondrion function, and reduced the levels of inflammatory factors. The neuroprotective effects were accompanied by the increased expression of PGC-1α. However, the beneficial changes were reversed after the inhibition of PGC-1α. These results indicated that ZSQGY effectively could improve depressive behaviors via the mechanisms that regulate synaptic structural plasticity, improve mitochondrion function, and alleviate neuroinflammation, which could, or partly, attribute to the regulation of PGC-1α.

5HT1AR-FGFR1 Heteroreceptor Complexes Differently Modulate GIRK Currents in the Dorsal Hippocampus and the Dorsal Raphe Serotonin Nucleus of Control Rats and of a Genetic Rat Model of Depression

The midbrain raphe serotonin (5HT) neurons provide the main ascending serotonergic projection to the forebrain, including hippocampus, which has a role in the pathophysiology of depressive disorder. Serotonin 5HT1A receptor (R) activation at the soma-dendritic level of serotonergic raphe neurons and glutamatergic hippocampal pyramidal neurons leads to a decrease in neuronal firing by activation of G protein-coupled inwardly-rectifying potassium (GIRK) channels. In this raphe-hippocampal serotonin neuron system, the existence of 5HT1AR-FGFR1 heteroreceptor complexes has been proven, but the functional receptor-receptor interactions in the heterocomplexes have only been investigated in CA1 pyramidal neurons of control Sprague Dawley (SD) rats. In the current study, considering the impact of the receptor interplay in developing new antidepressant drugs, the effects of 5HT1AR-FGFR1 complex activation were investigated in hippocampal pyramidal neurons and in midbrain dorsal raphe serotonergic neurons of SD rats and of a genetic rat model of depression (the Flinders Sensitive Line (FSL) rats of SD origin) using an electrophysiological approach. The results showed that in the raphe-hippocampal 5HT system of SD rats, 5HT1AR-FGFR1 heteroreceptor activation by specific agonists reduced the ability of the 5HT1AR protomer to open the GIRK channels through the allosteric inhibitory interplay produced by the activation of the FGFR1 protomer, leading to increased neuronal firing. On the contrary, in FSL rats, FGFR1 agonist-induced inhibitory allosteric action at the 5HT1AR protomer was not able to induce this effect on GIRK channels, except in CA2 neurons where we demonstrated that the functional receptor-receptor interaction is needed for producing the effect on GIRK. In keeping with this evidence, hippocampal plasticity, evaluated as long-term potentiation induction ability in the CA1 field, was impaired by 5HT1AR activation both in SD and in FSL rats, which did not develop after combined 5HT1AR-FGFR1 heterocomplex activation in SD rats. It is therefore proposed that in the genetic FSL model of depression, there is a significant reduction in the allosteric inhibition exerted by the FGFR1 protomer on the 5HT1A protomer-mediated opening of the GIRK channels in the 5HT1AR-FGFR1 heterocomplex located in the raphe-hippocampal serotonin system. This may result in an enhanced inhibition of the dorsal raphe 5HT nerve cell and glutamatergic hippocampal CA1 pyramidal nerve cell firing, which we propose may have a role in depression.

Regulation of dendritic spines in the amygdala following sleep deprivation

The amygdala is a hub of emotional circuits involved in the regulation of cognitive and emotional behaviors and its critically involved in emotional reactivity, stress regulation, and fear memory. Growing evidence suggests that the amygdala plays a key role in the consolidation of emotional memories during sleep. Neuroimaging studies demonstrated that the amygdala is selectively and highly activated during rapid eye movement sleep (REM) and sleep deprivation induces emotional instability and dysregulation of the emotional learning process. Regulation of dendritic spines during sleep represents a morphological correlate of memory consolidation. Several studies indicate that dendritic spines are remodeled during sleep, with evidence for broad synaptic downscaling and selective synaptic upscaling in several cortical areas and the hippocampus. Currently, there is a lack of information regarding the regulation of dendritic spines in the amygdala during sleep. In the present work, we investigated the effect of 5 h of sleep deprivation on dendritic spines in the mouse amygdala. Our data demonstrate that sleep deprivation results in differential dendritic spine changes depending on both the amygdala subregions and the morphological subtypes of dendritic spines. We observed decreased density of mushroom spines in the basolateral amygdala of sleep deprived mice, together with increased neck length and decreased surface area and volume. In contrast, we observed greater densities of stubby spines in sleep deprived mice in the central amygdala, indicating that downscaling selectively occurs in this spine type. Greater neck diameters for thin spines in the lateral and basolateral nuclei of sleep deprived mice, and decreases in surface area and volume for mushroom spines in the basolateral amygdala compared to increases in the cental amygdala provide further support for spine type-selective synaptic downscaling in these areas during sleep. Our findings suggest that sleep promotes synaptic upscaling of mushroom spines in the basolateral amygdala, and downscaling of selective spine types in the lateral and central amygdala. In addition, we observed decreased density of phosphorylated cofilin immunoreactive and growth hormone immunoreactive cells in the amygdala of sleep deprived mice, providing further support for upscaling of dendritic spines during sleep. Overall, our findings point to region-and spine type-specific changes in dendritic spines during sleep in the amygdala, which may contribute to consolidation of emotional memories during sleep.

Epigenetic modulation: Research progress on histone acetylation levels in major depressive disorders

Depression is a serious mental illness and a prevalent condition with multiple aetiologies. The impact of the current therapeutic strategies is limited and the pathogenesis of the illness is not well understood. According to previous studies, depression onset is influenced by a variety of environmental and genetic factors, including chronic stress, aberrant changes in gene expression, and hereditary predisposition. Transcriptional regulation in eukaryotes is closely related to chromosome packing and is controlled by histone post-translational modifications. The development of new antidepressants may proceed along a new path with medications that target epigenetics. Histone deacetylase inhibitors (HDACis) are a class of compounds that interfere with the function of histone deacetylases (HDACs). This review explores the relationship between HDACs and depression and focuses on the current knowledge on their regulatory mechanism in depression and the potential therapeutic use of HDACis with antidepressant efficacy in preclinical research. Future research on inhibitors is also proposed and discussed.

The antidepressant-like effect elicited by vitamin D3 is associated with BDNF/TrkB-related synaptic protein synthesis

Vitamin D₃ (cholecalciferol) has been shown to exert antidepressant-like responses, but the role BDNF/TrkB-related synaptic plasticity in this effect remains to be established. Thus, this study investigated the time-course antidepressant-like response of vitamin D₃ in female and male mice and the possible role of BDNF/TrkB signaling in this response. The repeated (7 and 21 days), but not acute (60 min), administration of vitamin D₃ (2.5 μg/kg, p.o.) exerted an antidepressant-like effect in female and male mice subjected to the tail suspension test, without altering the basal locomotor activity in the open-field test. Notably, vitamin D₃ caused a similar time-dependent antidepressant-like effect in male and female mice, suggesting that this behavioral response in the tail suspension test might not be affected by sex differences. Vitamin D₃ administration for 21 days, but not for 7 days or 1 h, augmented BDNF levels in the hippocampus and prefrontal cortex of mice. No effects on phospho-CREB/CREB levels were detected in the hippocampus and prefrontal cortex after chronic vitamin D₃ administration. Additionally, vitamin D₃ increased TrkB, GluA1, and PSD-95 levels in the prefrontal cortex, but not in the hippocampus. Furthermore, an upregulation of synapsin level was observed in both brain regions after vitamin D₃ administration. These findings reinforce and extend the notion that vitamin D₃ is effective to produce antidepressant-like responses in male and female mice and provide novel evidence that this effect could be associated with BDNF/TrkB-related synaptic protein synthesis. Finally, vitamin D₃ could be a feasible nutritional strategy for the management of depression.

