Chronic Unpredictable Mild Stress Rat Model Research Articles

Quercetin alleviates chronic unpredictable mild stress-induced depression-like behavior by inhibiting NMDAR1 with α2δ-1 in rats.

Depression is a serious mental disorder and the most prevalent cause of disability and suicide worldwide. Chronic unpredictable mild stress (CUMS) can lead to a significant acceleration of depression development. Quercetin (Que) is a flavonoid compound with a wide range of pharmacological effects. Recent studies have shown that quercetin can improve CUMS-induced depression-like behavior, but the mechanism of its improvement is still unclear. α2δ-1 is a regulatory subunit of voltage-gated calcium channel, which can interact with N-methyl-D-aspartate receptor (NMDAR) to form a complex. In this study, we found that Que could inhibit the increase of α2δ-1 and NMDAR expression in rat hypothalamus induced by CUMS. In pain, chronic hypertension and other studies have shown that α2δ-1 interacts with the NMDAR to form a complex, which subsequently affects the expression level of NMDAR. Consequently, the present study aimed to investigate the antidepressant effect of Que invivo and invitro and to explore its mechanism of action in terms of the interaction between α2δ-1 and NMDAR. Rats were randomly exposed to two stressors every day for 4 weeks to establish a CUMS rat model, then sucrose preference test (SPT), forced swimming test (FST), tail suspension test (TST), and open field test (OFT) were performed to detect the behavior of CUMS rats, so as to evaluate whether the CUMS rat model was successfully established and the improvement effect of Que on CUMS-induced depression-like behavior in rats. Experimental techniques such as serum enzyme-linked immunosorbent assay (ELISA), immunofluorescence, Western blot, and co-immunoprecipitation, as well as invitro experiments, were used to investigate the mechanisms by which Que exerts its antidepressant effects. Behavioral and ELISA test results showed that Que could produce a reduction in the excitability of the hypothalamic-pituitary-adrenal (HPA) axis in CUMS rats and lead to significant improvements in their depressive behavior. Western blot, immunofluorescence, and co-immunoprecipitation experiments showed that Que produced a decrease in NMDAR1 and α2δ-1 expression levels and interfered with α2δ-1 and NMDAR1 binding. In addition, the neural regulation mechanism of Que on antidepressant effect in PC12 cells knocked out α2δ-1 gene was further verified. Cellular experiments demonstrated that Que led to a reversal of up-regulation of NMDAR1 and α2δ-1 expression levels in corticosterone-injured PC12 cells, while Que had no effects on NMDAR1 expression in PC12 cells with the α2δ-1 gene knockout. Que has a good antidepressant effect and can significantly improve the depression-like behavior caused by CUMS. It exerts antidepressant effects by inhibiting the expression level of α2δ-1, interfering with the interaction between α2δ-1 and NMDAR, and then reducing the excitability of the HPA axis.

Deciphering the antidepressant effects of Rosa damascena essential oil mediated through the serotonergic synapse signaling pathway

Ethnopharmacological relevanceRosa damascena is an ancient plant with significance in both medicine and perfumery that have a variety of therapeutic properties, including antidepressant, anti-anxiety, and anti-stress effects. Rose damascena essential oil (REO) has been used to treat depression, anxiety and other neurological related disorders in Iranian traditional medicine. However, its precise mechanism of action remains elusive. Aim of the studyThe aim of this study was to investigate the impact and mechanism underlying the influence of REO on chronic unpredictable mild stress (CUMS) rats. Materials and methodsGas chromatography-mass spectrometry (GC-MS) technique coupling was used to analyze of the components of REO. A CUMS rat model was replicated to assess the antidepressant effects of varying doses of REO. This assessment encompassed behavioral evaluations, biochemical index measurements, and hematoxylin-eosin staining. For a comprehensive analysis of hippocampal tissues, we employed transcriptomics and incorporated weighting coefficients by means of network pharmacology. These measures allowed us to explore differentially expressed genes and biofunctional pathways affected by REO in the context of depression treatment. Furthermore, GC-MS metabolomics was employed to assess metabolic profiles, while a joint analysis in Metscape facilitated the construction of a network elucidating the links between differentially expressed genes and metabolites, thereby elucidating potential relationships and clarifying key pathways regulated by REO. Finally, the expression of relevant proteins in the key pathways was determined through immunohistochemistry and Western blot analysis. Molecular docking was utilized to investigate the interactions between active components and key targets, thereby validating the experimental results. ResultsREO alleviated depressive-like behavior, significantly elevated levels of the neurotransmitter 5-hydroxytryptamine (5-HT), and reduced hippocampal neuronal damage in CUMS rats. This therapeutic effect may be associated with the modulation of the serotonergic synapse signaling pathway. Furthermore, REO rectified metabolic disturbances, primarily through the regulation of amino acid metabolic pathways. Joint analysis revealed five differentially expressed genes (EEF1A1, LOC729197, ATP8A2, NDST4, and GAD2), suggesting their potential in alleviating depressive symptoms by modulating the serotonergic synapse signaling pathway and tryptophan metabolism. REO also modulated the 5-HT2A-mediated extracellular regulated protein kinases-cAMP-response element binding protein-brain-derived neurotrophic factor (ERK-CREB-BDNF) pathway. In addition, molecular docking results indicated that citronellol, geraniol and (E,E)-farnesol in REO may serve as key active ingredients responsible for its antidepressant effects. ConclusionsThis study is the first to report that REO can effectively alleviate CUMS-induced depression-like effects in rats. Additionally, the study offers a comprehensive understanding of its intricate antidepressant mechanism from a multi-omics and multi-level perspective. Our findings hold promise for the clinical application and further development of this essential oil.

