Activating newborn neurons suppresses depression and anxiety-like behaviors

Huddling promotes adult neurogenesis in the brain regions related to social behavior in cold-exposed Brandt's voles

Social thermoregulation behaviors such as huddling among individuals can be important for energy conservation and thermoregulatory processes. Beyond that, whether huddling behavior regulates neural plasticity in the brain remains unknown. We hypothesized that huddling regulates adult neurogenesis in brain regions related to social behavior and thermoregulation. We found that cold-exposed voles had decreased aggression and increased social interaction in association with higher oxytocin but lower vasopressin hormones compared to warm-exposed voles. Cold decreased the level of cell proliferation labeling indicated by BrdU (a marker for cell proliferation) in the anterior part of the subventricular zone (SVZ) in the brain, and notably, cold-huddling (CH) voles had a higher number of proliferating cells in the hypothalamus than cold-separated (CS) voles. Moreover, CH voles displayed higher cell survival in the central amygdala and paraventricular nuclei (PVN) of the hypothalamus (both regions were related to social behavior) in comparison to CS or warm-huddling (WH) voles, respectively. Furthermore, the CH voles had more BrdU/NeuN (markers for new neurons) double-labeled cells in the SVZ than WH voles, and also more BrdU/GFAP (markers for new glial cells) double-labeled cells in SVZ and dentate gyrus compared to WH and CS voles. In addition, the newly-generated neurons differentiated into more oxytocinergic neurons in the PVN of the CH voles. Together, these data support the notion that huddling behavior is beneficial for brain plasticity by protecting cell proliferation, survival, and differentiation, and may be involved in regulating social behavior in small mammals in cold environments.

Implications of hippocampal excitatory amino acid transporter 2 in modulating anxiety and visceral pain in a mouse model of inflammatory bowel disease

Inflammatory bowel disease (IBD) is characterized by chronic inflammation and significantly impairs quality of life through anxiety-like behaviors and visceral pain. Early evaluation of the risk of anxiety-like behaviors and visceral pain in IBD patients, along with targeted treatment, may benefit disease management. Visceral pain and anxiety-like behavior are often accompanied by neurological damage. Previous studies have shown that abnormal accumulation of glutamate can cause excitatory neurotoxic effects, leading to central nervous system (CNS) damage. Excitatory amino acid transporters (EAATs), particularly EAAT2, are known to regulate glutamate levels. The impact of hippocampal EAAT2 modulation on these clinical features in IBD is yet to be evaluated. Therefore, we designed this experiment to test this hypothesis. This study aimed to investigate the impact of altered levels of hippocampal EAAT2 on anxiety-like behaviors and visceral pain in mice with IBD. We observed reduced EAAT2 expression, increased glutamate levels, elevated N-methyl-d-aspartate receptors (NMDAR) expression, and obvious glutamate toxicity in the hippocampus of dextran sulfate sodium (DSS) induced IBD model mice. These mice exhibited significant visceral pain and anxiety-like behaviors. In summary, the reduced expression of EAAT2 in the hippocampus of individuals with IBD leads to elevated glutamate levels, resulting in neuronal damage and ultimately contributing to visceral pain and anxiety-like behaviors. These findings suggest that EAAT2 could serve as a therapeutic target for neurologically derived IBD symptoms.

Hesperidin produces antidepressant effects by activating AMPA receptor: enhancing synaptic proteins to promote hippocampal neuronal activities

Hesperidin treatments reduce depressive symptoms in mouse models of depression, but the mechanism that mediates its antidepressant effects is unclear. This study shows that hesperidin exerts its antidepressant effects by activating α-amino-3-hydroxy-5-methyl-4-isoxazole-propionic acid (AMPA) receptor to promote synaptic and neuronal function in the hippocampus. The optimal dose of hesperidin (10 mg/kg) for the antidepressant potential was determined after 7 consecutive days of treatments, demonstrating decreased latency to eat and increased food consumption in novelty suppressed feeding, and decreased immobility time in tail suspension test (TST). Moreover, the optimal dose also reversed the depressive phenotypes of Institute of Cancer Research mice exposed to chronic unpredictable mild stress (CUMS), including reduced immobility time in the TST and increased sucrose preference in the sucrose preference test. In addition, hesperidin increased the expression of AMPA receptor protein (Glur1) and synaptic proteins (BDNF, PSD95, synapsin1) in the hippocampus of CUMS-exposed mice. Furthermore, inhibition of AMPA receptor activity by NBQX blocked the effect of hesperidin in reversing the depressive phenotypes, upregulated the expression of synaptic proteins (BDNF, PSD95, synapsin1) and cFOS-positive cells in the hippocampus, and increased the number of Ki67-positive cells in the dentate gyrus of the hippocampus of CUMS-exposed mice. These results help to further understand the antidepressant mechanism of hesperidin and provide new ideas for the future development of antidepressant drugs.

Environmental Enrichment Exposure Alleviates Geriatric Depressive-Like Symptoms through Regulating Neurogenesis and Neuroinflammation

Environmental enrichment (EE) is a significant approach to influencing brain function by altering the environment and changing living conditions and has been shown to modulate mood-related diseases, including depression. Among the elderly, depression is particularly prevalent and is often linked to social isolation. However, the specific role of EE in social isolation-related geriatric depression remains imprecise. This study was intended to explore the status of EE exposure in geriatric depression and to uncover its underlying mechanisms. We utilized 19-month-old male C57BL/6J mice, which are equivalent to humans aged 50-60 years, and induced depression through social isolation. After 2 weeks of social isolation, mice were identified as depressive by using the sugar preference test and then classified into either standard or enrichment environment groups for 4 weeks. Subsequently, conventional indices associated with depression, including neurogenesis, neurotrophic factors, and neuroinflammation, were measured. Results display that EE alleviated the depressive-like symptoms in elderly mice and enriched their social activities. Concurrently, EE regulated levels of certain neurotransmitters in the hippocampus, including the systems of glutamate, tyrosine, and histamine. Moreover, the ability of neurogenesis also increased in the hippocampus of EE mice. At the neuroinflammation level, the activation of Natural Killer (NK) cells and ARG1+ microglia is considered a major contributor to mediating the effects of EE-regulated geriatric depression. Collectively, these results underline the importance of EE in the treatment of geriatric depression and partially elucidate its underlying mechanism, offering valuable suggestions for treating social isolation--related depression via environmental modulation.

Chronic stress enhances glycolysis and promotes tumorigenesis

Depression is a well-known risk factor for tumors, but the mechanisms other than inflammation are unclear. Aerobic glycolysis is considered to be a critical element in the reprogramming of energy metabolism in malignant tumors, and impaired glycolysis has been reported in the brains of chronic stress mice. Therefore, this study aimed to explore the role of glycolysis in which depression promotes tumorigenesis. We examined the impacts of chronic unpredictable mild stress (CUMS) on the growth and metastasis of breast cancer (BC) and lung cancer (LC). CUMS was used to construct a mouse depression model, BALB/c mice were injected with 4T1-Luc cells in the right subcutaneous mammary fat pad, and C57BL/6 mice were injected with Lewis-Luc cells in the tail vein. The experiments were conducted through behavioral experiments, live imaging techniques of small animals, Western blot, Glycolytic metabolites measurement, Hematoxylin and eosin staining (H&E staining), Nissl staining, and immunohistochemical (IHC) tests. The findings showed that both CUMS and tumors induced depressive-like behavior, neuronal damage, and impaired synaptic plasticity in mice, while CUMS also enhanced tumor development and metastasis in both BC and LC. In the brain, both CUMS and tumor alone and in combination less influence glycolytic products and enzyme levels. However, CUMS significantly enhanced the levels of aerobic glycolytic products and enzymes in tumor tissue. Collectively, our results provide insights into how glycolysis is regulated in the brain, leading to depression-like behavior, and how depression, in turn, enhanced glycolysis and promoted tumorigenesis.

Heterogeneities of Site-Specific N-Glycosylation in the Hippocampus of Depression-like Behavior Models in Mice Induced by Acute Stress and Chronic Stress

It is well established that acute and chronic stress contributes to the onset and progression of depression, but the underlying mechanisms have not been elucidated. Here an integrated N-glycoproteomic and proteomic analysis was performed to investigate heterogeneities of glycoprotein and site-specific glycosylation between the hippocampi of control, acute stress-affected (AS), and chronic mild stress-affected (CMS) mice. 1063 unique intact N-glycopeptides, 116 N-glycan compositions, and 512 glycosylation sites were identified. CMS and AS had significant effects on glycosylation. CMS reduced multiantenna glycosylation (N8H8 and N6H5F1S1) more strongly, while AS reduced multiantenna glycosylation (N5H3F1) more strongly. CMS inhibited high-mannose synthesis with high polymerization (N2H9 and N2H8), while AS inhibited high-mannose synthesis with low polymerization (N2H6, H2H5). Furthermore, 26 and 39 glycosylation-related genes (GRGs) were identified in the AS and CMS groups, separately. Functional enrichment analysis for GRGs in the AS and CMS groups exhibited that the up-regulated functions were leading edge membrane and cell adhesion molecule binding; meanwhile, the down-regulated functions were cAMP signaling pathways. Finally, tSNE analysis based on ScRNA-seq revealed that core GRGs were highly expressed in astrocytes. All of these findings improve our understanding of glycosylation in stress-related depression, providing valuable data resources for depression pathogenesis exploration and novel therapeutic target discovery.

