Hippocampal Salt-Inducible Kinase 2 Plays a Role in Depression via the CREB-Regulated Transcription Coactivator 1-cAMP Response Element Binding-Brain-Derived Neurotrophic Factor Pathway

Divergent effects of chronic continuous and intermittent social defeat stress on emotional behaviors: Impact on phosphorylated CREB and BDNF protein levels in the rat hippocampus

Chronic psychosocial stress stands as a significant heterogeneous risk factor for psychiatric disorders. The brain's physiological response to such stress varies based on the frequency and intensity of stress episodes. However, whether stress episodes divergently could affect hippocampal cyclic AMP response element-binding protein (CREB)-brain-derived neurotrophic factor (BDNF) signaling remains unclear, a key regulator of psychiatric symptoms. We aimed to assess how two distinct patterns of social defeat stress exposure impact anxiety- and depression-like behaviors, fear, and hippocampal CREB-BDNF signaling in adult male rats. To explore this, adult male Sprague-Dawley rats were subjected to psychosocial stress using a Resident/Intruder paradigm for ten consecutive days (continuous social defeat stress: [CS]) or ten social defeat stress over the course of 21 days (intermittent social defeat stress [IS]). Behavioral tests (including novelty-suppressed feeding test, forced swimming test, and contextually conditioned fear) were conducted. Protein expression levels of phosphorylated CREB and BDNF in the dorsal and ventral hippocampi were examined. CS led to heightened anxiety-like behavior, fear, and increased levels of phosphorylated CREB in both the dorsal and ventral hippocampi. Conversely, IS resulted in increased anxiety-like behavior and behavioral despair alongside decreased levels of phosphorylated CREB and BDNF, particularly in the dorsal hippocampus. These findings indicate that chronic psychosocial stress divergently affects hippocampal CREB-BDNF signaling and emotional regulation depending on the stress episode. Such insights could enhance our understanding of the molecular basis of the heterogeneity of psychiatric disorders and facilitate the development of innovative treatment approaches to patients with psychiatric disorders.

The hippocampal salt-inducible kinase 2-CREB-regulated transcription co-activator 1 system mediates the antidepressant actions of paroxetine in mice

The hippocampal salt-inducible kinase 2 (SIK2)-CREB-regulated transcription co-activator 1 (CRTC1) system has been demonstrated to participate in not only the pathogenesis of depression but also the antidepressant mechanisms of several antidepressant medications including fluoxetine, paroxetine, and mirtazapine. Like fluoxetine, paroxetine is also a widely used selective serotonin (5-HT) reuptake inhibitor (SSRI). Recent studies have indicated that paroxetine also modulates several pharmacological targets other than the 5-HT system. Here, we speculate that paroxetine regulates the hippocampal SIK2-CRTC1 system. Chronic stress models of depression, various behavioral tests, western blotting, co-immunoprecipitation, quantitative real-time reverse transcription PCR, and genetic knockdown were used together in the present study. Our results show that the antidepressant actions of paroxetine in mice models of depression were accompanied by its preventing effects against chronic stress on hippocampal SIK2, CRTC1, and CRTC1-CREB binding. In contrast, genetic knockdown of hippocampal CRTC1 notably abrogated the antidepressant effects of paroxetine in mice. In summary, regulating hippocampal SIK2 and CRTC1 participates in the antidepressant mechanism of paroxetine, extending the knowledge of its pharmacological targets.

Cucurbitacin B Exerts Significant Antidepressant-Like Effects in a Chronic Unpredictable Mild Stress Model of Depression: Involvement of the Hippocampal BDNF-TrkB System

BACKGROUND

Although depression has been a serious neuropsychiatric disorder worldwide, current antidepressants used in clinical practice have various weaknesses, including delayed onset and low rates of efficacy. Recently, the development of new antidepressants from natural herbal medicine has become one of the important research hotspots. Cucurbitacin B is a natural compound widely distributed in the Cucurbitaceae and Cruciferae families and has many pharmacological activities. The present study aimed to investigate whether cucurbitacin B possess antidepressant-like effects in mice.

METHODS

The antidepressant-like effects of cucurbitacin B on mice behaviors were explored using the forced swim test, tail suspension test, open field test, sucrose preference test, and a chronic unpredictable mild stress model of depression together. Then, western blotting and immunofluorescence were used to examine the effects of cucurbitacin B on the brain-derived neurotrophic factor (BDNF)-tyrosine kinase B (TrkB) signaling cascade and neurogenesis in the hippocampus of mice. Furthermore, BDNF-short hairpin RNA, K252a, and p-chlorophenylalanine methyl ester were adopted together to determine the antidepressant mechanism of cucurbitacin B.

RESULTS

It was found that administration of cucurbitacin B indeed produced notable antidepressant-like effects in mice, which were accompanied with significant promotion in both the hippocampal BDNF-TrkB pathway and neurogenesis. The antidepressant mechanism of cucurbitacin B involves the hippocampal BDNF-TrkB system but not the serotonin system.

CONCLUSIONS

Cucurbitacin B has the potential to be a novel antidepressant candidate.

Activation of mTORC1 Signaling Cascade in Hippocampus and Medial Prefrontal Cortex Is Required for Antidepressant Actions of Vortioxetine in Mice

BACKGROUND

Although thought of as a multimodal-acting antidepressant targeting the serotonin system, more molecules are being shown to participate in the antidepressant mechanism of vortioxetine. A previous report has shown that vortioxetine administration enhanced the expression of rapamycin complex 1 (mTORC1) in neurons. It has been well demonstrated that mTORC1 participates in not only the pathogenesis of depression but also the pharmacological mechanisms of many antidepressants. Therefore, we speculate that the antidepressant mechanism of vortioxetine may require mTORC1.

METHODS

Two mouse models of depression (chronic social defeat stress and chronic unpredictable mild stress) and western blotting were first used together to examine whether vortioxetine administration produced reversal effects against the chronic stress-induced downregulation in the whole mTORC1 signaling cascade in both the hippocampus and medial prefrontal cortex (mPFC). Then, LY294002, U0126, and rapamycin were used together to explore whether the antidepressant effects of vortioxetine in mouse models of depression were attenuated by pharmacological blockade of the mTORC1 system. Furthermore, lentiviral-mTORC1-short hairpin RNA-enhanced green fluorescence protein (LV-mTORC1-shRNA-EGFP) was adopted to examine if genetic blockade of mTORC1 also abolished the antidepressant actions of vortioxetine in mice.

RESULTS

Vortioxetine administration produced significant reversal effects against the chronic stress-induced downregulation in the whole mTORC1 signaling cascade in both the hippocampus and mPFC. Both pharmacological and genetic blockade of the mTORC1 system notably attenuated the antidepressant effects of vortioxetine in mice.

CONCLUSIONS

Activation of the mTORC1 system in the hippocampus and mPFC is required for the antidepressant actions of vortioxetine in mice.

The antidepressant-like effects of escitalopram in mice require salt-inducible kinase 1 and CREB-regulated transcription co-activator 1 in the paraventricular nucleus of the hypothalamus

BACKGROUND

The salt-inducible kinase 1 (SIK1)-CREB-regulated transcription co-activator 1 (CRTC1) system in the paraventricular nucleus (PVN) of the hypothalamus has been demonstrated to participate in not only depression neurobiology but also the antidepressant mechanisms of fluoxetine, paroxetine, venlafaxine, and duloxetine. Like fluoxetine and paroxetine, escitalopram is also a well-known selective serotonin (5-HT) reuptake inhibitor (SSRI). However, recently it has been found that escitalopram can modulate a lot of targets other than the 5-HT system. Here, we speculate that escitalopram produces effects on the SIK1-CRTC1 system in the PVN.

METHODS

Two mice models of depression (chronic social defeat stress (CSDS) and chronic unpredictable mild stress (CUMS)), various behavioral tests, enzyme linked immunosorbent assay (ELISA), western blotting, co-immunoprecipitation (Co-IP), quantitative real-time reverse transcription PCR (qRT-PCR), immunofluorescence, and adeno-associated virus (AAV)-mediated gene transfer were used together in the present study.

RESULTS

It was found that escitalopram administration not only significantly prevented the hyperactivity of the hypothalamic-pituitary-adrenal (HPA) axis induced by CSDS and CUMS, but also notably reversed the effects of CSDS and CUMS on SIK1, CRTC1, and CRTC1-CREB binding in the PVN of mice. AAV-based genetic knock-down of SIK1 in PVN neurons evidently abolished the antidepressant-like effects of escitalopram in mice.

LIMITATION

A shortage of this study is that only rodent models of depression were used, while human samples were not included.

CONCLUSIONS

In summary, regulating the SIK1-CRTC1 system in the PVN participates in the antidepressant mechanism of escitalopram, which extends the knowledge of the pharmacological actions of escitalopram.

