Hippocampal neurogenesis dysfunction linked to depressive-like behaviors in a neuroinflammation induced model of depression

Leptin reduces LPS-induced A1 reactive astrocyte activation and inflammation via inhibiting p38-MAPK signaling pathway

Neurotoxic A1 reactive astrocytes are induced by inflammatory stimuli. Leptin has been confirmed to have neuroprotective properties. However, its effect on the activation of A1 astrocytes in infectious inflammation is unclear. In the current study, astrocytes cultured from postnatal day 1 Sprague-Dawley rats were stimulated with lipopolysaccharide (LPS) to induce an acute in vitro inflammatory response. Leptin was applied 6 h later to observe its protective effects. The viability of the astrocytes was assessed. A1 astrocyte activation was determined by analyzing the gene expression of C3, H2-D1, H2-T23, and Serping 1 and secretion of pro-inflammatory cytokines IL-6 and TNF-α. The levels of phospho-p38 (pp38) and nuclear factor-κB (NF-κB) phosphor-p65 (pp65) were measured to explore the possible signaling pathways. Additionally, an LPS-induced inflammatory animal model was established to investigate the in vivo effects of leptin on A1 astrocytic activation. Results showed that in the in vitro culture system, LPS stimulation caused elevated expression of A1 astrocyte-specific genes and the secretion of pro-inflammatory cytokines, indicating the activation of A1 astrocytes. Leptin treatment significantly reversed the LPS induced upregulation in a dose-dependent manner. Similarly, LPS upregulated pp38, NF-κB pp65 protein and inflammatory cytokines were successfully reduced by leptin. In the LPS-induced animal model, the amelioratory effect of leptin on A1 astrocyte activation and inflammation was further confirmed, showed by the reduced sickness behaviors, A1 astrocyte genesis and inflammatory cytokines in vivo. Our results demonstrate that leptin efficiently inhibits LPS-induced neurotoxic activation of A1 astrocytes and neuroinflammation by suppressing p38-MAPK signaling pathway.

Brain Specific RagA Overexpression Triggers Depressive-Like Behaviors in Mice via Activating ADORA2A Signaling Pathway

Neuroinflammation hallmarks the pathology of depression although the etiological complexity has not yet been resolved. Previous studies demonstrate that bacterial lipopolysaccharide induces depressive-like behaviors by activating RagA-mTOR-p70S6K signaling pathway. The current project aims to investigate whether and how brain-specific RagA overexpression triggers depressive-like behaviors in mice. Full-length RagA cDNA is cloned into the mammalian expression vector under the control of brain specific promoter, and subsequently overexpressed in the brain of mouse embryos. Indeed, RagA transgenic mice exhibit depressive-like behaviors and memory impairments. RNA-seq profiling of the prefrontal cortex (PFC) transcriptome highlights adenosine A2a receptor (ADORA2A) as a key differentially expressed gene (DEG). Western blotting confirms that ADORA2A and phospho-p70S6K are markedly elevated in RagA transgenic mice. Behavioral assessments demonstrate that ADORA2A inhibitor istradefylline markedly attenuates depressive-like behaviors. Further metabolomics reveals that N-acetylserotonin and several depression-related metabolites are downregulated while proteomic profiling showed that OLIG1 and other proteins are significantly regulated in RagA transgenic mice. Collectively, RagA overexpression alters the expression patterns of signaling proteins and the metabolism of depression-associated metabolites. RagA may cause depressive-like behaviors in mice via activating p70S6K/ADORA2A signaling pathway. Thus, RagA-p70S6K-ADORA2A signaling pathway may be a target for the development of new antidepressant therapies.

Antidepressant effect of PT-31, an α₂-adrenoceptor agonist, on lipopolysaccharide-induced depressive-like behavior in mice

Increasing evidence indicates that neuroinflammation, oxidative stress, and neurotrophic factors play a key role in the pathophysiology of major depressive disorder (MDD). In addition, the attenuation of inflammatory response has been considered a putative mechanism for MDD treatment. PT-31 is an imidazolidine derivative and a putative α₂-adrenoceptor agonist that has previously demonstrated antinociceptive activity. The present study aimed to investigate the effect of PT-31 on depressive-like behavior and lipopolysaccharide-induced neurochemical changes. To this end, mice received intraperitoneally saline or lipopolysaccharide (600 µg/kg), and 5 h postinjection animals were orally treated with saline, PT-31 (3, 10, and 30 mg/kg), or fluoxetine (30 mg/kg). Mice were subjected to the open field test (OFT) 6 and 24 h after lipopolysaccharide administration and to the tail suspension test (TST) 24 h postlipopolysaccharide. Subsequently, animals were euthanized, and brains were dissected for neurochemical analyses. The administration of lipopolysaccharide-induced sickness- and depressive-like behaviors, besides promoting an increase in myeloperoxidase activity and a reduction in brain-derived neurotrophic factor (BDNF) levels. Noteworthy, PT-31 3 mg/kg attenuated lipopolysaccharide-induced decreased locomotor activity 6 h after lipopolysaccharide in the OFT. All tested doses of PT-31 significantly reduced the immobility time of animals in the TST and attenuated lipopolysaccharide-induced increased myeloperoxidase activity in the cortex of mice. Our results demonstrate that PT-31 ameliorates behavioral changes promoted by lipopolysaccharide in OFT and TST, which is possibly mediated by attenuation of the inflammatory response.

'Unpredictable chronic mild stress does not exacerbate memory impairment or altered neuronal and glial plasticity in the hippocampus of middle-aged vitamin D deficient mice'

Vitamin D deficiency is a worldwide health concern, especially in the elderly population. Much remains unknown about the relationship between vitamin D deficiency (VDD), stress-induced cognitive dysfunctions and depressive-like behaviour. In this study, 4-month-old male C57Bl/6J mice were fed with control or vitamin D free diet for 6 months, followed by unpredictable chronic stress (UCMS) for 8 weeks. VDD induced cognitive impairment and reduced grooming behaviour, but did not induce depressive-like behaviour. While UCMS in vitamin D sufficient mice induced expected depressive-like phenotype and impairments in the contextual fear memory, chronic stress did not manifest as an additional risk factor for memory impairments and depressive-like behaviour in VDD mice. In fact, UCMS restored self-care behaviour in VDD mice. At the histopathological level, VDD mice exhibited cell loss in the granule cell layer, reduced survival of newly generated cells, accompanied with an increased number of apoptotic cells and alterations in glial morphology in the hippocampus; however, these effects were not exacerbated by UCMS. Interestingly, UCMS reversed VDD induced loss of microglial cells. Moreover, tyrosine hydroxylase levels decreased in the striatum of VDD mice, but not in stressed VDD mice. These findings indicate that long-term VDD in adulthood impairs cognition but does not augment behavioural response to UCMS in middle-aged mice. While VDD caused cell loss and altered glial response in the DG of the hippocampus, these effects were not exacerbated by UCMS and could contribute to mechanisms regulating altered stress response.