Subregional activity in the dentate gyrus is amplified during elevated cognitive demands

Neural activity in the dentate gyrus (DG) is required for the detection and discrimination of novelty, context and patterns, amongst other cognitive processes. Prior work has demonstrated that there are differences in the activation of granule neurons in the supra and infrapyramidal blades of the DG during a range of hippocampal dependent tasks. Here we used an automated touch screen pattern separation task combined to temporally controlled tagging of active neurons to determine how performance in a cognitively demanding task affected patterns of neural activity in the DG. We found an increase in the blade-biased activity of suprapyramidal mature granule cells (mGCs) during the performance of a high cognitive demand segment of the task, with a further characteristic distribution of active neurons along the apex to blade, and hilar to molecular layer axes. Chemogenetic inhibition of adult-born granule cells (abDGCs) beyond a critical window of their maturation significantly impaired performance of mice during high-demand conditions but not when cognitive demand was low. abDGC inhibition also elevated the total activity of mGCs and disturbed the patterned distribution of active mGCs even in mice that eventually succeeded in the task. Conversely chemogenetic inhibition of mGCs reduced success in the high cognitive demand portion of this task and decreased the global number of active GCs without affecting the patterned distribution of active cells. These findings demonstrate how a high cognitive demand pattern separation task preferentially activates mGCs in subregions of the DG and are consistent with a modulatory role for abDGCs on the dentate circuit which in part governs the spatially organized patterns of activity of mGCs.

Optogenetics and chemogenetics: key tools for modulating neural circuits in rodent models of depression

Optogenetics and chemogenetics are emerging neuromodulation techniques that have attracted significant attention in recent years. These techniques enable the precise control of specific neuronal types and neural circuits, allowing researchers to investigate the cellular mechanisms underlying depression. The advancement in these techniques has significantly contributed to the understanding of the neural circuits involved in depression; when combined with other emerging technologies, they provide novel therapeutic targets and diagnostic tools for the clinical treatment of depression. Additionally, these techniques have provided theoretical support for the development of novel antidepressants. This review primarily focuses on the application of optogenetics and chemogenetics in several brain regions closely associated with depressive-like behaviors in rodent models, such as the ventral tegmental area, nucleus accumbens, prefrontal cortex, hippocampus, dorsal raphe nucleus, and lateral habenula and discusses the potential and challenges of optogenetics and chemogenetics in future research. Furthermore, this review discusses the potential and challenges these techniques pose for future research and describes the current state of research on sonogenetics and odourgenetics developed based on optogenetics and chemogenetics. Specifically, this study aimed to provide reliable insights and directions for future research on the role of optogenetics and chemogenetics in the neural circuits of depressive rodent models.

mPFC DCC coupling with CaMKII+ neuronal excitation participates in behavioral despair in male mice

A longed lack of control over harmful stimuli can lead to learned helplessness (LH), a significant factor in depression. However, the cellular and molecular mechanisms underlying LH, and eventually behavioral despair, remain largely unknown. The deleted in colorectal cancer (dcc) gene is associated with the risk of depression. However, the therapeutic potential and regulation mechanism of DCC in behavioral despair are still uncertain. In this study, we showed that depressive stimulators, including LH, lipopolysaccharide, and unpredictable chronic mild stress, triggered an elevation in DCC expression in the medial prefrontal cortex (mPFC). Additionally, elevated DCC expression in the mPFC was crucial in inducing behavioral despair, as evidenced by the induction of behavioral despair in normal mice and exacerbation of behavioral despair in LH mice upon DCC overexpression. By contrast, neutralizing DCC activity ameliorated LH-induced behavioral despair. Importantly, we elucidated that pathological DCC expression was attributable to the excessive excitation of CaMKII+ neurons in a manner dependent on the calpain-mediated degradation of SCOP and aberrant phosphorylation of the ERK signaling pathway. In addition, the increase in DCC expression led to a decreased excitability threshold in CaMKII+ neurons in the mPFC, which was supported by the observation that the ligand netrin 1 increased the frequency of action potential firing and of spontaneous excitatory postsynaptic currents in CaMKII+ neurons. In conclusion, our data indicate that LH triggers the excessive excitation of CaMKII+ neurons and activation of calpain-SCOP/ERK signaling to promote DCC expression, and DCC represents a crucial target for the treatment of LH-induced behavioral despair in male mice.

Ectopic expression of the cation-chloride cotransporter KCC2 in blood exosomes as a biomarker for functional rehabilitation

Background

Traumatic brain injury (TBI) is a major cause of disabilities in industrialized countries. Cognitive decline typically occurs in the chronic phase of the condition, following cellular and molecular processes. In this study, we described the use of KCC2, a neuronal-specific potassium-chloride cotransporter, as a potent biomarker to predict cognitive dysfunction after TBI.

Methods

Using neuronal and total exosome collections from the blood serum of the controls and patients with TBI, we were able to anticipate the decline in cognitive performance.

Results

After TBI, we observed a significant and persistent loss of KCC2 expression in the blood exosomes, which was correlated with the changes in the network activity and cellular processes such as secondary neurogenesis. Furthermore, we established a correlation between this decrease in KCC2 expression and the long-term consequences of brain trauma and identified a link between the loss of KCC2 expression and the emergence of depressive-like behavior observed in the mice.

Conclusion

We successfully validated our previous findings, supporting the potential therapeutic benefits of bumetanide in mitigating post-traumatic depression (PTD) following TBI. This effect was correlated with the recovery of KCC2 expression in the blood exosomes, the prevention of extensive neuronal loss among the interneurons, and changes in secondary neurogenesis.

Memory-related neurophysiological mechanisms in the hippocampus underlying stress susceptibility

Stress-induced psychiatric symptoms, such as increased anxiety, decreased sociality, and depression, differ considerably across individuals. The cognitive model of depression proposes that biased negative memory is a crucial determinant in the development of mental stress-induced disorders. Accumulating evidence from both clinical and animal studies has demonstrated that such biased memory processing could be triggered by the hippocampus, a region well known to be involved in declarative memories. This review mainly describes how memory-related neurophysiological mechanisms in the hippocampus and their interactions with other related brain regions are involved in the regulation of stress susceptibility and discusses potential interventions to prevent and treat stress-related psychiatric symptoms. Further neurophysiological insights based on memory mechanisms are expected to devise personalized prevention and therapy to confer stress resilience.

Sphingosine-1-phosphate receptor 3 activation promotes sociability and regulates transcripts important for anxiolytic-like behavior

We previously demonstrated that sphingosine-1-phosphate receptor 3 (S1PR3) in the medial prefrontal cortex (mPFC) prevents reductions in sociability normally caused by stress. S1PR3 is a ubiquitously expressed G-protein coupled receptor that regulates immune system function, although its regulation of other biological processes is not well understood. Pharmacological activators of S1PR3 might provide important insights for understanding the neural substrates underlying sociability. Here we show that in mice, systemic injections of an S1PR3-specific agonist, CYM5541, promotes sociability in males and females whereas an S1PR3-specific antagonist, CAY10444, increases amygdala activation and increases social avoidance, particularly in females. S1PR3 expression is increased in the mPFC and dentate gyrus of females compared to males. RNA sequencing in the mPFC reveals that S1PR3 activation alters the expression of transcripts related to immune function, neurotransmission, transmembrane ion transport, and intracellular signaling. This work provides evidence that S1PR3 agonists, which have classically been used as immune modulators, might also be used to promote social behavior and, potentially, relieve symptoms of social anxiety. S1PR3 might be an important hub gene for mitigating maladaptive effects of stress as it reduces inflammatory processes, increases transcripts linked to anxiolytic neurotransmission, and promotes social behavior.

Microglial double stranded DNA accumulation induced by DNase II deficiency drives neuroinflammation and neurodegeneration

BACKGROUND

Deoxyribonuclease 2 (DNase II) is pivotal in the clearance of cytoplasmic double stranded DNA (dsDNA). Its deficiency incurs DNA accumulation in cytoplasm, which is a hallmark of multiple neurodegenerative diseases. Our previous study showed that neuronal DNase II deficiency drove tau hyperphosphorylation and neurodegeneration (Li et al., Transl Neurodegener 13:39, 2024). Although it has been verified that DNase II participates in type I interferons (IFN-I) mediated autoinflammation and senescence in peripheral systems, the role of microglial DNase II in neuroinflammation and neurodegenerative diseases such as Alzheimer's disease (AD) is still unknown.