SARS-CoV-2 envelope protein triggers depression-like behaviors and dysosmia via TLR2-mediated neuroinflammation in mice

BACKGROUND

Depression and dysosmia have been regarded as primary neurological symptoms in COVID-19 patients, the mechanism of which remains unclear. Current studies have demonstrated that the SARS-CoV-2 envelope (E) protein is a pro-inflammatory factor sensed by Toll-like receptor 2 (TLR2), suggesting the pathological feature of E protein is independent of viral infection. In this study, we aim to ascertain the role of E protein in depression, dysosmia and associated neuroinflammation in the central nervous system (CNS).

METHODS

Depression-like behaviors and olfactory function were observed in both female and male mice receiving intracisternal injection of E protein. Immunohistochemistry was applied in conjunction with RT-PCR to evaluate glial activation, blood-brain barrier status and mediators synthesis in the cortex, hippocampus and olfactory bulb. TLR2 was pharmacologically blocked to determine its role in E protein-related depression-like behaviors and dysosmia in mice.

RESULTS

Intracisternal injection of E protein evoked depression-like behaviors and dysosmia in both female and male mice. Immunohistochemistry suggested that the E protein upregulated IBA1 and GFAP in the cortex, hippocampus and olfactory bulb, while ZO-1 was downregulated. Moreover, IL-1β, TNF-α, IL-6, CCL2, MMP2 and CSF1 were upregulated in both cortex and hippocampus, whereas IL-1β, IL-6 and CCL2 were upregulated in the olfactory bulb. Furtherly, inhibiting microglia, rather than astrocytes, alleviated depression-like behaviors and dysosmia induced by E protein. Finally, RT-PCR and immunohistochemistry suggested that TLR2 was upregulated in the cortex, hippocampus and olfactory bulb, the blocking of which mitigated depression-like behaviors and dysosmia induced by E protein.

CONCLUSIONS

Our study demonstrates that envelope protein could directly induce depression-like behaviors, dysosmia, and obvious neuroinflammation in CNS. TLR2 mediated depression-like behaviors and dysosmia induced by envelope protein, which could serve as a promising therapeutic target for neurological manifestation in COVID-19 patients.

The salt-inducible kinases inhibitor HG-9-91-01 exhibits antidepressant-like actions in mice exposed to chronic unpredictable mild stress

Major depressive disorder is a frequently occurring neuropsychiatric disorder throughout the world. However, the limited and delayed therapeutic efficacy of monoaminergic medications has led to intensive research efforts to develop novel antidepressants. We have previously demonstrated that hippocampal salt-inducible kinase 2 (SIK2) plays a role in the pathogenesis of depression via regulating the downstream CREB-regulated transcription coactivator 1 (CRTC1)-cAMP response element-binding protein (CREB)-brain derived neurotrophic factor (BDNF) pathway. HG-9-91-01 is a potent and selective inhibitor of salt-inducible kinases (SIKs). The present study aims to explore whether HG-9-91-01 has antidepressant-like actions in male C57BL/6J mice. The chronic unpredictable mild stress (CUMS) model of depression, various behavioral tests, western blotting, co-immunoprecipitation, immunofluorescence, stereotactic infusion, and viral-mediated genetic knockdown were used together. It was found that hippocampal infusion of HG-9-91-01 induced significant antidepressant-like effects in the CUMS model, accompanied with preventing the enhancement of CUMS on the hippocampal SIK2 expression and cytoplasmic translocation of CRTC1. HG-9-91-01 treatment also reversed the decreasing effects of CUMS on the BDNF signaling cascade and adult neurogenesis in the hippocampus. Moreover, the antidepressant-like actions of HG-9-91-01 in mice required the hippocampal CRTC1-CREB-BDNF pathway. In conclusion, HG-9-91-01 has potential of being a novel antidepressant candidate.

The Mechanisms Underlying the Pharmacological Effects of GuiPi Decoction on Major Depressive Disorder based on Network Pharmacology and Molecular Docking

BACKGROUND AND AIM

Major Depressive Disorder (MDD) is a common affective disorder. GuiPi decoction (GPD) is used to treat depression in China, Japan, and Korea. However, its effective ingredients and antidepressant mechanisms remain unclear. We attempted to reveal the potential mechanisms of GPD in the treatment of MDD by network pharmacology and molecular docking. In addition, we conducted an enzymatic activity assay to validate the results of molecular docking.

METHODS

GPD-related compounds and targets, and MDD-related targets were retrieved from databases and literature. The herb-compound-target network was constructed by Cytoscape. The protein- protein interaction network was built using the STRING database to find key targets of GPD on MDD. Enrichment analysis of shared targets was analyzed by MetaCore database to obtain the potential pathway and biological process of GPD on MDD. The main active compounds treating MDD were screened by molecular docking. The PDE4s inhibitors were screened and verified by an enzyme activity assay.

RESULTS

GPD contained 1222 ingredients and 190 potential targets for anti-MDD. Possible biological processes regulated by GPD were neurophysiological processes, blood vessel morphogenesis, Camp Responsive Element Modulator (CREM) pathway, and Androgen Receptor (AR) signaling crosstalk in MDD. Potential pathways in MDD associated with GPD include neurotransmission, cell differentiation, androgen signaling, and estrogen signaling. Fumarine, m-cresol, quercetin, betasitosterol, fumarine, taraxasterol, and lupeol in GPD may be the targets of SLC6A4, monoamine oxidase A (MAOA), DRD2, OPRM1, HTR3A, Albumin (ALB), and NTRK1, respectively. The IC50 values of trifolin targeting Phosphodiesterase (PDE) 4A and girinimbine targeting PDE4B1 were 73.79 μM and 31.86 μM, respectively. The IC50 values of girinimbine and benzo[a]carbazole on PDE4B2 were 51.62 μM and 94.61 μM, respectively.

CONCLUSION

Different compounds in GPD may target the same protein, and the same component in GPD can target multiple targets. These results suggest that the effects of GPD on MDD are holistic and systematic, unlike the pattern of one drug-one target.

Cordycepin improved neuronal synaptic plasticity through CREB-induced NGF upregulation driven by MG-M2 polarization: a microglia-neuron symphony in AD

PURPOSE

Microglia-neuron crosstalk is critically involved in synaptic plasticity and degeneration by releasing diverse mediators in Alzheimer's disease (AD). Therefore, determining contributors that modulate the systemic microenvironment is essential. Cordycepin (CCS) is a novel neuroprotective compound obtained from Cordyceps militaris. However, the anti-AD efficacy and potential mechanism of CCS treatment remain unclear. This study aimed to elucidate the microglia-neuron symphony in AD after CCS treatment and to explore the possible mechanisms of its neuroprotective efficacy.

METHODS AND RESULTS

CCS treatment improved learning and memory impairment in 9-month-old APP/PS1 mice by behavioral tests. CCS polarized the microglia from M1 to M2, inhibited neuronal apoptosis and promoted synaptic remodeling accompanied by in vivo and in vitro upregulation of NGF. The cAMP-response element-binding protein (CREB) was also activated after MG-M2 polarization. Further, we verified that the sg3 promoter region of NGF (-1018 to -1011) is the key binding site for CREB-induced NGF transcription, which increased NGF expression and secretion. Finally, microglia-derived NGF was confirmed as an important mediator in microglia-neuron symphony to improve the neuronal microenvironment after CCS treatment.

CONCLUSIONS

CCS improved the neuronal synaptic plasticity and senescence by promoting MG-M2 activation driven by CREB-induced NGF upregulation and facilitated symphony communication between the microglia and neuron in AD. This study provides a new perspective on the development of a novel strategy for anti-AD therapy and offers new targets for anti-AD drug development.

Salt-inducible kinase 1-CREB-regulated transcription coactivator 1 signalling in the paraventricular nucleus of the hypothalamus plays a role in depression by regulating the hypothalamic-pituitary-adrenal axis

Elucidating the molecular mechanism underlying the hyperactivity of the hypothalamic-pituitary-adrenal axis during chronic stress is critical for understanding depression and treating depression. The secretion of corticotropin-releasing hormone (CRH) from neurons in the paraventricular nucleus (PVN) of the hypothalamus is controlled by salt-inducible kinases (SIKs) and CREB-regulated transcription co-activators (CRTCs). We hypothesised that the SIK-CRTC system in the PVN might contribute to the pathogenesis of depression. Thus, the present study employed chronic social defeat stress (CSDS) and chronic unpredictable mild stress (CUMS) models of depression, various behavioural tests, virus-mediated gene transfer, enzyme-linked immunosorbent assay, western blotting, co-immunoprecipitation, quantitative real-time reverse transcription polymerase chain reaction, and immunofluorescence to investigate this connection. Our results revealed that both CSDS and CUMS induced significant changes in SIK1-CRTC1 signalling in PVN neurons. Both genetic knockdown of SIK1 and genetic overexpression of CRTC1 in the PVN simulated chronic stress, producing a depression-like phenotype in naive mice, and the CRTC1-CREB-CRH pathway mediates the pro-depressant actions induced by SIK1 knockdown in the PVN. In contrast, both genetic overexpression of SIK1 and genetic knockdown of CRTC1 in the PVN protected against CSDS and CUMS, leading to antidepressant-like effects in mice. Moreover, stereotactic infusion of TAT-SIK1 into the PVN also produced beneficial effects against chronic stress. Furthermore, the SIK1-CRTC1 system in the PVN played a role in the antidepressant actions of fluoxetine, paroxetine, venlafaxine, and duloxetine. Collectively, SIK1 and CRTC1 in PVN neurons are closely involved in depression neurobiology, and they could be viable targets for novel antidepressants.