Endovascular Stem Cell Therapy Promotes Neuronal Remodeling to Enhance Post Stroke Recovery by Alleviating Endoplasmic Reticulum Stress Modulated by BDNF Signaling

BACKGROUND AND PURPOSE

The impact of increased BDNF expression in brain by endovascular delivered mesenchymal stem cells (MSCs) post stroke towards modulating endoplasmic reticulum (ER) stress mediated neuronal remodeling has not been directly studied. Therefore, the present study investigates ER stress mediated neuronal remodeling following IA MSCs infusion in rodent model of ischemic stroke.

METHODS

Ovariectomized Sprague Dawley rats were subjected to MCAO followed by 1 × 10⁵ IA MSCs administration at 6 h. Infarct and functional outcomes at different time points post-stroke were evaluated. Further, various genes and protein expression studies were performed to determine the underlying mechanisms of the effect of IA MSCs towards ER stress mediated neuronal remodeling.

RESULTS

Post-stroke IA MSCs administration significantly increased BDNF expression and decreased ER stress markers expression at day 1 post-stroke. A gradual rise in the expression of growth associate protein-43 (GAP 43) and spinophilin were observed at 7, 14- and 28-days post-stroke indicating an increase in neuronal remodeling towards functional restoration.

CONCLUSIONS

The results suggest that IA MSCs post-stroke can modulate neuronal remodeling by BDNF-mediated reduction in ER stress that contribute towards functional recovery.

Convergent molecular and structural neuroimaging signatures of first-episode depression

BACKGROUND

Convergent studies have demonstrated morphological abnormalities in various brain regions in depression patients. However, the molecular underpinnings of the structural impairments remain largely unknown, despite a pressing need for treatment targets and mechanisms. Here, we investigated the gray matter volume (GMV) alteration in patients with depression and its underlying molecular architecture.

METHODS

We recruited 195 first-episode, treatment-naïve depression patients and 78 gender-, age-, and education level-matched healthy controls (HCs) who underwent high-resolution T1-weighted magnetic resonance scans. Voxel-based morphometry (VBM) was adopted to calculate the GMV differences between two groups. Then we analyzed the spatial correlation between depression-induced alteration in GMV and density maps of 10 receptors/transporters deriving from prior molecular imaging in healthy people.

RESULTS

Compared to HCs, the depression group had significantly increased GMV in the left ventral portions of the ventral medial prefrontal cortex, parahippocampal gyrus, amygdala, the right superior parietal lobule and precuneus while decreased GMV in the bilateral hippocampus extending to the thalamus and cerebellum. The GMV alteration introduced by depression was spatially correlated with serotonin receptors (5-HT1a, 5-HT1b, and 5-HT2a), dopamine receptors (D1 and D2) and GABAergic receptor (GABAa) densities.

LIMITATIONS

The conclusions drawn in this study were obtained from a single dataset.

CONCLUSIONS

This study reveals abnormal GMV alteration and provides a series of neurotransmitters receptors possibly related to GMV alteration in depression, which facilitates an integrative understanding of the molecular mechanism underlying the structural abnormalities in depression and may provide clues to new treatment strategies.

Steroid Hormone Interaction with Dendritic Spines: Implications for Neuropsychiatric Disease

Dendritic spines, key sites for neural plasticity, are influenced by gonadal steroids. In this chapter, we review the effects of gonadal steroids on dendritic spine density in areas important to cognitive function, the hippocampus, and prefrontal cortex. Most of these animal model studies investigated the effects of estrogen in females, but we also include more recent data on androgen effects in both males and females. The underlying genomic and non-genomic mechanisms related to gonadal steroid-induced spinogenesis are also reviewed. Subsequently, we discuss possible reasons for the observed sex differences in many neuropsychiatric diseases, which appear to be caused, in part, by aberrant synaptic connections that may involve dendritic spine pathology. Overall, knowledge concerning the regulation of dendritic spines by gonadal hormones has grown since the initial discoveries in the 1990s, and current research points to a potential role for aberrant spine functioning in many neuropsychiatric disorders.

WITHDRAWN: The cerebrospinal fluid-contacting nucleus contributes to depression- like behaviors via MKP-1 in rats

This article has been withdrawn at the request of the author(s) and/or editor. The Publisher apologizes for any inconvenience this may cause. The full Elsevier Policy on Article Withdrawal can be found at https://www.elsevier.com/about/our-business/policies/article-withdrawal

Neurobiological mechanisms of mood disorders: Stress vulnerability and resilience

Stress is an important factor in the development of several human pathologies. The response of rodents and humans to stress depends on many factors; some people and rodents develop stress-related mood disorders, such as depression and anxiety in humans, depression-like and anxiety-like behavior in mice and rats, while others report no new psychological symptoms in response to chronic or acute stress, and are considered susceptible and resilient to stress, respectively. Resilience is defined as the ability to thrive in the face of adversity and is a learned process that can help protect against occupational stressors and mental illnesses. There is growing interest in the underlying mechanisms involved in resilience and vulnerability to depression caused by stress, and some studies have demonstrated that individual variability in the way animals and humans respond to stress depends on several mechanisms, such as oxidative stress, neuronal plasticity, immunology and genetic factors, among others not discussed in this review, this review provides a general overview about this mechanism.

Microglia Involves in the Immune Inflammatory Response of Poststroke Depression: A Review of Evidence

Poststroke depression (PSD) does not exist before and occurs after the stroke. PSD can appear shortly after the onset of stroke or be observed in the weeks and months after the acute or subacute phase of stroke. The pathogenesis of PSD is unclear, resulting in poor treatment effects. With research advancement, immunoactive cells in the central nervous system, particularly microglia, play a role in the occurrence and development of PSD. Microglia affects the homeostasis of the central nervous system through various factors, leading to the occurrence of depression. The research progress of microglia in PSD has been summarized to review the evidence regarding the pathogenesis and treatment target of PSD in the future.

Early pharmacological interventions for universal prevention of post-traumatic stress disorder (PTSD)

BACKGROUND

Post-traumatic stress disorder (PTSD) is a severe and debilitating condition. Several pharmacological interventions have been proposed with the aim to prevent or mitigate it. These interventions should balance efficacy and tolerability, given that not all individuals exposed to a traumatic event will develop PTSD. There are different possible approaches to preventing PTSD; universal prevention is aimed at individuals at risk of developing PTSD on the basis of having been exposed to a traumatic event, irrespective of whether they are showing signs of psychological difficulties.

OBJECTIVES

To assess the efficacy and acceptability of pharmacological interventions for universal prevention of PTSD in adults exposed to a traumatic event.

SEARCH METHODS

We searched the Cochrane Common Mental Disorders Controlled Trial Register (CCMDCTR), CENTRAL, MEDLINE, Embase, two other databases and two trials registers (November 2020). We checked the reference lists of all included studies and relevant systematic reviews. The search was last updated on 13 November 2020.