The antidepressant-like effect of NevGro® Forte in chronic unpredictable mild stress (CUMS) model of depression in rats

Depression is a leading cause of disability worldwide and it is a major contributor to the overall global burden of disease. Almost 320 million individuals globally are left untreated with depression and it has the highest prevalence. Although there are multiple conventional antidepressant types available, patients are still left untreated due to inadequate pharmacological effectiveness as well as the high rate of remissions, side effects, and patients’ non-compliance. Therefore, this study aims to determine the therapeutic effects of NevGro® Forte. The NevGro® Forte that contains a combination of three types of mushrooms, Lignosus rhinocerotis, Ganoderma lucidum and Hericium erinaceus, has been reported to have the therapeutic potential for alleviating depressive symptoms. Sixty Sprague Dawley rats induced to chronic unpredictable mild stress (CUMS) protocol were orally treated with NevGro® Forte daily for 4 weeks. Histological analysis was performed to probe the role of neurogenesis in mediating the therapeutic effect of NevGro® Forte. Fluoxetine (FLX) was orally administered to validate the neurogenesis-dependent mechanism of NevGro® Forte. The present study exhibited that 4 weeks of NevGro® Forte treatment ameliorated the depressive symptoms in CUMS rat model. There is a significant improvement in body weight, brain’s weight, and increased thickness of the pyramidal layer in the hippocampus following the treatment of NevGro® Forte. Scanning electron microscopy also revealed decreased degeneration characterised by flattened with less dense surface composition in the hippocampus. This research shows a positive outcome of using NevGro® Forte in ameliorating depressive symptoms.

Association between rare earth elements and depression: Evidence from pilot mice model of chronic unpredictable mild stress-induced depression and human studies of major depressive disorder

The etiology of Major Depressive Disorder (MDD) has been associated with levels of trace elements in the human body. The source of trace elements in the human body may be rare earth elements (REEs). Our study aimed to identify the potential relationship between t REEs in blood and brain samples and depression from two paths: animal experiments and population studies. In the animal experiments, 35 adult Sprague–Dawley rats were randomly allocated to the control group (n = 14) and treatment group (n = 21), which received the chronic unpredictable mild stress (CUMS) procedure for four weeks and further categorized into the sensitive group (n = 9) and resilient group (n = 12) by sucrose water preference test. Then, all rats were executed to obtain serum and brain tissue samples. We also recruited 197 participants and divided them into the major depressive disorder (MDD) group (n = 100) and the control group (n = 97) then serum samples were collected for REEs detection. Our finding reported that significant differences were found in the levels of La and Ce in blood samples from different groups in the CUMS rat model (sensitive group < resilient group < control group) (all p < 0.05), with similar patterns for other elements (Pr, Nd, and Y) (but p > 0.5). No significant inter-group difference was reported in rat brain tissue samples. After adjusting for demographic variables, we found that the concentrations of all five REEs (La, Ce, Pr, Nd, Y) were lower in depression group than in control group (all p < 0.01). The current conjoint animal and human data supported appropriate levels of REEs have a certain protective effect on body health. These results may be attributed to Hormesis effects. Whether the possible favorable effects of REEs on improving symptoms of depression or can be applied to drug development remains to be further investigated.