SVCT2-mediated ascorbic acid uptake buffers stress responses via DNA hydroxymethylation reprogramming of S100 calcium-binding protein A4 gene

Vitamin C, a key antioxidant in the central nervous system, cycles between ascorbic acid and dehydroascorbic acid under pathophysiological conditions. Clinical evidence supports that the absence of vitamin C may be linked to depressive symptoms, but much less is known about the mechanism. Herein, we show that chronic stress disrupts the expression of ascorbic acid transporter, sodium-dependent vitamin C transport 2, and induces a deficiency in endogenous ascorbic acid in the medial prefrontal cortex, leading to depressive-like behaviors by disturbing redox-dependent DNA methylation reprogramming. Attractively, ascorbic acid (100 mg/kg-1000 mg/kg, intraperitoneal injection, as bioequivalent of an intravenous drip dose of 0.48 g-4.8 g ascorbic acid per day in humans) produces rapid-acting antidepressant effects via triggering DNA demethylation catalyzed by ten-eleven translocation dioxygenases. In particular, the mechanistic studies by both transcriptome sequencing and methylation sequencing have shown that S100 calcium binding protein A4, a potentially protective factor against oxidative stress and brain injury, mediates the antidepressant activity of ascorbic acid via activating erb-b2 receptor tyrosine kinase 4 (ErbB4)-brain derived neurotrophic factor (BDNF) signaling pathway. Overall, our findings reveal a novel nutritional mechanism that couples stress to aberrant DNA methylation underlying depressive-like behaviors. Therefore, application of vitamin C may be a potential strategy for the treatment of depression.

Jujuboside B Reverse CUMS-Promoted Tumor Progression via Blocking PI3K/Akt and MAPK/ERK and Dephosphorylating CREB Signaling

Background

Jujuboside B (JUB) is a saponins isolated from the seeds of Zizyphi jujuba var. spinosi, which is used to treat mental illness and is reported recently to induce cancer cell apoptosis. As our previous research showed chronic stress promoted tumor growth, this work aims to investigate whether JUB exert antitumor effect in addition to its antidepressant effect and possible mechanism.

Methods

56 female C57BL/6 mice were grouped into 7 groups: A (blank control), B (tumor-bearing control), C (tumor-bearing + JUB), D (CUMS control), E (CUMS + JUB), F (tumor-bearing + CUMS), and G (tumor-bearing + CUMS + JUB). Groups C, E, G, B, D, and F were administered, respectively, with JUB (40 mg/kg/day) or vehicle for 2 weeks. Serum 5-HT, Trp (tryptophane), inflammatory cytokines TNF-α, IL-4, -6, and -10 levels were detected by ELISA. The tumors in groups B and F were isolated for RNA-seq sequencing. Protein and mRNA expression of Bax, Bcl-2, p-PI3K, p-Akt, p-MAPK, p-ERK, and p-CREB in tumor tissues were detected. In vitro, A549 cells were stimulated with JUB (60 μmol/L), in which proliferation rate and colony formation rate were detected. The PI3K/Akt and, MAPK/ERK pathway were measured.

Results

Chronic stress successfully induced the depression-like phenotype (group D vs. A) and promoted tumor growth (group B vs. F). JUB significantly ameliorated the depression-like phenotype and increased 5-HT, Trp levels (group D vs. E), and reversing CUMS-induced tumor progression. Meanwhile, JUB decreased inflammatory cytokine levels. Chronic stress upregulated the phosphorylation levels of PI3K/Akt/MAPK/ERK/CREB; JUB reversed this regulation. JUB significantly inhibited cell viability, colony formation rate, and downregulated the phosphorylation levels of PI3K/Akt/MAPK/ERK/CREB in vitro.

Conclusions

JUB reverses CUMS-promoted tumor progression in tumor-bearing mice with depression-like phenotype. JUB exerts the dual beneficial effect on tumor growth and depression-like phenotype by blocking the signal transduction pathway of PI3K/Akt, MAPK/ERK, and dephosphorylating the downstream signaling regulator CREB.

Ginsenoside Rh2 administration produces crucial antidepressant-like effects in a CUMS-induced mice model of depression

INTRODUCTION

The most striking feature of depression is sadness and a loss of interest in activities, which represents a major cause of disability globally. Therefore, it is necessary to identify novel antidepressants for clinical practice. Ginsenoside Rh2 (Rh2) is one of the major bioactive ginsenosides that can be extracted from Panax ginseng and has been demonstrated to improve both memory and learning. The purpose of this study was to provide broad insight into the mechanisms underlying depression and gain greater insights into antidepressant therapy.

METHODS

In this study, we first established an effective and feasible depression animal model of chronic unpredictable mild stress (CUMS) and behavioral testing was evaluated by the forced swim test (FST), the tail suspension test (TST) and the sucrose preference test. Following pretreatment with Rh2 (10 and 20 mg/kg), the immobility time of mice was reduced without affecting locomotor activity in both the FST and TST. Western blotting and immunofluorescence were used to investigate the activation of the hippocampal BDNF signaling pathway and hippocampal neurogenesis.

RESULTS

Different concentrations of Rh2 significantly reduced depressive-like symptoms in CUMS-induced mice and downregulated the effects of the BDNF signaling cascade and neurogenesis in the hippocampus. Furthermore, the administration of K252a completely prevented the antidepressant-like activity of Rh2 in mice.

CONCLUSION

The results indicated that Rh2 possesses the antidepression action via the positive regulation of the BDNF-TrkB pathway.

Antidepressant-like activity of oroxylin A in mice models of depression: A behavioral and neurobiological characterization

Depression is a mood disorder which causes a huge economic burden to both families and societies. However, those monoamine-based antidepressants used in clinical practice have been found to have various limitations. Therefore, currently it is very necessary to explore novel antidepressant targets and medications. As a main active component extracted from Scutellariae radix, oroxylin A possesses many pharmacological functions such as anti-cancer, anti-inflammation and neuroprotection. Here, the present study aims to investigate whether oroxylin A possess antidepressant-like actions using the chronic unpredictable mild stress (CUMS) and chronic restraint stress (CRS) models of depression, forced swim test, tail suspension test, open field test, sucrose preference test, western blotting, immunofluorescence and viral-mediated gene interference. Our results revealed that treatment of oroxylin A fully prevented both the CUMS-induced and CRS-induced depressive-like behaviors in mice. Moreover, the protecting effects of oroxylin A against CUMS and CRS on mice behaviors were accompanied with a significant enhancement on the levels of brain-derived neurotrophic factor (BDNF), phosphorylated tyrosine kinase B (pTrkB), phosphorylated cAMP-response element binding protein (pCREB) and neurogenesis in the hippocampus. Furthermore, genetic knockdown of BDNF and TrkB in the hippocampus remarkably abolished the antidepressant-like efficacy of oroxylin A in both the CUMS and CRS models of depression, proving that the hippocampal BDNF-TrkB system participates in the antidepressant mechanism of oroxylin A. In summary, our findings are the first evidence showing that oroxylin A possesses potential of being an antidepressant candidate.

Mongolian Medicine Areca Thirteen Pill (GY-13) Improved Depressive Syndrome via upregulating cAMP/PKA/CREB/BDNF signaling pathway

ETHNOPHARMACOLOGICAL RELEVANCE

Areca Thirteen Pill, also called Gao You-13 (GY-13), is a traditional Mongolian herbal formula and has been extensively used to treat depression in Mongolian areas, which belongs to Heyi disease in Mongolian medicine. Major depressive disorder is a serious psychiatric disease, only one-third of individuals with depression are responsive to current antidepressants in clinic. Growing attention has been attracted by traditional herbal medicines in fighting depression because they are considered safer alternatives to pharmacotherapy.

AIM OF THE STUDY

To reveal the mechanism of GY-13 in the treatment of depression.

MATERIALS AND METHODS

The rat depression model was established by chronic unpredictable mild stress (CUMS), and primary hippocampal neurons were used to construct a glutamate-induced excitotoxicity model. The antidepressant effect of GY-13 was then assessed by performing sucrose preference tests, open field tests, and body weight measurements on rats. The expression of cAMP and PKA, mRNA levels of brain-derived neurotrophic factor (BDNF) and cAMP response element binding protein (CREB), and hippocampal neuronal apoptosis were measured.