Gypenoside-14 Reduces Depression via Downregulation of the Nuclear Factor Kappa B (NF-kB) Signaling Pathway on the Lipopolysaccharide (LPS)-Induced Depression Model

Neuroinflammation is a common pathogenetic sign of depression and is closely linked to the development of depression. Many clinical anti-inflammatory drugs act as antidepressants by reducing the neuroinflammatory response. Previous research found that gypenosides and their bioactive compound gypenoside-14 (GP-14) had neuroprotective effects against hypoxia-induced injury and reduced neuroinflammation-related high-altitude cerebral edema. Here we investigated the effects of GP-14 on the lipopolysaccharide (LPS)-induced depression-like behavior model. LPS (0.5 mg/kg) was injected into mice intraperitoneally for 7 consecutive days to induce depression-like behavior, which is considered a model for the exacerbation of depression. GP-14 in the amount of 100 mg/kg was simultaneously administered by gavage for 7 days. In the LPS-induced depression model, GP-14 not only attenuated depression-like behavior but also improved the anxiety-like behavior of the mice. Additionally, GP-14 treatment mitigated learning and cognitive decline in depressed mice. ELISA and immunofluorescence staining results revealed that GP-14 inhibited the upregulation of pro-inflammatory cytokines, including tumor necrosis factor-α (TNF-α), interleukin-1β (IL-1β), and interleukin-6 (IL-6), and suppressed the activation of astrocytes induced with LPS, indicating its potent anti-inflammatory effect. GP-14 pretreatment in C8 cells and primary astrocytes can inhibit the activation of the NF-κB signaling pathway and downregulate the levels of pro-inflammatory factors. In summary, our findings showed that GP-14 had significant anti-inflammation and anti-depression properties; thus, GP-14 could be a promising lead compound for treating depression.

Brain-Derived Estrogen Regulates Neurogenesis, Learning and Memory with Aging in Female Rats

Although 17β-estradiol (E2) can be locally synthesized in the brain, whether and how brain-derived E2 (BDE2) impacts neurogenesis with aging is largely unclear. In this study, we examined the hippocampal neural stem cells, neurogenesis, and gliogenesis of 1, 3, 6, 14, and 18-month (Mon) female rats. Female forebrain neuronal aromatase knockout (FBN-ARO-KO) rats and letrozole-treated rats were also employed. We demonstraed that (1) the number of neural stem cells declined over 14-Mon age, and the differentiation of astrocytes and microglia markedly elevated and exhibited excessive activation. KO rats showed declines in astrocyte A2 subtype and elevation in A1 subtype at 18 Mon; (2) neurogenesis sharply dropped from 1-Mon age; (3) KO suppressed dentate gyrus (DG) neurogenesis at 1, 6 and 18 Mon. Additionally, KO and letrozole treatment led to declined neurogenesis at 1-Mon age, compared to age-matched WT controls; (4) FBN-ARO-KO inhibited CREB-BDNF activation, and decreased protein levels of neurofilament, spinophilin and PSD95. Notably, hippocampal-dependent spatial learning and memory was impaired in juvenile (1 Mon) and adulthood (6 Mon) KO rats. Taken together, we demonstrated that BDE2 plays a pivotal role for hippocampal neurogenesis, as well as learning and memory during female aging, especially in juvenile and middle age.

Short-Term Irisin Treatment Enhanced Neurotrophin Expression Differently in the Hippocampus and the Prefrontal Cortex of Young Mice

As a result of physical exercise, muscle releases multiple exerkines, such as "irisin", which is thought to induce pro-cognitive and antidepressant effects. We recently demonstrated in young healthy mice the mitigation of depressive behaviors induced by consecutive 5 day irisin administration. To understand which molecular mechanisms might be involved in such effect, we here studied, in a group of mice previously submitted to a behavioral test of depression, the gene expression of neurotrophins and cytokines in the hippocampus and prefrontal cortex (PFC), two brain areas frequently investigated in the depression pathogenesis. We found significantly increased mRNA levels of nerve growth factor (NGF) and fibroblast growth factor 2 (FGF-2) in the hippocampus and brain-derived growth factor (BDNF) in the PFC. We did not detect a difference in the mRNA levels of interleukin 6 (IL-6) and IL-1β in both brain regions. Except for BDNF in the PFC, two-way ANOVA analysis did not reveal sex differences in the expression of the tested genes. Overall, our data evidenced a site-specific cerebral modulation of neurotrophins induced by irisin treatment in the hippocampus and the PFC, contributing to the search for new antidepressant treatments targeted at single depressive events with short-term protocols.

Eucommiae cortex polysaccharides attenuate gut microbiota dysbiosis and neuroinflammation in mice exposed to chronic unpredictable mild stress: Beneficial in ameliorating depressive-like behaviors

BACKGROUND

Chronic stress alters gut microbiota composition, as well as induces inflammatory responses and behavioral deficits. Eucommiae cortex polysaccharides (EPs) have been reported to remodel gut microbiota and ameliorate obesogenic diet-induced systemic low-grade inflammation, but their role in stress-induced behavioral and physiological changes is poorly understood.

METHODS

Male Institute of Cancer Research (ICR) mice were exposed to chronic unpredictable stress (CUMS) for 4 weeks and then supplemented with EPs at a dose of 400 mg/kg once per day for 2 weeks. Behavioral test-specific antidepressant and anxiolytic effects of EPs were assessed in FST, TST, EPM, and OFT. Microbiota composition and inflammation were detected using 16S ribosomal RNA (rRNA) gene sequencing, quantitative RT-PCR, western blot, and immunofluorescence.

RESULTS

We found that EPs ameliorated gut dysbiosis caused by CUMS, as evidenced by increasing the abundance of Lactobacillaceae and suppressing the expansion of the Proteobacteria, thereby mitigating intestinal inflammation and barrier derangement. Importantly, EPs reduced the release of bacterial-derived lipopolysaccharides (LPS, endotoxin) and inhibited the microglia-mediated TLR4/NFκB/MAPK signaling pathway, thereby attenuating the pro-inflammatory response in the hippocampus. These contributed to restoring the rhythm of hippocampal neurogenesis and alleviating behavioral abnormalities in CUMS mice. Correlation analysis showed that the perturbed-gut microbiota was strongly correlated with behavioral abnormalities and neuroinflammation.

LIMITATIONS

This study did not clarify the causal relationship between EPs remodeling the gut microbiota and improved behavior in CUMS mice.

CONCLUSIONS

EPs exert ameliorative effects on CUMS-induced neuroinflammation and depression-like symptoms, which may be strongly related to their beneficial effects on gut microbial composition.

Patchouli alcohol ameliorates depression-like behaviors through inhibiting NLRP3-mediated neuroinflammation in male stress-exposed mice

BACKGROUND

Microglia-mediated neuroinflammation contributes to major depressive disorder (MDD). Targeting microglia is a promising strategy for treating MDD. Patchouli alcohol (PA), an active component of Pogostemon cablin, has anti-inflammatory and neuroprotective effects.

PURPOSE

In this study, we investigate the microglia-mediated neurogenesis pathway in which PA ameliorates depressive-like behaviors in stress-induced animal model of depression.

METHODS

C57BL/6J male mice were exposed to chronic mild stress (CMS) for 4 weeks, then administered PA intraperitoneally at 10, 20 or 40 mg/kg once per day for 3 weeks. The antidepressant effects of PA were evaluated in the sucrose preference test, forced swimming test, and tail suspension test. Microglial phenotypes and activation of the NLRP3 inflammation were analyzed using RT-PCR, western blotting and immunofluorescence staining. Effects of PA on neurogenesis were analyzed in vitro and in vivo using immunofluorescence staining.