The regulatory effect of Angelicae Sinensis Radix on neuroendocrine-immune network and sphingolipid metabolism in CUMS-induced model of depression

Ethnopharmacological relevanceConventional antidepressants therapy remains unsatisfactory due to the disadvantages of delayed clinical onset of action and side effects. Traditional Chinese Medicine (TCM) with good efficacy and higher safety have received much attention. Angelicae Sinensis Radix (AS), a well-known TCM, has been proved to exhibit the efficacy of antidepression recently. Aim of the studyThe purpose of this study was to investigate the potential anti-depressant mechanisms of AS based on chronic unpredictable mild stress (CUMS) rat model. Materials and methodsIn this study, behavioral experiments, molecular biology techniques, and ultra performance liquid chromatography-triple-time of flight mass spectrometer (UPLC-Triple-TOF/MS) were combined to explore the potential antidepressant mechanisms of AS based on CUMS rat model. ResultsThe results demonstrated that AS could reduce the contents of serum hypothalamic-pituitary-adrenal (HPA) axis hormones in CUMS rats, including corticotropin-releasing hormone (CRH), adrenocorticotropic hormone (ACTH) and cortisol (CORT). In addition, AS regulated the percentage of CD4+ T lymphocytes, the ratio of CD4+/CD8+, and the levels of serum cytokines such as IL-1β, IL-4, IL-6, and TNF-α in CUMS rats. Lipidomics showed that 31 lipids were related to depression and AS could regulate the lipid metabolism alteration induced by CUMS, particularly sphingolipid metabolism. Finally, the key proteins in sphingolipid metabolic pathways in hippocampus of CUMS rats could be back-regulated by AS, including serine palmitoyl transferase (SPTLC2), ceramide synthase (CerS2), sphingomyelinase (SPHK1), and neutral sphingomyelinase (nSMase). ConclusionAS could alleviate NEI network disorder and restore the levels of sphingolipid metabolites and key proteins in CUMS rats. The underlying mechanism by which AS relieved depression-like behavior in CUMS rats may be through modulation of NEI and disturbances in sphingolipid metabolism.

Anxiolytic- and antidepressant-like effects of Bacillus coagulans Unique IS-2 mediate via reshaping of microbiome gut-brain axis in rats.

Due to the rising cases of treatment-refractory affective disorders, the discovery of newer therapeutic approaches is needed. In recent times, probiotics have garnered notable attention in managing stress-related disorders. Herein, we examined the effect of Bacillus coagulans Unique IS-2® probiotic on anxiety- and depression-like phenotypes employing maternal separation (MS) and chronic-unpredictable mild stress (CUMS) model in rats. Both male and female Sprague-Dawley rats were subjected to MS+CUMS. Probiotic treatment was provided for 6 weeks via drinking water. Anxiety- and depression-like phenotypes were assessed using sucrose-preference test (SPT), forced-swimming test (FST), elevated-plus maze test (EPM), and open-field test (OFT). Blood, brain, intestine, and fecal samples were obtained for biochemical and molecular studies. Stress-exposed rats drank less sucrose solution, showed increased passivity, and explored less in open-arms in SPT, FST, and EPM, respectively. These stress-generated neurobehavioral aberrations were alleviated by 6-week of Bacillus coagulans Unique IS-2 treatment. The overall locomotor activity in OFT remained unchanged. The decreased levels of BDNF and serotonin and increased levels of C-reactive protein, TNF-α, IL-1β, and dopamine, in the hippocampus and/or frontal cortex of stress-exposed rats were reversed following probiotic treatment. Administration of probiotic also restored the systemic levels of L-tryptophan, L-kynurenine, kynurenic-acid, and 3-hydroxyanthranilic acid, villi/crypt ratio, goblet-cell count, Firmicutes to Bacteroides ratio, and levels of acetate, propionate, and butyrate in fecal samples. These results indicate remodeling of the microbiome gut-brain axis in Bacillus coagulans Unique IS-2 recipient rats. However, protein levels of doublecortin, GFAP, and zona occludens in the hippocampus and occludin-immunoreactivity in the intestine remained unchanged. No prominent sex-specific changes were noted. Anxiolytic- and antidepressant-like effects of Bacillus coagulans Unique IS-2 in MS+CUMS rat model may be mediated via reshaping the microbiome gut-brain axis.

A preliminary study on the diversity of butyrate-producing bacteria in response to the treatment of depression with Xiaoyaosan.

Butyrate-producing bacteria generate butyrate, which has antidepressant effects. Xiaoyaosan (XYS), a traditional Chinese medicine (TCM) used to treat depression, may improve depression-like behaviour by modulating the gut microbiota. However, the functional groups and mechanisms of action in the XYS treatment of depression remain unknown. This study aimed to analyse with clone sequencing the changes in intestinal butyrate-producing bacteria in XYS-treated chronic unpredictable mild stress (CUMS) rats. We successfully established the XYS-treated CUMS rat model of depression. Rat faecal samples were collected before, during, and after the experiment, and butyryl-CoA:acetate CoA-transferase gene primers were selected for PCR amplification to determine the diversity of butyrate-producing bacteria. The results showed that XYS increased intestinal butyrate-producing bacterial diversity in CUMS rats regarding phylum and genus numbers; the number of phyla increased to two, distributed in Firmicutes and Bacteroides, and four genera were distributed in Eubacterium sp., Roseburia sp., Clostridium sp. and Bacteroides sp. Only one phylum and two genera were present in the model group without XYS treatment. Our findings indicate that XYS can improve depression-like behaviour by regulating intestinal butyrate-producing bacteria diversity, particularly Roseburia sp. and Eubacterium sp., thus providing new insights into the targeted regulation of the intestinal flora to treat depression.

