Stress, depression, and neuroplasticity: a convergence of mechanisms

Resveratrol alleviates depressive-like behavior via the activation of SIRT1/NF-κB signaling pathway in microglia

BACKGROUND

Currently, the pathogenesis of depression remains poorly understood, leading to many patients receiving ineffective treatment. Resveratrol has demonstrated beneficial effects in the prevention and treatment of depression. However, it remains unknown whether resveratrol administration can counteract depression-like behaviors by regulating the SIRT1/NF-κB signaling pathway.

METHODOLOGY/PRINCIPAL FINDINGS

Male C57BL/6 mice were randomly assigned to a control group, a depression group, and a resveratrol group. The depression model was established using chronic unpredictable mild stress (CUMS) for 5 weeks. Behavioral tests were conducted to assess depressive-like behaviors. The expression levels of SIRT1 and NF-κB in the hippocampus of mice and BV2 microglial cells were measured. After 5 weeks of modeling, the results indicated that mice in the depression group exhibited significant depressive-like behaviors and inhibited activation of the SIRT1/NF-κB signaling pathway. In contrast, resveratrol administration effectively reversed these changes. Results from in vitro experiments showed that LPS stimulation increased microglial activity and downregulated the SIRT1/NF-κB signaling pathway in microglia; however, resveratrol treatment mitigated these effects.

CONCLUSIONS/SIGNIFICANCE

Our findings suggested that resveratrol can alleviate CUMS-induced depression-like behaviors via the activation of the Sirt1/NF-κB pathway in microglia.

Depression vulnerability and gray matter integrity of interoceptive networks in remitted depressed outpatients

BACKGROUND

Interoception, the representation of internal body states, plays an important role in mental health. While functional neuroimaging links Major Depressive Disorder (MDD) relapse vulnerability to stress-induced inhibition of sensorimotor regions, its association with structural changes in interoceptive networks remains unclear.

METHODS

A secondary analysis explored relationships between gray matter volume and relapse vulnerability in remitted MDD patients (N = 85), with two data acquisitions surrounding eight-weeks of prophylactic psychotherapy followed by a two-year follow-up. Participants were randomly assigned to either Cognitive Behavioral Therapy or Mindfulness-Based Cognitive Therapy (MBCT). Mixed-effects models were applied to study the relationships between cortical thickness, time, and intervention type with clinical variables such as relapse status, residual symptoms, and decentering, adjusting for relevant covariates. Analyses were conducted at whole brain levels as well as in pre-defined regions of interest, focusing on sensory regions implicated by prior research.

RESULTS

Relapse was consistently linked to greater cortical thickness in the left superior circular sulcus of the insula and the left anterior occipital sulcus. Residual symptoms correlated with increased cortical thickness in the left insula and right precentral regions, while decentering was linked to reduced thickness in the middle temporal and inferior parietal regions. MBCT participants showed greater cortical thickness increases in the right superior temporal gyrus over time.

CONCLUSIONS

MDD vulnerability was unexpectedly linked to greater cortical thickness in sensory and prefrontal brain regions, suggesting that depression vulnerability may reflect maladaptive skill acquisition. MBCT may promote gray matter growth in the right superior temporal region.

TRIAL REGISTRATION

ClinicalTrials.govNCT01178424.

URB597 modulates neuroplasticity, neuroinflammatory, and Nrf2/HO-1 signaling pathways in the hippocampus and prefrontal cortex of male and female rats in a stress-induced model of depression

Major depressive disorder is often associated with cognitive impairments, and neuroinflammation is considered a key contributor to the onset of depression. Pharmacological inhibition of fatty acid amide hydrolase (FAAH), which augments endocannabinoid signaling, has emerged as a promising approach to treating depression. The main purpose of this study is to asses the influence of FAAH inhibitor URB597 on inflammatory response and oxidative stress in chronic unpredictable stress (CUS)-induced depressive female and male rats and to explore the underlying molecular mechanisms. Chronically stressed animals showed long-term memory deficits, while URB597 improved memory only in stressed males. URB597 treatment enhanced levels of brain-derived neurotrophic factor (BDNF) in the hippocampus and mPFC of stressed female and male rats and increased phosphorylated calcium/calmodulin-dependent protein kinase II (pCaMKII) levels in the hippocampus and mPFC of CUS males. Additionally, increased phosphorylation of JAK2 and STAT3 in the hippocampus and mPFC of CUS male and female rats, was reduced following URB597 treatment. URB597 decreased the CUS-enhanced iNOS protein expression in the hippocampus and mPFC of both sexes. Furthermore, URB597 normalized CUS-induced reductions in Nrf2 and HO-1 levels in the mPFC of both sexes, with no changes in the hippocampus. Our findings suggest that URB597 may inhibit the CUS-induced neuroinflammatory response by suppressing the pro-inflammatory mediators and the activation of the JAK2/STAT3 signaling in the hippocampus and mPFC of both sexes. URB597 treatment contributed to synaptic plasticity in a sex-specific manner by upregulating brain CaMKII signaling in males. URB597 also exerts neuroprotective effects through region-specific antioxidant properties. These results have implications for sex-specific treatment strategies in stress-related neuropsychiatric disorders.

Sex-specific GABAergic microcircuits that switch vulnerability into resilience to stress and reverse the effects of chronic stress exposure

Clinical and preclinical studies have identified somatostatin (SST)-positive interneurons as critical elements that regulate the vulnerability to stress-related psychiatric disorders. Conversely, disinhibition of SST neurons in mice results in resilience to the behavioral effects of chronic stress. Here, we established a low-dose chronic chemogenetic protocol to map these changes in positively and negatively motivated behaviors to specific brain regions. AAV-hM3Dq-mediated chronic activation of SST neurons in the prelimbic cortex (PLC) had antidepressant drug-like effects on anxiety- and anhedonia-like motivated behaviors in male but not female mice. Analogous manipulation of the ventral hippocampus (vHPC) had such effects in female but not male mice. Moreover, the activation of SST neurons in the PLC of male mice and the vHPC of female mice resulted in stress resilience. Activation of SST neurons in the PLC reversed prior chronic stress-induced defects in motivated behavior in males but was ineffective in females. Conversely, activation of SST neurons in the vHPC reversed chronic stress-induced behavioral alterations in females but not males. Quantitation of c-Fos+ and FosB+ neurons in chronic stress-exposed mice revealed that chronic activation of SST neurons leads to a paradoxical increase in pyramidal cell activity. Collectively, these data demonstrate that GABAergic microcircuits driven by dendrite targeting interneurons enable sex- and brain-region-specific neural plasticity that promotes stress resilience and reverses stress-induced anxiety- and anhedonia-like motivated behavior. The data provide a rationale for the lack of antidepressant efficacy of benzodiazepines and superior efficacy of dendrite-targeting, low-potency GABAA receptor agonists, independent of sex and despite striking sex differences in the relevant brain substrates.

Default mode network-basal ganglia network connectivity predicts the transition to postherpetic neuralgia

Background

Neuroimaging studies have revealed aberrant network functional connectivity in postherpetic neuralgia (PHN) patients. However, there is a lack of knowledge regarding the relationship between the brain network connectivity during the acute period and disease prognosis.

Objective

The purpose of this study was to detect characteristic network connectivity in the process of herpes zoster (HZ) pain chronification and to identify whether abnormal network connectivity in the acute period can predict the outcome of patients with HZ.

Methods

In this cross-sectional study, 31 patients with PHN, 33 with recuperation from herpes zoster (RHZ), and 28 with acute herpes zoster (AHZ) were recruited and underwent resting-state functional magnetic resonance imaging (fMRI). We investigated the differences in the connectivity of four resting-state networks (RSN) among the three groups. Receiver operating characteristic (ROC) curve analysis was performed to identify whether abnormal network connectivity in the acute period could predict the outcome of patients with HZ.

Results

First, we found within-basal ganglia network (BGN) and default mode network (DMN)-BGN connectivity differences, with PHN patients showing increased DMN-BGN connectivity compared to AHZ and RHZ patients, while RHZ patients showing increased within-BGN connectivity compared to AHZ and PHN patients. Moreover, DMN-BGN connectivity was associated with the ID pain score in patients with AHZ. Finally, the DMN-BGN connectivity of AHZ patients could predict the outcome of HZ patients with sensitivity and specificity of 77.8 % and 63.2 %, respectively.

Conclusions

Our results provide evidence that DMN-BGN connectivity during the acute period confers a risk for the development of chronic pain and can act as a neuroimaging biomarker to predict the outcome of patients with HZ.

Depression-like effects induced by chronic unpredictable mild stress in mice are rapidly reversed by a partial negative allosteric modulator of mGlu5 receptor, M-5MPEP

RATIONALE

Due to the numerous limitations of ketamine as a rapid-acting antidepressant drug (RAAD), research is still being conducted to find an effective and safe alternative to this drug. Recent studies indicate that the partial mGlu5 receptor negative allosteric modulator (NAM), 2-(2-(3-methoxyphenyl)ethynyl)-5-methylpyridine (M-5MPEP), has therapeutic potential as an antidepressant.

OBJECTIVES

The study aimed to investigate the potential rapid antidepressant-like effect of M-5MPEP in a mouse model of depression and to determine the mechanism of this action.