RESULTS

The results indicate that GY-13 significantly improves depression-like behavior, rescues decreased cAMP， PKA, recovers the mRNA levels of CREB and BDNF, and increases the proliferative activity of hippocampus. In addition, blockade of PKA reverses the effects of GY-13 treatment on CREB mRNA, BDNF mRNA levels. In vitro, GY-13 treatment increased hippocampal proliferative activity and attenuated Glu-induced apoptosis of hippocampal neurons as well as reduced CREB mRNA and BDNF mRNA expression levels.

CONCLUSIONS

Our research demonstrated that GY-13 treatment exerted a potent antidepressant action via activation of cAMP/CREB/BDNF signaling pathway, promoting proliferation, and suppressing apoptosis. This research provides molecular biological ground for developing GY-13 into a potent alternative for the intervention of depression.

Microglia in depression: an overview of microglia in the pathogenesis and treatment of depression

Major depressive disorder is a highly debilitating psychiatric disorder involving the dysfunction of different cell types in the brain. Microglia are the predominant resident immune cells in the brain and exhibit a critical role in depression. Recent studies have suggested that depression can be regarded as a microglial disease. Microglia regulate inflammation, synaptic plasticity, and the formation of neural networks, all of which affect depression. In this review, we highlighted the role of microglia in the pathology of depression. First, we described microglial activation in animal models and clinically depressed patients. Second, we emphasized the possible mechanisms by which microglia recognize depression-associated stress and regulate conditions. Third, we described how antidepressants (clinical medicines and natural products) affect microglial activation. Thus, this review aimed to objectively analyze the role of microglia in depression and focus on potential antidepressants. These data suggested that regulation of microglial actions might be a novel therapeutic strategy to counteract the adverse effects of devastating mental disorders.

Downregulation of CRTC1 Is Involved in CUMS-Induced Depression-Like Behavior in the Hippocampus and Its RNA Sequencing Analysis

Chronic stress is an important risk factor for mood disorders including depression. The decreased level of CREB (cAMP-responsive element binding)-regulated transcription coactivator 1 (CRTC1) expression in hippocampus may be involved in depression-like behavior in some stress-induced depression models. But the mechanism of CRTC1 in mediating depression-like behavior remains unknown. In this study, chronic unpredictable mild stress (CUMS)-treated mice showed depression-like behavior accompanied by the downregulation of CRTC1 in the hippocampus. Adeno-associated virus (AAV)-CRTC1-mediated overexpression of CRTC1 in the hippocampus by stereotactic brain injection could significantly prevent depression-like behavior in CUMS-treated mice. The above data reveal that the downregulation of hippocampal CRTC1 expression participates in CUMS-induced depression-like behavior. In order to explore the key targets regulated by CRTC1, AAV-mediated CRTC1 short hairpin (shRNA) was constructed to achieve knockdown of CRTC1 in the hippocampus, and then the hippocampi were collected for RNA-sequencing (RNA-seq). The RNA-seq data show that upregulated genes were enriched in stress and immune system-associated GO terms and pathways such as response to stress and external stimulus and regulation of immune response and that downregulated genes were enriched in neural activity such as synaptic transmission and cognitive behavior. We further provided RT-qPCR data that the inflammation-related factors including Gpr84, Tlr2, Lyz2, and Icam1 were significantly upregulated in the hippocampus of both CUMS- and CRTC1 shRNA-induced models, some of them were also validated in protein levels by Western blotting. We propose a hypothesis that CUMS induces downregulation of CRTC1, which might lead to depression-like behavior via neuroinflammation pathway. This study provides new explanation for the inflammatory hypothesis of depression and some clues for exploring the molecular mechanism of CRTC1 regulation.

Salt-inducible kinase 2 (SIK2) inhibitor ARN-3236 attenuates bleomycin-induced pulmonary fibrosis in mice

Background

Pulmonary fibrosis is a fatal lung disease with complex pathogenesis and limited effective therapies. Salt-inducible kinase 2 (SIK2) is a kinase that phosphorylates CRTCs and regulates many physiological processes. However, the role of SIK2 on pulmonary fibrosis remains unclear, and whether SIK2 inhibitor can attenuate pulmonary fibrosis is unknown.

Method

We subjected human fetal lung fibroblasts (HFLs) to transforming growth factor-β1 (5 ng/mL) for 12 h, and examined the expression of SIK2, CRTCs and pCRTCs in fibroblasts by western-blot. To address the roles of SIK2 and CRTCs involved in the progression of pulmonary fibrosis, HFLs were treated with a small-molecule inhibitor ARN-3236 or by siRNA-mediated knockdown of SIK2 expression. Pulmonary fibrosis model was established with mice by exposing to bleomycin, and assessed by H&E and Masson’s trichrome staining. COL1A and α-SMA distributions were detected in lung tissues by immunohistochemical staining.

Results

We discovered that SIK2 and phosphorylated-CRTC2 were expressed at a low basal level in normal lung tissues and quiescent fibroblasts, but increased in fibrotic lung tissues and activated fibroblasts. Inhibition of SIK2 by ARN-3236 prevented the fibroblasts differentiation and extracellular matrix expression in HFLs and attenuated bleomycin-induced pulmonary fibrosis in mice. Mechanistically, inactivation of SIK2 resulted in the dephosphorylation and nuclear translocation of CRTC2. Within the nucleus, CRTC2 binds to CREB, promoting CREB-dependent anti-fibrotic actions.

Conclusion

In conclusion, our results elucidated a previously unexplored role of SIK2 in pulmonary fibrosis, and identified SIK2 as a new target for anti-fibrosis medicines.

The antidepressant-like effect of formononetin on chronic corticosterone-treated mice

Previous studies reported the neuroprotective effects of formononetin (FMN), however, whether it has antidepressant-like effects have not been reported. To evaluate the antidepressant-like effects of FMN, a mice model of depression was established by chronic corticosterone (CORT) injection. The serum corticosterone levels and hippocampal protein expression were detected by ELISA and Western blot. Nissl staining was used to observe the damage of hippocampal neurons and immunofluorescence was used to observe the neurogenesis in the hippocampus. Our results showed that FMN significantly increased the sucrose preference and shorten the immobility time in the forced swimming test in CORT-treated mice. Moreover, FMN reduced the serum corticosterone levels, upregulated the protein expression levels of the glucocorticoid receptor (GR), and brain-derived neurotrophic factor (BDNF) in the hippocampus, protected against the CORT-induced neuronal impairment, and promoted the neurogenesis in the hippocampus. Taken together, the present study was the first to demonstrate the antidepressant-like effects of FMN in the CORT-induced mice model of depression, which may contribute to the discovery of a new candidate for treating depression.

Hippocampal NR6A1 impairs CREB-BDNF signaling and leads to the development of depression-like behaviors in mice

Chronic stress exposure is a risk factor that can induce the development of depression-like behaviors by impairing the hippocampal cyclic adenosine monophosphate-response element binding protein (CREB)-brain-derived neurotrophic factor (BDNF) signaling, but its underlying mechanisms remain largely unknown. We identified an orphan receptor that can suppress the activity of CREB, nuclear receptor sub-family 6, group A, member 1 (NR6A1), in mouse brain neurons. Given the critical role of the impaired CREB-BDNF signaling in depression, we speculate that the neuronal NR6A1 may mediate the pathogenesis of depression. Results showed that chronic unpredictable stress (CUS) markedly increased the expression levels of hippocampal NR6A1 protein, which reduced hippocampal CREB phosphorylation and BDNF protein expression. Overexpression of hippocampal NR6A1 in stress-naïve mice simulated chronic stress, inducing depression-like behaviors in the tail suspension test, forced swimming test, and sucrose preference test, and impairing the hippocampal CREB-BDNF signaling cascade. Genetic knockdown of hippocampal NR6A1 did not affect mouse behaviors but prevented the CUS-induced depression-like behaviors in mice and impairment in hippocampal CREB-BDNF signaling. Furthermore, genetic knockdown of hippocampal CREB or BDNF abrogated the preventive effect of hippocampal NR6A1 down-regulation on CUS-induced depression-like behaviors in mice. Collectively, these results for the first time identified a nuclear expression of NR6A1 in mouse brain neurons, and showed that the abnormally increased NR6A1 protein in the hippocampus in mice treated with or without chronic stress can impair the CREB-BDNF signaling cascade and lead to the development of depression-like behaviors. Hippocampal NR6A1 could be a novel target for the development of antidepressants.

New Insights Into the Pivotal Role of CREB-Regulated Transcription Coactivator 1 in Depression and Comorbid Obesity

Depression and obesity are major public health concerns, and there is mounting evidence that they share etiopathophysiological mechanisms. The neurobiological pathways involved in both mood and energy balance regulation are complex, multifactorial and still incompletely understood. As a coactivator of the pleiotropic transcription factor cAMP response element-binding protein (CREB), CREB-regulated transcription coactivator 1 (CRTC1) has recently emerged as a novel regulator of neuronal plasticity and brain functions, while CRTC1 dysfunction has been associated with neurodegenerative and psychiatric diseases. This review focuses on recent evidence emphasizing the critical role of CRTC1 in the neurobiology of depression and comorbid obesity. We discuss the role of CRTC1 downregulation in mediating chronic stress-induced depressive-like behaviors, and antidepressant response in the light of the previously characterized Crtc1 knockout mouse model of depression. The putative role of CRTC1 in the alteration of brain energy homeostasis observed in depression is also discussed. Finally, we highlight rodent and human studies supporting the critical involvement of CRTC1 in depression-associated obesity.