RESULTS

Behavioral assessments showed that PA alleviated depressive-like behaviors in CMS-exposed mice. CMS induced microglial activation and pro-inflammatory profiles, which were blocked by PA treatment. PA attenuated the activation of NLRP3 inflammasome, leading to decreases in the levels of caspase-1, ASC, IL-1β, and IL-18 in the hippocampus of CMS-exposed mice. In primary microglia cultures, PA inhibited LPS-induced NLRP3 inflammasome activation. PA rescued inflammation-inhibited neurogenesis in vivo and in vitro.

CONCLUSIONS

Our results suggest that PA inhibits the NLRP3 inflammasome and ameliorates microglia-mediated neurogenesis impairment, contributing to antidepressant effects. Thus, PA may be a novel treatment for inflammation-driven mental disorders.

IGF2 inhibits hippocampal over-activated microglia and alleviates depression-like behavior in LPS- treated male mice

Over-activated microglia and inflammatory mediators are found in patients with depression, while manipulation of the microglia function might represent a potential therapeutic strategy. Insulin-like growth factor 2 (IGF2) has been implicated in bacterial infections and autoimmune disorders, but the role of IGF2 on the active phenotype of microglia and neuroinflammation has not been well established. IGF2 influences in modulating microglia responding to neuroinflammation induced by lipopolysaccharide（LPS）challenge will be carefully examined. In the current study, we verified that systemic IGF2 treatment could produce an anti-depression effect in LPS-treated mice. Particularly, we found that systemic IGF2 treatment inhibited microglia over-activation and prevented its transformation to a pro-inflammatory phenotype, thereby protecting hippocampal neurogenesis. Since microglia reactive to neuroinflammation is a common feature of neuropsychiatric disorders, the discoveries from the present study may provide therapeutic innovation for these diseases.

A hybrid machine learning model of depression estimation in home-based older adults: a 7-year follow-up study

BACKGROUND

Our aim was to explore whether a two-step hybrid machine learning model has the potential to discover the onset of depression in home-based older adults.

METHODS

Depression data (collected in the year 2011, 2013, 2015 and 2018) of home-based older Chinese (n = 2,548) recruited in the China Health and Retirement Longitudinal Study were included in the current analysis. The long short-term memory network (LSTM) was applied to identify the risk factors of participants in 2015 utilizing the first 2 waves of data. Based on the identified predictors, three ML classification algorithms (i.e., gradient boosting decision tree, support vector machine and random forest) were evaluated with a 10-fold cross-validation procedure and a metric of the area under the receiver operating characteristic curve (AUROC) to estimate the depressive outcome.

RESULTS

Time-varying predictors of the depression were successfully identified by LSTM (mean squared error =0.8). The mean AUCs of the three predictive models had a range from 0.703 to 0.749. Among the prediction variables, self-reported health status, cognition, sleep time, self-reported memory and ADL (activities of daily living) disorder were the top five important variables.

CONCLUSIONS

A two-step hybrid model based on "LSTM+ML" framework can be robust in predicting depression over a 5-year period with easily accessible sociodemographic and health information.

Methanolic Extract of Aerva javanica Leaves Prevents LPS-Induced Depressive Like Behavior in Experimental Mice

Aim

Depression is a chronic recurrent neuropsychiatric disorder associated with inflammation. This study explored the pharmacological activities of Aerva javanica leaves crude extract (Aj.Cr) on lipopolysaccharide (LPS)-induced depressive-like behavior in experimental mice.

Methods

Aj.Cr was evaluated for its phenolic and flavonoid contents, bioactive potential, amino acid profiling and enzyme inhibition assays using different analytical techniques followed by in-silico molecular docking was performed. In addition, three ligands identified in HPLC analysis and standard galantamine were docked to acetyl cholinesterase (AchE) enzyme to assess the ligand interaction along with their binding affinities. In in-vivo analysis, mice were given normal saline (10 mL/kg), imipramine (10 mg/kg) and Aj.Cr (100, 300, and 500 mg/kg) orally for 14-consecutive days. On the 14th day, respective treatment was given 30-minutes before intra-peritoneal administration of (0.83 mg/kg) LPS. Open field, forced swim and tail suspension tests were performed 24-hours after LPS injection, followed by a sucrose preference test 48-hours later. Serum corticosterone levels, as well as levels of nitric oxide (NO), malondialdehyde (MDA), glutathione (GSH), superoxide dismutase (SOD), catalase (CAT), tumor necrosis factor-alpha (TNF-), interleukin-1β (IL-1β), interleukin-6 (IL-6), brain-derived neurotrophic factor (BDNF) and catecholamines were determined in brain tissues.

Results

In-vitro results revealed that crude extract of Aj.Cr possesses anti-depressant agents with solid antioxidant potential. In-vivo analysis showed that LPS significantly increased depressive-like behavior followed by alteration in serum and tissue biomarkers as compared to normal control (p < 0.001). While imipramine and Aj.Cr (100, 300, and 500 mg/kg) treated groups significantly (p<0.05) improved the depressive-like behavior and biomarkers when compared to the LPS group.

Conclusion

The mitigation of LPS-induced depressive-like behavior by Aj.Cr may be linked to the modulation of oxidative stress, neuro-inflammation and catecholamines due to the presence of potent bioactive compounds exerting anti-depressant effects.

Hippocampal neurogenesis promotes effortful responding but does not regulate effort-based choice

A fundamental trait of depression is low motivation. Hippocampal neurogenesis has been associated with motivational deficits but detailed evidence on how it regulates human-relevant behavioral traits is still missing. We used the hGFAP-TK rat model to deplete actively dividing neural stem cells in the rat hippocampus. Use of the effort-discounting operant task allowed us to identify specific and detailed deficits in motivation behavior. In this task, rats are given a choice between small and large food rewards, where 2-20 lever presses are required to obtain the large reward (four sugar pellets) versus one press to receive the smaller reward (two sugar pellets). We found that depleting adult neurogenesis did not affect effort-based choice or general motivation to complete the task. However, lack of adult neurogenesis reduced the pressing rate and thus increased time to complete the required presses to obtain a reward. In summary, the present study finds that adult hippocampal neurogenesis specifically reduces response vigor to obtain rewards and thus deepens our understanding in how neurogenesis shapes depression.

Research progress on classical traditional chinese medicine formula xiaoyaosan in the treatment of depression

Depression is an emotional disorder that is problematic in psychiatry owing to its unclear etiology and unknown pathogenesis. Traditional Chinese medicine formulations such as Xiaoyaosan have been widely used throughout history to treat depression. In this review, we have focused on recent evidences elucidating the links between Xiaoyaosan and the treatment of depression. Data from animal and clinical studies, focusing on the pharmacological mechanisms, clinical applications, and effective materials that form the basis for the treatment of depression are presented and discussed. We found that the antidepressant effects of Xiaoyaosan are related to the effects of monoamine neurotransmitters, regulation of the hypothalamic-pituitary-adrenal axis, neuroplasticity, synaptic plasticity, inflammatory response, neuroprotection, brain-gut axis, regulation of intestinal microbiota, oxidative stress, and autophagy for reducing neuronal apoptosis. This review highlights the current evidence supporting the use of Xiaoyaosan as an antidepressant and provides an overview of the potential mechanisms involved.