METHODS

Chronic unpredictable mild stress (CUMS) was used as an animal model of depression. The effects of single and four-day administration of M-5MPEP on CUMS-induced animal behaviors reflecting anhedonia, apathy, and helplessness were studied. Western blot was applied to measure the levels of proteins potentially involved in a rapid antidepressant effect, including mammalian target of rapamycin (mTOR), eukaryotic elongation factor 2 (eEF2), tropomyosin receptor kinase B (TrkB), and serotonin transporter (SERT), both in the hippocampus and the prefrontal cortex (PFC). Furthermore, excitatory synaptic transmission and long-term potentiation (LTP) were measured in the medial PFC (mPFC).

RESULTS

We showed that M-5MPEP administration for four consecutive days abolished CUMS-induced apathy- and anhedonia-like symptoms in a mouse model of depression. We also found that these effects were accompanied by changes in hippocampal TrkB levels and mTOR and eEF2 levels in the PFC. Using electrophysiological techniques, we showed that the four-day M-5MPEP treatment reversed chronic stress-induced increases in excitatory synaptic potential and CUMS-impaired LTP in the mPFC.

CONCLUSIONS

Partial mGlu5 receptor NAM, M-5MPEP, appears to be a potentially effective new RAAD and deserves further study.

Advances in the study of NMDA receptors in depression pathogenesis and the antidepressant efficacy of their antagonists

N-methyl-D-aspartate receptors (NMDA receptors) play a crucial role as ionotropic glutamate receptors in regulating neuroplasticity, learning, memory, and a range of psychiatric disorders. Studies indicate that dysfunction of NMDA receptors is a key pathological mechanism in depression, where abnormal activation can result in neuronal excitotoxicity, excessive extracellular calcium ion accumulation, and disrupted neuroplasticity. As a non-competitive NMDA receptor antagonist, ketamine quickly relieves depressive symptoms by decreasing the activity of extracellular NMDA receptors and activating the mTOR signaling pathway. The treatment can improve severe depression and suicide thoughts within hours, but its potential for hallucinations, dissociative symptoms, and dependency restricts its broader application. Esketamine has demonstrated improvements in both side effects and efficacy and has received FDA approval, while other compounds with NMDA receptor modulating functions, such as memantine and rapastinel, are also showing potential in exploration. Future studies should concentrate on the molecular mechanisms of NMDA receptors, aiming to develop safer and more effective medications, and refine treatment strategies to offer personalized choices and longer-lasting efficacy for the treatment of depression.

Investigating glymphatic function and bed nucleus of the stria terminalis-based functional connectivity in Parkinson's disease with and without depression

Glymphatic activity and the bed nucleus of the stria terminalis (BNST) have been implicated in the pathogenesis of Parkinson's disease (PD) with depression (PDD). This study aimed to investigate glymphatic function and BNST-based functional connectivity (FC) and potential biomarkers in PDD. The diffusion tensor imaging analysis along the perivascular space (DTI-ALPS) index combined with BNST-based FC and support vector machine were applied to 24 PDD, 24 PD with non-depression (PDND), and 25 healthy controls. We found that (1) the DTI-ALPS indices (p < 0.001), the right BNST-based FC values (p < 0.001, FWE small volume correction) were significantly different among three groups; (2) the FC features in the right mPFC (mPFC_R), right MTG (MTG_R), and right ITG (ITG_R) can distinguish PDD from PDND; (3) the right BNST-based FC values, DTI-ALPS indices, and HAMD scores were correlated with each other (r = -0.620, p = 0.004; r = 0.651, p = 0.002; r = -0.53, p = 0.016). Impaired glymphatic function and altered BNST-based FC values are strongly associated with PD, and brain regions with differences in the right BNST-based FC values may serve as potential biomarkers for classifying clinical subtypes of PD. These findings provide new insights into the pathogenesis of depression in PD. This study protocol was registered on the Chinese Clinical Trial Registry (ChiCTR2000038411, September 22, 2020, https://www.chictr.org.cn/showproj.html?proj=56715 ).

Decoding chronic stress: From behavioral-molecular dynamics in mice to clinical implications of cortisol and IL-17 in depression severity

BACKGROUNDS

The etiology of depression involves chronic stress, a recognized determinant of onset and severity. This study adopts a translational approach, utilizing a mouse model and a clinical cohort to explore the relationship between chronic stress, molecular changes, and depression severity.

METHODS

In the mouse model, mice were exposed to varying frequencies of chronic stressors over several weeks, followed by behavioral assessments to confirm depressive-like behaviors and measurement of serum indicators to analyze their relationship with stress intensity. In the clinical cohort, we recruited 239 participants, including 137 patients with diagnosed depression and 102 healthy controls, and analyzed their plasma profiles for cortisol and inflammatory cytokines. The clinical cohort revealed distinctive plasma profiles, identifying cortisol and IL-17 as potential markers. Machine learning models were developed using these markers to distinguish depression severity.

RESULTS

The study revealed subtle behavioral-molecular changes in mice subjected to varying chronic stress intensities, confirming dose-response relationships. It identified cortisol and IL-17 as potential biomarkers for distinguishing depression severity and developed machine learning models demonstrating robust diagnostic capabilities.

LIMITATIONS

There is a substantial disparity in the number of individuals among different groups in the clinical participants.

CONCLUSION

The study establishes a correlation between cortisol, IL-17, and chronic stress intensity, suggesting the latter accelerates depression progression. Cortisol and IL-17 exhibit diagnostic potential, providing insights into depression progression and guiding targeted interventions. This research advances our understanding of stressinduced molecular changes in depression, contributing to the comprehension of the intricate relationship between chronic stress, molecular alterations, and depression severity.

Alcohol-Induced Changes in Brain Microstructure: Uncovering Novel Pathophysiological Mechanisms of AUD Using Translational DTI in Humans and Rodents

Alcohol use disorder (AUD) induces significant structural alterations in both gray and white matter, contributing to cognitive and functional impairments. This chapter presents a translational neuroimaging approach using diffusion-weighted MRI in humans and rodents to uncover novel pathophysiological mechanisms underlying AUD. Our studies demonstrate that increased mean diffusivity (MD) in gray matter reflects microglial reactivity and reduced extracellular space tortuosity, leading to enhanced volume neurotransmission. In white matter, fractional anisotropy (FA) reductions indicate progressive deterioration of key tracts, particularly the fimbria/fornix, linked to impaired cognitive flexibility. Importantly, longitudinal analyses reveal that white matter degeneration continues during early abstinence, suggesting that neuroinflammation and demyelination persist beyond alcohol cessation. Finally, we discuss how neuromodulatory interventions, such as transcranial magnetic stimulation (TMS), may promote recovery by enhancing myelin plasticity. These findings provide crucial insights into AUD's neurobiological underpinnings and highlight potential therapeutic targets for improving treatment outcomes.

An integrated approach to understanding the effects of exposome on neuroplasticity

Anthropogenic factors are those that occur due to human activities. The exposome is proposed to complement the genome, wherein an individual's exposure begins before birth. The range of exposures includes physical, chemical, dietary, lifestyle, biological, and occupational sources. Exposome has a positive or negative influence on neuroplasticity during different stages of life. A comprehensive study of the exposome is thus necessary to incorporate these factors and their influence on the individual, community, and the population as a whole. Exposomic research and global health present significant opportunities for interdisciplinary research. This review gives an overview of the exposome and its influence on neuroplasticity. It proposes methods to study the exposome on neuroplasticity across the lifespan of the individual. This is possible with the use of self-reported data, large-scale cohort formation, physiological sensors, neuroimaging, omics, molecular biology, and systems approaches. These approaches aim to provide a holistic understanding of an individual's neurological well-being and its implications for the population at large. This will also enable the designing of novel preventive and treatment strategies for managing neurological disorders.

Neural Stem Cell-Derived Astrogliogenesis: The Hidden Player of the Adult Hippocampal Cytogenic Niche

The adult mammalian brain exhibits remarkable forms of neural plasticity, enabling it to adapt and reorganize in response to internal and external stimuli. These plastic mechanisms include cytogenesis, the capacity of producing new neuronal and glial cells in restricted brain regions through processes known as neuro- and gliogenesis, respectively. Although many advances have been made in understanding adult brain plastic processes associated with cell genesis, as well as its functional and behavioral implications, most of the evidence is focused on neuronal cells. Even though astrocytes play a critical role in maintaining a neurochemical and electrophysiological homeostasis in the brain and provide a pivotal support to neuronal activity, the molecular mechanisms underlying the formation and functional integration of newly formed astroglial cells are poorly understood. However, some studies have provided key insights into the molecular mechanisms driving the generation of adult neural stem cell (NSC)-derived astrocytes, focusing on the dentate gyrus of the hippocampal cytogenic niche. Recent work has demonstrated that intrinsic and extrinsic factors can modulate astrogliogenesis. In the context of neuropathogenesis, this mechanism may be compromised in the hippocampus, contributing to functional and behavioral impairments. Here, we review the mechanisms underlying NSC-derived hippocampal astrogliogenesis, examining current perspectives on how adult-born astrocytes develop in the adult brain, their functional relevance, and the intricate regulation of the astrogliogenic process.