SELECTION CRITERIA

We included randomised clinical trials on adults exposed to any kind of traumatic event. We considered comparisons of any medication with placebo or with another medication. We excluded trials that investigated medications as an augmentation to psychotherapy.

DATA COLLECTION AND ANALYSIS

We used standard Cochrane methodological procedures. In a random-effects model, we analysed dichotomous data as risk ratios (RR) and number needed to treat for an additional beneficial/harmful outcome (NNTB/NNTH). We analysed continuous data as mean differences (MD) or standardised mean differences (SMD).

MAIN RESULTS

We included 13 studies which considered eight interventions (hydrocortisone, propranolol, dexamethasone, omega-3 fatty acids, gabapentin, paroxetine, PulmoCare enteral formula, Oxepa enteral formula and 5-hydroxytryptophan) and involved 2023 participants, with a single trial contributing 1244 participants. Eight studies enrolled participants from emergency departments or trauma centres or similar settings. Participants were exposed to a range of both intentional and unintentional traumatic events. Five studies considered participants in the context of intensive care units with traumatic events consisting of severe physical illness. Our concerns about risk of bias in the included studies were mostly due to high attrition and possible selective reporting. We could meta-analyse data for two comparisons: hydrocortisone versus placebo, but limited to secondary outcomes; and propranolol versus placebo. No study compared hydrocortisone to placebo at the primary endpoint of three months after the traumatic event. The evidence on whether propranolol was more effective in reducing the severity of PTSD symptoms compared to placebo at three months after the traumatic event is inconclusive, because of serious risk of bias amongst the included studies, serious inconsistency amongst the studies' results, and very serious imprecision of the estimate of effect (SMD -0.51, 95% confidence interval (CI) -1.61 to 0.59; I² = 83%; 3 studies, 86 participants; very low-certainty evidence). No study provided data on dropout rates due to side effects at three months post-traumatic event. The evidence on whether propranolol was more effective than placebo in reducing the probability of experiencing PTSD at three months after the traumatic event is inconclusive, because of serious risk of bias amongst the included studies, and very serious imprecision of the estimate of effect (RR 0.77, 95% CI 0.31 to 1.92; 3 studies, 88 participants; very low-certainty evidence). No study assessed functional disability or quality of life.  Only one study compared gabapentin to placebo at the primary endpoint of three months after the traumatic event, with inconclusive evidence in terms of both PTSD severity and probability of experiencing PTSD, because of imprecision of the effect estimate, serious risk of bias and serious imprecision (very low-certainty evidence). We found no data on dropout rates due to side effects, functional disability or quality of life. For the remaining comparisons, the available data are inconclusive or missing in terms of PTSD severity reduction and dropout rates due to adverse events. No study assessed functional disability.

AUTHORS' CONCLUSIONS

This review provides uncertain evidence only regarding the use of hydrocortisone, propranolol, dexamethasone, omega-3 fatty acids, gabapentin, paroxetine, PulmoCare formula, Oxepa formula, or 5-hydroxytryptophan as universal PTSD prevention strategies. Future research might benefit from larger samples, better reporting of side effects and inclusion of quality of life and functioning measures.

Analysis of hyperforin (St. John's wort) action at TRPC6 channel leads to the development of a new class of antidepressant drugs

St. John's wort is an herb, long used in folk medicine for the treatment of mild depression. Its antidepressant constituent, hyperforin, has properties such as chemical instability and induction of drug-drug interactions that preclude its use for individual pharmacotherapies. Here we identify the transient receptor potential canonical 6 channel (TRPC6) as a druggable target to control anxious and depressive behavior and as a requirement for hyperforin antidepressant action. We demonstrate that TRPC6 deficiency in mice not only results in anxious and depressive behavior, but also reduces excitability of hippocampal CA1 pyramidal neurons and dentate gyrus granule cells. Using electrophysiology and targeted mutagenesis, we show that hyperforin activates the channel via a specific binding motif at TRPC6. We performed an analysis of hyperforin action to develop a new antidepressant drug that uses the same TRPC6 target mechanism for its antidepressant action. We synthesized the hyperforin analog Hyp13, which shows similar binding to TRPC6 and recapitulates TRPC6-dependent anxiolytic and antidepressant effects in mice. Hyp13 does not activate pregnan-X-receptor (PXR) and thereby loses the potential to induce drug-drug interactions. This may provide a new approach to develop better treatments for depression, since depression remains one of the most treatment-resistant mental disorders, warranting the development of effective drugs based on naturally occurring compounds.

Detection of Microstructural Medial Prefrontal Cortex Changes Using Magnetic Resonance Imaging Texture Analysis in a Post-Traumatic Stress Disorder Rat Model

BACKGROUND

Radiomics is characterized by high-throughput extraction of texture features from medical images and the mining of information that can potentially be used to define neuroimaging markers in many neurological or psychiatric diseases. However, there have been few studies concerning MRI radiomics in post-traumatic stress disorder (PTSD). The study's aims were to appraise changes in microstructure of the medial prefrontal cortex (mPFC) in a PTSD animal model, specifically single-prolonged stress (SPS) rats, by using MRI texture analysis. The feasibility of using a radiomics approach to classify PTSD rats was examined.

METHODS

Morris water maze and elevated plus maze were used to assess behavioral changes in the rats. Two hundred and sixty two texture features were extracted from each region of interest in T2-weighted images. Stepwise discriminant analysis (SDA) and LASSO regression were used to perform feature selection and radiomics signature building to identify mPFC radiomics signatures consisting of optimal features, respectively. Receiver operating characteristic curve plots were used to evaluate the classification performance. Immunofluorescence techniques were used to examine the expression of glial fibrillary acidic protein (GFAP) and neuronal nuclei (NeuN) in the mPFC. Nuclear pycnosis was detected using 4',6-diamidino-2-phenylindole (DAPI) staining.

RESULTS

Behavioral results indicated decreased learning and spatial memory performance and increased anxiety-like behavior after SPS stimulation. SDA analysis showed that the general non-cross-validated and cross-validated discrimination accuracies were 86.5% and 80.4%. After LASSO dimensionality reduction, 10 classification models were established. For classifying PTSD rats between the control and each SPS group, these models achieved AUCs of 0.944, 0.950, 0.959, and 0.936. Among four SPS groups, the AUCs were 0.927, 0.943, 0.967, 0.916, 0.932, and 0.893, respectively. The number of GFAP-positive cells and intensity of GFAP-IR within the mPFC increased 1 day after SPS treatment, and then decreased. The intensity of NeuN-IR and number of NeuN-positive cells significantly decreased from 1 to 14 days after SPS stimulation. The brightness levels of DAPI-stained nuclei increased in SPS groups.

CONCLUSION

Non-invasive MRI radiomics features present an efficient and sensitive way to detect microstructural changes in the mPFC after SPS stimulation, and they could potentially serve as a novel neuroimaging marker in PTSD diagnosis.

