The VGF-derived peptide TLQP62 produces antidepressant-like effects in mice via the BDNF/TrkB/CREB signaling pathway

The effects of acupuncture on depression by regulating BDNF-related balance via lateral habenular nucleus BDNF/TrkB/CREB signaling pathway in rats

Depression is a major mental disease worldwide, causing dysfunction of Lateral Habenular (LHb). As a non-invasive alternative, acupuncture (AP) has been widely used to treat depression in clinic, yet few basic studies have been focused on the effects and mechanism of acupuncture on synaptic plasticity in LHb. Therefore, this study aimed to explore the potential mechanism of the antidepressant effect of acupuncture. Male Sprague-Dawley (SD) rats were randomly divided into control, chronic unpredictable mild stress (CUMS), AP, fluoxetine (FLX), acupoint catgut embedding (ACE), sham-ACE groups (n = 9/group). Rats were given a 28-day treatment at the Shangxing (GV23) and Fengfu (GV16) acupoints with acupuncture, ACE, sham-ACE or fluoxetine (2.1 mg/kg). The results showed that AP, FLX and ACE suppressed the behavioral deficits, increased the level of the 5-hydroxytryptamine and FNDC5/IRISIN in serum, also reduced the expression of pro-BDNF impacted by CUMS. Both AP and FLX ameliorated the %area of IBA-1, GFAP, BrdU and DCX in the LHb and increased the expression of BDNF/TrkB/CREB, with non-significant difference between the two groups These findings suggest that AP therapy relieves depression-related manifestations in depressed rats, suggesting a potential mechanism via the BDNF/TrkB/CREB pathway in LHb.

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

ETHNOPHARMACOLOGICAL RELEVANCE

Uncaria rhynchophylla ([Mi] Jack) (gouteng) exerts antidepressive effects. Rhynchophylline (RH), a major component of U. rhynchophylla, exerts similar pharmacological effects to those of gouteng. Thus, RH may have antidepressive effects.

AIM OF THE STUDY

To investigate the anti-depressive effects of RH in chronic unpredictable mild stress (CUMS)-induced depressive mice. The anti-depressive mechanism of RH determined by measuring the 5-HT levels, the expressions of cAMP-response element binding protein (CREB) and brain-derived neurotrophic factor (BDNF) in cortex and hippocampus.

MATERIALS AND METHODS

The behaviors of CUMS-induced depressive mice were measured using an open field test (OFT), forced swimming test (FST), and tail suspension test (TST). 5-HT levels were measured using an ELISA kits. The expressions of BDNF and CREB were determined using western blot test.

RESULTS

RH increased the frequency of rearing and grooming in the OFT and decreased the immobility time in the FST and TST. RH effectively increased the 5-HT level and BDNF and CREB expressions in the cortex and hippocampus.

CONCLUSION

Our findings indicate that the antidepressive mechanism of RH is related to increased levels of 5-HT from regulating CREB and BDNF expressions in cortex and hippocampus.

Neurotrophin Crosstalk in the Etiology and Treatment of Neuropsychiatric and Neurodegenerative Disease

This article reviews the current progress in our understanding of the mechanisms by which growth factors, including brain-derived neurotrophic factor (BDNF) and vascular endothelial growth factor (VEGF), and select neurotrophin-regulated gene products, such as VGF (non-acronymic) and VGF-derived neuropeptides, function in the central nervous system (CNS) to modulate neuropsychiatric and neurodegenerative disorders, with a discussion of the possible therapeutic applications of these growth factors to major depressive disorder (MDD) and Alzheimer’s disease (AD). BDNF and VEGF levels are generally decreased regionally in the brains of MDD subjects and in preclinical animal models of depression, changes that are associated with neuronal atrophy and reduced neurogenesis, and are reversed by conventional monoaminergic and novel ketamine-like antidepressants. Downstream of neurotrophins and their receptors, VGF was identified as a nerve growth factor (NGF)- and BDNF-inducible secreted protein and neuropeptide precursor that is produced and trafficked throughout the CNS, where its expression is greatly influenced by neuronal activity and exercise, and where several VGF-derived peptides modulate neuronal activity, function, proliferation, differentiation, and survival. Moreover, levels of VGF are reduced in the CSF of AD subjects, where it has been repetitively identified as a disease biomarker, and in the hippocampi of subjects with MDD, suggesting possible shared mechanisms by which reduced levels of VGF and other proteins that are similarly regulated by neurotrophin signaling pathways contribute to and potentially drive the pathogenesis and progression of co-morbid neuropsychiatric and neurodegenerative disorders, particularly MDD and AD, opening possible therapeutic windows.

VGF: A prospective biomarker and therapeutic target for neuroendocrine and nervous system disorders

Neuroendocrine regulatory polypeptide VGF (nerve growth factor inducible) was firstly found in the rapid induction of nerve growth factor on PC12 cells. It was selectively distributed in neurons and many neuroendocrine tissues. This paper reviewed the latest literatures on the gene structure, transcriptional regulation, protein processing, distribution and potential receptors of VGF. The neuroendocrine roles of VGF and its derived polypeptides in regulating energy, water electrolyte balance, circadian rhythm and reproductive activities were also summarized. Furthermore, based on the experimental evidence in vivo and in vitro, dysregulation of VGF in different neuroendocrine diseases and the possible mechanism mediated by VGF polypeptides were discussed. We next discussed the potential as the clinical diagnosis and therapy for VGF related diseases in the future.

MicroRNA-139-5p acts as a suppressor gene for depression by targeting nuclear receptor subfamily 3, group C, member 1

MicroRNA-139-5p (miR-139-5p) is one of the most differentially expressed miRNAs in the brain between healthy people and depressed patients. However, its function in depression is unclear. Therefore, we investigated the function of miR-139-5p in depression. Here, miR-139-5p expression was found to be upregulated in the model group. MiR-139-5p inhibition could increase sucrose preference and decrease mice immobility time after chronic corticosterone (CORT) injection. Furthermore, compared with the antago-NC group, 3 weeks of antagomiR-139-5p treatment significantly decreased miR-139-5p level in model group hippocampus, increased sucrose preference index, reduced neuron damages, and enhanced the levels of nuclear receptor subfamily 3 group C member 1 (NR3C1), brain-derived neurotrophic factor (BDNF), phosphorylated/total tyrosine kinase receptor B (p-TrkB/TrkB), phosphorylated/total cAMP-response element-binding protein (p-CREB/CREB) and phosphorylated/total extracellular regulated protein kinases (p-ERK/ERK). Moreover, as a potential target for miR-139-5p, NR3C1 level was reduced by miR-139-5p mimic. Altogether, by activating the BDNF-TrkB signaling pathway, miR-139-5p inhibition plays an antidepressant-like role and might serve as an effective depression target (Fig. graphical abstract).

Chronic Administration of Thymoquinone Enhances Adult Hippocampal Neurogenesis and Improves Memory in Rats Via Regulating the BDNF Signaling Pathway

Thymoquinone is a pharmacologically active component of Nigella sativa Linn. seeds. Despite the diverse neuropharmacological attributes of TQ, limited reports related to adult neurogenesis and memory research are available. In this study, we investigated the effects of TQ on the proliferation and neural differentiation of cultured neural stem/progenitor cells (NSCs/NPCs). We also investigated the effect of TQ chronic administration on neurogenesis and memory in adult rats. Under proliferation conditions, TQ (0.05-0.3 μM) significantly increased NSCs/NPCs viability, neurosphere diameter, and cell count. TQ treatment under differentiation conditions increased the proportion of cells positive for Tuj1 (a neuronal marker). Furthermore, chronic oral administration of TQ (25 mg/kg/day for 12 weeks) to adult rats increased the number of bromodeoxyuridine (BrdU)-immunopositive cells double-stained with a mature neuronal marker, neuronal nuclei (NeuN), and a proliferation marker, doublecortin (Dcx), in the dentate gyrus of the hippocampus. TQ-administered rats showed a profound beneficial effect on avoidance-related learning ability, associated with an increase in the hippocampal mRNA and protein levels of brain-derived neurotrophic factor (BDNF), as measured by both real-time PCR and ELISA. Western blot analysis revealed that TQ stimulates the phosphorylation of cAMP-response element-binding protein (CREB), the upstream signaling molecule in the BDNF pathway. Furthermore, chronic administration of TQ decreased lipid peroxide and reactive oxygen species levels in the hippocampus. Taken together, our results suggest that TQ plays a role in memory improvement in adult rats and that the CREB/BDNF signaling pathways are involved in mediating the actions of TQ in hippocampal neurogenesis.