Effects of Variations in Daily Cortisol Pattern and Long-Term Cortisol Output on Hippocampal Subfield Volumes in the Adult Human Brain

Background

Animal models of adult chronic stress indicate that the cornu ammonis 1-3 (CA1-3) and dentate gyrus (DG) hippocampal subfields are most susceptible to cellular changes associated with prolonged psychogenic stressors and glucocorticoid overexposure. However, no study reported to date has examined associations between long-term cortisol output, chronic stress, and hippocampal subfield volumes in healthy adults experiencing different levels of chronic stress. The main goal of the current study was to test whether higher long-term cortisol output measured by hair cortisol concentration would be associated with atrophy of CA1-3 and DG hippocampal subfields.

Methods

We examined associations between short- and long-term cortisol output and hippocampal subfield volumes in healthy adults (N = 40). High-resolution structural magnetic resonance imaging datasets were acquired together with diurnal salivary cortisol and hair cortisol measures. Hair cortisol concentration was analyzed using the high-resolution liquid chromatography-mass spectrometry method.

Results

Higher hair cortisol concentration was associated with smaller volumes of all hippocampal subfields in the anterior hippocampus and smaller DG volumes in both the anterior and posterior hippocampus. We found that a larger increase in morning cortisol level after awakening was associated with smaller DG and CA1-3 volumes, while a smaller decrease in cortisol level in the afternoon from awakening was associated with smaller CA1-3 volume in the anterior hippocampus. The observed associations between cortisol and hippocampal subfield volumes were not predicted by individual chronic stress levels or history of childhood trauma.

Conclusions

Our results suggest that both increased hair cortisol concentration and daily cortisol fluctuations can have a negative impact on the CA1-3 and DG subfields.

From memory disorders to the development of depression: A system approach

In this review, a hypothesis explaining the origin and genesis of depression development from the perspective of a holistic functional system of behavioral control is proposed. The core of the functional system is the memory apparatus, on which all other key components of the behavioral control system (sensory information, motivation, reinforcement, and motor activity) are interlocked. In the organization of memory traces (engrams) there are two inputs, sensory and motivational, through which the stimulus-stimulus (S-S) and stimulus-motor (S-R) engrams are formed. These engrams are organized and actualized by means of forward and backward conditional connections between cortical representations of sensory information and motivational structures of the brain. Through feedback connections from reinforcing (emotional) input to the memory apparatus, the S-S and S-R engrams are consolidated or weakened depending on the strength of reward or negative events. Depression begins with a breakdown in memory mechanisms. These breakdowns are related to problems with the three mentioned memory inputs: sensory, motivational, and reinforcing (emotional). Disruptions in sensory and motivational input lead to an inability to form new memory engrams, their actualization and retrieval. This creates difficulty in solving current and past unresolved problems, eliciting more accumulation and increasing difficulties in their solving. Unresolved tasks lead to weakening of the reinforcing input, and further impairment of consolidation of the acting engrams. Another reason for the weakening of reinforcing input is excessive action of directly harmful events or constant chronic stress. The review presents the current literature and some data from our laboratory in favor of each memory input's contribution and their impact on the development of depression, when they are problematic.

Safety in treatment: Classical pharmacotherapeutics and new avenues for addressing maternal depression and anxiety during pregnancy

We aimed to review clinical research on the safety profiles of antidepressant drugs and associations with maternal depression and neonatal outcomes. We focused on neuroendocrine changes during pregnancy and their effects on antidepressant pharmacokinetics. Pregnancy-induced alterations in drug disposition and metabolism impacting mothers and their fetuses are discussed. We considered evidence for the risks of antidepressant use during pregnancy. Teratogenicity associated with ongoing treatment, new prescriptions during pregnancy, or pausing medication while pregnant was examined. The Food and Drug Administration advises caution regarding prenatal exposure to most drugs, including antidepressants, largely owing to a dearth of safety studies caused by the common exclusion of pregnant individuals in clinical trials. We contrasted findings on antidepressant use with the lack of treatment where detrimental effects to mothers and children are well researched. Overall, drug classes such as selective serotonin reuptake inhibitors and serotonin norepinephrine reuptake inhibitors appear to have limited adverse effects on fetal health and child development. In the face of an increasing prevalence of major mood and anxiety disorders, we assert that individuals should be counseled before and during pregnancy about the risks and benefits of antidepressant treatment given that withholding treatment has possible negative outcomes. Moreover, newer therapeutics, such as ketamine and κ-opioid receptor antagonists, warrant further investigation for use during pregnancy. SIGNIFICANCE STATEMENT: The safety of antidepressant use during pregnancy remains controversial owing to an incomplete understanding of how drug exposure affects fetal development, brain maturation, and behavior in offspring. This leaves pregnant people especially vulnerable, as pregnancy can be a highly stressful experience for many individuals, with stress being the biggest known risk factor for developing a mood or anxiety disorder. This review focuses on perinatal pharmacotherapy for treating mood and anxiety disorders, highlighting the current knowledge and gaps in our understanding of consequences of treatment.

Spatially resolved mapping of cells associated with human complex traits

Depicting spatial distributions of disease-relevant cells is crucial for understanding disease pathology1,2. Here we present genetically informed spatial mapping of cells for complex traits (gsMap), a method that integrates spatial transcriptomics data with summary statistics from genome-wide association studies to map cells to human complex traits, including diseases, in a spatially resolved manner. Using embryonic spatial transcriptomics datasets covering 25 organs, we benchmarked gsMap through simulation and by corroborating known trait-associated cells or regions in various organs. Applying gsMap to brain spatial transcriptomics data, we reveal that the spatial distribution of glutamatergic neurons associated with schizophrenia more closely resembles that for cognitive traits than that for mood traits such as depression. The schizophrenia-associated glutamatergic neurons were distributed near the dorsal hippocampus, with upregulated expression of calcium signalling and regulation genes, whereas depression-associated glutamatergic neurons were distributed near the deep medial prefrontal cortex, with upregulated expression of neuroplasticity and psychiatric drug target genes. Our study provides a method for spatially resolved mapping of trait-associated cells and demonstrates the gain of biological insights (such as the spatial distribution of trait-relevant cells and related signature genes) through these maps.

A Methodological Evaluation of Four Different Paired Associative Stimulation Paradigms in Healthy Controls

Background/Objectives: Plasticity deficits play a key role in the pathophysiology of various psychiatric and neurological disorders. Paired associative stimulation (PAS) leverages Hebbian principles to induce synaptic plasticity in the human brain. By repeatedly pairing (1) the peripheral nerve stimulation of the median nerve with (2) transcranial magnetic stimulation over the primary motor cortex (M1) at different inter-stimulus intervals (25 ms; PAS-25, or 10 ms; PAS-10), corticospinal excitability can be increased (PAS-25, mimicking long-term potentiation (LTP)) or decreased (PAS-10, mimicking long-term depression (LTD)). However, variations in the number of pairings and inter-pair intervals lack consensus. The aim of the study was to evaluate four different PAS paradigms, i.e., PAS-10 and PAS-25 with both 180 versus 225 pairings each, to establish the most reliable PAS protocols for LTP- and LTD-like cortical changes. Methods: In a randomized, double-blind, crossover study, 14 healthy participants underwent PAS-10 and PAS-25 with 180 and 225 pairings. Excitability was assessed by quantifying the EMG response amplitude of a hand muscle to a single stimulus. Results: PAS-25 with 225 pairings produced a robust enhancement of corticospinal excitability, while PAS-25 with 180 pairings was less effective. Surprisingly, PAS-10 with both 180 and 225 pairings also increased excitability. Conclusions: While all four PAS paradigms enhanced M1 excitability, PAS-25 with 225 pairings induced the strongest group-level effects and was most time-efficient. Significant individual variability of PAS responses suggests that optimizing PAS parameters, including pairing number and interstimulus intervals, may be necessary for personalized approaches.

Advances in discerning the mechanisms underlying depression and resiliency: relation to the neurobiology of stress and the effects of antidepressants

Depression denotes a dysregulated stress response with significant mental and health implications. This review examines the neurobiological mechanisms underlying depression and resilience, focusing on how stress mediators influence vulnerability to severe stressors contrasted with resilience. We analyze structural and functional alterations in key brain regions, genetic factors, and potential therapeutic interventions. Understanding these mechanisms offers insights into preventing depression onset instead of solely treating its manifestations.

Identification of a stress-sensitive endogenous opioid-containing neuronal population in the paranigral ventral tegmental area

Nociceptin/orphanin FQ (N/OFQ), an endogenous opioid neuropeptide, and its G-protein coupled receptor NOPR have been implicated in motivation, feeding behaviors, and aversion. Stress-induced dysfunction in these states is central to the development of numerous psychiatric disorders, and the N/OFQ-NOPR system's role in reward- and stress-related responses has driven broad interest in NOPR as a therapeutic target for anxiety and depression. However, the impact of stress on N/OFQ signaling in the context of its influence on discrete midbrain reward circuitry remains unknown. To this end, we focused on a possible candidate population of N/OFQ neurons in the paranigral ventral tegmental area (pnVTA PNOC ) that have been shown to act locally on NOPR-containing VTA dopamine neurons to suppress motivation. Here we report and characterize pnVTA PNOC sensitivity to stress exposure and identify a functional excitatory and inhibitory afferent input to this subpopulation from the lateral hypothalamus (LH). Our results indicate that pnVTA PNOC neurons become recruited during exposure to a range of acute stressor types, whereas the GABAergic input from the LH to this population is suppressed by predator odor stress, providing a mechanism for disinhibition of these neurons. These findings suggest that this N/OFQ population in the pnVTA could act as a critical bridge between stress and motivation through interactions with upstream hypothalamic circuitry.