Helicid Reverses the Effect of Overexpressing NCALD, Which Blocks the sGC/cGMP/PKG Signaling Pathway in the CUMS-Induced Rat Model.

Background Increasing evidence has shown that apoptosis in the hippocampus is closely related to depressive-like behavior. We previously reported that helicid had good antidepressant activities, which manifested as the alleviation of depression-like behaviors and the reversal of the high expression of neurocalcin delta (NCALD) in chronic unpredictable mild stress (CUMS) rats. The aim of this study was, therefore, to characterize the antidepressant-like effects and underlying mechanism of helicid on CUMS rats by silencing NCALD and using rescue experiments. Methods We developed the CUMS rat model using CUMS stimulation from week 0 to week 6. The rats were treated with helicid, or NCALD silenced, then we overexpressed NCALD using adeno-associated virus. We also measured the protein levels of sGCα1, sGCβ1, PKG1/2, and cleaved caspase-3 in hippocampal tissues using western blotting and measured cGMP using an ELISA. Results Treating CUMS rats by silencing NCALD or by the administration of helicid improved the depressive-like behavior. The levels of proteins, including sGC, PKG, cleaved caspase-3, and cGMP, in hippocampus all decreased. NCALD overexpression reversed these decreases and reversed the alleviation of depression-like behaviors in CUMS rats. Limitation. We only detected the antidepressant effects of helicid in the hippocampus; therefore, other parts of brain should also be studied. Conclusions Inhibition of NCALD, as well as helicid administration, alleviated antidepressant-like behavior by regulating the expressions of apoptotic cytokines and the sGC/cGMP/PKG signaling pathway. Overexpressing NCALD reversed the amelioration effects of silenced NCALD and helicid administration.

Identification of key genes and crucial pathways for major depressive disorder using peripheral blood samples and chronic unpredictable mild stress rat models.

BackgroundAccurate diagnosis of major depressive disorder (MDD) remains difficult, and one of the key challenges in diagnosing MDD is the lack of reliable diagnostic biomarkers. The objective of this study was to explore gene networks and identify potential biomarkers for MDD.MethodsIn the present study, we performed a comprehensive analysis of the mRNA expression profiles using blood samples of four patients with MDD and four controls by RNA sequencing. Differentially expressed genes (DEGs) were screened, and functional and pathway enrichment analyses were performed using the Database for Annotation, Visualization, and Integrated Discovery. All DEGs were inputted to the STRING database to build a PPI network, and the top 10 hub genes were screened using the cytoHubba plugin of the Cytoscape software. The relative expression of 10 key genes was identified by quantitative real-time polymerase chain reaction (qRT-PCR) of blood samples from 50 MDD patients and 50 controls. Plasma levels of SQSTM1 and TNFα were measured using an enzyme-linked immunosorbent assay in blood samples of 44 MDD patients and 44 controls. A sucrose preference test was used to evaluate depression-like behavior in chronic unpredictable mild stress (CUMS) model rats. Immunofluorescence assay and western blotting were performed to study the expression of proteins in the brain samples of CUMS model ratsResultsWe identified 247 DEGs that were closely associated with MDD. Gene ontology analyses suggested that the DEGs were mainly enriched in negative regulation of transcription by RNA polymerase II promoter, cytoplasm, and protein binding. Moreover, Kyoto Encyclopedia of Genes and Genomes pathway analysis suggested that the DEGs were significantly enriched in the MAPK signaling pathway. Ten hub genes were screened through the PPI network, and qRT-PCR assay revealed that one and six genes were downregulated and upregulated, respectively; however, SMARCA2, PPP3CB, and RAB5C were not detected. Pathway enrichment analysis for the 10 genes showed that the mTOR signaling pathway was also enriched. A strong positive correlation was observed between SQSTM1 and TNFα protein levels in patients with MDD. LC3 II and SQSTM1 protein levels were increased in the CUMS rat model; however, p-mTOR protein levels were decreased. The sucrose preference values decreased in the CUMS rat model.ConclusionsWe identified 247 DEGs and constructed an MDD-specific network; thereafter, 10 hub genes were selected for further analysis. Our results provide novel insights into the pathogenesis of MDD. Moreover, SQSTM1, which is related to autophagy and inflammatory reactions, may play a key role in MDD. SQSTM1 may be used as a promising therapeutic target in MDD; additionally, more molecular mechanisms have been suggested that should be focused on in future in vivo and in vitro studies.