Risk of Dementia in Posttraumatic Stress Disorder

Several studies have investigated the risk of dementia in posttraumatic stress disorder (PTSD) using a varying methodology. Epidemiological studies have found an increased risk of dementia with PTSD in Vietnam veterans as well as the general population. Laboratory studies reported the accelerated formation of β-amyloid and tau, which represent the primary pathology of Alzheimer's dementia in animal models of PTSD. These investigations were conducted against a background of cognitive impairment and atrophy of the hippocampus and certain cortical areas in patients with PTSD. Very few studies have investigated the pathological basis in humans for the reported association of PTSD with dementia. This important gap in the literature has recently been partly addressed by very few studies that estimated the burden of β-amyloid and tau. The PET studies did not show an association between PTSD and the specific pathology of Alzheimer's disease or signs of neurodegenerative diseases underlying other dementia syndromes. Another study demonstrated decreased plasma β-amyloid load and increased plasma β-amyloid 42/40 ratio in PTSD without PET evaluation. While PTSD is associated with an increased risk of dementia syndrome in general, there is no convincing evidence that it causes or accelerates the pathology of Alzheimer's disease, which causes the most common type of dementia. Factors that may account for the association between PTSD and a clinical diagnosis of dementia are discussed in this review.

Trophic factors as potential therapies for treatment of major mental disorders

Notwithstanding major advances in psychotherapeutics, their efficacy and specificity remain limited. The slow onset of beneficial outcomes and numerous adverse effects of widely used medications remain of chief concern, warranting in-depth studies. The majority of frontline therapies are thought to enhance the endogenous monoaminergic drive, to initiate a cascade of molecular events leading to lasting functional and structural plasticity. They also involve alterations in trophic factor signalling, including brain-derived neurotrophic factor (BDNF), VGF (non-acronymic), vascular endothelial growth factor (VEGF), fibroblast growth factor 2 (FGF2), glial cell-derived neurotrophic factor (GDNF), and others. In several major mental disorders, emerging data suggest protective and restorative effects of trophic factors in preclinical models, when applied on their own. Antidepressant outcomes of VGF and FGF2, for instance, were shown in experimental animals, while BDNF and GDNF prove useful in the treatment of addiction, schizophrenia, and autism spectrum disorders. The main challenge with the effective translation of these and other findings in the clinic is the knowledge gap in action mechanisms with potential risks, as well as the lack of effective platforms for validation under clinical settings. Herein, we review the state-of-the-art and advances in the therapeutic use of trophic factors in several major neuropsychiatric disorders.

Chronic Stress Weakens Connectivity in the Prefrontal Cortex: Architectural and Molecular Changes

Chronic exposure to uncontrollable stress causes loss of spines and dendrites in the prefrontal cortex (PFC), a recently evolved brain region that provides top-down regulation of thought, action, and emotion. PFC neurons generate top-down goals through recurrent excitatory connections on spines. This persistent firing is the foundation for higher cognition, including working memory, and abstract thought. However, exposure to acute uncontrollable stress drives high levels of catecholamine release in the PFC, which activates feedforward calcium-cAMP signaling pathways to open nearby potassium channels, rapidly weakening synaptic connectivity to reduce persistent firing. Chronic stress exposures can further exacerbate these signaling events leading to loss of spines and resulting in marked cognitive impairment. In this review, we discuss how stress signaling mechanisms can lead to spine loss, including changes to BDNF-mTORC1 signaling, calcium homeostasis, actin dynamics, and mitochondrial actions that engage glial removal of spines through inflammatory signaling. Stress signaling events may be amplified in PFC spines due to cAMP magnification of internal calcium release. As PFC dendritic spine loss is a feature of many cognitive disorders, understanding how stress affects the structure and function of the PFC will help to inform strategies for treatment and prevention.

The Neurocircuitry of Posttraumatic Stress Disorder and Major Depression: Insights Into Overlapping and Distinct Circuit Dysfunction-A Tribute to Ron Duman

The neurocircuitry that contributes to the pathophysiology of posttraumatic stress disorder and major depressive disorder, psychiatric conditions that exhibit a high degree of comorbidity, likely involves both overlapping and unique structural and functional changes within multiple limbic brain regions. In this review, we discuss neurobiological alterations that are associated with posttraumatic stress disorder and major depressive disorder and highlight both similarities and differences that may exist between these disorders to argue for the existence of a shared neurobiology. We highlight the key contributions based on preclinical studies, emerging from the late Professor Ronald Duman's research, that have shaped our understanding of the neurocircuitry that contributes to both the etiopathology and treatment of major depressive disorder and posttraumatic stress disorder.

BDNF Impact on Biological Markers of Depression-Role of Physical Exercise and Training

Depression is the most common and devastating psychiatric disorder in the world. Its symptoms, especially during the pandemic, are observed in all age groups. Exercise training (ET) is well known as a non-pharmacological strategy to alleviate clinical depression. The brain-derived neurotrophic factor (BDNF) is one of the biological factors whose expression and secretion are intensified in response to ET. BDNF is also secreted by contracted skeletal muscle that likely exerts para-, auto- and endocrine effects, supporting the crosstalk between skeletal muscle and other distant organs/tissues, such as the nervous system. This finding suggests that they communicate and work together to induce improvements on mood, cognition, and learning processes as BDNF is the main player in the neurogenesis, growth, and survival of neurons. Therefore, BDNF has been recognized as a therapeutic factor in clinical depression, especially in response to ET. The underlying mechanisms through which ET impacts depression are varied. The aim of this review was to provide information of the biological markers of depression such as monoamines, tryptophan, endocannabinoids, markers of inflammatory processes (oxidative stress and cytokines) stress and sex hormones and their relationship to BDNF. In addition, we reviewed the effects of ET on BNDF expression and how it impacts depression as well as the potential mechanisms mediating this process, providing a better understanding of underlying ET-related mechanisms in depression.

Macro- and Microscale Stress-Associated Alterations in Brain Structure: Translational Link With Depression

Major depressive disorder (MDD) is a stress-related disorder associated with many cytoarchitectural and neurochemical changes. However, the majority of these changes cannot be reliably detected in the living brain. The examination of animal stress models and postmortem human brain tissue has significantly contributed to our understanding of the pathophysiology of MDD. Ronald Duman's work in humans and in rodent models was critical to the investigation of the contribution of synaptic deficits to MDD and chronic stress pathology, their role in the development and expression of depressive-like behavior, and reversal by novel drugs. Here, we review evidence from magnetic resonance imaging in humans and animals that suggests that corticolimbic alterations are associated with depression symptomatology. We also discuss evidence of cytoarchitectural alterations affecting neurons, astroglia, and synapses in MDD and highlight how similar changes are described in rodent chronic stress models and are linked to the emotion-related behavioral deficits. Finally, we report on the latest approaches developed to measure the synaptic and astroglial alterations in vivo, using positron emission tomography, and how it can inform on the contribution of MDD-associated cytoarchitectural alterations to the symptomatology and the treatment of stress-related disorders.