Deficit of satellite oligodendrocytes of neurons in the rostral part of the head of the caudate nucleus in schizophrenia

Increasing evidence implicates compromised myelin integrity and oligodendrocyte abnormalities in the dysfunction of neuronal networks in schizophrenia. We previously reported a deficiency of myelinating oligodendrocytes (OL), oligodendrocyte progenitors (OP) and satellite oligodendrocytes of neurons (Sat-OL) in the prefrontal cortex and the inferior parietal cortex - cortical hubs of the frontoparietal cognitive network and default mode network (DMN) altered in schizophrenia. Deficiency of OL and OP was also detected in the head of the caudate nucleus (HCN), which accumulates cortical projections from the associative cortex and is the central node of these networks. However, the number of Sat-Ol per neuron in schizophrenia has not been studied in the HCN. In the current study we estimated the number of Sat-Ol per neuron in the rostral part of the HCN in schizophrenia (n = 18) compared to healthy controls (n = 18) in the same section collection that was previously used to study the number Ol and OP. We found a significant decrease of the number of Sat-Ol per neuron (- 50%, p < 0.001) in schizophrenia as compared to normal controls. Considering that the rostral part of the HCN is an individual network-specific projection zone of the DMN, the deficit of Sat-Ol found in schizophrenia may be related to the dysfunctional DMN-HCN connections, which has been repeatedly described in schizophrenia. The dramatic decrease of the number of Sat-Ol per neuron may be partially related to a pronounced excess of dopamine concentration in the rostral part of the HCN in schizophrenia.

Modulation of netrin-1/DCC signaling pathway by Jiawei Kongsheng Zhenzhong Pill improves synaptic structural plasticity in PSD rats

Jiawei Kongsheng Zhenzhong Pill(JKZP) is based on Kongsheng Zhenzhong Pill contained in the Tang Dynasty's "Thousand Golden Prescriptions," which exhibited good anti-ischemic and antidepressant effects in the previous study. However, its specific effects on post-stroke depression (PSD) and the mechanism are not clear. This study aimed to investigate the effects of JKZP in the treatment of PSD and related mechanisms. The decoction of JKZP was first analyzed for its medicinal chemical composition and screened for representative components of JKZP. The Middle cerebral artery occlusion (MCAO) method combined with solitary rearing and chronic unpredictable mild stress (CUMS) was used to establish a rat model of PSD, and to observe the effects of JKZP on the behavior and synaptic plasticity of PSD rats, and to investigate the mechanism of JKZP in the treatment of PSD by detecting the mRNA level, protein expression and activity of Netrin-1/DCC signaling pathway-related proteins. The results showed that the JKZP decoction contained loganin, β-asarone and other pharmaceutical ingredients, which have been reported to protect against cerebral ischemic injury and antidepressant effects. JKZP significantly improved the depression-like behavior of PSD rats and improved the damage to pyramidal neurons in the medial prefrontal cortex (mPFC) of PSD rats. Moreover, JKZP increased the density of dendritic spines in the mPFC of PSD rats, improved synaptic gap width and thickness of the post-synaptic density, and increased the number of synaptic vesicles. The results of Real-Time quantitative reverse transcription PCR (qRT-PCR), Western blotting, and pull-down assays revealed that JKZP increased netrin-1, deleted in colorectal cancer (DCC), and focal adhesion kinase (FAK) mRNA and protein expression, elevated the p-FAK/FAK ratio, and decreased myosin II protein expression and Ras homolog gene family member A (RhoA-GTP) activity in the mPFC of PSD rats. Taken together, JKZP can affect synaptic structural remodeling and improve depressive manifestations and neuronal damage in PSD rats by regulating the expression and activity of signaling molecules related to the netrin-1/DCC signaling pathway.

Paranode length in the prefrontal cortex of subjects with major depression and rats under chronic unpredictable stress

Experimental studies of major depressive disorder (MDD) and stress reveal connectivity disturbances of the prefrontal cortex (PFC) that may involve molecular and morphological changes in myelin and the axons it enwraps. These alterations may also affect the nodes of Ranvier (NR), myelin-bare axon stretches along myelin sheaths necessary for action potential propagation, as well as the paranodes, specialized regions of the myelin sheath flanking NRs. Thus, we investigated whether paranode length and the labeling of paranode marker CASPR in PFC white matter (WM) differed in MDD subjects and chronic stress-exposed rats, as compared to their respective controls. Histological sections were obtained from postmortem PFC blocks of 11 subjects with MDD diagnosis and 11 non-psychiatric controls as well as from 6 rats subjected to chronic unpredictable stress (CUS) and 6 non-stressed controls. NRs and paranodes were detected by immunofluorescence with specific antibodies to paranodal protein CASPR. Differences in paranode length and CASPR immunoreactivity were assessed by analysis of covariance and t-tests. In MDD, both paranode length and overall CASPR immunoreactivity were significantly lower than in non-psychiatric controls, while paranode length and CASPR labeling were positively correlated with age. However, those variables did not statistically differ between CUS-exposed and non-exposed rats. Shorter paranodes and lower CASPR immunoreactivity in MDD subjects suggest alterations in paranodal myelin, which may contribute to depression-related connectivity changes. However, without comparable changes in CUS-exposed rats, mechanisms other than the stress response cannot be ruled out as contributors to paranode alterations in MDD.

Dietary texture-driven masticatory activity and its impact on stress tolerance

OBJECTIVES

Although previous studies suggest that dietary texture-driven masticatory activity is correlated with stress tolerance, the underlying mechanisms, including neurotransmitter dynamics, remain unclear. This study investigated the effects of dietary texture-driven masticatory activity on stress tolerance in mice.

METHODS

Behavioral responses to stress were assessed using the repeated social defeat stress (R-SDS) and social interaction test (SIT) model. Neurotransmitter levels in stress-related brain regions were analyzed in mice fed a solid diet (promoting masticatory activity) or a powdered diet (decreasing masticatory activity).

RESULTS

Mice fed the powdered diet exhibited reduced stress tolerance compared with those fed the solid diet. Following the R-SDS, the powdered diet group displayed elevated gamma-aminobutyric acid (GABA) and norepinephrine levels in the prefrontal cortex. Before stress treatment, glutamic acid levels increased and those of choline decreased in the amygdala, whereas dopamine levels decreased in the powdered diet group after the R-SDS. In the locus coeruleus, mice on the powdered diet showed decreased glutamic acid and adenosine levels, alongside increased GABA levels. Serotonin levels decreased in the powdered diet group after the R-SDS, with no changes observed after the SIT. In the ventral hippocampus, GABA levels increased in the powdered diet group but decreased after the SIT.

CONCLUSIONS

This study demonstrates a correlation between masticatory activity and stress tolerance, evidenced by both behavioral and neurotransmitter changes. These findings suggest that reduced masticatory activity due to dietary texture contributes to decreased stress resilience.

Iron metabolism dysfunction in neuropsychiatric disorders: Implications for therapeutic intervention

Iron is a trace metal that takes part in the maintenance of body homeostasis by, for instance, aiding in energy production and immunity. A body of evidence now demonstrates that dysfunction in iron metabolism can have detrimental effects and is intricately associated with the development of neuropsychiatric disorders, including Major Depressive Disorder (MDD), anxiety, and schizophrenia. For instance, changes in serum and central nervous system (CNS) levels of iron and in proteins mediating iron metabolism have been documented in patients grappling with the aforementioned diseases. By contrast, targeting iron metabolism by using iron chelators, for instance, has proven to be effective in alleviating disease burden. Therefore, here we review the state-of-the-art regarding the role of iron metabolism and its dysfunction in the context of neuropsychiatric disorders. Furthermore, we discuss how targeting iron metabolism can be an effective therapeutic option to tackle this class of diseases. Finally, we discuss the mechanisms linking this dysfunction to behavioral changes in these disorders. Harnessing the knowledge of iron metabolism is not only key to the characterization of novel molecular targets and disease biomarkers but also crucial to drug repurposing and drug design.

Mathematical modeling and optimal control of depression dynamics influenced by saboteurs

Depression disorder affects millions globally, characterized by symptoms such as profound sadness, loss of interest in activities, and disruptions in eating and sleeping patterns. Understanding depression within the context of chronic pain is essential for developing effective management and intervention strategies. This study utilizes mathematical modeling to analyze depression trends using empirical data from Spain spanning from 2011 to 2022. Our depression model incorporates distinct compartments for primary and secondary depressed populations, along with a category for individuals categorized as saboteurs, who may actively influence the depression prevalence. We calculated the basic reproduction number [Formula: see text] and identified four equilibrium points and evaluated their stability. Additionally, sensitivity analysis was conducted to assess the impact of [Formula: see text] on depression prevalence. Furthermore, optimal control strategies were explored for the model. These strategies aim to improve treatment adherence, encourage doctor consultations, promote self-medication practices, and enhance recovery rates, ultimately aiming to reduce spread of depressive disorders and associated mortality. Data fitting was conducted using Python, and simulations were carried out in MATLAB to ensure rigorous validation of the model.