The deleterious effect of stress-induced depression on rat liver: Protective role of resveratrol and dimethyl fumarate via inhibiting the MAPK/ERK/JNK pathway.

This study aimed to uncover the protective potentiality of resveratrol and dimethyl fumarate (DMF) in the liver of a chronic unpredictable mild stress (CUMS)-induced depression animal model. Resveratrol and DMF significantly alleviated CUMS-induced behavioral abnormalities in stressed rats through improving sucrose preference in sucrose preference test and decreasing immobility time in a forced swimming test. They also mitigated serum corticosterone levels and elevated serum serotonin levels, which were formerly disturbed in CUMS rats. The hepatoprotective effect is evidenced by improvement in hepatic histopathological examinations, as well asnormalized serum alanine aminotransferase and aspartate aminotransferase activities. Molecular signaling of resveratrol and DMF was estimated by diminishing hepatic expression of phosphorylated p38 mitogen-activated protein kinase (MAPK), extracellular signal-regulated kinase1/2 (ERK1/2), and c-Jun N-terminal kinase (JNK). Consequently, they improved the hepatic antioxidant and anti-inflammatory activities as elaborated by the normalization of total antioxidant capacity, glutathione, malondialdehyde, nuclear factor-κB, tumor necrosis factor-α, and myeloperoxidase levels. In addition, they inhibited hepatocyte apoptosis as evidenced by the increased expression of B-cell lymphoma 2, the decreased expression of Bax, as well asthe suppressed activity of caspase-3. In conclusion, resveratrol and DMF purveyed a significant anti-depressant effect, which may be mediated, at least in part, via inhibiting the MAPK/ERK/JNK pathway in the CUMS rat model.

CUMS Promotes the Development of Premature Ovarian Insufficiency Mediated by Nerve Growth Factor and Its Receptor in Rats.

This study aimed to investigate whether chronic unpredictable mild stress (CUMS) affects follicular development in ovaries through the nerve growth factor (NGF)/high affinity nerve growth factor receptor, the Tropomyosin-related kinase A (TrkA) receptor, mediated signaling pathway and to reveal the relationship between chronic stress and premature ovarian insufficiency (POI) development. In this experiment, a CUMS rat model was constructed. It was found that serum estradiol (E2), anti-Mullerian hormone (AMH), and gonadotropin-releasing hormone (GnRH) levels decreased, while follicle-stimulating hormone (FSH) levels increased. The expression of NGF, TrkA, p75, and FSHR in ovarian tissue decreased significantly. The expression levels of TrkA and p75 protein in ovarian stroma and small follicles were observed by an immunofluorescence assay. In addition, the numbers of small follicles were significantly reduced. The expression of TrkA, p75, and FSHR in CUMS ovarian tissue was upregulated by exogenous NGF in vitro. Furthermore, after treatment with NGF combined with FSH, E2 secretion in ovarian tissue culture supernatant of CUMS rats also increased significantly. Therefore, CUMS downregulates NGF and TrkA and promotes the occurrence of POI in rats. Exogenous NGF and FSH can upregulate the NGF receptor, E2, and AMH in vitro, and improve the rat ovarian function. Future studies may associate these results with female population.

Optimization of food deprivation and sucrose preference test in SD rat model undergoing chronic unpredictable mild stress.

BackgroundThe chronic unpredictable mild stress (CUMS) model has long been considered the best model for exploring the pathophysiological mechanisms underlying depression. However, there are no widely recognised standards for strategies for modeling and for behavioral testing. The present study aimed to optimize the protocols for food deprivation and the sucrose preference test (SPT) for the CUMS model.MethodsWe first evaluated the effects of different long periods of food deprivation on the body weight of Sprague Dawley (SD) rats by testing food deprivation for 24 hours (8:00‐8:00+), food deprivation for 12 hours during the daytime (8:00‐20:00) and food deprivation for 12 hours at night (20:00‐8:00+). Next, we established a SD rat CUMS model with 15 different stimulations, and used body weight measurement, SPT, forced swim test (FST), open field test (OFT) and Morris water maze (MWM) test to verify the success of the modeling. In the SPT, consumption of sucrose and pure water within 1 and 12 hours was measured.ResultsTwelve hours of food deprivation during the daytime (8:00‐20:00) had no effect on body weight, while 12 hours of food deprivation at night (20:00‐8:00+) and 24 hours of food deprivation (8:00‐8:00+) significantly reduced the mean body weight of the SD rats. When SPT was used to verify the successful establishment of the CUMS rat model, sucrose consumption measured within 12 hours was less variable than that measured within 1 hour.ConclusionsTwelve hours of food deprivation in the daytime (8:00‐20:00) may be considered a mild stimulus for the establishment of a CUMS rat model. Measuring sucrose consumption over 12 hours is recommended for SPT.