Paradoxical changes in mood-related behaviors on continuous social isolation after weaning

Continuous social isolation (SI) from an early developmental stage may have different effects in youth and adulthood. Moreover, SI is reported to impair neuronal plasticity. In this study, we used post-weaning rats to compare the impact of continuous SI on depressive-like, anxiety-related, and fear-related behaviors and neuronal plasticity in puberty and adulthood. Furthermore, we assessed the effect of lithium on behavioral changes and neuronal plasticity. Continuous SI after weaning induced depressive-like behaviors in puberty; however, in adulthood, depressive-like and anxiety-related behaviors did not increase, but—paradoxically—decreased in comparison with the controls. The decreased expression of neuronal plasticity-related proteins in the hippocampus in puberty was more prominent in the prefrontal cortex and hippocampus in adulthood. In contrast, SI after weaning tended to decrease fear-related behaviors in puberty, a decrease which was more prominent in adulthood with increased neuronal plasticity-related protein expression in the amygdala. Lithium administration over the last 14 days of the SI-induced period removed the behavioral and expression changes of neuronal plasticity-related proteins observed in puberty and adulthood. Our findings suggest that the extension of the duration of SI from an early developmental stage does not simply worsen depressive-like behaviors; rather, it induces a behavior linked to neuronal plasticity damage. Lithium may improve behavioral changes in puberty and adulthood by reversing damage to neuronal plasticity. The mechanisms underlying the depressive-like and anxiety-related behaviors may differ from those underlying fear-related behaviors.

Chronic restraint stress induces changes in the cerebral Galpha 12/13 and Rho-GTPase signaling network

Background

Evidence indicates that Gα12, Gα13, and its downstream effectors, RhoA and Rac1, regulate neuronal morphology affected by stress. This study was aimed at investigating whether repeated stress influences the expression of proteins related to the Gα12/13 intracellular signaling pathway in selected brain regions sensitive to the effects of stress. Furthermore, the therapeutic impact of β(1)adrenergic receptors (β1AR) blockade was assessed.

Methods

Restraint stress (RS) model in mice (2 h/14 days) was used to assess prolonged stress effects on the mRNA expression of Gα12, Gα13, RhoA, Rac1 in the prefrontal cortex (PFC), hippocampus (HIP) and amygdala (AMY). In a separate study, applying RS model in rats (3–4 h/1 day or 14 days), we evaluated stress effects on the expression of Gα12, Gα11, Gαq, RhoA, RhoB, RhoC, Rac1/2/3 in the HIP. Betaxolol (BET), a selective β1AR antagonist, was introduced (5 mg/kg/p.o./8–14 days) in the rat RS model to assess the role of β1AR in stress effects. RT-qPCR and Western Blot were used for mRNA and protein assessments, respectively.

Results

Chronic RS decreased mRNA expression of Gα12 and increased mRNA for Rac1 in the PFC of mice. In the mice AMY, decreased mRNA expression of Gα12, Gα13 and RhoA was observed. Fourteen days of RS exposure increased RhoA protein level in the rats’ HIP in the manner dependent on β1AR activity.

Conclusions

Together, these results suggest that repeated RS affects the expression of genes and proteins known to be engaged in neural plasticity, providing potential targets for further studies aimed at unraveling the molecular mechanisms of stress-related neuropsychiatric diseases.

Supplementary Information

The online version contains supplementary material available at 10.1007/s43440-021-00294-4.

Sleep and Memory Consolidation Dysfunction in Psychiatric Disorders: Evidence for the Involvement of Extracellular Matrix Molecules

Sleep disturbances and memory dysfunction are key characteristics across psychiatric disorders. Recent advances have revealed insight into the role of sleep in memory consolidation, pointing to key overlap between memory consolidation processes and structural and molecular abnormalities in psychiatric disorders. Ongoing research regarding the molecular mechanisms involved in memory consolidation has the potential to identify therapeutic targets for memory dysfunction in psychiatric disorders and aging. Recent evidence from our group and others points to extracellular matrix molecules, including chondroitin sulfate proteoglycans and their endogenous proteases, as molecules that may underlie synaptic dysfunction in psychiatric disorders and memory consolidation during sleep. These molecules may provide a therapeutic targets for decreasing strength of reward memories in addiction and traumatic memories in PTSD, as well as restoring deficits in memory consolidation in schizophrenia and aging. We review the evidence for sleep and memory consolidation dysfunction in psychiatric disorders and aging in the context of current evidence pointing to the involvement of extracellular matrix molecules in these processes.

Mechanistic interplay of various mediators involved in mediating the neuroprotective effect of daphnetin

Daphnetin is a 7, 8 dihydroxy coumarin isolated from different medicinal plants of the Thymelaeaceae family and exhibits copious pharmacological activities including neuroprotection, anti-cancer, anti-malarial, anti-inflammatory, anti-parasitic and anti-arthritic activity. It has been proved to be an effective neuroprotective agent in several preclinical animal studies and cell line examinations. It is found to interact with different cellular mediators and signaling pathways to confer protection against neurodegeneration. The reactive oxygen species and inflammatory mediators are the major culprits of different neurodegenerative diseases. Oxidative stress activates the pro-apoptotic proteins and inhibits anti-apoptotic proteins, leading to neuronal cell death. Daphnetin restores cellular redox balance by upregulating the antioxidants level (GSH and SOD), anti-apoptotic protein (Bcl-2), as well as by reducing the levels of proinflammatory cytokines, executioner caspase-3, pro-apoptotic-Bax, and oxidative stress markers. Furthermore, activation of Nrf-2/HO-1 signaling and upregulation of HSP-70 governs the protection elicited by daphnetin against oxidative stress-induced neuronal apoptosis. Daphnetin modulated inhibition of JNK-MAPK, JAK-STAT, and TLR-4/NF-κB signaling pathways also contributed to its neuroprotective effect. The positive effects of daphnetin have been also related to its AChE, BChE, and BACE-1 inhibitory potential. The present review has been designed to explore the mechanistic interplay of various mediators in mediating the neuroprotective effects of daphnetin.

Common and Specific Alterations of Amygdala Subregions in Major Depressive Disorder With and Without Anxiety: A Combined Structural and Resting-State Functional MRI Study

Anxious major depressive disorder is a common subtype of major depressive disorder; however, its unique neural mechanism is not well-understood currently. Using multimodal MRI data, this study examined common and specific alterations of amygdala subregions between patients with and without anxiety. No alterations were observed in the gray matter volume or intra-region functional integration in either patient group. Compared with the controls, both patient groups showed decreased functional connectivity between the left superficial amygdala and the left putamen, and between the right superficial amygdala and the bilateral anterior cingulate cortex and medial orbitofrontal cortex, while only patients with anxiety exhibited decreased activity in the bilateral laterobasal and superficial amygdala. Moreover, the decreased activity correlated negatively with the Hamilton depression scale scores in the patients with anxiety. These findings provided insights into the pathophysiologic processes of anxious major depressive disorder and may help to develop new and effective treatment programs.