Architecturally Mediated Allostasis and Neurosustainability: A Proposed Theoretical Framework for the Impact of the Built Environment on Neurocognitive Health

The global rise in mental health-related disorders represents a significant health and wellbeing challenge, imposing a substantial social and economic burden on individuals, communities, and healthcare systems. According to the World Health Organization, one in four people globally will be affected by mental or neurological disorders at some point in their lives, highlighting a significant global health concern that warrants carefully considered and innovative responses. While mental health challenges arise from complex, multifaceted factors, emerging research indicates that the built environment-the architecture of our homes, workplaces, and public spaces-may exert a critical but underappreciated influence on mental health outcomes. This paper outlines a novel theoretical framework for how visual stressors in the built environment might trigger neurophysiological stress responses via the HPA and SAM axes, potentially contributing over time to allostatic load. In this paper, it is proposed that chronic physiological strain can alter neuroplastic processes and neurogenesis in key brain regions-such as the hippocampus, prefrontal cortex (PFC), anterior cingulate cortex (ACC), and amygdala-thereby affecting cognitive health, emotional regulation, and overall mental wellbeing. Drawing on the principle of neurosustainability, this paper suggests that long-term exposure to stress-inducing environments may create feedback loops, particularly involving the amygdala, that have downstream effects on other brain areas and may be linked to adverse mental health outcomes such as depression. By presenting this framework, this paper aims to inspire further inquiry and applied experimental research into the intersection of neurophysiology, mental health, and the built environment, with a particular emphasis on rigorous testing and validation of the proposed mechanisms, that may then be translated into practical architectural design strategies for supporting health and wellbeing. In doing so, it is hoped that this work may contribute to a more holistic approach to improving mental health that integrates the creation of nurturing, resilient spaces into the broader public health agenda.

Possible antidepressant mechanism of acupuncture: targeting neuroplasticity

Major depressive disorder (MDD) is a highly prevalent and severely disabling psychiatric disorder that decreases quality of life and imposes substantial economic burden. Acupuncture has emerged as an effective adjunctive treatment for depression, it regulates neurotransmitters involved in mood regulation and modulates the activity of specific brain regions associated with emotional processing, as evidenced by neuroimaging and biochemical studies. Despite these insights, the precise neuroplastic mechanisms through which acupuncture exerts its antidepressant effects remain not fully elucidated. This review aims to summarize the current knowledge on acupuncture's modulation of neuroplasticity in depression, with a focus on the neuroplasticity-based targets associated with acupuncture's antidepressant effects. We encapsulate two decades of research into the neurobiological mechanisms underpinning the efficacy of acupuncture in treating depression. Additionally, we detail the acupoints and electroacupuncture parameters used in the treatment of depression to better serve clinical application.

Chronic Stress and Headaches: The Role of the HPA Axis and Autonomic Nervous System

Chronic stress significantly influences the pathogenesis of headache disorders, affecting millions worldwide. This review explores the intricate relationship between stress and headaches, focusing on the dysregulation of the hypothalamic-pituitary-adrenal (HPA) axis and autonomic nervous system (ANS). Persistent stress could lead to neuroinflammation, increased pain sensitivity, and vascular changes that could contribute to headache development and progression. The bidirectional nature of this relationship creates a vicious cycle, with recurrent headaches becoming a source of additional stress. Dysregulation of the HPA axis and ANS imbalance could amplify susceptibility to headaches, intensifying their frequency and severity. While pharmacological interventions remain common, non-pharmacological approaches targeting stress reduction, such as cognitive-behavioral therapy, biofeedback, and relaxation techniques, offer promising avenues for comprehensive headache management. By addressing the underlying stress-related mechanisms, these approaches provide a sustainable strategy to reduce headache frequency and improve patients' quality of life.

Emerging Medications for Treatment-Resistant Depression: A Review with Perspective on Mechanisms and Challenges

Background/Objectives: Non-response to initial treatment options for major depressive disorder (MDD) is a common clinical challenge with profound deleterious impacts for affected patients. Few treatments have received regulatory approval for treatment-resistant depression (TRD). Methods: A systematic search of United States and European Union clinical trials registries was conducted to identify Phase II, III, or IV clinical trials, with a last update posted on or after 1 January 2020, that were evaluating medications for TRD. For both the US and EU registries, the condition term "treatment resistant depression" and associated lower-level terms (per registry search protocol) were used. For the US registry, a secondary search using the condition term "depressive disorders" and the modifying term "inadequate" was also performed to capture registrations not tagged as TRD. Two additional searches were also conducted in the US registry for the terms "suicide" and "anhedonia" as transdiagnostic targets of investigational medications. Trials were categorized based on the primary mechanism of action of the trial's investigational medication. Results: Fifty clinical trials for TRD, 20 for anhedonia, and 25 for suicide were identified. Glutamate system modulation was the mechanism currently with the most compounds in development, including antagonists and allosteric modulators of NMDA receptors, AMPA receptors, metabotropic type 2/3 glutamate receptors, and intracellular effector molecules downstream of glutamate signaling. Psychedelics have seen the greatest surge among mechanistic targets in the past 5 years, however, with psilocybin in particular garnering significant attention. Other mechanisms included GABA modulators, monoamine modulators, anti-inflammatory/immune-modulating agents, and an orexin type 2 receptor antagonist. Conclusions: These investigations offer substantial promise for more efficacious and potentially personalized medication approaches for TRD. Challenges for detecting efficacy in TRD include the heterogeneity within the TRD population stemming from the presumed variety of biological dysfunctions underlying the disorder, comorbid disorders, chronic psychosocial stressors, and enduring effects of prior serotonergic antidepressant medication treatments.

Behavioral Animal Models and Neural-Circuit Framework of Depressive Disorder

Depressive disorder is a chronic, recurring, and potentially life-endangering neuropsychiatric disease. According to a report by the World Health Organization, the global population suffering from depression is experiencing a significant annual increase. Despite its prevalence and considerable impact on people, little is known about its pathogenesis. One major reason is the scarcity of reliable animal models due to the absence of consensus on the pathology and etiology of depression. Furthermore, the neural circuit mechanism of depression induced by various factors is particularly complex. Considering the variability in depressive behavior patterns and neurobiological mechanisms among different animal models of depression, a comparison between the neural circuits of depression induced by various factors is essential for its treatment. In this review, we mainly summarize the most widely used behavioral animal models and neural circuits under different triggers of depression, aiming to provide a theoretical basis for depression prevention.

Structural connectivity of thalamic subnuclei in major depressive disorder: An ultra-high resolution diffusion MRI study at 7-Tesla

BACKGROUND

The thalamus serves as a central relay station within the brain, and thalamic connectional anomalies are increasingly thought to be present in major depressive disorder (MDD). However, the use of conventional MRI scanners and acquisition techniques has prevented a thorough examination of the thalamus and its subnuclear connectional profile. We combined ultra-high field diffusion MRI acquired at 7.0 Tesla to map the white matter connectivity of thalamic subnuclei.

METHODS

Fifty-three MDD patients and 12 healthy controls (HCs) were involved in the final analysis. FreeSurfer was used to segment the thalamic subnuclei, and MRtrix was used to perform the preprocessing and tractography. Fractional anisotropy, axial diffusivity, mean diffusivity, radial diffusivity, and streamline count of thalamic subnuclear tracts were measured as proxies of white matter microstructure. Bayesian multilevel model was used to assess group differences in white matter metrics for each thalamic subnuclear tract and the association between these white matter metrics and clinical features in MDD.

RESULTS

Evidence was found for reduced whiter matter metrics of the tracts spanning from all thalamic subnuclei among MDD versus HC participants. Moreover, evidence was found that white matter in various thalamic subnuclear tracts is related to medication status, age of onset and recurrence in MDD.

CONCLUSIONS

Structural connectivity was generally reduced in thalamic subnuclei in MDD participants. Several clinical characteristics are related to perturbed subnuclear thalamic connectivity with cortical and subcortical circuits that govern sensory processing, emotional function, and goal-directed behavior.

Evaluation of Nanocurcumin Effects on Depressive-Like Behaviors in Rats and Determination of Serum BDNF and Serotonin Levels

INTRODUCTION

Major depressive disorder (MDD) is a highly prevalent psychiatric condition worldwide, and it is the leading cause of disability globally. Turmeric, an aromatic perennial herb widely used in traditional Asian medicine and cuisine, contains curcumin, which has several biological effects, including a pseudoantidepressant effect. However, curcumin's low bioavailability limits its effectiveness. This study evaluated nanocurcumin (NCUR) effects on depressive-like behaviors and examined serum BDNF and serotonin levels in a chronic stress model in rats. Behavioral assessments and biochemical indicators elucidated NCUR's antidepressant-like properties.

