Chronic Unpredictable Stress-induced Depression Research Articles

Interleukin-11Rα2 in the hypothalamic arcuate nucleus affects depression-related behaviors and the AKT-BDNF pathway

Depression is a widespread emotional disorder with complex pathogenesis. An essential function of the hypothalamus is to regulate emotional disorders. However, further investigation is required to identify the pathogenic genes and molecular mechanisms that contribute to the onset of depression within the hypothalamus. Through RNA-sequencing analysis, this study identified the upregulated expression of interleukin-11 receptor alpha 2 (IL-11Rα2) in the hypothalamus of mice with chronic unpredictable stress (CUS)-induced depression. This substantial increase in IL-11Rα2, not IL-11Rα1 expression levels in the hypothalamus under the influence of CUS was found to be associated with depression-related behaviors. We further showed that IL-11Rα2 is expressed in the arcuate nucleus (ARC) proopiomelanocortin (POMC) neurons of the hypothalamus. Male and female mice exhibited behaviors association with depression, when IL-11Rα2 or its ligand IL-11 was overexpressed in the ARC POMC neurons through the action of an adeno-associated virus. In addition, reductions in the expression levels of proteins involved in the protein kinase B signaling pathways and brain-derived neurotrophic factor were observed upon overexpression of IL-11Rα2 in the hypothalamic ARC. This study emphasizes the importance of IL-11Rα2 in the hypothalamus ARC in the development of depression, and presents it as a potential novel target for depression treatment.

Fermented goat milk by selenium-enriched Lactobacillus paracasei alleviates depressive psychological disturbance.

Depression is a prevalent psychiatric disease with the characteristic of persistently gloomy mood. The treatment of depression with traditional therapeutic medications suffers from low efficacy and adverse side effects due to the extremely unpredictable courses and uneven responses to treatment. The goal of this paper was to investigate the preparation of selenium-enriched fermented goat milk and the potential mechanism of its intervention on the chronic unpredictable stress-induced depression mice model. The results showed that Se-Lactobacillus paracasei 20241 (Se-20241) significantly alleviated depressive behavior, reversed the upregulation of inflammatory factors, and attenuated glucocorticoid resistance. Meanwhile, the results showed a modulatory function on oxidative stress dysfunction in the liver, hippocampus, and prefrontal cortex. The change in abundance of Ileibacterium, Muribaculaceae, Turicibacter, Dubosiella, and Bifidobacterium was also modified. These results provided the theoretical groundwork for the development of psychoactive probiotic supplements for depressed patients and clarified the probable mechanism of Se-20241 for antidepressant impact on the CUMS model.

Neuroprotective effect of bromelain on BDNF-TRKB signalling pathway in chronic unpredictable stress-induced depression model

BackgroundBromelain is a mixture of protease enzyme extract from the fruit or stem of the pineapple plant. It has a wide range of biological actions, and it is most commonly used as an anti-inflammatory agent. This study was designed to investigate the antidepressant effect of bromelain on chronic unpredictable stress (CUS)-induced depression in rat models by targeting various molecular mechanisms.ResultWe studied the in silico analysis of the antidepressant potential of bromelain by docking with various proteins involved in the pathophysiology of depression. As a result of in silico studies, bromelain showed good binding energy with IL1β, 5-HT, BDNF, CREB, and TrkB. The mRNA expression of BDNF, TrkB, AKT, ERK, and IL-1β was studied by qRT-PCR. Gene expression studies showed a significant decrease in BDNF, TrkB, AKT, and ERK in chronic unpredictable stress, whereas there was a significant increase in the case of the bromelain- and fluoxetine-treated group. Since neuroinflammation is also one of the major concerns in the pathophysiology of depression, pro-inflammatory cytokines were also studied along with apoptotic markers using ELISA. ELISA results showed a significant increase in inflammatory cytokines in CUS, and it was significantly decreased in the case of the bromelain- and fluoxetine-treated group. Similarly, there was an increased concentration of pro-apoptotic protein in the CUS group, whereas it was decreased in the bromelain and fluoxetine groups.ConclusionsFrom the results, it is clear that bromelain exerts an antidepressive effect by preventing neuroinflammation and neurodegeneration and by enhancing neurogenesis and neuroplasticity.Graphical abstract

Antidepressive mechanisms of rhynchophylline in mice with chronic unpredictable stress-induced depression.