Structural and functional characteristics of the hippocampus in depressive-like recipients after transplantation of in vitro caffeine-modulated immune cells

The hippocampus is a key anatomical brain region associated with depression. On the other hand, immune cells and their releasing cytokines play an essential role in stress and depression. Noteworthy that the most of psychoactive drugs produce unidirectional effects on the cells of both nervous and immune systems. This suggests the immunotherapy for behavioral disorders based on the treatment with autologous immune cells in which functional activity was modulated ex vivo by a psychoactive drug. Here, we treated the immune cells of depressive-like mice in vitro with caffeine (100 μg per 15 × 10⁶ cells). The effects of caffeine-treated immune cells transplantation on neuronal density, production of brain-derived neurotrophic factor (BDNF) and a number of cytokines in the hippocampus of depressive-like syngeneic animals were studied. In depressive-like recipients, an increase in the density of pyramidal neurons in CA1 and CA3 hippocampal regions, accompanied with augmented level of BDNF, decreased levels of pro-inflammatory (IL-1β, IL-6, INF-γ, and TNF-α) and increased levels of anti-inflammatory (IL-10 and IL-4) cytokines was found. The mechanisms of the revealed structural and functional alterations in the hippocampus of depressive-like recipients after transplantation of caffeine-treated immune cells are discussed.

Effect of M2 Macrophage-Derived Soluble Factors on Behavioral Patterns and Cytokine Production in Various Brain Structures in Depression-Like Mice

We studied the effect of soluble factors derived from human macrophages polarized to M2 phenotype under conditions of serum deprivation (M2-SF) on behavioral pattern and cytokine production in various brain structures in mice with modeled stress-induced depression. Intranasal administration of M2-SF for 7 days led to stimulation of locomotor and exploratory activities and a decrease in emotional reactivity in the open-field test as well as reduction in depression-like behavior in Porsolt forced swimming test and a decrease in anxiety and anhedonia. Correction of depression-like behavior was accompanied by down-regulation of proinflammatory cytokines (IL-1β, IL-6, TNFα, and IFNγ) in pathogenetically important brain structures (striatum, hippocampus, and frontal cortex). These data indicate that the antidepressant potential of M2 type macrophages can be mediated by the anti-inflammatory effects of M2-SF.

The Vulnerability of the Developing Brain: Analysis of Highly Expressed Genes in Infant C57BL/6 Mouse Hippocampus in Relation to Phenotypic Annotation Derived From Mutational Studies

The hippocampus has been shown to have a major role in learning and memory, but also to participate in the regulation of emotions. However, its specific role(s) in memory is still unclear. Hippocampal damage or dysfunction mainly results in memory issues, especially in the declarative memory but, in animal studies, has also shown to lead to hyperactivity and difficulty in inhibiting responses previously taught. The brain structure is affected in neuropathological disorders, such as Alzheimer's, epilepsy, and schizophrenia, and also by depression and stress. The hippocampus structure is far from mature at birth and undergoes substantial development throughout infant and juvenile life. The aim of this study was to survey genes highly expressed throughout the postnatal period in mouse hippocampus and which have also been linked to an abnormal phenotype through mutational studies to achieve a greater understanding about hippocampal functions during postnatal development. Publicly available gene expression data from C57BL/6 mouse hippocampus was analyzed; from a total of 5 time points (at postnatal day 1, 10, 15, 21, and 30), 547 genes highly expressed in all of these time points were selected for analysis. Highly expressed genes are considered to be of potential biological importance and appear to be multifunctional, and hence any dysfunction in such a gene will most likely have a large impact on the development of abilities during the postnatal and juvenile period. Phenotypic annotation data downloaded from Mouse Genomic Informatics database were analyzed for these genes, and the results showed that many of them are important for proper embryo development and infant survival, proper growth, and increase in body size, as well as for voluntary movement functions, motor coordination, and balance. The results also indicated an association with seizures that have primarily been characterized by uncontrolled motor activity and the development of proper grooming abilities. The complete list of genes and their phenotypic annotation data have been compiled in a file for easy access.

Steroid hormones and hippocampal neurogenesis in the adult mammalian brain

Hippocampal neurogenesis persists across the lifespan in many species, including rodents and humans, and is associated with cognitive performance and the pathogenesis of neurodegenerative disease and psychiatric disorders. Neurogenesis is modulated by steroid hormones that change across development and differ between the sexes in rodents and humans. Here, we discuss the effects of stress and glucocorticoid exposure from gestation to adulthood as well as the effects of androgens and estrogens in adulthood on neurogenesis in the hippocampus. Throughout the review we highlight sex differences in the effects of steroid hormones on neurogenesis and how they may relate to hippocampal function and disease. These data highlight the importance of examining age and sex when evaluating the effects of steroid hormones on hippocampal neurogenesis.

The Entorhinal Cortex and Adult Neurogenesis in Major Depression

Depression is characterized by impairments in adult neurogenesis. Reduced hippocampal function, which is suggestive of neurogenesis impairments, is associated with depression-related phenotypes. As adult neurogenesis operates in an activity-dependent manner, disruption of hippocampal neurogenesis in depression may be a consequence of neural circuitry impairments. In particular, the entorhinal cortex is known to have a regulatory effect on the neural circuitry related to hippocampal function and adult neurogenesis. However, a comprehensive understanding of how disruption of the neural circuitry can lead to neurogenesis impairments in depression remains unclear with respect to the regulatory role of the entorhinal cortex. This review highlights recent findings suggesting neural circuitry-regulated neurogenesis, with a focus on the potential role of the entorhinal cortex in hippocampal neurogenesis in depression-related cognitive and emotional phenotypes. Taken together, these findings may provide a better understanding of the entorhinal cortex-regulated hippocampal neurogenesis model of depression.

Adult hippocampal neurogenesis in the context of lipopolysaccharide-induced neuroinflammation: A molecular, cellular and behavioral review

The continuous generation of new neurons occurs in at least two well-defined niches in the adult rodent brain. One of these areas is the subgranular zone of the dentate gyrus (DG) in the hippocampus. While the DG is associated with contextual and spatial learning and memory, hippocampal neurogenesis is necessary for pattern separation. Hippocampal neurogenesis begins with the activation of neural stem cells and culminates with the maturation and functional integration of a portion of the newly generated glutamatergic neurons into the hippocampal circuits. The neurogenic process is continuously modulated by intrinsic factors, one of which is neuroinflammation. The administration of lipopolysaccharide (LPS) has been widely used as a model of neuroinflammation and has yielded a body of evidence for unveiling the detrimental impact of inflammation upon the neurogenic process. This work aims to provide a comprehensive overview of the current knowledge on the effects of the systemic and central administration of LPS upon the different stages of neurogenesis and discuss their effects at the molecular, cellular, and behavioral levels.

Sex differences and similarities in the neuroimmune response to central administration of poly I:C

BACKGROUND

The neuroimmune system is required for normal neural processes, including modulation of cognition, emotion, and adaptive behaviors. Aberrant neuroimmune activation is associated with dysregulation of memory and emotion, though the precise mechanisms at play are complex and highly context dependent. Sex differences in neuroimmune activation and function further complicate our understanding of its roles in cognitive and affective regulation.

METHODS

Here, we characterized the physiological sickness and inflammatory response of the hippocampus following intracerebroventricular (ICV) administration of a synthetic viral mimic, polyinosinic:polycytidylic acid (poly I:C), in both male and female C57Bl/6N mice.