METHODS

In this experimental study, 30 adult male rats were randomly divided into six groups and exposed to unexpected chronic mild stress (UCMS). The groups included: control (CG), stress control (SCG), fluoxetine (FLU) treatment (20 mg/kg), and three NCUR doses (20, 40, and 80 mg/kg). Before UCMS exposure, rats underwent a sucrose preference test (SPT). Depressive behaviors were then assessed using the open field test (OFT), forced swimming test (FST), and tail suspension test (TST) on days 27 and 28. Blood samples were collected on day 28 to measure serum Brain derived neurotrophic factor (BDNF) and serotonin levels using enzyme-linked immunosorbent assay (ELISA).

RESULTS

NCUR treatment significantly alleviated depressive-like behaviors in stressed rats. The sucrose preference index of the SCG decreased after 26 days of stress, while NCUR (all doses) and FLU reversed this effect. In the FST and TST, immobility time was significantly reduced in the NCUR and FLU groups compared to the SCG (p < 0.05). The OFT also showed that the SCG had significantly fewer crossings compared to treated groups (p < 0.05). Additionally, NCUR treatment significantly increased serum BDNF and serotonin levels compared to the SCG.

CONCLUSIONS

This study demonstrates that NCUR exerts antidepressant-like effects, improving depressive behaviors and increasing BDNF and serotonin levels in rats exposed to chronic stress. NCUR may offer a promising alternative for the treatment of MDD.

Physical Activity and Depression in Breast Cancer Patients: Mechanisms and Therapeutic Potential

Breast cancer is a significant traumatic experience that often leads to chronic stress and mental health challenges. Research has consistently shown that physical activity-especially exercise-can alleviate depressive symptoms; however, the specific biological mechanisms underlying these antidepressant effects remain unclear. In this review, we comprehensively summarize the biological mechanisms of depression and the antidepressant mechanisms of physical activity and explore the biological processes through which exercise exerts its antidepressant effects in breast cancer patients. We focus on the impact of physical activity on inflammation, the endocrine system, glutamate, and other aspects, all of which play crucial roles in the pathophysiology of depression. Moreover, we discuss the heterogeneity of depression in breast cancer patients and the complex interactions between its underlying mechanisms. Additionally, we propose that a deeper understanding of these mechanisms in the breast cancer population can guide the design and implementation of exercise-based interventions that maximize the antidepressant benefits of physical activity. Finally, we summarize the current research and propose future research directions.

Association of inflammation cytokines with cognitive function in first-episode major depressive disorder

Objective

Abnormal cognitive functioning is a core symptom of Major Depressive Disorder (MDD) and is strongly correlated with MDD prognosis. Current studies suggest that the occurrence of MDD may be related to oxidative stress-induced inflammation, hypothalamic-pituitary-adrenal axis disorders, diminished monoamine function and microbe-brain-gut axis, among other pathways. In recent years, the relationship between the immune-inflammatory response and MDD has been a hot topic of research, but how the relationship between immunoinflammation and cognitive function is manifested in MDD is still unclear. In this study, we examined cognitive function characteristics, serum inflammatory factors, brain-derived neurotrophic factor, and their correlations before and after pharmacological treatment(paroxetine hydrochloride tablets) in patients with first-episode major depressive disorder, aiming to identify objective biomarkers for cognitive function assessment.

Methods

We included 22 patients with first-episode major depressive disorder and 27 healthy volunteers from the community during the same period. The Hamilton Depression Scale-17 (HAMD-17) assessed the severity of depressive symptoms at baseline and after 8 weeks of treatment. The Repeatable Battery for the Assessment of Neuropsychological Status(RBANS) evaluated cognitive function, and serum samples were collected to determine levels of inflammatory and neurotrophic factors at these two time points. For healthy volunteers, only HAMD-17 scale scores, RBANS scale scores, and serum samples were taken at baseline. Spearman's correlation analyzed the relationship between inflammatory factors, neurotrophic factors, and cognitive function. Multiple linear regression determined factors affecting cognitive function in first-time patients.

Results

Baseline findings indicated that patients' IL-6 and TNF-α levels exceeded those of healthy individuals, while their IFN-α levels were below; their scores in language, attention, delayed memory, and the RBANS scale were also lower than healthy counterparts. Post-treatment, patients' BDNF, IL-6, and TNF-α levels remained higher than those of healthy subjects, and their IFN-α levels were still lower; their language and attention scores were also inferior. Association analyses revealed an association between BDNF and visuospatial/constructional ability scores and language scores in patients with MDD at baseline, and a positive relationship between TNF-α and attention score. Multiple regression analysis indicated an association between TNF-α levels and attention scores in MDD patients at baseline.

Conclusions

Our study concludes that TNF-α and BDNF correlate with cognitive function in MDD at baseline, and furthermore, TNF-α could potentially serve as an objective biomarker to support the assessment of attentional function at baseline.

MicroRNA-specific targets for neuronal plasticity, neurotransmitters, neurotrophic factors, and gut microbes in the pathogenesis and therapeutics of depression

Depression is of great concern because of the huge burden, and it is impacted by various epigenetic modifications, e.g., histone modification, covalent modifications in DNA, and silencing mechanisms of non-coding protein genes, e.g., microRNAs (miRNAs). MiRNAs are a class of endogenous non-coding RNAs. Alternations in specific miRNAs have been observed both in depressive patients and experimental animals. Also, miRNAs are highly expressed in the central nervous system and can be delivered to different tissues via tissue-specific exosomes. However, the mechanism of miRNAs' involvement in the pathological process of depression is not well understood. Therefore, we summarized and discussed the role of miRNAs in depression. Conclusively, miRNAs are involved in the pathology of depression by causing structural and functional changes in synapses, mediating neuronal regeneration, differentiation, and apoptosis, regulating the gut microbes and the expression of various neurotransmitters and BDNF, and mediating inflammatory and immune responses. Moreover, miRNAs can predict the efficacy of antidepressant medications and explain the mechanism of action of antidepressant drugs and aerobic exercise to prevent and assist in treating depression.

Gelsemium low doses protect against serum deprivation-induced stress on mitochondria in neuronal cells

ETHNOPHARMACOLOGICAL RELEVANCE

Gelsemium dynamized dilutions (GDD) are known as a remedy for a wide range of behavioral and psychological symptoms of depression and anxiety at ultra-low doses, yet the underlying mechanisms of the mode of action of G. sempervirens itself are not well understood.

AIM OF THE STUDY

The present study was designed to examine the neuroprotective effects of Gelsemium preparations in counteracting stress-related mitochondrial dysfunctions in neuronal cells.

MATERIALS AND METHODS

We started by studying how serum deprivation affects the mitochondrial functions of human neuroblastoma (SH-SY5Y) cells. Next, we looked into the potential of various Gelsemium dilutions to improve cell survival and ATP levels. After identifying the most effective dilutions, 3C and 5C, we tested their ability to protect SH-SY5Y cells from stress-induced mitochondrial deficits. We measured total and mitochondrial superoxide anion radicals using fluorescent dyes dihydroethidium (DHE) and the red mitochondrial superoxide indicator (MitoSOX). Additionally, we assessed total nitric oxide levels with 4,5-diaminofluorescein diacetate (DAF-2DA), examined the redox state using pRA305 cells stably transfected with a plasmid encoding a redox-sensitive green fluorescent protein, and analyzed mitochondrial network morphology using an automated high-content analysis device, Cytation3. Furthermore, we investigated bioenergetics by measuring ATP production with a bioluminescence assay (ViaLighTM HT) and evaluated mitochondrial respiration (OCR) and glycolysis (ECAR) using the Seahorse Bioscience XF24 Analyzer. Finally, we determined cell survival using an MTT reduction assay.

RESULTS

Our research indicates that Gelsemium dilutions (3C and 5C) exhibited neuroprotective effects by: - Normalizing total and mitochondrial superoxide anion radicals and total nitric oxide levels. - Regulating the mitochondrial redox environment and mitochondrial networks morphology. - Increasing ATP generation as well as OCR and ECAR levels, thereby reducing the viability loss induced by serum withdrawal stress.

CONCLUSIONS

These findings highlight that dynamized Gelsemium preparations may have neuroprotective effects against stress-induced cellular changes in the brain by regulating mitochondrial functions, essential for the survival, plasticity, and function of neurons in depression.

The elevated open platform stress suppresses excitatory synaptic transmission in the layer V anterior cingulate cortex

There are various forms of stress including; physical, psychological and social stress. Exposure to physical stress can lead to physical sensations (e.g. hyperalgesia) and negative emotions including anxiety and depression in animals and humans. Recently, our studies in mice have shown that acute physical stress induced by the elevated open platform (EOP) can provoke long-lasting mechanical hypersensitivity. This effect appears to be related to activity in the anterior cingulate cortex (ACC) at the synaptic level. Indeed, EOP exposure induces synaptic plasticity in layer II/III pyramidal neurons from the ACC. However, it is still unclear whether or not EOP exposure alters intrinsic properties and synaptic transmission in layer V pyramidal neurons. This is essential because these neurons are known to be a primary output to subcortical structures which may ultimately impact the behavioral stress response. Here, we studied both intrinsic properties and excitatory/inhibitory synaptic transmission by using whole-cell patch-clamp method in brain slice preparations. The EOP exposure did not change intrinsic properties including resting membrane potentials and action potentials. In contrast, EOP exposure suppressed the frequency of miniature and spontaneous excitatory synaptic transmission with an alteration of kinetics of AMPA/GluK receptors. EOP exposure also reduced evoked synaptic transmission induced by electrical stimulation. Furthermore, we investigated projection-selective responses of the mediodorsal thalamus to the layer V ACC neurons. EOP exposure produced short-term depression in excitatory synaptic transmission on thalamo-ACC projections. These results suggest that the EOP stress provokes abnormal excitatory synaptic transmission in layer V pyramidal neurons of the ACC.