METHODS

The levels of microglial DNase II in triple transgenic AD mice (3xTg-AD) were measured by immunohistochemistry. The cognitive performance of microglial DNase II deficient WT and AD mice was determined using the Morris water maze test, Y-maze test, novel object recognition test and open filed test. To investigate the impact of microglial DNase II deficiency on microglial morphology, cyclic GMP-AMP synthase (cGAS)-stimulator of interferon genes (STING) pathway and IFN-I pathway, neuroinflammation, synapses loss, amyloid pathology and tauopathy, the levels of cGAS-STING and IFN-I pathway related protein, gliosis and proinflammatory cytokines, synaptic protein, complement protein, Aβ levels, phosphorylated tau in the brains of the microglial DNase II deficient WT and AD mice were evaluated by immunolabeling, immunoblotting, q-PCR or ELISA.

RESULTS

We found that the levels of DNase II were significantly decreased in the microglia of 3xTg-AD mice. Microglial DNase II deficiency altered microglial morphology and transcriptional signatures, activated the cGAS-STING and IFN-I pathway, initiated neuroinflammation, led to synapse loss via complement-dependent pathway, increased Aβ levels and tauopathy, and induced cognitive decline.

CONCLUSIONS

Our study shows the effect of microglial DNase II deficiency and cytoplasmic accumulated dsDNA on neuroinflammation, and reveals the initiatory mechanism of AD pathology, suggesting that DNase II is a potential target for neurodegenerative diseases.

Anxiety-like behaviors in rats exposed to the single and combined program of running exercise and environmental enrichment

Exercise (Ex) and environmental enrichment (EE) as the nondrug solutions have positive effects on cognitive behaviors and also increase the ability to cope with anxiety, fear, and stress. In this research, we decided to investigate the simultaneous effect of Ex and EE on anxiety-like behaviors and hippocampal neurogenesis markers in healthy rats. A total of 40 male Wistar rats were divided into four treatment groups: control, EE, Ex, and EE + Ex. Animals in EE groups were housed in large cages (50 × 50 × 50 cm) equipped with toys and objects of different shapes for 3 weeks. Ex-animals were forced to run on a treadmill once a day for 3 consecutive weeks. Open field (OF) and elevated plus maze (EPM) tests were used to evaluate anxiety behaviors. The hippocampal expression of early neurogenesis markers, doublecortin, and sex determining region Y-box 2, were measured using real-time-PCR. Ex and EE animals separately did not show any significant performance in reducing anxiety levels, neither in EPM nor in OF compared with the control group. When animals were treated with EE and Ex simultaneously, they showed significantly reduced anxiety in both EPM and OF tests compared with the control as well as Ex and EE groups separately. Both treatments in combination were also more effective than individual groups in increasing the neurogenesis molecular markers within the hippocampus. This study proposes that Ex in combination with cognitive engagement is more efficient in alleviating anxiety responses and that can develop a nonpharmacological and multidomain policy that may prevent or delay psychophysiological symptoms.

Adult Hippocampal Neurogenesis as a Therapeutic Target in Fetal Alcohol Spectrum Disorder

This review is focused on adult hippocampal neurogenesis as a potential therapeutic target in fetal alcohol spectrum disorder (FASD). Adult hippocampal neurogenesis refers to the production of new hippocampal dentate granule cells (DGCs) from a replenishable pool of neural stem and progenitor cells throughout life. Adult-generated DGCs have been shown to exert a profound influence on hippocampal network activity in experimental animals and have been implicated in the regulation of many hippocampal-dependent behaviors and emotional states, including certain forms of learning and memory, anxiety, mood, and stress resilience. While adult hippocampal neurogenesis in humans remains controversial, many studies support its existence and impact on hippocampal function in human health and disease. Here, we review mechanisms of adult hippocampal neurogenesis under physiological conditions, as described primarily in rodent brain, its impact on network activity and behavior, and the negative effects of developmental alcohol exposure on this process. We then explore hippocampal neurogenesis as a potential target for FASD therapy using pharmacological and neurophysiological approaches known to stimulate adult hippocampal neurogenesis, currently available for clinical use in FASD patients.

Regulation of neural stem cells by innervating neurons

The adult central nervous system (CNS) hosts several niches, in which the neural stem and precursor cells (NPCs) reside. The subventricular zone (SVZ) lines the lateral brain ventricles and the subgranular zone (SGZ) is located in the dentate gyrus of the hippocampus. SVZ and SGZ NPCs replace neurons and glia in the homeostatic as well as diseased or injured states. Recently, NPCs have been found to express neurotransmitter receptors, respond to electrical stimulation and interact with neurons, suggesting that neuron-NPC communication is an emerging critical regulator of NPC biology. In this review, we discuss reports that demonstrate neuronal innervation and control of the neurogenic niches. We discuss the role of innervating neurons in regulating NPC fates, such as activation, proliferation, and differentiation. Our review focuses primarily on the innervation of the SVZ niche by the following neuronal types: glutamatergic, GABAergic projection and interneurons, cholinergic, dopaminergic, serotonergic, neuropeptidergic, nitrergic, and noradrenergic. We also discuss the origins of SVZ niche innervating neurons, such as striatum, cortex, basal ganglia, raphe nuclei, substantia nigra and ventral tegmental area, hypothalamus, and locus coeruleus. Our review highlights the various roles of innervating neurons in SVZ NPC fates in a spatiotemporal manner and emphasizes a need for future investigation into the impact of neuronal innervation on NPC gliogenesis.

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.

Revealing the Mechanism of Hemerocallis citrina Baroni in Depression Treatment Through Integrated Network Pharmacology and Transcriptomic Analysis

Background/Objectives: Hemerocallis citrina Baroni (HCB) is a traditional herb for the treatment of depression in China. However, the active constituents and the underlying mechanisms of its antidepressant effects remain unclear. The aim of this study was to identify the bioactive constituents of HCB and elucidate its underlying mechanism for the treatment of depression. Methods: The constituents of HCB were systematically analyzed using UHPLC-Q-Orbitrap HRMS. Its antidepressant effect was evaluated by chronic unpredictable mild stress (CUMS)-induced depression. The mechanism of HCB in treating depression was investigated through network pharmacology and molecular docking. Subsequently, its potential mechanism for the treatment of depression was carried out by RNA sequencing. Finally, the mechanism was further verified by Western blot. Results: A total of 62 chemical constituents were identified from HCB using UHPLC-Q-Orbitrap HRMS, including 17 flavonoids, 11 anthraquinones, 11 alkaloids, 10 caffeoylquinic acid derivatives, five phenolic acids, five triterpenoids, and three phenylethanosides, 13 of which were identified as potential active constituents targeting 49 depression-associated proteins. Furthermore, HCB was found to significantly reduce cognitive impairment, anxiety-like behavior, and anhedonia-like behavior. The expression levels of 5-hydroxytryptamine (5-HT), dopamine (DA), and brain-derived neurotrophic factor (BDNF) were elevated in the hippocampal CA3 region. Results from network pharmacology and transcriptomics indicated that the PI3K/Akt/CREB signaling pathway is essential for the therapeutic effects of HCB on depression. Research in the field of molecular biology has conclusively demonstrated that HCB is associated with an increase in the expression levels of several important proteins. Specifically, there was a notable upregulation of phosphorylated PI3K (p-PI3K) relative to its unphosphorylated form PI3K, as well as an elevation in the ratio of phosphorylated Akt (p-Akt) to total Akt. Additionally, the study observed increased levels of phosphorylated CREB (p-CREB) compared to its unphosphorylated CREB. Conclusions: This study provides compelling evidence that HCB possesses the ability to mitigate the symptoms of depression through its influence on the PI3K/Akt/CREB signaling pathway. HCB could be developed as a promising therapeutic intervention for individuals struggling with depression, offering new avenues for treatment strategies that target this particular signaling mechanism.