Construction and Analysis of a Diagnostic Model Based on Differential Expression Genes in Patients With Major Depressive Disorder

Background: Major depressive disorder (MDD) is a common and severe psychiatric disorder with a heavy burden on the individual and society. However, the prevalence varies significantly owing to the lack of auxiliary diagnostic biomarkers. To identify the shared differential expression genes (DEGs) with potential diagnostic value in both the hippocampus and whole blood, a systematic and integrated bioinformatics analysis was carried out. Methods: Two datasets from the Gene Expression Omnibus database (GSE53987 and GSE98793) were downloaded and analyzed separately. A weighted gene co-expression network analysis was performed to construct the co-expression gene network of DEGs from GSE53987, and the most disease-related module was extracted. The shared DEGs from the module and GSE98793 were identified using a Venn diagram. Functional pathway prediction was used to identify the most disease-related DEGs. Finally, several DEGs were chosen, and their potential diagnostic value was determined by receiver operating characteristic curve analysis. Results: After weighted gene co-expression network analysis, the most MDD-related module (MEgrey) was identified, and 623 DEGs were extracted from this module. The intersection between MEgrey and GSE98793 was calculated, and 163 common DEGs were identified. The co-expression network of 163 DEGs from these was then reconstructed. All hub genes were identified based on the connective degree of the reconstructed co-expression network. Based on the results of functional pathway enrichment, 17 candidate hub genes were identified. Finally, logistic regression and receiver operating characteristic curves showed that three candidate hub genes (CEP350, SMAD5, and HSPG2) had relatively high auxiliary value in the diagnosis of MDD. Conclusion: Our results showed that the combination of CEP350, SMAD5, and HSPG2 has a relatively high diagnostic value for MDD. Pathway enrichment analysis also showed that these genes may play an important role in the pathogenesis of MDD. These results suggest a potentially important role for this gene combination in clinical practice.

Synaptic Microenvironment in Depressive Disorder: Insights from Synaptic Plasticity

Depression is a major disease that can affect both mental and physical health, limits psychosocial functioning and diminishes the quality of life. But its complex pathogenesis remains poorly understood. The dynamic changes of synaptic structure and function, known as synaptic plasticity, occur with the changes of different cellular microenvironment and are closely related to learning and memory function. Accumulating evidence implies that synaptic plasticity is integrally involved in the pathological changes of mood disorders, especially in depressive disorder. However, the complex dynamic process of synaptic plasticity is influenced by many factors. Here, we reviewed and discussed various factors affecting synaptic plasticity in depression, and proposed a specific framework named synaptic microenvironment, which may be critical for synaptic plasticity under pathological conditions. Based on this concept, we will show how we understand the balance between the synaptic microenvironment and the synaptic plasticity network in depression. Finally, we point out the clinical significance of the synaptic microenvironment in depression.

Minocycline alleviates depression-like symptoms by rescuing decrease in neurogenesis in dorsal hippocampus via blocking microglia activation/phagocytosis

Clinical studies examining the potential of anti-inflammatory agents, specifically of minocycline, as a treatment for depression has shown promising results. However, mechanistic insights into the neuroprotective and anti-inflammatory actions of minocycline need to be provided. We evaluated the effect of minocycline on chronic mild stress (CMS) induced depressive-like behavior, and behavioral assays revealed minocycline ameliorate depressive behaviors. Multiple studies suggest a role of microglia in depression, revealing that microglia activation correlates with a decrease in neurogenesis and increased depressive-like behavior. The effect of minocycline on microglia activation in different areas of the dorsal or ventral hippocampus in stressed mice was examined by immunohistochemistry. We observed the increase in the number of activated microglia expressing CD68 after exposure to three weeks of chronic stress, whereas no changes in total microglia number were observed. These changes were observed throughout the DG, CA1 and CA2 regions in dorsal hippocampus but restricted to the DG of the ventral hippocampus. In vitro experiments including western blotting and phagocytosis assay were used to investigate the effect of minocycline on microglia activation. Activation of primary microglia by LPS in vitro causes and ERK1/2 activation, enhancement of iNOS expression and phagocytic activity, and alterations in cellular morphology that are reversed by minocycline exposure, suggesting that minocycline directly acts on microglia to reduce phagocytic potential. Our results suggest the most probable mechanism by which minocycline reverses the pathogenic phagocytic potential of neurotoxic M1 microglia, and reduces the negative phenotypes associated with reduced neurogenesis caused by exposure to chronic stress.

Mitochondrial gene signature in the prefrontal cortex for differential susceptibility to chronic stress

Mitochondrial dysfunction was highlighted as a crucial vulnerability factor for the development of depression. However, systemic studies assessing stress-induced changes in mitochondria-associated genes in brain regions relevant to depression symptomatology remain scarce. Here, we performed a genome-wide transcriptomic study to examine mitochondrial gene expression in the prefrontal cortex (PFC) and nucleus accumbens (NAc) of mice exposed to multimodal chronic restraint stress. We identified mitochondria-associated gene pathways as most prominently affected in the PFC and with lesser significance in the NAc. A more detailed mitochondrial gene expression analysis revealed that in particular mitochondrial DNA-encoded subunits of the oxidative phosphorylation complexes were altered in the PFC. The comparison of our data with a reanalyzed transcriptome data set of chronic variable stress mice and major depression disorder subjects showed that the changes in mitochondrial DNA-encoded genes are a feature generalizing to other chronic stress-protocols as well and might have translational relevance. Finally, we provide evidence for changes in mitochondrial outputs in the PFC following chronic stress that are indicative of mitochondrial dysfunction. Collectively, our work reinforces the idea that changes in mitochondrial gene expression are key players in the prefrontal adaptations observed in individuals with high behavioral susceptibility and resilience to chronic stress.

CAPON Is a Critical Protein in Synaptic Molecular Networks in the Prefrontal Cortex of Mood Disorder Patients and Contributes to Depression-Like Behavior in a Mouse Model

Aberrant regulation and activity of synaptic proteins may cause synaptic pathology in the prefrontal cortex (PFC) of mood disorder patients. Carboxy-terminal PDZ ligand of NOS1 (CAPON) is a critical scaffold protein linked to synaptic proteins like nitric oxide synthase 1, synapsins. We hypothesized that CAPON is altered together with its interacting synaptic proteins in the PFC in mood disorder patients and may contribute to depression-like behaviors in mice subjected to chronic unpredictable mild stress (CUMS). Here, we found that CAPON-immunoreactivity (ir) was significantly increased in the dorsolateral PFC (DLPFC) and anterior cingulate cortex in major depressive disorder (MDD), which was accompanied by an upregulation of spinophilin-ir and a downregulation of synapsin-ir. The increases in CAPON and spinophilin and the decrease in synapsin in the DLPFC of MDD patients were also seen in the PFC of CUMS mice. CAPON-ir positively correlated with spinophilin-ir (but not with synapsin-ir) in mood disorder patients. CAPON colocalized with spinophilin in the DLPFC of MDD patients and interacted with spinophilin in human brain. Viral-mediated CAPON downregulation in the medial PFC notably reversed the depression-like behaviors in the CUMS mice. These data suggest that CAPON may contribute to aspects of depressive behavior, possibly as an interacting protein for spinophilin in the PFC.