Uncaria rhynchophylla ([Mi] Jack) (gouteng) exerts antidepressive effects. Rhynchophylline (RH), a major component of U. rhynchophylla, exerts similar pharmacological effects to those of gouteng. Thus, RH may have antidepressive effects. To investigate the anti-depressive effects of RH in chronic unpredictable mild stress (CUMS)-induced depressive mice. The anti-depressive mechanism of RH determined by measuring the 5-HT levels, the expressions of cAMP-response element binding protein (CREB) and brain-derived neurotrophic factor (BDNF) in cortex and hippocampus. The behaviors of CUMS-induced depressive mice were measured using an open field test (OFT), forced swimming test (FST), and tail suspension test (TST). 5-HT levels were measured using an ELISA kits. The expressions of BDNF and CREB were determined using western blot test. RH increased the frequency of rearing and grooming in the OFT and decreased the immobility time in the FST and TST. RH effectively increased the 5-HT level and BDNF and CREB expressions in the cortex and hippocampus. Our findings indicate that the antidepressive mechanism of RH is related to increased levels of 5-HT from regulating CREB and BDNF expressions in cortex and hippocampus.

Antidepressant and anxiolytic-like activities of the dichloromethane/methanol extract of Crateva adansonii in mice exposed to chronic mild stress

Crateva adansonii (CA) is traditionally used in the treatment of epilepsy and memory loss. This work aims to evaluate the antidepressant and anxiolytic activities of the dichloromethane/methanol extract of CA trunk bark in a chronic unpredictable stress-induced depression (UCMS) model in mice. After exposure of mice to UCMS for 42 days, anhedonia was assessed using the sucrose preference test, antidepressant effects by the forced swim and caudal suspension tests, anxiolytic effects by the light/dark compartment (LDB) and open arena (OF) tests. Oxidative stress parameters Malondialdehyde (MDA), Superoxide Dismutase (SOD), Catalase (CAT), and Reduced Glutathione (GSH) were assessed. The results showed that multiple administrations of C. adansonii extract (150 and 300 mg/kg, resulted in a significant increase from 38.5% to 64.9% (p<0.001) in sucrose intake and a decrease from 47 seconds to 14 seconds in the immobility time in the forced swim test compared to the UCMS group. The extract significantly (p<0.001) reversed the time spent in the dark box at 150 mg/kg, and the number of groomings at 150 and 300 mg/kg compared to the UCMS group in the LDB and OF test. There was also a significant (p<0.001) improvement in SOD, GSH, and a reversal of MDA. The extract of CA improved symptoms of depression and anxiety in mice treated with different dose. The effects observed would be due to the presence in the extract of polyphenols such as flavonoids. These effects would justify the use of this extract in traditional medicine.

Effects of Chronic LY341495 on Hippocampal mTORC1 Signaling in Mice with Chronic Unpredictable Stress-Induced Depression.