GR/P300 Regulates MKP1 Signaling Pathway and Mediates Depression-like Behavior in Prenatally Stressed Offspring

Accumulating evidence suggests that prenatal stress (PNS) increases offspring susceptibility to depression, but the underlying mechanisms remain unclear. We constructed a mouse model of prenatal stress by spatially restraining pregnant mice from 09:00-11:00 daily on Days 5-20 of gestation. In this study, western blot analysis, quantitative real-time PCR (qRT‒PCR), immunofluorescence, immunoprecipitation, chromatin immunoprecipitation (ChIP), and mifepristone rescue assays were used to investigate alterations in the GR/P300-MKP1 and downstream ERK/CREB/TRKB pathways in the brains of prenatally stressed offspring to determine the pathogenesis of the reduced neurogenesis and depression-like behaviors in offspring induced by PNS. We found that prenatal stress leads to reduced hippocampal neurogenesis and depression-like behavior in offspring. Prenatal stress causes high levels of glucocorticoids to enter the fetus and activate the hypothalamic‒pituitary‒adrenal (HPA) axis, resulting in decreased hippocampal glucocorticoid receptor (GR) levels in offspring. Furthermore, the nuclear translocation of GR and P300 (an acetylation modifying enzyme) complex in the hippocampus of PNS offspring increased significantly. This GR/P300 complex upregulates MKP1, which is a negative regulator of the ERK/CREB/TRKB signaling pathway associated with depression. Interestingly, treatment with a GR antagonist (mifepristone, RU486) increased hippocampal GR levels and decreased MKP1 expression, thereby ameliorating abnormal neurogenesis and depression-like behavior in PNS offspring. In conclusion, our study suggested that the regulation of the MKP1 signaling pathway by GR/P300 is involved in depression-like behavior in prenatal stress-exposed offspring and provides new insights and ideas for the fetal hypothesis of mental health.

The extraordinary "ordinary magic" of resilience

In this essay, I will briefly sample different instances of the utilization of the concept of resilience, attempting to complement a comprehensive representation of the field in the special issue of Development and Psychopathology inspired by the 42nd Minnesota Symposium on Child Psychology, hosted by the Institute of Child Development at the University of Minnesota and held in October of 2022. Having established the general context of the field, I will zoom in on some of its features, which I consider "low-hanging fruit" and which can be harvested in a systematic way to advance the study of resilience in the context of the future of developmental psychopathology.

Mapping of c-Fos Expression in Rat Brain Sub/Regions Following Chronic Social Isolation: Effective Treatments of Olanzapine, Clozapine or Fluoxetine

The c-Fos as a marker of cell activation is used to identify brain regions involved in stimuli processing. This review summarizes a pattern of c-Fos immunoreactivity and the overlapping brain sub/regions which may provide hints for the identification of neural circuits that underlie depressive- and anxiety-like behaviors of adult male rats following three and six weeks of chronic social isolation (CSIS), relative to controls, as well as the antipsychotic-like effects of olanzapine (Olz), and clozapine (Clz), and the antidepressant-like effect of fluoxetine (Flx) in CSIS relative to CSIS alone. Additionally, drug-treated controls relative to control rats were also characterized. The overlapping rat brain sub/regions with increased expression of c-Fos immunoreactivity following three or six weeks of CSIS were the retrosplenial granular cortex, c subregion, retrosplenial dysgranular cortex, dorsal dentate gyrus, paraventricular nucleus of the thalamus (posterior part, PVP), lateral/basolateral (LA/BL) complex of the amygdala, caudate putamen, and nucleus accumbens shell. Increased activity of the nucleus accumbens core following exposure of CSIS rats either to Olz, Clz, and Flx treatments was found, whereas these treatments in controls activated the LA/BL complex of the amygdala and PVP. We also outline sub/regions that might represent potential neuroanatomical targets for the aforementioned antipsychotics or antidepressant treatments.

Stress-induced obesity in mice causes cognitive decline associated with inhibition of hippocampal neurogenesis and dysfunctional gut microbiota

Effects of stress on obesity have been thoroughly studied in high-fat diet fed mice, but not in normal diet fed mice, which is important to clarify because even on a normal diet, some individuals will become obese under stress conditions. Here we compared mice that showed substantial weight gain or loss under chronic mild stress while on a normal diet; we compared the two groups in terms of cognitive function, hypothalamic-pituitary-adrenal signaling, neurogenesis and activation of microglia in hippocampus, gene expression and composition of the gut microbiome. Chronic mild stress induced diet-independent obesity in approximately 20% of animals, and it involved inflammatory responses in peripheral and central nervous system as well as hyperactivation of the hypothalamic-pituitary-adrenal signaling and of microglia in the hippocampus, which were associated with cognitive deficits and impaired hippocampal neurogenesis. It significantly increased in relative abundance at the phylum level (Firmicutes), at the family level (Prevotellaceae ucg - 001 and Lachnospiraceae NK4a136), at the genus level (Dubosiella and Turicibacter) for some enteric flora, while reducing the relative abundance at the family level (Lactobacillaceae and Erysipelotrichaceae), at the genus level (Bacteroidota, Alistipes, Alloprevotella, Bifidobacterium and Desulfovibrio) for some enteric flora. These results suggest that stress, independently of diet, can induce obesity and cognitive decline that involve dysfunctional gut microbiota. These insights imply that mitigation of hypothalamic-pituitary-adrenal signaling and microglial activation as well as remodeling of gut microbiota may reverse stress-induced obesity and associated cognitive decline.

The role of exercise-related FNDC5/irisin in depression

The complexity of depression presents a significant challenge to traditional treatment methods, such as medication and psychotherapy. Recent studies have shown that exercise can effectively reduce depressive symptoms, offering a new alternative for treating depression. However, some depressed patients are unable to engage in regular physical activity due to age, physical limitations, and other factors. Therefore, pharmacological agents that mimic the effects of exercise become a potential treatment option. A newly discovered myokine, irisin, which is produced during exercise via cleavage of its precursor protein fibronectin type III domain-containing protein 5 (FNDC5), plays a key role in regulating energy metabolism, promoting adipose tissue browning, and improving insulin resistance. Importantly, FNDC5 can promote neural stem cell differentiation, enhance neuroplasticity, and improve mood and cognitive function. This review systematically reviews the mechanisms of action of exercise in the treatment of depression, outlines the physiology of exercise-related irisin, explores possible mechanisms of irisin's antidepressant effects. The aim of this review is to encourage future research and clinical applications of irisin in the prevention and treatment of depression.

Acupuncture may play a key role in anti-depression through various mechanisms in depression

Depression has emerged as a significant global health concern, exerting a profound impact on individuals, as evidenced by its high prevalence and associated suicide rates. Considering its pervasive nature, the absence of optimal treatment modalities remains a challenge. Acupuncture has garnered substantial clinical and experimental validation for its efficacy in addressing diverse forms of depression, including postpartum, post-stroke, and adolescent depression. This article endeavors to elucidate the distinctive attributes and underlying mechanisms of acupuncture in the contemporary treatment of depression. Research has demonstrated that acupuncture exerts diverse physiological effects in animal models of depression, encompassing modulation of the brain, serum, and brain-gut axis. These effects are attributed to various mechanisms, including anti-inflammatory and anti-oxidative actions, promotion of neuronal plasticity, neuroprotection, neurotrophic effects, modulation of neurotransmitters, regulation of endocrine and immune functions, and modulation of cell signal pathways. Currently, the therapeutic mechanism of acupuncture involves the engagement of multiple targets, pathways, and bidirectional regulation. Hence, acupuncture emerges as a promising alternative medical modality, exhibiting substantial research prospects and meriting comprehensive worth further study and dissemination.

Salidroside exerts antidepressant-like action by promoting adult hippocampal neurogenesis through SIRT1/PGC-1α signalling

Depression is one of the major mental disorders, which seriously endangers human health, brings a serious burden to patients’ families. In this study, we intended to further explore the antidepressant-like effect and possible molecular mechanisms of Salidroside (SAL). We built corticosterone (CORT)-induced depressive mice model and used behavioural tests to evaluate depression behaviour. To explore the molecular mechanisms of SAL, we employed a variety of methods such as immunofluorescence, western blot, pharmacological interference, etc. The results demonstrated that SAL both at 25 mg/kg and 50 mg/kg can reduce immobility time in the tail suspension test (TST). At the same time, SAL treatment could restore the reduced sugar water intake preference in the sucrose preference test (SPT) in CORT-induced depressive mice and reduce the immobility time in TST and forced swimming experiments (FST). In addition, SAL treatment reversed the reduction in the number of Ki-67, BrdU, and NeuN in the hippocampus due to CORT treatment. SAL treatment also restored the expression of SIRT1, PGC-1α, brain-derived neurotrophic factor (BDNF) and other proteins in the hippocampus. In addition, after blocking SIRT1 signalling with EX527, we found that the treatment with SAL failed to reduce the immobility time in TST and FST, the level of SIRT1 and PGC-1α activity were correspondingly downregulated, and the expression of DCX and Ki-67 in the hippocampus failed to be activated. These findings suggested that SAL exerts antidepressant-like effects by promoting hippocampal neurogenesis through the SIRT1/PGC-1α signalling pathway.