Nitric Oxide and Cyclic Guanosine Monophosphate Signaling Mediates the Antidepressant Effects of Acupuncture in the Rat Model of Chronic Unpredictable Mild Stress.

BackgroundDepression is a major mood disorder. Some patients have been reported to improve following acupuncture. This study aimed to investigate the effects of acupuncture on behaviors associated with depression in the chronic unpredictable mild stress (CUMS) rat model. The expression of signaling pathway components of nitric oxide (NO) and cyclic guanosine monophosphate (cGMP) in the rat hippocampus and plasma were also measured.Material/MethodsMale Sprague-Dawley rats (N=40) were divided into the control group (N=10), the model group (N=10), the acupuncture group (N=10), and the non-acupuncture group (N=10). The rat model was established by orphaning combined with chronic unpredictable mild stress (CUMS) for six weeks. The acupuncture group was given 21 days of treatment using acupoints (AP) or non-acupoints (NP). Rat behaviors associated with depression were tested using the sucrose preference test (SPT), the open field test (OFT), and the elevated plus maze (EPM) test. Enzyme-linked immunoassay (ELISA) and reverse transcription-polymerase chain reaction (RT-PCR) were used to detect the expression of inducible nitric oxide synthase (iNOS), neuronal nitric oxide synthase (nNOS), and the N-methyl-D-aspartate (NMDA) receptor subunits, NR1, NR2A, and NR2B in the rat plasma and hippocampus.ResultsAcupuncture reversed the behaviors associated with depression in the CUMS rat model and reduced the expression of components of the NO and cGMP pathway in the rat hippocampus and plasma.ConclusionsIn the CUMS rat model, treatment with acupuncture reduced behaviors associated with depression, and these effects were associated with changes in the NO and cGMP signaling pathway.

Effects of chronic stress on intestinal amino acid pathways

Major depressive disorder (MDD) is a debilitating mental disorder with a high prevalence and severe impacts on quality of life. However, the pathophysiological mechanisms underlying MDD remain poorly understood. Here, we used high-performance liquid chromatography with ultraviolet detection-based targeted metabolomics to identify amino acid changes in the small intestine, in a rat model of chronic unpredictable mild stress (CUMS). Pearson's correlation analysis was conducted to investigate the correlations between amino acid changes and behavioral outcomes. Western blot analysis was employed to verify intestinal amino acid transport function. Moreover, we performed an integrated analysis of related differential amino acids in the hippocampus, peripheral blood mononuclear cells (PBMCs), urine and cerebellum identified in our previous studies using the CUMS rat model to further our understanding of amino acid metabolism in depression. Decreased concentrations of glutamine and glycine and upregulation of aspartic acid were found in CUMS model rats. These changes were significantly correlated with depressive-like behaviors. Western blot analysis revealed that CUMS rats exhibited a reduction in the expression levels of amino acid transporters ASCT2 and B0AT1, as well as an increase in LAT1 expression. Impaired transport of glycine and glutamine into the small intestine may contribute to a central deficiency. The current findings suggest that the glycine and glutamine uptake systems may be potential therapeutic targets for depression. The integrated analysis strategy used in the current study may provide new insight into the cellular and molecular mechanisms underlying the gut-brain axis, and help to elucidate the pathophysiological changes in central and peripheral systems in depression.

L-theanine ameliorate depressive-like behavior in a chronic unpredictable mild stress rat model via modulating the monoamine levels in limbic-cortical-striatal-pallidal-thalamic-circuit related brain regions.

L-theanine, originally found in green tea, elicits various physiological effects, such as promoting relaxation, improving concentration and learning ability, and providing antianxiety-like and antidepressant-like properties. This study aims to investigate the effects of L-theanine (2mg/kg) on monoamine levels in an animal model of depression. The effect of l-theanine on the symptoms of depression was examined through the open-field test, sucrose preference test, and forced swim test. The monoamine neurotransmitters that involve serotonin (5-HT), norepinephrine (NE), and dopamine (DA) were measured in the limbic-cortical-striatal-pallidal-thalamic (LCSPT)-circuit related brain regions, including the prefrontal cortex (PFC), nucleus accumbens (NAC), striatum (ST), amygdala, and hippocampus (HIP). L-theanine ameliorated the depressive-like behaviors in the chronic unpredictable mild stress (CUMS) rat model. In the PFC, NAC, and HIP, L-theanine administration significantly increased the levels of 5-HT, NE, and DA. In the ST, the levels of 5-HT and DA were increased after the administration of L-theanine. However, in the HIP, only the level of DA significantly changed after the treatment of L-theanine. Taken together, these results indicated that L-theanine has possibly antidepressant-like effects in the CUMS rat model, which could be mediated by the monoamine neurotransmitters in the LCSPT-circuit related brain regions.