An increase in VGF expression through a rapid, transcription-independent, autofeedback mechanism improves cognitive function

The release of neuropeptides from dense core vesicles (DCVs) modulates neuronal activity and plays a critical role in cognitive function and emotion. The granin family is considered a master regulator of DCV biogenesis and the release of DCV cargo molecules. The expression of the VGF protein (nonacronymic), a secreted neuropeptide precursor that also belongs to the extended granin family, has been previously shown to be induced in the brain by hippocampus-dependent learning, and its downregulation is mechanistically linked to neurodegenerative diseases such as Alzheimer's disease and other mood disorders. Currently, whether changes in translational efficiency of Vgf and other granin mRNAs may be associated and regulated with learning associated neural activity remains largely unknown. Here, we show that either contextual fear memory training or the administration of TLQP-62, a peptide derived from the C-terminal region of the VGF precursor, acutely increases the translation of VGF and other granin proteins, such as CgB and Scg2, via an mTOR-dependent signaling pathway in the absence of measurable increases in mRNA expression. Luciferase-based reporter assays confirmed that the 3'-untranslated region (3'UTR) of the Vgf mRNA represses VGF translation. Consistently, the truncation of the endogenous Vgf mRNA 3'UTR results in substantial increases in VGF protein expression both in cultured primary neurons and in brain tissues from knock in mice expressing a 3'UTR-truncation mutant encoded by the modified Vgf gene. Importantly, Vgf 3'UTR-truncated mice exhibit enhanced memory performance and reduced anxiety- and depression-like behaviors. Our results therefore reveal a rapid, transcription-independent induction of VGF and other granin proteins after learning that are triggered by the VGF-derived peptide TLQP-62. Our findings suggest that the rapid, positive feedforward increase in the synthesis of granin family proteins might be a general mechanism to replenish DCV cargo molecules that have been released in response to neuronal activation and is crucial for memory function and mood stability.

Kefir peptides exhibit antidepressant-like activity in mice through the BDNF/TrkB pathway

Depression is a prevalent, stress-related mental disorder that can lead to serious psychiatric diseases with morbidity and high mortality. Although some functional fermented dairy drinks have promising anxiolytic and antidepressant effects, the mechanism is still not clear. To determine the antidepressant-like effect and the potential molecule mechanism of kefir peptides (KP), various behavioral tests, including the elevated plus maze test, open field test, forced swimming test, and tail suspension test, were used. Administration of 150 mg/kg KP in mice reduced the duration of immobility in the forced swimming test and tail suspension test, elevated the time spent in the open arm and center zone in the elevated plus maze test, and increased the total distance traveled, average speed, and time spent in the center zone in the open field test compared with the mock group. These results indicated that KP dramatically ameliorated the depression-like behaviors. Kefir peptides were further isolated and identified using high-performance liquid chromatography and liquid chromatography-tandem mass spectrometry, from which 3 peptides were identified and designated KFP-1, KFP-3, and KFP-5. Among these peptides, administration of KFP-3 (15 AA residues) remarkably decreased immobility time in the forced swimming test and increased mobility time in the tail suspension test. Therefore, KFP-3 may be the major active peptide with antidepressant activity in KP. Overexpression of brain-derived neurotrophic factor, phosphorylated tropomyosin receptor kinase B, and phosphorylated ERK1/2 protein levels could be detected in the hippocampus under KP administration. Therefore, we suggest that KP improves depressive-like behaviors by activating the brain-derived neurotrophic factor-phosphorylated tropomyosin receptor kinase B signaling pathway. Kefir peptides may serve as a new type of antidepressant dairy product and may provide potent antidepressant effects for clinical use.

Phloridzin ameliorates type 2 diabetes-induced depression in mice by mitigating oxidative stress and modulating brain-derived neurotrophic factor

PURPOSE

Type 2 diabetes (T2D) is linked with depression due to insulin resistance, oxidative stress and disruption of neurotrophic factors. We evaluated potential benefits of phloridzin in ameliorating depressive symptoms in T2D.

METHODS

Adult male Swiss-albino mice (25-30 g) on high-fat-diet (HFD) for 2 weeks were administered with streptozotocin (STZ; 35 mg/kg, intraperitoneal) to induce T2D. Seven days after STZ administration, diabetic mice on HFD were distributed into different groups. Animals were subjected daily to oral treatment of saline (0.25 ml), fluoxetine (10-20 mg/kg) or phloridzin (10-20 mg/kg) for a period of 4 weeks. One hour after last dose, the immobility time of animals was evaluated in forced swim test (FST) and tail suspension test (TST). To further confirm the mechanisms involved in antidepressant effect of phloridzin, biochemical parameters like brain derived neurotropic factor (BDNF), glutathione (GSH), extracellular signal-regulated kinase (ERK), tyrosine receptor kinase B (TrkB) and cAMP-response element binding protein (CREB) were estimated in the brain.

RESULTS

Animals with T2D showed a significant increase in immobility as compared to control in FST and TST. However, 4 weeks administration of fluoxetine or phloridzin attenuated this effect. A significant decline in GSH, BDNF, TrkB, CREB and ERK levels were noticed in the brain of mice with T2D. These changes were also attenuated by administration of phloridzin.

CONCLUSIONS

Phloridzin may ameliorates T2D-induced depression by mitigating the oxidative stress, and up-regulation of neurotrophins in the brain. Therefore, phloridzin can be used as a therapeutic intervention for the management of depression co-morbid with T2D.

2-Phenylethylamine (PEA) Ameliorates Corticosterone-Induced Depression-Like Phenotype via the BDNF/TrkB/CREB Signaling Pathway

Depression is a serious medical illness that is one of the most prevalent psychiatric disorders. Corticosterone (CORT) increases depression-like behavior, with some effects on anxiety-like behavior. 2-Phenethylamine (PEA) is a monoamine alkaloid that acts as a central nervous system stimulant in humans. Here, we show that PEA exerts antidepressant effects by modulating the Brain-derived neurotrophic factor (BDNF)/tropomyosin receptor kinase B (TrkB)/cAMP response element binding protein (CREB) signaling pathway in CORT-induced depression. To investigate the potential effects of PEA on CORT-induced depression, we first treated CORT (50 μM)-induced hippocampal neurons with 100 μM PEA for 24 h. We found that treatment with CORT altered dendritic spine architecture; however, treatment with PEA rescued dendritic spine formation via regulation of BDNF/TrkB/CREB signaling. Next, we used a mouse model of CORT-induced depression. Mice were treated with CORT (20 mg/kg) for 21 days, followed by assessments of a battery of depression-like behaviors. During the final four days of CORT exposure, the mice were treated with PEA (50 mg/kg). We found that CORT injection promoted depression-like behavior and significantly decreased BDNF and TrkB expression in the hippocampus. However, treatment with PEA significantly ameliorated the behavioral and biochemical changes induced by CORT. Our findings reveal that PEA exerts antidepressant effects by modulating the BDNF/TrkB/CREB signaling pathway in a mouse model of CORT-induced depression.

Multiscale causal networks identify VGF as a key regulator of Alzheimer's disease

Though discovered over 100 years ago, the molecular foundation of sporadic Alzheimer's disease (AD) remains elusive. To better characterize the complex nature of AD, we constructed multiscale causal networks on a large human AD multi-omics dataset, integrating clinical features of AD, DNA variation, and gene- and protein-expression. These probabilistic causal models enabled detection, prioritization and replication of high-confidence master regulators of AD-associated networks, including the top predicted regulator, VGF. Overexpression of neuropeptide precursor VGF in 5xFAD mice partially rescued beta-amyloid-mediated memory impairment and neuropathology. Molecular validation of network predictions downstream of VGF was also achieved in this AD model, with significant enrichment for homologous genes identified as differentially expressed in 5xFAD brains overexpressing VGF. Our findings support a causal role for VGF in protecting against AD pathogenesis and progression.