Sex-specific effects of intermittent fasting on hippocampal neurogenesis via the gut-brain axis

Intermittent fasting (IF) is a widely used dietary strategy that has shown several advantageous impacts on general health and aging. IF has recently been linked to the control of neurogenesis, a crucial process for emotional control, memory, and learning, in the hippocampus. Nevertheless, there is little knowledge about the sex-specific impacts of IF on hippocampal neurogenesis and the related mechanisms, which were investigated in this study among both male and female rats, together with analyzing the involvement of the flora-gut-brain axis in facilitating these effects. Our findings show that IF favorably affects hippocampus neurogenesis in female mice relative to male mice, suggesting a sex-specific mechanism. In addition, IF influenced the diversity of the gut microbiota and decreased the synthesis of fructose-1-phosphate (F-1-P), which is believed together with fructose metabolism to be linked to neurological damage and cognitive decline. Collectively, these data indicate that the connection between the flora-gut-brain axis and hippocampus neurogenesis is significant.

The multifaceted effects of fluoxetine treatment on cognitive functions

Fluoxetine, the prototypical selective serotonin reuptake inhibitor (SSRI), is widely used to treat major depressive disorder (MDD) and a variety of other central nervous system conditions, primarily due to its established clinical safety profile. Although its efficacy in treating depression is well-recognized, the impact of fluoxetine on cognitive functions remains inconsistent and elusive. In this review, we first examine the well-substantiated biological mechanisms underlying fluoxetine's antidepressant effects, which include serotonin reuptake inhibition and activation of TrkB receptors-key to brain-derived neurotrophic factor (BDNF) signaling. Subsequently, we delve into the cognitive side effects observed in both preclinical and clinical studies, affecting domains such as memory, attention, and executive functions. While certain studies indicate cognitive improvements in patients with underlying disorders, there is also evidence of negative effects, influenced by variables like gender, duration of treatment, age, disease pathology, and the specifics of cognitive testing. Significantly, the negative cognitive outcomes reported in preclinical research often involve healthy, non-diseased animals. This review underscores the necessity for heightened caution in fluoxetine prescription and further investigation into its potentially detrimental cognitive effects, even when used prophylactically.

Humid heat environment causes anxiety-like disorder via impairing gut microbiota and bile acid metabolism in mice

Climate and environmental changes threaten human mental health, but the impacts of specific environmental conditions on neuropsychiatric disorders remain largely unclear. Here, we show the impact of a humid heat environment on the brain and the gut microbiota using a conditioned housing male mouse model. We demonstrate that a humid heat environment can cause anxiety-like behaviour in male mice. Microbial 16 S rRNA sequencing analysis reveals that a humid heat environment caused gut microbiota dysbiosis (e.g., decreased abundance of Lactobacillus murinus), and metabolomics reveals an increase in serum levels of secondary bile acids (e.g., lithocholic acid). Moreover, increased neuroinflammation is indicated by the elevated expression of proinflammatory cytokines in the serum and cortex, activated PI3K/AKT/NF-κB signalling and a microglial response in the cortex. Strikingly, transplantation of the microbiota from mice reared in a humid heat environment readily recapitulates these abnormalities in germ-free mice, and these abnormalities are markedly reversed by Lactobacillus murinus administration. Human samples collected during the humid heat season also show a decrease in Lactobacillus murinus abundance and an increase in the serum lithocholic acid concentration. In conclusion, gut microbiota dysbiosis induced by a humid heat environment drives the progression of anxiety disorders by impairing bile acid metabolism and enhancing neuroinflammation, and probiotic administration is a potential therapeutic strategy for these disorders.

Ablated Sonic Hedgehog Signaling in the Dentate Gyrus of the Dorsal and Ventral Hippocampus Impairs Hippocampal-Dependent Memory Tasks and Emotion in a Rat Model of Depression

Specific memory processes and emotional aberrations in depression can be attributed to the different dorsal-ventral regions of the hippocampus. However, the molecular mechanisms underlying the differential functions of the dorsal hippocampus (dHip) and ventral hippocampus (vHip) remain unclear. As Sonic Hedgehog (Shh) is involved in the dorsal-ventral patterning of the neural tube and its signaling is dysregulated by chronic unpredictable mild stress (CUMS), we investigated its role in influencing the differential functions of the dHip and vHip. Here, CUMS downregulated the expression of Shh signaling markers, including Shh and its downstream effectors GLI family zinc finger 12 (Gli1/2), Patched (Ptch), and smoothened (Smo), in both the dHip and vHip of rats, though more so in the vHip. Additionally, Shh knockdown in the dorsal or ventral dentate gyrus (DG) resulted in restrained neurogenic activity in newborn neurons, especially in immature neurons through decreased expression of Shh signaling markers. Furthermore, Shh knockdown in the DG of the dHip led to memory impairment by inhibiting experience-dependent activation of immature neurons, whereas its knockdown in the DG of the vHip led to an emotional handicap by delaying the maturation of immature neurons. Finally, Shh knockdown in either the dDG or vDG of hippocampus abolished the corresponding cognitive enhancement and emotional recovery of fluoxetine. In conclusion, Shh is essential to maintain the functional heterogeneity of dHip and vHip in depressed rat, which was mainly mediating by local changes of dependent activation and maturity of immature neurons, respectively.

Chronic chemogenetic activation of hippocampal progenitors enhances adult neurogenesis and modulates anxiety-like behavior and fear extinction learning

Adult hippocampal neurogenesis is a lifelong process that involves the integration of newborn neurons into the hippocampal network, and plays a role in cognitive function and the modulation of mood-related behavior. Here, we sought to address the impact of chemogenetic activation of adult hippocampal progenitors on distinct stages of progenitor development, including quiescent stem cell activation, progenitor turnover, differentiation and morphological maturation. We find that hM3Dq-DREADD-mediated activation of nestin-positive adult hippocampal progenitors recruits quiescent stem cells, enhances progenitor proliferation, increases doublecortin-positive newborn neuron number, accompanied by an acceleration of differentiation and morphological maturation, associated with increased dendritic complexity. Behavioral analysis indicated anxiolytic behavioral responses in transgenic mice subjected to chemogenetic activation of adult hippocampal progenitors at timepoints when newborn neurons are predicted to integrate into the mature hippocampal network. Furthermore, we noted an enhanced fear memory extinction on a contextual fear memory learning task in transgenic mice subjected to chemogenetic activation of adult hippocampal progenitors. Our findings indicate that hM3Dq-DREAD-mediated chemogenetic activation of adult hippocampal progenitors impacts distinct aspects of hippocampal neurogenesis, associated with the regulation of anxiety-like behavior and fear memory extinction.

Hippocampal mitophagy contributes to spatial memory via maintaining neurogenesis during the development of mice

BACKGROUND

Impaired mitochondrial dynamics have been identified as a significant contributing factor to reduced neurogenesis under pathological conditions. However, the relationship among mitochondrial dynamics, neurogenesis, and spatial memory during normal development remains unclear. This study aims to elucidate the role of mitophagy in spatial memory mediated by neurogenesis during development.

METHODS

Adolescent and adult male mice were used to assess spatial memory performance. Immunofluorescence staining was employed to evaluate levels of neurogenesis, and mitochondrial dynamics were assessed through western blotting and transmission electron microscopy. Pharmacological interventions further validated the causal relationship among mitophagy, neurogenesis, and behavioral performance during development.

RESULTS

The study revealed differences in spatial memory between adolescent and adult mice. Diminished neurogenesis, accompanied by reduced mitophagy, was observed in the hippocampus of adult mice compared to adolescent subjects. Pharmacological induction of mitophagy in adult mice with UMI-77 resulted in enhanced neurogenesis and prolonged spatial memory retention. Conversely, inhibition of mitophagy with Mdivi-1 in adolescent mice led to reduced hippocampal neurogenesis and impaired spatial memory.

CONCLUSION

The observed decline in spatial memory in adult mice is associated with decreased mitophagy, which affects neurogenesis in the dentate gyrus. This underscores the therapeutic potential of enhancing mitophagy to counteract age- or disease-related cognitive decline.

Aging Modulates the Ability of Quiescent Radial Glia-Like Stem Cells in the Hippocampal Dentate Gyrus to be Recruited into Division by Pro-neurogenic Stimuli

A delicate balance between quiescence and division of the radial glia-like stem cells (RGLs) ensures continuation of adult hippocampal neurogenesis (AHN) over the lifespan. Transient or persistent perturbations of this balance due to a brain pathology, drug administration, or therapy can lead to unfavorable long-term outcomes such as premature depletion of the RGLs, decreased AHN, and cognitive deficit. Memantine, a drug used for alleviating the symptoms of Alzheimer's disease, and electroconvulsive seizure (ECS), a procedure used for treating drug-resistant major depression or bipolar disorder, are known strong AHN inducers; they were earlier demonstrated to increase numbers of dividing RGLs. Here, we demonstrated that 1-month stimulation of quiescent RGLs by either memantine or ECS leads to premature exhaustion of their pool and altered AHN at later stages of life and that aging of the brain modulates the ability of the quiescent RGLs to be recruited into the cell cycle by these AHN inducers. Our findings support the aging-related divergence of functional features of quiescent RGLs and have a number of implications for the practical assessment of drugs and treatments with respect to their action on quiescent RGLs at different stages of life in animal preclinical studies.