In several rodent models, acute administration of the metabotropic glutamate 2/3 (mGlu2/3) receptor antagonist LY341495 induced antidepressant-like effects via a mechanism of action similar to that of ketamine. However, the effects of chronic mGlu2/3 antagonism have not yet been explored. Therefore, we investigated the effects of chronic LY341495 treatment on the mechanistic target of rapamycin complex 1 (mTORC1) signaling and the levels of synaptic proteins in mice subjected to chronic unpredictable stress (CUS). LY341495 (1 mg/kg) was administered daily for 4 weeks to mice with and without CUS exposure. After the final treatment, the forced swimming test (FST) was used to assess antidepressant-like effects. The hippocampal levels of mTORC1-related proteins were derived by Western blotting. Chronic LY341495 treatment reversed the CUS-induced behavioral effects of FST. CUS significantly reduced the phosphorylation of mTORC1 and downstream effectors [eukaryotic translation initiation factor 4E-binding protein 1 (4E-BP-1) and small ribosomal protein 6 (S6)], as well as the expression of synaptic proteins postsynaptic density-95 (PSD-95) and AMPA receptor subunit GluR1 (GluA1) in the hippocampus. However, chronic LY341495 treatment rescued these deficits. Our results suggest that the activation of hippocampal mTORC1 signaling is related to the antidepressant effect of chronic LY341495 treatment in an animal model of CUS-induced depression.

Beneficial effects of running exercise on hippocampal microglia and neuroinflammation in chronic unpredictable stress-induced depression model rats

Running exercise has been shown to relieve symptoms of depression, but the mechanisms underlying the antidepressant effects are unclear. Microglia and concomitant dysregulated neuroinflammation play a pivotal role in the pathogenesis of depression. However, the effects of running exercise on hippocampal neuroinflammation and the number and activation of microglia in depression have not been studied. In this study, rats were subjected to chronic unpredictable stress (CUS) for 5 weeks followed by treadmill running for 6 weeks. The depressive-like symptoms of the rats were assessed with a sucrose preference test (SPT). Immunohistochemistry and stereology were performed to quantify the total number of ionized calcium-binding adapter molecule 1 (Iba1)+ microglia, and immunofluorescence was used to quantify the density of Iba1+/cluster of differentiation 68 (CD68)+ in subregions of the hippocampus. The levels of proinflammatory cytokines in the hippocampus were measured by qRT-PCR and ELISA. The results showed that running exercise reversed the decreased sucrose preference of rats with CUS-induced depression. In addition, CUS increased the number of hippocampal microglia and microglial activation in rats, but running exercise attenuated the CUS-induced increases in the number of microglia in the hippocampus and microglial activation in the dentate gyrus (DG) of the hippocampus. Furthermore, CUS significantly increased the hippocampal levels of inflammatory factors, and the increases in inflammatory factors in the hippocampus were suppressed by running exercise. These results suggest that the antidepressant effects of exercise may be mediated by reducing the number of microglia and inhibiting microglial activation and neuroinflammation in the hippocampus.

Memantine treatment exerts an antidepressant-like effect by preventing hippocampal mitochondrial dysfunction and memory impairment via upregulation of CREB/BDNF signaling in the rat model of chronic unpredictable stress-induced depression

Mitochondrial and cognitive dysfunctions have long been associated with major depressive disorders (MDDs). Studies have shown that Memantine, an N-methyl-D-aspartate (NMDA) receptor antagonist, possesses an antidepressant-like effect. Hence, the NMDA receptor can be a better therapeutic target for MDD. Therefore, the present study was designed to study the impact of Memantine on mitochondrial functional status and depression-like symptoms in the chronic unpredictable stress (CUS) model of depression. CUS for 28 days resulted in depression-like symptoms (as indicated by increased immobility time in the forced swim test) and a decline in the spatial learning and retention memory in the Morris water maze (MWM) test, which was prevented by Memantine (10 mg/kg/day) treatment. We observed elevated plasma corticosterone (CORT) levels, microdialysates glutamate concentration, and synaptosomal calcium (Ca2+) ion levels after 28 days of CUS. Memantine treatment prevented only increased plasma CORT and synaptosomal Ca2+ ion levels. Memantine treatment also restored CUS induced increase in oxidative stress parameters [increased neuronal nitric oxide synthase (nNOS) expression, nitric oxide (NO) levels, lipid peroxidation (LPO) and superoxide dismutase (SOD) activity], decrease in mitochondrial electron transport chain (ETC) enzymes activity and mitochondrial membrane potential (MMP). CUS also reduced the expression of cell survival genes, cyclic-AMP response element-binding protein (CREB), and brain-derived nerve growth factor (BDNF), which was reversed by treatment with Memantine. CUS, however, caused a non-significant decrease in the hippocampal adenosine triphosphate (ATP) levels and a non-significant increase in the expression of pro-apoptotic genes, Caspase 3, and the number of TUNEL positive cells, indicating that hippocampal mitochondrial dysfunction caused due to CUS was not severe enough to affect overall energy production, mitochondrial integrity, and cellular apoptosis status. Thus, Memantine treatment exerts an antidepressant-like effect by preventing CUS induced excitotoxicity, oxidative stress, and enhancing CUS induced decrease in mitochondrial functioning and expression of cell survival genes via upregulation of stress-responsive CREB/BDNF signaling.