Novel antidepressant effects of Paeonol alleviate neuronal injury with concomitant alterations in BDNF, Rac1 and RhoA levels in chronic unpredictable mild stress rats.

Increasing evidence has suggested that major depressive disorder (MDD) is highly associated with brain-derived neurotrophic factor (BDNF) levels, dendrites atrophy, and loss of dendritic spines, especially in emotion-associated brain regions including the hippocampus. Paeonol is a kind of polyphenols natural product with a variety of therapeutic effects. Recent studies have reported its antidepressant effects. However, it is unclear what signaling pathways contribute to improve MDD. The present study investigated the effect of Paeonol on hippocampal neuronal morphology and its possible signaling pathways in chronic unpredictable mild stress (CUMS) rat model. Using CUMS rat model, the antidepressant-like effect of Paeonol was validated via depression-related behavioral tests. Neuronal morphology in hippocampal CA1 and DG was assessed using ImageJ's Sholl plugin and RESCONSTRUCT software. BDNF signaling pathway-related molecules was determined by Western blotting. Paeonol attenuated CUMS-induced depression-like behaviors, which were accompanied by hippocampal neuronal morphological alterations. After Paeonol treatment for 4weeks, the dendritic length and complexity and the density of dendritic spines markedly increased in the hippocampal CA1 and the dentate gyrus (DG). However, CUMS or Paeonol treatment does not selectively affect dendritic spine types. Simultaneously, administration of Paeonol deterred CUMS-induced cofilin1 activation that is essential for remolding of dendritic spines. The induction of CUMS downregulated BDNF levels and upregulated Rac1/RhoA levels; however, the tendency of these was inhibited by treatment with Paeonol. Our data suggest that BDNF-Rac1/RhoA pathway may be involved in attenuation of CUMS-induced behavioral and neuronal damage by Paeonol that may represent a novel therapeutic agent for depression.

Apocynum venetum leaf extract reverses depressive-like behaviors in chronically stressed rats by inhibiting oxidative stress and apoptosis

BackgroundMajor depressive disorder (MDD) is a common but serious psychiatric disorder, but current treatments are inadequate for approximately half of the patients with MDD. Thus, better methods of treatment are urgently needed. This study aimed to investigate the antidepressant-like effects and potential mechanism of Apocynum venetum leaf extract (AVLE) in chronic unpredictable mild stress (CUMS) rat model of depression. Materials and methodsThe CUMS rat model of depression was used to investigate the antidepressant-like activity and relevant mechanism of AVLE (30, 60, and 125 mg/kg, i.g.). Behavioral tests, including sucrose preference test (SPT), open field test (OFT), and forced swimming test (FST) were conducted to assess anhedonic, despairing, and spontaneous behaviors, respectively. The activity of the hypothalamic-pituitary-adrenal (HPA) axis was evaluated by measuring the serum adrenocorticotrophic hormone (ACTH) and corticosterone (CORT) concentrations. The underlying mechanism was further explored by assessing oxidative stress parameters, cell apoptosis, and brain-derived neurotrophic factor (BDNF) expression in the rat hippocampus exposed to CUMS. ResultsThe AVLE (36, 60, 125 mg/kg) treatment exerted antidepressant-like effects in CUMS-exposed rats similar to fluoxetine (10 mg/kg). The AVLE treatment reduced the serum CORT and ACTH levels in CUMS rats. It also increased the activities and gene expression of antioxidant enzymes (SOD, CAT, and GPx) and decreased the ROS generation levels and the lipid peroxidation marker MDA in the rat hippocampus subjected to CUMS. Additionally, it suppressed the apoptosis of hippocampus cells by modulating Bcl-2/Bax pathways and improved the hippocampal BDNF expressions of CUMS rats. ConclusionOur findings suggested that AVLE exerted antidepressant-like effects in CUMS rats, which was possibly mediated by the prevention of oxidative stress, the inhibition of hippocampal neuronal apoptosis, and the upregulation of the hippocampal BDNF level.