Repurposing Ketamine in the Therapy of Depression and Depression-Related Disorders: Recent Advances and Future Potential

Depression represents a prevalent and enduring mental disorder of significant concern within the clinical domain. Extensive research indicates that depression is very complex, with many interconnected pathways involved. Most research related to depression focuses on monoamines, neurotrophic factors, the hypothalamic-pituitary-adrenal axis, tryptophan metabolism, energy metabolism, mitochondrial function, the gut-brain axis, glial cell-mediated inflammation, myelination, homeostasis, and brain neural networks. However, recently, Ketamine, an ionotropic N-methyl-D-aspartate (NMDA) receptor antagonist, has been discovered to have rapid antidepressant effects in patients, leading to novel and successful treatment approaches for mood disorders. This review aims to summarize the latest findings and insights into various signaling pathways and systems observed in depression patients and animal models, providing a more comprehensive view of the neurobiology of anxious-depressive-like behavior. Specifically, it highlights the key mechanisms of ketamine as a rapid-acting antidepressant, aiming to enhance the treatment of neuropsychiatric disorders. Moreover, we discuss the potential of ketamine as a prophylactic or therapeutic intervention for stress-related psychiatric disorders.

RNA-Seq time-course analysis of neural precursor cell transcriptome in response to herpes simplex Virus-1 infection

The neurogenic niches within the central nervous system serve as essential reservoirs for neural precursor cells (NPCs), playing a crucial role in neurogenesis. However, these NPCs are particularly vulnerable to infection by the herpes simplex virus 1 (HSV-1). In the present study, we investigated the changes in the transcriptome of NPCs in response to HSV-1 infection using bulk RNA-Seq, compared to those of uninfected samples, at different time points post infection and in the presence or absence of antivirals. The results showed that NPCs upon HSV-1 infection undergo a significant dysregulation of genes playing a crucial role in aspects of neurogenesis, including genes affecting NPC proliferation, migration, and differentiation. Our analysis revealed that the CREB signaling, which plays a crucial role in the regulation of neurogenesis and memory consolidation, was the most consistantly downregulated pathway, even in the presence of antivirals. Additionally, cholesterol biosynthesis was significantly downregulated in HSV-1-infected NPCs. The findings from this study, for the first time, offer insights into the intricate molecular mechanisms that underlie the neurogenesis impairment associated with HSV-1 infection.

FBXL20 promotes synaptic impairment in depression disorder via degrading vesicle-associated proteins

BACKGROUND

Synaptic plasticity changes in presynaptic terminals or postsynaptic membranes play a critical role in cognitive impairments and emotional disorders, but the underlying molecular mechanisms in depression remain largely unknown.

METHODS

The regulation effects of F-box and leucine-rich repeat protein 20 (FBXL20), vesicular glutamate transporter 1 (VGLUT1) and vesicle-associated membrane protein 1 (VAMP1) on synaptic plasticity and depressive-like behaviors examined by proteomics analysis, viral stereotaxic injection, transmission electron microscope and biochemical methods. The glutamate release detected by fluorescent probe in cultured primary pyramidal neurons.

RESULTS

We found that chronic unpredictable mild stress (CUMS) induced significant synaptic deficits within hippocampus of depressed rats, accompanied with the decreased expression of VGLUT1 and VAMP1. Moreover, knockdown of VGLUT1 or VAMP1 in hippocampal pyramidal neurons resulted in abnormal glutamatergic neurotransmitter release. In addition, we found that the E3 ubiquitin ligase FBXL20 was increased within hippocampus, which may promote ubiquitination and degradation of VGLUT1 and VAMP1, and thus resulted in the reduction of glutamatergic neurotransmitter release, the disruptions of synaptic transmission and the induction of depression-like behaviors in rats. In contrast, shRNA knockdown of FBXL20 within the hippocampus of depressed rats significantly ameliorated synaptic damage and depression-like behaviors.

LIMITATION

Only one type of depression model was used in the present study, while other animal models should be used in the future to confirm the underlying mechanisms reported here.

CONCLUSIONS

This study provides new insights that inhibiting FBXL20 pathway in depressed rats may be an effective strategy to rescue synaptic transmission and depression-like behaviors.

Higenamine exerts antidepressant effect by improving the astrocytic gap junctions and inflammatory response

BACKGROUND

Depression is a refractory psychiatric disorder closely associated with dysfunction of the gap junctions (GJs) between astrocytes as well as neuroinflammation. Higenamine (Hig) is a potent cardiotonic ingredient in Fuzi (i.e., Aconitum carmichaeli Debx.) with anti-inflammatory and antioxidant effects, which has a significant protective effect on damaged nerve cells and has great potential for the treatment of neuropsychiatric diseases.

METHODS

Rats were stimulated by chronic unpredictable stress (CUS) for 28 days while given Hig (5, 10, 20 mg/kg) and then analyzed behaviorally by the open field test, sucrose preference test, and forced swimming test. Changes in astrocyte GJs function and morphology were observed by dye transfer and transmission electron microscopy, respectively. Expression and phosphorylation of connexin 43 (Cx43) were analyzed by Western blot. Also, considering the close relationship between depression and neuroinflammation, we determined the inflammatory response in serum with ELISA kits and analyzed the expression of inflammation-related proteins with Western blot.

RESULTS

Hig ameliorated CUS-induced depression-like behavior in rats. Hig administration improved gap junctional dysfunction in astrocytes, reduced gap junctional gaps and elevated the expression of Cx43 and decreased the phosphorylation of Cx43. Meanwhile, Hig administration was also able to attenuate the inflammatory response that occurs after CUS in rats.

LIMITATIONS

For the role of Cx43 in depression, we did not validate it more deeply in animal models with knockout Cx43. In addition, GJs dysfunction might be associated with the inflammatory response seen in depression, but this needs to be further investigated.

CONCLUSIONS

Hig ameliorates depression and exerts its antidepressant effect possibly by improving the dysfunctional GJs between astrocytes and the inflammatory response.

Linkage of CDC42 and T-helper cell ratio with anxiety, depression and quality of life in ST-elevation myocardial infarction

Objective: To investigate the correlations between CDC42 and T-cell subsets concerning anxiety, depression and quality of life in ST-elevation myocardial infarction patients undergoing percutaneous coronary intervention. Methods: Sera from 156 participants were analyzed for CDC42 levels and Th1, Th2, Th17 and Treg cells. Results: CDC42 correlated with reduced Th1/Th2 and Th17/Treg ratios, lower anxiety and depression, and higher EuroQol visual analog scale (EQ-VAS) score. The Th17/Treg ratio correlated with elevated anxiety, depression, EuroQol-5 dimensions score and decreased EQ-VAS score. The Th1/Th2 ratio was positively related to the EQ-VAS score. Conclusion: CDC42 correlates with reduced Th1/Th2 and Th17/Treg ratios, reduced anxiety and depression, and improved quality of life in ST-elevation myocardial infarction patients undergoing percutaneous coronary intervention.

Ketamine's rapid and sustained antidepressant effects are driven by distinct mechanisms

Administration of multiple subanesthetic doses of ketamine increases the duration of antidepressant effects relative to a single ketamine dose, but the mechanisms mediating this sustained effect are unclear. Here, we demonstrate that ketamine's rapid and sustained effects on affective behavior are mediated by separate and temporally distinct mechanisms. The rapid effects of a single dose of ketamine result from increased activity of immature neurons in the hippocampal dentate gyrus without an increase in neurogenesis. Treatment with six doses of ketamine over two weeks doubled the duration of behavioral effects after the final ketamine injection. However, unlike ketamine's rapid effects, this more sustained behavioral effect did not correlate with increased immature neuron activity but instead correlated with increased numbers of calretinin-positive and doublecortin-positive immature neurons. This increase in neurogenesis was associated with a decrease in bone morphogenetic protein (BMP) signaling, a known inhibitor of neurogenesis. Injection of a BMP4-expressing lentivirus into the dentate gyrus maintained BMP signaling in the niche and blocked the sustained - but not the rapid - behavioral effects of ketamine, indicating that decreased BMP signaling is necessary for ketamine's sustained effects. Thus, although the rapid effects of ketamine result from increased activity of immature neurons in the dentate gyrus without requiring an increase in neurogenesis, ketamine's sustained effects require a decrease in BMP signaling and increased neurogenesis along with increased neuron activity. Understanding ketamine's dual mechanisms of action should help with the development of new rapid-acting therapies that also have safe, reliable, and sustained effects.