MiR-497 promotes microglia activation and proinflammatory cytokines production in chronic unpredictable stress-induced depression via targeting FGF2

Depression is one of important prevalent psychiatric disorders worldwide. MiR-497 is considered as a diagnostic biomarker and a promising therapeutic target in cancers. However, the role of miR-497 in depression remains unknown. In this study, we demonstrated that CUS induced depression-like behaviors and overexpression of miR-497 in rats. Interestingly, knockdown miR-497 ameliorated CUS-induced depressive-like behavior in rats. Moreover, knockdown of miR-497 inhibited the activation of microglia and the production of proinflammatory cytokines including IL-6, IL-1β, MCP-1 and TNF-α in CUS-induced rats. Luciferase activity assay proved that Fibroblast Growth Factor-2 (FGF2) was a direct target of miR-497 and modulated by miR-497 in microglia. In rescue experiments, overexpression of FGF2 inhibited miR-497-induced proinflammatory cytokines and iNOS expression. These results showed that miR-497 aggravated hippocampal microglial activation in CUS-induced depression in rat via targeting FGF2, providing a novel potential target for treatment of depression.

Compound Chai Jin Jie Yu Tablets, Acts as An Antidepressant by Promoting Synaptic Function in the Hippocampal Neurons

ObjectiveTo investigate the effectiveness of compound Chai Jin Jie Yu Tablets (CJJYT) in ameliorating cognitive impairment associated with depression and its potential mechanism of action. MethodsIn vitro experiments, the hippocampus was isolated from the whole brain of the fetal rat and cultured into hippocampal neuron cells. 50 μM corticosterone (CORT) was added to each group 18 h before the experiment for modeling depression, with the exception of the control group. After modeling, the blank serum group was added with 10% blank serum, the CJJYT group and the venlafaxine group were added with the corresponding 10% drug-containing serum, and the control group and the model group were added with equal volumes of culture medium. The intracellular Ca2+ mean fluorescence intensity, miniature excitatory postsynaptic current (mEPSC) current amplitude, and frequency of different hippocampal neurons were evaluated as indicators of synaptic function in the hippocampal neurons. In addition, the expression of synaptic plasticity related proteins, synaptophysin-α (SYN-α), N-methyl-D-aspartate receptor 2A (NR2A), N-methyl-D- aspartate receptor 2B (NR2B), post synaptic density 95 protein (PSD-95), calcium/calmodulin dependent protein kinaseⅡ (CaMKⅡ) and synaptic associated protein (SynGAP) were detected in the hippocampal neurons by immunofluorescence staining and high content analysis (HCA) system. Then, reverse transcription-polymerase chain reaction (RT-PCR) was used to detect the mRNA expression levels of SYN-α, NR2A, NR2B, PSD- 95, CaMKⅡ and SynGAP. For in vivo experiments, except for those in the blank control group, all rats were treated within a single cage for chronic unpredictable stress-induced depression modeling and subjected to corresponding drug interventions. Behavioral tests were used to detect depressive behavior and determine learning, memory and other cognitive abilities, whereas enzyme-linked immunosorbent assay (ELISA) was used to detect the CORT levels. Golgi-Cox staining was used to observe changes in the synaptic morphology of parahippocampal gyrus CA1 area (CA1) and dentategyrus (DG). ResultsIn vitro, CJJYT treatment reduced the intracellular Ca2+ mean flurorescence intensity in the hippocampal neurons (P < 0.05), causing a reduction in the frequency and current amplitude of mEPSC (P < 0.05), and thus inhibited the excessive activation of post-synaptic receptors. CJJYT treatment reduced the protein and mRNA expression of SYN-α, NR2A, NR2B and PSD-95 in the hippocampal neurons (P < 0.05), increased the mRNA and protein expression of CaMKⅡ and SynGAP (P < 0.05), and thereby improved the synaptic plasticity of the hippocampal neurons. In vivo, CJJYT intervention improved sucrose preference, voluntary activity , learning and memory ability of Morris water maze test, and suppressed appetite (P < 0.05), and increased the despair feeling of forced swimming test (P < 0.05). The CORT level was reduced (P < 0.05), leading to the repair of synaptic damage in the hippocampal neurons. ConclusionsCJJYT can improve the synaptic function of hippocampal neurons and has obvious protective effects on neurons. It can repair the structural damage in the hippocampal neurons, improving the cognitive ability of the depressed model rats. The mechanism of CJJYT improving cognition in depressed rats may be related to the transmission and function of SYN-α/NR and its downstream neurotransmitters.