RESULTS

We observed that poly I:C induced weight loss, fever, and elevations of cytokine and chemokines in the hippocampus of both sexes. Specifically, we found transient increases in gene expression and protein levels of IL-1α, IL-1β, IL-4, IL-6, TNFα, CCL2, and CXCL10, where males showed a greater magnitude of response compared with females. Only males showed increased IFNα and IFNγ in response to poly I:C, whereas both males and females exhibited elevations of IFNβ, demonstrating a specific sex difference in the anti-viral response in the hippocampus.

CONCLUSION

Our data suggest that type I interferons are one potential node mediating sex-specific cytokine responses and neuroimmune effects on cognition. Together, these findings highlight the importance of using both males and females and analyzing a broad set of inflammatory markers in order to identify the precise, sex-specific roles for neuroimmune dysregulation in neurological diseases and disorders.

Microglia Function on Precursor Cells in the Adult Hippocampus and Their Responsiveness to Serotonin Signaling

Microglia are the resident immune cells of the adult brain that become activated in response to pathogen- or damage-associated stimuli. The acute inflammatory response to injury, stress, or infection comprises the release of cytokines and phagocytosis of damaged cells. Accumulating evidence indicates chronic microglia-mediated inflammation in diseases of the central nervous system, most notably neurodegenerative disorders, that is associated with disease progression. To understand microglia function in pathology, knowledge of microglia communication with their surroundings during normal state and the release of neurotrophins and growth factors in order to maintain homeostasis of neural circuits is of importance. Recent evidence shows that microglia interact with serotonin, the neurotransmitter crucially involved in adult neurogenesis, and known for its role in antidepressant action. In this chapter, we illustrate how microglia contribute to neuroplasticity of the hippocampus and interact with local factors, e.g., BDNF, and external stimuli that promote neurogenesis. We summarize the recent findings on the role of various receptors in microglia-mediated neurotransmission and particularly focus on microglia’s response to serotonin signaling. We review microglia function in neuroinflammation and neurodegeneration and discuss their novel role in antidepressant mechanisms. This synopsis sheds light on microglia in healthy brain and pathology that involves serotonin and may be a potential therapeutic model by which microglia play a crucial role in the maintenance of mood.

Discovering the Potentials of Medicinal Mushrooms in Combating Depression - A Review

Depression is the most common form of mental illness and the major cause of disability worldwide. Symptoms of depression, including feelings of intense sadness and hopelessness, may occur after a specific event or in response to a gradual decline in health and functional status, often associated with aging. Current therapies for treating these symptoms include antidepressant drugs, counseling and behavioral therapy. However, antidepressant drugs are associated with mild to severe adverse effects, which has prompted the need for better treatment options. Medicinal mushrooms are valuable sources of food and medicine and are increasingly being used as supplements or as alternative medicines in standard healthcare. Numerous studies have provided insights into the neuroprotective effects of medicinal mushrooms, which are attributed to their antioxidant, anti-neuroinflammatory, cholinesterase inhibitory and neuroprotective properties. In this review, we comprehensively examine the role of these medicinal mushrooms in the treatment of depression. However, to apply these natural products in clinical settings, the therapeutic agent needs to be properly evaluated, including the active ingredients, the presence of synergistic effects, efficient extraction methods, and stabilization of the active ingredients for delivery into the body as well as crossing the blood-brain barrier.

Impact of impaired glucose metabolism on responses to a psychophysical stressor: modulation by ketamine

RATIONALE

There is evidence that hypoglycemia, a metabolic stressor, can negatively impact mood and motivation, and can interact with other stressors to potentiate their effects on behavior and physiology.

OBJECTIVES/METHODS

The current study in male Sprague-Dawley rats explored the interaction between impaired glucose metabolism induced by 0, 200, or 300 mg/kg 2-deoxy-D-glucose (2-DG) and a psychophysical stressor induced by forced swimming stress (FSS; 6 sessions, 10 min/session). The endpoints of interest were blood glucose levels, progressive behavioral immobility, and saccharin preference (2-bottle choice test). Furthermore, it was investigated whether pre-treatment with 0, 10, or 20 mg/kg ketamine could modify the interaction between 2-DG and FSS on these endpoints.

RESULTS

It was found that 2-DG increased blood glucose levels equally in all experimental groups, accelerated the immobile response to FSS, and suppressed saccharin preference 1 week following termination of stress exposure. As well, pre-treatment with ketamine blocked the effects of combined 2-DG and FSS on immobility and saccharin preference without affecting blood glucose levels and produced an anti-immobility effect that was observed during a drug-free test swim 1 week following administration.

CONCLUSIONS

Overall, these findings demonstrate that impaired glucose metabolism can potentiate the effects of a psychophysical stressor, and that this interaction can be modulated pharmacologically by ketamine.

Quercetin alleviates chronic unpredictable mild stress-induced depressive-like behaviors by promoting adult hippocampal neurogenesis via FoxG1/CREB/ BDNF signaling pathway

Quercetin, a naturally occurring flavonoid, has been reported to exert antidepressant effects, however, the underlying mechanisms are still uncertain. Recent studies have demonstrated that Forkhead box transcription factor G1 (FoxG1) regulates the process of adult hippocampal neurogenesis (AHN) and exerts neuroprotective effects. In this study, we explored whether quercetin plays an anti-depressant role via regulation of FoxG1 signaling in mice and revealed the potential mechanisms. To explore the antidepressant effects of quercetin, mice were subjected to behavioral tests after a chronic unpredictable mild stress (CUMS) exposure. We found that chronic quercetin treatment (15 mg/kg, 30 mg/kg) obviously restored the weight loss of mice caused by CUMS and alleviated CUMS-induced depression-like behaviors, such as increased sucrose consumption, improved locomotor activity and shorten immobility time. In addition, to clarify the relationship between quercetin and AHN, we detected neurogenesis markers in the dentate gyrus (DG) of the hippocampus. Furthermore, FoxG1-siRNA was employed and then stimulated with quercetin to further investigate the mechanism by which FoxG1 participates in the antidepressant effects of quercetin. Our results indicate that chronic quercetin treatment dramatically increased the number of doublecortin (DCX)-positive and BrdU/NeuN-double positive cells. Besides, the expression levels of FoxG1, p-CREB and Brain-derived neurotrophic factor (BDNF) were also enhanced by quercetin in the DG. Strikingly, quercetin failed to reverse the levels of p-CREB and BDNF after FoxG1-siRNA was performed in SH-SY5Y cells and Neural Progenitor Cells (NPCs). Our results thus far suggest that quercetin might exert antidepressant effects via promotion of AHN by FoxG1/CREB/ BDNF signaling pathway.

Neural Circuitry-Neurogenesis Coupling Model of Depression

Depression is characterized by the disruption of both neural circuitry and neurogenesis. Defects in hippocampal activity and volume, indicative of reduced neurogenesis, are associated with depression-related behaviors in both humans and animals. Neurogenesis in adulthood is considered an activity-dependent process; therefore, hippocampal neurogenesis defects in depression can be a result of defective neural circuitry activity. However, the mechanistic understanding of how defective neural circuitry can induce neurogenesis defects in depression remains unclear. This review highlights the current findings supporting the neural circuitry-regulated neurogenesis, especially focusing on hippocampal neurogenesis regulated by the entorhinal cortex, with regard to memory, pattern separation, and mood. Taken together, these findings may pave the way for future progress in neural circuitry-neurogenesis coupling studies of depression.