Ketamine and its metabolite, (2R,6R)-HNK, restore hippocampal LTP and long-term spatial memory in the Wistar-Kyoto rat model of depression

Accumulating evidence implicates dysregulation of hippocampal synaptic plasticity in the pathophysiology of depression. However, the effects of ketamine on synaptic plasticity and their contribution to its mechanism of action as an antidepressant, are still unclear. We investigated ketamine’s effects on in vivo dorsal hippocampal (dHPC) synaptic plasticity and their role in mediating aspects of antidepressant activity in the Wistar-Kyoto (WKY) model of depression. dHPC long-term potentiation (LTP) was significantly impaired in WKY rats compared to Wistar controls. Importantly, a single low dose (5 mg/kg, ip) of ketamine or its metabolite, (2R,6R)-HNK, rescued the LTP deficit in WKY rats at 3.5 h but not 30 min following injection, with residual effects at 24 h, indicating a delayed, sustained facilitatory effect on dHPC synaptic plasticity. Consistent with the observed dHPC LTP deficit, WKY rats exhibited impaired hippocampal-dependent long-term spatial memory as measured by the novel object location recognition test (NOLRT), which was effectively restored by pre-treatment with both ketamine or (2R,6R)-HNK. In contrast, in WKYs, which display abnormal stress coping, ketamine, but not (2R,6R)-HNK, had rapid and sustained effects in the forced swim test (FST), a commonly used preclinical screen for antidepressant-like activity. The differential effects of (2R,6R)-HNK observed here reveal a dissociation between drug effects on FST immobility and dHPC synaptic plasticity. Therefore, in the WKY rat model, restoring dHPC LTP was not correlated with ketamine’s effects in FST, but importantly, may have contributed to the reversal of hippocampal-dependent cognitive deficits, which are critical features of clinical depression. Our findings support the theory that ketamine may reverse the stress-induced loss of connectivity in key neural circuits by engaging synaptic plasticity processes to “reset the system”.

[The effect of multichannel electrostimulation of neck nervous structures on the brain connectivity of patients with depressive disorders]

AIM

To study neurophysiological processes during multichannel electrostimulation in patients with depressive disorder.

MATERIAL AND METHODS

The study involved 6 patients with depressive disorder (F33). The technology noninvasive multichannel stimulation of neck neural struct SYMPATHOKOR-01 device. Clinical and psychometric methods, functional neuroimaging (fMRTP) and multichannel electroencephalography (EEG) were used to assess treatment effect.

RESULTS

In all patients, fMRTP and EEG results show the disturbances of brain connectivity, which are correlated with the clinical state of the disease, before treatment. After five stimulation procedures, there is an increase in functional connection of the medial prefrontal cortex (according to rs-fMRI results) and an increase in the synchronization of various parts of the cortex (EEG results).

CONCLUSION

The results demonstrate the possibilities of multichannel electrical stimulation of the neck nervous structures to restore the intracerebral connections disturbed during depression due to the activation of neuroplasticity.

Hippocampal CD39/ENTPD1 promotes mouse depression-like behavior through hydrolyzing extracellular ATP

Emerging evidence implicates that low levels of ATP in the extracellular space may contribute to the pathophysiology of major depressive disorder (MDD). The concentration of extracellular ATP is regulated by its hydrolase ectonucleotide tri(di)phosphohydrolase (ENTPD). However, the role of ENTPD in depression remains poorly understood. Here we examine the role of CD39 (known as ENTPD1) in mouse depression-like behavior induced by chronic social defeat stress (CSDS). We demonstrate that CSDS enhances the expression and activity of CD39 in hippocampus. The CD39 functional analog apyrase also induces depression-like behavior, which can be ameliorated by ATP replenishment. Pharmacological inhibition and genetic silencing of CD39 has an antidepressant-like effect via increasing hippocampal extracellular ATP concentration, accompanied with an increase in hippocampal neurogenesis and dendritic spine numbers in defeated mice. These results suggest that hippocampal CD39 contributes to CSDS-induced depression-like behavior via hydrolyzing extracellular ATP, indicating that CD39 may be a promising new target for the treatment of depression.

Serotonin induces Arcadlin in hippocampal neurons

The monoamine hypothesis does not fully explain the delayed onset of recovery after antidepressant treatment or the mechanisms of recovery after electroconvulsive therapy (ECT). The common mechanism that operates both in ECT and monoaminergic treatment presumably involves molecules induced in both of these conditions. A spine density modulator, Arcadlin (Acad), the rat orthologue of human Protocadherin-8 (PCDH8) and of Xenopus and zebrafish Paraxial protocadherin (PAPC), is induced by both electroconvulsive seizure (ECS) and antidepressants; however, its cellular mechanism remains elusive. Here we confirm induction of Arcadlin upon stimulation of an N-methyl-d-aspartate (NMDA) receptor in cultured hippocampal neurons. Stimulation of an NMDA receptor also induced acute (20 min) and delayed (2 h) phosphorylation of the p38 mitogen-activated protein (MAP) kinase; the delayed phosphorylation was not obvious in Acad^-/- neurons, suggesting that it depends on Arcadlin induction. Exposure of highly mature cultured hippocampal neurons to 1-10 μM serotonin for 4 h resulted in Arcadlin induction and p38 MAP kinase phosphorylation. Co-application of the NMDA receptor antagonist d-(-)-2-amino-5-phosphonopentanoic acid (APV) completely blocked Arcadlin induction and p38 MAP kinase phosphorylation. Finally, administration of antidepressant fluoxetine in mice for 16 days induced Arcadlin expression in the hippocampus. Our data indicate that the Arcadlin-p38 MAP kinase pathway is a candidate neural network modulator that is activated in hippocampal neurons under the dual regulation of serotonin and glutamate and, hence, may play a role in antidepressant therapies.

"Braking" the Prefrontal Cortex: The Role of Glucocorticoids and Interneurons in Stress Adaptation and Pathology

The medial prefrontal cortex (mPFC) receives information regarding stimuli and appropriately orchestrates neurophysiological, autonomic, and behavioral responses to stress. The cellular and neurochemical heterogeneity of the mPFC and its projections are key to fine-tuning of stress responses and adaptation. Output of the mPFC is mediated by glutamatergic pyramidal neurons whose activity is coordinated by an intricate network of interneurons. Excitatory/inhibitory (E/I) balance in the mPFC is critical for appropriate responsiveness to stress, and E/I imbalance occurs in numerous neuropsychiatric disorders that co-occur with chronic stress. Moreover, there is mounting data suggesting that chronic stress may precipitate E/I imbalance. This review will provide information regarding the cellular and anatomical makeup of the mPFC and discuss the impact of acute and chronic stress in adulthood and early life on interneuron function, with implications for E/I balance affecting functional connectivity. Specifically, the review will highlight the importance of interneuron type, connectivity, and location (both layer- and subregion-specific). The discussion of local mPFC networks will focus on stress context, including stressor duration (acute vs. chronic) and timing (early life vs. adulthood), as these factors have significant implications for the interpretation of experiments and mPFC E/I balance. Indeed, interneurons appear to play a prominent role in prefrontal adaptation, and a better understanding of the interactions between stress and interneuron function may yield insight to the transition from adaptation to pathology. Ultimately, determining the mechanisms mediating adaptive versus pathologic plasticity will promote the development of novel treatments for neuropsychiatric disorders related to prefrontal E/I imbalance.