Optimized integration of fluoxetine and 7, 8-dihydroxyflavone as an efficient therapy for reversing depressive-like behavior in mice during the perimenopausal period

Fluoxetine (FLX) has been considered as an effective anti-depressant drug. Besides, previous studies reported reasonable anti-depressant effects for 7, 8-dihydroxyflavone (7, 8 DHF). However, the combination of FLX and 7, 8 DHF in a well-established depression model has not been explored. In this study, we demonstrate that the 7, 8 DHF can improve the anti-depressant efficacy of FLX in a chronic unpredictable mild stress (CUMS)-induced depression during the perimenopausal period. The corresponding mechanism of FLX+7, 8 DHF therapy and the effect of ANA-12 are also investigated. Moreover, the influences of 7, 8 DHF (5 mg/kg/day), FLX (18 mg/kg/day), and ANA-12 (0.5 mg/kg/day) on a depressive-like behavior are displayed. Inflammatory, autophagic and apoptotic changes of hippocampus and cortex are examined by using western blot, immunofluorescence, and Real-Time Quantitative reverse transcription-polymerase chain reaction (RT-qPCR) techniques. The protein levels of phosphatidylinositol 3 kinase (PI3K)/ protein kinase B (Akt)/mechanistic target of rapamycin (mTOR)/phosphorylated extracellular signal-regulated kinase1/2 (p-ErK 1/2)/brain-derived neurotrophic factor (BDNF)/tropomyosin-related kinase B (TrkB) of hippocampus and cortex are assessed by western blot. The combined FLX and 7, 8 DHF treatment can significantly improve depressive-like behavior in sucrose preference and forced swimming tests accompanied by a noticeable upregulation of autophagy, neuronal nuclei (NeuN), ionized calcium-binding adaptor molecule 1 (Iba1) expressions, and PI3K/Akt/ mTOR/ p-ErK 1/2 signaling pathways. Besides, an obvious increase of the brain-derived neurotrophic factor (BDNF) and TrkB levels are observed with down-regulated inflammation and apoptosis. These findings suggest that the integrated FLX and 7, 8 DHF holds a potential as an efficient treatment to ameliorate depressive-like behavior in perimenopausal patients.

Human VGF-Derived Antidepressant Neuropeptide TLQP62 Promotes SH-SY5Y Neurite Outgrowth

TLQP62 is a neuropeptide derived from the neurotrophin-inducible VGF (non-acronymic) protein with antidepressant-like properties capable of inducing increased memory on the mouse hippocampus by promoting neurogenesis and synaptic plasticity through brain-derived neurotropic factor (BDNF) and its receptor tyrosine receptor kinase B (TrkB). Human SH-SY5Y neuroblastoma-derived cell line is widely used in neuroscience research and is known to undergo neurodifferentiation in the presence of all-trans retinoic acid by upregulating the expression of TrkB, making cells responsive to BDNF. As TLQP62 promotes BDNF expression, which in turn activates a BDNF/TrkB/CREB (cAMP response element-binding protein) pathway that upregulates VGF expression, there is a VGF-BDNF regulatory loop that seems to regulate neurogenesis. Therefore, here, we evaluate by morphological observation the ability of human TLQP62 to induce neuritogenesis of human SH-SY5Y neuroblastoma-derived cell line in a retinoic acid and BDFN-like way, making this cell line a suitable cell model for further studies concerning TLQP62 molecular mechanisms and signalling pathways. SIGNIFICANCE STATEMENT: VGF has been widely explored for its role in emotional behaviour and neuropsychiatric illness (Bartolomucci et al. 2011). Although VGF levels were found reduced in leukocytes of depressed patients, after antidepressant treatment or voluntary exercise, those levels were found to be restored in the hippocampus (Hunsberger et al. 2007; Thakker-Varia et al. 2007). Administration to hippocampal cells of TLQP62 produced an increase in synaptic charge that could explain this antidepressants effects (Alder et al. 2003). This interesting role of TLQP62 in the brain, especially in the hippocampus, makes this neuropeptide an attractive target for further investigation of its role in neurogenesis, learning, memory, and neurological disorders, and possible treatment development. Thus, the identification of a receptor(s) for this peptide and associated signalling pathway(s) is of high importance, as well as a proper cell model to perform those studies.

Reduced serum VGF levels are linked with suicide risk in Chinese Han patients with major depressive disorder

BACKGROUND

VGF (nonacronymic) is a neuropeptide that plays an important role in the pathogenesis of major depressive disorder (MDD). However, no studies have yet investigated VGF levels in patients with MDD who are at risk of suicide. The purpose of the present study was to determine whether serum VGF levels are related to suicide risk in patients with MMD.

METHODS

A total of 107 patients with MDD and 40 normal control participated in the present study. The risk of suicide was assessed using the Nurses Global Assessment of Suicide Risk (NGASR). On this basis, 60 patients were assigned to a high-risk group (NGASR≥9) and 47 were assigned to a low-risk group (NGASR< 9). The severity of depression was measured using the 17-item Hamilton Depression Rating Scale (HDRS). Levels of serum VGF were determined using a double antibody sandwich enzyme-linked immunosorbent assay.

RESULTS

Serum VGF levels in the high-risk group (883.34 ± 139.67 pg/mL) were significantly lower than in the low-risk group (1020.56 ± 131.76 pg/mL) and in the control group (1107.00 ± 155.38 pg/mL) (F = 31.90, p < 0.001). In patients with MDD, suicide risk was significantly negatively correlated with VGF levels (r = - 0.55, p = 0.001).

CONCLUSIONS

Reduced serum VGF levels are related to risk of suicide in patients with MDD, so VGF may be a biomarker of suicide risk in MDD.

The potential therapeutic effects of the gut microbiome manipulation by synbiotic containing-Lactobacillus plantarum on neuropsychological performance of diabetic rats

Background

The manipulation of gut microbiota as a target has been suggested to reduce the risks for a number of diseases such as type 2 diabetes mellitus (T2DM). Conversely, T2DM is associated with complications such as gut and brain disorders. Furthermore, the impact of probiotics and prebiotics to improve T2DM complications are reported. Thus, the present study seeks to investigate the therapeutic and neuropsychological effects of L. plantarum and inulin in diabetic rats.

Methods

Throughout the investigation, L. plantarum, inulin or their combination (synbiotic) was administered to diabetic rats. in the end, fecal samples were collected to evaluate the gut microbial composition. Then behavioral tests were conducted. Subsequently, the obtainment of the prefrontal cortex (PFC) and hippocampal samples.

Results

Our data demonstrated that administration of L. plantarum and inulin could improve gut dysbiosis and oxidative stress status. In addition, it could ameliorate serotonin and BDNF/TrkB signaling pathway. Notably, a strong correlation between the gut microbiota changes and cognition responses was observed. Interestingly, synbiotics intake exploited a rather powerful effect on oxidative stress markers.

Conclusion

The findings confirm that there is a beneficial therapeutic potential of supplements, especially symbiotic. Moreover, neuropsychological improvement associated with balanced gut microbiome.

Chronic unpredictable mild stress induced depression-like behaviours and glutamate-glutamine cycling dysfunctions in both blood and brain of mice

CONTEXT

Currently, there is no cure or early preclinical diagnostic assay available for depression. Recently, depression has been observed in association with metabolic abnormalities of the glutamate (Glu)-glutamine (Gln) cycling, which is regulated by Glu, Gln and γ-aminobutyric acid (GABA) amino acids.

OBJECTIVE

The purpose of this study is to determine the changes of Glu, Gln and GABA in blood and brain of chronic unpredictable mild stress (CUMS) induced mice and to clarify the depression biomarkers in the Glu-Gln cycling.

MATERIALS AND METHODS

Male Kunming mice were divided into model group and control group randomly (n = 12). The depression model of mice was established by CUMS stimulation for 56 days. The liquid chromatography-fluorescence method was used for simultaneous determination of Glu, Gln and GABA in the plasma and brain of mice. o-Phthalaldehyde and β-mercaptoethanol were used as pre-column derivatization reagents. Neurotransmitters were analysed on high performance liquid chromatography (HPLC) on an HPH C18 column in combination with a fluorescence detector.