Ibrutinib alleviates LPS-induced neuroinflammation and synaptic defects in a mouse model of depression

Previous studies have demonstrated a close association between an altered immune system and major depressive disorders, and inhibition of neuroinflammation may represent an alternative mechanism to treat depression. Recently, the anti-inflammatory activity of ibrutinib has been reported. However, the effect of ibrutinib on neuroinflammation-induced depression and its underlying mechanism has not been comprehensively studied. Therefore, we aimed to elucidate the potential anti-depressive role and mechanism of ibrutinib against neuroinflammation-induced depression and synaptic defects. Our results showed that ibrutinib treatment significantly reduced lipopolysaccharide (LPS)-induced depressive-like behaviors and neuroinflammation via inhibiting NF-kB activation, decreasing proinflammatory cytokine levels, and normalizing redox signaling and its downstream components, including Nrf2, HO-1, and SOD2, as well as glial cell activation markers, such as Iba-1 and GFAP. Further, ibrutinib treatment inhibited LPS-activated inflammasome activation by targeting NLRP3/P38/Caspase-1 signaling. Interestingly, LPS reduced the number of dendritic spines and expression of BDNF, and synaptic-related markers, including PSD95, snap25, and synaptophysin, were improved by ibrutinib treatment in the hippocampal area of the mouse brain. In conclusion, our findings suggest that ibrutinib can alleviate neuroinflammation and synaptic defects, suggesting it has antidepressant potential against LPS-induced neuroinflammation and depression.

Capsiate Intake with Exercise Training Additively Reduces Fat Deposition in Mice on a High-Fat Diet, but Not without Exercise Training

While exercise training (ET) is an efficient strategy to manage obesity, it is recommended with a dietary plan to maximize the antiobesity functions owing to a compensational increase in energy intake. Capsiate is a notable bioactive compound for managing obesity owing to its capacity to increase energy expenditure. We aimed to examine whether the antiobesity effects of ET can be further enhanced by capsiate intake (CI) and determine its effects on resting energy expenditure and metabolic molecules. Mice were randomly divided into four groups (n = 8 per group) and fed high-fat diet. Mild-intensity treadmill ET was conducted five times/week; capsiate (10 mg/kg) was orally administered daily. After 8 weeks, resting metabolic rate and metabolic molecules were analyzed. ET with CI additively reduced the abdominal fat rate by 18% and solely upregulated beta-3-adrenoceptors in adipose tissue (p = 0.013) but did not affect the metabolic molecules in skeletal muscles. Surprisingly, CI without ET significantly increased the abdominal fat rate (p = 0.001) and reduced energy expenditure by 9%. Therefore, capsiate could be a candidate compound for maximizing the antiobesity effects of ET by upregulating beta-3-adrenoceptors in adipose tissue, but CI without ET may not be beneficial in managing obesity.

Comparison of Regression and Machine Learning Methods in Depression Forecasting Among Home-Based Elderly Chinese: A Community Based Study

BACKGROUND

Depression is highly prevalent and considered as the most common psychiatric disorder in home-based elderly, while study on forecasting depression risk in the elderly is still limited. In an endeavor to improve accuracy of depression forecasting, machine learning (ML) approaches have been recommended, in addition to the application of more traditional regression approaches.

METHODS

A prospective study was employed in home-based elderly Chinese, using baseline (2011) and follow-up (2013) data of the China Health and Retirement Longitudinal Study (CHARLS), a nationally representative cohort study. We compared four algorithms, including the regression-based models (logistic regression, lasso, ridge) and ML method (random forest). Model performance was assessed using repeated nested 10-fold cross-validation. As the main measure of predictive performance, we used the area under the receiver operating characteristic curve (AUC).

RESULTS

The mean AUCs of the four predictive models, logistic regression, lasso, ridge, and random forest, were 0.795, 0.794, 0.794, and 0.769, respectively. The main determinants were life satisfaction, self-reported memory, cognitive ability, ADL (activities of daily living) impairment, CESD-10 score. Life satisfaction increased the odds ratio of a future depression by 128.6% (logistic), 13.8% (lasso), and 13.2% (ridge), and cognitive ability was the most important predictor in random forest.

CONCLUSIONS

The three regression-based models and one ML algorithm performed equally well in differentiating between a future depression case and a non-depression case in home-based elderly. When choosing a model, different considerations, however, such as easy operating, might in some instances lead to one model being prioritized over another.

The innate immune system and neurogenesis as modulating mechanisms of electroconvulsive therapy in pre-clinical studies

BACKGROUND

Electroconvulsive therapy (ECT) is a powerful and fast-acting anti-depressant strategy, often used in treatment-resistant patients. In turn, patients with treatment-resistant depression often present an increased inflammatory response. The impact of ECT on several pathophysiological mechanisms of depression has been investigated, with a focus which has largely been on cellular and synaptic plasticity. Although changes in the immune system are known to influence neurogenesis, these processes have principally been explored independently from each other in the context of ECT.

OBJECTIVE

The aim of this review was to compare the time-dependent consequences of acute and chronic ECT on concomitant innate immune system and neurogenesis-related outcomes measured in the central nervous system in pre-clinical studies.

RESULTS

During the few hours following acute electroconvulsive shock (ECS), the expression of the astrocytic reactivity marker glial fibrillary acidic protein (GFAP) and inflammatory genes, such as cyclooxygenase-2 (COX2), were significantly increased together with the neurogenic brain-derived neurotrophic factor (BDNF) and cell proliferation. Similarly, chronic ECS caused an initial upregulation of the same astrocytic marker, immune genes, and neurogenic factors. Interestingly, over time, inflammation appeared to be dampened, while glial activation and neurogenesis were maintained, after either acute or chronic ECS.

CONCLUSION

Regardless of treatment duration ECS would seemingly trigger a rapid increase in inflammatory molecules, dampened over time, as well as a long-lasting activation of astrocytes and production of growth and neurotrophic factors, leading to cell proliferation. This suggests that both innate immune system response and neurogenesis might contribute to the efficacy of ECT.

Structural and biochemical imaging reveals systemic LPS-induced changes in the rat brain

Despite mounting evidence for the role of inflammation in Major Depressive Disorder (MDD), in vivo preclinical investigations of inflammation-induced negative affect using whole brain imaging modalities are scarce, precluding a valid model within which to evaluate pharmacological interventions. Here we used an E. coli lipopolysaccharide (LPS)-based model of inflammation-induced depressive signs in rats to explore brain changes using multimodal neuroimaging methods. During the acute phase of the LPS response (2 h post injection), prior to the emergence of a task-quantifiable depressive phenotype, striatal glutamine levels and splenial, retrosplenial, and peri-callosal hippocampal cortex volumes were greater than at baseline. LPS-induced depressive behaviors observed at 24 h, however, occurred concurrently with lower than control levels of striatal glutamine and a reversibility of volume expansion (i.e., shrinkage of splenial, retrosplenial, and peri-callosal hippocampal cortex to baseline volumes). In both striatum and hippocampus at 24 h, mRNA expression in LPS relative to control animals demonstrated alterations in enzymes and transporters regulating glutamine homeostasis. Collectively, the observed behavioral, in vivo structural and metabolic, and mRNA expression alterations suggest a critical role for astrocytic regulation of inflammation-induced depressive behaviors.