Hippocampal MSK1 regulates the behavioral and biological responses of mice to chronic social defeat stress: Involving of the BDNF-CREB signaling and neurogenesis

Depression is one of the most common psychiatric diseases in the 21st century, while its pathogenesis is not yet fully understood. Currently, besides to the monoaminergic system, the brain-derived neurotrophic factor (BDNF)-cAMP response element-binding protein (CREB) signaling is one of the most attractive signaling pathways for treating depression. Mitogen and stress-activated kinase (MSK) 1 and 2 are nuclear proteins activated downstream of the ERK1/2 or p38 MAPK pathways, and it has been demonstrated that MSKs are involved in the BDNF-CREB signaling. Here we assumed that MSKs may play a role in depression, and various methods including the chronic social defeat stress (CSDS) model of depression, western blotting, immunofluorescence and virus-mediated gene transfer were used together. It was found that CSDS fully enhanced the expression of both phosphorylated MSK1 and total MSK1 in the hippocampus but not the medial prefrontal cortex (mPFC). CSDS did not influence the expression of phosphorylated MSK2 and total MSK2 in the two brain regions. Genetic over-expression of hippocampal MSK1 fully prevented not only the CSDS-induced depressive-like behaviors but also the CSDS-induced dysfunction in the hippocampal BDNF-CREB signaling and neurogenesis in mice, while genetic knockdown of hippocampal MSK1 aggravated the CSDS-induced depressive-like symptomatology in mice. Our results collectively suggest that although CSDS evidently enhances the activity of hippocampal MSK1, it is not a contributor to the CSDS-induced dysfunction in the brain but a defensive feedback regulator which protects against CSDS. Therefore, hippocampal MSK1 participates in the pathogenesis of depression and is a feasible and potential antidepressant target.

Deletion of Crtc1 leads to hippocampal neuroenergetic impairments associated with depressive-like behavior

Mood disorders (MD) are a major burden on society as their biology remains poorly understood, challenging both diagnosis and therapy. Among many observed biological dysfunctions, homeostatic dysregulation, such as metabolic syndrome (MeS), shows considerable comorbidity with MD. Recently, CREB-regulated transcription coactivator 1 (CRTC1), a regulator of brain metabolism, was proposed as a promising factor to understand this relationship. Searching for imaging biomarkers and associating them with pathophysiological mechanisms using preclinical models can provide significant insight into these complex psychiatric diseases and help the development of personalized healthcare. Here, we used neuroimaging technologies to show that deletion of Crtc1 in mice leads to an imaging fingerprint of hippocampal metabolic impairment related to depressive-like behavior. By identifying a deficiency in hippocampal glucose metabolism as the underlying molecular/physiological origin of the markers, we could assign an energy-boosting mood-stabilizing treatment, ebselen, which rescued behavior and neuroimaging markers. Finally, our results point toward the GABAergic system as a potential therapeutic target for behavioral dysfunctions related to metabolic disorders. This study provides new insights on Crtc1's and MeS's relationship to MD and establishes depression-related markers with clinical potential.

MiRNA-132/212 regulates tight junction stabilization in blood-brain barrier after stroke

MicroRNA-132/212 has been supposed as a critical gene related to the blood–brain barrier (BBB) protection after stroke, but its regulation pathway including the upstream regulator and downstream targets is still unclear. Herein, we demonstrated the cAMP response element-binding protein (CREB)-regulated transcription coactivator-1 (CRTC1) to be the upstream regulator of miRNA-132/212 using CRTC1 knockout and wild-type mice. CRTC1 deletion led to the reduction of miRNA-132/212 expression in mice brain after ischemic stroke, significantly increased infarct volume, and aggravated BBB permeability with worsening neurological deficits. Furthermore, we identified that miRNA-132 repressed Claudin-1, tight junction-associated protein-1 (TJAP-1), and RNA-binding Fox-1 (RBFox-1) by directly binding to their respective 3′-untranslated regions, which alleviated the ischemic damage by enhancing neuronal survival and BBB integrity. Moreover, the co-culture of endothelial cells with CRTC1-deficient neurons aggravated the cell vulnerability to hypoxia, also supporting the idea that miRNA-132/212 cluster is regulated by CRTC1 and acts as a crucial role in the mitigation of ischemic damage. This work is a step forward for understanding the role of miRNA-132/212 in neurovascular interaction and may be helpful for potential gene therapy of ischemic stroke.

Hippocampal miR-206-3p participates in the pathogenesis of depression via regulating the expression of BDNF

As a widely-known neuropsychiatric disorder, the exact pathogenesis of depression remains elusive. MiRNA-206 (miR-206) is conventionally known as one of the myomiRs and has two forms: miR-206-3p and miR-206-5p. Recently, miR-206 has been demonstrated to regulate the biosynthesis of brain-derived neurotrophic factor (BDNF), a very popular target involved in depression and antidepressant responses. Here we assumed that miR-206 may play a role in depression, and various methods including the chronic social defeat stress (CSDS) model of depression, quantitative real-time reverse transcription PCR, western blotting, immuofluorescence and virus-mediated gene transfer were used together. It was found that CSDS robustly increased the level of miR-206-3p but not miR-206-5p in the hippocampus. Both genetic overexpression of hippocampal miR-206-3p and intranasal administration of AgomiR-206-3p induced not only notable depressive-like behaviors but also significantly decreased hippocampal BDNF signaling cascade and neurogenesis in naïve C57BL/6J mice. In contrast, both genetic knockdown of hippocampal miR-206-3p and intranasal administration of AntagomiR-206-3p produced significant antidepressant-like effects in the CSDS model of depression. Furthermore, it was found that the antidepressant-like effects induced by miR-206-3p inhibition require the hippocampal BDNF-TrkB system. Taken together, hippocampal miR-206-3p participates in the pathogenesis of depression by regulating BDNF biosynthesis and is a feasible antidepressant target.

Fluoride Stimulates Anxiety- and Depression-like Behaviors Associated with SIK2-CRTC1 Signaling Dysfunction

Using Sprague-Dawley rats and rat PC12 cells treated with sodium fluoride (NaF), we investigated the effects of SIK2-CRTC1 signaling on the neurobehavioral toxicity induced by fluoride. The in vivo results demonstrated that NaF treatment induced anxiety- and depression-like behaviors in juvenile rats, resulting in histological and ultrastructural abnormalities in the rat hippocampus and medial prefrontal cortex. Moreover, NaF exposure induced neuronal loss and excessive apoptosis. We also found that NaF elevated the expression of SIK2 and reduced the expression of CRTC1, brain-derived neurotrophic factor (BDNF), and VGF. The in vitro results showed that NaF suppressed cell viability, induced SIK2-CRTC1 signaling dysfunction, and caused excessive apoptosis in PC12 cells. Notably, targeted knockout of SIK2 with SIK2-siRNA or blocking of SIK2-CRTC1 signaling with 7,8-dihydroxyflavone (7,8-DHF) (as well as venlafaxine) can reduce apoptosis and increase cell viability in vitro. These findings suggest that neuronal death resulting from abnormal SIK2-CRTC1 signaling contributes to neurobehavioral toxicity induced by fluoride.

Brain-derived neurotrophic factor upregulates synaptic GluA1 in the amygdala to promote depression in response to psychological stress

Psychological stress impairs neuronal structure and function and leads to emotional disorders, but the underlying mechanisms have not yet been fully elucidated. The amygdala is closely correlated with emotional regulation. In the present study, we analyzed whether the amygdala plasticity is regulated by psychological stress and explored their regulatory mechanism. We established a mouse psychological stress model using an improved communication box, wherein mice were exposed to chronic fear and avoided physical stress interference. After the 14-day psychological stress paradigm, mice exhibited significantly increased depressive behaviors (decreased sucrose consumption in the sucrose preference test and longer immobility time in the forced swimming test). HPLC, ELISA, and molecular and morphological evidences showed that psychological stress increased the content of glutamate and the expression of glutamatergic neurons, upregulated the content of the stress hormone corticosterone, and activated the CREB/BDNF pathway in the amygdala. Furthermore, psychological stress induced an increased density of dendritic spines and LTD impairment in the amygdala. Importantly, virus-mediated silencing of BDNF in the basolateral amygdala (BLA) nuclei reversed the depression-like behaviors and the increase of synaptic GluA1 and its phosphorylation at Ser831 and Ser845 sites in psychologically stressed mice. This process was likely achieved through mTOR signaling activation. Finally, we treated primary amygdala neurons with corticosterone to mimic psychological stress; corticosterone-induced upregulation of GluA1 was prevented by BDNF and mTOR antagonists. Thus, activation of the CREB/BDNF pathway in the amygdala following psychological stress upregulates synaptic GluA1 via mTOR signaling, which dysregulates synaptic plasticity of the amygdala, eventually promoting depression.