RESULTS

The method was simple, highly sensitive and showed excellent linearity with regression coefficients higher than 0.999, good accuracy (95-108%) and good inter-day precision (RSD <15%) for all analytes. Limit of quantification (LOQ) values were established as 0.01, 0.01 and 0.005 μg/mL for Glu, Gln and GABA. The GABA in the CUMS mouse brain (p < 0.01) was significantly increased and Gln in plasma (p < 0.01) and brain (p < 0.01) were both decreased.

CONCLUSIONS

Our study demonstrates that the Gln in plasma can be used as a biological marker of depression.

VGF has Roles in the Pathogenesis of Major Depressive Disorder and Schizophrenia: Evidence from Transgenic Mouse Models

Mental disorders, such as major depressive disorder and schizophrenia, are complex multigenetic conditions, but focused studies of single genes might reveal genes involved in the pathogenesis of mental disorders, including major depressive disorder and schizophrenia. Several candidate genes have been identified using transgenic mice. VGF nerve growth factor inducible (VGF) is a neuropeptide expression of which is induced by nerve growth factor (NGF). VGF is robustly and exclusively synthesized in neuronal and neuroendocrine cells. In central nervous system (CNS), VGF is extensively expressed especially in the cerebral cortex, hippocampus, and hypothalamus. VGF has many roles in the CNS, such as promotion of synaptic plasticity, neurogenesis, and neurite outgrowth. In clinical studies, altered expression and genetic mutations of VGF have been reported in patients with major depressive disorder and schizophrenia. On this basis, studies using transgenic mice to overexpress or knockout VGF have been performed to investigate the roles of upregulation or downregulation of VGF. In this review, we will discuss studies of the roles of VGF using transgenic mice and its relevance to pathologies in major depressive disorder and schizophrenia.

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.

Chromodomain Y-like Protein-Mediated Histone Crotonylation Regulates Stress-Induced Depressive Behaviors

BACKGROUND

Major depressive disorder is a prevalent and life-threatening illness in modern society. The susceptibility to major depressive disorder is profoundly influenced by environmental factors, such as stressful lifestyle or traumatic events, which could impose maladaptive transcriptional program through epigenetic regulation. However, the underlying molecular mechanisms remain elusive. Here, we examined the role of histone crotonylation, a novel type of histone modification, and chromodomain Y-like protein (CDYL), a crotonyl-coenzyme A hydratase and histone methyllysine reader, in this process.

METHODS

We used chronic social defeat stress and microdefeat stress to examine the depressive behaviors. In addition, we combined procedures that diagnose behavioral strategy in male mice with histone extraction, viral-mediated CDYL manipulations, RNA sequencing, chromatin immunoprecipitation, Western blot, and messenger RNA quantification.

RESULTS

The results indicate that stress-susceptible rodents exhibit lower levels of histone crotonylation in the medial prefrontal cortex concurrent with selective upregulation of CDYL. Overexpression of CDYL in the prelimbic cortex, a subregion of the medial prefrontal cortex, increases microdefeat-induced social avoidance behaviors and anhedonia in mice. Conversely, knockdown of CDYL in the prelimbic cortex prevents chronic social defeat stress-induced depression-like behaviors. Mechanistically, we show that CDYL inhibits structural synaptic plasticity mainly by transcriptional repression of neuropeptide VGF nerve growth factor inducible, and this activity is dependent on its dual effect on histone crotonylation and H3K27 trimethylation on the VGF promoter.

CONCLUSIONS

Our results demonstrate that CDYL-mediated histone crotonylation plays a critical role in regulating stress-induced depression, providing a potential therapeutic target for major depressive disorder.

Higher serum VGF protein levels discriminate bipolar depression from major depressive disorder

Misdiagnosis between major depressive disorder (MDD) and bipolar depression (BD) is quite common. Our previous study found significantly lower serum VGF (non-acronymic) in MDD patients. However, it is unclear whether same changes occur in BD patients. Therefore, we aimed to investigate the relationship between serum VGF levels in BD and MDD patients. General information, scores of 17-item Hamilton Depression Rating Scale (HDRS), and fasting blood samples of all participants including 30 MDD patients, 20 BD patients, and 30 healthy controls (HC) were collected. Serum VGF levels were measured by Enzyme-linked immunosorbent assay kits. Pearson correlation analysis was used to analyze correlations between serum VGF levels and clinical information. Receiver operating characteristic (ROC) curve and likelihood ratios (LRs) were used to analyze the differential potential of serum VGF. Serum VGF levels were significantly lower in MDD patients but higher in BD patients compared with HC (both P_Tukey < 0.01). No correlation was found between serum VGF levels and any data of subjects. The optimal cutoff for serum VGF in discriminating BD patients from MDD patients was ≥1093.85 pg/ml (AUC = 0.990, sensitivity of 95%, specificity of 100% and accuracy of 95%). LRs further confirmed the differential efficiency of serum VGF in distinguishing BD and MDD patients with +LR of infinity and -LR of 0. The results suggest that serum VGF level changed significantly in MDD and BD patients and serum VGF may be an indicator for differentiating BD patients from MDD patients.

Essential roles of neuropeptide VGF regulated TrkB/mTOR/BICC1 signaling and phosphorylation of AMPA receptor subunit GluA1 in the rapid antidepressant-like actions of ketamine in mice

Previous studies have suggested that rapid reductions in depression-like behaviors are observed in response to sub-anesthetic-doses of ketamine, an N-methyl-d-aspartate receptor (NMDAR) antagonist. Neuropeptide VGF (non-acronymic) is a critical effector of depression-like behaviors and is thought to be involved in the antidepressant actions of ketamine that have been demonstrated. However, the mechanism underlying the involvement of VGF in the anti-depressant action of ketamine remains unclear. We found that single dose ketamine treatment reversed CSDS-induced depression-like behaviors and decrease of VGF in the PFC of mice. To investigate the involvement of VGF in the antidepressant-like effects of ketamine, a lentivirus vector for VGF was constructed to knockdown the expression of VGF in the prefrontal cortex (PFC) of mice. The biochemical and behavioral effects of this VGF knockdown were examined, using the open field, forced swim, and sucrose preference tests. Our results show that knockdown of VGF increased the immobility time and decreased the sucrose preference in mice. These effects were not improved by ketamine administration. In addition, we found that knockdown of VGF significantly decreased the expression of phosphorylation of tropomyosin receptor kinase B (TrkB), mammalian target of rapamycin (mTOR), and α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid (AMPA) receptor subunit GluA1 Ser845 and increased the expression of bicaudal C homolog 1 (BICC1) in the mouse PFC, and blocked the regulation of TrkB/mTOR/BICC1 signaling and GluA1 phosphorylation by ketamine. Our results indicate that the rapid onset antidepressant-like actions of ketamine require VGF to regulate TrkB/mTOR/BICC1 signaling and AMPA receptor GluA1 phosphorylation.

Novel behavioral assays of spontaneous and precipitated THC withdrawal in mice

BACKGROUND

A subset of cannabis users develop some degree of Cannabis Use Disorder (CUD). Although behavioral therapy has some success in treating CUD, many users relapse, often citing altered sleep, mood, and irritability. Preclinical animal tests of cannabinoid withdrawal focus primarily on somatic-related behaviors precipitated by a cannabinoid receptor antagonist. The goal of the present study was to develop novel cannabinoid withdrawal assays that are either antagonist-precipitated or spontaneously induced by abstinence.

METHODS

C57BL/6 J mice were repeatedly administered the phytocannabinoid Δ⁹-tetrahydrocannabinol (THC; 1, 10 or 50 mg/kg, s.c.), the synthetic cannabinoid receptor agonist JWH-018 (1 mg/kg, s.c.), or vehicle (1:1:18 parts ethanol:Kolliphor EL:saline, s.c.) for 6 days. Withdrawal was precipitated with the cannabinoid receptor inverse agonist rimonabant (3 mg/kg, i.p.) or elicited via abstinence (i.e., spontaneous withdrawal), and putative stress-related behavior was scored. Classic somatic signs of cannabinoid withdrawal were also quantified.