Reduced Hippocampal Volume and Its Relationship With Verbal Memory and Negative Symptoms in Treatment-Naive First-Episode Adolescent-Onset Schizophrenia

Accumulating neuroimaging evidence has shown remarkable volume reductions in the hippocampi of patients with schizophrenia. However, the relationship among hippocampal morphometry, clinical symptoms, and cognitive impairments in schizophrenia is still unclear. In this study, high-resolution structural magnetic resonance imaging data were acquired in 36 patients with adolescent-onset schizophrenia (AOS, age range: 13-18 years) and 30 age-, gender-, and education-matched typically developing controls (TDCs). Hippocampal volume was assessed automatically through volumetric segmentation and measurement. After adjusting for total intracranial volume, we found reduced hippocampal volume in individuals with AOS compared with TDCs, and the hippocampal volume was positively correlated with verbal memory and negatively correlated with negative symptoms in AOS. In addition, mediation analysis revealed the indirect effect of hippocampal volume on negative symptoms via verbal memory impairment. When the negative symptoms were represented by 2 dimensions of deficits in emotional expression (EXP) and deficits in motivation and pleasure (MAP), the indirect effect was significant for EXP but not for MAP. Our findings provide further evidence of hippocampal volume reduction in AOS and highlight verbal memory impairment as a mediator to influence the relationship between hippocampal morphometry and negative symptoms, especially the EXP dimension of negative symptoms, in individuals with AOS.

Expression and Significance of MicroRNA155 in Serum of Patients with Cerebral Small Vessel Disease

Objective

This study aimed to investigate the changes and significance of microRNA155 levels in serum of patients with cerebral small vessel disease (CSVD).

Methods

Thirty patients with CSVD who met the inclusion criteria were selected and divided into eight patients with lacunar infarction (LI) group and 22 patients with multiple lacunar infarction (MLI) combined with white matter lesions (WML) group according to the results of head magnetic resonance imaging (MRI). Thirty samples from healthy volunteers without abnormalities after head MRI examination were selected as the control group. The levels of serum microRNA155 in each group were determined by real-time polymerase chain reaction, and the correlation between microRNA155 in the serum of patients with CSVD and the increase of imaging lesions was analyzed by Spearman correlation analysis.

Results

Compared with the control group, the serum microRNA155 level in the LI group, MLI combined with WML group increased, the difference was statistically significant (p<0.05); serum microRNA155 level was positively correlated with the increase of imaging lesions (p<0.05).

Conclusion

The change of serum microRNA155 level in patients with CSVD may be one of its self-protection mechanisms, and the intensity of this self-protection mechanism is positively correlated with the number of CSVD lesions.

Effect of Toll-like receptor 4 on depressive-like behaviors induced by chronic social defeat stress

INTRODUCTION

A growing body of evidence suggests that stress is an important factor in depression, and pro-inflammatory cytokines contribute to the occurrence and development of depression in both animal models and human patients. Toll-like receptor 4 (TLR4) has been shown to be a key innate immune pattern recognition receptor involved in the regulation of stress responses and inflammation. However, the exact effects of TLR4 on depressive-like behaviors induced by chronic social defeat stress (CSDS) are not known.

METHODS

In this study, the effects of TLR4 on depressive-like behaviors were investigated in an animal model of depression induced by CSDS. The depressive-like behaviors were assessed by forced swimming test (FST), social interaction test (SIT), and light-dark box test (LDT). The protein expressions of TLR4 and tumor necrosis factor-α (TNF-α) in the hippocampus were measured using Western blotting.

RESULTS

We found that CSDS increased TLR4 protein levels in the hippocampus and induced behavioral despair in FST, social avoidance in SIT, and anxiety-like behavior in LDT. Fluoxetine normalized the increased expression of TLR4 and reversed behavioral despair, social avoidance, as well as anxiety-like behavior induced by CSDS. However, directly blocking TLR4, by using either TLR4 inhibitor TAK-242 or knockout of TLR4, only inhibited behavioral despair, but not social avoidance or anxiety-like behavior induced by CSDS.

CONCLUSIONS

These results demonstrate a specific modulating role of TLR4 in behavioral despair induced by CSDS and suggest that TAK-242 may be a beneficial treatment for patients with behavioral despair.

Inhibition of JNK ameliorates depressive-like behaviors and reduces the activation of pro-inflammatory cytokines and the phosphorylation of glucocorticoid receptors at serine 246 induced by neuroinflammation

Depression is associated with immune dysregulation and the aberrant activity of the hypothalamic-pituitary-adrenal (HPA) axis. However, the neurobiological molecular mechanisms underlying these associations remain unclear. c-Jun amino-terminal kinase (JNK), an important modulator in inflammation and stress responses, is often critically implicated in the development of central nervous system diseases. However, whether and how JNK mediates neuroinflammation-induced depression remains largely unknown. In this study, we investigated the role of JNK in depressive-like behaviors induced by central lipopolysaccharide (LPS) infusion. The results showed that LPS infusion led to depressive-like behaviors, accompanied by increased proinflammatory cytokine expression, increased JNK activation, and upregulated glucocorticoid receptor (GR) phosphorylation at serine 246 (pGR-Ser²⁴⁶) in the habenula (Hb), amygdala (Amyg) and medial prefrontal cortex (mPFC). Treatment with SP600125, a known JNK inhibitor, prevented the LPS-induced hyper-activation of JNK and alleviated depressive-like behaviors. Moreover, LPS-induced increases in the expression levels of TNF-α, IL-1β and pGR-Ser²⁴⁶ in these brain regions were reduced when the rats were treated with SP600125. Our results show, for the first time, that JNK activities in the Hb, Amyg, and mPFC are involved in the modulation of neuroinflammation-induced depression and participate in the regulation of the expression of proinflammatory cytokines and GR phosphorylation, which are pathological factors associated with depression. Our findings provide new insights into the mechanism of neuroinflammation-associated depression and suggest that the JNK pathway may be a potential target for treating inflammation-related depression.

MicroRNA-382-5p Targets Nuclear Receptor Subfamily 3 Group C Member 1 to Regulate Depressive-Like Behaviors Induced by Chronic Unpredictable Mild Stress in Rats

BACKGROUND

Depression is an emotional disorder characterized by depression, lack of pleasure, and cognitive and sleep disorders. It is a systemic disease with a complex pathogenesis. In this study, we will be focused to investigate their associations and the exact functional mechanisms of miR-382-5p and NR3C1 in depression.

MATERIALS AND METHODS

We measured the expressions of microRNA-382-5p (miR-382-5p) and NR3C1 in the hippocampus by chronic unpredictable mild stress (CUMS). Depression behavior test including novelty-suppressed feeding test (NSFT), sucrose preference test (SPT), and forced swim test (FST) on rats have been conducted to examine the roles and functions of miR-382-5p and NR3C1 on depression-like behaviors by lentivirus vectors.

RESULTS

Up-regulation of miR-382-5p and down-regulation of NR3C1 were observed in rats' hippocampus induced by CUMS. miR-382-5p targeted NR3C1 and inhibited the expressions of NR3C1 in rats' hippocampus. miR-382-5p could significantly change the depression behaviors induced by CUMS. NR3C1 downstream BDNF and p-TrkB were also oppositely associated with miR-382-5p in rats' hippocampus.

CONCLUSION

Through our experiments and analysis, we found that the associations between miR-382-5p and NR3C1 could affect the depression-like behaviors.