Hippocampal PPARα Plays a Role in the Pharmacological Mechanism of Vortioxetine, a Multimodal-Acting Antidepressant

As a well-known multimodal-acting antidepressant, vortioxetine is thought to aim at several serotonin (5-HT) receptors and the 5-HT transporter. However, recently more and more proteins besides 5-HT are being reported to participate in the antidepressant mechanism of vortioxetine. As a widely known nuclear hormone receptor, peroxisome proliferator activated receptor α (PPARα) possesses transcriptional activity and is very important in the brain. Several reports have suggested that hippocampal PPARα is implicated in antidepressant responses. Here we speculate that hippocampal PPARα may participate in the antidepressant mechanism of vortioxetine. In this study, chronic unpredictable mild stress (CUMS), chronic social defeat stress (CSDS), behavioral tests, the western blotting and adenovirus associated virus (AAV)-mediated gene knockdown methods were used together. It was found that vortioxetine administration significantly reversed the inhibitory actions of both CUMS and CSDS on the hippocampal PPARα expression. Pharmacological blockade of PPARα notably prevented the antidepressant actions of vortioxetine in the CUMS and CSDS models. Moreover, genetic knockdown of PPARα in the hippocampus also significantly blocked the protecting effects of vortioxetine against both CUMS and CSDS. Therefore, the antidepressant effects of vortioxetine in mice require hippocampal PPARα.

Down-regulation of MST1 in hippocampus protects against stress-induced depression-like behaviours and synaptic plasticity impairments

Depression is a common mental disorder, and its main environmental risk factor is chronic stress. The activation of mammalian STE20-like kinase 1 (MST1), a key factor involved in the underlying pathophysiology of stress, can trigger synaptic plasticity impairment, neuronal dysfunction and neuroinflammation. However, it is unclear whether down-regulation of MST1 in the hippocampus protects against stress-induced behavioural dysfunctions. In this study, three mouse models were used to assess the role of MST1 in stress. Various behavioural tests, in vivo electrophysiological recordings, Western blotting, Golgi staining and immunofluorescence assay were used. The data showed that the level of phospho-MST1 (T183) was significantly increased in the hippocampus of mice subjected to chronic unpredictable mild stress (CUMS) and that mice with MST1 overexpression showed depression-like behaviours. Importantly, the impairment of cognitive functions and the hippocampal synaptic plasticity induced by CUMS were significantly improved by MST1 knockdown, suggesting that MST1 down-regulation effectively protected against stress-induced behavioural dysfunctions. Moreover, MST1 knockdown suppressed CUMS-induced microglial activation, reduced the abnormal expression of inflammatory cytokines and impeded the activation of p38, implying that the antidepressant-like effects of MST1 knockdown were associated with inhibiting the p38 pathway. These findings suggest that hippocampal MST1 is an essential regulator of stress, which can be an ideal target for the development of antidepressants in the future.

Nuts and bolts of the salt-inducible kinases (SIKs)

The salt-inducible kinases, SIK1, SIK2 and SIK3, most closely resemble the AMP-activated protein kinase (AMPK) and other AMPK-related kinases, and like these family members they require phosphorylation by LKB1 to be catalytically active. However, unlike other AMPK-related kinases they are phosphorylated by cyclic AMP-dependent protein kinase (PKA), which promotes their binding to 14-3-3 proteins and inactivation. The most well-established substrates of the SIKs are the CREB-regulated transcriptional co-activators (CRTCs), and the Class 2a histone deacetylases (HDAC4/5/7/9). Phosphorylation by SIKs promotes the translocation of CRTCs and Class 2a HDACs to the cytoplasm and their binding to 14-3-3s, preventing them from regulating their nuclear binding partners, the transcription factors CREB and MEF2. This process is reversed by PKA-dependent inactivation of the SIKs leading to dephosphorylation of CRTCs and Class 2a HDACs and their re-entry into the nucleus. Through the reversible regulation of these substrates and others that have not yet been identified, the SIKs regulate many physiological processes ranging from innate immunity, circadian rhythms and bone formation, to skin pigmentation and metabolism. This review summarises current knowledge of the SIKs and the evidence underpinning these findings, and discusses the therapeutic potential of SIK inhibitors for the treatment of disease.

Sigma-1 receptor ligands improves ventricular repolarization-related ion remodeling in rats with major depression disorder

RATIONALE

It has been reported that patients with major depressive disorder (MDD) are prone to developing ventricular arrhythmias. Moreover, the Sigma-1 receptor not only plays a crucial role in MDD but has also been shown to have antiarrhythmic properties. The Sigma-1 receptor is a common receptor related to depression and ventricular arrhythmias.

OBJECTIVE

We analyzed the effects of the Sigma-1 receptor on depression and ventricular repolarization-related ion remodeling in MDD rats.

METHODS

MDD was induced in rats by chronic unpredictable mild stress (CUMS), and 28 days later, the rats were subjected to behavior tests. Protein expression was measured by western blotting, and cardiac morphological changes were observed by Masson staining. Electrophysiological measurement of the myocardium was performed with the whole-cell patch-clamp technique.

RESULTS

Compared with the control rats, the MDD rats exhibited lower transient outward potassium current (Ito) and L-type calcium current (ICa-L) amplitudes. On the other hand, a trend of depolarization of Ito and hyperpolarization of ICa-L was observed in the MDD rats. Thus, we investigated the effect of fluvoxamine, a Sigma-1 receptor agonist, on Ito and ICa-L. Fluvoxamine enhanced Ito and altered its current kinetics, as shown by acceleration of activation and recovery from inactivation. In contrast, fluvoxamine inhibited the Ca2+ by hyperpolarizing the steady-state activation of ICa-L. All these effects were blocked by BD1047.

CONCLUSION

Taken together, our results indicate that Sigma-1 receptor modulates the functions of Ito and ICa-L to possibly exert antiarrhythmic effects.

Wfs1 and Related Molecules as Key Candidate Genes in the Hippocampus of Depression

Background

Depression is a prevalent mental disorder, which is difficult to diagnose and treat due to its unclear pathogenic mechanisms. The discovery of novel and effective therapeutic targets for depression is urgently needed. The hippocampus is a crucial region involved in depression and has been a therapeutic target for many antidepressants. Thus, it is beneficial for comprehensive research to be carried out on the molecular mechanisms of the hippocampus involved in the pathogenesis of depression. This study aims to investigate the differentially expressed genes (DEG) in the hippocampus in a chronic unpredictable mild stress (CUMS) mouse model.

Method

The study obtained GSE84183 from the GEO database. The R language screened the differential expression genes (DEG) in the hippocampus tissue of depressed mice, and the enrichment pathways of DEGs were analyzed. A protein-protein interaction (PPI) network was constructed in the STRING database and visualized in Cytoscape software. MicroRNAs for these DEGs were obtained from TarBase and mortar base databases, and transcription factors (TF) related to DEG were predicted from the ENCODE database. Both networks used the visual analysis platform NetworkAnalyst. Finally, the microRNA-TF network was integrated based on the above two networks and imported into Cytoscape for further analysis.

Results

This study screened 325 differentially expressed genes, containing 42 downregulated genes and 283 upregulated genes. Most of these genes are enriched in the cell cycle and the chemokine signaling pathway. Meanwhile, Wfs1, one of the top ten DEGs, was identified as the key regulator of the cell cycle and the participator in the highest number of modules screened out in PPI networks. Wfs1-related molecules, including UBTF, mmu-mir-17-5p, and mmu-mir-7b-5p, were therefore screened out. Furthermore, we confirmed the downregulation of Wfs1 and upregulation of UBTF/mmu-mir-17-5p/mmu-mir-7b-5p in the hippocampus of the CUMS mouse model. Our data indicate that Wfs1 and related molecules were predicted to be associated with the pathological process of depression. This research provided potential new molecular targets of stress-induced depression.

The Selective SIK2 Inhibitor ARN-3236 Produces Strong Antidepressant-Like Efficacy in Mice via the Hippocampal CRTC1-CREB-BDNF Pathway

Depression is a widespread chronic medical illness affecting thoughts, mood, and physical health. However, the limited and delayed therapeutic efficacy of monoaminergic drugs has led to intensive research efforts to develop novel antidepressants. ARN-3236 is the first potent and selective inhibitor of salt-inducible kinase 2 (SIK2). In this study, a multidisciplinary approach was used to explore the antidepressant-like actions of ARN-3236 in mice. Chronic social defeat stress (CSDS) and chronic unpredictable mild stress (CUMS) models of depression, various behavioral tests, high performance liquid chromatography-tandem mass spectrometry, stereotactic infusion, viral-mediated gene transfer, western blotting, co-immunoprecipitation and immunofluorescence were used together. It was found that ARN-3236 could penetrate the blood-brain barrier. Repeated ARN-3236 administration induced significant antidepressant-like effects in both the CSDS and CUMS models of depression, accompanied with fully preventing the stress-enhanced SIK2 expression and cytoplasmic translocation of cyclic adenosine monophosphate response element binding protein (CREB)-regulated transcription coactivator 1 (CRTC1) in the hippocampus. ARN-3236 treatment also completely reversed the down-regulating effects of CSDS and CUMS on the hippocampal brain-derived neurotrophic factor (BDNF) system and neurogenesis. Moreover, we demonstrated that the hippocampal CRTC1-CREB-BDNF pathway mediated the antidepressant-like efficacy of ARN-3236. Collectively, ARN-3236 possesses strong protecting effects against chronic stress, and could be a novel antidepressant beyond monoaminergic drugs.