Regulation of the kynurenine metabolism pathway by Xiaoyao San and the underlying effect in the hippocampus of the depressed rat

Ethnopharmacological relevanceXiaoyao San (XYS) is a classic Chinese herbal formula for treatment of depression. The present study aimed to investigate the antidepressant effects of XYS in a rat model of chronic unpredictable mild stress (CUMS) and the underlying mechanisms. Materials and methodsA CUMS rat model of depression was established via 4 weeks of unpredictable stimulation. Then the rats were orally administered paroxetine and XYS for 2 weeks with continued stress. Behavioral assessments, including an open field test (OFT), sucrose preference test (SPT) and forced swim test (FST), were conducted to evaluate the antidepressant effects of XYS. The concentrations in rat plasma of tryptophan (Trp) and its metabolic products, including kynurenine (Kyn) and quinolinic acid (QUIN), were determined using high performance liquid chromatography tandem mass spectrometry with electrochemical detection (HPLC-MS/MS). The mRNA and protein levels in rat hippocampus of depression-related brain derived neurotrophic factor (BDNF), cyclic AMP response element binding protein (CREB) and nerve cell adhesion molecule (NCAM) were determined by real-time qPCR and Western blot, respectively. Enzyme Linked Immunosorbent Assay (ELISA) was used to detect the activities of indoleamine 2,3-dioxygenase (IDO) and kynurenine-3-monooxygenase (KMO) in rat plasma. ResultsThe results showed that a successful CUMS rat model was established through 4 weeks of continuous unpredictable stimulation, as indicated by the significant decrease in locomotor activity and increase in immobility time in the OFT, reduction in body weight and food intake etc. Compared with the normal group, the concentrations of Kyn and QUIN had significantly (p < 0.05) decreased at day 28 in the control group, but then improved after drug treatment with paroxetine and XYS. There were no obvious changes in the activities of IDO and KMO. Compared with the normal group, the mRNA of NCAM, CREB and BDNF were significantly down-regulated (p < 0.001) in the control group, BDNF gene was up-regulated by paroxetine or XYS treatment, NCAM and CREB gene did not change in XYS group, protein expressions of BDNF and CREB were significantly increased, and NCAM was significantly reduced (p < 0.05). ConclusionsXYS reversed the abnormalities of the tryptophan-kynurenine metabolic pathways in depressed rats and achieved an excellent antidepressant effect. Its direct impact may be observed as changes in biological indicators in rat hippocampus tissue.

Antidepressant-like effects of Marasmiusandrosaceus metabolic exopolysaccharides on chronic unpredictable mild stress-induced rat model.

Marasmiusandrosaceus (M. androsaceus), a medicinal fungus, has various pharmacological activities including antidepression. The present study investigated the effects of exopolysaccharides obtained during M.androsaceus submerged fermentation in a chronic unpredictable mild stress (CUMS)‑induced depression rat model. Similar to fluoxetine (positive drug), 4‑week administration of M.androsaceus exopolysaccharides (MEPS) at doses of 6, 30and 150mg/kg strongly enhanced bodyweight gain and sucrose consumption, and reduced the immobility time in forced swimming test and tail suspension test in CUMS rats. MEPS resulted in significant enhancement on the levels of noradrenalin, dopamine, 5‑hydroxytryptamine (5‑HT), and 5‑hydroxyindoleacetic acid in the serum and hypothalamus of CUMS rats, as detected by ELISA. Western blotting results revealed that MEPS upregulated the protein expression levels of tyrosine hydroxylase in the hypothalamus of CUMS rats. In conclusion, these results confirmed the antidepressant‑like effects of MEPS, and suggested that the monoamine neurotransmitter system is involved in its antidepressive effects in a CUMS rat model. The present study provided evidence for the clinical application of MEPS as an effective agent against depression.

2D-gel based proteomics unravels neurogenesis and energetic metabolism dysfunction of the olfactory bulb in CUMS rat model

Major depression is a devastating psychiatric disease worldwide currently. A reduced olfactory sensitivity in MDD patients was well evidenced. We previously interrogated the mechanism of decreasing hippocampus neurogenesis in CUMS rat model of depression. The Olfactory Bulb (OB) is crucial part of the olfactory system which functions in post-developmental neurogenesis. However, the mechanism of the dysfunction of OB induced by CUMS is still largely unknown. Herein, by using the chronic unpredictable mild stress (CUMS) rat model of depression, differential protein expression between the OB proteomes of CUMS and control group was interrogated through two-dimensional electrophoresis coupling with matrix-assisted laser desorption ionization-time of flight tandem mass spectrometry. Twenty nine differential protein expression was analyzed by Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway over-representation and Ingenuity pathways analysis (IPA). Seven identified differential proteins were selected for Western blotting validation. This study provides insight that neurogenesis and Energy metabolism disorder is involved in OB dysfunction induced by CUMS.