Xiaoyao Pills Prevent Lipopolysaccharide-Induced Depression by Inhibiting Inflammation and Protecting Nerves

Lipopolysaccharides are pro-inflammation mediators that can induce inflammation in the serum, hippocampus, and cortex of animals. And lipopolysaccharide-induced neuroinflammatory state resulted in significant depression-like behaviors, including reduced locomotor activity in the open field test, reduced saccharin preference, added immobility time in tail suspension test and forced swimming test, decreased comb time in the splash test, and increased latency to food in the novelty suppressed feeding test time, and reduced the levels of neurotrophic factors and synaptic proteins, and decreased Nissl bodies. Treatment with Xiaoyao Pills ameliorated the depression-like behavior, decreased the levels of inflammatory indicators, increased those of neurotrophic factors and synaptic proteins, and restored Nissl bodies. Our study suggests that lipopolysaccharides induce inflammation and nerve injury, thereby leading to depression. Xiaoyao Pills could be considered a potential therapeutic candidate for inflammation-induced depression.

Neurogenesis and antidepressant action

A theoretical framework is proposed to gain insight into the pathogenesis of major depressive disorder (MDD). Despite being a relatively weak argument, the neurogenesis theory is suggested to compensate for the limitations of the monoamine theory. In the adult hippocampus, neurogenesis is functionally related to regulation of the hypothalamic-pituitary-adrenal (HPA) axis, inflammatory processes, cognitive functions and other aspects that contribute to etiological factors that lead to MDD and promote recovery from MDD. Despite a lack of investigation into neurogenesis and antidepressant action, it is proposed that chronic administration of antidepressant(s) can induce the recruitment and integration of newborn neurons into the dentate gyrus and, ultimately, lead to the remission of MDD. The extant body of literature indicates that the suppression of neurogenesis per se may be associated with an impaired response to antidepressant treatment rather than with the induction of depressive-like behaviors. Moreover, recent studies have shown that increasing the survival rate and incorporation of new neurons can alleviate depressive-like behaviors and promote stress resilience. According to the neurogenic reserve hypothesis, hippocampal neurogenesis supports specific cortical functions, including executive functions, pattern separation and contextual information processing, control over the HPA axis and behavioral coping mechanisms in response to stressful situations. Therefore, hippocampal neurogenesis may be a promising biological indicator of stress resilience and antidepressant response in patients with MDD.

The Role of BDNF in the Neuroimmune Axis Regulation of Mood Disorders

The neuroimmune system plays a crucial role in the regulation of mood disorders. Moreover, recent studies show that brain-derived neurotrophic factor (BDNF), a member of the neurotrophin family, is a key regulator in the neuroimmune axis. However, the potential mechanism of BDNF action in the neuroimmune axis' regulation of mood disorders remains unclear. Therefore, in this review, we focus on the recent progress of BDNF in influencing mood disorders, by participating in alterations of the neuroimmune axis. This may provide evidence for future studies in this field.

Protocatechuic acid attenuate depressive-like behavior in olfactory bulbectomized rat model: behavioral and neurobiochemical investigations

The main objective of the present study is to investigate potential effects of PCA in OBX induced depressive-like behavior in rat model. PCA was administered at a dose of 100 mg/kg and 200 mg/kg, by per oral in OBX and sham operated rats. Behavioral (ambulatory and rearing activity and immobility time), neurochemical [serotonin (5-HT), dopamine (DA), norepinephrine (NE) and brain derived neurotrophic factor (BDNF) expression], biochemical (MDA formation, IL-6, TNF-α and antioxidants) changes in hippocampus and cerebral cortex along with serum corticosterone were investigated. Experimental findings reveals that OBX subjected rats showed alteration in behaviors like, increase in immobility time, ambulatory and rearing behaviors significantly, reduced BDNF level, 5-HT, DA,NE and antioxidant parameters along with increased serum corticosterone, MDA formation, IL-6, and TNF-α in hippocampus and cerebral cortex compared to sham operated rats. Administration of PCA significantly attenuated behavioral and neurobiochemical alterations, thus, its antidepressant-like activity is largely mediated through modulation of neurotransmitter, endocrine and immunologic systems, mainly by improvements of BDNF, 5-HT, DA, NE, reduced MDA, IL-6, and TNF-α in hippocampus and cerebral cortex.

Minocycline prevents the development of depression-like behavior and hippocampal inflammation in a rat model of Alzheimer's disease

RATIONALE

Considerable clinical and experimental studies have shown that depression-related disorders are the most common neuropsychiatric symptoms in Alzheimer's disease (AD), affecting as many as 20-40% of patients. An increasing amount of evidence shows that monoamine-based antidepressant treatments are not completely effective for depression treatment in patients with dementia. Minocycline, a second-generation tetracycline antibiotic, has been gaining research and clinical attention for the treatment of different neuropsychiatric disorders, and more recently depression symptom in humans.

METHODS

In the present study, we investigated the effects of Aβ1-42 administration alone or in combination with minocycline treatment on depression-like behaviors and anti/pro-inflammatory cytokines such as interleukin(IL)-10, IL-β, and tumor necrosis factor (TNF)-α in the hippocampus of rats.

RESULTS

Our results showed that Aβ1-42 administration increased depression-related behaviors in sucrose preference test, tail suspension test, novelty-suppressed feeding test, and forced swim test. We also found significant increases in IL-1β and TNF-α levels in the hippocampus of Aβ1-42-treated rats. Interestingly, minocycline treatment significantly reversed depression-related behaviors and the levels of hippocampal cytokines in Aβ1-42-treated rats.

CONCLUSION

These findings support the idea that there is a significant relationship among AD, depression-related symptoms, and pro-inflammatory cytokines in the brain, and suggest that antidepressant-like impacts of minocycline could be due to its anti-inflammatory properties. This drug could be of potential interest for the treatment of depression in patients with Alzheimer's disease.

miR‑155 mediates inflammatory injury of hippocampal neuronal cells via the activation of microglia

MicroRNA (miR)-155 has a crucial role in various cellular functions, including differentiation of hematopoietic cells, immunization, inflammation and cardiovascular diseases. The present study aimed to investigate the roles and mechanisms of miR-155 in treatment-resistant depression (TRD). A Cell Counting Kit-8 assay and flow cytometry were performed to assess the cell viability and apoptosis of microglial cells, respectively. Western blotting and reverse transcription-quantitative polymerase chain reaction assays were used to evaluate the associated protein and mRNA expression, respectively. The results revealed that miR-155 reduced the cell viability of BV-2 microglial cells, and miR-155 enhanced the expression levels of pro-inflammatory cytokines in BV-2 microglial cells. Furthermore, conditioned medium from miR-155-treated microglia decreased the cell viability of HT22 hippocampal cells. miR-155-treated microglia increased the apoptosis of neuronal hippocampal cells by modulating the expression levels of apoptosis regulator Bax, apoptosis regulator Bcl-2, pro-caspase-3 and cleaved-caspase-3. The cell cycle distribution was disrupted by miR-155-treated microglia through induction of S phase arrest. Furthermore, the overexpression of suppressor of cytokine signaling 1 reversed the pro-apoptotic effect of activated microglia on hippocampal neuronal cells. In conclusion, the present results suggested that miR-155 mediated the inflammatory injury in hippocampal neuronal cells by activating the microglial cells. The potential effects of miR-155 on the activation of microglial cells suggest that miR-155 may be an effective target for TRD therapies.