Characterization of EGR-1 Expression in the Auditory Cortex Following Kanamycin-Induced Hearing Loss in Mice

Deprivation of acoustic input during a critical period leads to abnormal auditory development in humans. The molecular basis underlying the susceptibility of auditory cortex to loss of afferent input remains largely unknown. The transcription factor early growth response-1 (EGR-1) expression in the visual cortex has been shown to be crucial in the formation of vision, but the role of EGR-1 during the process of auditory function formation is still unclear. In this study, we presented data showing that EGR-1 was expressed in the neurons of the primary auditory cortex (A1) in mice. We observed that the auditory deprivation induced by kanamycin during the auditory critical period leads to laminar-specific alteration of neuronal distribution and EGR-1 expression in A1. In addition, MK-801 administration inhibited the expression of EGR-1 in A1 and aggravated the abnormal cortical electric response caused by kanamycin injection. Finally, we showed that the expression of PI3K, the phosphorylation of Akt, as well as the phosphorylation of cAMP-responsive element-binding protein (CREB) were decreased in A1 after kanamycin-induced hearing loss. These results characterized the expression of EGR-1 in A1 in response to the acoustic input and suggested the involvement of EGR-1 in auditory function formation.

Natural volatile oils derived from herbal medicines: A promising therapy way for treating depressive disorder

Depression is a common global mental disorder that seriously harms human physical and mental health. With the development of society, the increase of pressure and the role of various other factors make the incidence of depression increase year by year. However, there is a lack of drugs that have a fast onset, significant effects, and few side effects. Some volatile oils from traditional natural herbal medicines are usually used to relieve depression and calm emotions, such as Lavender essential oil and Acorus tatarinowii essential oil. It was reported that these volatile oils, are easy to enter the brain through the blood-brain barrier and have good antidepressant effects with little toxicity and side effects. In this review, we summarized the classification of depression, and listed the history of using volatile oils to fight depression in some countries. Importantly, we summarized the anti-depressant natural volatile oils and their monomers from herbal medicine, discussed the anti-depressive mechanisms of the volatile oils from natural medicine. The volatile oils of natural medicine and antidepressant drugs were compared and analyzed, and the application of volatile oils was explained from the clinical use and administration routes. This review would be helpful for the development of potential anti-depressant medicine and provide new alternative treatments for depressive disorders.

Antidepressant-like activity of L-701324 in mice: A behavioral and neurobiological characterization

Antidepressants currently used in clinical practice have limitations such as low efficacy, slow onset and various adverse reactions. It has become necessary to develop novel antidepressants beyond monoaminergic drugs. L-701,324 is a potent NMDA receptor antagonist, and the purpose of this study was to investigate the possible antidepressant effects of L-701,324 in mice. Here, various methods including the forced swim test (FST), tail suspension test (TST), chronic unpredictable mild stress (CUMS) model of depression, western blotting and immunofluorescence, were used together. A single injection of L-701,324 exhibited antidepressant-like potential in the FST and TST without affecting the locomotor activity of mice. Repeated injection of L-701,324 not only prevented CUMS-induced depressive-like behaviors in mice, but also ameliorated the downregulating effects of CUMS on the hippocampal BDNF signaling cascade and neurogenesis. Furthermore, K252a, a potent inhibitor of the BDNF system, fully blocked the antidepressant-like activity of L-701,324 in mice. K252a administration also abolished the activating actions of L-701,324 on the hippocampal BDNF signaling cascade and neurogenesis in CUMS-treated mice. Collectively, these data indicated that L-701,324 possesses antidepressant-like activity in mice, which was mediated, at least in part, by promoting the hippocampal BDNF system.

CRTC1 signaling involvement in depression-like behavior of prenatally stressed offspring rat

A large body of literature has demonstrated that prenatal stress (PS) can induce depression-like behavior in the offspring. However, the underlying mechanism remains largely unknown. CREB-regulated transcriptional coactivator 1(CRTC1) has recently been shown to involve in mood regulation. This research aims to investigate whether CRTC1 signaling was involved in the depression-like behavior of prenatally stressed offspring rats. Sucrose preference test (SPT), forced swimming test (FST) and open field test (OFT) were adopted to test the depression-like behavior in the male offspring rats, and CRTC1 signaling was measured. The results showed that there were significantly reduced sucrose intake in SPT and prolonged immobility time in FST in PS-exposure offspring rats. It was also found decreased levels of total CRTC1, nuclear CRTC1, calcineurin, brain-derived neurotrophic factor (BDNF) and c-fos, but increased cytoplasmic p-CRTC1 in the hippocampus (HIP) and prefrontal cortex (PFC) of the offspring rats. Furthermore, the mRNA level of CRTC1, calcineurin, BDNF, c-fos were down-regulated. Abnormal expression of CRTC1 signaling could be alleviated by fluoxetine treatment. In conclusion, our research indicated that the aberration of CRTC1 expression and/or phosphorylation activity might play a vital role in PS-induced depression-like behavior of offspring rats.

Imipramine exerts antidepressant-like effects in chronic stress models of depression by promoting CRTC1 expression in the mPFC

Recent studies have suggested that CREB-regulated transcription coactivator 1 (CRTC1) plays a role in the pathophysiology of depression. Although imipramine is thought to prevent the reuptake of synaptic serotonin and norepinephrine, its antidepressant-like mechanisms remain elusive. In this study, the effects of imipramine on CRTC1 were studied in several models of depression, including the chronic restraint stress (CRS), chronic unpredictable mild stress (CUMS) and chronic social defeat stress (CSDS) models. We examined whether repeated imipramine administration can reverse the effects of CRS, CUMS and CSDS on CRTC1 expression in both the hippocampus and medial prefrontal cortex (mPFC). Furthermore, genetic knockdown of CRTC1 by CRTC1-shRNA was used to determine whether CRTC1 is necessary for the antidepressant-like effects of imipramine in mice. Our results showed that imipramine reversed the down-regulating effects of CRS, CUMS and CSDS on CRTC1 expression in the mPFC but not the hippocampus, and that CRTC1-shRNA fully abolished the antidepressant-like actions of imipramine in mice. In conclusion, CRTC1 in the mPFC is involved in the antidepressant mechanism of imipramine.

LIMK1/2 in the mPFC Plays a Role in Chronic Stress-Induced Depressive-Like Effects in Mice

BACKGROUND

Depression is one of the most common forms of mental illness and also a leading cause of disability worldwide. Developing novel antidepressant targets beyond the monoaminergic systems is now popular and necessary. LIM kinases, including LIM domain kinase 1 and 2 (LIMK1/2), play a key role in actin and microtubule dynamics through phosphorylating cofilin. Since depression is associated with atrophy of neurons and reduced connectivity, here we speculate that LIMK1/2 may play a role in the pathogenesis of depression.

METHODS

In this study, the chronic unpredictable mild stress (CUMS), chronic restraint stress (CRS), and chronic social defeat stress (CSDS) models of depression, various behavioral tests, stereotactic injection, western blotting, and immunofluorescence methods were adopted.

RESULTS

CUMS, CRS, and CSDS all significantly enhanced the phosphorylation levels of LIMK1 and LIMK2 in the medial prefrontal cortex (mPFC) but not the hippocampus of mice. Administration of fluoxetine, the most commonly used selective serotonin reuptake inhibitor in clinical practice, fully reversed the effects of CUMS, CRS, and CSDS on LIMK1 and LIMK2 in the mPFC. Moreover, pharmacological inhibition of LIMK1 and LIMK2 in the mPFC by LIMKi 3 infusions notably prevented the pro-depressant effects of CUMS, CRS, and CSDS in mice.

CONCLUSIONS

In summary, these results suggest that LIMK1/2 in the mPFC has a role in chronic stress-induced depressive-like effects in mice and could be a novel pharmacological target for developing antidepressants.

Farnesoid X Receptor-Mediated Cytoplasmic Translocation of CRTC2 Disrupts CREB-BDNF Signaling in Hippocampal CA1 and Leads to the Development of Depression-Like Behaviors in Mice

BACKGROUND

We recently identified neuronal expression of farnesoid X receptor (FXR), a bile acid receptor known to impair autophagy by inhibiting cyclic adenosine monophosphate response element-binding protein (CREB), a protein whose underfunctioning is linked to neuroplasticity and depression. In this study, we hypothesize that FXR may mediate depression via a CREB-dependent mechanism.