RESULTS

Precipitated THC withdrawal significantly increased plasma corticosterone. Precipitated withdrawal from either THC or JWH-018 suppressed marble burying, increased struggling in the tail suspension test, and elicited somatic withdrawal behaviors. The monoacylglycerol lipase inhibitor JZL184 attenuated somatic precipitated withdrawal but had no effect on marble burying or struggling. Spontaneous THC or JWH-018 withdrawal-induced paw tremors, head twitches, and struggled in the tail suspension test after 24-48 h abstinence. JZL184 or THC attenuated these spontaneous withdrawal-induced behaviors.

CONCLUSION

Outcomes from tail suspension and marble burying tests reveal that THC withdrawal is multifaceted, eliciting and suppressing behaviors in these tests, in addition to inducing well-documented somatic signs of withdrawal.

Visual Experience-Dependent Expression of Fn14 Is Required for Retinogeniculate Refinement

Sensory experience influences the establishment of neural connectivity through molecular mechanisms that remain unclear. Here, we employ single-nucleus RNA sequencing to investigate the contribution of sensory-driven gene expression to synaptic refinement in the dorsal lateral geniculate nucleus of the thalamus, a region of the brain that processes visual information. We find that visual experience induces the expression of the cytokine receptor Fn14 in excitatory thalamocortical neurons. By combining electrophysiological and structural techniques, we show that Fn14 is dispensable for early phases of refinement mediated by spontaneous activity but that Fn14 is essential for refinement during a later, experience-dependent period of development. Refinement deficits in mice lacking Fn14 are associated with functionally weaker and structurally smaller retinogeniculate inputs, indicating that Fn14 mediates both functional and anatomical rearrangements in response to sensory experience. These findings identify Fn14 as a molecular link between sensory-driven gene expression and vision-sensitive refinement in the brain.

Role of a VGF/BDNF/TrkB Autoregulatory Feedback Loop in Rapid-Acting Antidepressant Efficacy

Members of the neurotrophin family and in particular brain-derived neurotrophic factor (BDNF) regulate the response to rapid- and slow-acting chemical antidepressants and voluntary exercise. Recent work suggests that rapid-acting antidepressants that modulate N-methyl-D-aspartate receptor (NMDA-R) signaling (e.g., ketamine and GLYX-13) require expression of VGF (non-acronymic), the BDNF-inducible secreted neuronal protein and peptide precursor, for efficacy. In addition, the VGF-derived C-terminal peptide TLQP-62 (named by its 4 N-terminal amino acids and length) has antidepressant efficacy following icv or intra-hippocampal administration, in the forced swim test (FST). Similar to ketamine, the rapid antidepressant actions of TLQP-62 require BDNF expression, mTOR activation (rapamycin-sensitive), and α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid (AMPA) receptor activation (NBQX-sensitive) and are associated with GluR1 insertion. We review recent findings that identify a rapidly induced autoregulatory feedback loop, which likely plays a critical role in sustained efficacy of rapid-acting antidepressants, depression-like behavior, and cognition, and requires VGF, its C-terminal peptide TLQP-62, BDNF/TrkB signaling, the mTOR pathway, and AMPA receptor activation and insertion.

VGF function in depression and antidepressant efficacy

Brain-derived neurotrophic factor (BDNF) is a critical effector of depression-like behaviors and antidepressant responses. Here, we show that VGF (non-acronymic), which is robustly regulated by BDNF/TrkB signaling, is downregulated in hippocampus (male/female) and upregulated in nucleus accumbens (NAc) (male) in depressed human subjects and in mice subjected to chronic social defeat stress (CSDS). Adeno-associated virus (AAV)-Cre-mediated Vgf ablation in floxed VGF mice, in dorsal hippocampus (dHc) or NAc, led to pro-depressant or antidepressant behaviors, respectively, while dHc- or NAc-AAV-VGF overexpression induced opposite outcomes. Mice with reduced VGF levels in the germ line (Vgf+/-) or in dHc (AAV-Cre-injected floxed mice) showed increased susceptibility to CSDS and impaired responses to ketamine treatment in the forced swim test. Floxed mice with conditional pan-neuronal (Synapsin-Cre) but not those with forebrain (αCaMKII-Cre) Vgf ablation displayed increased susceptibility to subthreshold social defeat stress, suggesting that neuronal VGF, expressed in part in inhibitory interneurons, regulates depression-like behavior. Acute antibody-mediated sequestration of VGF-derived C-terminal peptides AQEE-30 and TLQP-62 in dHc induced pro-depressant effects. Conversely, dHc TLQP-62 infusion had rapid antidepressant efficacy, which was reduced in BDNF floxed mice injected in dHc with AAV-Cre, and in NBQX- and rapamycin-pretreated wild-type mice, these compounds blocking α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid (AMPA) receptor and mammalian target of rapamycin (mTOR) signaling, respectively. VGF is therefore a critical modulator of depression-like behaviors in dHc and NAc. In hippocampus, the antidepressant response to ketamine is associated with rapid VGF translation, is impaired by reduced VGF expression, and as previously reported, requires coincident, rapid BDNF translation and release.

Beneficial Effects of Gagam-Palmultang on Scopolamine-Induced Memory Deficits in Mice

From text mining of Dongeuibogam, the 7 herbs in Palmultang can be considered effective candidates for memory enhancement. We sought to determine whether Gagam-Palmultang, comprising these 7 herbs, ameliorates scopolamine-induced memory impairment in mice, by focusing on the central cholinergic system and memory-related signaling molecules. Behavioral tests were performed after inducing memory impairment by scopolamine administration. The cholinergic system activity and memory-related molecules were examined in the hippocampus by enzyme-linked immunosorbent, western blot, and immunofluorescence assays. Gagam-Palmultang ameliorated scopolamine-induced memory impairment in the Morris water maze test, producing a significant improvement in the mean time required to find the hidden platform. Treatment with Gagam-Palmultang reduced acetylcholinesterase activity and expression in the hippocampus induced by scopolamine. The diminished phosphorylated phosphatidylinositide 3-kinase (PI3K), extracellular signal-regulated kinase (ERK), cAMP response element-binding protein (CREB), and mature brain-derived neurotrophic factor (mBDNF) expressions caused by scopolamine administration were attenuated by treatment with Gagam-Palmultang. This treatment also promoted neuronal cell proliferation in the hippocampus. Gagam-Palmultang has beneficial effects against scopolamine-induced memory impairments, which are exerted via modulation of the cholinergic system as well as the PI3K and ERK/CREB/BDNF signaling pathway. Therefore, this multiherb formula may be a useful therapeutic agent for diseases associated with memory impairments.

LRRK2 G2019S Induces Anxiety/Depression-like Behavior before the Onset of Motor Dysfunction with 5-HT1A Receptor Upregulation in Mice

Mutations in the leucine-rich repeat kinase 2 (LRRK2) gene are the most common genetic cause of Parkinson's disease (PD). The neuropathology of LRRK2 mutation-related PD, including increased dopaminergic neurodegeneration and Lewy bodies, is indistinguishable from that of idiopathic PD. The subtle nonmotor phenotypes of LRRK2 mutation-related PD have not been fully evaluated. In the present study, we examined anxiety/depression-like behaviors and accompanying neurochemical changes in differently aged transgenic (Tg) mice expressing human mutant LRRK2 G2019S. Through multiple behavioral tests, including light-dark test, elevated plus maze, sucrose preference test, forced swimming test, and tail-suspension test, we found that anxiety/depression-like behavior appeared in middle-aged (43-52 weeks) Tg mice before the onset of PD-like motor dysfunction. These behavioral tests were performed using both male and female mice, and there were no sex-related differences in behavioral changes in the middle-aged Tg mice. Along with behavioral changes, serotonin levels also significantly declined in the hippocampus of Tg mice. Additionally, increases in the expression of the 5-HT_1A receptor (5-HT_1AR) grew more significant with aging and were detected in the hippocampus, amygdala, and dorsal raphe nucleus. In vitro study using the serotonergic RN46A and hippocampal HT22 cells showed that 5-HT_1AR upregulation was related to enhanced expression of LRRK2 G2019S and was attenuated by the LRRK2 inhibitor LRRK2-IN-1. Wild-type LRRK2 had no significant effect on 5-HT_1AR transcription. The present study provides the first in vivo and in vitro evidence demonstrating abnormal regulation of 5-HT_1AR along with the manifestation of anxiety/depression-like, nonmotor symptom in PD related to LRRK2.SIGNIFICANCE STATEMENT Parkinson's disease (PD), the second most common neurodegenerative disorder, is clinically characterized by motor dysfunctions. In most cases, various nonmotor symptoms present several years before the onset of the classical motor features of PD and severely affect the quality of life of patients. Here, we demonstrate the causative role of leucine-rich repeat kinase 2 (LRRK2), a common PD-linked mutation, in the development of anxiety/depression-like behaviors. We found that age-dependent 5-HT_1A receptor upregulation in the hippocampus, amygdala, and dorsal raphe nucleus is accompanied by the expression of the LRRK2 mutant phenotype. Our findings demonstrating a potential mechanism for nonmotor psychiatric symptoms produced by LRRK2 mutation suggest that directly targeting the 5-HT_1A receptor can improve the therapeutic efficacy of drugs for PD-associated depression.

