Involvement of kynurenine pathway between inflammation and glutamate in the underlying etiopathology of CUMS-induced depression mouse model.

Inflammation and glutamate (GLU) are widely thought to participate in the pathogenesis of depression, and current evidence suggests that the development of depression is associated with the activation of the kynurenine pathway (KP). However, the exact mechanism of KP among the inflammation, GLU and depression remain poorly understood. In this study, we examined the involvement of KP, inflammation and GLU in depressive phenotype induced by chronic unpredictable mild stress (CUMS) in C57B/6 J mice. Our results showed that CUMS caused depressive like-behavior in the sucrose preference test, tail suspension test and forced swimming test. From a molecular perspective, CUMS upregulated the peripheral and central inflammatory response and activated indoleamine 2,3-dioxygenase (IDO), the rate-limiting enzyme of KP, which converts tryptophan (TRP) into kynurenine (KYN). KYN is a precursor for QA in microglia, which could activate the N-methyl-D-aspartate receptor (NMDAR), increasing the GLU release, mirrored by increased IDO activity, quinolinic acid and GLU levels in the hippocampus, prefrontal cortex and serum. However, intervention with IDO inhibitor 1-methyl-DL-tryptophan (50 mg/kg/s.c.) and 1-methyl-L-tryptophan (15 mg/kg/i.p.) reversed the depressive-like behaviors and adjusted central and peripheral KP's metabolisms levels as well as GLU content, but the inflammation levels were not completely affected. These results provide certain evidence that KP may be a vital pathway mediated by IDO linking inflammation and glutamate, contributing to depression.

Integrated meta-analysis, data mining, and animal experiments to investigate the efficacy and potential pharmacological mechanism of a TCM tonic prescription, Jianpi Tongmai formula, in depression.

BACKGROUND: Depression is a common psychiatric disorder and has become a growing public health issue. Traditional Chinese medicine (TCM) tonic prescriptions have been clinically proven to be an effective treatment for depression. PURPOSE: This study aimed to identify the core prescription to improve depression among the numerous TCM tonic prescriptions. METHODS AND RESULTS: First, we used meta-analysis to clarify the efficacy and safety of tonic prescriptions in depression among 37 studies and identified 16 effective tonic prescriptions. Second, we conducted data mining to analyze the tonic prescriptions and identified important nourishing herbs. Third, based on the data mining results, we constructed a Delphi experiment to investigate the effects of these important nourishing herbs in depression. Combining the results of Delphi expert questionnaires and weight analysis, a core TCM tonic prescription, Jianpi Tongmai formula (JPTMF) for the treatment of depression, was constructed and was composed of invigorating Spleen qi herbs. Fourth, we verified that JPTMF can improve chronic unpredictable mild stress (CUMS) induced depression-like behaviors in mice. Fifth, we predicted that the mechanism of JPTMF in the treatment of depression was mainly associated with chemical synaptic transmission and neuroinflammation through network pharmacology and determined preliminary confirmation through animal experiments. CONCLUSION: This study was undertaken to evaluate the efficacy of TCM tonic prescriptions on depression and construct a core TCM tonic prescription, JPTMF, through a progressive analysis. Network pharmacology and animal experiments verified the reliability of JPTMF. The proposal of JPTMF is of innovative significance, and may provide far-reaching implications for improving depression by using nourishing herbs. Furthermore, the integrated methods applied in this study provide an innovative paradigm for the standardization and scientific basis of TCM research.

Astrocytic Kir4.1 regulates NMDAR/calpain signaling axis in lipopolysaccharide-induced depression-like behaviors in mice.