Basolateral amygdala volume in affective disorders using 7T MRI in vivo

Background

The basolateral complex of the amygdala is a crucial neurobiological site for Pavlovian conditioning. Investigations into volumetric alterations of the basolateral amygdala in individuals with major depressive disorder (MDD) have yielded conflicting results. These may be reconciled in an inverted U-shape allostatic growth trajectory. This hypothesized trajectory unfolds with an initial phase of volumetric expansion, driven by enhanced dendritic arborization and synaptic plasticity. The increase in volume is followed by a reduction phase, as glucocorticoid exposure cumulatively results in excitotoxic damage, reflecting allostatic load.

Methods

7T magnetic resonance brain imaging was conducted on a total of 84 participants (mean age 38 ± 12 years), comprising 20 unmedicated and 20 medicated individuals with MDD, 21 individuals suffering from bipolar disorder and 23 healthy controls. We employed FreeSurfer 7.3.2 for automatic high-resolution segmentation of nine amygdala subnuclei. We conducted analyses of covariance, with volumes of the basolateral complex, the lateral nucleus and, exploratively, the whole amygdala, as dependent variables, while controlling for the total intracranial volume and sex. Quadratic regressions were computed within the MDD group and in relevant subgroups to investigate the presence of a U-shaped relationship between the number of preceding major depressive episodes or the duration of the disease since the first episode and the dependent variables.

Results

Diagnostic groups did not exhibit statistically significant differences in the volumes of the basolateral amygdala (left F (3,75) = 0.66, p >.05; right F (3,76) = 1.80, p >.05), the lateral nucleus (left F (3,75) = 1.22, p >.05; right F (3,76) = 2.30, p >.05)), or the whole amygdala (left F (3,75) = 0.48, p >.05; right F (3,76) = 1.58, p >.05). No quadratic associations were observed between surrogate parameters of disease progression and any of the examined amygdala volumes. There were no significant correlations between subregion volumes and clinical characteristics.

Conclusion

We found no evidence for the hypothesis of an inverted U-shaped volumetric trajectory of the basolateral amygdala in MDD. Future research with larger sample sizes, including the measurement of genetic and epigenetic markers, will hopefully further elucidate this compelling paradigm.

Serotonergic psychedelic 5-MeO-DMT alters plasticity-related gene expression and generates anxiolytic effects in stressed mice

Serotonergic psychedelics have potential therapeutic effects in treating anxiety and mood disorders, often after a single dose, and are suggested to have plasticity-inducing action. However, a comprehensive mechanism of action is still lacking. Here, we investigated how a single dose of the short-acting 5-methoxy-N,N-dimethyltryptamine (5-MeO-DMT) acts on gene expression from microdissected brain regions (anterior cingulate cortex - ACC; basolateral amygdala - BLA; ventral hippocampus CA1 region - vCA1 and dentate gyrus-DG) of naive and stressed mice. Specifically, we compared gene expression of Arc, Zif268, BDNF, CREB, mTORC1, NR2A, TRIP8b, and NFkB in mice injected with 5-MeO-DMT or saline at different time points (1 h, 5 h, or 5 days prior). 5-MeO-DMT altered mRNA expression of immediate early genes Arc and ZiF268 in the ACC, BLA, and vCA1, while NR2A expression was decreased after 5 h in the vCA1. We also found a long-term increase in TRIP8b, a gene related to the modulation of neuronal activity, in the vCA1 after 5 days. Behaviorally, 5-MeO-DMT treated mice showed mixed anxiolytic and anxiogenic effects in the elevated plus maze and open field test 24 h or 5 days after treatment. However, pre-treated mice subjected to acute stress showed both lower corticosterone levels and robust anxiolytic effects of 5-MeO-DMT administration. Together, our findings provide insights into the molecular actions of 5-MeO-DMT in the brain related to anxiolytic effects of behavior.

A New Augmentation Strategy against Depression Combining SSRIs and the N-terminal Fragment of Galanin (1-15)

Depression is one of the most disabling mental disorders, with the second highest social burden; its prevalence has grown by more than 27% in recent years, affecting 246 million in 2021. Despite the wide range of antidepressants available, more than 50% of patients show treatment-resistant depression. In this review, we summarized the progress in developing a new augmentation strategy based on combining the N-terminal fragment of Galanin (1-15) and SSRI-type antidepressants in animal models.

Mismatch Negativity as an Index of Auditory Short-Term Plasticity: Associations with Cortisol, Inflammation, and Gray Matter Volume in Youth at Clinical High Risk for Psychosis

Mismatch negativity (MMN) event-related potential (ERP) component reduction, indexing N-methyl-D-aspartate receptor (NMDAR)-dependent auditory echoic memory and short-term plasticity, is a well-established biomarker of schizophrenia that is sensitive to psychosis risk among individuals at clinical high-risk (CHR-P). Based on the NMDAR-hypofunction model of schizophrenia, NMDAR-dependent plasticity is predicted to contribute to aberrant neurodevelopmental processes involved in the pathogenesis of schizophrenia during late adolescence or young adulthood, including gray matter loss. Moreover, stress and inflammation disrupt plasticity. Therefore, using data collected during the 8-center North American Prodrome Longitudinal Study (NAPLS-2), we explored relationships between MMN amplitudes and salivary cortisol, gray matter volumes, and inflammatory cytokines. Participants included 303 CHR-P individuals with baseline electroencephalography (EEG) data recorded during an MMN paradigm as well as structural magnetic resonance imaging (MRI) and salivary cortisol, of which a subsample (n = 57) also completed blood draws. More deficient MMN amplitudes were associated with greater salivary cortisol and pro-inflammatory cytokine levels in future CHR-Converters, but not among those who did not convert to psychosis within the next two years. More deficient MMN amplitude was also associated with smaller total gray matter volume across participants regardless of future clinical outcomes, and with subcortical gray matter volumes among future CHR-Converters only. These findings are consistent with the theory that deficient NMDAR-dependent plasticity results in an overabundance of weak synapses that are subject to over-pruning during psychosis onset, contributing to gray matter loss. Further, MMN plasticity mechanisms may interact with stress, cortisol, and neuroinflammatory processes, representing a proximal influence of psychosis.

Metabolomics in Depression: What We Learn from Preclinical and Clinical Evidences

Depression is one of the predominant common mental illnesses that affects millions of people of all ages worldwide. Random mood changes, loss of interest in routine activities, and prevalent unpleasant senses often characterize this common depreciated mental illness. Subjects with depressive disorders have a likelihood of developing cardiovascular complications, diabesity, and stroke. The exact genesis and pathogenesis of this disease are still questionable. A significant proportion of subjects with clinical depression display inadequate response to antidepressant therapies. Hence, clinicians often face challenges in predicting the treatment response. Emerging reports have indicated the association of depression with metabolic alterations. Metabolomics is one of the promising approaches that can offer fresh perspectives into the diagnosis, treatment, and prognosis of depression at the metabolic level. Despite numerous studies exploring metabolite profiles post-pharmacological interventions, a quantitative understanding of consistently altered metabolites is not yet established. The article gives a brief discussion on different biomarkers in depression and the degree to which biomarkers can improve treatment outcomes. In this review article, we have systemically reviewed the role of metabolomics in depression along with current challenges and future perspectives.

The effect of exercise on depression and gut microbiota: Possible mechanisms

Exercise can effectively prevent and treat depression and anxiety, with gut microbiota playing a crucial role in this process. Studies have shown that exercise can influence the diversity and composition of gut microbiota, which in turn affects depression through immune, endocrine, and neural pathways in the gut-brain axis. The effectiveness of exercise varies based on its type, intensity, and duration, largely due to the different changes in gut microbiota. This article summarizes the possible mechanisms by which exercise affects gut microbiota and how gut microbiota influences depression. Additionally, we reviewed literature on the effects of exercise on depression at different intensities, types, and durations to provide a reference for future exercise-based therapies for depression.