Reduced serum VGF levels were reversed by antidepressant treatment in depressed patients

OBJECTIVES

VGF, a non-acronymic neuropeptide, is important in the pathogenesis of major depressive disorder (MDD) and in the functioning and efficacy of some antidepressant drugs. In this study we assessed whether serum VGF levels change in MDD patients and if antidepressant treatments can restore these changes.

METHODS

We measured serum VGF concentrations using sandwich ELISA in drug-free MDD patients before treatment began (n = 26) and at 8 weeks after antidepressant treatment (n = 26) with escitalopram and duloxetine, two common antidepressants. The severity of depression was assessed with the 17-item Hamilton Depression Rating Scale (HDRS).

RESULTS

VGF serum levels were significantly lower in MDD patients compared to controls (P = .002), even after controlling for the effects of age and education (P = .037), and they were reversed by 8 weeks of drug treatment (P < .0001). Both escitalopram and duloxetine restored the decreased serum VGF levels (P < .05). We observed no correlation between VGF levels and HDRS scores in pre-treatment MDD patients (P = .879).

CONCLUSIONS

The results suggest that VGF may be implicated in the pathophysiology of MDD and in the mechanisms underlying the action of antidepressants, and serum VGF may be regarded as a trait parameter for MDD.

Schisandrin rescues depressive-like behaviors induced by chronic unpredictable mild stress via GDNF/ERK1/2/ROS and PI3K/AKT/NOX signaling pathways in mice

The current study aimed to prove the antidepressant-like effects and the probable mechanisms of Schisandrin on depression, which induced by chronic unpredictable mild stress (CUMS) in mice. Four weeks of CUMS exposure resulted in depressive-like behavior, as indicated by the significant decrease in sucrose consumption and increase the immobility time in the forced swim test, but without any influence on the locomotor activity. Further, there were significant downregulations of GDNF/ERK1/2/ROS and PI3K/AKT/NOX signaling pathways in the hippocampus and prefrontal cortex in depressed mice. Treatment of mice with Schisandrin (30mg/kg) and Fluoxetine (10mg/kg) significantly ameliorated all the behavioral and biochemical changes induced by CUMS. These results suggest that Schisandrin produces an antidepressant-like effect in CUMS-induced mice, which possibly mediated, at least in part, by rectifying the signaling pathways of GDNF/ERK1/2/ROS and PI3K/AKT/NOX.

Neuropeptide VGF C-Terminal Peptide TLQP-62 Alleviates Lipopolysaccharide-Induced Memory Deficits and Anxiety-like and Depression-like Behaviors in Mice: The Role of BDNF/TrkB Signaling

Peripheral inflammatory responses affect central nervous system (CNS) function, manifesting in symptoms of memory deficits, depression, and anxiety. Previous studies have revealed that neuropeptide VGF (nonacronymic) C-terminal peptide TLQP-62 rapidly reinforces brain-derived neurotrophic factor (BDNF)/tropomyosin receptor kinase B (TrkB) signaling, regulating memory consolidation and antidepressant-like action. However, whether it is beneficial for lipopolysaccharide (LPS)-induced neuropsychiatric dysfunction in mice is unknown. Herein, we explored the involvement of BDNF/TrkB signaling and biochemical alterations in inflammatory or oxidative stress markers in the alleviating effects of TLQP-62 on LPS-induced neuropsychiatric dysfunction. The mice were treated with TLQP-62 (2 μg/side) via intracerebroventricular (i.c.v.) injection 1 h before LPS (0.5 mg/kg, i.p.) administration. Our results showed that a single treatment with LPS (0.5 mg/kg, i.p) is sufficient to produce recognition memory deficits (in the novel object recognition test), depression-like behavior (in the forced swim test and sucrose preference test), and anxiety-like behavior (in the elevated zero maze). However, pretreatment with TLQP-62 prevented LPS-induced behavioral dysfunction, neuroinflammatory, and oxidative responses. In addition, our results further demonstrated that a reduction in BDNF expression mediated by BDNF-shRNA lentivirus significantly blocked the effects of TLQP-62, suggesting the critical role of BDNF/TrkB signaling in the neuroprotective effects of TLQP-62 in the mice. In conclusion, TLQP-62 could be a therapeutic approach for neuropsychiatric disorders, which are closely associated with neuroinflammation and oxidative stress.

Lentivirus-mediated interleukin-1β (IL-1β) knock-down in the hippocampus alleviates lipopolysaccharide (LPS)-induced memory deficits and anxiety- and depression-like behaviors in mice

Background

Recent evidence has suggested that peripheral inflammatory responses induced by lipopolysaccharides (LPS) play an important role in neuropsychiatric dysfunction in rodents. Interleukin-1β (IL-1β), a pro-inflammatory cytokine, has been proposed to be a key mediator in a variety of behavioral dysfunction induced by LPS in mice. Thus, inhibition of IL-1β may have a therapeutic benefit in the treatment of neuropsychiatric disorders. However, the precise underlying mechanism of knock-down of IL-1β in repairing behavioral changes by LPS remains unclear.

Methods

The mice were treated with either IL-1β shRNA lentivirus or non-silencing shRNA control (NS shRNA) lentivirus by microinjection into the dentate gyrus (DG) regions of the hippocampus. After 7 days of recovery, LPS (1 mg/kg, i.p.) or saline was administered. The behavioral task for memory deficits was conducted in mice by the novel object recognition test (NORT), the anxiety-like behaviors were evaluated by the elevated zero maze (EZM), and the depression-like behaviors were examined by the sucrose preference test (SPT) and the forced swimming test (FST). Furthermore, the levels of malondialdehyde (MDA), superoxide dismutase (SOD), nuclear factor erythroid-derived 2-like 2 (Nrf2), heme oxygenase 1 (HO1), IL-1β, tumor necrosis factor (TNF-α), neuropeptide VGF (non-acronymic), and brain-derived neurotrophic factor (BDNF) were assayed.

Results

Our results demonstrated that IL-1β knock-down in the hippocampus significantly attenuated the memory deficits and anxiety- and depression-like behaviors induced by LPS in mice. In addition, IL-1β knock-down ameliorated the oxidative and neuroinflammatory responses and abolished the downregulation of VGF and BDNF induced by LPS.

Conclusions

Collectively, our findings suggest that IL-1β is necessary for the oxidative and neuroinflammatory responses produced by LPS and offers a novel drug target in the IL-1β/oxidative/neuroinflammatory/neurotrophic pathway for treating neuropsychiatric disorders that are closely associated with neuroinflammation, oxidative stress, and the downregulation of VGF and BDNF.

The Requirement of L-Type Voltage-Dependent Calcium Channel (L-VDCC) in the Rapid-Acting Antidepressant-Like Effects of Scopolamine in Mice

BACKGROUND

Previous studies have shown that a low dose of scopolamine produces rapid-acting antidepressant-like actions in rodents. Understanding the mechanisms underlying this effect and the dose-dependent variations of drug responses remains an important task. L-type voltage-dependent calcium channels were found to mediate rapid-acting antidepressant effects of certain medications (e.g., ketamine). Therefore, it is of great interest to determine the involvement of L-type voltage-dependent calcium channels in the action of scopolamine.