The activation of Nod-like receptor protein 3 (NLRP3) inflammasome propagates pro-inflammatory signaling cascades linking to depression-like behaviors. However, the signaling pathway contributing to NLRP3 inflammasome activation and depression-like behaviors is still not clear. In this study, we evidenced that lipopolysaccharide (LPS) injection (i.p.) triggered depression-like behaviors, promoted the expression of Kir4.1, p-GluN2B and calpain-1, and activated NLRP3 inflammasome. The blockage of N-methyl-d-aspartate receptors (NMDAR) by memantine reduced LPS-induced depression-like behaviors, NLRP3 inflammasome and astrocyte activation, and calpain-1 expression. Additionally, memantine also inhibited LPS-induced reduction of postsynaptic density protein 95 (PSD-95) and Arc expression. Specific reduction of Kir4.1 in astrocytes attenuated LPS-induced expression of NLRP3 and calpain-1, and phosphorylation of GluN2B. Interestingly, LPS-induced expression of calpain-1 largely co-localized with GFAP, indicating the specific function of calpain-1 in astrocytes. Together, these data indicate that astrocytic Kir4.1 could regulate NMDAR/calpain-1 signaling axis, contributing to depression-like behaviors, likely through regulating NLRP3 inflammasome activation.

Polygonatum sibiricum polysaccharide prevents depression-like behaviors by reducing oxidative stress, inflammation, and cellular and synaptic damage.

ETHNOPHARMACOLOGICAL RELEVANCE: According to traditional Chinese medicine (TCM) theory (Yi Xue Zheng Zhuan), the main factors associated with the pathogenesis of depression are deficiencies relating to five zang organs, Qi, and blood. Polygonatum sibiricum F. Delaroche (PS), which may avert these pathological changes, has been used in a variety of formulas to treat depression. However, the effects and mechanism of action of PS, alone, and especially those of its main active component PS polysaccharide (PSP), on depression remain unexplored. AIM OF THE STUDY: To determine the effects of PSP on depression-like behaviors and to elucidate its mechanism of action. METHODS: PSP was isolated from dried PS rhizomes and qualified using transmission electron microscopy and Fourier transform infrared spectroscopy. Lipopolysaccharide (LPS) and chronic unpredictable mild stress (CUMS)-induced depression models were used to evaluate the antidepressive effects of PSP. Veinal blood and brain tissue were collected to determine the levels of hippocampal 5-HT, serum cortisol (CORT), brain and serum cytokines, and hippocampal oxidation-related indicators. The protein expression levels of phosphorylated extracellular signal-regulated kinase (p-ERK1/2), nuclear factor kappa-light-chain-enhancer of activated B cells (NF-κB), glial fibrillary acidic protein (GFAP), phosphorylated protein kinase B (p-Akt), phosphorylation of the mammalian target of rapamycin (mTOR), caspase-3, GluA1 and GluA2, and GluN2A and GluN2B were determined using western blotting and immunofluorescence. Nissl staining was performed to detect histopathological changes in brain tissues. RESULTS: Injection of LPS (i.p.) induced depression-like behaviors, reduced the level of hippocampal 5-HT, increased the serum CORT level and hippocampal oxidative stress (ROS), and prompted the activation of ERK1/2, NF-κB, and GFAP and an inflammatory response. Conversely, PSP administration reduced these changes and prevented depression-like behaviors. PSP administration also promoted hippocampal expression of p-Akt, p-mTOR, GluA1, and GluA2; reduced the expression of caspase-3, GluN2A, and GluN2B; and prohibited the loss of granular cells in the DG region. CONCLUSION: These results indicate that PSP prevents depression-like behaviors, and synaptic and neuronal damage probably by reducing ROS/HPA axis hyperfunction and the inflammatory response.

Ginsenoside Rg1 Prevents PTSD-Like Behaviors in Mice Through Promoting Synaptic Proteins, Reducing Kir4.1 and TNF-α in the Hippocampus.