The molecular mechanism of polysaccharides in combating major depressive disorder: A comprehensive review

Major depressive disorder (MDD) is a complex psychiatric condition with diverse etiological factors. Typical pathological features include decreased cerebral cortex, subcortical structures, and grey matter volumes, as well as monoamine transmitter dysregulation. Although medications exist to treat MDD, unmet needs persist due to limited efficacy, induced side effects, and relapse upon drug withdrawal. Polysaccharides offer promising new therapies for MDD, demonstrating antidepressant effects with minimal side effects and multiple targets. These include neurotransmitter, neurotrophin, neuroinflammation, hypothalamic-pituitary-adrenal axis, mitochondrial function, oxidative stress, and intestinal flora regulation. This review explores the latest advancements in understanding the pharmacological actions and mechanisms of polysaccharides in treating major depression. We discuss the impact of polysaccharides' diverse structures and properties on their pharmacological actions, aiming to inspire new research directions and facilitate the discovery of novel anti-depressive drugs.

The Antidepressant Effect of Magnolol on Depression-Like Behavior of CORT-Treated Mice

Although the antidepressant-like effect of magnolol has been revealed in previous reports, the mechanism remains unclear. In this study, the antidepressant-like effect of magnolol on corticosterone-induced (CORT-induced) mice was investigated in vivo. After 21 days of CORT induction, the mice showed marked depressive-like behaviors, with a decrease in sucrose preference score and an increase in immobility time in the tail suspension test (TST) and forced swimming test (FST). Pretreatment with either magnolol (50 mg/kg, i.p.) or the kappa opioid receptor (KOR) antagonist nor-BNI (10 mg/kg, i.p.) prevented CORT-induced depression-like behavior and reduced CORT-induced dynorphin (DYN A) elevation in the hippocampal ventral DG. However, no depression-like behavior was observed in mice with KOR downregulation in the ventral DG. We further found that upregulation of DYN A in the DG caused depression-like behavior, which was blocked by intraperitoneal injection of nor-BNI and modulated by magnolol. The present study demonstrated that magnolol could ameliorate CORT-induced depression-like behaviors, by modulating the DYN A/KOR system in the ventral DG of the hippocampus.

Altered in vivo early neurogenesis traits in patients with depression: Evidence from neuron-derived extracellular vesicles and electroconvulsive therapy

BACKGROUND

The neurogenesis hypothesis is a promising candidate etiologic hypothesis for depression, and it is associated with electroconvulsive therapy (ECT). However, human in vivo molecular-level evidence is lacking.

OBJECTIVE

We used neuron-derived extracellular vesicles (NDEVs) as a "window to the neurons" to explore the in vivo neurogenesis status associated with ECT in patients with treatment-resistant depression (TRD).

METHODS

In this study, we enrolled 40 patients with TRD and 35 healthy controls (HCs). We isolated NDEVs from the plasma of each participant to test the levels of doublecortin (DCX), a marker of neurogenesis, and cluster of differentiation (CD) 81, a marker of EVs. We also assessed the plasma levels of brain-derived neurotrophic factor (BDNF), a protein that is known to be associated with ECT and neuroplastic processes.

RESULTS

Our findings indicated that both the levels of DCX in NDEVs and BDNF in plasma were significantly lower in TRD patients compared to HCs at baseline, but increased following ECTs. Conversely, levels of CD81 in NDEVs were found higher in TRD patients at baseline, but did not change after the ECT treatments. Exploratory analyses revealed that lower levels of BDNF in plasma and DCX in NDEVs, along with higher CD81 levels in NDEVs, were associated with more severe depressive symptoms and reduced cognitive function at baseline. Furthermore, higher baseline CD81 concentrations in NDEVs were correlated with greater decreases in depression symptoms.

CONCLUSIONS

We first present human in vivo evidence of early neurogenesis using DCX through NDEVs: decreased in TRD patients, increased after ECTs.

Dentate Gyrus Microstructure Is Associated With Resilience After Exposure to Maternal Stress Across Two Human Cohorts

BACKGROUND

Maternal stress (MS) is a well-documented risk factor for impaired emotional development in offspring. Rodent models implicate the dentate gyrus (DG) of the hippocampus in the effects of MS on offspring depressive-like behaviors, but mechanisms in humans remain unclear. Here, we tested whether MS was associated with depressive symptoms and DG micro- and macrostructural alterations in offspring across 2 independent cohorts.

METHODS

We analyzed DG diffusion tensor imaging-derived mean diffusivity (DG-MD) and volume in a three-generation family risk for depression study (TGS; n = 69, mean age = 35.0 years) and in the Adolescent Brain Cognitive Development (ABCD) Study (n = 5196, mean age = 9.9 years) using generalized estimating equation models and mediation analysis. MS was assessed by the Parenting Stress Index (TGS) and a measure compiled from the Adult Response Survey from the ABCD Study. The Patient Health Questionnaire-9 and rumination scales (TGS) and the Child Behavior Checklist (ABCD Study) measured offspring depressive symptoms at follow-up. The Schedule for Affective Disorders and Schizophrenia-Lifetime interview was used to assign depression diagnoses.

RESULTS

Across cohorts, MS was associated with future symptoms and higher DG-MD (indicating disrupted microstructure) in offspring. Higher DG-MD was associated with higher symptom scores measured 5 years (in the TGS) and 1 year (in the ABCD Study) after magnetic resonance imaging. In the ABCD Study, DG-MD was increased in high-MS offspring who had depressive symptoms at follow-up, but not in offspring who remained resilient or whose mother had low MS.

CONCLUSIONS

Converging results across 2 independent samples extend previous rodent studies and suggest a role for the DG in exposure to MS and offspring depression.

Gut microbiota-derived short-chain fatty acids ameliorate methamphetamine-induced depression- and anxiety-like behaviors in a Sigmar-1 receptor-dependent manner

Methamphetamine (Meth) abuse can cause serious mental disorders, including anxiety and depression. The gut microbiota is a crucial contributor to maintaining host mental health. Here, we aim to investigate if microbiota participate in Meth-induced mental disorders, and the potential mechanisms involved. Here, 15 mg/kg Meth resulted in anxiety- and depression-like behaviors of mice successfully and suppressed the Sigma-1 receptor (SIGMAR1)/BDNF/TRKB pathway in the hippocampus. Meanwhile, Meth impaired gut homeostasis by arousing the Toll-like receptor 4 (TLR4)-related colonic inflammation, disturbing the gut microbiome and reducing the microbiota-derived short-chain fatty acids (SCFAs). Moreover, fecal microbiota from Meth-administrated mice mediated the colonic inflammation and reproduced anxiety- and depression-like behaviors in recipients. Further, SCFAs supplementation optimized Meth-induced microbial dysbiosis, ameliorated colonic inflammation, and repressed anxiety- and depression-like behaviors. Finally, Sigmar1 knockout (Sigmar1-/-) repressed the BDNF/TRKB pathway and produced similar behavioral phenotypes with Meth exposure, and eliminated the anti-anxiety and -depression effects of SCFAs. The activation of SIGMAR1 with fluvoxamine attenuated Meth-induced anxiety- and depression-like behaviors. Our findings indicated that gut microbiota-derived SCFAs could optimize gut homeostasis, and ameliorate Meth-induced mental disorders in a SIGMAR1-dependent manner. This study confirms the crucial role of microbiota in Meth-related mental disorders and provides a potential preemptive therapy.

Adolescent traumatic brain injury leads to incremental neural impairment in middle-aged mice: role of persistent oxidative stress and neuroinflammation

BACKGROUND

Traumatic brain injury (TBI) increases the risk of mental disorders and neurodegenerative diseases in the chronic phase. However, there is limited neuropathological or molecular data on the long-term neural dysfunction and its potential mechanism following adolescent TBI.

METHODS

A total of 160 male mice aged 8 weeks were used to mimic moderate TBI by controlled cortical impact. At 1, 3, 6 and 12 months post-injury (mpi), different neurological functions were evaluated by elevated plus maze, forced swimming test, sucrose preference test and Morris water maze. The levels of oxidative stress, antioxidant response, reactive astrocytes and microglia, and expression of inflammatory cytokines were subsequently assessed in the ipsilateral hippocampus, followed by neuronal apoptosis detection. Additionally, the morphological complexity of hippocampal astrocytes was evaluated by Sholl analysis.

RESULTS

The adolescent mice exhibited persistent and incremental deficits in memory and anxiety-like behavior after TBI, which were sharply exacerbated at 12 mpi. Depression-like behaviors were observed in TBI mice at 6 mpi and 12 mpi. Compared with the age-matched control mice, apoptotic neurons were observed in the ipsilateral hippocampus during the chronic phase of TBI, which were accompanied by enhanced oxidative stress, and expression of inflammatory cytokines (IL-1β and TNF-α). Moreover, the reactive astrogliosis and microgliosis in the ipsilateral hippocampus were observed in the late phase of TBI, especially at 12 mpi.