METHODS

Depression was induced in male C57BL6/J mice via chronic unpredictable stress (CUS). Subjects underwent behavioral testing to identify depression-like behaviors. A variety of molecular biology techniques, including viral-mediated gene transfer, Western blot, co-immunoprecipitation, and immunofluorescence, were used to correlate depression-like behaviors with underlying molecular and physiological events.

RESULTS

Overexpression of FXR, whose levels were upregulated by CUS in hippocampal CA1, induced or aggravated depression-like behaviors in stress-naïve and CUS-exposed mice, while FXR short hairpin RNA (shRNA) ameliorated such symptoms in CUS-exposed mice. The behavioral effects of FXR were found to be associated with changes in CREB-brain-derived neurotrophic factor (BDNF) signaling, as FXR overexpression aggravated CUS-induced reduction in BDNF levels while the use of FXR shRNA or disruption of FXR-CREB signaling reversed the CUS-induced reduction in the phosphorylated CREB and BDNF levels. Molecular analysis revealed that FXR shRNA prevented CUS-induced cytoplasmic translocation of CREB-regulated transcription coactivator 2 (CRTC2); CRTC2 overexpression and CRTC2 shRNA abrogated the regulatory effect of FXR overexpression or FXR shRNA on CUS-induced depression-like behaviors.

CONCLUSIONS

In stress conditions, increased FXR in the CA1 inhibits CREB by targeting CREB and driving the cytoplasmic translocation of CRTC2. Uncoupling of the FXR-CREB complex may be a novel strategy for depression treatment.

MicroRNA-132 regulates salt-dependent steady-state renin levels in mice

The body's salt and fluid balance is regulated by the renin-angiotensin-aldosterone system. Generation of prostaglandin-E2 (PGE2) in a cyclo-oxygenase-2 (COX-2)-dependent manner in the macula densa, the salt-sensing cells of the kidney, plays a dominant role in renin regulation. Here we show that miR-132 directly targets Cox-2 and affects subsequent PGE2 and renin levels. MiR-132 is induced and reduced by low- and high salt treatment, respectively, in a p38- and ERK1/2-independent and CREB- and salt inducible kinase-dependent manner. Silencing of miR-132 in mice increases macula densa COX-2 expression and elevates PGE2 and renin levels, which are abrogated by the selective COX-2-inhibitor Celecoxib. Furthermore, a low or high salt diet induces and reduces macula densa miR-132 expression, while low salt diet combined with silencing miR-132 further increases renin levels. Taken together, we demonstrate a posttranscriptional regulatory role for salt-dependent miR-132 in fine-tuning the steady-state levels of renin.

Hippocampal overexpression of chordin protects against the chronic social defeat stress-induced depressive-like effects in mice

Depression is a serious and worldwide neuropsychiatric disesase, and developing novel antidepressant targets beyond the monoaminergic systems is now popular and necessary. Bone morphogenetic protein (BMP) signals modulate numerous developmental, physiological, and homeostatic processes. The functions of BMPs are also regulated by secreted extracellular antagonists such as chordin and noggin. Chordin has abundant expression in adult brain, and may play critical role in the central nervous system. In this study, the chronic social defeat stress (CSDS) model of depression, various behavioral tests, western blotting, quantitative real-time reverse transcription PCR, immunohistochemistry, recombinant mouse chordin protein and AAV-Chordin-EGFP were together used to explore the role of chordin in the pathogenesis of depression. It was found that CSDS significantly decreased the expression of chordin in the hippocampus but not other related brain regions. Moreover, both pharmacological and genetic overexpression of hippocampal chordin fully protected against the CSDS-induced depressive-like effects in mice. Collectively, hippocampal chordin could be a novel antidepressant target, and this study further highlights the importance of the hippocampal BMP system in the pathophysiology of depression.

Allicin ameliorates obesity comorbid depressive-like behaviors: involvement of the oxidative stress, mitochondrial function, autophagy, insulin resistance and NOX/Nrf2 imbalance in mice

The increased prevalence of obesity has been a major medical and public health problem in the past decades. In obese status, insulin resistance and sustained oxidative stress damage might give rise to behavioral deficits. The anti-obesity and anti-oxidant effects of allicin have been previously reported in peripheral tissues. In the present study, the functions and mechanisms of allicin involved in the prevention of high-fat diet (HFD)-induced depressive-like behaviors were investigated to better understand the pharmacological activities of allicin. Obese mice (five weeks of age) were treated with allicin (50, 100, and 200 mg/kg) by gavage for 15 weeks and behavioral test (sucrose preference, open field, and tail suspension) were performed. Furthermore, markers of oxidative stress, mitochondrial function, autophagy, and insulin resistance were measured in the hippocampal tissue. Finally, the levels of NADPH oxidase (NOX2, NOX4) and the nuclear factor erythroid 2-related factor 2 (Nrf2) pathway were evaluated in the hippocampus. The body weight, metabolic disorders, and depressive-like behaviors in obese mice were ameliorated by allicin. The depressive-like behaviors presented in the obese mice were accompanied by remarkably excessive reactive oxygen species (ROS) production and oxidative stress, damaged mitochondrial function, imbalanced autophagy, and enhanced insulin resistance in the hippocampus. We found that allicin improved the above undesirable effects in the obese mice. Furthermore, allicin significantly decreased NOX2 and NOX4 levels and activated the Nrf2 pathway. Allicin attenuated depressive-like behaviors triggered by long-term HFD consumption by inhibiting ROS production and oxidative stress, improving mitochondrial function, regulating autophagy, and reducing insulin resistance in the hippocampus via optimization of NOX/Nrf2 imbalance.

Synapse-to-Nucleus Signaling in Neurodegenerative and Neuropsychiatric Disorders

Synapse-to-nucleus signaling is critical for converting signals received at synapses into transcriptional programs essential for cognition, memory, and emotion. This neuronal mechanism usually involves activity-dependent translocation of synaptonuclear factors from synapses to the nucleus resulting in regulation of transcriptional programs underlying synaptic plasticity. Acting as synapse-to-nucleus messengers, amyloid precursor protein intracellular domain associated-1 protein, cAMP response element binding protein (CREB)-regulated transcription coactivator-1, Jacob, nuclear factor kappa-light-chain-enhancer of activated B cells, RING finger protein 10, and SH3 and multiple ankyrin repeat domains 3 play essential roles in synapse remodeling and plasticity, which are considered the cellular basis of memory. Other synaptic proteins, such as extracellular signal-regulated kinase, calcium/calmodulin-dependent protein kinase II gamma, and CREB2, translocate from dendrites or cytosol to the nucleus upon synaptic activity, suggesting that they could contribute to synapse-to-nucleus signaling. Notably, some synaptonuclear factors converge on the transcription factor CREB, indicating that CREB signaling is a key hub mediating integration of synaptic signals into transcriptional programs required for neuronal function and plasticity. Although major efforts have been focused on identification and regulatory mechanisms of synaptonuclear factors, the relevance of synapse-to-nucleus communication in brain physiology and pathology is still unclear. Recent evidence, however, indicates that synaptonuclear factors are implicated in neuropsychiatric, neurodevelopmental, and neurodegenerative disorders, suggesting that uncoupling synaptic activity from nuclear signaling may prompt synapse pathology, contributing to a broad spectrum of brain disorders. This review summarizes current knowledge of synapse-to-nucleus signaling in neuron survival, synaptic function and plasticity, and memory. Finally, we discuss how altered synapse-to-nucleus signaling may lead to memory and emotional disturbances, which is relevant for clinical and therapeutic strategies in neurodegenerative and neuropsychiatric diseases.

Anti-depressant effects of oil from fructus gardeniae via PKA-CREB-BDNF signaling

The dried ripe fruit of Gardenia jasminoides Ellis was usually applied as an herb medicine in Traditional Chinese Medicine. It was suggested that the Gardenia jasminoides oil extract (oil from Fructus Gardeniae [OFG]) might serve as a potential treatment for depression, whereas its pathogenesis still remained not fully understood. The present research was conducted to evaluate the anti-depressive effect of OFG in mice and explore its potential mechanism. The OFG and ketamine (KET) were intragastrically and intraperitoneally treated, respectively. Thereafter, the animals were subjected to the behavior tests. The expressions of protein kinase A (PKA), brain derived neurotrophic factor (BDNF), cAMP response element-binding protein (CREB) in hippocampus were detected by Western blot. The selective PKA inhibitor H-89 was also applied to confirm the mechanism. As a result, OFG and KET treatment improved the behavior performance. Furthermore, the administrations of OFG effectively enhanced the expressions of PKA, p-CREB, and BDNF. With the application of selective PKA inhibitor H-89, the ameliorated effects caused by OFG were blocked, but not by KET. In conclusion, the presented work indicated that OFG-exerted protective effect on depression through PKA-CREB-BDNF signaling.