Ginsenoside Rg1 is efficient to prevent or treat mental disorders. However, the mechanisms underlying the effects of ginsenoside Rg1 on post-traumatic stress disorder (PTSD) are still not known. In this study, single-prolonged stress (SPS) regime, as well as injection of lipopolysaccharide (LPS), was used to produce PTSD-like behaviors in C57 mice, and the effects of ginsenoside Rg1 (10, 20, 40 mg/kg/d, ip, for 14 days) on PTSD-like behaviors were evaluated. Our results showed that ginsenoside Rg1 promoted fear extinction and prevented depression-like behaviors in both LPS and SPS models. Importantly, ginsenoside Rg1 alleviated LPS- or SPS-stimulated expression of pro-inflammatory cytokines (IL-1ß and TNF-α), activation of astrocytes and microglia, and reduction of hippocampal synaptic proteins (PSD95, Arc, and GluA1). Ginsenoside Rg1 also reduced the increase of hippocampal Kir4.1 and GluN2A induced by PTSD regime. Importantly, reducing hippocampal astroglial Kir4.1 expression promoted fear extinction and improved depression-like behaviors in LPS-treated mice. Additionally, intracerebroventricular injection of TNF-α caused an impairment of fear extinction and promoted Kir4.1 expression in the hippocampus. Together, our study reveals novel protective effects of ginsenoside Rg1 against PTSD-like behaviors in mice, likely via promoting synaptic proteins, reducing Kir4.1 and TNF-α in the hippocampus.

Calpain inhibition ameliorates depression-like behaviors by reducing inflammation and promoting synaptic protein expression in the hippocampus.

Protease activity correlates with depressive or suicidal behaviors, with calpain activation being especially implicated in depression-like behaviors. However, the role of calpain in depression-like behaviors is currently unknown. In this study, the lipopolysaccharide (LPS) - and chronic unpredictable mild stress (CUMS)-induced depression models were used to evaluate the antidepressant effects of calpain inhibitors. Potential mechanisms were determined using pharmacological and biochemical methods. We found that i. p. injection of a calpain inhibitor, calpeptin, prevented LPS-induced depression-like behaviors, activation of astrocytes, inflammation, and reduction of synaptic protein expression levels. LPS injection (i.p.) promoted calpain activity, which degraded suprachiasmatic nucleus circadian oscillatory protein (SCOP). This led to the activation of ERK and nuclear translocation of nuclear factor kappa-B (NF-κB), the promotion of cytokine release, and the reduction of Arc, and PSD95 expression in the hippocampus. In contrast, i. p. injection of calpeptin blocked these changes. Furthermore, intraventricular injection of calpain inhibitor (PD150606) or an ERK inhibitor ameliorated the LPS-induced depression-like behaviors. Administration of calpeptin also remedied CUMS-induced depression-like behaviors, degradation of SCOP, activation of astrocytes, and reduction of synaptic protein expression levels. Finally, we also demonstrated that memantine, an N-methyl-d-aspartic acid (NMDA) receptor antagonist blocks LPS-induced degradation of SCOP. Together, our results show that calpain inhibition ameliorates depression-like behaviors, probably by reducing inflammation and promoting synaptic protein expression in the hippocampus.

Curculigoside facilitates fear extinction and prevents depression-like behaviors in a mouse learned helplessness model through increasing hippocampal BDNF.

Curculigoside (CUR) is the main active component of traditional Chinese medicine Curculigoorchioides Gaertn (Xianmao in Chinese), which exhibits a variety of pharmacological activities. In this study we investigated the effects of CUR on fear extinction and related depression-like behaviors in mice. In fear conditioning task, we found that administration of CUR (1.6, 8, 40 mg·kg-1·d-1, ip, for 7 days) did not affect memory consolidation, but CUR at higher doses (8, 40 mg·kg-1·d-1) significantly facilitated fear extinction, especially on D3 and D4. Moreover, CUR administration significantly ameliorated the fear conditioning-induced depression-like behaviors, likely through promoting fear extinction. We showed that CUR increased the expression of brain-derived neurotrophic factor (BDNF) and phosphorylation of tropomyosin receptor kinase B (TrkB) in the hippocampus, and activated protein kinase B (Akt)-mammalian target of the rapamycin (mTOR) signaling pathway. Administration of the selective TrkB agonist 7,8-dihydroxyflavone (7,8-DHF, 5 mg·kg-1·d-1, ip) also facilitated fear extinction, ameliorated depression-like behaviors. We established a mouse learned helplessness (LH) model to evaluate the antidepressant activity of CUR. The spatial memory was assessed in Morris water maze. We showed that LH-induced depression-like behaviors, including prolonged immobility times in forced swim and tail suspension tests as well as spatial memory impairments; LH also downregulated BDNF expression and the Akt-mTOR signaling pathway in the hippocampus. Administration of CUR (1.6, 8, 40 mg·kg-1·d-1, ip, for 14 days) or 7,8-DHF (5 mg·kg-1·d-1, ip, for 3 days) prevented LH-induced depression-like behaviors and promoted BDNF expression and the Akt-mTOR signaling pathway. In conclusion, CUR can accelerate the fear memory extinction and ameliorate depression-like behaviors in mice via promoting BDNF expression and activating the Akt-mTOR signaling pathway in the hippocampus.