Ghrelin Inhibits Inflammasomes Activation in Astrocytes, Alleviates Pyroptosis, and Prevents Lipopolysaccharide-induced Depression-like Behavior in Mice

Depression is the leading cause of disability worldwide and places a significant burden on society. Neuroinflammation is closely associated with the pathophysiology of depression. Increasing evidence suggests that astrocytes, as the most abundant glial cells in the brain, are involved in the occurrence and development of depression due to morphological abnormalities and dysfunction. Astrocytes express the NOD-like receptor protein 2 (NLRP2) and NLRP3 inflammasomes, and the activation of inflammasomes induces pyroptosis. Ghrelin, a gastrointestinal peptide, plays vital role in regulating inflammation and alleviating stress. Therefore, we proposed a hypothesis that ghrelin inhibits the activation of inflammasomes on astrocytes, reduces pyroptosis, and consequently prevents depression. We used lipopolysaccharide (LPS)-induced mouse depression model and cultured primary astrocytes in vitro to explore the mechanism of the antidepressant effect of ghrelin. Our results showed that ghrelin effectively inhibited acute inflammatory responses and damage in the hippocampus and prefrontal cortex. The activation of NLRP2 and NLRP3 in astrocytes induced by LPS was significantly inhibited by ghrelin. Pretreatment with ghrelin effectively suppressed LPS-induced upregulation of pyroptosis-related proteins and mRNA. Ghrelin alleviated cell membrane pore formation and cell swelling, ultimately improved LPS-induced depression-like behavior. In vitro, ghrelin prevented the LPS-induced upregulation of pyroptosis-related proteins and mRNA expression in astrocytes, and inhibited the initiation and assembly of NLRP2 and NLRP3. Ghrelin exhibits antidepressant effects, inhibits inflammasomes activation in astrocytes, and prevents pyroptosis, suggesting a novel strategy for treating depression. This groundbreaking study reveals new avenues for targeting potential therapeutic interventions to alleviate depression.

Neuromolecular and behavioral effects of cannabidiol on depressive-associated behaviors and neuropathic pain conditions in mice

BACKGROUND AND AIMS

Neuropathic pain (NP) has a high incidence in the general population, is closely related to anxiety disorders, and has a negative impact on the quality of life. Cannabidiol (CBD), as a natural product, has been extensively studied for its potential therapeutic effects on symptoms such as pain and depression (DP). However, the mechanism of CBD in improving NP with depression is not fully understood.

METHODS

First, we used bioinformatics tools to deeply mine the intersection genes associated with NP, DP, and CBD. Secondly, the core targets were screened by Protein-protein interaction network, Gene Ontology, Kyoto Encyclopedia of Genes and Genomes analysis, molecular docking and molecular dynamics simulation. Next, the effects of CBD intervention on pain and depressive behaviors in the spinal nerve ligation (SNL) mouse model were evaluated using behavioral tests, and dose-response curves were plotted. After the optimal intervention dose was determined, the core targets were verified by Western blot (WB) and Quantitative Polymerase Chain Reaction (qPCR). Finally, we investigated the potential mechanism of CBD by Nissl staining, Immunofluorescence (IF) and Transmission Electron Microscopy (TEM).

RESULTS

A total of five core genes of CBD most associated with NP and DP were screened by bioinformatics analysis, including PTGS2, GPR55, SOD1, CYP1A2 and NQO1. Behavioral test results showed that CBD by intraperitoneal administration 5 mg/kg can significantly improve the pain behavior and depressive state of SNL mice. WB, qPCR, IF, and TEM experiments further confirmed the regulatory effects of CBD on key molecules.

CONCLUSION

In this study, we found five targets of CBD in the treatment of NP with DP. These findings provide further theoretical and experimental basis for CBD as a potential therapeutic agent.

BDNF/Cyclin D1 Signaling System and Cognitive Performance After Perampanel and Lacosamide Treatment Singly or in Combination in an Experimental Model of Temporal Lobe Epilepsy

Epilepsy is a common brain function disorder. The present study aims to evaluate the long-term effect of perampanel (PRM) and lacosamide (LCM), administered singly in a high-dose or in a low-dose combination of both, on comorbid anxiety, cognitive impairment, BDNF, and Cyclin D1 hippocampal expression in an experimental model of temporal lobe epilepsy with lithium-pilocarpine. PRM (3 mg/kg, p.o.)/LCM (30 mg/kg, p.o.) or PRM+LCM (0.5 mg/kg + 3 mg/kg, p.o.) treatments were administered three hours after the lithium-pilocarpine-induced status epilepticus and continued for up to ten weeks in adult Wistar rats. Our study demonstrated that perampanel and lacosamide administered singly in high doses improved epilepsy-associated cognitive impairment through ameliorating anxiety and facilitating passive learning and memory, with spatial and recognition memory measured in the elevated plus maze, step-through, Y-maze, and object recognition tests, respectively. In addition, the combination of both drugs in low doses demonstrated similar anxiolytic and cognitive-improving effects compared to the singly administered drugs. Moreover, the three experimental groups enhanced the hippocampal expression of the neurotrophic factor BDNF and mitigated the increased levels of the apoptotic factor Cyclin D1. These beneficial effects could be essential mechanisms through which administered anticonvulsants preserve neuronal survival and homeostasis in the CNS and especially in the hippocampus.

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.

Circuit mechanisms underlying sexually dimorphic outcomes of early life stress

Stress during early life influences brain development and can affect social, motor, and emotional processes. We describe a striking sex difference in the effects of early life stress (ELS), which produces anhedonia and anxiety-like behaviors in female adolescent mice, as reported previously, but repetitive behavioral pathology and social deficits in male adolescent mice. Notably, this parallels sex differences seen in the prevalence of psychiatric symptoms: depression and anxiety disorders are more common in girls and women, whereas neurodevelopmental disorders like autism spectrum disorder and Tourette syndrome are markedly more common in boys and men. We characterized the effects of ELS on the medial prefrontal cortex (mPFC) and on its projections to the dorsal striatum (dStr) and lateral septum (LS). ELS males, but not females, developed hyperactivity in the cortico-striatal circuit and hypoactivity in the cortico-septal circuit. Chemogenetic manipulation of cortico-striatal projection neurons modulates repetitive behavioral pathology and social behaviors in stressed males, and anhedonia in stressed females. Activation of cortico-septal projection neurons rescues social deficits in stressed males. We conclude that early life stress produces sexually dimorphic behavioral effects, with potential relevance to human psychiatric symptoms, through its differential effects on cortico-striatal and cortico-septal circuits.

Exercise habits in adolescence and old age are positively associated with geriatric depressive symptoms: the Bunkyo Health Study

Introduction

Exercise is a crucial method for preventing geriatric depression. In this cross-sectional study, we investigated the associations between exercise habits in adolescence and old age and geriatric depressive symptoms.

Methods

This study used baseline data from the Bunkyo Health Study, a prospective observational cohort study investigating the preventive effects of physical activity on causative diseases requiring long-term care. This analysis included 1,629 older adults (687 men and 942 women) aged 65-84 years who participated in the Bunkyo Health Study. Participants were divided into four groups according to their exercise habits in adolescence and old age: never exercised (none-none; NN), exercised only in old age (none-active; NA), exercised only in adolescence (active-none; AN), and exercised in adolescence and old age (active-active; AA). Geriatric depressive symptoms were defined as the short version of the Geriatric Depression Scale score ≥ 5, including depression tendency. Multivariate-adjusted logistic regression models were used to estimate the odds ratios (ORs) and associated 95% confidence intervals in each group for the prevalence of geriatric depressive symptoms compared with the NN group.

Results

The ORs for geriatric depressive symptoms were notably lower in the AN, NA, and AA groups than in the NN group in both older men and older women.

Conclusion

These results indicate that older adults with exercise habits in adolescence and/or in old age exhibit a lower prevalence of geriatric depressive symptoms.

Integrated Long Noncoding RNA and Messenger RNA Expression Analysis Identifies Molecules Specifically Associated With Resiliency and Susceptibility to Depression and Antidepressant Response

Background

Depression involves maladaptive processes impairing an individual's ability to interface with the environment appropriately. Long noncoding RNAs (lncRNAs) are gaining traction for their role in higher-order brain functioning. Recently, we reported that lncRNA coexpression modules may underlie abnormal responses to stress in rats showing depression-like behavior. The current study explored the global expression regulation of lncRNAs and messenger RNAs (mRNAs) in the hippocampus of rats showing susceptibility (learned helplessness [LH]) or resiliency (non-LH) to depression and fluoxetine response to LH (LH+FLX).

Methods

Multiple comparison analysis was performed with an analysis of variance via the aov and summary function in the R platform to identify the differential expression of mRNAs and lncRNAs among LH, non-LH, tested control, and LH+FLX groups. Weighted gene coexpression network analysis was used to identify distinctive modules and pathways associated with each phenotype. A machine learning analysis was conducted to screen the critical target genes. Based on the combined analysis, the regulatory effects of lncRNAs on mRNA expression were explored.

Results

Multiple comparison analyses revealed differentially expressed mRNAs and lncRNAs with each phenotype. Integrated bioinformatics analysis identified novel transcripts, specific modules, and regulatory pairs of mRNA-lncRNA in each phenotype. In addition, the machine learning approach predicted lncRNA-regulated Spp2 and Olr25 genes in developing LH behavior, whereas joint analysis of mRNA-lncRNA pairs identified Mboat7, Lmod1, I l 18, and Rfx5 genes in depression-like behavior and Adam6 and Tpra1 in antidepressant response.

Conclusions

The study shows a novel role for lncRNAs in the development of specific depression phenotypes and in identifying newer targets for therapeutic development.