Loss of Prefrontal Cortical Higher Cognition with Uncontrollable Stress: Molecular Mechanisms, Changes with Age, and Relevance to Treatment

The newly evolved prefrontal cortex (PFC) generates goals for "top-down" control of behavior, thought, and emotion. However, these circuits are especially vulnerable to uncontrollable stress, with powerful, intracellular mechanisms that rapidly take the PFC "off-line." High levels of norepinephrine and dopamine released during stress engage α1-AR and D1R, which activate feedforward calcium-cAMP signaling pathways that open nearby potassium channels to weaken connectivity and reduce PFC cell firing. Sustained weakening with chronic stress leads to atrophy of dendrites and spines. Understanding these signaling events helps to explain the increased susceptibility of the PFC to stress pathology during adolescence, when dopamine expression is increased in the PFC, and with advanced age, when the molecular "brakes" on stress signaling are diminished by loss of phosphodiesterases. These mechanisms have also led to pharmacological treatments for stress-related disorders, including guanfacine treatment of childhood trauma, and prazosin treatment of veterans and civilians with post-traumatic stress disorder.

The protective effects of Ghrelin/GHSR on hippocampal neurogenesis in CUMS mice

Ghrelin is an orexigenic hormone that also plays an important role in mood disorders. Our previous studies demonstrated that ghrelin administration could protect against depression-like behaviors of chronic unpredictable mild stress (CUMS) in rodents. However, the mechanism related to the effect of ghrelin on CUMS mice has yet to be revealed. This article shows that ghrelin (5 nmol/kg/day for 2 weeks, i.p.) decreased depression-like behaviors induced by CUMS and increased hippocampal integrity (neurogenesis and spine density) measured via Ki67, 5-bromo-2-deoxyuridine (BrdU), doublecortin (DCX) labeling and Golgi-cox staining, which were decreased under CUMS. The behavioral phenotypes of Growth hormone secretagogue receptor (Ghsr)-null and wild type (WT) mice were evaluated under no stress condition and after CUMS exposure to determine the effect of Ghsr knockout on the behavioral phenotypes and stress susceptibility of mice. Ghsr-null mice exhibited depression-like behaviors under no stress condition. CUMS induced similar depression- and anxiety-like behavioral manifestations in both Ghsr-null and WT mice. A similar pattern of behavioral changes was observed after hippocampal GHSR knockdown. Additionally, both Ghsr knockout as well as CUMS exhibited deleterious effects on neurogenesis and spine density in the dentate gyrus (DG). Besides, CCK8 assay and 5-Ethynyl-2'-deoxyuridine (EdU) incorporation assay showed that ghrelin has a proliferative effect on primary cultured hippocampal neural stem cells (NSCs) and this proliferation was blocked by D-Lys3-GHRP-6 (DLS, the antagonist of GHSR, 100 μM) pretreatment. Ghrelin-induced proliferation is associated with the inhibition of G1 arrest, and this inhibition was blocked by LY294002 (specific inhibitor of PI3K, 20 μM). Furthermore, the in vivo data displayed that LY294002 (50 nmol, i.c.v.) can significantly block the antidepressant-like action of exogenous ghrelin treatment. All these results suggest that ghrelin/GHSR signaling maintains the integrity of hippocampus and has an inherent neuroprotective effect whether facing stress or not.

Progesterone and fluoxetine treatments of postpartum depressive-like behavior in rat model

Research studies have indicated that alterations in plasma progesterone levels might be associated with the hippocampal synaptic plasticity of postpartum depressive-like behavior. Herein, we assess both progesterone and fluoxetine effects in adult female Sprague-Dawley rats with postpartum depressive-like behavior. Depressive-like behavior of postpartum rats was established using chronic ultra-mild stress (CUMS) method for 1 week from gestation day 15. Postpartum rats that showed depressive-like behavior were treated with either progesterone (subcutaneously, 0.5 mg/kg) from gestation day 17 to gestation day 22 or fluoxetine (by gavage, 10 mg/kg/day) for 4 weeks after birth. Open field and sucrose preference tests were conducted at the start, week 2 and week 4 postpartum. Golgi staining, immunofluorescence and Western blot analyses of rats' hippocampi were conducted on week 4 postpartum. Results showed CUMS increases depressive-like behavior, however, treatment with progesterone and fluoxetine improves this behavior. Both progesterone and fluoxetine treatments increase the numbers of dendritic spines pyramidal neurons in the CA3 region of the hippocampus as well as protein expression levels of microtubule-associated protein 2 (MAP-2) and synaptophysin (SYP). CUMS-induced decrement of MAP-2 and SYP protein expressions can be prevented by treatment with progesterone in advanced pregnant stage and fluoxetine in the postpartum period.

Integrin αVβ3 Function Influences Citalopram Immobility Behavior in the Tail Suspension Test

Human studies first identified genetic and expression interactions between integrin β3 and serotonin (5-HT) transporter (SERT) genes. This association has been further strengthened by our discovery that integrin β3-containing receptors (αvβ3) physically interact with, and thereby define, a subpopulation of SERTs that may represent the main target of selective serotonin reuptake inhibitors (SSRIs). In this study, we examine how integrin αvβ3 function influences the behavioral response to the highly SSRI citalopram in the tail suspension test. Mice bearing a conditional deletion of the integrin β3 gene in neurons, or those expressing a constitutively active αvβ3 receptor, have decreased sensitivity to citalopram, when compared to wild-type littermates. To identify potential signaling pathways downstream of integrin αvβ3 that could be altered in these mouse lines, and consequently influence citalopram response in vivo, we performed antibody array analyses of midbrain synaptosomes isolated from mice bearing genetically altered integrin β3. We then pharmacologically targeted focal adhesion (FAK) and extracellular-signal-regulated (ERK) kinases and determined that FAK and ERK activity are critical for the actions of citalopram. Taken together, our studies have revealed a complex relationship between integrin αvβ3 function, SERT-dependent 5-HT uptake, and the effective dose of citalopram in the TST, thus implicating a role for integrin signaling pathways in the behavioral response to SSRIs.

Omega-3 Polyunsaturated Fatty Acid Deficiency and Progressive Neuropathology in Psychiatric Disorders: A Review of Translational Evidence and Candidate Mechanisms

Meta-analytic evidence indicates that mood and psychotic disorders are associated with both omega-3 polyunsaturated fatty acid (omega-3 PUFA) deficits and progressive regional gray and white matter pathology. Although the association between omega-3 PUFA insufficiency and progressive neuropathological processes remains speculative, evidence from translational research suggests that omega-3 PUFA insufficiency may represent a plausible and modifiable risk factor not only for enduring neurodevelopmental abnormalities in brain structure and function, but also for increased vulnerability to neurodegenerative processes. Recent evidence from human neuroimaging studies suggests that lower omega-3 PUFA intake/status is associated with accelerated gray matter atrophy in healthy middle-aged and elderly adults, particularly in brain regions consistently implicated in mood and psychotic disorders, including the amygdala, anterior cingulate, hippocampus, prefrontal cortex, and temporal cortex. Human neuroimaging evidence also suggests that both low omega-3 PUFA intake/status and psychiatric disorders are associated with reductions in white matter microstructural integrity and increased rates of white matter hyperintensities. Preliminary evidence suggests that increasing omega-3 PUFA status is protective against gray matter atrophy and deficits in white matter microstructural integrity in patients with mood and psychotic disorders. Plausible mechanisms mediating this relationship include elevated pro-inflammatory signaling, increased synaptic regression, and reductions in cerebral perfusion. Together these associations encourage additional neuroimaging research to directly investigate whether increasing omega-3 PUFA status can mitigate neuropathological processes in patients with, or at high risk for, psychiatric disorders.