Postnatal calpeptin treatment causes hippocampal neurodevelopmental defects in neonatal rats.

Our previous studies showed that the early use of calpain inhibitors reduces calpain activity in multiple brain regions, and that postnatal treatment with calpeptin may lead to cerebellar motor dysfunction. However, it remains unclear whether postnatal calpeptin application affects hippocampus-related behaviors. In this study, Sprague-Dawley rats were purchased from the Animal Center of Anhui Medical University of China. For the experiments in the adult stage, rats were intraperitoneally injected with calpeptin, 2 mg/kg, once a day, on postnatal days 7-14. Then on postnatal day 60, the Morris water maze test was used to evaluate spatial learning and memory abilities. The open field test was carried out to assess anxiety-like activities. Phalloidin staining was performed to observe synaptic morphology in the hippocampus. Immunohistochemistry was used to count the number of NeuN-positive cells in the hippocampal CA1 region. DiI was applied to label dendritic spines. Calpeptin administration impaired spatial memory, caused anxiety-like behavior in adulthood, reduced the number and area of apical dendritic spines, and decreased actin polymerization in the hippocampus, but did not affect the number of NeuN-positive cells in the hippocampal CA1 region. For the neonatal experiments, neonatal rats were intraperitoneally injected with calpeptin, 2 mg/kg, on postnatal days 7 and 8. Western blot assay was performed to analyze the protein levels of Akt, Erk, p-Akt, p-Erk1/2, Erk1/2, SCOP, PTEN, mTOR, p-mTOR, CREB and p-CREB in the hippocampus. SCOP expression was increased, and the phosphorylation levels of Akt, mTOR and CREB were reduced in the hippocampus. These findings show that calpeptin administration after birth affects synaptic development in neonatal rats by inhibiting the Akt/mTOR signaling pathway, thereby perturbing hippocampal function. Therefore, calpeptin administration after birth is a risk factor for neurodevelopmental defects.

Basolateral amygdala calpain is required for extinction of contextual fear-memory.

Extinction of fear-memory is essential for emotional and mental changes. However, the mechanisms underlying extinction of fear-memory are largely unknown. Calpain is a type of calcium-dependent protease that plays a critical role in memory consolidation and reconsolidation. Whether calpain functions in extinction of fear-memory is unknown, as are the molecular mechanisms. In this study, we investigated the pivotal role of calpain in extinction of fear-memory in mice, and assessed its mechanism. Conditioned stimulation/unconditioned stimulation-conditioned stimulation paradigms combined with pharmacological methods were employed to evaluate the action of calpain in memory extinction. Our data demonstrated that intraperitoneal or intra-basolateral amygdala (BLA) injection of calpain inhibitors could eliminate extinction of fear-memory in mice. Moreover, extinction of fear-memory paradigm-activated BLA calpain activity, which degraded suprachiasmatic nucleus circadian oscillatory protein (SCOP) and phosphatase and tensin homolog (PTEN), subsequently contributing to activation of a protein kinase B (AKT)-mammalian target of the rapamycin (mTor) signaling pathway. Additionally, cAMP-response element binding protein (CREB) phosphorylation was also augmented following extinction of fear-memory. Calpain inhibitor blocked the signaling pathway activation induced by extinction of fear-memory. Additionally, intra-BLA injection of rapamycin or cycloheximide also blocked the extinction of fear-memory. Conversely, intra-BLA injection of PTEN inhibitor, bpV, reversed the effect of calpeptin on extinction of fear-memory. Together, our data confirmed the function of BLA calpain in extinction of fear-memory, likely via degrading PTEN and activating AKT-mTor-dependent protein synthesis.