METHODS

Herein, we investigated the mechanisms underlying behavioral responses to various doses of scopolamine in mice to clarify the involvement of L-type voltage-dependent calcium channels in its modes of action. Open field test, novel object recognition test, and forced swimming test were performed on mice administered varied doses of scopolamine (0.025, 0.05, 0.1, 1, and 3 mg/kg, i.p.) alone or combined with L-type voltage-dependent calcium channel blocker verapamil (5 mg/kg, i.p.). Then, the changes in brain-derived neurotrophic factor and neuropeptide VGF (nonacronymic) levels in the hippocampus and prefrontal cortex of these mice were analyzed.

RESULTS

Low doses of scopolamine (0.025 and 0.05 mg/kg) produced significant antidepressant-like effects in the forced swimming test, while higher doses (1 and 3 mg/kg) resulted in significant memory deficits and depressive-like behaviors. Moreover, the behavioral changes in responses to various doses may be related to the upregulation (0.025 and 0.05 mg/kg) and downregulation (1 and 3 mg/kg) of brain-derived neurotrophic factor and VGF in the hippocampus and prefrontal cortex in mice. We further found that the rapid-acting antidepressant-like effects and the upregulation on brain-derived neurotrophic factor and VGF produced by a low dose of scopolamine (0.025 mg/kg) were completely blocked by verapamil.

CONCLUSIONS

These results indicate that L-type voltage-dependent calcium channels are likely involved in the behavioral changes in response to various doses of scopolamine through the regulation of brain-derived neurotrophic factor and VGF levels.

Antidepressant-like effects and cognitive enhancement of Schisandra chinensis in chronic unpredictable mild stress mice and its related mechanism

The aim of this study was to evaluate whether Schisandra chinensis extract (SCE) administration influences chronic unpredictable mild stress (CUMS)-induced depression and cognitive impairment, and explores underlying mechanisms. Sucrose preference test (SPT) and forced swimming test (FST) were used for assessing depressive symptoms, and Y-maze, Morris water maze were used for evaluating cognition processes. The results showed that CUMS (4 weeks) was effective in producing both depression and memory deficits in mice. Additionally, CUMS exposure significantly decreased brain derived neurotrophic factor (BDNF) levels in hippocampus as indicated by ELISA, immunohistochemistry and immunofluorescence assays, accompanied by down-regulated tyrosine kinase receptor B (TrkB)/cAMP-response element binding protein (CREB)/extracellular signal-regulated kinase (ERK) and phosphatidylinositol 3 kinase (PI3K)/ protein kinase B (AKT)/ glycogen synthase kinase-3β (GSK-3β) signaling pathways. Chronic administration of SCE (600 or 1200 mg/kg, i.g.) significantly prevented all these CUMS-induced behavioral and biochemical alterations. It suggested that SCE could improve the depression-like emotional status and associated cognitive deficits in CUMS mice, which might be mediated by regulation of BDNF levels in hippocampus, as well as up-regulating of TrkB/CREB/ERK and PI3K/AKT/GSK-3β pathways.

Profiles of VGF Peptides in the Rat Brain and Their Modulations after Phencyclidine Treatment

From the VGF precursor protein originate several low molecular weight peptides, whose distribution in the brain and blood circulation is not entirely known. Among the VGF peptides, those containing the N-terminus portion were altered in the cerebro-spinal fluid (CSF) and hypothalamus of schizophrenia patients. "Hence, we aimed to better investigate the involvement of the VGF peptides in schizophrenia by studying their localization in the brain regions relevant for the disease, and revealing their possible modulations in response to certain neuronal alterations occurring in schizophrenia". We produced antibodies against different VGF peptides encompassing the N-terminus, but also C-terminus-, TLQP-, GGGE- peptide sequences, and the so named NERP-3 and -4. These antibodies were used to carry out specific ELISA and immunolocalization studies while mass spectrometry (MS) analysis was also performed to recognize the intact brain VGF fragments. We used a schizophrenia rat model, in which alterations in the prepulse inhibition (PPI) of the acoustic startle response occurred after PCP treatment. In normal rats, all the VGF peptides studied were distributed in the brain areas examined including hypothalamus, prefrontal cortex, hippocampus, accumbens and amygdaloid nuclei and also in the plasma. By liquid chromatography-high resolution mass, we identified different intact VGF peptide fragments, including those encompassing the N-terminus and the NERPs. PCP treatment caused behavioral changes that closely mimic schizophrenia, estimated by us as a disruption of PPI of the acoustic startle response. The PCP treatment also induced selective changes in the VGF peptide levels within certain brain areas. Indeed, an increase in VGF C-terminus and TLQP peptides was revealed in the prefrontal cortex (p < 0.01) where they were localized within parvoalbumin and tyrosine hydroxylase (TH) containing neurons, respectively. Conversely, in the nucleus accumbens, PCP treatment produced a down-regulation in the levels of VGF C-terminus-, N-terminus- and GGGE- peptides (p < 0.01), expressed in GABAergic- (C-terminus/GGGE) and somatostatin- (N-terminus) neurons. These results confirm that VGF peptides are widely distributed in the brain and modulated in specific areas involved in schizophrenia.

Neuropeptide VGF Promotes Maturation of Hippocampal Dendrites That Is Reduced by Single Nucleotide Polymorphisms

The neuropeptide VGF (non-acronymic) is induced by brain-derived neurotrophic factor and promotes hippocampal neurogenesis, as well as synaptic activity. However, morphological changes induced by VGF have not been elucidated. Developing hippocampal neurons were exposed to VGF through bath application or virus-mediated expression in vitro. VGF-derived peptide, TLQP-62, enhanced dendritic branching, and outgrowth. Furthermore, VGF increased dendritic spine density and the proportion of immature spines. Spine formation was associated with increased synaptic protein expression and co-localization of pre- and postsynaptic markers. Three non-synonymous single nucleotide polymorphisms (SNPs) were selected in human VGF gene. Transfection of N2a cells with plasmids containing these SNPs revealed no relative change in protein expression levels and normal protein size, except for a truncated protein from the premature stop codon, E525X. All three SNPs resulted in a lower proportion of N2a cells bearing neurites relative to wild-type VGF. Furthermore, all three mutations reduced the total length of dendrites in developing hippocampal neurons. Taken together, our results suggest VGF enhances dendritic maturation and that these effects can be altered by common mutations in the VGF gene. The findings may have implications for people suffering from psychiatric disease or other conditions who may have altered VGF levels.

The antidepressant-like effects of biperiden may involve BDNF/TrkB signaling-mediated BICC1 expression in the hippocampus and prefrontal cortex of mice

Preclinical and clinical studies suggest that neuronal muscarinic acetylcholine receptor (M-AchR) antagonists have antidepressant-like properties. Despite the recent interest in bicaudal C homolog 1 gene (BICC1) as a target for the treatment of depression, the upstream signaling molecules that regulate BICC1 are unknown, and very few studies have addressed the involvement of BICC1 in the antidepressant-like effects of the selective M1-AchR inhibitor, biperiden. Growing evidence indicates that activation of brain-derived neurotrophic factor (BDNF)/tropomyosin-related kinase receptor B (TrkB) signaling may be involved in antidepressant-like activities. In this study, we investigated the role of BDNF/TrkB signaling in the regulation of BICC1 expression in the chronic unpredictable stress (CUS) mouse model of depression. Furthermore, we also examined whether BDNF/TrkB signaling contributes to the antidepressant-like effects of biperiden via down-regulation of BICC1 in the hippocampus and prefrontal cortex of mice. Our current data show that CUS exposure induced significant depression-like behaviors, down-regulation of BDNF/TrkB signaling and up-regulation of BICC1 in the hippocampus and prefrontal cortex of mice. However, biperiden significantly alleviated the CUS-induced abnormalities. Moreover, we found that the effects of biperiden were antagonized by pretreatment with the TrkB antagonist K252a. Our results indicate that BDNF/TrkB signaling may be the major upstream mediator of BICC1 involvement in the antidepressant-like effects of biperiden.