CONCLUSION

Adolescent TBI leads to incremental cognitive dysfunction, and depression- and anxiety-like behaviors in middle-aged mice. The chronic persistent neuroinflammation and oxidative stress account for the neuronal loss and neural dysfunction in the ipsilateral hippocampus. Our results provide evidence for the pathogenesis of chronic neural damage following TBI and shed new light on the treatment of TBI-induced late-phase neurological dysfunction.

Social withdrawal and anxiety-like behavior have an impact on zebrafish adult neurogenesis

Introduction

Accumulating evidence highlights the key role of adult neurogenesis events in environmental challenges, cognitive functions and mood regulation. Abnormal hippocampal neurogenesis has been implicated in anxiety-like behaviors and social impairments, but the possible mechanisms remain elusive.

Methods

The present study questioned the contribution of altered excitation/inhibition as well as excessive neuroinflammation in regulating the neurogenic processes within the Social Decision-Making (SDM) network, using an adult zebrafish model displaying NMDA receptor hypofunction after sub-chronic MK-801 administration. For this, the alterations in cell proliferation and newborn cell densities were evaluated using quantitative 5-Bromo-2'-Deoxyuridine (BrdU) methodology.

Results

In short-term survival experiments. MK-801-treated zebrafish displayed decreased cell proliferation pattern within distinct neurogenic zones of telencephalic and preoptic SDM nodes, in parallel to the social withdrawal and anxiety-like comorbidity. BrdU+ cells co-expressed the pro-inflammatory marker IL-1β solely in MK-801-treated zebrafish, indicating a role of inflammation. Following the cessation of drug treatment, significant increases in the BrdU+ cell densities were accompanied by the normalization of the social and anxiety-like phenotype. Importantly, most labeled cells in neurogenic zones showed a radial glial phenotype while a population of newborn cells expressed the early neuronal marker TOAD or mGLuR5, the latter suggesting the possible involvement of metabotropic glutamate receptor 5 in neurogenic events.

Discussion

Overall, our results indicate the role of radial glial cell proliferation in the overlapping pathologies of anxiety and social disorders, observed in many neuropsychiatric disorders and possibly represent potential novel targets for amelioration of these symptoms.

Roles of microglia in adult hippocampal neurogenesis in depression and their therapeutics

Adult hippocampal neurogenesis generates functional neurons from neural progenitor cells in the hippocampal dentate gyrus (DG) to complement and repair neurons and neural circuits, thus benefiting the treatment of depression. Increasing evidence has shown that aberrant microglial activity can disrupt the appropriate formation and development of functional properties of neurogenesis, which will play a crucial role in the occurrence and development of depression. However, the mechanisms of the crosstalk between microglia and adult hippocampal neurogenesis in depression are not yet fully understood. Therefore, in this review, we first introduce recent discoveries regarding the roles of microglia and adult hippocampal neurogenesis in the etiology of depression. Then, we systematically discuss the possible mechanisms of how microglia regulate adult hippocampal neurogenesis in depression according to recent studies, which involve toll-like receptors, microglial polarization, fractalkine-C-X3-C motif chemokine receptor 1, hypothalamic-pituitary-adrenal axis, cytokines, brain-derived neurotrophic factor, and the microbiota-gut-brain axis, etc. In addition, we summarize the promising drugs that could improve the adult hippocampal neurogenesis by regulating the microglia. These findings will help us understand the complicated pathological mechanisms of depression and shed light on the development of new treatment strategies for this disease.

Bumetanide induces post-traumatic microglia-interneuron contact to promote neurogenesis and recovery

Although the Na-K-Cl cotransporter (NKCC1) inhibitor bumetanide has prominent positive effects on the pathophysiology of many neurological disorders, the mechanism of action is obscure. Attention paid to elucidating the role of Nkcc1 has mainly been focused on neurons, but recent single cell mRNA sequencing analysis has demonstrated that the major cellular populations expressing NKCC1 in the cortex are non-neuronal. We used a combination of conditional transgenic animals, in vivo electrophysiology, two-photon imaging, cognitive behavioural tests and flow cytometry to investigate the role of Nkcc1 inhibition by bumetanide in a mouse model of controlled cortical impact (CCI). Here, we found that bumetanide rescues parvalbumin-positive interneurons by increasing interneuron-microglia contacts shortly after injury. The longitudinal phenotypic changes in microglia were significantly modified by bumetanide, including an increase in the expression of microglial-derived BDNF. These effects were accompanied by the prevention of CCI-induced decrease in hippocampal neurogenesis. Treatment with bumetanide during the first week post-CCI resulted in significant recovery of working and episodic memory as well as changes in theta band oscillations 1 month later. These results disclose a novel mechanism for the neuroprotective action of bumetanide mediated by an acceleration of microglial activation dynamics that leads to an increase in parvalbumin interneuron survival following CCI, possibly resulting from increased microglial BDNF expression and contact with interneurons. Salvage of interneurons may normalize ambient GABA, resulting in the preservation of adult neurogenesis processes as well as contributing to bumetanide-mediated improvement of cognitive performance.

Mitochondria of intestinal epithelial cells in depression: Are they at a crossroads of gut-brain communication?

The role of gut dysbiosis in depression is well established. However, recent studies have shown that gut microbiota is regulated by intestinal epithelial cell (IEC) mitochondria, which has yet to receive much attention. This review summarizes the recent developments about the critical role of IEC mitochondria in actively maintaining gut microbiota, intestinal metabolism, and immune homeostasis. We propose that IEC mitochondrial dysfunction alters gut microbiota composition, participates in cell fate, mediates oxidative stress, activates the peripheral immune system, causes peripheral inflammation, and transmits peripheral signals through the vagus and enteric nervous systems. These pathological alterations lead to brain inflammation, disruption of the blood-brain barrier, activation of the hypothalamic-pituitary-adrenal axis, activation of microglia and astrocytes, induction of neuronal loss, and ultimately depression. Furthermore, we highlight the prospect of treating depression through the mitochondria of IECs. These new findings suggest that the mitochondria of IECs may be a newly found important factor in the pathogenesis of depression and represent a potential new strategy for treating depression.

Cell type-specific NRBF2 orchestrates autophagic flux and adult hippocampal neurogenesis in chronic stress-induced depression

Dysfunctional autophagy and impairment of adult hippocampal neurogenesis (AHN) each contribute to the pathogenesis of major depressive disorder (MDD). However, whether dysfunctional autophagy is linked to aberrant AHN underlying MDD remains unclear. Here we demonstrate that the expression of nuclear receptor binding factor 2 (NRBF2), a component of autophagy-associated PIK3C3/VPS34-containing phosphatidylinositol 3-kinase complex, is attenuated in the dentate gyrus (DG) under chronic stress. NRBF2 deficiency inhibits the activity of the VPS34 complex and impairs autophagic flux in adult neural stem cells (aNSCs). Moreover, loss of NRBF2 disrupts the neurogenesis-related protein network and causes exhaustion of aNSC pool, leading to the depression-like phenotype. Strikingly, overexpressing NRBF2 in aNSCs of the DG is sufficient to rescue impaired AHN and depression-like phenotype of mice. Our findings reveal a significant role of NRBF2-dependent autophagy in preventing chronic stress-induced AHN impairment and suggest the therapeutic potential of targeting NRBF2 in MDD treatment.

Exosome-sheathed ROS-responsive nanogel to improve targeted therapy in perimenopausal depression

The development of natural membranes as coatings for nanoparticles to traverse the blood-brain barrier (BBB) presents an effective approach for treating central nervous system (CNS) disorders. In this study, we have designed a nanogel loaded with PACAP and estrogen (E2), sheathed with exosomes and responsive to reactive oxygen species (ROS), denoted as HA NGs@exosomes. The objective of this novel design is to serve as a potent drug carrier for the targeted treatment of perimenopausal depression. The efficient cellular uptake and BBB penetration of HA NGs@exosomes has been demonstrated in vitro and in vivo. Following intranasal intervention with HA NGs@exosomes, ovariectomized mice under chronic unpredictable mild stress (CUMS) have shown improved behavioral performance, indicating that HA NGs@exosomes produced a rapid-onset antidepressant effect. Moreover, HA NGs@exosomes exhibit notable antioxidant and anti-inflammatory properties and may regulate the expression of pivotal proteins in the PACAP/PAC1 pathway to promote synaptic plasticity. Our results serve as a proof-of-concept for the utility of exosome-sheathed ROS-responsive nanogel as a promising drug carrier for the treatment of perimenopausal depression.