Enhanced Antidepressant-Like Effects of Electroacupuncture Combined with Citalopram in a Rat Model of Depression

Currently, antidepressants are the dominative treatment for depression, but they have limitations in efficacy and may even produce troublesome side effects. Electroacupuncture (EA) has been reported to have therapeutic benefits in the treatment of depressive disorders. The present study was conducted to determine whether EA could enhance the antidepressant efficacy of a low dose of citalopram (an SSRI antidepressant) in the chronic unpredictable stress-induced depression model rats. Here, we show that a combined treatment with 2 Hz EA and 5 mg/kg citalopram for three weeks induces a significant improvement in depressive-like symptoms as detected by sucrose preference test, open field test, and forced swimming test, whereas these effects were not observed with either of the treatments alone. Further investigations revealed that 2 Hz EA plus 5 mg/kg citalopram produced a remarkably increased expression of BDNF and its receptor TrkB in the hippocampus compared with those measured in the vehicle group. Our findings suggest that EA combined with a low dose of citalopram could produce greater therapeutic effects, thereby, predictive of a reduction in drug side effects.

Glia atrophy in the hippocampus of chronic unpredictable stress-induced depression model rats is reversed by electroacupuncture treatment

Background Growing evidence indicates that glia atrophy contributes to the pathophysiology and possibly the pathogenesis of major depressive disorder. Electroacupuncture (EA), one of Chinese traditional therapy, has potent antidepressant-like effect in many clinical studies. The mechanism by which EA improves behavioral deficits is still unclear. Method Chronic unpredictable stress (CUS)-induced depression model rats were used to study the effect of EA treatment. EA was performed on acupoints ‘Bai-Hui’ (Du 20) and unilateral ‘An-Mian’ (EX 17) once daily for three consecutive weeks，two weeks post CUS procedure. The antidepressant-like effect of EA treatment was analyzed by physical state (PS) and open field test (OFT). Astrocytic marker glial fibrillary acidic protein (GFAP) level in the hippocampus was detected by immunohistochemsitry, Western blot analysis and reverse transcription-polymerase chain reaction (RT-PCR). Results Exposure to CUS resulted in a decrease of behavioral activity, whereas a daily session of EA treatment significantly reversed the behavioral deficit of these depression model rats. Moreover, the levels of GFAP mRNA and protein were decreased in the hippocampus of depression model rats. Intriguingly, EA treatment blocked effectively the decreased GFAP level. Limitation The relative small number of the depression model rats may cause some bias of behavioral tests. Conclusion EA has potential antidepressant-like effect on CUS-induced depression model rats, which might be mediated by affecting the glial atrophy in the hippocampus.