Schisandra chinensis produces the antidepressant-like effects in repeated corticosterone-induced mice via the BDNF/TrkB/CREB signaling pathway

The present study aimed to examine the antidepressant-like effects and the possible mechanisms of Schisandra chinensis on depressive-like behavior induced by repeated corticosterone injections in mice. Here we evaluated the effect of an ethanol extract of the dried fruit of S. chinensis (EESC) on BDNF/TrkB/CREB signaling in the hippocampus and the prefrontal cortex. Three weeks of corticosterone injections in mice resulted in depressive-like behavior, as indicated by the significant decrease in sucrose consumption and increase the immobility time in the forced swim test, but without any influence on the locomotor activity. Further, there was a significant increase in serum corticosterone level and a significant downregulation of BDNF/TrkB/CREB signaling pathway in the hippocampus and prefrontal cortex in CORT-treated mice. Treatment of mice with EESC (600mg/kg) significantly ameliorated all the behavioral and biochemical changes induced by corticosterone. Moreover, pharmacological inhibition of BDNF signaling by K252a abolished entirely the antidepressant-like effect triggered by chronic EESC treatment. These results suggest that EESC produces an antidepressant-like effect in CORT-induced depression in mice, which is possibly mediated, at least in part, by rectifying the stress-based hypothalamic-pituitary-adrenal (HPA) axis dysfunction paradigm and upregulation of BDNF/TrkB/CREB signaling pathway.

Nanoparticles combined with growth factors: recent progress and applications

Increasing attention has been focused on the applications of nanoparticles combined with growth factors (NPs/GFs) due to the substantial functions of GFs in regenerative medicine and disease treatments.

VGF and Its C-Terminal Peptide TLQP-62 Regulate Memory Formation in Hippocampus via a BDNF-TrkB-Dependent Mechanism

Regulated expression and secretion of BDNF, which activates TrkB receptor signaling, is known to play a critical role in cognition. Identification of additional modulators of cognitive behavior that regulate activity-dependent BDNF secretion and/or potentiate TrkB receptor signaling would therefore be of considerable interest. In this study, we show in the adult mouse hippocampus that expression of the granin family gene Vgf and secretion of its C-terminal VGF-derived peptide TLQP-62 are required for fear memory formation. We found that hippocampal VGF expression and TLQP-62 levels were transiently induced after fear memory training and that sequestering secreted TLQP-62 peptide in the hippocampus immediately after training impaired memory formation. Reduced VGF expression was found to impair learning-evoked Rac1 induction and phosphorylation of the synaptic plasticity markers cofilin and synapsin in the adult mouse hippocampus. Moreover, TLQP-62 induced acute, transient activation of the TrkB receptor and subsequent CREB phosphorylation in hippocampal slice preparations and its administration immediately after training enhanced long-term memory formation. A critical role of BDNF-TrkB signaling as a downstream effector in VGF/TLQP-62-mediated memory consolidation was further revealed by posttraining activation of BDNF-TrkB signaling, which rescued impaired fear memory resulting from hippocampal administration of anti-VGF antibodies or germline VGF ablation in mice. We propose that VGF is a critical component of a positive BDNF-TrkB regulatory loop and, upon its induced expression by memory training, the TLQP-62 peptide rapidly reinforces BDNF-TrkB signaling, regulating hippocampal memory consolidation.

SIGNIFICANCE STATEMENT

Identification of the cellular and molecular mechanisms that regulate long-term memory formation and storage may provide alternative treatment modalities for degenerative and neuropsychiatric memory disorders. The neurotrophin BDNF plays a prominent role in cognitive function, and rapidly and robustly induces expression of VGF, a secreted neuronal peptide precursor. VGF knock-out mice have impaired fear and spatial memory. Our study shows that VGF and VGF-derived peptide TLQP-62 are transiently induced after fear memory training, leading to increased BDNF/TrkB signaling, and that sequestration of hippocampal TLQP-62 immediately after training impairs memory formation. We propose that TLQP-62 is a critical component of a positive regulatory loop that is induced by memory training, rapidly reinforces BDNF-TrkB signaling, and is required for hippocampal memory consolidation.

PI3K/AKT/mTOR signaling-mediated neuropeptide VGF in the hippocampus of mice is involved in the rapid onset antidepressant-like effects of GLYX-13

BACKGROUND

VGF (nonacryonimic) and phosphatidylinositol 3-kinase (PI3K)/AKT (also known as protein kinase B, PKB)/mammalian target of rapamycin (mTOR) signaling play pivotal roles in depression. However, whether phosphatidylinositol 3-kinase/AKT/mTOR signaling-mediated VGF participates in rapid-acting antidepressant-like actions of GLYX-13 is unclear.

METHODS

Herein, we evaluated the effects of acute treatment of GLYX-13 (0.5, 5, and 10mg/kg, i.p.) in the forced swim test. In addition, we assessed whether the acute treatment with GLYX-13 reverses the depressive-like behaviors induced by chronic unpredictable mild stress. Furthermore, we determined whether the Vgf knockdown in hippocampus of mice blocks the effects of GLYX-13. Moreover, we also demonstrated the effects of intra-hippocampus infusion of LY294002 (10 nmol/side), a specific phosphatidylinositol 3-kinase inhibitor prior to the treatment of GLYX-13 in the forced swim test. Lastly, whether alpha-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid (AMPA) receptor and mTOR activation involves in the antidepressant-like effects of GLYX-13 was examined.

RESULTS

Our results shown that GLYX-13 dose-dependently reversed the depressive-like behaviors in forced swim test. Additionally, GLYX-13 significantly reversed the downregulation of phosphorylation of AKT, mTOR, and eukaryotic elongation factor 2 as well as VGF induced by chronic unpredictable mild stress in hippocampus. Further, Vgf knockdown in hippocampus of mice significantly blocked the rapid-acting antidepressant-like effects and upregulation on phosphatidylinositol 3-kinase/AKT/mTOR/VGF signaling of GLYX-13. Moreover, intra-hippocampus infusion of LY294002 significantly abolished the antidepressant-like effects and upregulation on phosphatidylinositol 3-kinase/AKT/mTOR/VGF signaling of GLYX-13. Finally, antidepressant-like effects of GLYX-13 required AMPA receptor and mTOR activation, as evidenced by the ability of NBQX and rapamycin to block the effects of GLYX-13, respectively.

CONCLUSIONS

Our results suggest that phosphatidylinositol 3-kinase/AKT/mTOR signaling-mediated VGF in hippocampus may be involved in the antidepressant-like effects of GLYX-13.

Neuroendocrine Role for VGF

The vgf gene (non-acronymic) is highly conserved and was identified on the basis of its rapid induction in vitro by nerve growth factor, although can also be induced by brain-derived neurotrophic factor, and glial-derived growth factor. The VGF gene gives rise to a 68 kDa precursor polypeptide, which is induced robustly, relatively selectively and is synthesized exclusively in neuronal and neuroendocrine cells. Post-translational processing by neuroendocrine specific prohormone convertases in these cells results in the production of a number of smaller peptides. The VGF gene and peptides are widely expressed throughout the brain, particularly in the hypothalamus and hippocampus, in peripheral tissues including the pituitary gland, the adrenal glands, and the pancreas, and in the gastrointestinal tract in both the myenteric plexus and in endocrine cells. VGF peptides have been associated with a number of neuroendocrine roles, and in this review, we aim to describe these roles to highlight the importance of VGF as therapeutic target for a number of disorders, particularly those associated with energy metabolism, pain, reproduction, and cognition.

Antidepressant-like effect of evodiamine on chronic unpredictable mild stress rats

Evodiamine is a major alkaloid compound extracted from the dry unripened fruit Evodia fructus (Evodia rutaecarpa Benth., Rutaceae), which has a variety of pharmacological activities. The present study aims to determine the antidepressant-like effect of evodiamine in a rat model of chronic unpredictable mild stress (CUMS). We identified that evodiamine could reverse the following CUMS-induced behavioural deficits and biochemical changes in rats: the decreases of sucrose preference, number of crossings, 5-HT and NA levels, as well as the increase of immobility time. Evodiamine treatments also ameliorated the corticosterone hypersecretion induced by CUMS. Furthermore, we found that evodiamine was able to up-regulate the expression of brain-derived neurotrophic factor (BDNF) and phosphorylated tropomyosin-related kinase B (pTrkB) without altering TrkB. This study suggests potential antidepressant-like effect of evodiamine on CUMS rats, and its underlying mechanisms can be potentially linked to their modulating effects on the monoamine transmitters and BDNF-TrkB signaling in the hippocampus.